Fractal analysis for assessing the level of modulation of IMRT fields

International Nuclear Information System (INIS)

Nauta, Marcel; Villarreal-Barajas, J. Eduardo; Tambasco, Mauro

2011-01-01

Purpose: To investigate the potential of three fractal dimension (FD) analysis methods (i.e., the variation, power spectrum, and variogram methods) as metrics for quantifying the degree of modulation in planned intensity modulated radiation therapy (IMRT) treatment fields, and compare the most suitable FD method to the number of monitor units (MUs), the average leaf gap, and the 2D modulation index (2D MI) for assessing modulation. Methods: The authors implemented, validated, and compared the variation, power spectrum, and variogram methods for computing the FD. Validation of the methods was done using mathematical fractional Brownian surfaces of known FD that ranged in size from 128 x 128 to 512 x 512. The authors used a test set consisting of seven head and neck carcinoma plans (50 prescribed treatment fields) to choose an FD cut-point that ensures no false positives (100% specificity) in distinguishing between moderate and high degrees of field modulation. The degree of field modulation was controlled by adjusting the fluence smoothing parameters in the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, CA). The moderate modulation fields were representative of the degree of modulation used clinically at the authors' institution. The authors performed IMRT quality assurance (QA) on the 50 test fields using the MapCHECK device. The FD cut-point was applied to a validation set consisting of four head and neck plans (28 fields). The area under the curve (AUC) from receiver operating characteristic (ROC) analysis was used to compare the ability of FD, number of MUs, average leaf gap, and the 2D MI for distinguishing between the moderate and high modulation fields. Results: The authors found the variogram FD method to be the most suitable for assessing the modulation complexity of IMRT fields for head and neck carcinomas. Pass rates as measured by the gamma criterion for the MapCHECK IMRT field measurements were higher for the moderately modulated

A comparison of HDR brachytherapy and IMRT techniques for dose escalation in prostate cancer: A radiobiological modeling study

Energy Technology Data Exchange (ETDEWEB)

Fatyga, M.; Williamson, J. F.; Dogan, N.; Todor, D.; Siebers, J. V.; George, R.; Barani, I.; Hagan, M. [Department of Radiation Oncology, Virginia Commonwealth University Medical Center, 401 College Street, Richmond, Virginia 23298 (United States)

2009-09-15

A course of one to three large fractions of high dose rate (HDR) interstitial brachytherapy is an attractive alternative to intensity modulated radiation therapy (IMRT) for delivering boost doses to the prostate in combination with additional external beam irradiation for intermediate risk disease. The purpose of this work is to quantitatively compare single-fraction HDR boosts to biologically equivalent fractionated IMRT boosts, assuming idealized image guided delivery (igIMRT) and conventional delivery (cIMRT). For nine prostate patients, both seven-field IMRT and HDR boosts were planned. The linear-quadratic model was used to compute biologically equivalent dose prescriptions. The cIMRT plan was evaluated as a static plan and with simulated random and setup errors. The authors conclude that HDR delivery produces a therapeutic ratio which is significantly better than the conventional IMRT and comparable to or better than the igIMRT delivery. For the HDR, the rectal gBEUD analysis is strongly influenced by high dose DVH tails. A saturation BED, beyond which no further injury can occur, must be assumed. Modeling of organ motion uncertainties yields mean outcomes similar to static plan outcomes.

An analysis of tolerance levels in IMRT quality assurance procedures

International Nuclear Information System (INIS)

Basran, Parminder S.; Woo, Milton K.

2008-01-01

Increased use of intensity modulated radiation therapy (IMRT) has resulted in increased efforts in patient quality assurance (QA). Software and detector systems intended to streamline the IMRT quality assurance process often report metrics, such as percent discrepancies between measured and computed doses, which can be compared to benchmark or threshold values. The purpose of this work is to examine the relationships between two different types of IMRT QA processes in order to define, or refine, appropriate tolerances values. For 115 IMRT plans delivered in a 3 month period, we examine the discrepancies between (a) the treatment planning system (TPS) and results from a commercial independent monitor unit (MU) calculation program; (b) TPS and results from a commercial diode-array measurement system; and (c) the independent MU calculation and the diode-array measurements. Statistical tests were performed to assess significance in the IMRT QA results for different disease site and machine models. There is no evidence that the average total dose discrepancy in the monitor unit calculation depends on the disease site. Second, the discrepancies in the two IMRT QA methods are independent: there is no evidence that a better --or worse--monitor unit validation result is related to a better--or worse--diode-array measurement result. Third, there is marginal benefit in repeating the independent MU calculation with a more suitable dose point, if the initial IMRT QA failed a certain tolerance. Based on these findings, the authors conclude at some acceptable tolerances based on disease site and IMRT QA method. Specifically, monitor unit validations are expected to have a total dose discrepancy of 3% overall, and 5% per beam, independent of disease site. Diode array measurements are expected to have a total absolute dose discrepancy of 3% overall, and 3% per beam, independent of disease site. The percent of pixels exceeding a 3% and 3 mm threshold in a gamma analysis should be

The influence of the image registration method on the adaptive radiotherapy. A proof of the principle in a selected case of prostate IMRT.

Science.gov (United States)

Berenguer, Roberto; de la Vara, Victoria; Lopez-Honrubia, Veronica; Nuñez, Ana Teresa; Rivera, Miguel; Villas, Maria Victoria; Sabater, Sebastia

2018-01-01

To analyse the influence of the image registration method on the adaptive radiotherapy of an IMRT prostate treatment, and to compare the dose accumulation according to 3 different image registration methods with the planned dose. The IMRT prostate patient was CT imaged 3 times throughout his treatment. The prostate, PTV, rectum and bladder were segmented on each CT. A Rigid, a deformable (DIR) B-spline and a DIR with landmarks registration algorithms were employed. The difference between the accumulated doses and planned doses were evaluated by the gamma index. The Dice coefficient and Hausdorff distance was used to evaluate the overlap between volumes, to quantify the quality of the registration. When comparing adaptive vs no adaptive RT, the gamma index calculation showed large differences depending on the image registration method (as much as 87.6% in the case of DIR B-spline). The quality of the registration was evaluated using an index such as the Dice coefficient. This showed that the best result was obtained with DIR with landmarks compared with the rest and it was always above 0.77, reported as a recommended minimum value for prostate studies in a multi-centre review. Apart from showing the importance of the application of an adaptive RT protocol in a particular treatment, this work shows that the election of the registration method is decisive in the result of the adaptive radiotherapy and dose accumulation. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Patient reported outcome measures (PROMs) following forward planned field-in field IMRT: Results from the Cambridge Breast IMRT trial

International Nuclear Information System (INIS)

Mukesh, Mukesh B.; Qian, Wendi; Wilkinson, Jennifer S.; Dorling, Leila; Barnett, Gillian C.; Moody, Anne M.; Wilson, Charles; Twyman, Nicola; Burnet, Neil G.; Wishart, Gordon C.; Coles, Charlotte E.

2014-01-01

Background: The use of intensity-modulated radiotherapy (IMRT) in breast cancer reduces clinician-assessed breast tissue toxicity including fibrosis, telangectasia and sub-optimal cosmesis. Patient reported outcome measures (PROMs) are also important as they provide the patient’s perspective. This longitudinal study reports on (a) the effect of forward planned field-in-field IMRT (∼simple IMRT) on PROMs compared to standard RT at 5 years after RT, (b) factors affecting PROMs at 5 years after RT and (c) the trend of PROMs over 5 years of follow up. Methods: PROMs were assessed at baseline (pre-RT), 6, 24 and 60 months after completion of RT using global health (EORTC QLQ C30) and 4 breast symptom questions (BR23). Also, 4 breast RT-specific questions were included at 6, 24 and 60 months: change in skin appearance, firmness to touch, reduction in breast size and overall change in breast appearance since RT. The benefits of simple IMRT over standard RT at 5 years after RT were assessed using standard t-test for global health and logistic regression analysis for breast symptom questions and breast RT-specific questions. Clinical factors affecting PROMs at 5 years were investigated using a multivariate analysis. A repeated mixed model was applied to explore the trend over time for each of PROMs. Results: (89%) 727/815, 84%, 81% and 61% patients completed questionnaires at baseline, 6, 24 and 60 months respectively. Patients reported worse toxicity for all four BR23 breast symptoms at 6 months, which then improved over time (p < 0.0001). They also reported improvement in skin appearance and breast hardness over time (p < 0.0001), with no significant change for breast shrinkage (p = 0.47) and overall breast appearance (p = 0.13). At 5 years, PROMs assessments did not demonstrate a benefit for simple IMRT over standard radiotherapy. Large breast volume, young age, baseline surgical cosmesis and post-operative infection were the most important variables to affect PROMs

Assessment of new radiation oncology technology and treatments in radiation oncology the ANROTAT project and collection of IMRT specific data

International Nuclear Information System (INIS)

Haworth, A.; Corry, J.; Kron, T.; Duchesne, G.; Ng, M.; Burmeister, B.

2010-01-01

Full text: Medical physicists (MP) are familiar with assessing new radiation oncology technology and treatments ( ROT A T) for their own departments but are not usually involved in providing advice to government for funding these technologies. This paper describes the role of the MP within the Commonwealth Government Department of Health and Aging initiative to develop a generic framework for assessment of ROTAT and the collection of data to support Med care Benefits Scheme (MBS) funding of IMRT. The clinical trials group TROG is developing a generic framework for the assessment of NROTAT. This will be tested and data collected to support applications for MBS funding of IMRT and IGRT. The tumour sites of nasopharynx, post-prostatectomy and anal canal have been selected to represent sites that are commonly, occasionally and rarely treated with IMRT respectively. Site selection for data collection will represent a broad range of clinical practices. Data quality is assured through TROG QA procedures and will include dosimetry audits. The final report will assess the clinical efficacy, cost effectiveness and safety of IMRT compared to 3DCRT. Existing clinical trial protocols form the basis for data collection and surrogate endpoints are being developed. Key publications have been identified that correlate specific dose-volume histogram parameters with clinical end-points, recognising limitations of these data in the 1MRT setting. Engagement of MPs within this project will help ensure collection of high quality data that ultimately aims to secure appropriate funding to ensure our patients receive best clinical care. (author)

A dose homogeneity and conformity evaluation between ViewRay and pinnacle-based linear accelerator IMRT treatment plans

OpenAIRE

Daniel L Saenz; Bhudatt R Paliwal; John E Bayouth

2014-01-01

ViewRay, a novel technology providing soft-tissue imaging during radiotherapy is investigated for treatment planning capabilities assessing treatment plan dose homogeneity and conformity compared with linear accelerator plans. ViewRay offers both adaptive radiotherapy and image guidance. The combination of cobalt-60 (Co-60) with 0.35 Tesla magnetic resonance imaging (MRI) allows for magnetic resonance (MR)-guided intensity-modulated radiation therapy (IMRT) delivery with multiple beams. This ...

IMRT plan verification in radiotherapy

International Nuclear Information System (INIS)

Vlk, P.

2006-01-01

This article describes the procedure for verification of IMRT (Intensity modulated radiation therapy) plan, which is used in the Oncological Institute of St. Elisabeth in Bratislava. It contains basic description of IMRT technology and developing a deployment plan for IMRT planning system CORVUS 6.0, the device Mimic (Multilammelar intensity modulated collimator) and the overall process of verifying the schedule created. The aim of verification is particularly good control of the functions of MIMIC and evaluate the overall reliability of IMRT planning. (author)

Adapting radiotherapy to hypoxic tumours

International Nuclear Information System (INIS)

Malinen, Eirik; Soevik, Aste; Hristov, Dimitre; Bruland, Oeyvind S; Olsen, Dag Rune

2006-01-01

In the current work, the concepts of biologically adapted radiotherapy of hypoxic tumours in a framework encompassing functional tumour imaging, tumour control predictions, inverse treatment planning and intensity modulated radiotherapy (IMRT) were presented. Dynamic contrast enhanced magnetic resonance imaging (DCEMRI) of a spontaneous sarcoma in the nasal region of a dog was employed. The tracer concentration in the tumour was assumed related to the oxygen tension and compared to Eppendorf histograph measurements. Based on the pO 2 -related images derived from the MR analysis, the tumour was divided into four compartments by a segmentation procedure. DICOM structure sets for IMRT planning could be derived thereof. In order to display the possible advantages of non-uniform tumour doses, dose redistribution among the four tumour compartments was introduced. The dose redistribution was constrained by keeping the average dose to the tumour equal to a conventional target dose. The compartmental doses yielding optimum tumour control probability (TCP) were used as input in an inverse planning system, where the planning basis was the pO 2 -related tumour images from the MR analysis. Uniform (conventional) and non-uniform IMRT plans were scored both physically and biologically. The consequences of random and systematic errors in the compartmental images were evaluated. The normalized frequency distributions of the tracer concentration and the pO 2 Eppendorf measurements were not significantly different. 28% of the tumour had, according to the MR analysis, pO 2 values of less than 5 mm Hg. The optimum TCP following a non-uniform dose prescription was about four times higher than that following a uniform dose prescription. The non-uniform IMRT dose distribution resulting from the inverse planning gave a three times higher TCP than that of the uniform distribution. The TCP and the dose-based plan quality depended on IMRT parameters defined in the inverse planning procedure

Adapting radiotherapy to hypoxic tumours

Science.gov (United States)

Malinen, Eirik; Søvik, Åste; Hristov, Dimitre; Bruland, Øyvind S.; Rune Olsen, Dag

2006-10-01

In the current work, the concepts of biologically adapted radiotherapy of hypoxic tumours in a framework encompassing functional tumour imaging, tumour control predictions, inverse treatment planning and intensity modulated radiotherapy (IMRT) were presented. Dynamic contrast enhanced magnetic resonance imaging (DCEMRI) of a spontaneous sarcoma in the nasal region of a dog was employed. The tracer concentration in the tumour was assumed related to the oxygen tension and compared to Eppendorf histograph measurements. Based on the pO2-related images derived from the MR analysis, the tumour was divided into four compartments by a segmentation procedure. DICOM structure sets for IMRT planning could be derived thereof. In order to display the possible advantages of non-uniform tumour doses, dose redistribution among the four tumour compartments was introduced. The dose redistribution was constrained by keeping the average dose to the tumour equal to a conventional target dose. The compartmental doses yielding optimum tumour control probability (TCP) were used as input in an inverse planning system, where the planning basis was the pO2-related tumour images from the MR analysis. Uniform (conventional) and non-uniform IMRT plans were scored both physically and biologically. The consequences of random and systematic errors in the compartmental images were evaluated. The normalized frequency distributions of the tracer concentration and the pO2 Eppendorf measurements were not significantly different. 28% of the tumour had, according to the MR analysis, pO2 values of less than 5 mm Hg. The optimum TCP following a non-uniform dose prescription was about four times higher than that following a uniform dose prescription. The non-uniform IMRT dose distribution resulting from the inverse planning gave a three times higher TCP than that of the uniform distribution. The TCP and the dose-based plan quality depended on IMRT parameters defined in the inverse planning procedure (fields

The use of IMRT in Germany

International Nuclear Information System (INIS)

Frenzel, Thorsten; Kruell, Andreas

2015-01-01

Intensity modulated radiotherapy (IMRT) is frequently used, but there are no data about current frequency regarding specific tumor sites and equipment used for quality assurance (QA). An online survey about IMRT was executed from April to October 2014 by the collaborative IMRT working group (AK IMRT) of the German Association of Medical Physicists (DGMP). A total of 23 German institutions took part in the survey. Most reports came from users working with Elekta, Varian, and Siemens treatment machines, but also from TomoTherapy and BrainLab. Most frequent IMRT technology was volumetric modulated arc therapy (58.37 %: VMAT/''rapid arc''), followed by step-and-shoot IMRT (14.66 %), dynamic MLC (dMLC: 14.53 %), TomoTherapy (9.25 %), and 3.2 % other techniques. Different commercial hard- and software solutions are available for QA, whereas many institutes still develop their own phantoms. Data of 26,779 patients were included in the survey; 44 % were treated using IMRT techniques. IMRT was most frequently used for anal cancer, (whole) craniospinal irradiation, head and neck cancer, prostate cancer, other tumors in the pelvic region, gynecological tumors (except for breast cancer), and brain tumors. An estimated 10 % of all patients treated in 2014 with radiation in Germany were included in the survey. It is representative for the members of the AK IMRT. IMRT may be on the way to replace other treatment techniques. However, many scientific questions are still open. In particular, it is unclear when the IMRT technique should not be used. (orig.) [de

Internal Audit of a Comprehensive IMRT Program for Prostate Cancer: A Model for Centers in Developing Countries?

International Nuclear Information System (INIS)

Koh, Wee Yao; Ren Wei; Mukherjee, Rahul K.; Chung, Hans T.

2009-01-01

Purpose: With improving regional prosperity, significant capital investments have been made to rapidly expand radiotherapy capacity across Southeast Asia. Yet little has been reported on the implementation of adequate quality assurance (QA) in patient management. The objective of this study is to perform an in-depth QA assessment of our definitive intensity-modulated radiotherapy (IMRT) program for prostate cancer since its inception. Methods and Materials: The department's prostate IMRT program was modeled after that of University of California San Francisco. A departmental protocol consisting of radiotherapy volume/dose and hormone sequencing/duration and a set of 18 dose objectives to the target and critical organs were developed, and all plans were presented at the weekly departmental QA rounds. All patients treated with definitive IMRT for nonmetastatic prostate cancer were retrospectively reviewed. Protocol adherence, dosimetry data, toxicities, and outcomes were evaluated. Results: Since 2005, 76 patients received IMRT: 54 with whole-pelvis and 22 with prostate-only treatment. Of the 1,140 recorded dosimetric end points, 39 (3.3%) did not meet the protocol criteria. At QA rounds, no plans required a revision. Only one major protocol violation was observed. Two and two cases of Grade 3-4 acute and late toxicities, respectively, were observed. Five (8.8%) patients developed proctitis, but only one required argon laser therapy. Conclusions: Our comprehensive, practice-adapted QA measures appeared to ensure that we were able to consistently generate conforming IMRT plans with acceptable toxicities. These measures can be easily integrated into other clinics contemplating on developing such a program.

Radiobiological impact of dose calculation algorithms on biologically optimized IMRT lung stereotactic body radiation therapy plans

International Nuclear Information System (INIS)

Liang, X.; Penagaricano, J.; Zheng, D.; Morrill, S.; Zhang, X.; Corry, P.; Griffin, R. J.; Han, E. Y.; Hardee, M.; Ratanatharathom, V.

2016-01-01

The aim of this study is to evaluate the radiobiological impact of Acuros XB (AXB) vs. Anisotropic Analytic Algorithm (AAA) dose calculation algorithms in combined dose-volume and biological optimized IMRT plans of SBRT treatments for non-small-cell lung cancer (NSCLC) patients. Twenty eight patients with NSCLC previously treated SBRT were re-planned using Varian Eclipse (V11) with combined dose-volume and biological optimization IMRT sliding window technique. The total dose prescribed to the PTV was 60 Gy with 12 Gy per fraction. The plans were initially optimized using AAA algorithm, and then were recomputed using AXB using the same MUs and MLC files to compare with the dose distribution of the original plans and assess the radiobiological as well as dosimetric impact of the two different dose algorithms. The Poisson Linear-Quadatric (PLQ) and Lyman-Kutcher-Burman (LKB) models were used for estimating the tumor control probability (TCP) and normal tissue complication probability (NTCP), respectively. The influence of the model parameter uncertainties on the TCP differences and the NTCP differences between AAA and AXB plans were studied by applying different sets of published model parameters. Patients were grouped into peripheral and centrally-located tumors to evaluate the impact of tumor location. PTV dose was lower in the re-calculated AXB plans, as compared to AAA plans. The median differences of PTV(D 95% ) were 1.7 Gy (range: 0.3, 6.5 Gy) and 1.0 Gy (range: 0.6, 4.4 Gy) for peripheral tumors and centrally-located tumors, respectively. The median differences of PTV(mean) were 0.4 Gy (range: 0.0, 1.9 Gy) and 0.9 Gy (range: 0.0, 4.3 Gy) for peripheral tumors and centrally-located tumors, respectively. TCP was also found lower in AXB-recalculated plans compared with the AAA plans. The median (range) of the TCP differences for 30 month local control were 1.6 % (0.3 %, 5.8 %) for peripheral tumors and 1.3 % (0.5 %, 3.4 %) for centrally located tumors. The lower

Dosimetric comparison of standard three-dimensional conformal radiotherapy followed by intensity-modulated radiotherapy boost schedule (sequential IMRT plan) with simultaneous integrated boost-IMRT (SIB IMRT) treatment plan in patients with localized carcinoma prostate.

Science.gov (United States)

Bansal, A; Kapoor, R; Singh, S K; Kumar, N; Oinam, A S; Sharma, S C

2012-07-01

DOSIMETERIC AND RADIOBIOLOGICAL COMPARISON OF TWO RADIATION SCHEDULES IN LOCALIZED CARCINOMA PROSTATE: Standard Three-Dimensional Conformal Radiotherapy (3DCRT) followed by Intensity Modulated Radiotherapy (IMRT) boost (sequential-IMRT) with Simultaneous Integrated Boost IMRT (SIB-IMRT). Thirty patients were enrolled. In all, the target consisted of PTV P + SV (Prostate and seminal vesicles) and PTV LN (lymph nodes) where PTV refers to planning target volume and the critical structures included: bladder, rectum and small bowel. All patients were treated with sequential-IMRT plan, but for dosimetric comparison, SIB-IMRT plan was also created. The prescription dose to PTV P + SV was 74 Gy in both strategies but with different dose per fraction, however, the dose to PTV LN was 50 Gy delivered in 25 fractions over 5 weeks for sequential-IMRT and 54 Gy delivered in 27 fractions over 5.5 weeks for SIB-IMRT. The treatment plans were compared in terms of dose-volume histograms. Also, Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) obtained with the two plans were compared. The volume of rectum receiving 70 Gy or more (V > 70 Gy) was reduced to 18.23% with SIB-IMRT from 22.81% with sequential-IMRT. SIB-IMRT reduced the mean doses to both bladder and rectum by 13% and 17%, respectively, as compared to sequential-IMRT. NTCP of 0.86 ± 0.75% and 0.01 ± 0.02% for the bladder, 5.87 ± 2.58% and 4.31 ± 2.61% for the rectum and 8.83 ± 7.08% and 8.25 ± 7.98% for the bowel was seen with sequential-IMRT and SIB-IMRT plans respectively. For equal PTV coverage, SIB-IMRT markedly reduced doses to critical structures, therefore should be considered as the strategy for dose escalation. SIB-IMRT achieves lesser NTCP than sequential-IMRT.

Stereotactic IMRT using a MMLC

International Nuclear Information System (INIS)

Hoban, P.; Short, R.; Biggs, D.; Rose, A.; Smee, R.; Schneider, M.

2001-01-01

Full text: The leaf width of the multileaf collimator (MLC) used for intensity modulated radiotherapy (IMRT ) largely determines the resolution of the intensity maps that define the entire profile of each beam. In turn it is this resolution, and consequently the achievable degree of beam modulation, that determines the ability to conform the 3D dose distribution to complex target volumes. As such, the leaf width is of more importance than in fixed-field MLC treatments where only the beam edges are affected.A Radionics micro-multileaf collimator (MMLC) with 4 mm leaf width, attached to a Siemens Primus linear accelerator, is in use for stereotactic IMRT at PbWH. Treatment planning is performed with the XPlan system including an integrated IMRT module. Cases treated have so far been with conventional fractionation, including both malignant and benign cranial lesions. Meningiomas in particular often require a complex dose distribution because of their en-plaque nature and/or proximity to the brainstem. Stereotactic localisation and fixation is with the Gill-Thomas-Cosman head-ring or Head and Neck localiser. Cases are typically planned both for fixed-field treatment and IMRT, with IMRT being used if significant benefit is seen. IMRT treatment with the Siemens MLC is also an option. A quality assurance system has been set up, including a flowchart/checklist and phantom dosimetry using TLDs. As expected, treatment plans show IMRT with the MMLC to consistently be the best option dosimetrically. In particular, for a given target coverage there is always better sparing of nearby organs at risk (OARs) with MMLC rather than MLC-based IMRT. Adjustments such as the inclusion of a margin around the target volume or an increase in the penalty for target underdosage improve coverage for MLC plans but generally at the expense of increased OAR involvement. MMLC IMRT treatments commonly require 30-50 fields and can be delivered in approximately 10-15 minutes using an autosequence

Adaptation hypothesis of biological efficiency of ionizing radiation

International Nuclear Information System (INIS)

Kudritskij, Yu.K.; Georgievskij, A.B.; Karpov, V.I.

1992-01-01

Adaptation hypothesis of biological efficiency of ionizing radiation is based on acknowledgement of invariance of fundamental laws and principles of biology related to unity of biota and media, evolution and adaptation for radiobiology. The basic arguments for adaptation hypothesis validity, its correspondence to the requirements imposed on scientific hypothes are presented

Hybrid IMRT plans-concurrently treating conventional and IMRT beams for improved breast irradiation and reduced planning time

International Nuclear Information System (INIS)

Mayo, Charles S.; Urie, Marcia M.; Fitzgerald, Thomas J.

2005-01-01

Purpose: To evaluate a hybrid intensity modulated radiation therapy (IMRT) technique as a class solution for treatment of the intact breast. Methods and materials: The following five plan techniques were compared for 10 breast patients using dose-volume histogram analysis: conventional wedged-field tangents (Tangents), forward-planned field-within-a-field tangents (FIF), IMRT-only tangents (IMRT tangents), conventional open plus IMRT tangents (4-field hybrid), and conventional open plus IMRT tangents with 2 anterior oblique IMRT beams (6-field hybrid). Results: The 4-field hybrid and FIF achieved dose distributions better than Tangents and IMRT tangents. The volume of tissue outside the planning target volume receiving ≥110% of prescribed dose was largest for IMRT tangents (average 158 cc) and least for 6-field hybrid (average 1 cc); the FIF and 4-field hybrid were comparable (average 15 cc). Heart volume ≥30 Gy averaged 13 cc for all techniques, except Tangents, for which it was 32 cc. Average total lung volume ≥20 Gy was 7% for all. Contralateral breast doses were < 3% for all. Planning time for hybrid techniques was significantly less than for conventional FIF technique. Conclusions: The 4-field hybrid technique is a viable class solution. The 6-field hybrid technique creates the most conformal dose distribution at the expense of more normal tissue receiving low dose

Evaluation of quality control tools for patients submitted to IMRT; Avaliacao das ferramentas de controle da qualidade para pacientes submetidos ao IMRT

Energy Technology Data Exchange (ETDEWEB)

Lavor, Milton; Rodrigues, Laura N.; Silva, Marco A., E-mail: miltonlavor@gmail.com [Universidade de Sao Paulo (HCFMRP/USP), Sao Paulo, SP (Brazil). Hospital das Clinicas. Servico de Radioterapia

2013-04-15

Intensity modulated radiation therapy (IMRT) is currently being implemented in a rapidly growing number of centers in Brazil. As consequence many institutions are now facing the problem of performing a comprehensive quality control program before and during the implementation of IMRT in the clinical practice. This paper proposes a methodology for quality control and presents the results and evaluations of the data obtained from the proposed methodology. Ionization chamber and two-dimensional array detector were performed in IMRT treatment planning in order to assess the absolute value of the total dose of all fields. The relative total dose distribution of all fields was measured with a radiochromic film and a two-dimensional array in a phantom. A comparison between measured and calculated dose distributions was performed using the gamma-index method, assessing the percentage of points that meet the criteria of ±3% dose difference and ±3mm distance to agreement. As a result and review of 113 tested IMRT beams using ionization chamber and 81 using two-dimensional array, the proposal was to take an action level of about ±5% compared to the treatment planning systems and measurements, for the verification of the dose in a single point at the low gradient dose region. Analysis of the two-dimensional array measurements showed that the gamma value was <1 for 97.7% of the data and for the film the gamma value was <1 for 96.6% of the data. This work can establish action levels required for quality control program proposed and implemented in the Department of Radiotherapy - Hospital das Clinicas in Sao Paulo that allows an accurate delivery of dose in 'sliding-window' IMRT with micro multi leaf collimator. (author)

Tomotherapy: IMRT and tomographic verification

International Nuclear Information System (INIS)

Mackie, T.R.

2000-01-01

Full text: External beam radiation therapy delivery began around the turn of the century with the use of one or a few kilovoltage beams directed to the presumed site of the tumor. Often the treatment lasted until erythema dose was reached. Delivering the beams rotationally allowed the dose to be focused on the tumor and the skin to be spared. With the advent of megavoltage radiation therapy in the 1950's, using Co-60 teletherapy and betatrons, the treatment could once again be delivered from only a few beam directions and the dose to the skin would be kept below tolerance. Fields were shaped by lead blocks and later by custom-made blocks fabricated from low-melting temperature heavy metal. Linear accelerators did not fundamentally change the way in which radiation was delivered. It is likely that this delivery paradigm would not have changed had it not been for the advent of computers. Brahme and Cormack showed in the late 1980's that highly conformal treatments could be delivered with non-uniform intensity beams. At that time the only way in which the intensity modulated beams could be delivered was using custom-milled compensators. Fabricating and using compensators for multiple fields is time-consuming and labor-intensive. Serial tomotherapy was the first successful delivery method for IMRT and went back to the earlier practice of rotation therapy. The NOMOS Peacock system uses a binary (on-off) multileaf collimator (MLC) system to modulate a fan beam of radiation. It uses an optimization system to determine when leaves should be opened and closed. The system delivers two beam slices at once and the couch is indexed to the next slices by precisely translating the couch. This approach was first used in 1994 and to-date has treated several thousand patients. Prior to the advent of IMRT, accelerator vendors introduced the multileaf collimator (MLC) to provide field shaping without the need to fabricate custom blocking. Most new linear accelerator purchases today

IMRT for adjuvant radiation in gastric cancer: A preferred plan?

International Nuclear Information System (INIS)

Ringash, Jolie; Perkins, Greg; Brierley, James; Lockwood, Gina; Islam, Mohammad; Catton, Pamela; Cummings, Bernard; Kim, John; Wong, Rebecca; Dawson, Laura

2005-01-01

Purpose: To assess the potential advantage of intensity-modulated radiotherapy (IMRT) over conformal planning for postoperative adjuvant radiotherapy in patients with gastric carcinoma. Methods and Materials: Twenty patients who had undergone treatment planning with conformal beam arrangements for 4500 cGy adjuvant radiotherapy between 2000 and 2001 underwent repeat planning using IMRT techniques. Conformal five-field plans were compared with seven- to nine-field coplanar sliding-window IMRT plans. For each patient, the cumulative dose-volume histograms and organ-dose summaries (without distributions or digitally reconstructed radiographs) were provided to two independent, 'blinded' GI radiation oncologists. The oncologists indicated which plan provided better planning target volume coverage and critical organ sparing, any safety concerns with either plan, and which plan they would choose to treat the patient. Results: In 18 (90%) of 20 cases, both oncologists chose the same plan. Cases with disagreement were given to a third 'blinded' reviewer. A 'preferred plan' could be determined in 19 (95%) of 20 cases. IMRT was preferred in 17 (89%) of 19 cases. In 4 (20%) of 20 IMRT plans at least one radiation oncologist had safety concerns because of the spinal cord dose (3 cases) or small bowel dose (2 cases). Of 42 ratings, IMRT was thought to provide better planning target volume coverage in 36 (86%) and better sparing of the spinal cord in 31 (74%) of 42, kidneys in 29 (69%), liver in 30 (71%), and heart in 29 (69%) of 42 ratings. The median underdose volume (1.7 vs. 4.1 cm 3 ), maximal dose to the spinal cord (36.85 vs. 45.65 Gy), and dose to 50% of the liver (17.29 vs. 27.97), heart (12.89 vs. 15.50 Gy), and left kidney (15.50 vs. 16.06 Gy) were lower with IMRT than with the conformal plans. Conclusion: Compared with the conformal plans, oncologists frequently preferred IMRT plans when using dose-volume histogram data. The advantages of IMRT plans include both

Letter to the Editor on 'Single-Arc IMRT?'.

Science.gov (United States)

Otto, Karl

2009-04-21

In the note 'Single Arc IMRT?' (Bortfeld and Webb 2009 Phys. Med. Biol. 54 N9-20), Bortfeld and Webb present a theoretical investigation of static gantry IMRT (S-IMRT), single-arc IMRT and tomotherapy. Based on their assumptions they conclude that single-arc IMRT is inherently limited in treating complex cases without compromising delivery efficiency. Here we present an expansion of their work based on the capabilities of the Varian RapidArc single-arc IMRT system. Using the same theoretical framework we derive clinically deliverable single-arc IMRT plans based on these specific capabilities. In particular, we consider the range of leaf motion, the ability to rapidly and continuously vary the dose rate and the choice of collimator angle used for delivery. In contrast to the results of Bortfeld and Webb, our results show that single-arc IMRT plans can be generated that closely match the theoretical optimum. The disparity in the results of each investigation emphasizes that the capabilities of the delivery system, along with the ability of the optimization algorithm to exploit those capabilities, are of particular importance in single-arc IMRT. We conclude that, given the capabilities available with the RapidArc system, single-arc IMRT can produce complex treatment plans that are delivered efficiently (in approximately 2 min).

Physical models of biological information and adaptation.

Science.gov (United States)

Stuart, C I

1985-04-07

The bio-informational equivalence asserts that biological processes reduce to processes of information transfer. In this paper, that equivalence is treated as a metaphor with deeply anthropomorphic content of a sort that resists constitutive-analytical definition, including formulation within mathematical theories of information. It is argued that continuance of the metaphor, as a quasi-theoretical perspective in biology, must entail a methodological dislocation between biological and physical science. It is proposed that a general class of functions, drawn from classical physics, can serve to eliminate the anthropomorphism. Further considerations indicate that the concept of biological adaptation is central to the general applicability of the informational idea in biology; a non-anthropomorphic treatment of adaptive phenomena is suggested in terms of variational principles.

CBCT-guided evolutive library for cervical adaptive IMRT.

Science.gov (United States)

Rigaud, Bastien; Simon, Antoine; Gobeli, Maxime; Lafond, Caroline; Leseur, Julie; Barateau, Anais; Jaksic, Nicolas; Castelli, Joël; Williaume, Danièle; Haigron, Pascal; De Crevoisier, Renaud

2018-04-01

In the context of adaptive radiation therapy (ART) for locally advanced cervical carcinoma (LACC), this study proposed an original cone-beam computed tomography (CBCT)-guided "Evolutive library" and evaluated it against four other known radiotherapy (RT) strategies. For 20 patients who underwent intensity-modulated radiation therapy (IMRT) for LACC, three planning CTs [with empty (EB), intermediate (IB), and full (FB) bladder volumes], a CT scan at 20 Gy and bi-weekly CBCTs for 5 weeks were performed. Five RT strategies were simulated for each patient: "Standard RT" was based on one IB planning CT; "internal target volume (ITV)-based RT" was an ITV built from the three planning CTs; "RT with one mid-treatment replanning (MidTtReplan)" corresponded to the standard RT with a replanning at 20 Gy; "Pretreatment library ART" using a planning library based on the three planning CTs; and the "Evolutive library ART", which was the "Pretreatment library ART" strategy enriched by including some CBCT anatomies into the library when the daily clinical target volume (CTV) shape differed from the ones in the library. Two planning target volume (PTV) margins of 7 and 10 mm were evaluated. All the strategies were geometrically compared in terms of the percentage of coverage by the PTV, for the CTV and the organs at risk (OAR) delineated on the CBCT. Inadequate coverage of the CTV and OARs by the PTV was also assessed using deformable image registration. The cumulated dose distributions of each strategy were likewise estimated and compared for one patient. The "Evolutive library ART" strategy involved a number of added CBCTs: 0 for 55%; 1 for 30%; 2 for 5%; and 3 for 10% of patients. Compared with the other four, this strategy provided the highest CTV geometric coverage by the PTV, with a mean (min-max) coverage of 98.5% (96.4-100) for 10 mm margins and 96.2% (93.0-99.7) for 7 mm margins (P < 0.05). Moreover, this strategy significantly decreased the geometric coverage of the bowel

Peripheral doses from pediatric IMRT

International Nuclear Information System (INIS)

Klein, Eric E.; Maserang, Beth; Wood, Roy; Mansur, David

2006-01-01

Peripheral dose (PD) data exist for conventional fields (≥10 cm) and intensity-modulated radiotherapy (IMRT) delivery to standard adult-sized phantoms. Pediatric peripheral dose reports are limited to conventional therapy and are model based. Our goal was to ascertain whether data acquired from full phantom studies and/or pediatric models, with IMRT treatment times, could predict Organ at Risk (OAR) dose for pediatric IMRT. As monitor units (MUs) are greater for IMRT, it is expected IMRT PD will be higher; potentially compounded by decreased patient size (absorption). Baseline slab phantom peripheral dose measurements were conducted for very small field sizes (from 2 to 10 cm). Data were collected at distances ranging from 5 to 72 cm away from the field edges. Collimation was either with the collimating jaws or the multileaf collimator (MLC) oriented either perpendicular or along the peripheral dose measurement plane. For the clinical tests, five patients with intracranial or base of skull lesions were chosen. IMRT and conventional three-dimensional (3D) plans for the same patient/target/dose (180 cGy), were optimized without limitation to the number of fields or wedge use. Six MV, 120-leaf MLC Varian axial beams were used. A phantom mimicking a 3-year-old was configured per Center for Disease Control data. Micro (0.125 cc) and cylindrical (0.6 cc) ionization chambers were appropriated for the thyroid, breast, ovaries, and testes. The PD was recorded by electrometers set to the 10 -10 scale. Each system set was uniquely calibrated. For the slab phantom studies, close peripheral points were found to have a higher dose for low energy and larger field size and when MLC was not deployed. For points more distant from the field edge, the PD was higher for high-energy beams. MLC orientation was found to be inconsequential for the small fields tested. The thyroid dose was lower for IMRT delivery than that predicted for conventional (ratio of IMRT/cnventional ranged from

Restricted Field IMRT Dramatically Enhances IMRT Planning for Mesothelioma

International Nuclear Information System (INIS)

Allen, Aaron M.; Schofield, Deborah; Hacker, Fred; Court, Laurence E.; Czerminska, Maria M.S.

2007-01-01

Purpose: To improve the target coverage and normal tissue sparing of intensity-modulated radiotherapy (IMRT) for mesothelioma after extrapleural pneumonectomy. Methods and Materials: Thirteen plans from patients previously treated with IMRT for mesothelioma were replanned using a restricted field technique. This technique was novel in two ways. It limited the entrance beams to 200 o around the target and three to four beams per case had their field apertures restricted down to the level of the heart or liver to further limit the contralateral lung dose. New constraints were added that included a mean lung dose of <9.5 Gy and volume receiving ≥5 Gy of <55%. Results: In all cases, the planning target volume coverage was excellent, with an average of 97% coverage of the planning target volume by the target dose. No change was seen in the target coverage with the new technique. The heart, kidneys, and esophagus were all kept under tolerance in all cases. The average mean lung dose, volume receiving ≥20 Gy, and volume receiving ≥5 Gy with the new technique was 6.6 Gy, 3.0%, and 50.8%, respectively, compared with 13.8 Gy, 15%, and 90% with the previous technique (p < 0.0001 for all three comparisons). The maximal value for any case in the cohort was 8.0 Gy, 7.3%, and 57.5% for the mean lung dose, volume receiving ≥20 Gy, and volume receiving ≥5 Gy, respectively. Conclusion: Restricted field IMRT provides an improved method to deliver IMRT to a complex target after extrapleural pneumonectomy. An upcoming Phase I trial will provide validation of these results

Evaluation tools of quality control for patients submitted to IMRT

International Nuclear Information System (INIS)

Lavor, Milton

2011-01-01

Intensity modulated radiation therapy (IMRT) is currently been implemented in a rapidly growing number of centers in Brazil. As consequence many institutions are now facing the problem of performing a comprehensive quality control program before and during the implementation of IMRT in the clinical routine practice. The aim of this work is to evaluate and propose a methodology for quality assurance in IMRT treatments. An ionization chamber and a two-dimensional array detector were performed to assess the absolute value of the total dose of all fields in one specific point. The relative total dose distribution of all fields was measured with a radiochromic film and a two-dimensional array at one depth in a phantom. A comparison between measured and calculated dose distributions was performed using the gamma-index method, assessing the percentage of points that meet the criteria of +-3% dose difference and +-3 mm distance to agreement. As a result of 113 tested IMRT beams using ionization chamber and 81 using two-dimensional array, the proposal was to take an action level of about +- 5% compared to the treatment planning systems and measurements, for the verification of the dose in a single point at the low gradient dose region. Analysis of the two-dimensional array measurements showed that the gamma value was <1 for 97.7% of the data and for the film the gamma value was <1 for 96.6% of the data. This can be concluded that for an accurate delivery of dose in 'sliding-window' IMRT with micro multileaf collimator, the absolute value of the total dose and the relative total dose distribution should be checked by absolute and relative dosimetry respectively. (author)

Dosimetry tools and techniques for IMRT

International Nuclear Information System (INIS)

Low, Daniel A.; Moran, Jean M.; Dempsey, James F.; Dong Lei; Oldham, Mark

2011-01-01

Intensity modulated radiation therapy (IMRT) poses a number of challenges for properly measuring commissioning data and quality assurance (QA) radiation dose distributions. This report provides a comprehensive overview of how dosimeters, phantoms, and dose distribution analysis techniques should be used to support the commissioning and quality assurance requirements of an IMRT program. The proper applications of each dosimeter are described along with the limitations of each system. Point detectors, arrays, film, and electronic portal imagers are discussed with respect to their proper use, along with potential applications of 3D dosimetry. Regardless of the IMRT technique utilized, some situations require the use of multiple detectors for the acquisition of accurate commissioning data. The overall goal of this task group report is to provide a document that aids the physicist in the proper selection and use of the dosimetry tools available for IMRT QA and to provide a resource for physicists that describes dosimetry measurement techniques for purposes of IMRT commissioning and measurement-based characterization or verification of IMRT treatment plans. This report is not intended to provide a comprehensive review of commissioning and QA procedures for IMRT. Instead, this report focuses on the aspects of metrology, particularly the practical aspects of measurements that are unique to IMRT. The metrology of IMRT concerns the application of measurement instruments and their suitability, calibration, and quality control of measurements. Each of the dosimetry measurement tools has limitations that need to be considered when incorporating them into a commissioning process or a comprehensive QA program. For example, routine quality assurance procedures require the use of robust field dosimetry systems. These often exhibit limitations with respect to spatial resolution or energy response and need to themselves be commissioned against more established dosimeters. A chain of

Rotational IMRT techniques compared to fixed gantry IMRT and Tomotherapy: multi-institutional planning study for head-and-neck cases

International Nuclear Information System (INIS)

Wiezorek, Tilo; Schubert, Kai; Wagner, Daniela; Wendt, Thomas G; Brachwitz, Tim; Georg, Dietmar; Blank, Eyck; Fotina, Irina; Habl, Gregor; Kretschmer, Matthias; Lutters, Gerd; Salz, Henning

2011-01-01

Recent developments enable to deliver rotational IMRT with standard C-arm gantry based linear accelerators. This upcoming treatment technique was benchmarked in a multi-center treatment planning study against static gantry IMRT and rotational IMRT based on a ring gantry for a complex parotid gland sparing head-and-neck technique. Treatment plans were created for 10 patients with head-and-neck tumours (oropharynx, hypopharynx, larynx) using the following treatment planning systems (TPS) for rotational IMRT: Monaco (ELEKTA VMAT solution), Eclipse (Varian RapidArc solution) and HiArt for the helical tomotherapy (Tomotherapy). Planning of static gantry IMRT was performed with KonRad, Pinnacle and Panther DAO based on step&shoot IMRT delivery and Eclipse for sliding window IMRT. The prescribed doses for the high dose PTVs were 65.1Gy or 60.9Gy and for the low dose PTVs 55.8Gy or 52.5Gy dependend on resection status. Plan evaluation was based on target coverage, conformity and homogeneity, DVHs of OARs and the volume of normal tissue receiving more than 5Gy (V 5Gy ). Additionally, the cumulative monitor units (MUs) and treatment times of the different technologies were compared. All evaluation parameters were averaged over all 10 patients for each technique and planning modality. Depending on IMRT technique and TPS, the mean CI values of all patients ranged from 1.17 to 2.82; and mean HI values varied from 0.05 to 0.10. The mean values of the median doses of the spared parotid were 26.5Gy for RapidArc and 23Gy for VMAT, 14.1Gy for Tomo. For fixed gantry techniques 21Gy was achieved for step&shoot+KonRad, 17.0Gy for step&shoot+Panther DAO, 23.3Gy for step&shoot+Pinnacle and 18.6Gy for sliding window. V 5Gy values were lowest for the sliding window IMRT technique (3499 ccm) and largest for RapidArc (5480 ccm). The lowest mean MU value of 408 was achieved by Panther DAO, compared to 1140 for sliding window IMRT. All IMRT delivery technologies with their associated TPS

A national dosimetric audit of IMRT

International Nuclear Information System (INIS)

Budgell, Geoff; Berresford, Joe; Trainer, Michael; Bradshaw, Ellie; Sharpe, Peter; Williams, Peter

2011-01-01

Background and purpose: A dosimetric audit of IMRT has been carried out within the UK between June 2009 and March 2010 in order to provide an independent check of safe implementation and to identify problems in the modelling and delivery of IMRT. Methods and materials: A mail based audit involving film and alanine dosimeters was utilized. Measurements were made for each individual field in an IMRT plan isocentrically in a flat water-equivalent phantom at a depth of 5 cm. The films and alanine dosimeters were processed and analysed centrally; additional ion chamber measurements were made by each participating centre. Results: 57 of 62 centres participated, with a total of 78 plans submitted. For the film measurements, all 176 fields from the less complex IMRT plans (including prostate and breast plans) achieved over 95% pixels passing a gamma criterion of 3%/3 mm within the 20% isodose. For the more complex IMRT plans (mainly head and neck) 8/245 fields (3.3%) achieved less than 95% pixels passing a 4%/4 mm gamma criterion. Of the alanine measurements, 4/78 (5.1%) of the measurements differed by >5% from the dose predicted by the treatment planning system. Three of these were large deviations of -77.1%, -29.1% and 14.1% respectively. Excluding the three measurements outside 10%, the mean difference was 0.05% with a standard deviation of 1.5%. The out of tolerance results have been subjected to further investigations. Conclusions: A dosimetric audit has been successfully carried out of IMRT implementation by over 90% of UK radiotherapy departments. The audit shows that modelling and delivery of IMRT is accurate, suggesting that the implementation of IMRT has been carried out safely.

An absorbed dose calorimeter for IMRT dosimetry

International Nuclear Information System (INIS)

Duane, S.; Aldehaybes, M.; Bailey, M.; Lee, N.D.; Thomas, C.G.; Palmans, H.

2012-01-01

A new calorimeter for dosimetry in small and complex fields has been built. The device is intended for the direct determination of absorbed dose to water in moderately small fields and in composite fields such as IMRT treatments, and as a transfer instrument calibrated against existing absorbed dose standards in conventional reference conditions. The geometry, materials and mode of operation have been chosen to minimize detector perturbations when used in a water phantom, to give a reasonably isotropic response and to minimize the effects of heat transfer when the calorimeter is used in non-reference conditions in a water phantom. The size of the core is meant to meet the needs of measurement in IMRT treatments and is comparable to the size of the air cavity in a type NE2611 ionization chamber. The calorimeter may also be used for small field dosimetry. Initial measurements in reference conditions and in an IMRT head and neck plan, collapsed to gantry angle zero, have been made to estimate the thermal characteristics of the device, and to assess its performance in use. The standard deviation (estimated repeatability) of the reference absorbed dose measurements was 0.02 Gy (0.6%). (authors)

Rotational IMRT techniques compared to fixed gantry IMRT and Tomotherapy: multi-institutional planning study for head-and-neck cases

Directory of Open Access Journals (Sweden)

Lutters Gerd

2011-02-01

Full Text Available Abstract Background Recent developments enable to deliver rotational IMRT with standard C-arm gantry based linear accelerators. This upcoming treatment technique was benchmarked in a multi-center treatment planning study against static gantry IMRT and rotational IMRT based on a ring gantry for a complex parotid gland sparing head-and-neck technique. Methods Treatment plans were created for 10 patients with head-and-neck tumours (oropharynx, hypopharynx, larynx using the following treatment planning systems (TPS for rotational IMRT: Monaco (ELEKTA VMAT solution, Eclipse (Varian RapidArc solution and HiArt for the helical tomotherapy (Tomotherapy. Planning of static gantry IMRT was performed with KonRad, Pinnacle and Panther DAO based on step&shoot IMRT delivery and Eclipse for sliding window IMRT. The prescribed doses for the high dose PTVs were 65.1Gy or 60.9Gy and for the low dose PTVs 55.8Gy or 52.5Gy dependend on resection status. Plan evaluation was based on target coverage, conformity and homogeneity, DVHs of OARs and the volume of normal tissue receiving more than 5Gy (V5Gy. Additionally, the cumulative monitor units (MUs and treatment times of the different technologies were compared. All evaluation parameters were averaged over all 10 patients for each technique and planning modality. Results Depending on IMRT technique and TPS, the mean CI values of all patients ranged from 1.17 to 2.82; and mean HI values varied from 0.05 to 0.10. The mean values of the median doses of the spared parotid were 26.5Gy for RapidArc and 23Gy for VMAT, 14.1Gy for Tomo. For fixed gantry techniques 21Gy was achieved for step&shoot+KonRad, 17.0Gy for step&shoot+Panther DAO, 23.3Gy for step&shoot+Pinnacle and 18.6Gy for sliding window. V5Gy values were lowest for the sliding window IMRT technique (3499 ccm and largest for RapidArc (5480 ccm. The lowest mean MU value of 408 was achieved by Panther DAO, compared to 1140 for sliding window IMRT. Conclusions All

Fluence complexity for IMRT field and simplification of IMRT verification

International Nuclear Information System (INIS)

Hanushova, Tereza; Vondarchek, Vladimir

2013-01-01

Intensity Modulated Radiation Therapy (IMRT) requires dosimetric verification of each patient’s plan, which is time consuming. This work deals with the idea of minimizing the number of fields for control, or even replacing plan verification by machine quality assurance (QA). We propose methods for estimation of fluence complexity in an IMRT field based on dose gradients and investigate the relation between results of gamma analysis and this quantity. If there is a relation, it might be possible to only verify the most complex field of a plan. We determine the average fluence complexity in clinical fields and design a test fluence corresponding to this amount of complexity which might be used in daily QA and potentially replace patient-related verification. Its applicability is assessed in clinical practice. The relation between fluence complexity and results of gamma analysis has been confirmed for plans but not for single fields. There is an agreement between the suggested test fluence and clinical fields in the average gamma parameter. A critical value of average gamma has been specified for the test fluence as a criterion for distinguishing between poorly and well deliverable plans. It will not be possible to only verify the most complex field of a plan but verification of individual plans could be replaced by a morning check of the suggested test fluence, together with a well-established set of QA tests. (Author)

Heterogeneity in head and neck IMRT target design and clinical practice

International Nuclear Information System (INIS)

Hong, Theodore S.; Tomé, Wolfgang A.; Harari, Paul M.

2012-01-01

Purpose: To assess patterns of H and N IMRT practice with particular emphasis on elective target delineation. Materials and methods: Twenty institutions with established H and N IMRT expertise were solicited to design clinical target volumes for the identical H and N cancer case. To limit contouring variability, a primary tonsil GTV and ipsilateral level II node were pre-contoured. Participants were asked to accept this GTV, and contour their recommended CTV and PTV. Dose prescriptions, contouring time, and recommendations regarding chemotherapy were solicited. Results: All 20 institutions responded. Remarkable heterogeneity in H and N IMRT design and practice was identified. Seventeen of 20 centers recommended treatment of bilateral necks whereas 3/20 recommended treatment of the ipsilateral neck only. The average CTV volume was 250 cm 3 (range 37–676 cm 3 ). Although there was high concordance in coverage of ipsilateral neck levels II and III, substantial variation was identified for levels I, V, and the contralateral neck. Average CTV expansion was 4.1 mm (range 0–15 mm). Eight of 20 centers recommended chemotherapy (cisplatin), whereas 12/20 recommended radiation alone. Responders prescribed on average 69 and 68 Gy to the tumor and metastatic node GTV, respectively. Average H and N target volume contouring time was 102.5 min (range 60–210 min). Conclusion: This study identifies substantial heterogeneity in H and N IMRT target definition, prescription, neck treatment, and use of chemotherapy among practitioners with established H and N IMRT expertise. These data suggest that continued efforts to standardize and simplify the H and N IMRT process are desirable for the safe and effective global advancement of H and N IMRT practice.

Intensity-modulated radiotherapy (IMRT) for carcinoma of the maxillary sinus: A comparison of IMRT planning systems

International Nuclear Information System (INIS)

Ahmed, Raef S.; Ove, Roger; Duan, Jun; Popple, Richard; Cobb, Glenn

2006-01-01

The treatment of maxillary sinus carcinoma with forward planning can be technically difficult when the neck also requires radiotherapy. This difficulty arises because of the need to spare the contralateral face while treating the bilateral neck. There is considerable potential for error in clinical setup and treatment delivery. We evaluated intensity-modulated radiotherapy (IMRT) as an improvement on forward planning, and compared several inverse planning IMRT platforms. A composite dose-volume histogram (DVH) was generated from a complex forward planned case. We compared the results with those generated by sliding window fixed field dynamic multileaf collimator (MLC) IMRT, using sets of coplanar beams. All setups included an anterior posterior (AP) beam, and 3-, 5-, 7-, and 9-field configurations were evaluated. The dose prescription and objective function priorities were invariant. We also evaluated 2 commercial tomotherapy IMRT delivery platforms. DVH results from all of the IMRT approaches compared favorably with the forward plan. Results for the various inverse planning approaches varied considerably across platforms, despite an attempt to prescribe the therapy similarly. The improvement seen with the addition of beams in the fixed beam sliding window case was modest. IMRT is an effective means of delivering radiotherapy reliably in the complex setting of maxillary sinus carcinoma with neck irradiation. Differences in objective function definition and optimization algorithms can lead to unexpected differences in the final dose distribution, and our evaluation suggests that these factors are more significant than the beam arrangement or number of beams

IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119

Energy Technology Data Exchange (ETDEWEB)

Ezzell, Gary A.; Burmeister, Jay W.; Dogan, Nesrin [Department of Radiation Oncology, Mayo Clinic Scottsdale, 5777 East Mayo Boulevard, MCSB Concourse, Phoenix, Arizona 89054 (United States); and others

2009-11-15

AAPM Task Group 119 has produced quantitative confidence limits as baseline expectation values for IMRT commissioning. A set of test cases was developed to assess the overall accuracy of planning and delivery of IMRT treatments. Each test uses contours of targets and avoidance structures drawn within rectangular phantoms. These tests were planned, delivered, measured, and analyzed by nine facilities using a variety of IMRT planning and delivery systems. Each facility had passed the Radiological Physics Center credentialing tests for IMRT. The agreement between the planned and measured doses was determined using ion chamber dosimetry in high and low dose regions, film dosimetry on coronal planes in the phantom with all fields delivered, and planar dosimetry for each field measured perpendicular to the central axis. The planar dose distributions were assessed using gamma criteria of 3%/3 mm. The mean values and standard deviations were used to develop confidence limits for the test results using the concept confidence limit=|mean|+1.96{sigma}. Other facilities can use the test protocol and results as a basis for comparison to this group. Locally derived confidence limits that substantially exceed these baseline values may indicate the need for improved IMRT commissioning.

DARS: a phase III randomised multicentre study of dysphagia- optimised intensity- modulated radiotherapy (Do-IMRT) versus standard intensity- modulated radiotherapy (S-IMRT) in head and neck cancer

International Nuclear Information System (INIS)

Petkar, Imran; Rooney, Keith; Roe, Justin W. G.; Patterson, Joanne M.; Bernstein, David; Tyler, Justine M.; Emson, Marie A.; Morden, James P.; Mertens, Kathrin; Miles, Elizabeth; Beasley, Matthew; Roques, Tom; Bhide, Shreerang A.; Newbold, Kate L.; Harrington, Kevin J.; Hall, Emma; Nutting, Christopher M.

