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Sample records for flattening filter-free 18-mv

  1. Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario

    OpenAIRE

    Mishra, Bibekananda; Selvam, T. Palani; Sharma, P. K. Dash

    2017-01-01

    Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP a...

  2. Efficient and accurate stereotactic radiotherapy using flattening filter free beams and HexaPOD robotic tables

    DEFF Research Database (Denmark)

    Nielsen, Morten; Hansen, C. R.; Brink, C.

    2016-01-01

    Flattening filter free (FFF) high dose rate beam technique was introduced for brain stereotactic radiosurgery (SRS) and lung Stereotactic Body Radiotherapy (SBRT). Furthermore, a HexaPOD treatment table was introduced for the brain SRS to enable correction of rotational setup errors. 19 filter fl...

  3. Treatment vault shielding for a flattening filter-free medical linear accelerator

    Science.gov (United States)

    Kry, Stephen F.; Howell, Rebecca M.; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N.

    2009-03-01

    The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m3 less concrete to shield the single-energy linac and 36 m3 less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

  4. Treatment vault shielding for a flattening filter-free medical linear accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kry, Stephen F; Howell, Rebecca M; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)], E-mail: sfkry@mdanderson.org

    2009-03-07

    The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m{sup 3} less concrete to shield the single-energy linac and 36 m{sup 3} less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

  5. Treatment vault shielding for a flattening filter-free medical linear accelerator

    International Nuclear Information System (INIS)

    Kry, Stephen F; Howell, Rebecca M; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N

    2009-01-01

    The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m 3 less concrete to shield the single-energy linac and 36 m 3 less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

  6. Beam properties and stability of a flattening-filter free 7 MV beam--An overview

    International Nuclear Information System (INIS)

    Dzierma, Yvonne; Licht, Norbert; Nuesken, Frank; Ruebe, Christian

    2012-01-01

    Purpose: Several works have recently focused on flattening-filter-free (FFF) beams of linear accelerators of various companies (in particular, Varian and Elekta), but no overview as yet exists for the flattening-filter free 7XU beam (Siemens Artiste). Methods: Dosimetric properties of the 7XU beam were measured in May and September 2011. We present depth dose curves and beam profiles, output factors, and MLC transmission and assess the stability of the measurements. The 7XU beam was commissioned in the Pinnacle³ treatment planning system (TPS), and modeling results including the spectrum are presented. Results: The percent depth dose curve of the 7XU beam is similar to the flat 6X beam line, with a slightly smaller surface dose. The beam profiles show the characteristic shape of flattening-filter free beams, with deviations between measurements of generally less than 1%. The output factors of the 7XU beam decrease more slowly than for the 6X beam. The MLC transmission is comparable but slightly less for the 7XU beam. The 7XU beam can be adequately modeled by the Pinnacle³ TPS, with successful dosimetric verification. The spectrum of the 7XU beam has lower photon fluence up to approximately 2.5 MeV and higher fluence beyond, with a slightly higher mean energy. Conclusions: The 7XU beam has been commissioned for clinical use after successful modeling, stability checks, and dosimetric verification.

  7. Multicentre knowledge sharing and planning/dose audit on flattening filter free beams for SBRT lung

    DEFF Research Database (Denmark)

    Hansen, C. R.; Sykes, J. R.; Barber, J.

    2015-01-01

    When implementing new technology into clinical practice, there will always be a need for large knowledge gain. The aim of this study was twofold, (I) audit the treatment planning and dose delivery of Flattening Filter Free (FFF) beam technology for Stereotactic Body Radiation Therapy (SBRT) of lung...... tumours across a range of treatment planning systems compared to the conventional Flatting Filter (FF) beams, (II) investigate how sharing knowledge between centres of different experience can improve plan quality. All vendor/treatment planning system (TPS) combinations investigated were able to produce...

  8. Flattening filter-free accelerators: a report from the AAPM Therapy Emerging Technology Assessment Work Group.

    Science.gov (United States)

    Xiao, Ying; Kry, Stephen F; Popple, Richard; Yorke, Ellen; Papanikolaou, Niko; Stathakis, Sotirios; Xia, Ping; Huq, Saiful; Bayouth, John; Galvin, James; Yin, Fang-Fang

    2015-05-08

    This report describes the current state of flattening filter-free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists. The Therapy Emerging Technology Assessment Work Group of the American Association of Physicists in Medicine (AAPM) formed a writing group to assess FFF technology. The published literature on FFF technology was reviewed, along with technical specifications provided by vendors. Based on this information, supplemented by the clinical experience of the group members, consensus guidelines and recommendations for implementation of FFF technology were developed. Areas in need of further investigation were identified. Removing the flattening filter increases beam intensity, especially near the central axis. Increased intensity reduces treatment time, especially for high-dose stereotactic radiotherapy/radiosurgery (SRT/SRS). Furthermore, removing the flattening filter reduces out-of-field dose and improves beam modeling accuracy. FFF beams are advantageous for small field (e.g., SRS) treatments and are appropriate for intensity-modulated radiotherapy (IMRT). For conventional 3D radiotherapy of large targets, FFF beams may be disadvantageous compared to flattened beams because of the heterogeneity of FFF beam across the target (unless modulation is employed). For any application, the nonflat beam characteristics and substantially higher dose rates require consideration during the commissioning and quality assurance processes relative to flattened beams, and the appropriate clinical use of the technology needs to be identified. Consideration also needs to be given to these unique characteristics when undertaking facility planning. Several areas still warrant further research and development. Recommendations pertinent to FFF technology, including acceptance testing, commissioning, quality assurance, radiation safety, and facility planning, are presented. Examples of clinical

  9. Surface dose investigation of the flattening filter-free photon beams.

    Science.gov (United States)

    Wang, Yuenan; Khan, Mohammad K; Ting, Joseph Y; Easterling, Stephen B

    2012-06-01

    Flattening filter-free (FFF) x-rays can provide more efficient use of photons and a significant increase of dose rate compared with conventional flattened x-rays, features that are especially beneficial for stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). The available data on the entrance doses of the FFF photon beams remain limited. The purpose of this study was to investigate the entrance dose of FFF photons in the buildup region and to compare it with that of conventional flattened photons. A Varian TrueBeam linear accelerator has been in full clinical operation with 6-MV and 10-MV FFF and flattened x-ray photons. Entrance dose at the surface was measured using a parallel plate ionization chamber in a solid water phantom with buildup depth = 0~15 mm for 6X and 0~25 mm for 10X. Different field size (FS) patterns were created in the Eclipse Treatment Planning System by multileaf collimator (MLC) rather than jaws (FS = 2 × 2, 3 × 3, 4 × 4, 6 × 6, and 10 × 10 cm(2) by MLC and jaw size = 2.2 × 2.2, 3.2 × 3.2, 4.2 × 4.2, 6 × 6, and 10 × 10 cm(2)). The smallest FS was about four times larger than the ion chamber dimension. All buildup dose measurements were normalized to FS = 10 × 10 cm(2) at the depth of dose maximum (dmax). Good repeatability was demonstrated and surface dose increased linearly with FS for both flattened and FFF photons. The entrance dose of the FFF photons was modestly larger than that of the corresponding flattened photons for both 6X and 10X for different FS ranging from 2 × 2 cm(2) to 10 × 10 cm(2). The FFF photons have a higher entrance dose than that of the corresponding flattened photons for FS smaller than 10 × 10 cm(2). However, the difference is not substantial and may be clinically insignificant. Published by Elsevier Inc.

  10. Definition of parameters for quality assurance of flattening filter free (FFF) photon beams in radiation therapy

    International Nuclear Information System (INIS)

    Fogliata, A.; Garcia, R.; Knöös, T.; Nicolini, G.; Clivio, A.; Vanetti, E.; Khamphan, C.; Cozzi, L.

    2012-01-01

    Purpose: Flattening filter free (FFF) beams generated by medical linear accelerators have recently started to be used in radiotherapy clinical practice. Such beams present fundamental differences with respect to the standard filter flattened (FF) beams, making the generally used dosimetric parameters and definitions not always viable. The present study will propose possible definitions and suggestions for some dosimetric parameters for use in quality assurance of FFF beams generated by medical linacs in radiotherapy. Methods: The main characteristics of the photon beams have been analyzed using specific data generated by a Varian TrueBeam linac having both FFF and FF beams of 6 and 10 MV energy, respectively. Results: Definitions for dose profile parameters are suggested starting from the renormalization of the FFF with respect to the corresponding FF beam. From this point the flatness concept has been translated into one of “unflatness” and other definitions have been proposed, maintaining a strict parallelism between FFF and FF parameter concepts. Conclusions: Ideas for quality controls used in establishing a quality assurance program when introducing FFF beams into the clinical environment are given here, keeping them similar to those used for standard FF beams. By following the suggestions in this report, the authors foresee that the introduction of FFF beams into a clinical radiotherapy environment will be as safe and well controlled as standard beam modalities using the existing guidelines.

  11. Structural shielding design of a 6 MV flattening filter free linear accelerator: Indian scenario

    Directory of Open Access Journals (Sweden)

    Bibekananda Mishra

    2017-01-01

    Full Text Available Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC operated with flattening filter (FF and flattening filter free (FFF modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP Report No. 151 and the other based on the monitor units (MUs delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.

  12. Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario.

    Science.gov (United States)

    Mishra, Bibekananda; Selvam, T Palani; Sharma, P K Dash

    2017-01-01

    Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.

  13. Acquiring beam data for a flattening-filter free linear accelerator using organic scintillators

    International Nuclear Information System (INIS)

    Beierholm, A.R.; Behrens, C.F.; Hoffmann, L.; Andersen, C.E.

    2013-01-01

    Fibre-coupled organic scintillators have been proven a credible alternative to clinically implemented methods for radiotherapy dosimetry, primarily due to their water equivalence and good spatial resolution. Furthermore, the fast response of the scintillators can be exploited to perform time-resolved dosimetry on a highly detailed level. In this study, we present beam data for a Varian TrueBeam linear accelerator, which is capable of delivering flattening-filter free (FFF 1 ) clinical X-ray beams. The beam data have been acquired using an in-house developed dosimetry system based on fibre-coupled organic scintillators. The presented data exhibit high accuracy and precision when compared with data obtained using commercial dosimetry methods, and agree well with results published in the literature. -- Highlights: •A dosimetry system based on fibre-coupled organic scintillators is presented. •The system is used for radiotherapy beams with and without flattening filter. •Measurements show good agreement with various commercial dosimeters

  14. Impact of a flattening filter free linear accelerator on structural shielding design

    International Nuclear Information System (INIS)

    Jank, Julia; Kragl, Gabriele; Georg, Dietmar; Medical University of Vienna

    2014-01-01

    Purpose: The present study aimed to assess the effects of a flattening filter free medical accelerator on structural shielding demands of a treatment vault of a medical linear accelerator. We tried to answer the question, to what extent the required thickness of the shielding barriers can be reduced if instead of the standard flattened photon beams unflattened ones are used. Material and Methods: We chose both an experimental as well as a theoretical approach. On the one hand we measured photon dose rates at protected places outside the treatment room and compared the obtained results for flattened and unflattened beams. On the other hand we complied with international guidelines for adequate treatment vault design and calculated the shielding barriers according to the therein given specifications. Measurements were performed with an Elekta Precise trademark linac providing nominal photon energies of 6 and 10 MV. This machine underwent already earlier some modifications in order to be able to operate both with and without a flattening filter. Photon dose rates were measured with a LB133-1 dose rate meter manufactured by Berthold. To calculate the thickness of shielding barriers we referred to the Austrian standard OeNORM S 5216 and to the US American NCRP Report No. 151. Results: We determined a substantial photon dose rate reduction for all measurement points and photon energies. For unflattened 6 MV beams a reduction factor ranging from 1.4 to 1.8 was identified. The corresponding values for unflattened 10 MV beams were 2.1 and 3.2. The performed shielding calculations indicated the same tendency: For all relevant radiation components we found a reduction in shielding thickness when unflattened beams were used. The required thickness of primary barriers was reduced up to 8.0%, the thickness of secondary barriers up to 11.4%, respectively. Conclusions: For an adequate dimensioning of treatment vault shielding barriers it is by no means irrelevant if the

  15. Impact of a flattening filter free linear accelerator on structural shielding design.

    Science.gov (United States)

    Jank, Julia; Kragl, Gabriele; Georg, Dietmar

    2014-03-01

    The present study aimed to assess the effects of a flattening filter free medical accelerator on structural shielding demands of a treatment vault of a medical linear accelerator. We tried to answer the question, to what extent the required thickness of the shielding barriers can be reduced if instead of the standard flattened photon beams unflattened ones are used. We chose both an experimental as well as a theoretical approach. On the one hand we measured photon dose rates at protected places outside the treatment room and compared the obtained results for flattened and unflattened beams. On the other hand we complied with international guidelines for adequate treatment vault design and calculated the shielding barriers according to the therein given specifications. Measurements were performed with an Elekta Precise™ linac providing nominal photon energies of 6 and 10 MV. This machine underwent already earlier some modifications in order to be able to operate both with and without a flattening filter. Photon dose rates were measured with a LB133-1 dose rate meter manufactured by Berthold. To calculate the thickness of shielding barriers we referred to the Austrian standard ÖNORM S 5216 and to the US American NCRP Report No. 151. We determined a substantial photon dose rate reduction for all measurement points and photon energies. For unflattened 6 MV beams a reduction factor ranging from 1.4 to 1.8 was identified. The corresponding values for unflattened 10 MV beams were 2.1 and 3.2. The performed shielding calculations indicated the same tendency: For all relevant radiation components we found a reduction in shielding thickness when unflattened beams were used. The required thickness of primary barriers was reduced up to 8.0%, the thickness of secondary barriers up to 11.4%, respectively. For an adequate dimensioning of treatment vault shielding barriers it is by no means irrelevant if the accommodated linac operates with or without a flattening filter. The

  16. Impact of a flattening filter free linear accelerator on structural shielding design

    Energy Technology Data Exchange (ETDEWEB)

    Jank, Julia [Klinikum - Klagenfurt am Woerthersee (Austria). Inst. fuer Strahlentherapie und Radioonkologie; Kragl, Gabriele [Medical University of Vienna/AKH Vienna (Austria). Div. Medical Radiation Physics; Georg, Dietmar [Medical University of Vienna/AKH Vienna (Austria). Div. Medical Radiation Physics; Medical University of Vienna (Austria). Christian Doppler Lab. for Medical Radiation Research for Radiation Oncology

    2014-04-01

    Purpose: The present study aimed to assess the effects of a flattening filter free medical accelerator on structural shielding demands of a treatment vault of a medical linear accelerator. We tried to answer the question, to what extent the required thickness of the shielding barriers can be reduced if instead of the standard flattened photon beams unflattened ones are used. Material and Methods: We chose both an experimental as well as a theoretical approach. On the one hand we measured photon dose rates at protected places outside the treatment room and compared the obtained results for flattened and unflattened beams. On the other hand we complied with international guidelines for adequate treatment vault design and calculated the shielding barriers according to the therein given specifications. Measurements were performed with an Elekta Precise trademark linac providing nominal photon energies of 6 and 10 MV. This machine underwent already earlier some modifications in order to be able to operate both with and without a flattening filter. Photon dose rates were measured with a LB133-1 dose rate meter manufactured by Berthold. To calculate the thickness of shielding barriers we referred to the Austrian standard OeNORM S 5216 and to the US American NCRP Report No. 151. Results: We determined a substantial photon dose rate reduction for all measurement points and photon energies. For unflattened 6 MV beams a reduction factor ranging from 1.4 to 1.8 was identified. The corresponding values for unflattened 10 MV beams were 2.1 and 3.2. The performed shielding calculations indicated the same tendency: For all relevant radiation components we found a reduction in shielding thickness when unflattened beams were used. The required thickness of primary barriers was reduced up to 8.0%, the thickness of secondary barriers up to 11.4%, respectively. Conclusions: For an adequate dimensioning of treatment vault shielding barriers it is by no means irrelevant if the

  17. An in vitro study of the radiobiological effects of flattening filter free radiotherapy treatments

    International Nuclear Information System (INIS)

    King, R B; Hyland, W B; McGarry, C K; Hounsell, A R; Cole, A J; Butterworth, K T; McMahon, S J; Redmond, K M; Trainer, C; Prise, K M

    2013-01-01

    Flattening filter free (FFF) linear accelerators allow for an increase in instantaneous dose-rate of the x-ray pulses by a factor of 2–6 over the conventional flattened output. As a result, radiobiological investigations are being carried out to determine the effect of these higher dose-rates on cell response. The studies reported thus far have presented conflicting results, highlighting the need for further investigation. To determine the radiobiological impact of the increased dose-rates from FFF exposures a Varian Truebeam medical linear accelerator was used to irradiate two human cancer cell lines in vitro, DU-145 prostate and H460 non-small cell lung, with both flattened and FFF 6 MV beams. The fluence profile of the FFF beam was modified using a custom-designed Nylon compensator to produce a similar dose profile to the flattened beam (6X) at the cell surface but at a higher instantaneous dose-rate. For both cell lines there appeared to be no significant change in cell survival. Curve fitting coefficients for DU145 cells irradiated with constant average dose-rates were 6X: α = 0.09 ± 0.03, β = 0.03 ± 0.01 and 6FFF: α = 0.14 ± 0.13, β = 0.03 ± 0.02 with a significance of p = 0.75. For H460 cells irradiated with the same instantaneous dose-rate but different average dose-rate the fit coefficients were 6FFF (low dose-rate): α = 0.21 ± 0.11, 0.07 ± 0.02 and 6FFF (high dose-rate): α = 0.21 ± 0.16, 0.07 ± 0.03, with p = 0.79. The results indicate that collective damage behaviour does not occur at the instantaneous dose-rates investigated here and that the use of either modality should result in the same clinical outcome, however this will require further validation in vivo. (note)

  18. Multicentre knowledge sharing and planning/dose audit on flattening filter free beams for SBRT lung

    Science.gov (United States)

    Hansen, C. R.; Sykes, J. R.; Barber, J.; West, K.; Bromley, R.; Szymura, K.; Fisher, S.; Sim, J.; Bailey, M.; Chrystal, D.; Deshpande, S.; Franji, I.; Nielsen, T. B.; Brink, C.; Thwaites, D. I.

    2015-01-01

    When implementing new technology into clinical practice, there will always be a need for large knowledge gain. The aim of this study was twofold, (I) audit the treatment planning and dose delivery of Flattening Filter Free (FFF) beam technology for Stereotactic Body Radiation Therapy (SBRT) of lung tumours across a range of treatment planning systems compared to the conventional Flatting Filter (FF) beams, (II) investigate how sharing knowledge between centres of different experience can improve plan quality. All vendor/treatment planning system (TPS) combinations investigated were able to produce acceptable treatment plans and the dose accuracy was clinically acceptable for all plans. By sharing knowledge between the different centres, the minor protocol violations (MPV) could be significantly reduced, from an average of 1.9 MPV per plan to 0.6 after such sharing of treatment planning knowledge. In particular, for the centres with less SBRT and/or volumetric- modulated arc therapy (VMAT) experience the MPV average per plan improved. All vendor/TPS combinations were also able to successfully deliver the FF and FFF SBRT VMAT plans. The plan quality and dose accuracy were found to be clinically acceptable.

  19. Multicentre knowledge sharing and planning/dose audit on flattening filter free beams for SBRT lung

    International Nuclear Information System (INIS)

    Hansen, C R; Nielsen, T B; Brink, C; Sykes, J R; Barber, J; West, K; Bromley, R; Szymura, K; Fisher, S; Sim, J; Bailey, M; Chrystal, D; Deshpande, S; Franji, I; Thwaites, D I

    2015-01-01

    When implementing new technology into clinical practice, there will always be a need for large knowledge gain. The aim of this study was twofold, (I) audit the treatment planning and dose delivery of Flattening Filter Free (FFF) beam technology for Stereotactic Body Radiation Therapy (SBRT) of lung tumours across a range of treatment planning systems compared to the conventional Flatting Filter (FF) beams, (II) investigate how sharing knowledge between centres of different experience can improve plan quality. All vendor/treatment planning system (TPS) combinations investigated were able to produce acceptable treatment plans and the dose accuracy was clinically acceptable for all plans. By sharing knowledge between the different centres, the minor protocol violations (MPV) could be significantly reduced, from an average of 1.9 MPV per plan to 0.6 after such sharing of treatment planning knowledge. In particular, for the centres with less SBRT and/or volumetric- modulated arc therapy (VMAT) experience the MPV average per plan improved. All vendor/TPS combinations were also able to successfully deliver the FF and FFF SBRT VMAT plans. The plan quality and dose accuracy were found to be clinically acceptable

  20. The impact of flattening-filter-free beam technology on 3D conformal RT

    Science.gov (United States)

    2013-01-01

    Background The removal of the flattening filter (FF) leads to non-uniform fluence distribution with a considerable increase in dose rate. It is possible to adapt FFF beams (flattening-filter-free) in 3D conformal radiation therapy (3D CRT) by using field in field techniques (FiF). The aim of this retrospective study is to clarify whether the quality of 3D CRT plans is influenced by the use of FFF beams. Method This study includes a total of 52 CT studies of RT locations that occur frequently in clinical practice. Dose volume targets were provided for the PTV of breast (n=13), neurocranium (n=11), lung (n=7), bone metastasis (n=10) and prostate (n=11) in line with ICRU report 50/62. 3D CRT planning was carried out using FiF methods. Two clinically utilized photon energies are used for a Siemens ARTISTE linear accelerator in FFF mode at 7MVFFF and 11MVFFF as well as in FF mode at 6MVFF and 10MVFF. The plan quality in relation to the PTV coverage, OAR (organs at risk) and low dose burden as well as the 2D dosimetric verification is compared with FF plans. Results No significant differences were found between FFF and FF plans in the mean dose for the PTV of breast, lung, spine metastasis and prostate. The low dose parameters V5Gy and V10Gy display significant differences for FFF and FF plans in some subgroups. The DVH analysis of the OAR revealed some significant differences. Significantly more fields (1.9 – 4.5) were necessary in the use of FFF beams for each location (p<0.0001) in order to achieve PTV coverage. All the tested groups displayed significant increases (1.3 – 2.2 times) in the average number of necessary MU with the use of FFF beams (p<0.001). Conclusions This study has shown that the exclusive use of a linear accelerator in FFF mode is feasible in 3D CRT. It was possible to realize RT plans in comparable quality in typical cases of clinical radiotherapy. The 2D dosimetric validation of the modulated fields verified the dose calculation and thus the

  1. Equivalent (uniform) square field sizes of flattening filter free photon beams

    Science.gov (United States)

    Lechner, Wolfgang; Kuess, Peter; Georg, Dietmar; Palmans, Hugo

    2017-10-01

    Various types of treatment units, such as CyberKnife, TomoTherapy and C-arm linear accelerators (LINACs) are operated using flattening filter free (FFF) photon beams. Their reference dosimetry, however, is currently based on codes of practice that provide data which were primarily developed and tested for high-energy photon beams with flattening filter (WFF). The aim of this work was to introduce equivalent uniform square field sizes of FFF beams to serve as a basis of a unified reference dosimetry procedure applicable to all aforementioned FFF machines. For this purpose, in-house determined experimental data together with published data of the ratio of doses at depths of 20 cm and 10 cm in water (D 20,10) were used to characterize the depth dose distribution of 6 and 10 MV WFF and FFF beams. These data were analyzed for field sizes ranging from 2  ×  2 cm2 to 40  ×  40 cm2. A scatter function that takes the lateral profiles of the individual beams into account was fitted to the experimental data. The lateral profiles of the WFF beams were assumed to be uniform, while those of the FFF beams were approximated using fourth or sixth order polynomials. The scatter functions of the FFF beams were recalculated using a uniform lateral profile (the same as the physical profile of the WFF beams), and are henceforth denoted as virtual uniform FFF beams (VUFFF). The field sizes of the VUFFF beams having the same scatter contribution as the corresponding FFF beams at a given field size were defined as the equivalent uniform square field (EQUSF) size. Data from four different LINACs with 18 different beams in total, as well as a CyberKnife beam, were analyzed. The average values of EQUSFs over all investigated LINACs of the conventional 10  ×  10 cm2 reference fields of 6 MV and 10 MV FFF beams for C-arm LINACs and machine-specific reference fields for CyberKnife and TomoTherapy were 9.5 cm, 9 cm, 5.0 cm and 6.5 cm respectively. The

  2. Improvement of the penumbra for small radiosurgical fields using flattening filter free low megavoltage beams

    Energy Technology Data Exchange (ETDEWEB)

    Yarahmadi, Mehran [Kurdistan Univ. of Medical Sciences, Sanandaj (Iran, Islamic Republic of); Allahverdi, Mahmoud; Nedaie, Hassan A.; Asnaashari, Khadijeh; Vaezzadeh, Sayed A. [Tehran Univ. of Medical Sciences, Tehran (Iran, Islamic Republic of); Sauer, Otto A. [Wuerzburg Univ. (Germany). Klinik und Poliklinik fuer Strahlentherapie

    2013-07-01

    Background: In stereotactic radiosurgery, sharp beam edges have clear advantages to spare normal tissues. In general, the dose gradient is a limiting factor in minimizing dose to nearby critical structures for clinical cases. Therefore the penumbral width should be diminished. Methods: A Varian Clinac 2100 linear accelerator equipped with in-house designed radiosurgical collimator was modeled using the EGSnrc/BEAMnrc Monte Carlo code and compared with the measurements. The 0.015 cm{sup 3} PinPoint chamber was used to measure the 6 MV photon beam characteristics and to validate Monte Carlo calculations. Additional to the standard (STD) linac, a flattening filter free (FFF) linac was simulated. Percent depth doses, beam profiles and output factors were calculated for small field sizes with diameter of 5, 10, 20 and 30 mm with DOSXYZnrc. The mean energy and photon fluence at the water surface were calculated with BEAMDP for both FFF linac and STD linacs. Results: The penumbra width (80%-20%) was decreased by 0.5, 0.3, 0.2 and 0.2 mm for field sizes of 5, 10, 20 and 30 mm respectively when removing the FF. The fluence of photons at the surface increased up to 3.6 times and the mean energy decreased by a factor of 0.69 when removing the FF. The penumbra width (80%-20%) decreased by 17% when a 2 MeV monoenergetic electron pencil beam incident on the target is used instead of 6.2 MeV. Conclusions: It was found that the penumbra of small field sizes is decreased by removing the FF. Likewise using low megavoltage photons reduced the beam penumbra maintaining adequate penetration and skin sparing. (orig.)

  3. Technical Note: A fast online adaptive replanning method for VMAT using flattening filter free beams

    Energy Technology Data Exchange (ETDEWEB)

    Ates, Ozgur; Ahunbay, Ergun E.; Li, X. Allen, E-mail: ali@mcw.edu [Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States); Moreau, Michel [Elekta, Inc., Maryland Heights, Missouri 63043 (United States)

    2016-06-15

    Purpose: To develop a fast replanning algorithm based on segment aperture morphing (SAM) for online replanning of volumetric modulated arc therapy (VMAT) with flattening filter free (FFF) beams. Methods: A software tool was developed to interface with a VMAT research planning system, which enables the input and output of beam and machine parameters of VMAT plans. The SAM algorithm was used to modify multileaf collimator positions for each segment aperture based on the changes of the target from the planning (CT/MR) to daily image [CT/CBCT/magnetic resonance imaging (MRI)]. The leaf travel distance was controlled for large shifts to prevent the increase of VMAT delivery time. The SAM algorithm was tested for 11 patient cases including prostate, pancreatic, and lung cancers. For each daily image set, three types of VMAT plans, image-guided radiation therapy (IGRT) repositioning, SAM adaptive, and full-scope reoptimization plans, were generated and compared. Results: The SAM adaptive plans were found to have improved the plan quality in target and/or critical organs when compared to the IGRT repositioning plans and were comparable to the reoptimization plans based on the data of planning target volume (PTV)-V100 (volume covered by 100% of prescription dose). For the cases studied, the average PTV-V100 was 98.85% ± 1.13%, 97.61% ± 1.45%, and 92.84% ± 1.61% with FFF beams for the reoptimization, SAM adaptive, and repositioning plans, respectively. The execution of the SAM algorithm takes less than 10 s using 16-CPU (2.6 GHz dual core) hardware. Conclusions: The SAM algorithm can generate adaptive VMAT plans using FFF beams with comparable plan qualities as those from the full-scope reoptimization plans based on daily CT/CBCT/MRI and can be used for online replanning to address interfractional variations.

  4. Poster — Thur Eve — 37: Respiratory gating with an Elekta flattening filter free photon beam

    International Nuclear Information System (INIS)

    Péloquin, S; Furstoss, C; Munger, P; Wierzbicki, W; Carrier, J-F

    2014-01-01

    In cases where surgery is not possible for lung cancer treatment, stereotactic body radiation therapy (SBRT) may be an option. One problem when treating this type of cancer is the motion of the lungs caused by the patient's respiration. It is possible to reduce the impact of this movement with the use of respiratory gating. By combining respiratory gating with a flattening filter free (FFF) photon beam linac, the increased treatment time caused by a reduced beam-on time of respiratory gating methods can be compensated by the inherent increased dose rate of FFF beams. This project's aim is to create hardware and software interfaces allowing free respiration gating on an Elekta Synergy-S linac specially modified to deliver 6 MV FFF photon beams. First, a printed circuit board was created for reading the signal from a Bellows Belt from Philips (a respiration monitor belt) and transmitting an On/Off signal to the accelerator. A software was also developed to visualize patient respiration. Secondly, a FFF model was created with the Pinnacle treatment planning system from Philips. Gamma (Γ) analysis (2%, 2 mm) was used to evaluate model. For fields going from 5.6 × 5.6 to 12 × 12 cm 2 , central axis depth dose model fitting shows an average gamma value of 0.2 and 100% of gamma values remain under the Γ = 1 limit. For smaller fields (0.8 × 0.8 and 1.6 × 1.6 cm 2 ), Pinnacle has more trouble trying to fit the measurements, overestimating dose in penumbra and buildup regions

  5. Technical Report: Evaluation of peripheral dose for flattening filter free photon beams

    Energy Technology Data Exchange (ETDEWEB)

    Covington, E. L.; Moran, J. M.; Owrangi, A. M.; Prisciandaro, J. I., E-mail: joannp@med.umich.edu [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109 (United States); Ritter, T. A. [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan 48109 and Department of Radiation Oncology, Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan 48105 (United States)

    2016-08-15

    Purpose: To develop a comprehensive peripheral dose (PD) dataset for the two unflattened beams of nominal energy 6 and 10 MV for use in clinical care. Methods: Measurements were made in a 40 × 120 × 20 cm{sup 3} (width × length × depth) stack of solid water using an ionization chamber at varying depths (dmax, 5, and 10 cm), field sizes (3 × 3 to 30 × 30 cm{sup 2}), and distances from the field edge (5–40 cm). The effects of the multileaf collimator (MLC) and collimator rotation were also evaluated for a 10 × 10 cm{sup 2} field. Using the same phantom geometry, the accuracy of the analytic anisotropic algorithm (AAA) and Acuros dose calculation algorithm was assessed and compared to the measured values. Results: The PDs for both the 6 flattening filter free (FFF) and 10 FFF photon beams were found to decrease with increasing distance from the radiation field edge and the decreasing field size. The measured PD was observed to be higher for the 6 FFF than for the 10 FFF for all field sizes and depths. The impact of collimator rotation was not found to be clinically significant when used in conjunction with MLCs. AAA and Acuros algorithms both underestimated the PD with average errors of −13.6% and −7.8%, respectively, for all field sizes and depths at distances of 5 and 10 cm from the field edge, but the average error was found to increase to nearly −69% at greater distances. Conclusions: Given the known inaccuracies of peripheral dose calculations, this comprehensive dataset can be used to estimate the out-of-field dose to regions of interest such as organs at risk, electronic implantable devices, and a fetus. While the impact of collimator rotation was not found to significantly decrease PD when used in conjunction with MLCs, results are expected to be machine model and beam energy dependent. It is not recommended to use a treatment planning system to estimate PD due to the underestimation of the out-of-field dose and the inability to calculate dose

  6. Characteristics of flattening filter free beams at low monitor unit settings

    Energy Technology Data Exchange (ETDEWEB)

    Akino, Yuichi [Department of Radiology, Osaka University Hospital, Suita, Osaka 565-0871, Japan and Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871 (Japan); Ota, Seiichi; Inoue, Shinichi; Mizuno, Hirokazu [Department of Radiology, Osaka University Hospital, Suita, Osaka 565-0871 (Japan); Sumida, Iori; Yoshioka, Yasuo; Ogawa, Kazuhiko [Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871 (Japan); Isohashi, Fumiaki [Oncology Center, Osaka University Hospital, Suita, Osaka 565-0871 (Japan)

    2013-11-15

    Purpose: Newer linear accelerators (linacs) have been equipped to deliver flattening filter free (FFF) beams. When FFF beams are used for step-and-shoot intensity-modulated radiotherapy (IMRT), the stability of delivery of small numbers of monitor units (MU) is important. The authors developed automatic measurement techniques to evaluate the stability of the dose profile, dose linearity, and consistency. Here, the authors report the performance of the Artiste™ accelerator (Siemens, Erlangen, Germany) in delivering low-MU FFF beams.Methods: A 6 MV flattened beam (6X) with 300 MU/min dose rate and FFF beams of 7 (7XU) and 11 MV (11XU), each with a 500 MU/min dose rate, were measured at 1, 2, 3, 5, 8, 10, and 20 MU settings. For the 2000 MU/min dose rate, the 7 (7XUH) and 11 MV (11XUH) beams were set at 10, 15, 20, 25, and 30 MU because of the limits of the minimum MU settings. Beams with 20 × 20 and 10 × 10 cm{sup 2} field sizes were alternately measured ten times in intensity modulated (IM) mode, with which Siemens linacs regulate beam delivery for step-and-shoot IMRT. The in- and crossplane beam profiles were measured using a Profiler™ Model 1170 (Sun Nuclear Corporation, Melbourne, FL) in multiframe mode. The frames of 20 × 20 cm{sup 2} beams were identified at the off-axis profile. The 6X beam profile was normalized at the central axis. The 7 and 11 MV FFF beam profiles were rescaled to set the dose at the central axis at 145% and 170%, respectively. Point doses were also measured using a Farmer-type ionization chamber and water-equivalent solid phantom to evaluate the linearity and consistency of low-MU beam delivery. The values displayed on the electrometer were recognized with a USB-type camera and read with open-source optical character recognition software.Results: The symmetry measurements of the 6X, 7XU, and 11XU beam profiles were better than 2% for beams ≥2 MU and improved with increasing MU. The variations in flatness of FFF beams ≥2 MU were

  7. Characteristics of flattening filter free beams at low monitor unit settings

    International Nuclear Information System (INIS)

    Akino, Yuichi; Ota, Seiichi; Inoue, Shinichi; Mizuno, Hirokazu; Sumida, Iori; Yoshioka, Yasuo; Ogawa, Kazuhiko; Isohashi, Fumiaki

    2013-01-01

    Purpose: Newer linear accelerators (linacs) have been equipped to deliver flattening filter free (FFF) beams. When FFF beams are used for step-and-shoot intensity-modulated radiotherapy (IMRT), the stability of delivery of small numbers of monitor units (MU) is important. The authors developed automatic measurement techniques to evaluate the stability of the dose profile, dose linearity, and consistency. Here, the authors report the performance of the Artiste™ accelerator (Siemens, Erlangen, Germany) in delivering low-MU FFF beams.Methods: A 6 MV flattened beam (6X) with 300 MU/min dose rate and FFF beams of 7 (7XU) and 11 MV (11XU), each with a 500 MU/min dose rate, were measured at 1, 2, 3, 5, 8, 10, and 20 MU settings. For the 2000 MU/min dose rate, the 7 (7XUH) and 11 MV (11XUH) beams were set at 10, 15, 20, 25, and 30 MU because of the limits of the minimum MU settings. Beams with 20 × 20 and 10 × 10 cm 2 field sizes were alternately measured ten times in intensity modulated (IM) mode, with which Siemens linacs regulate beam delivery for step-and-shoot IMRT. The in- and crossplane beam profiles were measured using a Profiler™ Model 1170 (Sun Nuclear Corporation, Melbourne, FL) in multiframe mode. The frames of 20 × 20 cm 2 beams were identified at the off-axis profile. The 6X beam profile was normalized at the central axis. The 7 and 11 MV FFF beam profiles were rescaled to set the dose at the central axis at 145% and 170%, respectively. Point doses were also measured using a Farmer-type ionization chamber and water-equivalent solid phantom to evaluate the linearity and consistency of low-MU beam delivery. The values displayed on the electrometer were recognized with a USB-type camera and read with open-source optical character recognition software.Results: The symmetry measurements of the 6X, 7XU, and 11XU beam profiles were better than 2% for beams ≥2 MU and improved with increasing MU. The variations in flatness of FFF beams ≥2 MU were ±5%. The

  8. Impact of flattening-filter-free radiation on the clonogenic survival of astrocytic cell lines

    Energy Technology Data Exchange (ETDEWEB)

    Steenken, Caroline; Fleckenstein, Jens; Kegel, Stefan; Jahnke, Lennart; Simeonova, Anna; Hartmann, Linda; Kuebler, Jens; Veldwijk, Marlon R.; Wenz, Frederik; Herskind, Carsten; Giordano, Frank Anton [Universitaetsmedizin Mannheim (UMM), Medical Faculty Mannheim, Heidelberg University, Department of Radiation Oncology, Mannheim (Germany)

    2015-07-15

    Flattening-filter-free (FFF) beams are increasingly used in radiotherapy as delivery times can be substantially reduced. However, the relative biologic effectiveness (RBE) of FFF may be increased relative to conventional flattened (FLAT) beams due to differences in energy spectra. Therefore, we investigated the effects of FFF and FLAT beams on the clonogenic survival of astrocytoma cells. Three cell lines (U251, U251-MGMT, and U87) were irradiated with 6-MV and 10-MV X-rays from a linear accelerator in FFF- or FLAT-beam modes at dose rates in the range of 0.5-24 Gy/min. The surviving fraction (SF) as function of dose (2-12 Gy) was determined by the colony formation assay and fitted by the linear-quadratic model. For both beams (FFF or FLAT), the cells were pelleted in conical 15-ml centrifuge tubes and irradiated at 2-cm depth in a 1 x 1-cm{sup 2} area on the central axis of a 30 x 30-cm{sup 2} field. Dosimetry was performed with a 0.3-cm{sup 3} rigid ionization chamber. RBE was determined for FFF versus FLAT irradiation. The RBE of FFF at 7.3-11.3 Gy was 1.027 ± 0.013 and 1.063 ± 0.018 relative to FLAT beams for 6- and 10-MV beams, respectively, and was only significantly higher than 1 for 10 MV. Significantly increased survival rates were seen for lower dose rates (0.5 Gy/min FLAT vs. 5 Gy/min FLAT) at higher doses (11.9 Gy), while no differences were seen at dose rates ≥ 1.4 Gy/min (1.4 Gy/min FFF vs. 14 Gy/min FFF and 2.4 Gy/min FFF vs. 24 Gy/min FFF). FFF beams showed only a slightly increased RBE relative to FLAT beams in this experimental set-up, which is unlikely to result in clinically relevant differences in outcome. (orig.) [German] Die Flattening-Filter-freie (FFF) Bestrahlungstechnik findet zunehmend Verwendung, da sich die Applikationsdauer der einzelnen Fraktionen deutlich verkuerzen laesst. Aufgrund der Unterschiede im Spektrum koennte die relative biologische Wirksamkeit (RBW) von FFF jedoch hoeher sein als bei konventioneller Technik (d.h. bei

  9. Dosimetric study of RapidArc plans with flattened beam (FB and flattening filter-free (FFF beam for localized prostate cancer based on physical indices

    Directory of Open Access Journals (Sweden)

    Birendra Kumar Rout

    2014-12-01

    Full Text Available Purpose: To identify the continual diversity between flattening photon beam (FB and Flattening Filter Free (FFF photon beams for localized prostate cancer; and to determine potential benefits and drawbacks of using unflattened beam for this type of treatment.Methods: Eight prostate cases including seminal vesicles selected for this study. The primary planning target volume (PTVP and boost planning target volume (PTVB were contoured. The total prescription dose was 78 Gy (56 Gy to PTVP and an additional 22 Gy to PTVB. For all cases, treatment plans using 6MV with FB and FFF beams with identical dose-volume constraints, arc angles and number of arcs were developed. The dose volume histograms for both techniques were compared for primary target volume and critical structures.Results: A low Sigma index (FFF: 1.65 + 0.361; FB: 1.725 + 0.39 indicating improved dose homogeneity in FFF beam. Conformity index (FFF: 0.994 + 0.01; FB: 0.993 + 0.01 is comparable for both techniques. Minimal difference of Organ at risk mean dose was observed. Normal tissue integral dose in FB plan resulted 1.5% lower than FFF plan. All the plans displayed significant increase (1.18 times for PTVP and 1.11 for PTBB in the average number of necessary MU with FFF beam.Conclusion: Diversity between FB and FFF beam plans were found. FFF beam accelerator has been utilized to develop clinically acceptable Rapid Arc treatment plans for prostate cancer with 6 MV.---------------------------------Cite this article as: Rout BK, Muralidhar KR, Ali M, Shekar MC, Kumar A. Dosimetric study of RapidArc plans with flattened beam (FB and flattening filter-free (FFF beam for localized prostate cancer based on physical indices. Int J Cancer Ther Oncol 2014; 2(4:02046.  DOI: 10.14319/ijcto.0204.6

  10. Comparison of the dosimetric parameters in linear accelerators with flattening filter-free (FFF) and flattening filter (FF)

    International Nuclear Information System (INIS)

    Souza, Anderson S.; Rostelato, Maria Elisa C.M.; Zeituni, Carlos A.; Moura, Eduardo S.; Rodrigues, Bruna T.; Souza, Daiane C.; Tiezzi, Rodrigo; Souza, Carla D.; Melo, Emerson R.; Camargo, Anderson R.; Batista, Talita Q.

    2015-01-01

    This paper discusses the main features associated with the dosimetric parameters between FFF and FF Linacs. A set of Varian TrueBeam Linac and Varian 23EX dosimetric measurements was acquired to perform the experimental measurements. The dose measurements were carried out in a water Blue phantom, with a waterproof ionization chambers: farmer ionization chamber (0.6 cm 3 ) and Exradin A1SL(0.053 cm 3 ) , for fields 5 x 5, 8 x 8, 10 x 10, 15 x 15, 30 x 30 cm 2 . The 6 MV FFF and FF was the energy used in this work. Percent Depth Dose (PDD) was the dosimetric parameters evaluated using a fixed Source Surface Distance of 100 cm. One depth were applied for the measurements, 10 cm (central axis) from the water surface. The 6 MV FFF showed less penetrating than the 6 MV FF. This is due to the removal flattening filter causes more lower energy photons on the central axis. The field sizes were equivalent for both FFF and FF. The main advantage in operate linear accelerators without flattening filter is due to the high doses rates delivered during the treatment. High doses rates could reduce the patient treatment time and may be beneficial for some treatment techniques such as IMRT and SRT. (author)

  11. SU-F-T-522: Dosimetric Study of Junction Dose in Double Isocenter Flatten and Flatten Filter Free IMRT and VMAT Plan Delivery

    Energy Technology Data Exchange (ETDEWEB)

    Samuvel, K; Yadav, G; Bhushan, M; Tamilarasu, S; Kumar, L; Suhail, M [Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, Delhi (India)

    2016-06-15

    Purpose: To quantify the dosimetric accuracy of junction dose in double isocenter flattened and flatten filter free(FFF) intensity modulated radiation therapy(IMRT) and volumetric modulated arc therapy(VMAT) plan delivery using pelvis phantom. Methods: Five large field pelvis patients were selected for this study. Double isocenter IMRT and VMAT treatment plans were generated in Eclipse Treatment planning System (V.11.0) using 6MV FB and FFF beams. For all the plans same distance 17.0cm was kept between one isocenter to another isocenter. IMRT Plans were made with 7 coplanar fields and VMAT plans were made with full double arcs. Dose calculation was performed using AAA algorithms with dose grid size of 0.25 cm. Verification plans were calculated on Scanditronix Wellhofer pelvis slab phantom. Measurement point was selected and calculated, where two isocenter plan fields are overlapping, this measurement point was kept at distance 8.5cm from both isocenter. The plans were delivered using Varian TrueBeamTM machine on pelvis slab phantom. Point dose measurements was carried out using CC13 ion chamber volume of 0.13cm3. Results: The measured junction point dose are compared with TPS calculated dose. The mean difference observed was 4.5%, 6.0%, 4.0% and 7.0% for IMRT-FB,IMRT-FFF, VMAT-FB and VMAT-FFF respectively. The measured dose results shows closer agreement with calculated dose in Flatten beam planning in both IMRT and VMAT, whereas in FFF beam plan dose difference are more compared with flatten beam plan. Conclusion: Dosimetry accuracy of Large Field junction dose difference was found less in Flatten beam compared with FFF beam plan delivery. Even though more dosimetric studies are required to analyse junction dose for FFF beam planning using multiple point dose measurements and fluence map verification in field junction area.

  12. Flattening filter free beams from TrueBeam and Versa HD units: Evaluation of the parameters for quality assurance

    Energy Technology Data Exchange (ETDEWEB)

    Fogliata, Antonella, E-mail: antonella.fogliata@humanitas.it; Reggiori, Giacomo; Stravato, Antonella; Scorsetti, Marta; Cozzi, Luca [Radiotherapy and Radiosurgery Department, Humanitas Research Hospital, Milan-Rozzano I-20098 (Italy); Fleckenstein, Jens; Schneider, Frank; Lohr, Frank [Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim D-68167 (Germany); Pachoud, Marc; Ghandour, Sarah [Radiation Oncology Department, Hôpital Riviera Chablais, Vevey CH-1800 (Switzerland); Krauss, Harald [Radio-Oncology Department, Kaiser Franz Josef Spital, Vienna A-1100 (Austria)

    2016-01-15

    Purpose: Flattening filter free (FFF) beams generated by medical linear accelerators are today clinically used for stereotactical and non-stereotactical radiotherapy treatments. Such beams differ from the standard flattened beams (FF) in the high dose rate and the profile shape peaked on the beam central axis. Definition of new parameters as unflatness and slope for FFF beams has been proposed based on a renormalization factor for FFF profiles. The present study aims to assess the dosimetric differences between FFF beams generated by linear accelerators from different vendors, and to provide renormalization and parameter data of the two kinds of units. Methods: Dosimetric data from two Varian TrueBeam and two Elekta Versa HD linear accelerators, all with 6 and 10 MV nominal accelerating potentials, FF and FFF modes have been collected. Renormalization factors and related fit parameters according to Fogliata et al. [“Definition of parameters for quality assurance of flattening filter free (FFF) photon beams in radiation therapy,” Med. Phys. 39, 6455–6464 (2012)] have been evaluated for FFF beams of both units and energies. Unflatness and slope parameters from profile curves were evaluated. Dosimetric differences in terms of beam penetration and near-the-surface dose were also assessed. Results: FFF profile parameters have been updated; renormalization factors and unflatness from the Varian units are consistent with the published data. Elekta FFF beam qualities, different from the Varian generated beams, tend to express similar behaviour as the FF beam of the corresponding nominal energy. TPR{sub 20,10} for 6 and 10 MV FF and FFF TrueBeam beams are 0.665, 0.629 (6 MV) and 0.738, 0.703 (10 MV). The same figures for Versa HD units are 0.684, 0.678 (6 MV) and 0.734, 0.721 (10 MV). Conclusions: Renormalization factor and unflatness parameters evaluated from Varian and Elekta FFF beams are provided, in particular renormalization factors table and fit parameters.

  13. SU-F-T-511: Feasibility Study of Using Flattening-Filter-Free Photon Beams to Deliver Conventional Flat Beam

    International Nuclear Information System (INIS)

    Potter, N; Lebron, S; Yan, G; Li, J; Liu, C; Lu, B

    2016-01-01

    Purpose: Various dosimetric benefits such as increased dose rate, and reduced leakage and out of field dose has led to the growth of FFF technology in the clinic. In this study, we concentrate on investigating the feasibility of using flattening-filter-free (FFF) beams to deliver conventional flat beams (CFB), since completely getting rid of the flattening-filter module from the gantry head can not only simplify the gantry design but also decrease the workload on machine maintain and quality assurance. Methods: The sliding window based IMRT technique was utilized to generate the CFB from the FFF beam for various beam configurations on the Elekta Versa HD. The flat beam reproducibility and MU efficiency were compared for each beam configuration among FFF planning, delivery and CFB planning. Results: Compared to the CFB plan, the 3%3mm passing rates of the FFF beams from both measurement and plan are 100% and 95%(or better) for 15×15 cm 2 or smaller field size and for any field size greater than 15×15 cm 2 at 10 cm depth, respectively. The largest discrepancy is about 5% and typically appears at the field shoulder area. The MU increase average was 80% for FFF compared to CFB, however has a minimal impact on treatment delivery time. Conclusion: The ability to deliver conventional flat treatments is not absent when operating in FFF mode. With proper TPS manipulation and beam modulation, FFF mode can achieve reasonable flat profiles and comparable dose coverage as CFB does for various conventional treatment techniques, such as four field box, or long spine treatment techniques. The ability to deliver most clinical treatments from the same treatment unit, will allow for less quality assurance as well as maintenance, and completely eliminate the need for the flattening filter on modern linacs.

  14. SU-F-T-511: Feasibility Study of Using Flattening-Filter-Free Photon Beams to Deliver Conventional Flat Beam

    Energy Technology Data Exchange (ETDEWEB)

    Potter, N; Lebron, S; Yan, G; Li, J; Liu, C; Lu, B [University Florida, Gainesville, FL (United States)

    2016-06-15

    Purpose: Various dosimetric benefits such as increased dose rate, and reduced leakage and out of field dose has led to the growth of FFF technology in the clinic. In this study, we concentrate on investigating the feasibility of using flattening-filter-free (FFF) beams to deliver conventional flat beams (CFB), since completely getting rid of the flattening-filter module from the gantry head can not only simplify the gantry design but also decrease the workload on machine maintain and quality assurance. Methods: The sliding window based IMRT technique was utilized to generate the CFB from the FFF beam for various beam configurations on the Elekta Versa HD. The flat beam reproducibility and MU efficiency were compared for each beam configuration among FFF planning, delivery and CFB planning. Results: Compared to the CFB plan, the 3%3mm passing rates of the FFF beams from both measurement and plan are 100% and 95%(or better) for 15×15 cm{sup 2} or smaller field size and for any field size greater than 15×15 cm{sup 2}at 10 cm depth, respectively. The largest discrepancy is about 5% and typically appears at the field shoulder area. The MU increase average was 80% for FFF compared to CFB, however has a minimal impact on treatment delivery time. Conclusion: The ability to deliver conventional flat treatments is not absent when operating in FFF mode. With proper TPS manipulation and beam modulation, FFF mode can achieve reasonable flat profiles and comparable dose coverage as CFB does for various conventional treatment techniques, such as four field box, or long spine treatment techniques. The ability to deliver most clinical treatments from the same treatment unit, will allow for less quality assurance as well as maintenance, and completely eliminate the need for the flattening filter on modern linacs.

  15. Comparison of k Q factors measured with a water calorimeter in flattening filter free (FFF) and conventional flattening filter (cFF) photon beams

    Science.gov (United States)

    de Prez, Leon; de Pooter, Jacco; Jansen, Bartel; Perik, Thijs; Wittkämper, Frits

    2018-02-01

    Recently flattening filter free (FFF) beams became available for application in modern radiotherapy. There are several advantages of FFF beams over conventional flattening filtered (cFF) beams, however differences in beam spectra at the point of interest in a phantom potentially affect the ion chamber response. Beams are also non-uniform over the length of a typical reference ion chamber and recombination is usually larger. Despite several studies describing FFF beam characteristics, only a limited number of studies investigated their effect on k Q factors. Some of those studies predicted significant discrepancies in k Q factors (0.4% up to 1.0%) if TPR20,10 based codes of practice (CoPs) were to be used. This study addresses the question to which extent k Q factors, based on a TPR20,10 CoP, can be applied in clinical reference dosimetry. It is the first study that compares k Q factors measured directly with an absorbed dose to water primary standard in FFF-cFF pairs of clinical photon beams. This was done with a transportable water calorimeter described elsewhere. The measurements corrected for recombination and beam radial non-uniformity were performed in FFF-cFF beam pairs at 6 MV and 10 MV of an Elekta Versa HD for a selection of three different Farmer-type ion chambers (eight serial numbers). The ratio of measured k Q factors of the FFF-cFF beam pairs were compared with the TPR20,10 CoPs of the NCS and IAEA and the %dd(10) x CoP of the AAPM. For the TPR20,10 based CoPs differences less than 0.23% were found in k Q factors between the corresponding FFF-cFF beams with standard uncertainties smaller than 0.35%, while for the %dd(10) x these differences were smaller than 0.46% and within the expanded uncertainty of the measurements. Based on the measurements made with the equipment described in this study the authors conclude that the k Q factors provided by the NCS-18 and IAEA TRS-398 codes of practice can be applied for flattening filter free beams without

  16. Treatment of breast cancer with simultaneous integrated boost in hybrid plan technique. Influence of flattening filter-free beams

    Energy Technology Data Exchange (ETDEWEB)

    Bahrainy, Marzieh; Kretschmer, Matthias; Joest, Vincent; Kasch, Astrid; Wuerschmidt, Florian; Dahle, Joerg; Lorenzen, Joern [Radiologische Allianz, Hamburg (Germany)

    2016-05-15

    The present study compares in silico treatment plans using hybrid plan technique during hypofractionated radiation of mammary carcinoma with simultaneous integrated boost (SIB). The influence of 6 MV photon radiation in flattening filter free (FFF) mode against the clinical standard flattening filter (FF) mode is to be examined. RT planning took place with FF and FFF radiation plans for 10 left-sided breast cancer patients. Hybrid plans were realised with two tangential IMRT fields and one VMAT field. The dose prescription was in line with the guidelines in the ARO-2010-01 study. The dosimetric verification took place with a manufacturer-independent measurement system. Required dose prescriptions for the planning target volumes (PTV) were achieved for both groups. The average dose values of the ipsi- and contralateral lung and the heart did not differ significantly. The overall average incidental dose to the left anterior descending artery (LAD) of 8.24 ± 3.9 Gy in the FFF group and 9.05 ± 3.7 Gy in the FF group (p < 0.05) were found. The dosimetric verifications corresponded to the clinical requirements. FFF-based RT plans reduced the average treatment time by 17 s/fraction. In comparison to the FF-based hybrid plan technique the FFF mode allows further reduction of the average LAD dose for comparable target volume coverage without adverse low-dose exposure of contralateral structures. The combination of hybrid plan technique and 6 MV photon radiation in the FFF mode is suitable for use with hypofractionated dose schemes. The increased dose rate allows a substantial reduction of treatment time and thus beneficial application of the deep inspiration breath hold technique. (orig.) [German] Vergleich der ''In-silico''-Bestrahlungsplaene der klinisch etablierten Hybridplan-Technik bei hypofraktionierter Bestrahlung des Mammakarzinoms mit simultan integriertem Boost (SIB). Untersucht wird der Einfluss von 6MV-Photonenstrahlung im Flattening-Filter-Free

  17. Characterisation of flattening filter free (FFF) beam properties for initial beam set-up and routine QA, independent of flattened beams

    Science.gov (United States)

    Paynter, D.; Weston, S. J.; Cosgrove, V. P.; Thwaites, D. I.

    2018-01-01

    Flattening filter free (FFF) beams have reached widespread use for clinical treatment deliveries. The usual methods for FFF beam characterisation for their quality assurance (QA) require the use of associated conventional flattened beams (cFF). Methods for QA of FFF without the need to use associated cFF beams are presented and evaluated against current methods for both FFF and cFF beams. Inflection point normalisation is evaluated against conventional methods for the determination of field size and penumbra for field sizes from 3 cm  ×  3 cm to 40 cm  ×  40cm at depths from dmax to 20 cm in water for matched and unmatched FFF beams and for cFF beams. A method for measuring symmetry in the cross plane direction is suggested and evaluated as FFF beams are insensitive to symmetry changes in this direction. Methods for characterising beam energy are evaluated and the impact of beam energy on profile shape compared to that of cFF beams. In-plane symmetry can be measured, as can cFF beams, using observed changes in profile, whereas cross-plane symmetry can be measured by acquiring profiles at collimator angles 0 and 180. Beam energy and ‘unflatness’ can be measured as with cFF beams from observed shifts in profile with changing beam energy. Normalising the inflection points of FFF beams to 55% results in an equivalent penumbra and field size measurement within 0.5 mm of conventional methods with the exception of 40 cm  ×  40 cm fields at a depth of 20 cm. New proposed methods are presented that make it possible to independently carry out set up and QA measurements on beam energy, flatness, symmetry and field size of an FFF beam without the need to reference to an equivalent flattened beam of the same energy. The methods proposed can also be used to carry out this QA for flattened beams, resulting in universal definitions and methods for MV beams. This is presented for beams produced by an Elekta linear accelerator, but is

  18. Monte Carlo evaluation of the potential benefits of flattening filter free beams from the Oncor® clinical linear accelerator.

    Science.gov (United States)

    Asadi, Amin; Razavi-Ratki, Seid Kazem; Jabbari, Keyvan; Najafzadeh, Milad; Nickfarjam, Abolfazl

    2018-01-01

    To evaluate the potential privileges of flattening filter-free (FFF) photon beams from Oncor® linac for 6 MV and 18 MV energies. A Monte Carlo (MC) model of Oncor® linac was built using BEAMnrc MCCode and verified by the measured data using 6 MV and 18 MV energies. A comprehensive set of data was also characterized for MC model of Oncor® machine running with and without flattening filter (FF) for 6 MV and 18 MV beams in six field sizes. The investigated characteristics included mean energy, energy spectrum, photon spatial fluence, superficial dose, percent depth dose (PDD), dose output, and out-of-field dose with two indexes of lateral dose profile and isodose curve at three depths. Using FFF enhanced the energy uniformity 3.4±0.11% (6 MV) and 2.05±0.09% (18 MV) times and improved dose output by factor of 2.91 (6 MV) and 4.2 (18 MV) on the central axis, respectively. Using FFF also reduced the PDD dependencies by 9.1% (6 MV) and 5.57% (18 MV). In addition, using FFF had a lower out-of-field dose due to the reduced head scatter and softer spectra. The findings in this study suggested that using FFF, Oncor® machine could achieve better treatment results with lower dose toxicity and a shorter beam-on time.

  19. Radiosurgery with flattening-filter-free techniques in the treatment of brain metastases. Plan comparison and early clinical evaluation

    International Nuclear Information System (INIS)

    Rieber, J.; Tonndorf-Martini, E.; Schramm, O.; Rhein, B.; Stefanowicz, S.; Lindel, K.; Debus, J.; Rieken, S.; Kappes, J.; Hoffmann, H.

    2016-01-01

    Radiosurgical treatment of brain metastases is well established in daily clinical routine. Utilization of flattening-filter-free beams (FFF) may allow for more rapid delivery of treatment doses and improve clinical comfort. Hence, we compared plan quality and efficiency of radiosurgery in FFF mode to FF techniques. Between November 2014 and June 2015, 21 consecutive patients with 25 brain metastases were treated with stereotactic radiosurgery (SRS) in FFF mode. Brain metastases received dose-fractionation schedules of 1 x 20 Gy or 1 x 18 Gy, delivered to the conformally enclosing 80 % isodose. Three patients with critically localized or large (>3 cm) brain metastases were treated with 6 x 5 Gy. Plan quality and efficiency were evaluated by analyzing conformity, dose gradients, dose to healthy brain tissue, treatment delivery time, and number of monitor units. FFF plans were compared to those using the FF method, and early clinical outcome and toxicity were assessed. FFF mode resulted in significant reductions in beam-on time (p [de

  20. SU-E-T-311: Dosimetric Comparison of Volumetric Modulated Arc Therapy Plans for Preoperative Radiotherapy Rectal Cancer Using Flattening Filter-Free and Flattening Filter Modes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, W; Zhang, J; Lu, J; Chen, C [Cancer Hospital of Shantou University Medical College, Shantou, Guangdong (China)

    2015-06-15

    Purpose: To compare the dosimetric difference of volumetric modulated arc therapy(VMAT) for preoperative radiotherapy rectal cancer using 6MV X-ray flattening filter free(FFF) and flattening filter(FF) modes. Methods: FF-VMAT and FFF-VMAT plans were designed to 15 rectal cancer patients with preoperative radiotherapy by planning treatment system(Eclipse 10.0),respectively. Dose prescription was 50 Gy in 25 fractions. All plans were normalized to 50 Gy to 95% of PTV. The Dose Volume Histogram (DVH), target and risk organ doses, conformity indexes (CI), homogeneity indexes (HI), low dose volume of normal tissue(BP), monitor units(MU) and treatment time (TT) were compared between the two kinds of plans. Results: FF-VMAT provided the lower Dmean, V105, HI, and higher CI as compared with FFF-VMAT. The small intestine of D5, Bladder of D5, Dmean, V40, V50, L-femoral head of V40, R-femoral head of Dmean were lower in FF-VMAT than in FFF-VMAT. FF-VMAT had higher BP of V5, but no significantly different of V10, V15, V20, V30 as compared with FFF-VMAT. FF-VMAT reduceed the monitor units(MU) by 21%(P<0.05), as well as the treatment time(TT) was no significantly different(P>0.05), as compared with FFF-VMAT. Conclusion: The plan qualities of FF and FFF VMAT plans were comparable and both clinically acceptable. FF-VMAT as compared with FFF-VMAT, showing better target coverage, some of OARs sparing, the MUs of FFF-VMAT were higher than FF-VMAT, yet were delivered within the same time. This work was supported by the Medical Scientific Research Foundation of Guangdong Procvince (A2014455 to Changchun Ma)

  1. SU-F-T-545: Dosimetric and Radiobiological Evaluation of Dose Calculation Algorithms On Prostate Stereotactic Body Radiotherapy Using Conventional Flattened and Flattening-Filter-Free Beam

    International Nuclear Information System (INIS)

    Kang, S; Suh, T; Chung, J; Eom, K; Lee, J

    2016-01-01

    Purpose: The purpose of this study is to evaluate the dosimetric and radiobiological impact of Acuros XB (AXB) and Anisotropic Analytic Algorithm (AAA) dose calculation algorithms on prostate stereotactic body radiation therapy plans with both conventional flattened (FF) and flattening-filter free (FFF) modes. Methods: For thirteen patients with prostate cancer, SBRT planning was performed using 10-MV photon beam with FF and FFF modes. The total dose prescribed to the PTV was 42.7 Gy in 7 fractions. All plans were initially calculated using AAA algorithm in Eclipse treatment planning system (11.0.34), and then were re-calculated using AXB with the same MUs and MLC files. The four types of plans for different algorithms and beam energies were compared in terms of homogeneity and conformity. To evaluate the radiobiological impact, the tumor control probability (TCP) and normal tissue complication probability (NTCP) calculations were performed. Results: For PTV, both calculation algorithms and beam modes lead to comparable homogeneity and conformity. However, the averaged TCP values in AXB plans were always lower than in AAA plans with an average difference of 5.3% and 6.1% for 10-MV FFF and FF beam, respectively. In addition, the averaged NTCP values for organs at risk (OARs) were comparable. Conclusion: This study showed that prostate SBRT plan were comparable dosimetric results with different dose calculation algorithms as well as delivery beam modes. For biological results, even though NTCP values for both calculation algorithms and beam modes were similar, AXB plans produced slightly lower TCP compared to the AAA plans.

  2. SU-F-T-545: Dosimetric and Radiobiological Evaluation of Dose Calculation Algorithms On Prostate Stereotactic Body Radiotherapy Using Conventional Flattened and Flattening-Filter-Free Beam

    Energy Technology Data Exchange (ETDEWEB)

    Kang, S; Suh, T [The catholic university of Korea, Seoul (Korea, Republic of); Chung, J; Eom, K [Seoul National University Bundang Hospital (Korea, Republic of); Lee, J [Konkuk University Medical Center (Korea, Republic of)

    2016-06-15

    Purpose: The purpose of this study is to evaluate the dosimetric and radiobiological impact of Acuros XB (AXB) and Anisotropic Analytic Algorithm (AAA) dose calculation algorithms on prostate stereotactic body radiation therapy plans with both conventional flattened (FF) and flattening-filter free (FFF) modes. Methods: For thirteen patients with prostate cancer, SBRT planning was performed using 10-MV photon beam with FF and FFF modes. The total dose prescribed to the PTV was 42.7 Gy in 7 fractions. All plans were initially calculated using AAA algorithm in Eclipse treatment planning system (11.0.34), and then were re-calculated using AXB with the same MUs and MLC files. The four types of plans for different algorithms and beam energies were compared in terms of homogeneity and conformity. To evaluate the radiobiological impact, the tumor control probability (TCP) and normal tissue complication probability (NTCP) calculations were performed. Results: For PTV, both calculation algorithms and beam modes lead to comparable homogeneity and conformity. However, the averaged TCP values in AXB plans were always lower than in AAA plans with an average difference of 5.3% and 6.1% for 10-MV FFF and FF beam, respectively. In addition, the averaged NTCP values for organs at risk (OARs) were comparable. Conclusion: This study showed that prostate SBRT plan were comparable dosimetric results with different dose calculation algorithms as well as delivery beam modes. For biological results, even though NTCP values for both calculation algorithms and beam modes were similar, AXB plans produced slightly lower TCP compared to the AAA plans.

  3. SU-E-T-153: Burst-Mode Modulated Arc Therapy with Flattening-Filter-Free Beams Versus Flattening-Filtered Beams

    Energy Technology Data Exchange (ETDEWEB)

    Kainz, K; Lawton, C; Li, X [Medical College of Wisconsin, Milwaukee, WI (United States)

    2015-06-15

    Purpose: To compare the dosimetry and delivery of burst-mode modulated arc radiotherapy using flattening-filter-free (FFF) and flattening-filtered (FF) beams. Methods: Burst-mode modulated arc therapy (mARC, Siemens) plans were generated for six prostate cases with FFF and FF beam models, using the Elekta Monaco v. 5.00 planning system. One 360-degree arc was used for five cases, and for one case two 360-degree coplanar arcs were used. The maximum number of optimization points (OPs) per arc was set to 91, and OPs with less than 4 MU were disregarded. All plans were delivered on the Siemens Artiste linear accelerator with 6MV FF (300 MU/min) and comparable-energy FFF (2000 MU/min, labeled as 7UF) beams. Results: For all cases studied, the plans with FFF beams exhibited DVHs for the PTV, rectum, and bladder that were nearly identical to those for the plans with FF beams. The FFF plan yielded reduced dose to the right femoral head for 5 cases, and lower mean dose to the left femoral head for 4 cases. For all but the two-arc case, the FFF and FF plans resulted in an identical number of segments. The total number of MUs was slightly lower for the FF plans for five cases. The total delivery time per fraction was substantially lower for the FFF plans, ranging from 25 to 50 percent among all cases, as compared to the FF plans. Conclusion: For mARC plans, FFF and FF beams provided comparable PTV coverage and rectum and bladder sparing. For the femoral heads, the mean dose was slightly lower in most cases when using the FFF beam. Although the flat beam plans typically required slightly fewer MUs, FFF beams required substantially less time to deliver a plan of similar quality. This work was supported by Siemens Medical Solutions and the MCW Cancer Center Fotsch Foundation.

  4. SU-E-T-377: Inaccurate Positioning Might Introduce Significant MapCheck Calibration Error in Flatten Filter Free Beams

    International Nuclear Information System (INIS)

    Wang, S; Chao, C; Chang, J

    2014-01-01

    Purpose: This study investigates the calibration error of detector sensitivity for MapCheck due to inaccurate positioning of the device, which is not taken into account by the current commercial iterative calibration algorithm. We hypothesize the calibration is more vulnerable to the positioning error for the flatten filter free (FFF) beams than the conventional flatten filter flattened beams. Methods: MapCheck2 was calibrated with 10MV conventional and FFF beams, with careful alignment and with 1cm positioning error during calibration, respectively. Open fields of 37cmx37cm were delivered to gauge the impact of resultant calibration errors. The local calibration error was modeled as a detector independent multiplication factor, with which propagation error was estimated with positioning error from 1mm to 1cm. The calibrated sensitivities, without positioning error, were compared between the conventional and FFF beams to evaluate the dependence on the beam type. Results: The 1cm positioning error leads to 0.39% and 5.24% local calibration error in the conventional and FFF beams respectively. After propagating to the edges of MapCheck, the calibration errors become 6.5% and 57.7%, respectively. The propagation error increases almost linearly with respect to the positioning error. The difference of sensitivities between the conventional and FFF beams was small (0.11 ± 0.49%). Conclusion: The results demonstrate that the positioning error is not handled by the current commercial calibration algorithm of MapCheck. Particularly, the calibration errors for the FFF beams are ~9 times greater than those for the conventional beams with identical positioning error, and a small 1mm positioning error might lead to up to 8% calibration error. Since the sensitivities are only slightly dependent of the beam type and the conventional beam is less affected by the positioning error, it is advisable to cross-check the sensitivities between the conventional and FFF beams to detect

  5. SU-E-T-435: Flattening Filter Free Beams for Head and Neck IMRT and VMAT Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Ghahremani, S; Chavez, R; Li, Y; Crownover, R; Baacke, D; Papanikolaou, N; Stathakis, S [University of Texas HSC SA, San Antonio, TX (United States)

    2015-06-15

    Purpose: To investigate if there is benefits of using flattening filter free (FFF) versus flattening filter (FF) beams during plan optimization for head and neck targets. Methods: Five head and neck cancer patients previously treated were selected for this study. Each plan was optimized for volumetric modulated arc therapy (VMAT) using 2 full arcs. Target volumes and the organs at risk (OAR) were outlined by the same physician. The prescription doses for each patient and the dose limits for each OAR were specified by the physician. For each patient four plans were created by varying the photon beam energy (6MV vs 10MV) and the use of FF or FFF. For each patient the prescription dose and OAR dose limits remained unchanged. Furthermore, the number of optimization iterations remained the same for each plan without user interference. The plans were compared using dose volume histograms, conformity and homogeneity indices. Results: Our results showed that the plans optimized with FF beams produced more homogeneous dose distributions in the PTV than the ones with FFF beams (0.92 vs. 0.86 and 0.92 vs.85 for 6MVFF, 6MVFFF, 10MVFF and 10MVFFF respectively). The conformity was better for FFF beams than for FF beams (1.26 vs. 1.20 and 1.27 vs. 1.21 for 6MVFF, 6MVFFF, 10MVFF and 10MVFFF respectively). The overall minimum, maximum and means doses were reduced for the FFF plans by approximately 4% to 6%. All FFF plans allowed more sparing of organs at risk by 7% to 9% on average. Only one 10MVFFF plan had a 1% higher dose than the respective 10MVFF for the spinal cord. Conclusion: The 6MVFFF and 10MVFFF beams illustrated the improvement of normal tissue sparing while achieving similar target dose distribution compared to 6MVFF and 10MVFF beams. Further investigation is required to determine the magnitude of improvement. case specific, fluence-based optimization improved both PTV and OAR dosimetry in 80% of cases.

  6. SU-F-T-521: Flattening-Filter-Free Beam Parameters Comparison From Different Linac Machine Types

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, A [King Faisal Specialist Hospital, Riyadh, Saudi Arabia, Arkansas Cancer Institute, Pine Bluff, AR (Saudi Arabia)

    2016-06-15

    Purpose: Novel linac machines, TrueBeam (TB) and Elekta Versa have updated head designing and software control system, include flattening-filter-free (FFF) photon and electron beams. Later on FFF beams were also introduced on C-Series machines. In this work FFF beams for same energy 6MV but from different machine versions were studied with reference to beam data parameters. Methods: The 6MV-FFF percent depth doses, profile symmetry and flatness, dose rate tables, and multi-leaf collimator (MLC) transmission factors were measured during commissioning process of both C-series and Truebeam machines. The scanning and dosimetric data for 6MV-FFF beam from Truebeam and C-Series linacs was compared. A correlation of 6MV-FFF beam from Elekta Versa with that of Varian linacs was also found. Results: The scanning files were plotted for both qualitative and quantitative analysis. The dosimetric leaf gap (DLG) for C-Series 6MV-FFF beam is 1.1 mm. Published values for Truebeam dosimetric leaf gap is 1.16 mm. 6MV MLC transmission factor varies between 1.3 % and 1.4 % in two separate measurements and measured DLG values vary between 1.32 mm and 1.33 mm on C-Series machine. MLC transmission factor from C-Series machine varies between 1.5 % and 1.6 %. Some of the measured data values from C-Series FFF beam are compared with Truebeam representative data. 6MV-FFF beam parameter values like dmax, OP factors, beam symmetry and flatness and additional parameters for C-Series and Truebeam liancs will be presented and compared in graphical form and tabular data form if selected. Conclusion: The 6MV flattening filter (FF) beam data from C-Series & Truebeam and 6MV-FFF beam data from Truebeam has already presented. This particular analysis to compare 6MV-FFF beam from C-Series and Truebeam provides opportunity to better elaborate FFF mode on novel machines. It was found that C-Series and Truebeam 6MV-FFF dosimetric and beam data was quite similar.

  7. A 4 MV flattening filter-free beam: commissioning and application to conformal therapy and volumetric modulated arc therapy

    International Nuclear Information System (INIS)

    Stevens, S W; Rosser, K E; Bedford, J L

    2011-01-01

    Recent studies have indicated that radiotherapy treatments undertaken on a flattening filter-free (FFF) linear accelerator have a number of advantages over treatments undertaken on a conventional linear accelerator. In addition, 4 MV photon beams may give improved isodose coverage for some treatment volumes at air/tissue interfaces, compared to when utilizing the clinical standard of 6 MV photons. In order to investigate these benefits, FFF beams were established on an Elekta Beam Modulator linear accelerator for 4 MV photons. Commissioning beam data were obtained for open and wedged fields. The measured data were then imported into a treatment planning system and a beam model was commissioned. The beam model was optimized to improve dose calculations at shallow, clinically relevant depths. Following verification, the beam model was utilized in a treatment planning study, including volumetric modulated arc therapy, for a selection of lung, breast/chest wall and larynx patients. Increased dose rates of around 800 MU min -1 were recorded for open fields (relative to 320 MU min -1 for filtered open fields) and reduced head scatter was inferred from output factor measurements. Good agreement between planned and delivered dose was observed in verification of treatment plans. The planning study indicated that with a FFF beam, equivalent (and in some cases improved) isodose profiles could be achieved for small lung and larynx treatment volumes relative to 4 MV filtered treatments. Furthermore, FFF treatments with wedges could be replicated using open fields together with an 'effective wedge' technique and isocentre shift. Clinical feasibility of a FFF beam was therefore demonstrated, with beam modelling, treatment planning and verification being successfully accomplished.

  8. SU-E-J-127: Implementation of An Online Replanning Tool for VMAT Using Flattening Filter-Free Beams

    Energy Technology Data Exchange (ETDEWEB)

    Ates, O; Ahunbay, E; Li, X [Medical College of Wisconsin, Milwaukee, WI (United States)

    2015-06-15

    Purpose: This is to report the implementation of an online replanning tool based on segment aperture morphing (SAM) for VMAT with flattening filter free (FFF) beams. Methods: Previously reported SAM algorithm modified to accommodate VMAT with FFF beams was implemented in a tool that was interfaced with a treatment planning system (Monaco, Elekta). The tool allows (1) to output the beam parameters of the original VMAT plan from Monaco, and (2) to input the apertures generated from the SAM algorithm into Monaco for the dose calculation on daily CT/CBCT/MRI in the following steps:(1) Quickly generating target contour based on the image of the day, using an auto-segmentation tool (ADMIRE, Elekta) with manual editing if necessary; (2) Morphing apertures based on the SAM in the original VMAT plan to account for the interfractional change of the target from the planning to the daily images; (3) Calculating dose distribution for new apertures with the same numbers of MU as in the original plan; (4) Transferring the new plan into a record & verify system (MOSAIQ, Elekta); (5) Performing a pre-delivery QA based on software; (6) Delivering the adaptive plan for the fraction.This workflow was implemented on a 16-CPU (2.6 GHz dual-core) hardware with GPU and was tested for sample cases of prostate, pancreas and lung tumors. Results: The online replanning process can be completed within 10 minutes. The adaptive plans generally have improved the plan quality when compared to the IGRT repositioning plans. The adaptive plans with FFF beams have better normal tissue sparing as compared with those of FF beams. Conclusion: The online replanning tool based on SAM can quickly generate adaptive VMAT plans using FFF beams with improved plan quality than those from the IGRT repositioning plans based on daily CT/CBCT/MRI and can be used clinically. This research was supported by Elekta Inc. (Crawley, UK)

  9. SU-E-J-127: Implementation of An Online Replanning Tool for VMAT Using Flattening Filter-Free Beams

    International Nuclear Information System (INIS)

    Ates, O; Ahunbay, E; Li, X

    2015-01-01

    Purpose: This is to report the implementation of an online replanning tool based on segment aperture morphing (SAM) for VMAT with flattening filter free (FFF) beams. Methods: Previously reported SAM algorithm modified to accommodate VMAT with FFF beams was implemented in a tool that was interfaced with a treatment planning system (Monaco, Elekta). The tool allows (1) to output the beam parameters of the original VMAT plan from Monaco, and (2) to input the apertures generated from the SAM algorithm into Monaco for the dose calculation on daily CT/CBCT/MRI in the following steps:(1) Quickly generating target contour based on the image of the day, using an auto-segmentation tool (ADMIRE, Elekta) with manual editing if necessary; (2) Morphing apertures based on the SAM in the original VMAT plan to account for the interfractional change of the target from the planning to the daily images; (3) Calculating dose distribution for new apertures with the same numbers of MU as in the original plan; (4) Transferring the new plan into a record & verify system (MOSAIQ, Elekta); (5) Performing a pre-delivery QA based on software; (6) Delivering the adaptive plan for the fraction.This workflow was implemented on a 16-CPU (2.6 GHz dual-core) hardware with GPU and was tested for sample cases of prostate, pancreas and lung tumors. Results: The online replanning process can be completed within 10 minutes. The adaptive plans generally have improved the plan quality when compared to the IGRT repositioning plans. The adaptive plans with FFF beams have better normal tissue sparing as compared with those of FF beams. Conclusion: The online replanning tool based on SAM can quickly generate adaptive VMAT plans using FFF beams with improved plan quality than those from the IGRT repositioning plans based on daily CT/CBCT/MRI and can be used clinically. This research was supported by Elekta Inc. (Crawley, UK)

  10. An online replanning method using warm start optimization and aperture morphing for flattening-filter-free beams.

    Science.gov (United States)

    Ahunbay, Ergun E; Ates, O; Li, X A

    2016-08-01

    In a situation where a couch shift for patient positioning is not preferred or prohibited (e.g., MR-linac), segment aperture morphing (SAM) can address target dislocation and deformation. For IMRT/VMAT with flattening-filter-free (FFF) beams, however, SAM method would lead to an adverse translational dose effect due to the beam unflattening. Here the authors propose a new two-step process to address both the translational effect of FFF beams and the target deformation. The replanning method consists of an offline and an online step. The offline step is to create a series of preshifted-plans (PSPs) obtained by a so-called "warm start" optimization (starting optimization from the original plan, rather than from scratch) at a series of isocenter shifts. The PSPs all have the same number of segments with very similar shapes, since the warm start optimization only adjusts the MLC positions instead of regenerating them. In the online step, a new plan is obtained by picking the closest PSP or linearly interpolating the MLC positions and the monitor units of the closest PSPs for the shift determined from the image of the day. This two-step process is completely automated and almost instantaneous (no optimization or dose calculation needed). The previously developed SAM algorithm is then applied for daily deformation. The authors tested the method on sample prostate and pancreas cases. The two-step interpolation method can account for the adverse dose effects from FFF beams, while SAM corrects for the target deformation. Plan interpolation method is effective in diminishing the unflat beam effect and may allow reducing the required number of PSPs. The whole process takes the same time as the previously reported SAM process (5-10 min). The new two-step method plus SAM can address both the translation effects of FFF beams and target deformation, and can be executed in full automation except the delineation of target contour required by the SAM process.