2016-01-01

Persistent dysphagia following primary chemoradiation (CRT) for head and neck cancers can have a devastating impact on patients’ quality of life. Single arm studies have shown that the dosimetric sparing of critical swallowing structures such as the pharyngeal constrictor muscle and supraglottic larynx can translate to better functional outcomes. However, there are no current randomised studies to confirm the benefits of such swallow sparing strategies. The aim of Dysphagia/Aspiration at risk structures (DARS) trial is to determine whether reducing the dose to the pharyngeal constrictors with dysphagia-optimised intensity- modulated radiotherapy (Do-IMRT) will lead to an improvement in long- term swallowing function without having any detrimental impact on disease-specific survival outcomes. The DARS trial (CRUK/14/014) is a phase III multicentre randomised controlled trial (RCT) for patients undergoing primary (chemo) radiotherapy for T1-4, N0-3, M0 pharyngeal cancers. Patients will be randomised (1:1 ratio) to either standard IMRT (S-IMRT) or Do-IMRT. Radiotherapy doses will be the same in both groups; however in patients allocated to Do-IMRT, irradiation of the pharyngeal musculature will be reduced by delivering IMRT identifying the pharyngeal muscles as organs at risk. The primary endpoint of the trial is the difference in the mean MD Anderson Dysphagia Inventory (MDADI) composite score, a patient-reported outcome, measured at 12 months post radiotherapy. Secondary endpoints include prospective and longitudinal evaluation of swallow outcomes incorporating a range of subjective and objective assessments, quality of life measures, loco-regional control and overall survival. Patients and speech and language therapists (SLTs) will both be blinded to treatment allocation arm to minimise outcome-reporting bias. DARS is the first RCT investigating the effect of swallow sparing strategies on improving long-term swallowing outcomes in pharyngeal cancers. An integral

Can All Centers Plan Intensity-Modulated Radiotherapy (IMRT) Effectively? An External Audit of Dosimetric Comparisons Between Three-Dimensional Conformal Radiotherapy and IMRT for Adjuvant Chemoradiation for Gastric Cancer

International Nuclear Information System (INIS)

Chung, Hans T.; Lee, Brian; Park, Eileen; Lu, Jiade J.; Xia Ping

2008-01-01

Purpose: To compare dosimetric endpoints between three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) at our center with limited IMRT experience, and to perform an external audit of the IMRT plans. Methods and Materials: Ten patients, who received adjuvant chemoradiation for gastric cancer, formed the study cohort. For standardization, the planning target volume (PTV) and organs at risk were recontoured with the assistance of a study protocol radiologic atlas. The cohort was replanned with CMS Xio to generate coplanar 3D-CRT and IMRT plans. All 10 datasets, including volumes but without the plans (i.e., blinded), were transmitted to an experienced center where IMRT plans were designed using Nomos Corvus (IMRT-C) and ADAC Pinnacle (IMRT-P). All IMRT plans were normalized to D95% receiving 45 Gy. Results: Intensity-modulated radiotherapy yielded higher PTV V45 (volume that receives ≥45 Gy) (p < 0.001) than 3D-CRT. No difference in V20 was seen in the right (p = 0.9) and left (p 0.3) kidneys, but the liver mean dose (p < 0.001) was superior with IMRT. For the external audit, IMRT-C (p = 0.002) and IMRT-P (p < 0.001) achieved significantly lower left kidney V20 than IMRT, and IMRT-P (p < 0.001) achieved lower right kidney V20 than IMRT. The IMRT-C (p = 0.003) but not IMRT-P (p = 0.6) had lower liver mean doses than IMRT. Conclusions: At our institution with early IMRT experience, IMRT improved PTV dose coverage and liver doses but not kidney doses. An external audit of IMRT plans showed that an experienced center can yield superior IMRT plans

Exclusive image guided IMRT vs. radical prostatectomy followed by postoperative IMRT for localized prostate cancer: a matched-pair analysis based on risk-groups

International Nuclear Information System (INIS)

Azelie, Caroline; Créhange, Gilles; Gauthier, Mélanie; Mirjolet, Céline; Cormier, Luc; Martin, Etienne; Peignaux-Casasnovas, Karine; Truc, Gilles; Chamois, Jérôme; Maingon, Philippe

2012-01-01

To investigate whether patients treated for a localized prostate cancer (PCa) require a radical prostatectomy followed by postoperative radiotherapy or exclusive radiotherapy, in the modern era of image guided IMRT. 178 patients with PCa were referred for daily exclusive image guided IMRT (IG-IMRT) using an on-line 3D ultra-sound based system and 69 patients were referred for postoperative IMRT without image guidance after radical prostatectomy (RP + IMRT). Patients were matched in a 1:1 ratio according to their baseline risk group before any treatment. Late toxicity was scored using the CTV v3.0 scale. Biochemical failure was defined as a postoperative PSA ≤ 0.1 ng/mL followed by 1 consecutive rising PSA for the postoperative group of patients and by the Phoenix definition (nadir + 2 ng/mL) for the group of patients treated with exclusive radiotherapy. A total of 98 patients were matched (49:49). From the start of any treatment, the median follow-up was 56.6 months (CI 95% = [49.6-61.2], range [18.2-115.1]). No patient had late gastrointestinal grade ≥ 2 toxicity in the IG-IMRT group vs. 4% in the RP + IMRT group. Forty two percent of the patients in both groups had late grade ≥ 2 genitourinary toxicity. The 5-year FFF rates in the IG-IMRT group and in the RP + IMRT groups were 93.1% [80.0-97.8] and 76.5% [58.3-87.5], respectively (p = 0.031). Patients with a localized PCa treated with IG-IMRT had better oncological outcome than patients treated with RP + IMRT. Further improvements in postoperative IMRT using image guidance and dose escalation are urgently needed

Radiation therapy technology innovations applied to the treatment of head and neck patients: - Clinical results of Intensity Modulated Radiotherapy (IMRT), - Contribution of Image Guided Radiotherapy (IGRT) in the management of head and neck patients treated with IMRT

International Nuclear Information System (INIS)

Graff-Cailleaud, Pierre

2011-01-01

Numerous and exciting technological innovations were recently developed in radiotherapy. We aimed to assess benefits in two specific fields. 1) Clinical results of Intensity Modulated Radiotherapy (IMRT) applied to the treatment of Head and Neck (H and N) patients. The first study was a long-term mono-centric prospective registration of all H and N patients treated with IMRT in our institution. Locoregional control was excellent and toxicities limited. Recurrences were in-field. Dosimetric recommendations (parotids mean dose) were established. The second study assessed the impact of IMRT on health-related quality of life for H and N patients through a multicentric matched-pair comparison with conventional radiotherapy. Outstanding benefits were observed particularly in the fields of salivary dysfunction and oral discomfort. 2) Contribution of Image Guided Radiotherapy (IGRT) in the management of H and N patients treated with IMRT. The first study was a monitoring of delivered dose, using 3D dose recalculation from Megavoltage Cone-Beam CT (CBCT), as a quality assurance measure of a panel of H and N IMRT patients aligned with IGRT. Dosimetric consequences of anatomical changes were assessed. Contribution of color-coded MVCBCT dose-difference maps was studied. The aim of the second study was to quantify the inherent relative mobility between anatomic regions of the H and N area and to assess the dosimetric impact of several different matching procedures. Recommendations for the use of CBCT images in a daily practice were established. (author) [fr

2-Step IMAT and 2-Step IMRT in three dimensions

International Nuclear Information System (INIS)

Bratengeier, Klaus

2005-01-01

In two dimensions, 2-Step Intensity Modulated Arc Therapy (2-Step IMAT) and 2-Step Intensity Modulated Radiation Therapy (IMRT) were shown to be powerful methods for the optimization of plans with organs at risk (OAR) (partially) surrounded by a target volume (PTV). In three dimensions, some additional boundary conditions have to be considered to establish 2-Step IMAT as an optimization method. A further aim was to create rules for ad hoc adaptations of an IMRT plan to a daily changing PTV-OAR constellation. As a test model, a cylindrically symmetric PTV-OAR combination was used. The centrally placed OAR can adapt arbitrary diameters with different gap widths toward the PTV. Along the rotation axis the OAR diameter can vary, the OAR can even vanish at some axis positions, leaving a circular PTV. The width and weight of the second segment were the free parameters to optimize. The objective function f to minimize was the root of the integral of the squared difference of the dose in the target volume and a reference dose. For the problem, two local minima exist. Therefore, as a secondary criteria, the magnitude of hot and cold spots were taken into account. As a result, the solution with a larger segment width was recommended. From plane to plane for varying radii of PTV and OAR and for different gaps between them, different sets of weights and widths were optimal. Because only one weight for one segment shall be used for all planes (respectively leaf pairs), a strategy for complex three-dimensional (3-D) cases was established to choose a global weight. In a second step, a suitable segment width was chosen, minimizing f for this global weight. The concept was demonstrated in a planning study for a cylindrically symmetric example with a large range of different radii of an OAR along the patient axis. The method is discussed for some classes of tumor/organ at risk combinations. Noncylindrically symmetric cases were treated exemplarily. The product of width and weight of

Biological Bases for Radiation Adaptive Responses in the Lung

Energy Technology Data Exchange (ETDEWEB)

Scott, Bobby R. [Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States); Lin, Yong [Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States); Wilder, Julie [Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States); Belinsky, Steven [Lovelace Biomedical and Environmental Research Inst., Albuquerque, NM (United States)

2015-03-01

Our main research objective was to determine the biological bases for low-dose, radiation-induced adaptive responses in the lung, and use the knowledge gained to produce an improved risk model for radiation-induced lung cancer that accounts for activated natural protection, genetic influences, and the role of epigenetic regulation (epiregulation). Currently, low-dose radiation risk assessment is based on the linear-no-threshold hypothesis, which now is known to be unsupported by a large volume of data.

IMRT for Image-Guided Single Vocal Cord Irradiation

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Osman, Sarah O.S., E-mail: s.osman@erasmusmc.nl [Department of Radiation Oncology, Erasmus Medical Center-Daniel den Hoed Cancer Center, Rotterdam (Netherlands); Astreinidou, Eleftheria; Boer, Hans C.J. de; Keskin-Cambay, Fatma; Breedveld, Sebastiaan; Voet, Peter; Al-Mamgani, Abrahim; Heijmen, Ben J.M.; Levendag, Peter C. [Department of Radiation Oncology, Erasmus Medical Center-Daniel den Hoed Cancer Center, Rotterdam (Netherlands)

2012-02-01

Purpose: We have been developing an image-guided single vocal cord irradiation technique to treat patients with stage T1a glottic carcinoma. In the present study, we compared the dose coverage to the affected vocal cord and the dose delivered to the organs at risk using conventional, intensity-modulated radiotherapy (IMRT) coplanar, and IMRT non-coplanar techniques. Methods and Materials: For 10 patients, conventional treatment plans using two laterally opposed wedged 6-MV photon beams were calculated in XiO (Elekta-CMS treatment planning system). An in-house IMRT/beam angle optimization algorithm was used to obtain the coplanar and non-coplanar optimized beam angles. Using these angles, the IMRT plans were generated in Monaco (IMRT treatment planning system, Elekta-CMS) with the implemented Monte Carlo dose calculation algorithm. The organs at risk included the contralateral vocal cord, arytenoids, swallowing muscles, carotid arteries, and spinal cord. The prescription dose was 66 Gy in 33 fractions. Results: For the conventional plans and coplanar and non-coplanar IMRT plans, the population-averaged mean dose {+-} standard deviation to the planning target volume was 67 {+-} 1 Gy. The contralateral vocal cord dose was reduced from 66 {+-} 1 Gy in the conventional plans to 39 {+-} 8 Gy and 36 {+-} 6 Gy in the coplanar and non-coplanar IMRT plans, respectively. IMRT consistently reduced the doses to the other organs at risk. Conclusions: Single vocal cord irradiation with IMRT resulted in good target coverage and provided significant sparing of the critical structures. This has the potential to improve the quality-of-life outcomes after RT and maintain the same local control rates.

IMRT for Image-Guided Single Vocal Cord Irradiation

International Nuclear Information System (INIS)

Osman, Sarah O.S.; Astreinidou, Eleftheria; Boer, Hans C.J. de; Keskin-Cambay, Fatma; Breedveld, Sebastiaan; Voet, Peter; Al-Mamgani, Abrahim; Heijmen, Ben J.M.; Levendag, Peter C.

2012-01-01

Purpose: We have been developing an image-guided single vocal cord irradiation technique to treat patients with stage T1a glottic carcinoma. In the present study, we compared the dose coverage to the affected vocal cord and the dose delivered to the organs at risk using conventional, intensity-modulated radiotherapy (IMRT) coplanar, and IMRT non-coplanar techniques. Methods and Materials: For 10 patients, conventional treatment plans using two laterally opposed wedged 6-MV photon beams were calculated in XiO (Elekta-CMS treatment planning system). An in-house IMRT/beam angle optimization algorithm was used to obtain the coplanar and non-coplanar optimized beam angles. Using these angles, the IMRT plans were generated in Monaco (IMRT treatment planning system, Elekta-CMS) with the implemented Monte Carlo dose calculation algorithm. The organs at risk included the contralateral vocal cord, arytenoids, swallowing muscles, carotid arteries, and spinal cord. The prescription dose was 66 Gy in 33 fractions. Results: For the conventional plans and coplanar and non-coplanar IMRT plans, the population-averaged mean dose ± standard deviation to the planning target volume was 67 ± 1 Gy. The contralateral vocal cord dose was reduced from 66 ± 1 Gy in the conventional plans to 39 ± 8 Gy and 36 ± 6 Gy in the coplanar and non-coplanar IMRT plans, respectively. IMRT consistently reduced the doses to the other organs at risk. Conclusions: Single vocal cord irradiation with IMRT resulted in good target coverage and provided significant sparing of the critical structures. This has the potential to improve the quality-of-life outcomes after RT and maintain the same local control rates.

Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors

International Nuclear Information System (INIS)

Nelms, Benjamin E.; Zhen Heming; Tome, Wolfgang A.

2011-01-01

Purpose: The purpose of this work is to determine the statistical correlation between per-beam, planar IMRT QA passing rates and several clinically relevant, anatomy-based dose errors for per-patient IMRT QA. The intent is to assess the predictive power of a common conventional IMRT QA performance metric, the Gamma passing rate per beam. Methods: Ninety-six unique data sets were created by inducing four types of dose errors in 24 clinical head and neck IMRT plans, each planned with 6 MV Varian 120-leaf MLC linear accelerators using a commercial treatment planning system and step-and-shoot delivery. The error-free beams/plans were used as ''simulated measurements'' (for generating the IMRT QA dose planes and the anatomy dose metrics) to compare to the corresponding data calculated by the error-induced plans. The degree of the induced errors was tuned to mimic IMRT QA passing rates that are commonly achieved using conventional methods. Results: Analysis of clinical metrics (parotid mean doses, spinal cord max and D1cc, CTV D95, and larynx mean) vs IMRT QA Gamma analysis (3%/3 mm, 2/2, 1/1) showed that in all cases, there were only weak to moderate correlations (range of Pearson's r-values: -0.295 to 0.653). Moreover, the moderate correlations actually had positive Pearson's r-values (i.e., clinically relevant metric differences increased with increasing IMRT QA passing rate), indicating that some of the largest anatomy-based dose differences occurred in the cases of high IMRT QA passing rates, which may be called ''false negatives.'' The results also show numerous instances of false positives or cases where low IMRT QA passing rates do not imply large errors in anatomy dose metrics. In none of the cases was there correlation consistent with high predictive power of planar IMRT passing rates, i.e., in none of the cases did high IMRT QA Gamma passing rates predict low errors in anatomy dose metrics or vice versa. Conclusions: There is a lack of correlation between

IMRT delivers lower radiation doses to dental structures than 3DRT in head and neck cancer patients.

Science.gov (United States)

Fregnani, Eduardo Rodrigues; Parahyba, Cláudia Joffily; Morais-Faria, Karina; Fonseca, Felipe Paiva; Ramos, Pedro Augusto Mendes; de Moraes, Fábio Yone; da Conceição Vasconcelos, Karina Gondim Moutinho; Menegussi, Gisela; Santos-Silva, Alan Roger; Brandão, Thais B

2016-09-07

Radiotherapy (RT) is frequently used in the treatment of head and neck cancer, but different side-effects are frequently reported, including a higher frequency of radiation-related caries, what may be consequence of direct radiation to dental tissue. The intensity-modulated radiotherapy (IMRT) was developed to improve tumor control and decrease patient's morbidity by delivering radiation beams only to tumor shapes and sparing normal tissue. However, teeth are usually not included in IMRT plannings and the real efficacy of IMRT in the dental context has not been addressed. Therefore, the aim of this study is to assess whether IMRT delivers lower radiation doses to dental structures than conformal 3D radiotherapy (3DRT). Radiation dose delivery to dental structures of 80 patients treated for head and neck cancers (oral cavity, tongue, nasopharynx and oropharynx) with IMRT (40 patients) and 3DRT (40 patients) were assessed by individually contouring tooth crowns on patients' treatment plans. Clinicopathological data were retrieved from patients' medical files. The average dose of radiation to teeth delivered by IMRT was significantly lower than with 3DRT (p = 0.007); however, only patients affected by nasopharynx and oral cavity cancers demonstrated significantly lower doses with IMRT (p = 0.012 and p = 0.011, respectively). Molars received more radiation with both 3DRT and IMRT, but the latter delivered significantly lower radiation in this group of teeth (p dental groups. Maxillary teeth received lower doses than mandibular teeth, but only IMRT delivered significantly lower doses (p = 0.011 and p = 0.003). Ipsilateral teeth received higher doses than contralateral teeth with both techniques and IMRT delivered significantly lower radiation than 3DRT for contralateral dental structures (p radiation doses to teeth than 3DRT, but only for some groups of patients and teeth, suggesting that this decrease was more likely due to the protection of

Health-Related Quality-of-Life Outcomes Following IMRT Versus Conventional Radiotherapy for Oropharyngeal Squamous Cell Carcinoma

International Nuclear Information System (INIS)

Yao Min; Karnell, Lucy H.; Funk, Gerry F.; Lu Heming; Dornfeld, Ken; Buatti, John M.

2007-01-01

Purpose: To compare health-related quality-of-life (HRQOL) outcomes of patients with oropharyngeal squamous cell carcinoma treated using intensity-modulated radiotherapy (IMRT) vs. conventional radiotherapy (CRT). Patients and Methods: Patients with oropharyngeal squamous cell carcinoma were extracted from the database of an ongoing longitudinal Outcome Assessment Project. Eligible criteria included (1) treated with definitive radiation, and (2) provided 12-month posttreatment HRQOL data. Excluded were 7 patients who received IMRT before October 1, 2002, during this institution's developmental phase of the IMRT technique. The HRQOL outcomes of patients treated with IMRT were compared with those of patients who received CRT. Results: Twenty-six patients treated using IMRT and 27 patients treated using CRT were included. Patients in the IMRT group were older and had more advanced-stage diseases and more patients received concurrent chemotherapy. However, the IMRT group had higher mean Head and Neck Cancer Inventory scores (which represent better outcomes) for each of the four head-and-neck cancer-specific domains, including eating, speech, aesthetics, and social disruption, at 12 months after treatment. A significantly greater percentage of patients in the CRT group had restricted diets compared with those in the IMRT group (48.0% vs. 16.0%, p = 0.032). At 3 months after treatment, both groups had significant decreases from pretreatment eating scores. However, the IMRT group had a significant improvement during the first year, but the CRT group had only small improvement. Conclusions: Proper delivery of IMRT can improve HRQOL for patients with oropharyngeal cancer compared with CRT

Performance assessment of a 2D array of plastic scintillation detectors for IMRT quality assurance

Science.gov (United States)

Guillot, Mathieu; Gingras, Luc; Archambault, Louis; Beddar, Sam; Beaulieu, Luc

2013-07-01

The purposes of this work are to assess the performance of a 2D plastic scintillation detectors array prototype for quality assurance in intensity-modulated radiation therapy (IMRT) and to determine its sensitivity and specificity to positioning errors of one multileaf collimator (MLC) leaf and one MLC leaf bank by applying the principles of signal detection theory. Ten treatment plans (step-and-shoot delivery) and one volumetric modulated arc therapy plan were measured and compared to calculations from two treatment-planning systems (TPSs) and to radiochromic films. The averages gamma passing rates per beam found for the step-and-shoot plans were 95.8% for the criteria (3%, 2 mm), 97.8% for the criteria (4%, 2 mm), and 98.1% for the criteria (3%, 3 mm) when measurements were compared to TPS calculations. The receiver operating characteristic curves for the one leaf errors and one leaf bank errors were determined from simulations (theoretical upper limits) and measurements. This work concludes that arrays of plastic scintillation detectors could be used for IMRT quality assurance in clinics. The use of signal detection theory could improve the quality of dosimetric verifications in radiation therapy by providing optimal discrimination criteria for the detection of different classes of errors.

Performance assessment of a 2D array of plastic scintillation detectors for IMRT quality assurance

International Nuclear Information System (INIS)

Guillot, Mathieu; Gingras, Luc; Archambault, Louis; Beaulieu, Luc; Beddar, Sam

2013-01-01

The purposes of this work are to assess the performance of a 2D plastic scintillation detectors array prototype for quality assurance in intensity-modulated radiation therapy (IMRT) and to determine its sensitivity and specificity to positioning errors of one multileaf collimator (MLC) leaf and one MLC leaf bank by applying the principles of signal detection theory. Ten treatment plans (step-and-shoot delivery) and one volumetric modulated arc therapy plan were measured and compared to calculations from two treatment-planning systems (TPSs) and to radiochromic films. The averages gamma passing rates per beam found for the step-and-shoot plans were 95.8% for the criteria (3%, 2 mm), 97.8% for the criteria (4%, 2 mm), and 98.1% for the criteria (3%, 3 mm) when measurements were compared to TPS calculations. The receiver operating characteristic curves for the one leaf errors and one leaf bank errors were determined from simulations (theoretical upper limits) and measurements. This work concludes that arrays of plastic scintillation detectors could be used for IMRT quality assurance in clinics. The use of signal detection theory could improve the quality of dosimetric verifications in radiation therapy by providing optimal discrimination criteria for the detection of different classes of errors. (paper)

Dosimetry of parotid glands in IMRT plan of nasopharyngeal carcinoma

International Nuclear Information System (INIS)

Lian Jiancheng; Yu Xinsheng; Jiang Guoliang

2007-01-01

Objective: To evaluate the effect of different intensity-modulated radiation therapy (IMRT) plan on the dosimetry of parotid in patients with nasopharyngeal carcinoma. Methods: Under the same constraints and objections, the IMRT plan of nasopharyngeal carcinoma with sparing unilateral parotid and the IMRT plan added plan tumor volume (PTV) margin for parotid gland was investigated. Results: Between conventional IMRT plan and the IMRT plan spared unilateral parotid, their target coverage, homogeneity index and conformal index of PTV 70 is similar. On PTV 60 , D min in the plan of sparing one parotid gland was more than that in normal IMRT plan (P 95 in the plan of sparing one parotid gland have improved (P 50%VOL and D mean of parotid gland were similar between the two plans. Between conventional IMRT plan and the IMRT plan added 2 or 3 mm margin for parotid gland, their target coverage, homogeneity index and conformal index of PTV 70 is similar. D min , D mean and D 95 of PTV 60 have decreased tendency from normal IMRT plan to 2 mm margin plan to 3 mm margin plan. D max of brainstem and spine cord have increased tendency from normal IMRT plan to 2 mm margin plan to 3 mm margin plan. Conclusions: The IMRT plan of nasopharyngeal carcinoma with sparing unilateral parotid may be adopted not to protect both two parotids, while PTV margin for parotid added as parotid move. (authors)

Experimental IMRT breast dosimetry in a thorax phantom

International Nuclear Information System (INIS)

Pimenta, Elsa B.; Campos, Tarcisio P.R.; Nogueira, Luciana B.; Lima, Andre C.S.

2017-01-01

Radiation therapy (RT) is an essential therapeutic method. RT is often used as adjuvant therapy in the treatment of breast cancer. The dose-volume restrictions of the organs at risk limit the prescribed dose to the target volume and biological and clinical effects may influence the final treatment outcome. The breast RT provides large risks to the adjacent organs and consequently the recommended dosimetry to the prescribed dose volume (PTV) is 50 Gy, lower than the most prescribed dose in other treatments (70-85 Gy). Such values implies in less tumor control compared to other sites. The present research proposal aimed to measure absorbed dose in a thorax phantom with synthetic breasts provided by an Intensity-Modulate Radiation Therapy (IMRT) protocol in a RT center. On the methodology, IMRT protocol was selected following recommendations from the Radiation Therapy Oncology Group (RTOG). Radiochromic films and a thorax simulator were prepared by the Ionizing Radiation Research Group (NRI). Dosimeters were calibrated on a selected linear accelerator (LINAC). The comparison of the dosimetry from treatment planning system (TPS), Xio (Elekta) and from experimental data was performed. The spatial distribution of the breast internal dose and in the adjacent organs was depicted by the experimental data. In the film's calibration, the quadratic polynomial fit presented a satisfactory coefficient. Two-dimensional dose profiles were obtained in the breast suggesting that films can supply details and information that TPS does not provide. At the phantom's dosimetry, the internal mean doses taken at the synthetic breast presented usual values above the prescribed dose, besides overall values were within the dosimetric MSKCC criterion. The non full reproduction of the build-up region in the films had occurred due to the asymmetrical positioning of the films in the inner breast, in addition to their non constant distance from the skin. The hot regions were present may be due to

IMRT delivers lower radiation doses to dental structures than 3DRT in head and neck cancer patients

International Nuclear Information System (INIS)

Fregnani, Eduardo Rodrigues; Parahyba, Cláudia Joffily; Morais-Faria, Karina; Fonseca, Felipe Paiva; Ramos, Pedro Augusto Mendes; Moraes, Fábio Yone de; Conceição Vasconcelos, Karina Gondim Moutinho da; Menegussi, Gisela; Santos-Silva, Alan Roger; Brandão, Thais B.

2016-01-01

Radiotherapy (RT) is frequently used in the treatment of head and neck cancer, but different side-effects are frequently reported, including a higher frequency of radiation-related caries, what may be consequence of direct radiation to dental tissue. The intensity-modulated radiotherapy (IMRT) was developed to improve tumor control and decrease patient’s morbidity by delivering radiation beams only to tumor shapes and sparing normal tissue. However, teeth are usually not included in IMRT plannings and the real efficacy of IMRT in the dental context has not been addressed. Therefore, the aim of this study is to assess whether IMRT delivers lower radiation doses to dental structures than conformal 3D radiotherapy (3DRT). Radiation dose delivery to dental structures of 80 patients treated for head and neck cancers (oral cavity, tongue, nasopharynx and oropharynx) with IMRT (40 patients) and 3DRT (40 patients) were assessed by individually contouring tooth crowns on patients’ treatment plans. Clinicopathological data were retrieved from patients’ medical files. The average dose of radiation to teeth delivered by IMRT was significantly lower than with 3DRT (p = 0.007); however, only patients affected by nasopharynx and oral cavity cancers demonstrated significantly lower doses with IMRT (p = 0.012 and p = 0.011, respectively). Molars received more radiation with both 3DRT and IMRT, but the latter delivered significantly lower radiation in this group of teeth (p < 0.001), whereas no significant difference was found for the other dental groups. Maxillary teeth received lower doses than mandibular teeth, but only IMRT delivered significantly lower doses (p = 0.011 and p = 0.003). Ipsilateral teeth received higher doses than contralateral teeth with both techniques and IMRT delivered significantly lower radiation than 3DRT for contralateral dental structures (p < 0.001). IMRT delivered lower radiation doses to teeth than 3DRT, but only for some groups of patients and

Software for simulating IMRT protocol

Energy Technology Data Exchange (ETDEWEB)

Fonseca, Thelma C.F.; Campos, Tarcisio P.R. de, E-mail: tcff@ufmg.b, E-mail: campos@nuclear.ufmg.b [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear

2009-07-01

The Intensity Modulated Radiation Therapy - IMRT is an advanced technique to cancer treatment widely used on oncology around the world. The present paper describes the SOFT-RT software which is a tool for simulating IMRT protocol. Also, it will be present a cerebral tumor case of studied in which three irradiation windows with distinct orientation were applied. The SOFT-RT collect and export data to MCNP code. This code simulates the photon transport on the voxel model. Later, a out-module from SOFT-RT import the results and express the dose-response superimposing dose and voxel model in a tree-dimensional graphic representation. The present paper address the IMRT software and its function as well a cerebral tumor case of studied is showed. The graphic interface of the SOFT-RT illustrates the example case. (author)

Software for simulating IMRT protocol

International Nuclear Information System (INIS)

Fonseca, Thelma C.F.; Campos, Tarcisio P.R. de

2009-01-01

The Intensity Modulated Radiation Therapy - IMRT is an advanced technique to cancer treatment widely used on oncology around the world. The present paper describes the SOFT-RT software which is a tool for simulating IMRT protocol. Also, it will be present a cerebral tumor case of studied in which three irradiation windows with distinct orientation were applied. The SOFT-RT collect and export data to MCNP code. This code simulates the photon transport on the voxel model. Later, a out-module from SOFT-RT import the results and express the dose-response superimposing dose and voxel model in a tree-dimensional graphic representation. The present paper address the IMRT software and its function as well a cerebral tumor case of studied is showed. The graphic interface of the SOFT-RT illustrates the example case. (author)

IMRT delivery verification using a spiral phantom

International Nuclear Information System (INIS)

Richardson, Susan L.; Tome, Wolfgang A.; Orton, Nigel P.; McNutt, Todd R.; Paliwal, Bhudatt R.

2003-01-01

In this paper we report on the testing and verification of a system for IMRT delivery quality assurance that uses a cylindrical solid water phantom with a spiral trajectory for radiographic film placement. This spiral film technique provides more complete dosimetric verification of the entire IMRT treatment than perpendicular film methods, since it samples a three-dimensional dose subspace rather than using measurements at only one or two depths. As an example, the complete analysis of the predicted and measured spiral films is described for an intracranial IMRT treatment case. The results of this analysis are compared to those of a single field perpendicular film technique that is typically used for IMRT QA. The comparison demonstrates that both methods result in a dosimetric error within a clinical tolerance of 5%, however the spiral phantom QA technique provides a more complete dosimetric verification while being less time consuming. To independently verify the dosimetry obtained with the spiral film, the same IMRT treatment was delivered to a similar phantom in which LiF thermoluminescent dosimeters were arranged along the spiral trajectory. The maximum difference between the predicted and measured TLD data for the 1.8 Gy fraction was 0.06 Gy for a TLD located in a high dose gradient region. This further validates the ability of the spiral phantom QA process to accurately verify delivery of an IMRT plan

Improved normal tissue sparing in head and neck radiotherapy using biological cost function based-IMRT.

Science.gov (United States)

Anderson, N; Lawford, C; Khoo, V; Rolfo, M; Joon, D L; Wada, M

2011-12-01

Intensity-modulated radiotherapy (IMRT) has reduced the impact of acute and late toxicities associated with head and neck radiotherapy. Treatment planning system (TPS) advances in biological cost function based optimization (BBO) and improved segmentation techniques have increased organ at risk (OAR) sparing compared to conventional dose-based optimization (DBO). A planning study was undertaken to compare OAR avoidance in DBO and BBO treatment planning. Simultaneous integrated boost treatment plans were produced for 10 head and neck patients using both planning systems. Plans were compared for tar get coverage and OAR avoidance. Comparisons were made using the BBO TPS Monte Carlo dose engine to eliminate differences due to inherent algorithms. Target coverage (V95%) was maintained for both solutions. BBO produced lower OAR doses, with statistically significant improvement to left (12.3%, p = 0.005) and right parotid mean dose (16.9%, p = 0.004), larynx V50_Gy (71.0%, p = 0.005), spinal cord (21.9%, p < 0.001) and brain stem dose maximums (31.5%, p = 0.002). This study observed improved OAR avoidance with BBO planning. Further investigations will be undertaken to review any clinical benefit of this improved planned dosimetry.

Comparison of dose distribution between 3DCRT and IMRT in middle thoracic and under thoracic esophageal carcinoma

International Nuclear Information System (INIS)

Li Dingjie; Liu Hailong; Mao Ronghu; Liu Ru; Guo Xiaoqi; Lei Hongchang; Wang Jianhua

2011-01-01

Objective: To compare the dose distribution between three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT) in treating esophageal carcinoma (middle thoracic section and under thoracic section) and to select reasonable treatment methods for esophagus cancer. Methods: Ten cases with cancer of the middle thoracic section and under thoracic section esophagus were chosen for a retrospective treatment-planning study. 3DCRT and IMRT plans were created for each patient: Some critical indicators were evolved in evaluating the treatment plans of IMRT (5B and 7B) and 3DCRT (3B), such as, PTV coverage and dose-volumes to irradiated normal structures. Evaluation indicators: prescription of 50 Gy. total lung volume (V5, V10, V20), mean lung dose (MLD), spinal cord (Dmax), heart (V40) and conformality index (CI). Each plan was evaluated with respect to dose distribution,dose-volume histograms (DVHs), and additional dosimetric endpoints described below. Results: There is no significance of CRT and IMRT technique in protection of total lung volume,mean lung dose, spinal cord (Dmax), target, CI and heart. Conclusion: As To radiotherapy of esophagus cancer of the middle thoracic section and under thoracic section, IMRT has no advantage compared with 3DCRT, the selection of plan should be adapted to the situations of every patient. (authors)

Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors

Energy Technology Data Exchange (ETDEWEB)

Nelms, Benjamin E.; Zhen Heming; Tome, Wolfgang A. [Canis Lupus LLC and Department of Human Oncology, University of Wisconsin, Merrimac, Wisconsin 53561 (United States); Department of Medical Physics, University of Wisconsin, Madison, Wisconsin 53705 (United States); Departments of Human Oncology, Medical Physics, and Biomedical Engineering, University of Wisconsin, Madison, Wisconsin 53792 (United States)

2011-02-15

Purpose: The purpose of this work is to determine the statistical correlation between per-beam, planar IMRT QA passing rates and several clinically relevant, anatomy-based dose errors for per-patient IMRT QA. The intent is to assess the predictive power of a common conventional IMRT QA performance metric, the Gamma passing rate per beam. Methods: Ninety-six unique data sets were created by inducing four types of dose errors in 24 clinical head and neck IMRT plans, each planned with 6 MV Varian 120-leaf MLC linear accelerators using a commercial treatment planning system and step-and-shoot delivery. The error-free beams/plans were used as ''simulated measurements'' (for generating the IMRT QA dose planes and the anatomy dose metrics) to compare to the corresponding data calculated by the error-induced plans. The degree of the induced errors was tuned to mimic IMRT QA passing rates that are commonly achieved using conventional methods. Results: Analysis of clinical metrics (parotid mean doses, spinal cord max and D1cc, CTV D95, and larynx mean) vs IMRT QA Gamma analysis (3%/3 mm, 2/2, 1/1) showed that in all cases, there were only weak to moderate correlations (range of Pearson's r-values: -0.295 to 0.653). Moreover, the moderate correlations actually had positive Pearson's r-values (i.e., clinically relevant metric differences increased with increasing IMRT QA passing rate), indicating that some of the largest anatomy-based dose differences occurred in the cases of high IMRT QA passing rates, which may be called ''false negatives.'' The results also show numerous instances of false positives or cases where low IMRT QA passing rates do not imply large errors in anatomy dose metrics. In none of the cases was there correlation consistent with high predictive power of planar IMRT passing rates, i.e., in none of the cases did high IMRT QA Gamma passing rates predict low errors in anatomy dose metrics or vice versa

AP-PA field orientation followed by IMRT reduces lung exposure in comparison to conventional 3D conformal and sole IMRT in centrally located lung tumors

Directory of Open Access Journals (Sweden)

Soyfer Viacheslav

2012-02-01

Full Text Available Abstract Little attention has been paid to the fact that intensity modulated radiation therapy (IMRT techniques do not easily enable treatment with opposed beams. Three treatment plans (3 D conformal, IMRT, and combined (anterior-posterior-posterio-anterior (AP-PA + IMRT of 7 patients with centrally-located lung cancer were compared for exposure of lung, spinal cord and esophagus. Combined IMRT and AP-PA techniques offer better lung tissue sparing compared to plans predicated solely on IMRT for centrally-located lung tumors.

Parotid gland sparing IMRT for head and neck cancer improves xerostomia related quality of life

International Nuclear Information System (INIS)

Rij, CM van; Oughlane-Heemsbergen, WD; Ackerstaff, AH; Lamers, EA; Balm, AJM; Rasch, CRN

2008-01-01

To assess the impact of intensity modulated radiotherapy (IMRT) versus conventional radiation on late xerostomia and Quality of Life aspects in head and neck cancer patients. Questionnaires on xerostomia in rest and during meals were sent to all patients treated between January 1999 and December 2003 with a T1-4, N0-2 M0 head and neck cancer, with parotid gland sparing IMRT or conventional bilateral neck irradiation to a dose of at least 60 Gy, who were progression free and had no disseminated disease (n = 192). Overall response was 85% (n = 163); 97% in the IMRT group (n = 75) and 77% in the control group (n = 88) the median follow-up was 2.6 years. The prevalence of complaints was compared between the two groups, correcting for all relevant factors at multivariate ordinal regression analysis. Patients treated with IMRT reported significantly less difficulty transporting and swallowing their food and needed less water for a dry mouth during day, night and meals. They also experienced fewer problems with speech and eating in public. Laryngeal cancer patients in general had fewer complaints than oropharynx cancer patients but both groups benefited from IMRT. Within the IMRT group the xerostomia scores were better for those patients with a mean parotid dose to the 'spared' parotid below 26 Gy. Parotid gland sparing IMRT for head and neck cancer patients improves xerostomia related quality of life compared to conventional radiation both in rest and during meals. Laryngeal cancer patients had fewer complaints but benefited equally compared to oropharyngeal cancer patients from IMRT

Planner concepts in IMRT planning

International Nuclear Information System (INIS)

Sahoo, Suvendu Kr.; Rath, A.K.; Patnaik, S.; Mishra, S.K.

2008-01-01

IMRT is the most sophisticated, innovative, three- dimensional conformal radiation treatment that delivers highly focused radiation with minimal impact to surrounding normal tissue. As it is a computer control technique, the planar should have adequate knowledge to execute the plan in proper way other wise it is very difficult to get the optimal plan. In this article we want to high light, planner should have the basic concepts before starting the IMRT planning

An implementation strategy for IMRT of ethmoid sinus cancer with bilateral sparing of the optic pathways

International Nuclear Information System (INIS)

Claus, Filip; Gersem, Werner de; Wagter, Carlos de; Severen, Robert van; Vanhoutte, Ilse; Duthoy, Wim; Remouchamps, Vincent; Duyse, Bart van.; Vakaet, Luc; Lemmerling, Marc; Vermeersch, Hubert; Neve, Wilfried de

2001-01-01

Purpose: To develop a protocol for the irradiation of ethmoid sinus cancer, with the aim of sparing binocular vision; of developing a strategy of intensity-modulated radiation therapy (IMRT) planning that produces dose distributions that (1) are consistent with the protocol prescriptions and (2) are deliverable by static segmental IMRT techniques within a 15-minute time slot; of fine tuning the implementation strategy to a class solution approach that is sufficiently automated and efficient, allowing routine clinical application; of reporting on the early clinical implementation involving 11 patients between February 1999 and July 2000. Patients and Methods: Eleven consecutive T1-4N0M0 ethmoid sinus cancer patients were enrolled in the study. For Patients 1-8, a first protocol was implemented, defining a planning target volume prescription dose of 60 to 66 Gy in 30-33 fractions and a maximum dose (Dmax) of 50 Gy to optic pathway structures and spinal cord and limit of 60 Gy to brainstem. For Patients 9-11, an adapted (now considered mature) protocol was implemented, defining a (planning target volume) prescription dose of 70 Gy in 35 fractions and a Dmax to optic pathway structures and brainstem of 60 Gy and to spinal cord of 50 Gy. Results: The class solution-directed strategy developed during this study reduced the protocol translation process from a few days to about 2 hours of planner time. The mature class solution involved the use of 7 beam incidences (20-37 segments), which could be delivered within a 15-minute time slot. Acute side effects were limited and mild. None of the patients developed dry eye syndrome or other visual disturbances. The follow-up period is too short for detection of retinopathy or optic nerve and chiasm toxicity. Conclusion: Conventional radiotherapy of ethmoid sinus tumors is associated with serious morbidity, including blindness. We hypothesize that IMRT has the potential to save binocular vision. The dose to the optic pathway

Statistical process control analysis for patient-specific IMRT and VMAT QA.

Science.gov (United States)

Sanghangthum, Taweap; Suriyapee, Sivalee; Srisatit, Somyot; Pawlicki, Todd

2013-05-01

This work applied statistical process control to establish the control limits of the % gamma pass of patient-specific intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) quality assurance (QA), and to evaluate the efficiency of the QA process by using the process capability index (Cpml). A total of 278 IMRT QA plans in nasopharyngeal carcinoma were measured with MapCHECK, while 159 VMAT QA plans were undertaken with ArcCHECK. Six megavolts with nine fields were used for the IMRT plan and 2.5 arcs were used to generate the VMAT plans. The gamma (3%/3 mm) criteria were used to evaluate the QA plans. The % gamma passes were plotted on a control chart. The first 50 data points were employed to calculate the control limits. The Cpml was calculated to evaluate the capability of the IMRT/VMAT QA process. The results showed higher systematic errors in IMRT QA than VMAT QA due to the more complicated setup used in IMRT QA. The variation of random errors was also larger in IMRT QA than VMAT QA because the VMAT plan has more continuity of dose distribution. The average % gamma pass was 93.7% ± 3.7% for IMRT and 96.7% ± 2.2% for VMAT. The Cpml value of IMRT QA was 1.60 and VMAT QA was 1.99, which implied that the VMAT QA process was more accurate than the IMRT QA process. Our lower control limit for % gamma pass of IMRT is 85.0%, while the limit for VMAT is 90%. Both the IMRT and VMAT QA processes are good quality because Cpml values are higher than 1.0.

Multi-institutional Comparison of Intensity Modulated Radiation Therapy (IMRT) Planning Strategies and Planning Results for Nasopharyngeal Cancer

Science.gov (United States)

Park, Sung Ho; Park, Suk Won; Oh, Do Hoon; Choi, Youngmin; Kim, Jeung Kee; Ahn, Yong Chan; Park, Won; Suh, Hyun Sook; Lee, Rena; Bae, Hoonsik

2009-01-01

The intensity-modulated radiation therapy (IMRT) planning strategies for nasopharyngeal cancer among Korean radiation oncology facilities were investigated. Five institutions with IMRT planning capacity using the same planning system were invited to participate in this study. The institutions were requested to produce the best plan possible for 2 cases that would deliver 70 Gy to the planning target volume of gross tumor (PTV1), 59.4 Gy to the PTV2, and 51.5 Gy to the PTV3 in which elective irradiation was required. The advised fractionation number was 33. The planning parameters, resultant dose distributions, and biological indices were compared. We found 2-3-fold variations in the volume of treatment targets. Similar degree of variation was found in the delineation of normal tissue. The physician-related factors in IMRT planning had more influence on the plan quality. The inhomogeneity index of PTV dose ranged from 4 to 49% in Case 1, and from 5 to 46% in Case 2. Variation in tumor control probabilities for the primary lesion and involved LNs was less marked. Normal tissue complication probabilities for parotid glands and skin showed marked variation. Results from this study suggest that greater efforts in providing training and continuing education in terms of IMRT planning parameters usually set by physician are necessary for the successful implementation of IMRT. PMID:19399266

Parotid gland sparing IMRT for head and neck cancer improves xerostomia related quality of life

Science.gov (United States)

van Rij, CM; Oughlane-Heemsbergen, WD; Ackerstaff, AH; Lamers, EA; Balm, AJM; Rasch, CRN

2008-01-01

Background and purpose To assess the impact of intensity modulated radiotherapy (IMRT) versus conventional radiation on late xerostomia and Quality of Life aspects in head and neck cancer patients. Patients and nethods Questionnaires on xerostomia in rest and during meals were sent to all patients treated between January 1999 and December 2003 with a T1-4, N0-2 M0 head and neck cancer, with parotid gland sparing IMRT or conventional bilateral neck irradiation to a dose of at least 60 Gy, who were progression free and had no disseminated disease (n = 192). Overall response was 85% (n = 163); 97% in the IMRT group (n = 75) and 77% in the control group (n = 88) the median follow-up was 2.6 years. The prevalence of complaints was compared between the two groups, correcting for all relevant factors at multivariate ordinal regression analysis. Results Patients treated with IMRT reported significantly less difficulty transporting and swallowing their food and needed less water for a dry mouth during day, night and meals. They also experienced fewer problems with speech and eating in public. Laryngeal cancer patients in general had fewer complaints than oropharynx cancer patients but both groups benefited from IMRT. Within the IMRT group the xerostomia scores were better for those patients with a mean parotid dose to the "spared" parotid below 26 Gy. Conclusion Parotid gland sparing IMRT for head and neck cancer patients improves xerostomia related quality of life compared to conventional radiation both in rest and during meals. Laryngeal cancer patients had fewer complaints but benefited equally compared to oropharyngeal cancer patients from IMRT. PMID:19068126

Parotid gland sparing IMRT for head and neck cancer improves xerostomia related quality of life

Directory of Open Access Journals (Sweden)

Balm AJM

2008-12-01

Full Text Available Abstract Background and purpose To assess the impact of intensity modulated radiotherapy (IMRT versus conventional radiation on late xerostomia and Quality of Life aspects in head and neck cancer patients. Patients and nethods Questionnaires on xerostomia in rest and during meals were sent to all patients treated between January 1999 and December 2003 with a T1-4, N0-2 M0 head and neck cancer, with parotid gland sparing IMRT or conventional bilateral neck irradiation to a dose of at least 60 Gy, who were progression free and had no disseminated disease (n = 192. Overall response was 85% (n = 163; 97% in the IMRT group (n = 75 and 77% in the control group (n = 88 the median follow-up was 2.6 years. The prevalence of complaints was compared between the two groups, correcting for all relevant factors at multivariate ordinal regression analysis. Results Patients treated with IMRT reported significantly less difficulty transporting and swallowing their food and needed less water for a dry mouth during day, night and meals. They also experienced fewer problems with speech and eating in public. Laryngeal cancer patients in general had fewer complaints than oropharynx cancer patients but both groups benefited from IMRT. Within the IMRT group the xerostomia scores were better for those patients with a mean parotid dose to the "spared" parotid below 26 Gy. Conclusion Parotid gland sparing IMRT for head and neck cancer patients improves xerostomia related quality of life compared to conventional radiation both in rest and during meals. Laryngeal cancer patients had fewer complaints but benefited equally compared to oropharyngeal cancer patients from IMRT.

Definitive Upfront Stereotactic Ablative Radiotherapy Combined with Image-Guided, Intensity Modulated Radiotherapy (IG-IMRT or IG-IMRT Alone for Locally Advanced Non-Small Cell Lung Cancer.

Directory of Open Access Journals (Sweden)

Alexander Chi

Full Text Available Image-guided (IG intensity-modulated radiotherapy (IMRT enables maximal tumor margin reduction for the sparing of organs at risk (OARs when used to treat locally advanced non-small cell lung cancer (NSCLC with definitive chemo-radiation. It also allows for the incorporation of stereotactic ablative radiotherapy (SABR into the treatment regimen. Here, we describe our initial experience in combining definitive upfront SABR to the primary lesion with chemo-radiation delivered with conventionally fractionated IG-IMRT to the remaining regional disease; along with clinical outcome following chemo-radiation with conventionally fractionated IG-IMRT alone in the treatment of locally advanced NSCLC.The clinical outcome of 29 patients with locally advanced NSCLC who underwent conventionally fractionated IG-IMRT, or definitive upfront SABR followed by IG-IMRT combined with chemotherapy (induction, concurrent, or both was retrospectively reviewed.After a median follow up of 23.7 months, the median overall survival (OS and progression-free survival (PFS were 19.8 and 11.3 months, respectively. The 2 year local, regional, and distant control was 60%, 62%, and 38%, respectively. No local failure was observed in 3 patients following SABR + IG-IMRT while 6/26 patients failed locally following IG-IMRT alone. SABR + IG-IMRT was well tolerated. No ≥ grade 3 radiation-related toxicity was observed.Definitive upfront SABR followed by IG-IMRT in selected patients with locally advanced NSCLC warrants further investigation in future clinical trials, while chemo-radiation with IG-IMRT alone was well tolerated.

Radiotherapy-induced secondary cancer risk for breast cancer: 3D conformal therapy versus IMRT versus VMAT

International Nuclear Information System (INIS)

Lee, Boram; Sung, Jiwon; Yoon, Myonggeun; Lee, Sunyoung

2014-01-01

This study evaluated the secondary cancer risk to various organs due to radiation treatment for breast cancer. Organ doses to an anthropomorphic phantom were measured using a photoluminescent dosimeter (PLD) for breast cancer treatment with 3D conformal radiation therapy (3D-CRT), intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT). Cancer risk based on the measured dose was calculated using the BEIR (Biological Effects of Ionizing Radiation) VII models. The secondary dose per treatment dose (50.4 Gy) to various organs ranged from 0.02 to 0.36 Gy for 3D-CRT, but from 0.07 to 8.48 Gy for IMRT and VMAT, indicating that the latter methods are associated with higher secondary radiation doses than 3D-CRT. The result of the homogeneity index in the breast target shows that the dose homogeneity of 3D-CRT was worse than those of IMRT and VMAT. The organ specific lifetime attributable risks (LARs) to the thyroid, contralateral breast and ipsilateral lung per 100 000 population were 0.02, 19.71, and 0.76 respectively for 3D-CRT, much lower than the 0.11, 463.56, and 10.59 respectively for IMRT and the 0.12, 290.32, and 12.28 respectively for VMAT. The overall estimation of LAR indicated that the radiation-induced cancer risk due to breast radiation therapy was lower with 3D-CRT than with IMRT or VMAT. (paper)

SU-E-J-67: Evaluation of Adaptive MLC Morphing for Online Correction of Prostate Cancer Radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Sandhu, R; Qin, A; Yan, D [William Beaumont Hospital, Royal Oak, MI (United States)

2015-06-15

Purpose: Online adaptive MLC morphing is desirable over translational couch shifts to accommodate target position as well as anatomic changes. A reliable method of adaptive MLC segment to target during prostate cancer IMRT treatment is proposed and evaluated by comparison with daily online-image guidance (IGRT) correction and online-IMRT planning. Methods: The MLC adaptive algorithm involves following steps; move the MLC segments according to target translational shifts, and then morph the segment shape to maintain the spatial relationship between the planning-target contour and MLC segment. Efficacy of this method was evaluated retrospectively using daily-CBCT images on seven prostate patients treated with seven-beam IMRT treatment to deliver 64Gy in 20 fractions. Daily modification was simulated with three approaches; daily-IGRT correction based on implanted radio-markers, adaptive MLC morphing, and online-IMRT planning, with no-residual variation. The selected dosimetric endpoints and nEUD (normalized equivalent uniform dose to online-IMRT planning) of each organ of interest were determined for evaluation and comparison. Results: For target(prostate), bladder and rectal-wall, the mean±sd of nEUD were 97.6%+3.2%, 103.9%±4.9% and 97.4%±1.1% for daily-IGRT correction; and 100.2%+0.2%, 108.9%±5.1% and 99.8%±1.2% for adaptive MLC morphing, respectively. For daily-IGRT correction, adaptive MLC morphing and online-IMRT planning, target D99 was <95% of the prescription dose in 30%, 0% and 0% of 140 fractions, respectively. For the rectal-wall, D5 exceeded 105% of the planned-D5 in 2.8%, 11.4% and 0% of 140 fractions, respectively. For the bladder, Dmax exceeded 105% of the planned-D5 in 2.8%, 5.6% and 0% of 140 fractions, respectively. D30 of bladder and rectal-wall were well within the planned-D30 for all three approaches. Conclusion: The proposed method of adaptive MLC morphing can be beneficial for the prostate patient population with large deformation and

SU-E-J-67: Evaluation of Adaptive MLC Morphing for Online Correction of Prostate Cancer Radiotherapy

International Nuclear Information System (INIS)

Sandhu, R; Qin, A; Yan, D

2015-01-01

Purpose: Online adaptive MLC morphing is desirable over translational couch shifts to accommodate target position as well as anatomic changes. A reliable method of adaptive MLC segment to target during prostate cancer IMRT treatment is proposed and evaluated by comparison with daily online-image guidance (IGRT) correction and online-IMRT planning. Methods: The MLC adaptive algorithm involves following steps; move the MLC segments according to target translational shifts, and then morph the segment shape to maintain the spatial relationship between the planning-target contour and MLC segment. Efficacy of this method was evaluated retrospectively using daily-CBCT images on seven prostate patients treated with seven-beam IMRT treatment to deliver 64Gy in 20 fractions. Daily modification was simulated with three approaches; daily-IGRT correction based on implanted radio-markers, adaptive MLC morphing, and online-IMRT planning, with no-residual variation. The selected dosimetric endpoints and nEUD (normalized equivalent uniform dose to online-IMRT planning) of each organ of interest were determined for evaluation and comparison. Results: For target(prostate), bladder and rectal-wall, the mean±sd of nEUD were 97.6%+3.2%, 103.9%±4.9% and 97.4%±1.1% for daily-IGRT correction; and 100.2%+0.2%, 108.9%±5.1% and 99.8%±1.2% for adaptive MLC morphing, respectively. For daily-IGRT correction, adaptive MLC morphing and online-IMRT planning, target D99 was <95% of the prescription dose in 30%, 0% and 0% of 140 fractions, respectively. For the rectal-wall, D5 exceeded 105% of the planned-D5 in 2.8%, 11.4% and 0% of 140 fractions, respectively. For the bladder, Dmax exceeded 105% of the planned-D5 in 2.8%, 5.6% and 0% of 140 fractions, respectively. D30 of bladder and rectal-wall were well within the planned-D30 for all three approaches. Conclusion: The proposed method of adaptive MLC morphing can be beneficial for the prostate patient population with large deformation and

A dosimetric comparison of two-phase adaptive intensity-modulated radiotherapy for locally advanced nasopharyngeal cancer

OpenAIRE

Chitapanarux, Imjai; Chomprasert, Kittisak; Nobnaop, Wannapa; Wanwilairat, Somsak; Tharavichitkul, Ekasit; Jakrabhandu, Somvilai; Onchan, Wimrak; Traisathit, Patrinee; Van Gestel, Dirk

2015-01-01

The purpose of this investigation was to evaluate the potential dosimetric benefits of a two-phase adaptive intensity-modulated radiotherapy (IMRT) protocol for patients with locally advanced nasopharyngeal cancer (NPC). A total of 17 patients with locally advanced NPC treated with IMRT had a second computed tomography (CT) scan after 17 fractions in order to apply and continue the treatment with an adapted plan after 20 fractions. To simulate the situation without adaptation, a hybrid plan w...

Experimental IMRT breast dosimetry in a thorax phantom

Energy Technology Data Exchange (ETDEWEB)

Pimenta, Elsa B.; Campos, Tarcisio P.R.; Nogueira, Luciana B.; Lima, Andre C.S., E-mail: elsabpimenta@gmail.com, E-mail: tprcampos@pq.cnpq.br, E-mail: lucibn19@yahoo.com.br, E-mail: radioterapia.andre@gmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil); Centro de Tratamento em Radioterapia, Betim, MG (Brazil)

2017-11-01

Radiation therapy (RT) is an essential therapeutic method. RT is often used as adjuvant therapy in the treatment of breast cancer. The dose-volume restrictions of the organs at risk limit the prescribed dose to the target volume and biological and clinical effects may influence the final treatment outcome. The breast RT provides large risks to the adjacent organs and consequently the recommended dosimetry to the prescribed dose volume (PTV) is 50 Gy, lower than the most prescribed dose in other treatments (70-85 Gy). Such values implies in less tumor control compared to other sites. The present research proposal aimed to measure absorbed dose in a thorax phantom with synthetic breasts provided by an Intensity-Modulate Radiation Therapy (IMRT) protocol in a RT center. On the methodology, IMRT protocol was selected following recommendations from the Radiation Therapy Oncology Group (RTOG). Radiochromic films and a thorax simulator were prepared by the Ionizing Radiation Research Group (NRI). Dosimeters were calibrated on a selected linear accelerator (LINAC). The comparison of the dosimetry from treatment planning system (TPS), Xio (Elekta) and from experimental data was performed. The spatial distribution of the breast internal dose and in the adjacent organs was depicted by the experimental data. In the film's calibration, the quadratic polynomial fit presented a satisfactory coefficient. Two-dimensional dose profiles were obtained in the breast suggesting that films can supply details and information that TPS does not provide. At the phantom's dosimetry, the internal mean doses taken at the synthetic breast presented usual values above the prescribed dose, besides overall values were within the dosimetric MSKCC criterion. The non full reproduction of the build-up region in the films had occurred due to the asymmetrical positioning of the films in the inner breast, in addition to their non constant distance from the skin. The hot regions were present may

IMRT limits nephrotoxicity after chemoradiotherapy for gastric cancer

International Nuclear Information System (INIS)

Trip, Anouk Kirsten; Nijkamp, Jasper; Tinteren, Harm van; Cats, Annemieke; Boot, Henk; Jansen, Edwin Petrus Marianus; Verheij, Marcel

2014-01-01

Objective: This observational study compares the effect of different radiotherapy techniques on late nephrotoxicity after postoperative chemoradiotherapy for gastric cancer. Patients and methods: Dosimetric parameters were compared between AP–PA, 3D-conformal and IMRT techniques. Renal function was measured by 99m Tc-MAG-3 renography, glomerular filtration rate (GFR) and the development of hypertension. Mixed effects models were used to compare renal function over time. Results: Eighty-seven patients treated between 2002 and 2010 were included, AP–PA (n = 31), 3D-conformal (n = 25) and IMRT (n = 31), all 45 Gy in 25 fractions. Concurrent chemotherapy: 5FU/leucovorin (n = 4), capecitabine (n = 37), and capecitabine/cisplatin (n = 46). Median follow-up time was 4.7 years (range 0.2–8). With IMRT, the mean dose to the left kidney was significantly lower. Left kidney function decreased progressively in the total study population, however with IMRT this occurred at a lower rate. A dose–effect relationship was present between mean dose to the left kidney and the left kidney function. GFR decreased only moderately in time, which was not different between techniques. Six patients developed hypertension, of whom none in the IMRT group. Conclusions: This study confirms progressive late nephrotoxicity in patients treated with postoperative chemoradiotherapy by different techniques for gastric cancer. Nephrotoxicity was less severe with IMRT and should be considered the preferred technique

IMRT limits nephrotoxicity after chemoradiotherapy for gastric cancer.

Science.gov (United States)

Trip, Anouk Kirsten; Nijkamp, Jasper; van Tinteren, Harm; Cats, Annemieke; Boot, Henk; Jansen, Edwin Petrus Marianus; Verheij, Marcel

2014-08-01

This observational study compares the effect of different radiotherapy techniques on late nephrotoxicity after postoperative chemoradiotherapy for gastric cancer. Dosimetric parameters were compared between AP-PA, 3D-conformal and IMRT techniques. Renal function was measured by (99m)Tc-MAG-3 renography, glomerular filtration rate (GFR) and the development of hypertension. Mixed effects models were used to compare renal function over time. Eighty-seven patients treated between 2002 and 2010 were included, AP-PA (n=31), 3D-conformal (n=25) and IMRT (n=31), all 45 Gy in 25 fractions. Concurrent chemotherapy: 5FU/leucovorin (n=4), capecitabine (n=37), and capecitabine/cisplatin (n=46). Median follow-up time was 4.7 years (range 0.2-8). With IMRT, the mean dose to the left kidney was significantly lower. Left kidney function decreased progressively in the total study population, however with IMRT this occurred at a lower rate. A dose-effect relationship was present between mean dose to the left kidney and the left kidney function. GFR decreased only moderately in time, which was not different between techniques. Six patients developed hypertension, of whom none in the IMRT group. This study confirms progressive late nephrotoxicity in patients treated with postoperative chemoradiotherapy by different techniques for gastric cancer. Nephrotoxicity was less severe with IMRT and should be considered the preferred technique. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Institutional Patient-specific IMRT QA Does Not Predict Unacceptable Plan Delivery

Energy Technology Data Exchange (ETDEWEB)

Kry, Stephen F., E-mail: sfkry@mdanderson.org [Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Molineu, Andrea [Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Kerns, James R.; Faught, Austin M.; Huang, Jessie Y.; Pulliam, Kiley B.; Tonigan, Jackie [Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas (United States); Alvarez, Paola [Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Stingo, Francesco [The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas (United States); Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Followill, David S. [Imaging and Radiation Oncology Core at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Health Science Center Houston, Graduate School of Biomedical Sciences, Houston, Texas (United States)

2014-12-01

Purpose: To determine whether in-house patient-specific intensity modulated radiation therapy quality assurance (IMRT QA) results predict Imaging and Radiation Oncology Core (IROC)-Houston phantom results. Methods and Materials: IROC Houston's IMRT head and neck phantoms have been irradiated by numerous institutions as part of clinical trial credentialing. We retrospectively compared these phantom results with those of in-house IMRT QA (following the institution's clinical process) for 855 irradiations performed between 2003 and 2013. The sensitivity and specificity of IMRT QA to detect unacceptable or acceptable plans were determined relative to the IROC Houston phantom results. Additional analyses evaluated specific IMRT QA dosimeters and analysis methods. Results: IMRT QA universally showed poor sensitivity relative to the head and neck phantom, that is, poor ability to predict a failing IROC Houston phantom result. Depending on how the IMRT QA results were interpreted, overall sensitivity ranged from 2% to 18%. For different IMRT QA methods, sensitivity ranged from 3% to 54%. Although the observed sensitivity was particularly poor at clinical thresholds (eg 3% dose difference or 90% of pixels passing gamma), receiver operator characteristic analysis indicated that no threshold showed good sensitivity and specificity for the devices evaluated. Conclusions: IMRT QA is not a reasonable replacement for a credentialing phantom. Moreover, the particularly poor agreement between IMRT QA and the IROC Houston phantoms highlights surprising inconsistency in the QA process.

Institutional Patient-specific IMRT QA Does Not Predict Unacceptable Plan Delivery

International Nuclear Information System (INIS)

Kry, Stephen F.; Molineu, Andrea; Kerns, James R.; Faught, Austin M.; Huang, Jessie Y.; Pulliam, Kiley B.; Tonigan, Jackie; Alvarez, Paola; Stingo, Francesco; Followill, David S.

2014-01-01

Purpose: To determine whether in-house patient-specific intensity modulated radiation therapy quality assurance (IMRT QA) results predict Imaging and Radiation Oncology Core (IROC)-Houston phantom results. Methods and Materials: IROC Houston's IMRT head and neck phantoms have been irradiated by numerous institutions as part of clinical trial credentialing. We retrospectively compared these phantom results with those of in-house IMRT QA (following the institution's clinical process) for 855 irradiations performed between 2003 and 2013. The sensitivity and specificity of IMRT QA to detect unacceptable or acceptable plans were determined relative to the IROC Houston phantom results. Additional analyses evaluated specific IMRT QA dosimeters and analysis methods. Results: IMRT QA universally showed poor sensitivity relative to the head and neck phantom, that is, poor ability to predict a failing IROC Houston phantom result. Depending on how the IMRT QA results were interpreted, overall sensitivity ranged from 2% to 18%. For different IMRT QA methods, sensitivity ranged from 3% to 54%. Although the observed sensitivity was particularly poor at clinical thresholds (eg 3% dose difference or 90% of pixels passing gamma), receiver operator characteristic analysis indicated that no threshold showed good sensitivity and specificity for the devices evaluated. Conclusions: IMRT QA is not a reasonable replacement for a credentialing phantom. Moreover, the particularly poor agreement between IMRT QA and the IROC Houston phantoms highlights surprising inconsistency in the QA process

An evaluation of gating window size, delivery method, and composite field dosimetry of respiratory-gated IMRT

International Nuclear Information System (INIS)

Hugo, Geoffrey D.; Agazaryan, Nzhde; Solberg, Timothy D.

2002-01-01

A respiratory gating system has been developed based on a commercial patient positioning system. The purpose of this study is to investigate the ability of the gating system to reproduce normal, nongated IMRT operation and to quantify the errors produced by delivering a nongated IMRT treatment onto a moving target. A moving phantom capable of simultaneous two-dimensional motion was built, and an analytical liver motion function was used to drive the phantom. Studies were performed to assess the effect of gating window size and choice of delivery method (segmented and dynamic multileaf collimation). Additionally, two multiple field IMRT cases were delivered to quantify the error in gated and nongated IMRT with motion. Dosimetric error between nonmoving and moving deliveries is related to gating window size. By reducing the window size, the error can be reduced. Delivery error can be reduced for both dynamic and segmented delivery with gating. For the implementation of dynamic IMRT delivery in this study, dynamic delivery was found to generate larger delivery errors than segmented delivery in most cases studied. For multiple field IMRT delivery, the largest errors were generated in regions where high field modulation was present parallel to the axis of motion. Gating was found to reduce these large errors to clinically acceptable levels

Engineering Design of an Adaptive Leg Prosthesis Using Biological Principles

DEFF Research Database (Denmark)

Lenau, Torben Anker; Dentel, Andy; Invarsdottir, Thorunn

2010-01-01

The biomimetic design process is explored through a design case: An adaptive leg prosthesis. The aim is to investigate if the biomimetic design process can be carried out with a minimum of biological knowledge and without using advanced design methods. In the design case biomimetic design was suc...... was successfully carried out using library search resulting in 14 biological analogies for the design problem 'shape adaption'. It is proposed that search results are handled using special cards describing the biological phenomena and the functional principles....

Automated IMRT planning with regional optimization using planning scripts.

Science.gov (United States)

Xhaferllari, Ilma; Wong, Eugene; Bzdusek, Karl; Lock, Michael; Chen, Jeff

2013-01-07

Intensity-modulated radiation therapy (IMRT) has become a standard technique in radiation therapy for treating different types of cancers. Various class solutions have been developed for simple cases (e.g., localized prostate, whole breast) to generate IMRT plans efficiently. However, for more complex cases (e.g., head and neck, pelvic nodes), it can be time-consuming for a planner to generate optimized IMRT plans. To generate optimal plans in these more complex cases which generally have multiple target volumes and organs at risk, it is often required to have additional IMRT optimization structures such as dose limiting ring structures, adjust beam geometry, select inverse planning objectives and associated weights, and additional IMRT objectives to reduce cold and hot spots in the dose distribution. These parameters are generally manually adjusted with a repeated trial and error approach during the optimization process. To improve IMRT planning efficiency in these more complex cases, an iterative method that incorporates some of these adjustment processes automatically in a planning script is designed, implemented, and validated. In particular, regional optimization has been implemented in an iterative way to reduce various hot or cold spots during the optimization process that begins with defining and automatic segmentation of hot and cold spots, introducing new objectives and their relative weights into inverse planning, and turn this into an iterative process with termination criteria. The method has been applied to three clinical sites: prostate with pelvic nodes, head and neck, and anal canal cancers, and has shown to reduce IMRT planning time significantly for clinical applications with improved plan quality. The IMRT planning scripts have been used for more than 500 clinical cases.

Phantoms for IMRT dose distribution measurement and treatment verification

International Nuclear Information System (INIS)

Low, Daniel A.; Gerber, Russell L.; Mutic, Sasa; Purdy, James A.

1998-01-01

Background: The verification of intensity-modulated radiation therapy (IMRT) patient treatment dose distributions is currently based on custom-built or modified dose measurement phantoms. The only commercially available IMRT treatment planning and delivery system (Peacock, NOMOS Corp.) is supplied with a film phantom that allows accurate spatial localization of the dose distribution using radiographic film. However, measurements using other dosimeters are necessary for the thorough verification of IMRT. Methods: We have developed a phantom to enable dose measurements using a cylindrical ionization chamber and the localization of prescription isodose curves using a matrix of thermoluminescent dosimetry (TLD) chips. The external phantom cross-section is identical to that of the commercial phantom, to allow direct comparisons of measurements. A supplementary phantom has been fabricated to verify the IMRT dose distributions for pelvis treatments. Results: To date, this phantom has been used for the verification of IMRT dose distributions for head and neck and prostate cancer treatments. Designs are also presented for a phantom insert to be used with polymerizing gels (e.g., BANG-2) to obtain volumetric dose distribution measurements. Conclusion: The phantoms have proven useful in the quantitative evaluation of IMRT treatments

Kidney-Sparing Methods for Extended-Field Intensity-Modulated Radiotherapy (EF-IMRT) in Cervical Carcinoma Treatment.

Science.gov (United States)

Kunogi, Hiroaki; Yamaguchi, Nanae; Terao, Yasuhisa; Sasai, Keisuke

2016-01-01

Coplanar extended-field intensity-modulated radiation therapy (EF-IMRT) targeting the whole-pelvic and para-aortic lymph nodes in patients with advanced cervical cancer results in impaired creatinine clearance. An improvement in renal function cannot be expected unless low-dose (approximately 10 Gy) kidney exposure is reduced. The dosimetric method should be considered during EF-IMRT planning to further reduce low-dose exposure to the kidneys. To assess the usefulness of non-coplanar EF-IMRT with kidney-avoiding beams to spare the kidneys during cervical carcinoma treatment in dosimetric analysis between non-coplanar and coplanar EF-IMRT, we compared the doses of the target organ and organs at risk, including the kidney, in 10 consecutive patients. To estimate the influence of EFRT on renal dysfunction, creatinine clearance values after treatment were also examined in 18 consecutive patients. Of these 18 patients, 10 patients who were included in the dosimetric analysis underwent extended field radiation therapy (EFRT) with concurrent chemotherapy, and eight patients underwent whole-pelvis radiation therapy with concurrent chemotherapy to treat cervical carcinoma between April 2012 and March 2015 at our institution. In the dosimetric analysis, non-coplanar EF-IMRT was effective at reducing low-dose (approximately 10 Gy) exposure to the kidneys, thus maintaining target coverage and sparing other organs at risk, such as the small bowel, rectum, and bladder, compared with coplanar EF-IMRT. Renal function in all 10 patients who underwent EFRT, including coplanar EF-IMRT (with kidney irradiation), was low after treatment, and differed significantly from that of the eight patients who underwent WPRT (no kidney irradiation) 6 months after the first day of treatment (P = 0.005). In conclusion, non-coplanar EF-IMRT should be considered in patients with advanced cervical cancer, particularly in patients with a long life expectancy or with pre-existing renal dysfunction.

After low and high dose-rate interstitial brachytherapy followed by IMRT radiotherapy for intermediate and high risk prostate cancer

International Nuclear Information System (INIS)

Nakamura, Satoshi; Murakami, Naoya; Inaba, Koji; Wakita, Akihisa; Kobayashi, Kazuma; Takahashi, Kana; Okamoto, Hiroyuki; Umezawa, Rei; Morota, Madoka; Sumi, Minako; Igaki, Hiroshi; Ito, Yoshinori; Itami, Jun

2016-01-01

The study aimed to compare urinary symptoms in patients with clinically localized prostate cancer after a combination of either low-dose-rate or high-dose-rate interstitial brachytherapy along with intensity-modulated radiation therapy (LDR-ISBT + IMRT or HDR-ISBT + IMRT). From June 2009 to April 2014, 16 and 22 patients were treated with LDR-ISBT + IMRT and HDR-ISBT + IMRT, respectively. No patient from these groups was excluded from this study. The prescribed dose of LDR-ISBT, HDR-ISBT, and IMRT was 115 Gy, 20 Gy in 2 fractions, and 46 Gy in 23 fractions, respectively. Obstructive and irritative urinary symptoms were assessed by the International Prostate Symptom Score (IPSS) examined before and after treatments. After ISBT, IPSS was evaluated in the 1st and 4th weeks, then every 2–3 months for the 1st year, and every 6 months thereafter. The median follow-up of the patients treated with LDR-ISBT + IMRT and HDR-ISBT + IMRT was 1070.5 days and 1048.5 days, respectively (p = 0.321). The IPSS-increment in the LDR-ISBT + IMRT group was greater than that in the HDR-ISBT + IMRT between 91 and 180 days after ISBT (p = 0.015). In the LDR-ISBT + IMRT group, the IPSS took longer time to return to the initial level than in the HDR-ISBT + IMRT group (in LDR-ISBT + IMRT group, the recovery time was 90 days later). The dose to urethra showed a statistically significant association with the IPSS-increment in the irritative urinary symptoms (p = 0.011). Clinical outcomes were comparable between both the groups. Both therapeutic modalities are safe and well suited for patients with clinically localized prostate cancer; however, it took patients longer to recover from LDR-ISBT + IMRT than from HDR-ISBT + IMRT. It is possible that fast dose delivery induced early symptoms and early recovery, while gradual dose delivery induced late symptoms and late recovery. Urethral dose reductions were associated with small increments in IPSS

Evaluation of the Delta4 phantom for IMRT and VMAT verification

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Bedford, James L; Lee, Young K; Wai, Philip; South, Christopher P; Warrington, Alan P

2009-01-01

The Delta 4 diode array phantom (Scandidos, Uppsala, Sweden) was evaluated for verification of segmental intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) on an Elekta linear accelerator (Crawley UK). The device was tested for angular sensitivity by irradiating it from 36 different gantry angles, and the responses of the device to various step-and-shoot segment doses and dose rates were evaluated using an ionization chamber as a comparison. The phantom was then compared with ionization chamber and film results for two prostate and pelvic nodes IMRT plans, two head and neck IMRT plans and two lung VMAT plans. These plans were calculated using Pinnacle 3 (Philips Radiation Oncology Systems, Madison, WI). The uniformity of angular response was better than 0.5% over the range of gantry angles. The uniformity of response of the Delta 4 to different segment monitor units and dose rates was better than 0.5%. The assessment of the IMRT and VMAT plans showed that the Delta 4 measured a dose within 2.5% of the ionization chamber, and compared to film recorded a slightly larger region (range -2% to +7%) agreeing with the planned dose to within 3% and 3 mm. The Delta 4 is a complex device and requires careful benchmarking, but following the successful completion of these measurements, the Delta 4 has been introduced into clinical use. (note)

Comparison of whole-field simultaneous integrated boost VMAT and IMRT in the treatment of nasopharyngeal cancer

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Jin, Xiance; Yi, Jinling; Zhou, Yongqiang; Yan, Huawei; Han, Ce; Xie, Congying, E-mail: billy07@wzhospital.cn

2013-01-01

To study the feasibility of using volumetric-modulated arc therapy (VMAT) to deliver whole-field simultaneous integrated boost (WF-SIB) to treat patients with nasopharyngeal cancer (NPC). WF-SIB intensity-modulated radiotherapy (IMRT) plans, one-arc WF-SIB VMAT plans, and two-arc WF-SIB VMAT plans were generated with identical objective functions for 8 patients with NPC of various stages. Isodose distributions and dose-volume histograms were evaluated. Dosimetric and biological quality indices of clinical target volume (CTV) and organs at risk (OARs) were calculated to study the optimization capability of these 3 modalities in the treatment of patients with NPC. The optimization time, delivery time, required monitor units (MUs), and delivery accuracy were also compared to investigate the feasibility of these 3 modalities. There was no significant difference (p = 0.92) in target coverage (TC) between WF-SIB IMRT (99.00 ± 0.79) and two-arc WF-SIB VMAT (97.98 ± 1.29). However, both had higher TC than one-arc VMAT plans (89.92 ± 6.32, p < 0.01). IMRT demonstrated the best protection of the spinal cord, whereas two-arc VMAT showed the minimum D{sub max} to OARs. No other significant differences were observed among these 3 modalities on CTV coverage and OAR sparing. The delivery and MU efficiency of one-arc and two-arc WF-SIB VMAT were greatly improved compared with WF-SIB IMRT. The optimization time of one-arc and two-arc WF-SIB VMAT plans were 5 and 10 times greater than that of WF-SIB IMRT, respectively. The delivery accuracy of WF-SIB VMAT was not affected by the increased freedom. For patients with NPC, one-arc WF-SIB VMAT might not be able to achieve sufficient TC, whereas two-arc WF-SIB VMAT was able to achieve reasonable TC. No significant advantage on OAR protection was demonstrated by VMAT compared with IMRT. WF-SIB VMAT has significantly shorter delivery times, but WF-SIB IMRT may still be the first treatment choice for patients with NPC.

Lhermitte's Sign Developing after IMRT for Head and Neck Cancer

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Dong C. Lim

2010-01-01

Full Text Available Background. Lhermitte's sign (LS is a benign form of myelopathy with neck flexion producing an unpleasant electric-shock sensation radiating down the extremities. Although rare, it can occur after head and neck radiotherapy. Results. We report a case of Lhermitte's developing after curative intensity-modulated radiotherapy (IMRT for a patient with locoregionally advanced oropharyngeal cancer. IMRT delivers a conformal dose of radiation in head and neck cancer resulting in a gradient of radiation dose throughout the spinal cord. Using IMRT, more dose is delivered to the anterior spinal cord than the posterior cord. Conclusions. Lhermitte's sign can develop after IMRT for head and neck cancer. We propose an anterior spinal cord structure, the spinothalamic tract to be the target of IMRT-caused LS.

Intensity modulated radiotherapy (IMRT) with compensators

International Nuclear Information System (INIS)

Salz, H.; Wiezorek, T.; Scheithauer, M.; Kleen, W.; Schwedas, M.; Wendt, T.G.

2002-01-01

The irradiation with intensity-modulated fields is possible with static as well as dynamic methods. In our university hospital, the intensity-modulated radiotherapy (IMRT) with compensators was prepared and used for the first time for patient irradiation in July 2001. The compensators consist of a mixture of tin granulate and wax, which is filled in a milled negative mould. The treatment planning is performed with Helax-TMS (MDS Nordion). An additional software is used for editing the modulation matrix ('Modifix'). Before irradiation of the first patient, extensive measurements have been carried out in terms of quality assurance of treatment planning and production of compensators. The results of the verification measurements have shown that IMRT with compensators possesses high spatial and dosimetric exactness. The calculated dose distributions are applied correctly. The accuracy of the calculated monitor units is normally better than 3%; in small volumes, further dosimetric inaccuracies between calculated and measured dose distributions are mostly less than 3%. Therefore, the compensators contribute to the achievement of high-level IMRT even when apparatuses without MLC are used. This paper describes the use of the IMRT with compensators, presents the limits of this technology, and discusses the first practical experiences. (orig.) [de

Three-dimensional dose accumulation in pseudo-split-field IMRT and brachytherapy for locally advanced cervical cancer.

Science.gov (United States)

Sun, Baozhou; Yang, Deshan; Esthappan, Jackie; Garcia-Ramirez, Jose; Price, Samantha; Mutic, Sasa; Schwarz, Julie K; Grigsby, Perry W; Tanderup, Kari

2015-01-01

Dose accumulation of split-field external beam radiotherapy (EBRT) and brachytherapy (BT) is challenging because of significant EBRT and BT dose gradients in the central pelvic region. We developed a method to determine biologically effective dose parameters for combined split-field intensity-modulated radiation therapy (IMRT) and image-guided BT in locally advanced cervical cancer. Thirty-three patients treated with split-field-IMRT to 45.0-51.2 Gy in 1.6-1.8 Gy per fraction to the elective pelvic lymph nodes and to 20 Gy to the central pelvis region were included in this study. Patients received six weekly fractions of high-dose rate BT to 6.5-7.3 Gy per fraction. A dose tracker software was developed to compute the equivalent dose in 2-Gy fractions (EQD2) to gross tumor volume (GTV), organs-at-risk and point A. Total dose-volume histogram parameters were computed on the 3D combined EQD2 dose based on rigid image registration. The dose accumulation uncertainty introduced by organ deformations between IMRT and BT was evaluated. According to International Commission on Radiation Unit and Measurement and GEC European Society for Therapeutic Radiology and Oncology recommendations, D98, D90, D50, and D2cm3 EQD2 dose-volume histogram parameters were computed. GTV D98 was 84.0 ± 26.5 Gy and D2cc was 99.6 ± 13.9 Gy, 67.4 ± 12.2 Gy, 75.0 ± 10.1 Gy, for bladder, rectum, and sigmoid, respectively. The uncertainties induced by organ deformation were estimated to be -1 ± 4 Gy, -3 ± 5 Gy, 2 ± 3 Gy, and -3 ± 5 Gy for bladder, rectum, sigmoid, and GTV, respectively. It is feasible to perform 3D EQD2 dose accumulation to assess high and intermediate dose regions for combined split-field IMRT and BT. Copyright © 2015 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Planning issues for IMRT

International Nuclear Information System (INIS)

Hoban, P.; Schneider, M.; Smee, R.

2001-01-01

Full text: Despite the 'inverse planning' stage of an intensity modulated radiotherapy (IMRT) treatment there remains a large number of variables that can, and must, be set manually. These variables can significantly affect the quality of the dose distribution arrived at by the optimisation. Clinical IMRT planning with the Radionics XPlan system for micro-multileaf collimator (MMLC) delivery has allowed for important lessons to be learned regarding the best beam and organ configurations prior to optimisation of beamlet weights. Important user-definable variables are beam directions, organ parameters (dose goals/penalties), and the margin (if any) around the planning target volume (PTV) used to aid coverage. Conventional stereotactic radiotherapy (SRT) treatments typically involve non-coplanar beams since there is often an advantage in terms of cranial organ at risk (OAR) sparing. IMRT can also benefit from such a configuration. The balance between target coverage and OAR sparing is largely controlled by user-defined goal doses and penalties. Once optimisation has been performed, intensity maps can be discretised into a selected number of levels. Less levels means less field segments and thus a shorter treatment time. Although IMRT beams attempt to spare structures which are in the 'beam's eye view' (BEV) of the target volume, sparing is greater if beams which minimise the involvement of OARs in their view are used. It has been found that the use of a margin is an effective way to ensure adequate PTV coverage. Alternatively the PTV penalties can be made larger. The best result is often obtained by the use of a 3-4 mm margin, whose penalty for underdosage is somewhat less than that for the PTV. Discretising the intensity maps to 4 or 5 levels is typically a good balance between shortening treatment time and not overly degrading the dose distribution. Beam configuration is still an important step in IMRT planning, even though optimisation of intensity maps is

The effect of concomitant chemotherapy on parotid gland function following head and neck IMRT

International Nuclear Information System (INIS)

Miah, Aisha B.; Gulliford, Sarah L.; Bhide, Shreerang A.; Zaidi, Shane H.; Newbold, Kate L.; Harrington, Kevin J.; Nutting, Christopher M.

2013-01-01

Purpose: To determine whether concomitant chemotherapy increases the incidence of high grade xerostomia following parotid-sparing intensity-modulated radiotherapy (IMRT) in patients with locally advanced head and neck squamous cell cancer. Materials and methods: The incidence of high grade (⩾G2) acute (CTCAEv3.0) and late (LENTSOMA and RTOG) xerostomia was compared between patients treated with either IMRT or concomitant chemo-IMRT (c-IMRT) in 2 prospective studies. Parotid gland mean tolerance doses (D 50 ) were reported using non-linear logistic regression analysis. Results: Thirty-six patients received IMRT alone and 60 patients received c-IMRT. Patients received 65 Gy in 30 daily fractions to the primary site and involved nodal groups and 54 Gy in 30 fractions to elective nodal groups, mean doses to the parotid glands were comparable. Concomitant cisplatin 100 mg/m 2 was administered on days 1 and 29 of IMRT. The incidence of ⩾G2 subjective xerostomia was similar in both groups; acute-64.7% (IMRT) versus 60.3% (c-IMRT), p = 0.83; late-43% (IMRT) versus 34% (c-IMRT), p = 0.51. Recovery of parotid salivary flow at 1 year was higher with IMRT (64% vs 50%), but not statistically significant (p = 0.15). D 50 for absence of parotid saliva flow at 1 year was 23.2 Gy (95% CI: 17.7–28.7) for IMRT and 21.1 Gy (11.8–30.3) for c-IMRT. Conclusion: Concomitant c-IMRT does not increase the incidence of acute or late xerostomia relative to IMRT alone

The effect of concomitant chemotherapy on parotid gland function following head and neck IMRT.

Science.gov (United States)

Miah, Aisha B; Gulliford, Sarah L; Bhide, Shreerang A; Zaidi, Shane H; Newbold, Kate L; Harrington, Kevin J; Nutting, Christopher M

2013-03-01

To determine whether concomitant chemotherapy increases the incidence of high grade xerostomia following parotid-sparing intensity-modulated radiotherapy (IMRT) in patients with locally advanced head and neck squamous cell cancer. The incidence of high grade (≥G2) acute (CTCAEv3.0) and late (LENTSOMA and RTOG) xerostomia was compared between patients treated with either IMRT or concomitant chemo-IMRT (c-IMRT) in 2 prospective studies. Parotid gland mean tolerance doses (D₅₀) were reported using non-linear logistic regression analysis. Thirty-six patients received IMRT alone and 60 patients received c-IMRT. Patients received 65 Gy in 30 daily fractions to the primary site and involved nodal groups and 54 Gy in 30 fractions to elective nodal groups, mean doses to the parotid glands were comparable. Concomitant cisplatin 100mg/m(2) was administered on days 1 and 29 of IMRT. The incidence of ≥G2 subjective xerostomia was similar in both groups; acute-64.7% (IMRT) versus 60.3% (c-IMRT), p=0.83; late-43% (IMRT) versus 34% (c-IMRT), p=0.51. Recovery of parotid salivary flow at 1 year was higher with IMRT (64% vs 50%), but not statistically significant (p=0.15). D₅₀ for absence of parotid saliva flow at 1 year was 23.2 Gy (95% CI: 17.7-28.7) for IMRT and 21.1 Gy (11.8-30.3) for c-IMRT. Concomitant c-IMRT does not increase the incidence of acute or late xerostomia relative to IMRT alone. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Combined Adjuvant Radiochemotherapy With IMRT/XELOX Improves Outcome With Low Renal Toxicity in Gastric Cancer

International Nuclear Information System (INIS)

Boda-Heggemann, Judit; Hofheinz, Ralf-Dieter; Weiss, Christel; Mennemeyer, Philipp; Mai, Sabine K.; Hermes, Petra; Wertz, Hansjoerg; Post, Stefan; Massner, Bernd; Hieber, Udo; Hochhaus, Andreas; Wenz, Frederik; Lohr, Frank

2009-01-01

Objectives: Adjuvant radiochemotherapy improves survival of patients with advanced gastric cancer. We assessed in two sequential cohorts whether improved radiotherapy technique (IMRT) together with intensified chemotherapy improves outcome vs. conventional three-dimensional conformal radiotherapy (3D-CRT) and standard chemotherapy in these patients while maintaining or reducing renal toxicity. Materials and Methods: Sixty consecutive patients treated for gastric cancer either with 3D-CRT (n = 27) and IMRT (n = 33) were evaluated. More than 70% had undergone D2 resection. Although there was a slight imbalance in R0 status between cohorts, N+ status was balanced. Chemotherapy consisted predominantly of 5-fluorouracil/folinic acid (n = 36) in the earlier cohort and mostly of oxaliplatin/capecitabine (XELOX, n = 24) in the later cohort. Primary end points were overall survival (OS), disease-free survival (DFS), and renal toxicity based on creatinine levels. Results: Median follow-up (FU) of all patients in the 3D-CRT group was 18 months and in the IMRT group 22 months (median FU of surviving patients 67 months in the 3D-CRT group and 25 months in the IMRT group). Overall median survival (and DFS) were 18 (13) months in the 3D-CRT group and both not reached in the IMRT group (p = 0.0492 and 0.0216). Actuarial 2-year survival was 37% and 67% in the 3D-CRT and IMRT groups, respectively. No late renal toxicity >Grade 2 (LENT-SOMA scale) was observed in either cohort. Conclusion: When comparing sequentially treated patient cohorts with similar characteristics, OS and DFS improved with the use of IMRT and intensified chemotherapy without signs of increased renal toxicity.

Is IMRT Superior or Inferior to 3DCRT in Radiotherapy for NSCLC? A Meta-Analysis.

Directory of Open Access Journals (Sweden)

Xingsheng Hu

Full Text Available There are no adequate data to determine whether intensity-modulated radiotherapy (IMRT is superior to three-dimensional conformal radiotherapy (3DCRT in the treatment of non-small cell lung cancer (NSCLC. This meta-analysis was conducted to compare the clinical outcomes of IMRT and 3DCRT in the treatment of NSCLC.No exclusions were made based on types of study design. We performed a literature search in PubMed, EMBASE and the Cochrane library databases from their inceptions to April 30, 2015. The overall survival (OS and relative risk (RR of radiation pneumonitis and radiation oesophagitis were evaluated. Two authors independently assessed the methodological quality and extracted data. Publication bias was evaluated by funnel plot using Egger's test results.From the literature search, 10 retrospective studies were collected, and of those, 5 (12,896 patients were selected for OS analysis, 4 (981 patients were selected for radiation pneumonitis analysis, and 4 (1339 patients were selected for radiation oesophagitis analysis. Cox multivariate proportional hazards models revealed that 3DCRT and IMRT had similar OS (HR = 0.96, P = 0.477 but that IMRT reduced the incidence of grade 2 radiation pneumonitis (RR = 0.74, P = 0.009 and increased the incidence of grade 3 radiation oesophagitis (RR = 2.47, P = 0.000.OS of IMRT for NSCLC is not inferior to that of 3DCRT, but IMRT significantly reduces the risk of radiation pneumonitis and increases the risk of radiation oesophagitis compared to 3DCRT.

Conformal intensity-modulated radiotherapy (IMRT) delivered by robotic linac - testing IMRT to the limit?

International Nuclear Information System (INIS)

Webb, S.

1999-01-01

In this paper it is proposed that intensity-modulated radiotherapy (IMRT) could be delivered optimally by a short-length linac mounted on a robotic arm. The robot would allow the linac to 'plant' narrow pencils of photon radiation with any orientation (excluding zones within which the linac and couch might collide) relative to the planning target volume (PTV). The treatment is specified by the trajectory of the robot and by the number of monitor units (MUs) delivered at each robotic orientation. An inverse-planning method to determine the optimum robotic trajectory is presented. It is shown that for complex PTVs, specifically those with concavities in their outline, the conformality of the treatment is improved by the use of a complex trajectory in comparison with a less complex constrained trajectory and this improvement is quantified. It is concluded that robotic linac delivery would lead to a great flexibility in those IMRT treatments requiring very complicated dose distributions with complex 3D shapes. However, even using very fast computers, the goal of determining whether robotic linac delivery is the ultimate IMRT cannot be conclusively reached at present. (author)

Integration method of 3D MR spectroscopy into treatment planning system for glioblastoma IMRT dose painting with integrated simultaneous boost

International Nuclear Information System (INIS)

Ken, Soléakhéna; Cassol, Emmanuelle; Delannes, Martine; Celsis, Pierre; Cohen-Jonathan, Elizabeth Moyal; Laprie, Anne; Vieillevigne, Laure; Franceries, Xavier; Simon, Luc; Supper, Caroline; Lotterie, Jean-Albert; Filleron, Thomas; Lubrano, Vincent; Berry, Isabelle

2013-01-01

To integrate 3D MR spectroscopy imaging (MRSI) in the treatment planning system (TPS) for glioblastoma dose painting to guide simultaneous integrated boost (SIB) in intensity-modulated radiation therapy (IMRT). For sixteen glioblastoma patients, we have simulated three types of dosimetry plans, one conventional plan of 60-Gy in 3D conformational radiotherapy (3D-CRT), one 60-Gy plan in IMRT and one 72-Gy plan in SIB-IMRT. All sixteen MRSI metabolic maps were integrated into TPS, using normalization with color-space conversion and threshold-based segmentation. The fusion between the metabolic maps and the planning CT scans were assessed. Dosimetry comparisons were performed between the different plans of 60-Gy 3D-CRT, 60-Gy IMRT and 72-Gy SIB-IMRT, the last plan was targeted on MRSI abnormalities and contrast enhancement (CE). Fusion assessment was performed for 160 transformations. It resulted in maximum differences <1.00 mm for translation parameters and ≤1.15° for rotation. Dosimetry plans of 72-Gy SIB-IMRT and 60-Gy IMRT showed a significantly decreased maximum dose to the brainstem (44.00 and 44.30 vs. 57.01 Gy) and decreased high dose-volumes to normal brain (19 and 20 vs. 23% and 7 and 7 vs. 12%) compared to 60-Gy 3D-CRT (p < 0.05). Delivering standard doses to conventional target and higher doses to new target volumes characterized by MRSI and CE is now possible and does not increase dose to organs at risk. MRSI and CE abnormalities are now integrated for glioblastoma SIB-IMRT, concomitant with temozolomide, in an ongoing multi-institutional phase-III clinical trial. Our method of MR spectroscopy maps integration to TPS is robust and reliable; integration to neuronavigation systems with this method could also improve glioblastoma resection or guide biopsies

SU-E-T-784: Using MLC Log Files for Daily IMRT Delivery Verification

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Stathakis, S; Defoor, D; Linden, P; Kirby, N; Papanikolaou, N [University of Texas HSC SA, San Antonio, TX (United States)

2015-06-15

Purpose: To verify daily intensity modulated radiation therapy (IMRT) treatments using multi-leaf collimator (MLC) log files. Methods: The MLC log files from a NovalisTX Varian linear accelerator were used in this study. The MLC files were recorded daily for all patients undergoing IMRT or volumetric modulated arc therapy (VMAT). The first record of each patient was used as reference and all records for subsequent days were compared against the reference. An in house MATLAB software code was used for the comparisons. Each MLC log file was converted to a fluence map (FM) and a gamma index (γ) analysis was used for the evaluation of each daily delivery for every patient. The tolerance for the gamma index was set to 2% dose difference and 2mm distance to agreement while points with signal of 10% or lower of the maximum value were excluded from the comparisons. Results: The γ between each of the reference FMs and the consecutive daily fraction FMs had an average value of 99.1% (ranged from 98.2 to 100.0%). The FM images were reconstructed at various resolutions in order to study the effect of the resolution on the γ and at the same time reduce the time for processing the images. We found that the comparison of images with the highest resolution (768×1024) yielded on average a lower γ (99.1%) than the ones with low resolution (192×256) (γ 99.5%). Conclusion: We developed an in-house software that allows us to monitor the quality of daily IMRT and VMAT treatment deliveries using information from the MLC log files of the linear accelerator. The information can be analyzed and evaluated as early as after the completion of each daily treatment. Such tool can be valuable to assess the effect of MLC positioning on plan quality, especially in the context of adaptive radiotherapy.

Intensity modulated radiotherapy (IMRT) in bilateral retinoblastoma

International Nuclear Information System (INIS)

Atalar, Banu; Ozyar, Enis; Gunduz, Kaan; Gungor, Gorkem

2010-01-01

External beam radiotherapy (EBRT) for retinoblastoma has traditionally been done with conventional radiotherapy techniques which resulted high doses to the surrounding normal tissues. A 20 month-old girl with group D bilateral retinoblastoma underwent intensity modulated radiotherapy (IMRT) to both eyes after failing chemoreduction and focal therapies including cryotherapy and transpupillary thermotherapy. In this report, we discuss the use of IMRT as a method for reducing doses to adjacent normal tissues while delivering therapeutic doses to the tumour tissues compared with 3-dimensional conformal radiotherapy (3DCRT). At one year follow-up, the patient remained free of any obvious radiation complications. Image guided IMRT provides better dose distribution than 3DCRT in retinoblastoma eyes, delivering the therapeutic dose to the tumours and minimizing adjacent tissue damage

Dose discrepancies in the buildup region and their impact on dose calculations for IMRT fields

International Nuclear Information System (INIS)

Hsu, Shu-Hui; Moran, Jean M.; Chen Yu; Kulasekere, Ravi; Roberson, Peter L.

2010-01-01

Purpose: Dose accuracy in the buildup region for radiotherapy treatment planning suffers from challenges in both measurement and calculation. This study investigates the dosimetry in the buildup region at normal and oblique incidences for open and IMRT fields and assesses the quality of the treatment planning calculations. Methods: This study was divided into three parts. First, percent depth doses and profiles (for 5x5, 10x10, 20x20, and 30x30 cm 2 field sizes at 0 deg., 45 deg., and 70 deg. incidences) were measured in the buildup region in Solid Water using an Attix parallel plate chamber and Kodak XV film, respectively. Second, the parameters in the empirical contamination (EC) term of the convolution/superposition (CVSP) calculation algorithm were fitted based on open field measurements. Finally, seven segmental head-and-neck IMRT fields were measured on a flat phantom geometry and compared to calculations using γ and dose-gradient compensation (C) indices to evaluate the impact of residual discrepancies and to assess the adequacy of the contamination term for IMRT fields. Results: Local deviations between measurements and calculations for open fields were within 1% and 4% in the buildup region for normal and oblique incidences, respectively. The C index with 5%/1 mm criteria for IMRT fields ranged from 89% to 99% and from 96% to 98% at 2 mm and 10 cm depths, respectively. The quality of agreement in the buildup region for open and IMRT fields is comparable to that in nonbuildup regions. Conclusions: The added EC term in CVSP was determined to be adequate for both open and IMRT fields. Due to the dependence of calculation accuracy on (1) EC modeling, (2) internal convolution and density grid sizes, (3) implementation details in the algorithm, and (4) the accuracy of measurements used for treatment planning system commissioning, the authors recommend an evaluation of the accuracy of near-surface dose calculations as a part of treatment planning commissioning.

Emphasizing Conformal Avoidance Versus Target Definition for IMRT Planning in Head-and-Neck Cancer

International Nuclear Information System (INIS)

Harari, Paul M.; Song Shiyu; Tome, Wolfgang A.

2010-01-01

Purpose: To describe a method for streamlining the process of elective nodal volume definition for head-and-neck (H and N) intensity-modulated radiotherapy (IMRT) planning. Methods and Materials: A total of 20 patients who had undergone curative-intent RT for H and N cancer underwent comprehensive treatment planning using three distinct, plan design techniques: conventional three-field design, target-defined IMRT (TD-IMRT), and conformal avoidance IMRT (CA-IMRT). For each patient, the conventional three-field design was created first, thereby providing the 'outermost boundaries' for subsequent IMRT design. In brief, TD-IMRT involved physician contouring of the gross tumor volume, high- and low-risk clinical target volume, and normal tissue avoidance structures on consecutive 1.25-mm computed tomography images. CA-IMRT involved physician contouring of the gross tumor volume and normal tissue avoidance structures only. The overall physician time for each approach was monitored, and the resultant plans were rigorously compared. Results: The average physician working time for the design of the respective H and N treatment contours was 0.3 hour for the conventional three-field design plan, 2.7 hours for TD-IMRT, and 0.9 hour for CA-IMRT. Dosimetric analysis confirmed that the largest volume of tissue treated to an intermediate (50 Gy) and high (70 Gy) dose occurred with the conventional three-field design followed by CA-IMRT and then TD-IMRT. However, for the two IMRT approaches, comparable results were found in terms of salivary gland and spinal cord protection. Conclusion: CA-IMRT for H and N treatment offers an alternative to TD-IMRT. The overall time for physician contouring was substantially reduced (approximately threefold), yielding a more standardized elective nodal volume. Because of the complexity of H and N IMRT target design, CA-IMRT might ultimately prove a safer and more reliable method to export to general radiation oncology practitioners, particularly

Inverse IMRT workflow process at Austin health

International Nuclear Information System (INIS)

Rykers, K.; Fernando, W.; Grace, M.; Liu, G.; Rolfo, A.; Viotto, A.; Mantle, C.; Lawlor, M.; Au-Yeung, D.; Quong, G.; Feigen, M.; Lim-Joon, D.; Wada, M.

2004-01-01

Full text: The work presented here will review the strategies adopted at Austin Health to bring IMRT into clinical use. IMRT is delivered using step and shoot mode on an Elekta Precise machine with 40 pairs of 1cm wide MLC leaves. Planning is done using CMS Focus/XiO. A collaborative approach for RO's, Physicists and RTs from concept to implementation was adopted. An overview will be given of the workflow for the clinic, the equipment used, tolerance levels and the lessons learned. 1. Strategic Planning for IMRT 2. Training a. MSKCC (New York) b.ESTRO (Amsterdam) c.Elekta (US and UK) 3. Linac testing and data acquisition a. Equipment and software review and selection b. Linac reliability/geometric and mechanical checks c. Draft Patient QA procedure d. EPI Image matching checks and procedures 4. Planning system checks a. export of dose matrix (options) b. dose calculation choices 5. IMRT Research Initiatives a. IMRT Planning Studies, Stabilisation, On-line Imaging 6. Equipment Procurement and testing a. Physics and Linac Equipment, Hardware, Software/Licences, Stabilisation 7. Establishing a DICOM Environment a. Prescription sending, Image transfer for EPI checks b. QA Files 8. Physics QA (Pre-Treatment) a.Clinical plan review; DVH checks b. geometry; dosimetry checks; DICOM checks c. 2D Distance to agreement; mm difference reports; Gamma function index 9. Documentation a.Protocol Development i. ICRU 50/62 reporting and prescribing b. QA for Physics c. QA for RT's d. Generation of a report for RO/patient history. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

Local control and intermediate-term cosmetic outcome following IMRT for nasal tumors. An update

Energy Technology Data Exchange (ETDEWEB)

Mukai, Yuki [University Hospital Zurich, Department of Radiation Oncology, Head Neck Cancer Center, Zurich (Switzerland); Yokohama City University Graduate School of Medicine, Department of Radiology, Yokohama (Japan); Janssen, Stefan [University Hospital Zurich, Department of Radiation Oncology, Head Neck Cancer Center, Zurich (Switzerland); Glanzmann, Christoph; Studer, Gabriela [University Hospital Zurich, Department of Radiation Oncology, Head Neck Cancer Center, Zurich (Switzerland); Cantonal Hospital Lucerne, Institute for Radiation Oncology, Lucerne (Switzerland); Holzmann, David [University Hospital Zurich, Department of Otorhinolaryngology, Head and Neck Surgery, Head Neck Cancer Center, Zurich (Switzerland)

2017-04-15

This study aims to evaluate local control and intermediate-term cosmetic outcome in patients with cancer of the nose treated with intensity-modulated radiotherapy (IMRT). From June 2008 to September 2015, 36 consecutive patients presenting with nasal cavity, ala of the nose, or nasal vestibule tumors were treated at the Department of Radiation Oncology, University Hospital Zurich either postoperatively (n = 14; 3/14 with nasal ablation) or with definitive IMRT (n = 22). Of these 36 patients, 8 presented with recurrent disease after surgery only and 1/36 with N1 disease. Concurrent systemic therapy was administered in 18/36 patients (50%). Nasal follow-up (FU) imaging documentation of 13 patients with preserved organ and >6 months FU offers a pre/post IMRT FU comparison. In addition, these patients' subjective evaluation of cosmesis was assessed. Mean/median FU was 41/33 months (range 5-92 months). Salvage ablation with curative intent was undergone by 3 patients with local relapse after definitive (n = 2) and postoperative (n = 1) IMRT. The 3-year local control, ultimate local control, and overall survival rates were 90, 97, and 90 %, respectively. Subjective and objective cosmetic outcome after IMRT is very satisfying so far. IMRT for nasal tumors was found to be effective and well tolerated. Intermediate-term cosmetic results are good. Radical surgical procedures may be saved for curative salvage treatment. (orig.) [German] Evaluation der Lokalkontrolle und des mittelfristigen kosmetischen Resultats nach intensitaetsmodulierter Radiotherapie (IMRT) von Patienten mit Nasentumoren. Von Juni 2008 bis September 2015 wurden an der Klinik fuer RadioOnkologie am UniversitaetsSpital Zuerich 36 konsekutive Patienten mit Tumoren der Nasenhoehle, der Nasenfluegel oder des Vestibulum nasi postoperativ (n = 14; 3/14 nach Nasenablation) oder definitiv IMRT-bestrahlt (n = 22). Von diesen 36 Patienten zeigten 8 ein Lokalrezidiv nach alleiniger vorangegangener Chirurgie und

Intensity-modulated radiotherapy (IMRT) and conventional three-dimensional conformal radiotherapy for high-grade gliomas: Does IMRT increase the integral dose to normal brain?

International Nuclear Information System (INIS)

Hermanto, Ulrich; Frija, Erik K.; Lii, MingFwu J.; Chang, Eric L.; Mahajan, Anita; Woo, Shiao Y.

2007-01-01

Purpose: To determine whether intensity-modulated radiotherapy (IMRT) treatment increases the total integral dose of nontarget tissue relative to the conventional three-dimensional conformal radiotherapy (3D-CRT) technique for high-grade gliomas. Methods and Materials: Twenty patients treated with 3D-CRT for glioblastoma multiforme were selected for a comparative dosimetric evaluation with IMRT. Original target volumes, organs at risk (OAR), and dose-volume constraints were used for replanning with IMRT. Predicted isodose distributions, cumulative dose-volume histograms of target volumes and OAR, normal tissue integral dose, target coverage, dose conformity, and normal tissue sparing with 3D-CRT and IMRT planning were compared. Statistical analyses were performed to determine differences. Results: In all 20 patients, IMRT maintained equivalent target coverage, improved target conformity (conformity index [CI] 95% 1.52 vs. 1.38, p mean by 19.8% and D max by 10.7%), optic chiasm (D mean by 25.3% and D max by 22.6%), right optic nerve (D mean by 37.3% and D max by 28.5%), and left optic nerve (D mean by 40.6% and D max by 36.7%), p ≤ 0.01. This was achieved without increasing the total nontarget integral dose by greater than 0.5%. Overall, total integral dose was reduced by 7-10% with IMRT, p < 0.001, without significantly increasing the 0.5-5 Gy low-dose volume. Conclusions: These results indicate that IMRT treatment for high-grade gliomas allows for improved target conformity, better critical tissue sparing, and importantly does so without increasing integral dose and the volume of normal tissue exposed to low doses of radiation

IMRT in hypopharyngeal tumors

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Studer, G.; Luetolf, U.M.; Davis, J.B.; Glanzmann, C. [Dept. of Radiation Oncology, Univ. Hospital, Zurich (Switzerland)

2006-06-15

Background and purpose: intensity-modulated radiation therapy (IMRT) data on hypopharyngeal cancer (HC) are scant. In this study, the authors report on early results in an own HC patient cohort treated with IMRT. A more favorable outcome as compared to historical data on conventional radiation techniques was expected. Patients and methods: 29 consecutive HC patients were treated with simultaneous integrated boost (SIB) IMRT between 01/2002 and 07/2005 (mean follow-up 16 months, range 4-44 months). Doses of 60-71 Gy with 2.0-2.2 Gy/fraction were applied. 26/29 patients were definitively irradiated, 86% received simultaneous cisplatin-based chemotherapy. 60% presented with locally advanced disease (T3/4 Nx, Tx N2c/3). Mean primary tumor volume measured 36.2 cm{sup 3} (4-170 cm{sup 3}), mean nodal volume 16.6 cm{sup 3} (0-97 cm{sup 3}). Results: 2-year actuarial local, nodal, distant control, and overall disease-free survival were 90%, 93%, 93%, and 90%, respectively. In 2/4 patients with persistent disease (nodal in one, primary in three), salvage surgery was performed. The mean dose to the spinal cord (extension of > 5-15 mm) was 26 Gy (12-38 Gy); the mean maximum (point) dose was 44.4 Gy (26-58.9 Gy). One grade (G) 3 dysphagia and two G4 reactions (laryngeal fibrosis, dysphagia), both following the schedule with 2.2 Gy per fraction, have been observed so far. Larynx preservation was achieved in 25/26 of the definitively irradiated patients (one underwent a salvage laryngectomy); 23 had no or minimal dysphagia (G0-1). Conclusion: excellent early disease control and high patient satisfaction with swallowing function in HC following SIB IMRT were observed; these results need to be confirmed based on a longer follow-up period. In order to avoid G4 reactions, SIB doses of < 2.2 Gy/fraction are recommended for large tumors involving laryngeal structures. (orig.)

Verification of eye lens dose in IMRT by MOSFET measurement.

Science.gov (United States)

Wang, Xuetao; Li, Guangjun; Zhao, Jianling; Song, Ying; Xiao, Jianghong; Bai, Sen

2018-04-17

The eye lens is recognized as one of the most radiosensitive structures in the human body. The widespread use of intensity-modulated radiotherapy (IMRT) complicates dose verification and necessitates high standards of dose computation. The purpose of this work was to assess the computed dose accuracy of eye lens through measurements using a metal-oxide-semiconductor field-effect transistor (MOSFET) dosimetry system. Sixteen clinical IMRT plans of head and neck patients were copied to an anthropomorphic head phantom. Measurements were performed using the MOSFET dosimetry system based on the head phantom. Two MOSFET detectors were imbedded in the eyes of the head phantom as the left and the right lens, covered by approximately 5-mm-thick paraffin wax. The measurement results were compared with the calculated values with a dose grid size of 1 mm. Sixteen IMRT plans were delivered, and 32 measured lens doses were obtained for analysis. The MOSFET dosimetry system can be used to verify the lens dose, and our measurements showed that the treatment planning system used in our clinic can provide adequate dose assessment in eye lenses. The average discrepancy between measurement and calculation was 6.7 ± 3.4%, and the largest discrepancy was 14.3%, which met the acceptability criterion set by the American Association of Physicists in Medicine Task Group 53 for external beam calculation for multileaf collimator-shaped fields in buildup regions. Copyright © 2018 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

Towards multidimensional radiotherapy (MD-CRT): biological imaging and biological conformality

International Nuclear Information System (INIS)

Ling, C. Clifton; Humm, John; Larson, Steven; Amols, Howard; Fuks, Zvi; Leibel, Steven; Koutcher, Jason A.

2000-01-01

Purpose: The goals of this study were to survey and summarize the advances in imaging that have potential applications in radiation oncology, and to explore the concept of integrating physical and biological conformality in multidimensional conformal radiotherapy (MD-CRT). Methods and Materials: The advances in three-dimensional conformal radiotherapy (3D-CRT) have greatly improved the physical conformality of treatment planning and delivery. The development of intensity-modulated radiotherapy (IMRT) has provided the 'dose painting' or 'dose sculpting' ability to further customize the delivered dose distribution. The improved capabilities of nuclear magnetic resonance imaging and spectroscopy, and of positron emission tomography, are beginning to provide physiological and functional information about the tumor and its surroundings. In addition, molecular imaging promises to reveal tumor biology at the genotype and phenotype level. These developments converge to provide significant opportunities for enhancing the success of radiotherapy. Results: The ability of IMRT to deliver nonuniform dose patterns by design brings to fore the question of how to 'dose paint' and 'dose sculpt', leading to the suggestion that 'biological' images may be of assistance. In contrast to the conventional radiological images that primarily provide anatomical information, biological images reveal metabolic, functional, physiological, genotypic, and phenotypic data. Important for radiotherapy, the new and noninvasive imaging methods may yield three-dimensional radiobiological information. Studies are urgently needed to identify genotypes and phenotypes that affect radiosensitivity, and to devise methods to image them noninvasively. Incremental to the concept of gross, clinical, and planning target volumes (GTV, CTV, and PTV), we propose the concept of 'biological target volume' (BTV) and hypothesize that BTV can be derived from biological images and that their use may incrementally improve

Parotid-sparing intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma: Preserved parotid function after IMRT on quantitative salivary scintigraphy, and comparison with historical data after conventional radiotherapy

International Nuclear Information System (INIS)

Hsiung, C.-Y.; Ting, H.-M.; Huang, H.-Y.; Lee, C.-H.; Huang, E.-Y.; Hsu, H.-C.

2006-01-01

Purpose: To evaluate the parotid function after parotid-sparing intensity-modulated radiotherapy (IMRT) in patients with nasopharyngeal carcinoma (NPC). Methods and Materials: From March 2003 to May 2004, 16 patients with nonmetastatic NPC underwent parotid-sparing IMRT. Eight of these patients had Stage III or IV NPC based on the 1997 American Joint Committee on Cancer staging system. The post-IMRT parotid function was evaluated by quantitative salivary scintigraphy and represented by the maximal excretion ratio (MER) of the parotid gland after sialogogue stimulation. The parotid function of 16 NPC patients who were previously treated with conventional radiotherapy was reviewed as the historical control. Results: In the parotid-sparing IMRT group, all 16 patients were alive and without cancer at the end of follow-up period (median, 24.2 months). The mean parotid MER was 53.5% before radiotherapy, 10.7% at 1 month post-IMRT, and 23.3% at 9 months post-IMRT. In the conventional radiotherapy group, the mean parotid MER was 0.6% at 6 to 12 months postradiotherapy. The difference was statistically significant (23.3% vs. 0.6%, p < 0.001, Mann-Whitney test). In the IMRT group, the mean parotid doses ranged from 33.2 Gy to 58.8 Gy (average, 43.9 Gy). The correlation between the mean parotid dose and the percentage decrease of parotid MER at 9 months post-IMRT (dMER) was statically significant (p = 0.008, Pearson correlation). Conclusions: Although the mean parotid doses are relatively high, the significant preservation of parotid function is achieved with IMRT for NPC patients. The significant correlation between mean parotid dose and parotid dMER demonstrates the dose-function relationship of the parotid gland

SU-E-P-47: Evaluation of Improvement of Esophagus Sparing in SBRT Lung Patients with Biologically Based IMRT Optimization

International Nuclear Information System (INIS)

Liang, X; Penagaricano, J; Paudel, N; Zhang, X; Morrill, S; Corry, P; Han, E; Hardee, M; Ratanatharathorn, V

2015-01-01

Purpose: To study the potential of improving esophageal sparing for stereotactic body radiation therapy (SBRT) lung cancer patients by using biological optimization (BO) compared to conventional dose-volume based optimization (DVO) in treatment planning. Methods: Three NSCLC patients (PTV (62.3cc, 65.1cc, and 125.1cc) adjacent to the heart) previously treated with SBRT were re-planned using Varian Eclipse TPS (V11) using DVO and BO. The prescription dose was 60 Gy in 5 fractions normalized to 95% of the PTV volume. Plans were evaluated by comparing esophageal maximum doses, PTV heterogeneity (HI= D5%/D95%), and Paddick’s conformity (CI) indices. Quality of the plans was assessed by clinically-used IMRT QA procedures. Results: By using BO, the maximum dose to the esophagus was decreased 1384 cGy (34.6%), 502 cGy (16.5%) and 532 cGy (16.2%) in patient 1, 2 and 3 respectively. The maximum doses to spinal cord and the doses to 1000 cc and 1500 cc of normal lung were comparable in both plans. The mean doses (Dmean-hrt) and doses to 15cc of the heart (V15-hrt) were comparable for patient 1 and 2. However for patient 3, with the largest PTV, Dmean-hrt and V15-hrt increased by 62.2 cGy (18.3%) and 549.9 cGy (24.9%) respectively for the BO plans. The mean target HI of BO plans (1.13) was inferior to the DVO plans (1.07). The same trend was also observed for mean CI in BO plans (0.77) versus DVO plans (0.83). The QA pass rates (3%, 3mm) were comparable for both plans. Conclusion: This study demonstrated that the use of biological models in treatment planning optimization can substantially improve esophageal sparing without compromising spinal cord and normal lung doses. However, for the large PTV case (125.1cc) we studied here, Dmean-hrt and V15-hrt increased substantially. The target HI and CI were inferior in the BO plans

PET/CT Staging Followed by Intensity-Modulated Radiotherapy (IMRT) Improves Treatment Outcome of Locally Advanced Pharyngeal Carcinoma: a matched-pair comparison

International Nuclear Information System (INIS)

Rothschild, Sacha; Studer, Gabriela; Seifert, Burkhardt; Huguenin, Pia; Glanzmann, Christoph; Davis, J Bernard; Lütolf, Urs M; Hany, Thomas F; Ciernik, I Frank

2007-01-01

Impact of non-pharmacological innovations on cancer cure rates is difficult to assess. It remains unclear, whether outcome improves with 2- [18-F]-fluoro-2-deoxyglucose-positron emission tomography and integrated computer tomography (PET/CT) and intensity-modulated radiotherapy (IMRT) for curative treatment of advanced pharyngeal carcinoma. Forty five patients with stage IVA oro- or hypopharyngeal carcinoma were staged with an integrated PET/CT and treated with definitive chemoradiation with IMRT from 2002 until 2005. To estimate the impact of PET/CT with IMRT on outcome, a case-control analysis on all patients with PET/CT and IMRT was done after matching with eighty six patients treated between 1991 and 2001 without PET/CT and 3D-conformal radiotherapy with respect to gender, age, stage, grade, and tumor location with a ratio of 1:2. Median follow-up was eighteen months (range, 6–49 months) for the PET/CT-IMRT group and twenty eight months (range, 1–168 months) for the controls. PET/CT and treatment with IMRT improved cure rates compared to patients without PET/CT and IMRT. Overall survival of patients with PET/CT and IMRT was 97% and 91% at 1 and 2 years respectively, compared to 74% and 54% for patients without PET/CT or IMRT (p = 0.002). The event-free survival rate of PET/CT-IMRT group was 90% and 80% at 1 and 2 years respectively, compared to 72% and 56% in the control group (p = 0.005). PET/CT in combination with IMRT and chemotherapy for pharyngeal carcinoma improve oncological therapy of pharyngeal carcinomas. Long-term follow-up is needed to confirm these findings

Dysphagia in head and neck cancer patients following intensity modulated radiotherapy (IMRT)

International Nuclear Information System (INIS)

Peponi, Evangelia; Glanzmann, Christoph; Willi, Bettina; Huber, Gerhard; Studer, Gabriela

2011-01-01

To evaluate the objective and subjective long term swallowing function, and to relate dysphagia to the radiation dose delivered to the critical anatomical structures in head and neck cancer patients treated with intensity modulated radiation therapy (IMRT, +/- chemotherapy), using a midline protection contour (below hyoid, ~level of vertebra 2/3). 82 patients with stage III/IV squamous cell carcinoma of the larynx, oropharynx, or hypopharynx, who underwent successful definitive (n = 63, mean dose 68.9Gy) or postoperative (n = 19, mean dose 64.2Gy) simultaneous integrated boost (SIB) -IMRT either alone or in combination with chemotherapy (85%) with curative intent between January 2002 and November 2005, were evaluated retrospectively. 13/63 definitively irradiated patients (21%) presented with a total gross tumor volume (tGTV) >70cc (82-173cc; mean 106cc). In all patients, a laryngo-pharyngeal midline sparing contour outside of the PTV was drawn. Dysphagia was graded according subjective patient-reported and objective observer-assessed instruments. All patients were re-assessed 12 months later. Dose distribution to the swallowing structures was calculated. At the re-assessment, 32-month mean post treatment follow-up (range 16-60), grade 3/4 objective toxicity was assessed in 10%. At the 32-month evaluation as well as at the last follow up assessment mean 50 months (16-85) post-treatment, persisting swallowing dysfunction grade 3 was subjectively and objectively observed in 1 patient (1%). The 5-year local control rate of the cohort was 75%; no medial marginal failures were observed. Our results show that sparing the swallowing structures by IMRT seems effective and relatively safe in terms of avoidance of persistent grade 3/4 late dysphagia and local disease control

Domestic comparison of radiation treatment techniques for breast cancer: 3D-CRT, IMRT and VMAT

Energy Technology Data Exchange (ETDEWEB)

Lee, Bo Ram; Yoon, Myong Geun [Dept. of Bio-convergence Engineering, College of Health Science, Korea University, Seoul (Korea, Republic of); Lee, Sun Young [Dept. of Radiation Oncology, Yusung Sun Medical Center, Daejeon (Korea, Republic of)

2013-09-15

The purpose of this study is to compare method in the treatment of breast cancer using dose index. And, it is to find the optimized treatment technique to the patient. The phantom filled with tissue-equivalent material were used simulation and treatment as techniques of 3D-CRT, IMRT, VMAT was planned using Eclipse v10. By using HI(homogeneity index), CI(Conformity index), OE (Organ equivalent dose), EAR(Excess Absolute Risk), were assessed for each treatment plans. HI and CI of 3D-CRT, IMRT, VMAT were calculated 16.89, 11.21, 9.55 and 0.59, 0.61, 0.83. The organ average doses of Lt lung, Rt lung, liver, heart, esophagus, cord, Lt breast, trachea and stomach were 0.01 ∼ 2.02 Gy, 0.36 ∼ 5.01 Gy, 0.25 ∼ 2.49 Gy, 0.14 ∼ 6.92 Gy, 0.03 ∼ 2.02 Gy, 0.01 ∼ 1.06 Gy, 0.25 ∼ 6.08 Gy, 0.08 ∼ 0.59 Gy, 0.01 ∼ 1.34 Gy, respectively. The OED, EAR of the IMRT and VMAT show higher than 3D-CRT. As the result of this study, we could confirm being higher dose index(HI, CI) in IMRT and VMAT than 3D-CRT, but doses of around normal organs was higher IMRT, VMAT than 3D-CRT.

Effect of a care plan based on Roy adaptation model biological dimension on stroke patients' physiologic adaptation level.

Science.gov (United States)

Alimohammadi, Nasrollah; Maleki, Bibi; Shahriari, Mohsen; Chitsaz, Ahmad

2015-01-01

Stroke is a stressful event with several functional, physical, psychological, social, and economic problems that affect individuals' different living balances. With coping strategies, patients try to control these problems and return to their natural life. The aim of this study is to investigate the effect of a care plan based on Roy adaptation model biological dimension on stroke patients' physiologic adaptation level. This study is a clinical trial in which 50 patients, affected by brain stroke and being admitted in the neurology ward of Kashani and Alzahra hospitals, were randomly assigned to control and study groups in Isfahan in 2013. Roy adaptation model care plan was administered in biological dimension in the form of four sessions and phone call follow-ups for 1 month. The forms related to Roy adaptation model were completed before and after intervention in the two groups. Chi-square test and t-test were used to analyze the data through SPSS 18. There was a significant difference in mean score of adaptation in physiological dimension in the study group after intervention (P adaptation in the patients affected by brain stroke in the study and control groups showed a significant increase in physiological dimension in the study group by 47.30 after intervention (P adaptation model biological dimension care plan can result in an increase in adaptation in patients with stroke in physiological dimension. Nurses can use this model for increasing patients' adaptation.