  11. SU-F-T-338: Flattening Filter Free Photon Beams Can Achieve the Same Plan Quality as Conventional Flattened Beams for Prostate Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Kolar, M; Szwedowski, R; Greskovich, J; Xia, P [Cleveland Clinic, Cleveland, OH (United States)

    2016-06-15

    Purpose: Some modern linear accelerators are equipped with one low energy flat beam and two flattening filter free (FFF) beams at high and low energies. The purpose of this study is to investigate whether the high energy FFF beam can produce the same plan quality as the conventional low energy flat beam, using a volumetric modulated arc (VMAT) technique for prostate patients. Methods: Ten prostate cancer patients were selected with a prescription of 78Gy. For each patient, three plans were created: (a) double arc flat 6MV plan used clinically; (b) double arc 10MV FFF plan; (c) single arc 10MV FFF plan. Each plan was prescribed so that at least 95% of the PTV received the prescription dose. The following dosimetric endpoints were evaluated: volume receiving 78Gy (V78) of the CTV and PTV, PTV conformality index (CI, ratio of prescription isodose volume to the PTV volume), bladder volume receiving 70Gy (V70) and 60Gy (V60), rectum volume receiving 70Gy (V70) and 50Gy (V50), dose to 10cc of the rectum, and volume of both femoral heads receiving 50Gy (V50). Total monitor units for each plan were recorded. Results: No significant difference was found for all dosimetric endpoints between all plans (p>0.05). Compared to the 6MV plans, monitor units were higher with the double arc 10MV FFF plans and lower with the single arc 10MV FFF plans, 29% and 4% respectively. Conclusion: Both single arc and double arc 10MV FFF VMAT can achieve equivalent plan quality as 6MV flat beam double arc treatment plans. With the gantry speed restriction, a high dose rate of 2400MU/min may allow the optimizer to use more MUs than actually needed. Single arc 10MV FFF VMAT plans are a reasonable alternative to double arc 6MV flat beam VMAT plans.

  12. SU-F-T-338: Flattening Filter Free Photon Beams Can Achieve the Same Plan Quality as Conventional Flattened Beams for Prostate Radiotherapy

    International Nuclear Information System (INIS)

    Kolar, M; Szwedowski, R; Greskovich, J; Xia, P

    2016-01-01

    Purpose: Some modern linear accelerators are equipped with one low energy flat beam and two flattening filter free (FFF) beams at high and low energies. The purpose of this study is to investigate whether the high energy FFF beam can produce the same plan quality as the conventional low energy flat beam, using a volumetric modulated arc (VMAT) technique for prostate patients. Methods: Ten prostate cancer patients were selected with a prescription of 78Gy. For each patient, three plans were created: (a) double arc flat 6MV plan used clinically; (b) double arc 10MV FFF plan; (c) single arc 10MV FFF plan. Each plan was prescribed so that at least 95% of the PTV received the prescription dose. The following dosimetric endpoints were evaluated: volume receiving 78Gy (V78) of the CTV and PTV, PTV conformality index (CI, ratio of prescription isodose volume to the PTV volume), bladder volume receiving 70Gy (V70) and 60Gy (V60), rectum volume receiving 70Gy (V70) and 50Gy (V50), dose to 10cc of the rectum, and volume of both femoral heads receiving 50Gy (V50). Total monitor units for each plan were recorded. Results: No significant difference was found for all dosimetric endpoints between all plans (p>0.05). Compared to the 6MV plans, monitor units were higher with the double arc 10MV FFF plans and lower with the single arc 10MV FFF plans, 29% and 4% respectively. Conclusion: Both single arc and double arc 10MV FFF VMAT can achieve equivalent plan quality as 6MV flat beam double arc treatment plans. With the gantry speed restriction, a high dose rate of 2400MU/min may allow the optimizer to use more MUs than actually needed. Single arc 10MV FFF VMAT plans are a reasonable alternative to double arc 6MV flat beam VMAT plans.

  13. Comparison of Flattening Filter (FF) and Flattening-Filter-Free (FFF) 6 MV photon beam characteristics for small field dosimetry using EGSnrc Monte Carlo code

    Science.gov (United States)

    Sangeetha, S.; Sureka, C. S.

    2017-06-01

    The present study is focused to compare the characteristics of Varian Clinac 600 C/D flattened and unflattened 6 MV photon beams for small field dosimetry using EGSnrc Monte Carlo Simulation since the small field dosimetry is considered to be the most crucial and provoking task in the field of radiation dosimetry. A 6 MV photon beam of a Varian Clinac 600 C/D medical linear accelerator operates with Flattening Filter (FF) and Flattening-Filter-Free (FFF) mode for small field dosimetry were performed using EGSnrc Monte Carlo user codes (BEAMnrc and DOSXYZnrc) in order to calculate the beam characteristics using Educated-trial and error method. These includes: Percentage depth dose, lateral beam profile, dose rate delivery, photon energy spectra, photon beam uniformity, out-of-field dose, surface dose, penumbral dose and output factor for small field dosimetry (0.5×0.5 cm2 to 4×4 cm2) and are compared with magna-field sizes (5×5 cm2 to 40×40 cm2) at various depths. The results obtained showed that the optimized beam energy and Full-width-half maximum value for small field dosimetry and magna-field dosimetry was found to be 5.7 MeV and 0.13 cm for both FF and FFF beams. The depth of dose maxima for small field size deviates minimally for both FF and FFF beams similar to magna-fields. The depths greater than dmax depicts a steeper dose fall off in the exponential region for FFF beams comparing FF beams where its deviations gets increased with the increase in field size. The shape of the lateral beam profiles of FF and FFF beams varies remains similar for the small field sizes less than 4×4 cm2 whereas it varies in the case of magna-fields. Dose rate delivery for FFF beams shows an eminent increase with a two-fold factor for both small field dosimetry and magna-field sizes. The surface dose measurements of FFF beams for small field size were found to be higher whereas it gets lower for magna-fields than FF beam. The amount of out-of-field dose reduction gets

  14. SU-F-T-283: A Novel Device to Enable Portal Dosimetry for Flattening Filter Free Beams

    Energy Technology Data Exchange (ETDEWEB)

    Faught, A; Wu, Q; Adamson, J [Duke University Medical Center, Durham, NC (United States)

    2016-06-15

    Purpose: Varian’s electronic portal imaging device (EPID) based portal dosimetry tool is a popular and effective means of performing IMRT QA. EPIDs for older models of the TrueBeam accelerator utilize a 40cmx30cm Image Detection Unit (IDU) that saturates at the center for standard source to imager distances with high dose rate flattening filter free (FFF) beams. This makes portal dosimetry not possible and an alternative means of IMRT QA necessary. We developed a filter that would attenuate the beam to a dose rate measureable by the IDU for portal dosimetry IMRT QA. Methods: Multipurpose 304 stainless steel plates were placed on an accessory tray to attenuate the beam. Profiles of an open field measured on the IDU were acquired with varying number of plates to assess the thickness needed to reduce the maximum dose rates of 6XFFF and 10XFFF beams to measurable levels. A new portal dose image prediction (PDIP) model was commissioned based on open field measurements with plates in position, and a modified beam profile was input to portal dosimetry calibration at the console to empirically correct for attenuation and scatter. The portal dosimetry tool was used to assess agreement between predicted and measured doses for open 25×25cm{sup 2} fields and intensity modulated fields using 6XFFF and 10XFFF beams. Results: Thicknesses of 2.5cm and 3.8cm of steel were required to reduce the highest dose rates to a measureable level for 6XFFF and 10XFFF, respectively. Gamma analysis using a 3%/3mm relative criterion with the filter in place and using the new PDIP model resulted in 98.2% and 93.6% of pixels passing while intensity modulated fields showed passing rates of 98.2% and 99.0%. Conclusion: Use of the filter allows for portal dosimetry to be used for IMRT QA of FFF plans in place of purchasing a second option for IMRT QA.

  15. An online replanning method using warm start optimization and aperture morphing for flattening-filter-free beams

    International Nuclear Information System (INIS)

    Ahunbay, Ergun E.; Ates, O.; Li, X. A.

    2016-01-01

    Purpose: In a situation where a couch shift for patient positioning is not preferred or prohibited (e.g., MR-linac), segment aperture morphing (SAM) can address target dislocation and deformation. For IMRT/VMAT with flattening-filter-free (FFF) beams, however, SAM method would lead to an adverse translational dose effect due to the beam unflattening. Here the authors propose a new two-step process to address both the translational effect of FFF beams and the target deformation. Methods: The replanning method consists of an offline and an online step. The offline step is to create a series of preshifted-plans (PSPs) obtained by a so-called “warm start” optimization (starting optimization from the original plan, rather than from scratch) at a series of isocenter shifts. The PSPs all have the same number of segments with very similar shapes, since the warm start optimization only adjusts the MLC positions instead of regenerating them. In the online step, a new plan is obtained by picking the closest PSP or linearly interpolating the MLC positions and the monitor units of the closest PSPs for the shift determined from the image of the day. This two-step process is completely automated and almost instantaneous (no optimization or dose calculation needed). The previously developed SAM algorithm is then applied for daily deformation. The authors tested the method on sample prostate and pancreas cases. Results: The two-step interpolation method can account for the adverse dose effects from FFF beams, while SAM corrects for the target deformation. Plan interpolation method is effective in diminishing the unflat beam effect and may allow reducing the required number of PSPs. The whole process takes the same time as the previously reported SAM process (5–10 min). Conclusions: The new two-step method plus SAM can address both the translation effects of FFF beams and target deformation, and can be executed in full automation except the delineation of target contour

  16. Monte Carlo simulation of beam characteristics from small fields based on TrueBeam flattening-filter-free mode

    International Nuclear Information System (INIS)

    Feng, Zhongsu; Yue, Haizhen; Zhang, Yibao; Wu, Hao; Cheng, Jinsheng; Su, Xu

    2016-01-01

    Through the Monte Carlo (MC) simulation of 6 and 10 MV flattening-filter-free (FFF) beams from Varian TrueBeam accelerator, this study aims to find the best incident electron distribution for further studying the small field characteristics of these beams. By incorporating the training materials of Varian on the geometry and material parameters of TrueBeam Linac head, the 6 and 10 MV FFF beams were modelled using the BEAMnrc and DOSXYZnrc codes, where the percentage depth doses (PDDs) and the off-axis ratios (OARs) curves of fields ranging from 4 × 4 to 40 × 40 cm 2 were simulated for both energies by adjusting the incident beam energy, radial intensity distribution and angular spread, respectively. The beam quality and relative output factor (ROF) were calculated. The simulations and measurements were compared using Gamma analysis method provided by Verisoft program (PTW, Freiburg, Germany), based on which the optimal MC model input parameters were selected and were further used to investigate the beam characteristics of small fields. The Full Width Half Maximum (FWHM), mono-energetic energy and angular spread of the resultant incident Gaussian radial intensity electron distribution were 0.75 mm, 6.1 MeV and 0.9° for the nominal 6 MV FFF beam, and 0.7 mm, 10.8 MeV and 0.3° for the nominal 10 MV FFF beam respectively. The simulation was mostly comparable to the measurement. Gamma criteria of 1 mm/1 % (local dose) can be met by all PDDs of fields larger than 1 × 1 cm 2 , and by all OARs of no larger than 20 × 20 cm 2 , otherwise criteria of 1 mm/2 % can be fulfilled. Our MC simulated ROFs agreed well with the measured ROFs of various field sizes (the discrepancies were less than 1 %), except for the 1 × 1 cm 2 field. The MC simulation agrees well with the measurement and the proposed model parameters can be clinically used for further dosimetric studies of 6 and 10 MV FFF beams

  17. An online replanning method using warm start optimization and aperture morphing for flattening-filter-free beams

    Energy Technology Data Exchange (ETDEWEB)

    Ahunbay, Ergun E., E-mail: eahunbay@mcw.edu; Ates, O.; Li, X. A. [Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226 (United States)

    2016-08-15

    Purpose: In a situation where a couch shift for patient positioning is not preferred or prohibited (e.g., MR-linac), segment aperture morphing (SAM) can address target dislocation and deformation. For IMRT/VMAT with flattening-filter-free (FFF) beams, however, SAM method would lead to an adverse translational dose effect due to the beam unflattening. Here the authors propose a new two-step process to address both the translational effect of FFF beams and the target deformation. Methods: The replanning method consists of an offline and an online step. The offline step is to create a series of preshifted-plans (PSPs) obtained by a so-called “warm start” optimization (starting optimization from the original plan, rather than from scratch) at a series of isocenter shifts. The PSPs all have the same number of segments with very similar shapes, since the warm start optimization only adjusts the MLC positions instead of regenerating them. In the online step, a new plan is obtained by picking the closest PSP or linearly interpolating the MLC positions and the monitor units of the closest PSPs for the shift determined from the image of the day. This two-step process is completely automated and almost instantaneous (no optimization or dose calculation needed). The previously developed SAM algorithm is then applied for daily deformation. The authors tested the method on sample prostate and pancreas cases. Results: The two-step interpolation method can account for the adverse dose effects from FFF beams, while SAM corrects for the target deformation. Plan interpolation method is effective in diminishing the unflat beam effect and may allow reducing the required number of PSPs. The whole process takes the same time as the previously reported SAM process (5–10 min). Conclusions: The new two-step method plus SAM can address both the translation effects of FFF beams and target deformation, and can be executed in full automation except the delineation of target contour

  18. TH-A-9A-10: Prostate SBRT Delivery with Flattening-Filter-Free Mode: Benefit and Accuracy

    International Nuclear Information System (INIS)

    Li, T; Yuan, L; Sheng, Y; Wu, Q

    2014-01-01

    Purpose: Flattening-filter-free (FFF) beam mode offered on TrueBeam™ linac enables delivering IMRT at 2400 MU/min dose rate. This study investigates the benefit and delivery accuracy of using high dose rate in the context of prostate SBRT. Methods: 8 prostate SBRT patients were retrospectively studied. In 5 cases treated with 600-MU/min dose rate, continuous prostate motion data acquired during radiation-beam-on was used to analyze motion range. In addition, the initial 1/3 of prostate motion trajectories during each radiation-beam-on was separated to simulate motion range if 2400-MU/min were used. To analyze delivery accuracy in FFF mode, MLC trajectory log files from an additional 3 cases treated at 2400-MU/min were acquired. These log files record MLC expected and actual positions every 20ms, and therefore can be used to reveal delivery accuracy. Results: (1) Benefit. On average treatment at 600-MU/min takes 30s per beam; whereas 2400-MU/min requires only 11s. When shortening delivery time to ~1/3, the prostate motion range was significantly smaller (p<0.001). Largest motion reduction occurred in Sup-Inf direction, from [−3.3mm, 2.1mm] to [−1.7mm, 1.7mm], followed by reduction from [−2.1mm, 2.4mm] to [−1.0mm, 2.4mm] in Ant-Pos direction. No change observed in LR direction [−0.8mm, 0.6mm]. The combined motion amplitude (vector norm) confirms that average motion and ranges are significantly smaller when beam-on was limited to the 1st 1/3 of actual delivery time. (2) Accuracy. Trajectory log file analysis showed excellent delivery accuracy with at 2400 MU/min. Most leaf deviations during beam-on were within 0.07mm (99-percentile). Maximum leaf-opening deviations during each beam-on were all under 0.1mm for all leaves. Dose-rate was maintained at 2400-MU/min during beam-on without dipping. Conclusion: Delivery prostate SBRT with 2400 MU/min is both beneficial and accurate. High dose rates significantly reduced both treatment time and intra-beam prostate

  19. Radiosurgery with flattening-filter-free techniques in the treatment of brain metastases. Plan comparison and early clinical evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Rieber, J.; Tonndorf-Martini, E.; Schramm, O.; Rhein, B.; Stefanowicz, S.; Lindel, K.; Debus, J.; Rieken, S. [University Hospital Heidelberg, Department of Radiation Oncology, Heidelberg (Germany); Heidelberg Institute of Radiation Oncology, Heidelberg (Germany); Kappes, J. [Heidelberg University, Translational Research Unit, Thoraxklinik, Heidelberg (Germany); Heidelberg University, Department of Pneumology, Thoraxklinik, Heidelberg (Germany); Member of the German Centre for Lung Research (DZL), Translational Lung Research Centre Heidelberg (TLRC-H), Heidelberg (Germany); Hoffmann, H. [Heidelberg University, Translational Research Unit, Thoraxklinik, Heidelberg (Germany); Heidelberg University, Department of Thoracic Surgery, Thoraxklinik, Heidelberg (Germany); Member of the German Centre for Lung Research (DZL), Translational Lung Research Centre Heidelberg (TLRC-H), Heidelberg (Germany)

    2016-11-15

    Radiosurgical treatment of brain metastases is well established in daily clinical routine. Utilization of flattening-filter-free beams (FFF) may allow for more rapid delivery of treatment doses and improve clinical comfort. Hence, we compared plan quality and efficiency of radiosurgery in FFF mode to FF techniques. Between November 2014 and June 2015, 21 consecutive patients with 25 brain metastases were treated with stereotactic radiosurgery (SRS) in FFF mode. Brain metastases received dose-fractionation schedules of 1 x 20 Gy or 1 x 18 Gy, delivered to the conformally enclosing 80 % isodose. Three patients with critically localized or large (>3 cm) brain metastases were treated with 6 x 5 Gy. Plan quality and efficiency were evaluated by analyzing conformity, dose gradients, dose to healthy brain tissue, treatment delivery time, and number of monitor units. FFF plans were compared to those using the FF method, and early clinical outcome and toxicity were assessed. FFF mode resulted in significant reductions in beam-on time (p < 0.001) and mean brain dose (p = 0.001) relative to FF-mode comparison plans. Furthermore, significant improvements in dose gradients and sharper dose falloffs were found for SRS in FFF mode (-1.1 %, -29.6 %; p ≤ 0.003), but conformity was slightly superior in SRS in FF mode (-1.3 %; p = 0.001). With a median follow-up time of 5.1 months, 6-month overall survival was 63.3 %. Local control was observed in 24 of 25 brain metastases (96 %). SRS in FFF mode is time efficient and provides similar plan quality with the opportunity of slightly reduced dose exposure to healthy brain tissue when compared to SRS in FF mode. Clinical outcomes appear promising and show only modest treatment-related toxicity. (orig.) [German] Die radiochirurgische Behandlung (SRS) von Hirnmetastasen wird vielfach in der klinischen Routine durchgefuehrt. Die zusaetzliche Anwendung von ausgleichsfilterfreien Bestrahlungstechniken (FFF) kann die Bestrahlungszeit

  20. Efficacy of flattening-filter-free beam in stereotactic body radiation therapy planning and treatment: A systematic review with meta-analysis

    International Nuclear Information System (INIS)

    Dang, Thu M.; Peters, Mitchell J.; Hickey, Brigid; Semciw, Adam

    2017-01-01

    A linear accelerator with the flattening-filter removed generates a non-uniform dose profile beam. We aimed to analyse and compare plan quality and treatment time between flattened beam (FB) and flattening-filter-free (FFF) beam to assess the efficacy of FFF beam for stereotactic body radiation therapy (SBRT). The search strategy was based around 3 concepts; radiation therapy, flattening-filter-free and treatment delivery. The years searched were restricted from 2010 to date of review (October 2015). All plan quality comparisons were between FFF and FB plans from the same data sets. We identified 210 potential studies based on the three searched concepts. All articles were screened by two authors for title and abstract and by three authors for full text. Ten studies met the eligibility criteria. Plan quality was evaluated using conformity index (CI), heterogeneity index (HI) and gradient index (GI). Dose to organs-at-risk (OAR) and healthy tissues were compared. Differences between beam-on-time (BOT) and treatment time (T × T) were also analysed. Normalized percentage ratios of CI and HI demonstrated no clinical differences among the studied articles. GI displayed small variations between the articles favouring FFF beam. The BOT with FFF is substantially reduced, and appears to impact the frequency of intra-fraction imaging which, in turn, affects total treatment time. Based on planning tumour volume (PTV) coverage, dose to OAR and healthy tissue sparing, FFF beam is clinically effective for the treatment of cancer patients using SBRT. We recommend the use of FFF beam for SBRT based on these factors and the reported overall treatment time reduction.

  1. Can volumetric modulated arc therapy with flattening filter free beams play a role in stereotactic body radiotherapy for liver lesions? A volume-based analysis

    International Nuclear Information System (INIS)

    Reggiori, Giacomo; Mancosu, Pietro; Castiglioni, Simona; Alongi, Filippo; Pellegrini, Chiara; Lobefalo, Francesca; Catalano, Maddalena; Fogliata, Antonella; Arcangeli, Stefano; Navarria, Piera; Cozzi, Luca; Scorsetti, Marta

    2012-01-01

    Purpose: To compare volumetric modulated arc therapy with flattening filter free (FFF) and flattening filter (FF) beams in patients with hepatic metastases subject to hypofractionated radiotherapy (RT). Methods: A planning study on 13 virtual lesions of increasing volume was performed. Two single arc plans were optimized with the RapidArc technique using either FFF or FF beams. A second planning study was performed on ten patients treated for liver metastases to validate conclusions. In all cases, a dose of 75 Gy in 3 fractions was prescribed to the planning target volume (PTV) and plans were evaluated in terms of coverage, homogeneity, conformity, mean dose to healthy liver and to healthy tissue. For each parameter, results were expressed in relative terms as the percentage ratio between FFF and FF data. Results: In terms of PTV coverage, conformity index favored FFF for targets of intermediate size while FF resulted more suitable for small ( 3 ) and large (>300 cm 3 ) targets. Plans optimized with FFF beams resulted in increased sparing of healthy tissue in ≅85% of cases. Despite the qualitative results, no statistically significant differences were found between FFF and FF results. Plans optimized with un-flattened beams resulted in higher average MU/Gy than plans with FF beams. A remarkable and significant difference was observed in the beam-on time (BOT) needed to deliver plans. The BOT for FF plans was 8.2 ± 1.0 min; for FFF plans BOT was 2.2 ± 0.2 min. Conclusions: RapidArc plans optimized using FFF were dosimetrically equivalent to those optimized using FF beams, showing the feasibility of SBRT treatments with FFF beams. Some improvement in healthy tissue sparing was observed when using the FFF modality due to the different beam's profile. The main advantage was a considerable reduction of beam-on time, relevant for SBRT techniques.

  2. The evaluation of properties for radiation therapy techniques with flattening filter-free beam and usefulness of time and economy to a patient with the radiation therapy

    International Nuclear Information System (INIS)

    Goo, Jang Hyeon; Won, Hui Su; Hong, Joo Wan; Chang, Nam Jun; Park, Jin Hong

    2014-01-01

    The aim of this study was to appraise properties for radiation therapy techniques and effectiveness of time and economy to a patient in the case of applying flattening filter-free (3F) and flattening filter (2F) beam to the radiation therapy. Alderson rando phantom was scanned for computed tomography image. Treatment plans for intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT) and stereotactic body radiation therapy (SBRT) with 3F and 2F beam were designed for prostate cancer. To evaluate the differences between the 3F and 2F beam, total monitor units (MUs), beam on time (BOT) and gantry rotation time (GRT) were used and measured with TrueBeam TM STx and Surveillance And Measurement (SAM) 940 detector was used for photoneutron emitted by using 3F and 2F. To assess temporal and economical aspect for a patient, total treatment periods and medical fees were estimated. In using 3F beam, total MUs in IMRT plan increased the highest up to 34.0% and in the test of BOT, GRT and photoneutron, the values in SBRT plan decreased the lowest 39.8, 38.6 and 48.1%, respectively. In the temporal and economical aspect, there were no differences between 3F and 2F beam in all of plans and the results showed that 10 days and 169,560 won was lowest in SBRT plan. According as the results, total MUs increased by using 3F beam than 2F beam but BOT, GRT and photoneutron decreased. From above the results, using 3F beam can decrease intra-fraction setup error and risk of radiation-induced secondary malignancy. But, using 3F beam did not make the benefits of temporal and economical aspect for a patient with the radiation therapy

  3. SU-E-T-670: Radiotherapy Vault Shielding Evaluation Method for a Flattening Filter-Free (FFF) Linac-Practical Considerations and Recommendations

    Energy Technology Data Exchange (ETDEWEB)

    Mihailidis, D [CAMC Cancer Center-Alliance Oncology and West Virginia University, Charleston, WV (United States)

    2015-06-15

    Purpose: To date, there isn’t formal approach for flattening filter-free (FFF) linac vault shielding evaluation, thus, we propose an extension to NCRP#151 to accommodate the recent large number of FFF linac installations.Methods and Materials: We extended the approach in NCRP#151 to design two Truebeam vaults in our new cancer center for hypofractionated treatments. Monte Carlo calculations have characterized primary, scattered, leakage and neutron radiations from FFF-modes. These calculations have shown that: a) FFF primary beam is softer on the central-axis compared to flattening filtered (FF), b) the lateral dose profile is peaked on the central axis and less integral target current is required to generate the same tumor dose with the FF beam. Thus, the TVLs for FFF mode are smaller than those of the FF mode and the scatter functions of the FF mode (NCRP#151) may not be appropriate for FFF-mode, c) the neutron source strength and fluence for 18X-FFF is smaller than 18X-FF, but it is not of a concern here, no 18X-FFF-mode is available on the linac under investigation. Results: These barrier thickness are smaller (12% reduction on the average) than those computed for conventional FF mode with same realistic primary workload since, the primary TVLs used here are smaller and the WL is smaller than the conventional (almost half reduced), keeping the TADR in tolerance. Conclusions: A comprehensive method for shielding barrier calculations based on dedicated data for FFF-mode linacs is highly desired. Meanwhile, we provide an extension to NCRP#151 to accommodate the shielding design of such installations. It is also shown that if a vault is already designed for IMRT/VMAT and SABR hypofractionated treatments with FFF-mode linac, the vault can also be used for a FFF mode linac replacement, leaving some leeway for slightly higher workload on the FFF linac.

  4. SU-E-T-670: Radiotherapy Vault Shielding Evaluation Method for a Flattening Filter-Free (FFF) Linac-Practical Considerations and Recommendations

    International Nuclear Information System (INIS)

    Mihailidis, D

    2015-01-01

    Purpose: To date, there isn’t formal approach for flattening filter-free (FFF) linac vault shielding evaluation, thus, we propose an extension to NCRP#151 to accommodate the recent large number of FFF linac installations.Methods and Materials: We extended the approach in NCRP#151 to design two Truebeam vaults in our new cancer center for hypofractionated treatments. Monte Carlo calculations have characterized primary, scattered, leakage and neutron radiations from FFF-modes. These calculations have shown that: a) FFF primary beam is softer on the central-axis compared to flattening filtered (FF), b) the lateral dose profile is peaked on the central axis and less integral target current is required to generate the same tumor dose with the FF beam. Thus, the TVLs for FFF mode are smaller than those of the FF mode and the scatter functions of the FF mode (NCRP#151) may not be appropriate for FFF-mode, c) the neutron source strength and fluence for 18X-FFF is smaller than 18X-FF, but it is not of a concern here, no 18X-FFF-mode is available on the linac under investigation. Results: These barrier thickness are smaller (12% reduction on the average) than those computed for conventional FF mode with same realistic primary workload since, the primary TVLs used here are smaller and the WL is smaller than the conventional (almost half reduced), keeping the TADR in tolerance. Conclusions: A comprehensive method for shielding barrier calculations based on dedicated data for FFF-mode linacs is highly desired. Meanwhile, we provide an extension to NCRP#151 to accommodate the shielding design of such installations. It is also shown that if a vault is already designed for IMRT/VMAT and SABR hypofractionated treatments with FFF-mode linac, the vault can also be used for a FFF mode linac replacement, leaving some leeway for slightly higher workload on the FFF linac

  5. The evaluation of properties for radiation therapy techniques with flattening filter-free beam and usefulness of time and economy to a patient with the radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Goo, Jang Hyeon; Won, Hui Su; Hong, Joo Wan; Chang, Nam Jun; Park, Jin Hong [Dept. of Radiation Oncology, Seoul national university Bundang hospital, Sungnam (Korea, Republic of)

    2014-12-15

    The aim of this study was to appraise properties for radiation therapy techniques and effectiveness of time and economy to a patient in the case of applying flattening filter-free (3F) and flattening filter (2F) beam to the radiation therapy. Alderson rando phantom was scanned for computed tomography image. Treatment plans for intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT) and stereotactic body radiation therapy (SBRT) with 3F and 2F beam were designed for prostate cancer. To evaluate the differences between the 3F and 2F beam, total monitor units (MUs), beam on time (BOT) and gantry rotation time (GRT) were used and measured with TrueBeam{sup TM} STx and Surveillance And Measurement (SAM) 940 detector was used for photoneutron emitted by using 3F and 2F. To assess temporal and economical aspect for a patient, total treatment periods and medical fees were estimated. In using 3F beam, total MUs in IMRT plan increased the highest up to 34.0% and in the test of BOT, GRT and photoneutron, the values in SBRT plan decreased the lowest 39.8, 38.6 and 48.1%, respectively. In the temporal and economical aspect, there were no differences between 3F and 2F beam in all of plans and the results showed that 10 days and 169,560 won was lowest in SBRT plan. According as the results, total MUs increased by using 3F beam than 2F beam but BOT, GRT and photoneutron decreased. From above the results, using 3F beam can decrease intra-fraction setup error and risk of radiation-induced secondary malignancy. But, using 3F beam did not make the benefits of temporal and economical aspect for a patient with the radiation therapy.

  6. Technical Note: On the impact of the incident electron beam energy on the primary dose component of flattening filter free photon beams.

    Science.gov (United States)

    Kuess, Peter; Georg, Dietmar; Palmans, Hugo; Lechner, Wolfgang

    2016-08-01

    For commercially available linear accelerators (Linacs), the electron energies of flattening filter free (FFF) and flattened (FF) beams are either identical or the electron energy of the FFF beam is increased to match the percentage depth dose curve (PDD) of the FF beam (in reference geometry). This study focuses on the primary dose components of FFF beams for both kinds of settings, studied on the same Linac. The measurements were conducted on a VersaHD Linac (Elekta, Crawley, UK) for both FF and FFF beams with nominal energies of 6 and 10 MV. In the clinical setting of the VersaHD, the energy of FFFM (Matched) beams is set to match the PDDs of the FF beams. In contrast the incident electron beam of the FFFU beam was set to the same energy as for the FF beam. Half value layers (HVLs) and a dual parameter beam quality specifier (DPBQS) were determined. For the 6 MV FFFM beam, HVL and DPBQS values were very similar compared to those of the 6 MV FF beam, while for the 10 MV FFFM and FF beams, only %dd(10)x and HVL values were comparable (differences below 1.5%). This shows that matching the PDD at one depth does not guarantee other beam quality dependent parameters to be matched. For FFFU beams, all investigated beam quality specifiers were significantly different compared to those for FF beams of the same nominal accelerator potential. The DPBQS of the 6 MV FF and FFFM beams was equal within the measurement uncertainty and was comparable to published data of a machine with similar TPR20,10 and %dd(10)x. In contrast to that, the DPBQS's two parameters of the 10 MV FFFM beam were substantially higher compared to those for the 10 MV FF beam. PDD-matched FF and FFF beams of both nominal accelerator potentials were observed to have similar HVL values, indicating similarity of their primary dose components. Using the DPBQS revealed that the mean attenuation coefficient was found to be the same within the uncertainty of 0.8% for 6 MV FF and 6 MV FFFM beams, while for 10 MV

  7. A Study of volumetric modulated arc therapy for stereotactic body radiation therapy in case of multi-target liver cancer using flattening filter free beam

    International Nuclear Information System (INIS)

    Yeom, Mi Sook; Yoon, In Ha; Hong, Dong Gi; Back, Geum Mun

    2015-01-01

    Stereotactic body radiation therapy (SBRT) has proved its efficacy in several patient populations with primary and metastatic limited tumors. Because SBRT prescription is high dose level than Conventional radiation therapy. SBRT plan is necessary for effective Organ at risk (OAR) protection and sufficient Planning target volume (PTV) dose coverage. In particular, multi-target cases may result excessive doses to OAR and hot spot due to dose overlap. This study evaluate usefulness of Volumetric modulated arc therapy (VMAT) in dosimetric and technical considerations using Flattening filter free (FFF) beam. The treatment plans for five patients, being treated on TrueBeam STx(Varian™, USA) with VMAT using 10MV FFF beam and Standard conformal radiotherapy (CRT) using 15MV Flattening filter (FF) beam. PTV, liver, duodenum, bowel, spinal cord, esophagus, stomach dose were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick's index(PCI) for the PTV was assessed. Total Monitor unit (MU) and beam on time was assessed. Average value of CI, HI and PCI for PTV was 1.381±0.028, 1.096±0.016, 0.944±0.473 in VMAT and 1.381± 0.042, 1.136±0.042, 1.534±0.465 in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT. VMAT for SBRT in multi-target liver cancer using FFF beam is effective treatment techniqe in dosimetric and technical considerations. VMAT decrease intra-fraction error due to treatment time shortening using high dose rate of FFF beam

  8. Establishing stereotactic body radiotherapy with flattening filter free techniques in the treatment of pulmonary lesions - initial experiences from a single institution

    International Nuclear Information System (INIS)

    Rieber, Juliane; Tonndorf-Martini, Eric; Schramm, Oliver; Rhein, Bernhard; König, Laila; Adeberg, Sebastian; Meyerhof, Eva; Mohr, Angela; Kappes, Jutta; Hoffmann, Hans; Debus, Jürgen; Rieken, Stefan

    2016-01-01

    Stereotactic body radiotherapy (SBRT) using flattening filter free (FFF)-techniques has been increasingly applied during the last years. However, clinical studies investigating this emerging technique are still rare. Hence, we analyzed toxicity and clinical outcome of pulmonary SBRT with FFF-techniques and performed dosimetric comparison to conventional techniques using flattening filters (FF). Between 05/2014 and 06/2015, 56 consecutive patients with 61 pulmonary lesions were treated with SBRT in FFF-mode. Central lesions received 8 × 7.5 Gy delivered to the conformally enclosing 80 %-isodose, while peripheral lesions were treated with 3 × 15 Gy, prescribed to the 65 %-isodose. Early and late toxicity (after 6 months) as well as initial clinical outcomes were evaluated. Furthermore, [deleted] plan quality and efficiency were evaluated by analyzing conformity, beam- on and total treatment delivery times in comparison to plans with FF-dose application. Median follow-up time was 9.3 months (range 1.5–18.0 months). Early toxicity was low with only 5 patients (8.9 %) reporting CTCAE 2° or higher side-effects. Only one patient (1.8 %) was diagnosed with radiation-induced pneumonitis CTCAE 3°, while 2 (3.6 %) patients suffered from pneumonitis CTCAE 2°. After 6 months, no toxicity greater than CTCAE 2° was reported. 1-year local progression-free survival, distant progression-free survival and overall survival were 92.8 %, 78.0 %, and 94.4 %, respectively. While plan quality was similar for FFF- and FF-plans in respect to conformity (p = 0.275), median beam-on time as well as total treatment time were significantly reduced for SBRT in FFF-mode compared to FF-mode (p ≤ 0.001, p ≤ 0.001). Patient treatment with SBRT using FFF-techniques is safe and provides promising clinical results with only modest toxicity at significantly increased dose delivery speed

  9. A Study of volumetric modulated arc therapy for stereotactic body radiation therapy in case of multi-target liver cancer using flattening filter free beam

    Energy Technology Data Exchange (ETDEWEB)

    Yeom, Mi Sook; Yoon, In Ha; Hong, Dong Gi; Back, Geum Mun [Dept. of Radiation Oncology, ASAN Medical Center, Seoul (Korea, Republic of)

    2015-06-15

    Stereotactic body radiation therapy (SBRT) has proved its efficacy in several patient populations with primary and metastatic limited tumors. Because SBRT prescription is high dose level than Conventional radiation therapy. SBRT plan is necessary for effective Organ at risk (OAR) protection and sufficient Planning target volume (PTV) dose coverage. In particular, multi-target cases may result excessive doses to OAR and hot spot due to dose overlap. This study evaluate usefulness of Volumetric modulated arc therapy (VMAT) in dosimetric and technical considerations using Flattening filter free (FFF) beam. The treatment plans for five patients, being treated on TrueBeam STx(Varian™, USA) with VMAT using 10MV FFF beam and Standard conformal radiotherapy (CRT) using 15MV Flattening filter (FF) beam. PTV, liver, duodenum, bowel, spinal cord, esophagus, stomach dose were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick's index(PCI) for the PTV was assessed. Total Monitor unit (MU) and beam on time was assessed. Average value of CI, HI and PCI for PTV was 1.381±0.028, 1.096±0.016, 0.944±0.473 in VMAT and 1.381± 0.042, 1.136±0.042, 1.534±0.465 in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT respectively. OAR dose in CRT plans evaluated 1.8 times higher than VMAT. Total MU in VMAT evaluated 1.3 times increase than CRT. Average beam on time was 6.8 minute in VMAT and 21.3 minute in CRT. VMAT for SBRT in multi-target liver cancer using FFF beam is effective treatment techniqe in dosimetric and technical considerations. VMAT decrease intra-fraction error due to treatment time shortening using high dose rate of FFF beam.

  10. Technical Note: On the impact of the incident electron beam energy on the primary dose component of flattening filter free photon beams

    International Nuclear Information System (INIS)

    Kuess, Peter; Georg, Dietmar; Lechner, Wolfgang; Palmans, Hugo

    2016-01-01

    Purpose: For commercially available linear accelerators (Linacs), the electron energies of flattening filter free (FFF) and flattened (FF) beams are either identical or the electron energy of the FFF beam is increased to match the percentage depth dose curve (PDD) of the FF beam (in reference geometry). This study focuses on the primary dose components of FFF beams for both kinds of settings, studied on the same Linac. Methods: The measurements were conducted on a VersaHD Linac (Elekta, Crawley, UK) for both FF and FFF beams with nominal energies of 6 and 10 MV. In the clinical setting of the VersaHD, the energy of FFF M (Matched) beams is set to match the PDDs of the FF beams. In contrast the incident electron beam of the FFF U beam was set to the same energy as for the FF beam. Half value layers (HVLs) and a dual parameter beam quality specifier (DPBQS) were determined. Results: For the 6 MV FFF M beam, HVL and DPBQS values were very similar compared to those of the 6 MV FF beam, while for the 10 MV FFF M and FF beams, only %dd(10) x and HVL values were comparable (differences below 1.5%). This shows that matching the PDD at one depth does not guarantee other beam quality dependent parameters to be matched. For FFF U beams, all investigated beam quality specifiers were significantly different compared to those for FF beams of the same nominal accelerator potential. The DPBQS of the 6 MV FF and FFF M beams was equal within the measurement uncertainty and was comparable to published data of a machine with similar TPR 20,10 and %dd(10) x . In contrast to that, the DPBQS’s two parameters of the 10 MV FFF M beam were substantially higher compared to those for the 10 MV FF beam. Conclusions: PDD-matched FF and FFF beams of both nominal accelerator potentials were observed to have similar HVL values, indicating similarity of their primary dose components. Using the DPBQS revealed that the mean attenuation coefficient was found to be the same within the uncertainty of

  11. Volumetric modulated arc therapy with flattening filter free beams for isolated abdominal/pelvic lymph nodes: report of dosimetric and early clinical results in oligometastatic patients

    Directory of Open Access Journals (Sweden)

    Alongi Filippo

    2012-12-01

    Full Text Available Abstract Background SBRT is a safe and efficient strategy to locally control multiple metastatic sites. While research in the physics domain for Flattening Filter Free Beams (FFF beams is increasing, there are few clinical data of FFF beams in clinical practice. Here we reported dosimentric and early clinical data of SBRT and FFF delivery in isolated lymph node oligometastatic patients. Methods Between October 2010 and March 2012, 34 patients were treated with SBRT for oligometastatic lymph node metastasis on a Varian TrueBeamTM treatment machine using Volumetric Modulated Arc Therapy (RapidArc. We retrospectively evaluated a total of 25 patients for isolated lymph node metastases in abdomen and/or pelvis treated with SBRT and FFF (28 treatments. Acute toxicity was recorded. Local control evaluation was scored by means of CT scan and/or PET scan. Results All dosimetric results are in line with what published for the same type of stereotactic abdominal lymph node metastases treatments and fractionation, using RapidArc. All 25 FFF SBRT patients completed the treatment. Acute gastrointestinal toxicity was minimal: one patient showed Grade 1 gastrointestinal toxicity. Three other patients presented Grade 2 toxicity. No Grade 3 or higher was recorded. All toxicities were recovered within one week. The preliminary clinical results at the median follow up of 195 days are: complete response in 12 cases, partial response in 11, stable disease in 5, with an overall response rate of 82%; no local progression was recorded. Conclusions Data of dosimetrical findings and acute toxicity are excellent for patients treated with SBRT with VMAT using FFF beams. Preliminary clinical results showed a high rate of local control in irradiated lesion. Further data and longer follow up are needed to assess late toxicity and definitive clinical outcomes.

  12. Development of a flattening filter free multiple source model for use as an independent, Monte Carlo, dose calculation, quality assurance tool for clinical trials.

    Science.gov (United States)

    Faught, Austin M; Davidson, Scott E; Popple, Richard; Kry, Stephen F; Etzel, Carol; Ibbott, Geoffrey S; Followill, David S

    2017-09-01

    The Imaging and Radiation Oncology Core-Houston (IROC-H) Quality Assurance Center (formerly the Radiological Physics Center) has reported varying levels of compliance from their anthropomorphic phantom auditing program. IROC-H studies have suggested that one source of disagreement between institution submitted calculated doses and measurement is the accuracy of the institution's treatment planning system dose calculations and heterogeneity corrections used. In order to audit this step of the radiation therapy treatment process, an independent dose calculation tool is needed. Monte Carlo multiple source models for Varian flattening filter free (FFF) 6 MV and FFF 10 MV therapeutic x-ray beams were commissioned based on central axis depth dose data from a 10 × 10 cm 2 field size and dose profiles for a 40 × 40 cm 2 field size. The models were validated against open-field measurements in a water tank for field sizes ranging from 3 × 3 cm 2 to 40 × 40 cm 2 . The models were then benchmarked against IROC-H's anthropomorphic head and neck phantom and lung phantom measurements. Validation results, assessed with a ±2%/2 mm gamma criterion, showed average agreement of 99.9% and 99.0% for central axis depth dose data for FFF 6 MV and FFF 10 MV models, respectively. Dose profile agreement using the same evaluation technique averaged 97.8% and 97.9% for the respective models. Phantom benchmarking comparisons were evaluated with a ±3%/2 mm gamma criterion, and agreement averaged 90.1% and 90.8% for the respective models. Multiple source models for Varian FFF 6 MV and FFF 10 MV beams have been developed, validated, and benchmarked for inclusion in an independent dose calculation quality assurance tool for use in clinical trial audits. © 2017 American Association of Physicists in Medicine.

  13. SU-E-T-339: Dosimetric Verification of Acuros XB Dose Calculation Algorithm On An Air Cavity for 6-MV Flattening Filter-Free Beam

    International Nuclear Information System (INIS)

    Kang, S; Suh, T; Chung, J

    2015-01-01

    Purpose: This study was to verify the accuracy of Acuros XB (AXB) dose calculation algorithm on an air cavity for a single radiation field using 6-MV flattening filter-free (FFF) beam. Methods: A rectangular slab phantom containing an air cavity was made for this study. The CT images of the phantom for dose calculation were scanned with and without film at measurement depths (4.5, 5.5, 6.5 and 7.5 cm). The central axis doses (CADs) and the off-axis doses (OADs) were measured by film and calculated with Analytical Anisotropic Algorithm (AAA) and AXB for field sizes ranging from 2 Χ 2 to 5 Χ 5 cm 2 of 6-MV FFF beams. Both algorithms were divided into AXB-w and AAA -w when included the film in phantom for dose calculation, and AXB-w/o and AAA-w/o in calculation without film. The calculated OADs for both algorithms were compared with the measured OADs and difference values were determined using root means squares error (RMSE) and gamma evaluation. Results: The percentage differences (%Diffs) between the measured and calculated CAD for AXB-w was most agreement than others. Compared to the %Diff with and without film, the %Diffs with film were decreased than without within both algorithms. The %Diffs for both algorithms were reduced with increasing field size and increased relative to the depth increment. RMSEs of CAD for AXB-w were within 10.32% for both inner-profile and penumbra, while the corresponding values of AAA-w appeared to 96.50%. Conclusion: This study demonstrated that the dose calculation with AXB within air cavity shows more accurate than with AAA compared to the measured dose. Furthermore, we found that the AXB-w was superior to AXB-w/o in this region when compared against the measurements

  14. Dosimetric comparison of deep inspiration breath hold and free breathing technique in stereotactic body radiotherapy for localized lung tumor using Flattening Filter Free beam

    Science.gov (United States)

    Mani, Karthick Raj; Bhuiyan, Md. Anisuzzaman; Alam, Md. Mahbub; Ahmed, Sharif; Sumon, Mostafa Aziz; Sengupta, Ashim Kumar; Rahman, Md. Shakilur; Azharul Islam, Md. S. M.

    2018-03-01

    Aim: To compare the dosimetric advantage of stereotactic body radiotherapy (SBRT) for localized lung tumor between deep inspiration breath hold technique and free breathing technique. Materials and methods: We retrospectively included ten previously treated lung tumor patients in this dosimetric study. All the ten patients underwent CT simulation using 4D-CT free breathing (FB) and deep inspiration breath hold (DIBH) techniques. Plans were created using three coplanar full modulated arc using 6 MV flattening filter free (FFF) bream with a dose rate of 1400 MU/min. Same dose constraints for the target and the critical structures for a particular patient were used during the plan optimization process in DIBH and FB datasets. We intend to deliver 50 Gy in 5 fractions for all the patients. For standardization, all the plans were normalized at target mean of the planning target volume (PTV). Doses to the critical structures and targets were recorded from the dose volume histogram for evaluation. Results: The mean right and left lung volumes were inflated by 1.55 and 1.60 times in DIBH scans compared to the FB scans. The mean internal target volume (ITV) increased in the FB datasets by 1.45 times compared to the DIBH data sets. The mean dose followed by standard deviation (x¯ ± σx¯) of ipsilateral lung for DIBH-SBRT and FB-SBRT plans were 7.48 ± 3.57 (Gy) and 10.23 ± 4.58 (Gy) respectively, with a mean reduction of 36.84% in DIBH-SBRT plans. Ipsilateral lung were reduced to 36.84% in DIBH plans compared to FB plans. Conclusion: Significant dose reduction in ipsilateral lung due to the lung inflation and target motion restriction in DIBH-SBRT plans were observed compare to FB-SBRT. DIBH-SBRT plans demonstrate superior dose reduction to the normal tissues and other critical structures.

  15. SU-E-T-591: Optimizing the Flattening Filter Free Beam Selection in RapidArc-Based Stereotactic Body Radiotherapy for Stage I Lung Cancer

    International Nuclear Information System (INIS)

    Huang, B-T; Lu, J-Y

    2015-01-01

    Purpose: To optimize the flattening filter free (FFF) beam energy selection in stereotactic body radiotherapy (SBRT) treatment for stage I lung cancer with different fraction schemes. Methods: Twelve patients suffering from stage I lung cancer were enrolled in this study. Plans were designed using 6XFFF and 10XFFF beams with the most widely used fraction schemes of 4*12 Gy, 3*18 Gy and 1*34 Gy, respectively. The plan quality was appraised in terms of planning target volume (PTV) coverage, conformity of the prescribed dose (CI100%), intermediate dose spillage (R50% and D2cm), organs at risk (OARs) sparing and beam-on time. Results: The 10XFFF beam predicted 1% higher maximum, mean dose to the PTV and 4–5% higher R50% compared with the 6XFFF beam in the three fraction schemes, whereas the CI100% and D2cm was similar. Most importantly, the 6XFFF beam exhibited 3–10% lower dose to all the OARs. However, the 10XFFF beam reduced the beam-on time by 31.9±7.2%, 38.7±2.8% and 43.6±4.0% compared with the 6XFFF beam in the 4*12 Gy, 3*18 Gy and 1*34 Gy schemes, respectively. Beam-on time was 2.2±0.2 vs 1.5±0.1, 3.3±0.9 vs 2.0±0.5 and 6.3±0.9 vs 3.5±0.4 minutes for the 6XFFF and 10XFFF one in the three fraction schemes. Conclusion: The 6XFFF beam obtains better OARs sparing in SBRT treatment for stage I lung cancer, but the 10XFFF one provides improved treatment efficiency. To balance the OARs sparing and intrafractional variation as a function of prolonged treatment time, the authors recommend to use the 6XFFF beam in the 4*12 Gy and 3*18 Gy schemes for better OARs sparing. However, for the 1*34 Gy scheme, the 10XFFF beam is recommended to achieve improved treatment efficiency

  16. Dosimetric Impact of the Interplay Effect During Stereotactic Lung Radiation Therapy Delivery Using Flattening Filter-Free Beams and Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Ong, Chin Loon; Dahele, Max; Slotman, Ben J.; Verbakel, Wilko F.A.R.

    2013-01-01

    Purpose: We investigated the dosimetric impact of the interplay effect during RapidArc stereotactic body radiation therapy for lung tumors using flattening filter-free (FFF) beams with different dose rates. Methods and Materials: Seven tumors with motion ≤20 mm, treated with 10-MV FFF RapidArc, were analyzed. A programmable phantom with sinusoidal longitudinal motion (30-mm diameter “tumor” insert; period = 5 s; individualized amplitude from planning 4-dimensional computed tomography) was used for dynamic dose measurements. Measurements were made with GafChromic EBT III films. Plans delivered the prescribed dose to 95% of the planning target volume, created by a 5-mm expansion of the internal target volume. They comprised 2 arcs and maximum dose rates of 400 and 2400 MU/min. For 2400 MU/min plans, measurements were repeated at 3 different initial breathing phases to model interplay over 2 to 3 fractions. For 3 cases, 2 extra plans were created using 1 full rotational arc (with contralateral lung avoidance sector) and 1 partial arc of 224° to 244°. Dynamic and convolved static measurements were compared by use of gamma analysis of 3% dose difference and 1 mm distance-to-agreement. Results: For 2-arc 2400 MU/min plans, maximum dose deviation of 9.4% was found in a single arc; 7.4% for 2 arcs (single fraction) and 99% of the area within the region of interest passed the gamma criteria when all 3 measurements with different initial phases were combined. Single-fraction single-arc plans showed higher dose deviations, which diminished when dose distributions were summed over 2 fractions. All 400 MU/min plans showed good agreement in a single fraction measurement. Conclusion: Under phantom conditions, single-arc and single-fraction 2400 MU/min FFF RapidArc lung stereotactic body radiation therapy is susceptible to interplay. Two arcs and ≥2 fractions reduced the effect to a level that appeared unlikely to be clinically significant

  17. Critical appraisal of RapidArc radiosurgery with flattening filter free photon beams for benign brain lesions in comparison to GammaKnife: a treatment planning study.

    Science.gov (United States)

    Abacioglu, Ufuk; Ozen, Zeynep; Yilmaz, Meltem; Arifoglu, Alptekin; Gunhan, Basri; Kayalilar, Namik; Peker, Selcuk; Sengoz, Meric; Gurdalli, Salih; Cozzi, Luca

    2014-05-21

    To evaluate the role of RapidArc (RA) for stereotactic radiosurgery (SRS) of benign brain lesions in comparison to GammaKnife (GK) based technique. Twelve patients with vestibular schwannoma (VS, n = 6) or cavernous sinus meningioma (CSM, n = 6) were planned for both SRS using volumetric modulated arc therapy (VMAT) by RA. 104 MV flattening filter free photon beams with a maximum dose rate of 2400 MU/min were selected. Data were compared against plans optimised for GK. A single dose of 12.5 Gy was prescribed. The primary objective was to assess treatment plan quality. Secondary aim was to appraise treatment efficiency. For VS, comparing best GK vs. RA plans, homogeneity was 51.7 ± 3.5 vs. 6.4 ± 1.5%; Paddick conformity Index (PCI) resulted 0.81 ± 0.03 vs. 0.84 ± 0.04. Gradient index (PGI) was 2.7 ± 0.2 vs. 3.8 ± 0.6. Mean target dose was 17.1 ± 0.9 vs. 12.9 ± 0.1 Gy. For the brain stem, D(1cm3) was 5.1 ± 2.0 Gy vs 4.8 ± 1.6 Gy. For the ipsilateral cochlea, D(0.1cm3) was 1.7 ± 1.0 Gy vs. 1.8 ± 0.5 Gy. For CSM, homogeneity was 52.3 ± 2.4 vs. 12.4 ± 0.6; PCI: 0.86 ± 0.05 vs. 0.88 ± 0.05; PGI: 2.6 ± 0.1 vs. 3.8 ± 0.5; D(1cm3) to brain stem was 5.4 ± 2.8 Gy vs. 5.2 ± 2.8 Gy; D(0.1cm3) to ipsi-lateral optic nerve was 4.2 ± 2.1 vs. 2.1 ± 1.5 Gy; D(0.1cm3) to optic chiasm was 5.9 ± 3.1 vs. 4.5 ± 2.1 Gy. Treatment time was 53.7 ± 5.8 (64.9 ± 24.3) minutes for GK and 4.8 ± 1.3 (5.0 ± 0.7) minutes for RA for schwannomas (meningiomas). SRS with RA and FFF beams revealed to be adequate and comparable to GK in terms of target coverage, homogeneity, organs at risk sparing with some gain in terms of treatment efficiency.

  18. SU-F-T-260: Using Portal Image Device for Pre-Treatment QA in Volumetric Modulated Arc Plans with Flattening Filter Free (FFF) Beams

    Energy Technology Data Exchange (ETDEWEB)

    Qu, H; Qi, P; Yu, N; Xia, P [The Cleveland Clinic Foundation, Cleveland, OH (United States)

    2016-06-15

    Purpose: To implement and validate a method of using electronic portal image device (EPID) for pre-treatment quality assurance (QA) of volumetric modulated arc therapy (VMAT) plans using flattering filter free (FFF) beams for stereotactic body radiotherapy (SBRT). Methods: On Varian Edge with 6MV FFF beam, open field (from 2×2 cm to 20×20 cm) EPID images were acquired with 200 monitor unit (MU) at the image device to radiation source distance of 150cm. With 10×10 open field and calibration unit (CU) provided by vendor to EPID image pixel, a dose conversion factor was determined by dividing the center dose calculated from the treatment planning system (TPS) to the corresponding CU readout on the image. Water phantom measured beam profile and the output factors for various field sizes were further correlated to those of EPID images. The dose conversion factor and correction factors were then used for converting the portal images to the planner dose distributions of clinical fields. A total of 28 VMAT fields of 14 SBRT plans (8 lung, 2 prostate, 2 liver and 2 spine) were measured. With 10% low threshold cutoff, the delivered dose distributions were compared to the reference doses calculated in water phantom from the TPS. A gamma index analysis was performed for the comparison in percentage dose difference/distance-to-agreement specifications. Results: The EPID device has a linear response to the open fields with increasing MU. For the clinical fields, the gamma indices between the converted EPID dose distributions and the TPS calculated 2D dose distributions were 98.7%±1.1%, 94.0%±3.4% and 70.3%±7.7% for the criteria of 3%/3mm, 2%/2mm and 1%/1mm, respectively. Conclusion: Using a portal image device, a high resolution and high accuracy portal dosimerty was achieved for pre-treatment QA verification for SBRT VMAT plans with FFF beams.

  19. SU-F-T-506: Development and Commissioning of the Effective and Efficient Grid Therapy Using High Dose Rate Flattening Filter Free Beam and Multileaf Collimator

    Energy Technology Data Exchange (ETDEWEB)

    Liu, M; Wen, N; Beyer, C; Siddiqui, F; Chetty, I; Zhao, B [Henry Ford Health System, Detroit, MI (United States)

    2016-06-15

    Purpose: Treating bulky tumors with grid therapy (GT) has demonstrated high response rates. Long delivery time (∼15min), with consequent increased risk of intrafraction motion, is a major disadvantage of conventional MLC-based GT (MLC-GT). The goal of this study was to develop and commission a MLC-GT technique with similar dosimetric characteristics, but more efficient delivery. Methods: Grid plan was designed with 10X-FFF (2400MU/min) beam and MLC in a commercial treatment planning system (TPS). Grid size was 1cm by 1cm and grid-to-grid distance was 2cm. Field-in-field technique was used to flatten the dose profile at depth of 10cm. Prescription was 15Gy at 1.5cm depth. Doses were verified at depths of 1.5cm, 5cm and 10cm. Point dose was measured with a plastic scintillator detector (PSD) while the planar dose was measured with calibrated Gafchromic EBT3 films in a 20cm think, 30cmx30cm solid water phantom. The measured doses were compared to the doses calculated in the treatment planning system. Percent depth dose (PDD) within the grid was also measured using EBT3 film. Five clinical cases were planned to compare beam-on time. Results: The valley-to-peak dose ratio at the 3 depths was approximately 10–15%, which is very similar to published result. The average point dose difference between the PSD measurements and TPS calculation is 2.1±0.6%. Film dosimetry revealed good agreement between the delivered and calculated dose. The average gamma passing rates at the 3 depths were 95% (3%, 1mm). The average percent difference between the measured PDD and calculated PDD was 2.1% within the depth of 20cm. The phantom plan delivery time was 3.6 min. Average beam-on time was reduced by 66.1±5.6% for the 5 clinical cases. Conclusion: An effective and efficient GT technique was developed and commissioned for the treatment of bulky tumors using FFF beam combined with MLC and automation. The Department of Radiation Oncology at Henry Ford Health System receives research

  20. Evaluation of an aSi-EPID with flattening filter free beams: Applicability to the GLAaS algorithm for portal dosimetry and first experience for pretreatment QA of RapidArc

    International Nuclear Information System (INIS)

    Nicolini, G.; Clivio, A.; Vanetti, E.; Cozzi, L.; Fogliata, A.; Krauss, H.; Fenoglietto, P.

    2013-01-01

    Purpose: To demonstrate the feasibility of portal dosimetry with an amorphous silicon mega voltage imager for flattening filter free (FFF) photon beams by means of the GLAaS methodology and to validate it for pretreatment quality assurance of volumetric modulated arc therapy (RapidArc).Methods: The GLAaS algorithm, developed for flattened beams, was applied to FFF beams of nominal energy of 6 and 10 MV generated by a Varian TrueBeam (TB). The amorphous silicon electronic portal imager [named mega voltage imager (MVI) on TB] was used to generate integrated images that were converted into matrices of absorbed dose to water. To enable GLAaS use under the increased dose-per-pulse and dose-rate conditions of the FFF beams, new operational source-detector-distance (SDD) was identified to solve detector saturation issues. Empirical corrections were defined to account for the shape of the profiles of the FFF beams to expand the original methodology of beam profile and arm backscattering correction. GLAaS for FFF beams was validated on pretreatment verification of RapidArc plans for three different TB linacs. In addition, the first pretreatment results from clinical experience on 74 arcs were reported in terms of γ analysis.Results: MVI saturates at 100 cm SDD for FFF beams but this can be avoided if images are acquired at 150 cm for all nominal dose rates of FFF beams. Rotational stability of the gantry-imager system was tested and resulted in a minimal apparent imager displacement during rotation of 0.2 ± 0.2 mm at SDD = 150 cm. The accuracy of this approach was tested with three different Varian TrueBeam linacs from different institutes. Data were stratified per energy and machine and showed no dependence with beam quality and MLC model. The results from clinical pretreatment quality assurance, provided a gamma agreement index (GAI) in the field area for six and ten FFF beams of (99.8 ± 0.3)% and (99.5 ± 0.6)% with distance to agreement and dose difference criteria

  1. SU-E-T-800: Verification of Acurose XB Dose Calculation Algorithm at Air Cavity-Tissue Interface Using Film Measurement for Small Fields of 6-MV Flattening Filter-Free Beams

    International Nuclear Information System (INIS)

    Kang, S; Suh, T; Chung, J

    2015-01-01

    Purpose: To verify the dose accuracy of Acuros XB (AXB) dose calculation algorithm at air-tissue interface using inhomogeneous phantom for 6-MV flattening filter-free (FFF) beams. Methods: An inhomogeneous phantom included air cavity was manufactured for verifying dose accuracy at the air-tissue interface. The phantom was composed with 1 and 3 cm thickness of air cavity. To evaluate the central axis doses (CAD) and dose profiles of the interface, the dose calculations were performed for 3 × 3 and 4 × 4 cm 2 fields of 6 MV FFF beams with AAA and AXB in Eclipse treatment plainning system. Measurements in this region were performed with Gafchromic film. The root mean square errors (RMSE) were analyzed with calculated and measured dose profile. Dose profiles were divided into inner-dose profile (>80%) and penumbra (20% to 80%) region for evaluating RMSE. To quantify the distribution difference, gamma evaluation was used and determined the agreement with 3%/3mm criteria. Results: The percentage differences (%Diffs) between measured and calculated CAD in the interface, AXB shows more agreement than AAA. The %Diffs were increased with increasing the thickness of air cavity size and it is similar for both algorithms. In RMSEs of inner-profile, AXB was more accurate than AAA. The difference was up to 6 times due to overestimation by AAA. RMSEs of penumbra appeared to high difference for increasing the measurement depth. Gamma agreement also presented that the passing rates decreased in penumbra. Conclusion: This study demonstrated that the dose calculation with AXB shows more accurate than with AAA for the air-tissue interface. The 2D dose distributions with AXB for both inner-profile and penumbra showed better agreement than with AAA relative to variation of the measurement depths and air cavity sizes

  2. SU-E-T-131: Dosimetric Impact and Evaluation of Different Heterogenity Algorithm in Volumetric Modulated Arc Therapy Plan for Stereotactic Ablative Radiotherapy Lung Treatment with the Flattening Filter Free Beam

    Energy Technology Data Exchange (ETDEWEB)

    Chung, J; Kim, J [Seoul National University Bundang Hospital, Seongnam, Kyeonggi-do (Korea, Republic of); Lee, J [Konkuk University Medical Center, Seoul, Seoul (Korea, Republic of); Kim, Y [Choonhae College of Health Sciences, Ulsan (Korea, Republic of)

    2014-06-01

    Purpose: The present study aimed to investigate the dosimetric impacts of the anisotropic analytic algorithm (AAA) and the Acuros XB (AXB) plan for lung stereotactic ablative radiation therapy using flattening filter-free (FFF) beam. We retrospectively analyzed 10 patients. Methods: We retrospectively analyzed 10 patients. The dosimetric parameters for the target and organs at risk (OARs) from the treatment plans calculated with these dose calculation algorithms were compared. The technical parameters, such as the computation times and the total monitor units (MUs), were also evaluated. Results: A comparison of DVHs from AXB and AAA showed that the AXB plan produced a high maximum PTV dose by average 4.40% with a statistical significance but slightly lower mean PTV dose by average 5.20% compared to the AAA plans. The maximum dose to the lung was slightly higher in the AXB compared to the AAA. For both algorithms, the values of V5, V10 and V20 for ipsilateral lung were higher in the AXB plan more than those of AAA. However, these parameters for contralateral lung were comparable. The differences of maximum dose for the spinal cord and heart were also small. The computation time of AXB was found fast with the relative difference of 13.7% than those of AAA. The average of monitor units (MUs) for all patients was higher in AXB plans than in the AAA plans. These results indicated that the difference between AXB and AAA are large in heterogeneous region with low density. Conclusion: The AXB provided the advantages such as the accuracy of calculations and the reduction of the computation time in lung stereotactic ablative radiotherapy (SABR) with using FFF beam, especially for VMAT planning. In dose calculation with the media of different density, therefore, the careful attention should be taken regarding the impacts of different heterogeneity correction algorithms. The authors report no conflicts of interest.

  3. SU-E-T-131: Dosimetric Impact and Evaluation of Different Heterogenity Algorithm in Volumetric Modulated Arc Therapy Plan for Stereotactic Ablative Radiotherapy Lung Treatment with the Flattening Filter Free Beam

    International Nuclear Information System (INIS)

    Chung, J; Kim, J; Lee, J; Kim, Y

    2014-01-01

    Purpose: The present study aimed to investigate the dosimetric impacts of the anisotropic analytic algorithm (AAA) and the Acuros XB (AXB) plan for lung stereotactic ablative radiation therapy using flattening filter-free (FFF) beam. We retrospectively analyzed 10 patients. Methods: We retrospectively analyzed 10 patients. The dosimetric parameters for the target and organs at risk (OARs) from the treatment plans calculated with these dose calculation algorithms were compared. The technical parameters, such as the computation times and the total monitor units (MUs), were also evaluated. Results: A comparison of DVHs from AXB and AAA showed that the AXB plan produced a high maximum PTV dose by average 4.40% with a statistical significance but slightly lower mean PTV dose by average 5.20% compared to the AAA plans. The maximum dose to the lung was slightly higher in the AXB compared to the AAA. For both algorithms, the values of V5, V10 and V20 for ipsilateral lung were higher in the AXB plan more than those of AAA. However, these parameters for contralateral lung were comparable. The differences of maximum dose for the spinal cord and heart were also small. The computation time of AXB was found fast with the relative difference of 13.7% than those of AAA. The average of monitor units (MUs) for all patients was higher in AXB plans than in the AAA plans. These results indicated that the difference between AXB and AAA are large in heterogeneous region with low density. Conclusion: The AXB provided the advantages such as the accuracy of calculations and the reduction of the computation time in lung stereotactic ablative radiotherapy (SABR) with using FFF beam, especially for VMAT planning. In dose calculation with the media of different density, therefore, the careful attention should be taken regarding the impacts of different heterogeneity correction algorithms. The authors report no conflicts of interest

  4. Sci—Sat AM: Stereo — 08: Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam

    International Nuclear Information System (INIS)

    Mestrovic, A; Fortin, D; Alexander, A

    2014-01-01

    Purpose: To determine the feasibility of using Volumetric Modulated Arc Therapy (VMAT) with a 10x Flattening Filter Free (FFF) beam for Stereotactic Ablative Radiotherapy (SABR) for low, intermediate and high risk prostate cancer. Methods and Materials: Ten anonymized patient CT data sets were used in this planning study. For each patient CT data set, three sets of contours were generated: 1) low risk, 2) intermediate risk, and 3) high risk scenarios. For each scenario, a single-arc and a double-arc VMAT treatment plans were created. Plans were generated with the Varian Eclipse™ treatment planning system for a Varian TrueBeam™ linac equipped with Millenium 120 MLC. Plans were created using a 10x-FFF beam with a maximum dose rate of 2400 MU/min. Dose prescription was 36.25Gy/5 fractions with the planning objective of covering 99% of the Planning Target Volume with the 95% of the prescription dose. Normal tissue constraints were based on provincial prostate SABR planning guidelines, derived from national and international prostate SABR protocols. Plans were evaluated and compared in terms of: 1) dosimetric plan quality, and 2) treatment delivery efficiency. Results: Both single-arc and double-arc VMAT plans were able to meet the planning goals for low, intermediate and high risk scenarios. No significant dosimetric differences were observed between the plans. However, the treatment time was significantly lower for a single-arc VMAT plans. Conclusions: Prostate SABR treatments are feasible with 10x-FFF VMAT technique. A single-arc VMAT offers equivalent dosimetric plan quality and a superior treatment delivery efficiency, compared to a double-arc VMAT

  5. Design of a treatment room for an 18 MV Linac

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez A, L.; Contreras S, H.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Perez L, L. H., E-mail: dameluis@hotmail.co [Instituto Zacatecano del Tumor, Apdo. Postal 294, 98000 Zacatecas (Mexico)

    2010-10-15

    In this work it has been calculated the treatment room for an 18 MV Linac. The walls thickness, the door and the maze were designed according to the NCRP Report 151 recommendations. The results of this work are contrasted with the Monte Carlo calculations performed with the MCNP5 code where dose equivalent due to neutrons and neutron spectra are estimated at different points inside and outside of the radiotherapy room, verify the shielding thickness obtained are enough to reduce the dose level allowed by the Mexican regulation. (Author)

  6. Neutron H*(10) estimation and measurements around 18MV linac.

    Science.gov (United States)

    Cerón Ramírez, Pablo Víctor; Díaz Góngora, José Antonio Irán; Paredes Gutiérrez, Lydia Concepción; Rivera Montalvo, Teodoro; Vega Carrillo, Héctor René

    2016-11-01

    Thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the dose of neutron radiation in a treatment room with a linear electron accelerator of 18MV. Measurements were carried out through neutron ambient dose monitors which include pairs of thermoluminescent dosimeters TLD 600 ( 6 LiF: Mg, Ti) and TLD 700 ( 7 LiF: Mg, Ti), which were placed inside a paraffin spheres. The measurements has allowed to use NCRP 151 equations, these expressions are useful to find relevant dosimetric quantities. In addition, photoneutrons produced by linac head were calculated through MCNPX code taking into account the geometry and composition of the linac head principal parts. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Integrating techniques for neutron dosimetry in Linac 18 MV

    International Nuclear Information System (INIS)

    Ceron R, P. V.; Diaz G, J. A. I.; Rivera M, T.; Paredes G, L. C.; Vega C, H. R.

    2015-10-01

    In this paper thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the neutron dose equivalent in a radiotherapy room with a linear electron accelerator of 18 MV. The equivalent dose was measured at isocenter to 1.42 m of target and at the entrance of the labyrinth of the room of a Novalis Tx. The neutron detectors were constructed with pairs of thermoluminescent dosimeters TLD 600 ( 6 LiF: Mg, Ti) and TLD 700 ( 7 LiF: Mg, Ti) which are placed inside a paraffin sphere of 20 cm in diameter. These measurements enabled the calculation of equivalent dose in the gate and the source term, using the relationships contained in the NCRP-151. Through the models carried out with the code MCNPX the absorbed dose distribution with regard to depth in a paraffin phantom are included and the neutron spectrum produced by the head, taking into account the geometry and component materials. The results are in the order of neutron milli sievert by gray of X-rays (mSv/Gy x) which are in the same order as those found in other reports for different accelerators. (Author)

  8. Radiological safety around a Linac of 18 MV

    International Nuclear Information System (INIS)

    Ceron R, P.; Rivera M, T.; Paredes G, L.; Azorin N, J.; Sanchez, A.; Vega C, H. R.

    2014-10-01

    There are now several neutron detection systems, such as proportional counters based on BF 3 , He 3 and Bonner sphere spectrometers. However, the cost and complexity of the implementation of such systems makes them inaccessible for dosimetry purposes in radiotherapy rooms (Rt) and other facilities with this type of radiation fields. For these reasons the use of a neutron detection system is proposed composed by a paraffin moderator media forming an array 4π (spheres) and several pairs of thermoluminescent dosimeters TLD 600/TLD 700 inside, in order to make useful measurements for radiation protection around high-energy lineal accelerators (Linacs). In the first part of this work the system response when irradiated with a source of Pu Be and their corresponding calibration factor is displayed. In the second part are presented the ambient dose equivalent (H(10)) due to neutrons at various points of a living of Rt with a Linac of 18 MV, which are in the order mSv/Gy by X-ray treatment. The measurements made are similar to those taken in the memories of the accelerator and in previous work for this type of facility. (Author)

  9. Radiological safety around a Linac of 18 MV; Seguridad radiologica alrededor de un LINAC de 18 MV

    Energy Technology Data Exchange (ETDEWEB)

    Ceron R, P.; Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Calz. Legaria No. 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Paredes G, L. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Azorin N, J. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico D. F. (Mexico); Sanchez, A. [IPN, Escuela Superior de Fisica y Matematicas, Av. IPN s/n, Edif. 9, Col. San Pedro Zacatenco, 07738 Mexico D. F. (Mexico); Vega C, H. R., E-mail: victceronr@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 09868 Zacatecas (Mexico)

    2014-10-15

    There are now several neutron detection systems, such as proportional counters based on BF{sub 3}, He{sub 3} and Bonner sphere spectrometers. However, the cost and complexity of the implementation of such systems makes them inaccessible for dosimetry purposes in radiotherapy rooms (Rt) and other facilities with this type of radiation fields. For these reasons the use of a neutron detection system is proposed composed by a paraffin moderator media forming an array 4π (spheres) and several pairs of thermoluminescent dosimeters TLD 600/TLD 700 inside, in order to make useful measurements for radiation protection around high-energy lineal accelerators (Linacs). In the first part of this work the system response when irradiated with a source of Pu Be and their corresponding calibration factor is displayed. In the second part are presented the ambient dose equivalent (H(10)) due to neutrons at various points of a living of Rt with a Linac of 18 MV, which are in the order mSv/Gy by X-ray treatment. The measurements made are similar to those taken in the memories of the accelerator and in previous work for this type of facility. (Author)

  10. Integrating techniques for neutron dosimetry in Linac 18 MV; Integrando tecnicas para dosimetria de neutrones en un Linac de 18 MV

    Energy Technology Data Exchange (ETDEWEB)

    Ceron R, P. V.; Diaz G, J. A. I.; Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, 11500 Mexico D. F. (Mexico); Paredes G, L. C. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

    2015-10-15

    In this paper thermoluminescent dosimetry, analytical techniques and Monte Carlo calculations were used to estimate the neutron dose equivalent in a radiotherapy room with a linear electron accelerator of 18 MV. The equivalent dose was measured at isocenter to 1.42 m of target and at the entrance of the labyrinth of the room of a Novalis Tx. The neutron detectors were constructed with pairs of thermoluminescent dosimeters TLD 600 ({sup 6}LiF: Mg, Ti) and TLD 700 ({sup 7}LiF: Mg, Ti) which are placed inside a paraffin sphere of 20 cm in diameter. These measurements enabled the calculation of equivalent dose in the gate and the source term, using the relationships contained in the NCRP-151. Through the models carried out with the code MCNPX the absorbed dose distribution with regard to depth in a paraffin phantom are included and the neutron spectrum produced by the head, taking into account the geometry and component materials. The results are in the order of neutron milli sievert by gray of X-rays (mSv/Gy x) which are in the same order as those found in other reports for different accelerators. (Author)

  11. Shielding provision in an old 6MV bunker for a new 18MV linac

    International Nuclear Information System (INIS)

    Howlett, S.J.; Ebert, M.A.; Kenny, W.

    2004-01-01

    Full text: In October 2003 the Newcastle Mater Hospital commenced clinical use of a new Varian 21EX which replaced it's 14 year old Varian Clinac l800. The 1800 had only been enabled for 6MV X-ray beam for most of its clinical use but was enabled for 18MV for a period in 2000. This was to make up for the loss of an 18MV beam from another Clinac 1800 which was being replaced in a bunker designed for that higher energy. The new 21EX would provide both 6MV and 18MV beams for routine clinical use. The original bunker had been designed for the lower energy and hence additional shielding was required to meet radiation dose limits recommended in ICRP 60 and adopted in ARPANSA RPS6. A general radiation survey was conducted around the bunker area when the 18MV beam was available on the older linear accelerator. This rather unique situation provided data which would normally be impossible to obtain. Photon activation in the neutron door was a source of increased dose levels in the control area. Commercial design was contracted for the additional barrier calculations and supply. Additional shielding was required on one primary barrier and the neutron door. Post installation surveys were conducted and the R and V system was used for usage figures. Using dose constraints for public and occupational exposure, various survey points were measured around the bunker. This data was assessed in terms of calculated requirements, actual requirements and the ALARA principle for radiation shielding design. Review of staff dose histories was also performed. The final survey calculations showed the additional shielding more than adequate for the usage of 18MV and 6MV photon beams. The availability of the R and V data gives supporting evidence for design of barriers to be adjusted on usage values as has been reported in an earlier work at this centre. The issue of occupancy arises in this work as dose histories indicate. Typically barrier design is always conservative and survey results on

  12. Dosimetric evaluation of fattening filter free photon beams

    International Nuclear Information System (INIS)

    Lechner, W.

    2014-01-01

    Very recently, conventional treatment machines able to deliver flattening filter free photon have been introduced into clinical practice. An Elekta Pricise linear accelerator LINAC which was able to deliver 6MV and 10 MV flattened (FF) and flattening filter free (FFF) photon beams was used throughout this work. The investigated modalities were 9-Field intensity modulated radiotherapy (Intensity modulated radiotherapy (IMRT)) and 360° - single arc volumetric modulated arc therapy (Volumetric modulated arc therapy (VMAT)) with flattened and unflattened photon beams. For treatment plan evaluation the concept of Pareto optimal fronts was employed. Additionally, the efficiency of these modalities was assessed. The evaluation of the treatment plan quality showed no significant difference between FF- and FFF-beams. With respect to treatment plan efficiency, a significant decrease of delivery time of IMRT treatment plans without flattening filter compared to those with filter was found. On average, the delivery time decreased by 18% and 4% for prostate and head-and-neck cases, respectively. In contrast to that, the delivery time of VMAT treatment plans without flatting filter was significantly increased by 22% and 16% for prostate and head- and-neck cases, respectively. The applicability of 14 different detectors to small field dosimetry in FF- as well as in FFF-beams was investigated by measuring output factors of 6MV and 10 MV FF- and FFF- beams. An additional MLC was attached to the treatment machine in order to generate field sizes between 0.6x0.6 cm 2 and 10x10 cm 2 . Alanine pellets were used as reference detectors for the calculation of correction factors for small field dosimetry. Compared to alanine, the solid sate detectors and the liquid filled ionization chamber generally overestimated the output factors of small fields, whereas the air filled ionzation chambers underestimated the output factors. For the shielded diodes the correction factors ranged between 8

  13. Ambient neutron dose equivalent outside concrete vault rooms for 15 and 18 MV radiotherapy accelerators

    International Nuclear Information System (INIS)

    Martinez-ovalle, S. A.; Barquero, R.; Gomez-ros, J. M.; Lallena, A. M.

    2012-01-01

    In this work, the ambient dose equivalent, H*(10), due to neutrons outside three bunkers that house a 15- and a 18-MV Varian Clinac 2100C/D and a 15-MV Elekta Inor clinical linacs, has been calculated. The Monte Carlo code MCNPX (v. 2.5) has been used to simulate the neutron production and transport. The complete geometries including linacs and full installations have been built up according to the specifications of the manufacturers and the planes provided by the corresponding medical physical services of the hospitals where the three linacs operate. Two of these installations, those lodging the Varian linacs, have an entrance door to the bunker while the other one does not, although it has a maze with two bends. Various treatment orientations were simulated in order to establish plausible annual equivalent doses. Specifically anterior-posterior, posterior-anterior, left lateral, right lateral orientations and an additional one with the gantry rotated 30 deg. have been studied. Significant dose rates have been found only behind the walls and the door of the bunker, near the entrance and the console, with a maximum of 12 μSv h -1 . Dose rates per year have been calculated assuming a conservative workload for the three facilities. The higher dose rates in the corresponding control areas were 799 μSv y -1 , in the case of the facility which operates the 15-MV Clinac, 159 μSv y -1 , for that with the 15-MV Elekta, and 21 μSv y -1 for the facility housing the 18-MV Varian. A comparison with measurements performed in similar installations has been carried out and a reasonable agreement has been found. The results obtained indicate that the neutron contamination does not increase the doses above the legal limits and does not produce a significant enhancement of the dose equivalent calculated. When doses are below the detection limits provided by the measuring devices available today, MCNPX simulation provides an useful method to evaluate neutron dose equivalents

  14. Dosimetric characterization of the 18-MV photon beam from the Siemens Mevatron 77 linear accelerator

    International Nuclear Information System (INIS)

    Palta, J.R.; Meyer, J.A.; Hogstrom, K.R.

    1984-01-01

    A comprehensive set of dosimetric measurements has been made on the Mevatron 77.80.67 18-MV photon beam. Percentage depth dose, dose in the buildup region, field size dependence of output, transmission through lead, tray attenuation, and isodose curves for the open and wedged fields were measured using an ionization chamber in water and polystyrene phantoms. These dosimetric measurements sufficiently characterized the beam to permit clinical use. The depth dose at 10-cm depth for a 10 x 10 cm 2 field at 100-cm source-to-skin distance (SSD) is 80.9%, which meets design specifications. Central axis depth-dose data were fitted to within 0.5% by a set of polynomial equations utilizing a two-dimensional linear regression analysis. Tissue--maximum ratios calculated from depth-dose data agree with measured data to within 2%. Output differences as large as 2.5% were measured for rectangular fields depending on which collimator jaws defined the long dimension of the field. The field size dependence of output was fit to within +- 0.1% by a linear regression. The half-value thickness of the beam was measured to be 13 mm of lead

  15. Neutron spectra and H*(10) around and 18 MV Linac by Ann's

    Energy Technology Data Exchange (ETDEWEB)

    Banuelos F, A.; Valero L, C.; Borja H, C. G.; Hernandez D, V. M.; Vega C, H. R., E-mail: alanb535@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2011-10-15

    Neutron spectra and ambient dose equivalent H*(10) were calculated for a radiotherapy room in 16 point-like detectors, 15 located inside the vault room and 1 located outside the bunker. The calculation was carried out using Monte Carlo Methods with the MCNP5 code for a generic radiotherapy room model operating with a 18 MV Linac, obtaining 16 neutron spectra with 47 energy bins, the H*(10) values were calculated from the neutron spectra by the use of the fluence-dose conversion factors. An artificial neural network were designed and trained to determine the neutron H*(10) in 15 different locations inside the vault room from the H*(10) dose calculated for the detector located outside the room, using the calculated dose values as training set, using the scaled conjugated gradient training algorithm. The mean squared error set for the network training was 1E(-14), adjusting the data in 99.992 %. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. The results shows the using this artificial intelligence technic as a useful tool for the neutron spectrometry and dosimetry by the simplification on the neutronic fields characterization inside radiotherapy rooms avoiding the use of traditional spectrometric systems. And once the H*(10) doses have been calculated, to take the appropriated actions to reduce or prevent the patient and working staff exposure to this undesirable neutron radiation. (Author)

  16. Neutron spectra and H*(10) around and 18 MV Linac by Ann's

    International Nuclear Information System (INIS)

    Banuelos F, A.; Valero L, C.; Borja H, C. G.; Hernandez D, V. M.; Vega C, H. R.