A planning and delivery study of a rotational IMRT technique with burst delivery

International Nuclear Information System (INIS)

Kainz, Kristofer; Chen, Guang-Pei; Chang, Yu-Wen; Prah, Douglas; Sharon Qi, X.; Shukla, Himanshu P.; Stahl, Johannes; Allen Li, X.

2011-01-01

Purpose: A novel rotational IMRT (rIMRT) technique using burst delivery (continuous gantry rotation with beam off during MLC repositioning) is investigated. The authors evaluate the plan quality and delivery efficiency and accuracy of this dynamic technique with a conventional flat 6 MV photon beam. Methods: Burst-delivery rIMRT was implemented in a planning system and delivered with a 160-MLC linac. Ten rIMRT plans were generated for five anonymized patient cases encompassing head and neck, brain, prostate, and prone breast. All plans were analyzed retrospectively and not used for treatment. Among the varied plan parameters were the number of optimization points, number of arcs, gantry speed, and gantry angle range (alpha) over which the beam is turned on at each optimization point. Combined rotational/step-and-shoot rIMRT plans were also created by superimposing multiple-segment static fields at several optimization points. The rIMRT trial plans were compared with each other and with plans generated using helical tomotherapy and VMAT. Burst-mode rotational IMRT plans were delivered and verified using a diode array, ionization chambers, thermoluminescent dosimeters, and film. Results: Burst-mode rIMRT can achieve plan quality comparable to helical tomotherapy, while the former may lead to slightly better OAR sparing for certain cases and the latter generally achieves slightly lower hot spots. Few instances were found in which increasing the number of optimization points above 36, or superimposing step-and-shoot IMRT segments, led to statistically significant improvements in OAR sparing. Using an additional rIMRT partial arc yielded substantial OAR dose improvements for the brain case. Measured doses from the rIMRT plan delivery were within 4% of the plan calculation in low dose gradient regions. Delivery time range was 228-375 s for single-arc rIMRT 200-cGy prescription with a 300 MU/min dose rate, comparable to tomotherapy and VMAT. Conclusions: Rotational IMRT

Peripheral doses of cranial pediatric IMRT performed with attenuator blocks; Doses perifericas de IMRT cranial pediatrica realizada com blocos atenuadores

Energy Technology Data Exchange (ETDEWEB)

Soboll, Danyel Scheidegger; Schitz, Ivette; Schelin, Hugo Reuters, E-mail: soboll@utfpr.edu.b, E-mail: iveteschitz@yahoo.com.b, E-mail: schelin@utfpr.edu.b [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Silva, Ricardo Goulart da, E-mail: ricardo.goulart@ymail.co [Hospital Angelina Caron, Campina Grande do Sul, PR (Brazil); Viamonte, Alfredo, E-mail: aviamonte@inca.gov.b [Instituto Nacional do Cancer (INCa), Rio de Janeiro, RJ (Brazil)

2011-10-26

This paper presents values of peripheral doses measured at six vital points of simulator objects which represent the ages of 2, 5 and 10 years old, submitted to a cranial IMRT procedure that applied compensator blocks interposed to 6 MV beams. The found values indicate that there is independence of dose with position of measurements and age of the patient, as the peripheral dose at the points nearest and the 2 year old simulator object where larger. The doses in thyroid reached the range of 1.4 to 2.9% of the dose prescribed in the isocenter, indicating that the peripheral doses for IMRT that employ compensator blocks can be greater than for the IMRT produced with sliding window technique

SU-E-T-16: A Hybrid VMAT/IMRT Technique for the Treatment of Nasopharyngeal Carcinoma

International Nuclear Information System (INIS)

Zhao, N; Yang, R; Wang, J

2014-01-01

Purpose: To investigate a Hybrid VMAT/IMRT technique which combines volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods: 2 full arcs VMAT, 9-field IMRT and Hybrid VMAT/IMRT plans were created for 10 patients with NPC. The Hybrid VMAT/IMRT technique consisted of 1 full VMAT arc and 7 IMRT fields. The dose distribution of planning target volume (PTV) and organs at risk (OARs) for Hybrid VMAT/IMRT was compared with IMRT and VMAT. The monitor units (MUs) were also evaluated. Results: The Hybrid VMAT/IMRT technique significantly improved target dose homogeneity compared with IMRT and VMAT for PTV70 and PTV54. For PTV70 and PTV60, the Hybrid VMAT/IMRT technique significantly improved target dose conformity compared with IMRT (0.62 vs 0.47; p<0.05 and 0.64 vs 0.58; p<0.05, respectively) and VMAT (0.62 vs 0.43; p<0.05 and 0.64 vs 0.6; p<0.05, respectively). The near maximum dose (D2%) of temporomandibular joint (TMJ), temporal lobe and mandible for Hybrid plans were 5.5%, 7.9% and 5.2% lower than IMRT plans (p<0.05). The mean dose of TMJ, temporal lobe, mandible and unspecified tissue for Hybrid plans were 12.8%, 11.4%, 4.2% and 4.1% lower than IMRT plans (p<0.05). The mean dose of right parotid, mandible and unspecified tissue for Hybrid plans were 3.3%, 2.4% and 3.1% lower than VMAT plans (p<0.05). The mean MUs needed for IMRT, VMAT and Hybrid plans were 2256, 507 and 1394, respectively. Conclusion: Hybrid VMAT/IMRT technique significantly improved the target dose homogeneity and conformity compared with IMRT and VMAT and reduced the dose of OARs and unspecified tissue compared with IMRT with fewer MUs. Compared with VMAT, Hybrid VMAT/IMRT technique can better protect parotid gland, mandible and unspecified tissue. Ruijie Yang was funded by the grant project: National Natural Science Foundation of China (No. 81071237). Other authors have no competing interest for this work

SU-E-T-16: A Hybrid VMAT/IMRT Technique for the Treatment of Nasopharyngeal Carcinoma

Energy Technology Data Exchange (ETDEWEB)

Zhao, N; Yang, R; Wang, J [Peking University Third Hospital, Beijing, Beijing (China)

2014-06-01

Purpose: To investigate a Hybrid VMAT/IMRT technique which combines volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC). Methods: 2 full arcs VMAT, 9-field IMRT and Hybrid VMAT/IMRT plans were created for 10 patients with NPC. The Hybrid VMAT/IMRT technique consisted of 1 full VMAT arc and 7 IMRT fields. The dose distribution of planning target volume (PTV) and organs at risk (OARs) for Hybrid VMAT/IMRT was compared with IMRT and VMAT. The monitor units (MUs) were also evaluated. Results: The Hybrid VMAT/IMRT technique significantly improved target dose homogeneity compared with IMRT and VMAT for PTV70 and PTV54. For PTV70 and PTV60, the Hybrid VMAT/IMRT technique significantly improved target dose conformity compared with IMRT (0.62 vs 0.47; p<0.05 and 0.64 vs 0.58; p<0.05, respectively) and VMAT (0.62 vs 0.43; p<0.05 and 0.64 vs 0.6; p<0.05, respectively). The near maximum dose (D2%) of temporomandibular joint (TMJ), temporal lobe and mandible for Hybrid plans were 5.5%, 7.9% and 5.2% lower than IMRT plans (p<0.05). The mean dose of TMJ, temporal lobe, mandible and unspecified tissue for Hybrid plans were 12.8%, 11.4%, 4.2% and 4.1% lower than IMRT plans (p<0.05). The mean dose of right parotid, mandible and unspecified tissue for Hybrid plans were 3.3%, 2.4% and 3.1% lower than VMAT plans (p<0.05). The mean MUs needed for IMRT, VMAT and Hybrid plans were 2256, 507 and 1394, respectively. Conclusion: Hybrid VMAT/IMRT technique significantly improved the target dose homogeneity and conformity compared with IMRT and VMAT and reduced the dose of OARs and unspecified tissue compared with IMRT with fewer MUs. Compared with VMAT, Hybrid VMAT/IMRT technique can better protect parotid gland, mandible and unspecified tissue. Ruijie Yang was funded by the grant project: National Natural Science Foundation of China (No. 81071237). Other authors have no competing interest for this work.

Genital marginal failures after intensity-modulated radiation therapy (IMRT) in squamous cell anal cancer: no higher risk with IMRT when compared to 3DCRT.

Science.gov (United States)

Dell'Acqua, V; Kobiela, J; Kraja, F; Leonardi, M C; Surgo, A; Zerella, M A; Arculeo, S; Fodor, C; Ricotti, R; Zampino, M G; Ravenda, S; Spinoglio, G; Biffi, R; Bazani, A; Luraschi, R; Vigorito, S; Spychalski, P; Orecchia, R; Glynne-Jones, R; Jereczek-Fossa, B A

2018-03-28

Intensity-modulated radiotherapy (IMRT) is considered the preferred option in squamous cell canal cancer (SCAC), delivering high doses to tumor volumes while minimizing dose to surrounding normal tissues. IMRT has steep dose gradients, but the technique is more demanding as deep understanding of target structures is required. To evaluate genital marginal failure in a cohort of patients with non-metastatic SCAC treated either with IMRT or 3DCRT and concurrent chemotherapy, 117 patients with SCAC were evaluated: 64 and 53 patients were treated with IMRT and 3DCRT techniques, respectively. All patients underwent clinical and radiological examination during their follow-up. Tumor response was evaluated with response evaluation criteria in solid tumors v1.1 guideline on regular basis. All patients' data were analyzed, and patients with marginal failure were identified. Concomitant chemotherapy was administered in 97 and 77.4% of patients in the IMRT and 3DCRT groups, respectively. In the IMRT group, the median follow-up was 25 months (range 6-78). Progressive disease was registered in 15.6% of patients; infield recurrence, distant recurrence and both infield recurrence and distant recurrence were identified in 5, 4 and 1 patient, respectively. Two out of 64 patients (3.1%) had marginal failures, localized at vagina/recto-vaginal septum and left perineal region. In the 3DCRT group, the median follow-up was 71.3 months (range 6-194 months). Two out of 53 patients (3.8%) had marginal failures, localized at recto-vaginal septum and perigenital structures. The rate of marginal failures was comparable in IMRT and 3DCRT groups (χ 2 test p = 0.85). In this series, the use of IMRT for the treatment of SCAC did not increase the rate of marginal failures offering improved dose conformity to the target. Dose constraints should be applied with caution-particularly in females with involvement of the vagina or the vaginal septum.

SU-G-TeP4-02: A Method for Evaluating the Direct Impact of Failed IMRT QAs On Patient Dose

International Nuclear Information System (INIS)

Geneser, S; Butkus, M

2016-01-01

Purpose: We developed a method to calculate patient doses corresponding to IMRT QA measurements in order to determine and assess the actual dose delivered for plans with failed (or borderline) IMRT QA. This work demonstrates the feasibility of automatically computing delivered patient dose from portal dosimetry measurements in the Varian TPS system, which would provide a valuable and clinically viable IMRT QA tool for physicists and physicians. Methods: IMRT QA fluences were measured using portal dosimetry, processed using in-house matlab software, and imported back into Eclipse to calculate dose on the planning CT. To validate the proposed workflow, the Eclipse calculated portal dose for a 5-field sliding window prostate boost plan was processed as described above. The resulting dose was compared to the planned dose and found to be within 0.5 Gy. Two IMRT QA results for the prostate boost plan (one that failed and one that passed) were processed and the resulting patient doses were evaluated. Results: The max dose difference between IMRT QA #1 and the original planned and approved dose is 4.5 Gy, while the difference between the planned and IMRT QA #2 dose is 4.0 Gy. The inferior portion of the PTV is slightly underdosed in both plans, and the superior portion is slightly overdosed. The patient dose resulting from IMRT QA #1 and #2 differs by only 0.5 Gy. With this new information, it may be argued that the evaluated plan alteration to obtain passing gamma analysis produced clinically irrelevant differences. Conclusion: Evaluation of the delivered QA dose on the planning CT provides valuable information about the clinical relevance of failed or borderline IMRT QAs. This particular workflow demonstrates the feasibility of pushing the measured IMRT QA portal dosimetry results directly back onto the patient planning CT within the Varian system.

SU-G-TeP4-02: A Method for Evaluating the Direct Impact of Failed IMRT QAs On Patient Dose

Energy Technology Data Exchange (ETDEWEB)

Geneser, S; Butkus, M [Yale University School of Medicine/YNHH Radiology, New Haven, CT (United States)

2016-06-15

Purpose: We developed a method to calculate patient doses corresponding to IMRT QA measurements in order to determine and assess the actual dose delivered for plans with failed (or borderline) IMRT QA. This work demonstrates the feasibility of automatically computing delivered patient dose from portal dosimetry measurements in the Varian TPS system, which would provide a valuable and clinically viable IMRT QA tool for physicists and physicians. Methods: IMRT QA fluences were measured using portal dosimetry, processed using in-house matlab software, and imported back into Eclipse to calculate dose on the planning CT. To validate the proposed workflow, the Eclipse calculated portal dose for a 5-field sliding window prostate boost plan was processed as described above. The resulting dose was compared to the planned dose and found to be within 0.5 Gy. Two IMRT QA results for the prostate boost plan (one that failed and one that passed) were processed and the resulting patient doses were evaluated. Results: The max dose difference between IMRT QA #1 and the original planned and approved dose is 4.5 Gy, while the difference between the planned and IMRT QA #2 dose is 4.0 Gy. The inferior portion of the PTV is slightly underdosed in both plans, and the superior portion is slightly overdosed. The patient dose resulting from IMRT QA #1 and #2 differs by only 0.5 Gy. With this new information, it may be argued that the evaluated plan alteration to obtain passing gamma analysis produced clinically irrelevant differences. Conclusion: Evaluation of the delivered QA dose on the planning CT provides valuable information about the clinical relevance of failed or borderline IMRT QAs. This particular workflow demonstrates the feasibility of pushing the measured IMRT QA portal dosimetry results directly back onto the patient planning CT within the Varian system.

Dosimetric Evaluation of Automatic Segmentation for Adaptive IMRT for Head-and-Neck Cancer

International Nuclear Information System (INIS)

Tsuji, Stuart Y.; Hwang, Andrew; Weinberg, Vivian; Yom, Sue S.; Quivey, Jeanne M.; Xia Ping

2010-01-01

Purpose: Adaptive planning to accommodate anatomic changes during treatment requires repeat segmentation. This study uses dosimetric endpoints to assess automatically deformed contours. Methods and Materials: Sixteen patients with head-and-neck cancer had adaptive plans because of anatomic change during radiotherapy. Contours from the initial planning computed tomography (CT) were deformed to the mid-treatment CT using an intensity-based free-form registration algorithm then compared with the manually drawn contours for the same CT using the Dice similarity coefficient and an overlap index. The automatic contours were used to create new adaptive plans. The original and automatic adaptive plans were compared based on dosimetric outcomes of the manual contours and on plan conformality. Results: Volumes from the manual and automatic segmentation were similar; only the gross tumor volume (GTV) was significantly different. Automatic plans achieved lower mean coverage for the GTV: V95: 98.6 ± 1.9% vs. 89.9 ± 10.1% (p = 0.004) and clinical target volume: V95: 98.4 ± 0.8% vs. 89.8 ± 6.2% (p 3 of the spinal cord 39.9 ± 3.7 Gy vs. 42.8 ± 5.4 Gy (p = 0.034), but no difference for the remaining structures. Conclusions: Automatic segmentation is not robust enough to substitute for physician-drawn volumes, particularly for the GTV. However, it generates normal structure contours of sufficient accuracy when assessed by dosimetric end points.

High-resolution pulmonary ventilation and perfusion PET/CT allows for functionally adapted intensity modulated radiotherapy in lung cancer

International Nuclear Information System (INIS)

Siva, Shankar; Thomas, Roshini; Callahan, Jason; Hardcastle, Nicholas; Pham, Daniel; Kron, Tomas; Hicks, Rodney J.; MacManus, Michael P.; Ball, David L.; Hofman, Michael S.

2015-01-01

Background and purpose: To assess the utility of functional lung avoidance using IMRT informed by four-dimensional (4D) ventilation/perfusion (V/Q) PET/CT. Materials and methods: In a prospective clinical trial, patients with non-small cell lung cancer (NSCLC) underwent 4D-V/Q PET/CT scanning before 60 Gy of definitive chemoradiation. Both “highly perfused” (HPLung) and “highly ventilated” (HVLung) lung volumes were delineated using a 70th centile SUV threshold, and a “ventilated lung volume” (VLung) was created using a 50th centile SUV threshold. For each patient four IMRT plans were created, optimised to the anatomical lung, HPLung, HVLung and VLung volumes, respectively. Improvements in functional dose volumetrics when optimising to functional volumes were assessed using mean lung dose (MLD), V5, V10, V20, V30, V40, V50 and V60 parameters. Results: The study cohort consisted of 20 patients with 80 IMRT plans. Plans optimised to HPLung resulted in a significant reduction of functional MLD by a mean of 13.0% (1.7 Gy), p = 0.02. Functional V5, V10 and V20 were improved by 13.2%, 7.3% and 3.8% respectively (p-values < 0.04). There was no significant sparing of dose to functional lung when adapting to VLung or HVLung. Plan quality was highly consistent with a mean PTV D95 and D5 ranging from 60.8 Gy to 61.0 Gy and 63.4 Gy to 64.5 Gy, respectively, and mean conformity and heterogeneity index ranging from 1.11 to 1.17 and 0.94 to 0.95, respectively. Conclusion: IMRT plans adapted to perfused but not ventilated lung on 4D-V/Q PET/CT allowed for reduced dose to functional lung whilst maintaining consistent plan quality

Overview of IMRT - definitions and basic concepts

International Nuclear Information System (INIS)

Mackie, T.R.

2008-01-01

A detailed advanced outline of the title topic is presented. Summary is formulated as follows: (i) Conventional MLC, developed for block replacement, require corrections and careful QA when when used for IMRT; (ii) There are both advantages and disadvantages of static or dynamic MLC delivery; (iii) Tomotherapy uses binary MLC systems specifically designed for IMRT; (iv) There are two types of optimization, grid of beamlets and direct aperture methods; (v) Optimization is controlled by objective functions. (P.A.)

Endocavitary in vivo Dosimetry for IMRT Treatments of Gynecologic Tumors

International Nuclear Information System (INIS)

Cilla, Savino; Macchia, Gabriella; Digesù, Cinzia; Deodato, Francesco; Sabatino, Domenico; Morganti, Alessio G.; Piermattei, Angelo

2011-01-01

The accuracy and reproducibility of endometrial carcinoma treatment with intensity-modulated radiotherapy (IMRT) was assessed by means of in vivo dosimetry. Six patients who had previously undergone radical hysterectomy for endometrial carcinoma were treated with IMRT using a vaginal applicator with radio-opaque fiducial markers. An ion-chamber inserted into the applicator supplied an endocavitary in vivo dosimetry for quality assurance purposes. The ratio R = D/D TPS between the in vivo measured dose D and the predicted dose by the treatment planning system D TPS was determined for every fraction of the treatment. Results showed that 90% and 100% of the ratios resulted equal to 1 within 5% and 10%, respectively. The mean value of the ratios distribution for the 6 patients was R = 0.995 and the SD = 0.034. The ratio R* between the measured and predicted total doses for each patient was near to 1, within 2%. The dosimetric results suggest that the use of a vaginal applicator in an image-guided approach could make the interfractions target position stable and reproducible, allowing a safe use of the IMRT technique in the treatment of postoperative vaginal vault. In vivo dosimetry may supply useful information about the discrimination of random vs. systematic errors. The workload is minimum and this in vivo dosimetry can be applied also in the clinical routine.

Independent calculation-based verification of IMRT plans using a 3D dose-calculation engine

International Nuclear Information System (INIS)

Arumugam, Sankar; Xing, Aitang; Goozee, Gary; Holloway, Lois

2013-01-01

Independent monitor unit verification of intensity-modulated radiation therapy (IMRT) plans requires detailed 3-dimensional (3D) dose verification. The aim of this study was to investigate using a 3D dose engine in a second commercial treatment planning system (TPS) for this task, facilitated by in-house software. Our department has XiO and Pinnacle TPSs, both with IMRT planning capability and modeled for an Elekta-Synergy 6 MV photon beam. These systems allow the transfer of computed tomography (CT) data and RT structures between them but do not allow IMRT plans to be transferred. To provide this connectivity, an in-house computer programme was developed to convert radiation therapy prescription (RTP) files as generated by many planning systems into either XiO or Pinnacle IMRT file formats. Utilization of the technique and software was assessed by transferring 14 IMRT plans from XiO and Pinnacle onto the other system and performing 3D dose verification. The accuracy of the conversion process was checked by comparing the 3D dose matrices and dose volume histograms (DVHs) of structures for the recalculated plan on the same system. The developed software successfully transferred IMRT plans generated by 1 planning system into the other. Comparison of planning target volume (TV) DVHs for the original and recalculated plans showed good agreement; a maximum difference of 2% in mean dose, − 2.5% in D95, and 2.9% in V95 was observed. Similarly, a DVH comparison of organs at risk showed a maximum difference of +7.7% between the original and recalculated plans for structures in both high- and medium-dose regions. However, for structures in low-dose regions (less than 15% of prescription dose) a difference in mean dose up to +21.1% was observed between XiO and Pinnacle calculations. A dose matrix comparison of original and recalculated plans in XiO and Pinnacle TPSs was performed using gamma analysis with 3%/3 mm criteria. The mean and standard deviation of pixels passing

Evaluation of dose coverage to target volume and normal tissue sparing in the adjuvant radiotherapy of gastric cancers: 3D-CRT compared with dynamic IMRT.

Science.gov (United States)

Murthy, Kk; Shukeili, Ka; Kumar, Ss; Davis, Ca; Chandran, Rr; Namrata, S

2010-01-01

To assess the potential advantage of intensity-modulated radiotherapy (IMRT) over 3D-conformal radiotherapy (3D-CRT) planning in postoperative adjuvant radiotherapy for patients with gastric carcinoma. In a retrospective study, for plan comparison, dose distribution was recalculated in 15 patients treated with 3D-CRT on the contoured structures of same CT images using an IMRT technique. 3D-conformal plans with three fields and four-fields were compared with seven-field dynamic IMRT plans. The different plans were compared by analyzing the dose coverage of planning target volume using TV(95), D(mean), uniformity index, conformity index and homogeneity index parameters. To assess critical organ sparing, D(mean), D(max), dose to one-third and two-third volumes of the OARs and percentage of volumes receiving more than their tolerance doses were compared. The average dose coverage values of PTV with 3F-CRT and 4F-CRT plans were comparable, where as IMRT plans achieved better target coverage(p3D-CRT plans. The doses to the liver and bowel reduced significantly (p3D-CRT plans. For all OARs the percentage of volumes receiving more than their tolerance doses were reduced with the IMRT plans. This study showed that a better target coverage and significant dose reduction to OARs could be achieved with the IMRT plans. The IMRT can be preferred with caution for organ motion. The authors are currently studying organ motion in the upper abdomen to use IMRT for patient treatment.

Consequences of leaf calibration errors on IMRT delivery

International Nuclear Information System (INIS)

Sastre-Padro, M; Welleweerd, J; Malinen, E; Eilertsen, K; Olsen, D R; Heide, U A van der

2007-01-01

IMRT treatments using multi-leaf collimators may involve a large number of segments in order to spare the organs at risk. When a large proportion of these segments are small, leaf positioning errors may become relevant and have therapeutic consequences. The performance of four head and neck IMRT treatments under eight different cases of leaf positioning errors has been studied. Systematic leaf pair offset errors in the range of ±2.0 mm were introduced, thus modifying the segment sizes of the original IMRT plans. Thirty-six films were irradiated with the original and modified segments. The dose difference and the gamma index (with 2%/2 mm criteria) were used for evaluating the discrepancies between the irradiated films. The median dose differences were linearly related to the simulated leaf pair errors. In the worst case, a 2.0 mm error generated a median dose difference of 1.5%. Following the gamma analysis, two out of the 32 modified plans were not acceptable. In conclusion, small systematic leaf bank positioning errors have a measurable impact on the delivered dose and may have consequences for the therapeutic outcome of IMRT

Multidimensional Computerized Adaptive Testing for Indonesia Junior High School Biology

Science.gov (United States)

Kuo, Bor-Chen; Daud, Muslem; Yang, Chih-Wei

2015-01-01

This paper describes a curriculum-based multidimensional computerized adaptive test that was developed for Indonesia junior high school Biology. In adherence to the Indonesian curriculum of different Biology dimensions, 300 items was constructed, and then tested to 2238 students. A multidimensional random coefficients multinomial logit model was…

A two isocenter IMRT technique with a controlled junction dose for long volume targets

International Nuclear Information System (INIS)

Zeng, G G; Heaton, R K; Catton, C N; Chung, P W; O'Sullivan, B; Lau, M; Parent, A; Jaffray, D A

2007-01-01

Most IMRT techniques have been designed to treat targets smaller than the field size of conventional linac accelerators. In order to overcome the field size restrictions in applying IMRT, we developed a two isocenter IMRT technique to treat long volume targets. The technique exploits an extended dose gradient throughout a junction region of 4-6 cm to minimize the impact of field match errors on a junction dose and manipulates the inverse planning and IMRT segments to fill in the dose gradient and achieve dose uniformity. Techniques for abutting both conventional fields with IMRT ('Static + IMRT') and IMRT fields ('IMRT + IMRT') using two separate isocenters have been developed. Five long volume sarcoma cases have been planned in Pinnacle (Philips, Madison, USA) using Elekta Synergy and Varian 2100EX linacs; two of the cases were clinically treated with this technique. Advantages were demonstrated with well-controlled junction target uniformity and tolerance to setup uncertainties. The junction target dose heterogeneity was controlled at a level of ±5%; for 3 mm setup errors at the field edges, the junction target dose changed less than 5% and the dose sparing to organs at risk (OARs) was maintained. Film measurements confirmed the treatment planning results

An IMRT dose distribution study using commercial verification software

International Nuclear Information System (INIS)

Grace, M.; Liu, G.; Fernando, W.; Rykers, K.

2004-01-01

Full text: The introduction of IMRT requires users to confirm that the isodose distributions and relative doses calculated by their planning system match the doses delivered by their linear accelerators. To this end the commercially available software, VeriSoft TM (PTW-Freiburg, Germany) was trialled to determine if the tools and functions it offered would be of benefit to this process. The CMS Xio (Computer Medical System) treatment planning system was used to generate IMRT plans that were delivered with an upgraded Elekta SL15 linac. Kodak EDR2 film sandwiched in RW3 solid water (PTW-Freiburg, Germany) was used to measure the IMRT fields delivered with 6 MV photons. The isodose and profiles measured with the film generally agreed to within ± 3% or ± 3 mm with the planned doses, in some regions (outside the IMRT field) the match fell to within ± 5%. The isodose distributions of the planning system and the film could be compared on screen and allows for electronic records of the comparison to be kept if so desired. The features and versatility of this software has been of benefit to our IMRT QA program. Furthermore, the VeriSoft TM software allows for quick and accurate, automated planar film analysis.Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

General strategy for the protection of organs at risk in IMRT therapy of a moving body

International Nuclear Information System (INIS)

Abolfath, Ramin M.; Papiez, Lech

2009-01-01

We investigated protection strategies of organs at risk (OARs) in intensity modulated radiation therapy (IMRT). These strategies apply to delivery of IMRT to moving body anatomies that show relative displacement of OAR in close proximity to a tumor target. We formulated an efficient genetic algorithm which makes it possible to search for global minima in a complex landscape of multiple irradiation strategies delivering a given, predetermined intensity map to a target. The optimal strategy was investigated with respect to minimizing the dose delivered to the OAR. The optimization procedure developed relies on variability of all parameters available for control of radiation delivery in modern linear accelerators, including adaptation of leaf trajectories and simultaneous modification of beam dose rate during irradiation. We showed that the optimization algorithms lead to a significant reduction in the dose delivered to OAR in cases where organs at risk move relative to a treatment target.

General strategy for the protection of organs at risk in IMRT therapy of a moving body

Energy Technology Data Exchange (ETDEWEB)

Abolfath, Ramin M.; Papiez, Lech [Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390 (United States)

2009-07-15

We investigated protection strategies of organs at risk (OARs) in intensity modulated radiation therapy (IMRT). These strategies apply to delivery of IMRT to moving body anatomies that show relative displacement of OAR in close proximity to a tumor target. We formulated an efficient genetic algorithm which makes it possible to search for global minima in a complex landscape of multiple irradiation strategies delivering a given, predetermined intensity map to a target. The optimal strategy was investigated with respect to minimizing the dose delivered to the OAR. The optimization procedure developed relies on variability of all parameters available for control of radiation delivery in modern linear accelerators, including adaptation of leaf trajectories and simultaneous modification of beam dose rate during irradiation. We showed that the optimization algorithms lead to a significant reduction in the dose delivered to OAR in cases where organs at risk move relative to a treatment target.

[68Ga]-DOTATOC-PET/CT for meningioma IMRT treatment planning

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Bamberg Michael

2009-11-01

Full Text Available Abstract Purpose The observation that human meningioma cells strongly express somatostatin receptor (SSTR 2 was the rationale to analyze retrospectively in how far DOTATOC PET/CT is helpful to improve target volume delineation for intensity modulated radiotherapy (IMRT. Patients and Methods In 26 consecutive patients with preferentially skull base meningioma, diagnostic magnetic resonance imaging (MRI and planning-computed tomography (CT was complemented with data from [68Ga]-DOTA-D Phe1-Tyr3-Octreotide (DOTATOC-PET/CT. Image fusion of PET/CT, diagnostic computed tomography, MRI and radiotherapy planning CT as well as target volume delineation was performed with OTP-Masterplan®. Initial gross tumor volume (GTV definition was based on MRI data only and was secondarily complemented with DOTATOC-PET information. Irradiation was performed as EUD based IMRT, using the Hyperion Software package. Results The integration of the DOTATOC data led to additional information concerning tumor extension in 17 of 26 patients (65%. There were major changes of the clinical target volume (CTV which modify the PTV in 14 patients, minor changes were realized in 3 patients. Overall the GTV-MRI/CT was larger than the GTV-PET in 10 patients (38%, smaller in 13 patients (50% and almost the same in 3 patients (12%. Most of the adaptations were performed in close vicinity to bony skull base structures or after complex surgery. Median GTV based on MRI was 18.1 cc, based on PET 25.3 cc and subsequently the CTV was 37.4 cc. Radiation planning and treatment of the DOTATOC-adapted volumes was feasible. Conclusion DOTATOC-PET/CT information may strongly complement patho-anatomical data from MRI and CT in cases with complex meningioma and is thus helpful for improved target volume delineation especially for skull base manifestations and recurrent disease after surgery.

A feasibility study of using conventional jaws to deliver complex IMRT plans for head and neck cancer

International Nuclear Information System (INIS)

Mu, G; Xia, P

2009-01-01

Previous studies have demonstrated that simple intensity-modulated radiotherapy (IMRT) plans can be produced with a series of rectangular segments formed by conventional jaws. This study investigates whether complex IMRT plans for head and neck cancer can be delivered with the conventional jaws efficiently. Six nasopharyngeal cancer patients, previously treated with multi-leaf collimator (MLC)-IMRT plans, were re-planned using conventional jaw delivery options. All IMRT plans were subject to the plan acceptance criteria of the RTOG-0225 protocol. For a selected patient, the maximum number of segments varied from five to nine per beam, and was tested for both jaws-only IMRT (JO-IMRT) plans and MLC-IMRT plans. Subsequently, JO-IMRT plans and MLC-IMRT on the same treatment planning system were attempted for all patients with identical beams. The dose distribution, dose volume histograms (DVH), the conformal index (COIN), the uniformity index and delivery efficiency were compared between the MLC-IMRT and JO-IMRT plans. All JO-IMRT plans met the RTOG-0225 criteria for tumor coverage and sensitive structures sparing. The corresponding MLC-IMRT and JO-IMRT plans show comparable conformality and uniformity, with average COINs of the planning gross tumor volume(pGTV) 37.7% ± 18.7% versus 37.9% ± 18.1%, and the average uniformity index 82.8% ± 2.5% versus 83.6% ± 3.1%, respectively. The average monitor unit for JO-IMRT plans was about twice that of MLC-IMRT plans. In conclusion, conventional jaws can be used solely to deliver complex IMRT plans for patients with nasopharyngeal cancer yet still within a practical delivery time.

A Comprehensive Comparison of IMRT and VMAT Plan Quality for Prostate Cancer Treatment

International Nuclear Information System (INIS)

Quan, Enzhuo M.; Li Xiaoqiang; Li Yupeng; Wang Xiaochun; Kudchadker, Rajat J.; Johnson, Jennifer L.; Kuban, Deborah A.; Lee, Andrew K.; Zhang Xiaodong

2012-01-01

Purpose: We performed a comprehensive comparative study of the plan quality between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) for the treatment of prostate cancer. Methods and Materials: Eleven patients with prostate cancer treated at our institution were randomly selected for this study. For each patient, a VMAT plan and a series of IMRT plans using an increasing number of beams (8, 12, 16, 20, and 24 beams) were examined. All plans were generated using our in-house–developed automatic inverse planning (AIP) algorithm. An existing eight-beam clinical IMRT plan, which was used to treat the patient, was used as the reference plan. For each patient, all AIP-generated plans were optimized to achieve the same level of planning target volume (PTV) coverage as the reference plan. Plan quality was evaluated by measuring mean dose to and dose–volume statistics of the organs at risk, especially the rectum, from each type of plan. Results: For the same PTV coverage, the AIP-generated VMAT plans had significantly better plan quality in terms of rectum sparing than the eight-beam clinical and AIP-generated IMRT plans (p < 0.0001). However, the differences between the IMRT and VMAT plans in all the dosimetric indices decreased as the number of beams used in IMRT increased. IMRT plan quality was similar or superior to that of VMAT when the number of beams in IMRT was increased to a certain number, which ranged from 12 to 24 for the set of patients studied. The superior VMAT plan quality resulted in approximately 30% more monitor units than the eight-beam IMRT plans, but the delivery time was still less than 3 min. Conclusions: Considering the superior plan quality as well as the delivery efficiency of VMAT compared with that of IMRT, VMAT may be the preferred modality for treating prostate cancer.

Quality assurance for online adapted treatment plans: Benchmarking and delivery monitoring simulation

International Nuclear Information System (INIS)

Li, Taoran; Wu, Qiuwen; Yang, Yun; Rodrigues, Anna; Yin, Fang-Fang; Jackie Wu, Q.

2015-01-01

Purpose: An important challenge facing online adaptive radiation therapy is the development of feasible and efficient quality assurance (QA). This project aimed to validate the deliverability of online adapted plans and develop a proof-of-concept online delivery monitoring system for online adaptive radiation therapy QA. Methods: The first part of this project benchmarked automatically online adapted prostate treatment plans using traditional portal dosimetry IMRT QA. The portal dosimetry QA results of online adapted plans were compared to original (unadapted) plans as well as randomly selected prostate IMRT plans from our clinic. In the second part, an online delivery monitoring system was designed and validated via a simulated treatment with intentional multileaf collimator (MLC) errors. This system was based on inputs from the dynamic machine information (DMI), which continuously reports actual MLC positions and machine monitor units (MUs) at intervals of 50 ms or less during delivery. Based on the DMI, the system performed two levels of monitoring/verification during the delivery: (1) dynamic monitoring of cumulative fluence errors resulting from leaf position deviations and visualization using fluence error maps (FEMs); and (2) verification of MLC positions against the treatment plan for potential errors in MLC motion and data transfer at each control point. Validation of the online delivery monitoring system was performed by introducing intentional systematic MLC errors (ranging from 0.5 to 2 mm) to the DMI files for both leaf banks. These DMI files were analyzed by the proposed system to evaluate the system’s performance in quantifying errors and revealing the source of errors, as well as to understand patterns in the FEMs. In addition, FEMs from 210 actual prostate IMRT beams were analyzed using the proposed system to further validate its ability to catch and identify errors, as well as establish error magnitude baselines for prostate IMRT delivery

Quality assurance for online adapted treatment plans: Benchmarking and delivery monitoring simulation

Energy Technology Data Exchange (ETDEWEB)

Li, Taoran, E-mail: taoran.li.duke@gmail.com; Wu, Qiuwen; Yang, Yun; Rodrigues, Anna; Yin, Fang-Fang; Jackie Wu, Q. [Department of Radiation Oncology, Duke University Medical Center Durham, North Carolina 27710 (United States)

2015-01-15

Purpose: An important challenge facing online adaptive radiation therapy is the development of feasible and efficient quality assurance (QA). This project aimed to validate the deliverability of online adapted plans and develop a proof-of-concept online delivery monitoring system for online adaptive radiation therapy QA. Methods: The first part of this project benchmarked automatically online adapted prostate treatment plans using traditional portal dosimetry IMRT QA. The portal dosimetry QA results of online adapted plans were compared to original (unadapted) plans as well as randomly selected prostate IMRT plans from our clinic. In the second part, an online delivery monitoring system was designed and validated via a simulated treatment with intentional multileaf collimator (MLC) errors. This system was based on inputs from the dynamic machine information (DMI), which continuously reports actual MLC positions and machine monitor units (MUs) at intervals of 50 ms or less during delivery. Based on the DMI, the system performed two levels of monitoring/verification during the delivery: (1) dynamic monitoring of cumulative fluence errors resulting from leaf position deviations and visualization using fluence error maps (FEMs); and (2) verification of MLC positions against the treatment plan for potential errors in MLC motion and data transfer at each control point. Validation of the online delivery monitoring system was performed by introducing intentional systematic MLC errors (ranging from 0.5 to 2 mm) to the DMI files for both leaf banks. These DMI files were analyzed by the proposed system to evaluate the system’s performance in quantifying errors and revealing the source of errors, as well as to understand patterns in the FEMs. In addition, FEMs from 210 actual prostate IMRT beams were analyzed using the proposed system to further validate its ability to catch and identify errors, as well as establish error magnitude baselines for prostate IMRT delivery

Quality assurance for online adapted treatment plans: benchmarking and delivery monitoring simulation.

Science.gov (United States)

Li, Taoran; Wu, Qiuwen; Yang, Yun; Rodrigues, Anna; Yin, Fang-Fang; Jackie Wu, Q

2015-01-01

An important challenge facing online adaptive radiation therapy is the development of feasible and efficient quality assurance (QA). This project aimed to validate the deliverability of online adapted plans and develop a proof-of-concept online delivery monitoring system for online adaptive radiation therapy QA. The first part of this project benchmarked automatically online adapted prostate treatment plans using traditional portal dosimetry IMRT QA. The portal dosimetry QA results of online adapted plans were compared to original (unadapted) plans as well as randomly selected prostate IMRT plans from our clinic. In the second part, an online delivery monitoring system was designed and validated via a simulated treatment with intentional multileaf collimator (MLC) errors. This system was based on inputs from the dynamic machine information (DMI), which continuously reports actual MLC positions and machine monitor units (MUs) at intervals of 50 ms or less during delivery. Based on the DMI, the system performed two levels of monitoring/verification during the delivery: (1) dynamic monitoring of cumulative fluence errors resulting from leaf position deviations and visualization using fluence error maps (FEMs); and (2) verification of MLC positions against the treatment plan for potential errors in MLC motion and data transfer at each control point. Validation of the online delivery monitoring system was performed by introducing intentional systematic MLC errors (ranging from 0.5 to 2 mm) to the DMI files for both leaf banks. These DMI files were analyzed by the proposed system to evaluate the system's performance in quantifying errors and revealing the source of errors, as well as to understand patterns in the FEMs. In addition, FEMs from 210 actual prostate IMRT beams were analyzed using the proposed system to further validate its ability to catch and identify errors, as well as establish error magnitude baselines for prostate IMRT delivery. Online adapted plans were

Implementation of a free software for quality control of IMRT

International Nuclear Information System (INIS)

Chinillace, N.; Alonso, S.; Cortina, T.; Reinado, D.; Ricos, B.; Diaz, S.; Campayo, J. M.

2011-01-01

In this paper we focus on implementation and launch of software that allows us to compare quantitatively the two-dimensional dose distributions calculated and measured experimentally in IMRT treatment. The tool we are using to make this comparison is the free software DoseLab. This is a program written in MatLab and open source, thereby allowing in some cases adapt the program to the needs of each user. This program will be able to calculate the gamma function of these distributions, a parameter that simultaneously evaluates the difference in dose between two pixels of the image and the distance between them, giving us an objective and quantitative, allowing us to decide if both distributions are compatible or not.

Poster - Thur Eve - 29: Detecting changes in IMRT QA using statistical process control.

Science.gov (United States)

Drever, L; Salomons, G

2012-07-01

Statistical process control (SPC) methods were used to analyze 239 measurement based individual IMRT QA events. The selected IMRT QA events were all head and neck (H&N) cases with 70Gy in 35 fractions, and all prostate cases with 76Gy in 38 fractions planned between March 2009 and 2012. The results were used to determine if the tolerance limits currently being used for IMRT QA were able to indicate if the process was under control. The SPC calculations were repeated for IMRT QA of the same type of cases that were planned after the treatment planning system was upgraded from Eclipse version 8.1.18 to version 10.0.39. The initial tolerance limits were found to be acceptable for two of the three metrics tested prior to the upgrade. After the upgrade to the treatment planning system the SPC analysis found that the a priori limits were no longer capable of indicating control for 2 of the 3 metrics analyzed. The changes in the IMRT QA results were clearly identified using SPC, indicating that it is a useful tool for finding changes in the IMRT QA process. Routine application of SPC to IMRT QA results would help to distinguish unintentional trends and changes from the random variation in the IMRT QA results for individual plans. © 2012 American Association of Physicists in Medicine.

Implementation of a free software for quality control of IMRT; Puesta en marcha de un soltware de libre distribucion para el control de calidad IMRT

Energy Technology Data Exchange (ETDEWEB)

Chinillace, N.; Alonso, S.; Cortina, T.; Reinado, D.; Ricos, B.; Diaz, S.; Campayo, J. M.

2011-07-01

In this paper we focus on implementation and launch of software that allows us to compare quantitatively the two-dimensional dose distributions calculated and measured experimentally in IMRT treatment. The tool we are using to make this comparison is the free software DoseLab. This is a program written in MatLab and open source, thereby allowing in some cases adapt the program to the needs of each user. This program will be able to calculate the gamma function of these distributions, a parameter that simultaneously evaluates the difference in dose between two pixels of the image and the distance between them, giving us an objective and quantitative, allowing us to decide if both distributions are compatible or not.

IMRT fluence map editing to control hot and cold spots

International Nuclear Information System (INIS)

Taylor Cook, J.; Tobler, Matt; Leavitt, Dennis D.; Watson, Gordon

2005-01-01

Manually editing intensity-modulated radiation therapy (IMRT) fluence maps effectively controls hot and cold spots that the IMRT optimization cannot control. Many times, re-optimizing does not reduce the hot spots or increase the cold spots. In fact, re-optimizing only places the hot and cold spots in different locations. Fluence-map editing provides manual control of dose delivery and provides the best treatment plan possible. Several IMRT treatments were planned using the Varian Eclipse planning system. We compare the effects on dose distributions between fluence-map editing and re-optimization, discuss techniques for fluence-map editing, and analyze differences between fluence editing on one beam vs. multiple beams. When editing a beam's fluence map, it is essential to choose a beam that least affects dose to the tumor and critical structures. Editing fluence maps gives an advantage in treatment planning and provides controlled delivery of IMRT dose

Current status of intensity-modulated radiation therapy (IMRT)

International Nuclear Information System (INIS)

Hatano, Kazuo; Araki, Hitoshi; Sakai, Mitsuhiro

2007-01-01

External-beam radiation therapy has been one of the treatment options for prostate cancer. The dose response has been observed for a dose range of 64.8-81 Gy. The problem of external-beam radiotherapy (RT) for prostate cancer is that as the dose increases, adverse effects also increase. Three-dimensional conformal radiation therapy (3D-CRT) has enabled us to treat patients with up to 72-76 Gy to the prostate, with a relatively acceptable risk of late rectal bleeding. Recently, intensity-modulated radiation therapy (IMRT) has been shown to deliver a higher dose to the target with acceptable low rates of rectal and bladder complications. The most important things to keep in mind when using an IMRT technique are that there is a significant trade-off between coverage of the target, avoidance of adjacent critical structures, and the inhomogeneity of the dose within the target. Lastly, even with IMRT, it should be kept in mind that a ''perfect'' plan that creates completely homogeneous coverage of the target volume and zero or small dose to the adjacent organs at risk is not always obtained. Participating in many treatment planning sessions and arranging the beams and beam weights create the best approach to the best IMRT plan. (author)

Biological stress response terminology: Integrating the concepts of adaptive response and preconditioning stress within a hormetic dose-response framework

International Nuclear Information System (INIS)

Calabrese, Edward J.; Bachmann, Kenneth A.; Bailer, A. John; Bolger, P. Michael; Borak, Jonathan; Cai, Lu; Cedergreen, Nina; Cherian, M. George; Chiueh, Chuang C.; Clarkson, Thomas W.; Cook, Ralph R.; Diamond, David M.; Doolittle, David J.; Dorato, Michael A.; Duke, Stephen O.; Feinendegen, Ludwig; Gardner, Donald E.; Hart, Ronald W.; Hastings, Kenneth L.; Hayes, A. Wallace; Hoffmann, George R.; Ives, John A.; Jaworowski, Zbigniew; Johnson, Thomas E.; Jonas, Wayne B.; Kaminski, Norbert E.; Keller, John G.; Klaunig, James E.; Knudsen, Thomas B.; Kozumbo, Walter J.; Lettieri, Teresa; Liu, Shu-Zheng; Maisseu, Andre; Maynard, Kenneth I.; Masoro, Edward J.; McClellan, Roger O.; Mehendale, Harihara M.; Mothersill, Carmel; Newlin, David B.; Nigg, Herbert N.; Oehme, Frederick W.; Phalen, Robert F.; Philbert, Martin A.; Rattan, Suresh I.S.; Riviere, Jim E.; Rodricks, Joseph; Sapolsky, Robert M.; Scott, Bobby R.; Seymour, Colin; Sinclair, David A.; Smith-Sonneborn, Joan; Snow, Elizabeth T.; Spear, Linda; Stevenson, Donald E.; Thomas, Yolene; Tubiana, Maurice; Williams, Gary M.; Mattson, Mark P.

2007-01-01

Many biological subdisciplines that regularly assess dose-response relationships have identified an evolutionarily conserved process in which a low dose of a stressful stimulus activates an adaptive response that increases the resistance of the cell or organism to a moderate to severe level of stress. Due to a lack of frequent interaction among scientists in these many areas, there has emerged a broad range of terms that describe such dose-response relationships. This situation has become problematic because the different terms describe a family of similar biological responses (e.g., adaptive response, preconditioning, hormesis), adversely affecting interdisciplinary communication, and possibly even obscuring generalizable features and central biological concepts. With support from scientists in a broad range of disciplines, this article offers a set of recommendations we believe can achieve greater conceptual harmony in dose-response terminology, as well as better understanding and communication across the broad spectrum of biological disciplines

Toward University Modeling Instruction—Biology: Adapting Curricular Frameworks from Physics to Biology

Science.gov (United States)

Manthey, Seth; Brewe, Eric

2013-01-01

University Modeling Instruction (UMI) is an approach to curriculum and pedagogy that focuses instruction on engaging students in building, validating, and deploying scientific models. Modeling Instruction has been successfully implemented in both high school and university physics courses. Studies within the physics education research (PER) community have identified UMI's positive impacts on learning gains, equity, attitudinal shifts, and self-efficacy. While the success of this pedagogical approach has been recognized within the physics community, the use of models and modeling practices is still being developed for biology. Drawing from the existing research on UMI in physics, we describe the theoretical foundations of UMI and how UMI can be adapted to include an emphasis on models and modeling for undergraduate introductory biology courses. In particular, we discuss our ongoing work to develop a framework for the first semester of a two-semester introductory biology course sequence by identifying the essential basic models for an introductory biology course sequence. PMID:23737628

Toward university modeling instruction--biology: adapting curricular frameworks from physics to biology.

Science.gov (United States)

Manthey, Seth; Brewe, Eric

2013-06-01

University Modeling Instruction (UMI) is an approach to curriculum and pedagogy that focuses instruction on engaging students in building, validating, and deploying scientific models. Modeling Instruction has been successfully implemented in both high school and university physics courses. Studies within the physics education research (PER) community have identified UMI's positive impacts on learning gains, equity, attitudinal shifts, and self-efficacy. While the success of this pedagogical approach has been recognized within the physics community, the use of models and modeling practices is still being developed for biology. Drawing from the existing research on UMI in physics, we describe the theoretical foundations of UMI and how UMI can be adapted to include an emphasis on models and modeling for undergraduate introductory biology courses. In particular, we discuss our ongoing work to develop a framework for the first semester of a two-semester introductory biology course sequence by identifying the essential basic models for an introductory biology course sequence.

SU-E-T-521: Feasibility Study of a Rotational Step-And-Shoot IMRT Treatment Planning Approach

International Nuclear Information System (INIS)

Zhu, X; Chang, S; Cullip, T; Yuan, L; Zhang, X; Lian, J; Tang, X; Tracton, G; Dooley, J

2014-01-01

Purpose: Rotational step-and-shot IMRT (r-IMRT) could improve delivery efficiency with good dose conformity, especially if it can leverage the burst mode of the accelerator where radiation is turned on/off momentarily while the gantry rotates continuously. The challenge for the r-IMRT planning is to minimize the number of beams to achieve a fast and smooth rotational delivery. Methods: Treatment plans for r-IMRT were created using an in-house treatment planning system. To generate the plan using a very few beams, gantry angle was optimized by weighting the beam monitoring unit (MU), and beam shape optimization was a combination of column search with k-means clustering. A prostate case and a head and neck case were planned using r-IMRT. The dosimetry is compared to s-IMRT planned with Varian Eclipse treatment planning system. Results: With the same PTV dose coverage D95=100%, the r-IMRT plans shows comparable sparing as the s-IMRT plans in the prostate for the rectum D10cc and the bladder Dmean, and in the head and neck for the spinal cord Dmax, the brain stem Dmax, the left/right parotid Dmean, the larynx Dmean, and the mandible Dmean. Both plans meet the established institutional clinical dosimetric criteria. The r-IMRT plan uses 19 beam/405 MU for the prostate, and 68 beam/880 MU for the head and neck, while the s-IMRT uses 7 beam/724 MU and 9 beam/1812 MU, respectively. Compared to the corresponding s-IMRT, r-IMRT has a reduction of MUs of 44% for the prostate case and 41% for the head and neck case. Conclusions: We have demonstrated the feasibility of a rotational step and shoot IMRT treatment planning approach that significantly shortens the conventional IMRT treatment beam-on time without degrading the dose comformity

SU-E-T-521: Feasibility Study of a Rotational Step-And-Shoot IMRT Treatment Planning Approach

Energy Technology Data Exchange (ETDEWEB)

Zhu, X [Univ. of North Carolina at Chapel Hill, Chapel Hill, NC (United States); Chang, S [UNC School of Medicine, Chapel Hill, NC (United States); Cullip, T [UNC Hospitals, Chapel Hill, NC (United States); Yuan, L; Zhang, X [Duke University, Durham, NC (United States); Lian, J; Tang, X [UniversityNorth Carolina, Chapel Hill, NC (United States); Tracton, G; Dooley, J [University of North Carolina, Chapel Hill, NC (United States)

2014-06-01

Purpose: Rotational step-and-shot IMRT (r-IMRT) could improve delivery efficiency with good dose conformity, especially if it can leverage the burst mode of the accelerator where radiation is turned on/off momentarily while the gantry rotates continuously. The challenge for the r-IMRT planning is to minimize the number of beams to achieve a fast and smooth rotational delivery. Methods: Treatment plans for r-IMRT were created using an in-house treatment planning system. To generate the plan using a very few beams, gantry angle was optimized by weighting the beam monitoring unit (MU), and beam shape optimization was a combination of column search with k-means clustering. A prostate case and a head and neck case were planned using r-IMRT. The dosimetry is compared to s-IMRT planned with Varian Eclipse treatment planning system. Results: With the same PTV dose coverage D95=100%, the r-IMRT plans shows comparable sparing as the s-IMRT plans in the prostate for the rectum D10cc and the bladder Dmean, and in the head and neck for the spinal cord Dmax, the brain stem Dmax, the left/right parotid Dmean, the larynx Dmean, and the mandible Dmean. Both plans meet the established institutional clinical dosimetric criteria. The r-IMRT plan uses 19 beam/405 MU for the prostate, and 68 beam/880 MU for the head and neck, while the s-IMRT uses 7 beam/724 MU and 9 beam/1812 MU, respectively. Compared to the corresponding s-IMRT, r-IMRT has a reduction of MUs of 44% for the prostate case and 41% for the head and neck case. Conclusions: We have demonstrated the feasibility of a rotational step and shoot IMRT treatment planning approach that significantly shortens the conventional IMRT treatment beam-on time without degrading the dose comformity.

Simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) in nasopharyngeal cancer

Energy Technology Data Exchange (ETDEWEB)

Studer, Gabriela [Dept. of Radiation Oncology, Univ. Hospital, Zurich (Switzerland); Peponi, Evangelia; Glanzmann, Christoph; Kunz, Guntram; Renner, Christoph; Tomuschat, Katja

2010-03-15

Purpose: To assess the efficacy and safety of using simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) to treat nasopharyngeal cancer (NPC) in a Caucasian cohort. Outcome was analyzed with respect to dose-volume histogram (DVH) values. Patients and Methods: Between 03/2002 and 01/2008, 39 NPC patients underwent SIB-IMRT (37 Caucasians; 31 males; mean age 53 years [16-78 years]). 41% presented with WHO (World Health Organization) type 1 unfavorable histology, 85% with stage III/IV disease. 19 patients had total gross tumor volume (GTV) 16-70 cm{sup 3} (mean 36 cm{sup 3}), while 16 had GTV > 70 cm{sup 3} (73-217 cm{sup 3}; mean 115 cm{sup 3}). All patients with stage II-IV disease received concomitant cisplatin. The prescribed SIB dose delivered to the planning target volume (PTV) was 70 Gy (2.00 Gy/fraction) in 17, 69.6 Gy (2.11 Gy/fraction) in 19, and 66 Gy (2.20 Gy/fraction) in three patients. Results: 3-year local relapse-free, nodal relapse-free, distant metastases-free, disease-free rates and overall survival were 86%, 89%, 85%, 72%, and 85% (median follow-up 30 months [8-71 months]). Histology was a significant prognostic factor concerning overall survival, with worst prognosis in WHO type 1 compared to type 2/3 (75% vs. 93%; p = 0.03). There was a trend in favor of WHO type 2/3 regarding local control (74% vs. 94%; p = 0.052). The PTV DVHs showed a slight left shift compared to reported series. Three patients developed grade 3 late effects (xerostomia [n=2], dysphagia [n=1], hearing loss [n=1]). Conclusion: In comparison with predominantly Asian NPC IMRT series in the literature, chemo-IMRT in the own Caucasian cohort, characterized by less radioresponsive WHO type 1, was equally effective. Treatment tolerance was excellent. (orig.)

Reducing Xerostomia After Chemo-IMRT for Head and Neck Cancer: Beyond Sparing the Parotid Glands

Science.gov (United States)

Little, Michael; Schipper, Matthew; Feng, Felix Y.; Vineberg, Karen; Cornwall, Craig; Murdoch-Kinch, Carol-Anne; Eisbruch, Avraham

2011-01-01

Purpose To assess whether in addition to sparing parotid glands (PGs), xerostomia after chemo-IMRT of head and neck cancer is affected by reducing doses to other salivary glands. Methods Prospective study: 78 patients with stages III/IV oropharynx/nasopharynx cancers received chemo-IMRT aiming to spare the parts outside the targets of bilateral PGs, oral cavity (OC) containing the minor salivary glands, and contralateral submandibular gland (SMG) (when contralateral level I was not a target). Pretherapy and periodically through 24 months, validated patient-reported xerostomia questionnaires (XQ) scores and observer-graded xerostomia were recorded, and stimulated and unstimulated saliva measured selectively from each of the PGs and SMGs. Mean OC doses served as surrogates of minor salivary glands dysfunction. Regression models assessed XQ and observer-graded xerostomia predictors. Results Statistically significant predictors of the XQ score in univariate analysis included OC, PG, and SMG mean doses, as well as baseline XQ score, time since RT, and both stimulated and unstimulated PG saliva flow rates. Similar factors were statistically significant predictors of observer-graded xerostomia. OC, PG and SMG mean doses were moderately inter-correlated (r=0.47–0.55). In multivariate analyses, after adjusting for PG and SMG doses, OC mean dose (p xerostomia. While scatter plots showed no thresholds, OC mean doses xerostomia at almost all post-therapy time points. Conclusion PG, SMG and OC mean doses were significant predictors of both patient-reported and observer-rated xerostomia after chemo-IMRT, with OC doses remaining significant after adjusting for PG and SMG doses. These results support efforts to spare all salivary glands by IMRT, beyond the PGs alone. PMID:22056067

Comparison of VMAT and IMRT strategies for cervical cancer patients using automated planning.

Science.gov (United States)

Sharfo, Abdul Wahab M; Voet, Peter W J; Breedveld, Sebastiaan; Mens, Jan Willem M; Hoogeman, Mischa S; Heijmen, Ben J M

2015-03-01

In a published study on cervical cancer, 5-beam IMRT was inferior to single arc VMAT. Here we compare 9, 12, and 20 beam IMRT with single and dual arc VMAT. For each of 10 patients, automated plan generation with the in-house Erasmus-iCycle optimizer was used to assist an expert planner in generating the five plans with the clinical TPS. For each patient, all plans were clinically acceptable with a high and similar PTV coverage. OAR sparing increased when going from 9 to 12 to 20 IMRT beams, and from single to dual arc VMAT. For all patients, 12 and 20 beam IMRT were superior to single and dual arc VMAT, with substantial variations in gain among the study patients. As expected, delivery of VMAT plans was significantly faster than delivery of IMRT plans. Often reported increased plan quality for VMAT compared to IMRT has not been observed for cervical cancer. Twenty and 12 beam IMRT plans had a higher quality than single and dual arc VMAT. For individual patients, the optimal delivery technique depends on a complex trade-off between plan quality and treatment time that may change with introduction of faster delivery systems. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Comparison of VMAT and IMRT strategies for cervical cancer patients using automated planning

International Nuclear Information System (INIS)

Sharfo, Abdul Wahab M.; Voet, Peter W.J.; Breedveld, Sebastiaan; Mens, Jan Willem M.; Hoogeman, Mischa S.; Heijmen, Ben J.M.

2015-01-01

Background and purpose: In a published study on cervical cancer, 5-beam IMRT was inferior to single arc VMAT. Here we compare 9, 12, and 20 beam IMRT with single and dual arc VMAT. Material and methods: For each of 10 patients, automated plan generation with the in-house Erasmus-iCycle optimizer was used to assist an expert planner in generating the five plans with the clinical TPS. Results: For each patient, all plans were clinically acceptable with a high and similar PTV coverage. OAR sparing increased when going from 9 to 12 to 20 IMRT beams, and from single to dual arc VMAT. For all patients, 12 and 20 beam IMRT were superior to single and dual arc VMAT, with substantial variations in gain among the study patients. As expected, delivery of VMAT plans was significantly faster than delivery of IMRT plans. Conclusions: Often reported increased plan quality for VMAT compared to IMRT has not been observed for cervical cancer. Twenty and 12 beam IMRT plans had a higher quality than single and dual arc VMAT. For individual patients, the optimal delivery technique depends on a complex trade-off between plan quality and treatment time that may change with introduction of faster delivery systems

Matching tomographic IMRT fields with static photon fields

International Nuclear Information System (INIS)

Sethi, A.; Leybovich, L.; Dogan, N.; Emami, B.

2001-01-01

The matching of abutting radiation fields presents a challenging problem in radiation therapy. Due to sharp penumbra of linear accelerator beams, small (1-2 mm) errors in field positioning can lead to large (>30%) hot or cold spots in the abutment region. With head and neck immobilization devices (thermoplastic mask/aquaplast) an average setup error of 3 mm has been reported. Therefore hot or cold spots approaching 50% of the prescription dose may occur along the matchline. Although abutting radiation fields have been investigated for static fields, there is no reported study regarding matching of tomographic IMRT and static fields. Compared to static fields, the matching of tomographic IMRT fields with static fields is more complicated. Since IMRT and static fields are planned on separate treatment planning computers, the dose in the abutment region is not specified. In addition, commonly used techniques for matching fields, such as feathering of junctions, are not practical. We have developed a method that substantially reduces dose inhomogeneity in the abutment region. In this method, a 'buffer zone' around the matchline was created and was included as part of the target for both IMRT and static field plans. In both fields, a small dose gradient (≤3%/mm) in the buffer zone was created. In the IMRT plan, the buffer zone was divided into three sections with dose varying from 83% to 25% of prescription dose. The static field dose profile was modified using either a specially designed physical (hard) or a dynamic (soft) wedge. When these modified fields were matched, the combined dose in the abutment region varied by ≤10% in the presence of setup errors spanning 4 mm (±2 mm) when the hard wedge was used and 10 mm (±5 mm) with the soft wedge

Dosimetry audit for a multi-centre IMRT head and neck trial

International Nuclear Information System (INIS)

Clark, Catharine H.; Hansen, Vibeke Nordmark; Chantler, Hannah; Edwards, Craig; James, Hayley V.; Webster, Gareth; Miles, Elizabeth A.; Guerrero Urbano, M. Teresa; Bhide, Shree A.; Bidmead, A. Margaret; Nutting, Christoper M.

2009-01-01

Background and purpose: PARSPORT was a multi-centre randomised trial in the UK which compared Intensity-Modulated Radiotherapy (IMRT) and conventional radiotherapy (CRT) for patients with head and neck cancer. The dosimetry audit goals were to verify the plan delivery in participating centres, ascertain what tolerances were suitable for head and neck IMRT trials and develop an IMRT credentialing program. Materials and methods: Centres enrolling patients underwent rigorous quality assurance before joining the trial. Following this each centre was visited for a dosimetry audit, which consisted of treatment planning system tests, fluence verification films, combined field films and dose point measurements. Results: Mean dose point measurements were made at six centres. For the primary planning target volume (PTV) the differences with the planned values for the IMRT and CRT arms were -0.6% (1.8% to -2.4%) and 0.7% (2.0% to -0.9%), respectively. Ninety-four percent of the IMRT fluence films for individual fields passed gamma criterion of 3%/3 mm and 75% of the films for combined fields passed gamma criterion 4%/3 mm (no significant difference between dynamic delivery and step and shoot delivery). Conclusions: This audit suggests that a 3% tolerance could be applied for PTV point doses. For dose distributions tolerances of 3%/3 mm on individual fields and 4%/3 mm for combined fields are proposed for multi-centre head and neck IMRT trials.

Image guided IMRT dosimetry using anatomy specific MOSFET configurations.

Science.gov (United States)

Amin, Md Nurul; Norrlinger, Bern; Heaton, Robert; Islam, Mohammad

2008-06-23

We have investigated the feasibility of using a set of multiple MOSFETs in conjunction with the mobile MOSFET wireless dosimetry system, to perform a comprehensive and efficient quality assurance (QA) of IMRT plans. Anatomy specific MOSFET configurations incorporating 5 MOSFETs have been developed for a specially designed IMRT dosimetry phantom. Kilovoltage cone beam computed tomography (kV CBCT) imaging was used to increase the positional precision and accuracy of the detectors and phantom, and so minimize dosimetric uncertainties in high dose gradient regions. The effectiveness of the MOSFET based dose measurements was evaluated by comparing the corresponding doses measured by an ion chamber. For 20 head and neck IMRT plans the agreement between the MOSFET and ionization chamber dose measurements was found to be within -0.26 +/- 0.88% and 0.06 +/- 1.94% (1 sigma) for measurement points in the high dose and low dose respectively. A precision of 1 mm in detector positioning was achieved by using the X-Ray Volume Imaging (XVI) kV CBCT system available with the Elekta Synergy Linear Accelerator. Using the anatomy specific MOSFET configurations, simultaneous measurements were made at five strategically located points covering high dose and low dose regions. The agreement between measurements and calculated doses by the treatment planning system for head and neck and prostate IMRT plans was found to be within 0.47 +/- 2.45%. The results indicate that a cylindrical phantom incorporating multiple MOSFET detectors arranged in an anatomy specific configuration, in conjunction with image guidance, can be utilized to perform a comprehensive and efficient quality assurance of IMRT plans.

The use of biologically related model (Eclipse for the intensity-modulated radiation therapy planning of nasopharyngeal carcinomas.

Directory of Open Access Journals (Sweden)

Monica W K Kan

Full Text Available Intensity-modulated radiation therapy (IMRT is the most common treatment technique for nasopharyngeal carcinoma (NPC. Physical quantities such as dose/dose-volume parameters are used conventionally for IMRT optimization. The use of biological related models has been proposed and can be a new trend. This work was to assess the performance of the biologically based IMRT optimization model installed in a popular commercial treatment planning system (Eclipse as compared to its dose/dose volume optimization model when employed in the clinical environment for NPC cases.Ten patients of early stage NPC and ten of advanced stage NPC were selected for this study. IMRT plans optimized using biological related approach (BBTP were compared to their corresponding plans optimized using the dose/dose volume based approach (DVTP. Plan evaluation was performed using both biological indices and physical dose indices such as tumor control probability (TCP, normal tissue complication probability (NTCP, target coverage, conformity, dose homogeneity and doses to organs at risk. The comparison results of the more complex advanced stage cases were reported separately from those of the simpler early stage cases.The target coverage and conformity were comparable between the two approaches, with BBTP plans producing more hot spots. For the primary targets, BBTP plans produced comparable TCP for the early stage cases and higher TCP for the advanced stage cases. BBTP plans reduced the volume of parotid glands receiving doses of above 40 Gy compared to DVTP plans. The NTCP of parotid glands produced by BBTP were 8.0 ± 5.8 and 7.9 ± 8.7 for early and advanced stage cases, respectively, while those of DVTP were 21.3 ± 8.3 and 24.4 ± 12.8, respectively. There were no significant differences in the NTCP values between the two approaches for the serial organs.Our results showed that the BBTP approach could be a potential alternative approach to the DVTP approach for NPC.

An inter-centre quality assurance network for IMRT verification: Results of the ESTRO QUASIMODO project

International Nuclear Information System (INIS)

Gillis, Sofie; Wagter, Carlos de; Bohsung, Joerg; Perrin, Bruce; Williams, Peter; Mijnheer, Ben J.

2005-01-01

Background and purpose: IMRT necessitates extension of existing inter-centre quality assurance programs due to its increased complexity. We assessed the feasibility of an inter-centre verification method for different IMRT techniques. Materials and methods: Eight European radiotherapy institutions of the QUASIMODO network, have designed an IMRT plan for a horseshoe-shaped PTV surrounding a cylindrical OAR in a simplified pelvic phantom. All centres applied common plan objectives but used their own equipment for planning and delivery. They verified the delivery of this plan according to a common protocol with radiographic film and ionisation chamber measurements. The irradiated films, the results of the ionisation chamber measurements and the computed dose distributions were sent to one analysis centre that compared the measured and computed dose distributions with the gamma method and composite dose-area histograms. Results: 4% (relative to the prescribed dose) and 3 mm (distance-to-agreement) were decided feasible gamma criteria. The composite dose-area histograms showed a maximum local deviation of 3.5% in the mean dose of the PTV and 5% in the OAR. Systematic differences could be identified, and in some cases explained. Conclusions: This multi-centre dosimetric verification study demonstrated both the feasibility of a multi-centre quality assurance network to evaluate any IMRT planning and delivery system combination, as well as the validity of the methodology involved

Is uniform target dose possible in IMRT plans in the head and neck?

International Nuclear Information System (INIS)

Vineberg, K.A.; Eisbruch, A.; Coselmon, M.M.; McShan, D.L.; Kessler, M.L.; Fraass, B.A.

2002-01-01

Purpose: Various published reports involving intensity-modulated radiotherapy (IMRT) plans developed using automated optimization (inverse planning) have demonstrated highly conformal plans. These reported conformal IMRT plans involve significant target dose inhomogeneity, including both overdosage and underdosage within the target volume. In this study, we demonstrate the development of optimized beamlet IMRT plans that satisfy rigorous dose homogeneity requirements for all target volumes (e.g., ±5%), while also sparing the parotids and other normal structures. Methods and Materials: The treatment plans of 15 patients with oropharyngeal cancer who were previously treated with forward-planned multisegmental IMRT were planned again using an automated optimization system developed in-house. The optimization system allows for variable sized beamlets computed using a three-dimensional convolution/superposition dose calculation and flexible cost functions derived from combinations of clinically relevant factors (costlets) that can include dose, dose-volume, and biologic model-based costlets. The current study compared optimized IMRT plans designed to treat the various planning target volumes to doses of 66, 60, and 54 Gy with varying target dose homogeneity while using a flexible optimization cost function to minimize the dose to the parotids, spinal cord, oral cavity, brainstem, submandibular nodes, and other structures. Results: In all cases, target dose uniformity was achieved through steeply varying dose-based costs. Differences in clinical plan evaluation metrics were evaluated for individual cases (eight different target homogeneity costlets), and for the entire cohort of plans. Highly conformal plans were achieved, with significant sparing of both the contralateral and ipsilateral parotid glands. As the homogeneity of the target dose distributions was allowed to decrease, increased sparing of the parotids (and other normal tissues) may be achieved. However, it

The MLC tongue-and-groove effect on IMRT dose distributions

Energy Technology Data Exchange (ETDEWEB)

Deng Jun [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States). E-mail: jun@reyes.stanford.edu; Pawlicki, Todd; Chen Yan; Li Jinsheng; Jiang, Steve B.; Ma, C.-M. [Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305 (United States)

2001-04-01

We have investigated the tongue-and-groove effect on the IMRT dose distributions for a Varian MLC. We have compared the dose distributions calculated using the intensity maps with and without the tongue-and-groove effect. Our results showed that, for one intensity-modulated treatment field, the maximum tongue-and-groove effect could be up to 10% of the maximum dose in the dose distributions. For an IMRT treatment with multiple gantry angles ({>=} 5), the difference between the dose distributions with and without the tongue-and-groove effect was hardly visible, less than 1.6% for the two typical clinical cases studied. After considering the patient setup errors, the dose distributions were smoothed with reduced and insignificant differences between plans with and without the tongue-and-groove effect. Therefore, for a multiple-field IMRT plan ({>=} 5), the tongue-and-groove effect on the IMRT dose distributions will be generally clinically insignificant due to the smearing effect of individual fields. The tongue-and-groove effect on an IMRT plan with small number of fields (<5) will vary depending on the number of fields in a plan (coplanar or non-coplanar), the MLC leaf sequences and the patient setup uncertainty, and may be significant (>5% of maximum dose) in some cases, especially when the patient setup uncertainty is small ({<=} 2 mm). (author)

Surviving Hypopharynx-Larynx Carcinoma in the Era of IMRT

International Nuclear Information System (INIS)

Studer, Gabriela; Peponi, Evangelia; Kloeck, Stephan; Dossenbach, Thomas; Huber, Gerhard; Glanzmann, Christoph

2010-01-01

Purpose: Outcome in locoregionally advanced laryngeal carcinoma and hypopharyngeal carcinoma after conventional radiation techniques is known for modest disease control and considerable late toxicity. Considering the lack of standardization in prescription dose for intensity-modulated radiotherapy (IMRT), we aimed to compare the results after our methods of simultaneously integrated boost IMRT with published results. Methods and Materials: Between March 2002 and December 2008, 65 hypopharyngeal, 31 supraglottic, and 27 locoregionally advanced glottic tumor patients underwent definitive IMRT (with simultaneous chemotherapy in 86%). Of these, 64% presented with locoregionally advanced disease. Mean follow-up was 26 months (range, 3-83 months), with a median of 21 months. Treatment (2.0-2.2Gy per fraction, 66-72.6Gy) followed a prospectively defined protocol. If the boost volume included more than half of the larynx or a substantial part of the pharynx, dose was limited to 2.0Gy per fraction. Results: The 2-year local, nodal, and locoregional control (LRC) rates for the entire cohort were 82%, 90%, and 77%, respectively; the disease-free and overall survival rates were 75% and 83%, respectively. The ultimate 2-year LRC rate, including salvage surgery, was 86%. Laryngectomy was required in 2 LRC patients needing tracheostoma already before; 2 further LRC patients needed tracheostomy before IMRT and remained tracheostoma dependent, and 3 patients remained feeding tube dependent after IMRT. Salvage laryngectomy was successful in 8 of 11. Of all 123 patients, 91 patients (74%) are locoregionally controlled and live with a functional laryngopharynx. Conclusions: Simultaneously integrated boost IMRT with limited acceptance of dose inhomogeneity resulted in very satisfactory disease control despite a slight left shift of planning target volume curves on the dose-volume histogram. Considering the treatment tolerance, a careful increase in dose in our patients seems possible

The science of adaptation. A framework for assessment

International Nuclear Information System (INIS)

Smit, B.; Burton, I.; Street, R.; Klein, R.J.T.; Maciver, D.C.

1999-01-01

This paper outlines what is meant by 'adaptation' to climate change, and how it might be addressed in the IPCC Assessments. Two roles of adaptation in the climate change field are identified: adaptation as part of impact assessment (where the key question is: what adaptations are likely?), and adaptation as part of the policy response (where the central question is: what adaptations are recommended?). The concept of adaptation has been adopted in several fields including climate impact assessment and policy development, risk management, and natural hazards research. A framework for systematically defining adaptations is based on three questions: (1) adaptation to what? (2) who or what adapts? and (3) how does adaptation occur? The paper demonstrates that, for adaptation purposes, climate extremes and variability are integral parts of climate change, along with shifts in mean conditions. Attributes for differentiating adaptations include purposefulness, timing, temporal and spatial scope, effects, form and performance. The framework provides a guide for the treatment of adaptation in the IPCC assessments, both in the assessment of impacts and in the evaluation of adaptive policy options. 64 refs

Reliable detection of fluence anomalies in EPID-based IMRT pretreatment quality assurance using pixel intensity deviations

International Nuclear Information System (INIS)

Gordon, J. J.; Gardner, J. K.; Wang, S.; Siebers, J. V.

2012-01-01

Purpose: This work uses repeat images of intensity modulated radiation therapy (IMRT) fields to quantify fluence anomalies (i.e., delivery errors) that can be reliably detected in electronic portal images used for IMRT pretreatment quality assurance. Methods: Repeat images of 11 clinical IMRT fields are acquired on a Varian Trilogy linear accelerator at energies of 6 MV and 18 MV. Acquired images are corrected for output variations and registered to minimize the impact of linear accelerator and electronic portal imaging device (EPID) positioning deviations. Detection studies are performed in which rectangular anomalies of various sizes are inserted into the images. The performance of detection strategies based on pixel intensity deviations (PIDs) and gamma indices is evaluated using receiver operating characteristic analysis. Results: Residual differences between registered images are due to interfraction positional deviations of jaws and multileaf collimator leaves, plus imager noise. Positional deviations produce large intensity differences that degrade anomaly detection. Gradient effects are suppressed in PIDs using gradient scaling. Background noise is suppressed using median filtering. In the majority of images, PID-based detection strategies can reliably detect fluence anomalies of ≥5% in ∼1 mm 2 areas and ≥2% in ∼20 mm 2 areas. Conclusions: The ability to detect small dose differences (≤2%) depends strongly on the level of background noise. This in turn depends on the accuracy of image registration, the quality of the reference image, and field properties. The longer term aim of this work is to develop accurate and reliable methods of detecting IMRT delivery errors and variations. The ability to resolve small anomalies will allow the accuracy of advanced treatment techniques, such as image guided, adaptive, and arc therapies, to be quantified.

Effects of organ motion on IMRT treatments with segments of few monitor units

International Nuclear Information System (INIS)

Seco, J.; Sharp, G. C.; Turcotte, J.; Gierga, D.; Bortfeld, T.; Paganetti, H.

2007-01-01

Interplay between organ (breathing) motion and leaf motion has been shown in the literature to have a small dosimetric impact for clinical conditions (over a 30 fraction treatment). However, previous studies did not consider the case of treatment beams made up of many few-monitor-unit (MU) segments, where the segment delivery time (1-2 s) is of the order of the breathing period (3-5 s). In this study we assess if breathing compromises the radiotherapy treatment with IMRT segments of low number of MUs. We assess (i) how delivered dose varies, from patient to patient, with the number of MU per segment, (ii) if this delivered dose is identical to the average dose calculated without motion over the path of the motion, and (iii) the impact of the daily variation of the delivered dose as a function of MU per segment. The organ motion was studied along two orthogonal directions, representing the left-right and cranial-caudal directions of organ movement for a patient setup in the supine position. Breathing motion was modeled as sin(x), sin 4 (x), and sin 6 (x), based on functions used in the literature to represent organ motion. Measurements were performed with an ionization chamber and films. For a systematic study of motion effects, a MATLAB simulation was written to model organ movement and dose delivery. In the case of a single beam made up of one single segment, the dose delivered to point in a moving target over 30 fractions can vary up to 20% and 10% for segments of 10 MU and 20 MU, respectively. This dose error occurs because the tumor spends most of the time near the edges of the radiation beam. In the case of a single beam made of multiple segments with low MU, we observed 2.4%, 3.3%, and 4.3% differences, respectively, for sin(x), sin 4 (x), and sin 6 (x) motion, between delivered dose and motion-averaged dose for points in the penumbra region of the beam and over 30 fractions. In approximately 5-10% of the cases, differences between the motion-averaged dose

Primary Molecular Disorders and Secondary Biological Adaptations in Bartter Syndrome

Science.gov (United States)

Deschênes, Georges; Fila, Marc

2011-01-01

Bartter syndrome is a hereditary disorder that has been characterized by the association of hypokalemia, alkalosis, and the hypertrophy of the juxtaglomerular complex with secondary hyperaldosteronism and normal blood pressure. By contrast, the genetic causes of Bartter syndrome primarily affect molecular structures directly involved in the sodium reabsorption at the level of the Henle loop. The ensuing urinary sodium wasting and chronic sodium depletion are responsible for the contraction of the extracellular volume, the activation of the renin-aldosterone axis, the secretion of prostaglandins, and the biological adaptations of downstream tubular segments, meaning the distal convoluted tubule and the collecting duct. These secondary biological adaptations lead to hypokalemia and alkalosis, illustrating a close integration of the solutes regulation in the tubular structures. PMID:21941653

Primary Molecular Disorders and Secondary Biological Adaptations in Bartter Syndrome

Directory of Open Access Journals (Sweden)

Georges Deschênes

2011-01-01

Full Text Available Bartter syndrome is a hereditary disorder that has been characterized by the association of hypokalemia, alkalosis, and the hypertrophy of the juxtaglomerular complex with secondary hyperaldosteronism and normal blood pressure. By contrast, the genetic causes of Bartter syndrome primarily affect molecular structures directly involved in the sodium reabsorption at the level of the Henle loop. The ensuing urinary sodium wasting and chronic sodium depletion are responsible for the contraction of the extracellular volume, the activation of the renin-aldosterone axis, the secretion of prostaglandins, and the biological adaptations of downstream tubular segments, meaning the distal convoluted tubule and the collecting duct. These secondary biological adaptations lead to hypokalemia and alkalosis, illustrating a close integration of the solutes regulation in the tubular structures.

The Adaptation Gap Report. Towards Global Assessment

DEFF Research Database (Denmark)

2017-01-01

The Paris Agreement, adopted in 2015, established the global goal on adaptation of enhancing adaptive capacity, strengthening resilience and reducing vulnerability to climate change, with a view to contributing to sustainable development and ensuring an adequate adaptation response in the context...... Change (UNFCCC) to prepare for the implementation of the Paris Agreement. In contrast to previous Adaptation Gap Reports, the 2017 report focuses on issues relating to frameworks, comprising concepts, methodologies and data, rather than on assessing a particular dimension of the adaptation gap. Future...... extensive external review. The Paris Agreement’s global goal on adaptation provides a new starting point and impetus for assessing progress on adaptation at the global level, but additional information is required for assessing such progress. The global goal on adaptation provides a collective vision...

Poster – 12: Radiological assessment of the secondary barrier shielding for IMRT treatments delivered through patient inhomogeneities

International Nuclear Information System (INIS)

Haseeb, Syed Abdul; Ahmad, Syed Bilal; Mirza, Sikander Majid

2016-01-01

Purpose: To assess the impact of radiation treatment delivery through patient inhomogeneities on the secondary barrier shielding requirements in IMRT treatments using Monte Carlo Simulations. Materials and Methods: Scatter factors were calculated at a distance of 1m from the center of a virtual phantom in Geant4.10.01. Phantom (30×30×30 cm 3 ) was inserted with lung (30×30×8 cm 3 ), stainless steel (5×5×5 cm 3 ) and aluminum (5×5×5 cm 3 ) to represent the inhomogeneities. Scatter factor was defined according to the NCRP-151 recommendations and was calculated for angles of 3° to 120° with respect to the beam’s central axis. A virtual radiation source, with energy sampled from a histogram representing 6 MV FFF beam, was used for irradiation with a field size of 15×15 cm 2 and SSD of 100 cm. Results: Irradiation through the inhomogeneity affects the patient scattered dose. For high Z material inhomogeneities the scattered dose is reduced due to significant attenuation of the primary radiation. On the other hand if the inhomogeneity is a low Z material such as lung the scattered dose is higher by a maximum of 26%. The average increase in scatter factors for the lung phantom was 17% for angles between 3° and 63° compared to the homogeneous water phantom. Conclusions: In IMRT type treatments delivered through low density patient inhomogeneities (lung) the scattered dose increases significantly. Considering a large proportion of patients receiving radiation therapy for lung cancers the increase in the scattered dose should be incorporated in the shielding calculations for the secondary barriers.

Automated IMRT planning in Pinnacle. A study in head-and-neck cancer

Energy Technology Data Exchange (ETDEWEB)

Kusters, J.M.A.M.; Kollenburg, P.G.M. van; Kunze-Busch, M.C.; Wendling, M.; Dijkema, T.; Kaanders, J.H.A.M. [Radboud University Medical Center, Department of Radiation Oncology, Nijmegen (Netherlands); Bzdusek, K. [Philips Healthcare, Philips Radiation Oncology Systems, Fitchburg, WI (United States); Kumar, P. [Philips Electronics India Ltd., Philips Innovation Campus, Bangalore (India)

2017-12-15

This study evaluates the performance and planning efficacy of the Auto-Planning (AP) module in the clinical version of Pinnacle 9.10 (Philips Radiation Oncology Systems, Fitchburg, WI, USA). Twenty automated intensity-modulated radiotherapy (IMRT) plans were compared with the original manually planned clinical IMRT plans from patients with oropharyngeal cancer. Auto-Planning with IMRT offers similar coverage of the planning target volume as the original manually planned clinical plans, as well as better sparing of the contralateral parotid gland, contralateral submandibular gland, larynx, mandible, and brainstem. The mean dose of the contralateral parotid gland and contralateral submandibular gland could be reduced by 2.5 Gy and 1.7 Gy on average. The number of monitor units was reduced with an average of 143.9 (18%). Hands-on planning time was reduced from 1.5-3 h to less than 1 h. The Auto-Planning module was able to produce clinically acceptable head and neck IMRT plans with consistent quality. (orig.) [German] Diese Studie untersucht die Leistungsfaehigkeit und Planungseffektivitaet des Auto-Planning-Moduls in der klinischen Version von Pinnacle 9.10 (Philips Radiation Oncology Systems, Fitchburg, WI, USA). Zwanzig automatisch erstellte Plaene fuer die intensitaetsmodulierte Strahlentherapie (IMRT) wurden mit den urspruenglichen manuell erstellten klinischen IMRT-Plaenen von Patienten mit Oropharynxkarzinom verglichen. Die automatisch erstellten IMRT-Plaene bieten eine vergleichbare Deckung des Planungszielvolumens (PTV) wie die urspruenglichen, manuell erstellten klinischen Plaene sowie eine verbesserte Schonung der kontralateralen Ohrspeicheldruese, der kontralateralen Unterkieferspeicheldruese, des Kehlkopfs, des Unterkiefers und des Hirnstamms. Die mittlere Dosis der kontralateralen Ohr- und kontralateralen Unterkieferspeicheldruese konnte um durchschnittlich 2,5 bzw. 1,7 Gy reduziert werden. Die Anzahl der Monitoreinheiten wurde im Durchschnitt um 143

Direct aperture optimization of breast IMRT and the dosimetric impact of respiration motion

International Nuclear Information System (INIS)

Zhang Guowei; Jiang Ziping; Shepard, David; Zhang Bin; Yu, Cedric

2006-01-01

We have studied the application of direct aperture optimization (DAO) as an inverse planning tool for breast IMRT. Additionally, we have analysed the impact of respiratory motion on the quality of the delivered dose distribution. From this analysis, we have developed guidelines for balancing the desire for a high-quality optimized plan with the need to create a plan that will not degrade significantly in the presence of respiratory motion. For a DAO optimized breast IMRT plan, the tangential fields incorporate a flash field to cover the range of respiratory motion. The inverse planning algorithm then optimizes the shapes and weights of additional segments that are delivered in combination with the open fields. IMRT plans were generated using DAO with the relative weights of the open segments varied from 0% to 95%. To assess the impact of breathing motion, the dose distribution for the optimized IMRT plan was recalculated with the isocentre sampled from a predefined distribution in a Monte Carlo convolution/superposition dose engine with the breast simulated as a rigid object. The motion amplitudes applied in this study ranged from 0.5 to 2.0 cm. For a range of weighting levels assigned to the open field, comparisons were made between the static plans and the plans recalculated with motion. For the static plans, we found that uniform dose distributions could be generated with relative weights for the open segments equal to and below 80% and unacceptable levels of underdosage were observed with the weights larger than 80%. When simulated breathing motion was incorporated into the dose calculation, we observed a loss in dose uniformity as the weight of the open field was decreased to below 65%. More quantitatively, for each 1% decrease in the weight, the per cent volume of the target covered by at least 95% of the prescribed dose decreased by approximately 0.10% and 0.16% for motion amplitudes equal to 1.5 cm and 2.0 cm, respectively. When taking into account the

Assessment of shoulder position variation and its impact on IMRT and VMAT doses for head and neck cancer

Directory of Open Access Journals (Sweden)

Neubauer Emily

2012-02-01

Full Text Available Abstract Background For radiotherapy of the head and neck, 5-point mask immobilization is used to stabilize the shoulders. Still, the daily position of the shoulders during treatment may be different from the position in the treatment plan despite correct isocenter setup. The purpose of this study was to determine the interfractional displacement of the shoulders relative to isocenter over the course of treatment and the associated dosimetric effect of this displacement. Methods The extent of shoulder displacements relative to isocenter was assessed for 10 patients in 5-point thermoplastic masks using image registration and daily CT-on-rails scans. Dosimetric effects on IMRT and VMAT plans were evaluated in Pinnacle based on simulation CTs modified to represent shoulder shifts between 3 and 15 mm in the superior-inferior, anterior-posterior, and right-left directions. The impact of clinically observed shoulder shifts on the low-neck dose distributions was examined. Results Shoulder motion was 2-5 mm in each direction on average but reached 20 mm. Superior shifts resulted in coverage loss, whereas inferior shifts increased the dose to the brachial plexus. These findings were generally consistent for both IMRT and VMAT plans. Over a course of observed shifts, the dose to 99% of the CTV decreased by up to 101 cGy, and the brachial plexus dose increased by up to 72 cGy. Conclusions he position of the shoulder affects target coverage and critical structure dose, and may therefore be a concern during the setup of head and neck patients, particularly those with low neck primary disease.

Does IMRT increase the peripheral radiation dose? A comparison of treatment plans 2000 and 2010

International Nuclear Information System (INIS)

Salz, Henning; Eichner, Regina; Wiezorek, Tilo

2012-01-01

It has been reported in several papers and textbooks that IMRT treatments increase the peripheral dose in comparison with non-IMRT fields. But in clinical practice not only open fields have been used in the pre-IMRT era, but also fields with physical wedges or composed fields. The aim of this work is to test the hypothesis of increased peripheral dose when IMRT is used compared to standard conformal radiotherapy. Furthermore, the importance of the measured dose differences in clinical practice is discussed and compared with other new technologies for the cases where an increase of the peripheral dose was observed. For cancers of the head and neck, the cervix, the rectum and for the brain irradiation due to acute leukaemia, one to four plans have been calculated with IMRT or conformal standard technique (non-IMRT). In an anthropomorphic phantom the dose at a distance of 30 cm in cranio-caudal direction from the target edge was measured with TLDs using a linear accelerator Oncor registered (Siemens) for both techniques. IMRT was performed using step-and-shoot technique (7 to 11 beams), non-IMRT plans with different techniques. The results depended on the site of irradiation. For head and neck cancers IMRT resulted in an increase of 0.05 - 0.09% of the prescribed total dose (Dptv) or 40 - 70 mGy (Dptv = 65 Gy), compared to non-IMRT technique without wedges or a decrease of 0.16% (approx. 100 mGy) of the prescribed total dose compared to non-IMRT techniques with wedges. For the cervical cancer IMRT resulted in an increased dose in the periphery (+ 0.07% - 0.15% of Dptv or 30 - 70 mGy at Dptv = 45 Gy), for the rectal cancer in a dose reduction (0.21 - 0.26% of Dptv or 100 - 130 mGy at Dptv = 50 Gy) and for the brain irradiation in an increase dose (+ 0.05% of Dptv = 18 Gy or 9 mSv). In summary IMRT does not uniformly cause increased radiation dose in the periphery in the model used. It can be stated that these dose values are smaller than reported in earlier papers

Variable beam dose rate and DMLC IMRT to moving body anatomy

International Nuclear Information System (INIS)

Papiez, Lech; Abolfath, Ramin M.

2008-01-01

Derivation of formulas relating leaf speeds and beam dose rates for delivering planned intensity profiles to static and moving targets in dynamic multileaf collimator (DMLC) intensity modulated radiation therapy (IMRT) is presented. The analysis of equations determining algorithms for DMLC IMRT delivery under a variable beam dose rate reveals a multitude of possible delivery strategies for a given intensity map and for any given target motion patterns. From among all equivalent delivery strategies for DMLC IMRT treatments specific subclasses of strategies can be selected to provide deliveries that are particularly suitable for clinical applications providing existing delivery devices are used. Special attention is devoted to the subclass of beam dose rate variable DMLC delivery strategies to moving body anatomy that generalize existing techniques of such deliveries in Varian DMLC irradiation methodology to static body anatomy. Few examples of deliveries from this subclass of DMLC IMRT irradiations are investigated to illustrate the principle and show practical benefits of proposed techniques.

Variable beam dose rate and DMLC IMRT to moving body anatomy

Energy Technology Data Exchange (ETDEWEB)

Papiez, Lech; Abolfath, Ramin M. [Department of Radiation Oncology, UTSouthwestern Medical Center, Dallas, Texas 75390 (United States)

2008-11-15

Derivation of formulas relating leaf speeds and beam dose rates for delivering planned intensity profiles to static and moving targets in dynamic multileaf collimator (DMLC) intensity modulated radiation therapy (IMRT) is presented. The analysis of equations determining algorithms for DMLC IMRT delivery under a variable beam dose rate reveals a multitude of possible delivery strategies for a given intensity map and for any given target motion patterns. From among all equivalent delivery strategies for DMLC IMRT treatments specific subclasses of strategies can be selected to provide deliveries that are particularly suitable for clinical applications providing existing delivery devices are used. Special attention is devoted to the subclass of beam dose rate variable DMLC delivery strategies to moving body anatomy that generalize existing techniques of such deliveries in Varian DMLC irradiation methodology to static body anatomy. Few examples of deliveries from this subclass of DMLC IMRT irradiations are investigated to illustrate the principle and show practical benefits of proposed techniques.

A dose homogeneity and conformity evaluation between ViewRay and pinnacle-based linear accelerator IMRT treatment plans

International Nuclear Information System (INIS)

Saenz, Daniel L.; Paliwal, Bhudatt R.; Bayouth, John E.

2014-01-01

ViewRay, a novel technology providing soft-tissue imaging during radiotherapy is investigated for treatment planning capabilities assessing treatment plan dose homogeneity and conformity compared with linear accelerator plans. ViewRay offers both adaptive radiotherapy and image guidance. The combination of cobalt-60 ( 60 Co) with 0.35 Tesla magnetic resonance imaging (MRI) allows for magnetic resonance (MR)-guided intensity-modulated radiation therapy (IMRT) delivery with multiple beams. This study investigated head and neck, lung, and prostate treatment plans to understand what is possible on ViewRay to narrow focus toward sites with optimal dosimetry. The goal is not to provide a rigorous assessment of planning capabilities, but rather a first order demonstration of ViewRay planning abilities. Images, structure sets, points, and dose from treatment plans created in Pinnacle for patients in our clinic were imported into ViewRay. The same objectives were used to assess plan quality and all critical structures were treated as similarly as possible. Homogeneity index (HI), conformity index (CI), and volume receiving 60 Co ViewRay treatments planned with its Monte Carlo treatment planning software were comparable with 6 MV plans computed with convolution superposition algorithm on Pinnacle treatment planning system. (author)

A dose homogeneity and conformity evaluation between ViewRay and pinnacle-based linear accelerator IMRT treatment plans.

Science.gov (United States)

Saenz, Daniel L; Paliwal, Bhudatt R; Bayouth, John E

2014-04-01

ViewRay, a novel technology providing soft-tissue imaging during radiotherapy is investigated for treatment planning capabilities assessing treatment plan dose homogeneity and conformity compared with linear accelerator plans. ViewRay offers both adaptive radiotherapy and image guidance. The combination of cobalt-60 (Co-60) with 0.35 Tesla magnetic resonance imaging (MRI) allows for magnetic resonance (MR)-guided intensity-modulated radiation therapy (IMRT) delivery with multiple beams. This study investigated head and neck, lung, and prostate treatment plans to understand what is possible on ViewRay to narrow focus toward sites with optimal dosimetry. The goal is not to provide a rigorous assessment of planning capabilities, but rather a first order demonstration of ViewRay planning abilities. Images, structure sets, points, and dose from treatment plans created in Pinnacle for patients in our clinic were imported into ViewRay. The same objectives were used to assess plan quality and all critical structures were treated as similarly as possible. Homogeneity index (HI), conformity index (CI), and volume receiving ViewRay treatments planned with its Monte Carlo treatment planning software were comparable with 6 MV plans computed with convolution superposition algorithm on Pinnacle treatment planning system.

Peripheral doses of cranial pediatric IMRT performed with attenuator blocks

International Nuclear Information System (INIS)

Soboll, Danyel Scheidegger; Schitz, Ivette; Schelin, Hugo Reuters; Silva, Ricardo Goulart da; Viamonte, Alfredo

2011-01-01

This paper presents values of peripheral doses measured at six vital points of simulator objects which represent the ages of 2, 5 and 10 years old, submitted to a cranial IMRT procedure that applied compensator blocks interposed to 6 MV beams. The found values indicate that there is independence of dose with position of measurements and age of the patient, as the peripheral dose at the points nearest and the 2 year old simulator object where larger. The doses in thyroid reached the range of 1.4 to 2.9% of the dose prescribed in the isocenter, indicating that the peripheral doses for IMRT that employ compensator blocks can be greater than for the IMRT produced with sliding window technique

Late dysphagia after IMRT for head and neck cancer and correlation with dose–volume parameters

International Nuclear Information System (INIS)

Mortensen, Hanna R.; Jensen, Kenneth; Aksglæde, Karin; Behrens, Marie; Grau, Cai

2013-01-01

Background and purpose: Many head and neck cancer (HNC) survivors experience diminished quality of life due to radiation-induced dysphagia. The aim of this study was to investigate frequency, intensity and dose–volume dependency for late dysphagia in HNC patients treated with curative IMRT. Materials and methods: Candidates for the study were 294 patients treated with primary IMRT from 2006 to 2010; a total of 259 patients accepted to participate by answering the EORTC QLQ-C30 and H and N35 questionnaires. A total of 65 patients were further examined with modified barium swallow (MBS) and saliva collection. Data on patient, tumor and treatment characteristics were prospectively recorded in the DAHANCA database. Dose–volume histograms (DVH) of swallowing-related structures were retrospectively analyzed. Results: QoL data showed low degree of dysphagia (QoL subscales scores of 17 and below) compared to objective measures. The most frequent swallowing dysfunction was retention; penetration and aspiration was less common. In general, objective measurements and observer-assessed late dysphagia correlated with dose to pharyngeal constrictor muscles (PCM), whereas QoL endpoints correlated with DVH parameters in the glottis/supraglottic larynx. Both xerostomia and dysphagia has been reduced after introduction of IMRT. Conclusions: Radiation-induced dysphagia is still important, with a high degree of retention and penetration. Introduction of parotid-sparing IMRT has reduced the severity of dysphagia, primarily through a major reduction in xerostomia. Dose–response relationships were found for specific dysphagia endpoints

Radiotherapy through intensity modulation (IMRT). A new modality in the treatment of head and neck cancer

International Nuclear Information System (INIS)

Besa de C, Pelayo; Venencia M, Daniel

2006-01-01

Objective: To describe the treatment and evaluate the advantages of IMRT in the treatment of head and neck cancer. Material and methods: Four years ago, at the Cancer Center of the Pontificia Universidad Catolica, the IMRT technique for the treatment of head and neck tumors was implemented. The IMRT technique is based on modifying the intensity of the radiation beam through a multisheet collimator in order to produce a more exact distribution in the radiation doses. The results are evaluated with dose/ volume histograms. The distributions of doses and toxicity for tridimensional con formed therapy (CRT-3D) and IMRT are compared. Results: The distribution of the dose in the dose/volume histograms showed a better coverage of the white volume (PTV), with IMRT. The doses received by the organs under risk: salivary glands, eyes, ears and brain diminish with IMRT. The spinal marrow is protected with IMRT without dividing the treatment area, preventing points with lower dosage that could reduce control of the tumor. Conclusions: IMRT achieves a better conformation of the dose obtaining a better coverage of the tumor and higher protection of the organs under risk

Automatic learning-based beam angle selection for thoracic IMRT

International Nuclear Information System (INIS)

Amit, Guy; Marshall, Andrea; Purdie, Thomas G.; Jaffray, David A.; Levinshtein, Alex; Hope, Andrew J.; Lindsay, Patricia; Pekar, Vladimir

2015-01-01

Purpose: The treatment of thoracic cancer using external beam radiation requires an optimal selection of the radiation beam directions to ensure effective coverage of the target volume and to avoid unnecessary treatment of normal healthy tissues. Intensity modulated radiation therapy (IMRT) planning is a lengthy process, which requires the planner to iterate between choosing beam angles, specifying dose–volume objectives and executing IMRT optimization. In thorax treatment planning, where there are no class solutions for beam placement, beam angle selection is performed manually, based on the planner’s clinical experience. The purpose of this work is to propose and study a computationally efficient framework that utilizes machine learning to automatically select treatment beam angles. Such a framework may be helpful for reducing the overall planning workload. Methods: The authors introduce an automated beam selection method, based on learning the relationships between beam angles and anatomical features. Using a large set of clinically approved IMRT plans, a random forest regression algorithm is trained to map a multitude of anatomical features into an individual beam score. An optimization scheme is then built to select and adjust the beam angles, considering the learned interbeam dependencies. The validity and quality of the automatically selected beams evaluated using the manually selected beams from the corresponding clinical plans as the ground truth. Results: The analysis included 149 clinically approved thoracic IMRT plans. For a randomly selected test subset of 27 plans, IMRT plans were generated using automatically selected beams and compared to the clinical plans. The comparison of the predicted and the clinical beam angles demonstrated a good average correspondence between the two (angular distance 16.8° ± 10°, correlation 0.75 ± 0.2). The dose distributions of the semiautomatic and clinical plans were equivalent in terms of primary target volume

IMRT QA using machine learning: A multi-institutional validation.

Science.gov (United States)

Valdes, Gilmer; Chan, Maria F; Lim, Seng Boh; Scheuermann, Ryan; Deasy, Joseph O; Solberg, Timothy D

2017-09-01

To validate a machine learning approach to Virtual intensity-modulated radiation therapy (IMRT) quality assurance (QA) for accurately predicting gamma passing rates using different measurement approaches at different institutions. A Virtual IMRT QA framework was previously developed using a machine learning algorithm based on 498 IMRT plans, in which QA measurements were performed using diode-array detectors and a 3%local/3 mm with 10% threshold at Institution 1. An independent set of 139 IMRT measurements from a different institution, Institution 2, with QA data based on portal dosimetry using the same gamma index, was used to test the mathematical framework. Only pixels with ≥10% of the maximum calibrated units (CU) or dose were included in the comparison. Plans were characterized by 90 different complexity metrics. A weighted poison regression with Lasso regularization was trained to predict passing rates using the complexity metrics as input. The methodology predicted passing rates within 3% accuracy for all composite plans measured using diode-array detectors at Institution 1, and within 3.5% for 120 of 139 plans using portal dosimetry measurements performed on a per-beam basis at Institution 2. The remaining measurements (19) had large areas of low CU, where portal dosimetry has a larger disagreement with the calculated dose and as such, the failure was expected. These beams need further modeling in the treatment planning system to correct the under-response in low-dose regions. Important features selected by Lasso to predict gamma passing rates were as follows: complete irradiated area outline (CIAO), jaw position, fraction of MLC leafs with gaps smaller than 20 or 5 mm, fraction of area receiving less than 50% of the total CU, fraction of the area receiving dose from penumbra, weighted average irregularity factor, and duty cycle. We have demonstrated that Virtual IMRT QA can predict passing rates using different measurement techniques and across multiple

Monte Carlo-based QA for IMRT of head and neck cancers

Science.gov (United States)

Tang, F.; Sham, J.; Ma, C.-M.; Li, J.-S.

2007-06-01

It is well-known that the presence of large air cavity in a dense medium (or patient) introduces significant electronic disequilibrium when irradiated with megavoltage X-ray field. This condition may worsen by the possible use of tiny beamlets in intensity-modulated radiation therapy (IMRT). Commercial treatment planning systems (TPSs), in particular those based on the pencil-beam method, do not provide accurate dose computation for the lungs and other cavity-laden body sites such as the head and neck. In this paper we present the use of Monte Carlo (MC) technique for dose re-calculation of IMRT of head and neck cancers. In our clinic, a turn-key software system is set up for MC calculation and comparison with TPS-calculated treatment plans as part of the quality assurance (QA) programme for IMRT delivery. A set of 10 off-the-self PCs is employed as the MC calculation engine with treatment plan parameters imported from the TPS via a graphical user interface (GUI) which also provides a platform for launching remote MC simulation and subsequent dose comparison with the TPS. The TPS-segmented intensity maps are used as input for the simulation hence skipping the time-consuming simulation of the multi-leaf collimator (MLC). The primary objective of this approach is to assess the accuracy of the TPS calculations in the presence of air cavities in the head and neck whereas the accuracy of leaf segmentation is verified by fluence measurement using a fluoroscopic camera-based imaging device. This measurement can also validate the correct transfer of intensity maps to the record and verify system. Comparisons between TPS and MC calculations of 6 MV IMRT for typical head and neck treatments review regional consistency in dose distribution except at and around the sinuses where our pencil-beam-based TPS sometimes over-predicts the dose by up to 10%, depending on the size of the cavities. In addition, dose re-buildup of up to 4% is observed at the posterior nasopharyngeal

Superior sulcus non-small cell lung carcinoma: A comparison of IMRT and 3D-RT dosimetry.

Science.gov (United States)

Truntzer, Pierre; Antoni, Delphine; Santelmo, Nicola; Schumacher, Catherine; Falcoz, Pierre-Emmanuel; Quoix, Elisabeth; Massard, Gilbert; Noël, Georges

2016-01-01

A dosimetric study comparing intensity modulated radiotherapy (IMRT) by TomoTherapy to conformational 3D radiotherapy (3D-RT) in patients with superior sulcus non-small cell lung cancer (NSCLC). IMRT became the main technique in modern radiotherapy. However it was not currently used for lung cancers. Because of the need to increase the dose to control lung cancers but because of the critical organs surrounding the tumors, the gains obtainable with IMRT is not still demonstrated. A dosimetric comparison of the planned target and organs at risk parameters between IMRT and 3D-RT in eight patients who received preoperative or curative intent irradiation. In the patients who received at least 66 Gy, the mean V95% was significantly better with IMRT than 3D-RT (p = 0.043). IMRT delivered a lower D2% compared to 3D-RT (p = 0.043). The IH was significantly better with IMRT (p = 0.043). The lung V 5 Gy and V 13 Gy were significantly higher in IMRT than 3D-RT (p = 0.043), while the maximal dose (D max) to the spinal cord was significantly lower in IMRT (p = 0.043). The brachial plexus D max was significantly lower in IMRT than 3D-RT (p = 0.048). For patients treated with 46 Gy, no significant differences were found. Our study showed that IMRT is relevant for SS-NSCLC. In patients treated with a curative dose, it led to a reduction of the exposure of critical organs, allowing a better dose distribution in the tumor. For the patients treated with a preoperative schedule, our results provide a basis for future controlled trials to improve the histological complete response by increasing the radiation dose.

A fast dose calculation method based on table lookup for IMRT optimization

International Nuclear Information System (INIS)

Wu Qiuwen; Djajaputra, David; Lauterbach, Marc; Wu Yan; Mohan, Radhe

2003-01-01

This note describes a fast dose calculation method that can be used to speed up the optimization process in intensity-modulated radiotherapy (IMRT). Most iterative optimization algorithms in IMRT require a large number of dose calculations to achieve convergence and therefore the total amount of time needed for the IMRT planning can be substantially reduced by using a faster dose calculation method. The method that is described in this note relies on an accurate dose calculation engine that is used to calculate an approximate dose kernel for each beam used in the treatment plan. Once the kernel is computed and saved, subsequent dose calculations can be done rapidly by looking up this kernel. Inaccuracies due to the approximate nature of the kernel in this method can be reduced by performing scheduled kernel updates. This fast dose calculation method can be performed more than two orders of magnitude faster than the typical superposition/convolution methods and therefore is suitable for applications in which speed is critical, e.g., in an IMRT optimization that requires a simulated annealing optimization algorithm or in a practical IMRT beam-angle optimization system. (note)

The number of beams in IMRT-theoretical investigations and implications for single-arc IMRT

International Nuclear Information System (INIS)

Bortfeld, Thomas

2010-01-01

The first purpose of this paper is to shed some new light on the old question of selecting the number of beams in intensity-modulated radiation therapy (IMRT). The second purpose is to illuminate the related issue of discrete static beam angles versus rotational techniques, which has recently re-surfaced due to the advancement of volumetric modulated arc therapy (VMAT). A specific objective is to find analytical expressions that allow one to address the points raised above. To make the problem mathematically tractable, it is assumed that the depth dose is flat and that the lateral dose profile can be approximated by polynomials, specifically Chebyshev polynomials of the first kind, of finite degree. The application of methods known from image reconstruction then allows one to answer the first question above as follows: the required number of beams is determined by the maximum degree of the polynomials used in the approximation of the beam profiles, which is a measure of the dose variability. There is nothing to be gained by using more beams. In realistic cases, in which the variability of the lateral dose profile is restricted in several ways, the required number of beams is of the order of 10-20. The consequence of delivering the beams with a 'leaf sweep' technique during continuous rotation of the gantry, as in VMAT, is also derived in an analytical form. The main effect is that the beams fan out, but the effect near the axis of rotation is small. This result can serve as a theoretical justification of VMAT. Overall the analytical derivations in this paper, albeit based on strong simplifications, provide new insights into, and a deeper understanding of, the beam angle problem in IMRT. The decomposition of the beam profiles into well-behaved and easily deliverable smooth functions, such as Chebyshev polynomials, could be of general interest in IMRT treatment planning.

Risk profile for osteoradionecrosis of the mandible in the IMRT era

Energy Technology Data Exchange (ETDEWEB)

Studer, Gabriela; Glanzmann, Christoph [University Hospital Zurich, Department of Radiation Oncology, Head Neck Cancer Center, Zurich (Switzerland); Bredell, Marius; Studer, Stephan [University Hospital Zurich, Department of Craniomaxillofacial and Oral Surgery, Head Neck Cancer Center, Zurich (Switzerland); Huber, Gerhard [University Hospital Zurich, Department of Otorhinolaryngology, Head Neck Cancer Center, Head and Neck Surgery, Zurich (Switzerland)

2016-01-15

The risk for osteoradionecrosis (ORN) of the mandible is positively related to bone volume exposed to >∝ 60 Gy. We hypothesized that in combined treatment, surgery may also be a risk factor. The impact of mandibular surgery on ORN in locally disease-free IMRT cohorts was retrospectively analyzed. Between October 2002 and October 2013, 531 of 715 patients with oral cavity cancer (OCC), mesopharyngeal cancer (MC), or salivary gland tumor were treated with the mandible bone exposed to ∝> 60 Gy (mean follow-up, 38 months; 7-143 months). Of the 531 patients, 36 developed ORN (7 %; 1.5 % with grade 3-4). The ORN rate in definitive IMRT MC (16/227) and in postoperative IMRT OCC patients with no mandibular surgery (3/46) was 7 % each; in OCC patients with mandibular surgery the rate was 29 % (15/60, p = 0.002). Marginal or periosteal bone resection was found to be a high risk factor (39 %, vs. 7 % followed by segmental or no resection, p < 0.0001). Marginal or periosteal bone resection of the mandible was identified as the highest ORN risk factor in our IMRT cohort. (orig.) [German] Das Risiko fuer die Entwicklung einer Kiefernekrose nach Radiotherapie (Osteoradionekrose, ORN) korreliert bekanntlich mit dem Knochenvolumen, das einer Dosis von ∝> 60 Gy ausgesetzt wurde. Hypothese war, dass die Chirurgie bei kombinierten Therapien ebenfalls einen Risikofaktor darstellt. Der Einfluss chirurgischer Interventionen am Kiefer auf das Risiko einer ORN wurde in unserem lokal krankheitsfreien IMRT-Kollektiv retrospektiv analysiert. Zwischen Oktober 2002 und Oktober 2013 wurden 531/715 Patienten mit Mundhoehlenkarzinomen (OCC), Mesopharynxkarzinomen (MC) oder Speicheldruesentumoren mit Dosen > 60 Gy am Kieferknochen behandelt (mittlere Beobachtungszeit 38 Monate; Spanne 7-143 Monate). Von 531 Patienten entwickelten 36 eine ORN (7 %; 1,5 % mit Grad 3-4). Die ORN-Rate nach definitiver IMRT bei MC (16/227) und nach postoperativer IMRT bei OCC ohne chirurgischen Eingriff am

Adaptive Fuzzy-Lyapunov Controller Using Biologically Inspired Swarm Intelligence

Directory of Open Access Journals (Sweden)

Alejandro Carrasco Elizalde

2008-01-01

Full Text Available The collective behaviour of swarms produces smarter actions than those achieved by a single individual. Colonies of ants, flocks of birds and fish schools are examples of swarms interacting with their environment to achieve a common goal. This cooperative biological intelligence is the inspiration for an adaptive fuzzy controller developed in this paper. Swarm intelligence is used to adjust the parameters of the membership functions used in the adaptive fuzzy controller. The rules of the controller are designed using a computing-with-words approach called Fuzzy-Lyapunov synthesis to improve the stability and robustness of an adaptive fuzzy controller. Computing-with-words provides a powerful tool to manipulate numbers and symbols, like words in a natural language.

Evaluation of the 'dose of the day' for IMRT prostate cancer patients derived from portal dose measurements and cone-beam CT

International Nuclear Information System (INIS)

Zijtveld, Mathilda van; Dirkx, Maarten; Breuers, Marcel; Kuipers, Ruud; Heijmen, Ben

2010-01-01

treatment delivery, resulting in mean underdosages of 16% in the prostate volume. Conclusions: A method to accurately assess the 'dose of the day' was evaluated for prostate cancer patients treated with IMRT. To correct for observed dose deviations off-line dose-adaptive strategies will be developed.

Expected treatment dose construction and adaptive inverse planning optimization: Implementation for offline head and neck cancer adaptive radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Yan Di; Liang Jian [Department of Radiation Oncology, Beaumont Health System, Royal Oak, Michigan 48073 (United States)

2013-02-15

Purpose: To construct expected treatment dose for adaptive inverse planning optimization, and evaluate it on head and neck (h and n) cancer adaptive treatment modification. Methods: Adaptive inverse planning engine was developed and integrated in our in-house adaptive treatment control system. The adaptive inverse planning engine includes an expected treatment dose constructed using the daily cone beam (CB) CT images in its objective and constrains. Feasibility of the adaptive inverse planning optimization was evaluated retrospectively using daily CBCT images obtained from the image guided IMRT treatment of 19 h and n cancer patients. Adaptive treatment modification strategies with respect to the time and the number of adaptive inverse planning optimization during the treatment course were evaluated using the cumulative treatment dose in organs of interest constructed using all daily CBCT images. Results: Expected treatment dose was constructed to include both the delivered dose, to date, and the estimated dose for the remaining treatment during the adaptive treatment course. It was used in treatment evaluation, as well as in constructing the objective and constraints for adaptive inverse planning optimization. The optimization engine is feasible to perform planning optimization based on preassigned treatment modification schedule. Compared to the conventional IMRT, the adaptive treatment for h and n cancer illustrated clear dose-volume improvement for all critical normal organs. The dose-volume reductions of right and left parotid glands, spine cord, brain stem and mandible were (17 {+-} 6)%, (14 {+-} 6)%, (11 {+-} 6)%, (12 {+-} 8)%, and (5 {+-} 3)% respectively with the single adaptive modification performed after the second treatment week; (24 {+-} 6)%, (22 {+-} 8)%, (21 {+-} 5)%, (19 {+-} 8)%, and (10 {+-} 6)% with three weekly modifications; and (28 {+-} 5)%, (25 {+-} 9)%, (26 {+-} 5)%, (24 {+-} 8)%, and (15 {+-} 9)% with five weekly modifications. Conclusions

Metabolic adaptation of a human pathogen during chronic infections - a systems biology approach

DEFF Research Database (Denmark)

Thøgersen, Juliane Charlotte

modeling to uncover how human pathogens adapt to the human host. Pseudomonas aeruginosa infections in cystic fibrosis patients are used as a model system for under-­‐ standing these adaptation processes. The exploratory systems biology approach facilitates identification of important phenotypes...... by classical molecular biology approaches where genes and reactions typically are investigated in a one to one relationship. This thesis is an example of how mathematical approaches and modeling can facilitate new biologi-­‐ cal understanding and provide new surprising ideas to important biological processes....... and metabolic pathways that are necessary or related to establishment of chronic infections. Archetypal analysis showed to be successful in extracting relevant phenotypes from global gene expression da-­‐ ta. Furthermore, genome-­‐scale metabolic modeling showed to be useful in connecting the genotype...

Poster – 12: Radiological assessment of the secondary barrier shielding for IMRT treatments delivered through patient inhomogeneities

Energy Technology Data Exchange (ETDEWEB)

Haseeb, Syed Abdul; Ahmad, Syed Bilal; Mirza, Sikander Majid [Pakistan Institute of Engineering and Applied Science, Nilore, Islamabad, Pakistan, Sunnybrook Health Sciences Center, Toronto, ON, Canada & Pakistan Institute of Engineering and Applied Science, Nilore, Islamabad, Pakistan, Pakistan Institute of Engineering and Applied Science, Nilore, Islamabad (Pakistan)

2016-08-15

Purpose: To assess the impact of radiation treatment delivery through patient inhomogeneities on the secondary barrier shielding requirements in IMRT treatments using Monte Carlo Simulations. Materials and Methods: Scatter factors were calculated at a distance of 1m from the center of a virtual phantom in Geant4.10.01. Phantom (30×30×30 cm{sup 3}) was inserted with lung (30×30×8 cm{sup 3}), stainless steel (5×5×5 cm{sup 3}) and aluminum (5×5×5 cm{sup 3}) to represent the inhomogeneities. Scatter factor was defined according to the NCRP-151 recommendations and was calculated for angles of 3° to 120° with respect to the beam’s central axis. A virtual radiation source, with energy sampled from a histogram representing 6 MV FFF beam, was used for irradiation with a field size of 15×15 cm{sup 2} and SSD of 100 cm. Results: Irradiation through the inhomogeneity affects the patient scattered dose. For high Z material inhomogeneities the scattered dose is reduced due to significant attenuation of the primary radiation. On the other hand if the inhomogeneity is a low Z material such as lung the scattered dose is higher by a maximum of 26%. The average increase in scatter factors for the lung phantom was 17% for angles between 3° and 63° compared to the homogeneous water phantom. Conclusions: In IMRT type treatments delivered through low density patient inhomogeneities (lung) the scattered dose increases significantly. Considering a large proportion of patients receiving radiation therapy for lung cancers the increase in the scattered dose should be incorporated in the shielding calculations for the secondary barriers.

A Clinical Concept for Interfractional Adaptive Radiation Therapy in the Treatment of Head and Neck Cancer

Energy Technology Data Exchange (ETDEWEB)

Jensen, Alexandra D., E-mail: Alexandra.Jensen@med.uni-heidelberg.de [Department of Radiation Oncology, University of Heidelberg, Heidelberg (Germany); Nill, Simeon [Department of Medical Physics, German Cancer Research Centre (DKFZ), Heidelberg (Germany); Huber, Peter E. [Clinical Co-Operation Unit Radiation Oncology, German Cancer Research Centre (DKFZ), Heidelberg (Germany); Bendl, Rolf [Department of Medical Physics, German Cancer Research Centre (DKFZ), Heidelberg (Germany); Debus, Juergen; Muenter, Marc W. [Department of Radiation Oncology, University of Heidelberg, Heidelberg (Germany)

2012-02-01

Purpose: To present an approach to fast, interfractional adaptive RT in intensity-modulated radiation therapy (IMRT) of head and neck tumors in clinical routine. Ensuring adequate patient position throughout treatment proves challenging in high-precision RT despite elaborate immobilization. Because of weight loss, treatment plans must be adapted to account for requiring supportive therapy incl. feeding tube or parenteral nutrition without treatment breaks. Methods and Materials: In-room CT position checks are used to create adapted IMRT treatment plans by stereotactic correlation to the initial setup, and volumes are adapted to the new geometry. New IMRT treatment plans are prospectively created on the basis of position control scans using the initial optimization parameters in KonRad without requiring complete reoptimization and thus facilitating quick replanning in daily routine. Patients treated for squamous cell head and neck cancer (SCCHN) in 2006-2007 were evaluated as to necessity/number of replannings, weight loss, dose, and plan parameters. Results: Seventy-two patients with SCCHN received IMRT to the primary site and lymph nodes (median dose 70.4 Gy). All patients received concomitant chemotherapy requiring supportive therapy by feeding tube or parenteral nutrition. Median weight loss was 7.8 kg, median volume loss was approximately 7%. Fifteen of 72 patients required adaptation of their treatment plans at least once. Target coverage was improved by up to 10.7% (median dose). The increase of dose to spared parotid without replanning was 11.7%. Replanning including outlining and optimization was feasible within 2 hours for each patient, and treatment could be continued without any interruptions. Conclusion: To preserve high-quality dose application, treatment plans must be adapted to anatomical changes. Replanning based on position control scans therefore presents a practical approach in clinical routine. In the absence of clinically usable online

A Clinical Concept for Interfractional Adaptive Radiation Therapy in the Treatment of Head and Neck Cancer

International Nuclear Information System (INIS)

Jensen, Alexandra D.; Nill, Simeon; Huber, Peter E.; Bendl, Rolf; Debus, Jürgen; Münter, Marc W.