    2011-10-01

    Neutron spectra and ambient dose equivalent H*(10) were calculated for a radiotherapy room in 16 point-like detectors, 15 located inside the vault room and 1 located outside the bunker. The calculation was carried out using Monte Carlo Methods with the MCNP5 code for a generic radiotherapy room model operating with a 18 MV Linac, obtaining 16 neutron spectra with 47 energy bins, the H*(10) values were calculated from the neutron spectra by the use of the fluence-dose conversion factors. An artificial neural network were designed and trained to determine the neutron H*(10) in 15 different locations inside the vault room from the H*(10) dose calculated for the detector located outside the room, using the calculated dose values as training set, using the scaled conjugated gradient training algorithm. The mean squared error set for the network training was 1E(-14), adjusting the data in 99.992 %. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. The results shows the using this artificial intelligence technic as a useful tool for the neutron spectrometry and dosimetry by the simplification on the neutronic fields characterization inside radiotherapy rooms avoiding the use of traditional spectrometric systems. And once the H*(10) doses have been calculated, to take the appropriated actions to reduce or prevent the patient and working staff exposure to this undesirable neutron radiation. (Author)

  17. A study on the photoneutron dose estimation in flattening filter mode and flattening filter free mode for medical linear accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Oh Nam [Dept. of Radiology, Mokpo Science University, Mokpo (Korea, Republic of); Lim, Cheong Hwan [Dept. of Radiological Science, Hanseo University, Seosan (Korea, Republic of)

    2017-06-15

    In this study, the generation of photoneutrons between the 10 MV FF mode and the FFF mode was evaluated and the amount of photoneutrons generated by the 10 MV and 15 MV energy changes in the FFF mode was evaluated. The generated neutrons were evaluated at 13 measurement points and the KTEPC was used to collect the generated neutrons. 10 MV FF mode was measured at 10 MV FF mode and FFF mode at all measurement points. In the superior direction, 0.455mSv and 0.152mSv were the largest, and more than 33% optical neutron was generated in FF. 10 MV in FFF mode, 15 MV in 15 MV, and 0.402 mSv in the direction of Superior, and 6.9% in the direction.

  18. Acquiring beam data for a flattening-filter free linear accelerator using organic scintillators

    DEFF Research Database (Denmark)

    Beierholm, Anders Ravnsborg; Behrens, C.F.; Hoffmann, L.

    2013-01-01

    Fibre-coupled organic scintillators have been proven a credible alternative to clinically implemented methods for radiotherapy dosimetry, primarily due to their water equivalence and good spatial resolution. Furthermore, the fast response of the scintillators can be exploited to perform time-reso...

  19. Relative measurements of fast neutron contamination in 18-MV photon beams from two linear accelerators and a betatron

    International Nuclear Information System (INIS)

    Gur, D.; Bukovitz, A.G.; Rosen, J.C.; Holmes, B.G.

    1979-01-01

    Fast neutron contamination in photon beams in the 20 MV range have been reported in recent years. In order to determine if the variations were due mainly to differences in measurement procedures, or inherent in the design of the accelerators, three different 18-MV (BJR) photon beams were compared using identical analytical techniques. The units studied were a Philips SL/75-20 and a Siemens Mevatron-20 linear accelerators and a Schimadzu betatron. Gamma spectroscopy of an activated aluminum foil was the method used. By comparing the relative amounts of neutron contamination, errors associated with absolute measurements such as detector efficiency and differences in activation foils were eliminated. Fast neutron contaminations per rad of x rays in a ratio of 6.7:3.7:1 were found for the Philips, Schimadzu and Siemens accelerators, respectively

  20. Fast and slow neutrons in an 18-MV photon beam from a Philips SL/75-20 linear accelerator

    International Nuclear Information System (INIS)

    Gur, D.; Rosen, J.C.; Bukovitz, A.G.; Gill, A.W.

    1978-01-01

    Fast- and slow-neutron contamination in an 18-MV photon beam from a Philips SL/75-20 linear accelerator has been measured. Aluminum and indium foils were activated to determine fast- and slow-neutron fluence, which were largely independent of field sizes. Measured fast-neutron fluences were typically 13.9 x 10 4 and 4.4 x 10 4 neutrons/cm 2 /rad of x ray inside and 5 cm outside the field, respectively. Slow-neutron fluences, 1.3 x 10 4 neutrons/cm 2 /rad of x ray, remained relatively constant inside and outside the field. The reported results are about three times higher than neutron fluences recently reported with a betatron operated at the same energy

  1. Eukaryotic cell flattening

    Science.gov (United States)

    Bae, Albert; Westendorf, Christian; Erlenkamper, Christoph; Galland, Edouard; Franck, Carl; Bodenschatz, Eberhard; Beta, Carsten

    2010-03-01

    Eukaryotic cell flattening is valuable for improving microscopic observations, ranging from bright field to total internal reflection fluorescence microscopy. In this talk, we will discuss traditional overlay techniques, and more modern, microfluidic based flattening, which provides a greater level of control. We demonstrate these techniques on the social amoebae Dictyostelium discoideum, comparing the advantages and disadvantages of each method.

  2. Artificial neural network for the determination of neutron spectra in the bunker of a Linac of 18 MV

    International Nuclear Information System (INIS)

    Banuelos F, A.; Borja H, C. G.; Valero L, C.; Guzman G, K. A.; Hernandez D, V. M.; Vega C, H. R.

    2011-11-01

    The neutron spectrum and equivalent of environmental dose H(10) were calculated for a radiotherapy room in 16 punctual detectors, 15 inside of and 1 outside of the same one. The calculations were carried out with the Monte Carlo method and with the code MCNP5 for a generic room model with a Linac of 18 MV, obtaining this way 16 spectra with 47 intervals of energy class, starting from these spectra the values of H(10) were calculated. On the other hand, an artificial neural network was designed and trained to determine the spectra by neutrons in 15 different locations inside the radiotherapy room starting from the value of H(10) in the detector 16 located in the exterior of the room, using as training data the spectra and calculated dose by neutrons, of which a medium quadratic error was obtained (m se) in the adjustment between the objective data and the exit data of m se=1E(-8). The results demonstrate that the use of the artificial intelligence as technique is an useful tool in the spectrometry and dosimetry of neutrons, since it simplifies the characterization process of neutron fields in radiotherapy rooms without the use of spectrometry systems, and that once the energy distribution of the neutrons produced by the Linac is known and the corresponding doses be calculated H(10), they can take the appropriate cautions for the security patient in treatment as well as for the personnel in the room. (Author)

  3. Simplified geometric model for the calculation of neutron yield in an accelerator of 18 MV for radiotherapy

    International Nuclear Information System (INIS)

    Paredes G, L.C.; Balcazar G, M.; Francois L, J.L.; Azorin N, J.

    2008-01-01

    The results of the neutrons yield in different components of the bolster of an accelerator Varian Clinac 2100C of 18 MV for radiotherapy are presented, which contribute to the radiation of flight of neutrons in the patient and bolster planes. For the calculation of the neutrons yield, a simplified geometric model of spherical cell for the armor-plating of the bolster with Pb and W was used. Its were considered different materials for the Bremsstrahlung production and of neutrons produced through the photonuclear reactions and of electro disintegration, in function of the initial energy of the electron. The theoretical result of the total yield of neutrons is of 1.17x10 -3 n/e, considering to the choke in position of closed, in the patient plane with a distance source-surface of 100 cm; of which 15.73% corresponds to the target, 58.72% to the primary collimator, 4.53% to the levelled filter of Fe, 4.87% to the levelled filter of Ta and 16.15% to the closed choke. For an initial energy of the electrons of 18 MeV, a half energy of the neutrons of 2 MeV was obtained. The calculated values for radiation of experimental neutrons flight are inferior to the maxima limit specified in the NCRP-102 and IEC-60601-201.Ed.2.0 reports. The absorbed dose of neutrons determined through the measurements with TLD dosemeters in the isocenter to 100 cm of the target when the choke is closed one, is approximately 3 times greater that the calculated for armor-plating of W and 1.9 times greater than an armor-plating of Pb. (Author)

  4. Treatment-Planning Study of Prostate Cancer Intensity-Modulated Radiotherapy With a Varian Clinac Operated Without a Flattening Filter

    International Nuclear Information System (INIS)

    Vassiliev, Oleg N.; Kry, Stephen F.; Kuban, Deborah A.; Salehpour, Mohammad; Mohan, Radhe; Titt, Uwe

    2007-01-01

    Purpose: To assess the feasibility of intensity-modulated radiotherapy for prostate cancer using photon beams from an accelerator operated without a flattening filter; and to determine potential benefits and drawbacks of using unflattened beams for this type of treatment. Methods and Materials: Intensity-modulated radiotherapy plans were generated for 10 patients with early-stage prostate cancer. For each patient, four plans were generated: with and without the flattening filter, at 6 and 18 MV. The prescription dose was 75.6 Gy to 98% of the planning target volume. The number of beams, their orientations, and optimization constraints were the same for all plans. Plans were generated with Eclipse 8.0 (Varian Medical Systems). Results: All the plans developed with unflattened beams were clinically acceptable. In terms of patient dose distributions, plans with unflattened beams were similar to the corresponding plans with flattened beams. Plans with unflattened beams required fewer monitor units (MUs) per plan: on average, by a factor of 2.0 at 6 MV and 2.6 at 18 MV, assuming that removal of the flattening filter was not followed by recalibration of MUs. Conclusions: Clinically acceptable intensity-modulated radiotherapy plans for prostate cancer can be developed with unflattened beams at both 6 and 18 MV. Dosimetrically, flattened and unflattened beams generated similar treatment plans. The plans with unflattened beams required substantially fewer MUs. The reduction in the number of MUs indicates corresponding reduction in beam-on time and in the amount of radiation outside the target

  5. Irradiation with x-rays of the energy 18 MV induces radioactivity in transfusion blood: Proposal of a safe method using 6 MV.

    Science.gov (United States)

    Frentzel, Katharina; Badakhshi, Harun

    2016-12-01

    To prevent a fatal transfusion-associated graft-versus-host disease, it is recommended to irradiate transfusion blood and blood components with ionizing radiation. Using x-rays from a linear accelerator of the radiotherapy department is an accepted alternative to gamma irradiation devices of the blood bank and to the orthovoltage units that are replacing the gamma irradiators today. However, the use of high energy x-rays may carry a potential risk of induced radioactivity. The objective of this study was to investigate the effect of two different energy levels, 6 and 18 MV, which are executed in routine clinical settings. The research question was if induced radioactivity occurs at one of these standard energy levels. The authors aimed to give a proposal for a blood irradiation procedure that certainly avoids induced radioactivity. For this study, the authors developed a blood bag phantom, irradiated it with x-ray energies of 6 and 18 MV, and measured the induced radioactivity in a well counter. Thereafter, the same irradiation and measuring procedure was performed with a unit of packed red blood cells. A feasible clinical procedure was developed using 6 MV and an acrylic box. With the irradiation planning system XiO, the authors generated an irradiation protocol for the linear accelerator Siemens ONCOR Anvant-Garde. Both measurement setups showed that there was induced radioactivity for 18 MV but not for 6 MV. The induced radioactivity for 18 MV was up to 190 times the background. This is significant and of clinical relevance especially since there are newborn and fetal blood recipients for whom every radiation exposure has to be strictly avoided. The irradiation of blood with x-rays from a linear accelerator of the radiotherapy department is safe and feasible, but by the current state of scientific knowledge, the authors recommend to use an x-ray energy of 6 MV or less to avoid induced radioactivity in transfusion blood.

  6. Radiation transmission of heavyweight and normal-weight concretes containing colemanite for 6 MV and 18 MV X-rays using linear accelerator

    International Nuclear Information System (INIS)

    Demir, F.; Budak, G.; Sahin, R.; Karabulut, A.; Oltulu, M.; Serifoglu, K.; Un, A.

    2010-01-01

    Accurate measurements have been made to determine radiation transmission of concretes produced with barite, colemanite and normal aggregate by using beam transmission method for 6 and 18 MV X-rays with a linear accelerator (LINAC). Linear attenuation coefficients of thirteen heavy- and four normal-weight concretes were calculated. It was determined that linear attenuation coefficient (μ, cm -1 ) decreased with colemanite concentration and increased with barite concentration in both types of the concretes.

  7. Dose-volume histogram comparison between static 5-field IMRT with 18-MV X-rays and helical tomotherapy with 6-MV X-rays.

    Science.gov (United States)

    Hayashi, Akihiro; Shibamoto, Yuta; Hattori, Yukiko; Tamura, Takeshi; Iwabuchi, Michio; Otsuka, Shinya; Sugie, Chikao; Yanagi, Takeshi

    2015-03-01

    We treated prostate cancer patients with static 5-field intensity-modulated radiation therapy (IMRT) using linac 18-MV X-rays or tomotherapy with 6-MV X-rays. As X-ray energies differ, we hypothesized that 18-MV photon IMRT may be better for large patients and tomotherapy may be more suitable for small patients. Thus, we compared dose-volume parameters for the planning target volume (PTV) and organs at risk (OARs) in 59 patients with T1-3 N0M0 prostate cancer who had been treated using 5-field IMRT. For these same patients, tomotherapy plans were also prepared for comparison. In addition, plans of 18 patients who were actually treated with tomotherapy were analyzed. The evaluated parameters were homogeneity indicies and a conformity index for the PTVs, and D2 (dose received by 2% of the PTV in Gy), D98, Dmean and V10-70 Gy (%) for OARs. To evaluate differences by body size, patients with a known body mass index were grouped by that index ( 25 kg/m(2)). For the PTV, all parameters were higher in the tomotherapy plans compared with the 5-field IMRT plans. For the rectum, V10 Gy and V60 Gy were higher, whereas V20 Gy and V30 Gy were lower in the tomotherapy plans. For the bladder, all parameters were higher in the tomotherapy plans. However, both plans were considered clinically acceptable. Similar trends were observed in 18 patients treated with tomotherapy. Obvious trends were not observed for body size. Tomotherapy provides equivalent dose distributions for PTVs and OARs compared with 18-MV 5-field IMRT. Tomotherapy could be used as a substitute for high-energy photon IMRT for prostate cancer regardless of body size. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  8. Lepton contamination and photon scatter produced by open field 18 MV X-ray beams in the build-up region

    International Nuclear Information System (INIS)

    Butson, M.J.; Cheung Tsang; Yu, P.K.N.

    2002-01-01

    18 MV X-ray beams used in radiotherapy have skin sparing properties as they produce a dose build-up effect whereby a smaller dose is delivered to the skin compared to dose at depth. Experimental results have shown that variations in the build-up dose significantly contribute to lepton contamination produced outside of the patient or the phantom in question. Monte Carlo simulations of 18 MV X-ray beams show that the surface dose contribution from in-phantom scatter alone is approximately 6% of the maximum dose. The contribution to dose from lepton contamination is found by comparison of Monte Carlo phantom photon scatter dose only and experimental data. Results show that the percentage contributions to dose from lepton contamination are approximately, 65%, 90% of dose at 0.05 mm (basal cell layer), 52%, 79% at 1 mm depth (dermal layer) and 15%, 26% at 10 mm depth (subcutaneous tissue) for 10 cmx10 cm 2 and 40 cmx40 cm 2 fields, respectively

  9. Lepton contamination and photon scatter produced by open field 18 MV X-ray beams in the build-up region

    Energy Technology Data Exchange (ETDEWEB)

    Butson, M.J. E-mail: mbutson@guessmail.com; Cheung Tsang; Yu, P.K.N

    2002-04-01

    18 MV X-ray beams used in radiotherapy have skin sparing properties as they produce a dose build-up effect whereby a smaller dose is delivered to the skin compared to dose at depth. Experimental results have shown that variations in the build-up dose significantly contribute to lepton contamination produced outside of the patient or the phantom in question. Monte Carlo simulations of 18 MV X-ray beams show that the surface dose contribution from in-phantom scatter alone is approximately 6% of the maximum dose. The contribution to dose from lepton contamination is found by comparison of Monte Carlo phantom photon scatter dose only and experimental data. Results show that the percentage contributions to dose from lepton contamination are approximately, 65%, 90% of dose at 0.05 mm (basal cell layer), 52%, 79% at 1 mm depth (dermal layer) and 15%, 26% at 10 mm depth (subcutaneous tissue) for 10 cmx10 cm{sup 2} and 40 cmx40 cm{sup 2} fields, respectively.

  10. Constituent Components of Out-of-Field Scatter Dose for 18-MV Intensity Modulated Radiation Therapy Versus 3-Dimensional Conformal Radiation Therapy: A Comparison With 6-MV and Implications for Carcinogenesis

    International Nuclear Information System (INIS)

    Ruben, Jeremy D.; Smith, Ryan; Lancaster, Craig M.; Haynes, Matthew; Jones, Phillip; Panettieri, Vanessa

    2014-01-01

    Purpose: To characterize and compare the components of out-of-field dose for 18-MV intensity modulated radiation therapy (IMRT) versus 3-dimensional conformal radiation therapy (3D-CRT) and their 6-MV counterparts and consider implications for second cancer induction. Methods and Materials: Comparable plans for each technique/energy were delivered to a water phantom with a sloping wall; under full scatter conditions; with field edge abutting but outside the bath to prevent internal/phantom scatter; and with shielding below the linear accelerator head to attenuate head leakage. Neutron measurements were obtained from published studies. Results: Eighteen-megavolt IMRT produces 1.7 times more out-of-field scatter than 18-MV 3D-CRT. In absolute terms, however, differences are just approximately 0.1% of central axis dose. Eighteen-megavolt IMRT reduces internal/patient scatter by 13%, but collimator scatter (C) is 2.6 times greater than 18-MV 3D-CRT. Head leakage (L) is minimal. Increased out-of-field photon scatter from 18-MV IMRT carries out-of-field second cancer risks of approximately 0.2% over and above the 0.4% from 18-MV 3D-CRT. Greater photoneutron dose from 18-MV IMRT may result in further maximal, absolute increased risk to peripheral tissue of approximately 1.2% over 18-MV 3D-CRT. Out-of-field photon scatter remains comparable for the same modality irrespective of beam energy. Machine scatter (C+L) from 18 versus 6 MV is 1.2 times higher for IMRT and 1.8 times for 3D-CRT. It is 4 times higher for 6-MV IMRT versus 3D-CRT. Reduction in internal scatter with 18 MV versus 6 MV is 27% for 3D-CRT and 29% for IMRT. Compared with 6-MV 3D-CRT, 18-MV IMRT increases out-of-field second cancer risk by 0.2% from photons and adds 0.28-2.2% from neutrons. Conclusions: Out-of-field photon dose seems to be independent of beam energy for both techniques. Eighteen-megavolt IMRT increases out-of-field scatter 1.7-fold over 3D-CRT because of greater collimator scatter despite

  11. Measurementof photo-neutron dose from an 18-MV medical linac using a foil activation method in view of radiation protection of patients

    International Nuclear Information System (INIS)

    Yuecel, Haluk; Kolbasi, Asuman; Yueksel, Alptug Oezer; Cobanbas, Ibrahim; Kaya, Vildan

    2016-01-01

    High-energy linear accelerators are increasingly used in the medical field. However, the unwanted photo-neutrons can also be contributed to the dose delivered to the patients during their treatments. In this study, neutron fluxes were measured in a solid water phantom placed at the isocenter 1-m distance from the head of an 18-MV linac using the foil activation method. The produced activities were measured with a calibrated well-type Ge detector. From the measured fluxes, the total neutron fluence was found to be (1.17 ± 0.06) X 10 7 n/cm 2 per Gy at the phantom surface in a 20 X 20 cm 2 X-ray field size. The maximum photo-neutron dose was measured to be 0.67 ± 0.04 mSv/Gy at d max = 5 cm depth in the phantom at isocenter. The present results are compared with those obtained for different field sizes of 10 X 10cm 2 , 15 X 15cm 2 , and 20 X 20cm 2 from 10-, 15-, and 18-MV linacs. Additionally, ambient neutron dose equivalents were determined at different locations in the room and they were found to be negligibly low. The results indicate that the photo-neutron dose at the patient position is not a negligible fraction of the therapeutic photon dose. Thus, there is a need for reduction of the contaminated neutron dose by taking some additional measures, for instance, neutron absorbing-protective materials might be used as aprons during the treatment

  12. Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-192 Internal and 18 MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method

    Directory of Open Access Journals (Sweden)

    Khosravi H.

    2015-03-01

    Full Text Available Background: Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions. Objective: The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC method for studying the effect of gold nanoparticles (GNPs in prostate dose distributions under the internal Ir-192 and external 18MV radiotherapy practices. Method: A Plexiglas phantom was made representing human pelvis. The GNP shaving 15 nm in diameter and 0.1 mM concentration were synthesized using chemical reduction method. Then, a new formulation of MAGIC-f gel was synthesized. The fabricated gel was poured in the tubes located at the prostate (with and without the GNPs and bladder locations of the phantom. The phantom was irradiated to an Ir-192 source and 18 MV beam of a Varian linac separately based on common radiotherapy procedures used for prostate cancer. After 24 hours, the irradiated gels were read using a Siemens 1.5 Tesla MRI scanner. The absolute doses at the reference points and isodose curves resulted from the experimental measurement of the gels and MC simulations following the internal and external radiotherapy practices were compared. Results: The mean absorbed doses measured with the gel in the presence of the GNPs in prostate were 15% and 8 % higher than the corresponding values without the GNPs under the internal and external radiation therapies, respectively. MC simulations also indicated a dose increase of 14 % and 7 % due to presence of the GNPs, for the same experimental internal and external radiotherapy practices, respectively. Conclusion: There was a good agreement between the dose enhancement factors (DEFs estimated with MC simulations and experiment gel measurements due to the GNPs. The results indicated that the polymer gel dosimetry method as developed and used in this study, can be recommended as a reliable method for investigating the DEF of GNPs in internal

  13. Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-192 Internal and 18 MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method.

    Science.gov (United States)

    Khosravi, H; Hashemi, B; Mahdavi, S R; Hejazi, P

    2015-03-01

    Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions. The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC) method for studying the effect of gold nanoparticles (GNPs) in prostate dose distributions under the internal Ir-192 and external 18MV radiotherapy practices. A Plexiglas phantom was made representing human pelvis. The GNP shaving 15 nm in diameter and 0.1 mM concentration were synthesized using chemical reduction method. Then, a new formulation of MAGIC-f gel was synthesized. The fabricated gel was poured in the tubes located at the prostate (with and without the GNPs) and bladder locations of the phantom. The phantom was irradiated to an Ir-192 source and 18 MV beam of a Varian linac separately based on common radiotherapy procedures used for prostate cancer. After 24 hours, the irradiated gels were read using a Siemens 1.5 Tesla MRI scanner. The absolute doses at the reference points and isodose curves resulted from the experimental measurement of the gels and MC simulations following the internal and external radiotherapy practices were compared. The mean absorbed doses measured with the gel in the presence of the GNPs in prostate were 15% and 8 % higher than the corresponding values without the GNPs under the internal and external radiation therapies, respectively. MC simulations also indicated a dose increase of 14 % and 7 % due to presence of the GNPs, for the same experimental internal and external radiotherapy practices, respectively. There was a good agreement between the dose enhancement factors (DEFs) estimated with MC simulations and experiment gel measurements due to the GNPs. The results indicated that the polymer gel dosimetry method as developed and used in this study, can be recommended as a reliable method for investigating the DEF of GNPs in internal and external radiotherapy practices.

  14. Ambient dose equivalent and personal points due to photoneutrons outside a facility that houses a linear accelerator of 18 MV varian; Equivalente de dosis ambiental y personal debida a fotoneutrones en puntos externos a una instalacion que alberga un acelerador lineal varian de 18 MV

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, S. A.; Barquero, R.; Gomez-Ros, J. M.; Lallena, A. M.; Ponzano, P. E.

    2011-07-01

    The use of linear accelerators (linacs) with energies above 10 MV radiotherapy treatments RT and IMRT, can improve the distribution of the absorbed dose in the treated area, increasing the effectiveness of radiation treatments. However and as shown in the scientific literature, the production of photoneutrons for energies above 10 MeV can contribute to exposure of both patient and occupationally exposed workers and the public in the vicinity of the installation. It is therefore necessary to determine the value of ambient dose equivalent and staff both inside and outside the facilities that house these accelerators, especially for energies of 15 and 18 MV.

  15. Analysis of latent variance reduction methods in phase space Monte Carlo calculations for 6, 10 and 18 MV photons by using MCNP code

    International Nuclear Information System (INIS)

    Ezzati, A.O.; Sohrabpour, M.

    2013-01-01

    In this study, azimuthal particle redistribution (APR), and azimuthal particle rotational splitting (APRS) methods are implemented in MCNPX2.4 source code. First of all, the efficiency of these methods was compared to two tallying methods. The APRS is more efficient than the APR method in track length estimator tallies. However in the energy deposition tally, both methods have nearly the same efficiency. Latent variance reduction factors were obtained for 6, 10 and 18 MV photons as well. The APRS relative efficiency contours were obtained. These obtained contours reveal that by increasing the photon energies, the contours depth and the surrounding areas were further increased. The relative efficiency contours indicated that the variance reduction factor is position and energy dependent. The out of field voxels relative efficiency contours showed that latent variance reduction methods increased the Monte Carlo (MC) simulation efficiency in the out of field voxels. The APR and APRS average variance reduction factors had differences less than 0.6% for splitting number of 1000. -- Highlights: ► The efficiency of APR and APRS methods was compared to two tallying methods. ► The APRS is more efficient than the APR method in track length estimator tallies. ► In the energy deposition tally, both methods have nearly the same efficiency. ► Variance reduction factors of these methods are position and energy dependent.

  16. WE-FG-BRA-05: Potential Clinical Benefit of LINAC Flattening-Filter-Free (FFF) Mode - Improvement of Treatment Therapeutic Ratio

    International Nuclear Information System (INIS)

    Chang, S; Rivera, J; Tian, H; Price, A; Santos, C; Zhang, Y

    2016-01-01

    Purpose: Ultrahigh dose-rate radiation at >40Gy/s has demonstrated astonishing normal-tissue sparing and tumor control in recent preclinical naive and tumor-bearing rodent studies when compared to the same radiation dose at a conventional dose-rate. The working mechanism of this fascinating dose-rate effect is currently under investigation. The aims of this work include investigating 1) whether LINAC FFF mode radiation at approximately 1Gy/s also has an improved therapeutic ratio compared to the same radiation dose at the conventional dose-rate of 0.05Gy/s, and 2) the dose-rate effect’s potential working mechanism by studying the expression of the P53 gene, linked to tumor suppression and cell regulation after radiation damage. Methods: We used mouse model C57BL/6J, the same as that used in the ultrahigh dose-rate studies, and exposed them to total body irradiation (TBI) using the Elekta Versa accelerator 10MV photons. Mice (N=20) were given a total dose of 12Gy in both the high dose-rate group (n=10) using the FFF-mode and the conventional dose-rate group (n=10) using the conventional does rate mode. The FFF-mode treatment setup consisted of a 15cm×15cm field size setting at 53.2cm SSD while the conventional-mode set-up consisted of a 10cm×10cm field size at 100SSD. Post-radiation, animals were monitored daily for survival analysis and signs of moribundity requiring euthanasia. In addition, mouse spleens were harvested for P53 analysis at different time points. Results: For 12Gy TBI, the 1.3Gy/s FFF-mode high dose-rate produced a statistically significant (p=0.02) improvement in mouse survival compared to the 0.05Gy/s conventional dose-rate. An initial P53 study at the time of death time-point indicates that high dose-rate radiation induced a stronger expression of P53 than conventional dose-rate radiation. Conclusion: Our pilot study indicates that the FFF-mode high dose-rate radiation, which has been used largely to improve clinical throughput, may provide the added clinical benefit of improving treatment therapeutic ratio. Animal Studies were performed within the LCCC Animal Studies Core Facility at the University of North Carolina at Chapel Hill. The LCCC Animal Studies Core is supported in part by an NCI Center Core Support Grant (CA16086) to the UNC Lineberger Comprehensive Cancer Center

  17. Interplay effect on a 6-MV flattening-filter-free linear accelerator with high dose rate and fast multi-leaf collimator motion treating breast and lung phantoms.

    Science.gov (United States)

    Netherton, Tucker; Li, Yuting; Nitsch, Paige; Shaitelman, Simona; Balter, Peter; Gao, Song; Klopp, Ann; Muruganandham, Manickam; Court, Laurence

    2018-06-01

    Using a new linear accelerator with high dose rate (800 MU/min), fast MLC motions (5.0 cm/s), fast gantry rotation (15 s/rotation), and 1 cm wide MLCs, we aimed to quantify the effects of complexity, arc number, and fractionation on interplay for breast and lung treatments under target motion. To study lung interplay, eight VMAT plans (1-6 arcs) and four-nine-field sliding-window IMRT plans varying in complexity were created. For the breast plans, four-four-field sliding-window IMRT plans were created. Using the Halcyon 1.0 linear accelerator, each plan was delivered five times each under sinusoidal breathing motion to a phantom with 20 implanted MOSFET detectors; MOSFET dose (cGy), delivery time, and MU/cGy values were recorded. Maximum and mean dose deviations were calculated from MOSFET data. The number of MOSFETs with at least 19 of 20 detectors agreeing with their expected dose within 5% per fraction was calculated across 10 6 iterations to model dose deviation as function of fraction number for all plan variants. To put interplay plans into clinical context, additional IMRT and VMAT plans were created and delivered for the sites of head and neck, prostate, whole brain, breast, pelvis, and lung. Average modulation and interplay effect were compared to those from conventional linear accelerators, as reported from previous studies. The mean beam modulation for plans created for the Halcyon 1.0 linear accelerator was 2.9 MU/cGy (two- to four-field IMRT breast plans), 6.2 MU/cGy (at least five-field IMRT), and 3.6 MU/cGy (four-arc VMAT). To achieve treatment plan objectives, Halcyon 1.0 VMAT plans require more arcs and modulation than VMAT on conventional linear accelerators. Maximum and mean dose deviations increased with increasing plan complexity under tumor motion for breast and lung treatments. Concerning VMAT plans under motion, maximum, and mean dose deviations were higher for one arc than for two arcs regardless of plan complexity. For plan variants with maximum dose deviations greater than 3.7%, dose deviation as a function of fraction number was protracted. For treatments on the Halcyon 1.0 linear accelerator, the convergence of dose deviation with fraction number happened more slowly than reported for conventional linear accelerators. However, if plan complexity is reduced for IMRT and if tumor motion is less than ~10-mm, interplay is greatly reduced. To minimize dose deviations across multiple fractions for dynamic targets, we recommend limiting treatment plan complexity and avoiding one-arc VMAT on the Halcyon 1.0 linear accelerator when interplay is a concern. © 2018 American Association of Physicists in Medicine.

  18. WE-FG-BRA-05: Potential Clinical Benefit of LINAC Flattening-Filter-Free (FFF) Mode - Improvement of Treatment Therapeutic Ratio

    Energy Technology Data Exchange (ETDEWEB)

    Chang, S [Department of Radiation Oncology, UNC School of Medicine, Chapel Hill, NC (United States); Department of Biomedical Engineering, University of North Carolina- Chapel Hill/ North Carolina State University, Chapel Hill, North Carolina (United States); Lineberger Clinical Cancer Center, University of North Carolina, Chapel Hill, NC (United States); Rivera, J [Department of Biomedical Engineering, University of North Carolina- Chapel Hill/ North Carolina State University, Chapel Hill, North Carolina (United States); Tian, H [Xuzhou Medical College, Xuzhou, Jiangsu (China); Lineberger Clinical Cancer Center, University of North Carolina, Chapel Hill, NC (United States); Price, A [Department of Radiation Oncology, UNC School of Medicine, Chapel Hill, NC (United States); Santos, C [Lineberger Clinical Cancer Center, University of North Carolina, Chapel Hill, NC (United States); Zhang, Y [Department of Radiation Oncology, UNC School of Medicine, Chapel Hill, NC (United States); Xuzhou Medical College, Xuzhou, Jiangsu (China); Lineberger Clinical Cancer Center, University of North Carolina, Chapel Hill, NC (United States)

    2016-06-15

    Purpose: Ultrahigh dose-rate radiation at >40Gy/s has demonstrated astonishing normal-tissue sparing and tumor control in recent preclinical naive and tumor-bearing rodent studies when compared to the same radiation dose at a conventional dose-rate. The working mechanism of this fascinating dose-rate effect is currently under investigation. The aims of this work include investigating 1) whether LINAC FFF mode radiation at approximately 1Gy/s also has an improved therapeutic ratio compared to the same radiation dose at the conventional dose-rate of 0.05Gy/s, and 2) the dose-rate effect’s potential working mechanism by studying the expression of the P53 gene, linked to tumor suppression and cell regulation after radiation damage. Methods: We used mouse model C57BL/6J, the same as that used in the ultrahigh dose-rate studies, and exposed them to total body irradiation (TBI) using the Elekta Versa accelerator 10MV photons. Mice (N=20) were given a total dose of 12Gy in both the high dose-rate group (n=10) using the FFF-mode and the conventional dose-rate group (n=10) using the conventional does rate mode. The FFF-mode treatment setup consisted of a 15cm×15cm field size setting at 53.2cm SSD while the conventional-mode set-up consisted of a 10cm×10cm field size at 100SSD. Post-radiation, animals were monitored daily for survival analysis and signs of moribundity requiring euthanasia. In addition, mouse spleens were harvested for P53 analysis at different time points. Results: For 12Gy TBI, the 1.3Gy/s FFF-mode high dose-rate produced a statistically significant (p=0.02) improvement in mouse survival compared to the 0.05Gy/s conventional dose-rate. An initial P53 study at the time of death time-point indicates that high dose-rate radiation induced a stronger expression of P53 than conventional dose-rate radiation. Conclusion: Our pilot study indicates that the FFF-mode high dose-rate radiation, which has been used largely to improve clinical throughput, may provide the added clinical benefit of improving treatment therapeutic ratio. Animal Studies were performed within the LCCC Animal Studies Core Facility at the University of North Carolina at Chapel Hill. The LCCC Animal Studies Core is supported in part by an NCI Center Core Support Grant (CA16086) to the UNC Lineberger Comprehensive Cancer Center.

  19. Surface dose measurements and comparison of unflattened and flattened photon beams

    Directory of Open Access Journals (Sweden)

    Ashokkumar Sigamani

    2016-01-01

    Full Text Available The purpose of this study was to evaluate the central axis dose in the build-up region and the surface dose of a 6 MV and 10 MV flattened photon beam (FB and flattening filter free (FFF therapeutic photon beam for different square field sizes (FSs for a Varian Truebeam linear accelerator using parallel-plate ionization chamber and Gafchromic film. Knowledge of dosimetric characteristics in the build-up region and surface dose of the FFF is essential for clinical care. The dose measurements were also obtained empirically using two different commonly used dosimeters: a p-type photon semiconductor dosimeter and a cylindrical ionization chamber. Surface dose increased linearly with FS for both FB and FFF photon beams. The surface dose values of FFF were higher than the FB FSs. The measured surface dose clearly increases with increasing FS. The FFF beams have a modestly higher surface dose in the build-up region than the FB. The dependence of source to skin distance (SSD is less significant in FFF beams when compared to the flattened beams at extended SSDs.

  20. Tenth value layers for 60Co gamma rays and for 4, 6, 10, 15, and 18 MV x rays in concrete for beams of cone angles between 0 degrees and 14 degrees calculated by Monte Carlo simulation.

    Science.gov (United States)

    Jaradat, Adnan K; Biggs, Peter J

    2007-05-01

    The calculation of shielding barrier thicknesses for radiation therapy facilities according to the NCRP formalism is based on the use of broad beams (that is, the maximum possible field sizes). However, in practice, treatment fields used in radiation therapy are, on average, less than half the maximum size. Indeed, many contemporary treatment techniques call for reduced field sizes to reduce co-morbidity and the risk of second cancers. Therefore, published tenth value layers (TVLs) for shielding materials do not apply to these very small fields. There is, hence, a need to determine the TVLs for various beam modalities as a function of field size. The attenuation of (60)Co gamma rays and photons of 4, 6, 10, 15, and 18 MV bremsstrahlung x ray beams by concrete has been studied using the Monte Carlo technique (MCNP version 4C2) for beams of half-opening angles of 0 degrees , 3 degrees , 6 degrees , 9 degrees , 12 degrees , and 14 degrees . The distance between the x-ray source and the distal surface of the shielding wall was fixed at 600 cm, a distance that is typical for modern radiation therapy rooms. The maximum concrete thickness varied between 76.5 cm and 151.5 cm for (60)Co and 18 MV x rays, respectively. Detectors were placed at 630 cm, 700 cm, and 800 cm from the source. TVLs have been determined down to the third TVL. Energy spectra for 4, 6, 10, 15, and 18 MV x rays for 10 x 10 cm(2) and 40 x 40 cm(2) field sizes were used to generate depth dose curves in water that were compared with experimentally measured values.

  1. Beam Characterization of 10-MV Photon Beam from Medical Linear Accelerator without Flattening Filter.

    Science.gov (United States)

    Shimozato, Tomohiro; Aoyama, Yuichi; Matsunaga, Takuma; Tabushi, Katsuyoshi

    2017-01-01

    This work investigated the dosimetric properties of a 10-MV photon beam emitted from a medical linear accelerator (linac) with no flattening filter (FF). The aim of this study is to analyze the radiation fluence and energy emitted from the flattening filter free (FFF) linac using Monte Carlo (MC) simulations. The FFF linac was created by removing the FF from a linac in clinical use. Measurements of the depth dose (DD) and the off-axis profile were performed using a three-dimensional water phantom with an ionization chamber. A MC simulation for a 10-MV photon beam from this FFF linac was performed using the BEAMnrc code. The off-axis profiles for the FFF linac exhibited a chevron-like distribution, and the dose outside the irradiation field was found to be lower for the FFF linac than for a linac with an FF (FF linac). The DD curves for the FFF linac included many contaminant electrons in the build-up region. Therefore, for clinical use, a metal filter is additionally required to reduce the effects of the electron contamination. The mean energy of the FFF linac was found to be lower than that of the FF linac owing to the absence of beam hardening caused by the FF.

  2. Simple exercises to flatten your potential

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Xi; Horn, Bart; Silverstein, Eva [Stanford Univ., Stanford, CA (United States). SLAC and Dept. of Physics; California Univ., Santa Barbara, CA (United States). Kavli Inst. for Theoretical Physics; Westphal, Alexander [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Stanford Univ., Stanford, CA (United States). SLAC and Dept. of Physics

    2010-11-15

    We show how backreaction of the inflation potential energy on heavy scalar fields can flatten the inflationary potential, as the heavy fields adjust to their most energetically favorable configuration. This mechanism operates in previous UV-complete examples of axion monodromy inflation - flattening a would-be quadratic potential to one linear in the inflaton field - but occurs more generally, and we illustrate the effect with several examples. Special choices of compactification minimizing backreaction may realize chaotic inflation with a quadratic potential, but we argue that a flatter potential such as power-law inflation V({phi}){proportional_to} {phi}{sup p} with p<2 is a more generic option at sufficiently large values of {phi}. (orig.)

  3. Simple exercises to flatten your potential

    International Nuclear Information System (INIS)

    Dong, Xi; Horn, Bart; Silverstein, Eva; California Univ., Santa Barbara, CA; Westphal, Alexander; Stanford Univ., Stanford, CA

    2010-11-01

    We show how backreaction of the inflation potential energy on heavy scalar fields can flatten the inflationary potential, as the heavy fields adjust to their most energetically favorable configuration. This mechanism operates in previous UV-complete examples of axion monodromy inflation - flattening a would-be quadratic potential to one linear in the inflaton field - but occurs more generally, and we illustrate the effect with several examples. Special choices of compactification minimizing backreaction may realize chaotic inflation with a quadratic potential, but we argue that a flatter potential such as power-law inflation V(φ)∝ φ p with p<2 is a more generic option at sufficiently large values of φ. (orig.)

  4. Flattening and radio emission among elliptical galaxies

    International Nuclear Information System (INIS)

    Disney, M.J.; Sparks, W.B.; Wall, J.V.

    1984-01-01

    In a sample of 132 bright elliptical galaxies it is shown that there is a strong correlation between radio activity and flattening in the sense that radio ellipticals are both apparently and inherently rounder than the average elliptical. Both extended and compact sources are subject to the same correlation. No galaxies with axial ratios below 0.65 are found to be radio emitters. (author)

  5. A Retina-Like Dual Band Organic Photosensor Array for Filter-Free Near-Infrared-to-Memory Operations.

    Science.gov (United States)

    Wang, Hanlin; Liu, Hongtao; Zhao, Qiang; Ni, Zhenjie; Zou, Ye; Yang, Jie; Wang, Lifeng; Sun, Yanqiu; Guo, Yunlong; Hu, Wenping; Liu, Yunqi

    2017-08-01

    Human eyes use retina photoreceptor cells to absorb and distinguish photons from different wavelengths to construct an image. Mimicry of such a process and extension of its spectral response into the near-infrared (NIR) is indispensable for night surveillance, retinal prosthetics, and medical imaging applications. Currently, NIR organic photosensors demand optical filters to reduce visible interference, thus making filter-free and anti-visible NIR imaging a challenging task. To solve this limitation, a filter-free and conformal, retina-inspired NIR organic photosensor is presented. Featuring an integration of photosensing and floating-gate memory modules, the device possesses an acute color distinguishing capability. In general, the retina-like photosensor transduces NIR (850 nm) into nonvolatile memory and acts as a dynamic photoswitch under green light (550 nm). In doing this, a filter-free but color-distinguishing photosensor is demonstrated that selectively converts NIR optical signals into nonvolatile memory. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Color-filter-free spatial visible light communication using RGB-LED and mobile-phone camera.

    Science.gov (United States)

    Chen, Shih-Hao; Chow, Chi-Wai

    2014-12-15

    A novel color-filter-free visible-light communication (VLC) system using red-green-blue (RGB) light emitting diode (LED) and mobile-phone camera is proposed and demonstrated for the first time. A feature matching method, which is based on the scale-invariant feature transform (SIFT) algorithm for the received grayscale image is used instead of the chromatic information decoding method. The proposed method is simple and saves the computation complexity. The signal processing is based on the grayscale image computation; hence neither color-filter nor chromatic channel information is required. A proof-of-concept experiment is performed and high performance channel recognition is achieved.

  7. Field flattening in superconducting beam transport magnets

    International Nuclear Information System (INIS)

    Morgan, G.H.

    1994-01-01

    Dipoles in which the beam traverses the midplane well away from tie magnet axis may benefit from flattening of the vertical field on the midplane. A procedure is described for doing so, making use of Chebyshev polynomials. In the case of the large aperture ''DX'' magnets located immediately on each side of the six intersection regions of the Relativistic Heavy Ion Powder (RHIC), a comparison is made of the field of coils optimized in this way and of coils optimized in the more common way by minimizing the leading coefficients of the Fourier expansion about the magnet axis. The comparison is of the integrated Fourier coefficients of the field expanded locally along the beam trajectory

  8. Beam induced heating reduction by bunch flattening

    CERN Document Server

    Argyropoulos, T; Esteban Müller, JF; Jakobsen, S; Mastoridis, T; Metral, E; Mounet, N; Papotti, G; Pieloni, T; Salvant, B; Shaposhnikova, E; Timko, H

    2014-01-01

    The main purpose of this MD was to modify the beam induced heating on some critical LHC components by flattening the bunch distribution by applying an RF phase modulation. In this way, the beam spectrum was modified so that the power spectral density is reduced at low frequencies (below 1.1 GHz), which is the band of frequencies where the beam interaction with different component impedances is most critical. We present temperature measurements showing the beneficial effect of this latter distribution on some of the monitored devices. Longitudinal peak detected Schottky spectrum was also acquired during the first part of the MD with the intention of estimating the synchrotron frequency shift due to the reactive part of the longitudinal impedance. In the second part of the MD, an attempt to cure the transverse instability during the beta-squeeze was done by reducing the RF voltage to lengthen the bunches and enhance Landau Damping.

  9. A controlled method to flatten warped wooden panels

    NARCIS (Netherlands)

    Van Gerven, G.; Ankersmit, B.; van Duin, P.H.J.C.; Jorissen, A.J.M.; Schellen, H.L.

    2016-01-01

    This article describes the research and subsequent treatment to flatten the warped wooden doors of a seventeenth-century cabinet. The aim was to flatten the veneered panels, in very strict climatic conditions and without lifting any veneer or damaging the surface finish of the exterior. In this

  10. A flattened cloud core in NGC 2024

    Science.gov (United States)

    Ho, Paul T. P.; Peng, Yun-Lou; Torrelles, Jose M.; Gomez, Jose F.; Rodriguez, Luis F.; Canto, Jorge

    1993-01-01

    The (J, K) (1, 1) and (2, 2) NH3 lines were mapped toward a molecular cloud core in NGC 2024 using the VLA in its C/D-configuration. This region is associated with one of the most highly collimated molecular outflows. We find that the molecular condensations associated with the far-infrared sources FIR 5, FIR 6, and FIR 7 have kinetic temperatures of about 40 K. We also find line broadening toward FIR 6 and FIR 7. This suggests that these condensations may not be protostars heated by gravitational energy released during collapse but that they have an internal heating source. A flattened structure of ammonia emission is found extending parallel to the unipolar CO outflow structure, but displaced systematically to the east. If the NH3 emission traces the denser gas environment, there is no evidence that a dense gas structure is confining the molecular outflow. Instead, the location of the high-velocity outflow along the surface of the NH3 structure suggests that a wind is sweeping material from the surface of this elongated cloud core.

  11. Monte Carlo-based investigations on the impact of removing the flattening filter on beam quality specifiers for photon beam dosimetry.

    Science.gov (United States)

    Czarnecki, Damian; Poppe, Björn; Zink, Klemens

    2017-06-01

    , namely (L¯/ρ)airwater, mean photon and electron energy. Furthermore, the results show that a beam profile correction is important for dose measurements with large ionization chambers in flattening filter free beams. © 2017 American Association of Physicists in Medicine.

  12. Discrete dislocation simulations of the flattening of nanoimprinted surfaces

    International Nuclear Information System (INIS)

    Zhang, Yunhe; Nicola, Lucia; Van der Giessen, Erik

    2010-01-01

    Simulations of rough surface flattening are performed on thin metal films whose roughness is created by nanoimprinting flat single crystals. The imprinting is carried out by means of a rigid template with equal flat contacts at varying spacing. The imprinted surfaces are subsequently flattened by a rigid platen, while the change of roughness and surface profile is computed. Attention is focused mainly on comparing the response of the film surfaces with those of identical films cleared of the dislocations and residual stresses left by the imprinting process. The aim of these studies is to understand to what extent the loading history affects deformation and roughness during flattening. The limiting cases of sticking and frictionless contact between rough surface and platen are analyzed. Results show that when the asperities are flattened such that the contact area is up to about one third of the surface area, the loading history strongly affects the flattening. Specifically, the presence of initial dislocations facilitates the squeezing of asperities independently of the friction conditions of the contact. For larger contact areas, the initial conditions affect only sticking contacts, while frictionless contacts lead to a homogeneous flattening of the asperities due to yield of the metal film. In all cases studied the final surface profile obtained after flattening has little to no resemblance to the original imprinted surface

  13. Sci-Fri PM: Radiation Therapy, Planning, Imaging, and Special Techniques - 06: Patient-specific QA Procedure for Gated VMAT SABR Treatments using 10x Beam in Flattening-Filter Free Mode

    Energy Technology Data Exchange (ETDEWEB)

    Mestrovic, Ante; Chitsazzadeh, Shadi; Wells, Derek M.; Gray, Stephen [University of Calgary, Tom Baker Cancer Centre, Tom Baker Cancer Centre (Canada)

    2016-08-15

    Purpose: To develop a highly sensitive patient specific QA procedure for gated VMAT stereotactic ablative radiotherapy (SABR) treatments. Methods: A platform was constructed to attach the translational stage of a Quasar respiratory motion phantom to a pinpoint ion chamber insert and move the ion chamber inside the ArcCheck. The Quasar phantom controller uses a patient-specific breathing pattern to translate the ion chamber in a superior-inferior direction inside the ArcCheck. With this system the ion chamber is used to QA the correct phase of the gated delivery and the ArcCheck diodes are used to QA the overall dose distribution. This novel approach requires a single plan delivery for a complete QA of a gated plan. The sensitivity of the gating QA procedure was investigated with respect to the following parameters: PTV size, exhale duration, baseline drift, gating window size. Results: The difference between the measured dose to a point in the penumbra and the Eclipse calculated dose was under 2% for small residual motions. The QA procedure was independent of PTV size and duration of exhale. Baseline drift and gating window size, however, significantly affected the penumbral dose measurement, with differences of up to 30% compared to Eclipse. Conclusion: This study described a highly sensitive QA procedure for gated VMAT SABR treatments. The QA outcome was dependent on the gating window size and baseline drift. Analysis of additional patient breathing patterns is currently undergoing to determine a clinically relevant gating window size and an appropriate tolerance level for this procedure.

  14. Experimental study of heat transfer performance in a flattened AGHP

    International Nuclear Information System (INIS)

    Tao Hanzhong; Zhang Hong; Zhuang Jun; Jerry Bowman, W.

    2008-01-01

    Round mini-axial grooved heat pipes (AGHP) with a diameter of 6 mm and a length of 210 mm were pressed into flattened heat pipes with a thickness of 3.5 mm, 3 mm, 2.5 mm and 2 mm, respectively. The article measured the heat transfer limit, thermal resistance and evaporation heat transfer coefficient of the said AGHPs and analyzed and studied the result. The result indicates: the heat transfer limit decreased with the increase of flattening degree. The heat transfer limit of the 2 mm thick flattened AGHP was only 1/4 of that of the φ 6 mm round AGHP. The thermal resistance of the 3.5-2.5 mm thick AGHPs basically maintained stable at around 0.08 deg. C/W, while the thermal resistance of the 2 mm thick flattened AGHP increased obviously. The variation of the heat transfer coefficient in evaporator section with the change of flattening degree follows a similar rule to the variation of thermal resistance. This article serves as a reference to understanding the heat transfer performance of mini AGHP and to electronic cooling design of AGHP

  15. Computer dosimetry for flattened and wedged fast-neutron beams

    International Nuclear Information System (INIS)

    Hogstrom, K.R.; Smith, A.R.; Almond, P.R.; Otte, V.A.; Smathers, J.B.

    1976-01-01

    Beam flattening by the use of polyethylene filters has been developed for the 50-MeV d→Be fast-neutron therapy beam at the Texas AandM Variable-Energy Cyclotron (TAMVEC) as a result of the need for a more uniform dose distribution at depth within the patient. A computer algorithm has been developed that allows the use of a modified decrement line method to calculate dose distributions; standard decrement line methods do not apply because of off-axis peaking. The dose distributions for measured flattened beams are transformed into distributions that are physically equivalent to an unflattened distribution. In the transformed space, standard decrement line theory yields a distribution for any field size which, by applying the inverse transformation, generates the flattened dose distribution, including the off-axis peaking. A semiempirical model has been constructed that allows the calculation of dose distributions for wedged beams from open-beam data

  16. Paint stripping with high power flattened Gaussian beams

    CSIR Research Space (South Africa)

    Forbes, A

    2009-08-01

    Full Text Available In this paper the researchers present results on improved paint stripping performance with an intra-cavity generated Flattened Gaussian Beam (FGB). A resonator with suitable diffractive optical elements was designed in order to produce a single mode...

  17. Continuous Flattening of a Regular Tetrahedron with Explicit Mappings

    Directory of Open Access Journals (Sweden)

    Jin-ichi Itoh

    2012-01-01

    Full Text Available We proved in [10] that each Platonic polyhedron P can be folded into a flat multilayered face of P by a continuous folding process of polyhedra. In this paper, we give explicit formulas of continuous functions for such a continuous flattening process in R³ for a regular tetrahedron.The article is published in the author’s wording.

  18. Monte Carlo study of in-field and out-of-field dose distributions from a linear accelerator operating with and without a flattening-filter

    International Nuclear Information System (INIS)

    Almberg, S. S.; Frengen, J.; Lindmo, T.

    2012-01-01

    Purpose: To compare dosimetric characteristics of 6 MV photon fields originating from a linear accelerator operating with (FF) and without (FFF) a flattening-filter. The main objective is to establish a FFF model that results in similar depth-dose and build-up profiles as the original FF model, and subsequently estimate and compare out-of-field dose distributions. Methods: The EGSnrc Monte Carlo user codes BEAMnrc and DOSXYZnrc are used for photon beam simulations of an Elekta linear accelerator and dose calculations in a water phantom, respectively. Three beam models were analyzed: (1) the conventional linear accelerator with the flattening-filter in place and incident electron energy 6.45 MeV (FF 6.45 MeV), (2) similar flattening-filter-free model (FFF 6.45 MeV), and (3) as (2) but with increased electron energy (FFF 8.0 MeV). The field size 5 × 5 cm 2 was used for characterization of dose output, depth dose profiles, and photon spectrum. The field size 40 × 40 cm 2 was used for characterization of cross-field photon energy, photon fluence, and dose distributions. Out-of-field dose distributions were analyzed in both in-plane and cross-plane directions for 5 × 5 cm 2 and 10 × 10 cm 2 fields. Results: Comparable depth dose distributions, including the build-up region, for FF and FFF fields were achieved by increasing the electron energy from 6.45 MeV to 8.0 MeV for the FFF beam. The FFF beams result in reduced out-of-field dose compared to the FF beam: the reduction was most apparent in the cross-plane direction and more pronounced by the FFF 8.0 MeV beam compared to the FFF 6.45 MeV beam. Differences in out-of-field dose due to direction (in-plane vs cross-plane) were up to 40% for the FF beam; this effect was significantly reduced for the FFF beams. As the flattening-filter is a major source of contaminating electrons, superficial out-of-field dose was expected, and was found to be, reduced for FFF beams. Conclusions: The build-up and depth

  19. Monte Carlo study of in-field and out-of-field dose distributions from a linear accelerator operating with and without a flattening-filter.

    Science.gov (United States)

    Almberg, S S; Frengen, J; Lindmo, T

    2012-08-01

    To compare dosimetric characteristics of 6 MV photon fields originating from a linear accelerator operating with (FF) and without (FFF) a flattening-filter. The main objective is to establish a FFF model that results in similar depth-dose and build-up profiles as the original FF model, and subsequently estimate and compare out-of-field dose distributions. The EGSnrc Monte Carlo user codes BEAMnrc and DOSXYZnrc are used for photon beam simulations of an Elekta linear accelerator and dose calculations in a water phantom, respectively. Three beam models were analyzed: (1) the conventional linear accelerator with the flattening-filter in place and incident electron energy 6.45 MeV (FF 6.45 MeV), (2) similar flattening-filter-free model (FFF 6.45 MeV), and (3) as (2) but with increased electron energy (FFF 8.0 MeV). The field size 5 × 5 cm(2) was used for characterization of dose output, depth dose profiles, and photon spectrum. The field size 40 × 40 cm(2) was used for characterization of cross-field photon energy, photon fluence, and dose distributions. Out-of-field dose distributions were analyzed in both in-plane and cross-plane directions for 5 × 5 cm(2) and 10 × 10 cm(2) fields. Comparable depth dose distributions, including the build-up region, for FF and FFF fields were achieved by increasing the electron energy from 6.45 MeV to 8.0 MeV for the FFF beam. The FFF beams result in reduced out-of-field dose compared to the FF beam: the reduction was most apparent in the cross-plane direction and more pronounced by the FFF 8.0 MeV beam compared to the FFF 6.45 MeV beam. Differences in out-of-field dose due to direction (in-plane vs cross-plane) were up to 40% for the FF beam; this effect was significantly reduced for the FFF beams. As the flattening-filter is a major source of contaminating electrons, superficial out-of-field dose was expected, and was found to be, reduced for FFF beams. The build-up and depth-dose characteristics of a conventional "6 MV" beam

  20. The flattening of the average potential in models with fermions

    International Nuclear Information System (INIS)

    Bornholdt, S.

    1993-01-01

    The average potential is a scale dependent scalar effective potential. In a phase with spontaneous symmetry breaking its inner region becomes flat as the averaging extends over infinite volume and the average potential approaches the convex effective potential. Fermion fluctuations affect the shape of the average potential in this region and its flattening with decreasing physical scale. They have to be taken into account to find the true minimum of the scalar potential which determines the scale of spontaneous symmetry breaking. (orig.)

  1. Electron Microscopic Visualization of Protein Assemblies on Flattened DNA Origami.

    Science.gov (United States)

    Mallik, Leena; Dhakal, Soma; Nichols, Joseph; Mahoney, Jacob; Dosey, Anne M; Jiang, Shuoxing; Sunahara, Roger K; Skiniotis, Georgios; Walter, Nils G

    2015-07-28

    DNA provides an ideal substrate for the engineering of versatile nanostructures due to its reliable Watson-Crick base pairing and well-characterized conformation. One of the most promising applications of DNA nanostructures arises from the site-directed spatial arrangement with nanometer precision of guest components such as proteins, metal nanoparticles, and small molecules. Two-dimensional DNA origami architectures, in particular, offer a simple design, high yield of assembly, and large surface area for use as a nanoplatform. However, such single-layer DNA origami were recently found to be structurally polymorphous due to their high flexibility, leading to the development of conformationally restrained multilayered origami that lack some of the advantages of the single-layer designs. Here we monitored single-layer DNA origami by transmission electron microscopy (EM) and discovered that their conformational heterogeneity is dramatically reduced in the presence of a low concentration of dimethyl sulfoxide, allowing for an efficient flattening onto the carbon support of an EM grid. We further demonstrated that streptavidin and a biotinylated target protein (cocaine esterase, CocE) can be captured at predesignated sites on these flattened origami while maintaining their functional integrity. Our demonstration that protein assemblies can be constructed with high spatial precision (within ∼2 nm of their predicted position on the platforms) by using strategically flattened single-layer origami paves the way for exploiting well-defined guest molecule assemblies for biochemistry and nanotechnology applications.

  2. Environment effects on the flattening distribution of galaxies

    International Nuclear Information System (INIS)

    Freitas Pacheco, J.A. de; Souza, R.E. de; Arakaki, L.

    1983-01-01

    The results of a study of environment effects on the flattening distribution of galaxies are presented. Samples of different morphological types in regions of high and low projected galaxian density were prepared using the Uppsala General Catalogue of Galaxies. No significant differences were detected for the E and Spiral galaxies. However this study suggest that there is an excess of flat S phi systems in regions of high galaxian density with respect the field systems. These 'flat' S phi's are interpreted as being gas stripped Sa galaxies and the consequences of such a hypothesis are also discussed. (Author) [pt

  3. Colon flattening by landmark-driven optimal quasiconformal mapping.

    Science.gov (United States)

    Zeng, Wei; Yang, Yi-Jun

    2014-01-01

    In virtual colonoscopy, colon conformal flattening plays an important role, which unfolds the colon wall surface to a rectangle planar image and preserves local shapes by conformal mapping, so that the cancerous polyps and other abnormalities can be easily and thoroughly recognized and visualized without missing hidden areas. In such maps, the anatomical landmarks (taeniae coli, flexures, and haustral folds) are naturally mapped to convoluted curves on 2D domain, which poses difficulty for comparing shapes from geometric feature details. Understanding the nature of landmark curves to the whole surface structure is meaningful but it remains challenging and open. In this work, we present a novel and effective colon flattening method based on quasiconformal mapping, which straightens the main anatomical landmark curves with least conformality (angle) distortion. It provides a canonical and straightforward view of the long, convoluted and folded tubular colon surface. The computation is based on the holomorphic 1-form method with landmark straightening constraints and quasiconformal optimization, and has linear time complexity due to the linearity of 1-forms in each iteration. Experiments on various colon data demonstrate the efficiency and efficacy of our algorithm and its practicability for polyp detection and findings visualization; furthermore, the result reveals the geometric characteristics of anatomical landmarks on colon surfaces.

  4. Beam propagation factor and Kurtosis parameter of different types of flattened Gaussian beams

    International Nuclear Information System (INIS)

    Saghafi, S.; Forbes, G.W.; Sheppard, C.J.R.

    1999-01-01

    Full text: The beam propagation factor, M 2 and the Kurtosis parameter, K, are considered for three different models of flattened Gaussian beams. Plots of M 2 versus K reveal similarities between these flattened beams. In fact, for this type of beam, it is possible to predict K from the value of M 2 We also determine the values of the parameters that characterize those different types of flattened Gaussian beam modes for any given value of M 2 . Finally, once K and M 2 have been measured for any flattened beam, these equations can be used to determine the closeness of this real beam to members of the three well-known classes of flattened beams. This can facilitate the analyses of the beam and its propagation. Copyright (1999) Australian Optical Society

  5. Removing paint from a metal substrate using a flattened top laser

    International Nuclear Information System (INIS)

    Shi Shu-Dong; Li Wei; Du Peng; Wang Meng; Song Feng; Liu Shu-Jing; Chen Nian-Jiang; Zhao Hong; Yang Wen-Shi

    2012-01-01

    In this paper, we investigate laser cleaning using a flattened top laser to remove paint coating from a metal substrate. Under the irradiation of a flattened top laser, the coating paint of the metal substrate can be removed efficiently by laser induced ablation, stress, and displacement force. The temperature distribution, stress, and displacement are calculated in the coating layer and substrate using finite element analysis. The effects of a Gaussian laser and a flattened top laser and the results of different diameters of laser spot are compared. The investigation shows that the flattened top laser can reduce the substrate damage and enhance the cleaning efficiency. This method meets the need of large area industrial cleaning applications by optimizing the flattened top laser parameters

  6. Removing paint from a metal substrate using a flattened top laser

    Science.gov (United States)

    Shi, Shu-Dong; Li, Wei; Du, Peng; Wang, Meng; Song, Feng; Liu, Shu-Jing; Chen, Nian-Jiang; Zhao, Hong; Yang, Wen-Shi

    2012-10-01

    In this paper, we investigate laser cleaning using a flattened top laser to remove paint coating from a metal substrate. Under the irradiation of a flattened top laser, the coating paint of the metal substrate can be removed efficiently by laser induced ablation, stress, and displacement force. The temperature distribution, stress, and displacement are calculated in the coating layer and substrate using finite element analysis. The effects of a Gaussian laser and a flattened top laser and the results of different diameters of laser spot are compared. The investigation shows that the flattened top laser can reduce the substrate damage and enhance the cleaning efficiency. This method meets the need of large area industrial cleaning applications by optimizing the flattened top laser parameters.

  7. Flattening the organization: implementing self-directed work groups.

    Science.gov (United States)

    Brandon, G M

    1996-01-01

    In response to tremendous growth of managed care and threats to financial stability and job security, the Greater Baltimore Medical Center (GBMC) restructured itself into independent business units. The radiology department at GBMC resolved to reduce cost per unit-of-service, improve service, determine optimal staffing levels and reduce the number of layers of organization. It was decided to achieve those goals by implementing self-directed work groups. Staff buy-in was critical to success of the project. To begin, the staff was educated intensively about current trends in healthcare, managed care and potential changes in the job market. The radiology department was allowed to reduce the size of its staff through attrition and worked hard to focus staff concern on the impact each individual could have on the bottom line and the resultant effect on job security. Self-directed work groups were designed on a matrix that used small "service teams" in combinations to form larger "work groups." Actual work and daily activities occur at the service team level; information exchange and major decisions occue at the work group level. Seventeen months after beginning the project and 10 months after implementation, the organization has flattened, staff members have adjusted well to new roles, there have been no lay-offs, and the matrix system of small and large groups have proved particularly valuable.

  8. Spectral Flattening at Low Frequencies in Crab Giant Pulses

    Science.gov (United States)

    Meyers, B. W.; Tremblay, S. E.; Bhat, N. D. R.; Shannon, R. M.; Kirsten, F.; Sokolowski, M.; Tingay, S. J.; Oronsaye, S. I.; Ord, S. M.

    2017-12-01

    We report on simultaneous wideband observations of Crab giant pulses with the Parkes radio telescope and the Murchison Widefield Array (MWA). The observations were conducted simultaneously at 732 and 3100 MHz with Parkes and at 120.96, 165.76, and 210.56 MHz with the MWA. Flux density calibration of the MWA data was accomplished using a novel technique based on tied-array beam simulations. We detected between 90 and 648 giant pulses in the 120.96-210.56 MHz MWA subbands above a 5.5σ threshold, while in the Parkes subbands we detected 6344 and 231 giant pulses above a threshold of 6σ at 732 and 3100 MHz, respectively. We show, for the first time over a wide frequency range, that the average spectrum of Crab giant pulses exhibits a significant flattening at low frequencies. The spectral index, α, for giant pulses evolves from a steep, narrow distribution with a mean α =-2.6 and width {σ }α =0.5 between 732 and 3100 MHz to a wide, flat distribution of spectral indices with a mean α =-0.7 and width {σ }α =1.4 between 120.96 and 165.76 MHz. We also comment on the plausibility of giant pulse models for fast radio bursts based on this spectral information.

  9. Second Cancer Risk after simultaneous integrated boost radiation therapy of right sided breast cancer with and without flattening filter

    Energy Technology Data Exchange (ETDEWEB)

    Dobler, Barbara; Maier, Johannes; Knott, Bernadette; Maerz, Manuel; Koelbl, Oliver [Regensburg University Medical Center, Department of Radiotherapy, Regensburg (Germany); Loeschel, Rainer [Ostbayerische Technische Hochschule Regensburg, Faculty of Computer Science and Mathematics, Regensburg (Germany)

    2016-10-15

    The aim of this study was to investigate if the flattening filter free mode (FFF) of a linear accelerator reduces the excess absolute risk (EAR) for second cancer as compared to the flat beam mode (FF) in simultaneous integrated boost (SIB) radiation therapy of right-sided breast cancer. Six plans were generated treating the whole breast to 50.4 Gy and a SIB volume to 63 Gy on CT data of 10 patients: intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and a tangential arc VMAT (tVMAT), each with flattening filter and without. The EAR was calculated for the contralateral breast and the lungs from dose-volume histograms (DVH) based on the linear-exponential, the plateau, and the full mechanistic dose-response model. Peripheral low-dose measurements were performed to compare the EAR in more distant regions as the thyroids and the uterus. FFF reduces the EAR significantly in the contralateral and peripheral organs for tVMAT and in the peripheral organs for VMAT. No reduction was found for IMRT. The lowest EAR for the contralateral breast and lung was achieved with tVMAT FFF, reducing the EAR by 25 % and 29 % as compared to tVMAT FF, and by 44 % to 58 % as compared to VMAT and IMRT in both irradiation modes. tVMAT FFF showed also the lowest peripheral dose corresponding to the lowest EAR in the thyroids and the uterus. The use of FFF mode allows reducing the EAR significantly when tVMAT is used as the treatment technique. When second cancer risk is a major concern, tVMAT FFF is considered the preferred treatment option in SIB irradiation of right-sided breast cancer. (orig.) [German] Ziel der Studie war es zu untersuchen, ob der ausgleichskoerperfreie Modus (FFF) bei der simultan integrierten Boost-(SIB-)Bestrahlung des rechtsseitigen Mammakarzinoms eine Reduktion des strahleninduzierten Sekundaermalignomrisikos (''excess absolute risk'', EAR) im Vergleich zur Bestrahlung mit Ausgleichskoerper (FF) erlaubt. Auf CT

  10. Dosimetric comparison of flattened and unflattened beams for stereotactic ablative radiotherapy of stage I non-small cell lung cancer

    Energy Technology Data Exchange (ETDEWEB)

    Hrbacek, Jan, E-mail: jan.hrbacek@psi.ch [Klinik für Radio-Onkologie, UniversitätsSpital Zürich, 8091 Zürich, Switzerland and Center for Proton Therapy, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Lang, Stephanie; Graydon, Shaun N.; Klöck, Stephan; Riesterer, Oliver [Klinik für Radio-Onkologie, UniversitätsSpital Zürich, 8091 Zürich (Switzerland)

    2014-03-15

    Purpose: To compare contribution and accuracy of delivery for two flattening filter free (FFF) beams of the nominal energy 6 and 10 MV and a 6 MV flattened beam for early stage lung cancer. Methods: For each of 11 patients with stage I nonsmall cell lung cancer three volumetric modulated arc therapy plans were prepared utilizing a 6 MV flattened photon beam (X6FF) and two nonflattened beams of nominal energy 6 and 10 MV (X6FFF, X10FFF). Optimization constraints were set to produce dose distributions that meet the criteria of the RTOG-0915 protocol. The radiation schedule used for plan comparison in all patients was 50 Gy in five fractions. Dosimetric parameters of planning target volume (PTV) and organs-at-risk and delivery times were assessed and compared. All plans were subject to verification using Delta{sup 4} unit (Scandidos, Sweden) and absolutely calibrated gafchromic films in a thorax phantom. Results: All plans had a qualitatively comparable outcome. Obtained dose distributions were conformal (CI < 1.17) and exhibited a steep dose fall-off outside the PTV. The ratio of monitor units for FFF versus FF plans in the authors' study ranged from 0.95 to 1.21 and from 0.93 to 1.25 for X6FFF/X6FF and X10FFF/X6FF comparisons, respectively. The ratio systematically increased with increasing size of the PTV (up to +25% for 150 cm{sup 3} PTV). Yet the integral dose to healthy tissue did not follow this trend. Comparison of cumulative dose volume histograms for a patient's body showed that X6FFF plans exhibit improved conformity and reduced the volume of tissue that received more than 50% of the prescription dose. Parameters related to dose gradient showed statistically significant improvement. CI{sub 50%}, CI{sub 60%}, CI{sub 80%}, and CI{sub 100%} were on average reduced by 4.6% (p < 0.001), 4.6% (p = 0.002), 3.1% (p = 0.002), and 1.2% (p = 0.039), respectively. Gradient measure was on average reduced by 4.2% (p < 0.001). Due to dose reduction in the

  11. Dosimetric Analysis of Unflattened (FFFB) and Flattened (FB) Photon Beam Energy for Gastric Cancers Using IMRT and VMAT-a Comparative Study.

    Science.gov (United States)

    Bhushan, Manindra; Yadav, Girigesh; Tripathi, Deepak; Kumar, Lalit; Kishore, Vimal; Dewan, Abhinav; Kumar, Gourav; Wahi, Inderjit Kaur; Gairola, Munish

    2018-03-08

    To evaluate the feasibility of flattening filter free beam (FFFB) for the treatment of gastric tumors and to review their benefits over 6MV flatten beam (6MV_FFB). Fifteen patients with histologically proven gastric carcinoma were selected. CT scans with slice thickness of 0.3 cm were acquired and planning target volume (PTV) and organ at risk (OAR) were delineated. Plans were made retrospectively for each patient for the prescription dose of 45 Gy/25 fractions to the PTV. Four isocentric plans were compared in the present study on Varian TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA, USA). PTV D98% was 44.41 ± 0.12, 44.38 ± 0.13, 44.59 ± 0.14, and 44.49 ± 0.19 Gy for IMRT 6MV_FFB, IMRT 6MV_FFFB, VMAT 6MV_FFB, and VMAT 6MV_FFFB respectively. 6MV_FFFB beam minimizes the mean heart dose D mean (P = 0.001). VMAT dominates over IMRT when it came to kidney doses V 12Gy (P = 0.02), V 23Gy (P = 0.015), V 28Gy (P = 0.011), and D max (P < 0.01). VMAT has significantly reduced the doses to kidneys. It was analyzed that 6MV_FFFB significantly reduces the dose to normal tissues (P = 0.006 and P = 0.018). VMAT significantly reduces the TMU, which is required to deliver the similar dose by IMRT (P < 0.01). Unflattened beam spares the organs at risk significantly to avoid the chances of secondary malignancies and reduces the intra-fraction motion during treatment due to provision of higher dose rate. Hence, we conclude that 6MV unflattened beam can be used to treat gastric carcinoma.

  12. SU-F-T-630: Energy Spectral Study On Lipiodol After Trans-Arterial Chemoembolization Using the Flattened and Unflattened Photon Beams

    Energy Technology Data Exchange (ETDEWEB)

    Kawahara, D [Radiation Therapy Section, Department of Clinical Support, Hiroshima University Hospital, Hiroshima (Japan); Medical and Dental Sciences Course, Graduate School of Biomedical & Health Sciences, Hiroshima University, Hiroshima (Japan); Ozawa, S; Nagata, Y [Department of Radiation Oncology, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima (Japan); Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima (Japan); Saito, A; Nishio, T; Suzuki, T [Department of Radiation Oncology, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima (Japan); Hioki, K; Masuda, H; Okumura, T; Ochi, Y; Nakashima, T; Ohno, Y [Radiation Therapy Section, Department of Clinical Support, Hiroshima University Hospital, Hiroshima (Japan); Tanaka, S [Department of Nuclear Engineering and Management, School of Engineering, University of Tokyo, Tokyo (Japan)

    2016-06-15

    Purpose: SBRT combining transarterial chemoembolization with Lipiodol is expected to improve local control. Our showed that the dose enhancement effect in the Lipiodol with 10X flattening filter free (FFF) was inserted. This study was to investigate the energy fluence variations of electron in the Lipiodol using flattened (FF) and FFF beams. Methods: FF and FFF for 6X and 10X beams by TrueBeam were used in this study. The Lipiodol (3 X 3 X 3 cm{sup 3}) was located at the depth of 5 cm in water, the dose enhancement factor (DEF) and energy fluence were calculated by Monte Carlo (MC) calculations (PHITS). Results: DEFs with FF and FFF of 6X were 17.1% and 24.3% at rebuild-up region in the Lipiodol (5.3cm depth), 7.0% and 17.0% at the center of Lipiodol (6.5cm depth), and −13.2% and −8.2% at behind Lipiodol (8.3cm depth). DEFs with FF and FFF of 10X were 21.7% and 15.3% at rebuild-up region, 8.2% and 10.5% at the center of Lipiodol, and −14.0% and −8.6% at behind Lipiodol. Spectral results showed that the FFF beam contained more low-energy (0–0.3MeV) component of electrons than FF beam, and FF beam contained more high-energy (over 0.3MeV) electrons than FFF beam in Lipiodol. Behind the Lipiodol, build-down effect with FF beam was larger than FFF beam because FF beam contained more high energy electrons. The difference of DEFs between FFF and FF beams for 6X were larger than for 10X. This is because 10X beam contained more high-energy electrons. Conclusion: It was found that the 6XFFF beam gives the largest change of energy fluence and the largest DEF in this study. These phenomena are mainly caused by component of low-energy electrons, and this energy is almost correspond to the boundary of photo electronic dominant and Compton scattering dominant region for photon beams.

  13. White light coronal structures and flattening during six total solar eclipses

    Directory of Open Access Journals (Sweden)

    B.A. Marzouk

    2016-12-01

    Flattening index is the first quantitative parameter introduced for analyses of the global structure of the solar corona. It varies with respect to the phase of the solar activity and sunspot number. In this paper we study the solar corona during the 1990, 1999, 2006, 2008, 2009 and 2012 total solar eclipses. We obtain flattening coefficients for all the six eclipses by using a new computer program. Our results are in a good agreement with published results.

  14. SU-E-T-493: Influence of Filtered and Flatting Filter Free Photon Beam of 10 Megavolts Energy On Rapid Arc Radiotherapy Planning for Cervix Carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Girigesh, Y; Kumar, L; Raman, K; Mishra, M [Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, Delhi (India)

    2015-06-15

    Purpose: Aim of this study is to determine the dosimetric influence of Filtered and Flatting Filter Free Photon Beam of 10 MV energy on RA planning for Ca. Cervix. Methods: CT data sets of eleven patients reported with carcinoma cervix were used for RA planning for 10MV -FFB and 10MV-FFFB. RA plans were generated using two full arcs.All RA plans were generated to deliver a dose of 50.4Gy in 28 fractions for PTV and ALARA for OAR’s. All plans were analysed for PTV Coverage, conformity Index, homogeneity index, dose to OAR’s, integral dose to normal tissue and total monitor units were studied. Results: DVH was used to evaluate RA plans for both 10MV-FFB and 10MV-FFFB photon beam. Planning results show a comparable PTV coverage for both energies. Results shows volume of PTV receiving prescription dose were 95.10+ 0.09% and 95.09 +0.11%, and volume of PTV receiving a dose of 107% is 0.45+0.96% and 5.25+8.9%, homogeneity index (HI) were 1.051+0.007 and 1.066+0.008, Conformity Index(CI) were 1.003+0.019 and 1.012+0.013, Mean Integral dose were 2.65+0.34 and 2.60+0.33(*10−5Gy.cm3) for 10MV-FFB and 10MV-FFFB respectively. 10MV-FB shows statistically significant (p<0.05) improvement in mean doses to bladder, rectum, bowel and mean total number of MU’s and also shows remarkable decrease in mean total no. of MU’s by 43.7% in comparison to 10MV-FFFB. There is statistically significant (p<0.05) difference found in CI and HI for 10MV-FB in comparison to 10MV -FFF beam. 10MV-FFFB shows statistically significant (p<0.05) for mean NTID and delivers 1.65 % less NTID in comparison to 10 MV- FB. Conclusion: 10MV-FB is superior to 10MV-FFFB for rapid arc planning in case of Cervix carcinomas, it offers better target coverage and OAR’s sparing, comparable mean Integral dose to normal tissues and 10 MV- FB also produced highly conformal and homogeneous dose distribution in comparison to 10MV-FFFB.

  15. Refrigerant charge, pressure drop, and condensation heat transfer in flattened tubes

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, M J; Newell, T A; Chato, J C [University of Illinois, Urbana, IL (United States). Dept. of Mechanical and Industrial Engineering; Infante Ferreira, C A [Delft University of Technology (Netherlands). Laboratory for Refrigeration and Indoor Climate Control

    2003-06-01

    Horizontal smooth and microfinned copper tubes with an approximate diameter of 9 mm were successively flattened in order to determine changes in flow field characteristics as a round tube is altered into a flattened tube profile. Refrigerants R134a and R410A were investigated over a mass flux range from 75 to 400 kg m{sup -2} s{sup -}2{sup 1} and a quality range from approximately 10-80%. For a given refrigerant mass flow rate, the results show that a significant reduction in refrigerant charge is possible. Pressure drop results show increases of pressure drop at a given mass flux and quality as a tube profile is flattened. Heat transfer results indicate enhancement of the condensation heat transfer coefficient as a tube is flattened. Flattened tubes with an 18{sup o} helix angle displayed the highest heat transfer coefficients. Smooth tubes and axial microfin tubes displayed similar levels of heat transfer enhancement. Heat transfer enhancement is dependent on the mass flux, quality and tube profile. (author)

  16. Extended maximum likelihood analysis of apparent flattenings of S0 and spiral galaxies

    International Nuclear Information System (INIS)

    Okamura, Sadanori; Takase, Bunshiro; Hamabe, Masaru; Nakada, Yoshikazu; Kodaira, Keiichi.

    1981-01-01

    Apparent flattenings of S0 and spiral galaxies compiled by Sandage et al. (1970) and van den Bergh (1977), and those listed in the Second Reference Catalogue (RC2) are analyzed by means of the extended maximum likelihood method which was recently developed in the information theory for statistical model identification. Emphasis is put on the possible difference in the distribution of intrinsic flattenings between S0's and spirals as a group, and on the apparent disagreements present in the previous results. The present analysis shows that (1) One cannot conclude on the basis of the data in the Reference Catalogue of Bright Galaxies (RCBG) that the distribution of intrinsic flattenings of spirals is almost identical to that of S0's; spirals have wider dispersion than S0's, and there are more round systems in spirals than in S0's. (2) The distribution of intrinsic flattenings of S0's and spirals derived from the data in RC2 again indicates a significant difference from each other. (3) The distribution of intrinsic flattenings of S0's exhibits different characteristics depending upon the surface-brightness level; the distribution with one component is obtained from the data at RCBG level (--23.5 mag arcsec -2 ) and that with two components at RC2 level (25 mag arcsec -2 ). (author)

  17. A Precise Method for Cloth Configuration Parsing Applied to Single-Arm Flattening

    Directory of Open Access Journals (Sweden)

    Li Sun

    2016-04-01

    Full Text Available In this paper, we investigate the contribution that visual perception affords to a robotic manipulation task in which a crumpled garment is flattened by eliminating visually detected wrinkles. In order to explore and validate visually guided clothing manipulation in a repeatable and controlled environment, we have developed a hand-eye interactive virtual robot manipulation system that incorporates a clothing simulator to close the effector-garment-visual sensing interaction loop. We present the technical details and compare the performance of two different methods for detecting, representing and interpreting wrinkles within clothing surfaces captured in high-resolution depth maps. The first method we present relies upon a clustering-based method for localizing and parametrizing wrinkles, while the second method adopts a more advanced geometry-based approach in which shape-topology analysis underpins the identification of the cloth configuration (i.e., maps wrinkles. Having interpreted the state of the cloth configuration by means of either of these methods, a heuristic-based flattening strategy is then executed to infer the appropriate forces, their directions and gripper contact locations that must be applied to the cloth in order to flatten the perceived wrinkles. A greedy approach, which attempts to flatten the largest detected wrinkle for each perception-iteration cycle, has been successfully adopted in this work. We present the results of our heuristic-based flattening methodology which relies upon clustering-based and geometry-based features respectively. Our experiments indicate that geometry-based features have the potential to provide a greater degree of clothing configuration understanding and, as a consequence, improve flattening performance. The results of experiments using a real robot (as opposed to simulated robot also confirm our proposition that a more effective visual perception system can advance the performance of cloth

  18. High-resolution transmission electron microscopy and energetics of flattened carbon nonoshells

    International Nuclear Information System (INIS)

    Bourgeois, L.N.; Bursill, L.A.