2012-01-01

Purpose: To present an approach to fast, interfractional adaptive RT in intensity-modulated radiation therapy (IMRT) of head and neck tumors in clinical routine. Ensuring adequate patient position throughout treatment proves challenging in high-precision RT despite elaborate immobilization. Because of weight loss, treatment plans must be adapted to account for requiring supportive therapy incl. feeding tube or parenteral nutrition without treatment breaks. Methods and Materials: In-room CT position checks are used to create adapted IMRT treatment plans by stereotactic correlation to the initial setup, and volumes are adapted to the new geometry. New IMRT treatment plans are prospectively created on the basis of position control scans using the initial optimization parameters in KonRad without requiring complete reoptimization and thus facilitating quick replanning in daily routine. Patients treated for squamous cell head and neck cancer (SCCHN) in 2006–2007 were evaluated as to necessity/number of replannings, weight loss, dose, and plan parameters. Results: Seventy-two patients with SCCHN received IMRT to the primary site and lymph nodes (median dose 70.4 Gy). All patients received concomitant chemotherapy requiring supportive therapy by feeding tube or parenteral nutrition. Median weight loss was 7.8 kg, median volume loss was approximately 7%. Fifteen of 72 patients required adaptation of their treatment plans at least once. Target coverage was improved by up to 10.7% (median dose). The increase of dose to spared parotid without replanning was 11.7%. Replanning including outlining and optimization was feasible within 2 hours for each patient, and treatment could be continued without any interruptions. Conclusion: To preserve high-quality dose application, treatment plans must be adapted to anatomical changes. Replanning based on position control scans therefore presents a practical approach in clinical routine. In the absence of clinically usable online

A clinical concept for interfractional adaptive radiation therapy in the treatment of head and neck cancer.

Science.gov (United States)

Jensen, Alexandra D; Nill, Simeon; Huber, Peter E; Bendl, Rolf; Debus, Jürgen; Münter, Marc W

2012-02-01

To present an approach to fast, interfractional adaptive RT in intensity-modulated radiation therapy (IMRT) of head and neck tumors in clinical routine. Ensuring adequate patient position throughout treatment proves challenging in high-precision RT despite elaborate immobilization. Because of weight loss, treatment plans must be adapted to account for requiring supportive therapy incl. feeding tube or parenteral nutrition without treatment breaks. In-room CT position checks are used to create adapted IMRT treatment plans by stereotactic correlation to the initial setup, and volumes are adapted to the new geometry. New IMRT treatment plans are prospectively created on the basis of position control scans using the initial optimization parameters in KonRad without requiring complete reoptimization and thus facilitating quick replanning in daily routine. Patients treated for squamous cell head and neck cancer (SCCHN) in 2006-2007 were evaluated as to necessity/number of replannings, weight loss, dose, and plan parameters. Seventy-two patients with SCCHN received IMRT to the primary site and lymph nodes (median dose 70.4 Gy). All patients received concomitant chemotherapy requiring supportive therapy by feeding tube or parenteral nutrition. Median weight loss was 7.8 kg, median volume loss was approximately 7%. Fifteen of 72 patients required adaptation of their treatment plans at least once. Target coverage was improved by up to 10.7% (median dose). The increase of dose to spared parotid without replanning was 11.7%. Replanning including outlining and optimization was feasible within 2 hours for each patient, and treatment could be continued without any interruptions. To preserve high-quality dose application, treatment plans must be adapted to anatomical changes. Replanning based on position control scans therefore presents a practical approach in clinical routine. In the absence of clinically usable online correction methods, this approach allows significant

Clinical Evaluation of Direct Aperture Optimization When Applied to Head-And-Neck IMRT

International Nuclear Information System (INIS)

Jones, Stephen; Williams, Matthew

2008-01-01

Direct Machine Parameter Optimization (DMPO) is a leaf segmentation program released as an optional item of the Pinnacle planning system (Philips Radiation Oncology Systems, Milpitas, CA); it is based on the principles of direct aperture optimization where the size, shape, and weight of individual segments are optimized to produce an intensity modulated radiation treatment (IMRT) plan. In this study, we compare DMPO to the traditional method of IMRT planning, in which intensity maps are optimized prior to conversion into deliverable multileaf collimator (MLC) apertures, and we determine if there was any dosimetric improvement, treatment efficiency gain, or planning advantage provided by the use of DMPO. Eleven head-and-neck patients treated with IMRT had treatment plans generated using each optimization method. For each patient, the same planning parameters were used for each optimization method. All calculations were performed using Pinnacle version 7.6c software and treatments were delivered using a step-and-shoot IMRT method on a Varian 2100EX linear accelerator equipped with a 120-leaf Millennium MLC (Varian Medical Systems, Palo Alto, CA). Each plan was assessed based on the calculation time, a conformity index, the composite objective value used in the optimization, the number of segments, monitor units (MUs), and treatment time. The results showed DMPO to be superior to the traditional optimization method in all areas. Considerable advantages were observed in the dosimetric quality of DMPO plans, which also required 32% less time to calculate, 42% fewer MUs, and 35% fewer segments than the conventional optimization method. These reductions translated directly into a 29% decrease in treatment times. While considerable gains were observed in planning and treatment efficiency, they were specific to our institution, and the impact of direct aperture optimization on plan quality and workflow will be dependent on the planning parameters, planning system, and

Intensity-modulated radiation therapy (IMRT) of cancers of the head and neck: Comparison of split-field and whole-field techniques

International Nuclear Information System (INIS)

Dabaja, Bouthaina; Salehpour, Mohammad R.; Rosen, Isaac; Tung, Sam; Morrison, William H.; Ang, K. Kian; Garden, Adam S.

2005-01-01

Background: Oropharynx cancers treated with intensity-modulated radiation (IMRT) are often treated with a monoisocentric or half-beam technique (HB). IMRT is delivered to the primary tumor and upper neck alone, while the lower neck is treated with a matching anterior beam. Because IMRT can treat the entire volume or whole field (WF), the primary aim of the study was to test the ability to plan cases using WF-IMRT while obtaining an optimal plan and acceptable dose distribution and also respecting normal critical structures. Methods and Materials: Thirteen patients with early-stage oropharynx cancers had treatment plans created with HB-IMRT and WF-IMRT techniques. Plans were deemed acceptable if they met the planning guidelines (as defined or with minor violations) of the Radiation Therapy Oncology Group protocol H0022. Comparisons included coverage to the planning target volume (PTV) of the primary (PTV66) and subclinical disease (PTV54). We also compared the ability of both techniques to respect the tolerance of critical structures. Results: The volume of PTV66 treated to >110% was less in 9 of the 13 patients in the WF-IMRT plan as compared to the HB-IMRT plan. The calculated mean volume receiving >110% for all patients planned with WF-IMRT was 9.3% (0.8%-25%) compared to 13.7% (2.7%-23.7%) with HB-IMRT (p = 0.09). The PTV54 volume receiving >110% of dose was less in 10 of the 13 patients planned with WF-IMRT compared to HB-IMRT. The mean doses to all critical structures except the larynx were comparable with each plan. The mean dose to the larynx was significantly less (p = 0.001), 18.7 Gy, with HB-IMRT compared to 47 Gy with WF-IMRT. Conclusions: Regarding target volumes, acceptable plans can be generated with either WF-IMRT or HB-IMRT. WF-IMRT has an advantage if uncertainty at the match line is a concern, whereas HB-IMRT, particularly in cases not involving the base of tongue, can achieve much lower doses to the larynx

A qualitative assessment of climate adaptation options and some estimates of adaptation costs

International Nuclear Information System (INIS)

Van Ierland, E.C.; De Bruin, K.; Dellink, R.B.; Ruijs, A.

2006-12-01

The Routeplanner project aims to provide a 'systematic assessment' of potential adaptation options to respond to climate change in the Netherlands in connection to spatial planning. The study is the result of a policy oriented project that took place between May and September 2006. The aim of the current study is to provide a 'qualitative assessment' of the direct and indirect effects of adaptation options and to provide an assessment of some of the costs and benefits of adaptation options. The present report presents and summarizes the results of all phases of the study: an inventory of adaptation options, a qualitative assessment of the effects of the adaptation options for the Netherlands in the long run, a database which allows to rank the various options according to a set of criteria and a relative ranking on the basis of these criteria. Finally, the report also contains the best available information on costs and benefits of various adaptation options.

BENEFITS OF INTENSITY-MODULATED RADIOTHERAPY (IMRT IN PATIENTS WITH HEAD AND NECK MALIGNANCIES- A SINGLE INSTITUTION EXPERIENCE

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Sherry Seasor Abraham

2017-09-01

Full Text Available BACKGROUND Radiotherapy and surgery are the principal curative modalities in treatment of head and neck cancer. Conventional twodimensional and three-dimensional conformal radiotherapy result in significant side effects and altered quality of life. IntensityModulated Radiotherapy (IMRT can spare the normal tissues, while delivering a curative dose to the tumour-bearing tissues. This study reveals the role of IMRT in head and neck cancer in view of normal tissue sparing with good tumour control. MATERIALS AND METHODS Radical radiotherapy was given using linear accelerator up to a dose of 66 to 70 gray in 30 to 33 fractions (intensity-modulated radiotherapy with simultaneous integrated boost over 6 to 7 weeks to 56 eligible patients. Concurrent cisplatin was given to patients with locally-advanced disease up to a dose of 40 mg/m2 weekly once along with radiation. The patients were monitored weekly once during the treatment for acute skin and mucosal toxicities using the RTOG scoring criteria. After the treatment, locoregional response was assessed and recorded at 6 weeks, 3 months and 6 months intervals. RESULTS Severe skin toxicity (grade III or more was seen in approximately 7% patients. Severe mucosal toxicity (grade III or more was seen in approximately 80% of patients. IMRT technique showed better skin sparing compared to 3D conformal radiotherapy. Severe mucosal toxicity was slightly higher in this study due to the simultaneous integrated boost technique used for dose intensification to the mucosa, which results in better primary tumour control. At the end of 6 months, 75% patients achieved locoregional control and residual/recurrent disease was seen in 25% of patients. IMRT offered good locoregional control with less skin toxicity and acceptable mucosal toxicity. The results were similar to the previous study reports using IMRT. CONCLUSION IMRT is a better treatment option in locally-advanced head and neck malignancies providing good

Assessing and adapting to climate change in the Blue Mountains, Oregon (USA: Overview, biogeography, and climate

Directory of Open Access Journals (Sweden)

Jessica E. Halofsky

2018-04-01

Full Text Available The Blue Mountains Adaptation Partnership (BMAP was established to increase climate change awareness, assess vulnerability to climate change, and develop science-based adaptation strategies for national forest lands in the Blue Mountains region of northeast Oregon and southeast Washington (USA. The BMAP process included (1 development of a science-management partnership, (2 a vulnerability assessment of the effects of climate change on natural resources and infrastructure, (3 development of adaptation options that will help reduce negative effects of climate change and assist the transition of biological systems and management to a changing climate, and (4 ongoing dialogue and activities related to climate change in the Blue Mountains region. This special issue of Climate Services describes social context and climate change vulnerability assessments for water use and infrastructure, vegetation, and riparian ecosystems of the Blue Mountains region, as well as adaptation options for natural resource management. This manuscript introduces the special issue, describing the management, biogeographic, and climatic context for the Blue Mountains region; the climate change vulnerability assessment and adaptation process used in BMAP; and the potential applications of the information described in the special issue. Although the institutional focus of information in the special issue is U.S. Forest Service lands (Malheur, Umatilla, and Wallowa-Whitman National Forests, the broader social context and adaptation options should be applicable to other lands throughout this region and the Pacific Northwest. Keywords: Climate change adaptation, Pacific Northwest, Resource management, Vulnerability assessment, Blue Mountains

Implementation of a Monte Carlo based inverse planning model for clinical IMRT with MCNP code

International Nuclear Information System (INIS)

He, Tongming Tony

2003-01-01

Inaccurate dose calculations and limitations of optimization algorithms in inverse planning introduce systematic and convergence errors to treatment plans. This work was to implement a Monte Carlo based inverse planning model for clinical IMRT aiming to minimize the aforementioned errors. The strategy was to precalculate the dose matrices of beamlets in a Monte Carlo based method followed by the optimization of beamlet intensities. The MCNP 4B (Monte Carlo N-Particle version 4B) code was modified to implement selective particle transport and dose tallying in voxels and efficient estimation of statistical uncertainties. The resulting performance gain was over eleven thousand times. Due to concurrent calculation of multiple beamlets of individual ports, hundreds of beamlets in an IMRT plan could be calculated within a practical length of time. A finite-sized point source model provided a simple and accurate modeling of treatment beams. The dose matrix calculations were validated through measurements in phantoms. Agreements were better than 1.5% or 0.2 cm. The beamlet intensities were optimized using a parallel platform based optimization algorithm that was capable of escape from local minima and preventing premature convergence. The Monte Carlo based inverse planning model was applied to clinical cases. The feasibility and capability of Monte Carlo based inverse planning for clinical IMRT was demonstrated. Systematic errors in treatment plans of a commercial inverse planning system were assessed in comparison with the Monte Carlo based calculations. Discrepancies in tumor doses and critical structure doses were up to 12% and 17%, respectively. The clinical importance of Monte Carlo based inverse planning for IMRT was demonstrated

Tolerance limits and methodologies for IMRT measurement-based verification QA: Recommendations of AAPM Task Group No. 218.

Science.gov (United States)

Miften, Moyed; Olch, Arthur; Mihailidis, Dimitris; Moran, Jean; Pawlicki, Todd; Molineu, Andrea; Li, Harold; Wijesooriya, Krishni; Shi, Jie; Xia, Ping; Papanikolaou, Nikos; Low, Daniel A

2018-04-01

Patient-specific IMRT QA measurements are important components of processes designed to identify discrepancies between calculated and delivered radiation doses. Discrepancy tolerance limits are neither well defined nor consistently applied across centers. The AAPM TG-218 report provides a comprehensive review aimed at improving the understanding and consistency of these processes as well as recommendations for methodologies and tolerance limits in patient-specific IMRT QA. The performance of the dose difference/distance-to-agreement (DTA) and γ dose distribution comparison metrics are investigated. Measurement methods are reviewed and followed by a discussion of the pros and cons of each. Methodologies for absolute dose verification are discussed and new IMRT QA verification tools are presented. Literature on the expected or achievable agreement between measurements and calculations for different types of planning and delivery systems are reviewed and analyzed. Tests of vendor implementations of the γ verification algorithm employing benchmark cases are presented. Operational shortcomings that can reduce the γ tool accuracy and subsequent effectiveness for IMRT QA are described. Practical considerations including spatial resolution, normalization, dose threshold, and data interpretation are discussed. Published data on IMRT QA and the clinical experience of the group members are used to develop guidelines and recommendations on tolerance and action limits for IMRT QA. Steps to check failed IMRT QA plans are outlined. Recommendations on delivery methods, data interpretation, dose normalization, the use of γ analysis routines and choice of tolerance limits for IMRT QA are made with focus on detecting differences between calculated and measured doses via the use of robust analysis methods and an in-depth understanding of IMRT verification metrics. The recommendations are intended to improve the IMRT QA process and establish consistent, and comparable IMRT QA

Incorporating prior knowledge into beam orientation optimization in IMRT

International Nuclear Information System (INIS)

Pugachev, Andrei M.S.; Lei Xing

2002-01-01

Purpose: Selection of beam configuration in currently available intensity-modulated radiotherapy (IMRT) treatment planning systems is still based on trial-and-error search. Computer beam orientation optimization has the potential to improve the situation, but its practical implementation is hindered by the excessive computing time associated with the calculation. The purpose of this work is to provide an effective means to speed up the beam orientation optimization by incorporating a priori geometric and dosimetric knowledge of the system and to demonstrate the utility of the new algorithm for beam placement in IMRT. Methods and Materials: Beam orientation optimization was performed in two steps. First, the quality of each possible beam orientation was evaluated using beam's-eye-view dosimetrics (BEVD) developed in our previous study. A simulated annealing algorithm was then employed to search for the optimal set of beam orientations, taking into account the BEVD scores of different incident beam directions. During the calculation, sampling of gantry angles was weighted according to the BEVD score computed before the optimization. A beam direction with a higher BEVD score had a higher probability of being included in the trial configuration, and vice versa. The inclusion of the BEVD weighting in the stochastic beam angle sampling process made it possible to avoid spending valuable computing time unnecessarily at 'bad' beam angles. An iterative inverse treatment planning algorithm was used for beam intensity profile optimization during the optimization process. The BEVD-guided beam orientation optimization was applied to an IMRT treatment of paraspinal tumor. The advantage of the new optimization algorithm was demonstrated by comparing the calculation with the conventional scheme without the BEVD weighting in the beam sampling. Results: The BEVD tool provided useful guidance for the selection of the potentially good directions for the beams to incident and was used

Automated IMRT planning in Pinnacle. A study in head-and-neck cancer

International Nuclear Information System (INIS)

Kusters, J.M.A.M.; Kollenburg, P.G.M. van; Kunze-Busch, M.C.; Wendling, M.; Dijkema, T.; Kaanders, J.H.A.M.; Bzdusek, K.; Kumar, P.

2017-01-01

This study evaluates the performance and planning efficacy of the Auto-Planning (AP) module in the clinical version of Pinnacle 9.10 (Philips Radiation Oncology Systems, Fitchburg, WI, USA). Twenty automated intensity-modulated radiotherapy (IMRT) plans were compared with the original manually planned clinical IMRT plans from patients with oropharyngeal cancer. Auto-Planning with IMRT offers similar coverage of the planning target volume as the original manually planned clinical plans, as well as better sparing of the contralateral parotid gland, contralateral submandibular gland, larynx, mandible, and brainstem. The mean dose of the contralateral parotid gland and contralateral submandibular gland could be reduced by 2.5 Gy and 1.7 Gy on average. The number of monitor units was reduced with an average of 143.9 (18%). Hands-on planning time was reduced from 1.5-3 h to less than 1 h. The Auto-Planning module was able to produce clinically acceptable head and neck IMRT plans with consistent quality. (orig.) [de

Fast online Monte Carlo-based IMRT planning for the MRI linear accelerator

Science.gov (United States)

Bol, G. H.; Hissoiny, S.; Lagendijk, J. J. W.; Raaymakers, B. W.

2012-03-01

The MRI accelerator, a combination of a 6 MV linear accelerator with a 1.5 T MRI, facilitates continuous patient anatomy updates regarding translations, rotations and deformations of targets and organs at risk. Accounting for these demands high speed, online intensity-modulated radiotherapy (IMRT) re-optimization. In this paper, a fast IMRT optimization system is described which combines a GPU-based Monte Carlo dose calculation engine for online beamlet generation and a fast inverse dose optimization algorithm. Tightly conformal IMRT plans are generated for four phantom cases and two clinical cases (cervix and kidney) in the presence of the magnetic fields of 0 and 1.5 T. We show that for the presented cases the beamlet generation and optimization routines are fast enough for online IMRT planning. Furthermore, there is no influence of the magnetic field on plan quality and complexity, and equal optimization constraints at 0 and 1.5 T lead to almost identical dose distributions.

Automated IMRT planning in Pinnacle : A study in head-and-neck cancer.

Science.gov (United States)

Kusters, J M A M; Bzdusek, K; Kumar, P; van Kollenburg, P G M; Kunze-Busch, M C; Wendling, M; Dijkema, T; Kaanders, J H A M

2017-12-01

This study evaluates the performance and planning efficacy of the Auto-Planning (AP) module in the clinical version of Pinnacle 9.10 (Philips Radiation Oncology Systems, Fitchburg, WI, USA). Twenty automated intensity-modulated radiotherapy (IMRT) plans were compared with the original manually planned clinical IMRT plans from patients with oropharyngeal cancer. Auto-Planning with IMRT offers similar coverage of the planning target volume as the original manually planned clinical plans, as well as better sparing of the contralateral parotid gland, contralateral submandibular gland, larynx, mandible, and brainstem. The mean dose of the contralateral parotid gland and contralateral submandibular gland could be reduced by 2.5 Gy and 1.7 Gy on average. The number of monitor units was reduced with an average of 143.9 (18%). Hands-on planning time was reduced from 1.5-3 h to less than 1 h. The Auto-Planning module was able to produce clinically acceptable head and neck IMRT plans with consistent quality.

Dosimetric comparison of RapidArc with fixed gantry dynamic IMRT for loco-regionally advanced nasopharyngeal carcinoma

International Nuclear Information System (INIS)

Wu Hao; Han Shukui; Sun Yan; Jiang Fan

2010-01-01

Objective: To compare the dosimetric difference of RapidArc and fixed gantry angle dynamic IMRT (dIMRT) for loco-regionally advanced nasopharyngeal carcinoma. Methods: Ten previously treated patients with loco-regionally advanced nasopharyngeal carcinoma were replanned with RapidArc and dIMRT, respectively. The prescription dose was GTV 70 Gy/33 f and PTV 60 Gy/33 f. All plans met the requirement: 95% of PTV was covered by 60 Gy. Dose-volume histogram data, isodose distribution, monitor units, and treatment time were compared. Results: Dose distribution has no significant difference between the two techniques. RapidArc reduced the dose of the brainstem, mandible, and other normal tissues compared with dIMRT. Mean monitor units were 589.5 and 1381.0 for RapidArc and dIMRT (reduced by 57% relatively). Mean treatment time was 2.33 min and 7.82 min for RapidArc and dIMRT (reduced by 70% relatively). Conclusions: Compared with dIMRT, RapidArc achieves equal target coverage and OAR sparing while using fewer monitor units and less time during radiotherapy for patient with loco-regionally advanced nasopharyngeal carcinoma. (authors)

Effect of photon-beam energy on VMAT and IMRT treatment plan quality and dosimetric accuracy for advanced prostate cancer

Energy Technology Data Exchange (ETDEWEB)

Pasler, Marlies; Wirtz, Holger; Lutterbach, Johannes [Lake Constance Radiation Oncology Center Singen-Friedrichshafen, Singen (Germany); Georg, Dietmar [Medical Univ. Vienna (Austria). Dept. of Radiotherapy

2011-12-15

The goal of the research was to evaluate treatment plan quality and dosimetric accuracy of volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) plans using 6, 10, and 15 MV photon beams for prostate cancer including lymph nodes. In this retrospective study, VMAT and IMRT plans were generated with the Pinnacle {sup copyright} treatment planning system (TPS) (V9.0) for 10 prostate cancer cases. Each plan consisted of two target volumes: PTV{sub B} included the prostate bed, PTV{sub PC+LN} contained PTV{sub B} and lymph nodes. For plan evaluation statistics, the homogeneity index, conformity index, mean doses, and near-max doses to organs at risk (OAR) were analyzed. Treatment time and number of monitor units were assessed to compare delivery efficiency. Dosimetric plan verification was performed with a 2D ionization chamber array placed in a full scatter phantom. Results: No differences were found for target and OAR parameters in low and high energy photon beam plans for both VMAT and IMRT. A slightly higher low dose volume was detected for 6 MV VMAT plans (normal tissue: D{sub mean} = 16.47 Gy) compared to 10 and 15 MV VMAT plans (D{sub mean} = 15.90 Gy and 15.74 Gy, respectively), similar to the findings in IMRT. In VMAT, > 96% of detector points passed the 3%/ 3 mm {gamma} criterion; marginally better accuracy was found in IMRT (> 97%). Conclusion: For static and rotational IMRT, 15 MV photons did not show advantages over 6 and 10 MV high energy photon beams in large volume pelvic plans. For the investigated TPS and linac combination, 10 MV photon beams can be used as the general purpose energy for intensity modulation.

Biology Reflective Assessment Curriculum

Science.gov (United States)

Bayley, Cheryl Ann

Often students and educators view assessments as an obligation and finality for a unit. In the current climate of high-stakes testing and accountability, the balance of time, resources and emphasis on students' scores related to assessment have been slanted considerably toward the summative side. This tension between assessment for accountability and assessment to inform teaching strains instruction and educators' ability to use that information to design learning opportunities that help students develop deeper conceptual understanding. A substantive body of research indicates that formative and reflective assessment can significantly improve student learning. Biology Reflective Assessment Curriculum (BRAC) examines support provided for high school science students through assessment practices. This investigation incorporates the usage of reflective assessments as a guiding practice for differentiated instruction and student choice. Reflective assessment is a metacognitive strategy that promotes self-monitoring and evaluation. The goals of the curriculum are to promote self-efficacy and conceptual understanding in students learning biology through developing their metacognitive awareness. BRAC was implemented in a high school biology classroom. Data from assessments, metacognitive surveys, self-efficacy surveys, reflective journals, student work, a culminating task and field notes were used to evaluate the effectiveness of the curriculum. The results suggest that students who develop their metacognitive skills developed a deeper conceptual understanding and improved feelings of self-efficacy when they were engaged in a reflective assessment unit embedded with student choice. BRAC is a tool for teachers to use assessments to assist students in becoming metacognitive and to guide student choice in learning opportunities.

Clinical and dosimetric evaluation of RapidArc versus standard sliding window IMRT in the treatment of head and neck cancer

Energy Technology Data Exchange (ETDEWEB)

Smet, Stephanie; Lambrecht, Maarten; Vanstraelen, Bianca; Nuyts, Sandra [University Hospitals Leuven, Department of Radiation Oncology, Leuven (Belgium)

2014-08-29

Several planning studies have already proven the substantial dosimetric advantages of RapidArc (RA) over standard intensity-modulated radiotherapy. We retrospectively compared RapidArc and standard sliding window IMRT (swIMRT) in locally advanced head and neck cancer, looking both at dosimetrics as well as toxicity and outcome. CT datasets of 78 patients treated with swIMRT and 79 patients treated with RA were included. To compare the resulting dose distributions, the dose-volume parameters were evaluated for the planning target volumes (PTVs), clinical target volumes (CTVs), and organs at risk (OARs), and the number of MU were calculated. Acute toxicity was assessed by the Common Toxicity Criteria version 3.0. PTV coverage with the 95 % isodose was slightly better for RA. Dose distribution has proven to be significantly more homogenous with RA and led to a reduction of 62 % in MU with better OAR sparing. As for toxicity, more grade 3 mucositis and dysphagia was observed for swIMRT, though we observed more grade 3 dermatitis for RA. In our retrospective analysis, RA had better target coverage and better sparing of the OAR. Overall, the grade of acute toxicity was lower for RA than for swIMRT for the same types of tumor locations, except for the grade of dermatitis. (orig.) [German] Mehrere Studien haben die dosimetrische Ueberlegenheit der RapidArc (RA) gegenueber der intensitaetsmodulierten Standard-Radiotherapie (IMRT) bereits gezeigt. In unserer Studie verglichen wir retrospektiv die RapidArc und die dynamische (''standard sliding window'') IMRT (swIMRT) bei lokal fortgeschrittenen Kopf-Hals-Karzinomen sowohl hinsichtlich dosimetrischer Daten als auchEffektivitaet und Toxizitaet. Die CT-Datenanalysen von 78 Patienten, die mit swIMRT behandelt wurden, und von 79 Patienten, welche RA erhalten hatten, wurden in die Studie aufgenommen. Um die darauf resultierenden applizierten Dosen vergleichen zu koennen, wurden die Dosis-Volumen-Parameter fuer

SU-E-J-125: A Novel IMRT Planning Technique to Spare Sacral Bone Marrow in Pelvic Cancer Patients

Energy Technology Data Exchange (ETDEWEB)

McGuire, S; Bhatia, S; Sun, W; Menda, Y; Ponto, L; Gross, B; Buatti, J [University Of Iowa, Iowa City, IA (United States)

2015-06-15

Purpose: Develop an IMRT planning technique that can preferentially spare sacral bone marrow for pelvic cancer patients. Methods: Six pelvic cancer patients (two each with anal, cervical, and rectal cancer) were enrolled in an IRB approved protocol to obtain FLT PET images at simulation, during, and post chemoradiation therapy. Initially, conventional IMRT plans were created to maintain target coverage and reduce dose to OARs such as bladder, bowel, rectum, and femoral heads. Simulation FLT PET images were used to create IMRT plans to spare bone marrow identified as regions with SUV of 2 or greater (IMRT-BMS) within the pelvic bones from top of L3 to 5mm below the greater trochanter without compromising PTV coverage or OAR sparing when compared to the initial IMRT plan. IMRT-BMS plans used 8–10 beam angles that surrounded the subject. These plans were used for treatment. Retrospectively, the same simulation FLT PET images were used to create IMRT plans that spared bone marrow located in the sacral pelvic bone region (IMRT-FAN) also without compromising PTV coverage or OAR sparing. IMRT-FAN plans used 16 beam angles every 12° anteriorly from 90° – 270°. Optimization objectives for the sacral bone marrow avoidance region were weighted to reduce ≥V10. Results: IMRT-FAN reduced dose to the sacral bone marrow for all six subjects. The average V5, V10, V20, and V30 differences from the IMRT-BMS plan were −2.2 ± 1.7%, −11.4 ± 3.6%, −17.6 ± 5.1%, and −19.1 ± 8.1% respectively. Average PTV coverage change was 0.5% ± 0.8% from the conventional IMRT plan. Conclusion: An IMRT planning technique that uses beams from the anterior and lateral directions reduced the volume of sacral bone marrow that receives ≤10Gy while maintaining PTV coverage and OAR sparing. Additionally, the volume of sacral bone marrow that received 20 or 30 Gy was also reduced.

Adaptable data management for systems biology investigations

Directory of Open Access Journals (Sweden)

Burdick David

2009-03-01

Full Text Available Abstract Background Within research each experiment is different, the focus changes and the data is generated from a continually evolving barrage of technologies. There is a continual introduction of new techniques whose usage ranges from in-house protocols through to high-throughput instrumentation. To support these requirements data management systems are needed that can be rapidly built and readily adapted for new usage. Results The adaptable data management system discussed is designed to support the seamless mining and analysis of biological experiment data that is commonly used in systems biology (e.g. ChIP-chip, gene expression, proteomics, imaging, flow cytometry. We use different content graphs to represent different views upon the data. These views are designed for different roles: equipment specific views are used to gather instrumentation information; data processing oriented views are provided to enable the rapid development of analysis applications; and research project specific views are used to organize information for individual research experiments. This management system allows for both the rapid introduction of new types of information and the evolution of the knowledge it represents. Conclusion Data management is an important aspect of any research enterprise. It is the foundation on which most applications are built, and must be easily extended to serve new functionality for new scientific areas. We have found that adopting a three-tier architecture for data management, built around distributed standardized content repositories, allows us to rapidly develop new applications to support a diverse user community.

Quality assurance device for four-dimensional IMRT or SBRT and respiratory gating using patient-specific intrafraction motion kernels.

Science.gov (United States)

Nelms, Benjamin E; Ehler, Eric; Bragg, Henry; Tomé, Wolfgang A

2007-09-17

Emerging technologies such as four-dimensional computed tomography (4D CT) and implanted beacons are expected to allow clinicians to accurately model intrafraction motion and to quantitatively estimate internal target volumes (ITVs) for radiation therapy involving moving targets. In the case of intensity-modulated (IMRT) and stereotactic body radiation therapy (SBRT) delivery, clinicians must consider the interplay between the temporal nature of the modulation and the target motion within the ITV. A need exists for a 4D IMRT/SBRT quality assurance (QA) device that can incorporate and analyze customized intrafraction motion as it relates to dose delivery and respiratory gating. We built a 4D IMRT/SBRT prototype device and entered (X, Y, Z)(T) coordinates representing a motion kernel into a software application that 1. transformed the kernel into beam-specific two-dimensional (2D) motion "projections," 2. previewed the motion in real time, and 3. drove a recision X-Y motorized device that had, atop it, a mounted planar IMRT QA measurement device. The detectors that intersected the target in the beam's-eye-view of any single phase of the breathing cycle (a small subset of all the detectors) were defined as "target detectors" to be analyzed for dose uniformity between multiple fractions. Data regarding the use of this device to quantify dose variation fraction-to-fraction resulting from target motion (for several delivery modalities and with and without gating) have been recently published. A combined software and hardware solution for patient-customized 4D IMRT/SBRT QA is an effective tool for assessing IMRT delivery under conditions of intrafraction motion. The 4D IMRT QA device accurately reproduced the projected motion kernels for all beam's-eye-view motion kernels. This device has been proved to, effectively quantify the degradation in dose uniformity resulting from a moving target within a static planning target volume, and, integrate with a commercial

Quality assurance device for four‐dimensional IMRT or SBRT and respiratory gating using patient‐specific intrafraction motion kernels

Science.gov (United States)

Ehler, Eric; Bragg, Henry; Tomé, Wolfgang A.

2007-01-01

Emerging technologies such as four‐dimensional computed tomography (4D CT) and implanted beacons are expected to allow clinicians to accurately model intrafraction motion and to quantitatively estimate internal target volumes (ITVs) for radiation therapy involving moving targets. In the case of intensity‐modulated (IMRT) and stereotactic body radiation therapy (SBRT) delivery, clinicians must consider the interplay between the temporal nature of the modulation and the target motion within the ITV. A need exists for a 4D IMRT/SBRT quality assurance (QA) device that can incorporate and analyze customized intrafraction motion as it relates to dose delivery and respiratory gating. We built a 4D IMRT/SBRT prototype device and entered (X, Y, Z)(T) coordinates representing a motion kernel into a software application that transformed the kernel into beam‐specific two‐dimensional (2D) motion “projections,”previewed the motion in real time, anddrove a precision X–Y motorized device that had, atop it, a mounted planar IMRT QA measurement device. The detectors that intersected the target in the beam's‐eye‐view of any single phase of the breathing cycle (a small subset of all the detectors) were defined as “target detectors” to be analyzed for dose uniformity between multiple fractions. Data regarding the use of this device to quantify dose variation fraction‐to‐fraction resulting from target motion (for several delivery modalities and with and without gating) have been recently published. A combined software and hardware solution for patient‐customized 4D IMRT/ SBRT QA is an effective tool for assessing IMRT delivery under conditions of intrafraction motion. The 4D IMRT QA device accurately reproduced the projected motion kernels for all beam's‐eye‐view motion kernels. This device has been proved to • effectively quantify the degradation in dose uniformity resulting from a moving target within a static planning target volume, and • integrate

Effect of beamlet step-size on IMRT plan quality

International Nuclear Information System (INIS)

Zhang Guowei; Jiang Ziping; Shepard, David; Earl, Matt; Yu, Cedric

2005-01-01

We have studied the degree to which beamlet step-size impacts the quality of intensity modulated radiation therapy (IMRT) treatment plans. Treatment planning for IMRT begins with the application of a grid that divides each beam's-eye-view of the target into a number of smaller beamlets (pencil beams) of radiation. The total dose is computed as a weighted sum of the dose delivered by the individual beamlets. The width of each beamlet is set to match the width of the corresponding leaf of the multileaf collimator (MLC). The length of each beamlet (beamlet step-size) is parallel to the direction of leaf travel. The beamlet step-size represents the minimum stepping distance of the leaves of the MLC and is typically predetermined by the treatment planning system. This selection imposes an artificial constraint because the leaves of the MLC and the jaws can both move continuously. Removing the constraint can potentially improve the IMRT plan quality. In this study, the optimized results were achieved using an aperture-based inverse planning technique called direct aperture optimization (DAO). We have tested the relationship between pencil beam step-size and plan quality using the American College of Radiology's IMRT test case. For this case, a series of IMRT treatment plans were produced using beamlet step-sizes of 1, 2, 5, and 10 mm. Continuous improvements were seen with each reduction in beamlet step size. The maximum dose to the planning target volume (PTV) was reduced from 134.7% to 121.5% and the mean dose to the organ at risk (OAR) was reduced from 38.5% to 28.2% as the beamlet step-size was reduced from 10 to 1 mm. The smaller pencil beam sizes also led to steeper dose gradients at the junction between the target and the critical structure with gradients of 6.0, 7.6, 8.7, and 9.1 dose%/mm achieved for beamlet step sizes of 10, 5, 2, and 1 mm, respectively

Reducing dose calculation time for accurate iterative IMRT planning

International Nuclear Information System (INIS)

Siebers, Jeffrey V.; Lauterbach, Marc; Tong, Shidong; Wu Qiuwen; Mohan, Radhe

2002-01-01

A time-consuming component of IMRT optimization is the dose computation required in each iteration for the evaluation of the objective function. Accurate superposition/convolution (SC) and Monte Carlo (MC) dose calculations are currently considered too time-consuming for iterative IMRT dose calculation. Thus, fast, but less accurate algorithms such as pencil beam (PB) algorithms are typically used in most current IMRT systems. This paper describes two hybrid methods that utilize the speed of fast PB algorithms yet achieve the accuracy of optimizing based upon SC algorithms via the application of dose correction matrices. In one method, the ratio method, an infrequently computed voxel-by-voxel dose ratio matrix (R=D SC /D PB ) is applied for each beam to the dose distributions calculated with the PB method during the optimization. That is, D PB xR is used for the dose calculation during the optimization. The optimization proceeds until both the IMRT beam intensities and the dose correction ratio matrix converge. In the second method, the correction method, a periodically computed voxel-by-voxel correction matrix for each beam, defined to be the difference between the SC and PB dose computations, is used to correct PB dose distributions. To validate the methods, IMRT treatment plans developed with the hybrid methods are compared with those obtained when the SC algorithm is used for all optimization iterations and with those obtained when PB-based optimization is followed by SC-based optimization. In the 12 patient cases studied, no clinically significant differences exist in the final treatment plans developed with each of the dose computation methodologies. However, the number of time-consuming SC iterations is reduced from 6-32 for pure SC optimization to four or less for the ratio matrix method and five or less for the correction method. Because the PB algorithm is faster at computing dose, this reduces the inverse planning optimization time for our implementation

Irradiation of head-and-neck tumors with intensity modulated radiotherapy (IMRT). Comparison between two IMRT techniques with 3D conformal irradiation

International Nuclear Information System (INIS)

Heeger, Jonas

2013-01-01

For 12 patients with inoperable head-neck carcinoma that were treated with 3D conformal irradiation techniques additional irradiation plans using IMRT were developed. It was shown that the IMRT techniques are superior to the 3D conformal technique. The new rapid arc technique is unclear with respect to the critical organs (parotid glands, spinal canal and mandibles) but is significantly advantageous for the other normal tissue with respect to conformity (steeper dose gradients) and thus radiation dose reduction. The resulting lower irradiation time and the reduced radiation exposure being important for the treatment economy and patients' comfort should favor the more planning intensive rapid arc technique.

Direct aperture optimization for IMRT using Monte Carlo generated beamlets

International Nuclear Information System (INIS)

Bergman, Alanah M.; Bush, Karl; Milette, Marie-Pierre; Popescu, I. Antoniu; Otto, Karl; Duzenli, Cheryl

2006-01-01

This work introduces an EGSnrc-based Monte Carlo (MC) beamlet does distribution matrix into a direct aperture optimization (DAO) algorithm for IMRT inverse planning. The technique is referred to as Monte Carlo-direct aperture optimization (MC-DAO). The goal is to assess if the combination of accurate Monte Carlo tissue inhomogeneity modeling and DAO inverse planning will improve the dose accuracy and treatment efficiency for treatment planning. Several authors have shown that the presence of small fields and/or inhomogeneous materials in IMRT treatment fields can cause dose calculation errors for algorithms that are unable to accurately model electronic disequilibrium. This issue may also affect the IMRT optimization process because the dose calculation algorithm may not properly model difficult geometries such as targets close to low-density regions (lung, air etc.). A clinical linear accelerator head is simulated using BEAMnrc (NRC, Canada). A novel in-house algorithm subdivides the resulting phase space into 2.5x5.0 mm 2 beamlets. Each beamlet is projected onto a patient-specific phantom. The beamlet dose contribution to each voxel in a structure-of-interest is calculated using DOSXYZnrc. The multileaf collimator (MLC) leaf positions are linked to the location of the beamlet does distributions. The MLC shapes are optimized using direct aperture optimization (DAO). A final Monte Carlo calculation with MLC modeling is used to compute the final dose distribution. Monte Carlo simulation can generate accurate beamlet dose distributions for traditionally difficult-to-calculate geometries, particularly for small fields crossing regions of tissue inhomogeneity. The introduction of DAO results in an additional improvement by increasing the treatment delivery efficiency. For the examples presented in this paper the reduction in the total number of monitor units to deliver is ∼33% compared to fluence-based optimization methods

The Molecular Biology Capstone Assessment: A Concept Assessment for Upper-Division Molecular Biology Students

Science.gov (United States)

Couch, Brian A.; Wood, William B.; Knight, Jennifer K.

2015-01-01

Measuring students' conceptual understandings has become increasingly important to biology faculty members involved in evaluating and improving departmental programs. We developed the Molecular Biology Capstone Assessment (MBCA) to gauge comprehension of fundamental concepts in molecular and cell biology and the ability to apply these concepts in…

Quantum Information Biology: From Theory of Open Quantum Systems to Adaptive Dynamics

Science.gov (United States)

Asano, Masanari; Basieva, Irina; Khrennikov, Andrei; Ohya, Masanori; Tanaka, Yoshiharu; Yamato, Ichiro

This chapter reviews quantum(-like) information biology (QIB). Here biology is treated widely as even covering cognition and its derivatives: psychology and decision making, sociology, and behavioral economics and finances. QIB provides an integrative description of information processing by bio-systems at all scales of life: from proteins and cells to cognition, ecological and social systems. Mathematically QIB is based on the theory of adaptive quantum systems (which covers also open quantum systems). Ideologically QIB is based on the quantum-like (QL) paradigm: complex bio-systems process information in accordance with the laws of quantum information and probability. This paradigm is supported by plenty of statistical bio-data collected at all bio-scales. QIB re ects the two fundamental principles: a) adaptivity; and, b) openness (bio-systems are fundamentally open). In addition, quantum adaptive dynamics provides the most generally possible mathematical representation of these principles.

SIFT: A method to verify the IMRT fluence delivered during patient treatment using an electronic portal imaging device

International Nuclear Information System (INIS)

Vieira, Sandra C.; Dirkx, Maarten L.P.; Heijmen, Ben J.M.; Boer, Hans C.J. de

2004-01-01

Purpose: Radiotherapy patients are increasingly treated with intensity-modulated radiotherapy (IMRT) and high tumor doses. As part of our quality control program to ensure accurate dose delivery, a new method was investigated that enables the verification of the IMRT fluence delivered during patient treatment using an electronic portal imaging device (EPID), irrespective of changes in patient geometry. Methods and materials: Each IMRT treatment field is split into a static field and a modulated field, which are delivered in sequence. Images are acquired for both fields using an EPID. The portal dose image obtained for the static field is used to determine changes in patient geometry between the planning CT scan and the time of treatment delivery. With knowledge of these changes, the delivered IMRT fluence can be verified using the portal dose image of the modulated field. This method, called split IMRT field technique (SIFT), was validated first for several phantom geometries, followed by clinical implementation for a number of patients treated with IMRT. Results: The split IMRT field technique allows for an accurate verification of the delivered IMRT fluence (generally within 1% [standard deviation]), even if large interfraction changes in patient geometry occur. For interfraction radiological path length changes of 10 cm, deliberately introduced errors in the delivered fluence could still be detected to within 1% accuracy. Application of SIFT requires only a minor increase in treatment time relative to the standard IMRT delivery. Conclusions: A new technique to verify the delivered IMRT fluence from EPID images, which is independent of changes in the patient geometry, has been developed. SIFT has been clinically implemented for daily verification of IMRT treatment delivery

SU-E-T-133: Assessing IMRT Treatment Delivery Accuracy and Consistency On a Varian TrueBeam Using the SunNuclear PerFraction EPID Dosimetry Software

Energy Technology Data Exchange (ETDEWEB)

Dieterich, S [UC Davis Medical Center, Sacramento, CA (United States); Trestrail, E; Holt, R [Pacific Crest Medical Physics, Chico, CA (United States); Saini, S [Sun Nuclear Corporation, Melbourne, FL (Australia); Pfeiffer, I [VMTH, UC Davis, Davis, CA (United States); Kent, M; Hansen, K [Surgical and Radiological Sciences, UC Davis, Davis, CA (United States)

2015-06-15

Purpose: To assess if the TrueBeam HD120 collimator is delivering small IMRT fields accurately and consistently throughout the course of treatment using the SunNuclear PerFraction software. Methods: 7-field IMRT plans for 8 canine patients who passed IMRT QA using SunNuclear Mapcheck DQA were selected for this study. The animals were setup using CBCT image guidance. The EPID fluence maps were captured for each treatment field and each treatment fraction, with the first fraction EPID data serving as the baseline for comparison. The Sun Nuclear PerFraction Software was used to compare the EPID data for subsequent fractions using a Gamma (3%/3mm) pass rate of 90%. To simulate requirements for SRS, the data was reanalyzed using a Gamma (3%/1mm) pass rate of 90%. Low-dose, low- and high gradient thresholds were used to focus the analysis on clinically relevant parts of the dose distribution. Results: Not all fractions could be analyzed, because during some of the treatment courses the DICOM tags in the EPID images intermittently change from CU to US (unspecified), which would indicate a temporary loss of EPID calibration. This technical issue is still being investigated. For the remaining fractions, the vast majority (7/8 of patients, 95% of fractions, and 96.6% of fields) are passing the less stringent Gamma criteria. The more stringent Gamma criteria caused a drop in pass rate (90 % of fractions, 84% of fields). For the patient with the lowest pass rate, wet towel bolus was used. Another patient with low pass rates experienced masseter muscle wasting. Conclusion: EPID dosimetry using the PerFraction software demonstrated that the majority of fields passed a Gamma (3%/3mm) for IMRT treatments delivered with a TrueBeam HD120 MLC. Pass rates dropped for a DTA of 1mm to model SRS tolerances. PerFraction pass rates can flag missing bolus or internal shields. Sanjeev Saini is an employee of Sun Nuclear Corporation. For this study, a pre-release version of PerFRACTION 1

Monte Carlo simulations to replace film dosimetry in IMRT verification

International Nuclear Information System (INIS)

Goetzfried, Thomas; Trautwein, Marius; Koelbi, Oliver; Bogner, Ludwig; Rickhey, Mark

2011-01-01

Patient-specific verification of intensity-modulated radiation therapy (IMRT) plans can be done by dosimetric measurements or by independent dose or monitor unit calculations. The aim of this study was the clinical evaluation of IMRT verification based on a fast Monte Carlo (MC) program with regard to possible benefits compared to commonly used film dosimetry. 25 head-and-neck IMRT plans were recalculated by a pencil beam based treatment planning system (TPS) using an appropriate quality assurance (QA) phantom. All plans were verified both by film and diode dosimetry and compared to MC simulations. The irradiated films, the results of diode measurements and the computed dose distributions were evaluated, and the data were compared on the basis of gamma maps and dose-difference histograms. Average deviations in the high-dose region between diode measurements and point dose calculations performed with the TPS and MC program were 0.7 ± 2.7% and 1.2 ± 3.1%, respectively. For film measurements, the mean gamma values with 3% dose difference and 3 mm distance-to-agreement were 0.74 ± 0.28 (TPS as reference) with dose deviations up to 10%. Corresponding values were significantly reduced to 0.34 ± 0.09 for MC dose calculation. The total time needed for both verification procedures is comparable, however, by far less labor intensive in the case of MC simulations. The presented study showed that independent dose calculation verification of IMRT plans with a fast MC program has the potential to eclipse film dosimetry more and more in the near future. Thus, the linac-specific QA part will necessarily become more important. In combination with MC simulations and due to the simple set-up, point-dose measurements for dosimetric plausibility checks are recommended at least in the IMRT introduction phase. (orig.)

A dosimetric comparison of two-phase adaptive intensity-modulated radiotherapy for locally advanced nasopharyngeal cancer

International Nuclear Information System (INIS)

Chitapanarux, Imjai; Chomprasert, Kittisak; Nobnaop, Wannapa; Wanwilairat, Somsak; Tharavichitkul, Ekasit; Jakrabhandu, Somvilai; Onchan, Wimrak; Patrinee, Traisathit; Gestel, Dirk Van

2015-01-01

The purpose of this investigation was to evaluate the potential dosimetric benefits of a two-phase adaptive intensity-modulated radiotherapy (IMRT) protocol for patients with locally advanced nasopharyngeal cancer (NPC). A total of 17 patients with locally advanced NPC treated with IMRT had a second computed tomography (CT) scan after 17 fractions in order to apply and continue the treatment with an adapted plan after 20 fractions. To simulate the situation without adaptation, a hybrid plan was generated by applying the optimization parameters of the original treatment plan to the anatomy of the second CT scan. The dose-volume histograms (DVHs) and dose statistics of the hybrid plan and the adapted plan were compared. The mean volume of the ipsilateral and contralateral parotid gland decreased by 6.1 cm 3 (30.5%) and 5.4 cm 3 (24.3%), respectively. Compared with the hybrid plan, the adapted plan provided a higher dose to the target volumes with better homogeneity, and a lower dose to the organs at risk (OARs). The Dmin of all planning target volumes (PTVs) increased. The Dmax of the spinal cord and brainstem were lower in 94% of the patients (1.6-5.9 Gy, P < 0.001 and 2.1-9.9 Gy, P < 0.001, respectively). The D mean of the contralateral parotid decreased in 70% of the patients (range, 0.2-4.4 Gy). We could not find a relationship between dose variability and weight loss. Our two-phase adaptive IMRT protocol improves dosimetric results in terms of target volumes and OARs in patients with locally advanced NPC. (author)

Assessment of radiation-induced second cancer risks in proton therapy and IMRT for organs inside the primary radiation field

Science.gov (United States)

Paganetti, Harald; Athar, Basit S.; Moteabbed, Maryam; Adams, Judith A.; Schneider, Uwe; Yock, Torunn I.

2012-10-01

There is clinical evidence that second malignancies in radiation therapy occur mainly within the beam path, i.e. in the medium or high-dose region. The purpose of this study was to assess the risk for developing a radiation-induced tumor within the treated volume and to compare this risk for proton therapy and intensity-modulated photon therapy (IMRT). Instead of using data for specific patients we have created a representative scenario. Fully contoured age- and gender-specific whole body phantoms (4 year and 14 year old) were uploaded into a treatment planning system and tumor volumes were contoured based on patients treated for optic glioma and vertebral body Ewing's sarcoma. Treatment plans for IMRT and proton therapy treatments were generated. Lifetime attributable risks (LARs) for developing a second malignancy were calculated using a risk model considering cell kill, mutation, repopulation, as well as inhomogeneous organ doses. For standard fractionation schemes, the LAR for developing a second malignancy from radiation therapy alone was found to be up to 2.7% for a 4 year old optic glioma patient treated with IMRT considering a soft-tissue carcinoma risk model only. Sarcoma risks were found to be below 1% in all cases. For a 14 year old, risks were found to be about a factor of 2 lower. For Ewing's sarcoma cases the risks based on a sarcoma model were typically higher than the carcinoma risks, i.e. LAR up to 1.3% for soft-tissue sarcoma. In all cases, the risk from proton therapy turned out to be lower by at least a factor of 2 and up to a factor of 10. This is mainly due to lower total energy deposited in the patient when using proton beams. However, the comparison of a three-field and four-field proton plan also shows that the distribution of the dose, i.e. the particular treatment plan, plays a role. When using different fractionation schemes, the estimated risks roughly scale with the total dose difference in%. In conclusion, proton therapy can

Can IMRT or Brachytherapy Reduce Dysphagia Associated With Chemoradiotherapy of Head and Neck Cancer? The Michigan and Rotterdam Experiences

International Nuclear Information System (INIS)

Eisbruch, Avraham; Levendag, Peter C.; Feng, Felix Y.; Teguh, David; Lyden, Teresa M.A.; Schmitz, Paul I.M.; Haxer, Marc; Noever, Inge; Chepeha, Douglas B.; Heijmen, Ben J.

2007-01-01

Purpose: Dysphagia is a major late complication of intensive chemoradiotherapy of head and neck cancer. The initial clinical results of intensity-modulated radiotherapy (IMRT), or brachytherapy, planned specifically to reduce dysphagia are presented. Patients and Methods: Previous research at Michigan University has suggested that the pharyngeal constrictors and glottic and supraglottic larynx are likely structures whose damage by chemo-RT causes dysphagia and aspiration. In a prospective Michigan trial, 36 patients with oropharyngeal (n = 31) or nasopharyngeal (n = 5) cancer underwent chemo-IMRT. IMRT cost functions included sparing noninvolved pharyngeal constrictors and the glottic and supraglottic larynx. After a review of published studies, the retropharyngeal nodes at risk were defined as the lateral, but not the medial, retropharyngeal nodes, which facilitated sparing of the swallowing structures. In Rotterdam, 77 patients with oropharyngeal cancer were treated with IMRT, three dimensional RT, or conventional RT; also one-half received brachytherapy. The dysphagia endpoints included videofluoroscopy and observer-assessed scores at Michigan and patient-reported quality-of-life instruments in both studies. Results: In both studies, the doses to the upper and middle constrictors correlated highly with the dysphagia endpoints. In addition, doses to the glottic and supraglottic larynx were significant in the Michigan series. In the Rotterdam series, brachytherapy (which reduced the doses to the swallowing structures) was the only significant factor on multivariate analysis. Conclusion: The dose-response relationships for the swallowing structures found in these studies suggest that reducing their doses, using either IMRT aimed at their sparing, or brachytherapy, might achieve clinical gains in dysphagia

Parotid gland shrinkage during IMRT predicts the time to Xerostomia resolution.

Science.gov (United States)

Sanguineti, Giuseppe; Ricchetti, Francesco; Wu, Binbin; McNutt, Todd; Fiorino, Claudio

2015-01-17

To assess the impact of mid-treatment parotid gland shrinkage on long term xerostomia during IMRT for oropharyngeal SCC. All patients treated with IMRT at a single Institution from November 2007 to June 2010 and undergoing weekly CT scans were selected. Parotid glands were contoured retrospectively on the mid treatment CT scan. For each parotid gland, the percent change relative to the planning volume was calculated and combined as weighted average. Patients were considered to be xerostomic if developed GR2+ dry mouth according to CTCAE v3.0. Predictors of the time to xerostomia resolution or downgrade to 1 were investigated at both uni- and multivariate analysis. 85 patients were selected. With a median follow up of 35.8 months (range: 2.4-62.6 months), the actuarial rate of xerostomia is 26.2% (SD: 5.3%) and 15.9% (SD: 5.3%) at 2 and 3 yrs, respectively. At multivariate analysis, mid-treatment shrink along with weighted average mean parotid dose at planning and body mass index are independent predictors of the time to xerostomia resolution. Patients were pooled in 4 groups based on median values of both mid-treatment shrink (cut-off: 19.6%) and mean WA parotid pl-D (cut-off: 35.7 Gy). Patients with a higher than median parotid dose at planning and who showed poor shrinkage at mid treatment are the ones with the outcome significantly worse (3-yr rate of xerostomia ≈ 50%) than the other three subgroups (3-yr rate of xerostomia ≈ 10%). For a given planned dose, patients whose parotids significantly shrink during IMRT are less likely to be long-term supplemental fluids dependent.

Dosimetric comparison of treatment techniques IMRT and VMAT for breast cancer; Comparacion dosimetrica de las tecnicas de tratamiento IMRT y VMAT para cancer en mama

Energy Technology Data Exchange (ETDEWEB)

Urbina, G. L. [Universidad Nacional de Ingenieria, Maestria en Fisica Medica, Av. Tupac Amaru s/n, Rimac, Lima 25 (Peru); Garcia, B. G., E-mail: gerlup@hotmail.com [Red AUNA, Clinica Delgado, Av. Angamos Cdra. 4 esquina Gral. Borgono, Miraflores, Lima (Peru)

2015-10-15

In this study the dosimetric distribution was compared in the different treatment techniques such as Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiation Therapy (IMRT) in female patients with breast cancer with stage II-B and III-A, 6 cases (both calculated on VMAT and IMRT) were studied, comparison parameter that are taken into account are: compliance rate, homogeneity index, monitor units, volume dose 50 Gy (D-50%) and 5 Gy (D-5%) volume dose. Comparisons are made in primary tumor volume to optimize treatment in patients with breast cancer, with IMRT using Step, Shoot and VMAT Monte Carlo algorithm, in addition to the organs at risk; the concern to make this work is due to technological advances in radiotherapy and the application of new treatment techniques, that increase the accuracy allowing treatment dose climbing delivering a higher dose to the patient. (Author)

Simulation of respiratory motion during IMRT dose delivery

International Nuclear Information System (INIS)

Mohn, Silje; Wasboe, Ellen

2011-01-01

Background. When intensity modulated radiation therapy (IMRT) is realised with dynamic multi-leaf collimators (MLC) and given under respiratory motion, dosimetric errors may occur. These errors are a consequence of the dose blurring and the interplay between the organ motion and the leaf motion. In the present study, a model for evaluating these dosimetric effects for patient-specific cases has been developed and tested. Material and methods. In the purpose written software, three dimensional (3D) dose distributions can be calculated both with and without a generated breathing cycle. To validate the presented model and illustrate its application, periodic breathing cycles were generated, where the starting phase was set randomly for each field during the calculations. Respiration in the anterior-posterior (AP), superior-inferior (SI) and left-right (LR) direction was tested and verified. To illustrate the application of the presented model, two 5-fields IMRT plans with different complexity were calculated with a 2 cm peak-to-peak motion in the AP direction for one fraction and for 25 fractions. Results. The results showed that the calculation method is of good accuracy, in particular for IMRT plans consisting of several fields, where 97% of the pixels within the body fulfilled a tolerance set to 4% dose difference and 4 mm distance to agreement (DTA). For the two IMRT plans with different complexity, pronounced respiratory induced dose errors, which increased with increasing complexity, were found for both one fraction and 25 fractions, but due to the random stating phase the interplay effect was considerably reduced for the plans consisting of 25 fractions. This illustrates how the dosimetric effects will vary depending on the dose plan and on the number of fractions investigated. Conclusion. For patient specific cases, the model can with good accuracy calculate 3D dose distributions both with and without respiratory motion, and evaluate the dosimetric effects

A leaf sequencing algorithm to enlarge treatment field length in IMRT

International Nuclear Information System (INIS)

Xia Ping; Hwang, Andrew B.; Verhey, Lynn J.

2002-01-01

With MLC-based IMRT, the maximum usable field size is often smaller than the maximum field size for conventional treatments. This is due to the constraints of the overtravel distances of MLC leaves and/or jaws. Using a new leaf sequencing algorithm, the usable IMRT field length (perpendicular to the MLC motion) can be mostly made equal to the full length of the MLC field without violating the upper jaw overtravel limit. For any given intensity pattern, a criterion was proposed to assess whether an intensity pattern can be delivered without violation of the jaw position constraints. If the criterion is met, the new algorithm will consider the jaw position constraints during the segmentation for the step and shoot delivery method. The strategy employed by the algorithm is to connect the intensity elements outside the jaw overtravel limits with those inside the jaw overtravel limits. Several methods were used to establish these connections during segmentation by modifying a previously published algorithm (areal algorithm), including changing the intensity level, alternating the leaf-sequencing direction, or limiting the segment field size. The algorithm was tested with 1000 random intensity patterns with dimensions of 21x27 cm2, 800 intensity patterns with higher intensity outside the jaw overtravel limit, and three different types of clinical treatment plans that were undeliverable using a segmentation method from a commercial treatment planning system. The new algorithm achieved a success rate of 100% with these test patterns. For the 1000 random patterns, the new algorithm yields a similar average number of segments of 36.9±2.9 in comparison to 36.6±1.3 when using the areal algorithm. For the 800 patterns with higher intensities outside the jaw overtravel limits, the new algorithm results in an increase of 25% in the average number of segments compared to the areal algorithm. However, the areal algorithm fails to create deliverable segments for 90% of these

SU-E-T-49: A Multi-Institutional Study of Independent Dose Verification for IMRT

International Nuclear Information System (INIS)

Baba, H; Tachibana, H; Kamima, T; Takahashi, R; Kawai, D; Sugawara, Y; Yamamoto, T; Sato, A; Yamashita, M

2015-01-01

Purpose: AAPM TG114 does not cover the independent verification for IMRT. We conducted a study of independent dose verification for IMRT in seven institutes to show the feasibility. Methods: 384 IMRT plans in the sites of prostate and head and neck (HN) were collected from the institutes, where the planning was performed using Eclipse and Pinnacle3 with the two techniques of step and shoot (S&S) and sliding window (SW). All of the institutes used a same independent dose verification software program (Simple MU Analysis: SMU, Triangle Product, Ishikawa, JP), which is Clarkson-based and CT images were used to compute radiological path length. An ion-chamber measurement in a water-equivalent slab phantom was performed to compare the doses computed using the TPS and an independent dose verification program. Additionally, the agreement in dose computed in patient CT images between using the TPS and using the SMU was assessed. The dose of the composite beams in the plan was evaluated. Results: The agreement between the measurement and the SMU were −2.3±1.9 % and −5.6±3.6 % for prostate and HN sites, respectively. The agreement between the TPSs and the SMU were −2.1±1.9 % and −3.0±3.7 for prostate and HN sites, respectively. There was a negative systematic difference with similar standard deviation and the difference was larger in the HN site. The S&S technique showed a statistically significant difference between the SW. Because the Clarkson-based method in the independent program underestimated (cannot consider) the dose under the MLC. Conclusion: The accuracy would be improved when the Clarkson-based algorithm should be modified for IMRT and the tolerance level would be within 5%

Clinical experience transitioning from IMRT to VMAT for head and neck cancer

Energy Technology Data Exchange (ETDEWEB)

Studenski, Matthew T., E-mail: matthew.studenski@jeffersonhospital.org [Department of Radiation Oncology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States); Bar-Ad, Voichita; Siglin, Joshua [Department of Radiation Oncology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States); Cognetti, David; Curry, Joseph [Department of Otolaryngology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States); Tuluc, Madalina [Department of Pathology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States); Harrison, Amy S. [Department of Radiation Oncology, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA (United States)

2013-07-01

To quantify clinical differences for volumetric modulated arc therapy (VMAT) versus intensity modulated radiation therapy (IMRT) in terms of dosimetric endpoints and planning and delivery time, twenty head and neck cancer patients have been considered for VMAT using Nucletron Oncentra MasterPlan delivered via an Elekta linear accelerator. Differences in planning time between IMRT and VMAT were estimated accounting for both optimization and calculation. The average delivery time per patient was obtained retrospectively using the record and verify software. For the dosimetric comparison, all contoured organs at risk (OARs) and planning target volumes (PTVs) were evaluated. Of the 20 cases considered, 14 had VMAT plans approved. Six VMAT plans were rejected due to unacceptable dose to OARs. In terms of optimization time, there was minimal difference between the two modalities. The dose calculation time was significantly longer for VMAT, 4 minutes per 358 degree arc versus 2 minutes for an entire IMRT plan. The overall delivery time was reduced by 9.2 ± 3.9 minutes for VMAT (51.4 ± 15.6%). For the dosimetric comparison of the 14 clinically acceptable plans, there was almost no statistical difference between the VMAT and IMRT. There was also a reduction in monitor units of approximately 32% from IMRT to VMAT with both modalities demonstrating comparable quality assurance results. VMAT provides comparable coverage of target volumes while sparing OARs for the majority of head and neck cases. In cases where high dose modulation was required for OARs, a clinically acceptable plan was only achievable with IMRT. Due to the long calculation times, VMAT plans can cause delays during planning but marked improvements in delivery time reduce patient treatment times and the risk of intra-fraction motion.

Dose distribution of IMRT and 3D-CRT on treating central non-small-cell lung cancer

International Nuclear Information System (INIS)

Zhu Xiaoyang; Yu Guangwei

2010-01-01

3D-CRT and IMRT were used in the radiation therapy of Central Non-small-cell lung cancer (NSCLC), and the dose difference of the methods was estimated. Thirty-two patients suffering with II class NSCLC were selected. Based on CT images, each patient was given 1 3D-CRT (3 dimensional conformal radiotherapy) and 2 IMRT(intensity modulated radiation therapy) treatment plans (5 fields and 7 fields), respectively, and the dose distribution was evaluated too. The results showed that PTVD mean and the PTV max , PTVD max (%) and CI of IMRT were both higher than those of 3D-CRT, but the uniformity was not as good as 3D-CRT. All indexes of lung and spinal cord treated with IMRT were lower than that treated with 3D-CRT. Moreover, there was no significance of the difference between 5 fields and 7 fields. In a conclusion, IMRT could not only decrease the target dose of NSCLC, but it can protect normal tissue from radiation damage effectively. And when IMRT was used, 5 fields might be enough. (authors)

A qualitative assessment of climate adaptation options and some estimates of adaptation costs

International Nuclear Information System (INIS)

Van Ierland, E.C.; De Bruin, K.; Dellink, R.B.; Ruijs, A.

2007-02-01

The Routeplanner project aims to provide a 'systematic assessment' of potential adaptation options to respond to climate change in the Netherlands in connection to spatial planning. The study is the result of a policy oriented project that took place between May and September 2006. The aim of the current study is to provide a 'qualitative assessment' of the direct and indirect effects of adaptation options and to provide an assessment of some of the costs and benefits of adaptation options. The present report presents and summarizes the results of all phases of the study: an inventory of adaptation options, a qualitative assessment of the effects of the adaptation options for the Netherlands in the long run, a database which allows to rank the various options according to a set of criteria and a relative ranking on the basis of these criteria. Finally, the report also contains the best available information on costs and benefits of various adaptation options. However, while conducting the study the project team observed that reliable information in this respect is in many cases still lacking and an urgent need exists for more detailed studies on costs and benefits of adaptation options and the design of the best options to cope with climate change

Pre-segmented 2-Step IMRT with subsequent direct machine parameter optimisation – a planning study

International Nuclear Information System (INIS)

Bratengeier, Klaus; Meyer, Jürgen; Flentje, Michael

2008-01-01

Modern intensity modulated radiotherapy (IMRT) mostly uses iterative optimisation methods. The integration of machine parameters into the optimisation process of step and shoot leaf positions has been shown to be successful. For IMRT segmentation algorithms based on the analysis of the geometrical structure of the planning target volumes (PTV) and the organs at risk (OAR), the potential of such procedures has not yet been fully explored. In this work, 2-Step IMRT was combined with subsequent direct machine parameter optimisation (DMPO-Raysearch Laboratories, Sweden) to investigate this potential. In a planning study DMPO on a commercial planning system was compared with manual primary 2-Step IMRT segment generation followed by DMPO optimisation. 15 clinical cases and the ESTRO Quasimodo phantom were employed. Both the same number of optimisation steps and the same set of objective values were used. The plans were compared with a clinical DMPO reference plan and a traditional IMRT plan based on fluence optimisation and consequent segmentation. The composite objective value (the weighted sum of quadratic deviations of the objective values and the related points in the dose volume histogram) was used as a measure for the plan quality. Additionally, a more extended set of parameters was used for the breast cases to compare the plans. The plans with segments pre-defined with 2-Step IMRT were slightly superior to DMPO alone in the majority of cases. The composite objective value tended to be even lower for a smaller number of segments. The total number of monitor units was slightly higher than for the DMPO-plans. Traditional IMRT fluence optimisation with subsequent segmentation could not compete. 2-Step IMRT segmentation is suitable as starting point for further DMPO optimisation and, in general, results in less complex plans which are equal or superior to plans generated by DMPO alone

How do precision medicine and system biology response to human body's complex adaptability?

Science.gov (United States)

Yuan, Bing

2016-12-01

In the field of life sciences, although system biology and "precision medicine" introduce some complex scientifific methods and techniques, it is still based on the "analysis-reconstruction" of reductionist theory as a whole. Adaptability of complex system increase system behaviour uncertainty as well as the difficulties of precise identifification and control. It also put systems biology research into trouble. To grasp the behaviour and characteristics of organism fundamentally, systems biology has to abandon the "analysis-reconstruction" concept. In accordance with the guidelines of complexity science, systems biology should build organism model from holistic level, just like the Chinese medicine did in dealing with human body and disease. When we study the living body from the holistic level, we will fifind the adaptability of complex system is not the obstacle that increases the diffificulty of problem solving. It is the "exceptional", "right-hand man" that helping us to deal with the complexity of life more effectively.

Analysis of results of checks IMRT in almost a thousand patients

International Nuclear Information System (INIS)

Richart, J.; Doval, S.; Perez-Calatayud, J.; Depieaggio, M.; Rodriguez, S.; Santos, M.

2013-01-01

Since November 2006 IMRT treatments being made in the mode of sliding-window in our Hospital. The major sites of application of this technique are: head and neck, prostate, and gynecological. Specific checks are performed of each plan both yield and analysis ionometric extent in which a dummy was exported IMRT plan. Over one thousand patients, the objective of this work is the presentation and analysis of results. (Author)

A case study of IMRT planning (Plan B) subsequent to a previously treated IMRT plan (Plan A)

International Nuclear Information System (INIS)

2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columbia (Canada))" data-affiliation=" (Department of Medical Physics and 2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columbia (Canada))" >Cao, F; 2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columbia (Canada))" data-affiliation=" (Department of Medical Physics and 2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columbia (Canada))" >Leong, C; 2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columbia (Canada))" data-affiliation=" (Department of Medical Physics and 2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columbia (Canada))" >Schroeder, J; 2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columbia (Canada))" data-affiliation=" (Department of Medical Physics and 2Department of Radiation Oncology, Fraser Valley Centre, BC Cancer Agency, Surrey, British Columbia (Canada))" >Lee, B

2014-01-01

Background and purpose: Treatment of the contralateral neck after previous ipsilateral intensity modulated radiation therapy (IMRT) for head and neck cancer is a challenging problem. We have developed a technique that limits the cumulative dose to the spinal cord and brainstem while maximizing coverage of a planning target volume (PTV) in the contralateral neck. Our case involves a patient with right tonsil carcinoma who was given ipsilateral IMRT with 70Gy in 35 fractions (Plan A). A left neck recurrence was detected 14 months later. The patient underwent a neck dissection followed by postoperative left neck radiation to a dose of 66 Gy in 33 fractions (Plan B). Materials and Methods: The spinal cord-brainstem margin (SCBM) was defined as the spinal cord and brainstem with a 1.0 cm margin. Plan A was recalculated on the postoperative CT scan but the fluence outside of SCBM was deleted. A further modification of Plan A resulted in a base plan that was summed with Plan B to evaluate the cumulative dose received by the spinal cord and brainstem. Plan B alone was used to evaluate for coverage of the contralateral neck PTV. Results: The maximum cumulative doses to the spinal cord with 0.5cm margin and brainstem with 0.5cm margin were 51.96 Gy and 45.60 Gy respectively. For Plan B, 100% of the prescribed dose covered 95% of PTVb1. Conclusion: The use of a modified ipsilateral IMRT plan as a base plan is an effective way to limit the cumulative dose to the spinal cord and brainstem while enabling coverage of a PTV in the contralateral neck.

Validation of the implementation of IMRT with three dosimetric methods of independent verification; Validacion de la puesta en marcha de la IMRT con tres metodos dosimetricos de verificacion independientes

Energy Technology Data Exchange (ETDEWEB)

Tortosa Oliver, R. A.; Chinillach ferrando, N.; Alonso Arrizabalaga, S.; Campayo Esteban, J. M.; Morales Marco, J. C.; Soler Catalan, P.; Andreu Martinez, F. J.

2013-07-01

The TG119 is a simple and clear framework to verify the implementation of IMRT technique in a radiotherapy service. Verifications of this document recommended tests conducted with the three dosimetric methods listed above, allow to affirm that our Center is within the margins of tolerance considered suitable in the TG119 for the clinical implementation of IMRT. (Author)

Comparison of dental health of patients with head and neck cancer receiving IMRT vs conventional radiation.

Science.gov (United States)

Duarte, Victor M; Liu, Yuan F; Rafizadeh, Sassan; Tajima, Tracey; Nabili, Vishad; Wang, Marilene B

2014-01-01

To analyze the dental health of patients with head and neck cancer who received comprehensive dental care after intensity-modulated radiation therapy (IMRT) compared with radiation therapy (RT). Historical cohort study. Veteran Affairs (VA) hospital. In total, 158 patients at a single VA hospital who were treated with RT or IMRT between 2003 and 2011 were identified. A complete dental evaluation was performed prior to radiation treatment, including periodontal probing, tooth profile, cavity check, and mobility. The dental treatment plan was formulated to eliminate current and potential dental disease. The rates of dental extractions, infections, caries, mucositis, xerostomia, and osteoradionecrosis (ORN) were analyzed, and a comparison was made between patients treated with IMRT and those treated with RT. Of the 158 patients, 99 were treated with RT and 59 were treated with IMRT. Compared with those treated with IMRT, significantly more patients treated with RT exhibited xerostomia (46.5% vs 16.9%; P radiation treatment (32.2% vs 11.1%; P = .002; OR, 3.8; 95% CI, 1.65-8.73). Patients who were treated with IMRT had fewer instances of dental disease, more salivary flow, and fewer requisite posttreatment extractions compared with those treated with RT. The number of posttreatment extractions has been reduced with the advent of IMRT and more so with a complete dental evaluation prior to treatment.

TU-C-BRE-01: KEYNOTE PRESENTATION - Emerging Frontiers in IMRT QA

Energy Technology Data Exchange (ETDEWEB)

Siebers, J [University of Virginia Health System, Charlottesville, VA (United States)

2014-06-15

As IMRT treatment processes advance and mature, so must the quality assurance processes being used to validate their delivery. In some respects, treatment delivery advancements (e.g. VMAT) have out-paced QA advancements. The purpose of this session is to describe new processes that are being implemented to bring IMRT QA up-to-date with the treatment delivery advances. It would explore emerging IMRT QA paradigms, including requirements-based IMRT QA which necessitates definition of delivery errors (e.g. patient dose error, leaf positioning error) and development of processes to ensure reliable error detection. Engineeringbased QA approaches, including use of IMRT treatment delivery process trees, fault tree analysis and failure modes effects analysis would be described. Approaches to detect errors such as (1) during treatment delivery validation using exit fluence detectors (e.g. EPIDs); (2) analysis of treatment delivery via use of machine parameter log files; (3) dose recalculation using (3a) treatment planning system; (3b) record-and-verify; or (3c) entrance and exit fluence measurement parameters would be explained. The relative advantages and disadvantages of each method would be discussed. Schemes for error classification and root cause analysis would be described – steps which are essential for future error prevention. For each QA method, testing procedures and results would be presented indicating the types of errors that can be detected, those that cannot be detected, and the reliability of the error detection method (for example determined via ROC analysis). For speakers, we are seeking to engage non-commercially biased experts. Those listed below are a sub-sample of possible qualified individuals.

TU-C-BRE-01: KEYNOTE PRESENTATION - Emerging Frontiers in IMRT QA

International Nuclear Information System (INIS)

Siebers, J

2014-01-01

As IMRT treatment processes advance and mature, so must the quality assurance processes being used to validate their delivery. In some respects, treatment delivery advancements (e.g. VMAT) have out-paced QA advancements. The purpose of this session is to describe new processes that are being implemented to bring IMRT QA up-to-date with the treatment delivery advances. It would explore emerging IMRT QA paradigms, including requirements-based IMRT QA which necessitates definition of delivery errors (e.g. patient dose error, leaf positioning error) and development of processes to ensure reliable error detection. Engineeringbased QA approaches, including use of IMRT treatment delivery process trees, fault tree analysis and failure modes effects analysis would be described. Approaches to detect errors such as (1) during treatment delivery validation using exit fluence detectors (e.g. EPIDs); (2) analysis of treatment delivery via use of machine parameter log files; (3) dose recalculation using (3a) treatment planning system; (3b) record-and-verify; or (3c) entrance and exit fluence measurement parameters would be explained. The relative advantages and disadvantages of each method would be discussed. Schemes for error classification and root cause analysis would be described – steps which are essential for future error prevention. For each QA method, testing procedures and results would be presented indicating the types of errors that can be detected, those that cannot be detected, and the reliability of the error detection method (for example determined via ROC analysis). For speakers, we are seeking to engage non-commercially biased experts. Those listed below are a sub-sample of possible qualified individuals

MO-FG-202-09: Virtual IMRT QA Using Machine Learning: A Multi-Institutional Validation

International Nuclear Information System (INIS)

Valdes, G; Scheuermann, R; Solberg, T; Chan, M; Deasy, J

2016-01-01

Purpose: To validate a machine learning approach to Virtual IMRT QA for accurately predicting gamma passing rates using different QA devices at different institutions. Methods: A Virtual IMRT QA was constructed using a machine learning algorithm based on 416 IMRT plans, in which QA measurements were performed using diode-array detectors and a 3%local/3mm with 10% threshold. An independent set of 139 IMRT measurements from a different institution, with QA data based on portal dosimetry using the same gamma index and 10% threshold, was used to further test the algorithm. Plans were characterized by 90 different complexity metrics. A weighted poison regression with Lasso regularization was trained to predict passing rates using the complexity metrics as input. Results: In addition to predicting passing rates with 3% accuracy for all composite plans using diode-array detectors, passing rates for portal dosimetry on per-beam basis were predicted with an error <3.5% for 120 IMRT measurements. The remaining measurements (19) had large areas of low CU, where portal dosimetry has larger disagreement with the calculated dose and, as such, large errors were expected. These beams need to be further modeled to correct the under-response in low dose regions. Important features selected by Lasso to predict gamma passing rates were: complete irradiated area outline (CIAO) area, jaw position, fraction of MLC leafs with gaps smaller than 20 mm or 5mm, fraction of area receiving less than 50% of the total CU, fraction of the area receiving dose from penumbra, weighted Average Irregularity Factor, duty cycle among others. Conclusion: We have demonstrated that the Virtual IMRT QA can predict passing rates using different QA devices and across multiple institutions. Prediction of QA passing rates could have profound implications on the current IMRT process.

MO-FG-202-09: Virtual IMRT QA Using Machine Learning: A Multi-Institutional Validation

Energy Technology Data Exchange (ETDEWEB)

Valdes, G; Scheuermann, R; Solberg, T [University of Pennsylvania, Philadelphia, PA (United States); Chan, M; Deasy, J [Memorial Sloan-Kettering Cancer Center, New York, NY (United States)

2016-06-15

Purpose: To validate a machine learning approach to Virtual IMRT QA for accurately predicting gamma passing rates using different QA devices at different institutions. Methods: A Virtual IMRT QA was constructed using a machine learning algorithm based on 416 IMRT plans, in which QA measurements were performed using diode-array detectors and a 3%local/3mm with 10% threshold. An independent set of 139 IMRT measurements from a different institution, with QA data based on portal dosimetry using the same gamma index and 10% threshold, was used to further test the algorithm. Plans were characterized by 90 different complexity metrics. A weighted poison regression with Lasso regularization was trained to predict passing rates using the complexity metrics as input. Results: In addition to predicting passing rates with 3% accuracy for all composite plans using diode-array detectors, passing rates for portal dosimetry on per-beam basis were predicted with an error <3.5% for 120 IMRT measurements. The remaining measurements (19) had large areas of low CU, where portal dosimetry has larger disagreement with the calculated dose and, as such, large errors were expected. These beams need to be further modeled to correct the under-response in low dose regions. Important features selected by Lasso to predict gamma passing rates were: complete irradiated area outline (CIAO) area, jaw position, fraction of MLC leafs with gaps smaller than 20 mm or 5mm, fraction of area receiving less than 50% of the total CU, fraction of the area receiving dose from penumbra, weighted Average Irregularity Factor, duty cycle among others. Conclusion: We have demonstrated that the Virtual IMRT QA can predict passing rates using different QA devices and across multiple institutions. Prediction of QA passing rates could have profound implications on the current IMRT process.

Radiation oncology - Linking technology and biology in the treatment of cancer

International Nuclear Information System (INIS)

Coleman, C. Norman

2002-01-01

Technical advances in radiation oncology including CT-simulation, 3D-conformal and intensity-modulated radiation therapy (IMRT) delivery techniques, and brachytherapy have allowed greater treatment precision and dose escalation. The ability to intensify treatment requires the identification of the critical targets within the treatment field, recognizing the unique biology of tumor, stroma and normal tissue. Precision is technology based while accuracy is biologically based. Therefore, the intensity of IMRT will undoubtedly mean an increase in both irradiation dose and the use of biological agents, the latter considered in the broadest sense. Radiation oncology has the potential and the opportunity to provide major contributions to the linkage between molecular and functional imaging, molecular profiling and novel therapeutics for the emerging molecular targets for cancer treatment. This process of 'credentialing' of molecular targets will require multi disciplinary imaging teams, clinicians and basic scientists. Future advances will depend on the appropriate integration of biology into the training of residents, continuing post graduate education, participation in innovative clinical research and commitment to the support of basic research as an essential component of the practice of radiation oncology

Process control analysis of IMRT QA: implications for clinical trials

International Nuclear Information System (INIS)

Pawlicki, Todd; Rice, Roger K; Yoo, Sua; Court, Laurence E; McMillan, Sharon K; Russell, J Donald; Pacyniak, John M; Woo, Milton K; Basran, Parminder S; Boyer, Arthur L; Bonilla, Claribel

2008-01-01

The purpose of this study is two-fold: first is to investigate the process of IMRT QA using control charts and second is to compare control chart limits to limits calculated using the standard deviation (σ). Head and neck and prostate IMRT QA cases from seven institutions in both academic and community settings are considered. The percent difference between the point dose measurement in phantom and the corresponding result from the treatment planning system (TPS) is used for analysis. The average of the percent difference calculations defines the accuracy of the process and is called the process target. This represents the degree to which the process meets the clinical goal of 0% difference between the measurements and TPS. IMRT QA process ability defines the ability of the process to meet clinical specifications (e.g. 5% difference between the measurement and TPS). The process ability is defined in two ways: (1) the half-width of the control chart limits, and (2) the half-width of ±3σ limits. Process performance is characterized as being in one of four possible states that describes the stability of the process and its ability to meet clinical specifications. For the head and neck cases, the average process target across institutions was 0.3% (range: -1.5% to 2.9%). The average process ability using control chart limits was 7.2% (range: 5.3% to 9.8%) compared to 6.7% (range: 5.3% to 8.2%) using standard deviation limits. For the prostate cases, the average process target across the institutions was 0.2% (range: -1.8% to 1.4%). The average process ability using control chart limits was 4.4% (range: 1.3% to 9.4%) compared to 5.3% (range: 2.3% to 9.8%) using standard deviation limits. Using the standard deviation to characterize IMRT QA process performance resulted in processes being preferentially placed in one of the four states. This is in contrast to using control charts for process characterization where the IMRT QA processes were spread over three of the

Improving IMRT delivery efficiency with reweighted L1-minimization for inverse planning

International Nuclear Information System (INIS)

Kim, Hojin; Becker, Stephen; Lee, Rena; Lee, Soonhyouk; Shin, Sukyoung; Candès, Emmanuel; Xing Lei; Li Ruijiang

2013-01-01

Purpose: This study presents an improved technique to further simplify the fluence-map in intensity modulated radiation therapy (IMRT) inverse planning, thereby reducing plan complexity and improving delivery efficiency, while maintaining the plan quality.Methods: First-order total-variation (TV) minimization (min.) based on L1-norm has been proposed to reduce the complexity of fluence-map in IMRT by generating sparse fluence-map variations. However, with stronger dose sparing to the critical structures, the inevitable increase in the fluence-map complexity can lead to inefficient dose delivery. Theoretically, L0-min. is the ideal solution for the sparse signal recovery problem, yet practically intractable due to its nonconvexity of the objective function. As an alternative, the authors use the iteratively reweighted L1-min. technique to incorporate the benefits of the L0-norm into the tractability of L1-min. The weight multiplied to each element is inversely related to the magnitude of the corresponding element, which is iteratively updated by the reweighting process. The proposed penalizing process combined with TV min. further improves sparsity in the fluence-map variations, hence ultimately enhancing the delivery efficiency. To validate the proposed method, this work compares three treatment plans obtained from quadratic min. (generally used in clinic IMRT), conventional TV min., and our proposed reweighted TV min. techniques, implemented by a large-scale L1-solver (template for first-order conic solver), for five patient clinical data. Criteria such as conformation number (CN), modulation index (MI), and estimated treatment time are employed to assess the relationship between the plan quality and delivery efficiency.Results: The proposed method yields simpler fluence-maps than the quadratic and conventional TV based techniques. To attain a given CN and dose sparing to the critical organs for 5 clinical cases, the proposed method reduces the number of segments

Improving IMRT delivery efficiency with reweighted L1-minimization for inverse planning

Energy Technology Data Exchange (ETDEWEB)

Kim, Hojin [Department of Radiation Oncology, Stanford University, Stanford, California 94305-5847 and Department of Electrical Engineering, Stanford University, Stanford, California 94305-9505 (United States); Becker, Stephen [Laboratoire Jacques-Louis Lions, Universite Pierre et Marie Curie, Paris 6, 75005 France (France); Lee, Rena; Lee, Soonhyouk [Department of Radiation Oncology, School of Medicine, Ewha Womans University, Seoul 158-710 (Korea, Republic of); Shin, Sukyoung [Medtronic CV RDN R and D, Santa Rosa, California 95403 (United States); Candes, Emmanuel [Department of Statistics, Stanford University, Stanford, California 94305-4065 (United States); Xing Lei; Li Ruijiang [Department of Radiation Oncology, Stanford University, Stanford, California 94305-5304 (United States)

2013-07-15

Purpose: This study presents an improved technique to further simplify the fluence-map in intensity modulated radiation therapy (IMRT) inverse planning, thereby reducing plan complexity and improving delivery efficiency, while maintaining the plan quality.Methods: First-order total-variation (TV) minimization (min.) based on L1-norm has been proposed to reduce the complexity of fluence-map in IMRT by generating sparse fluence-map variations. However, with stronger dose sparing to the critical structures, the inevitable increase in the fluence-map complexity can lead to inefficient dose delivery. Theoretically, L0-min. is the ideal solution for the sparse signal recovery problem, yet practically intractable due to its nonconvexity of the objective function. As an alternative, the authors use the iteratively reweighted L1-min. technique to incorporate the benefits of the L0-norm into the tractability of L1-min. The weight multiplied to each element is inversely related to the magnitude of the corresponding element, which is iteratively updated by the reweighting process. The proposed penalizing process combined with TV min. further improves sparsity in the fluence-map variations, hence ultimately enhancing the delivery efficiency. To validate the proposed method, this work compares three treatment plans obtained from quadratic min. (generally used in clinic IMRT), conventional TV min., and our proposed reweighted TV min. techniques, implemented by a large-scale L1-solver (template for first-order conic solver), for five patient clinical data. Criteria such as conformation number (CN), modulation index (MI), and estimated treatment time are employed to assess the relationship between the plan quality and delivery efficiency.Results: The proposed method yields simpler fluence-maps than the quadratic and conventional TV based techniques. To attain a given CN and dose sparing to the critical organs for 5 clinical cases, the proposed method reduces the number of segments

Dosimetry investigation of MOSFET for clinical IMRT dose verification.

Science.gov (United States)

Deshpande, Sudesh; Kumar, Rajesh; Ghadi, Yogesh; Neharu, R M; Kannan, V

2013-06-01

In IMRT, patient-specific dose verification is followed regularly at each centre. Simple and efficient dosimetry techniques play a very important role in routine clinical dosimetry QA. The MOSFET dosimeter offers several advantages over the conventional dosimeters such as its small detector size, immediate readout, immediate reuse, multiple point dose measurements. To use the MOSFET as routine clinical dosimetry system for pre-treatment dose verification in IMRT, a comprehensive set of experiments has been conducted, to investigate its linearity, reproducibility, dose rate effect and angular dependence for 6 MV x-ray beam. The MOSFETs shows a linear response with linearity coefficient of 0.992 for a dose range of 35 cGy to 427 cGy. The reproducibility of the MOSFET was measured by irradiating the MOSFET for ten consecutive irradiations in the dose range of 35 cGy to 427 cGy. The measured reproducibility of MOSFET was found to be within 4% up to 70 cGy and within 1.4% above 70 cGy. The dose rate effect on the MOSFET was investigated in the dose rate range 100 MU/min to 600 MU/min. The response of the MOSFET varies from -1.7% to 2.1%. The angular responses of the MOSFETs were measured at 10 degrees intervals from 90 to 270 degrees in an anticlockwise direction and normalized at gantry angle zero and it was found to be in the range of 0.98 ± 0.014 to 1.01 ± 0.014. The MOSFETs were calibrated in a phantom which was later used for IMRT verification. The measured calibration coefficients were found to be 1 mV/cGy and 2.995 mV/cGy in standard and high sensitivity mode respectively. The MOSFETs were used for pre-treatment dose verification in IMRT. Nine dosimeters were used for each patient to measure the dose in different plane. The average variation between calculated and measured dose at any location was within 3%. Dose verification using MOSFET and IMRT phantom was found to quick and efficient and well suited for a busy radiotherapy

Retrospective analysis of 'gamma distribution' based IMRT QA criteria

International Nuclear Information System (INIS)

Wen, C.; Chappell, R.A.

2010-01-01

Full text: IMRT has been implemented into clinical practice at Royal Hobart Hospital (RHH) since mid 2006 for treating patients with Head and Neck (H and N) or prostate tumours. A local quality assurance (QA) acceptance criteria based on 'gamma distribution' for approving IMRT plan was developed and implemented in early 2007. A retrospective analysis of such criteria over 194 clinical cases will be presented. The RHH IMRT criteria was established with assumption that gamma distribution obtained through inter-comparison of 2 D dose maps between planned and delivered was governed by a positive-hail' normal distribution. A commercial system-MapCheck was used for 2 D dose map comparison with a built-in gamma analysis tool. Gamma distribution histogram was generated and recorded for all cases. By retrospectively analysing those distributions using curve fitting technique, a statistical gamma distribution can be obtained and evaluated. This analytical result can be used for future IMRT planing and treatment delivery. The analyses indicate that gamma distribution obtained through MapCheckTM is well under the normal distribution, particularly for prostate cases. The applied pass/fail criteria is not overly sensitive to identify 'false fails' but can be further tighten-up for smaller field while for larger field found in both H and N and prostate cases, the criteria was correctly applied. Non-uniform distribution of detectors in MapCheck and experience level of planners are two major factors to variation in gamma distribution among clinical cases. This criteria derived from clinical statistics is superior and more accurate than single-valued criteria for lMRT QA acceptance procedure. (author)

A Method for Correcting IMRT Optimizer Heterogeneity Dose Calculations

International Nuclear Information System (INIS)

Zacarias, Albert S.; Brown, Mellonie F.; Mills, Michael D.

2010-01-01

Radiation therapy treatment planning for volumes close to the patient's surface, in lung tissue and in the head and neck region, can be challenging for the planning system optimizer because of the complexity of the treatment and protected volumes, as well as striking heterogeneity corrections. Because it is often the goal of the planner to produce an isodose plan with uniform dose throughout the planning target volume (PTV), there is a need for improved planning optimization procedures for PTVs located in these anatomical regions. To illustrate such an improved procedure, we present a treatment planning case of a patient with a lung lesion located in the posterior right lung. The intensity-modulated radiation therapy (IMRT) plan generated using standard optimization procedures produced substantial dose nonuniformity across the tumor caused by the effect of lung tissue surrounding the tumor. We demonstrate a novel iterative method of dose correction performed on the initial IMRT plan to produce a more uniform dose distribution within the PTV. This optimization method corrected for the dose missing on the periphery of the PTV and reduced the maximum dose on the PTV to 106% from 120% on the representative IMRT plan.

Adaptive Behaviour Assessment System: Indigenous Australian Adaptation Model (ABAS: IAAM)

Science.gov (United States)

du Plessis, Santie

2015-01-01

The study objectives were to develop, trial and evaluate a cross-cultural adaptation of the Adaptive Behavior Assessment System-Second Edition Teacher Form (ABAS-II TF) ages 5-21 for use with Indigenous Australian students ages 5-14. This study introduced a multiphase mixed-method design with semi-structured and informal interviews, school…

Assessing institutional capacities to adapt to climate change: integrating psychological dimensions in the Adaptive Capacity Wheel

Science.gov (United States)

Grothmann, T.; Grecksch, K.; Winges, M.; Siebenhüner, B.

2013-12-01

Several case studies show that social factors like institutions, perceptions and social capital strongly affect social capacities to adapt to climate change. Together with economic and technological development they are important for building social capacities. However, there are almost no methodologies for the systematic assessment of social factors. After reviewing existing methodologies we identify the Adaptive Capacity Wheel (ACW) by Gupta et al. (2010), developed for assessing the adaptive capacity of institutions, as the most comprehensive and operationalised framework to assess social factors. The ACW differentiates 22 criteria to assess 6 dimensions: variety, learning capacity, room for autonomous change, leadership, availability of resources, fair governance. To include important psychological factors we extended the ACW by two dimensions: "adaptation motivation" refers to actors' motivation to realise, support and/or promote adaptation to climate; "adaptation belief" refers to actors' perceptions of realisability and effectiveness of adaptation measures. We applied the extended ACW to assess adaptive capacities of four sectors - water management, flood/coastal protection, civil protection and regional planning - in northwestern Germany. The assessments of adaptation motivation and belief provided a clear added value. The results also revealed some methodological problems in applying the ACW (e.g. overlap of dimensions), for which we propose methodological solutions.

Implementation of dosimetric quality control on IMRT and VMAT treatments in radiotherapy using diodes; Implementacion de control de calidad dosimetrico en tratamientos de IMRT y VMAT en radioterapia usando diodos

Energy Technology Data Exchange (ETDEWEB)

Gonzales, A.; Garcia, B.; Ramirez, J.; Marquina, J., E-mail: andres.gonzales@aliada.com.pe [ALIADA, Oncologia Integral, Av. Jose Galvez Barrenechea 1044, San Isidro, Lima 27 (Peru)

2014-08-15

To implement quality control of IMRT and VMAT treatments Rapid Arc radiotherapy using diode array. Were tested 90 patients with IMRT and VMAT Rapid Arc, comparing the planned dose to the dose administered, used the Map-Check-2 and Arc-Check of Sun Nuclear, they using the gamma factor for calculating and using comparison parameters 3% / 3m m. The statistic shows that the quality controls of the 90 patients analyzed, presented a percentage of diodes that pass the test between 96,7% and 100,0% of the irradiated diodes. Implemented in Clinical ALIADA Oncologia Integral, the method for quality control of IMRT and VMAT treatments Rapid Arc radiotherapy using diode array. (Author)

The molecular biology capstone assessment: a concept assessment for upper-division molecular biology students.

Science.gov (United States)

Couch, Brian A; Wood, William B; Knight, Jennifer K

2015-03-02

Measuring students' conceptual understandings has become increasingly important to biology faculty members involved in evaluating and improving departmental programs. We developed the Molecular Biology Capstone Assessment (MBCA) to gauge comprehension of fundamental concepts in molecular and cell biology and the ability to apply these concepts in novel scenarios. Targeted at graduating students, the MBCA consists of 18 multiple-true/false (T/F) questions. Each question consists of a narrative stem followed by four T/F statements, which allows a more detailed assessment of student understanding than the traditional multiple-choice format. Questions were iteratively developed with extensive faculty and student feedback, including validation through faculty reviews and response validation through student interviews. The final assessment was taken online by 504 students in upper-division courses at seven institutions. Data from this administration indicate that the MBCA has acceptable levels of internal reliability (α=0.80) and test-retest stability (r=0.93). Students achieved a wide range of scores with a 67% overall average. Performance results suggest that students have an incomplete understanding of many molecular biology concepts and continue to hold incorrect conceptions previously documented among introductory-level students. By pinpointing areas of conceptual difficulty, the MBCA can provide faculty members with guidance for improving undergraduate biology programs. © 2015 B. A. Couch et al. CBE—Life Sciences Education © 2015 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

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.

Comparison and Limitations of DVH-Based NTCP Models Derived From 3D-CRT and IMRT Data for Prediction of Gastrointestinal Toxicities in Prostate Cancer Patients by Using Propensity Score Matched Pair Analysis

Energy Technology Data Exchange (ETDEWEB)

Troeller, Almut [Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan (United States); Department of Radiotherapy and Radiation Oncology, Ludwig-Maximilians-Universität, Munich (Germany); Yan, Di, E-mail: dyan@beaumont.edu [Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan (United States); Marina, Ovidiu; Schulze, Derek [Department of Radiation Oncology, William Beaumont Health System, Royal Oak, Michigan (United States); Alber, Markus [Department of Oncology, Aarhus University Hospital, Aarhus (Denmark); Parodi, Katia [Department of Medical Physics, Ludwig-Maximilians-Universität, Munich (Germany); Belka, Claus; Söhn, Matthias [Department of Radiotherapy and Radiation Oncology, Ludwig-Maximilians-Universität, Munich (Germany)

2015-02-01

Purpose: This study compared normal tissue complication probability (NTCP) modeling of chronic gastrointestinal toxicities following prostate cancer treatment for 2 treatment modalities. Possible factors causing discrepancies in optimal NTCP model parameters between 3-dimensional conformal radiation therapy (3D-CRT) and intensity modulated RT (IMRT) were analyzed and discussed, including the impact of patient characteristics, image guidance, toxicity scoring bias, and NTCP model limitations. Methods and Materials: Rectal wall dose-volume histograms of 1115 patients treated for prostate cancer under an adaptive radiation therapy protocol were used to model gastrointestinal toxicity grade ≥2 (according to Common Terminology Criteria for Adverse Events). A total of 457 patients were treated with 3D-CRT and 658 with IMRT. 3D-CRT patients were matched to IMRT patients based on various patient characteristics, using a propensity score–based algorithm. Parameters of the Lyman equivalent uniform dose and cut-off dose logistic regression NTCP models were estimated for the 2 matched treatment modalities and the combined group. Results: After they were matched, the 3D-CRT and IMRT groups contained 275 and 550 patients with a large discrepancy of 28.7% versus 7.8% toxicities, respectively (P<.001). For both NTCP models, optimal parameters found for the 3D-CRT groups did not fit the IMRT patients well and vice versa. Models developed for the combined data overestimated NTCP for the IMRT patients and underestimated NTCP for the 3D-CRT group. Conclusions: Our analysis did not reveal a single definitive cause for discrepancies of model parameters between 3D-CRT and IMRT. Patient characteristics and bias in toxicity scoring, as well as image guidance alone, are unlikely causes of the large discrepancy of toxicities. Whether the cause was inherent to the specific NTCP models used in this study needs to be verified by future investigations. Because IMRT is increasingly used

Reducing Xerostomia After Chemo-IMRT for Head-and-Neck Cancer: Beyond Sparing the Parotid Glands

Energy Technology Data Exchange (ETDEWEB)

Little, Michael [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States); Schipper, Matthew [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States); Cancer Center Biostatistics Core, University of Michigan, Ann Arbor, MI (United States); Feng, Felix Y.; Vineberg, Karen [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States); Cornwall, Craig; Murdoch-Kinch, Carol-Anne [Hospital Dentistry, University of Michigan, Ann Arbor, MI (United States); Eisbruch, Avraham, E-mail: eisbruch@umich.edu [Department of Radiation Oncology, University of Michigan, Ann Arbor, MI (United States)

2012-07-01

Purpose: To assess whether, in addition to sparing the parotid glands (PGs), xerostomia after chemotherapy plus intensity-modulated radiotherapy (chemo-IMRT) for head-and-neck cancer is affected by reducing the dose to the other salivary glands. Patients and Methods: In a prospective study, 78 patients with Stage III-IV oropharynx/nasopharynx cancer underwent chemo-IMRT, with the aim of sparing the parts of the bilateral PGs, oral cavity (OC) containing the minor salivary glands, and contralateral submandibular gland (SMG) outside the target (when contralateral level I was not a target). Before therapy and periodically for 24 months, validated patient-reported xerostomia questionnaire (XQ) scores and observer-graded xerostomia scores were recorded. Also, the stimulated and unstimulated saliva was measured selectively from each of the PGs and SMGs. The mean OC doses served as surrogates of minor salivary gland dysfunction. Regression models assessed the XQ and observer-graded xerostomia predictors. Results: Statistically significant predictors of the XQ score on univariate analysis included the OC, PG, and SMG mean doses and the baseline XQ score, time since RT, and both stimulated and unstimulated PG saliva flow rates. Similar factors were statistically significant predictors of observer-graded xerostomia. The OC, PG, and SMG mean doses were moderately intercorrelated (r = 0.47-0.55). On multivariate analyses, after adjusting for the PG and SMG doses, the OC mean dose (p < .0001), interval from RT (p < .0001), and stimulated PG saliva (p < .0025) were significant predictors of the XQ scores and the OC mean dose and time for observer-graded xerostomia. Although scatter plots showed no thresholds, an OC mean dose of <40 Gy and contralateral SMG mean dose of <50 Gy were each associated with low patient-reported and observer-rated xerostomia at almost all post-therapy points. Conclusion: The PG, SMG, and OC mean doses were significant predictors of both patient

Reducing Xerostomia After Chemo-IMRT for Head-and-Neck Cancer: Beyond Sparing the Parotid Glands

International Nuclear Information System (INIS)

Little, Michael; Schipper, Matthew; Feng, Felix Y.; Vineberg, Karen; Cornwall, Craig; Murdoch-Kinch, Carol-Anne; Eisbruch, Avraham

2012-01-01

Purpose: To assess whether, in addition to sparing the parotid glands (PGs), xerostomia after chemotherapy plus intensity-modulated radiotherapy (chemo-IMRT) for head-and-neck cancer is affected by reducing the dose to the other salivary glands. Patients and Methods: In a prospective study, 78 patients with Stage III-IV oropharynx/nasopharynx cancer underwent chemo-IMRT, with the aim of sparing the parts of the bilateral PGs, oral cavity (OC) containing the minor salivary glands, and contralateral submandibular gland (SMG) outside the target (when contralateral level I was not a target). Before therapy and periodically for 24 months, validated patient-reported xerostomia questionnaire (XQ) scores and observer-graded xerostomia scores were recorded. Also, the stimulated and unstimulated saliva was measured selectively from each of the PGs and SMGs. The mean OC doses served as surrogates of minor salivary gland dysfunction. Regression models assessed the XQ and observer-graded xerostomia predictors. Results: Statistically significant predictors of the XQ score on univariate analysis included the OC, PG, and SMG mean doses and the baseline XQ score, time since RT, and both stimulated and unstimulated PG saliva flow rates. Similar factors were statistically significant predictors of observer-graded xerostomia. The OC, PG, and SMG mean doses were moderately intercorrelated (r = 0.47–0.55). On multivariate analyses, after adjusting for the PG and SMG doses, the OC mean dose (p < .0001), interval from RT (p < .0001), and stimulated PG saliva (p < .0025) were significant predictors of the XQ scores and the OC mean dose and time for observer-graded xerostomia. Although scatter plots showed no thresholds, an OC mean dose of <40 Gy and contralateral SMG mean dose of <50 Gy were each associated with low patient-reported and observer-rated xerostomia at almost all post-therapy points. Conclusion: The PG, SMG, and OC mean doses were significant predictors of both patient

Verification of patient position and delivery of IMRT by electronic portal imaging

International Nuclear Information System (INIS)

Fielding, Andrew L.; Evans, Philip M.; Clark, Catharine H.

2004-01-01

Background and purpose: The purpose of the work presented in this paper was to determine whether patient positioning and delivery errors could be detected using electronic portal images of intensity modulated radiotherapy (IMRT). Patients and methods: We carried out a series of controlled experiments delivering an IMRT beam to a humanoid phantom using both the dynamic and multiple static field method of delivery. The beams were imaged, the images calibrated to remove the IMRT fluence variation and then compared with calibrated images of the reference beams without any delivery or position errors. The first set of experiments involved translating the position of the phantom both laterally and in a superior/inferior direction a distance of 1, 2, 5 and 10 mm. The phantom was also rotated 1 and 2 deg. For the second set of measurements the phantom position was kept fixed and delivery errors were introduced to the beam. The delivery errors took the form of leaf position and segment intensity errors. Results: The method was able to detect shifts in the phantom position of 1 mm, leaf position errors of 2 mm, and dosimetry errors of 10% on a single segment of a 15 segment IMRT step and shoot delivery (significantly less than 1% of the total dose). Conclusions: The results of this work have shown that the method of imaging the IMRT beam and calibrating the images to remove the intensity modulations could be a useful tool in verifying both the patient position and the delivery of the beam

Dosimetric comparison of treatment techniques IMRT and VMAT for breast cancer

International Nuclear Information System (INIS)

Urbina, G. L.; Garcia, B. G.

2015-10-01

In this study the dosimetric distribution was compared in the different treatment techniques such as Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiation Therapy (IMRT) in female patients with breast cancer with stage II-B and III-A, 6 cases (both calculated on VMAT and IMRT) were studied, comparison parameter that are taken into account are: compliance rate, homogeneity index, monitor units, volume dose 50 Gy (D-50%) and 5 Gy (D-5%) volume dose. Comparisons are made in primary tumor volume to optimize treatment in patients with breast cancer, with IMRT using Step, Shoot and VMAT Monte Carlo algorithm, in addition to the organs at risk; the concern to make this work is due to technological advances in radiotherapy and the application of new treatment techniques, that increase the accuracy allowing treatment dose climbing delivering a higher dose to the patient. (Author)

Micro ionization chamber dosimetry in IMRT verification: Clinical implications of dosimetric errors in the PTV

International Nuclear Information System (INIS)

Sanchez-Doblado, Francisco; Capote, Roberto; Rosello, Joan V.; Leal, Antonio; Lagares, Juan I.; Arrans, Rafael; Hartmann, Guenther H.

2005-01-01

Background and purpose: Absolute dose measurements for Intensity Modulated Radiotherapy (IMRT) beamlets is difficult due to the lack of lateral electron equilibrium. Recently we found that the absolute dosimetry in the penumbra region of the IMRT beamlet, can suffer from significant errors (Capote et al., Med Phys 31 (2004) 2416-2422). This work has the goal to estimate the error made when measuring the Planning Target Volume's (PTV) absolute dose by a micro ion chamber (μIC) in typical IMRT treatment. The dose error comes from the assumption that the dosimetric parameters determining the absolute dose are the same as for the reference conditions. Materials and Methods: Two IMRT treatment plans for common prostate carcinoma case, derived by forward and inverse optimisation, were considered. Detailed geometrical simulation of the μIC and the dose verification set-up was performed. The Monte Carlo (MC) simulation allows us to calculate the delivered dose to water and the dose delivered to the active volume of the ion chamber. However, the measured dose in water is usually derived from chamber readings assuming reference conditions. The MC simulation provides needed correction factors for ion chamber dosimetry in non reference conditions. Results: Dose calculations were carried out for some representative beamlets, a combination of segments and for the delivered IMRT treatments. We observe that the largest dose errors (i.e. the largest correction factors) correspond to the smaller contribution of the corresponding IMRT beamlets to the total dose delivered in the ionization chamber within PTV. Conclusion: The clinical impact of the calculated dose error in PTV measured dose was found to be negligible for studied IMRT treatments

MO-D-213-05: Sensitivity of Routine IMRT QA Metrics to Couch and Collimator Rotations

International Nuclear Information System (INIS)

Alaei, P

2015-01-01

Purpose: To assess the sensitivity of gamma index and other IMRT QA metrics to couch and collimator rotations. Methods: Two brain IMRT plans with couch and/or collimator rotations in one or more of the fields were evaluated using the IBA MatriXX ion chamber array and its associated software (OmniPro-I’mRT). The plans were subjected to routine QA by 1) Creating a composite planar dose in the treatment planning system (TPS) with the couch/collimator rotations and 2) Creating the planar dose after “zeroing” the rotations. Plan deliveries to MatriXX were performed with all rotations set to zero on a Varian 21ex linear accelerator. This in effect created TPS-created planar doses with an induced rotation error. Point dose measurements for the delivered plans were also performed in a solid water phantom. Results: The IMRT QA of the plans with couch and collimator rotations showed clear discrepancies in the planar dose and 2D dose profile overlays. The gamma analysis, however, did pass with the criteria of 3%/3mm (for 95% of the points), albeit with a lower percentage pass rate, when one or two of the fields had a rotation. Similar results were obtained with tighter criteria of 2%/2mm. Other QA metrics such as percentage difference or distance-to-agreement (DTA) histograms produced similar results. The point dose measurements did not obviously indicate the error due to location of dose measurement (on the central axis) and the size of the ion chamber used (0.6 cc). Conclusion: Relying on Gamma analysis, percentage difference, or DTA to determine the passing of an IMRT QA may miss critical errors in the plan delivery due to couch/collimator rotations. A combination of analyses for composite QA plans, or per-beam analysis, would detect these errors

SU-C-BRD-03: Closing the Loop On Virtual IMRT QA

International Nuclear Information System (INIS)

Valdes, G; Scheuermann, R; Y, H C.; Olszanski, A; Bellerive, M; Solberg, T

2015-01-01

Purpose: To develop an algorithm that predicts a priori IMRT QA passing rates. Methods: 416 IMRT plans from all treatment sites were planned in Eclipse version 11 and delivered using a dynamic sliding window technique on Clinac iX or TrueBeam linacs (Varian Medical Systems, Palo Alto, CA). The 3%/3mm and 2%/2mm local distance to agreement (DTA) were recorded during clinical operations using a commercial 2D diode array (MapCHECK 2, Sun Nuclear, Melbourne, FL). Each plan was characterized by 37 metrics that describe different failure modes between the calculated and measured dose. Machine-learning algorithms (MLAs) were trained to learn the relation between the plan characteristics and each passing rate. Minimization of the cross validated error, together with maximum a posteriori estimation (MAP), were used to choose the model parameters. Results: 3%/3mm local DTA can be predicted with an error smaller than 3% for 98% of the plans. For the remaining 2% of plans, the residual error was within 5%. For 2%/2mm local DTA passing rates, 96% percent of the plans were successfully predicted with an error smaller than 5%. All high-risk plans that failed the 2%/2mm local criteria were correctly identified by the algorithm. The most important metric to describe the passing rates was determined to be the MU per Gray (modulation factor). Conclusions: Logs files and independent dose calculations have been suggested as possible substitutes for measurement based IMRT QA. However, none of these methods answer the fundamental question of whether a plan can be delivered with a clinically acceptable error given the limitations of the linacs and the treatment planning system. Predicting the IMRT QA passing rates a priori closes that loop. For additional robustness, virtual IMRT QA can be combined with Linac QA and log file analysis to confirm appropriate delivery

SU-C-BRD-03: Closing the Loop On Virtual IMRT QA

Energy Technology Data Exchange (ETDEWEB)

Valdes, G; Scheuermann, R; Y, H C.; Olszanski, A; Bellerive, M; Solberg, T [University of Pennsylvania, Philadelphia, PA (United States)

2015-06-15

Purpose: To develop an algorithm that predicts a priori IMRT QA passing rates. Methods: 416 IMRT plans from all treatment sites were planned in Eclipse version 11 and delivered using a dynamic sliding window technique on Clinac iX or TrueBeam linacs (Varian Medical Systems, Palo Alto, CA). The 3%/3mm and 2%/2mm local distance to agreement (DTA) were recorded during clinical operations using a commercial 2D diode array (MapCHECK 2, Sun Nuclear, Melbourne, FL). Each plan was characterized by 37 metrics that describe different failure modes between the calculated and measured dose. Machine-learning algorithms (MLAs) were trained to learn the relation between the plan characteristics and each passing rate. Minimization of the cross validated error, together with maximum a posteriori estimation (MAP), were used to choose the model parameters. Results: 3%/3mm local DTA can be predicted with an error smaller than 3% for 98% of the plans. For the remaining 2% of plans, the residual error was within 5%. For 2%/2mm local DTA passing rates, 96% percent of the plans were successfully predicted with an error smaller than 5%. All high-risk plans that failed the 2%/2mm local criteria were correctly identified by the algorithm. The most important metric to describe the passing rates was determined to be the MU per Gray (modulation factor). Conclusions: Logs files and independent dose calculations have been suggested as possible substitutes for measurement based IMRT QA. However, none of these methods answer the fundamental question of whether a plan can be delivered with a clinically acceptable error given the limitations of the linacs and the treatment planning system. Predicting the IMRT QA passing rates a priori closes that loop. For additional robustness, virtual IMRT QA can be combined with Linac QA and log file analysis to confirm appropriate delivery.

Molecular PET imaging for biology-guided adaptive radiotherapy of head and neck cancer.

Science.gov (United States)

Hoeben, Bianca A W; Bussink, Johan; Troost, Esther G C; Oyen, Wim J G; Kaanders, Johannes H A M

2013-10-01

Integration of molecular imaging PET techniques into therapy selection strategies and radiation treatment planning for head and neck squamous cell carcinoma (HNSCC) can serve several purposes. First, pre-treatment assessments can steer decisions about radiotherapy modifications or combinations with other modalities. Second, biology-based objective functions can be introduced to the radiation treatment planning process by co-registration of molecular imaging with planning computed tomography (CT) scans. Thus, customized heterogeneous dose distributions can be generated with escalated doses to tumor areas where radiotherapy resistance mechanisms are most prevalent. Third, monitoring of temporal and spatial variations in these radiotherapy resistance mechanisms early during the course of treatment can discriminate responders from non-responders. With such information available shortly after the start of treatment, modifications can be implemented or the radiation treatment plan can be adapted tailing the biological response pattern. Currently, these strategies are in various phases of clinical testing, mostly in single-center studies. Further validation in multicenter set-up is needed. Ultimately, this should result in availability for routine clinical practice requiring stable production and accessibility of tracers, reproducibility and standardization of imaging and analysis methods, as well as general availability of knowledge and expertise. Small studies employing adaptive radiotherapy based on functional dynamics and early response mechanisms demonstrate promising results. In this context, we focus this review on the widely used PET tracer (18)F-FDG and PET tracers depicting hypoxia and proliferation; two well-known radiation resistance mechanisms.

Analysis of Local Control in Patients Receiving IMRT for Resected Pancreatic Cancers

International Nuclear Information System (INIS)

Yovino, Susannah; Maidment, Bert W.; Herman, Joseph M.; Pandya, Naimish; Goloubeva, Olga; Wolfgang, Chris; Schulick, Richard; Laheru, Daniel; Hanna, Nader; Alexander, Richard; Regine, William F.

2012-01-01

Purpose: Intensity-modulated radiotherapy (IMRT) is increasingly incorporated into therapy for pancreatic cancer. A concern regarding this technique is the potential for geographic miss and decreased local control. We analyzed patterns of first failure among patients treated with IMRT for resected pancreatic cancer. Methods and Materials: Seventy-one patients who underwent resection and adjuvant chemoradiation for pancreas cancer are included in this report. IMRT was used for all to a median dose of 50.4 Gy. Concurrent chemotherapy was 5-FU–based in 72% of patients and gemcitabine-based in 28%. Results: At median follow-up of 24 months, 49/71 patients (69%) had failed. The predominant failure pattern was distant metastases in 35/71 patients (49%). The most common site of metastases was the liver. Fourteen patients (19%) developed locoregional failure in the tumor bed alone in 5 patients, regional nodes in 4 patients, and concurrently with metastases in 5 patients. Median overall survival (OS) was 25 months. On univariate analysis, nodal status, margin status, postoperative CA 19-9 level, and weight loss during treatment were predictive for OS. On multivariate analysis, higher postoperative CA19-9 levels predicted for worse OS on a continuous basis (p < 0.01). A trend to worse OS was seen among patients with more weight loss during therapy (p = 0.06). Patients with positive nodes and positive margins also had significantly worse OS (HR for death 2.8, 95% CI 1.1–7.5; HR for death 2.6, 95% CI 1.1–6.2, respectively). Grade 3-4 nausea and vomiting was seen in 8% of patients. Late complication of small bowel obstruction occurred in 4 (6%) patients. Conclusions: This is the first comprehensive report of patterns of failure among patients treated with adjuvant IMRT for pancreas cancer. IMRT was not associated with an increase in local recurrences in our cohort. These data support the use of IMRT in the recently activated EORTC/US Intergroup/RTOG 0848 adjuvant

Dose planning objectives in anal canal cancer IMRT: the TROG ANROTAT experience

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Brown, Elizabeth, E-mail: elizabeth@mebrown.net [Princess Alexandra Hospital, Brisbane, Queensland (Australia); Cray, Alison [Peter MacCallum Cancer Cancer Centre, Box Hill, Victoria (Australia); Haworth, Annette [Peter MacCallum Cancer Cancer Centre, Box Hill, Victoria (Australia); University of Melbourne, Melbourne, Victoria (Australia); Chander, Sarat [Peter MacCallum Cancer Cancer Centre, Box Hill, Victoria (Australia); Lin, Robert [Medica Oncology, Hurstville, New South Wales (Australia); Subramanian, Brindha; Ng, Michael [Radiation Oncology Victoria, Melbourne, Victoria (Australia); Princess Alexandra Hospital, Brisbane, Queensland (Australia)

2015-06-15

Intensity modulated radiotherapy (IMRT) is ideal for anal canal cancer (ACC), delivering high doses to irregular tumour volumes whilst minimising dose to surrounding normal tissues. Establishing achievable dose objectives is a challenge. The purpose of this paper was to utilise data collected in the Assessment of New Radiation Oncology Treatments and Technologies (ANROTAT) project to evaluate the feasibility of ACC IMRT dose planning objectives employed in the Australian situation. Ten Australian centres were randomly allocated three data sets from 15 non-identifiable computed tomography data sets representing a range of disease stages and gender. Each data set was planned by two different centres, producing 30 plans. All tumour and organ at risk (OAR) contours, prescription and dose constraint details were provided. Dose–volume histograms (DVHs) for each plan were analysed to evaluate the feasibility of dose planning objectives provided. All dose planning objectives for the bone marrow (BM) and femoral heads were achieved. Median planned doses exceeded one or more objectives for bowel, external genitalia and bladder. This reached statistical significance for bowel V30 (P = 0.04), V45 (P < 0.001), V50 (P < 0.001), external genitalia V20 (P < 0.001) and bladder V35 (P < 0.001), V40 (P = 0.01). Gender was found to be the only significant factor in the likelihood of achieving the bowel V50 (P = 0.03) and BM V30 constraints (P = 0.04). The dose planning objectives used in the ANROTAT project provide a good starting point for ACC IMRT planning. To facilitate clinical implementation, it is important to prioritise OAR objectives and recognise factors that affect the achievability of these objectives.