    1998-01-01

    When examined under a high-resolution transmission electron microscope, carbon soot produced alongside buckytubes in an arc-discharge is found to contain a small percentage of flattened carbon shells. These objects are shown to be small graphite flakes which eliminated their dangling bonds by terminating their edges with highly curved junctions. Ideal models for these structures are presented, and their energy estimated. The calculations show that the establishment of highly curved junctions is energetically favourable for a graphite flake in an inert atmosphere. Flattened shells also appear more stable than their 'inflated' counterparts (fullerene 'onions' and buckytubes) when the shell dimensions obey specific criteria.(authors)

  19. Multivariate density estimation using dimension reducing information and tail flattening transformations for truncated or censored data

    DEFF Research Database (Denmark)

    Buch-Kromann, Tine; Nielsen, Jens

    2012-01-01

    This paper introduces a multivariate density estimator for truncated and censored data with special emphasis on extreme values based on survival analysis. A local constant density estimator is considered. We extend this estimator by means of tail flattening transformation, dimension reducing prior...

  20. The equivalent square concept for the head scatter factor based on scatter from flattening filter

    International Nuclear Information System (INIS)

    Kim, Siyong; Palta, Jatinder R.; Zhu, Timothy C.

    1998-01-01

    The equivalent field relationship between square and circular fields for the head scatter factor was evaluated at the source plane. The method was based on integrating the head scatter parameter for projected shaped fields in the source plane and finding a field that produced the same ratio of head scatter to primary dose on the central axis. A value of σ/R≅0.9 was obtained, where σ was one-half of the side length of the equivalent square and R was the radius of the circular field. The assumptions were that the equivalent field relationship for head scatter depends primarily on the characteristics of scatter from the flattening filter, and that the differential scatter-to-primary ratio of scatter from the flattening filter decreases linearly with the radius, within the physical radius of the flattening filter. Lam and co-workers showed empirically that the area-to-perimeter ratio formula, when applied to an equivalent square formula at the flattening filter plane, gave an accurate prediction of the head scatter factor. We have analytically investigated the validity of the area-to-perimeter ratio formula. Our results support the fact that the area-to-perimeter ratio formula can also be used as the equivalent field formula for head scatter at the source plane. The equivalent field relationships for wedge and tertiary collimator scatter were also evaluated. (author)

  1. The equivalent square concept for the head scatter factor based on scatter from flattening filter

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Siyong; Palta, Jatinder R.; Zhu, Timothy C. [Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida (United States)

    1998-06-01

    The equivalent field relationship between square and circular fields for the head scatter factor was evaluated at the source plane. The method was based on integrating the head scatter parameter for projected shaped fields in the source plane and finding a field that produced the same ratio of head scatter to primary dose on the central axis. A value of {sigma}/R{approx_equal}0.9 was obtained, where {sigma} was one-half of the side length of the equivalent square and R was the radius of the circular field. The assumptions were that the equivalent field relationship for head scatter depends primarily on the characteristics of scatter from the flattening filter, and that the differential scatter-to-primary ratio of scatter from the flattening filter decreases linearly with the radius, within the physical radius of the flattening filter. Lam and co-workers showed empirically that the area-to-perimeter ratio formula, when applied to an equivalent square formula at the flattening filter plane, gave an accurate prediction of the head scatter factor. We have analytically investigated the validity of the area-to-perimeter ratio formula. Our results support the fact that the area-to-perimeter ratio formula can also be used as the equivalent field formula for head scatter at the source plane. The equivalent field relationships for wedge and tertiary collimator scatter were also evaluated. (author)

  2. Dispersion-flattened-fiber based optical thresholder for multiple-access-interference suppression in OCDMA system.

    Science.gov (United States)

    Wang, Xu; Hamanaka, Taro; Wada, Naoya; Kitayama, Ken-Ichi

    2005-07-11

    An optical thresholding technique based on super-continuum generation in dispersion flattened fiber is proposed and experimentally demonstrated to enable data-rate detection in optical code division multiple access networks. The proposed scheme exhibits an excellent discrimination between a desired signal and interference signals with features of pulse reshaping, low insertion loss, polarization independency as well as reasonable operation power.

  3. Reef flattening effects on total richness and species responses in the Caribbean

    NARCIS (Netherlands)

    Newman, Steven P.; Meesters, E.H.; Dryden, Charlie S.; Williams, Stacey M.; Sanchez, Cristina; Mumby, Peter J.; Polunin, Nicholas V.C.

    2015-01-01

    There has been ongoing flattening of Caribbean coral reefs with the loss of habitat having severe implications for these systems. Complexity and its structural components are important to fish species richness and community composition, but little is known about its role for other taxa or

  4. Flattening of the electrocardiographic T-wave is a sign of proarrhythmic risk and a reflection of action potential triangulation

    DEFF Research Database (Denmark)

    Bhuiyan, Tanveer Ahmed; Graff, Claus; Kanters, J.K.

    2013-01-01

    Drug-induced triangulation of the cardiac action potential is associated with increased risk of arrhythmic events. It has been suggested that triangulation causes a flattening of the electrocardiographic T-wave but the relationship between triangulation, T-wave flattening and onset of arrhythmia ...

  5. Highly birefringent photonic crystal fiber with ultra-flattened negative dispersion over S + C + L + U bands

    DEFF Research Database (Denmark)

    Habib, Selim; Khandker, Emran

    2015-01-01

    We present a new cladding design for photonic crystal fiber (PCF) on a decagonal structure to simultaneously achieve ultra-flattened large negative dispersion and ultrahigh birefringence. Numerical results confirm that the proposed PCFexhibits ultra-flattened large negative dispersion over the S ...

  6. Rapid flattening of butterfly pitch angle distributions of radiation belt electrons by whistler-mode chorus

    Science.gov (United States)

    Yang, Chang; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Wang, Shui; Spence, H. E.; Reeves, G. D.; Baker, D. N.; Blake, J. B.; Funsten, H. O.

    2016-08-01

    Van Allen radiation belt electrons exhibit complex dynamics during geomagnetically active periods. Investigation of electron pitch angle distributions (PADs) can provide important information on the dominant physical mechanisms controlling radiation belt behaviors. Here we report a storm time radiation belt event where energetic electron PADs changed from butterfly distributions to normal or flattop distributions within several hours. Van Allen Probes observations showed that the flattening of butterfly PADs was closely related to the occurrence of whistler-mode chorus waves. Two-dimensional quasi-linear STEERB simulations demonstrate that the observed chorus can resonantly accelerate the near-equatorially trapped electrons and rapidly flatten the corresponding electron butterfly PADs. These results provide a new insight on how chorus waves affect the dynamic evolution of radiation belt electrons.

  7. Separation of simultaneous sources using a structural-oriented median filter in the flattened dimension

    Science.gov (United States)

    Gan, Shuwei; Wang, Shoudong; Chen, Yangkang; Chen, Xiaohong; Xiang, Kui

    2016-01-01

    Simultaneous-source shooting can help tremendously shorten the acquisition period and improve the quality of seismic data for better subsalt seismic imaging, but at the expense of introducing strong interference (blending noise) to the acquired seismic data. We propose to use a structural-oriented median filter to attenuate the blending noise along the structural direction of seismic profiles. The principle of the proposed approach is to first flatten the seismic record in local spatial windows and then to apply a traditional median filter (MF) to the third flattened dimension. The key component of the proposed approach is the estimation of the local slope, which can be calculated by first scanning the NMO velocity and then transferring the velocity to the local slope. Both synthetic and field data examples show that the proposed approach can successfully separate the simultaneous-source data into individual sources. We provide an open-source toy example to better demonstratethe proposed methodology.

  8. Rapid flattening of butterfly pitch angle distributions of radiation belt electrons by whistler-mode chorus

    International Nuclear Information System (INIS)

    Yang, Chang; Changsha University of Science and Technology, Changsha; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan

    2016-01-01

    Van Allen radiation belt electrons exhibit complex dynamics during geomagnetically active periods. Investigation of electron pitch angle distributions (PADs) can provide important information on the dominant physical mechanisms controlling radiation belt behaviors. In this paper, we report a storm time radiation belt event where energetic electron PADs changed from butterfly distributions to normal or flattop distributions within several hours. Van Allen Probes observations showed that the flattening of butterfly PADs was closely related to the occurrence of whistler-mode chorus waves. Two-dimensional quasi-linear STEERB simulations demonstrate that the observed chorus can resonantly accelerate the near-equatorially trapped electrons and rapidly flatten the corresponding electron butterfly PADs. Finally, these results provide a new insight on how chorus waves affect the dynamic evolution of radiation belt electrons.

  9. A MongoDB-Based Management of Planar Spatial Data with a Flattened R-Tree

    Directory of Open Access Journals (Sweden)

    Longgang Xiang

    2016-07-01

    Full Text Available This paper addresses how to manage planar spatial data using MongoDB, a popular NoSQL database characterized as a document-oriented, rich query language and high availability. The core idea is to flatten a hierarchical R-tree structure into a tabular MongoDB collection, during which R-tree nodes are represented as collection documents and R-tree pointers are expressed as document identifiers. By following this strategy, a storage schema to support R-tree-based create, read, update, and delete (CRUD operations is designed and a module to manage planar spatial data by consuming and maintaining flattened R-tree structure is developed. The R-tree module is then seamlessly integrated into MongoDB, so that users could manipulate planar spatial data with existing command interfaces oriented to geodetic spatial data. The experimental evaluation, using real-world datasets with diverse coverage, types, and sizes, shows that planar spatial data can be effectively managed by MongoDB with our flattened R-tree and, therefore, the application extent of MongoDB will be greatly enlarged. Our work resulted in a MongoDB branch with R-tree support, which has been released on GitHub for open access.

  10. Optimization of pump parameters for gain flattened Raman fiber amplifiers based on artificial fish school algorithm

    Science.gov (United States)

    Jiang, Hai Ming; Xie, Kang; Wang, Ya Fei

    2011-11-01

    In this work, a novel metaheuristic named artificial fish school algorithm is introduced into the optimization of pump parameters for the design of gain flattened Raman fiber amplifiers for the first time. Artificial fish school algorithm emulates three simple social behaviors of a fish in a school, namely, preying, swarming and following, to optimize a target function. In this algorithm the pump wavelengths and power levels are mapped respectively to the state of a fish in a school, and the gain of a Raman fiber amplifier is mapped to the concentration of a food source for the fish school to search. Application of this algorithm to the design of a C-band gain flattened Raman fiber amplifier leads to an optimized amplifier that produces a flat gain spectrum with 0.63 dB in band ripple for given conditions. This result demonstrates that the artificial fish school algorithm is efficient for the optimization of pump parameters of gain flattened Raman fiber amplifiers.

  11. Effect of Pipe Flattening in API X65 Linepipe Steels Having Bainite vs. Ferrite/Pearlite Microstructures

    Directory of Open Access Journals (Sweden)

    Singon Kang

    2018-05-01

    Full Text Available The influence of microstructure on pipe flattening response was assessed using two different commercially produced U-ing, O-ing, and expansion (UOE pipes from API X65 steels having either a bainitic microstructure (steel B or a ferrite/pearlite microstructure (steel FP. A four-point bending apparatus and distinctive procedure were used to minimize strain localization during flattening. The flattened specimens were sectioned at different positions through the thickness, and tensile tested in both the longitudinal (LD and transverse directions (TD to assess the through-thickness variation in properties. Yield strength (YS distributions in the LD show V-shaped profiles through thickness in both steels, whereas the YS in the TD nearest the outside diameter (OD surface is reduced. These variations in YS are due to the Bauschinger effect associated with the compressive flattening pre-strain. The uniform elongation (UE of steel FP is almost independent of specimen position through the thickness, but for steel B there is a substantial reduction of the UE at both the inside and outside diameter positions and this reduction is greater in the LD. This work confirms that flattened pipe mechanical properties exhibit an important dependence on their microstructure type and it is postulated that the flattening procedure also influences the mechanical properties.

  12. Wet plume atop of the flattening slab: Insight into intraplate volcanism in East Asia

    Science.gov (United States)

    He, Lijuan

    2017-08-01

    Geophysical observations imply the intraplate volcanism in East Asia is related to dehydration of slab stagnating in the transition zone. To better understand the dynamics of such process, a thermochemical mantle convection model is constructed to simulate numerically the thermal evolution of slab and the transportation of water in the process of slab downgoing, flattening and stagnation. Equation of water transfer is included, and water effects on density and viscosity are considered. Model results indicate the warming of slab by surrounding mantle is rather slow. Water could be successfully dragged into the transition zone if the reference viscosity of the hydrous layer (with initial water of 2 wt%) is higher than 1017 Pa s and that of mantle is 1021 Pa s. Wet plumes could then originate in the flat-lying part of the slab, relatively far from the trench. Generally, the viscosity of the hydrous layer governs the initiation of wet plume, whereas the viscosity of the overlying mantle wedge controls the activity of the ascending wet plumes - they are more active in the weaker wedge. The complex fluid flow superposed by corner flow and free thermal convection influences greatly the water transport pattern in the upper mantle. Modeling results together with previous modeling infer three stages of water circulation in the big mantle wedge: 1) water is brought into the mantle transition zone by downward subducting slab under some specific thermo-rheological conditions, otherwise water is released at shallow depth near wedge tip; 2) wet plume generates from surface of the flattening slab warmed by surrounding mantle, and 3) water spreads over the big mantle wedge. Wet plume from the flattening Pacific Plate arrives at the lithospheric base and induces melting, which can explain the intraplate Cenozoic volcanoes in East Asia.

  13. Second-order infinitesimal bendings of surfaces of revolution with flattening at the poles

    International Nuclear Information System (INIS)

    Sabitov, I Kh

    2014-01-01

    We study infinitesimal bendings of surfaces of revolution with flattening at the poles. We begin by considering the minimal possible smoothness class C 1 both for surfaces and for deformation fields. Conditions are formulated for a given harmonic of a first-order infinitesimal bending to be extendable into a second order infinitesimal bending. We finish by stating a criterion for nonrigidity of second order for closed surfaces of revolution in the analytic class. We also give the first concrete example of such a nonrigid surface. Bibliography: 15 entries

  14. Second-order infinitesimal bendings of surfaces of revolution with flattening at the poles

    Energy Technology Data Exchange (ETDEWEB)

    Sabitov, I Kh [M. V. Lomonosov Moscow State University, Faculty of Mechanics and Mathematics, Moscow (Russian Federation)

    2014-12-31

    We study infinitesimal bendings of surfaces of revolution with flattening at the poles. We begin by considering the minimal possible smoothness class C{sup 1} both for surfaces and for deformation fields. Conditions are formulated for a given harmonic of a first-order infinitesimal bending to be extendable into a second order infinitesimal bending. We finish by stating a criterion for nonrigidity of second order for closed surfaces of revolution in the analytic class. We also give the first concrete example of such a nonrigid surface. Bibliography: 15 entries.

  15. Power flattening and reactivity suppression strategies for the Canadian supercritical water reactor concept

    International Nuclear Information System (INIS)

    McDonald, M.; Colton, A.; Pencer, J.

    2015-01-01

    The Canadian supercritical water-cooled reactor (SCWR) is a conceptual heavy water moderated, supercritical light water cooled pressure tube reactor. In contrast to current heavy water power reactors, the Canadian SCWR will be a batch fuelled reactor. Associated with batch fuelling is a large beginning-of-cycle excess reactivity. Furthermore, radial power peaking arising as a consequence of batch refuelling must be mitigated in some way. In this paper, burnable neutron absorber (BNA) added to fuel and absorbing rods inserted into the core are considered for reactivity management and power flattening. A combination of approaches appears adequate to reduce the core radial power peaking, while also providing reactivity suppression. (author)

  16. Three-dimensional liquid flattened Luneburg lens with ultra-wide viewing angle and frequency band

    Science.gov (United States)

    Wu, Lingling; Tian, Xiaoyong; Yin, Ming; Li, Dichen; Tang, Yiping

    2013-08-01

    Traditional Luneburg lens is a dielectric spherical antenna. It can focus the incoming collimated electromagnetic waves on its spherical surface, which causes the incompatibility with the planar feeding and receiving devices. Furthermore, the difficulties in the fabrication process also limited its applications. In this paper, a three-dimensional flattened Luneburg lens with a field-of-view angle up to 180° has been realized based on a liquid medium approach and a 3D-printing process. The fabricated three-dimensional lens showed a broadband transmission characteristic from 12.4 GHz to 18 GHz. The performance of the proposed lens was demonstrated by simulation and experimental results.

  17. Human impacts flatten rainforest-savanna gradient and reduce adaptive diversity in a rainforest bird.

    Directory of Open Access Journals (Sweden)

    Adam H Freedman

    2010-09-01

    Full Text Available Ecological gradients have long been recognized as important regions for diversification and speciation. However, little attention has been paid to the evolutionary consequences or conservation implications of human activities that fundamentally change the environmental features of such gradients. Here we show that recent deforestation in West Africa has homogenized the rainforest-savanna gradient, causing a loss of adaptive phenotypic diversity in a common rainforest bird, the little greenbul (Andropadus virens. Previously, this species was shown to exhibit morphological and song divergence along this gradient in Central Africa. Using satellite-based estimates of forest cover, recent morphological data, and historical data from museum specimens collected prior to widespread deforestation, we show that the gradient has become shallower in West Africa and that A. virens populations there have lost morphological variation in traits important to fitness. In contrast, we find no loss of morphological variation in Central Africa where there has been less deforestation and gradients have remained more intact. While rainforest deforestation is a leading cause of species extinction, the potential of deforestation to flatten gradients and inhibit rainforest diversification has not been previously recognized. More deforestation will likely lead to further flattening of the gradient and loss of diversity, and may limit the ability of species to persist under future environmental conditions.

  18. The DBI action, higher-derivative supergravity, and flattening inflaton potentials

    International Nuclear Information System (INIS)

    Bielleman, Sjoerd; Ibáñez, Luis E.; Pedro, Francisco G.; Valenzuela, Irene; Wieck, Clemens

    2016-01-01

    In string theory compactifications it is common to find an effective Lagrangian for the scalar fields with a non-canonical kinetic term. We study the effective action of the scalar position moduli of Type II Dp-branes. In many instances the kinetic terms are in fact modified by a term proportional to the scalar potential itself. This can be linked to the appearance of higher-dimensional supersymmetric operators correcting the Kähler potential. We identify the supersymmetric dimension-eight operators describing the α"′ corrections captured by the D-brane Dirac-Born-Infeld action. Our analysis then allows an embedding of the D-brane moduli effective action into an N=1 supergravity formulation. The effects of the potential-dependent kinetic terms may be very important if one of the scalars is the inflaton, since they lead to a flattening of the scalar potential. We analyze this flattening effect in detail and compute its impact on the CMB observables for single-field inflation with monomial potentials.

  19. Tellurite composite microstructured optical fibers with ultra-flattened and zero dispersion

    Science.gov (United States)

    Duan, Zhongchao; Liao, Meisong; Tomas, Kohoutek; Tong, Hoangtuan; Asano, Koji; Suzuki, Takenobu; Ohishi, Yasutake

    2012-04-01

    We report the fabrication of tellurite composite microstructured optical fiber (CMOF) with ultra-flattened zero dispersion (+/-3 ps/nm/Km) over 200nm band. To obtain this dispersion profile together with high nonlinearity, one ring of air holes and two layers of glass cladding are employed in the tellurite CMOF. The core of fiber is made of TeO2-Li2O-WO3 -MoO3-Nb2O5 (TLWMN) tellurite glass which possesses high linear and nonlinear refractive indices. The refractive index (n) at 1544nm and nonlinear refractive index (n2) of TLWMN glass is 2.08 and 3.78×10-11 esu, respectively. TeO2-ZnO-Na2O-La2O3 (TZNL) glass with n of 1.96 at 1544 nm and TeO2-ZnO-Li2O-Na2O-P2O5 (TZLNP) glass with low refractive index n of 1.63 at 1544 nm are used as the first cladding and the second cladding, respectively. Six small air holes are located between the core and the first glass cladding. Such kind of fiber with ~1.7 μm core and ~0.6 μm air holes are fabricated by a rod-in-tube method. The chromatic dispersion of the fiber is calculated by the fully vectorial finite difference method (FV-FDM) and becomes (+/-3 ps/nm/Km) in the wide range from 1.53 μm to 1.72 μm. And the nonlinear coefficient of present fiber is about 3.47 m-1W-1 which is much higher than that of silica MOFs. Furthermore, broad and flattened supercontinuum generation is demonstrated in 30-cm-long fiber with femtosecond laser pumping at 1557 nm. This kind of fiber has promising potential in nonlinear applications owing to the high nonlinearity and flattened dispersion profile.

  20. Single-fraction flattening filter–free volumetric modulated arc therapy for lung cancer: Dosimetric results and comparison with flattened beams technique

    Energy Technology Data Exchange (ETDEWEB)

    Barbiero, Sara [Medical Physics Division, Centro di Riferimento Oncologico, Aviano (Italy); Specialty School in Medical Physics, University of Pisa, Pisa (Italy); Rink, Alexandra [Radiation Physics Department, Princess Margaret Cancer Centre, University Health Network, Toronto (Canada); Department of Radiation Oncology, University of Toronto, Toronto (Canada); Matteucci, Fabrizio [Radiation Oncology Department, S.Chiara University Hospital, Pisa (Italy); Fedele, David [Radiotherapy Department, Casa di Cura S. Rossore, Pisa (Italy); Paiar, Fabiola; Pasqualetti, Francesco [Radiation Oncology Department, S.Chiara University Hospital, Pisa (Italy); Avanzo, Michele, E-mail: mavanzo@cro.it [Medical Physics Division, Centro di Riferimento Oncologico, Aviano (Italy)

    2016-01-01

    Purpose: To report on single-fraction stereotactic body radiotherapy (RT) (SBRT) with flattening filter (FF)–free (FFF) volumetric modulated arc therapy (VMAT) for lung cancer and to compare dosimetric results with VMAT with FF. Methods and materials: Overall, 25 patients were treated with 6-MV FFF VMAT (Varian TrueBeam STx LINAC) to a prescribed dose of 24 Gy in a single fraction. Treatment plans were recreated using FF VMAT. Dose-volume indices, monitor units (MU), and treatment times were compared between FFF and FF VMAT techniques. Results: Dose constraints to PTV, spinal cord, and lungs were reached in FFF and FF plans. In FFF plans, average conformity index was 1.13 (95% CI: 1.07 to1.38). Maximum doses to spinal cord, heart, esophagus, and trachea were 2.9 Gy (95% CI: 0.4 to 6.7 Gy), 0.8 Gy (95% CI: 0 to 3.6 Gy), 3.3 Gy (95% CI: 0.02 to 13.9 Gy), and 1.5 Gy (95% CI: 0 to 4.9 Gy), respectively. Average V7 Gy, V7.4 Gy, and mean dose to the healthy lung were 126.5 cc (95% CI: 41.3 to 248.9 cc), 107.3 cc (95% CI: 18.7 to 232.8 cc), and 1.1 Gy (95% CI: 0.3 to 2.2 Gy), respectively. No statistically significant differences were found in dosimetric results and MU between FF and FFF treatments. Treatment time was reduced by an average factor of 2.31 (95% CI: 2.15 to 2.43) from FF treatments to FFF, and the difference was statistically significant. Conclusions: FFF VMAT for lung SBRT provides equivalent dosimetric results to the target and organs at risk as FF VMAT while significantly reducing treatment time.

  1. Spectra and neutron dose of an 18 MV Linac using two geometric models of the head

    International Nuclear Information System (INIS)

    Barrera, M. T.; Pino, F.; Barros, H.; Sajo-Bohus, L.; Davila, J.; Salcedo, E.; Vega C, H. R.; Benites R, J. L.

    2015-10-01

    Full text: Using the Monte Carlo method, by MCNP5 code, simulations were performed with different source terms and 2 geometric models of the head to obtain spectra in energy, flow and doses of photo-neutrons at different positions on the stretcher and in the radiotherapy room. The simplest model was a spherical shell of tungsten; the second was the complete model of a heterogeneous head of an accelerator Varian ix. In both models Tosi function was used as a source term. In addition, for the second model Sheikh-Bagheri distribution was used for photons and photo-neutrons were generated. Also in both models the radiotherapy room of Gurve group of the Teaching Medical Center La Trinidad was included, which is equipped with an accelerator Varian Clinic 2100. In this Center passive detectors PADC (Cr-39) were irradiated with neutron converters, with 18 MeV photons radiation. The measured neutron flow was compared with that obtained with Monte Carlo calculations. The Monte Carlo flows are similar to those measured at the isocenter. The simplest model underestimates the neutron flow compared with the calculated flows with the heterogeneous model of the head. (Author)

  2. A quantitative analysis of rotary, ultrasonic and manual techniques to treat proximally flattened root canals

    Directory of Open Access Journals (Sweden)

    Fabiana Soares Grecca

    2007-04-01

    Full Text Available OBJECTIVE: The efficiency of rotary, manual and ultrasonic root canal instrumentation techniques was investigated in proximally flattened root canals. MATERIAL AND METHODS: Forty human mandibular left and right central incisors, lateral incisors and premolars were used. The pulp tissue was removed and the root canals were filled with red die. Teeth were instrumented using three techniques: (i K3 and ProTaper rotary systems; (ii ultrasonic crown-down technique; and (iii progressive manual technique. Roots were bisected longitudinally in a buccolingual direction. The instrumented canal walls were digitally captured and the images obtained were analyzed using the Sigma Scan software. Canal walls were evaluated for total canal wall area versus non-instrumented area on which dye remained. RESULTS: No statistically significant difference was found between the instrumentation techniques studied (p<0.05. CONCLUSION: The findings of this study showed that no instrumentation technique was 100% efficient to remove the dye.

  3. Broadband tunability of gain-flattened quantum-well semiconductor lasers with an external grating

    International Nuclear Information System (INIS)

    Mittelstein, M.; Mehuys, D.; Yariv, A.; Sarfaty, R.; Ungar, J.E.

    1989-01-01

    Semiconductor injection lasers are known to be tunable over a range of order kΒ · T. Quantum-well lasers, in particular, are shown to exhibit flattened, broadband gain spectra at a particular pumping condition. The gain requirement for a grating-tuned external cavity configuration is examined and is applied to a semiconductor quantum-well laser with an optimized length of gain region. The coupled-cavity formalism is employed to examine the conditions for continuous tuning. The possible tuning range of double-heterostructure lasers is compared to that of quantum-well lasers. The predicted broadband tunability of quantum-well lasers is confirmed experimentally by grating-tuning of uncoated lasers exceeding 120 nm, with single, longitudinal mode output power exceeding 300 mW

  4. Microstructure of AZ31 Magnesium Alloy deformed by indentation-flattening compound deformation technology

    Science.gov (United States)

    Wang, Minghao; Wang, Zhongtang; Yu, Xiaolin

    2018-03-01

    Characteristic of indentation-flattening compound deformation technology (IFCDT) is discussed, and the parameters of IFCDT are defined. Performance of magnesium alloy AZ31 sheet deformed by IFCDT is researched. The effect of IFCDT coefficient, temperature and reduction ratio on the microstructure of magnesium alloy sheet is analyzed. The research results show that the volume fraction of the twin crystal decreases gradually and the average grain size increases with increasing of coefficient of IFCDT. With increase of the reduction ratio, the volume fraction of the twin crystal gradually increases, and the average grain size also increases. With increase of deformation temperature, the volume fraction of the twin crystal decreases gradually, and the twin crystal grain size increases.

  5. Scalable and reusable micro-bubble removal method to flatten large-area 2D materials

    Science.gov (United States)

    Pham, Phi H. Q.; Quach, Nhi V.; Li, Jinfeng; Burke, Peter J.

    2018-04-01

    Bubbles generated during electro-delamination and chemical etch during large-area two-dimensional (2D) material transfer has been shown to cause rippling, and consequently, results in tears and wrinkles in the transferred film. Here, we demonstrate a scalable and reusable method to remove surface adhered micro-bubbles by using hydrophobic surfaces modified by self-assembled monolayers (SAMs). Bubble removal allows the 2D film to flatten out and prevents the formation of defects. Electrical characterization was used to verify improved transfer quality and was confirmed by increased field-effect mobility and decreased sheet resistance. Raman spectroscopy was also used to validate enhanced electrical quality following transfer. The bubble removal method can be applied to an assortment of 2D materials using diverse hydrophobic SAM variants. Our studies can be integrated into large scale applications and will lead to improved large-area 2D electronics in general.

  6. Flattening of the resonance spectrum of hadrons from κ-deformed Poincare algebra

    International Nuclear Information System (INIS)

    Dey, J.; Ferreira, P.L.; Tomio, L.; Choudhury, R.R.

    1994-02-01

    It was recently defined by Lukierski a κ-deformed Poincare algebra which is characterized by having the energy-momentum and angular momentum sub-algebras not deformed. Further Biedenharn showed that on gauging the κ-deformed electron with the electromagnetic field, one can set a limit on the allowed value of the deformation parameter ε ≡ 1/κ < 1 fm. It is shown that one gets Regge like angular excitations, J, of the mesons, non-strange and strange baryons, with a value of ε ∼ 0.082 fm and predict a flattening with J of the corresponding trajectories. The Regge fit improves on including deformation, particularly for the baryon spectrum. (author)

  7. Surface dose measurements in and out of field. Implications for breast radiotherapy with megavoltage photon beams

    Energy Technology Data Exchange (ETDEWEB)

    Lonski, Peta; Kron, Tomas [Peter MacCallum Cancer Centre, Melbourne (Australia); RMIT Univ., Melbourne (Australia); Ramachandran, Prabhakar; Franich, Rick [Peter MacCallum Cancer Centre, Melbourne (Australia)

    2017-07-01

    This study examines the difference in surface dose between flat and flattening filter free (FFF) photon beams in the context of breast radiotherapy. The surface dose was measured for 6 MV, 6 MV FFF, 10 MV, 10 MV FFF and 18 MV photon beams using a thin window ionisation chamber for various field sizes. Profiles were acquired to ascertain the change in surface dose off-axis. Out-of-field measurements were included in a clinically representative half beam block tangential breast field. In the field centres of FFF beams the surface dose was found to be increased for small fields and decreased for large fields compared to flat beams. For FFF beams, surface dose was found to decrease off-axis and resulted in lower surface dose out-of-field compared to flat beams.

  8. Investigation of the accuracy of MV radiation isocentre calculations in the Elekta cone-beam CT software XVI

    DEFF Research Database (Denmark)

    Zimmermann, S. J.; Rowshanfarzad, P.; Ebert, M. A.

    2015-01-01

    ) and the radiation field centre (RFC) is calculated. A software package was developed for accurate calculation of the linac isocentre position. This requires precise determination of the position of the ball bearing and the RFC. Results: Data were acquired for 6 MV, 18 MV and flattening filter free (FFF) 6 MV FFF...... radiation isocentre prior to routine use of the cone-beam CT system. The isocentre determination method used in the XVI software is not available to users. The aim of this work is to perform an independent evaluation of the Elekta XVI 4.5 software for isocentre verification with focus on the robustness...... iView GT software. Two images were acquired at each cardinal gantry angle (-180o, -90o , 0o, 90o) at two opposing collimator angles. The images were exported to the conebeam CT software XVI 4.5 where the difference between the ball bearing position in the XYZ-room coordinates (IEC61217...

  9. CT study of the performance of reciprocating and oscillatory motions in flattened root canal areas

    Directory of Open Access Journals (Sweden)

    Cacio MOURA-NETTO

    2015-01-01

    Full Text Available Root canal preparation is an important step in endodontic treatment. The anatomical complexity of the middle third of the root compromises the effective cleaning of this area. Thus, advances have been made in instrumentation techniques and instruments for this purpose. The aim of this study was to evaluate the effects of three different instrumentation systems on the enlargement of the middle thirds of root canals in mandibular incisors. The preparation methods used were the reciprocating systems Reciproc (Group I and WaveOne (Group II and the oscillatory system Tilos (Group III. Comparisons were made by three-dimensional image reconstruction with cone-beam computed tomography before and after instrumentation. Changes in area, perimeter, centering ability, and pattern of preparation were analyzed. The results were subjected to ANOVA complemented by the Tukey’s test. Changes in area, perimeter, and tendency of transportation showed similar results among groups. The transportation index of the Tilos system was significantly lower than that of the other groups. Qualitative analysis of the preparation pattern showed that the Tilos system had a more uniform preparation, although Reciproc and WaveOne preparations appeared more rounded, incompatible with the original canal anatomy. There was similarity in the systems’ performance on flattened areas, although the Tilos system presented a better pattern of root canal preparation and a lower index of transportation.

  10. CT study of the performance of reciprocating and oscillatory motions in flattened root canal areas

    International Nuclear Information System (INIS)

    Moura-Netto, Cacio; Palo, Renato Miotto; Pinto, Larissa Fernanda; Daltoe, Gisele; Mello-Moura, Anna Carolina Volpi

    2015-01-01

    Abstract: Root canal preparation is an important step in endodontic treatment. The anatomical complexity of the middle third of the root compromises the effective cleaning of this area. Thus, advances have been made in instrumentation techniques and instruments for this purpose. The aim of this study was to evaluate the effects of three different instrumentation systems on the enlargement of the middle thirds of root canals in mandibular incisors. The preparation methods used were the reciprocating systems Reciproc (Group I) and WaveOne (Group II) and the oscillatory system Tilos (Group III). Comparisons were made by three-dimensional image reconstruction with cone-beam computed tomography before and after instrumentation. Changes in area, perimeter, centering ability, and pattern of preparation were analyzed. The results were subjected to ANOVA complemented by the Tukey’s test. Changes in area, perimeter, and tendency of transportation showed similar results among groups. The transportation index of the Tilos system was significantly lower than that of the other groups. Qualitative analysis of the preparation pattern showed that the Tilos system had a more uniform preparation, although Reciproc and WaveOne preparations appeared more rounded, incompatible with the original canal anatomy. There was similarity in the systems’ performance on flattened areas, although the Tilos system presented a better pattern of root canal preparation and a lower index of transportation. (author)

  11. Design of broadband dispersion flattened fiber for DWDM system: Performance analysis using various modulation formats

    Science.gov (United States)

    Goel, Aditya; Pandey, Gaurav

    2018-05-01

    In this paper, unique design of an optimal broadband optical dispersion flattened fiber (DFF) is proposed, which is capable of supporting the data rate of the order of Tb/s. The analysis of the single mode fiber for the design of the proposed DFF has been carried out by employing the quadratic Finite Element Method (FEM) with generalized refractive index (R. I.) profile. The minimization of the dispersion with respect to various profile parameters within the specified wavelength band is the essential optimization criteria. Computations show that a DFF can be designed where the overall dispersion can be restricted within ± 1 ps/km-nm over the entire spectral span ranging from 1290 to 1540 nm (250 nm) exhibiting a very small maximum value of dispersion slope (± 0.02 ps / (nm2-km)) in particular. The detailed performance analysis of the proposed DFF with different modulation techniques has been carried out in order to critically evaluate the performance of the DFF with respect to various significant parameters. The results suggest an excellent design of broadband optical waveguide capable of supporting high-speed data rate (40 Tb/s) through the single DFF, ideally suitable for the long haul dense wavelength division multiplexing (DWDM) optical transmission systems.

  12. Oxytocin and vasopressin flatten dominance hierarchy and enhance behavioral synchrony in part via anterior cingulate cortex.

    Science.gov (United States)

    Jiang, Yaoguang; Platt, Michael L

    2018-05-29

    The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) influence social functions in many mammals. In humans and rhesus macaques, OT delivered intranasally can promote prosocial behavior in certain contexts. Yet the precise neural mechanisms mediating these behavioral effects remain unclear. Here we show that treating a group of male macaque monkeys intranasally with aerosolized OT relaxes their spontaneous social interactions with other monkeys. OT reduces differences in social behavior between dominant and subordinate monkeys, thereby flattening the status hierarchy. OT also increases behavioral synchrony within a pair. Intranasal delivery of aerosolized AVP reproduces the effects of OT with greater efficacy. Remarkably, all behavioral effects are replicated when OT or AVP is injected focally into the anterior cingulate gyrus (ACCg), a brain area linked to empathy and other-regarding behavior. ACCg lacks OT receptors but is rich in AVP receptors, suggesting exogenous OT may shape social behavior, in part, via nonspecific binding. Notably, OT and AVP alter behaviors of both the treated monkey and his untreated partner, consistent with enhanced feedback through reciprocal social interactions. These findings bear important implications for use of OT in both basic research and as a therapy for social impairments in neurodevelopmental disorders.

  13. Medical Radioisotope Production in a Power-Flattened ADS Fuelled with Uranium and Plutonium Dioxides

    Directory of Open Access Journals (Sweden)

    Gizem Bakır

    2016-01-01

    Full Text Available This study presents the medical radioisotope production performance of a conceptual accelerator driven system (ADS. Lead-bismuth eutectic (LBE is selected as target material. The subcritical fuel core is conceptually divided into ten equidistant subzones. The ceramic (natural U, PuO2 fuel mixture and the materials used for radioisotope production (copper, gold, cobalt, holmium, rhenium, thulium, mercury, palladium, thallium, molybdenum, and yttrium are separately prepared as cylindrical rods cladded with carbon/carbon composite (C/C and these rods are located in the subzones. In order to obtain the flattened power density, percentages of PuO2 in the mixture of UO2 and PuO2 in the subzones are adjusted in radial direction of the fuel zone. Time-dependent calculations are performed at 1000 MW thermal fission power (Pth for one hour using the BURN card. The neutronic results show that the investigated ADS has a high neutronic capability, in terms of medical radioisotope productions, spent fuel transmutation and energy multiplication. Moreover, a good quasiuniform power density is achieved in each material case. The peak-to-average fission power density ratio is in the range of 1.02–1.28.

  14. CT study of the performance of reciprocating and oscillatory motions in flattened root canal areas

    Energy Technology Data Exchange (ETDEWEB)

    Moura-Netto, Cacio, E-mail: caciomn@usp.br [Universidade Cruzeiro do Sul (UNICSUL), Sao Paulo, SP (Brazil). Fac. de Odontologia; Palo, Renato Miotto [Universidade Estadual Paulista Julio de Mesquita Filho (ICT/UNESP), Sao Jose dos Campos, SP (Brazil). Instituto de Ciencia e Tecnologia; Pinto, Larissa Fernanda; Daltoe, Gisele; Mello-Moura, Anna Carolina Volpi [Universidade Ibirapuera (UNIB), Sao Paulo, SP (Brazil). Fac. de Odontologia

    2015-03-01

    Abstract: Root canal preparation is an important step in endodontic treatment. The anatomical complexity of the middle third of the root compromises the effective cleaning of this area. Thus, advances have been made in instrumentation techniques and instruments for this purpose. The aim of this study was to evaluate the effects of three different instrumentation systems on the enlargement of the middle thirds of root canals in mandibular incisors. The preparation methods used were the reciprocating systems Reciproc (Group I) and WaveOne (Group II) and the oscillatory system Tilos (Group III). Comparisons were made by three-dimensional image reconstruction with cone-beam computed tomography before and after instrumentation. Changes in area, perimeter, centering ability, and pattern of preparation were analyzed. The results were subjected to ANOVA complemented by the Tukey’s test. Changes in area, perimeter, and tendency of transportation showed similar results among groups. The transportation index of the Tilos system was significantly lower than that of the other groups. Qualitative analysis of the preparation pattern showed that the Tilos system had a more uniform preparation, although Reciproc and WaveOne preparations appeared more rounded, incompatible with the original canal anatomy. There was similarity in the systems’ performance on flattened areas, although the Tilos system presented a better pattern of root canal preparation and a lower index of transportation. (author)

  15. Infinitesimal and global rigidity and inflexibility of surfaces of revolution with flattening at the poles

    International Nuclear Information System (INIS)

    Sabitov, I Kh

    2013-01-01

    The subject of this article is one of the most important questions of classical geometry: the theory of bendings and infinitesimal bendings of surfaces. These questions are studied for surfaces of revolution and, unlike previous well-known works, we make only minimal smoothness assumptions (the class C 1 ) in the initial part of our study. In this class we prove local existence and uniqueness theorems for infinitesimal bendings. We then consider the analytic class and establish simple criteria for rigidity and inflexibility of compact surfaces. These criteria depend on the values of certain integer characteristics related to the order of flattening of the surface at its poles. We also show that in the nonanalytic situation there exist nonrigid surfaces with any given order of flattening at the poles. Bibliography: 22 titles

  16. Ultra-flattened nearly-zero dispersion and ultrahigh nonlinear slot silicon photonic crystal fibers with ultrahigh birefringence

    Science.gov (United States)

    Liao, Jianfei; Xie, Yingmao; Wang, Xinghua; Li, Dongbo; Huang, Tianye

    2017-07-01

    A slot silicon photonic crystal fiber (PCF) is proposed to simultaneously achieve ultrahigh birefringence, large nonlinearity and ultra-flattened nearly-zero dispersion over a wide wavelength range. By taking advantage on the slot effect, ultrahigh birefringence up to 0.0736 and ultrahigh nonlinear coefficient up to 211.48 W-1 m-1 for quasi-TE mode can be obtained at the wavelength of 1.55 μm. Moreover, ultra-flattened dispersion of 0.49 ps/(nm km) for quasi-TE mode can be achieved over a 180 nm wavelength range with low dispersion slope of 1.85 × 10-3 ps/(nm2 km) at 1.55 μm. Leveraging on these advantages, the proposed slot PCF has great potential for efficient all-optical signal processing applications.

  17. Start-up fuel and power flattening of sodium-cooled candle core

    International Nuclear Information System (INIS)

    Takaki, Naoyuki; Sagawa, Yu; Umino, Akitake; Sekimoto, Hiroshi

    2013-01-01

    The hard neutron spectrum and unique power shape of CANDLE enable its distinctive performances such as achieving high burnup more than 30% and exempting necessity of both enrichment and reprocessing. On the other hand, they also cause several challenging problems. One is how the initial fuel can be prepared to start up the first CANDLE reactor because the equilibrium fuel composition that enables stable CANDLE burning is complex both in axial and radial directions. Another prominent problem is high radial power peaking factor that worsens averaged burnup, namely resource utilization factor in once-through mode and shorten the life time of structure materials. The purposes of this study are to solve these two problems. Several ideas for core configurations and startup fuel using single enrichment uranium and iron as a substitute of fission products are studied. As a result, it is found that low enriched uranium is applicable to ignite the core but all concepts examined here exceeded heat limits. Adjustment in enrichment and height of active and burnt zone is opened for future work. Sodium duct assemblies and thorium fuel assemblies loaded in the center region are studied as measures to reduce radial power peaking factor. Replacing 37 fuels by thorium fuel assemblies in the zeroth to third row provides well-balanced performance with flattened radial power distribution. The CANDLE core loaded with natural uranium in the outer and thorium in the center region achieved 35.6% of averaged burnup and 7.0 years of cladding life time owing to mitigated local fast neutron irradiation at the center. Using thorium with natural or depleted uranium in CANDLE reactor is also beneficial to diversifying fission resource and extending available term of fission energy without expansion of needs for enrichment and reprocessing

  18. Audio segmentation using Flattened Local Trimmed Range for ecological acoustic space analysis

    Directory of Open Access Journals (Sweden)

    Giovany Vega

    2016-06-01

    Full Text Available The acoustic space in a given environment is filled with footprints arising from three processes: biophony, geophony and anthrophony. Bioacoustic research using passive acoustic sensors can result in thousands of recordings. An important component of processing these recordings is to automate signal detection. In this paper, we describe a new spectrogram-based approach for extracting individual audio events. Spectrogram-based audio event detection (AED relies on separating the spectrogram into background (i.e., noise and foreground (i.e., signal classes using a threshold such as a global threshold, a per-band threshold, or one given by a classifier. These methods are either too sensitive to noise, designed for an individual species, or require prior training data. Our goal is to develop an algorithm that is not sensitive to noise, does not need any prior training data and works with any type of audio event. To do this, we propose: (1 a spectrogram filtering method, the Flattened Local Trimmed Range (FLTR method, which models the spectrogram as a mixture of stationary and non-stationary energy processes and mitigates the effect of the stationary processes, and (2 an unsupervised algorithm that uses the filter to detect audio events. We measured the performance of the algorithm using a set of six thoroughly validated audio recordings and obtained a sensitivity of 94% and a positive predictive value of 89%. These sensitivity and positive predictive values are very high, given that the validated recordings are diverse and obtained from field conditions. The algorithm was then used to extract audio events in three datasets. Features of these audio events were plotted and showed the unique aspects of the three acoustic communities.

  19. Evaluation of treatment plan quality of IMRT and VMAT with and without flattening filter using Pareto optimal fronts.

    Science.gov (United States)

    Lechner, Wolfgang; Kragl, Gabriele; Georg, Dietmar

    2013-12-01

    To investigate the differences in treatment plan quality of IMRT and VMAT with and without flattening filter using Pareto optimal fronts, for two treatment sites of different anatomic complexity. Pareto optimal fronts (POFs) were generated for six prostate and head-and-neck cancer patients by stepwise reduction of the constraint (during the optimization process) of the primary organ-at-risk (OAR). 9-static field IMRT and 360°-single-arc VMAT plans with flattening filter (FF) and without flattening filter (FFF) were compared. The volume receiving 5 Gy or more (V5 Gy) was used to estimate the low dose exposure. Furthermore, the number of monitor units (MUs) and measurements of the delivery time (T) were used to assess the efficiency of the treatment plans. A significant increase in MUs was found when using FFF-beams while the treatment plan quality was at least equivalent to the FF-beams. T was decreased by 18% for prostate for IMRT with FFF-beams and by 4% for head-and-neck cases, but increased by 22% and 16% for VMAT. A reduction of up to 5% of V5 Gy was found for IMRT prostate cases with FFF-beams. The evaluation of the POFs showed an at least comparable treatment plan quality of FFF-beams compared to FF-beams for both treatment sites and modalities. For smaller targets the advantageous characteristics of FFF-beams could be better exploited. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  20. Enhanced piezoelectricity in A B O3 ferroelectrics via intrinsic stress-driven flattening of the free-energy profile

    Science.gov (United States)

    Feng, Yu; Li, Wei-Li; Yu, Yang; Jia, He-Nan; Qiao, Yu-Long; Fei, Wei-Dong

    2017-11-01

    An approach to greatly enhance the piezoelectric properties (˜4 00 pC/N) of the tetragonal BaTi O3 polycrystal using a small number of A -site acceptor-donor substitutions [D. Xu et al., Acta Mater. 79, 84 (2014), 10.1016/j.actamat.2014.07.023] has been proposed. In this study, Pb (ZrTi ) O3 (PZT) based polycrystals with various crystal symmetries (tetragonal, rhombohedral, and so on) were chosen to investigate the piezoelectricity enhancement mechanism. X-ray diffraction results show that doping generates an intrinsic uniaxial compressive stress along the [001] pc direction in the A B O3 lattices. Piezoelectric maps in the parameter space of temperature and Ti concentration in the PZT and doped system show a more significant enhancement effect of L i+-A l3 + codoping in tetragonal PZT than in the rhombohedral phase. Phenomenological thermodynamic analysis indicates that the compressive stress results in more serious flattening of the free-energy profile in tetragonal PZT, compared with that in the rhombohedral phase. The chemical stress obtained by this acceptor-donor codoping can be utilized to optimize the piezoelectric performance on the tetragonal-phase site of the morphotropic phase boundary in the PZT system. The present study provides a promising route to the large piezoelectric effect induced by chemical-stress-driven flattening of the free-energy profile.

  1. Theory of pixel lensing towards M31 II, The velocity anisotropy and flattening of the MACHO distribution

    CERN Document Server

    Kerins, E; Evans, N W; Baillon, Paul; Carr, B J; Giraud-Héraud, Yannick; Gould, A; Hewett, P C; Kaplan, J; Paulin-Henriksson, S; Smartt, S J; Tsapras, Y; Valls-Gabaud, D

    2003-01-01

    The POINT-AGAPE collaboration is currently searching for massive compact halo objects (MACHOs) towards the Andromeda galaxy (M31). The survey aims to exploit the high inclination of the M31 disk, which causes an asymmetry in the spatial distribution of M31 MACHOs. Here, we investigate the effects of halo velocity anisotropy and flattening on the asymmetry signal using simple halo models. For a spherically symmetric and isotropic halo, we find that the underlying pixel-lensing rate in far-disk M31 MACHOs is more than 5 times the rate of near-disk events. We find that the asymmetry is increased further by about 30% if the MACHOs occupy radial orbits rather than tangential orbits, but is substantially reduced if the MACHOs lie in a flattened halo. However, even for haloes with a minor-to-major axis ratio q = 0.3, the numbers of M31 MACHOs in the far-side outnumber those in the near-side by a factor of ~2. We show that, if positional information is exploited in addition to number counts, then the number of candid...

  2. A Monte Carlo Study of the Photon Spectrum due to the Different Materials Used in the Construction of Flattening Filters of LINAC

    Directory of Open Access Journals (Sweden)

    J. S. Estepa Jiménez

    2017-01-01

    Full Text Available Different types the spectrum of photons were studied; they were emitted from the flattening filter of a LINAC Varian 2100 C/D that operates at 15 MV. The simplified geometry of the LINAC head was calculated using the MCNPX code based on the studies of the materials of the flattening filter, namely, SST, W, Pb, Fe, Ta, Al, and Cu. These materials were replaced in the flattening filter to calculate the photon spectra at the output of this device to obtain the spectrum that makes an impact with the patient. The different spectra obtained were analyzed and compared to the emission from the original spectra configuration of the LINAC, which uses material W. In the study, different combinations of materials were considered in order to establish differences between the use of different materials and the original material, with the objective of establishing advantages and disadvantages from a clinical standpoint.

  3. Contribution of CRUST2.0 components to the tri-axiality of the Earth and equatorial flattening of the core

    Directory of Open Access Journals (Sweden)

    Sun Rong

    2013-08-01

    Full Text Available Equatorial flattening of the core were previously estimated to be 5 × 10−4 by using seismically derived density anomaly, and 1.7748280 × 10−5 by assuming that the ratio of polar flattening to equatorial flattening of the core is the same as that of the whole Earth. In this study, we attempted to explain the difference by applying a density-contrast stripping process to the crust in the second method. We use the CRUST2.0 model to estimate the inertia-moment contribution resulted from the density-contrast structure in the crust to a tri-axial Earth. The contribution of the density contrast in the crust was removed layer by layer. The layers include topography, bathymetry, ice, soft sediment, hard sediment, upper crust, middle crust, lower crust and the reference crust. For the boundaries of the topography and bathymetry layers, we used ETOPO5 values with a resolution of 5'. For boundaries of other layers, we used values from the CRUST2.0 model with a resolution of 2°. After the contribution of density contrast is stripped, the equatorial flattening of the core was found to be 6.544 × 10−5, which is still one order of magnitude smaller than the result given by the first method. This suggests that at least one of the methods is not correct. The influence of the uncertainty in the equatorial flattening of the core on the Free Core Nutation frequency is small, but its effect on the gravitational torque acting on the tri-axial inner core cannot be ignored. So an accurate determination of the equatorial flattening of the core is still necessary.

  4. Flattening and manipulation of the electronic structure of h-BN/Rh(111) nanomesh upon Sn intercalation

    Science.gov (United States)

    Sugiyama, Yuya; Bernard, Carlo; Okuyama, Yuma; Ideta, Shin-ichiro; Tanaka, Kiyohisa; Greber, Thomas; Hirahara, Toru

    2018-06-01

    We have deposited Sn on corrugated hexagonal boron nitride (h-BN) nanomeshs formed on Rh(111) and found that Sn atoms are intercalated between h-BN and Rh, flattening the h-BN. Our reflection high-energy electron diffraction (RHEED) analysis showed that the average in-plane lattice constant of h-BN increases due to the loss of the corrugation. Furthermore, electronic structure measurements based on angle-resolved photoemission spectroscopy (ARPES) showed that the h-BN π band width increases significantly while the σ band width does not change as much. These behaviors were partly different from previous reports on the intercalation of h-BN/Rh system. Our results offer a novel, simple method to control the electronic structure of h-BN.

  5. Binding Direction-Based Two-Dimensional Flattened Contact Area Computing Algorithm for Protein-Protein Interactions.

    Science.gov (United States)

    Kang, Beom Sik; Pugalendhi, GaneshKumar; Kim, Ku-Jin

    2017-10-13

    Interactions between protein molecules are essential for the assembly, function, and regulation of proteins. The contact region between two protein molecules in a protein complex is usually complementary in shape for both molecules and the area of the contact region can be used to estimate the binding strength between two molecules. Although the area is a value calculated from the three-dimensional surface, it cannot represent the three-dimensional shape of the surface. Therefore, we propose an original concept of two-dimensional contact area which provides further information such as the ruggedness of the contact region. We present a novel algorithm for calculating the binding direction between two molecules in a protein complex, and then suggest a method to compute the two-dimensional flattened area of the contact region between two molecules based on the binding direction.

  6. Binding Direction-Based Two-Dimensional Flattened Contact Area Computing Algorithm for Protein–Protein Interactions

    Directory of Open Access Journals (Sweden)

    Beom Sik Kang

    2017-10-01

    Full Text Available Interactions between protein molecules are essential for the assembly, function, and regulation of proteins. The contact region between two protein molecules in a protein complex is usually complementary in shape for both molecules and the area of the contact region can be used to estimate the binding strength between two molecules. Although the area is a value calculated from the three-dimensional surface, it cannot represent the three-dimensional shape of the surface. Therefore, we propose an original concept of two-dimensional contact area which provides further information such as the ruggedness of the contact region. We present a novel algorithm for calculating the binding direction between two molecules in a protein complex, and then suggest a method to compute the two-dimensional flattened area of the contact region between two molecules based on the binding direction.

  7. Trapped fast particle destabilization of internal kink mode for the locally flattened q-profile with an inflection point

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xian-Qu [Institute of Fusion Science, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhang, Rui-Bin; Meng, Guo [State Key Lab of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China)

    2016-07-15

    The destabilization of ideal internal kink modes by trapped fast particles in tokamak plasmas with a “shoulder”-like equilibrium current is investigated. It is found that energetic particle branch of the mode is unstable with the driving of fast-particle precession drifts and corresponds to a precessional fishbone. The mode with a low stability threshold is also more easily excited than the conventional precessional fishbone. This is different from earlier studies for the same equilibrium in which the magnetohydrodynamic (MHD) branch of the mode is stable. Furthermore, the stability and characteristic frequency of the mode are analyzed by solving the dispersion relation and comparing with the conventional fishbone. The results suggest that an equilibrium with a locally flattened q-profile, may be modified by localized current drive (or bootstrap current, etc.), is prone to the onset of the precessional fishbone branch of the mode.

  8. Synthesis and structural characterisation of iron(II) and copper(II) diphosphates containing flattened metal oxotetrahedra

    International Nuclear Information System (INIS)

    Keates, Adam C.; Wang, Qianlong; Weller, Mark T.

    2014-01-01

    Single crystal and bulk polycrystalline forms of K 2 MP 2 O 7 (M=Fe(II), Cu(II)) have been synthesised and their structures determined from single crystal X-ray diffraction data. Both compounds crystallize in the tetragonal system, space group P-42 1 m. Their structures are formed from infinite sheets of linked oxopolyhedra of the stoichiometry [MP 2 O 7 ] 2− with potassium cations situated between the layers. The MO 4 tetrahedra share oxygen atoms with [P 2 O 7 ] 4− diphosphate groups and the potassium ions have KO 8 square prismatic geometry. In both compounds the M(II) centre has an unusual strongly flattened, tetrahedral coordination to oxygen, as a result of the Jahn–Teller (JT) effect for the high spin d 6 Fe(II) and p-orbital mixing or a second order JT effect for d 9 Cu(II) centres in four fold coordination. The uncommon transition metal ion environments found in these materials are reflected in their optical absorption spectra and magnetism data. - Graphical abstract: The structures of the tetragonal polymorphs of K 2 MP 2 O 7 , M=Cu(II), Fe(II), consist of infinite sheets of stoichiometry [MP 2 O 7 ] 2− , formed from linked pyrophosphate groups and MO 4 tetrahedra, separated by potassium ions. In both compounds the unusual tetrahedral coordination of the M(II) centre is strongly flattened as a result of Jahn–Teller (JT) effects for high spin, d 6 Fe(II) and p-orbital mixing and second-order JT effects for d 9 Cu(II). Display Omitted - Highlights: • Tetrahedral copper and iron(II) coordinated by oxygen. • New layered phosphate structure. • Jahn–Teller and d 10 distorted coordinations

  9. Influence of surface flattening on biodiversity of terrestrial arthropods during early stages of brown coal spoil heap restoration.

    Science.gov (United States)

    Moradi, Jabbar; Potocký, Pavel; Kočárek, Petr; Bartuška, Martin; Tajovský, Karel; Tichánek, Filip; Frouz, Jan; Tropek, Robert

    2018-08-15

    Heterogeneity of environmental conditions is the crucial factor supporting biodiversity in various habitats, including post-mining sites. The effects of micro-topographic heterogeneity on biodiversity and conservation potential of arthropod communities in post-industrial habitats had not been studied before now. At one of the largest European brown coal spoil heaps, we sampled eight groups of terrestrial arthropods with different life strategies (moths, spiders, ground beetles, ants, orthopteroids, centipedes, millipedes, and woodlice), in successionally young plots (5-18 y), with a heterogeneous wavy surface after heaping, and compared the communities with plots flattened by dozing. A combination of the standardized quantitative sampling, using two different methods, and a paired design of the plot selection enabled a robust analysis. Altogether, we recorded 380 species of the focal arthropods, 15 of them nationally threatened. We revealed the importance of the micro-topographic heterogeneity for the formation of the biodiversity of arthropods in their secondary refuges. The communities with higher biodiversity and conservation value were detected in the plots with heterogeneous surfaces; exceptions were ground beetles and millipedes. The surface flattening, often the first step of technical reclamation projects, thus suppress biodiversity of most terrestrial arthropods during the restoration of post-mining sites. Since the communities of both surface types differed, the proportional presence on both surfaces could be more efficient in supporting the local biodiversity. We suggest reducing the surface dozing for the cases with other concerns only, to achieve a proportional representation of both surface types. Such a combination of different restoration approaches would, thus, efficiently support high biodiversity of groups with various needs. Copyright © 2018 Elsevier Ltd. All rights reserved.

  10. The first astronomical hypothesis based on cinematographical observations: Costa Lobo's 1912 evidence for polar flattening of the moon

    Science.gov (United States)

    Bonifácio, Vitor; Malaquias, Isabel; Fernandes, João

    2010-07-01

    Acceptance by the scientific community of results obtained with new technology can be a complex process. A particularly good example is provided by the unexpected hypothesis raised by Francisco Miranda da Costa Lobo upon examination of the cinematographic film obtained during the solar eclipse of 17 April 1912. Contrary to contemporary practice this eclipse was eagerly awaited in view of its astrometrical rather than astrophysical scientific interest. The observation of this hybrid eclipse provided, in theory, a good opportunity to improve several astrometric parameters, and in particular the Moon's apparent diameter. Observations were performed from Portugal to Russia and, for the first time, movie cameras were widely deployed to register astronomical phenomena. Upon analysing the film obtained at Ovar (Portugal), Costa Lobo realised that during totality Baily's Beads were not symmetrically distributed around the Moon. As an explanation and opposing current belief he proposed a lunar flattening in the range 1/1156 to 1/380. Initially other eclipse observers supported Costa Lobo's claim. In particular, Father Willaert obtained a flattening value of 1/2050 from his cinematographic film taken at Namur (Belgium). However, these results were quickly disregarded by the international astronomical community which favoured an explanation based upon the irregularities of the lunar profile. In this paper we recall the characteristics of the 17 April 1912 eclipse and the cinematographic observations, and review the results obtained. We conclude that the lack of attention paid by the astronomical community to the new cinematographical results and Camille Flammarion's superficial analysis of the data were instrumental in the rejection of Costa Lobo's hypothesis.

  11. Spectra and neutron dose of an 18 MV Linac using two geometric models of the head; Espectros y dosis por neutrones de un Linac de 18 MV usando dos modelos geometricos del cabezal

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, M. T.; Pino, F.; Barros, H.; Sajo-Bohus, L. [Universidad Simon Bolivar, Laboratorio de Fisica Nuclear, Sartenejas, Baruta 1080-A, Caracas (Venezuela, Bolivarian Republic of); Davila, J. [Fisica Medica C. A., Av. Francisco de Miranda s/n, Los Palos Grandes, 1060 Miranda (Venezuela, Bolivarian Republic of); Salcedo, E. [Centro Medico Docente La Trinidad, Av. de El Haltillo, Caracas (Venezuela, Bolivarian Republic of); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico); Benites R, J. L., E-mail: mariate9590@gmail.com [Centro de Cancerologia de Nayarit, Servicio de Seguridad Radiologica, Calz. de la Cruz 118 Sur, 63000 Tepic, Nayarit (Mexico)

    2015-10-15

    Full text: Using the Monte Carlo method, by MCNP5 code, simulations were performed with different source terms and 2 geometric models of the head to obtain spectra in energy, flow and doses of photo-neutrons at different positions on the stretcher and in the radiotherapy room. The simplest model was a spherical shell of tungsten; the second was the complete model of a heterogeneous head of an accelerator Varian ix. In both models Tosi function was used as a source term. In addition, for the second model Sheikh-Bagheri distribution was used for photons and photo-neutrons were generated. Also in both models the radiotherapy room of Gurve group of the Teaching Medical Center La Trinidad was included, which is equipped with an accelerator Varian Clinic 2100. In this Center passive detectors PADC (Cr-39) were irradiated with neutron converters, with 18 MeV photons radiation. The measured neutron flow was compared with that obtained with Monte Carlo calculations. The Monte Carlo flows are similar to those measured at the isocenter. The simplest model underestimates the neutron flow compared with the calculated flows with the heterogeneous model of the head. (Author)

  12. A new photonic crystal fiber design on the high negative ultra-flattened dispersion for both X and Y polarization modes

    DEFF Research Database (Denmark)

    Mahmud, Russel Reza; Razzak, S. M Abdur; Hasan, Md Imran

    2016-01-01

    Analysis of numerical design and properties of a new silica based photonic crystal fiber (PCF) are proposed in this manuscript. The design performs ultra-flattened negative chromatic dispersion (UNCD) in the optical windows 2nd and 3rd involving O to U bands in the infrared (IF) portion. The guid...

  13. Photoneutron Flux Measurement via Neutron Activation Analysis in a Radiotherapy Bunker with an 18 MV Linear Accelerator

    Science.gov (United States)

    Çeçen, Yiğit; Gülümser, Tuğçe; Yazgan, Çağrı; Dapo, Haris; Üstün, Mahmut; Boztosun, Ismail

    2017-09-01

    In cancer treatment, high energy X-rays are used which are produced by linear accelerators (LINACs). If the energy of these beams is over 8 MeV, photonuclear reactions occur between the bremsstrahlung photons and the metallic parts of the LINAC. As a result of these interactions, neutrons are also produced as secondary radiation products (γ,n) which are called photoneutrons. The study aims to map the photoneutron flux distribution within the LINAC bunker via neutron activation analysis (NAA) using indium-cadmium foils. Irradiations made at different gantry angles (0°, 90°, 180° and 270°) with a total of 91 positions in the Philips SLI-25 linear accelerator treatment room and location-based distribution of thermal neutron flux was obtained. Gamma spectrum analysis was carried out with high purity germanium (HPGe) detector. Results of the analysis showed that the maximum neutron flux in the room occurred at just above of the LINAC head (1.2x105 neutrons/cm2.s) which is compatible with an americium-beryllium (Am-Be) neutron source. There was a 90% decrease of flux at the walls and at the start of the maze with respect to the maximum neutron flux. And, just in front of the LINAC door, inside the room, neutron flux was measured less than 1% of the maximum.

  14. Photoneutron Flux Measurement via Neutron Activation Analysis in a Radiotherapy Bunker with an 18 MV Linear Accelerator

    Directory of Open Access Journals (Sweden)

    Çeçen Yiğit

    2017-01-01

    Full Text Available In cancer treatment, high energy X-rays are used which are produced by linear accelerators (LINACs. If the energy of these beams is over 8 MeV, photonuclear reactions occur between the bremsstrahlung photons and the metallic parts of the LINAC. As a result of these interactions, neutrons are also produced as secondary radiation products (γ,n which are called photoneutrons. The study aims to map the photoneutron flux distribution within the LINAC bunker via neutron activation analysis (NAA using indium-cadmium foils. Irradiations made at different gantry angles (0°, 90°, 180° and 270° with a total of 91 positions in the Philips SLI-25 linear accelerator treatment room and location-based distribution of thermal neutron flux was obtained. Gamma spectrum analysis was carried out with high purity germanium (HPGe detector. Results of the analysis showed that the maximum neutron flux in the room occurred at just above of the LINAC head (1.2x105 neutrons/cm2.s which is compatible with an americium-beryllium (Am-Be neutron source. There was a 90% decrease of flux at the walls and at the start of the maze with respect to the maximum neutron flux. And, just in front of the LINAC door, inside the room, neutron flux was measured less than 1% of the maximum.

  15. Synthesis and structural characterisation of iron(II) and copper(II) diphosphates containing flattened metal oxotetrahedra

    Energy Technology Data Exchange (ETDEWEB)

    Keates, Adam C. [School of Chemistry, University of Southampton, Southampton, Hampshire SO17 1B,. UK (United Kingdom); Wang, Qianlong [Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY (United Kingdom); Weller, Mark T., E-mail: m.t.weller@bath.ac.uk [Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY (United Kingdom)

    2014-02-15

    Single crystal and bulk polycrystalline forms of K{sub 2}MP{sub 2}O{sub 7} (M=Fe(II), Cu(II)) have been synthesised and their structures determined from single crystal X-ray diffraction data. Both compounds crystallize in the tetragonal system, space group P-42{sub 1}m. Their structures are formed from infinite sheets of linked oxopolyhedra of the stoichiometry [MP{sub 2}O{sub 7}]{sup 2−} with potassium cations situated between the layers. The MO{sub 4} tetrahedra share oxygen atoms with [P{sub 2}O{sub 7}]{sup 4−} diphosphate groups and the potassium ions have KO{sub 8} square prismatic geometry. In both compounds the M(II) centre has an unusual strongly flattened, tetrahedral coordination to oxygen, as a result of the Jahn–Teller (JT) effect for the high spin d{sup 6} Fe(II) and p-orbital mixing or a second order JT effect for d{sup 9} Cu(II) centres in four fold coordination. The uncommon transition metal ion environments found in these materials are reflected in their optical absorption spectra and magnetism data. - Graphical abstract: The structures of the tetragonal polymorphs of K{sub 2}MP{sub 2}O{sub 7}, M=Cu(II), Fe(II), consist of infinite sheets of stoichiometry [MP{sub 2}O{sub 7}]{sup 2−}, formed from linked pyrophosphate groups and MO{sub 4} tetrahedra, separated by potassium ions. In both compounds the unusual tetrahedral coordination of the M(II) centre is strongly flattened as a result of Jahn–Teller (JT) effects for high spin, d{sup 6} Fe(II) and p-orbital mixing and second-order JT effects for d{sup 9} Cu(II). Display Omitted - Highlights: • Tetrahedral copper and iron(II) coordinated by oxygen. • New layered phosphate structure. • Jahn–Teller and d{sup 10} distorted coordinations.

  16. Effect of ultrasound streaming on the disinfection of flattened root canals prepared by rotary and reciprocating systems.

    Science.gov (United States)

    Vasconcelos, Layla Reginna Silva Munhoz de; Midena, Raquel Zanin; Minotti, Paloma Gagliardi; Pereira, Thais Cristina; Duarte, Marco Antonio Hungaro; Andrade, Flaviana Bombarda de

    2017-01-01

    New technical and scientific developments have been advocated to promote the success of the endodontic treatment. In addition to rotary and reciprocating systems, irrigating solution agitation has been suggested and passive ultrasonic irrigation (PUI) is the most used. To evaluate, in vitro, the effect of ultrasound streaming (US) in the disinfection of flattened root canal systems prepared by the ProTaper, BioRaCe and Reciproc systems, utilizing the microbiological culture. Extracted human mandibular incisors (n=84) were used. Suspensions of Enterococcus faecalis (ATCC 29212) were standardized and inserted along with the teeth immersed in brain-heart infusion (BHI) broth. The contamination was made following a protocol during 5 days. The teeth were randomly divided into six groups: G1, ProTaper Universal; G2, ProTaper Universal with US; G3, BioRaCe; G4, BioRaCe with US; G5, Reciproc; and G6, Reciproc with US. Irrigation was performed with saline solution. After biomechanical preparation, microbiological samples were performed with sterilized paper points, which were diluted and spread on BHI agar; after 48 h, the colony forming units (CFU/mL) were counted for each sample. Groups using ultrasonic agitation presented a greater antibacterial effect than the other ones, even using saline solution as irrigant. The ProTaper Universal system showed the best antibacterial activity of the tested systems (median of 0 CFU/mL with and without surfactant or ultrasonic activation [PUI]). Even with PUI, Reciproc (median of 2.5 CFU/mL with PUI and 5 without it) could not reduce as many colonies as ProTaper Universal without US. The BioRaCe system had greater bacterial reduction when using US (median of 0 CFU/mL with PUI and 30 without it). US promoted greater reduction in the number of bacteria in the flattened root canals prepared with nickel-titanium mechanized systems. Regarding the instruments used, the ProTaper Universal system was the most effective in reducing the

  17. Effect of ultrasound streaming on the disinfection of flattened root canals prepared by rotary and reciprocating systems

    Directory of Open Access Journals (Sweden)

    Layla Reginna Silva Munhoz de Vasconcelos

    Full Text Available Abstract New technical and scientific developments have been advocated to promote the success of the endodontic treatment. In addition to rotary and reciprocating systems, irrigating solution agitation has been suggested and passive ultrasonic irrigation (PUI is the most used. Objective: To evaluate, in vitro, the effect of ultrasound streaming (US in the disinfection of flattened root canal systems prepared by the ProTaper, BioRaCe and Reciproc systems, utilizing the microbiological culture. Methodology: Extracted human mandibular incisors (n=84 were used. Suspensions of Enterococcus faecalis (ATCC 29212 were standardized and inserted along with the teeth immersed in brain-heart infusion (BHI broth. The contamination was made following a protocol during 5 days. The teeth were randomly divided into six groups: G1, ProTaper Universal; G2, ProTaper Universal with US; G3, BioRaCe; G4, BioRaCe with US; G5, Reciproc; and G6, Reciproc with US. Irrigation was performed with saline solution. After biomechanical preparation, microbiological samples were performed with sterilized paper points, which were diluted and spread on BHI agar; after 48 h, the colony forming units (CFU/mL were counted for each sample. Results: Groups using ultrasonic agitation presented a greater antibacterial effect than the other ones, even using saline solution as irrigant. The ProTaper Universal system showed the best antibacterial activity of the tested systems (median of 0 CFU/mL with and without surfactant or ultrasonic activation [PUI]. Even with PUI, Reciproc (median of 2.5 CFU/mL with PUI and 5 without it could not reduce as many colonies as ProTaper Universal without US. The BioRaCe system had greater bacterial reduction when using US (median of 0 CFU/mL with PUI and 30 without it. Conclusions: US promoted greater reduction in the number of bacteria in the flattened root canals prepared with nickel-titanium mechanized systems. Regarding the instruments used, the Pro

  18. A new design of photonic crystal fiber with ultra-flattened dispersion to simultaneously minimize the dispersion and confinement loss

    Science.gov (United States)

    Olyaee, Saeed; Taghipour, Fahimeh

    2011-02-01

    Photonic crystal fibers (PCFs) are highly suitable transmission media for wavelength-division-multiplexing (WDM) systems, in which low and ultra-flattened dispersion of PCFs is extremely desirable. It is also required to concurrently achieve both a low confinement loss as well as a large effective area in a wide range of wavelengths. Relatively low dispersion with negligible variation has become feasible in the wavelength range of 1.1 to 1.8μm through the proposed design in this paper. According to a new structure of PCF presented in this study, the dispersion slope is 6.8×10-4ps/km.nm2 and the confinement loss reaches below 10-6 dB/km in this range, while at the same time an effective area of more than 50μm2 has been attained. For the analysis of this PCF, finite-difference time-domain (FDTD) method with the perfectly matched layers (PML) boundary conditions has been used.

  19. Optimal grasp planning for a dexterous robotic hand using the volume of a generalized force ellipsoid during accepted flattening

    Directory of Open Access Journals (Sweden)

    Peng Jia

    2017-01-01

    Full Text Available A grasp planning method based on the volume and flattening of a generalized force ellipsoid is proposed to improve the grasping ability of a dexterous robotic hand. First, according to the general solution of joint torques for a dexterous robotic hand, a grasping indicator for the dexterous hand—the maximum volume of a generalized external force ellipsoid and the minimum volume of a generalized contact internal force ellipsoid during accepted flattening—is proposed. Second, an optimal grasp planning method based on a task is established using the grasping indicator as an objective function. Finally, a simulation analysis and grasping experiment are performed. Results show that when the grasping experiment is conducted with the grasping configuration and positions of contact points optimized using the proposed grasping indicator, the root-mean-square values of the joint torques and contact internal forces of the dexterous hand are at a minimum. The effectiveness of the proposed grasping planning method is thus demonstrated.

  20. Rearrangement of fuel assemblies in the RBMK type reactors to flatten power distribution and improve the fuel cycle

    International Nuclear Information System (INIS)

    Mityaev, Yu.I.; Vikulov, V.K.

    1982-01-01

    A possibility of increasing the burnup of uranium fuel unloaded from the RBMK type reactors is investigated. Three variants of a two-zone reactor-refueling are considered: 1. the simplest variant of continuous refueling used at present, when the central and peripherical reactor zones are additionally fueled independently by similar fuel assemblies (FA); 2. the variant under which new FA are loaded to the peripherical zone and are used there up to the same burnup as in the first case, then all the peripherical FA (PFA) are rearranged to the centre and they are used there up to maximum burnup; 3. the same as in the second variant, but not all the PFA are rearranged to the centre but only FA with small fuel burnup. It is shown by calculation that average fuel burnup for the third refueling variant is several per cent higher at the optimal burnup of rearranged FA. Besides, flattening of fuel channel power is improved in this case, that permits to increase uranium enrichment and burnup at the same maximum power. It essentially improves economic parameters of the reactor. It is concluded that realization of the considered variant of fuel refueling will produce the most essential effect for reactors refueled without shutdown

  1. Efficient design of gain-flattened multi-pump Raman fiber amplifiers using least squares support vector regression

    Science.gov (United States)

    Chen, Jing; Qiu, Xiaojie; Yin, Cunyi; Jiang, Hao

    2018-02-01

    An efficient method to design the broadband gain-flattened Raman fiber amplifier with multiple pumps is proposed based on least squares support vector regression (LS-SVR). A multi-input multi-output LS-SVR model is introduced to replace the complicated solving process of the nonlinear coupled Raman amplification equation. The proposed approach contains two stages: offline training stage and online optimization stage. During the offline stage, the LS-SVR model is trained. Owing to the good generalization capability of LS-SVR, the net gain spectrum can be directly and accurately obtained when inputting any combination of the pump wavelength and power to the well-trained model. During the online stage, we incorporate the LS-SVR model into the particle swarm optimization algorithm to find the optimal pump configuration. The design results demonstrate that the proposed method greatly shortens the computation time and enhances the efficiency of the pump parameter optimization for Raman fiber amplifier design.

  2. Computerized mappings of the cerebral cortex: a multiresolution flattening method and a surface-based coordinate system

    Science.gov (United States)

    Drury, H. A.; Van Essen, D. C.; Anderson, C. H.; Lee, C. W.; Coogan, T. A.; Lewis, J. W.

    1996-01-01

    We present a new method for generating two-dimensional maps of the cerebral cortex. Our computerized, two-stage flattening method takes as its input any well-defined representation of a surface within the three-dimensional cortex. The first stage rapidly converts this surface to a topologically correct two-dimensional map, without regard for the amount of distortion introduced. The second stage reduces distortions using a multiresolution strategy that makes gross shape changes on a coarsely sampled map and further shape refinements on progressively finer resolution maps. We demonstrate the utility of this approach by creating flat maps of the entire cerebral cortex in the macaque monkey and by displaying various types of experimental data on such maps. We also introduce a surface-based coordinate system that has advantages over conventional stereotaxic coordinates and is relevant to studies of cortical organization in humans as well as non-human primates. Together, these methods provide an improved basis for quantitative studies of individual variability in cortical organization.

  3. Comparison of Head Scatter Factor for 6MV and 10MV flattened (FB) and Unflattened (FFF) Photon Beam using indigenously Designed Columnar Mini Phantom.

    Science.gov (United States)

    Ashokkumar, Sigamani; Nambi Raj, N Arunai; Sinha, Sujit Nath; Yadav, Girigesh; Thiyagarajan, Rajesh; Raman, Kothanda; Mishra, Manindra Bhushan

    2014-07-01

    To measure and compare the head scatter factor for flattened (FB) and unflattened (FFF) of 6MV and 10MV photon beam using indigenously designed mini phantom. A columnar mini phantom was designed as recommended by AAPM Task Group 74 with low and high atomic number materials at 10 cm (mini phantom) and at approximately twice the depth of maximum dose water equivalent thickness (brass build-up cap). Scatter in the accelerator (Sc) values of 6MV-FFF photon beams are lesser than that of the 6MV-FB photon beams (0.66-2.8%; Clinac iX, 2300CD) and (0.47-1.74%; True beam) for field sizes ranging from 10 × 10 cm(2) to 40 × 40 cm(2). Sc values of 10MV-FFF photon beams are lesser (0.61-2.19%; True beam) than that of the 10MV-FB photons beams for field sizes ranging from 10 × 10 cm(2) to 40 × 40 cm(2). The SSD had no influence on head scatter for both flattened and unflattened beams and irrespective of head design of the different linear accelerators. The presence of field shaping device influences the Sc values. The collimator exchange effect reveals that the opening of the upper jaw increases Sc irrespective of FB or FFF photon beams and different linear accelerators, and it is less significant in FFF beams. Sc values of 6MV-FB square field were in good agreement with that of AAPM, TG-74 published data for Varian (Clinac iX, 2300CD) accelerator. Our results confirm that the removal of flattening filter decreases in the head scatter factor compared to flattened beam. This could reduce the out-of-field dose in advanced treatment delivery techniques.

  4. Rotation profile flattening and toroidal flow shear reversal due to the coupling of magnetic islands in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Tobias, B.; Grierson, B. A.; Okabayashi, M. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Chen, M.; Domier, C. W.; Luhmann, N. C.; Muscatello, C. M. [University of California at Davis, Davis, California 95616 (United States); Classen, I. G. J. [Dutch Institute for Fundamental Fusion Energy Research, DIFFER, Rhinjuizen (Netherlands); Fitzpatrick, R. [University of Texas at Austin, Austin, Texas 78705 (United States); Olofsson, K. E. J.; Paz-Soldan, C. [General Atomics, San Diego, California 92121 (United States)

    2016-05-15

    The electromagnetic coupling of helical modes, even those having different toroidal mode numbers, modifies the distribution of toroidal angular momentum in tokamak discharges. This can have deleterious effects on other transport channels as well as on magnetohydrodynamic (MHD) stability and disruptivity. At low levels of externally injected momentum, the coupling of core-localized modes initiates a chain of events, whereby flattening of the core rotation profile inside successive rational surfaces leads to the onset of a large m/n = 2/1 tearing mode and locked-mode disruption. With increased torque from neutral beam injection, neoclassical tearing modes in the core may phase-lock to each other without locking to external fields or structures that are stationary in the laboratory frame. The dynamic processes observed in these cases are in general agreement with theory, and detailed diagnosis allows for momentum transport analysis to be performed, revealing a significant torque density that peaks near the 2/1 rational surface. However, as the coupled rational surfaces are brought closer together by reducing q{sub 95}, additional momentum transport in excess of that required to attain a phase-locked state is sometimes observed. Rather than maintaining zero differential rotation (as is predicted to be dynamically stable by single-fluid, resistive MHD theory), these discharges develop hollow toroidal plasma fluid rotation profiles with reversed plasma flow shear in the region between the m/n = 3/2 and 2/1 islands. The additional forces expressed in this state are not readily accounted for, and therefore, analysis of these data highlights the impact of mode coupling on torque balance and the challenges associated with predicting the rotation dynamics of a fusion reactor—a key issue for ITER.

  5. Wavelength conversion, time demultiplexing and multicasting based on cross-phase modulation and four-wave mixing in dispersion-flattened highly nonlinear photonic crystal fiber

    International Nuclear Information System (INIS)

    Hui, Zhan-Qiang; Zhang, Jian-Guo

    2012-01-01

    We propose the use of cross-phase modulation (XPM) and four-wave mixing (FWM) in dispersion-flattened highly nonlinear photonic crystal fibers (HNL-PCFs) to implement the functionalities of wavelength conversion, simultaneous time demultiplexing and wavelength multicasting in optical time-division multiplexing (OTDM) systems. The experiments on wavelength conversion at 80 Gbit s −1 and OTDM demultiplexing from 80 to 10 Gbit s −1 with wavelength multicasting of two channels are successfully demonstrated to validate the proposed scheme, which are carried out by using two segments of dispersion-flattened HNL-PCFs with lengths of 100 and 50 m, respectively. Moreover, the bit error rate (BER) performance is also measured. The results show that our designed system can achieve a power penalty of less than 4.6 dB for two multicasting channels with a 24 nm wavelength span at the BER of 10 −9 when compared with the 10 Gbit/s back-to-back measurement. The proposed system is transparent to bit rate since only an ultrafast third-order nonlinear effect is used. The resulting configuration is compact, robust and reliable, benefiting from the use of dispersion-flattened HNL-PCFs with short lengths. This also makes the proposed system more flexible in the operational wavelengths than those based on dispersion-shifted fibers and traditional highly nonlinear fibers. (paper)

  6. Comparative study of the parameters associated with quality control and absorbed dose in linear accelerators with (FF) and without (FFF) flattening filter

    International Nuclear Information System (INIS)

    Souza, Anderson Sorgatti de

    2017-01-01

    Teletherapy, radiation therapy with linear accelerators, for cancer treatment has being used for years with good clinical results.Since the 90's the removal of the flattening filter, item placed at the gantry of the machine, has shown better results for the treatment of some cancers thus being extensively studied. Treatments with Intensity Modulated Radiotherapy (IMRT) and Stereotaxic Radiotherapy (SRT) were more efficient without the flattening filter. Varian Oncology released the TrueBeam in 2012, a accelerator capable of operating with or without the flattening filter. The aim of this work is to access homogeneity of the percentage depth dose (PDP) and beam quality index (TPR20/10), two important parameters used in patient dose calculations. The data used for analysis were obtained with the Israelita Albert Einstein Hospital (HIAE), Real Portugues Hospital (RHP) and 3 more institutions located in the United States. The statistical data analysis allowed to observe the parameters behaviors. In general, they were very homogeneous, with errors smaller than 1% confirming the conformance of the TrueBeam accelerators. (author)

  7. Flattened optical frequency-locked multi-carrier generation by cascading one DML and one phase modulator driven by different RF frequency clocks

    International Nuclear Information System (INIS)

    Li, Xinying; Yu, Jianjun; Zhang, Junwen; Chi, Nan

    2013-01-01

    We propose a novel scheme for flattened optical frequency-locked multi-carrier generation based on one directly modulated laser (DML) and one phase modulator (PM) in cascade driven by different sinusoidal radio-frequency (RF) clocks. We experimentally demonstrate that when the clock frequencies for the cascaded DML and the PM are respectively 12.5 GHz and 25 GHz, over 24 optical subcarriers can be generated with 12.5-GHz frequency spacing and amplitude fluctuation less than 3 dB. Furthermore, the number of generated optical subcarriers can be further increased when we increase the driving power for the DML. (letter)

  8. SU-C-213-05: Evaluation of a Composite Copper-Plastic Material for a 3D Printed Radiation Therapy Bolus

    Energy Technology Data Exchange (ETDEWEB)

    Vitzthum, L; Ehler, E; Sterling, D; Reynolds, T; Higgins, P; Dusenbery, K [University of Minnesota, Minneapolis, MN (United States)

    2015-06-15

    Purpose: To evaluate a novel 3D printed bolus fabricated from a copper-plastic composite as a thin flexible, custom fitting device that can replicate doses achieved with conventional bolus techniques. Methods: Two models of bolus were created on a 3D printer using a composite copper-PLA/PHA. Firstly, boluses were constructed at thicknesses of 0.4, 0.6 and 0.8 mm. Relative dose measurements were performed under the bolus with an Attix Chamber as well as with radiochromic film. Results were compared to superficial Attix Chamber measurements in a water equivalent material to determine the dosimetric water equivalence of the copper-PLA/PHA plastic. Secondly, CT images of a RANDO phantom were used to create a custom fitting bolus across the anterolateral scalp. Surface dose with the bolus placed on the RANDO phantom was measured with radiochromic film at tangential angles with 6, 10, 10 flattening filter free (FFF) and 18 MV photon beams. Results: Mean surface doses for 6, 10, 10FFF and 18 MV were measured as a percent of Dmax for the flat bolus devices of each thickness. The 0.4 mm thickness bolus was determined to be near equivalent to 2.5 mm depth in water for all four energies. Surface doses ranged from 59–63% without bolus and 85–90% with the custom 0.4 mm copper-plastic bolus relative to the prescribed dose for an oblique tangential beam arrangement on the RANDO phantom. Conclusion: Sub-millimeter thickness, 3D printed composite copper-PLA/PHA bolus can provide a build-up effect equivalent to conventional bolus. At this thickness, the 3D printed bolus allows a level of flexure that may provide more patient comfort than current 3D printing materials used in bolus fabrication while still retaining the CT based custom patient shape. Funding provided by an intra-department grant of the University of Minnesota Department of Radiation Oncology.

  9. SU-C-213-05: Evaluation of a Composite Copper-Plastic Material for a 3D Printed Radiation Therapy Bolus

    International Nuclear Information System (INIS)

    Vitzthum, L; Ehler, E; Sterling, D; Reynolds, T; Higgins, P; Dusenbery, K

    2015-01-01

    Purpose: To evaluate a novel 3D printed bolus fabricated from a copper-plastic composite as a thin flexible, custom fitting device that can replicate doses achieved with conventional bolus techniques. Methods: Two models of bolus were created on a 3D printer using a composite copper-PLA/PHA. Firstly, boluses were constructed at thicknesses of 0.4, 0.6 and 0.8 mm. Relative dose measurements were performed under the bolus with an Attix Chamber as well as with radiochromic film. Results were compared to superficial Attix Chamber measurements in a water equivalent material to determine the dosimetric water equivalence of the copper-PLA/PHA plastic. Secondly, CT images of a RANDO phantom were used to create a custom fitting bolus across the anterolateral scalp. Surface dose with the bolus placed on the RANDO phantom was measured with radiochromic film at tangential angles with 6, 10, 10 flattening filter free (FFF) and 18 MV photon beams. Results: Mean surface doses for 6, 10, 10FFF and 18 MV were measured as a percent of Dmax for the flat bolus devices of each thickness. The 0.4 mm thickness bolus was determined to be near equivalent to 2.5 mm depth in water for all four energies. Surface doses ranged from 59–63% without bolus and 85–90% with the custom 0.4 mm copper-plastic bolus relative to the prescribed dose for an oblique tangential beam arrangement on the RANDO phantom. Conclusion: Sub-millimeter thickness, 3D printed composite copper-PLA/PHA bolus can provide a build-up effect equivalent to conventional bolus. At this thickness, the 3D printed bolus allows a level of flexure that may provide more patient comfort than current 3D printing materials used in bolus fabrication while still retaining the CT based custom patient shape. Funding provided by an intra-department grant of the University of Minnesota Department of Radiation Oncology

  10. SU-G-JeP2-09: Minimal Skin Dose Increase in Longitudinal Rotating Biplanar Linac-MR Systems: Examination of Radiation Energy and Flattening Filter Design

    Energy Technology Data Exchange (ETDEWEB)

    Fallone, B; Keyvanloo, A; Burke, B; St Aubin, J; Baillie, D; Wachowicz, K; Warkentin, B; Steciw, S [Cross Cancer Institute, Edmonton, AB (Canada)

    2016-06-15

    Purpose: To quantify increase in entrance skin-dose due to magnetic fields of the Alberta longitudinal linac-MR by examining the effect of radiation energy and flattening filter, using Monte Carlo calculations and accurate 3-D models of the magnetic field. Methods: The 3-D magnetic fields generated by the bi-planar Linac-MR are calculated with FEM using Opera-3D. BEAMnrc simulates the particle phase-space in the presence of the rapidly decaying fringe field of 0.5T MRI assembled with a Varian 600C linac with an isocentre distance of 130 cm for 6 MV and 10 MV beams. Skin doses are calculated at an average depth of 70 µm using DOSXYZnrc with varying SSDs and field sizes. Furthermore, flattening filters are reshaped to compensate for the significant drop in dose rate due to increased SAD of 130 cm and skin-doses are evaluated. Results: The confinement effect of the MRI fringe field on the contaminant electrons is minimal. For SSDs of 100 – 120 cm the increase in skin dose is ∼6% – 19% and ∼1% – 9% for the 6 and 10 MV beams, respectively. For 6MV, skin dose increases from ∼10.5% to 1.5%. for field-size increases of 5×5 cm2 to 20×20 cm2. For 10 MV, skin dose increases by ∼6% for a 5×5 cm2 field, and decreases by ∼1.5% for a 20×20 cm2 field. The reshaped flattening filter increases the dose rate from 355 MU/min to 529 MU/min (6 MV) or 604 MU/min (10 MV), while the skin-dose increases by only an additional ∼2.6% (all percent increases in skin dose are relative to Dmax). Conclusion: There is minimal increase in the entrance skin dose and minimal/no decrease in the dose rate of the Alberta longitudinal linac-MR system. There is even lower skin-dose increase at 10 MV. Funding: Alberta Innovates - Health Solutions (AIHS) Conflict of Interest: Fallone is a co-founder and CEO of MagnetTx Oncology Solutions (under discussions to license Alberta bi-planar linac MR for commercialization)

  11. Numerical Analysis of Index-Guiding Photonic Crystal Fibers with Low Confinement Loss and Ultra-Flattened Dispersion by FDFD Method

    Directory of Open Access Journals (Sweden)

    M. Pourmahyabadi

    2009-09-01

    Full Text Available In this article, perfectly matched layer (PML for the boundary treatment and an efficient compact two dimensional finite-difference frequency-domain (2-D FDFD method were combined to model photonic crystal fibers (PCF. For photonic crystal fibers, if we assume that the propagation constant along the propagation direction is fixed, three-dimensional hybrid guided modes can be calculated by using only a two-dimensional mesh. An index-guiding PCF with an array of air-holes surrounding the silica core region has special characteristics compared with conventional single-mode fibers (SMFs. Using this model, the fundamental characteristics of single mode photonic crystal fibers (SMPCFs such as confinement loss, bending loss, effective mode area and chromatic dispersion are numerically investigated. The results revealed that low confinement loss and zero-flattened chromatic dispersion can be obtained by varying the air-holes diameter of each ring along the PCF radius. In this work, an especial PCF with nearly zero-flattened dispersion (1.3 ps/nm/km over a wide wavelength range which covers O, E, S, C, L and U telecommunication wavelength bands and low confinement loss (0.06 dB/km at 1.55μm is designed. Macro-bending loss performance of the designed PCF is also studied and it is found that the fiber shows low bending losses for the smallest feasible bending radius of 5 mm. Also, it is revealed that the temperature sensitivity of PCFs is very low in compared with the conventional fibers.

  12. Multi-phase simulation of fast ion profile flattening due to Alfvén eigenmodes in a DIII-D experiment

    International Nuclear Information System (INIS)

    Todo, Y.; Van Zeeland, M.A.; Bierwage, A.; Heidbrink, W.W.

    2014-01-01

    A multi-phase simulation that is a combination of classical simulation and hybrid simulation for energetic particles interacting with a magnetohydrodynamic (MHD) fluid is developed to simulate the nonlinear dynamics on the slowing down time scale of the energetic particles. The hybrid simulation code is extended with realistic beam deposition profile, collisions and losses, and is used for both the classical and hybrid phases. The code is run without MHD perturbations in the classical phase, while the interaction between the energetic particles and the MHD fluid is simulated in the hybrid phase. In a multi-phase simulation of DIII-D discharge #142111, the stored beam ion energy is saturated due to Alfvén eigenmodes (AE modes) at a level lower than in the classical simulation. After the stored fast ion energy is saturated, the hybrid simulation is run continuously. It is demonstrated that the fast ion spatial profile is significantly flattened due to the interaction with the multiple AE modes with amplitude v/v A  ∼ δB/B ∼ O(10 −4 ). The dominant AE modes are toroidal Alfvén eigenmodes (TAE modes), which is consistent with the experimental observation at the simulated moment. The amplitude of the temperature fluctuations brought about by the TAE modes is of the order of 1% of the equilibrium temperature. This is also comparable with electron cyclotron emission measurements in the experiment. (paper)

  13. Determination of the secondary energy from the electron beam with a flattening foil by computer. Percentage depth dose curve fitting using the specific higher order polynomial

    Energy Technology Data Exchange (ETDEWEB)

    Kawakami, H [Kyushu Univ., Beppu, Oita (Japan). Inst. of Balneotherapeutics

    1980-09-01

    A computer program written in FORTRAN is described for determining the secondary energy of the electron beam which passed through a flattening foil, using a time-sharing computer service. The procedure of this program is first to fit the specific higher order polynomial to the measured percentage depth dose curve. Next, the practical range is evaluated by the point of intersection R of the line tangent to the fitted curve at the inflection point P and the given dose E, as shown in Fig. 2. Finally, the secondary energy corresponded to the determined practical range can be obtained by the experimental equation (2.1) between the practial range R (g/cm/sup 2/) and the electron energy T (MeV). A graph for the fitted polynomial with the inflection points and the practical range can be plotted on a teletype machine by request of user. In order to estimate the shapes of percentage depth dose curves correspond to the electron beams of different energies, we tried to find some specific functional relationships between each coefficient of the fitted seventh-degree equation and the incident electron energies. However, exact relationships could not be obtained for irreguarity among these coefficients.

  14. Effect of flattened surface morphology of anodized aluminum oxide templates on the magnetic properties of nanoporous Co/Pt and Co/Pd thin multilayered films

    Science.gov (United States)

    Nguyen, T. N. Anh; Fedotova, J.; Kasiuk, J.; Bayev, V.; Kupreeva, O.; Lazarouk, S.; Manh, D. H.; Vu, D. L.; Chung, S.; Åkerman, J.; Altynov, V.; Maximenko, A.

    2018-01-01

    For the first time, nanoporous Al2O3 templates with smoothed surface relief characterized by flattened interpore areas were used in the fabrication of Co/Pd and Co/Pt multilayers (MLs) with strong perpendicular magnetic anisotropy (PMA). Alternating gradient magnetometry (AGM) revealed perfectly conserved PMA in the Co/Pd and Co/Pt porous MLs (antidot arrays) with a ratio of remanent magnetization (Mr) to saturation magnetization (MS) of about 0.99, anisotropy fields (Ha) of up to 2.6 kOe, and a small deviation angle of 8° between the easy magnetization axis and the normal to the film surface. The sufficient magnetic hardening of the porous MLs with enhanced coercive field HC of up to ∼1.9 kOe for Co/Pd and ∼1.5 kOe for Co/Pt MLs, as compared to the continuous reference samples (∼1.5-2 times), is associated with the pinning of the magnetic moments on the nanopore edges. Application of the Stoner-Wohlfarth model for fitting the experimental M/MS(H) curves yielded clear evidence of the predominantly coherent rotation mechanism of magnetization reversal in the porous films.

  15. Fiber-coupled radioluminescence dosimetry with saturated Al2O3:C crystals: Characterization in 6 and 18 MV photon beams

    DEFF Research Database (Denmark)

    Andersen, Claus Erik; Damkjær, Sidsel Marie Skov; Kertzscher Schwencke, Gustavo Adolfo Vladimir

    2011-01-01

    Radioluminescence (RL) and optically stimulated luminescence (OSL) from carbon-doped aluminum oxide crystals can be used for medical dosimetry in external beam radiotherapy and remotely afterloaded brachytherapy. The RL/OSL signals are guided from the treatment room to the readout instrumentation...... using optical fiber cables, and in vivo dosimetry can be carried out in real time while the dosimeter probes are in the patient. The present study proposes a new improved readout protocol based solely on the RL signal from Al2O3:C. The key elements in the protocol are that Al2O3:C is pre-dosed with 20...... ((−0.21 ± 0.01)%/ °C), and dose-delivery rate ((−0.22 ± 0.01)% per 100 MU/min). A temporal gating technique was used for separation of RL and stem signals (i.e. Cerenkov light and fluorescence induced in the optical fiber cable during irradiation). The new readout protocol was a substantial improvement...

  16. Multibeam collection for COOK18MV: Multibeam data collected aboard Melville from 2002-01-04 to 2002-01-13, Papeete, French Polynesia to Lyttelton, New Zealand

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set is part of a larger set of data called the Multibeam Bathymetry Database (MBBDB) where other similar data can be found at...

  17. Multibeam collection for MGLN18MV: Multibeam data collected aboard Melville from 2007-05-02 to 2007-05-24, Yokohama, Japan to Yokohama, Japan

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set is part of a larger set of data called the Multibeam Bathymetry Database (MBBDB) where other similar data can be found at...

  18. INTEGRAL FIELD SPECTROSCOPY AND MULTI-WAVELENGTH IMAGING OF THE NEARBY SPIRAL GALAXY NGC 5668 : AN UNUSUAL FLATTENING IN METALLICITY GRADIENT

    Energy Technology Data Exchange (ETDEWEB)

    Marino, R. A.; Gil de Paz, A.; Castillo-Morales, A.; Perez-Gonzalez, P. G.; Gallego, J.; Zamorano, J. [CEI Campus Moncloa, UCM-UPM, Departamento de Astrofisica y CC. de la Atmosfera, Facultad de CC. Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Munoz-Mateos, J. C. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Sanchez, S. F. [Centro Astronomico Hispano Aleman, Calar Alto (CSIC-MPG), C/Jesus Durban Remon 2-2, E-04004 Almeria (Spain); Alonso-Herrero, A. [Instituto de Fisica de Cantabria, CSIC-UC, Avenida de los Castros s/n, 39005 Santander (Spain); Boissier, S., E-mail: ramarino@fis.ucm.es [Laboratoire dAstrophysique de Marseille, OAMP, Universite Aix-Marseille and CNRS UMR 6110, 38 rue Frederic Joliot-Curie, 13388 Marseille cedex 13 (France)

    2012-07-20

    We present an analysis of the full bidimensional optical spectral cube of the nearby spiral galaxy NGC 5668, observed with the Pmas fiber PAcK Integral Field Unit (IFU) at the Calar Alto observatory 3.5 m telescope. We make use of broadband imaging to provide further constraints on the evolutionary history of the galaxy. This data set will allow us to improve our understanding of the mechanisms that drive the evolution of disks. We investigated the properties of 62 H II regions and concentric rings in NGC 5668 and derived maps in ionized-gas attenuation and chemical (oxygen) abundances. We find that while inward of r {approx}36'' {approx} 4.4 kpc {approx} 0.36 (D{sub 25}/2) the derived O/H ratio follows the radial gradient typical of spiral galaxies, the abundance gradient beyond r {approx} 36'' flattens out. The analysis of the multi-wavelength surface brightness profiles of NGC 5668 is performed by fitting these profiles with those predicted by chemo-spectrophotometric evolutionary models of galaxy disks. From this, we infer a spin and circular velocity of {lambda} = 0.053 and v{sub c} = 167 km s{sup -1}, respectively. The metallicity gradient and rotation curve predicted by this best-fitting galaxy model nicely match the values derived from the IFU observations, especially within r {approx}36''. The same is true for the colors despite some small offsets and a reddening in the bluest colors beyond that radius. On the other hand, deviations of some of these properties in the outer disk indicate that a secondary mechanism, possibly gas transfer induced by the presence of a young bar, must have played a role in shaping the recent chemical and star formation histories of NGC 5668.

  19. INTEGRAL FIELD SPECTROSCOPY AND MULTI-WAVELENGTH IMAGING OF THE NEARBY SPIRAL GALAXY NGC 5668 : AN UNUSUAL FLATTENING IN METALLICITY GRADIENT

    International Nuclear Information System (INIS)

    Marino, R. A.; Gil de Paz, A.; Castillo-Morales, A.; Pérez-González, P. G.; Gallego, J.; Zamorano, J.; Muñoz-Mateos, J. C.; Sánchez, S. F.; Alonso-Herrero, A.; Boissier, S.

    2012-01-01

    We present an analysis of the full bidimensional optical spectral cube of the nearby spiral galaxy NGC 5668, observed with the Pmas fiber PAcK Integral Field Unit (IFU) at the Calar Alto observatory 3.5 m telescope. We make use of broadband imaging to provide further constraints on the evolutionary history of the galaxy. This data set will allow us to improve our understanding of the mechanisms that drive the evolution of disks. We investigated the properties of 62 H II regions and concentric rings in NGC 5668 and derived maps in ionized-gas attenuation and chemical (oxygen) abundances. We find that while inward of r ∼36'' ∼ 4.4 kpc ∼ 0.36 (D 25 /2) the derived O/H ratio follows the radial gradient typical of spiral galaxies, the abundance gradient beyond r ∼ 36'' flattens out. The analysis of the multi-wavelength surface brightness profiles of NGC 5668 is performed by fitting these profiles with those predicted by chemo-spectrophotometric evolutionary models of galaxy disks. From this, we infer a spin and circular velocity of λ = 0.053 and v c = 167 km s –1 , respectively. The metallicity gradient and rotation curve predicted by this best-fitting galaxy model nicely match the values derived from the IFU observations, especially within r ∼36''. The same is true for the colors despite some small offsets and a reddening in the bluest colors beyond that radius. On the other hand, deviations of some of these properties in the outer disk indicate that a secondary mechanism, possibly gas transfer induced by the presence of a young bar, must have played a role in shaping the recent chemical and star formation histories of NGC 5668.

  20. Flattening the Military Force Structure

    National Research Council Canada - National Science Library

    Nickolas, James

    2000-01-01

    .... Viewing change through the lens of organizational theory, the monograph traces the historical development of the two fields of study - organizational behavior/development and management/leadership...

  1. Flattening Access to the Transmission Superhighway

    Energy Technology Data Exchange (ETDEWEB)

    Zibelman, Audrey

    2005-07-01

    ISO/RTO development in the future needs to occur not as a result of regulatory mandate, but rather because the entire industry and the investment sector recognize that ISO/RTOs provide the optimal business environment both to develop a robust grid and, equally important, to provide the focus necessary to serve regional markets.

  2. Flattening the inflaton potential beyond minimal gravity

    Directory of Open Access Journals (Sweden)

    Lee Hyun Min

    2018-01-01

    Full Text Available We review the status of the Starobinsky-like models for inflation beyond minimal gravity and discuss the unitarity problem due to the presence of a large non-minimal gravity coupling. We show that the induced gravity models allow for a self-consistent description of inflation and discuss the implications of the inflaton couplings to the Higgs field in the Standard Model.

  3. Device for flattening statistically distributed pulses

    International Nuclear Information System (INIS)

    Il'kanaev, G.I.; Iskenderov, V.G.; Rudnev, O.V.; Teller, V.S.

    1976-01-01

    The description is given of a device that converts the series of statistically distributed pulses into a pseudo-uniform one. The inlet pulses switch over the first counter, and the second one is switched over by the clock pulses each time the uniformity of the counters' states is violated. This violation is recorded by the logic circuit which passes to the output the clock pulses in the amount equal to that of the pulses that reached the device inlet. Losses at the correlation between the light velocity and the sampling rate up to 0.3 do not exceed 0.7 per cent for the memory of pulse counters 3, and 0.035 per cent for memory 7

  4. A general approach to query flattening

    NARCIS (Netherlands)

    van Ruth, J.

    The translation of queries from complex data models to simpler data models is a recurring theme in the construction of efficient data management systems. In this paper we propose a general framework to guide the translation from data models with nested types to a flat relational model (query

  5. Flattening Queries over Nested Data Types

    NARCIS (Netherlands)

    van Ruth, J.

    2006-01-01

    The theory developed in this thesis provides a method to improve the efficiency of querying nested data. The roots of this research lie in the tension between data model expressiveness and performance. Obviously, more expressive data models are more convenient for application programmers. For many

  6. Comparative study of the parameters associated with quality control and absorbed dose in linear accelerators with (FF) and without (FFF) flattening filter; Estudo comparativo dos parametros associados a dose absorvida e controle de qualidade em aceleradores lineares com filtro aplainador (FF) e sem filtro aplainador (FFF)

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Anderson Sorgatti de

    2017-11-01

    Teletherapy, radiation therapy with linear accelerators, for cancer treatment has being used for years with good clinical results.Since the 90's the removal of the flattening filter, item placed at the gantry of the machine, has shown better results for the treatment of some cancers thus being extensively studied. Treatments with Intensity Modulated Radiotherapy (IMRT) and Stereotaxic Radiotherapy (SRT) were more efficient without the flattening filter. Varian Oncology released the TrueBeam in 2012, a accelerator capable of operating with or without the flattening filter. The aim of this work is to access homogeneity of the percentage depth dose (PDP) and beam quality index (TPR20/10), two important parameters used in patient dose calculations. The data used for analysis were obtained with the Israelita Albert Einstein Hospital (HIAE), Real Portugues Hospital (RHP) and 3 more institutions located in the United States. The statistical data analysis allowed to observe the parameters behaviors. In general, they were very homogeneous, with errors smaller than 1% confirming the conformance of the TrueBeam accelerators. (author)

  7. Ratiometric, filter-free optical sensor based on a complementary metal oxide semiconductor buried double junction photodiode.

    Science.gov (United States)

    Yung, Ka Yi; Zhan, Zhiyong; Titus, Albert H; Baker, Gary A; Bright, Frank V

    2015-07-16

    We report a complementary metal oxide semiconductor integrated circuit (CMOS IC) with a buried double junction (BDJ) photodiode that (i) provides a real-time output signal that is related to the intensity ratio at two emission wavelengths and (ii) simultaneously eliminates the need for an optical filter to block Rayleigh scatter. We demonstrate the BDJ platform performance for gaseous NH3 and aqueous pH detection. We also compare the BDJ performance to parallel results obtained by using a slew scanned fluorimeter (SSF). The BDJ results are functionally equivalent to the SSF results without the need for any wavelength filtering or monochromators and the BDJ platform is not prone to errors associated with source intensity fluctuations or sensor signal drift. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Photon and photoneutron spectra produced in radiotherapy Linacs

    International Nuclear Information System (INIS)

    Vega C, H. R.; Martinez O, S. A.; Benites R, J. L.; Lallena, A. M.

    2011-10-01

    A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10 -6 and 1 MeV. Neutron and Bremsstrahlung spectra show the same features regardless of the linac voltage. The amount of photons and neutrons produced by the 15 MV linac is smaller than that found for the 18 MV linac. As expected, Bremsstrahlung spectra ends according to the voltage used to accelerate the electrons. (Author)

  9. Photon and photoneutron spectra produced in radiotherapy Linacs

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Martinez O, S. A. [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Av. Central del Norte Km. 1, Via Paipa Tunja, Boyaca (Colombia); Benites R, J. L. [Universidad Autonoma de Nayarit, Postgrado CBAP, Carretera Tepic Compostela Km. 9, Xalisco, Nayarit (Mexico); Lallena, A. M., E-mail: fermineutron@yahoo.com [Universida de Granada, Departamento de Fisica Atomica, Molecular y Nuclear, E-18071 Granada (Spain)

    2011-10-15

    A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10{sup -6} and 1 MeV. Neutron and Bremsstrahlung spectra show the same features regardless of the linac voltage. The amount of photons and neutrons produced by the 15 MV linac is smaller than that found for the 18 MV linac. As expected, Bremsstrahlung spectra ends according to the voltage used to accelerate the electrons. (Author)

  10. Quantum gravity fluctuations flatten the Planck-scale Higgs potential

    Science.gov (United States)

    Eichhorn, Astrid; Hamada, Yuta; Lumma, Johannes; Yamada, Masatoshi

    2018-04-01

    We investigate asymptotic safety of a toy model of a singlet-scalar extension of the Higgs sector including two real scalar fields under the impact of quantum-gravity fluctuations. Employing functional renormalization group techniques, we search for fixed points of the system which provide a tentative ultraviolet completion of the system. We find that in a particular regime of the gravitational parameter space the canonically marginal and relevant couplings in the scalar sector—including the mass parameters—become irrelevant at the ultraviolet fixed point. The infrared potential for the two scalars that can be reached from that fixed point is fully predicted and features no free parameters. In the remainder of the gravitational parameter space, the values of the quartic couplings in our model are predicted. In light of these results, we discuss whether the singlet-scalar could be a dark-matter candidate. Furthermore, we highlight how "classical scale invariance" in the sense of a flat potential of the scalar sector at the Planck scale could arise as a consequence of asymptotic safety.

  11. Polar Flattening and the Strength of Halogen Bonding

    Czech Academy of Sciences Publication Activity Database

    Sedlák, Robert; Kolář, Michal H.; Hobza, Pavel

    2015-01-01

    Roč. 11, č. 10 (2015), s. 4727-4732 ISSN 1549-9618 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388963 Keywords : density functional theory * interaction energies * halogen bonding Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.301, year: 2015

  12. Installation Management Command - Flattening or Flat-lining?

    Science.gov (United States)

    2012-03-22

    3624 Market Street, Philadelphia, PA 19104, (215) 662-5606. The Commission on Higher Education is an institutional accrediting agency recognized by...3624 Market Street, Philadelphia, PA 19104, (215) 662-5606. The Commission on Higher Education is an institutional accrediting agency recognized by...for functional support. Key account management is a concept used in the corporate realm, with companies such as Pepsi Bottling Group, International

  13. VT USGS NED Hydro-flattened DEM (30 meter) - statewide

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) VTHYDRODEM was created to produce a "hydrologically correct" DEM, compliant with the Vermont Hydrography Dataset (VHD) in support of the "flow...

  14. Generation and application of high power flattened Gaussian beams

    CSIR Research Space (South Africa)

    Forbes, A

    2009-07-01

    Full Text Available -0.03 -0.02 -0.01 0 0.01 0.02 0.03 Radius (m) M i r r o r S u r f a c e ( µ µ µ µ m ) Fox–Li analysis 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 50 100 150 200 250 300 Round Trip # L o s s 0 0.2 0.4 0...Repetition rate 5 JPulse energy 1.5 kWAverage power TEA CO2 laser movie Single mode or multimode? E~250 mJ, M2 ~ 1.1 E~6.3 J, M2 ~ 25 Design and fabrication of an intra-cavity DOE 0 2 4 6 8 10 12 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 Radius (m) M i...

  15. Is the dark matter halo of the Milky Way flattened?

    Czech Academy of Sciences Publication Activity Database

    Růžička, Adam; Palouš, Jan; Theis, Ch.

    2007-01-01

    Roč. 461, č. 1 (2007), s. 155-169 ISSN 0004-6361 R&D Projects: GA MŠk(CZ) LC06014 Institutional research plan: CEZ:AV0Z10030501 Keywords : N-body simulations * galaxies * interactions * Magellanic clouds Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.259, year: 2007

  16. A Flattened Hierarchical Scheduler for Real-Time Virtual Machines

    OpenAIRE

    Drescher, Michael Stuart

    2015-01-01

    The recent trend of migrating legacy computer systems to a virtualized, cloud-based environment has expanded to real-time systems. Unfortunately, modern hypervisors have no mechanism in place to guarantee the real-time performance of applications running on virtual machines. Past solutions to this problem rely on either spatial or temporal resource partitioning, both of which under-utilize the processing capacity of the host system. Paravirtualized solutions in which the guest communicates it...

  17. Beatification: Flattening Poisson brackets for plasma theory and computation

    Science.gov (United States)

    Morrison, P. J.; Viscondi, T. F.; Caldas, I.

    2017-10-01

    A perturbative method called beatification is presented for producing nonlinear Hamiltonian fluid and plasma theories. Plasma Hamiltonian theories, fluid and kinetic, are naturally described in terms of noncanonical variables. The beatification procedure amounts to finding a transformation that removes the explicit variable dependence from a noncanonical Poisson bracket and replaces it with a fixed dependence on a chosen state in the phase space. As such, beatification is a major step toward casting the Hamiltonian system in its canonical form, thus enabling or facilitating the use of analytical and numerical techniques that require or favor a representation in terms of canonical, or beatified, Hamiltonian variables. Examples will be given. U.S. D.O.E No. #DE-FG02-04ER-54742.

  18. Morphometrical analysis of cleaning capacity using nickel-titanium rotary instrumentation associated with irrigating solutions in mesio-distal flattened root canals Análise morfológica da capacidade de limpeza promovida pela instrumentação rotatória, associada à soluções irrigantes, com limas de níquel-titânio em canais radiculares com achatamento mesio-distal

    Directory of Open Access Journals (Sweden)

    Melissa Andréia Marchesan

    2003-03-01

    Full Text Available Variations in the internal anatomy of root canals may interfere with the success of root canal because tissue remnants may remain in the isthmus, re-entrances and ramifications of flattened root canals making instrumentation more difficult. Successful root canal treatment depends fundamentally on shaping, cleaning, disinfection and obturation. This study verified the quality of cleaning of ProFile .04 rotary technique associated with different irrigating solutions: 0.5% sodium hypochlorite, calcium hydroxide + Tergentol and 2% chlorhexidine in canals with mesio-distal flattening. Twelve human mandibular central incisors were randomly divided into 3 groups and instrumented up to ProFile 0.4 #35 file after cervical preparation, and processed histologically. After optical microscopic evaluation, statistical analysis showed that the percentage of cleaning of the three irrigating solutions was statistically different. Two-by-two comparisons classified the irrigating solutions in increasing order of cleaning: calcium hydroxide + Tergentol As variações da anatomia interna de cada canal radicular podem interferir no sucesso da terapêutica endodôntica devido ao fato de que em canais radiculares achatados, pode persistir remanescentes teciduais em istmos, reentrâncias e ramificações dificultando a execução das técnicas de instrumentação. O sucesso do tratamento dos canais radiculares depende fundamentalmente do preparo da forma, limpeza, desinfecção e obturação. Poucos trabalhos avaliaram a limpeza dos canais radiculares após a instrumentação rotatória. O presente trabalho verificou a qualidade de limpeza dos canais radiculares, por meio da microscopia óptica, promovida pela técnica de instrumentação rotatória associada ao hipoclorito de sódio 0,5%, HCT20 e clorexidina, em canais achatados no sentido mésio-distal. Doze incisivos centrais inferiores humanos foram divididos aleatoriamente em três grupos para que fossem

  19. Tunable microwave photonic filter free from baseband and carrier suppression effect not requiring single sideband modulation using a Mach-Zenhder configuration.

    Science.gov (United States)

    Mora, José; Ortigosa-Blanch, Arturo; Pastor, Daniel; Capmany, José

    2006-08-21

    We present a full theoretical and experimental analysis of a novel all-optical microwave photonic filter combining a mode-locked fiber laser and a Mach-Zenhder structure in cascade to a 2x1 electro-optic modulator. The filter is free from the carrier suppression effect and thus it does not require single sideband modulation. Positive and negative coefficients are obtained inherently in the system and the tunability is achieved by controlling the optical path difference of the Mach-Zenhder structure.

  20. An investigation of accelerator head scatter and output factor in air

    International Nuclear Information System (INIS)

    Ding, George X.

    2004-01-01

    Our purpose in this study was to investigate whether the Monte Carlo simulation can accurately predict output factors in air. Secondary goals were to study the head scatter components and investigate the collimator exchange effect. The Monte Carlo code, BEAMnrc, was used in the study. Photon beams of 6 and 18 MV were from a Varian Clinac 2100EX accelerator and the measurements were performed using an ionization chamber in a mini-phantom. The Monte Carlo calculated in air output factors was within 1% of measured values. The simulation provided information of the origin and the magnitude of the collimator exchange effect. It was shown that the collimator backscatter to the beam monitor chamber played a significant role in the beam output factors. However the magnitude of the scattered dose contributions from the collimator at the isocenter is negligible. The maximum scattered dose contribution from the collimators was about 0.15% and 0.4% of the total dose at the isocenter for a 6 and 18 MV beam, respectively. The scattered dose contributions from the flattening filter at the isocenter were about 0.9-3% and 0.2-6% of the total dose for field sizes of 4x4 cm 2 -40x40 cm 2 for the 6 and 18 MV beam, respectively. The study suggests that measurements of head scatter factors be done at large depth well beyond the depth of electron contamination. The insight information may have some implications for developing generalized empirical models to calculate the head scatter

  1. Neutron and photon spectra in LINACs

    International Nuclear Information System (INIS)

    Vega-Carrillo, H.R.; Martínez-Ovalle, S.A.; Lallena, A.M.; Mercado, G.A.; Benites-Rengifo, J.L.

    2012-01-01

    A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10 –6 and 1 MeV. Neutron and the Bremsstrahlung spectra show the same features regardless of the linac voltage. - Highlights: ► With MCNPX code realistic models of two LINACs were built. ► Photon and neutron spectra below the flattening filter and at the isocenter were calculated. ► Neutron spectrum at the flattening filter was compared against the Tosi et al. source-term model. ► Tosi et al. model underestimates the neutron contribution below 1 MeV. ► Photon spectra look alike to those published in literature.

  2. Neutronics design of accelerator-driven system for power flattening and beam current reduction

    International Nuclear Information System (INIS)

    Nishihara, Kenji; Iwanaga, Kohei; Tsujimoto, Kazufumi; Kurata, Yuji; Oigawa, Hiroyuki; Iwasaki, Tomohiko

    2008-01-01

    In the present neutronics design of the Accelerator-Driven System (ADS) cooled by lead-bismuth eutectic (LBE), we investigated several methods to reduce the power peak and beam current, and estimated the temperature reductions of the cladding tube and beam window from the conventional design. The methods are adjustment of inert matrix ratio in fuel in each burn-up cycle, multiregion design in terms of pin radius or inert matrix content, and modification of the level of the beam window position and the height of the central fuel assemblies. As a result, we optimized the ADS combined with the adjustment of the inert matrix ratio in each burn-up cycle, multiregion design in terms of inert matrix content and deepened window level. The maximum temperatures of the optimized ADS at the surface of the cladding tube and the beam window were reduced by 91 and 38degC, respectively. The maximum beam current was improved from 20.3 to 15.6 mA. (author)

  3. Exhaustion measured by the SF-36 vitality scale is associated with a flattened diurnal cortisol profile

    DEFF Research Database (Denmark)

    Lindeberg, Sara I; Eek, Frida; Lindbladh, Eva

    2008-01-01

    cortisol profile. The study population included 78 working individuals. The study group was dichotomised into exhausted and non-exhausted groups by means of the SF-36 vitality scale. Salivary cortisol was measured at three times during 1 workday: at awakening, 30min after awakening, and in the evening....... The results showed that diurnal cortisol variation was significantly reduced in exhausted individuals. The difference in cortisol variation was mainly due to lowered morning cortisol in the exhausted group. Differences in cortisol levels at each sampling time or in mean diurnal output of cortisol were...... not statistically significant. The results would support the notion that exhaustion is associated with HPA axis hypoactivity as assessed by salivary cortisol. Furthermore, the SF-36 vitality provides a measure of exhaustion that may be useful in epidemiological studies in order to explore long-term health effects...

  4. Triangulation of the monophasic action potential causes flattening of the electrocardiographic T-wave

    DEFF Research Database (Denmark)

    Bhuiyan, Tanveer Ahmed; Graff, Claus; Thomsen, Morten Bækgaard

    2012-01-01

    of the action potential under the effect of the IKr blocker sertindole and associated these changes to concurrent changes in the morphology of electrocardiographic T-waves in dogs. We show that, under the effect of sertindole, the peak changes in the morphology of action potentials occur at time points similar......It has been proposed that triangulation on the cardiac action potential manifests as a broadened, more flat and notched T-wave on the ECG but to what extent such morphology characteristics are indicative of triangulation is more unclear. In this paper, we have analyzed the morphological changes...... to those observed for the peak changes in T-wave morphology on the ECG. We further show that the association between action potential shape and ECG shape is dose-dependent and most prominent at the time corresponding to phase 3 of the action potential....

  5. Revisiting the Digital Divide in the Context of a "Flattening" World

    Science.gov (United States)

    Subramony, Deepak Prem

    2014-01-01

    This article employs a variety of theoretical lenses to describe the nature and ramifications of the Digital Divide, which, the author states, continues to remain one of the biggest social challenges to confront the human race in modern times--even as technological advances, globalization, and other socioeconomic shifts are rendering digital media…

  6. Challenging hierarchy in healthcare teams - ways to flatten gradients to improve teamwork and patient care.

    Science.gov (United States)

    Green, B; Oeppen, R S; Smith, D W; Brennan, P A

    2017-06-01

    In healthcare, mistakes that are potentially harmful or fatal to patients are often the result of poor communication between members of a team. This is particularly important in high-risk areas such as operating theatres or during any intervention, and the ability to challenge colleagues who are in authority when something does not seem right or is clearly wrong, is crucial. Colleagues in oral and maxillofacial surgery recognised the importance of this as early as 2004, and it is now well known that failure or reluctance to challenge others who might be wrong can severely compromise a patient's safety. The Royal College of Surgeons of Edinburgh runs popular regular courses (Non-technical Skills for Surgeons, NOTSS) that teach how to ensure safety through good communication and teamwork. In this paper we introduce the concept of hierarchical challenge, and discuss models and approaches to address situations when problems arise within a team. Copyright © 2017 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  7. Flattening the Learning Curve: SOF as the Supported Command in the Irregular Warfare Environment

    Science.gov (United States)

    2012-06-01

    franchises can get this right, then surely so could the United States military. The endstate should always be to become more effective and efficient...may set the conditions for Joint and integrated GPF/SOF training on a more permanent basis. Of course, the disadvantage is that any training with

  8. Hybrid organic–inorganic inks flatten the energy landscape in colloidal quantum dot solids

    KAUST Repository

    Liu, Mengxia

    2016-11-14

    Bandtail states in disordered semiconductor materials result in losses in open-circuit voltage (Voc) and inhibit carrier transport in photovoltaics. For colloidal quantum dot (CQD) films that promise low-cost, large-area, air-stable photovoltaics, bandtails are determined by CQD synthetic polydispersity and inhomogeneous aggregation during the ligand-exchange process. Here we introduce a new method for the synthesis of solution-phase ligand-exchanged CQD inks that enable a flat energy landscape and an advantageously high packing density. In the solid state, these materials exhibit a sharper bandtail and reduced energy funnelling compared with the previous best CQD thin films for photovoltaics. Consequently, we demonstrate solar cells with higher Voc and more efficient charge injection into the electron acceptor, allowing the use of a closer-to-optimum bandgap to absorb more light. These enable the fabrication of CQD solar cells made via a solution-phase ligand exchange, with a certified power conversion efficiency of 11.28%. The devices are stable when stored in air, unencapsulated, for over 1,000 h.

  9. VT Lidar Hydro-flattened DEM (0.7 meter) - 2014 - Chittenden, Lamoille, Orleans, & Washington Counties

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata applies to the following collection area(s): Eastern VT 2014 0.7m and Digital Elevation Model (DEM) dataset of the following...

  10. Dispersion-Flattened Composite Highly Nonlinear Fibre Optimised for Broadband Pulsed Four-Wave Mixing

    DEFF Research Database (Denmark)

    Lillieholm, Mads; Galili, Michael; Oxenløwe, Leif Katsuo

    2016-01-01

    We present a segmented composite HNLF optimised for mitigation of dispersion-fluctuation impairments for broadband pulsed four-wave mixing. The HNLF-segmentation allows for pulsed FWMprocessing of a 13-nm wide input WDM-signal with -4.6-dB conversion efficiency...

  11. An interactive local flattening operator to support digital investigations on artwork surfaces.

    Science.gov (United States)

    Pietroni, Nico; Massimiliano, Corsini; Cignoni, Paolo; Scopigno, Roberto

    2011-12-01

    Analyzing either high-frequency shape detail or any other 2D fields (scalar or vector) embedded over a 3D geometry is a complex task, since detaching the detail from the overall shape can be tricky. An alternative approach is to move to the 2D space, resolving shape reasoning to easier image processing techniques. In this paper we propose a novel framework for the analysis of 2D information distributed over 3D geometry, based on a locally smooth parametrization technique that allows us to treat local 3D data in terms of image content. The proposed approach has been implemented as a sketch-based system that allows to design with a few gestures a set of (possibly overlapping) parameterizations of rectangular portions of the surface. We demonstrate that, due to the locality of the parametrization, the distortion is under an acceptable threshold, while discontinuities can be avoided since the parametrized geometry is always homeomorphic to a disk. We show the effectiveness of the proposed technique to solve specific Cultural Heritage (CH) tasks: the analysis of chisel marks over the surface of a unfinished sculpture and the local comparison of multiple photographs mapped over the surface of an artwork. For this very difficult task, we believe that our framework and the corresponding tool are the first steps toward a computer-based shape reasoning system, able to support CH scholars with a medium they are more used to. © 2011 IEEE

  12. 2009 - 2011 CA Coastal Conservancy Coastal Lidar Project: Hydro-flattened Bare Earth DEM

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Light Detection and Ranging (LiDAR) data is remotely sensed high-resolution elevation data collected by an airborne collection platform. This LiDAR dataset is a...

  13. Ultrafast electron injection at the cationic porphyrin-graphene interface assisted by molecular flattening

    KAUST Repository

    Aly, Shawkat Mohammede; Parida, Manas R.; Alarousu, Erkki; Mohammed, Omar F.

    2014-01-01

    The steady-state and femtosecond (fs) time-resolved data clearly demonstrate that the charge transfer (CT) process at the porphyrin-graphene carboxylate (GC) interfaces can be tuned from zero to very sufficient and ultrafast by changing the electronic structure of the meso unit and the redox properties of the porphyrin cavity. This journal is © the Partner Organisations 2014.

  14. Get Flat, or Get Flattened: Adapting to the Forces of Globalization

    Science.gov (United States)

    2015-02-25

    down leadership interest in preparing the joint force for the emerging security environment. The CCJO defines the operational problem as determining...proportional to the square of the number of users in the 8 An idea, behavior, style , or usage that...centralized, totalizing, and autocratic . To increase efficiency and maximize revenue to pay for the war governments centralized their administrations

  15. Flattening and truncation of stellar discs in edge-on spiral galaxies

    NARCIS (Netherlands)

    Kregel, M; van der Kruit, PC; de Grijs, R

    We analyse the global structure of the old stellar discs in 34 edge-on spiral galaxies. The radial and vertical exponential scale parameters of the discs are obtained by applying an improved two-dimensional decomposition technique to our I -band photometry. We find a clear increase in the disc

  16. Trends in CPAP adherence over twenty years of data collection: a flattened curve.

    Science.gov (United States)

    Rotenberg, Brian W; Murariu, Dorian; Pang, Kenny P

    2016-08-19

    Obstructive sleep apnea (OSA) is a common disorder, and continuous airway positive pressure (CPAP) is considered to be the gold standard of therapy. CPAP however is known to have problems with adherence, with many patients eventually abandoning the device. The purpose of this paper is to assess secular trends in CPAP adherence over the long term to see if there have been meaningful improvements in adherence in light of the multiple interventions proposed to do so. A comprehensive systematic literature review was conducted using the Medline-Ovid, Embase, and Pubmed databases, searching for data regarding CPAP adherence over a twenty year timeframe (1994-2015). Data was assessed for quality and then extracted. The main outcome measure was reported CPAP non-adherence. Secondary outcomes included changes in CPAP non-adherence when comparing short versus long-term, and changes in terms of behavioral counseling. Eighty-two papers met study inclusion/exclusion criteria. The overall CPAP non-adherence rate based on a 7-h/night sleep time that was reported in studies conducted over the twenty year time frame was 34.1 %. There was no significant improvement over the time frame. Behavioral intervention improved adherence rates by ~1 h per night on average. The rate of CPAP adherence remains persistently low over twenty years worth of reported data. No clinically significant improvement in CPAP adherence was seen even in recent years despite efforts toward behavioral intervention and patient coaching. This low rate of adherence is problematic, and calls into question the concept of CPAP as gold-standard of therapy for OSA.

  17. Portal imaging improvement with a low energy un flattened beam in high energy medical accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Krutman, Y; Faermann, S; Tsechanski, A [Ben-Gurion Univ. of the Negev, Beersheba (Israel)

    1996-12-01

    In this work we present a further improvement of the portal film option, for a Clinac 18 accelerator with a 10 MV therapeutic x-ray beam. This is done by lowering the nominal photon energy to 4 MV, therefore increasing the relative contribution of the low energy portion of the x-ray spectrum. Improvement of the image quality is demonstrated with a portal film scale tray, and with an anthropomorphic phantom, a graphical analysis demonstrates the improvement on image (authors).

  18. VT Lidar Hydro-flattened DEM (0.7 meter) - 2015 - Windham County

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata applies to the following collection area(s): Windham County 2015 0.7m and Digital Elevation Model (DEM) dataset of the following...

  19. Hybrid organic–inorganic inks flatten the energy landscape in colloidal quantum dot solids

    KAUST Repository

    Liu, Mengxia; Voznyy, Oleksandr; Sabatini, Randy; Arquer, F.  Pelayo Garcí a de; Munir, Rahim; Balawi, Ahmed  Hesham; Lan, Xinzheng; Fan, Fengjia; Walters, Grant; Kirmani, Ahmad R.; Hoogland, Sjoerd; Laquai, Fré dé ric; Amassian, Aram; Sargent, Edward  H.

    2016-01-01

    Bandtail states in disordered semiconductor materials result in losses in open-circuit voltage (Voc) and inhibit carrier transport in photovoltaics. For colloidal quantum dot (CQD) films that promise low-cost, large-area, air-stable photovoltaics, bandtails are determined by CQD synthetic polydispersity and inhomogeneous aggregation during the ligand-exchange process. Here we introduce a new method for the synthesis of solution-phase ligand-exchanged CQD inks that enable a flat energy landscape and an advantageously high packing density. In the solid state, these materials exhibit a sharper bandtail and reduced energy funnelling compared with the previous best CQD thin films for photovoltaics. Consequently, we demonstrate solar cells with higher Voc and more efficient charge injection into the electron acceptor, allowing the use of a closer-to-optimum bandgap to absorb more light. These enable the fabrication of CQD solar cells made via a solution-phase ligand exchange, with a certified power conversion efficiency of 11.28%. The devices are stable when stored in air, unencapsulated, for over 1,000 h.

  20. SU-F-T-429: Craniospinal Irradiation by VMAT Technique: Impact of FFF Beam and High Resolution MLC On Plan Quality

    Energy Technology Data Exchange (ETDEWEB)

    Ganesh, T; Sarkar, B; Munshi, A; Mohanti, B [Fortis Memorial Research Institute, Gurgaon, Haryana (India)

    2016-06-15

    Purpose: Objective of this study was to evaluate the impact of using flattening filter free (FFF) beam with 0.5 cm multileaf collimator (MLC) leaves over conventional flattened beam with 1 cm leaf width MLC on the treatment plan quality in cranio-spinal irradiation (CSI). Methods: For five medulloblastoma cases (3 males and 2 females), who were previously treated by volumetric modulated arc therapy (VMAT) technique using conventional flattened beam shaped by 1 cm width MLC leaves, four test plans were generated and compared against the delivered plan. These retrospective plans consisted of four different combinations of flattened and FFF beams from Elekta’s Agility treatment head with 0.5 cm width MLC leaves. Sparing of organs at risks (OAR) in terms of dose to 5%, 50%, 75% and 90% volumes, mean and maximum dose were evaluated. Results: All plans satisfied the planning objective of covering 95% of PTV by at least 95% of prescription dose. Marginal variation of dose spillage was observed between different VMAT plans at very low dose range (1–5 Gy). Variation in dose statistics for PTVs and OARs were within 1% or 1 Gy. Amongst the five plans, the plan with flattened beam with 1 cm MLC had the highest number of MUs, 2.13 times higher than the plan with Agility MLC with FFF beam that had the least number of MUs. No statistically significant difference (p≥0.05) was observed between the reference plan and the retrospectively generated plans in terms of PTV coverage, cold spot, hot spot and organ at risk doses. Conclusion: In the treatment of CSI cases by VMAT technique, FFF beams and/or finer width MLC did not exhibit advantage over the flattened beams or wider MLC in terms of plan quality except for reduction in MUs.

  1. The characterization of unflattened photon beams from a 6 MV linear accelerator

    International Nuclear Information System (INIS)

    Cashmore, Jason

    2008-01-01

    Commissioning data have been measured for an Elekta Precise linear accelerator running at 6 MV without a flattening filter with the aim of studying the effects of flattening filter removal on machine operation and beam characterization. Modern radiotherapy practice now routinely relies on the use of fluence modifying techniques such as IMRT, i.e. the active production of non-flat beams. For these techniques the flattening filter should not be necessary. It is also possible that the increased intensity around the central axis associated with unflattened beams may be useful for conventional treatment planning by acting as a field-in-field or integrated boost technique. For this reason open and wedged field data are presented. Whilst problems exist in running the machine filter free clinically, this paper shows that in many ways the beam is actually more stable, exhibiting almost half the variation in field symmetry for changes in steering and bending currents. Dosimetric benefits are reported here which include a reduction in head scatter by approx. 70%, decreased penumbra (0.5 mm), lower dose outside of the field edge (11%) and a doubling in dose rate (2.3 times for open and 1.9 times for wedged fields). Measurements also show that reduced scatter also reduces leakage radiation by approx. 60%, significantly lowering whole body doses. The greatest benefit of filter-free use is perceived to be for IMRT where increased dose rate combined with reduced head scatter and leakage radiation should lead to improved dose calculation, giving simpler, faster and more accurate dose delivery with reduced dose to normal tissues

  2. Field size dependence of wedge factor: miniphantom vs full phantom measurements

    International Nuclear Information System (INIS)

    Allen Li, X.; Szanto, J.; Soubra, M.; Gerig, L. H.

    1995-01-01

    It is empirically known that the transmission factor for wedge in a high-energy photon beam is dependent upon field size and depth of measurement. The field-size dependence of wedge factors may be attributed to changes in (i) head scatter, (ii) phantom scatter, and (iii) backscatter from the wedge into the linac monitor chamber. In this work we present the results of studies designed to examine each of these factors in isolation. The wedge factors for wedges with nominal wedge angles of 15 deg. , 30 deg. , 45 deg. and 60 deg. were measured with a 3-g/cm 2 -diameter narrow cylindrical phantom (miniphantom), a brass cap with 1.5-g/cm 2 side-wall thickness and a full water phantom for 6-, 10- and 18-MV photon beams. The measurements were performed with and without flattening filter in place. The wedge factors measured with the miniphantom and the brass cap exclude the phantom scatter contribution. It has been found that the field-size behaviour of wedge factor measured with full water phantom is similar to that measured with the miniphantom and cap. This indicates that the head scatter radiation is the major contributor to the field size dependence of wedge factors. Wedge factors measured with water phantom are up to 5.0% smaller than those measured with miniphantom. This difference increases with wedge angle. When Measured with the flattening filter removed, the field size dependence of the wedge factor is reduced. This justify that the flattening filter is one of the major contributors to head scatters. The measurement results made with the brass cap agree well with those made by using the miniphantom. By measuring the monitor chamber output, it is found that the backscatters from the wedge into the linac ion chamber have little effect on the field size dependence of the wedge factor

  3. A new form of spondyloperipheral dysplasia with facial dysmorphism, flattened vertebrae, hypoplastic pelvis, brachydactyly and soft tissue syndactyly

    International Nuclear Information System (INIS)

    Kitoh, Hiroshi

    2001-01-01

    We report the case of a 9-year-old Japanese boy with spondyloperipheral skeletal dysplasia associated with facial dysmorphism, pelvic abnormalities, and distinctive hands and feet. Radiographic manifestations included mild platyspondyly with posterior scalloping, small flared ilia with shallow acetabulae, mesomelic shortening of long bones, marked delay of carpal bone maturation, and brachydactyly with hypoplastic middle and terminal phalanges bilaterally in both hands and feet. There was bilateral soft tissue syndactyly of the 2nd and 3rd interdigital spaces of the hands, the 2nd interdigital space of the feet, with hypoplastic nails. The clinical and radiographic manifestations in this case appear to represent a unique type of skeletal dysplasia. (orig.)

  4. Efficiency of different techniques of physical flattening by fuel while selection of optimum arrangement of large fast reactor core

    International Nuclear Information System (INIS)

    Grachev, E.A.; Dejnega, N.L.; Mitin, A.M.

    1974-01-01

    Results are given of calculations for selecting the parameters of the large fast breeder reactor core (1500 Mw) operating on oxide fuel with a sodium coolant. A complex optimum criterion was selected for energy intensity, energy distribution, breeding ratio and critical load factor, run duration, burning, reactivity variations, influence of CV3, fuel overloads, and calculated fue fuel expenses. The effectivities of various methods for physical grading of fuel (enrichment and composition) were examined in accordance with the optimum criterion. Parameters of reactor cores optimum arrangements are presented. Continuous reactor operation during 0.8-1.0 yr. at energy intensity more than 400 kW was shown to be essential for attaining the optimum chosen. Accounting for the CV3 system and partial fuel overloads, the methods of balancing energy release either by enriching fuel or by changing its composition proved to be almost equally effective. All calculations were performed with the aid of a 18-4-RZ-15B program on the basis of a BNAB-26 constant system [ru

  5. Standard anatomical and visual space for the mouse retina: computational reconstruction and transformation of flattened retinae with the Retistruct package.

    Directory of Open Access Journals (Sweden)

    David C Sterratt

    Full Text Available The concept of topographic mapping is central to the understanding of the visual system at many levels, from the developmental to the computational. It is important to be able to relate different coordinate systems, e.g. maps of the visual field and maps of the retina. Retinal maps are frequently based on flat-mount preparations. These use dissection and relaxing cuts to render the quasi-spherical retina into a 2D preparation. The variable nature of relaxing cuts and associated tears limits quantitative cross-animal comparisons. We present an algorithm, "Retistruct," that reconstructs retinal flat-mounts by mapping them into a standard, spherical retinal space. This is achieved by: stitching the marked-up cuts of the flat-mount outline; dividing the stitched outline into a mesh whose vertices then are mapped onto a curtailed sphere; and finally moving the vertices so as to minimise a physically-inspired deformation energy function. Our validation studies indicate that the algorithm can estimate the position of a point on the intact adult retina to within 8° of arc (3.6% of nasotemporal axis. The coordinates in reconstructed retinae can be transformed to visuotopic coordinates. Retistruct is used to investigate the organisation of the adult mouse visual system. We orient the retina relative to the nictitating membrane and compare this to eye muscle insertions. To align the retinotopic and visuotopic coordinate systems in the mouse, we utilised the geometry of binocular vision. In standard retinal space, the composite decussation line for the uncrossed retinal projection is located 64° away from the retinal pole. Projecting anatomically defined uncrossed retinal projections into visual space gives binocular congruence if the optical axis of the mouse eye is oriented at 64° azimuth and 22° elevation, in concordance with previous results. Moreover, using these coordinates, the dorsoventral boundary for S-opsin expressing cones closely matches the horizontal meridian.

  6. Real-Time Wavelet-Based Coordinated Control of Hybrid Energy Storage Systems for Denoising and Flattening Wind Power Output

    Directory of Open Access Journals (Sweden)

    Tran Thai Trung

    2014-10-01

    Full Text Available Since the penetration level of wind energy is continuously increasing, the negative impact caused by the fluctuation of wind power output needs to be carefully managed. This paper proposes a novel real-time coordinated control algorithm based on a wavelet transform to mitigate both short-term and long-term fluctuations by using a hybrid energy storage system (HESS. The short-term fluctuation is eliminated by using an electric double-layer capacitor (EDLC, while the wind-HESS system output is kept constant during each 10-min period by a Ni-MH battery (NB. State-of-charge (SOC control strategies for both EDLC and NB are proposed to maintain the SOC level of storage within safe operating limits. A ramp rate limitation (RRL requirement is also considered in the proposed algorithm. The effectiveness of the proposed algorithm has been tested by using real time simulation. The simulation model of the wind-HESS system is developed in the real-time digital simulator (RTDS/RSCAD environment. The proposed algorithm is also implemented as a user defined model of the RSCAD. The simulation results demonstrate that the HESS with the proposed control algorithm can indeed assist in dealing with the variation of wind power generation. Moreover, the proposed method shows better performance in smoothing out the fluctuation and managing the SOC of battery and EDLC than the simple moving average (SMA based method.

  7. VT Data - Lidar Hydro-flattened DEM (0.7m) 2016, Essex, Caledonia, Orange, and Windsor Counties

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata applies to the following collection area(s): Middle CT River subbasin 2016 0.7m and Digital Elevation Model (DEM) dataset of the...

  8. Flattening the Energy Response of a Scintillator Based Gamma Dose Rate Meter Coupled to SiPM

    International Nuclear Information System (INIS)

    Knafo, Y.; Manor, A.; Ginzburg, D.; Ellenbogen, M.; Osovizky, A.; Wengrowicz, U.; Ghelman, M.; Seif, R.; Mazor, T.; Kadmon, Y.; Cohen, Y.

    2014-01-01

    Among the newest emerging technologies that are used in the design of personal gamma radiation detection instruments, the silicon photomultiplier (SiPM) light sensor is playing an important role. This type of photo sensor is characterized by low power consumption, small dimensions and high gain. These special characteristics present applicable alternatives for the replacement of traditional gamma sensors based on scintillator coupled to Photomultiplier tubes (PMT) or on Geiger-Muller(G.M.) sensors. For health physics applications, flat energy response is required for a wide range of radio-nuclides emitting gamma rays of different energies. Scintillation based radiation instrumentation provides count rate and amplitude of the measured pulses. These pulses can be split in different bins corresponding to the energy of the measured isotopes and their intensity. The count rate and the energy of the measured events are related to the dose rate. The conversion algorithm applys a different calibration factor for each energy bin in order to provide an accurate dose rate response for a wide range of gamma energies. This work describes the utilization of an innovative approach for dose rate conversion by using the abilities of newest 32-bit microcontroller based ARM core architecture

  9. Water flattens graphene wrinkles: laser shock wrapping of graphene onto substrate-supported crystalline plasmonic nanoparticle arrays.

    Science.gov (United States)

    Hu, Yaowu; Lee, Seunghyun; Kumar, Prashant; Nian, Qiong; Wang, Wenqi; Irudayaraj, Joseph; Cheng, Gary J

    2015-12-21

    Hot electron injection into an exceptionally high mobility material can be realized in graphene-plasmonic nanoantenna hybrid nanosystems, which can be exploited for several front-edge applications including photovoltaics, plasmonic waveguiding and molecular sensing at trace levels. Wrinkling instabilities of graphene on these plasmonic nanostructures, however, would cause reactive oxygen or sulfur species to diffuse and react with the materials, decrease charge transfer rates and block intense hot-spots. No ex situ graphene wrapping technique has been explored so far to control these wrinkles. Here, we present a method to generate seamless integration by using water as a flyer to transfer the laser shock pressure to wrap graphene onto plasmonic nanocrystals. This technique decreases the interfacial gap between graphene and the covered substrate-supported plasmonic nanoparticle arrays by exploiting a shock pressure generated by the laser ablation of graphite and the water impermeable nature of graphene. Graphene wrapping of chemically synthesized crystalline gold nanospheres, nanorods and bipyramids with different field confinement capabilities is investigated. A combined experimental and computational method, including SEM and AFM morphological investigation, molecular dynamics simulation, and Raman spectroscopy characterization, is used to demonstrate the effectiveness of this technique. Graphene covered gold bipyramid exhibits the best result among the hybrid nanosystems studied. We have shown that the hybrid system fabricated by laser shock can be used for enhanced molecular sensing. The technique developed has the characteristics of tight integration, and chemical/thermal stability, is instantaneous in nature, possesses a large scale and room temperature processing capability, and can be further extended to integrate other 2D materials with various 0-3D nanomaterials.

  10. Comparison of three retreatment techniques with ultrasonic activation in flattened canals using micro-computed tomography and scanning electron microscopy.

    Science.gov (United States)

    Bernardes, R A; Duarte, M A H; Vivan, R R; Alcalde, M P; Vasconcelos, B C; Bramante, C M

    2015-08-17

    To use micro-CT to quantitatively evaluate the amount of residual filling material after using several techniques to remove root fillings with and without ultrasonic activation and to analyse the cleanliness of the root canal walls and dentine tubules with scanning electron microscopy (SEM). The root canals of one hundred and eight human mandibular incisors were selected and instrumented with rotary files using the BioRace system up to file size 40, .04 taper. After instrumentation, the teeth were filled using a hybrid technique with gutta-percha and sealer then divided into three groups according to the method used for removing the root filling: G1-Reciproc (using only instrument R50), G2-ProTaper Universal retreatment system and G3-Manual (hand files and Gates-Glidden burs). All groups were divided into two subgroups depending on whether ultrasonic agitation was used with the irrigants. Micro-CT scans were taken before and after removal of the filling material to detect residual material in the canal. After micro-CT analysis, the roots were cut in half, imaged by SEM and scored based on the amount of surface covered by root filling remnants. The data were analysed statistically using a significance level of 5%. All groups had retained material in the root canals after instrumentation. The Reciproc method was associated with less retained material than the ProTaper and Manual methods. Ultrasonic activation significantly reduced the amount of residual root filling in all groups (P material. Ultrasonic activation improved the removal of root filling material in all groups. © 2015 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  11. Wheel running improves REM sleep and attenuates stress-induced flattening of diurnal rhythms in F344 rats.

    Science.gov (United States)

    Thompson, Robert S; Roller, Rachel; Greenwood, Benjamin N; Fleshner, Monika

    2016-05-01

    Regular physical activity produces resistance to the negative health consequences of stressor exposure. One way that exercise may confer stress resistance is by reducing the impact of stress on diurnal rhythms and sleep; disruptions of which contribute to stress-related disease including mood disorders. Given the link between diurnal rhythm disruptions and stress-related disorders and that exercise both promotes stress resistance and is a powerful non-photic biological entrainment cue, we tested if wheel running could reduce stress-induced disruptions of sleep/wake behavior and diurnal rhythms. Adult, male F344 rats with or without access to running wheels were instrumented for biotelemetric recording of diurnal rhythms of locomotor activity, heart rate, core body temperature (CBT), and sleep (i.e. REM, NREM, and WAKE) in the presence of a 12 h light/dark cycle. Following 6 weeks of sedentary or exercise conditions, rats were exposed to an acute stressor known to disrupt diurnal rhythms and produce behaviors associated with mood disorders. Prior to stressor exposure, exercise rats had higher CBT, more locomotor activity during the dark cycle, and greater %REM during the light cycle relative to sedentary rats. NREM and REM sleep were consolidated immediately following peak running to a greater extent in exercise, compared to sedentary rats. In response to stressor exposure, exercise rats expressed higher stress-induced hyperthermia than sedentary rats. Stressor exposure disrupted diurnal rhythms in sedentary rats; and wheel running reduced these effects. Improvements in sleep and reduced diurnal rhythm disruptions following stress could contribute to the health promoting and stress protective effects of exercise.

  12. Time dependent pre-treatment EPID dosimetry for standard and FFF VMAT.

    Science.gov (United States)

    Podesta, Mark; Nijsten, Sebastiaan M J J G; Persoon, Lucas C G G; Scheib, Stefan G; Baltes, Christof; Verhaegen, Frank

    2014-08-21

    Methods to calibrate Megavoltage electronic portal imaging devices (EPIDs) for dosimetry have been previously documented for dynamic treatments such as intensity modulated radiotherapy (IMRT) using flattened beams and typically using integrated fields. While these methods verify the accumulated field shape and dose, the dose rate and differential fields remain unverified. The aim of this work is to provide an accurate calibration model for time dependent pre-treatment dose verification using amorphous silicon (a-Si) EPIDs in volumetric modulated arc therapy (VMAT) for both flattened and flattening filter free (FFF) beams. A general calibration model was created using a Varian TrueBeam accelerator, equipped with an aS1000 EPID, for each photon spectrum 6 MV, 10 MV, 6 MV-FFF, 10 MV-FFF. As planned VMAT treatments use control points (CPs) for optimization, measured images are separated into corresponding time intervals for direct comparison with predictions. The accuracy of the calibration model was determined for a range of treatment conditions. Measured and predicted CP dose images were compared using a time dependent gamma evaluation using criteria (3%, 3 mm, 0.5 sec). Time dependent pre-treatment dose verification is possible without an additional measurement device or phantom, using the on-board EPID. Sufficient data is present in trajectory log files and EPID frame headers to reliably synchronize and resample portal images. For the VMAT plans tested, significantly more deviation is observed when analysed in a time dependent manner for FFF and non-FFF plans than when analysed using only the integrated field. We show EPID-based pre-treatment dose verification can be performed on a CP basis for VMAT plans. This model can measure pre-treatment doses for both flattened and unflattened beams in a time dependent manner which highlights deviations that are missed in integrated field verifications.

  13. Determination of the quality index (Q) for photon beams at arbitrary field sizes.

    Science.gov (United States)

    Sauer, Otto A

    2009-09-01

    A commonly used beam quality index (Q) for high-energy photon beams is the tissue phantom ratio (TPR20,10) for a square field of 10 x 10 cm2 and SDD of 100 cm. On some specialized radiotherapy treatment equipment such a reference collimator setting is not achievable. Likewise a flat beam profile, not explicitly required in dosimetry protocols, but certainly influences the measurement of Q, is not always produced. In this work, a method was developed in order to determine Q at any field size, especially for small and nonflattened beams. An analytical relationship was derived between TPR20,10 for arbitrary field sizes and Q [the TPR20,10 (10 x 10 cm2)] as quality index. The proposed model equation was fitted to the measured and published data in order to achieve three general fit parameters. The procedure was then tested with published data from TomoTherapy and CyperKnife treatment devices. For standard flattened photon fields, the uncertainty in Q measured at any field size using the parameters derived from this study is better than 1%. In flattening-filter free beams, the proposed procedure results in a reliable Q for any field size setting. A method is introduced and successfully tested in order to measure the beam quality under nonstandard conditions. It can be used, e.g., to get energy dependent correction factors as tabulated in dosimetry codes of practice even if standard conditions are not adjustable.

  14. Comparison of noise power spectrum methodologies in measurements by using various electronic portal imaging devices in radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Son, Soon Yong [Dept. of Radiological Technology, Wonkwang Health Science University, Iksan (Korea, Republic of); Choi, Kwan Woo [Dept. of Radiology, Asan Medical Center, Seoul (Korea, Republic of); Jeong, Hoi Woun [Dept. of Radiological Technology, Baekseok Culture University College, Cheonan (Korea, Republic of); Kwon, Kyung Tae [Dep. of Radiological Technology, Dongnam Health University, Suwon (Korea, Republic of); Kim, Ki Won [Dept. of Radiology, Kyung Hee University Hospital at Gang-dong, Seoul (Korea, Republic of); Lee, Young Ah; Son, Jin Hyun; Min, Jung Whan [Shingu University College, Sungnam (Korea, Republic of)

    2016-03-15

    The noise power spectrum (NPS) is one of the most general methods for measuring the noise amplitude and the quality of an image acquired from a uniform radiation field. The purpose of this study was to compare different NPS methodologies by using megavoltage X-ray energies. The NPS evaluation methods in diagnostic radiation were applied to therapy using the International Electro-technical Commission standard (IEC 62220-1). Various radiation therapy (RT) devices such as TrueBeamTM(Varian), BEAMVIEWPLUS(Siemens), iViewGT(Elekta) and ClinacR iX (Varian) were used. In order to measure the region of interest (ROI) of the NPS, we used the following four factors: the overlapping impact, the non-overlapping impact, the flatness and penumbra. As for NPS results, iViewGT(Elekta) had the higher amplitude of noise, compared to BEAMVIEWPLUS (Siemens), TrueBeamTM(Varian) flattening filter, ClinacRiXaS1000(Varian) and TrueBeamTM(Varian) flattening filter free. The present study revealed that various factors could be employed to produce megavoltage imaging (MVI) of the NPS and as a baseline standard for NPS methodologies control in MVI.

  15. A flexible Monte Carlo tool for patient or phantom specific calculations: comparison with preliminary validation measurements

    Science.gov (United States)

    Davidson, S.; Cui, J.; Followill, D.; Ibbott, G.; Deasy, J.

    2008-02-01

    The Dose Planning Method (DPM) is one of several 'fast' Monte Carlo (MC) computer codes designed to produce an accurate dose calculation for advanced clinical applications. We have developed a flexible machine modeling process and validation tests for open-field and IMRT calculations. To complement the DPM code, a practical and versatile source model has been developed, whose parameters are derived from a standard set of planning system commissioning measurements. The primary photon spectrum and the spectrum resulting from the flattening filter are modeled by a Fatigue function, cut-off by a multiplying Fermi function, which effectively regularizes the difficult energy spectrum determination process. Commonly-used functions are applied to represent the off-axis softening, increasing primary fluence with increasing angle ('the horn effect'), and electron contamination. The patient dependent aspect of the MC dose calculation utilizes the multi-leaf collimator (MLC) leaf sequence file exported from the treatment planning system DICOM output, coupled with the source model, to derive the particle transport. This model has been commissioned for Varian 2100C 6 MV and 18 MV photon beams using percent depth dose, dose profiles, and output factors. A 3-D conformal plan and an IMRT plan delivered to an anthropomorphic thorax phantom were used to benchmark the model. The calculated results were compared to Pinnacle v7.6c results and measurements made using radiochromic film and thermoluminescent detectors (TLD).

  16. Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 04: On 3D Fabrication of Phantoms and Experimental Verification of Patient Dose Computation Algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Rao; Zavan, Rodolfo; McGeachy, Philip; Madamesila, Joseph; Villarreal-Barajas, Jose Eduardo [Radiation Oncology, Washington University School of Medicine, St Louis, MO, USA, Instituto de Física de São Carlos, Universidade de São Paulo, SP, Brazil, CancerCare Manitoba, Winnipeg,Manitoba, Physics and Astronomy, University of Calgary, Calgary, Alberta (Canada)

    2016-08-15

    Purpose: Transport based dose calculation algorithm Acuros XB (AXB) has been shown to accurately account for heterogeneities mostly through comparisons with Monte Carlo simulations. This study aims at providing additional experimental verification for AXB for flattened and unflattened clinical energies in low density phantoms of the same material. Materials and Methods: Polystyrene slabs were created using a bench-top 3D printer. Six slabs were printed at varying densities from 0.23 g/cm{sup 3} to 0.68 g/cm{sup 3}, corresponding to different density humanoid tissues. The slabs were used to form different single and multilayer geometries. Dose was calculated with AXB 11.0.31 for 6MV, 15MV flattened and 6FFF (flattening filter free) energies for field sizes of 2×2 cm{sup 2} and 5×5 cm{sup 2}. The phantoms containing radiochromic EBT3 films were irradiated. Absolute dose profiles and 2D gamma analyses were performed for 96 dose planes. Results: For all single slab, multislab configurations and energies, absolute dose differences between the AXB calculation and film measurements remained <3% for both fields, with slightly poor disagreement in penumbra. The gamma index at 2% / 2mm averaged 98% in all combinations of fields, phantoms and photon energies. Conclusions: The transport based dose algorithm AXB is in good agreement with the experimental measurements for small field sizes using 6MV, 6FFF and 15MV beams adjacent to low density heterogeneous media. This work provides sufficient experimental ground to support the use of AXB for heterogeneous dose calculation purposes.

  17. Surface flattening processes of metal layer and their effect on transport properties of magnetic tunnel junctions with Al-N barrier

    International Nuclear Information System (INIS)

    Yoshimura, S.; Nozawa, T.; Shoyama, T.; Tsunoda, M.; Takahashi, M.

    2005-01-01

    In order to form ultrathin insulating layer in magnetic tunnel junctions (MTJs), two surface flatting processes of metal films are investigated. Oxygen-additive sputter-deposition process was applied to the bottom Cu electrode and the Al layer to be nitrided. Dry-etching process was applied for the surface treatment of lower Co-Fe layer. As a result, the surface roughness of stacked ultrathin Al layer to be nitrided is reduced from 3.2A to 1.7A, and the tunnel magnetoresistance (TMR) ratio of the MTJs increases from 1% to 26% while maintaining resistance-area product (RxA) less than 5x10 2 Ω μm 2 in the Co-Fe/Al(6A)-N/Co-Fe MTJs. We conclude that the decrease of the surface roughness of Al layer is one of the key factors to realize high performance MTJs with low RxA and high TMR ratio

  18. Generation of Flattened Multicarrier Signals from a Single Laser Source for 330 Gbps WDM-PON Transmission over 25 km SSMF

    Science.gov (United States)

    Ullah, Sibghat; Liu, Bo; Ullah, Rahat; Ahmad, Muhammad; Wang, Fu; Zhang, Lijia; Xin, Xiangjun; Memon, Kamran Ali; Khalid, Hafiz Ahmad

    2017-12-01

    A novel technique is proposed for optical frequency comb generation with a budget friendly system. A Mach-Zehnder modulator is used in connectivity with continuous wave optical signal which is filtered by rectangle optical filter and the signal is then amplified by erbium-doped fiber amplifier. With a frequency spacing of 10 GHz 33 useable OFC lines were generated with good tone to noise ratio which is quite impressive for such a cost effective setup. Each generated carrier carries differential phase shift keying based data of 10 Gbps. A total of 330 Gbps multiplexed data is successfully transmitted through a standard single mode fiber length of 25-km. During the downlink transmission the power penalties are observed to be negligible. The resulted eye diagrams are wide and promises to be a good system for wavelength division multiplexed-passive optical network.

  19. From the semicircular vault to the flattened vault in masonry bridges. The influence of rise/span ratio and the resistant backfill in the breaking load

    Directory of Open Access Journals (Sweden)

    J. R. Urruchi-Rojo

    2017-04-01

    Full Text Available The shape of the vaults in masonry bridges has evolved during the history, so that we can find bibliography where, besides recommending one way of build instead of others depending on the period, is also prescribed the way to carry out the backfill of the extrados. All of this emerged initially as a result of the experiences acquired during the construction and the observation of bridges. Hence, during the 18th century new formulations started to arise, but they led to one result in some cases and to the opposite in others. This article tries to make a comparison between some of these formulations, as well as carrying out an analysis of the influence of both, the lowering rise/span ratio of the vaults and the presence of a resistant backfill in its extrados, on the variation of the breaking load.

  20. Gain flattened L-band EDFA based on upgraded C-band EDFA using forward ASE pumping in an EDF section

    DEFF Research Database (Denmark)

    Buxens Azcoaga, Alvaro Juan; Poulsen, Henrik Nørskov; Clausen, Anders

    2000-01-01

    A novel method is presented for implementing an L-band erbium doped fibre amplifier (EDFA) making use of forward amplified spontaneous emission pumping, from a commercially available c-band EDFA, in an erbium doped fibre. Tuning of the length of erbium doped fibre enables a flat gain characteristic...... to be obtained with a low noise figure over the entire L-band window....

  1. Wavelength conversion of a 40 Gb/s RZ-DPSK signal using four-wave mixing in a dispersion-flattened highly nonlinear photonic crystal fiber

    DEFF Research Database (Denmark)

    Andersen, Peter Andreas; Tokle, Torger; Geng, Yan

    2005-01-01

    Wavelength conversion of a 40-Gb/s return-to-zero differential phase-shift keying signal is demonstrated in a highly nonlinear photonic crystal fiber (HNL-PCF) for the first time. A conversion efficiency of -20 dB for a pump power of 23 dBm and a conversion bandwidth of 31 nm, essentially limited...

  2. The Effects of Flattening the Effective Marginal Rate Structure in Australia: Policy Simulations Using the Melbourne Institute Tax and Transfer Simulator

    OpenAIRE

    John Creedy; Guyonne Kalb; Hsein Kew

    2001-01-01

    This paper uses the Melbourne Institute Tax and Transfer Simulator (MITTS) to examine the effects of a reduction in the means-tested benefit taper, or withdrawal, rates in Australia to 30 per cent. That is, all taper rates of 50 per cent and 70 per cent in the 1998 system are reduced to 30 per cent, while leaving all basic benefit levels unchanged. This change is therefore expected to ‘flatten’ the tax structure by reducing the high marginal tax rates applying to those with relatively low inc...

  3. SU-F-T-621: Impact of Vacuum and Treatment Couch On Surface Dose in Stereotactic Body Radiation Therapy With and Without a Flattening Filter

    Energy Technology Data Exchange (ETDEWEB)

    Lan, HT; Lu, SH; Kuo, SH; Tsai, YC; Chen, LH; Wen, SY; Wang, CW [National Taiwan University Hospital, Taipei City, Taiwan (China)

    2016-06-15

    Purpose: When treating lung cancer patients with stereotactic body radiation therapy (SBRT), better immobilization is needed for accurate delivery of high-dose radiation. However, using a treatment couch (TrueBeamTM) and vacuum bag (BlueBAGTM) may increase the surface dose and skin toxicity. This study investigated the influence of couch and vacuum bag on the surface dose. Methods: The relative surface dose (D{sub 0}/DMAX) was measured in an ion-chamber (Markus-type PTW, 0.05cm{sup 3}) with a solid water phantom and SSD to 100 cm. A comprehensive comparison of different parameter settings, including the different energies (6MV-FFF, 10MV-FF, and 10MV-FFF), field sizes (3 X 3 cm{sup 2}, 5 × 5 cm{sup 2}, 8 × x cm{sup 2} , 10 × 10 cm{sup 2}, and 15 × 15 cm{sup 2}), thickness of the vacuum bag (5mm, 15mm, 30mm, 39mm and 55mm), and couch (with and without), was performed. Results: The FFF increases the surface dose as compared to FF mode. In a similar setting with field of 10 × 10 cm{sup 2}, FFF mode increases the surface dose from 26.0% to 32.8% for 6 MV, and 17.4% to 21.5% for 10 MV. When the beam passes through the couch, the surface dose increases to 3.6, 4.6, 2.9, and 3.7 times for 6 MV-FF, 10 MV-FF, 6 MV-FFF, and 10 MV-FFF, respectively. At the same energy, the surface dose increases to 3.93, 4.11, 4.23, 4.16 and 4.24 times at 5 mm, 15 mm, 30 mm, 39 mm and 55 mm thickness of the vacuum, respectively. Conclusion: Using a couch and vacuum significantly increases the surface dose. For SBRT with a superficial target close to the couch and immobilization vacuum, reduction of vacuum thickness and careful attention to skin dose in planning would be helpful in avoiding severe skin toxicity.

  4. SU-F-BRE-11: Neutron Measurements Around the Varian TrueBeam Linac

    Energy Technology Data Exchange (ETDEWEB)

    Maglieri, R; Seuntjens, J; Kildea, J [McGill University, Montreal, QC (Canada); Liang, L; DeBlois, F [Jewish General Hospital, Montreal, QC (Canada); Evans, M [Montreal General Hospital, Montreal, QC (Canada); Licea, A [Canadian Nuclear Safety Comission, Ottawa, Ontario (Canada); Dubeau, J; Witharana, S [Detec, Gatineau, QC (Canada)

    2014-06-15

    Purpose: With the emergence of flattening filter free (FFF) photon beams, several authors have noted many advantages to their use. One such advantage is the decrease in neutron production by photonuclear reactions in the linac head. In the present work we investigate the reduction in neutrons from a Varian TrueBeam linac using the Nested Neutron Spectrometer (NNS, Detec). The neutron spectrum, total fluence and source strength were measured and compared for 10 MV with and without flattening filter and the effect of moderation by the room and maze was studied for the 15 MV beam. Methods: The NNS, similar to traditional Bonner sphere detectors but operated in current mode, was used to measure the neutron fluence and spectrum. The NNS was validated for use in high dose rate environments using Monte Carlo simulations and calibrated at NIST and NRC Canada. Measurements were performed at several positions within the treatment room and maze with the linac jaws closed to maximize neutron production. Results: The measurements showed a total fluence reduction between 35-40% in the room and maze when the flattening filter was removed. The neutron source strength Qn was calculated from in-room fluence measurements and was found to be 0.042 × 10{sup 2} n/Gy, 0.026 × 10{sup 2} n/Gy and 0.59 × 101{sup 2} n/Gy for the 10 MV, the 10 MV FFF and 15 MV beams, respectively. We measured ambient equivalent doses of 11 mSv/hr, 7 mSv/hr and 218 mSv/hr for the 10 MV, 10 MV FFF and 15 MV by the head. Conclusion: Our measurements revealed a decrease in total fluence, neutron source strength and equivalent dose of approximately 35-40% across the treatment room for the FFF compared to FF modes. This demonstrates, as expected, that the flattening filter is a major component of the neutron production for the TrueBeam. The authors greatly acknowledge support form the Canadian Nuclear Commission and the Natural Sciences and Engineering Research Council of Canada through the CREATE program. Co

  5. TH-E-BRE-04: An Online Replanning Algorithm for VMAT

    International Nuclear Information System (INIS)

    Ahunbay, E; Li, X; Moreau, M

    2014-01-01

    Purpose: To develop a fast replanning algorithm based on segment aperture morphing (SAM) for online replanning of volumetric modulated arc therapy (VMAT) with flattening filtered (FF) and flattening filter free (FFF) beams. Methods: A software tool was developed to interface with a VMAT planning system ((Monaco, Elekta), enabling the output of detailed beam/machine parameters of original VMAT plans generated based on planning CTs for FF or FFF beams. A SAM algorithm, previously developed for fixed-beam IMRT, was modified to allow the algorithm to correct for interfractional variations (e.g., setup error, organ motion and deformation) by morphing apertures based on the geometric relationship between the beam's eye view of the anatomy from the planning CT and that from the daily CT for each control point. The algorithm was tested using daily CTs acquired using an in-room CT during daily IGRT for representative prostate cancer cases along with their planning CTs. The algorithm allows for restricted MLC leaf travel distance between control points of the VMAT delivery to prevent SAM from increasing leaf travel, and therefore treatment delivery time. Results: The VMAT plans adapted to the daily CT by SAM were found to improve the dosimetry relative to the IGRT repositioning plans for both FF and FFF beams. For the adaptive plans, the changes in leaf travel distance between control points were < 1cm for 80% of the control points with no restriction. When restricted to the original plans' maximum travel distance, the dosimetric effect was minimal. The adaptive plans were delivered successfully with similar delivery times as the original plans. The execution of the SAM algorithm was < 10 seconds. Conclusion: The SAM algorithm can quickly generate deliverable online-adaptive VMAT plans based on the anatomy of the day for both FF and FFF beams

  6. TH-E-BRE-04: An Online Replanning Algorithm for VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Ahunbay, E; Li, X [Medical College of Wisconsin, Milwaukee, WI (United States); Moreau, M [Elekta, Inc, Verona, WI (Italy)

    2014-06-15

    Purpose: To develop a fast replanning algorithm based on segment aperture morphing (SAM) for online replanning of volumetric modulated arc therapy (VMAT) with flattening filtered (FF) and flattening filter free (FFF) beams. Methods: A software tool was developed to interface with a VMAT planning system ((Monaco, Elekta), enabling the output of detailed beam/machine parameters of original VMAT plans generated based on planning CTs for FF or FFF beams. A SAM algorithm, previously developed for fixed-beam IMRT, was modified to allow the algorithm to correct for interfractional variations (e.g., setup error, organ motion and deformation) by morphing apertures based on the geometric relationship between the beam's eye view of the anatomy from the planning CT and that from the daily CT for each control point. The algorithm was tested using daily CTs acquired using an in-room CT during daily IGRT for representative prostate cancer cases along with their planning CTs. The algorithm allows for restricted MLC leaf travel distance between control points of the VMAT delivery to prevent SAM from increasing leaf travel, and therefore treatment delivery time. Results: The VMAT plans adapted to the daily CT by SAM were found to improve the dosimetry relative to the IGRT repositioning plans for both FF and FFF beams. For the adaptive plans, the changes in leaf travel distance between control points were < 1cm for 80% of the control points with no restriction. When restricted to the original plans' maximum travel distance, the dosimetric effect was minimal. The adaptive plans were delivered successfully with similar delivery times as the original plans. The execution of the SAM algorithm was < 10 seconds. Conclusion: The SAM algorithm can quickly generate deliverable online-adaptive VMAT plans based on the anatomy of the day for both FF and FFF beams.

  7. SU-G-BRB-05: Automation of the Photon Dosimetric Quality Assurance Program of a Linear Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Lebron, S; Lu, B; Yan, G; Li, J; Liu, C [University of Florida, Gainesville, FL (United States)

    2016-06-15

    Purpose: To develop an automated method to calculate a linear accelerator (LINAC) photon radiation field size, flatness, symmetry, output and beam quality in a single delivery for flattened (FF) and flattening-filter-free (FFF) beams using an ionization chamber array. Methods: The proposed method consists of three control points that deliver 30×30, 10×10 and 5×5cm{sup 2} fields (FF or FFF) in a step-and-shoot sequence where the number of monitor units is weighted for each field size. The IC Profiler (Sun Nuclear Inc.) with 5mm detector spacing was used for this study. The corrected counts (CCs) were calculated and the locations of the maxima and minima values of the first-order gradient determined data of each sub field. Then, all CCs for each field size are summed in order to obtain the final profiles. For each profile, the radiation field size, symmetry, flatness, output factor and beam quality were calculated. For field size calculation, a parameterized gradient method was used. For method validation, profiles were collected in the detector array both, individually and as part of the step-and-shoot plan, with 9.9cm buildup for FF and FFF beams at 90cm source-to-surface distance. The same data were collected with the device (plus buildup) placed on a movable platform to achieve a 1mm resolution. Results: The differences between the dosimetric quantities calculated from both deliveries, individually and step-and-shoot, were within 0.31±0.20% and 0.04±0.02mm. The differences between the calculated field sizes with 5mm and 1mm resolution were ±0.1mm. Conclusion: The proposed single delivery method proved to be simple and efficient in automating the photon dosimetric monthly and annual quality assurance.

  8. Technical Note: Evaluation of the systematic accuracy of a frameless, multiple image modality guided, linear accelerator based stereotactic radiosurgery system

    Energy Technology Data Exchange (ETDEWEB)

    Wen, N., E-mail: nwen1@hfhs.org; Snyder, K. C.; Qin, Y.; Li, H.; Siddiqui, M. S.; Chetty, I. J. [Department of Radiation Oncology, Henry Ford Health System, 2799 West Brand Boulevard, Detroit, Michigan 48202 (United States); Scheib, S. G.; Schmelzer, P. [Varian Medical System, Täfernstrasse 7, Dättwil AG 5405 (Switzerland)

    2016-05-15

    Purpose: To evaluate the total systematic accuracy of a frameless, image guided stereotactic radiosurgery system. Methods: The localization accuracy and intermodality difference was determined by delivering radiation to an end-to-end prototype phantom, in which the targets were localized using optical surface monitoring system (OSMS), electromagnetic beacon-based tracking (Calypso®), cone-beam CT, “snap-shot” planar x-ray imaging, and a robotic couch. Six IMRT plans with jaw tracking and a flattening filter free beam were used to study the dosimetric accuracy for intracranial and spinal stereotactic radiosurgery treatment. Results: End-to-end localization accuracy of the system evaluated with the end-to-end phantom was 0.5 ± 0.2 mm with a maximum deviation of 0.9 mm over 90 measurements (including jaw, MLC, and cone measurements for both auto and manual fusion) for single isocenter, single target treatment, 0.6 ± 0.4 mm for multitarget treatment with shared isocenter. Residual setup errors were within 0.1 mm for OSMS, and 0.3 mm for Calypso. Dosimetric evaluation based on absolute film dosimetry showed greater than 90% pass rate for all cases using a gamma criteria of 3%/1 mm. Conclusions: The authors’ experience demonstrates that the localization accuracy of the frameless image-guided system is comparable to robotic or invasive frame based radiosurgery systems.

  9. Sci-Thur AM: YIS – 02: Imaging dose distributions through the detection of radiation-induced acoustic waves

    Energy Technology Data Exchange (ETDEWEB)

    Hickling, Susannah; Lei, Hao; Hobson, Maritza; Leger, Pierre; Wang, Xueding; El Naqa, Issam [University of Michigan, McGill University, McGill University , University of Michigan, University of Michigan/McGill University (United States)

    2016-08-15

    Purpose: X-ray acoustic computed tomography (XACT) is an emerging technique that images the dose deposited within an object following linac irradiation by detecting acoustic waves induced via the photoacoustic effect. This work shows that XACT images can be formed in soft-tissue equivalent material and that dosimetric information can be extracted from such images. Methods: Acoustic waves induced in a water tank following irradiation by a 10 MV flattening filter free photon beam were detected with an immersion ultrasound transducer at 60 angles surrounding the radiation field. A back-projection algorithm was used to reconstruct an XACT image from the detected transducer signals. Profiles extracted from XACT images were compared to profiles measured with ion chambers as per the current clinical protocol. Results: XACT images were successfully formed of simple 4 cm × 4 cm and 6 cm × 3 cm fields, as well as of more complicated multi-leaf collimator defined fields. For the 6 cm × 3 cm field, 74% and 87% of the XACT profile points in the 6 cm and 3 cm dimensions, respectively, passed a 7% / 4 mm gamma test when compared to ion chamber measurements. In a complicated puzzle piece shaped field, 86% of the pixels in an extracted profile passed a 7% / 4 mm gamma test. Conclusions: XACT is capable of imaging the dose distribution delivered by a variety of field sizes and shapes in water, and is a viable technique for both water tank and in vivo dosimetry.

  10. Evaluation of image quality for various electronic portal imaging devices in radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Son, Soon Yong; Choi, Kwan Woo [Dept. of Radiology, Asan Medical Center, Seoul (Korea, Republic of); Kim, Jung Min [Dept. of College of Health Science, Radiologic Science, Korea University, Seoul (Korea, Republic of); and others

    2015-12-15

    In megavoltage (MV) radiotherapy, delivering the dose to the target volume is important while protecting the surrounding normal tissue. The purpose of this study was to evaluate the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE) using an edge block in megavoltage X-ray imaging (MVI). We used an edge block, which consists of tungsten with dimensions of 19 (thickness) × 10 (length) × 1 (width) cm3 and measured the pre-sampling MTF at 6 MV energy. Various radiation therapy (RT) devices such as TrueBeamTM (Varian), BEAMVIEWPLUS (Siemens), iViewGT (Elekta) and Clinac®iX (Varian) were used. As for MTF results, TrueBeamTM(Varian) flattening filter free(FFF) showed the highest values of 0.46 mm-1and1.40mm-1for MTF 0.5 and 0.1. In NPS, iViewGT (Elekta) showed the lowest noise distribution. In DQE, iViewGT (Elekta) showed the best efficiency at a peak DQE and 1 mm-1DQE of 0.0026 and 0.00014, respectively. This study could be used not only for traditional QA imaging but also for quantitative MTF, NPS, and DQE measurement for development of an electronic portal imaging device (EPID)

  11. Deep Inspiration Breath Hold—Based Radiation Therapy: A Clinical Review

    Energy Technology Data Exchange (ETDEWEB)

    Boda-Heggemann, Judit, E-mail: judit.boda-heggemann@umm.de [Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim (Germany); Knopf, Antje-Christin [The Institute of Cancer Research, Royal Cancer Hospital, London (United Kingdom); Simeonova-Chergou, Anna; Wertz, Hansjörg; Stieler, Florian; Jahnke, Anika; Jahnke, Lennart; Fleckenstein, Jens; Vogel, Lena; Arns, Anna; Blessing, Manuel; Wenz, Frederik; Lohr, Frank [Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim (Germany)

    2016-03-01

    Several recent developments in linear accelerator–based radiation therapy (RT) such as fast multileaf collimators, accelerated intensity modulation paradigms like volumeric modulated arc therapy and flattening filter-free (FFF) high-dose-rate therapy have dramatically shortened the duration of treatment fractions. Deliverable photon dose distributions have approached physical complexity limits as a consequence of precise dose calculation algorithms and online 3-dimensional image guided patient positioning (image guided RT). Simultaneously, beam quality and treatment speed have continuously been improved in particle beam therapy, especially for scanned particle beams. Applying complex treatment plans with steep dose gradients requires strategies to mitigate and compensate for motion effects in general, particularly breathing motion. Intrafractional breathing-related motion results in uncertainties in dose delivery and thus in target coverage. As a consequence, generous margins have been used, which, in turn, increases exposure to organs at risk. Particle therapy, particularly with scanned beams, poses additional problems such as interplay effects and range uncertainties. Among advanced strategies to compensate breathing motion such as beam gating and tracking, deep inspiration breath hold (DIBH) gating is particularly advantageous in several respects, not only for hypofractionated, high single-dose stereotactic body RT of lung, liver, and upper abdominal lesions but also for normofractionated treatment of thoracic tumors such as lung cancer, mediastinal lymphomas, and breast cancer. This review provides an in-depth discussion of the rationale and technical implementation of DIBH gating for hypofractionated and normofractionated RT of intrathoracic and upper abdominal tumors in photon and proton RT.

  12. Technical Note: Evaluation of the systematic accuracy of a frameless, multiple image modality guided, linear accelerator based stereotactic radiosurgery system

    International Nuclear Information System (INIS)

    Wen, N.; Snyder, K. C.; Qin, Y.; Li, H.; Siddiqui, M. S.; Chetty, I. J.; Scheib, S. G.; Schmelzer, P.

    2016-01-01

    Purpose: To evaluate the total systematic accuracy of a frameless, image guided stereotactic radiosurgery system. Methods: The localization accuracy and intermodality difference was determined by delivering radiation to an end-to-end prototype phantom, in which the targets were localized using optical surface monitoring system (OSMS), electromagnetic beacon-based tracking (Calypso®), cone-beam CT, “snap-shot” planar x-ray imaging, and a robotic couch. Six IMRT plans with jaw tracking and a flattening filter free beam were used to study the dosimetric accuracy for intracranial and spinal stereotactic radiosurgery treatment. Results: End-to-end localization accuracy of the system evaluated with the end-to-end phantom was 0.5 ± 0.2 mm with a maximum deviation of 0.9 mm over 90 measurements (including jaw, MLC, and cone measurements for both auto and manual fusion) for single isocenter, single target treatment, 0.6 ± 0.4 mm for multitarget treatment with shared isocenter. Residual setup errors were within 0.1 mm for OSMS, and 0.3 mm for Calypso. Dosimetric evaluation based on absolute film dosimetry showed greater than 90% pass rate for all cases using a gamma criteria of 3%/1 mm. Conclusions: The authors’ experience demonstrates that the localization accuracy of the frameless image-guided system is comparable to robotic or invasive frame based radiosurgery systems.

  13. A Monte Carlo investigation of low-Z target image quality generated in a linear accelerator using Varian's VirtuaLinac

    International Nuclear Information System (INIS)

    Parsons, David; Robar, James L.; Sawkey, Daren

    2014-01-01

    Purpose: The focus of this work was the demonstration and validation of VirtuaLinac with clinical photon beams and to investigate the implementation of low-Z targets in a TrueBeam linear accelerator (Linac) using Monte Carlo modeling. Methods: VirtuaLinac, a cloud based web application utilizing Geant4 Monte Carlo code, was used to model the Linac treatment head components. Particles were propagated through the lower portion of the treatment head using BEAMnrc. Dose distributions and spectral distributions were calculated using DOSXYZnrc and BEAMdp, respectively. For validation, 6 MV flattened and flattening filter free (FFF) photon beams were generated and compared to measurement for square fields, 10 and 40 cm wide and at d max for diagonal profiles. Two low-Z targets were investigated: a 2.35 MeV carbon target and the proposed 2.50 MeV commercial imaging target for the TrueBeam platform. A 2.35 MeV carbon target was also simulated in a 2100EX Clinac using BEAMnrc. Contrast simulations were made by scoring the dose in the phosphor layer of an IDU20 aSi detector after propagating through a 4 or 20 cm thick phantom composed of water and ICRP bone. Results: Measured and modeled depth dose curves for 6 MV flattened and FFF beams agree within 1% for 98.3% of points at depths greater than 0.85 cm. Ninety three percent or greater of points analyzed for the diagonal profiles had a gamma value less than one for the criteria of 1.5 mm and 1.5%. The two low-Z target photon spectra produced in TrueBeam are harder than that from the carbon target in the Clinac. Percent dose at depth 10 cm is greater by 3.6% and 8.9%; the fraction of photons in the diagnostic energy range (25–150 keV) is lower by 10% and 28%; and contrasts are lower by factors of 1.1 and 1.4 (4 cm thick phantom) and 1.03 and 1.4 (20 cm thick phantom), for the TrueBeam 2.35 MV/carbon and commercial imaging beams, respectively. Conclusions: VirtuaLinac is a promising new tool for Monte Carlo modeling of novel

  14. Photon energy-modulated radiotherapy: Monte Carlo simulation and treatment planning study

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Min; Kim, Jung-in; Heon Choi, Chang; Chie, Eui Kyu; Kim, Il Han; Ye, Sung-Joon [Interdiciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, 110-744, Korea and Department of Radiation Oncology, Seoul National University Hospital, Seoul, 110-744 (Korea, Republic of); Interdiciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, 110-744 (Korea, Republic of); Department of Radiation Oncology, Seoul National University Hospital, Seoul, 110-744 (Korea, Republic of); Interdiciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, 110-744 (Korea, Republic of) and Department of Radiation Oncology, Seoul National University Hospital, Seoul, 110-744 (Korea, Republic of); Interdiciplinary Program in Radiation Applied Life Science, Seoul National University, Seoul, 110-744 (Korea, Republic of); Department of Radiation Oncology, Seoul National University Hospital, Seoul, 110-744 (Korea, Republic of) and Department of Intelligent Convergence Systems, Seoul National University, Seoul, 151-742 (Korea, Republic of)

    2012-03-15

    Purpose: To demonstrate the feasibility of photon energy-modulated radiotherapy during beam-on time. Methods: A cylindrical device made of aluminum was conceptually proposed as an energy modulator. The frame of the device was connected with 20 tubes through which mercury could be injected or drained to adjust the thickness of mercury along the beam axis. In Monte Carlo (MC) simulations, a flattening filter of 6 or 10 MV linac was replaced with the device. The thickness of mercury inside the device varied from 0 to 40 mm at the field sizes of 5 x 5 cm{sup 2} (FS5), 10 x 10 cm{sup 2} (FS10), and 20 x 20 cm{sup 2} (FS20). At least 5 billion histories were followed for each simulation to create phase space files at 100 cm source to surface distance (SSD). In-water beam data were acquired by additional MC simulations using the above phase space files. A treatment planning system (TPS) was commissioned to generate a virtual machine using the MC-generated beam data. Intensity modulated radiation therapy (IMRT) plans for six clinical cases were generated using conventional 6 MV, 6 MV flattening filter free, and energy-modulated photon beams of the virtual machine. Results: As increasing the thickness of mercury, Percentage depth doses (PDD) of modulated 6 and 10 MV after the depth of dose maximum were continuously increased. The amount of PDD increase at the depth of 10 and 20 cm for modulated 6 MV was 4.8% and 5.2% at FS5, 3.9% and 5.0% at FS10 and 3.2%-4.9% at FS20 as increasing the thickness of mercury from 0 to 20 mm. The same for modulated 10 MV was 4.5% and 5.0% at FS5, 3.8% and 4.7% at FS10 and 4.1% and 4.8% at FS20 as increasing the thickness of mercury from 0 to 25 mm. The outputs of modulated 6 MV with 20 mm mercury and of modulated 10 MV with 25 mm mercury were reduced into 30%, and 56% of conventional linac, respectively. The energy-modulated IMRT plans had less integral doses than 6 MV IMRT or 6 MV flattening filter free plans for tumors located in the

  15. Investigation of Reduction of the Uncertainty of Monte Carlo Dose Calculations in Oncor® Clinical Linear Accelerator Simulation Using the DBS Variance Reduction Technique in Monte Carlo Code BEAMnrc

    Directory of Open Access Journals (Sweden)

    Amin Asadi

    2017-10-01

    Full Text Available Purpose: To study the benefits of Directional Bremsstrahlung Splitting (DBS dose variance reduction technique in BEAMnrc Monte Carlo (MC code for Oncor® linac at 6MV and 18MV energies. Materials and Method: A MC model of Oncor® linac was built using BEAMnrc MC Code and verified by the measured data for 6MV and 18MV energies of various field sizes. Then Oncor® machine was modeled running DBS technique, and the efficiency of total fluence and spatial fluence for electron and photon, the efficiency of dose variance reduction of MC calculations for PDD on the central beam axis and lateral dose profile across the nominal field was measured and compared. Result: With applying DBS technique, the total fluence of electron and photon increased in turn 626.8 (6MV and 983.4 (6MV, and 285.6 (18MV and 737.8 (18MV, the spatial fluence of electron and photon improved in turn 308.6±1.35% (6MV and 480.38±0.43% (6MV, and 153±0.9% (18MV and 462.6±0.27% (18MV. Moreover, by running DBS technique, the efficiency of dose variance reduction for PDD MC dose calculations before maximum dose point and after dose maximum point enhanced 187.8±0.68% (6MV and 184.6±0.65% (6MV, 156±0.43% (18MV and 153±0.37% (18MV, respectively, and the efficiency of MC calculations for lateral dose profile remarkably on the central beam axis and across the treatment field raised in turn 197±0.66% (6MV and 214.6±0.73% (6MV, 175±0.36% (18MV and 181.4±0.45% (18MV. Conclusion: Applying dose variance reduction technique of DBS for modeling Oncor® linac with using BEAMnrc MC Code surprisingly improved the fluence of electron and photon, and it therefore enhanced the efficiency of dose variance reduction for MC calculations. As a result, running DBS in different kinds of MC simulation Codes might be beneficent in reducing the uncertainty of MC calculations. 

  16. A treatment planning and delivery comparison of volumetric modulated arc therapy with or without flattening filter for gliomas, brain metastases, prostate, head/neck and early stage lung cancer

    DEFF Research Database (Denmark)

    Gasic, Daniel; Ohlhues, Lars; Brodin, N. Patrik

    2014-01-01

    generated using STD- and FFF-VMAT for both 6 MV and 10 MV, and were compared with respect to plan quality, monitor units and delivery time using Wilcoxon signed rank tests. RESULTS: For H&N and high-grade gliomas, there was a significant difference in homogeneity index in favor for STD-VMAT (p

  17. Experimental investigation of the photoneutron production out of the high-energy photon fields at linear accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeon Su; Yoon, In Ha; Bae, Sun Myeong; Kang, Tae Young; Baek, Geum Mun; Kim, Sung Hwan; Nam, Uk Won; Lee, Jae Jin; Park, Yeong Sik [Dept. of Radiation Oncology, ASAN Medical Center, Seoul (Korea, Republic of)

    2014-12-15

    Photoneutron dose in high-energy photon radiotherapy at linear accelerator increase the risk for secondary cancer. The purpose of this investigation is to evaluate the dose variation of photoneutron with different treatment method, flattening filter, dose rate and gantry angle in radiation therapy with high-energy photon beam (E≥8 MeV). TrueBeam STxTM(Ver1.5, Varian, USA) and Korea Tissue Equivalent Proportional Counter (KTEPC) were used to detect the photoneutron dose out of the high-energy photon field. Complex Patient plans using Eclipse planning system (Version 10.0, Varian, USA) was used to experiment with different treatment technique(IMRT, VMAT), condition of flattening filter and three different dose rate. Scattered photoneutron dose was measured at eight different gantry angles with open field (Field size : 5×5cm). The mean values of the detected photoneutron dose from IMRT and VMAT were 449.7 μSv, 2940.7 μSv. The mean values of the detected photoneutron dose with Flattening Filter(FF) and Flattening Filter Free(FFF) were measured as 2940.7 μSv, 232.0 μSv. The mean values of the photoneutron dose for each test plan (case 1, case 2 and case 3) with FFF at the three different dose rate (400, 1200, 2400 MU/min) were 3242.5 μSv, 3189.4 μSv, 3191.2 μSv with case 1, 3493.2 μSv, 3482.6 μSv, 3477.2 μSv with case 2 and 4592.2 μSv, 4580.0 μSv, 4542.3 μSv with case 3, respectively. The mean values of the photoneutron dose at eight different gantry angles ( 0° , 45°, 90°, 135°, 180°, 225°, 270° , 315°) were measured as 3.2 μSv, 4.3 μSv, 5.3 μSv, 11.3 μSv, 14.7 μSv, 11.2 μSv, 3.7 μSv, 3.0 μSv at 10 MV and as 373.7 μSv, 369.6 μSv, 384.4 μSv, 423.6 μSv, 447.1 μSv, 448.0 μSv, 384.5 μSv, 377.3 μSv at 15MV. As a result, it is possible to reduce photoneutron dose using FFF mode and VMAT method with TrueBeam STxTM. The risk for secondary cancer of the patients will be decreased with continuous evaluation of the photoneutron dose.

  18. SU-F-T-577: Comparison of Small Field Dosimetry Measurements in Fields Shaped with Conical Applicators On Two Different Accelerating Systems

    Energy Technology Data Exchange (ETDEWEB)

    Muir, B; McEwen, M [National Research Council, Ottawa, ON (Canada); Belec, J; Vandervoort, E [Ottawa Hospital General Campus, Ottawa, ON (Canada); Christiansen, E [Carleton University, Ottawa, ON (Canada)

    2016-06-15

    Purpose: To investigate small field dosimetry measurements and associated uncertainties when conical applicators are used to shape treatment fields from two different accelerating systems. Methods: Output factor measurements are made in water in beams from the CyberKnife radiosurgery system, which uses conical applicators to shape fields from a (flattening filter-free) 6 MV beam, and in a 6 MV beam from the Elekta Precise linear accelerator (with flattening filter) with BrainLab external conical applicators fitted to shape the field. The measurements use various detectors: (i) an Exradin A16 ion chamber, (ii) two Exradin W1 plastic scintillation detectors, (iii) a Sun Nuclear Edge diode, and (iv) two PTW microDiamond synthetic diamond detectors. Profiles are used for accurate detector positioning and to specify field size (FWHM). Output factor measurements are corrected with detector specific correction factors taken from the literature where available and/or from Monte Carlo simulations using the EGSnrc code system. Results: Differences in measurements of up to 1.7% are observed with a given detector type in the same beam (i.e., intra-detector variability). Corrected results from different detectors in the same beam (inter-detector differences) show deviations up to 3 %. Combining data for all detectors and comparing results from the two accelerators results in a 5.9% maximum difference for the smallest field sizes (FWHM=5.2–5.6 mm), well outside the combined uncertainties (∼1% for the smallest beams) and/or differences among detectors. This suggests that the FWHM of a measured profile is not a good specifier to compare results from different small fields with the same nominal energy. Conclusion: Large differences in results for both intra-detector variability and inter-detector differences suggest potentially high uncertainties in detector-specific correction factors. Differences between the results measured in circular fields from different accelerating

  19. Motion induced interplay effects for VMAT radiotherapy.

    Science.gov (United States)

    Edvardsson, Anneli; Nordström, Fredrik; Ceberg, Crister; Ceberg, Sofie

    2018-04-19

    The purpose of this study was to develop a method to simulate breathing motion induced interplay effects for volumetric modulated arc therapy (VMAT), to verify the proposed method with measurements, and to use the method to investigate how interplay effects vary with different patient- and machine specific parameters. VMAT treatment plans were created on a virtual phantom in a treatment planning system (TPS). Interplay effects were simulated by dividing each plan into smaller sub-arcs using an in-house developed software and shifting the isocenter for each sub-arc to simulate a sin 6 breathing motion in the superior-inferior direction. The simulations were performed for both flattening-filter (FF) and flattening-filter free (FFF) plans and for different breathing amplitudes, period times, initial breathing phases, dose levels, plan complexities, CTV sizes, and collimator angles. The resulting sub-arcs were calculated in the TPS, generating a dose distribution including the effects of motion. The interplay effects were separated from dose blurring and the relative dose differences to 2% and 98% of the CTV volume (ΔD 98% and ΔD 2% ) were calculated. To verify the simulation method, measurements were carried out, both static and during motion, using a quasi-3D phantom and a motion platform. The results of the verification measurements during motion were comparable to the results of the static measurements. Considerable interplay effects were observed for individual fractions, with the minimum ΔD 98% and maximum ΔD 2% being  -16.7% and 16.2%, respectively. The extent of interplay effects was larger for FFF compared to FF and generally increased for higher breathing amplitudes, larger period times, lower dose levels, and more complex treatment plans. Also, the interplay effects varied considerably with the initial breathing phase, and larger variations were observed for smaller CTV sizes. In conclusion, a method to simulate motion induced interplay effects was

  20. SU-E-T-370: Evaluating Plan Quality and Dose Delivery Accuracy of Tomotherapy SBRT Treatments for Lung Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Blake, S; Thwaites, D [University of Sydney, Sydney, NSW (Australia); Hansen, C [Odense University Hospital, Odense C (Denmark); Deshpande, S; Phan, P; Franji, I [Liverpool & Macarthur Cancer Therapy Centres, Liverpool, NSW (United Kingdom); Holloway, L [Ingham Institute, Sydney, NSW (Australia)

    2015-06-15

    Purpose: This study evaluated the plan quality and dose delivery accuracy of stereotactic body radiotherapy (SBRT) helical Tomotherapy (HT) treatments for lung cancer. Results were compared with those previously reported by our group for flattening filter (FF) and flattening filter free (FFF) VMAT treatments. This work forms part of an ongoing multicentre and multisystem planning and dosimetry audit on FFF beams for lung SBRT. Methods: CT datasets and DICOM RT structures delineating the target volume and organs at risk for 6 lung cancer patients were selected. Treatment plans were generated using the HT treatment planning system. Tumour locations were classified as near rib, near bronchial tree or in free lung with prescribed doses of 48Gy/4fr, 50Gy/5fr and 54Gy/3fr respectively. Dose constraints were specified by a modified RTOG0915 protocol used for an Australian SBRT phase II trial. Plan quality was evaluated using mean PTV dose, PTV volume receiving 100% of the prescribed dose (V100%), target conformity (CI=VD100%/VPTV) and low dose spillage (LDS=VD50%/VPTV). Planned dose distributions were compared to those measured using an ArcCheck phantom. Delivery accuracy was evaluated using a gamma-index pass rate of 95% with 3% (of max dose) and 3mm criteria. Results: Treatment plans for all patients were clinically acceptable in terms of quality and accuracy of dose delivery. The following DVH metrics are reported as averages (SD) of all plans investigated: mean PTV dose was 115.3(2.4)% of prescription, V100% was 98.8(0.9)%, CI was 1.14(0.03) and LDS was 5.02(0.37). The plans had an average gamma-index passing rate of 99.3(1.3)%. Conclusion: The results reported in this study for HT agree within 1 SD to those previously published by our group for VMAT FF and FFF lung SBRT treatments. This suggests that HT delivers lung SBRT treatments of comparable quality and delivery accuracy as VMAT using both FF and FFF beams.

  1. Motion induced interplay effects for VMAT radiotherapy

    Science.gov (United States)

    Edvardsson, Anneli; Nordström, Fredrik; Ceberg, Crister; Ceberg, Sofie

    2018-04-01

    The purpose of this study was to develop a method to simulate breathing motion induced interplay effects for volumetric modulated arc therapy (VMAT), to verify the proposed method with measurements, and to use the method to investigate how interplay effects vary with different patient- and machine specific parameters. VMAT treatment plans were created on a virtual phantom in a treatment planning system (TPS). Interplay effects were simulated by dividing each plan into smaller sub-arcs using an in-house developed software and shifting the isocenter for each sub-arc to simulate a sin6 breathing motion in the superior–inferior direction. The simulations were performed for both flattening-filter (FF) and flattening-filter free (FFF) plans and for different breathing amplitudes, period times, initial breathing phases, dose levels, plan complexities, CTV sizes, and collimator angles. The resulting sub-arcs were calculated in the TPS, generating a dose distribution including the effects of motion. The interplay effects were separated from dose blurring and the relative dose differences to 2% and 98% of the CTV volume (ΔD98% and ΔD2%) were calculated. To verify the simulation method, measurements were carried out, both static and during motion, using a quasi-3D phantom and a motion platform. The results of the verification measurements during motion were comparable to the results of the static measurements. Considerable interplay effects were observed for individual fractions, with the minimum ΔD98% and maximum ΔD2% being  ‑16.7% and 16.2%, respectively. The extent of interplay effects was larger for FFF compared to FF and generally increased for higher breathing amplitudes, larger period times, lower dose levels, and more complex treatment plans. Also, the interplay effects varied considerably with the initial breathing phase, and larger variations were observed for smaller CTV sizes. In conclusion, a method to simulate motion induced interplay effects was

  2. SU-F-T-658: Out-Of-Field Dose Comparison for TrueBeam Low Energy Beams for Extended Distances: Measurement Vs Monte Carlo Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wijesooriya, K [University of Virginia Health Systems, Charlottesville, VA (United States); University of Virginia, Charlottesville, VA (United States); Liyanage, N; Kaluarachchi, M [University of Virginia, Charlottesville, VA (United States); Sawkey, D [Varian Medical Systems, Palo Alto, CA (United States)

    2016-06-15

    Purpose: Patient dose far from the treatment field is comprised of scatter from within the patient, and treatment head leakage. We quantify the treatment head leakage for TrueBeam linear accelerator for 6X and 6X-FFF beams by comparing measurements to Monte Carlo simulations for a variety of jaw sizes and collimator rotations. This work is conceptually similar to that of Kry et al. (Medical Physics 2006; 33: 4405), who considered a Clinac linear accelerator. Methods: Measurements were made using an EXRADIN A101 ion chamber positioned in the patient plane, at distances up to 100 cm from isocenter. Simulations were done using VirtuaLinac, the GEANT4-based Monte Carlo model of the TrueBeam treatment head, and an in-house (U. Virginia) GEANT4-based code. In-house code modelled an ion chamber with build-up, based on a CT scan of the chamber. VirtuaLinac included a detailed model of the treatment head shielding, and was run on the Amazon Web Services cloud to generate spherical phase space files surrounding the treatment head. These phase space files were imported into the in-house code. Results: Initial comparisons between measurements and simulation showed an excess of dose in the in-plane direction, away from the gantry, in the simulations. This was traced to an incomplete model of the shielding—specifically, the component holding the primary collimator was smaller in the model than in the TrueBeam. Modifications were made to VirtuaLinac to more closely match the engineering drawings. In the in-plane direction, the lowest out of field dose was away from gantry (negative abscissa values) at around 60 cm from isocenter, for fields smaller than 10×10 cm2. Out of field dose decreased with decreasing jaw size. Flattening-filter free beam produced out-of-field doses as low as 65% of those with flattened beam. Conclusion: Doses determined from simulation and measurement were in close agreement. Funding support from the Jefferson Trust Foundation.

  3. TH-C-19A-03: Characterization of the Dose Per Pulse Dependence of Various Detectors Used in Quality Assurance of FFF Treatment Plans

    Energy Technology Data Exchange (ETDEWEB)

    Karan, T [Stronach Regional Cancer Center, Newmarket, ON (Canada); Viel, F; Atwal, P; Gete, E; Camborde, M; Horwood, R; Strgar, V; Duzenli, C [British Columbia Cancer Agency, Vancouver, BC (Canada)

    2014-06-15

    Purpose: To present the dose per pulse dependence of various QA devices under Flattening Filter Free (FFF) conditions. Methods: Air and liquid filled ion chamber arrays, diode arrays, radiochromic film and optically stimulated luminescence detectors were investigated. All detectors were irradiated under similar conditions of varying dose per pulse on a TrueBeam linac. Dose per pulse was controlled by varying SSD from 70 to 160 cm providing a range from ~0.5 to ~3 mGy per pulse. MU rates of up to 2400 MU/min for 10X FFF and 1400 MU/min for the 6X FFF beam were used. Beam pulses were counted using the Profiler™ diode array and pulse timing was confirmed by examining linac node files. Delivered doses were calculated with the Eclipse™ treatment planning system. Results: The detectors show a range of behaviors depending on the detector type, as expected. Diode arrays show up to 4% change in sensitivity (sensitivity increases with increasing dose per pulse) over the range tested. Air and liquid ion chambers arrays show a change in sensitivity of up to 3% (air) and 6% (liquid) (sensitivity decreases with increasing dose per pulse) while film and OSLD do not demonstrate a dependence on dose per pulse. Conclusion: Dependence of detector response on dose per pulse varies considerably depending on detector design. Interplay between dose per pulse and MU rate also exists for some detectors. Due diligence is required to characterize detector response prior to implementation of a QA protocol for FFF treatment delivery. During VMAT delivery, the MU rate may also vary dramatically within a treatment fraction. We intend to further investigate the implications of this for VMAT FFF patient specific quality assurance. T Karan and F Viel have received partial funding through the Varian Research program.

  4. TH-C-19A-03: Characterization of the Dose Per Pulse Dependence of Various Detectors Used in Quality Assurance of FFF Treatment Plans

    International Nuclear Information System (INIS)

    Karan, T; Viel, F; Atwal, P; Gete, E; Camborde, M; Horwood, R; Strgar, V; Duzenli, C

    2014-01-01

    Purpose: To present the dose per pulse dependence of various QA devices under Flattening Filter Free (FFF) conditions. Methods: Air and liquid filled ion chamber arrays, diode arrays, radiochromic film and optically stimulated luminescence detectors were investigated. All detectors were irradiated under similar conditions of varying dose per pulse on a TrueBeam linac. Dose per pulse was controlled by varying SSD from 70 to 160 cm providing a range from ~0.5 to ~3 mGy per pulse. MU rates of up to 2400 MU/min for 10X FFF and 1400 MU/min for the 6X FFF beam were used. Beam pulses were counted using the Profiler™ diode array and pulse timing was confirmed by examining linac node files. Delivered doses were calculated with the Eclipse™ treatment planning system. Results: The detectors show a range of behaviors depending on the detector type, as expected. Diode arrays show up to 4% change in sensitivity (sensitivity increases with increasing dose per pulse) over the range tested. Air and liquid ion chambers arrays show a change in sensitivity of up to 3% (air) and 6% (liquid) (sensitivity decreases with increasing dose per pulse) while film and OSLD do not demonstrate a dependence on dose per pulse. Conclusion: Dependence of detector response on dose per pulse varies considerably depending on detector design. Interplay between dose per pulse and MU rate also exists for some detectors. Due diligence is required to characterize detector response prior to implementation of a QA protocol for FFF treatment delivery. During VMAT delivery, the MU rate may also vary dramatically within a treatment fraction. We intend to further investigate the implications of this for VMAT FFF patient specific quality assurance. T Karan and F Viel have received partial funding through the Varian Research program

  5. MO-FG-BRA-07: Theranostic Gadolinium-Based AGuIX Nanoparticles for MRI-Guided Radiation Therapy

    International Nuclear Information System (INIS)

    Detappe, A; Rottmann, J; Kunjachan, S; Berbeco, R; Tillement, O

    2015-01-01

    Purpose: AGuIX are gadolinium-based nanoparticles, initially developed for MRI, that have a potential role in radiation therapy as a radiosensitizer. Our goal is to demonstrate that these nanoparticles can both be used as an MRI contrast agent, as well as to obtain local dose enhancement in a pancreatic tumor when delivered in combination with an external beam irradiation. Methods: We performed in vitro cell uptake and radiosensitization studies of a pancreatic cancer cell line in a low energy (220kVp) beam, a standard clinical 6MV beam (STD) and a flattening filter free clinical 6MV beam (FFF). After injection of 40mM of nanoparticles, a biodistribution study was performed in vivo on mice with subcutaneous xenograft pancreatic tumors. In vivo radiation therapy studies were performed at the time point of maximum tumor uptake. Results: The concentration of AGuIX nanoparticles in Panc-1 pancreatic cancer cells, determined in vitro by MRI and ICPMS, peaks after 30 minutes with 0.3% of the initial concentration (5mg/g). Clonogenic assays show a significant effect (p<0.05) when the AGuIX are coupled with MV photon irradiation (DEF20%=1.31). Similar AGuIX tumor uptake is found in vivo by both MRI and ICPMS 30 minutes after intravenous injection. For long term survival studies, the choice of the radiation dose is determined with 5 control groups (3mice/group) irradiated with 0, 5, 10, 15, and 20Gy. Afterwards, 4 groups (8mice/group) are used to evaluate the effect of the nanoparticles. A Logrank test is performed as a statistical test to evaluate the effect of the nanoparticles. Conclusion: The combination of the MRI contrast and radiosensitization properties of gadolinium nanoparticles reveals a strong potential for usage with MRI-guided radiation therapy

  6. Low Z target switching to increase tumor endothelial cell dose enhancement during gold nanoparticle-aided radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Berbeco, Ross I., E-mail: rberbeco@partners.org; Detappe, Alexandre [Department of Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115 (United States); Tsiamas, Panogiotis [Department of Radiation Oncology, St. Jude Children’s Hospital, Memphis, Tennessee 38105 (United States); Parsons, David; Yewondwossen, Mammo; Robar, James [Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 1V7 (Canada)

    2016-01-15

    Purpose: Previous studies have introduced gold nanoparticles as vascular-disrupting agents during radiation therapy. Crucial to this concept is the low energy photon content of the therapy radiation beam. The authors introduce a new mode of delivery including a linear accelerator target that can toggle between low Z and high Z targets during beam delivery. In this study, the authors examine the potential increase in tumor blood vessel endothelial cell radiation dose enhancement with the low Z target. Methods: The authors use Monte Carlo methods to simulate delivery of three different clinical photon beams: (1) a 6 MV standard (Cu/W) beam, (2) a 6 MV flattening filter free (Cu/W), and (3) a 6 MV (carbon) beam. The photon energy spectra for each scenario are generated for depths in tissue-equivalent material: 2, 10, and 20 cm. The endothelial dose enhancement for each target and depth is calculated using a previously published analytic method. Results: It is found that the carbon target increases the proportion of low energy (<150 keV) photons at 10 cm depth to 28% from 8% for the 6 MV standard (Cu/W) beam. This nearly quadrupling of the low energy photon content incident on a gold nanoparticle results in 7.7 times the endothelial dose enhancement as a 6 MV standard (Cu/W) beam at this depth. Increased surface dose from the low Z target can be mitigated by well-spaced beam arrangements. Conclusions: By using the fast-switching target, one can modulate the photon beam during delivery, producing a customized photon energy spectrum for each specific situation.

  7. SU-E-T-471: Small Field Jaw/MLC Reference Data

    International Nuclear Information System (INIS)

    Kerns, J; Alvarez, P; Followill, D; Lowenstein, J; Molineu, A; Summers, P; Kry, S

    2014-01-01

    Purpose: In recent years the need for small field data of MLCs has increased due to the use of intensity-modulated radiation (IMRT), but moreover the use of stereotactic body radiation (SBRT) has increased, which uses not simply small field sizes, but small jaw and field sizes together. Having reference data for these small fields that is reliable would be invaluable to the physics community. Our study has gathered these values and the data distributions from the Radiological Physics Center's (RPC) site visits between 1990 and the present. Methods: For all measurements, the RPC used a 25 × 25 × 25cm water phantom placed at 100cm SSD. All measurements were made with an Exradin A16 cylindrical ion chamber at an effective depth of 10 cm. A total of 42 Varian machine measurements were used to compose the data for a 6 MV beam and 5 TrueBeam 6 MV flattening filter free (FFF) beams were used for FFF data. Results: Jaw/MLC fields were measured for both 6 MV and 6 MF FFF beams with the jaws and MLCs both at the following field sizes: 6×6, 4×4, 3×3, and 2×2cm. Measurements were normalized to the 10×10 field readings (defined by the jaws and MLC). Spread in the data was minimal and demonstrates a high level of accuracy of acquired data. Conclusion: Small field Jaw/MLC reference data for Varian 6MV and 6 MV FFF beams has been analyzed and presented here, composed of the aggregation of numerous RPC site visits. Obtaining reliable small field data remains difficult, however the RPC has collected high fidelity small field Jaw/MLC data. The data are presented as a reference along with their distributions, in such a way that the physicist can act based upon their own desired agreement with the reference data

  8. SU-G-JeP1-01: A Combination of Real Time Electromagnetic Localization and Tracking with Cone Beam Computed Tomography in Stereotactic Radiosurgery for Brain Tumors

    International Nuclear Information System (INIS)

    Muralidhar, K Raja; Pangam, Suresh; Ponaganti, Srinivas; Krishna, Jayarama; Sujana, Kolla V; Komanduri, Priya K

    2016-01-01

    Purpose: 1. online verification of patient position during treatment using calypso electromagnetic localization and tracking system. 2. Verification and comparison of positional accuracy between cone beam computed tomography and calypso system. 3. Presenting the advantage of continuation localization in Stereotactic radiosurgery treatments. Methods: Ten brain tumor cases were taken for this study. Patients with head mask were under gone Computed Tomography (CT). Before scanning, mask was cut on the fore head area to keep surface beacons on the skin. Slice thickness of 0.65 mm were taken for this study. x, y, z coordinates of these beacons in TPS were entered into tracking station. Varian True Beam accelerator, equipped with On Board Imager was used to take Cone beam Computed Tomography (CBCT) to localize the patient. Simultaneously Surface beacons were used to localize and track the patient throughout the treatment. The localization values were compared in both systems. For localization CBCT considered as reference. Tracking was done throughout the treatment using Calypso tracking system using electromagnetic array. This array was in tracking position during imaging and treatment. Flattening Filter free beams of 6MV photons along with Volumetric Modulated Arc Therapy was used for the treatment. The patient movement was observed throughout the treatment ranging from 2 min to 4 min. Results: The average variation observed between calypso system and CBCT localization was less than 0.5 mm. These variations were due to manual errors while keeping beacon on the patient. Less than 0.05 cm intra-fraction motion was observed throughout the treatment with the help of continuous tracking. Conclusion: Calypso target localization system is one of the finest tools to perform radiosurgery in combination with CBCT. This non radiographic method of tracking is a real beneficial method to treat patients confidently while observing real-time motion information of the patient.

  9. SU-G-JeP1-01: A Combination of Real Time Electromagnetic Localization and Tracking with Cone Beam Computed Tomography in Stereotactic Radiosurgery for Brain Tumors

    Energy Technology Data Exchange (ETDEWEB)

    Muralidhar, K Raja; Pangam, Suresh; Ponaganti, Srinivas; Krishna, Jayarama; Sujana, Kolla V; Komanduri, Priya K [American Oncology Institute, Hyderabad, Telangana (India)

    2016-06-15

    Purpose: 1. online verification of patient position during treatment using calypso electromagnetic localization and tracking system. 2. Verification and comparison of positional accuracy between cone beam computed tomography and calypso system. 3. Presenting the advantage of continuation localization in Stereotactic radiosurgery treatments. Methods: Ten brain tumor cases were taken for this study. Patients with head mask were under gone Computed Tomography (CT). Before scanning, mask was cut on the fore head area to keep surface beacons on the skin. Slice thickness of 0.65 mm were taken for this study. x, y, z coordinates of these beacons in TPS were entered into tracking station. Varian True Beam accelerator, equipped with On Board Imager was used to take Cone beam Computed Tomography (CBCT) to localize the patient. Simultaneously Surface beacons were used to localize and track the patient throughout the treatment. The localization values were compared in both systems. For localization CBCT considered as reference. Tracking was done throughout the treatment using Calypso tracking system using electromagnetic array. This array was in tracking position during imaging and treatment. Flattening Filter free beams of 6MV photons along with Volumetric Modulated Arc Therapy was used for the treatment. The patient movement was observed throughout the treatment ranging from 2 min to 4 min. Results: The average variation observed between calypso system and CBCT localization was less than 0.5 mm. These variations were due to manual errors while keeping beacon on the patient. Less than 0.05 cm intra-fraction motion was observed throughout the treatment with the help of continuous tracking. Conclusion: Calypso target localization system is one of the finest tools to perform radiosurgery in combination with CBCT. This non radiographic method of tracking is a real beneficial method to treat patients confidently while observing real-time motion information of the patient.

  10. SU-E-T-394: The Use of Jaw Tracking in Intensity Modulated and Volumetric Modulated Arc Radiotherapy for Spine Stereotactic Radiosurgery

    Energy Technology Data Exchange (ETDEWEB)

    Chin, K; Wen, N; Huang, Y; Kim, J; Zhao, B; Siddiqui, S; Chetty, I; Ryu, S [Henry Ford Health System, Detroit, MI (United States)

    2014-06-01

    Purpose: To evaluate the potential advantages of jaw tracking for intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in spine radiosurgery. Methods: VMAT and IMRT plans were retrospectively generated for ten patients. Six plans for each patient were created in the Eclipse treatment planning system for a Varian Truebeam equipped with a Millennium 120 MLC. Plans were created to study IMRT and VMAT plans with and without jaw tracking, as well as IMRT plans of different flattening filter free (FFF) energies. Plans were prescribed to the 90% isodose line to 16 or 18 Gy in one fraction to cover 95% of the target. Planning target volume (PTV) coverage, conformity index (CI), dose to spinal cord, distance to fall off from the 90% to 50% isodose line (DTF), as well as delivery time were evaluated. Ion chamber and film measurements were performed to verify calculated and measured dose distributions. Results: Jaw tracking decreased the spinal cord dose for both IMRT and VMAT plans, but a larger decrease was seen with the IMRT plans (p=0.004 vs p=0.04). The average D10% for the spinal cord was least for the 6MV FFF IMRT plan with jaw tracking and was greatest for the 10MV FFF plan without jaw tracking. Treatment times between IMRT and VMAT plans with or without jaw tracking were not significantly different. Measured plans showed greater than 98.5% agreement for planar dose gamma analysis (3%/2 mm) and less than 2.5% for point dose analysis compared to calculated plans. Conclusion: Jaw tracking can be used to help decrease spinal cord dose without any change in treatment delivery or calculation accuracy. Lower dose to the spinal cord was achieved using 6 MV beams compared to 10 MV beams, though 10 MV may be justified in some cases to decrease skin dose.

  11. MO-FG-BRA-05: Dosimetric and Radiobiological Validation of Respiratory Gating in Conventional and Hypofractionated Radiotherapy of the Lung: Effect of Dose, Dose Rate, Gating Window and Breathing Pattern

    Energy Technology Data Exchange (ETDEWEB)

    Cervino, L; Soultan, D; Pettersson, N; Yock, A; Cornell, M; Aguilera, J; Murphy, J; Advani, S; Moiseenko, V [University of California, San Diego, La Jolla, CA (United States); Gill, B [British Columbia Cancer Agency, Vancouver, BC (Canada)

    2016-06-15

    Purpose: to evaluate the dosimetric and radiobiological consequences from having different gating windows, dose rates, and breathing patterns in gated VMAT lung radiotherapy. Methods: A novel 3D-printed moving phantom with central high and peripheral low tracer uptake regions was 4D FDG-PET/CT-scanned using ideal, patient-specific regular, and irregular breathing patterns. A scan of the stationary phantom was obtained as a reference. Target volumes corresponding to different uptake regions were delineated. Simultaneous integrated boost (SIB) 6 MV VMAT plans were produced for conventional and hypofractionated radiotherapy, using 30–70 and 100% cycle gating scenarios. Prescribed doses were 200 cGy with SIB to 240 cGy to high uptake volume for conventional, and 800 with SIB to 900 cGy for hypofractionated plans. Dose rates of 600 MU/min (conventional and hypofractionated) and flattening filter free 1400 MU/min (hypofractionated) were used. Ion chamber measurements were performed to verify delivered doses. Vials with A549 cells placed in locations matching ion chamber measurements were irradiated using the same plans to measure clonogenic survival. Differences in survival for the different doses, dose rates, gating windows, and breathing patterns were analyzed. Results: Ion chamber measurements agreed within 3% of the planned dose, for all locations, breathing patterns and gating windows. Cell survival depended on dose alone, and not on gating window, breathing pattern, MU rate, or delivery time. The surviving fraction varied from approximately 40% at 2Gy to 1% for 9 Gy and was within statistical uncertainty relative to that observed for the stationary phantom. Conclusions: Use of gated VMAT in PET-driven SIB radiotherapy was validated using ion chamber measurements and cell survival assays for conventional and hypofractionated radiotherapy.

  12. Measurement and modeling of out-of-field doses from various advanced post-mastectomy radiotherapy techniques

    Science.gov (United States)

    Yoon, Jihyung; Heins, David; Zhao, Xiaodong; Sanders, Mary; Zhang, Rui

    2017-12-01

    More and more advanced radiotherapy techniques have been adopted for post-mastectomy radiotherapies (PMRT). Patient dose reconstruction is challenging for these advanced techniques because they increase the low out-of-field dose area while the accuracy of out-of-field dose calculations by current commercial treatment planning systems (TPSs) is poor. We aim to measure and model the out-of-field radiation doses from various advanced PMRT techniques. PMRT treatment plans for an anthropomorphic phantom were generated, including volumetric modulated arc therapy with standard and flattening-filter-free photon beams, mixed beam therapy, 4-field intensity modulated radiation therapy (IMRT), and tomotherapy. We measured doses in the phantom where the TPS calculated doses were lower than 5% of the prescription dose using thermoluminescent dosimeters (TLD). The TLD measurements were corrected by two additional energy correction factors, namely out-of-beam out-of-field (OBOF) correction factor K OBOF and in-beam out-of-field (IBOF) correction factor K IBOF, which were determined by separate measurements using an ion chamber and TLD. A simple analytical model was developed to predict out-of-field dose as a function of distance from the field edge for each PMRT technique. The root mean square discrepancies between measured and calculated out-of-field doses were within 0.66 cGy Gy-1 for all techniques. The IBOF doses were highly scattered and should be evaluated case by case. One can easily combine the measured out-of-field dose here with the in-field dose calculated by the local TPS to reconstruct organ doses for a specific PMRT patient if the same treatment apparatus and technique were used.

  13. TH-CD-201-06: Experimental Characterization of Acoustic Signals Generated in Water Following Clinical Photon and Electron Beam Irradiation

    International Nuclear Information System (INIS)

    Hickling, S; El Naqa, I

    2016-01-01

    Purpose: Previous work has demonstrated the detectability of acoustic waves induced following the irradiation of high density metals with radiotherapy linac photon beams. This work demonstrates the ability to experimentally detect such acoustic signals following both photon and electron irradiation in a more radiotherapy relevant material. The relationship between induced acoustic signal properties in water and the deposited dose distribution is explored, and the feasibility of exploiting such signals for radiotherapy dosimetry is demonstrated. Methods: Acoustic waves were experimentally induced in a water tank via the thermoacoustic effect following a single pulse of photon or electron irradiation produced by a clinical linac. An immersion ultrasound transducer was used to detect these acoustic waves in water and signals were read out on an oscilloscope. Results: Peaks and troughs in the detected acoustic signals were found to correspond to the location of gradients in the deposited dose distribution following both photon and electron irradiation. Signal amplitude was linearly related to the dose per pulse deposited by photon or electron beams at the depth of detection. Flattening filter free beams induced large acoustic signals, and signal amplitude decreased with depth after the depth of maximum dose. Varying the field size resulted in a temporal shift of the acoustic signal peaks and a change in the detected signal frequency. Conclusion: Acoustic waves can be detected in a water tank following irradiation by linac photon and electron beams with basic electronics, and have characteristics related to the deposited dose distribution. The physical location of dose gradients and the amount of dose deposited can be inferred from the location and magnitude of acoustic signal peaks. Thus, the detection of induced acoustic waves could be applied to photon and electron water tank and in vivo dosimetry. This work was supported in part by CIHR grants MOP-114910 and MOP

  14. A combination of high dose rate (10X FFF/2400 MU/min/10 MV X-rays) and total low dose (0.5 Gy) induces a higher rate of apoptosis in melanoma cells in vitro and superior preservation of normal melanocytes.

    Science.gov (United States)

    Sarojini, Sreeja; Pecora, Andrew; Milinovikj, Natasha; Barbiere, Joseph; Gupta, Saakshi; Hussain, Zeenathual M; Tuna, Mehmet; Jiang, Jennifer; Adrianzen, Laura; Jun, Jaewook; Catello, Laurice; Sanchez, Diana; Agarwal, Neha; Jeong, Stephanie; Jin, Youngjin; Remache, Yvonne; Goy, Andre; Ndlovu, Alois; Ingenito, Anthony; Suh, K Stephen

    2015-10-01

    The aim of this study was to determine the apoptotic effects, toxicity, and radiosensitization of total low dose irradiation delivered at a high dose rate in vitro to melanoma cells, normal human epidermal melanocytes (HEM), or normal human dermal fibroblasts (HDF) and to study the effect of mitochondrial inhibition in combination with radiation to enhance apoptosis in melanoma cells. Cells irradiated using 10X flattening filter-free (FFF) 10 MV X-rays at a dose rate of 400 or 2400 MU/min and a total dose of 0.25-8 Gy were analyzed by cell/colony counting, MitoTracker, MTT, and DNA-damage assays, as well as by quantitative real-time reverse transcriptase PCR in the presence or absence of mitochondrial respiration inhibitors. A dose rate of 2400 MU/min killed on average five-fold more melanoma cells than a dose rate 400 MU/min at a total dose of 0.5 Gy and preserved 80% survival of HEM and 90% survival of HDF. Increased apoptosis at the 2400 MU/min dose rate is mediated by greater DNA damage, reduced cell proliferation, upregulation of apoptotic genes, and downregulation of cell cycle genes. HEM and HDF were relatively unharmed at 2400 MU/min. Radiation induced upregulation of mitochondrial respiration in both normal and cancer cells, and blocking the respiration with inhibitors enhanced apoptosis only in melanoma cells. A high dose rate with a low total dose (2400 MU/min, 0.5 Gy/10X FFF 10 MV X-rays) enhances radiosensitivity of melanoma cells while reducing radiotoxicity toward HEM and HDF. Selective cytotoxicity of melanoma cells is increased by blocking mitochondrial respiration.

  15. TU-H-BRA-08: The Design and Characteristics of a Novel Compact Linac-Based MRI Guided Radiation Therapy (MR-IGRT) System

    International Nuclear Information System (INIS)

    Mutic, S; Low, D; Chmielewski, T; Fought, G; Hernandez, M; Kawrakow, I; Sharma, A; Shvartsman, S; Dempsey, J

    2016-01-01

    Purpose: To describe the design and characteristics of a novel linac-based MRI guided radiation therapy system that addresses RF and magnetic field interference and that can be housed in conventional radiotherapy vaults. Methods: The MR-IGRT system will provide simultaneous MR imaging combined with both simple (3D) and complex (IMRT, SBRT, SRS) techniques. The system is a combination of a) double-donut split solenoidal superconducting 0.345T MRI; and b) a 90 cm isocenter ring-gantry mounted 6MV, flattening filter-free linac coupled with a stacked doubly-focused multileaf collimator with 4 mm resolution. A novel RF shielding and absorption technology was developed to isolate the beam generating RF emissions from the MR, while a novel magnetic shielding sleeve system was developed to place the magnetic field-sensitive components in low-magnetic field regions. The system design produces high spatial resolution radiation beams with state-of-the art radiation dose characteristics and simultaneous MR imaging. Results: Prototype testing with a spectrum analyzer has demonstrated complete elimination of linac RF inside the treatment room. The magnetic field inside of the magnetic shielding was well below the specification, allowing the linear accelerator to operate normally. A novel on-gantry shimming system maintained < 25 ppm magnetic field homogeneity over a 45 cm spherical field of view for all gantry angles. Conclusion: The system design demonstrates the feasibility coupling a state-of-the art linac system with a 0.345T MRI, enabling highly conformal radiation therapy with simultaneous MR image guidance. S. Mutic’s employer (Washington University) has grant with ViewRay; D. Low is former ViewRay scientific advisory board member (ended October 2015); T. Chmielewski, G. Fought, M. Hernandez, I. Kawrakow, A. Sharma, S. Shvartsman, J. Dempsey are employees of ViewRay with stock options (Dempsey has leadership role and Dempsey/Kawrakow have stock).

  16. SU-E-T-394: The Use of Jaw Tracking in Intensity Modulated and Volumetric Modulated Arc Radiotherapy for Spine Stereotactic Radiosurgery

    International Nuclear Information System (INIS)

    Chin, K; Wen, N; Huang, Y; Kim, J; Zhao, B; Siddiqui, S; Chetty, I; Ryu, S

    2014-01-01

    Purpose: To evaluate the potential advantages of jaw tracking for intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in spine radiosurgery. Methods: VMAT and IMRT plans were retrospectively generated for ten patients. Six plans for each patient were created in the Eclipse treatment planning system for a Varian Truebeam equipped with a Millennium 120 MLC. Plans were created to study IMRT and VMAT plans with and without jaw tracking, as well as IMRT plans of different flattening filter free (FFF) energies. Plans were prescribed to the 90% isodose line to 16 or 18 Gy in one fraction to cover 95% of the target. Planning target volume (PTV) coverage, conformity index (CI), dose to spinal cord, distance to fall off from the 90% to 50% isodose line (DTF), as well as delivery time were evaluated. Ion chamber and film measurements were performed to verify calculated and measured dose distributions. Results: Jaw tracking decreased the spinal cord dose for both IMRT and VMAT plans, but a larger decrease was seen with the IMRT plans (p=0.004 vs p=0.04). The average D10% for the spinal cord was least for the 6MV FFF IMRT plan with jaw tracking and was greatest for the 10MV FFF plan without jaw tracking. Treatment times between IMRT and VMAT plans with or without jaw tracking were not significantly different. Measured plans showed greater than 98.5% agreement for planar dose gamma analysis (3%/2 mm) and less than 2.5% for point dose analysis compared to calculated plans. Conclusion: Jaw tracking can be used to help decrease spinal cord dose without any change in treatment delivery or calculation accuracy. Lower dose to the spinal cord was achieved using 6 MV beams compared to 10 MV beams, though 10 MV may be justified in some cases to decrease skin dose

  17. Gafchromic EBT-XD film: Dosimetry characterization in high-dose, volumetric-modulated arc therapy.

    Science.gov (United States)

    Miura, Hideharu; Ozawa, Shuichi; Hosono, Fumika; Sumida, Naoki; Okazue, Toshiya; Yamada, Kiyoshi; Nagata, Yasushi

    2016-11-08

    Radiochromic films are important tools for assessing complex dose distributions. Gafchromic EBT-XD films have been designed for optimal performance in the 40-4,000 cGy dose range. We investigated the dosimetric characteristics of these films, including their dose-response, postexposure density growth, and dependence on scanner orientation, beam energy, and dose rate with applications to high-dose volumetric-modulated arc therapy (VMAT) verification. A 10 MV beam from a TrueBeam STx linear accelerator was used to irradiate the films with doses in the 0-4,000 cGy range. Postexposure coloration was analyzed at postirradiation times ranging from several minutes to 48 h. The films were also irradiated with 6 MV (dose rate (DR): 600 MU/min), 6 MV flattening filter-free (FFF) (DR: 1,400 MU/ min), and 10 MV FFF (DR: 2,400 MU/min) beams to determine the energy and dose-rate dependence. For clinical examinations, we compared the dose distribu-tion measured with EBT-XD films and calculated by the planning system for four VMAT cases. The red channel of the EBT-XD film exhibited a wider dynamic range than the green and blue channels. Scanner orientation yielded a variation of ~ 3% in the net optical density (OD). The difference between the film front and back scan orientations was negligible, with variation of ~ 1.3% in the net OD. The net OD increased sharply within the first 6 hrs after irradiation and gradually afterwards. No significant difference was observed for the beam energy and dose rate, with a variation of ~ 1.5% in the net OD. The gamma passing rates (at 3%, 3 mm) between the film- measured and treatment planning system (TPS)-calculated dose distributions under a high dose VMAT plan in the absolute dose mode were more than 98.9%. © 2016 The Authors.

  18. Inverse planning in the age of digital LINACs: station parameter optimized radiation therapy (SPORT)

    Science.gov (United States)

    Xing, Lei; Li, Ruijiang

    2014-03-01

    The last few years have seen a number of technical and clinical advances which give rise to a need for innovations in dose optimization and delivery strategies. Technically, a new generation of digital linac has become available which offers features such as programmable motion between station parameters and high dose-rate Flattening Filter Free (FFF) beams. Current inverse planning methods are designed for traditional machines and cannot accommodate these features of new generation linacs without compromising either dose conformality and/or delivery efficiency. Furthermore, SBRT is becoming increasingly important, which elevates the need for more efficient delivery, improved dose distribution. Here we will give an overview of our recent work in SPORT designed to harness the digital linacs and highlight the essential components of SPORT. We will summarize the pros and cons of traditional beamlet-based optimization (BBO) and direct aperture optimization (DAO) and introduce a new type of algorithm, compressed sensing (CS)-based inverse planning, that is capable of automatically removing the redundant segments during optimization and providing a plan with high deliverability in the presence of a large number of station control points (potentially non-coplanar, non-isocentric, and even multi-isocenters). We show that CS-approach takes the interplay between planning and delivery into account and allows us to balance the dose optimality and delivery efficiency in a controlled way and, providing a viable framework to address various unmet demands of the new generation linacs. A few specific implementation strategies of SPORT in the forms of fixed-gantry and rotational arc delivery are also presented.

  19. Inverse planning in the age of digital LINACs: station parameter optimized radiation therapy (SPORT)

    International Nuclear Information System (INIS)

    Xing, Lei; Li, Ruijiang

    2014-01-01

    The last few years have seen a number of technical and clinical advances which give rise to a need for innovations in dose optimization and delivery strategies. Technically, a new generation of digital linac has become available which offers features such as programmable motion between station parameters and high dose-rate Flattening Filter Free (FFF) beams. Current inverse planning methods are designed for traditional machines and cannot accommodate these features of new generation linacs without compromising either dose conformality and/or delivery efficiency. Furthermore, SBRT is becoming increasingly important, which elevates the need for more efficient delivery, improved dose distribution. Here we will give an overview of our recent work in SPORT designed to harness the digital linacs and highlight the essential components of SPORT. We will summarize the pros and cons of traditional beamlet-based optimization (BBO) and direct aperture optimization (DAO) and introduce a new type of algorithm, compressed sensing (CS)-based inverse planning, that is capable of automatically removing the redundant segments during optimization and providing a plan with high deliverability in the presence of a large number of station control points (potentially non-coplanar, non-isocentric, and even multi-isocenters). We show that CS-approach takes the interplay between planning and delivery into account and allows us to balance the dose optimality and delivery efficiency in a controlled way and, providing a viable framework to address various unmet demands of the new generation linacs. A few specific implementation strategies of SPORT in the forms of fixed-gantry and rotational arc delivery are also presented.

  20. TU-H-BRA-08: The Design and Characteristics of a Novel Compact Linac-Based MRI Guided Radiation Therapy (MR-IGRT) System

    Energy Technology Data Exchange (ETDEWEB)

    Mutic, S [Washington University School of Medicine, Saint Louis, MO (United States); Low, D [UCLA, Los Angeles, CA (United States); Chmielewski, T; Fought, G; Hernandez, M; Kawrakow, I; Sharma, A; Shvartsman, S; Dempsey, J [ViewRay, Inc., Oakwood Village, OH (United States)

    2016-06-15

    Purpose: To describe the design and characteristics of a novel linac-based MRI guided radiation therapy system that addresses RF and magnetic field interference and that can be housed in conventional radiotherapy vaults. Methods: The MR-IGRT system will provide simultaneous MR imaging combined with both simple (3D) and complex (IMRT, SBRT, SRS) techniques. The system is a combination of a) double-donut split solenoidal superconducting 0.345T MRI; and b) a 90 cm isocenter ring-gantry mounted 6MV, flattening filter-free linac coupled with a stacked doubly-focused multileaf collimator with 4 mm resolution. A novel RF shielding and absorption technology was developed to isolate the beam generating RF emissions from the MR, while a novel magnetic shielding sleeve system was developed to place the magnetic field-sensitive components in low-magnetic field regions. The system design produces high spatial resolution radiation beams with state-of-the art radiation dose characteristics and simultaneous MR imaging. Results: Prototype testing with a spectrum analyzer has demonstrated complete elimination of linac RF inside the treatment room. The magnetic field inside of the magnetic shielding was well below the specification, allowing the linear accelerator to operate normally. A novel on-gantry shimming system maintained < 25 ppm magnetic field homogeneity over a 45 cm spherical field of view for all gantry angles. Conclusion: The system design demonstrates the feasibility coupling a state-of-the art linac system with a 0.345T MRI, enabling highly conformal radiation therapy with simultaneous MR image guidance. S. Mutic’s employer (Washington University) has grant with ViewRay; D. Low is former ViewRay scientific advisory board member (ended October 2015); T. Chmielewski, G. Fought, M. Hernandez, I. Kawrakow, A. Sharma, S. Shvartsman, J. Dempsey are employees of ViewRay with stock options (Dempsey has leadership role and Dempsey/Kawrakow have stock).

  1. SU-F-T-461: Dosimetric Evaluation of Indigenous Farmer Type Chamber FAR65- GB for Reference Dosimetry of FFF MV Photon Beam

    Energy Technology Data Exchange (ETDEWEB)

    Patwe, P; Mhatre, V; Dandekar, P [Sir HN RF Hospital, Mumbai, Maharashtra (India)

    2016-06-15

    Purpose: Indigenous Farmer type chamber FAR 65 GB is a reference class 0.6 cc ion chamber. It can be used for dosimetric evaluation of photon and high energy electron beams. We studied dosimetric characteristics of the chamber for 6MV and 10MV Flattening filter free FFF photon beams available on trueBEAM STx Linac. Methods: The study was carried out on trueBEAM STx Linac having 6 and 10 MV FFF photon beam with maximum dose rate 1400 and 2400 MU per min respectively. The dosimetric device to be evaluated is Rosalina Instruments FAR 65-GB Ion Chamber with active volume 0.65 cc, total active length 23.1cm, inner diameter of cylinder 6.2mm, wall thickness 0.4mm, inner electrode diameter 1mm. Inner and outer electrodes are made from Aluminium 2.7 gm per cc and graphite 1.82 gm per cc respectively. The ion chamber was placed along central axis of beam at 10cm depth and irradiated for 10cm × 10cm field size at SAD of 100 cm in plastic phantom. We studied Precision, Dose Linearity, Dose Rate dependence, directional dependence, Recombination effect. Recombination effect was determined using standard two-voltage method. Results: 1. Measurements were reproducible std deviation of 0.0105 and type A uncertainty 0.003265 under same set of reference conditions 2. Chamber exhibit dose linearity over a wider dose range. 3. Chamber shows dose rate independence for all available dose rate range. 4. Response of chamber with the angle of incidence of radiation is constant. 5. Recombination correction factors were 1.01848 and 1.02537 for dose rate 1400 and 2400 MU per min resp. Conclusion: Our study reveals that the chamber is prone to saturation effect at dose rate of 2400 MU per min. FAR 65-GB can be used for reference dosimetry of FFF MV photon beam with proper calculation of recombination effect.

  2. SU-C-202-07: Protocol and Hardware for Improved Flood Field Calibration of TrueBeam FFF Cine Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Adamson, J; Faught, A; Yin, F [Duke University Medical Center, Durham, NC (United States)

    2016-06-15

    Purpose: Flattening filter free photon energies are commonly used for high dose treatments such as SBRT, where localization accuracy is essential. Often, MV cine imaging may be employed to verify correct localization. TrueBeam Electronic Portal Imaging Devices (EPIDs) equipped with the 40×30cm{sup 2} Image Detection Unit (IDU) are prone to image saturation at the image center especially for higher dose rates. While saturation often does not occur for cine imaging during treatment because the beam is attenuated by the patient, the flood field calibration is affected when the standard calibration procedure is followed. Here we describe the hardware and protocol to achieve improved image quality for this model of TrueBeam EPID. Methods: A stainless steel filter of uniform thickness was designed to have sufficient attenuation to avoid panel saturation for both 6XFFF and 10XFFF at the maximum dose rates (1400 MU/min & 2400 MU/min, respectively). The cine imaging flood field calibration was then acquired with the filter in place for the FFF energies under the standard calibration geometry (SDD=150cm). Image quality during MV cine was assessed with & without the modified flood field calibration using a low contrast resolution phantom and an anthropomorphic phantom. Results: When the flood field is acquired using the standard procedure (no filter in place), a pixel gain artifact is clearly present in the image center (r=3cm for 10XFFF at 2400 MU/min) which appears similar to and may be mis-attributed to panel saturation in the subject image. The artifact obscured all low contrast inserts at the image center and was also visible on the anthropomorphic phantom. Using the filter for flood field calibration eliminated the artifact. Conclusion: Use of a modified flood field calibration procedure improves image quality for cine MV imaging with TrueBeams equipped with the 40×30cm{sup 2} IDU.

  3. Dosimetric validation of Monaco treatment planning system on an Elekta VersaHD linear accelerator.

    Science.gov (United States)

    Narayanasamy, Ganesh; Saenz, Daniel L; Defoor, Dewayne; Papanikolaou, Niko; Stathakis, Sotirios

    2017-11-01

    The purpose of this study is to perform dosimetric validation of Monaco treatment planning system version 5.1. The Elekta VersaHD linear accelerator with high dose rate flattening filter-free photon modes and electron energies was used in this study. The dosimetric output of the new Agility head combined with the FFF photon modes warranted this investigation into the dosimetric accuracy prior to clinical usage. A model of the VersaHD linac was created in Monaco TPS by Elekta using commissioned beam data including percent depth dose curves, beam profiles, and output factors. A variety of 3D conformal fields were created in Monaco TPS on a combined Plastic water/Styrofoam phantom and validated against measurements with a calibrated ion chamber. Some of the parameters varied including source to surface distance, field size, wedges, gantry angle, and depth for all photon and electron energies. In addition, a series of step and shoot IMRT, VMAT test plans, and patient plans on various anatomical sites were verified against measurements on a Delta 4 diode array. The agreement in point dose measurements was within 2% for all photon and electron energies in the homogeneous phantom and within 3% for photon energies in the heterogeneous phantom. The mean ± SD gamma passing rates of IMRT test fields yielded 93.8 ± 4.7% based on 2% dose difference and 2 mm distance-to-agreement criteria. Eight previously treated IMRT patient plans were replanned in Monaco TPS and five measurements on each yielded an average gamma passing rate of 95% with 6.7% confidence limit based on 3%, 3 mm gamma criteria. This investigation on dosimetric validation ensures accuracy of modeling VersaHD linac in Monaco TPS thereby improving patient safety. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

  4. Dose properties of x-ray beams produced by laser-wakefield-accelerated electrons

    International Nuclear Information System (INIS)

    Kainz, K K; Hogstrom, K R; Antolak, J A; Almond, P R; Bloch, C D

    2005-01-01

    Given that laser wakefield acceleration (LWFA) has been demonstrated experimentally to accelerate electron beams to energies beyond 25 MeV, it is reasonable to assess the ability of existing LWFA technology to compete with conventional radiofrequency linear accelerators in producing electron and x-ray beams for external-beam radiotherapy. We present calculations of the dose distributions (off-axis dose profiles and central-axis depth dose) and dose rates of x-ray beams that can be produced from electron beams that are generated using state-of-the-art LWFA. Subsets of an LWFA electron energy distribution were propagated through the treatment head elements (presuming an existing design for an x-ray production target and flattening filter) implemented within the EGSnrc Monte Carlo code. Three x-ray energy configurations (6 MV, 10 MV and 18 MV) were studied, and the energy width ΔE of the electron-beam subsets varied from 0.5 MeV to 12.5 MeV. As ΔE increased from 0.5 MeV to 4.5 MeV, we found that the off-axis and central-axis dose profiles for x-rays were minimally affected (to within about 3%), a result slightly different from prior calculations of electron beams broadened by scattering foils. For ΔE of the order of 12 MeV, the effect on the off-axis profile was of the order of 10%, but the central-axis depth dose was affected by less than 2% for depths in excess of about 5 cm beyond d max . Although increasing ΔE beyond 6.5 MeV increased the dose rate at d max by more than 10 times, the absolute dose rates were about 3 orders of magnitude below those observed for LWFA-based electron beams at comparable energies. For a practical LWFA-based x-ray device, the beam current must be increased by about 4-5 orders of magnitude. (note)

  5. Automatically gated image-guided breath-hold IMRT is a fast, precise, and dosimetrically robust treatment for lung cancer patients

    Energy Technology Data Exchange (ETDEWEB)

    Simeonova-Chergou, Anna; Jahnke, Anika; Siebenlist, Kerstin; Stieler, Florian; Mai, Sabine; Boda-Heggemann, Judit; Wenz, Frederik; Lohr, Frank; Jahnke, Lennart [University Medical Center Mannheim, University of Heidelberg, Department of Radiotherapy and Oncology, Mannheim (Germany)

    2016-03-15

    High-dose radiotherapy of lung cancer is challenging. Tumors may move by up to 2 cm in craniocaudal and anteroposterior directions as a function of breathing cycle. Tumor displacement increases with treatment time, which consequentially increases the treatment uncertainty. This study analyzed whether automatically gated cone-beam-CT (CBCT)-controlled intensity modulated fast deep inspiration breath hold (DIBH) stereotactic body radiation therapy (SBRT) in flattening filter free (FFF) technique and normofractionated lung DIBH intensity-modulated radiotherapy (IMRT)/volumetric-modulated arc therapy (VMAT) treatments delivered with a flattening filter can be applied with sufficient accuracy within a clinically acceptable timeslot. Plans of 34 patients with lung tumors were analyzed. Of these patients, 17 received computer-controlled fast DIBH SBRT with a dose of 60 Gy (5 fractions of 12 Gy or 12 fractions of 5 Gy) in an FFF VMAT technique (FFF-SBRT) every other day and 17 received conventional VMAT with a flattening filter (conv-VMAT) and 2-Gy daily fractional doses (cumulative dose 50-70 Gy). FFF-SBRT plans required more monitor units (MU) than conv-VMAT plans (2956.6 ± 885.3 MU for 12 Gy/fraction and 1148.7 ± 289.2 MU for 5 Gy/fraction vs. 608.4 ± 157.5 MU for 2 Gy/fraction). Total treatment and net beam-on times were shorter for FFF-SBRT plans than conv-VMAT plans (268.0 ± 74.4 s vs. 330.2 ± 93.6 s and 85.8 ± 25.3 s vs. 117.2 ± 29.6 s, respectively). Total slot time was 13.0 min for FFF-SBRT and 14.0 min for conv-VMAT. All modalities could be delivered accurately despite multiple beam-on/-off cycles and were robust against multiple interruptions. Automatically gated CBCT-controlled fast DIBH SBRT in VMAT FFF technique and normofractionated lung DIBH VMAT can be applied with a low number of breath-holds in a short timeslot, with excellent dosimetric accuracy. In clinical routine, these approaches combine optimally reduced lung tissue irradiation with maximal

  6. Dosimetric evaluation of photon dose calculation under jaw and MLC shielding

    International Nuclear Information System (INIS)

    Fogliata, A.; Clivio, A.; Vanetti, E.; Nicolini, G.; Belosi, M. F.; Cozzi, L.

    2013-01-01

    Purpose: The accuracy of photon dose calculation algorithms in out-of-field regions is often neglected, despite its importance for organs at risk and peripheral dose evaluation. The present work has assessed this for the anisotropic analytical algorithm (AAA) and the Acuros-XB algorithms implemented in the Eclipse treatment planning system. Specifically, the regions shielded by the jaw, or the MLC, or both MLC and jaw for flattened and unflattened beams have been studied.Methods: The accuracy in out-of-field dose under different conditions was studied for two different algorithms. Measured depth doses out of the field, for different field sizes and various distances from the beam edge were compared with the corresponding AAA and Acuros-XB calculations in water. Four volumetric modulated arc therapy plans (in the RapidArc form) were optimized in a water equivalent phantom, PTW Octavius, to obtain a region always shielded by the MLC (or MLC and jaw) during the delivery. Doses to different points located in the shielded region and in a target-like structure were measured with an ion chamber, and results were compared with the AAA and Acuros-XB calculations. Photon beams of 6 and 10 MV, flattened and unflattened were used for the tests.Results: Good agreement between calculated and measured depth doses was found using both algorithms for all points measured at depth greater than 3 cm. The mean dose differences (±1SD) were −8%± 16%, −3%± 15%, −16%± 18%, and −9%± 16% for measurements vs AAA calculations and −10%± 14%, −5%± 12%, −19%± 17%, and −13%± 14% for Acuros-XB, for 6X, 6 flattening-filter free (FFF), 10X, and 10FFF beams, respectively. The same figures for dose differences relative to the open beam central axis dose were: −0.1%± 0.3%, 0.0%± 0.4%, −0.3%± 0.3%, and −0.1%± 0.3% for AAA and −0.2%± 0.4%, −0.1%± 0.4%, −0.5%± 0.5%, and −0.3%± 0.4% for Acuros-XB. Buildup dose was overestimated with AAA, while Acuros-XB gave

  7. Scatter factor corrections for elongated fields

    International Nuclear Information System (INIS)

    Higgins, P.D.; Sohn, W.H.; Sibata, C.H.; McCarthy, W.A.

    1989-01-01

    Measurements have been made to determine scatter factor corrections for elongated fields of Cobalt-60 and for nominal linear accelerator energies of 6 MV (Siemens Mevatron 67) and 18 MV (AECL Therac 20). It was found that for every energy the collimator scatter factor varies by 2% or more as the field length-to-width ratio increases beyond 3:1. The phantom scatter factor is independent of which collimator pair is elongated at these energies. For 18 MV photons it was found that the collimator scatter factor is complicated by field-size-dependent backscatter into the beam monitor

  8. Dosimetry and evaluating the effect of treatment parameters on the leakage of multi leaf collimators in ONCOR linear accelerators

    Directory of Open Access Journals (Sweden)

    Keyvan Jabbari

    2016-01-01

    Conclusions: The amount of leakage was more for 18 MV compare to 6 MV The percentage of the leakage for both energies is less than the 5% value which is recommended by protocols. The fluctuation of the MLC leakage reduced by increasing the field size and depth.

  9. Sensitivity and variability of Presage dosimeter formulations in sheet form with application to SBRT and SRS QA

    Energy Technology Data Exchange (ETDEWEB)

    Dumas, Michael, E-mail: mdumas1127@gmail.com [Department of Radiation Oncology, Wayne State University School of Medicine and Karmanos Cancer Institute Detroit, Detroit, Michigan 48201 and Department of Radiation Oncology, Henry Ford Hospital, Detroit, Michigan 48202 (United States); Rakowski, Joseph T. [Department of Radiation Oncology, Wayne State University School of Medicine and Karmanos Cancer Institute Detroit, Detroit, Michigan 48201 (United States)

    2015-12-15

    Purpose: To measure sensitivity and stability of the Presage dosimeter in sheet form for various chemical concentrations over a range of clinical photon energies and examine its use for stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) QA. Methods: Presage polymer dosimeters were formulated to investigate and optimize their sensitivity and stability. The dosimeter is composed of clear polyurethane base, leucomalachite green (LMG) reporting dye, and bromoform radical initiator in 0.9–1.0 mm thick sheets. The chemicals are mixed together for 2 min, cast in an aluminum mold, and left to cure at 60 psi for a minimum of two days. Dosimeter response was characterized at energies Co-60, 6 MV, 10 MV flattening-filter free, 15 MV, 50 kVp (mean 19.2 keV), and Ir-192. The dosimeters were scanned by a Microtek Scanmaker i800 at 300 dpi, 2{sup 16} bit depth per color channel. Red component images were analyzed with ImageJ and RIT. SBRT QA was done with gamma analysis tolerances of 2% and 2 mm DTA. Results: The sensitivity of the Presage dosimeter increased with increasing concentration of bromoform. Addition of tin catalyst decreased curing time and had negligible effect on sensitivity. LMG concentration should be at least as high as the bromoform, with ideal concentration being 2% wt. Gamma Knife SRS QA measurements of relative output and profile widths were within 2% of manufacturer’s values validated at commissioning, except the 4 mm collimator relative output which was within 3%. The gamma pass rate of Presage with SBRT was 73.7%, compared to 93.1% for EBT2 Gafchromic film. Conclusions: The Presage dosimeter in sheet form was capable of detecting radiation over all tested photon energies and chemical concentrations. The best sensitivity and photostability of the dosimeter were achieved with 2.5% wt. LMG and 8.2% wt. bromoform. Scanner used should not emit any UV radiation as it will expose the dosimeter, as with the Epson 10000 XL scanner

  10. TU-H-BRC-06: Temperature Simulation of Tungsten and W25Re Targets to Deliver High Dose Rate 10 MV Photons

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J; Trovati, S; Loo, B; Maxim, P; Fahrig, R [Stanford University School of Medicine, Stanford, California (United States); Borchard, P [Tibaray Inc, San Francisco, CA (United States)

    2016-06-15

    Purpose: To study the impact of electron beam size, target thickness, and target temperature on the ability of the flattening filter-free mode (FFF) treatment head to deliver high-dose-rate irradiations. Methods: The dose distribution and transient temperature of the X-ray target under 10 MeV electron beam with pulse length of 5 microseconds, and repetition rate of 1000 Hz was studied. A MCNP model was built to calculate the percentage depth dose (PPD) distribution in a water phantom at a distance of 100 cm. ANSYS software was used to run heat transfer simulations. The PPD and temperature for both tungsten and W25Re targets for different electron beam sizes (FHWM 0.2, 0.5, 1 and 2 mm) and target thickness (0.2 to 2 mm) were studied. Results: Decreasing the target thickness from 1 mm to 0.5 mm, caused a surface dose increase about 10 percent. For both target materials, the peak temperature was about 1.6 times higher for 0.5 mm electron beam compared to the 1 mm beam after reaching their equilibrium. For increasing target thicknesses, the temperature rise caused by the first pulse is similar for all thicknesses, however the temperature difference for subsequent pulses becomes larger until a constant ratio is reached. The target peak temperature after reaching equilibrium can be calculated by adding the steady state temperature and the amplitude of the temperature oscillation. Conclusion: This work indicates the potential to obtain high dose rate irradiation by selecting target material, geometry and electron beam parameters. W25Re may not outperformed tungsten when the target is thick due to its relatively low thermal conductivity. The electron beam size only affects the target temperature but not the PPD. Thin target is preferred to obtain high dose rate and low target temperature, however, the resulting high surface dose is a major concern. NIH funding:R21 EB015957-01; DOD funding:W81XWH-13-1-0165 BL, PM, PB, and RF are founders of TibaRay, Inc. BL is also a borad

  11. TU-H-BRC-06: Temperature Simulation of Tungsten and W25Re Targets to Deliver High Dose Rate 10 MV Photons

    International Nuclear Information System (INIS)

    Wang, J; Trovati, S; Loo, B; Maxim, P; Fahrig, R; Borchard, P

    2016-01-01

    Purpose: To study the impact of electron beam size, target thickness, and target temperature on the ability of the flattening filter-free mode (FFF) treatment head to deliver high-dose-rate irradiations. Methods: The dose distribution and transient temperature of the X-ray target under 10 MeV electron beam with pulse length of 5 microseconds, and repetition rate of 1000 Hz was studied. A MCNP model was built to calculate the percentage depth dose (PPD) distribution in a water phantom at a distance of 100 cm. ANSYS software was used to run heat transfer simulations. The PPD and temperature for both tungsten and W25Re targets for different electron beam sizes (FHWM 0.2, 0.5, 1 and 2 mm) and target thickness (0.2 to 2 mm) were studied. Results: Decreasing the target thickness from 1 mm to 0.5 mm, caused a surface dose increase about 10 percent. For both target materials, the peak temperature was about 1.6 times higher for 0.5 mm electron beam compared to the 1 mm beam after reaching their equilibrium. For increasing target thicknesses, the temperature rise caused by the first pulse is similar for all thicknesses, however the temperature difference for subsequent pulses becomes larger until a constant ratio is reached. The target peak temperature after reaching equilibrium can be calculated by adding the steady state temperature and the amplitude of the temperature oscillation. Conclusion: This work indicates the potential to obtain high dose rate irradiation by selecting target material, geometry and electron beam parameters. W25Re may not outperformed tungsten when the target is thick due to its relatively low thermal conductivity. The electron beam size only affects the target temperature but not the PPD. Thin target is preferred to obtain high dose rate and low target temperature, however, the resulting high surface dose is a major concern. NIH funding:R21 EB015957-01; DOD funding:W81XWH-13-1-0165 BL, PM, PB, and RF are founders of TibaRay, Inc. BL is also a borad

  12. SU-F-T-87: Comparison of Advanced Radiotherapy Techniques for Post- Mastectomy Breast Cancer Patients

    Energy Technology Data Exchange (ETDEWEB)

    Heins, D; Zhang, R [Louisiana State University, Baton Rouge, LA (United States); Hogstrom, K; Sanders, M [Mary Bird Perkins Cancer Center, Baton Rouge, LA (United States)

    2016-06-15

    Purpose: To determine if bolus electron conformal therapy (Bolus-ECT) combined with intensity modulated x-ray therapy (IMXT) and flattening filter free volumetric modulated arc therapy (FFF-VMAT (6x and 10x)) can maintain equal or better dose coverage than standard volumetric modulated arc therapy (Std-VMAT) while reducing doses to organs at risk (OARs). Methods: Bolus-ECT with IMXT, FFF-VMAT, and Std-VMAT treatment plans were produced for ten post-mastectomy radiotherapy (PMRT) patients previously treated at our clinic. The treatment plans were created on commercially available treatment planning system (TPS) and all completed treatment plans were reviewed and approved by a radiation oncologist. The plans were evaluated based on planning target volume (PTV) coverage, tumor control probability (TCP), dose homogeneity index (DHI), conformity index (CI), and dose to organs at risk (OAR). Results: All techniques produced clinically acceptable PMRT plans. Overall, Bolus-ECT with IMXT exhibited higher maximum dose compared to all VMAT techniques. Bolus-ECT with IMXT and FFF-VMAT10x had slightly improved TCP over FFF-VMAT6x and Std-VMAT. However, all VMAT techniques showed improved CI and DHI over Bolus-ECT with IMXT. All techniques showed very similar mean lung dose. Bolus-ECT with IMXT exhibited a reduced mean heart dose over Std-VMAT. Both FFF-VMAT techniques had higher mean heart dose compared to Std-VMAT. In addition, Bolus-ECT with IMXT was able to reduce mean dose to the contralateral breast compared to Std-VMAT and both FFF-VMAT techniques had comparable but slightly reduced dose compared to Std-VMAT. Conclusion: This work has shown that Bolus-ECT with IMXT produces clinically acceptable plans while reducing OAR doses. Both FFF-VMAT techniques are comparable to Std-VMAT with slight improvements. Even though all VMAT techniques produce more homogenous and conformal dose distributions, Bolus-ECT with IMXT is a viable option for treating post-mastectomy patients

  13. Monte Carlo validation of the TrueBeam 10XFFF phase–space files for applications in lung SABR

    International Nuclear Information System (INIS)

    Teke, Tony; Duzenli, Cheryl; Bergman, Alanah; Viel, Francis; Atwal, Parmveer; Gete, Ermias

    2015-01-01

    Purpose: To establish the clinical acceptability of universal Monte Carlo phase–space data for the 10XFFF (flattening filter free) photon beam on the Varian TrueBeam Linac, including previously unreported data for small fields, output factors, and inhomogeneous media. The study was particularly aimed at confirming the suitability for use in simulations of lung stereotactic ablative radiotherapy treatment plans. Methods: Monte Carlo calculated percent depth doses (PDDs), transverse profiles, and output factors for the TrueBeam 10 MV FFF beam using generic phase–space data that have been released by the Varian MC research team were compared with in-house measurements and published data from multiple institutions (ten Linacs from eight different institutions). BEAMnrc was used to create field size specific phase–spaces located underneath the jaws. Doses were calculated with DOSXYZnrc in a water phantom for fields ranging from 1 × 1 to 40 × 40 cm 2 . Particular attention was paid to small fields (down to 1 × 1 cm 2 ) and dose per pulse effects on dosimeter response for high dose rate 10XFFF beams. Ion chamber measurements were corrected for changes in ion collection efficiency (P ion ) with increasing dose per pulse. MC and ECLIPSE ANISOTROPIC ANALYTICAL ALGORITHM (AAA) calculated PDDs were compared to Gafchromic film measurement in inhomogeneous media (water, bone, lung). Results: Measured data from all machines agreed with Monte Carlo simulations within 1.0% and 1.5% for PDDs and in-field transverse profiles, respectively, for field sizes >1 × 1 cm 2 in a homogeneous water phantom. Agreements in the 80%–20% penumbra widths were better than 2 mm for all the fields that were compared. For all the field sizes considered, the agreement between their measured and calculated output factors was within 1.1%. Monte Carlo results for dose to water at water/bone, bone/lung, and lung/water interfaces as well as within lung agree with film measurements to within 2

  14. Toward a web-based real-time radiation treatment planning system in a cloud computing environment.

    Science.gov (United States)

    Na, Yong Hum; Suh, Tae-Suk; Kapp, Daniel S; Xing, Lei

    2013-09-21

    To exploit the potential dosimetric advantages of intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), an in-depth approach is required to provide efficient computing methods. This needs to incorporate clinically related organ specific constraints, Monte Carlo (MC) dose calculations, and large-scale plan optimization. This paper describes our first steps toward a web-based real-time radiation treatment planning system in a cloud computing environment (CCE). The Amazon Elastic Compute Cloud (EC2) with a master node (named m2.xlarge containing 17.1 GB of memory, two virtual cores with 3.25 EC2 Compute Units each, 420 GB of instance storage, 64-bit platform) is used as the backbone of cloud computing for dose calculation and plan optimization. The master node is able to scale the workers on an 'on-demand' basis. MC dose calculation is employed to generate accurate beamlet dose kernels by parallel tasks. The intensity modulation optimization uses total-variation regularization (TVR) and generates piecewise constant fluence maps for each initial beam direction in a distributed manner over the CCE. The optimized fluence maps are segmented into deliverable apertures. The shape of each aperture is iteratively rectified to be a sequence of arcs using the manufacture's constraints. The output plan file from the EC2 is sent to the simple storage service. Three de-identified clinical cancer treatment plans have been studied for evaluating the performance of the new planning platform with 6 MV flattening filter free beams (40 × 40 cm(2)) from the Varian TrueBeam(TM) STx linear accelerator. A CCE leads to speed-ups of up to 14-fold for both dose kernel calculations and plan optimizations in the head and neck, lung, and prostate cancer cases considered in this study. The proposed system relies on a CCE that is able to provide an infrastructure for parallel and distributed computing. The resultant plans from the cloud computing are

  15. Toward a web-based real-time radiation treatment planning system in a cloud computing environment

    International Nuclear Information System (INIS)

    Na, Yong Hum; Kapp, Daniel S; Xing, Lei; Suh, Tae-Suk

    2013-01-01

    To exploit the potential dosimetric advantages of intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT), an in-depth approach is required to provide efficient computing methods. This needs to incorporate clinically related organ specific constraints, Monte Carlo (MC) dose calculations, and large-scale plan optimization. This paper describes our first steps toward a web-based real-time radiation treatment planning system in a cloud computing environment (CCE). The Amazon Elastic Compute Cloud (EC2) with a master node (named m2.xlarge containing 17.1 GB of memory, two virtual cores with 3.25 EC2 Compute Units each, 420 GB of instance storage, 64-bit platform) is used as the backbone of cloud computing for dose calculation and plan optimization. The master node is able to scale the workers on an ‘on-demand’ basis. MC dose calculation is employed to generate accurate beamlet dose kernels by parallel tasks. The intensity modulation optimization uses total-variation regularization (TVR) and generates piecewise constant fluence maps for each initial beam direction in a distributed manner over the CCE. The optimized fluence maps are segmented into deliverable apertures. The shape of each aperture is iteratively rectified to be a sequence of arcs using the manufacture’s constraints. The output plan file from the EC2 is sent to the simple storage service. Three de-identified clinical cancer treatment plans have been studied for evaluating the performance of the new planning platform with 6 MV flattening filter free beams (40 × 40 cm 2 ) from the Varian TrueBeam TM STx linear accelerator. A CCE leads to speed-ups of up to 14-fold for both dose kernel calculations and plan optimizations in the head and neck, lung, and prostate cancer cases considered in this study. The proposed system relies on a CCE that is able to provide an infrastructure for parallel and distributed computing. The resultant plans from the cloud computing are

  16. SU-D-BRB-04: Plan Quality Comparison of Intracranial Stereotactic Radiosurgery (SRS) for Gamma Knife and VMAT Treatments

    Energy Technology Data Exchange (ETDEWEB)

    Keeling, V; Algan, O; Ahmad, S; Hossain, S [University of Oklahoma Health Sciences Center, Oklahoma City, OK (United States)

    2015-06-15

    Purpose: To compare treatment plan quality of intracranial stereotactic radiosurgery (SRS) for VMAT (RapidArc) and Gamma Knife (GK) systems. Methods: Ten patients with 24 tumors (seven with 1–2 and three with 4–6 lesions), previously treated with GK 4C (prescription doses ranging from 14–23 Gy) were re-planned for RapidArc. Identical contour sets were kept on MRI images for both plans with tissues assigned a CT number of zero. RapidArc plans were performed using 6 MV flattening-filter-free (FFF) beams with dose rate of 1400 MU/minute using two to eight arcs with the following combinations: 2 full coplanar arcs and the rest non-coplanar half arcs. Beam selection was based on target depth. Areas that penetrated more than 10 cm of tissue were avoided by creating smaller arcs or using avoidance sectors in optimization. Plans were optimized with jaw tracking and a high weighting to the normal-brain-tissue and Normal-Tissue-Objective without compromising PTV coverage. Plans were calculated on a 1 mm grid size using AAA algorithm and then normalized so that 99% of each target volume received the prescription dose. Plan quality was assessed by target coverage using Paddick Conformity Index (PCI), sparing of normal-brain-tissue through analysis of V4, V8, and V12 Gy, and integral dose. Results: In all cases critical structure dose criteria were met. RapidArc had a higher PCI than GK plans for 23 out of 24 lesions. The average PCI was 0.76±0.21 for RapidArc and 0.46±0.20 for GK plans (p≤0.001), respectively. Integral dose and normal-brain-tissue doses for all criteria were lower for RapidArc in nearly all patients. The average ratio of GK to RapidArc plans was 1.28±0.27 (p=0.018), 1.31±0.25 (p=0.017), 1.81±0.43 (p=0.005), and 1.50±0.61 (p=0.006) for V4, V8, and V12 Gy, and integral dose, respectively. Conclusion: VMAT was capable of producing higher quality treatment plans than GK when using optimal beam geometries and proper optimization techniques.

  17. SU-G-TeP2-03: Comparison of Standard Dosimetry Protocol in Japan and AAPM TG-51 Addendum in Order to Establish Optimal Dosimetry for FFF Beam

    Energy Technology Data Exchange (ETDEWEB)

    Matsunaga, T; Adachi, Y [Department of Radiology, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka (Japan); Hayashi, N [Graduate School of Health Sciences, Fujita Health University, Tayoake, Aichi (Japan); Nozue, M [Department of Radiation Oncology, Seirei Hamamtsu General Hospital, Hamamatsu, Shizuoka (Japan)

    2016-06-15

    Purpose: Japan Standard Dosimetry of Absorbed dose to water in external beam radiotherapy (JSDP12) is widely used to measure radiation dose in radiotherapy. However, JSDP12 does not take flattening-filter-free (FFF) beam into consideration. In addition, JSDP12 applied TPR20,10 for dose quality index for photon beam. The purpose of this study is to compare JSDP12 with AAPM TG-51 addendum in order to establish optimal dosimetry procedure for FFF beam. Method: We evaluated the ion-recombination factor (ks) and the correction factor of radial beam profile (Prp) in FFF beam dosimetry. The ks was introduced by 2 voltages method and verified by Jaffe’s plot. The Prp was given by both film measurement and calculation of treatment planning system, and compared them. Next, we compared the dose quality indexes (kQ) between TPR20,10 method and PDD(10)x method. Finally we considered optimal dosimetry protocol for FFF photon beam using JSDP12 with referring TG-51 addendum protocols. The FFF photon beams of 6 MV (6X-FFF) and 10 MV (10X-FFF) from TrueBeam were investigated in this study. Results: The ks for 6X-FFF and 10X-FFF beams were 1.005 and 1.010, respectively. The Prp of 0.6 cc ionization chamber for 6X-FFF and 10X-FFF beams (Film, TPS) were (1.004, 1.008) and (1.005, 1.008), respectively. The kQ for 6X-FFF and 10X-FFF beams (JSDP12, TG-51 addendum) were (0.9950, 0.9947) and (0.9851, 0.9845), respectively. The most effective factor for uncertainty in FFF photon beam measurement was Prp for JSDP12 formalism. Total dosimetric differences between JSDP12 and TG-51 addendum for 6X-FFF and 10X-FFF were -0.47% and -0.73%, respectively. Conclusion: The total dosimetric difference between JSDP12 and TG-51 addendum was within 1%. The introduction of kQ given by JSDP is feasible for FFF photon beam dosimetry. However, we think Prp should be considered for optimal dosimetry procedure even if JSDP12 is used for FFF photon beam dosimetry.

  18. SU-E-T-338: Dosimetric Study of Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiation Therapy (IMRT) for Stereotactic Body Radiation Therapy (SBRT) in Early Stage Lung Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, I; Quinn, K; Seebach, A; Wang, H [OSF Saint Anthony Medical Center, Rockford, IL (United States); Yah, R [University of Illinois College of Medicine at Rockford, Rockford, IL (United States)

    2015-06-15

    Purpose: This study evaluates the dosimetric differences using volumetric modulated arc therapy (VMAT) in patients previously treated with intensity modulated radiation therapy IMRT for stereotactic body radiotherapy (SBRT) in early stage lung cancer. Methods: We evaluated 9 consecutive medically inoperable lung cancer patients at the start of the SBRT program who were treated with IMRT from November 2010 to October 2011. These patients were treated using 6 MV energy. The 9 cases were then re-planned with VMAT performed with arc therapy using 6 MV flattening filter free (FFF) energy with the same organs at risk (OARS) constraints. Data collected for the treatment plans included target coverage, beam on time, dose to OARS and gamma pass rate. Results: Five patients were T1N0 and four patients were T2N0 with all tumors less than 5 cm. The average GTV was 13.02 cm3 (0.83–40.87) and average PTV was 44.65 cm3 (14.06–118.08). The IMRT plans had a mean of 7.2 angles (6–9) and 5.4 minutes (3.6–11.1) per plan. The VMAT plans had a mean of 2.8 arcs (2–3) and 4.0 minutes (2.2–6.0) per plan. VMAT had slightly more target coverage than IMRT with average increase in D95 of 2.68% (1.24–5.73) and D99 of 3.65% (0.88–8.77). VMAT produced lower doses to all OARs. The largest reductions were in maximum doses to the spinal cord with an average reduction of 24.1%, esophagus with an average reduction of 22.1%, and lung with an average reduction in the V20 of 16.3% The mean gamma pass rate was 99.8% (99.2–100) at 3 mm and 3% for VMAT with comparable values for IMRT. Conclusion: These findings suggest that using VMAT for SBRT in early stage lung cancer is superior to IMRT in terms of dose coverage, OAR dose and a lower treatment delivery time with a similar gamma pass rate.

  19. SU-E-T-508: End to End Testing of a Prototype Eclipse Module for Planning Modulated Arc Therapy On the Siemens Platform

    International Nuclear Information System (INIS)

    Huang, L; Sarkar, V; Spiessens, S; Rassiah-Szegedi, P; Huang, Y; Salter, B; Zhao, H; Szegedi, M

    2014-01-01

    Purpose: The latest clinical implementation of the Siemens Artiste linac allows for delivery of modulated arcs (mARC) using full-field flattening filter free (FFF) photon beams. The maximum doserate of 2000 MU/min is well suited for high dose treatments such as SBRT. We tested and report on the performance of a prototype Eclipse TPS module supporting mARC capability on the Artiste platform. Method: our spine SBRT patients originally treated with 12/13 field static-gantry IMRT (SGIMRT) were chosen for this study. These plans were designed to satisfy RTOG0631 guidelines with a prescription of 16Gy in a single fraction. The cases were re-planned as mARC plans in the prototype Eclipse module using the 7MV FFF beam and required to satisfy RTOG0631 requirements. All plans were transferred from Eclipse, delivered on a Siemens Artiste linac and dose-validated using the Delta4 system. Results: All treatment plans were straightforwardly developed, in timely fashion, without challenge or inefficiency using the prototype module. Due to the limited number of segments in a single arc, mARC plans required 2-3 full arcs to yield plan quality comparable to SGIMRT plans containing over 250 total segments. The average (3%/3mm) gamma pass-rate for all arcs was 98.5±1.1%, thus demonstrating both excellent dose prediction by the AAA dose algorithm and excellent delivery fidelity. Mean delivery times for the mARC plans(10.5±1.7min) were 50-70% lower than the SGIMRT plans(26±2min), with both delivered at 2000 MU/min. Conclusion: A prototype Eclipse module capable of planning for Burst Mode modulated arc delivery on the Artiste platform has been tested and found to perform efficiently and accurately for treatment plan development and delivered-dose prediction. Further investigation of more treatment sites is being carried out and data will be presented

  20. The sensitivity of gamma-index method to the positioning errors of high-definition MLC in patient-specific VMAT QA for SBRT

    International Nuclear Information System (INIS)

    Kim, Jung-in; Park, So-Yeon; Kim, Hak Jae; Kim, Jin Ho; Ye, Sung-Joon; Park, Jong Min

    2014-01-01

    To investigate the sensitivity of various gamma criteria used in the gamma-index method for patient-specific volumetric modulated arc therapy (VMAT) quality assurance (QA) for stereotactic body radiation therapy (SBRT) using a flattening filter free (FFF) photon beam. Three types of intentional misalignments were introduced to original high-definition multi-leaf collimator (HD-MLC) plans. The first type, referred to Class Out, involved the opening of each bank of leaves. The second type, Class In, involved the closing of each bank of leaves. The third type, Class Shift, involved the shifting of each bank of leaves towards the ground. Patient-specific QAs for the original and the modified plans were performed with MapCHECK2 and EBT2 films. The sensitivity of the gamma-index method using criteria of 1%/1 mm, 1.5%/1.5 mm, 1%/2 mm, 2%/1 mm and 2%/2 mm was investigated with absolute passing rates according to the magnitudes of MLCs misalignments. In addition, the changes in dose-volumetric indicators due to the magnitudes of MLC misalignments were investigated. The correlations between passing rates and the changes in dose-volumetric indicators were also investigated using Spearman’s rank correlation coefficient (γ). The criterion of 2%/1 mm was able to detect Class Out and Class In MLC misalignments of 0.5 mm and Class Shift misalignments of 1 mm. The widely adopted clinical criterion of 2%/2 mm was not able to detect 0.5 mm MLC errors of the Class Out or Class In types, and also unable to detect 3 mm Class Shift errors. No correlations were observed between dose-volumetric changes and gamma passing rates (γ < 0.8). Gamma criterion of 2%/1 mm was found to be suitable as a tolerance level with passing rates of 90% and 80% for patient-specific VMAT QA for SBRT when using MapCHECK2 and EBT2 film, respectively

  1. SU-E-J-126: An Online Replanning Method for FFF Beams Without Couch Shift

    International Nuclear Information System (INIS)

    Ahunbay, E; Ates, O; Li, X

    2015-01-01

    Purpose: In a situation that couch shift for patient positioning is not preferred or prohibited (e.g., MR-Linac), segment aperture morphing (SAM) can address target dislocation and deformation. For IMRT/VMAT with flattening filter free (FFF) beams, however, SAM method would lead to an adverse translational dose effect due to the beam unflattening. Here we propose a new 2-step process to address both the translational effect of FFF beams and the target deformation. Methods: The replanning method consists of an offline and an online steps. The offline step is to create a series of pre-shifted plans (PSP) obtained by a so called “warm start” optimization (starting optimization from the original plan, rather from scratch) at a series of isocenter shifts with fixed distance (e.g. 2 cm, at x,y,z = 2,0,0 ; 2,2,0 ; 0,2,0; …;− 2,0,0). The PSPs all have the same number of segments with very similar shapes, since the warm-start optimization only adjusts the MLC positions instead of regenerating them. In the online step, a new plan is obtained by linearly interpolating the MLC positions and the monitor units of the closest PSPs for the shift determined from the image of the day. This two-step process is completely automated, and instantaneously fast (no optimization or dose calculation needed). The previously-developed SAM algorithm is then applied for daily deformation. We tested the method on sample prostate and pancreas cases. Results: The two-step interpolation method can account for the adverse dose effects from FFF beams, while SAM corrects for the target deformation. The whole process takes the same time as the previously reported SAM process (5–10 min). Conclusion: The new two-step method plus SAM can address both the translation effects of FFF beams and target deformation, and can be executed in full automation requiring no additional time from the SAM process. This research was supported by Elekta inc. (Crawley, UK)

  2. SU-C-201-02: Dosimetric Verification of SBRT with FFF-VMAT Using a 3-D Radiochromic/Optical-CT Dosimetry System

    Energy Technology Data Exchange (ETDEWEB)

    Na, Y; Black, P; Wuu, C [Columbia University, New York, NY (United States); Adamovics, J [Department of Chemistry and Biology, Rider University, Skillman, NJ (United States)

    2016-06-15

    Purpose: With an increasing use of small field size and high dose rate irradiation in the advances of radiotherapy techniques, such as stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS), an in-depth quality assurance (QA) system is required. The purpose of this study is to investigate a high resolution optical CT-based 3D radiochromic dosimetry system for SBRT with intensity modulated radiotherapy (IMRT) and flattening filter free (FFF) volumetric modulated arc therapy (VMAT). Methods: Cylindrical PRESAGE radiochromic dosimeters of 10cm height and 11cm diameter were used to validate SBRT. Four external landmarks were placed on the surface of each dosimeter to define the isocenter of target. SBRT plans were delivered using a Varian TrueBeam™ linear accelerator (LINAC). Three validation plans, SBRT with IMRT (6MV 600MU/min), FFF-VMAT (10MV 2400MU/min), and mixed FFF-VMAT (6MV 1400MU/min, 10MV 2400MU/min), were delivered to the PRESAGE dosimeters. Each irradiated PRESAGE dosimeter was scanned using a single laser beam optical CT scanner and reconstructed with a 1mm × 1mm high spatial resolution. The comparison of measured dose distributions of irradiated PRESAGE dosimeters to those calculated by Pinnacle{sup 3} treatment planning system (TPS) were performed with a 10% dose threshold, 3% dose difference (DD), and 3mm distance-to-agreement (DTA) Gamma criteria. Results: The average pass rates for the gamma comparisons between PRESAGE and Pinnacle{sup 3} in the transverse, sagittal, coronal planes were 94.6%, 95.9%, and 96.4% for SBRT with IMRT, FFF-VMAT, and mixed FFF-VMAT plans, respectively. A good agreement of the isodose distributions of those comparisons were shown at the isodose lines 50%, 70%, 80%, 90% and 98%. Conclusion: This study demonstrates the feasibility of the high resolution optical CT-based 3D radiochromic dosimetry system for validation of SBRT with IMRT and FFF-VMAT. This dosimetry system offers higher precision QA with 3D

  3. TU-CD-304-08: Feasibility of a VMAT-Based Spatially Fractionated Grid Therapy Technique

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, B; Liu, M; Huang, Y; Kim, J; Brown, S; Siddiqui, F; Chetty, I; Wen, N [Henry Ford Health System, Detroit, MI (United States); Jin, J [Georgia Regents University, Augusta, GA (Georgia)

    2015-06-15

    Purpose: Grid therapy (GT) uses spatially modulated radiation doses to treat large tumors without significant toxicities. Incorporating 3D conformal-RT or IMRT improved single-field GT by reducing dose to normal tissues spatially through the use of multiple fields. The feasibility of a MLC-based, inverse-planned multi-field GT technique has been demonstrated. Volumetric modulated arc therapy (VMAT) provides conformal dose distributions with the additional potential advantage of reduced treatment times. In this study, we characterize a new VMAT-based GT (VMAT-GT) technique with respect to its deliverability and dosimetric accuracy. Methods: A lattice of 5mm-diameter spheres was created as the boost volume within a large treatment target. A simultaneous boost VMAT (RapidArc) plan with 8Gy to the target and 20Gy to the boost volume was generated using the Eclipse treatment planning system (AAA-v11). The linac utilized HD120 MLC and 6MV flattening-filter free beam. Four non-coplanar arcs, with couch angles at 0, 45, 90 and 317° were used. Collimator angles were at 45 and 315°. The plan was mapped to a phantom. Calibrated Gafchromic EBT3 films were used to measure the delivered dose. Results: The VMAT plan generated a highly spatially modulated dose distribution in the target. D95%, D50%, D5% for the spheres and the targets in Gy were 18.9, 20.6, 23 and 8.0, 9.6, 14.8, respectively. D50% for a 1cm ring 1cm outside the target was 3.0Gy. The peak-to-valley ratio of this technique is comparable to previously proposed techniques, but the MUs were reduced by almost 50%. Film dosimetry showed good agreement between calculated and delivered dose, with an overall gamma passing rate of >98% (3% and 1mm). The point dose differences at sphere centers varied from 2–8%. Conclusion: The deliverability and dose calculation accuracy of the proposed VMAT-GT technique demonstrates that ablative radiation doses are deliverable to large tumors safely and efficiently.

  4. SU-E-J-126: An Online Replanning Method for FFF Beams Without Couch Shift

    Energy Technology Data Exchange (ETDEWEB)

    Ahunbay, E; Ates, O; Li, X [Medical College of Wisconsin, Milwaukee, WI (United States)

    2015-06-15

    Purpose: In a situation that couch shift for patient positioning is not preferred or prohibited (e.g., MR-Linac), segment aperture morphing (SAM) can address target dislocation and deformation. For IMRT/VMAT with flattening filter free (FFF) beams, however, SAM method would lead to an adverse translational dose effect due to the beam unflattening. Here we propose a new 2-step process to address both the translational effect of FFF beams and the target deformation. Methods: The replanning method consists of an offline and an online steps. The offline step is to create a series of pre-shifted plans (PSP) obtained by a so called “warm start” optimization (starting optimization from the original plan, rather from scratch) at a series of isocenter shifts with fixed distance (e.g. 2 cm, at x,y,z = 2,0,0 ; 2,2,0 ; 0,2,0; …;− 2,0,0). The PSPs all have the same number of segments with very similar shapes, since the warm-start optimization only adjusts the MLC positions instead of regenerating them. In the online step, a new plan is obtained by linearly interpolating the MLC positions and the monitor units of the closest PSPs for the shift determined from the image of the day. This two-step process is completely automated, and instantaneously fast (no optimization or dose calculation needed). The previously-developed SAM algorithm is then applied for daily deformation. We tested the method on sample prostate and pancreas cases. Results: The two-step interpolation method can account for the adverse dose effects from FFF beams, while SAM corrects for the target deformation. The whole process takes the same time as the previously reported SAM process (5–10 min). Conclusion: The new two-step method plus SAM can address both the translation effects of FFF beams and target deformation, and can be executed in full automation requiring no additional time from the SAM process. This research was supported by Elekta inc. (Crawley, UK)

  5. The impact of the oxygen scavenger on the dose-rate dependence and dose sensitivity of MAGIC type polymer gels

    Science.gov (United States)

    Khan, Muzafar; Heilemann, Gerd; Kuess, Peter; Georg, Dietmar; Berg, Andreas

    2018-03-01

    Recent developments in radiation therapy aimed at more precise dose delivery along with higher dose gradients (dose painting) and more efficient dose delivery with higher dose rates e.g. flattening filter free (FFF) irradiation. Magnetic-resonance-imaging based polymer gel dosimetry offers 3D information for precise dose delivery techniques. Many of the proposed polymer gels have been reported to exhibit a dose response, measured as relaxation rate ΔR2(D), which is dose rate dependent. A lack of or a reduced dose-rate sensitivity is very important for dosimetric accuracy, especially with regard to the increasing clinical use of FFF irradiation protocols with LINACs at high dose rates. Some commonly used polymer gels are based on Methacrylic-Acid-Gel-Initiated-by-Copper (MAGIC). Here, we report on the dose sensitivity (ΔR2/ΔD) of MAGIC-type gels with different oxygen scavenger concentration for their specific dependence on the applied dose rate in order to improve the dosimetric performance, especially for high dose rates. A preclinical x-ray machine (‘Yxlon’, E  =  200 kV) was used for irradiation to cover a range of dose rates from low \\dot{D} min  =  0.6 Gy min-1 to high \\dot{D} max  =  18 Gy min-1. The dose response was evaluated using R2-imaging of the gel on a human high-field (7T) MR-scanner. The results indicate that all of the investigated dose rates had an impact on the dose response in polymer gel dosimeters, being strongest in the high dose region and less effective for low dose levels. The absolute dose rate dependence \\frac{(Δ R2/Δ D)}{Δ \\dot{D}} of the dose response in MAGIC-type gel is significantly reduced using higher concentrations of oxygen scavenger at the expense of reduced dose sensitivity. For quantitative dose evaluations the relative dose rate dependence of a polymer gel, normalized to its sensitivity is important. Based on this normalized sensitivity the dose rate sensitivity was reduced distinctly

  6. Benchmarking the mARC performance. Treatment time and dosimetric linearity

    Energy Technology Data Exchange (ETDEWEB)

    Dzierma, Yvonne; Nuesken, Frank; Licht, Norbert; Ruebe, Christian [Universitaetsklinikum des Saarlandes, Homburg/Saar (Germany). Klinik fuer Strahlentherapie und Radioonkologie

    2016-07-01

    The mARC technique is a hybrid rotational IMRT modality operating in ''burst mode''. While it is generally assumed that it will be slower than VMAT, the real limits of operation have not been defined so far. We here present the first systematic study of the technical limits on mARC treatment. The following scenarios are considered: 18, 30, 36 or 45 arclets per rotation (spacing between 20 and 8 ), flat and flattening-filter-free (FFF) energy, arclet width 4 or 2 , from 1 MU/arclet to 1000 MU/plan. All scenarios are irradiated, treatment times are measured and treatment parameters reported. Dose linearity was assessed by point dose measurements of the 18 arclet plans with 1-30 MU per arclet. Minimum treatment times (no MLC movement, few MUs) depend strongly on the number of arclets per rotation (1 minute for 18 arclets to 1:50 min for 45 arclets), and rise linearly with MU/arclets after a given cut-off value depending on scenario, arclet width and available maximum dose rate. MLC movement adds up to 2 minutes of treatment time, but generally less (ca. 45 seconds in realistic plans). The rules by which irradiation parameters are selected by the firmware can be partly discovered. The choice of dose rate is most clearly defined. For the flat 6 MV energy, the highest available dose rate (300 MU/min) is always applied. For FFF 7 MV dose rate is reduced for arclets with few MUs, so that an arclet is irradiated in no less than 0.3 s. Only for the case of 1 MU/arclet can this constraint not be met (the technical limit on the dose rate if 500 MU/min for FFF 7 MV). In this case, dosimetric linearity is reduced. In all other instances, deviations from linearity at low MU remain below 2%. Treatment times of down to 90 seconds are technically achievable for treatment with FFF beams using up to 36 arclets per rotation (arclet spacing every 10 ) for up to 900 MU/plan, comparable to VMAT treatment times. The values provided here are meant to serve as a reference

  7. Quality of tri-Co-60 MR-IGRT treatment plans in comparison with VMAT treatment plans for spine SABR.

    Science.gov (United States)

    Choi, Chang Heon; Park, So-Yeon; Kim, Jung-In; Kim, Jin Ho; Kim, Kyubo; Carlson, Joel; Park, Jong Min

    2017-02-01

    To investigate the plan quality of tri-Co-60 intensity-modulated radiation therapy (IMRT) plans for spine stereotactic ablative radiotherapy (SABR). A total of 20 patients with spine metastasis were retrospectively selected. For each patient, a tri-Co-60 IMRT plan and a volumetric-modulated arc therapy (VMAT) plan were generated. The spinal cords were defined based on MR images for the tri-Co-60 IMRT, while isotropic 1-mm margins were added to the spinal cords for the VMAT plans. The VMAT plans were generated with 10-MV flattening filter-free photon beams of TrueBeam STx ™ (Varian Medical Systems, Palo Alto, CA), while the tri-Co-60 IMRT plans were generated with the ViewRay ™ system (ViewRay inc., Cleveland, OH). The initial prescription dose was 18 Gy (1 fraction). If the tolerance dose of the spinal cord was not met, the prescription dose was reduced until the spinal cord tolerance dose was satisfied. The mean dose to the target volumes, conformity index and homogeneity index of the VMAT and tri-Co-60 IMRT were 17.8 ± 0.8 vs 13.7 ± 3.9 Gy, 0.85 ± 0.20 vs 1.58 ± 1.29 and 0.09 ± 0.04 vs 0.24 ± 0.19, respectively. The integral doses and beam-on times were 16,570 ± 1768 vs 22,087 ± 2.986 Gy cm 3 and 3.95 ± 1.13 vs 48.82 ± 10.44 min, respectively. The tri-Co-60 IMRT seems inappropriate for spine SABR compared with VMAT. Advances in knowledge: For spine SABR, the tri-Co-60 IMRT is inappropriate owing to the large penumbra, large leaf width and low dose rate of the ViewRay system.

  8. A novel implementation of mARC treatment for non-dedicated planning systems using converted IMRT plans

    International Nuclear Information System (INIS)

    Dzierma, Yvonne; Nuesken, Frank; Licht, Norbert; Ruebe, Christian

    2013-01-01

    The modulated arc (mARC) technique has recently been introduced by Siemens as an analogue to VMAT treatment. However, up to now only one certified treatment planning system supports mARC planning. We therefore present a conversion algorithm capable of converting IMRT plans created by any treatment planning system into mARC plans, with the hope of expanding the availability of mARC to a larger range of clinical users and researchers. As additional advantages, our implementation offers improved functionality for planning hybrid arcs and provides an equivalent step-and-shoot plan for each mARC plan, which can be used as a back-up concept in institutions where only one linac is equipped with mARC. We present a feasibility study to outline a practical implementation of mARC plan conversion using Philips Pinnacle and Prowess Panther. We present examples for three different kinds of prostate and head-and-neck plans, for 6 MV and flattening-filter-free (FFF) 7 MV photon energies, which are dosimetrically verified. It is generally more difficult to create good quality IMRT plans in Pinnacle using a large number of beams and few segments. We present different ways of optimization as examples. By careful choosing the beam and segment arrangement and inversion objectives, we achieve plan qualities similar to our usual IMRT plans. The conversion of the plans to mARC format yields functional plans, which can be irradiated without incidences. Absolute dosimetric verification of both the step-and-shoot and mARC plans by point dose measurements showed deviations below 5% local dose, mARC plans deviated from step-and-shoot plans by no more than 1%. The agreement between GafChromic film measurements of planar dose before and after mARC conversion is excellent. The comparison of the 3D dose distribution measured by PTW Octavius 729 2D-Array with the step-and-shoot plans and with the TPS is well above the pass criteria of 90% of the points falling within 5% local dose and 3 mm distance

  9. SU-E-T-485: Investigation of a Synthetic Diamond Detector for Tomotherapy Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Knill, C; Nalichowski, A; Halford, R [Karmanos Cancer Institute, Detroit, MI (United States); Zakjevskii, V; Zhuang, L [Wayne State University School of Medicine, Detroit, MI (United States); Snyder, M; Burmeister, J [Karmanos Cancer Institute, Detroit, MI (United States); Wayne State University School of Medicine, Detroit, MI (United States)

    2014-06-01

    Purpose: Tomotherapy treatments are characterized by rotational deliveries of flattening-filter free fields resulting in high-gradient dose distributions. Small volume, rotationally independent detectors are needed for accurate dosimetry. PTWs microDiamond detector, with its small sensitive volume (0.004mm{sup 3}), could potentially be an ideal detector for Tomotherapy. The microDiamond detector was tested against a small volume Exradin A1SL ion chamber for Tomotherapy open-field and IMRT commissioning measurements. Methods: Custom detector holders were fabricated to allow A1SL and microDiamond measurements in the Tomotherapy Cheese phantom and a square solid water phantom. The microDiamond rotational dependence within the Tomotherapy phantom was tested by incrementally rotating the detector in between static-gantry angle Tomotherapy irradiations. Longitudinal Tomotherapy profiles, for all field sizes, were measured with the microDiamond and A1SL detectors at 1.5cm depth in the square phantom, and compared to film. Detector axes were aligned parallel to table motion. Per TG-119 recommendations, both detectors were calibrated to known doses in phantoms and used to measure high-dose points in TG-119 H and N and Prostate plans. The measurements were compared to the treatment planning system and subsequently compared to published TG-119 confidence limits. Results: The microDiamond angular dependence was less than 0.5%. The average difference between the detectors and film-measured longitudinal profile 80–20% penumbras were 0.03+/-0.04mm and 1.36+/-0.22mm for the microDiamond and A1SL, respectively. The average difference between the detector and filmmeasured field sizes were 0.07+/-0.01mm and 0.09+/-0.02mm for the microDiamond and A1SL, respectively. The measured confidence limits were 0.023 and 0.015 for microDiamond and A1SL, respectively. TG-119 reported a confidence limit of 0.034. Conclusion: The microDiamond measured open-field longitudinal Tomotherapy profiles

  10. SU-E-T-533: Evaluation of Dose Calculation Accuracy for Small Elongated Targets On the Edge Linac

    International Nuclear Information System (INIS)

    Qin, Y; Wen, N; Snyder, K; Huang, Y; Zhao, B; Bellon, M; Li, H; Song, K; Kim, J; Gordon, J; Chetty, I

    2014-01-01

    Purpose: To evaluate output factors and dose calculation accuracy on a novel SRS linear accelerator, the Edge (Varian), for treatments of small, elongated targets using flattening filter free (FFF) beam. Methods: Total scatter/output factors (OF’s) for 24 elongated, small, high definition multi-leaf collimator (HDMLC)-defined fields were measured on the Edge machine using 6X FFF beam. 3 detectors were used in water tank: CC01 ion chamber (active volume 10cc), stereotactic photon diode (SFD) (active diameter 0.6mm, active thickness 0.06mm), Edge detector (active volume 0.0019cc). The 24 MLC apertures have widths ranging from 5 to 20mm and length/width ratio from 0.25 to 5. Readings were cross calibrated with CC04 at field size 3×3 cm. A beam model was developed using commissioning measurements for treatment planning in Eclipse (AAA, version 11). One representative patient case (IMRT, target volume 0.2cc, 4×4×14mm) was calculated using AAA 11 and delivered on the Edge. Results: Due to volume averaging effects, CC01 readings were 11.2±0.9% lower than SFD readings for 5mm field sizes. The Edge diode showed a uniform over-response of 2.6±0.7% compared to SFD. Calculation using AAA v11 showed the best agreement with SFD measurements (2.4±1.7% lower than SFD). The largest difference between AAA v11 and SFD occurs at 5mm field sizes. For the patient plan, dose delivered on Edge was measured to be 2.2% higher than AAA v11 calculation. Conclusion: Cross-calibrated SFD output measurements presented the best agreement with commissioned AAA v11 beam model. Field sizes smaller than 1cm posed challenges to both the detectors and the calculation algorithm. For the representative patient with small elongated target, AAA v11 and measurements agreed within ~2% on the Edge linac. Although encouraging, a more comprehensive study is required to validate the overall algorithmic accuracy

  11. Monte Carlo validation of the TrueBeam 10XFFF phase–space files for applications in lung SABR

    Energy Technology Data Exchange (ETDEWEB)

    Teke, Tony, E-mail: tteke2@bccancer.bc.ca [Medical Physics, BC Cancer Agency—Centre for the Southern Interior, Kelowna, British Columbia V1Y 5L3 (Canada); Duzenli, Cheryl; Bergman, Alanah; Viel, Francis; Atwal, Parmveer; Gete, Ermias [Medical Physics, BC Cancer Agency—Vancouver Centre, Vancouver, British Columbia V5Z 4E6 (Canada)

    2015-12-15

    Purpose: To establish the clinical acceptability of universal Monte Carlo phase–space data for the 10XFFF (flattening filter free) photon beam on the Varian TrueBeam Linac, including previously unreported data for small fields, output factors, and inhomogeneous media. The study was particularly aimed at confirming the suitability for use in simulations of lung stereotactic ablative radiotherapy treatment plans. Methods: Monte Carlo calculated percent depth doses (PDDs), transverse profiles, and output factors for the TrueBeam 10 MV FFF beam using generic phase–space data that have been released by the Varian MC research team were compared with in-house measurements and published data from multiple institutions (ten Linacs from eight different institutions). BEAMnrc was used to create field size specific phase–spaces located underneath the jaws. Doses were calculated with DOSXYZnrc in a water phantom for fields ranging from 1 × 1 to 40 × 40 cm{sup 2}. Particular attention was paid to small fields (down to 1 × 1 cm{sup 2}) and dose per pulse effects on dosimeter response for high dose rate 10XFFF beams. Ion chamber measurements were corrected for changes in ion collection efficiency (P{sub ion}) with increasing dose per pulse. MC and ECLIPSE ANISOTROPIC ANALYTICAL ALGORITHM (AAA) calculated PDDs were compared to Gafchromic film measurement in inhomogeneous media (water, bone, lung). Results: Measured data from all machines agreed with Monte Carlo simulations within 1.0% and 1.5% for PDDs and in-field transverse profiles, respectively, for field sizes >1 × 1 cm{sup 2} in a homogeneous water phantom. Agreements in the 80%–20% penumbra widths were better than 2 mm for all the fields that were compared. For all the field sizes considered, the agreement between their measured and calculated output factors was within 1.1%. Monte Carlo results for dose to water at water/bone, bone/lung, and lung/water interfaces as well as within lung agree with film

  12. Refinement of MLC modeling improves commercial QA dosimetry system for SRS and SBRT patient-specific QA.

    Science.gov (United States)

    Hillman, Yair; Kim, Josh; Chetty, Indrin; Wen, Ning

    2018-04-01

    Mobius 3D (M3D) provides a volumetric dose verification of the treatment planning system's calculated dose using an independent beam model and a collapsed cone convolution superposition algorithm. However, there is a lack of investigation into M3D's accuracy and effectiveness for stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) quality assurance (QA). Here, we collaborated with the vendor to develop a revised M3D beam model for SRS/SBRT cases treated with a 6X flattening filter-free (FFF) beam and high-definition multiple leaf collimator (HDMLC) on an Edge linear accelerator. Eighty SRS/SBRT cases, planned with AAA dose algorithm and validated with Gafchromic film, were compared to M3D dose calculations using 3D gamma analysis with 2%/2 mm gamma criteria and a 10% threshold. A revised beam model was developed by refining the HD-MLC model in M3D to improve small field dose calculation accuracy and beam profile agreement. All cases were reanalyzed using the revised beam model. The impact of heterogeneity corrections for lung cases was investigated by applying lung density overrides to five cases. For the standard and revised beam models, respectively, the mean gamma passing rates were 94.6% [standard deviation (SD): 6.1%] and 98.0% [SD: 1.7%] (for the overall patient), 88.2% [SD: 17.3%] and 93.8% [SD: 6.8%] (for the brain PTV), 71.4% [SD: 18.4%] and 81.5% [SD: 14.3%] (for the lung PTV), 83.3% [SD: 16.7%] and 67.9% [SD: 23.0%] (for the spine PTV), and 78.6% [SD: 14.0%] and 86.8% [SD: 12.5%] (for the PTV of all other sites). The lung PTV mean gamma passing rates improved from 74.1% [SD: 7.5%] to 89.3% [SD: 7.2%] with the lung density overridden. The revised beam model achieved an output factor within 3% of plastic scintillator measurements for 2 × 2 cm 2 MLC field size, but larger discrepancies are still seen for smaller field sizes which necessitate further improvement of the beam model. Special attention needs to be paid to small field

  13. SU-F-T-476: Performance of the AS1200 EPID for Periodic Photon Quality Assurance

    Energy Technology Data Exchange (ETDEWEB)

    DeMarco, J; Fraass, B; Yang, W; McKenzie Boehnke, E [Cedars-Sinai Medical Center, Los Angeles, CA (United States); Moran, J [University Michigan Medical Center, Ann Arbor, MI (United States); Barnes, M [Calvary Mater Hospital Newcastle, Warratah, NSW (Australia); Greer, P [Calvary Mater Newcastle, Newcastle (Australia); Kim, G [University of California, San Diego, La Jolla, CA (United States)

    2016-06-15

    Purpose: To assess the dosimetric performance of a new amorphous silicon flat-panel electronic portal imaging device (EPID) suitable for high-intensity, flattening-filter-free delivery mode. Methods: An EPID-based QA suite was created with automation to periodically monitor photon central-axis output and two-dimensional beam profile constancy as a function of gantry angle and dose-rate. A Varian TrueBeamTM linear accelerator installed with Developer Mode was used to customize and deliver XML script routines for the QA suite using the dosimetry mode image acquisition for an aS1200 EPID. Automatic post-processing software was developed to analyze the resulting DICOM images. Results: The EPID was used to monitor photon beam output constancy (central-axis), flatness, and symmetry over a period of 10 months for four photon beam energies (6x, 15x, 6xFFF, and 10xFFF). EPID results were consistent to those measured with a standard daily QA check device. At the four cardinal gantry angles, the standard deviation of the EPID central-axis output was <0.5%. Likewise, EPID measurements were independent for the wide range of dose rates (including up to 2400 mu/min for 10xFFF) studied with a standard deviation of <0.8% relative to the nominal dose rate for each energy. Also, profile constancy and field size measurements showed good agreement with the reference acquisition of 0° gantry angle and nominal dose rate. XML script files were also tested for MU linearity and picket-fence delivery. Using Developer Mode, the test suite was delivered in <60 minutes for all 4 photon energies with 4 dose rates per energy and 5 picket-fence acquisitions. Conclusion: Dosimetry image acquisition using a new EPID was found to be accurate for standard and high-intensity photon beams over a broad range of dose rates over 10 months. Developer Mode provided an efficient platform to customize the EPID acquisitions by using custom script files which significantly reduced the time. This work was funded

  14. Dosimetric comparison of different treatment modalities for stereotactic radiotherapy.

    Science.gov (United States)

    Hsu, Shih-Ming; Lai, Yuan-Chun; Jeng, Chien-Chung; Tseng, Chia-Ying

    2017-09-16

    The modalities for performing stereotactic radiotherapy (SRT) on the brain include the cone-based linear accelerator (linac), the flattening filter-free (FFF) volumetric modulated arc therapy (VMAT) linac, and tomotherapy. In this study, the cone-based linac, FFF-VMAT linac, and tomotherapy modalities were evaluated by measuring the differences in doses delivered during brain SRT and experimentally assessing the accuracy of the output radiation doses through clinical measurements. We employed a homemade acrylic dosimetry phantom representing the head, within which a thermoluminescent dosimeter (TLD) and radiochromic EBT3 film were installed. Using the conformity/gradient index (CGI) and Paddick methods, the quality of the doses delivered by the various SRT modalities was evaluated. The quality indicators included the uniformity, conformity, and gradient indices. TLDs and EBT3 films were used to experimentally assess the accuracy of the SRT dose output. The dose homogeneity indices of all the treatment modalities were lower than 1.25. The cone-based linac had the best conformity for all tumors, regardless of the tumor location and size, followed by the FFF-VMAT linac; tomography was the worst-performing treatment modality in this regard. The cone-based linac had the best gradient, regardless of the tumor location and size, whereas the FFF-VMAT linac had a better gradient than tomotherapy for a large tumor diameter (28 mm). The TLD and EBT3 measurements of the dose at the center of tumors indicated that the average difference between the measurements and the calculated dose was generally less than 4%. When the 3% 3-mm gamma passing rate metric was used, the average passing rates of all three treatment modalities exceeded 98%. Regarding the dose, the cone-based linac had the best conformity and steepest dose gradient for tumors of different sizes and distances from the brainstem. The results of this study suggest that SRT should be performed using the cone

  15. SU-F-T-637: Single-Isocenter Versus Multiple-Isocenter VMAT SRS for Unusual Multiple Metastasis Case with Two Widely Separated Lesions

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, EM; Popple, RA; Fiveash, JB [The University of Alabama at Birmingham, Birmingham, AL (United States)

    2016-06-15

    Purpose: Single-isocenter (SI) volumetric modulated arc therapy has been shown to be an effective and efficient approach to multiple metastasis radiosurgery. However, certain extreme cases raise the question of whether multiple-isocenter (MI) approaches can still generate superior plans. In this study, we ask this question with respect to a clinical case with two very widely separated lesions. Methods: A patient with two widely separated (d = 12cm) tumors was treated with SI-VMAT SRS using 10MV flattening filter free (FFF) beam with high-definition multi-leaf collimator (HD-MLC, 2.5/5mm) in two non-coplanar arcs using concentric rings to enforce steep gradient. Because of lesion positioning with respect to collimator angle selection, lesions were treated by 5mm leaves. We re-planned the case with a congruent arc arrangement but separate isocenter for each lesion. In this manner, lesions were treated by 2.5mm leaves. Conformity index (CI), V50%, and mean brain dose were compared. Results: Neither conformity (CI-SI = 1.12, CI-MI = 1.08) nor V50% (V50%-SI =8.82cc, V50%-MI =8.81cc) were improved by utilizing a separate isocenter for each lesion. Mean brain dose was slightly reduced (dmean-SI = 118.4 cGy, dmean-MI = 88.7 cGy) by using multiple isocenters. Conclusion: For this case with a lesion at the apex of the brain and another distantly located at the base of skull, employing a separate isocenter for each target did not meaningfully improve plan quality. Single-isocenter VMAT has been shown feasible and equivalent to multiple-isocenter VMAT for multiple metastasis cases in general. In this extreme case, single- and multiple- isocenter VMAT were also equivalent. If rotational setup errors are appropriately corrected, the increased delivery efficiency of the single-isocenter approach renders it preferable to the multiple isocenter approach. Dr’s Thomas, Popple, and Fiveash have all received honoraria from Varian Medical Systems for discussing their experiences with

  16. SU-F-T-629: Effect of Multi-Leaf Collimator (MLC) Width On Plan Quality of Single-Isocenter VMAT Intracranial Stereotactic Radiosurgery for Multiple Metastases

    International Nuclear Information System (INIS)

    Kraus, J; Thomas, E; Wu, X; Fiveash, J; Popple, R

    2016-01-01

    Purpose: Single-isocenter VMAT has been shown able to create high quality plans for complex intracranial multiple metastasis SRS cases. Linacs capable of the technique are typically outfitted with an MLC that consists of a combination of 5 mm and 10 mm leaves (standard) or 2.5 mm and 5 mm leaves (high-definition). In this study, we test the hypothesis that thinner collimator leaves are associated with improved plan quality. Methods: Ten multiple metastasis cases were identified and planned for VMAT SRS using a 10 MV flattening filter free beam. Plans were created for a standard (std) and a high-definition (HD) MLC. Published values for leaf transmission factor and dosimetric leaf gap were utilized. All other parameters were invariant. Conformity (plan and individual target), moderate isodose spill (V50%), and low isodose spill (mean brain dose) were selected for analysis. Results: Compared to standard MLC, HD-MLC improved overall plan conformity (median: Paddick CI-HD = 0.83, Paddick CI-std = 0.79; p = 0.004 and median: RTOG CI-HD =1.18, RTOG CI-std =1.24; p = 0.01 ), improved individual lesion conformity (median: Paddick CI-HD,i =0.77, Paddick CI-std,i =0.72; p < 0.001 and median: RTOG CI-HD,i = 1.28, RTOG CI-std,i =1.35; p < 0.001), improved moderate isodose spill (median: V50%-HD = 37.0 cc, V50%-std = 45.7 cc; p = 0.002), and improved low dose spill (median: dmean-HD = 2.90 Gy, dmean-std = 3.19 Gy; p = 0.002). Conclusion: For the single-isocenter VMAT SRS of multiple metastasis plans examined, use of HD-MLC modestly improved conformity, moderate isodose, and low isodose spill compared to standard MLC. However, in all cases we were able to generate clinically acceptable plans with the standard MLC. More work is need to further quantify the difference in cases with higher numbers of small targets and to better understand any potential clinical significance. This research was supported in part by Varian Medical Systems.

  17. SU-F-T-629: Effect of Multi-Leaf Collimator (MLC) Width On Plan Quality of Single-Isocenter VMAT Intracranial Stereotactic Radiosurgery for Multiple Metastases

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, J; Thomas, E; Wu, X; Fiveash, J; Popple, R [University Alabama Birmingham, Birmingham, AL (United States)

    2016-06-15

    Purpose: Single-isocenter VMAT has been shown able to create high quality plans for complex intracranial multiple metastasis SRS cases. Linacs capable of the technique are typically outfitted with an MLC that consists of a combination of 5 mm and 10 mm leaves (standard) or 2.5 mm and 5 mm leaves (high-definition). In this study, we test the hypothesis that thinner collimator leaves are associated with improved plan quality. Methods: Ten multiple metastasis cases were identified and planned for VMAT SRS using a 10 MV flattening filter free beam. Plans were created for a standard (std) and a high-definition (HD) MLC. Published values for leaf transmission factor and dosimetric leaf gap were utilized. All other parameters were invariant. Conformity (plan and individual target), moderate isodose spill (V50%), and low isodose spill (mean brain dose) were selected for analysis. Results: Compared to standard MLC, HD-MLC improved overall plan conformity (median: Paddick CI-HD = 0.83, Paddick CI-std = 0.79; p = 0.004 and median: RTOG CI-HD =1.18, RTOG CI-std =1.24; p = 0.01 ), improved individual lesion conformity (median: Paddick CI-HD,i =0.77, Paddick CI-std,i =0.72; p < 0.001 and median: RTOG CI-HD,i = 1.28, RTOG CI-std,i =1.35; p < 0.001), improved moderate isodose spill (median: V50%-HD = 37.0 cc, V50%-std = 45.7 cc; p = 0.002), and improved low dose spill (median: dmean-HD = 2.90 Gy, dmean-std = 3.19 Gy; p = 0.002). Conclusion: For the single-isocenter VMAT SRS of multiple metastasis plans examined, use of HD-MLC modestly improved conformity, moderate isodose, and low isodose spill compared to standard MLC. However, in all cases we were able to generate clinically acceptable plans with the standard MLC. More work is need to further quantify the difference in cases with higher numbers of small targets and to better understand any potential clinical significance. This research was supported in part by Varian Medical Systems.

  18. Do technological advances in linear accelerators improve dosimetric outcomes in stereotaxy? A head-on comparison of seven linear accelerators using volumetric modulated arc therapy-based stereotactic planning.

    Science.gov (United States)

    Sarkar, B; Pradhan, A; Munshi, A

    2016-01-01

    Linear accelerator (Linac) based stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) using volumetric modulated arc therapy (VMAT) has been used for treating small intracranial lesions. Recent development in the Linacs such as inbuilt micro multileaf collimator (MLC) and flattening filter free (FFF) beam are intended to provide a better dose conformity and faster delivery when using VMAT technique. This study was aimed to compare the dosimetric outcomes and monitor units (MUs) of the stereotactic treatment plans for different commercially available MLC models and beam profiles. Ten patients having 12 planning target volume (PTV)/gross target volume's (GTVs) who received the SRS/SRT treatment in our clinic using Axesse Linac (considered reference arm gold standard) were considered for this study. The test arms comprised of plans using Elekta Agility with FFF, Elekta Agility with the plane beam, Elekta APEX, Varian Millennium 120, Varian Millennium 120HD, and Elekta Synergy in Monaco treatment planning system. Planning constraints and calculation grid spacing were not altered in the test plans. To objectively evaluate the efficacy of MLC-beam model, the resultant dosimetric outcomes were subtracted from the reference arm parameters. V95%, V100%, V105%, D1%, maximum dose, and mean dose of PTV/GTV showed a maximum inter MLC - beam model variation of 1.5% and 2% for PTV and GTV, respectively. Average PTV conformity index and heterogeneity index shows a variation in the range 0.56-0.63 and 1.08-1.11, respectively. Mean dose difference (excluding Axesse) for all organs varied between 1.1 cGy and 74.8 cGy (mean dose = 6.1 cGy standard deviation [SD] = 26.9 cGy) and 1.7 cGy-194.5 cGy (mean dose 16.1 cGy SD = 57.2 cGy) for single and multiple fraction, respectively. The dosimetry of VMAT-based SRS/SRT treatment plan had minimal dependence on MLC and beam model variations. All tested MLC and beam model could fulfil the desired PTV coverage and organs at risk

  19. SU-G-TeP2-08: Evaluation of Plastic Scintillator Detector for Small Field Stereotactic Patient-Specific Quality Assurance

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Y; Gardner, S; Huang, Y; Kim, J; Wen, N; Chetty, I [Henry Ford Health System, Detroit, MI (United States)

    2016-06-15

    Purpose: To evaluate the performance of a commercial plastic scintillator detector (PSD) for small-field stereotactic patient-specific quality assurance using flattening-filter-free (FFF) beams. Methods: A total of ten spherical targets (volume range:[0.03cc–2cc]) were planned using Dynamic Conformal Arc(DCA-10 plans) and Volumetric Modulated Arc Therapy(VMAT-10 plans) techniques in Eclipse(AAA v.11, 1mm dose calculation grid size). Additionally, 15 previously-treated cranial and spine SRS plans were evaluated (6 DCA, 9 VMAT, volume range:[0.04cc–119.02cc]). All measurements were acquired using Varian Edge equipped with HDMLC. Three detectors were used: PinPoint ion chamber (PTW;active volume 0.015cc), Exradin W1 PSD (Standard Imaging;active volume 0.002cc), and Gafchromic EBT3 film (Ashland). PinPoint and PSD were positioned perpendicular to beam axis in a Lucy phantom (Standard Imaging). Films were placed at isocenter in solid water. Calibration films were delivered for absolute dose analysis. Results: For large spherical targets(>1.5cc) with DCA, all detectors agreed within 1% of AAA calculations. As target volume decreased, PSD measured higher doses than AAA (maximum difference: 3.3% at 0.03cc target), while PinPoint chamber measured lower doses (maximum difference:-3.8% at 0.03cc target). Inter-detector differences between pinpoint and PSD increased with decreasing target size; differences>5% were observed for targets<0.09cc. Similar trends for inter-detector behavior were observed for clinical plans. For target sizes<0.08cc, PSD measured>5% higher dose than PinPoint chamber (maximum difference: 9.25% at 0.04cc target). Film demonstrated agreement of −0.19±1.47% with PSD for all spherical targets, and agreement within −0.98±2.25% for all 15 clinical targets. Unlike DCA, VMAT plans did not show improved AAA-to-detector agreements for large targets. Conclusion: For all targets, the PSD measurements agreed with film within 1.0%, on average. For small

  20. An end-to-end examination of geometric accuracy of IGRT using a new digital accelerator equipped with onboard imaging system.

    Science.gov (United States)

    Wang, Lei; Kielar, Kayla N; Mok, Ed; Hsu, Annie; Dieterich, Sonja; Xing, Lei

    2012-02-07

    The Varian's new digital linear accelerator (LINAC), TrueBeam STx, is equipped with a high dose rate flattening filter free (FFF) mode (6 MV and 10 MV), a high definition multileaf collimator (2.5 mm leaf width), as well as onboard imaging capabilities. A series of end-to-end phantom tests were performed, TrueBeam-based image guided radiation therapy (IGRT), to determine the geometric accuracy of the image-guided setup and dose delivery process for all beam modalities delivered using intensity modulated radiation therapy (IMRT) and RapidArc. In these tests, an anthropomorphic phantom with a Ball Cube II insert and the analysis software (FilmQA (3cognition)) were used to evaluate the accuracy of TrueBeam image-guided setup and dose delivery. Laser cut EBT2 films with 0.15 mm accuracy were embedded into the phantom. The phantom with the film inserted was first scanned with a GE Discovery-ST CT scanner, and the images were then imported to the planning system. Plans with steep dose fall off surrounding hypothetical targets of different sizes were created using RapidArc and IMRT with FFF and WFF (with flattening filter) beams. Four RapidArc plans (6 MV and 10 MV FFF) and five IMRT plans (6 MV and 10 MV FFF; 6 MV, 10 MV and 15 MV WFF) were studied. The RapidArc plans with 6 MV FFF were planned with target diameters of 1 cm (0.52 cc), 2 cm (4.2 cc) and 3 cm (14.1 cc), and all other plans with a target diameter of 3 cm. Both onboard planar and volumetric imaging procedures were used for phantom setup and target localization. The IMRT and RapidArc plans were then delivered, and the film measurements were compared with the original treatment plans using a gamma criteria of 3%/1 mm and 3%/2 mm. The shifts required in order to align the film measured dose with the calculated dose distributions was attributed to be the targeting error. Targeting accuracy of image-guided treatment using TrueBeam was found to be within 1 mm. For irradiation of the 3 cm target, the gammas (3%, 1

  1. 16 CFR 1631.4 - Test procedure.

    Science.gov (United States)

    2010-01-01

    ... operation. (2) Flattening frame. A steel plate, 22.86 × 22.86 cm. (9 × 9 in.) 6.35 mm. (1/4 in.) thick with..., traffic surface up, exercising care that the specimen is horizontal and flat. Place the flattening frame....) of the edge of the hole in the flattening frame at any point. (4) When all combustion has ceased...

  2. Neutron leakage measurements from a medical linear accelerator

    International Nuclear Information System (INIS)

    Palta, J.R.; Hogstrom, K.R.; Tannanonta, C.

    1984-01-01

    The McCall method has been used to measure neutron leakage from the Mevatron 77, 18- and 15-MV photon beams. Gold foil activation has been used employing a beta counting technique for the 18-MV beam and a gamma counting technique for both the 18- and 15-MV beam. The two counting techniques were used to evaluate their relative merit. The measurements were made at various locations in the patient-treatment plane for different field sizes. The results show that the thermal-neutron dose equivalent contributes only about 1%--2% of the total neutron dose equivalent. At 100 cm, the neutron dose equivalent for the 18-MV beam is approximately six times that of the 15-MV beam, slightly exceeding the 0.1% of the useful beam criteria used by some of the regulatory agencies. In light of the uncertainty in fluence to dose equivalent conversion factors, the increased dose equivalent above 0.1% is insignificant

  3. Validating dose rate calibration of radiotherapy photon beams through IAEA/WHO postal audit dosimetry service

    International Nuclear Information System (INIS)

    Jangda, A.Q.; Hussein, S.

    2012-01-01

    In external beam radiation therapy (EBRT), the quality assurance (QA) of the radiation beam is crucial to the accurate delivery of the prescribed dose to the patient. One of the dosimetric parameters that require monitoring is the beam output, specified as the dose rate on the central axis under reference conditions. The aim of this project was to validate dose rate calibration of megavoltage photon beams using the International Atomic Energy Agency (IAEA)/World Health Organisation (WHO) postal audit dosimetry service. Three photon beams were audited: a 6 MV beam from the low-energy linac and 6 and 18 MV beams from a dual high-energy linac. The agreement between our stated doses and the IAEA results was within 1% for the two 6 MV beams and within 2% for the 18 MV beam. The IAEA/WHO postal audit dosimetry service provides an independent verification of dose rate calibration protocol by an international facility. (author)

  4. Validating dose rate calibration of radiotherapy photon beams through IAEA/WHO postal audit dosimetry service.

    Science.gov (United States)

    Jangda, Abdul Qadir; Hussein, Sherali

    2012-05-01

    In external beam radiation therapy (EBRT), the quality assurance (QA) of the radiation beam is crucial to the accurate delivery of the prescribed dose to the patient. One of the dosimetric parameters that require monitoring is the beam output, specified as the dose rate on the central axis under reference conditions. The aim of this project was to validate dose rate calibration of megavoltage photon beams using the International Atomic Energy Agency (IAEA)/World Health Organisation (WHO) postal audit dosimetry service. Three photon beams were audited: a 6 MV beam from the low-energy linac and 6 and 18 MV beams from a dual high-energy linac. The agreement between our stated doses and the IAEA results was within 1% for the two 6 MV beams and within 2% for the 18 MV beam. The IAEA/WHO postal audit dosimetry service provides an independent verification of dose rate calibration protocol by an international facility.

  5. Determination of the neutron spectra in the treatment room of a linear accelerator for radiotherapy

    International Nuclear Information System (INIS)

    Vega C, H.R.; Barquero, R.; Mendez, R.; Iniguez, M.P.

    2003-01-01

    By means of a series of measures and Monte Carlo calculations the dosimetric characteristics of the photoneutrons have been determined that take place in volume to a linear accelerator of radiotherapy of 18 MV, LINAC, mark Siemens Mevatron model. The measures were carried out with thermoluminescent dosemeters TLD 600 and TLD 700 that were naked exposed and confined with cover of Cd and Sn, inside a sphere of paraffin and inside spheres Bonner. (Author)

  6. Determination of the neutron spectra in the treatment room of a linear accelerator for radiotherapy; Determinacion de los espectros de neutrones en la sala de tratamiento de un acelerador lineal para radioterapia

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R. [Universidad Autonoma de Zacatecas, Cuerpo Academico de Radiobiologia, A.P. 336, 98000 Zacatecas (Mexico); Barquero, R. [Hospital Universitario Rio Hortega, Valladolid (Spain); Mendez, R.; Iniguez, M.P. [Depto. de Fisica Teorica, Atomica, Molecular y Nuclear, Universidad de Valladolid, 47011 Valladolid (Spain)

    2003-07-01

    By means of a series of measures and Monte Carlo calculations the dosimetric characteristics of the photoneutrons have been determined that take place in volume to a linear accelerator of radiotherapy of 18 MV, LINAC, mark Siemens Mevatron model. The measures were carried out with thermoluminescent dosemeters TLD 600 and TLD 700 that were naked exposed and confined with cover of Cd and Sn, inside a sphere of paraffin and inside spheres Bonner. (Author)

  7. Measurement of changes in linear accelerator photon energy through flatness variation using an ion chamber array

    International Nuclear Information System (INIS)

    Gao Song; Balter, Peter A.; Rose, Mark; Simon, William E.

    2013-01-01

    Purpose: To compare the use of flatness versus percent depth dose (PDD) for determining changes in photon beam energy for a megavoltage linear accelerator. Methods: Energy changes were accomplished by adjusting the bending magnet current by up to ±15% in 5% increments away from the value used clinically. Two metrics for flatness, relative flatness in the central 80% of the field (Flat) and average maximum dose along the diagonals normalized by central axis dose (F DN ), were measured using a commercially available planner ionization chamber array. PDD was measured in water at depths of 5 and 10 cm in 3 × 3 cm 2 and 10 × 10 cm 2 fields using a cylindrical chamber. Results: PDD was more sensitive to changes in energy when the beam energy was increased than when it was decreased. For the 18-MV beam in particular, PDD was not sensitive to energy reductions below the nominal energy. The value of Flat was found to be more sensitive to decreases in energy than to increases, with little sensitivity to energy increases above the nominal energy for 18-MV beams. F DN was the only metric that was found to be sensitive to both increases and reductions of energy for both the 6- and 18-MV beams. Conclusions: Flatness based metrics were found to be more sensitive to energy changes than PDD, In particular, F DN was found to be the most sensitive metric to energy changes for photon beams of 6 and 18 MV. The ionization chamber array allows this metric to be conveniently measured as part of routine accelerator quality assurance.

  8. Variation of beam characteristics for physical and enhanced dynamic wedge from a dual energy accelerator

    International Nuclear Information System (INIS)

    Varatharaj, C.; Ravikumar, M.; Sathiyan, S.; Supe, Sanjay S.

    2008-01-01

    The use of Megavoltage X-ray sources of radiation, with their skin-sparing qualities in radiation therapy has been a boon in relieving patient discomfort and allowing higher tumor doses to be given with fewer restrictions due to radiation effects in the skin. The aim of this study was to compare few of the dosimetric characteristics of a physical and enhanced dynamic wedge from a dual energy (6-18 MV) linear accelerator

  9. Skin dose variation: influence of energy

    International Nuclear Information System (INIS)

    Cheung, T.; Yu, P.K.N.; Butson, M.J.; Cancer Services, Wollongong, NSW

    2004-01-01

    Full text: This research aimed to quantitatively evaluate the differences in percentage dose of maximum for 6MV and 18MV x-ray beams within the first lcm of interactions. Thus provide quantitative information regarding the basal, dermal and subcutaneous dose differences achievable with these two types of high-energy x-ray beams. Percentage dose of maximum build up curves are measured for most clinical field sizes using 6MV and 18MV x-ray beams. Calculations are performed to produce quantitative results highlighting the percentage dose of maximum differences delivered to various depths within the skin and subcutaneous tissue region by these two beams Results have shown that basal cell layer doses are not significantly different for 6MV and 18Mv x-ray beams At depths beyond the surface and basal cell layer there is a measurable and significant difference in delivered dose. This variation increases to 20% of maximum and 22% of maximum at Imm and 1cm depths respectively. The percentage variations are larger for smaller field sizes where the photon in phantom component of the delivered dose is the most significant contributor to dose By producing graphs or tables of % dose differences in the build up region we can provide quantitative information to the oncologist for consideration (if skin and subcutaneous tissue doses are of importance) during the beam energy selection process for treatment. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

  10. Radiotherapy high energy surface dose measurements: effects of chamber polarity

    International Nuclear Information System (INIS)

    Cheung, T.; Yu, P.K.N.; Butson, M.J.; Cancer Services, Wollongong, NSW

    2004-01-01

    Full text: The effects of chamber polarity have been investigated for the measurement of 6MV and 18MV x-ray surface dose using a parallel plate ionization chamber. Results have shown that a significant difference in measured ionization is recorded between to polarities at 6MV and 18MV at the phantom surface. A polarity ratio ranging from 1 062 to 1 005 is seen for 6MV x-rays at the phantom surface for field sizes 5cm x 5cm to 40cm x 40cm when comparing positive to negative polarity. These ratios range from 1.024 to 1.004 for 18MV x-rays with the same field sizes. When these charge reading are compared to the D max readings of the same polarity it is found that these polarity effects are minimal for the calculation of percentage dose results with variations being less than 1% of maximum. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

  11. Dose attenuation by a carbon fiber linac couch and modeling with a treatment planning system

    International Nuclear Information System (INIS)

    Sanchez Galiano, P.; Garcia Sancho, J.M.; Crelgo, D.; Pamos, M.; Fernandez, J.; Vivanco, J.

    2010-01-01

    The purpose of this work is to investigate the attenuation caused by a carbon fiber linac treatment couch and the ability of a commercial radiotherapy treatment planning system to simulate it. The attenuation caused by an Exact treatment couch in a Varian Clinac 2100 C/D was characterized in detail. Both 6 MV and 18 MV photon beams were studied. The treatment couch was modeled and incorporated to Elekta XiO treatment planning system. Measured and computed attenuation values were compared. As a result we found that the attenuation caused by this complex treatment couch is strongly dependent on the incidence angle of the beam. The measured attenuation values reach 16% for 6 MV and 10% for 18 MV. The model incorporated to the treatment planning software allows reducing the differences between measured and calculated data below 2.5% and 2.0% for 6 MV and 18 MV respectively. In conclusion, it is strongly recommended accounting for the perturbation caused by this carbon fiber treatment couch when the beam intersects it. The treatment planning system studied can simulate this treatment couch accurately. Clinical implementation of the described method requires a reliable procedure to reproduce the same patient geometry in the treatment delivery and planning. (Author).

  12. Dose attenuation by a carbon fiber linac couch and modeling with a treatment planning system; Medida de la atenuacion producida por la mesa de tratamiento de un acelerador lineal y su modelado en un sistema de planificacion

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Galiano, P.; Garcia Sancho, J.M.; Crelgo, D.; Pamos, M.; Fernandez, J.; Vivanco, J.

    2010-07-01

    The purpose of this work is to investigate the attenuation caused by a carbon fiber linac treatment couch and the ability of a commercial radiotherapy treatment planning system to simulate it. The attenuation caused by an Exact{copyright} treatment couch in a Varian{copyright} Clinac{copyright} 2100 C/D was characterized in detail. Both 6 MV and 18 MV photon beams were studied. The treatment couch was modeled and incorporated to Elekta{copyright} XiO{copyright} treatment planning system. Measured and computed attenuation values were compared. As a result we found that the attenuation caused by this complex treatment couch is strongly dependent on the incidence angle of the beam. The measured attenuation values reach 16% for 6 MV and 10% for 18 MV. The model incorporated to the treatment planning software allows reducing the differences between measured and calculated data below 2.5% and 2.0% for 6 MV and 18 MV respectively. In conclusion, it is strongly recommended accounting for the perturbation caused by this carbon fiber treatment couch when the beam intersects it. The treatment planning system studied can simulate this treatment couch accurately. Clinical implementation of the described method requires a reliable procedure to reproduce the same patient geometry in the treatment delivery and planning. (Author).

  13. Multibeam tomotherapy: A new treatment unit devised for multileaf collimation, intensity-modulated radiation therapy

    International Nuclear Information System (INIS)

    Achterberg, Nils; Mueller, Reinhold G.

    2007-01-01

    A fully integrated system for treatment planning, application, and verification for automated multileaf collimator (MLC) based, intensity-modulated, image-guided, and adaptive radiation therapy (IMRT, IGRT and ART, respectively) is proposed. Patient comfort, which was the major development goal, will be achieved through a new unit design and short treatment times. Our device for photon beam therapy will consist of a new dual energy linac with five fixed treatment heads positioned evenly along one plane but one electron beam generator only. A minimum of moving parts increases technical reliability and reduces motion times to a minimum. Motion is allowed solely for the MLCs, the robotic patient table, and the small angle gantry rotation of ±36 deg. . Besides sophisticated electron beam guidance, this compact setup can be built using existing modules. The flattening-filter-free treatment heads are characterized by reduced beam-on time and contain apertures restricted in one dimension to the area of maximum primary fluence output. In the case of longer targets, this leads to a topographic intensity modulation, thanks to the combination of ''step and shoot'' MLC delivery and discrete patient couch motion. Owing to the limited number of beam directions, this multislice cone beam serial tomotherapy is referred to as ''multibeam tomotherapy.'' Every patient slice is irradiated by one treatment head at any given moment but for one subfield only. The electron beam is then guided to the next head ready for delivery, while the other heads are preparing their leaves for the next segment. The ''Multifocal MLC-positioning'' algorithm was programmed to enable treatment planning and optimize treatment time. We developed an overlap strategy for the longitudinally adjacent fields of every beam direction, in doing so minimizing the field match problem and the effects of possible table step errors. Clinical case studies show for the same or better planning target volume coverage

  14. Treatment planning for radiotherapy with very high-energy electron beams and comparison of VHEE and VMAT plans

    International Nuclear Information System (INIS)

    Bazalova-Carter, Magdalena; Qu, Bradley; Palma, Bianey; Jensen, Christopher; Maxim, Peter G.; Loo, Billy W.; Hårdemark, Björn; Hynning, Elin

    2015-01-01

    plan, OAR doses were up to 70% lower and the integral dose was 33% lower for VHEE compared to 6 MV VMAT. Additionally, VHEE conformity indices (CI 100 = 1.09 and CI 50 = 4.07) were better than VMAT conformity indices (CI 100 = 1.30 and CI 50 = 6.81). The 100 MeV VHEE lung plan resulted in mean dose decrease to all OARs by up to 27% for the same target coverage compared to the clinical 6 MV flattening filter-free (FFF) VMAT plan. The 100 MeV prostate plan resulted in 3% mean dose increase to the penile bulb and the urethra, but all other OAR mean doses were lower compared to the 15 MV VMAT plan. The lung case CI 100 and CI 50 conformity indices were 3% and 8% lower, respectively, in the VHEE plan compared to the VMAT plan. The prostate case CI 100 and CI 50 conformity indices were 1% higher and 8% lower, respectively, in the VHEE plan compared to the VMAT plan. Conclusions: The authors have developed a treatment planning workflow for MC dose calculation of pencil beams and optimization for treatment planning of VHEE radiotherapy. The authors have demonstrated that VHEE plans resulted in similar or superior dose distributions for pediatric, lung, and prostate cases compared to clinical VMAT plans

  15. Evaluating efficiency of coaxial MLC VMAT plan for spine SBRT

    Energy Technology Data Exchange (ETDEWEB)

    Son, Sang Jun; Mun, Jun Ki; Kim, Dae Ho; Yoo, Suk Hyun [Dept. of Radiation Oncology, Seoul National University Hospital, Seoul (Korea, Republic of)

    2014-12-15

    The purpose of the study is to evaluate the efficiency of Coaxial MLC VMAT plan (Using 273° and 350° collimator angle) That the leaf motion direction aligned with axis of OAR (Organ at risk, It means spinal cord or cauda equine in this study.) compare to Universal MLC VMAT plan (using 30° and 330 ° collimator angle) for spine SBRT. The 10 cases of spine SBRT that treated with VMAT planned by Coaxial MLC and Varian TBX were enrolled. Those cases were planned by Eclipse (Ver. 10.0.42, Varian, USA), PRO3 (Progressive Resolution Optimizer 10.0.28) and AAA (Anisotropic Analytic Algorithm Ver. 10.0.28) with coplanar 260 ° arcs and 10MV FFF (Flattening filter free). Each arc has 273° and 350 ° collimator angle, respectively. The Universal MLC VMAT plans are based on existing treatment plans. Those plans have the same parameters of existing treatment plans but collimator angle. To minimize the dose difference that shows up randomly on optimizing, all plans were optimized and calculated twice respectively. The calculation grid is 0.2 cm and all plans were normalized to the target V100%=90%. The indexes of evaluation are V10Gy, D0.03cc, Dmean of OAR (Organ at risk, It means spinal cord or cauda equine in this study.), H.I (Homogeneity index) of the target and total MU. All Coaxial VMAT plans were verified by gamma test with Mapcheck2 (Sun Nuclear Co., USA), Mapphan (Sun Nuclear Co., USA) and SNC patient (Sun Nuclear Co., USA Ver 6.1.2.18513). The difference between the coaxial and the universal VMAT plans are follow. The coaxial VMAT plan is better in the V10Gy of OAR, Up to 4.1%, at least 0.4%, the average difference was 1.9% and In the D0.03cc of OAR, Up to 83.6 cGy, at least 2.2 cGy, the average difference was 33.3 cGy. In Dmean, Up to 34.8 cGy, at least -13.0 cGy, the average difference was 9.6 cGy that say the coaxial VMAT plans are better except few cases. H.I difference Up to 0.04, at least 0.01, the average difference was 0.02 and the difference of average

  16. Characteristics of a novel treatment system for linear accelerator-based stereotactic radiosurgery.

    Science.gov (United States)

    Wen, Ning; Li, Haisen; Song, Kwang; Chin-Snyder, Karen; Qin, Yujiao; Kim, Jinkoo; Bellon, Maria; Gulam, Misbah; Gardner, Stephen; Doemer, Anthony; Devpura, Suneetha; Gordon, James; Chetty, Indrin; Siddiqui, Farzan; Ajlouni, Munther; Pompa, Robert; Hammoud, Zane; Simoff, Michael; Kalkanis, Steven; Movsas, Benjamin; Siddiqui, M Salim

    2015-07-08

    The purpose of this study is to characterize the dosimetric properties and accuracy of a novel treatment platform (Edge radiosurgery system) for localizing and treating patients with frameless, image-guided stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). Initial measurements of various components of the system, such as a comprehensive assessment of the dosimetric properties of the flattening filter-free (FFF) beams for both high definition (HD120) MLC and conical cone-based treatment, positioning accuracy and beam attenuation of a six degree of freedom (6DoF) couch, treatment head leakage test, and integrated end-to-end accuracy tests, have been performed. The end-to-end test of the system was performed by CT imaging a phantom and registering hidden targets on the treatment couch to determine the localization accuracy of the optical surface monitoring system (OSMS), cone-beam CT (CBCT), and MV imaging systems, as well as the radiation isocenter targeting accuracy. The deviations between the percent depth-dose curves acquired on the new linac-based system (Edge), and the previously published machine with FFF beams (TrueBeam) beyond D(max) were within 1.0% for both energies. The maximum deviation of output factors between the Edge and TrueBeam was 1.6%. The optimized dosimetric leaf gap values, which were fitted using Eclipse dose calculations and measurements based on representative spine radiosurgery plans, were 0.700 mm and 1.000 mm, respectively. For the conical cones, 6X FFF has sharper penumbra ranging from 1.2-1.8 mm (80%-20%) and 1.9-3.8 mm (90%-10%) relative to 10X FFF, which has 1.2-2.2mm and 2.3-5.1mm, respectively. The relative attenuation measurements of the couch for PA, PA (rails-in), oblique, oblique (rails-out), oblique (rails-in) were: -2.0%, -2.5%, -15.6%, -2.5%, -5.0% for 6X FFF and -1.4%, -1.5%, -12.2%, -2.5%, -5.0% for 10X FFF, respectively, with a slight decrease in attenuation versus field size. The systematic

  17. Comparative analysis of {sup 60}Co intensity-modulated radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Fox, Christopher [Sun Nuclear Corporation, 425-A Pineda Court, Melbourne, FL 32940 (United States); Romeijn, H Edwin; Lynch, Bart; Dempsey, James F [Department of Radiation Oncology, University of Florida, Gainesville, FL 32610-0385 (United States); Men, Chunhua [Department of Industrial and Systems Engineering, University of Florida, Gainesville, FL 32611-6595 (United States); Aleman, Dionne M [Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario (Canada)], E-mail: chrisfox@sunnuclear.com, E-mail: romeijn@ise.ufl.edu, E-mail: lynchb@ufl.edu, E-mail: chhmen@ufl.edu, E-mail: aleman@mie.utoronto.edu, E-mail: dempsey@ufl.edu

    2008-06-21

    In this study, we perform a scientific comparative analysis of using {sup 60}Co beams in intensity-modulated radiation therapy (IMRT). In particular, we evaluate the treatment plan quality obtained with (i) 6 MV, 18 MV and {sup 60}Co IMRT; (ii) different numbers of static multileaf collimator (MLC) delivered {sup 60}Co beams and (iii) a helical tomotherapy {sup 60}Co beam geometry. We employ a convex fluence map optimization (FMO) model, which allows for the comparison of plan quality between different beam energies and configurations for a given case. A total of 25 clinical patient cases that each contain volumetric CT studies, primary and secondary delineated targets, and contoured structures were studied: 5 head-and-neck (H and N), 5 prostate, 5 central nervous system (CNS), 5 breast and 5 lung cases. The DICOM plan data were anonymized and exported to the University of Florida optimized radiation therapy (UFORT) treatment planning system. The FMO problem was solved for each case for 5-71 equidistant beams as well as a helical geometry for H and N, prostate, CNS and lung cases, and for 3-7 equidistant beams in the upper hemisphere for breast cases, all with 6 MV, 18 MV and {sup 60}Co dose models. In all cases, 95% of the target volumes received at least the prescribed dose with clinical sparing criteria for critical organs being met for all structures that were not wholly or partially contained within the target volume. Improvements in critical organ sparing were found with an increasing number of equidistant {sup 60}Co beams, yet were marginal above 9 beams for H and N, prostate, CNS and lung. Breast cases produced similar plans for 3-7 beams. A helical {sup 60}Co beam geometry achieved similar plan quality as static plans with 11 equidistant {sup 60}Co beams. Furthermore, 18 MV plans were initially found not to provide the same target coverage as 6 MV and {sup 60}Co plans; however, adjusting the trade-offs in the optimization model allowed equivalent target

  18. Comparative analysis of 60Co intensity-modulated radiation therapy

    International Nuclear Information System (INIS)

    Fox, Christopher; Romeijn, H Edwin; Lynch, Bart; Dempsey, James F; Men, Chunhua; Aleman, Dionne M

    2008-01-01

    In this study, we perform a scientific comparative analysis of using 60 Co beams in intensity-modulated radiation therapy (IMRT). In particular, we evaluate the treatment plan quality obtained with (i) 6 MV, 18 MV and 60 Co IMRT; (ii) different numbers of static multileaf collimator (MLC) delivered 60 Co beams and (iii) a helical tomotherapy 60 Co beam geometry. We employ a convex fluence map optimization (FMO) model, which allows for the comparison of plan quality between different beam energies and configurations for a given case. A total of 25 clinical patient cases that each contain volumetric CT studies, primary and secondary delineated targets, and contoured structures were studied: 5 head-and-neck (H and N), 5 prostate, 5 central nervous system (CNS), 5 breast and 5 lung cases. The DICOM plan data were anonymized and exported to the University of Florida optimized radiation therapy (UFORT) treatment planning system. The FMO problem was solved for each case for 5-71 equidistant beams as well as a helical geometry for H and N, prostate, CNS and lung cases, and for 3-7 equidistant beams in the upper hemisphere for breast cases, all with 6 MV, 18 MV and 60 Co dose models. In all cases, 95% of the target volumes received at least the prescribed dose with clinical sparing criteria for critical organs being met for all structures that were not wholly or partially contained within the target volume. Improvements in critical organ sparing were found with an increasing number of equidistant 60 Co beams, yet were marginal above 9 beams for H and N, prostate, CNS and lung. Breast cases produced similar plans for 3-7 beams. A helical 60 Co beam geometry achieved similar plan quality as static plans with 11 equidistant 60 Co beams. Furthermore, 18 MV plans were initially found not to provide the same target coverage as 6 MV and 60 Co plans; however, adjusting the trade-offs in the optimization model allowed equivalent target coverage for 18 MV. For plans with comparable

  19. Effect of intervention on development of hip posture in very preterm babies.

    OpenAIRE

    Downs, J A; Edwards, A D; McCormick, D C; Roth, S C; Stewart, A L

    1991-01-01

    Preterm babies are physiologically hypotonic, which causes their posture to be flattened when lying in the prone position. This flattened posture may persist beyond term. In a prospective, randomised, controlled, double blind trial of postural support carried out on 45 babies born at less than 33 weeks of gestation, we showed that infants positioned with specific hip support during the period of intensive care had significantly fewer features of flattened posture at the age equivalent to term.

  20. Dispersion induced penalty for a 1xN passive interferometric optical MUX/DEMUX and its reduction using all-pass filters

    DEFF Research Database (Denmark)

    Leick, Lasse; Peucheret, Christophe

    2002-01-01

    The cascadability of 1timesN passband flattened interferometer DEMUX is investigated numerically. The passband flattening process results in detrimental dispersion induced penalty at 10 Gbit/s which can be significantly reduced with all-pass filters on the input arm......The cascadability of 1timesN passband flattened interferometer DEMUX is investigated numerically. The passband flattening process results in detrimental dispersion induced penalty at 10 Gbit/s which can be significantly reduced with all-pass filters on the input arm...

  1. Command and Control in a Joint Operational Environment: The Hybrid Control Maxim

    National Research Council Canada - National Science Library

    Becker, Mark

    2000-01-01

    Will the technology of netcentricity affect the organizational structure of joint military organizations such that the organizational hierarchy becomes flattened and the command, control, coordination...

  2. Digital demodulator for wide bandwidth SAR

    DEFF Research Database (Denmark)

    Jørgensen, Jørn Hjelm

    2000-01-01

    A novel approach to the design of efficient digital quadrature demodulators for wide bandwidth SAR systems is described. Efficiency is obtained by setting the intermediate frequency to 1/4 the ADC sampling frequency. One channel is made filter-free by synchronizing the local oscillator...

  3. Effect of low-density lateral interfaces on soft-tissue doses

    International Nuclear Information System (INIS)

    Hunt, Margie A.; Desobry, Gregory E.; Fowble, Barbara; Coia, Lawrence R.

    1997-01-01

    Purpose: Doses at the interface between tissue and low-density inhomogeneities with the interface positioned perpendicular to the beam direction have been well studied. When the inhomogeneity lies parallel to the beam direction (i.e., a lateral interface), the resulting dose distribution is not as well known. Lateral lung--soft-tissue interfaces are common in many fields used to treat malignancies in the thorax region including tangential breast fields and anteroposterior fields for lung and esophageal cancer. The purpose of this study was to evaluate the dose distribution along lateral interfaces and to determine the implications for treatment. Methods and Materials: A polystyrene and cork slab phantom was irradiated from the side to simulate treatment fields with lateral lung--soft-tissue interfaces. The beam was positioned with the isocenter in polystyrene and the field edge in cork. Cork slabs (0.6-2.5 cm) were used to simulate different thicknesses of lung between the field edge and the target volume. Measurements were made using a parallel plate ionization chamber. With the chamber position held constant, polystyrene slabs were added between the cork and the chamber to study the dose distribution in the interface region. Interface doses were studied as a function of the amount of cork in the field, field size, beam energy (6-18 MV), and depth. Results: Doses in the interface region were lower by as much as 10% compared to doses in a homogeneous phantom. For a given cork width and field size, the magnitude of the underdose increased by several percent as the x-ray energy increased from 6 to 18 MV. The underdose at the interface was 5% for 6 MV and 8% for 18 MV X-rays with a 1-cm cork width. For a 2.5-cm cork width, underdoses of 2.5% and 3% at distances up to 2.5 and 4 mm lateral to the interface were observed for 6- and 18-MV X-rays, respectively. However, doses right at the interface were 1% greater for 6 MV and 3% less for 18 MV than doses in a homogeneous

  4. 49 CFR 178.68 - Specification 4E welded aluminum cylinders.

    Science.gov (United States)

    2010-10-01

    ... in ASTM E 8 (IBR, see § 171.7 of this subchapter). (ii) Cross-head speed of the testing machine may... psi. (ii) One-half of the minimum tensile strength of the material as required in paragraph (j) of... result in rejection of the lot. (i) Flattening test. After hydrostatic testing, a flattening test is...

  5. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    The varying flattening is also revealed by the geometry of folds. The apparent buckle shortening of folds which ranges between 49 and 67 per cent with a majority of the folds having shortening values between 50% and 55% (exclusive of layer parallel strain) and inverse thickness method strain up to 50%. Besides flattening ...

  6. Is the Mercier criterion relevant to stellarator stability?

    International Nuclear Information System (INIS)

    Carreras, B.A.; Lynch, V.E.; Ichiguchi, K.; Wakatani, M.; Tatsuno, T.

    2001-01-01

    Local flattening of the pressure profile at the resonant surfaces may significantly change the stellarator stability properties. This flattening may be an intrinsic consequence of the three-dimensional nature of the equilibrium and may invalidate the local stability criteria often used in stellarator design. (author)

  7. Beam Profile Disturbances from Implantable Pacemakers or Implantable Cardioverter-Defibrillator Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Gossman, Michael S., E-mail: mgossman@tsrcc.com [Tri-State Regional Cancer Center, Medical Physics Section, Ashland, KY (United States); Comprehensive Heart and Vascular Associates, Heart and Vascular Center, Ashland, KY (United States); Medtronic, Inc., External Research Program, Mounds View, MN (United States); Nagra, Bipinpreet; Graves-Calhoun, Alison; Wilkinson, Jeffrey [Tri-State Regional Cancer Center, Medical Physics Section, Ashland, KY (United States); Comprehensive Heart and Vascular Associates, Heart and Vascular Center, Ashland, KY (United States); Medtronic, Inc., External Research Program, Mounds View, MN (United States)

    2011-01-01

    The medical community is advocating for progressive improvement in the design of implantable cardioverter-defibrillators and implantable pacemakers to accommodate elevations in dose limitation criteria. With advancement already made for magnetic resonance imaging compatibility in some, a greater need is present to inform the radiation oncologist and medical physicist regarding treatment planning beam profile changes when such devices are in the field of a therapeutic radiation beam. Treatment plan modeling was conducted to simulate effects induced by Medtronic, Inc.-manufactured devices on therapeutic radiation beams. As a continuation of grant-supported research, we show that radial and transverse open beam profiles of a medical accelerator were altered when compared with profiles resulting when implantable pacemakers and cardioverter-defibrillators are placed directly in the beam. Results are markedly different between the 2 devices in the axial plane and the sagittal planes. Vast differences are also presented for the therapeutic beams at 6-MV and 18-MV x-ray energies. Maximum changes in percentage depth dose are observed for the implantable cardioverter-defibrillator as 9.3% at 6 MV and 10.1% at 18 MV, with worst distance to agreement of isodose lines at 2.3 cm and 1.3 cm, respectively. For the implantable pacemaker, the maximum changes in percentage depth dose were observed as 10.7% at 6 MV and 6.9% at 18 MV, with worst distance to agreement of isodose lines at 2.5 cm and 1.9 cm, respectively. No differences were discernible for the defibrillation leads and the pacing lead.

  8. Increased dose near the skin due to electromagnetic surface beacon transponder.

    Science.gov (United States)

    Ahn, Kang-Hyun; Manger, Ryan; Halpern, Howard J; Aydogan, Bulent

    2015-05-08

    The purpose of this study was to evaluate the increased dose near the skin from an electromagnetic surface beacon transponder, which is used for localization and tracking organ motion. The bolus effect due to the copper coil surface beacon was evaluated with radiographic film measurements and Monte Carlo simulations. Various beam incidence angles were evaluated for both 6 MV and 18 MV experimentally. We performed simulations using a general-purpose Monte Carlo code MCNPX (Monte Carlo N-Particle) to supplement the experimental data. We modeled the surface beacon geometry using the actual mass of the glass vial and copper coil placed in its L-shaped polyethylene terephthalate tubing casing. Film dosimetry measured factors of 2.2 and 3.0 enhancement in the surface dose for normally incident 6 MV and 18 MV beams, respectively. Although surface dose further increased with incidence angle, the relative contribution from the bolus effect was reduced at the oblique incidence. The enhancement factors were 1.5 and 1.8 for 6 MV and 18 MV, respectively, at an incidence angle of 60°. Monte Carlo simulation confirmed the experimental results and indicated that the epidermal skin dose can reach approximately 50% of the dose at dmax at normal incidence. The overall effect could be acceptable considering the skin dose enhancement is confined to a small area (~ 1 cm2), and can be further reduced by using an opposite beam technique. Further clinical studies are justified in order to study the dosimetric benefit versus possible cosmetic effects of the surface beacon. One such clinical situation would be intact breast radiation therapy, especially large-breasted women.

  9. Technical Note: Initial characterization of the new EBT-XD Gafchromic film.

    Science.gov (United States)

    Grams, Michael P; Gustafson, Jon M; Long, Kenneth M; de los Santos, Luis E Fong

    2015-10-01

    To assess the dosimetric accuracy and energy dependence of the new EBT-eXtended Dose (XD) Gafchromic film and to compare the lateral response artifact (LRA) between EBT-XD and EBT3 film. EBT3 and EBT-XD calibration curves were created by exposing films to known doses from 0 to 3000 cGy using a 6 MV beam. To assess the accuracy and dynamic range of EBT-XD, a 60° enhanced dynamic wedge (EDW) was used to deliver a dose range of approximately 200-2900 cGy. Comparison to treatment planning system (TPS) calculation was made using a gamma analysis with 2%/2 mm passing criteria. To assess and compare the LRA between EBT3 and EBT-XD, 21 × 21 cm(2) open fields delivered doses of 1000, 2000, and 3000 cGy to both types of film. Films were placed at the center of the scanner, and ratios of measured to TPS predicted doses were calculated at 50 and 80 mm lateral from the scanner center in order to quantitatively assess the LRA. To evaluate the energy dependence of EBT-XD film, seven known doses ranging from 400 to 3000 cGy were delivered using both 6 and 18 MV beams and the resulting optical densities (ODs) compared. The gamma passing rate was 99.1% for the 6 MV EDW delivery. EBT-XD film exhibited minimal LRA (XD films exposed to known doses from 6 to 18 MV beams were XD is greatly reduced when compared to EBT3. This in combination with its accuracy from 0 to 3000 cGy and minimal energy dependence from 6 to 18 MV makes EBT-XD film well suited for dosimetric measurements in high dose SRS/SBRT applications.

  10. Comments on shielding for dual energy accelerators

    International Nuclear Information System (INIS)

    Rossi, M. C.; Lincoln, H. M.; Quarin, D. J.; Zwicker, R. D.

    2008-01-01

    Determination of shielding requirements for medical linear accelerators has been greatly facilitated by the publication of the National Council on Radiation Protection and Measurements (NCRP) latest guidelines on this subject in NCRP Report No. 151. In the present report the authors review their own recent experience with patient treatments on conventional dual energy linear accelerators to examine the various input parameters needed to follow the NCRP guidelines. Some discussion is included of workloads, occupancy, use factors, and field size, with the effects of intensity modulated radiotherapy (IMRT) treatments included. Studies of collimator settings showed average values of 13.1x16.2 cm 2 for 6 MV and 14.1x16.8 cm 2 for 18 MV conventional ports, and corresponding average unblocked areas of 228 and 254 cm 2 , respectively. With an average of 77% of the field area unblocked, this gives a mean irradiated area of 196 cm 2 for the 18 MV beam, which dominates shielding considerations for most dual energy machines. Assuming conservatively small room dimensions, a gantry bin angle of 18 deg. was found to represent a reasonable unit for tabulation of use factors. For conventional 18 MV treatments it was found that the usual treatment angles of 0, 90, 180, and 270 deg. were still favored, and use factors of 0.25 represent reasonable estimates for these beams. As expected, the IMRT fields (all at 6 MV) showed a high degree of gantry angle randomization, with no bin having a use factor in excess of 0.10. It is concluded that unless a significant number of patients are treated with high energy IMRT, the traditional use factors of 0.25 are appropriate for the dominant high energy beam

  11. Comments on shielding for dual energy accelerators.

    Science.gov (United States)

    Rossi, M C; Lincoln, H M; Quarin, D J; Zwicker, R D

    2008-06-01

    Determination of shielding requirements for medical linear accelerators has been greatly facilitated by the publication of the National Council on Radiation Protection and Measurements (NCRP) latest guidelines on this subject in NCRP Report No. 151. In the present report the authors review their own recent experience with patient treatments on conventional dual energy linear accelerators to examine the various input parameters needed to follow the NCRP guidelines. Some discussion is included of workloads, occupancy, use factors, and field size, with the effects of intensity modulated radiotherapy (IMRT) treatments included. Studies of collimator settings showed average values of 13.1 x 16.2 cm2 for 6 MV and 14.1 x 16.8 cm2 for 18 MV conventional ports, and corresponding average unblocked areas of 228 and 254 cm2, respectively. With an average of 77% of the field area unblocked, this gives a mean irradiated area of 196 cm2 for the 18 MV beam, which dominates shielding considerations for most dual energy machines. Assuming conservatively small room dimensions, a gantry bin angle of 18 degrees was found to represent a reasonable unit for tabulation of use factors. For conventional 18 MV treatments it was found that the usual treatment angles of 0, 90, 180, and 270 degrees were still favored, and use factors of 0.25 represent reasonable estimates for these beams. As expected, the IMRT fields (all at 6 MV) showed a high degree of gantry angle randomization, with no bin having a use factor in excess of 0.10. It is concluded that unless a significant number of patients are treated with high energy IMRT, the traditional use factors of 0.25 are appropriate for the dominant high energy beam.

  12. Three-dimensional conformal pancreas treatment: comparison of four- to six-field techniques

    International Nuclear Information System (INIS)

    Higgins, Patrick D.; Sohn, Jason W.; Fine, Robert M.; Schell, Michael C.

    1995-01-01

    Purpose: We compare practical conformal treatment approaches to pancreatic cancer using 6 and 18 MV photons and contrast those approaches against standard techniques. Methods and Materials: A four-field conformal technique for treating pancreas cancer has been developed using nonopposed 18 MV photons. This approach has been extended to 6 MV photon application by the addition of one to two fields. These techniques have been optimized to increase sparing of normal liver and bowel, compared with opposed-field methods, to improve patient tolerance of high doses. In this study we compare these techniques in a simulated tumor model in a cylindrical phantom. Dose-volume analysis is used to quantify differences between the conformal, nonopposed techniques with conformal, opposed field methods. This model is also used to evaluate the effect of 1-2 cm setup errors on dose-volume coverage. Results: Dose-volume analysis demonstrates that five-to-six field conformal treatments using 6 MV photons provides similar or better dose coverage and normal tissue sparing characteristics as an optimized 18 MV, four-field approach when 1-2 cm margins are included for setup uncertainty. All approaches using nonopposed beam geometry provide significant reduction in the volume of tissue encompassed by the 30-50% isodose surfaces, as compared with four-field box techniques. Conclusions: Three-dimensional (3D) conformal treatments can be designed that significantly improve dose-volume characteristics over conventional treatment designs without costing unacceptable amounts of machine time. Further, deep intraabdominal sites can be adequately accessed and treated on intermediate energy machines with a relatively moderate increase in machine time

  13. The influence of x-ray energy on lung dose uniformity in total-body irradiation

    International Nuclear Information System (INIS)

    Ekstrand, Kenneth; Greven, Kathryn; Wu Qingrong

    1997-01-01

    Purpose: In this study we examine the influence of x-ray energy on the uniformity of the dose within the lung in total-body irradiation treatments in which partial transmission blocks are used to control the lung dose. Methods and Materials: A solid water phantom with a cork insert to simulate a lung was irradiated by x-rays with energies of either 6, 10, or 18 MV. The source to phantom distance was 3.9 meters. The cork insert was either 10 cm wide or 6 cm wide. Partial transmission blocks with transmission factors of 50% were placed anterior to the cork insert. The blocks were either 8 or 4 cm in width. Kodak XV-2 film was placed in the midline of the phantom to record the dose. Midplane dose profiles were measured with a densitometer. Results: For the 10 cm wide cork insert the uniformity of the dose over 80% of the block width varied from 6.6% for the 6 MV x-rays to 12.2% for the 18 MV x-rays. For the 6 cm wide cork insert the uniformity was comparable for all three x-ray energies, but for 18 MV the central dose increased by 9.4% compared to the 10 cm wide insert. Conclusion: Many factors must be considered in optimizing the dose for total-body irradiation. This study suggests that for AP/PA techniques lung dose uniformity is superior with 6 MV irradiation. The blanket recommendation that the highest x-ray energy be used in TBI is not valid for all situations

  14. Dosimetry and microdosimetry using LET spectrometer based on the track-etch detector: radiotherapy Bremsstrahlung beam, onboard aircraft radiation field

    International Nuclear Information System (INIS)

    Jadrnickova, I.; Spurny, F.

    2006-01-01

    The spectrometer of linear energy transfer (Let) based on the chemically etched poly-allyl-diglycol-carbonate (P.A.D.C.) track-etch detector was developed several years ago in our institute. This Let spectrometer enables determining Let of particles approximately from 10 to 700 keV/μm. From the Let spectra, dose characteristics can be calculated. The contribution presents the Let spectra and other dosimetric characteristics obtained onboard a commercial aircraft during more than 6 months long exposure and in the 18 MV radiotherapy Bremsstrahlung beam. (authors)

  15. The superconducting linac booster at the ANU

    International Nuclear Information System (INIS)

    Weisser, D.C.

    1995-02-01

    This report outlines the progress of the installation of the superconducting Linac booster at the Australian National University. The Linac is based upon four modules, three of which contain three split-loop resonators. The fourth cryostat was intended to be a superbuncher and so houses only one resonator. The first stage of Linac operation will employ only three modules with 2 MV/m from each resonator. It is expected that the implementation of all nine modules, in subsequent stages, would boost beams by 18 MV/q. The project has fostered productive international collaboration between UK and Australian scientists. 1 tab., 6 figs

  16. Peripheral dose in photon beams from a linear accelerator with a multileaf collimator

    International Nuclear Information System (INIS)

    Lope Lope, R.; Lozano Flores, F.; Gracia Sorrosal, J.; Font Gomez, J.A.; Hernandez Vitoria, A.

    2001-01-01

    Radiation doses outside the radiotherapy treatment field are of radiation protection interest when anatomical structures with very low dose tolerances might be involved. One of the major sources of peripheral dose, scatter from secondary collimators, depends on the configuration of the collimator. In this study, peripheral dose was measured at two depths for 6 and 18 MV photons from a linac Primus (Siemens) with a multileaf collimator (MLC). Comparative measurements were made both with leaves and with the upper jaw positioned at the field edge near to the detector. Configuring the MLC leaves at the field edge yielded a reduction in peripheral dose. (author)

  17. Dose to radiation therapists from activation at high-energy accelerators used for conventional and intensity-modulated radiation therapy

    International Nuclear Information System (INIS)

    Rawlinson, J. Alan; Islam, Mohammad K.; Galbraith, Duncan M.

    2002-01-01

    The increased beam-on times which characterize intensity-modulated radiation therapy (IMRT) could lead to an increase in the dose received by radiation therapists due to induced activity. To examine this, gamma ray spectrometry was used to identify the major isotopes responsible for activation at a representative location in the treatment room of an 18 MV accelerator (Varian Clinac 21EX). These were found to be 28 Al, 56 Mn, and 24 Na. The decay of the dose rate measured at this location following irradiation was analyzed in terms of the known half-lives to yield saturation dose rates of 9.6, 12.4, and 6.2 μSv/h, respectively. A formalism was developed to estimate activation dose (μSv/week) due to successive patient irradiation cycles, characterized by the number of 18 MV fractions per week, F, the number of MU per fraction, M, the in-room time between fractions, t d (min), and the treatment delivery time t r ' (min). The results are represented by the sum of two formulas, one for the dose from 28 Al≅1.8x10 -3 F M (1-e -0.3t r ' )/t r ' and one for the dose from the other isotopes ≅1.1x10 -6 F 1.7 Mt d . For conventional therapy doses are about 60 μ Sv/week for an 18 MV workload of 60 000 MU/week. Irradiation for QA purposes can significantly increase the dose. For IMRT as currently practiced, lengthy treatment delivery times limit the number of fractions that can be delivered per week and hence limit the dose to values similar to those in conventional therapy. However for an IMRT regime designed to maximize patient throughput, doses up to 330 μSv/week could be expected. To reduce dose it is recommended that IMRT treatments should be delivered at energies lower than 18 MV, that in multienergy IMRT, high-energy treatments should be scheduled in the latter part of the day, and that equipment manufacturers should strive to minimize activation in the design of high-energy accelerators

  18. Improving radiochromic film's sensitivity by wrapping it with UV phosphor

    International Nuclear Information System (INIS)

    Geso, Moshi; Ackerly, Trevor; Patterson, William

    2004-01-01

    The main advantage of radiochromic-film dosimeters is the coupling of rapid full planar-acquisition, high-spatial resolution and dose linearity. Their main limitation, however, is their low radiation sensitivity. This precludes their application to measuring doses below a few Gy. Radiochromic films are sensitive to ultraviolet radiation. In this note the results of exposing radiochromic films to x rays through an UV imaging cassette, which converts and amplifies x rays to UV radiation, are presented. These results indicate a clear increase (around 50%) in radiochromic film's sensitivity to MV x rays (6, 10, and 18 MV) when exposed through the UV phosphor

  19. Electrostatic field distributions in the Harwell Tandem accelerator

    International Nuclear Information System (INIS)

    Read, P.M.

    1981-11-01

    The electrostatic field distributions in the Harwell Tandem accelerator have been precisely calculated using the electrostatics program FINALE. The results indicate that the accelerator which presently has an upper voltage limit of 6.5 MV has the potential to operate at 8 MV. Such an upgrade could be achieved by a modification to the high voltage terminal. Replacement of the existing accelerator tubes with accelerator tubes capable of a gradient of 1.8 MV/m would also be required. The existing stack may also require replacement. The terminal modification itself would reduce the terminal to tank breakdown frequency. (author)

  20. Characterization of materials for prosthetic implants using the BEAMnrc Monte Carlo code

    International Nuclear Information System (INIS)

    Spezi, E; Palleri, F; Angelini, A L; Ferri, A; Baruffaldi, F

    2007-01-01

    Metallic implants degrade image quality and perturb severely the patient dose distribution in external beam radiotherapy. Furthermore, conventional treatment planning systems (TPS) do not accurately account for tissue heterogeneities, especially at the interfaces where high Z gradients are present. This work deals with the accurate and systematic characterization of materials used for prosthetic implants. The dose calculation engine used in this investigation is the BEAMnrc Monte Carlo code. A detailed comparison versus experimental data was carried out for two clinical photon beam energies (6MV and 18MV). Our results show that in both cases a very good agreement (within ± 2%) between calculations and experiments was achieved

  1. Feasibility study of using PET to determine nitrogen concentration after high energy photon irradiation

    International Nuclear Information System (INIS)

    Alghamdi, A.A.; Spyrou, N.M.; Al-Mokhlef, J.; Alhaj, A.

    2007-01-01

    The technique of photon activation analysis (PAA) is widely employed in many fields as an effective non-invasive tool for measuring elemental compositions and concentrations. In recent years there has been a revival and growing interest of PAA in general and for medical applications in particular. The feasibility of using a PET scanner (Ecat Exact 931) to determine nitrogen concentration in a dead rabbit is described. This method is based on the photon activation of 14 N(γ,n) 13 N (T 1/2 = 9.9 min) using an 18 MV photon beam Medical Linear Accelerator (Varian 2300EX). (author)

  2. SU-E-T-336: Dosimetric Properties of a New Solid Water High Equivalency Phantom for High-Energy Photon Beams

    International Nuclear Information System (INIS)

    Araki, F; Ohno, T; Onitsuka, R; Shimohigashi, Y

    2015-01-01

    Purpose: To investigate dosimetric properties in high-energy photon beams for a Solid Water High Equivalency (SWHE, SW557) phantom (Gammex) which was newly developed as water mimicking material. Methods: The mass density of SWHE and SWHE/water electron density ratio are 1.032 g/cm 3 and 1.005 according to the manufacturer information, respectively. SWHE is more water equivalent material in physical characteristics and uniformity than conventional SW457. This study calculated the relative ionization ratio of water and SWHE as a function of depth from the cavity dose in PTW30013 and Exradin A19 Farmer-type ionization chambers using Monte Caro simulations. The simulation was performed with a 10 x 10 cm 2 field at SAD of 100 cm for 4, 6, 10, 15, and 18 MV photons. The ionization ratio was also measured with the PTW30013 chamber for 6 and 15 MV photons. In addition, the overall perturbation factor of both chambers was calculated for both phantoms. Results: The relative ionization ratio curves for water and SWHE was in good agreement for all photon energies. The ionization ratio of water/SWHE for both chambers was 0.999–1.002, 0.999–1.002, 1.001–1.004, 1.004–1.007, and 1.006–1.010 at depths of over the buildup region for 4, 6, 10, 15, and 18 MV photons, respectively. The ionization ratio of water/SWHE increased up to 1% with increasing the photon energy. The measured ionization ratio of water/SWHE for 6 and 15 MV photons agreed well with calculated values. The overall perturbation factor for both chambers was 0.983–0.988 and 0.978–0.983 for water and SWHE, respectively, in a range from 4 MV to 18 MV. Conclusion: The depth scaling factor of water/SWHE was equal to unity for all photon energies. The ionization ratio of water/SWHE at a reference depth was equal to unity for 4 and 6 MV and larger up to 0.7% than unity for 18 MV

  3. SU-F-T-371: Development of a Linac Monte Carlo Model to Calculate Surface Dose

    Energy Technology Data Exchange (ETDEWEB)

    Prajapati, S; Yan, Y; Gifford, K [UT MD Anderson Cancer Center, Houston, TX (United States)

    2016-06-15

    Purpose: To generate and validate a linac Monte Carlo (MC) model for surface dose prediction. Methods: BEAMnrc V4-2.4.0 was used to model 6 and 18 MV photon beams for a commercially available linac. DOSXYZnrc V4-2.4.0 calculated 3D dose distributions in water. Percent depth dose (PDD) and beam profiles were extracted for comparison to measured data. Surface dose and at depths in the buildup region was measured with radiochromic film at 100 cm SSD for 4 × 4 cm{sup 2} and 10 × 10 cm{sup 2} collimator settings for open and MLC collimated fields. For the 6 MV beam, films were placed at depths ranging from 0.015 cm to 2 cm and for 18 MV, 0.015 cm to 3.5 cm in Solid Water™. Films were calibrated for both photon energies at their respective dmax. PDDs and profiles were extracted from the film and compared to the MC data. The MC model was adjusted to match measured PDD and profiles. Results: For the 6 MV beam, the mean error(ME) in PDD between film and MC for open fields was 1.9%, whereas it was 2.4% for MLC. For the 18 MV beam, the ME in PDD for open fields was 2% and was 3.5% for MLC. For the 6 MV beam, the average root mean square(RMS) deviation for the central 80% of the beam profile for open fields was 1.5%, whereas it was 1.6% for MLC. For the 18 MV beam, the maximum RMS for open fields was 3%, and was 3.1% for MLC. Conclusion: The MC model of a linac agreed to within 4% of film measurements for depths ranging from the surface to dmax. Therefore, the MC linac model can predict surface dose for clinical applications. Future work will focus on adjusting the linac MC model to reduce RMS error and improve accuracy.

  4. Fiber-coupled Al2O3:C radioluminescence dosimetry for total body irradiations

    DEFF Research Database (Denmark)

    Buranurak, Siritorn; Andersen, Claus E.

    2016-01-01

    in the context of Total Body Irradiations (TBIs) where patients are treated with large fields of 6 or 18 MV photons at an extended source-to-surface distance (SSD). The study shows that Al2O3:C dosimetry using the saturated-RL protocol may be suitable for real-time in vivo dosimetry during TBI treatments from...... the perspective of the good agreement with alanine dosimetry and other critical phantom tests, including the ability to cope with the large stem signal experienced during TBI treatments at extended SSD. In contrast, the chromatic stem removal technique often used for organic plastic scintillators did not work...

  5. Effect of scattered electrons on the ‘Magic Plate’ transmission array detector response

    Science.gov (United States)

    Alrowaili, Z. A.; Lerch, M.; Petasecca, M.; Carolan, M.; Rosenfeld, A.

    2017-02-01

    Transmission type detectors can provide a measure of the energy fluence and if they are real-time systems that do not significantly attenuate the radiation beam have a distinct advantage over the current method as Quality Assurance (QA) could in principle be done during the actual patient treatment. The use of diode arrays in QA holds much promise due to real-time operation and feedback when compared to other methods e.g. films which are not real-time. The goal of this work is to describe the characterization of the radiation response of a silicon diode array called the Magic Plate (MP) when operated in transmission mode (MPTM). The response linearity of MPTM was excellent (R2=1). When the MP was placed in linac block tray position; the change in PDD at phantom surface (SSD 100 cm) for a 10 × 10 cm2 was -0.037 %, -0.178 % and -0.949 % for 6 MV, 10 MV and 18 MV beams. Therefore, MP does not provide a significant increase in skin dose to the patient and the percentage depth doses showed an excellent agreement with and without MPTM for 6 MV, 10 MV and 18 MV beams.

  6. Effect of scattered electrons on the ‘Magic Plate’ transmission array detector response

    International Nuclear Information System (INIS)

    Alrowaili, Z A; Lerch, M; Petasecca, M; Rosenfeld, A; Carolan, M

    2017-01-01

    Transmission type detectors can provide a measure of the energy fluence and if they are real-time systems that do not significantly attenuate the radiation beam have a distinct advantage over the current method as Quality Assurance (QA) could in principle be done during the actual patient treatment. The use of diode arrays in QA holds much promise due to real-time operation and feedback when compared to other methods e.g. films which are not real-time. The goal of this work is to describe the characterization of the radiation response of a silicon diode array called the Magic Plate (MP) when operated in transmission mode (MPTM). The response linearity of MPTM was excellent (R2=1). When the MP was placed in linac block tray position; the change in PDD at phantom surface (SSD 100 cm) for a 10 × 10 cm 2 was -0.037 %, -0.178 % and -0.949 % for 6 MV, 10 MV and 18 MV beams. Therefore, MP does not provide a significant increase in skin dose to the patient and the percentage depth doses showed an excellent agreement with and without MPTM for 6 MV, 10 MV and 18 MV beams. (paper)

  7. Monte Carlo based water/medium stopping-power ratios for various ICRP and ICRU tissues

    International Nuclear Information System (INIS)

    Fernandez-Varea, Jose M; Carrasco, Pablo; Panettieri, Vanessa; Brualla, Lorenzo

    2007-01-01

    Water/medium stopping-power ratios, s w,m , have been calculated for several ICRP and ICRU tissues, namely adipose tissue, brain, cortical bone, liver, lung (deflated and inflated) and spongiosa. The considered clinical beams were 6 and 18 MV x-rays and the field size was 10 x 10 cm 2 . Fluence distributions were scored at a depth of 10 cm using the Monte Carlo code PENELOPE. The collision stopping powers for the studied tissues were evaluated employing the formalism of ICRU Report 37 (1984 Stopping Powers for Electrons and Positrons (Bethesda, MD: ICRU)). The Bragg-Gray values of s w,m calculated with these ingredients range from about 0.98 (adipose tissue) to nearly 1.14 (cortical bone), displaying a rather small variation with beam quality. Excellent agreement, to within 0.1%, is found with stopping-power ratios reported by Siebers et al (2000a Phys. Med. Biol. 45 983-95) for cortical bone, inflated lung and spongiosa. In the case of cortical bone, s w,m changes approximately 2% when either ICRP or ICRU compositions are adopted, whereas the stopping-power ratios of lung, brain and adipose tissue are less sensitive to the selected composition. The mass density of lung also influences the calculated values of s w,m , reducing them by around 1% (6 MV) and 2% (18 MV) when going from deflated to inflated lung

  8. The response of Kodak EDR2 film in high-energy electron beams.

    Science.gov (United States)

    Gerbi, Bruce J; Dimitroyannis, Dimitri A

    2003-10-01

    Kodak XV2 film has been a key dosimeter in radiation therapy for many years. The advantages of the recently introduced Kodak EDR2 film for photon beam dosimetry have been the focus of several IMRT verification dosimetry publications. However, no description of this film's response to electron beams exists in the literature. We initiated a study to characterize the response and utility of this film for electron beam dosimetry. We exposed a series of EDR2 films to 6, 9, 12, 16, and 20 MeV electrons in addition to 6 and 18 MV x rays to develop standard characteristic curves. The linac was first calibrated to ensure that the delivered dose was known accurately. All irradiations were done at dmax in polystyrene for both photons and electrons, all films were from the same batch, and were developed at the same time. We also exposed the EDR2 films in a solid water phantom to produce central axis depth dose curves. These data were compared against percent depth dose curves measured in a water phantom using an IC-10 ion chamber, Kodak XV2 film, and a PTW electron diode. The response of this film was the same for both 6 and 18 MV x rays, but showed an apparent energy-dependent enhancement for electron beams. The response of the film also increased with increasing electron energy. This caused the percent depth dose curves using film to be shifted toward the surface compared to the ion chamber data.

  9. Development of a computational model for the calculation of neutron dose equivalent in laminated primary barriers of radiotherapy rooms; Desenvolvimento de um modelo computacional para calculo do equivalente de dose de neutrons em barreiras primarias laminadas de salas de radioterapia

    Energy Technology Data Exchange (ETDEWEB)

    Rezende, Gabriel Fonseca da Silva

    2015-06-01

    Many radiotherapy centers acquire 15 and 18 MV linear accelerators to perform more effective treatments for deep tumors. However, the acquisition of these equipment must be accompanied by an additional care in shielding planning of the rooms that will house them. In cases where space is restricted, it is common to find primary barriers made of concrete and metal. The drawback of this type of barrier is the photoneutron emission when high energy photons (e.g. 15 and 18 MV spectra) interact with the metallic material of the barrier. The emission of these particles constitutes a problem of radiation protection inside and outside of radiotherapy rooms, which should be properly assessed. A recent work has shown that the current model underestimate the dose of neutrons outside the treatment rooms. In this work, a computational model for the aforementioned problem was created from Monte Carlo Simulations and Artificial Intelligence. The developed model was composed by three neural networks, each being formed of a pair of material and spectrum: Pb18, Pb15 and Fe18. In a direct comparison with the McGinley method, the Pb18 network exhibited the best responses for approximately 78% of the cases tested; the Pb15 network showed better results for 100% of the tested cases, while the Fe18 network produced better answers to 94% of the tested cases. Thus, the computational model composed by the three networks has shown more consistent results than McGinley method. (author)

  10. A theoretical model for the production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226.

    Science.gov (United States)

    Melville, G; Fan Liu, Sau; Allen, B J

    2006-09-01

    Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. We are investigating the reduction of radium by transmutation on a small scale by bombarding Ra-226 with high-energy photons from a medical linear accelerator (linac) to produce Ra-225, which subsequently decays to Ac-225, which can be used as a generator to produce Bi-213 for use in 'targeted alpha therapy' for cancer. This paper examines the possibility of producing Ac-225 with a linac using an accurate theoretical model in which the bremsstrahlung photon spectrum at 18 MV linac electron energy is convoluted with the corresponding photonuclear cross sections of Ra-226. The total integrated yield can then be obtained and is compared with a computer simulation. This study shows that at 18 MV, the photonuclear reaction on Ra-226 can produce low activities of Ac-225 with a linac. However, a high power linac with high current, pulse length and frequency is needed to produce practical amounts of Ac-225 and a useful reduction of Ra-226.

  11. Leakage of the Siemens 160 MLC multileaf collimator on a dual energy linear accelerator

    International Nuclear Information System (INIS)

    Klueter, Sebastian; Sroka-Perez, Gabriele; Schubert, Kai; Debus, Juergen

    2011-01-01

    Multileaf collimators (MLCs) have been in clinical use for many years and meanwhile are commonly used to deliver intensity-modulated radiotherapy (IMRT) beams. For this purpose it is important to know their dosimetric properties precisely, one of them being inter- and intraleaf leakage. The Siemens 160 MLC features a single focus design with flat-sided and tilted leaves instead of tongue-and-groove. The leakage performance of the 160 MLC was investigated on a dual energy linear accelerator Siemens ARTISTE with 6 MV and 18 MV photon energies. While the intraleaf leakage amounted to nearly the same dose for 6 and for 18 MV, a much higher interleaf leakage for 6 MV was measured. It could be reduced by simply rotating the collimator, and also by changing the voltage applied to the beam steering coils. The leakage of the 160 MLC is shown to be sensitive to beam alignment. This is of special interest for dual energy accelerators, as the two focal spots of both energies, neither in position nor in shape, do not necessarily always coincide. As a consequence of that, a higher leakage can be expected for one out of two energies for the 160 MLC. (note)

  12. Development of a computational model for the calculation of neutron dose equivalent in laminated primary barriers of radiotherapy rooms

    International Nuclear Information System (INIS)

    Rezende, Gabriel Fonseca da Silva

    2015-01-01

    Many radiotherapy centers acquire 15 and 18 MV linear accelerators to perform more effective treatments for deep tumors. However, the acquisition of these equipment must be accompanied by an additional care in shielding planning of the rooms that will house them. In cases where space is restricted, it is common to find primary barriers made of concrete and metal. The drawback of this type of barrier is the photoneutron emission when high energy photons (e.g. 15 and 18 MV spectra) interact with the metallic material of the barrier. The emission of these particles constitutes a problem of radiation protection inside and outside of radiotherapy rooms, which should be properly assessed. A recent work has shown that the current model underestimate the dose of neutrons outside the treatment rooms. In this work, a computational model for the aforementioned problem was created from Monte Carlo Simulations and Artificial Intelligence. The developed model was composed by three neural networks, each being formed of a pair of material and spectrum: Pb18, Pb15 and Fe18. In a direct comparison with the McGinley method, the Pb18 network exhibited the best responses for approximately 78% of the cases tested; the Pb15 network showed better results for 100% of the tested cases, while the Fe18 network produced better answers to 94% of the tested cases. Thus, the computational model composed by the three networks has shown more consistent results than McGinley method. (author)

  13. 7 CFR 51.1015 - Serious damage.

    Science.gov (United States)

    2010-01-01

    ...) which occurs as small spots over more than 25 percent of the fruit surface, or as solid scarring (not...) Sunburn which causes decided flattening of the fruit, marked drying or dark discoloration of the skin...

  14. Intra- and interobserver agreement of computed tomography in assessment of the mandibular condyle

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Bong Hae; Jung, Yun Hoa [Pusan National Univ. College of Dentistry, Pusan (Korea, Republic of)

    2007-12-15

    To study the intra- and interobserver agreement of multidetector row computed tomography (MDCT) in interpretation of degenerative changes of the mandibular condyle. Five observers independently evaluated one hundred temporomandibular joint MDCT images for signs of osteophytes, erosion, sclerosis and flattening. The intra- and interobserve agreements were calculated by using Kappa statistics. The intraobserver agreement was substantial for erosion (k=0.75), flattening (k=0.74) and sclerosis (k=0.72) and almost perfect for osteophytes (k=0.84). The interobserver agreement was fair for flattening (k=0.39), moderate for erosion (k=0.58) and sclerosis (k=0.48) and substantial for osteophytes (k=0.75). This study shows that we can expert good agreement for the presence of osteophytes, but not for flattening in the interpretation of MDCT images of the condyle.

  15. 49 CFR 178.53 - Specification 4D welded steel cylinders for aircraft use.

    Science.gov (United States)

    2010-10-01

    ... the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed 1/8... tensile strength. In this instance, the flattening test is not required. (2) An elongation of at least 20...

  16. 49 CFR 178.65 - Specification 39 non-reusable (non-refillable) cylinders.

    Science.gov (United States)

    2010-10-01

    ... Check analysis Carbon, maximum percent 0.12 0.15 Phosphorus, maximum percent .04 .05 Sulfur, maximum... circumferential weld if it is located at a 45 degree angle to the ring, ±5 degrees. (3) The flattening must be...

  17. Novel Design for Centrifugal Countercurrent Chromatography: II. Studies on Novel Geometries of Zigzag Toroidal Tubing

    Science.gov (United States)

    Yang, Yi; Aisa, Haji Akber; Ito, Yoichiro

    2009-01-01

    The toroidal column using a zigzag pattern has been improved in both retention of the stationary phase and peak resolution. To further improve the retention of stationary phase and peak resolution, a series of novel geometric designs of tubing (plain, mid-clamping, flattened and flat-twisted tubing) was evaluated their performance in CCC. The results showed that the tubing which was flattened vertically against centrifugal force (vert-flattened tubing) produced the best peak resolution among them. Using vert-flattened tubing a series of experiments was performed to study the effects of column capacity and sample size. The results indicated that a 0.25 ml capacity column is ideal for analysis of small amount samples. PMID:20454530

  18. Safety effects of cross-section design for two-lane roads. Volume 1

    Science.gov (United States)

    1987-10-01

    This study was intended to quantify the benefits and costs resulting from lane widening, shoulder widening, shoulder surfacing, sideslope flattening, and roadside improvements. Detailed traffic, accident, and roadway data were collected on 4,951 mile...

  19. Genetics Home Reference: Kniest dysplasia

    Science.gov (United States)

    ... may include a rounded upper back that also curves to the side ( kyphoscoliosis ), severely flattened bones of ... Information What information about a genetic condition can statistics provide? Why are some genetic conditions more common ...

  20. Command and Control Systems: Outlooks for a Digitized Future

    National Research Council Canada - National Science Library

    McCaffery, Michael

    2001-01-01

    .... In the first subject area: organizations, commercial firms have adapted to leverage technology by moving from hierarchies to flat and networked organizational structures Force XXI proposes a 'flattened organization to achieve...

  1. Flowering Trees

    Indian Academy of Sciences (India)

    Srimath

    shaped corolla. Fruit is large, ellipsoidal, green with a hard and smooth shell containing numerous flattened seeds, which are embedded in fleshy pulp. Calabash tree is commonly grown in the tropical gardens of the world as a botanical oddity.

  2. Discovering the Rotation of our own Galaxy

    Indian Academy of Sciences (India)

    IAS Admin

    more than two decades at the Raman Research. Institute in ... two most basic measurements of the motions of nearby stars. ... Kapetyn had built a quantitative model of a flattened ..... variables to make sure that the formulae really describe.

  3. What Is the Pancreas?

    Science.gov (United States)

    ... Pancreas Function of the Pancreas What is the pancreas? The pancreas is a long flattened gland located ... controller of blood sugar levels. Where is the pancreas? The pancreas is located deep in the abdomen. ...

  4. Photonic crystal fibers used in a multi-wavelength source and as transmission fiber in a WDM system

    DEFF Research Database (Denmark)

    Andersen, Peter Andreas; Zsigri, Beata; Peucheret, Christophe

    2004-01-01

    We present a WDM system based entirely on photonic crystal fibers. It includes a novel dispersion flattened highly nonlinear PCF to generate supercontinuum used in a multiwavelength pulse source and a 5.6 km transmission PCF.......We present a WDM system based entirely on photonic crystal fibers. It includes a novel dispersion flattened highly nonlinear PCF to generate supercontinuum used in a multiwavelength pulse source and a 5.6 km transmission PCF....

  5. Control of Dispersion in Hollow Core Photonic Crystal Fibers

    DEFF Research Database (Denmark)

    Roberts, John

    2007-01-01

    The dispersion of hollow core photonic crystal fibers can be tailored by modifying a single ring of holes in the cladding. The dispersion can be lowered and flattened, or alternatively greatly increased, in a controlled manner.......The dispersion of hollow core photonic crystal fibers can be tailored by modifying a single ring of holes in the cladding. The dispersion can be lowered and flattened, or alternatively greatly increased, in a controlled manner....

  6. Examining explanations for fundamental frequency's contribution to speech intelligibility in noise

    Science.gov (United States)

    Schlauch, Robert S.; Miller, Sharon E.; Watson, Peter J.

    2005-09-01

    Laures and Weismer [JSLHR, 42, 1148 (1999)] reported that speech with natural variation in fundamental frequency (F0) is more intelligible in noise than speech with a flattened F0 contour. Cognitive-linguistic based explanations have been offered to account for this drop in intelligibility for the flattened condition, but a lower-level mechanism related to auditory streaming may be responsible. Numerous psychoacoustic studies have demonstrated that modulating a tone enables a listener to segregate it from background sounds. To test these rival hypotheses, speech recognition in noise was measured for sentences with six different F0 contours: unmodified, flattened at the mean, natural but exaggerated, reversed, and frequency modulated (rates of 2.5 and 5.0 Hz). The 180 stimulus sentences were produced by five talkers (30 sentences per condition). Speech recognition for fifteen listeners replicate earlier findings showing that flattening the F0 contour results in a roughly 10% reduction in recognition of key words compared with the natural condition. Although the exaggerated condition produced results comparable to those of the flattened condition, the other conditions with unnatural F0 contours all yielded significantly poorer performance than the flattened condition. These results support the cognitive, linguistic-based explanations for the reduction in performance.

  7. SU-F-T-330: Characterization of the Clinically Released ScandiDos Discover Diode Array for In-Vivo Dose Monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Saenz, D; Gutierrez, A [University of Texas Health Science Center San Antonio, San Antonio, TX (United States)

    2016-06-15

    Purpose: The ScandiDos Discover has obtained FDA clearance and is now clinically released. We studied the essential attenuation and beam hardening components as well as tested the diode array’s ability to detect changes in absolute dose and MLC leaf positions. Methods: The ScandiDos Discover was mounted on the heads of an Elekta VersaHD and a Varian 23EX. Beam attenuation measurements were made at 10 cm depth for 6 MV and 18 MV beam energies. The PDD(10) was measured as a metric for the effect on beam quality. Next, a plan consisting of two orthogonal 10 × 10 cm2 fields was used to adjust the dose per fraction by scaling monitor units to test the absolute dose detection sensitivity of the Discover. A second plan (conformal arc) was then delivered several times independently on the Elekta VersaHD. Artificially introduced MLC position errors in the four central leaves were then added. The errors were incrementally increased from 1 mm to 4 mm and back across seven control points. Results: The absolute dose measured at 10 cm depth decreased by 1.2% and 0.7% for 6 MV and 18 MV beam with the Discover, respectively. Attenuation depended slightly on the field size but only changed the attenuation by 0.1% across 5 × 5 cm{sup 2} and 20 − 20 cm{sup 2} fields. The change in PDD(10) for a 10 − 10 cm{sup 2} field was +0.1% and +0.6% for 6 MV and 18 MV, respectively. Changes in monitor units from −5.0% to 5.0% were faithfully detected. Detected leaf errors were within 1.0 mm of intended errors. Conclusion: A novel in-vivo dosimeter monitoring the radiation beam during treatment was examined through its attenuation and beam hardening characteristics. The device tracked with changes in absolute dose as well as introduced leaf position deviations.

  8. Commissioning of a PTW 34070 large-area plane-parallel ionization chamber for small field megavoltage photon dosimetry.

    Science.gov (United States)

    Kupfer, Tom; Lehmann, Joerg; Butler, Duncan J; Ramanathan, Ganesan; Bailey, Tracy E; Franich, Rick D

    2017-11-01

    This study investigates a large-area plane-parallel ionization chamber (LAC) for measurements of dose-area product in water (DAP w ) in megavoltage (MV) photon fields. Uniformity of electrode separation of the LAC (PTW34070 Bragg Peak Chamber, sensitive volume diameter: 8.16 cm) was measured using high-resolution microCT. Signal dependence on angle α of beam incidence for square 6 MV fields of side length s = 20 cm and 1 cm was measured in air. Polarity and recombination effects were characterized in 6, 10, and 18 MV photons fields. To assess the lateral setup tolerance, scanned LAC profiles of a 1 × 1 cm 2 field were acquired. A 6 MV calibration coefficient, N D ,w, LAC , was determined in a field collimated by a 5 cm diameter stereotactic cone with known DAP w . Additional calibrations in 10 × 10 cm 2 fields at 6, 10, and 18 MV were performed. Electrode separation is uniform and agrees with specifications. Volume-averaging leads to a signal increase proportional to ~1/cos(α) in small fields. Correction factors for polarity and recombination range between 0.9986 to 0.9996 and 1.0007 to 1.0024, respectively. Off-axis displacement by up to 0.5 cm did not change the measured signal in a 1 × 1 cm 2 field. N D ,w, LAC was 163.7 mGy cm -2 nC -1 and differs by +3.0% from the coefficient derived in the 10 × 10 cm 2 6 MV field. Response in 10 and 18 MV fields increased by 1.0% and 2.7% compared to 6 MV. The LAC requires only small correction factors for DAP w measurements and shows little energy dependence. Lateral setup errors of 0.5 cm are tolerated in 1 × 1 cm 2 fields, but beam incidence must be kept as close to normal as possible. Calibration in 10 × 10 fields is not recommended because of the LAC's over-response. The accuracy of relative point-dose measurements in the field's periphery is an important limiting factor for the accuracy of DAP w measurements. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on

  9. Experimental verification of a commercial Monte Carlo-based dose calculation module for high-energy photon beams

    International Nuclear Information System (INIS)

    Kuenzler, Thomas; Fotina, Irina; Stock, Markus; Georg, Dietmar

    2009-01-01

    The dosimetric performance of a Monte Carlo algorithm as implemented in a commercial treatment planning system (iPlan, BrainLAB) was investigated. After commissioning and basic beam data tests in homogenous phantoms, a variety of single regular beams and clinical field arrangements were tested in heterogeneous conditions (conformal therapy, arc therapy and intensity-modulated radiotherapy including simultaneous integrated boosts). More specifically, a cork phantom containing a concave-shaped target was designed to challenge the Monte Carlo algorithm in more complex treatment cases. All test irradiations were performed on an Elekta linac providing 6, 10 and 18 MV photon beams. Absolute and relative dose measurements were performed with ion chambers and near tissue equivalent radiochromic films which were placed within a transverse plane of the cork phantom. For simple fields, a 1D gamma (γ) procedure with a 2% dose difference and a 2 mm distance to agreement (DTA) was applied to depth dose curves, as well as to inplane and crossplane profiles. The average gamma value was 0.21 for all energies of simple test cases. For depth dose curves in asymmetric beams similar gamma results as for symmetric beams were obtained. Simple regular fields showed excellent absolute dosimetric agreement to measurement values with a dose difference of 0.1% ± 0.9% (1 standard deviation) at the dose prescription point. A more detailed analysis at tissue interfaces revealed dose discrepancies of 2.9% for an 18 MV energy 10 x 10 cm 2 field at the first density interface from tissue to lung equivalent material. Small fields (2 x 2 cm 2 ) have their largest discrepancy in the re-build-up at the second interface (from lung to tissue equivalent material), with a local dose difference of about 9% and a DTA of 1.1 mm for 18 MV. Conformal field arrangements, arc therapy, as well as IMRT beams and simultaneous integrated boosts were in good agreement with absolute dose measurements in the

  10. Effect of processing time delay on the dose response of Kodak EDR2 film.

    Science.gov (United States)

    Childress, Nathan L; Rosen, Isaac I

    2004-08-01

    Kodak EDR2 film is a widely used two-dimensional dosimeter for intensity modulated radiotherapy (IMRT) measurements. Our clinical use of EDR2 film for IMRT verifications revealed variations and uncertainties in dose response that were larger than expected, given that we perform film calibrations for every experimental measurement. We found that the length of time between film exposure and processing can affect the absolute dose response of EDR2 film by as much as 4%-6%. EDR2 films were exposed to 300 cGy using 6 and 18 MV 10 x 10 cm2 fields and then processed after time delays ranging from 2 min to 24 h. An ion chamber measured the relative dose for these film exposures. The ratio of optical density (OD) to dose stabilized after 3 h. Compared to its stable value, the film response was 4%-6% lower at 2 min and 1% lower at 1 h. The results of the 4 min and 1 h processing time delays were verified with a total of four different EDR2 film batches. The OD/dose response for XV2 films was consistent for time periods of 4 min and 1 h between exposure and processing. To investigate possible interactions of the processing time delay effect with dose, single EDR2 films were irradiated to eight different dose levels between 45 and 330 cGy using smaller 3 x 3 cm2 areas. These films were processed after time delays of 1, 3, and 6 h, using 6 and 18 MV photon qualities. The results at all dose levels were consistent, indicating that there is no change in the processing time delay effect for different doses. The difference in the time delay effect between the 6 and 18 MV measurements was negligible for all experiments. To rule out bias in selecting film regions for OD measurement, we compared the use of a specialized algorithm that systematically determines regions of interest inside the 10 x 10 cm2 exposure areas to manually selected regions of interest. There was a maximum difference of only 0.07% between the manually and automatically selected regions, indicating that the use of

  11. Comparative evaluation of Kodak EDR2 and XV2 films for verification of intensity modulated radiation therapy.

    Science.gov (United States)

    Dogan, Nesrin; Leybovich, Leonid B; Sethi, Anil

    2002-11-21

    Film dosimetry provides a convenient tool to determine dose distributions, especially for verification of IMRT plans. However, the film response to radiation shows a significant dependence on depth, energy and field size that compromise the accuracy of measurements. Kodak's XV2 film has a low saturation dose (approximately 100 cGy) and, consequently, a relatively short region of linear dose-response. The recently introduced Kodak extended range EDR2 film was reported to have a linear dose-response region extending to 500 cGy. This increased dose range may be particularly useful in the verification of IMRT plans. In this work, the dependence of Kodak EDR2 film's response on the depth, field size and energy was evaluated and compared with Kodak XV2 film. Co-60, 6 MV, 10 MV and 18 MV beams were used. Field sizes were 2 x 2, 6 x 6, 10 x 10, 14 x 14, 18 x 18 and 24 x 24 cm2. Doses for XV2 and EDR2 films were 80 cGy and 300 cGy, respectively. Optical density was converted to dose using depth-corrected sensitometric (Hurter and Driffield, or H&D) curves. For each field size, XV2 and EDR2 depth-dose curves were compared with ion chamber depth-dose curves. Both films demonstrated similar (within 1%) field size dependence. The deviation from the ion chamber for both films was small forthe fields ranging from 2 x 2 to 10 x 10 cm2: < or =2% for 6, 10 and 18 MV beams. No deviation was observed for the Co-60 beam. As the field size increased to 24 x 24 cm2, the deviation became significant for both films: approximately 7.5% for Co-60, approximately 5% for 6 MV and 10 MV, and approximately 6% for 18 MV. During the verification of IMRT plans, EDR2 film showed a better agreement with the calculated dose distributions than the XV2 film.

  12. Technical Note: Initial characterization of the new EBT-XD Gafchromic film

    Energy Technology Data Exchange (ETDEWEB)

    Grams, Michael P., E-mail: grams.michael@mayo.edu; Gustafson, Jon M.; Long, Kenneth M.; Fong de los Santos, Luis E. [Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota 55905 (United States)

    2015-10-15

    Purpose: To assess the dosimetric accuracy and energy dependence of the new EBT-eXtended Dose (XD) Gafchromic film and to compare the lateral response artifact (LRA) between EBT-XD and EBT3 film. Methods: EBT3 and EBT-XD calibration curves were created by exposing films to known doses from 0 to 3000 cGy using a 6 MV beam. To assess the accuracy and dynamic range of EBT-XD, a 60° enhanced dynamic wedge (EDW) was used to deliver a dose range of approximately 200–2900 cGy. Comparison to treatment planning system (TPS) calculation was made using a gamma analysis with 2%/2 mm passing criteria. To assess and compare the LRA between EBT3 and EBT-XD, 21 × 21 cm{sup 2} open fields delivered doses of 1000, 2000, and 3000 cGy to both types of film. Films were placed at the center of the scanner, and ratios of measured to TPS predicted doses were calculated at 50 and 80 mm lateral from the scanner center in order to quantitatively assess the LRA. To evaluate the energy dependence of EBT-XD film, seven known doses ranging from 400 to 3000 cGy were delivered using both 6 and 18 MV beams and the resulting optical densities (ODs) compared. Results: The gamma passing rate was 99.1% for the 6 MV EDW delivery. EBT-XD film exhibited minimal LRA (<1%) up to 3000 cGy. In contrast, EBT3 demonstrated an under-response of 11.3% and 22.7% at lateral positions of 50 and 80 mm, respectively, for the 3000 cGy exposure. Differences between ODs of the EBT-XD films exposed to known doses from 6 to 18 MV beams were <0.8% suggesting minimal energy dependence throughout this energy range. Conclusions: The LRA of EBT-XD is greatly reduced when compared to EBT3. This in combination with its accuracy from 0 to 3000 cGy and minimal energy dependence from 6 to 18 MV makes EBT-XD film well suited for dosimetric measurements in high dose SRS/SBRT applications.

  13. Technical Note: Initial characterization of the new EBT-XD Gafchromic film

    International Nuclear Information System (INIS)

    Grams, Michael P.; Gustafson, Jon M.; Long, Kenneth M.; Fong de los Santos, Luis E.

    2015-01-01

    Purpose: To assess the dosimetric accuracy and energy dependence of the new EBT-eXtended Dose (XD) Gafchromic film and to compare the lateral response artifact (LRA) between EBT-XD and EBT3 film. Methods: EBT3 and EBT-XD calibration curves were created by exposing films to known doses from 0 to 3000 cGy using a 6 MV beam. To assess the accuracy and dynamic range of EBT-XD, a 60° enhanced dynamic wedge (EDW) was used to deliver a dose range of approximately 200–2900 cGy. Comparison to treatment planning system (TPS) calculation was made using a gamma analysis with 2%/2 mm passing criteria. To assess and compare the LRA between EBT3 and EBT-XD, 21 × 21 cm 2 open fields delivered doses of 1000, 2000, and 3000 cGy to both types of film. Films were placed at the center of the scanner, and ratios of measured to TPS predicted doses were calculated at 50 and 80 mm lateral from the scanner center in order to quantitatively assess the LRA. To evaluate the energy dependence of EBT-XD film, seven known doses ranging from 400 to 3000 cGy were delivered using both 6 and 18 MV beams and the resulting optical densities (ODs) compared. Results: The gamma passing rate was 99.1% for the 6 MV EDW delivery. EBT-XD film exhibited minimal LRA (<1%) up to 3000 cGy. In contrast, EBT3 demonstrated an under-response of 11.3% and 22.7% at lateral positions of 50 and 80 mm, respectively, for the 3000 cGy exposure. Differences between ODs of the EBT-XD films exposed to known doses from 6 to 18 MV beams were <0.8% suggesting minimal energy dependence throughout this energy range. Conclusions: The LRA of EBT-XD is greatly reduced when compared to EBT3. This in combination with its accuracy from 0 to 3000 cGy and minimal energy dependence from 6 to 18 MV makes EBT-XD film well suited for dosimetric measurements in high dose SRS/SBRT applications

  14. Testing of the analytical anisotropic algorithm for photon dose calculation

    International Nuclear Information System (INIS)

    Esch, Ann van; Tillikainen, Laura; Pyykkonen, Jukka; Tenhunen, Mikko; Helminen, Hannu; Siljamaeki, Sami; Alakuijala, Jyrki; Paiusco, Marta; Iori, Mauro; Huyskens, Dominique P.

    2006-01-01

    The analytical anisotropic algorithm (AAA) was implemented in the Eclipse (Varian Medical Systems) treatment planning system to replace the single pencil beam (SPB) algorithm for the calculation of dose distributions for photon beams. AAA was developed to improve the dose calculation accuracy, especially in heterogeneous media. The total dose deposition is calculated as the superposition of the dose deposited by two photon sources (primary and secondary) and by an electron contamination source. The photon dose is calculated as a three-dimensional convolution of Monte-Carlo precalculated scatter kernels, scaled according to the electron density matrix. For the configuration of AAA, an optimization algorithm determines the parameters characterizing the multiple source model by optimizing the agreement between the calculated and measured depth dose curves and profiles for the basic beam data. We have combined the acceptance tests obtained in three different departments for 6, 15, and 18 MV photon beams. The accuracy of AAA was tested for different field sizes (symmetric and asymmetric) for open fields, wedged fields, and static and dynamic multileaf collimation fields. Depth dose behavior at different source-to-phantom distances was investigated. Measurements were performed on homogeneous, water equivalent phantoms, on simple phantoms containing cork inhomogeneities, and on the thorax of an anthropomorphic phantom. Comparisons were made among measurements, AAA, and SPB calculations. The optimization procedure for the configuration of the algorithm was successful in reproducing the basic beam data with an overall accuracy of 3%, 1 mm in the build-up region, and 1%, 1 mm elsewhere. Testing of the algorithm in more clinical setups showed comparable results for depth dose curves, profiles, and monitor units of symmetric open and wedged beams below d max . The electron contamination model was found to be suboptimal to model the dose around d max , especially for physical

  15. Measurement of off-axis and peripheral skin dose using radiochromic film

    International Nuclear Information System (INIS)

    Butson, Martin J.; Yu, P.K.N.; Metcalfe, P.E.

    1998-01-01

    A radiotherapy skin dose profile can be obtained with radiochromic film. The central axis skin dose relative to D max for a 10x10cm 2 field size was found to be 22%, 17% and 15.5% for 6 MV, 10 MV and 18 MV photon beams. Peripheral dose increased with increasing field size. At 10 MV the skin dose 2 cm outside the geometric field edge was measured as 6%, 10% and 17% for 10x10cm 2 , 20x20cm 2 and 30x30cm 2 field sizes respectively. Off-axis skin dose decreased as distance increased from central axis for fields with Perspex block trays. For a 20x20cm 2 field, an approximately 5-8% drop in percentage skin dose was observed from central axis to the beam edge. (author)

  16. Voltage conditioning and beam performance of the 2OUR Pelletron at JAERI

    International Nuclear Information System (INIS)

    Norton, G.A.; Sundquist, M.L.; Daniel, R.E.; Rathmell, R.D.

    1982-01-01

    The Pelletron Model 2OUR was formally accepted by the Japan Atomic Energy Research Institute in Tokai, Japan, on August 10, 1982. The 2OUR is a 20 MV, folded tandem with a 300 kV injector with four ion sources on the injector deck. The 2OUR is equipped with an internal ion source and nanosecond bunching and pulsing system in the high voltage terminal. This ion source and pulsing system is designed to produce intense peak currents of proton and deuteron beams. The accelerator is also equipped with an external nanosecond bunching and pulsing system for nanosecond pulsed beams in the tandem mode for ions up to mass 240. The formal acceptance of the accelerator was based on operation at 18 MV. However, the 2OUR has operated in a very stable fashion, accelerating an oxygen beam with a terminal potential of 18.5 MV. Mechanical deficiencies outside of the accelerating tube presently limit operation below 20 MV

  17. Verification of a table of phantom scatter factors for radiotherapy treatment planning

    International Nuclear Information System (INIS)

    Arts, J.K.; Bailey, M.J.; Hill, R.

    2004-01-01

    Full text: Many commercially available treatment planning systems require the medical physicist to measure and enter significant quantities of data for the verification of physics based algorithms. The CMS XiO (St. Louis, USA) treatment planning system requires a table of phantom scatter factors amongst other data. In a previous paper by Storchi et al, a table of phantom scatter factors is described. This table gives the phantom scatter factor as a function of field size and quality index determined from a collection of measured data for the total scatter factor and the collimator scatter factor from 25 different beam qualities ranging from 4MV up to 25MV. These factors have been determined at a fixed reference depth of 10cm for square fields of various sizes. This work investigates the claim that this table can be used as an alternative to calculated phantom scatter curve from measured data of a particular treatment unit. According to definition, it is difficult to directly measure the phantom scatter correction factor (Sp). This problem can be solved using the relation; S cp (A) = S c (A)S p (A) where S cp (A)) is the measured total scatter factor for a field size of square side dimension, A and S c (A) is the measured collimator scatter factor for a field size of square side dimension, A (Khan et al 1980, van Gasteren et al 1991). The total scatter correction factor (Sc,p) was measured in a full phantom, and the collimator scatter factor (Sc) measured using an ESTRO mini-phantom. These factors were measured on three Siemens linear accelerators (Concord, USA) with energies 6MV and 18MV and square field sizes ranging from 4x4cm to 40x40cm. The Primus and KD Mevatron produced 6 and 18MV X-rays and the MXE Mevatron produced 6Mv X-rays only. The values for Sp were calculated by rearranging equation (1). Phantom scatter factors were calculated from the data provided by Storchi et al using the quality index of each beam. For comparison, a set of Sp values was

  18. Calculation of effective dose in whole body in dependence of angle of collimator for photon fields

    International Nuclear Information System (INIS)

    Fuenzalida, M.; Varon, C.; Piriz, G.; Banguero, Y.; Lozano, E.; Mancilla, C.

    2011-01-01

    The objective of this work is to obtain quantifiable data of whole body effective dose for photons fields of 6 MV and 18 MV in function of the collimator angle of a Varian Clinac 21EX lineal accelerator. It has been made a variety of studies which investigate the form to reduce the dose in whole body with photons fields, specially over the potential risks and the influence of the collimator angle, as performed Stanthakis et al. [1] with the Monte Carlo method. As a result of this work, the values of whole body effective doses are higher with a 0 deg collimator than with a 90 deg collimator, and as the field size increases, the effective doses difference in whole body, between 0 deg and 90 deg collimator angle, for both energies, becomes smaller. (author)

  19. AAA and PBC calculation accuracy in the surface build-up region in tangential beam treatments. Phantom and breast case study with the Monte Carlo code PENELOPE

    International Nuclear Information System (INIS)

    Panettieri, Vanessa; Barsoum, Pierre; Westermark, Mathias; Brualla, Lorenzo; Lax, Ingmar

    2009-01-01

    Background and purpose: In tangential beam treatments accurate dose calculation of the absorbed dose in the build-up region is of major importance, in particular when the target has superficial extension close to the skin. In most analytical treatment planning systems (TPSs) calculations depend on the experimental measurements introduced by the user in which accuracy might be limited by the type of detector employed to perform them. To quantify the discrepancy between analytically calculated and delivered dose in the build-up region, near the skin of a patient, independent Monte Carlo (MC) simulations using the PENELOPE code were performed. Dose distributions obtained with MC simulations were compared with those given by the Pencil Beam Convolution (PBC) algorithm and the Analytical Anisotropic Algorithm (AAA) implemented in the commercial TPS Eclipse. Material and methods: A cylindrical phantom was used to approximate the breast contour of a patient for MC simulations and the TPS. Calculations of the absorbed doses were performed for 6 and