Esophagus and contralateral lung-sparing IMRT for locally advanced lung cancer in the community hospital setting

Directory of Open Access Journals (Sweden)

Johnny eKao

2015-06-01

Full Text Available Background: The optimal technique for performing lung IMRT remains poorly defined. We hypothesize that improved dose distributions associated with normal tissue sparing IMRT can allow for safe dose escalation resulting in decreased acute and late toxicity. Methods: We performed a retrospective analysis of 82 consecutive lung cancer patients treated with curative intent from 1/10 to 9/14. From 1/10 to 4/12, 44 patients were treated with the community standard of 3-dimensional conformal radiotherapy or IMRT without specific esophagus or contralateral lung constraints (standard RT. From 5/12 to 9/14, 38 patients were treated with normal tissue-sparing IMRT with selective sparing of contralateral lung and esophagus. The study endpoints were dosimetry, toxicity and overall survival.Results: Despite higher mean prescribed radiation doses in the normal tissue-sparing IMRT cohort (64.5 Gy vs. 60.8 Gy, p=0.04, patients treated with normal tissue-sparing IMRT had significantly lower lung V20, V10, V5, mean lung, maximum esophagus and mean esophagus doses compared to patients treated with standard RT (p≤0.001. Patients in the normal tissue-sparing IMRT group had reduced acute grade ≥3 esophagitis (0% vs. 11%, p<0.001, acute grade ≥2 weight loss (2% vs. 16%, p=0.04, late grade ≥2 pneumonitis (7% vs. 21%, p=0.02. The 2-year overall survival was 52% with normal tissue-sparing IMRT arm compared to 28% for standard RT (p=0.015.Conclusion: These data provide proof of principle that suboptimal radiation dose distributions are associated with significant acute and late lung and esophageal toxicity that may result in hospitalization or even premature mortality. Strict attention to contralateral lung and esophageal dose volume constraints are feasible in the community hospital setting without sacrificing disease control.

Adoption: biological and social processes linked to adaptation.

Science.gov (United States)

Grotevant, Harold D; McDermott, Jennifer M

2014-01-01

Children join adoptive families through domestic adoption from the public child welfare system, infant adoption through private agencies, and international adoption. Each pathway presents distinctive developmental opportunities and challenges. Adopted children are at higher risk than the general population for problems with adaptation, especially externalizing, internalizing, and attention problems. This review moves beyond the field's emphasis on adoptee-nonadoptee differences to highlight biological and social processes that affect adaptation of adoptees across time. The experience of stress, whether prenatal, postnatal/preadoption, or during the adoption transition, can have significant impacts on the developing neuroendocrine system. These effects can contribute to problems with physical growth, brain development, and sleep, activating cascading effects on social, emotional, and cognitive development. Family processes involving contact between adoptive and birth family members, co-parenting in gay and lesbian adoptive families, and racial socialization in transracially adoptive families affect social development of adopted children into adulthood.

Influence of the order of introduction of a set of objectives in IMRT treatment schedules prostate

International Nuclear Information System (INIS)

Maravilla Limorte, M.; Gomez Martin, C.; Alonso Iracheta, L.; Bejar Navarro, M. J.; Capuz Suarez, A. B.; Comenares Fernandez, R.; Moris Pablos, R.; Rot Sanjuan, M. J.

2011-01-01

The purpose of this paper is to analyze to what extent could influence the order in which you enter the target calculation algorithm of planning. For this, assesses the implications-both-dosimetric calculation as derived from the implementation of 3 IMRT optimization methods, which only differ in regard to the order of introduction of a fixed set of objectives.

Influence of intra-fractional breathing movement in step-and-shoot IMRT

International Nuclear Information System (INIS)

Schaefer, M; Muenter, M W; Thilmann, C; Sterzing, F; Haering, P; Combs, S E; Debus, J

2004-01-01

Efforts have been made to extend the application of intensity-modulated radiotherapy to a variety of organs. One of the unanswered questions is whether breathing-induced organ motion may lead to a relevant over- or underdosage, e.g., in treatment plans for the irradiation of lung cancer. Theoretical considerations have been made concerning the different kinds of IMRT but there is still a lack of experimental data. We examined 18 points in a fraction of a clinical treatment plan of a NSCLC delivered in static IMRT with a new phantom and nine ionization chambers. Measurements were performed at a speed of 12 and 16 breathing cycles per minute. The dose differences between static points and moving target points ranged between -2.4% and +5.5% (mean: +0.2%, median: -0.1%) when moving with 12 cycles min -1 and between -3.6% and +5.0% (mean: -0.4%, median: -0.6%) when moving with 16 cycles min -1 . All differences of measurements with and without movements were below 5%, with one exception. In conclusion, our results underline that at least in static IMRT breathing effects (concerning target dose coverage) due to interplay effects between collimator leaf movement and target movement are of secondary importance and will not reduce the clinical value of IMRT in the step-and-shoot technique for irradiation of thoracic targets. (note)

Computational model to simulate the interplay effect in dynamic IMRT delivery

International Nuclear Information System (INIS)

Yoganathan, S A; Maria Das, K J; Kumar, Shaleen

2014-01-01

The purpose of this study was to develop and experimentally verify a patient specific model for simulating the interplay effect in a DMLC based IMRT delivery. A computational model was developed using MATLAB program to incorporate the interplay effect in a 2D beams eye view fluence of dynamic IMRT fields. To simulate interplay effect, the model requires two inputs: IMRT field (DMLC file with dose rate and MU) and the patient specific respiratory motion. The interplay between the DMLC leaf motion and target was simulated for three lung patients. The target trajectory data was acquired using RPM system during the treatment simulation. The model was verified experimentally for the same patients using Imatrix 2D array device placed over QUASAR motion platform in CL2100 linac. The simulated fluences and measured fluences were compared with the TPS generated static fluence (no motion) using an in-house developed gamma evaluation program (2%/2mm). The simulated results were well within agreement with the measured. Comparison of the simulated and measured fluences with the TPS static fluence resulted 55.3% and 58.5% pixels passed the gamma criteria. A patient specific model was developed and validated for simulating the interplay effect in the dynamic IMRT delivery. This model can be clinically used to quantify the dosimetric uncertainty due to the interplay effect prior to the treatment delivery.

IMRT QA: Selecting gamma criteria based on error detection sensitivity

Energy Technology Data Exchange (ETDEWEB)

Steers, Jennifer M. [Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California 90048 and Physics and Biology in Medicine IDP, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90095 (United States); Fraass, Benedick A., E-mail: benedick.fraass@cshs.org [Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, California 90048 (United States)

2016-04-15

Purpose: The gamma comparison is widely used to evaluate the agreement between measurements and treatment planning system calculations in patient-specific intensity modulated radiation therapy (IMRT) quality assurance (QA). However, recent publications have raised concerns about the lack of sensitivity when employing commonly used gamma criteria. Understanding the actual sensitivity of a wide range of different gamma criteria may allow the definition of more meaningful gamma criteria and tolerance limits in IMRT QA. We present a method that allows the quantitative determination of gamma criteria sensitivity to induced errors which can be applied to any unique combination of device, delivery technique, and software utilized in a specific clinic. Methods: A total of 21 DMLC IMRT QA measurements (ArcCHECK®, Sun Nuclear) were compared to QA plan calculations with induced errors. Three scenarios were studied: MU errors, multi-leaf collimator (MLC) errors, and the sensitivity of the gamma comparison to changes in penumbra width. Gamma comparisons were performed between measurements and error-induced calculations using a wide range of gamma criteria, resulting in a total of over 20 000 gamma comparisons. Gamma passing rates for each error class and case were graphed against error magnitude to create error curves in order to represent the range of missed errors in routine IMRT QA using 36 different gamma criteria. Results: This study demonstrates that systematic errors and case-specific errors can be detected by the error curve analysis. Depending on the location of the error curve peak (e.g., not centered about zero), 3%/3 mm threshold = 10% at 90% pixels passing may miss errors as large as 15% MU errors and ±1 cm random MLC errors for some cases. As the dose threshold parameter was increased for a given %Diff/distance-to-agreement (DTA) setting, error sensitivity was increased by up to a factor of two for select cases. This increased sensitivity with increasing dose

Six years of experience in the planning and verification of the IMRT dynamics with portal dosimetry; Seis anos de expereincia en la planificacion y verificacion de la IMRT dinamica con portal dosimetry

Energy Technology Data Exchange (ETDEWEB)

Molina Lopez, M. Y.; Pardo Perez, E.; Ruiz Maqueda, S.; Castro Novais, J.; Diaz Gavela, A. A.

2013-07-01

The objective of this study is the make a review of the method of verification of the IMRT throughout the 6 years of functioning of the service of-radiophysics and radiology protection, analyzing the parameters of each field evaluation to the 718 made IMRT during this period. (Author)

IMRT and radiation protection in the prostate cancer therapy; IMRT e a protecao radiologica no tratamento do cancer de prostata

Energy Technology Data Exchange (ETDEWEB)

Santos, Helena C.; Silva, Andre R.M.; Oliveira, Claudia F.M., E-mail: andrerichard88@bol.com.br [Instituto Federal de Educacao, Ciencia e Tecnologia de Pernambuco (IFPE), Recife, PE (Brazil)

2015-07-01

This study aims to specify the technological advances that IMRT presents relative to other traditional radiotherapy, particularly to conformal radiotherapy three dimensional (3D-TCR) and benefits compared to the side effects caused by from treatment of radiotherapy.

Assessing the components of adaptive capacity to improve conservation and management efforts under global change.

Science.gov (United States)

Nicotra, Adrienne B; Beever, Erik A; Robertson, Amanda L; Hofmann, Gretchen E; O'Leary, John

2015-10-01

Natural-resource managers and other conservation practitioners are under unprecedented pressure to categorize and quantify the vulnerability of natural systems based on assessment of the exposure, sensitivity, and adaptive capacity of species to climate change. Despite the urgent need for these assessments, neither the theoretical basis of adaptive capacity nor the practical issues underlying its quantification has been articulated in a manner that is directly applicable to natural-resource management. Both are critical for researchers, managers, and other conservation practitioners to develop reliable strategies for assessing adaptive capacity. Drawing from principles of classical and contemporary research and examples from terrestrial, marine, plant, and animal systems, we examined broadly the theory behind the concept of adaptive capacity. We then considered how interdisciplinary, trait- and triage-based approaches encompassing the oft-overlooked interactions among components of adaptive capacity can be used to identify species and populations likely to have higher (or lower) adaptive capacity. We identified the challenges and value of such endeavors and argue for a concerted interdisciplinary research approach that combines ecology, ecological genetics, and eco-physiology to reflect the interacting components of adaptive capacity. We aimed to provide a basis for constructive discussion between natural-resource managers and researchers, discussions urgently needed to identify research directions that will deliver answers to real-world questions facing resource managers, other conservation practitioners, and policy makers. Directing research to both seek general patterns and identify ways to facilitate adaptive capacity of key species and populations within species, will enable conservation ecologists and resource managers to maximize returns on research and management investment and arrive at novel and dynamic management and policy decisions. © 2015 Society for

Dosimetric comparison of helical tomotherapy, RapidArc, and a novel IMRT and Arc technique for esophageal carcinoma

International Nuclear Information System (INIS)

Martin, Spencer; Chen, Jeff Z.; Rashid Dar, A.; Yartsev, Slav

2011-01-01

Purpose: To compare radiotherapy treatment plans for mid- and distal-esophageal cancer with primary involvement of the gastroesophageal (GE) junction using a novel IMRT and Arc technique (IMRT and Arc), helical tomotherapy (HT), and RapidArc (RA1 and RA2). Methods and materials: Eight patients treated on HT for locally advanced esophageal cancer with radical intent were re-planned for RA and IMRT and Arc. RA plans employed single and double arcs (RA1 and RA2, respectively), while IMRT and Arc plans had four fixed-gantry IMRT fields and a conformal arc. Dose-volume histogram statistics, dose uniformity, and dose homogeneity were analyzed to compare treatment plans. Results: RA2 plans showed significant improvement over RA1 plans in terms of OAR dose and PTV dose uniformity and homogeneity. HT plan provided best dose uniformity (p = 0.001) and dose homogeneity (p = 0.002) to planning target volume (PTV), while IMRT and Arc and RA2 plans gave lowest dose to lungs among four radiotherapy techniques with acceptable PTV dose coverage. Mean V 10 of the lungs was significantly reduced by the RA2 plans compared to IMRT and Arc (40.3%, p = 0.001) and HT (66.2%, p 15 of the lungs for the RA2 plans also showed significant improvement over the IMRT and Arc (25.2%, p = 0.042) and HT (34.8%, p = 0.027) techniques. These improvements came at the cost of higher doses to the heart volume compared to HT and IMRT and Arc techniques. Mean lung dose (MLD) for the IMRT and Arc technique (21.2 ± 5.0% of prescription dose) was significantly reduced compared to HT (26.3%, p = 0.004), RA1 (23.3%, p = 0.028), and RA2 (23.2%, p = 0.017) techniques. Conclusion: The IMRT and Arc technique is a good option for treating esophageal cancer with thoracic involvement. It achieved optimal low dose to the lungs and heart with acceptable PTV coverage. HT is a good option for treating esophageal cancer with little thoracic involvement as it achieves superior dose conformality and uniformity. The RA2

Validation of the implementation of IMRT with three dosimetric methods of independent verification

International Nuclear Information System (INIS)

Tortosa Oliver, R. A.; Chinillach ferrando, N.; Alonso Arrizabalaga, S.; Campayo Esteban, J. M.; Morales Marco, J. C.; Soler Catalan, P.; Andreu Martinez, F. J.

2013-01-01

The TG119 is a simple and clear framework to verify the implementation of IMRT technique in a radiotherapy service. Verifications of this document recommended tests conducted with the three dosimetric methods listed above, allow to affirm that our Center is within the margins of tolerance considered suitable in the TG119 for the clinical implementation of IMRT. (Author)

A mathematical framework for virtual IMRT QA using machine learning.

Science.gov (United States)

Valdes, G; Scheuermann, R; Hung, C Y; Olszanski, A; Bellerive, M; Solberg, T D

2016-07-01

It is common practice to perform patient-specific pretreatment verifications to the clinical delivery of IMRT. This process can be time-consuming and not altogether instructive due to the myriad sources that may produce a failing result. The purpose of this study was to develop an algorithm capable of predicting IMRT QA passing rates a priori. From all treatment, 498 IMRT plans sites were planned in eclipse version 11 and delivered using a dynamic sliding window technique on Clinac iX or TrueBeam Linacs. 3%/3 mm local dose/distance-to-agreement (DTA) was recorded using a commercial 2D diode array. Each plan was characterized by 78 metrics that describe different aspects of their complexity that could lead to disagreements between the calculated and measured dose. A Poisson regression with Lasso regularization was trained to learn the relation between the plan characteristics and each passing rate. Passing rates 3%/3 mm local dose/DTA can be predicted with an error smaller than 3% for all plans analyzed. The most important metrics to describe the passing rates were determined to be the MU factor (MU per Gy), small aperture score, irregularity factor, and fraction of the plan delivered at the corners of a 40 × 40 cm field. The higher the value of these metrics, the worse the passing rates. The Virtual QA process predicts IMRT passing rates with a high likelihood, allows the detection of failures due to setup errors, and it is sensitive enough to detect small differences between matched Linacs.

Assessing institutional capacities to adapt to climate change - integrating psychological dimensions in the Adaptive Capacity Wheel

Science.gov (United States)

Grothmann, T.; Grecksch, K.; Winges, M.; Siebenhüner, B.

2013-03-01

Several case studies show that "soft social factors" (e.g. institutions, perceptions, social capital) strongly affect social capacities to adapt to climate change. Many soft social factors can probably be changed faster than "hard social factors" (e.g. economic and technological development) and are therefore particularly important for building social capacities. However, there are almost no methodologies for the systematic assessment of soft social factors. Gupta et al. (2010) have developed the Adaptive Capacity Wheel (ACW) for assessing the adaptive capacity of institutions. The ACW differentiates 22 criteria to assess six dimensions: variety, learning capacity, room for autonomous change, leadership, availability of resources, fair governance. To include important psychological factors we extended the ACW by two dimensions: "adaptation motivation" refers to actors' motivation to realise, support and/or promote adaptation to climate. "Adaptation belief" refers to actors' perceptions of realisability and effectiveness of adaptation measures. We applied the extended ACW to assess adaptive capacities of four sectors - water management, flood/coastal protection, civil protection and regional planning - in North Western Germany. The assessments of adaptation motivation and belief provided a clear added value. The results also revealed some methodological problems in applying the ACW (e.g. overlap of dimensions), for which we propose methodological solutions.

Methods for isolation and viability assessment of biological organisms

Science.gov (United States)

Letant, Sonia Edith; Baker, Sarah Elyse; Bond, Tiziana; Chang, Allan Shih-Ping

2015-02-03

Isolation of biological or chemical organisms can be accomplished using a surface enhanced Raman scattering (SERS) system. The SERS system can be a single or a stacked plurality of photonic crystal membranes with noble-metal lined through pores for flowing analyte potentially containing the biological or chemical organisms. The through pores can be adapted to trap individual biological or chemical organisms and emit SERS spectra, which can then be detected by a detector and further analyzed for viability of the biological or chemical organism.

Node-positive left-sided breast cancer. Does VMAT improve treatment plan quality with respect to IMRT?

Energy Technology Data Exchange (ETDEWEB)

Pasler, M.; Bartelt, S.; Lutterbach, J. [Lake Constance Radiation Oncology Center Singen, Friedrichshafen (Germany); Georg, D. [Medical University Vienna/AKH Wien, Vienna (Austria). Dept. of Radiooncology; Medical University Vienna (Austria). Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology

2013-05-15

Purpose: The aim of the present work was to explore plan quality and dosimetric accuracy of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) for lymph node-positive left-sided breast cancer. Methods: VMAT and IMRT plans were generated with the Pinnacle{sup 3} V9.0 treatment planning system for 10 lymph node-positive left-sided breast cancer patients. VMAT plans were created using a single arc and IMRT was performed with 4 beams using 6, 10, and 15 MV photon energy, respectively. Plans were evaluated both manually and automatically using ArtiView trademark. Dosimetric plan verification was performed with a 2D ionization chamber array placed in a full scatter phantom. Results: Photon energy had no significant influence on plan quality for both VMAT and IMRT. Large variability in low doses to the heart was found due to patient anatomy (range V{sub 5} {sub Gy} 26.5-95 %). Slightly more normal tissue dose was found for VMAT (e.g., V{sub Tissue30%} = 22 %) than in IMRT (V{sub Tissue30%} = 18 %). The manual and ArtiView trademark plan evaluation coincided very accurately for most dose metrics (difference < 1 %). In VMAT, 96.7 % of detector points passed the 3 %/3 mm gamma criterion; marginally better accuracy was found in IMRT (98.3 %). Conclusion: VMAT for node-positive left-sided breast cancer retains target homogeneity and coverage when compared to IMRT and allows maximum doses to organs at risk to be reduced. ArtiView trademark enables fast and accurate plan evaluation. (orig.)

Theoretical and practical model for implementing intensity modulated radiotherapy (IMRT) based on openness in head and neck tumors

International Nuclear Information System (INIS)

Napoles Morales, Misleidy; Yanes Lopez, Yaima; Ascension, Yudith; Alfonso La Guardia, Rodolfo; Calderon, Carlos

2009-01-01

Certain requirements have been internationally recommended for the transition from radiation therapy (3D-CRT) to intensity modulated radiation therapy (IMRT). They have been filling in clinical practice in the physical, dosimetry and quality of treatment. Prior to the implementation of IMRT have been developed preclinical will proceed according to the treatment planning techniques in the real images of patients, validating the rationale for the transition from the point of view and radiobiological dosimetry. The comparison was based on a group of patients eligible for IMRT, which were actually treated with 3D-CRT. IMRT plans were designed and applied to virtually the same patients, simulating the IMRT treatment. The prescribed dose and fractionation were similar in both techniques, to be able to compare radiobiology. The results show the rationality of IMRT in terms of reducing complications and the possibility of scaling doses in the PTV. Were used Dose Volume Histograms (HDV) obtained from the dosimetric calculations for radiobiological evaluation of treatment plans, letting through a software: 'Albireo Target' version 4.0.1.2008 calculate the equivalent uniform dose (EUD) for tumor and organs of risks (OAR) and tumor control probability (TCP) and the likelihood of damage to healthy tissue (NTCP). The results obtained with IMRT plans were more significant than with 3D-CRT especially in terms of EUD for organs at risk and NTCP. These results allow us to create the definitive basis for the implementation of IMRT in our environment. (Author)

SU-E-T-198: Hippocampal-Sparing Radiotherapy (HSRT) for Patients with Head and Neck Cancer (HNC) Using Intensity-Modulated Radiation Therapy (IMRT)

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Dunlop, A; Welsh, L; Nutting, C; Harrington, K; Bhide, S; Newbold, K

2014-06-01

Purpose: There is increasing evidence that decline in cognitive function following brain radiotherapy (RT) is related to the radiation dose delivered to the hippocampi. In this work we evaluate the feasibility of using IMRT to generate HSRT plans in HNC. Methods: A planning study was undertaken for ten representative patients with HNC previously treated with radical (chemo)-RT using standard IMRT techniques. The hippocampi were delineated according to the RTOG hippocampal contouring atlas, on a T1w- MRI scan that was registered with the RT planning CT. LINAC-based, clinically acceptable, HSRT plans were generated and assessed using the Pinnacle3 treatment planning system. Results: Using a VMAT technique, a reduction in hippocampal dose was achievable in six cases. For these cases, the EQD2-D40% of the bilateral hippocampi was significantly reduced by HSRT (p = 0.006) from a median of 18.8Gy (range 14.4–34.6) to 6.5 Gy (4.2–9.5) for the delivered and HSRT plans respectively. Plans were also generated using a fixed-field IMRT technique with non-coplanar beams that were designed to avoid the bilateral hippocampi, resulting in a median EQD2-D40% of 11.2Gy (8.0–14.5). Both HSRT techniques also resulted in lower doses to the whole brain, brain stem, and cerebellum. The HSRT plans resulted in higher doses to some regions of non-contoured normaltissue, but the magnitude of these dose differences is unlikely to be of clinical significance in terms of acute and late toxicity. Conclusion: This study has demonstrated that it is possible, in many cases, to adapt treatment plans for HNC to significantly reduce dose to the hippocampi. This reduction in dose would be predicted to Resultin a significant reduction in the probability of subsequent decline in cognitive function following RT. Our results point towards the need for the collection of prospective data on cognitive outcomes for the HNC patient population treated with radical (chemo)-RT.

SU-E-T-198: Hippocampal-Sparing Radiotherapy (HSRT) for Patients with Head and Neck Cancer (HNC) Using Intensity-Modulated Radiation Therapy (IMRT)

International Nuclear Information System (INIS)

Dunlop, A; Welsh, L; Nutting, C; Harrington, K; Bhide, S; Newbold, K

2014-01-01

Purpose: There is increasing evidence that decline in cognitive function following brain radiotherapy (RT) is related to the radiation dose delivered to the hippocampi. In this work we evaluate the feasibility of using IMRT to generate HSRT plans in HNC. Methods: A planning study was undertaken for ten representative patients with HNC previously treated with radical (chemo)-RT using standard IMRT techniques. The hippocampi were delineated according to the RTOG hippocampal contouring atlas, on a T1w- MRI scan that was registered with the RT planning CT. LINAC-based, clinically acceptable, HSRT plans were generated and assessed using the Pinnacle3 treatment planning system. Results: Using a VMAT technique, a reduction in hippocampal dose was achievable in six cases. For these cases, the EQD2-D40% of the bilateral hippocampi was significantly reduced by HSRT (p = 0.006) from a median of 18.8Gy (range 14.4–34.6) to 6.5 Gy (4.2–9.5) for the delivered and HSRT plans respectively. Plans were also generated using a fixed-field IMRT technique with non-coplanar beams that were designed to avoid the bilateral hippocampi, resulting in a median EQD2-D40% of 11.2Gy (8.0–14.5). Both HSRT techniques also resulted in lower doses to the whole brain, brain stem, and cerebellum. The HSRT plans resulted in higher doses to some regions of non-contoured normaltissue, but the magnitude of these dose differences is unlikely to be of clinical significance in terms of acute and late toxicity. Conclusion: This study has demonstrated that it is possible, in many cases, to adapt treatment plans for HNC to significantly reduce dose to the hippocampi. This reduction in dose would be predicted to Resultin a significant reduction in the probability of subsequent decline in cognitive function following RT. Our results point towards the need for the collection of prospective data on cognitive outcomes for the HNC patient population treated with radical (chemo)-RT

Serial tomotherapy vs. MLC-IMRT (Multileaf Collimator Intensity Modulated Radiotherapy) for simultaneous boost treatment large intracerebral lesions

International Nuclear Information System (INIS)

Wolff, Dirk; Lohr, Frank; Mai, Sabine; Polednik, Martin; Wenz, Frederik; Dobler, Barbara

2009-01-01

Introduction: Recent data suggest that a radiosurgery boost treatment for up to three brain metastases in addition to whole brain radiotherapy (WBRT) is beneficial. Sequential treatment of multiple metastatic lesions is time-consuming and optimal normal tissue sparing is not trivial for larger metastases when separate plans are created and are only superimposed afterwards. Sequential Tomotherapy with noncoplanar arcs and Multi-field IMRT may streamline the process and enable easy simultaneous treatment. We compared plans for 2-3 intracerebral targets calculated with Intensity Modulated Radiotherapy (IMRT) based on treatment with MLC or sequential Tomotherapy using the Peacock-System. Treatment time was not to exceed 90 min on a linac with standart dose rate. MIMiC plans without treatment-time restrictions were created as a benchmark. Materials and methods: Calculations are based on a Siemens KD2 linac with a dose rate of 200 MU/min. Step-and-Shoot IMRT is performed with a standard MLC (2 x 29 leaves, 1 cm), serial Tomotherapy with the Multivane-Collimator MIMiC (NOMOS Inc. USA). Treatment plans are created with Corvus 5.0. To create plans with good conformity we chose a noncoplanar beam- and arc geometry for each approach (IMRT 4-, MIMiC 5-couch angles). The benchmark MIMiC plans with maximally steep dose gradients had 9 couch angles. For plan comparison reasons, 10Gy were prescribed to 90% of the PTV. Steepness of dose gradients, homogeneity and conformity were assessed by the following parameters: Volume encompassed by certain isodoses outside the target as well as homogeneity and conformity as indicated by Homogeneity- and Conformity-Index. Results: Plans without treatment-time restrictions had slightest dose to organ at risk (OAR), normal tissue and least Conformity-index. MIMiC- and MLC-IMRT based plans can be treated within the intended period of 90 min, all plans met the required dose. MLC based plans resulted in higher dose to organs at risk (OAR) and dose

Development of a quality control system in intensity modulated radiotherapy (IMRT)

International Nuclear Information System (INIS)

Souza, Roberto Salomon de; Braz, Delson

2013-01-01

The more complex the technique of radiotherapy is, the more refined the quality control must be. The technique of Intensity Modulated Radiotherapy (IMRT) is one of the technological innovations that gained space in the whole worlds in the last decade whose parameters of quality control are not fully established yet. The present work developed a phantom for quality control in IMRT to be implemented in the routine of the Radiotherapy Quality Control Program (PQRT) of the Brazilian National Cancer Institute (INCa). The device consists of a block formed by several polystyrene slice with TDLs and radiochromic film inserted. It should be sent (or taken) to the Program participating institutions to be irradiated under certain conditions and then be returned to the PQRT., where the discrepancy degree between the planned treatment and those effectively delivered will be evaluated. The system was validated through the test cases and the pilot program preformed in nine radiotherapy centers that perform IMRT in the southeast region of Brazil. (author)

Quality correction factors of composite IMRT beam deliveries: Theoretical considerations

International Nuclear Information System (INIS)

Bouchard, Hugo

2012-01-01

Purpose: In the scope of intensity modulated radiation therapy (IMRT) dosimetry using ionization chambers, quality correction factors of plan-class-specific reference (PCSR) fields are theoretically investigated. The symmetry of the problem is studied to provide recommendable criteria for composite beam deliveries where correction factors are minimal and also to establish a theoretical limit for PCSR delivery k Q factors. Methods: The concept of virtual symmetric collapsed (VSC) beam, being associated to a given modulated composite delivery, is defined in the scope of this investigation. Under symmetrical measurement conditions, any composite delivery has the property of having a k Q factor identical to its associated VSC beam. Using this concept of VSC, a fundamental property of IMRT k Q factors is demonstrated in the form of a theorem. The sensitivity to the conditions required by the theorem is thoroughly examined. Results: The theorem states that if a composite modulated beam delivery produces a uniform dose distribution in a volume V cyl which is symmetric with the cylindrical delivery and all beams fulfills two conditions in V cyl : (1) the dose modulation function is unchanged along the beam axis, and (2) the dose gradient in the beam direction is constant for a given lateral position; then its associated VSC beam produces no lateral dose gradient in V cyl , no matter what beam modulation or gantry angles are being used. The examination of the conditions required by the theorem lead to the following results. The effect of the depth-dose gradient not being perfectly constant with depth on the VSC beam lateral dose gradient is found negligible. The effect of the dose modulation function being degraded with depth on the VSC beam lateral dose gradient is found to be only related to scatter and beam hardening, as the theorem holds also for diverging beams. Conclusions: The use of the symmetry of the problem in the present paper leads to a valuable theorem showing

A silicon strip detector dose magnifying glass for IMRT dosimetry

International Nuclear Information System (INIS)

Wong, J. H. D.; Carolan, M.; Lerch, M. L. F.; Petasecca, M.; Khanna, S.; Perevertaylo, V. L.; Metcalfe, P.; Rosenfeld, A. B.

2010-01-01

Purpose: Intensity modulated radiation therapy (IMRT) allows the delivery of escalated radiation dose to tumor while sparing adjacent critical organs. In doing so, IMRT plans tend to incorporate steep dose gradients at interfaces between the target and the organs at risk. Current quality assurance (QA) verification tools such as 2D diode arrays, are limited by their spatial resolution and conventional films are nonreal time. In this article, the authors describe a novel silicon strip detector (CMRP DMG) of high spatial resolution (200 μm) suitable for measuring the high dose gradients in an IMRT delivery. Methods: A full characterization of the detector was performed, including dose per pulse effect, percent depth dose comparison with Farmer ion chamber measurements, stem effect, dose linearity, uniformity, energy response, angular response, and penumbra measurements. They also present the application of the CMRP DMG in the dosimetric verification of a clinical IMRT plan. Results: The detector response changed by 23% for a 390-fold change in the dose per pulse. A correction function is derived to correct for this effect. The strip detector depth dose curve agrees with the Farmer ion chamber within 0.8%. The stem effect was negligible (0.2%). The dose linearity was excellent for the dose range of 3-300 cGy. A uniformity correction method is described to correct for variations in the individual detector pixel responses. The detector showed an over-response relative to tissue dose at lower photon energies with the maximum dose response at 75 kVp nominal photon energy. Penumbra studies using a Varian Clinac 21EX at 1.5 and 10.0 cm depths were measured to be 2.77 and 3.94 mm for the secondary collimators, 3.52 and 5.60 mm for the multileaf collimator rounded leaf ends, respectively. Point doses measured with the strip detector were compared to doses measured with EBT film and doses predicted by the Philips Pinnacle treatment planning system. The differences were 1.1%�

From analytic inversion to contemporary IMRT optimization: radiation therapy planning revisited from a mathematical perspective.

Science.gov (United States)

Censor, Yair; Unkelbach, Jan

2012-04-01

In this paper we look at the development of radiation therapy treatment planning from a mathematical point of view. Historically, planning for Intensity-Modulated Radiation Therapy (IMRT) has been considered as an inverse problem. We discuss first the two fundamental approaches that have been investigated to solve this inverse problem: Continuous analytic inversion techniques on one hand, and fully-discretized algebraic methods on the other hand. In the second part of the paper, we review another fundamental question which has been subject to debate from the beginning of IMRT until the present day: The rotation therapy approach versus fixed angle IMRT. This builds a bridge from historic work on IMRT planning to contemporary research in the context of Intensity-Modulated Arc Therapy (IMAT). Copyright © 2011 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Comparative dosimetric analysis of IMRT and VMAT (RapidArc in brain, head and neck, breast and prostate malignancies

Directory of Open Access Journals (Sweden)

Mirza Athar Ali

2015-03-01

Full Text Available Purpose: Intensity modulated radiotherapy (IMRT in the recent past has established itself as a gold standard for organs at risk (OAR sparing, target coverage and dose conformity. With the advent of a rotational treatment technology such as volumetric modulated arc therapy (VMAT, an inter-comparison is warranted to address the advantages and disadvantages of each technique. Methods: Twenty patients were selected retrospectively from our patient database. Sites included were brain, head and neck, chest wall, and prostate, with five patients for each site. For all the selected patients, both the IMRT and VMAT treatment plans were generated. Plan comparison was done in terms of OAR dose, dose homogeneity index (HI, dose conformity index (CI, target coverage, low isodose volumes, monitor units (MUs, and treatment time.Results: The VMAT showed better sparing of “parotids minus planning target volume (PTV”, spinal cord and head of femur as compared to the IMRT. The lung V40 for VMAT was lower, whereas the lung V10, contralateral lung mean dose, contralateral breast mean dose and mean body dose were lower with IMRT for chest wall cases. Both the VMAT and IMRT achieved comparable HI except for the brain site, where IMRT scored over VMAT. The CI achieved by the IMRT and VMAT were similar except for chest wall cases, whereas the VMAT achieved better dose conformity. The target coverage was comparable with both the plans. The VMAT clearly scored over IMRT in terms of average MUs (486 versus 812 respectively and average treatment time (2.54 minutes versus 5.54 minutes per treatment session. Conclusion: The VMAT (RapidArc has a potential to generate treatment plans for various anatomical sites which are comparable with the corresponding IMRT plans in terms of OAR sparing and plan quality parameters. The VMAT significantly reduces treatment time as compared to the IMRT, thus VMAT can increase the throughput of a busy radiotherapy department.

Evaluation of intrafraction patient movement for CNS and head and neck IMRT

International Nuclear Information System (INIS)

Kim, Siyong; Akpati, Hilary C.; Kielbasa, Jerrold E.; Li, Jonathan G.; Liu, Chihray; Amdur, Robert J.; Palta, Jatinder R.

2004-01-01

Intrafraction patient motion is much more likely in intensity-modulated radiation therapy (IMRT) than in conventional radiotherapy primarily due to longer beam delivery times in IMRT treatment. In this study, we evaluated the uncertainty of intrafraction patient displacement in CNS and head and neck IMRT patients. Immobilization is performed in three steps: (1) the patient is immobilized with thermoplastic facemask, (2) the patient displacement is monitored using a commercial stereotactic infrared IR camera (ExacTrac, BrainLab) during treatment, and (3) repositioning is carried out as needed. The displacement data were recorded during beam-on time for the entire treatment duration for 5 patients using the camera system. We used the concept of cumulative time versus patient position uncertainty, referred to as an uncertainty time histogram (UTH), to analyze the data. UTH is a plot of the accumulated time during which a patient stays within the corresponding movement uncertainty. The University of Florida immobilization procedure showed an effective immobilization capability for CNS and head and neck IMRT patients by keeping the patient displacement less than 1.5 mm for 95% of treatment time (1.43 mm for 1, and 1.02 mm for 1, and less than 1.0 mm for 3 patients). The maximum displacement was 2.0 mm

Reduced Toxicity With Intensity Modulated Radiation Therapy (IMRT) for Desmoplastic Small Round Cell Tumor (DSRCT): An Update on the Whole Abdominopelvic Radiation Therapy (WAP-RT) Experience

Energy Technology Data Exchange (ETDEWEB)

Desai, Neil B. [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York (United States); Stein, Nicholas F. [Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York (United States); LaQuaglia, Michael P. [Department of Surgery, Memorial Sloan-Kettering Cancer Center, New York, New York (United States); Alektiar, Kaled M. [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York (United States); Kushner, Brian H.; Modak, Shakeel; Magnan, Heather M. [Department of Pediatrics, Memorial Sloan-Kettering Cancer Center, New York, New York (United States); Goodman, Karyn [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York (United States); Wolden, Suzanne L., E-mail: woldens@mskcc.org [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York (United States)

2013-01-01

Purpose: Desmoplastic small round cell tumor (DSRCT) is a rare malignancy typically involving the peritoneum in young men. Whole abdominopelvic radiation therapy (WAP-RT) using conventional 2-dimensional (2D) radiation therapy (RT) is used to address local recurrence but has been limited by toxicity. Our objectives were to assess the benefit of intensity modulated radiation therapy (IMRT) on toxicity and to update the largest series on radiation for DSRCT. Methods and Materials: The records of 31 patients with DSRCT treated with WAP-RT (22 with 2D-RT and 9 with IMRT) between 1992 and 2011 were retrospectively reviewed. All received multi-agent chemotherapy and maximal surgical debulking followed by 30 Gy of WAP-RT. A further focal boost of 12 to 24 Gy was used in 12 cases. Boost RT and autologous stem cell transplantation were nearly exclusive to patients treated with 2D-RT. Toxicities were assessed with the Common Terminology Criteria for Adverse Events. Dosimetric analysis compared IMRT and simulated 2D-RT dose distributions. Results: Of 31 patients, 30 completed WAP-RT, with a median follow-up after RT of 19 months. Acute toxicity was reduced with IMRT versus 2D-RT: P=.04 for gastrointestinal toxicity of grade 2 or higher (33% vs 77%); P=.02 for grade 4 hematologic toxicity (33% vs 86%); P=.01 for rates of granulocyte colony-stimulating factor; and P=.04 for rates of platelet transfusion. Post treatment red blood cell and platelet transfusion rates were also reduced (P=.01). IMRT improved target homogeneity ([D05-D95]/D05 of 21% vs 46%) and resulted in a 21% mean bone dose reduction. Small bowel obstruction was the most common late toxicity (23% overall). Updated 3-year overall survival and progression-free survival rates were 50% and 24%, respectively. Overall survival was associated with distant metastasis at diagnosis on multivariate analysis. Most failures remained intraperitoneal (88%). Conclusions: IMRT for consolidative WAP-RT in DSRCT improves

Fast IMRT with narrow high energy scanned photon beams

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Andreassen, Bjoern; Straaring t, Sara Janek; Holmberg, Rickard; Naefstadius, Peder; Brahme, Anders [Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University, P.O. Box 260, SE-171 76 Stockholm (Sweden); Department of Hospital Physics, Karolinska University Hospital, SE-171 76 Stockholm (Sweden); Department of Medical Radiation Physics, Karolinska Institutet and Stockholm University, P.O. Box 260, SE-171 76 Stockholm, Sweden and Department of Hospital Physics, Karolinska University Hospital, SE-171 76 Stockholm (Sweden)

2011-08-15

beam spots resulting in a uniformity of collimated 80%-20% penumbra of 9 mm at a primary electron energy of 50 MeV. For the more complex cardioid shaped dose distribution, they used 270 spots, which at a pulse repetition frequency of 200 Hz is completed every 1.36 s. Conclusions: The present measurements indicate that the use of narrow scanned photon beams is a flexible and fast method to deliver advanced intensity modulated beams. Fast scanned photon IMRT should, therefore, be a very interesting modality in the delivery of biologically optimized radiation therapy with the possibility for in vivo treatment verification with PET-CT imaging.

Beam angle selection for intensity-modulated radiotherapy (IMRT) treatment of unresectable pancreatic cancer: are noncoplanar beam angles necessary?

Science.gov (United States)

Chang, D S; Bartlett, G K; Das, I J; Cardenes, H R

2013-09-01

External beam radiation therapy with concurrent chemotherapy (CRT) is widely used for the treatment of unresectable pancreatic cancer. Noncoplanar (NCP) 3D conformal radiotherapy (3DCRT) and coplanar (CP) IMRT have been reported to lower the radiation dose to organs at risk (OARs). The purpose of this article is to examine the utility of noncoplanar beam angles in IMRT for the management of pancreatic cancer. Sixteen patients who were treated with CRT for unresectable adenocarcinoma of the pancreatic head or neck were re-planned using CP and NCP beams in 3DCRT and IMRT with the Varian Eclipse treatment planning system. Compared to CP IMRT, NCP IMRT had similar target coverage with slightly increased maximum point dose, 5,799 versus 5,775 cGy (p = 0.008). NCP IMRT resulted in lower mean kidney dose, 787 versus 1,210 cGy (p kidney dose, but did not improve other dose-volume criteria. The use of NCP beam angles is preferred only in patients with risk factors for treatment-related kidney dysfunction.

Dosimetric Comparison Between 3DCRT and IMRT Using Different Multileaf Collimators in the Treatment of Brain Tumors

International Nuclear Information System (INIS)

Ding Meisong; Newman, Francis M.S.; Chen Changhu; Stuhr, Kelly; Gaspar, Laurie E.

2009-01-01

We investigated the differences between 3-dimensional conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT), and the impact of collimator leaf-width on IMRT plans for the treatment of nonspherical brain tumors. Eight patients treated by 3DCRT with Novalis were selected. We developed 3 IMRT plans with different multileaf collimators (Novalis m3, Varian MLC-120, and Varian MLC-80) with the same treatment margins, number of beams, and gantry positions as in the 3DCRT treatment plans. Treatment planning utilized the BrainLAB treatment planning system. For each patient, the dose constraints and optimization parameters remained identical for all plans. The heterogeneity index, the percentage target coverage, critical structures, and normal tissue volumes receiving 50% of the prescription dose were calculated to compare the dosimetric difference. Equivalent uniform dose (EUD) and tumor control probability (TCP) were also introduced to evaluate the radiobiological effect for different plans. We found that IMRT significantly improved the target dose homogeneity compared to the 3DCRT. However, IMRT showed the same radiobiological effect as 3DCRT. For the brain tumors adjacent to (or partially overlapping with) critical structures, IMRT dramatically spared the volume of the critical structures to be irradiated. In IMRT plans, the smaller collimator leaf width could reduce the volume of critical structures irradiated to the 50% level for those partially overlapping with the brain tumors. For relatively large and spherical brain tumors, the smaller collimator leaf widths give no significant benefit

Comparison between intensity modulated radiotherapy (IMRT) and 3D tangential beams technique used in patients with early-stage breast cancer who received breast-conserving therapy

International Nuclear Information System (INIS)

Sas-Korczynska, B.; Kokoszka, A.; Korzeniowski, S.; Sladowska, A.; Rozwadowska-Bogusz, B.; Lesiak, J.; Dyczek, S.

2010-01-01

Background: The most often found complications in patients with breast cancer who received radiotherapy are cardiac and pulmonary function disorders and development of second malignancies. Aim: To compare the intensity modulated radiotherapy with the 3D tangential beams technique in respect of dose distribution in target volume and critical organs they generate in patients with early-stage breast cancer who received breast-conserving therapy. Materials and methods: A dosimetric analysis was performed to assess the three radiotherapy techniques used in each of 10 consecutive patients with early-stage breast cancer treated with breast-conserving therapy. Radiotherapy was planned with the use of all the three techniques: 3D tangential beams with electron boost, IMRT with electron boost, and intensity modulated radiotherapy with simultaneous integrated boost. Results: The use of the IMRT techniques enables more homogenous dose distribution in target volume. The range of mean and median dose to the heart and lung was lower with the IMRT techniques in comparison to the 3D tangential beams technique. The range of mean dose to the heart amounted to 0.3 - 3.5 Gy for the IMRT techniques and 0.4 - 4.3 for the tangential beams technique. The median dose to the lung on the irradiated side amounted to 4.9 - 5 Gy for the IMRT techniques and 5.6 Gy for the 3D tangential beams technique. Conclusion: The application of the IMRT techniques in radiotherapy patients with early-stage breast cancer allows to obtain more homogenous dose distribution in target volume, while permitting to reduce the dose to critical organs. (authors)

The biological basis for environmental quality assessments

International Nuclear Information System (INIS)

Karpov, V.I.; Kudritsky, Y.K.; Georgievsky, A.B.

1991-01-01

A systematic approach is required to environmental quality assessments with regard to the Baltic regions in order to address the problem of pollution abatement. The proposed systematization of adaptive states stems from the general theory of adaptation. The various types of adaption are described. (AB)

Specific patient verification of IMRT plans using two-dimensional array of ionization chambers.)

International Nuclear Information System (INIS)

Rodriguez Zayas, Michael; Perez Guevara, Adrian; Reyes Gonzalez, Tommy; Gonzalez Perez, Yelina; Sola Rodriguez, Yeline; Caballero, Roberto; Lopez Lopez, Alberto; Castro Crespo, Diosdado

2009-01-01

The most common procedures to validate treatments with IMRT combine planning and administration which introduces the specific patient approach. IMRT is being introduced in Cuba, so it is a study to use as verification for each IMRT treatment plan with the collapsed beam method (Collapsed beams). We present three case studies to look at different situations and presentation of data. The treatment beam and collapsed obtained with an Elekta Precise linear accelerator and TPS PrecisePLAN respectively. The system used to measure a two-dimensional array of ionization chambers and VeriSoft system, both of the firm PTW. Dummy is used as solid sheets of water. The dose difference is evaluated using the gamma index applied to dose map resulting of the comparison between measured and simulated projections. Also the dose absolute is measured using a cylindrical chamber with United electrometer, which is compare with the results of the TPS. In the cases studied are shown along two perpendicular profiles. Tolerance is taken as the gamma index (5%, 5 mm). The method of collapsed beams under two- dimensional beam ionization chambers has been accepted for verification of IMRT treatments at the Radiotherapy Service of the Hospital Hermanos Ameijeiras. (Author)

Adjuvant IMRT/XELOX radiochemotherapy improves long-term overall- and disease-free survival in advanced gastric cancer

International Nuclear Information System (INIS)

Boda-Heggemann, J.; Schneider, V.; Weiss, C.

2013-01-01

Purpose: In a retrospective analysis, adjuvant intensity-modulated radiation therapy (IMRT) combined with modern chemotherapy improved advanced gastric cancer survival rates compared to a combination of three-dimensional conformal radiation therapy (3D-CRT) and conventional chemotherapy. We report on the long-term outcomes of two consecutive patient cohorts that were treated with either IMRT and intensive chemotherapy, or 3D-CRT and conventional chemotherapy. Patients and methods: Between 2001 and 2008, 65 consecutive gastric cancer patients received either 3D-CRT (n = 27) or IMRT (n = 38) following tumor resection. Chemotherapy comprised predominantly 5-fluorouracil/folinic acid (5-FU/FA) in the earlier cohort and capecitabine plus oxaliplatin (XELOX) in the latter. The primary endpoints were overall survival (OS) and disease-free survival (DFS). Results: Median OS times were 18 and 43 months in the 3D-CRT and IMRT groups, respectively (p = 0.0602). Actuarial 5-year OS rates were 26 and 47 %, respectively. Within the IMRT group, XELOX gave better results than 5-FU/FA in terms of OS, but this difference was not statistically significant. The primary cause of death in both groups was distant metastasis. Median DFS times were 14 and 35 months in the 3D-CRT and IMRT groups, respectively (p = 0.0693). Actuarial 5-year DFS rates were 22 and 44 %, respectively. Among patients receiving 5-FU/FA, DFS tended to be better in the IMRT group, but this was not statistically significant. A similar analysis for the XELOX group was not possible as 3D-CRT was almost never used to treat these patients. No late toxicity exceeding grade 3 or secondary tumors were observed. Conclusion: After a median follow-up period of over 5 years, OS and DFS were improved in the IMRT/XELOX treated patients compared to the 3D-CRT/5-FU/FA group. Long-term observation revealed no clinical indications of therapy-induced secondary tumors or renal toxicity. (orig.)

Adjuvant IMRT/XELOX radiochemotherapy improves long-term overall- and disease-free survival in advanced gastric cancer

Energy Technology Data Exchange (ETDEWEB)

Boda-Heggemann, J.; Schneider, V. [Heidelberg Univ., Universitaetsmedizin Mannheim (Germany). Dept. of Radiation Oncology; Weiss, C. [Heidelberg Univ., Universitaetsmedizin Mannheim (Germany). Dept. of Biomathematics and Medical Statistics] [and others

2013-05-15

Purpose: In a retrospective analysis, adjuvant intensity-modulated radiation therapy (IMRT) combined with modern chemotherapy improved advanced gastric cancer survival rates compared to a combination of three-dimensional conformal radiation therapy (3D-CRT) and conventional chemotherapy. We report on the long-term outcomes of two consecutive patient cohorts that were treated with either IMRT and intensive chemotherapy, or 3D-CRT and conventional chemotherapy. Patients and methods: Between 2001 and 2008, 65 consecutive gastric cancer patients received either 3D-CRT (n = 27) or IMRT (n = 38) following tumor resection. Chemotherapy comprised predominantly 5-fluorouracil/folinic acid (5-FU/FA) in the earlier cohort and capecitabine plus oxaliplatin (XELOX) in the latter. The primary endpoints were overall survival (OS) and disease-free survival (DFS). Results: Median OS times were 18 and 43 months in the 3D-CRT and IMRT groups, respectively (p = 0.0602). Actuarial 5-year OS rates were 26 and 47 %, respectively. Within the IMRT group, XELOX gave better results than 5-FU/FA in terms of OS, but this difference was not statistically significant. The primary cause of death in both groups was distant metastasis. Median DFS times were 14 and 35 months in the 3D-CRT and IMRT groups, respectively (p = 0.0693). Actuarial 5-year DFS rates were 22 and 44 %, respectively. Among patients receiving 5-FU/FA, DFS tended to be better in the IMRT group, but this was not statistically significant. A similar analysis for the XELOX group was not possible as 3D-CRT was almost never used to treat these patients. No late toxicity exceeding grade 3 or secondary tumors were observed. Conclusion: After a median follow-up period of over 5 years, OS and DFS were improved in the IMRT/XELOX treated patients compared to the 3D-CRT/5-FU/FA group. Long-term observation revealed no clinical indications of therapy-induced secondary tumors or renal toxicity. (orig.)

Total dural irradiation: RapidArc versus static-field IMRT: A case study

Energy Technology Data Exchange (ETDEWEB)

Kelly, Paul J., E-mail: paulj.kelly@hse.ie [Department of Radiation Oncology, Dana Farber/Brigham and Women' s Cancer Center, Harvard Medical School, Boston, MA (United States); Mannarino, Edward; Lewis, John Henry; Baldini, Elizabeth H.; Hacker, Fred L. [Department of Radiation Oncology, Dana Farber/Brigham and Women' s Cancer Center, Harvard Medical School, Boston, MA (United States)

2012-07-01

The purpose of this study was to compare conventional fixed-gantry angle intensity-modulated radiation therapy (IMRT) with RapidArc for total dural irradiation. We also hypothesize that target volume-individualized collimator angles may produce substantial normal tissue sparing when planning with RapidArc. Five-, 7-, and 9-field fixed-gantry angle sliding-window IMRT plans were generated for comparison with RapidArc plans. Optimization and normal tissue constraints were constant for all plans. All plans were normalized so that 95% of the planning target volume (PTV) received at least 100% of the dose. RapidArc was delivered using 350 Degree-Sign clockwise and counterclockwise arcs. Conventional collimator angles of 45 Degree-Sign and 315 Degree-Sign were compared with 90 Degree-Sign on both arcs. Dose prescription was 59.4 Gy in 33 fractions. PTV metrics used for comparison were coverage, V{sub 107}%, D1%, conformality index (CI{sub 95}%), and heterogeneity index (D{sub 5}%-D{sub 95}%). Brain dose, the main challenge of this case, was compared using D{sub 1}%, Dmean, and V{sub 5} Gy. Dose to optic chiasm, optic nerves, globes, and lenses was also compared. The use of unconventional collimator angles (90 Degree-Sign on both arcs) substantially reduced dose to normal brain. All plans achieved acceptable target coverage. Homogeneity was similar for RapidArc and 9-field IMRT plans. However, heterogeneity increased with decreasing number of IMRT fields, resulting in unacceptable hotspots within the brain. Conformality was marginally better with RapidArc relative to IMRT. Low dose to brain, as indicated by V5Gy, was comparable in all plans. Doses to organs at risk (OARs) showed no clinically meaningful differences. The number of monitor units was lower and delivery time was reduced with RapidArc. The case-individualized RapidArc plan compared favorably with the 9-field conventional IMRT plan. In view of lower monitor unit requirements and shorter delivery time, Rapid

Dosimetric verification of IMRT plans

International Nuclear Information System (INIS)

Bulski, W.; Cheimicski, K.; Rostkowska, J.

2012-01-01

Intensity modulated radiotherapy (IMRT) is a complex procedure requiring proper dosimetric verification. IMRT dose distributions are characterized by steep dose gradients which enable to spare organs at risk and allow for an escalation of the dose to the tumor. They require large number of radiation beams (sometimes over 10). The fluence measurements for individual beams are not sufficient for evaluation of the total dose distribution and to assure patient safety. The methods used at the Centre of Oncology in Warsaw are presented. In order to measure dose distributions in various cross-sections the film dosimeters were used (radiographic Kodak EDR2 films and radiochromic Gafchromic EBT films). The film characteristics were carefully examined. Several types of tissue equivalent phantoms were developed. A methodology of comparing measured dose distributions against the distributions calculated by treatment planning systems (TPS) was developed and tested. The tolerance level for this comparison was set at 3% difference in dose and 3 mm in distance to agreement. The so called gamma formalism was used. The results of these comparisons for a group of over 600 patients are presented. Agreement was found in 87 % of cases. This film dosimetry methodology was used as a benchmark to test and validate the performance of commercially available 2D and 3D matrices of detectors (ionization chambers or diodes). The results of these validations are also presented. (authors)

Implementation of random set-up errors in Monte Carlo calculated dynamic IMRT treatment plans

International Nuclear Information System (INIS)

Stapleton, S; Zavgorodni, S; Popescu, I A; Beckham, W A

2005-01-01

The fluence-convolution method for incorporating random set-up errors (RSE) into the Monte Carlo treatment planning dose calculations was previously proposed by Beckham et al, and it was validated for open field radiotherapy treatments. This study confirms the applicability of the fluence-convolution method for dynamic intensity modulated radiotherapy (IMRT) dose calculations and evaluates the impact of set-up uncertainties on a clinical IMRT dose distribution. BEAMnrc and DOSXYZnrc codes were used for Monte Carlo calculations. A sliding window IMRT delivery was simulated using a dynamic multi-leaf collimator (DMLC) transport model developed by Keall et al. The dose distributions were benchmarked for dynamic IMRT fields using extended dose range (EDR) film, accumulating the dose from 16 subsequent fractions shifted randomly. Agreement of calculated and measured relative dose values was well within statistical uncertainty. A clinical seven field sliding window IMRT head and neck treatment was then simulated and the effects of random set-up errors (standard deviation of 2 mm) were evaluated. The dose-volume histograms calculated in the PTV with and without corrections for RSE showed only small differences indicating a reduction of the volume of high dose region due to set-up errors. As well, it showed that adequate coverage of the PTV was maintained when RSE was incorporated. Slice-by-slice comparison of the dose distributions revealed differences of up to 5.6%. The incorporation of set-up errors altered the position of the hot spot in the plan. This work demonstrated validity of implementation of the fluence-convolution method to dynamic IMRT Monte Carlo dose calculations. It also showed that accounting for the set-up errors could be essential for correct identification of the value and position of the hot spot

Implementation of random set-up errors in Monte Carlo calculated dynamic IMRT treatment plans

Science.gov (United States)

Stapleton, S.; Zavgorodni, S.; Popescu, I. A.; Beckham, W. A.

2005-02-01

The fluence-convolution method for incorporating random set-up errors (RSE) into the Monte Carlo treatment planning dose calculations was previously proposed by Beckham et al, and it was validated for open field radiotherapy treatments. This study confirms the applicability of the fluence-convolution method for dynamic intensity modulated radiotherapy (IMRT) dose calculations and evaluates the impact of set-up uncertainties on a clinical IMRT dose distribution. BEAMnrc and DOSXYZnrc codes were used for Monte Carlo calculations. A sliding window IMRT delivery was simulated using a dynamic multi-leaf collimator (DMLC) transport model developed by Keall et al. The dose distributions were benchmarked for dynamic IMRT fields using extended dose range (EDR) film, accumulating the dose from 16 subsequent fractions shifted randomly. Agreement of calculated and measured relative dose values was well within statistical uncertainty. A clinical seven field sliding window IMRT head and neck treatment was then simulated and the effects of random set-up errors (standard deviation of 2 mm) were evaluated. The dose-volume histograms calculated in the PTV with and without corrections for RSE showed only small differences indicating a reduction of the volume of high dose region due to set-up errors. As well, it showed that adequate coverage of the PTV was maintained when RSE was incorporated. Slice-by-slice comparison of the dose distributions revealed differences of up to 5.6%. The incorporation of set-up errors altered the position of the hot spot in the plan. This work demonstrated validity of implementation of the fluence-convolution method to dynamic IMRT Monte Carlo dose calculations. It also showed that accounting for the set-up errors could be essential for correct identification of the value and position of the hot spot.

WE-G-BRF-01: Adaptation to Intrafraction Tumor Deformation During Intensity-Modulated Radiotherapy: First Proof-Of-Principle Demonstration

International Nuclear Information System (INIS)

Ge, Y; OBrien, R; Shieh, C; Booth, J; Keall, P

2014-01-01

Purpose: Intrafraction tumor deformation limits targeting accuracy in radiotherapy and cannot be adapted to by current motion management techniques. This study simulated intrafractional treatment adaptation to tumor deformations using a dynamic Multi-Leaf Collimator (DMLC) tracking system during Intensity-modulated radiation therapy (IMRT) treatment for the first time. Methods: The DMLC tracking system was developed to adapt to the intrafraction tumor deformation by warping the planned beam aperture guided by the calculated deformation vector field (DVF) obtained from deformable image registration (DIR) at the time of treatment delivery. Seven single phantom deformation images up to 10.4 mm deformation and eight tumor system phantom deformation images up to 21.5 mm deformation were acquired and used in tracking simulation. The intrafraction adaptation was simulated at the DMLC tracking software platform, which was able to communicate with the image registration software, reshape the instantaneous IMRT field aperture and log the delivered MLC fields.The deformation adaptation accuracy was evaluated by a geometric target coverage metric defined as the sum of the area incorrectly outside and inside the reference aperture. The incremental deformations were arbitrarily determined to take place equally over the delivery interval. The geometric target coverage of delivery with deformation adaptation was compared against the delivery without adaptation. Results: Intrafraction deformation adaptation during dynamic IMRT plan delivery was simulated for single and system deformable phantoms. For the two particular delivery situations, over the treatment course, deformation adaptation improved the target coverage by 89% for single target deformation and 79% for tumor system deformation compared with no-tracking delivery. Conclusion: This work demonstrated the principle of real-time tumor deformation tracking using a DMLC. This is the first step towards the development of an

The Adaptation Gap Report - a Preliminary Assessment

DEFF Research Database (Denmark)

Alverson, Keith; Olhoff, Anne; Noble, Ian

This first Adaptation Gap report provides an equally sobering assessment of the gap between adaptation needs and reality, based on preliminary thinking on how baselines, future goals or targets, and gaps between them might be defined for climate change adaptation. The report focuses on gaps...... in developing countries in three important areas: finance, technology and knowledge....

Preliminary results of the assessment of intensity modulated radiotherapy (IMRT) for prostatic and head and neck tumors (STIC 2001); Resultats preliminaires de l'evaluation de la radiotherapie conformationnelle avec modulation d'intensite (RCMI) pour le traitement des cancers prostatiques et ORL (STIC 2001)

Energy Technology Data Exchange (ETDEWEB)

Marchal, C.; Lapeyre, M.; Beckendorf, V.; Aletti, P.; Marchesi, V. [Centre Alexis-Vautrin, Dept. de Radiotherapie, 54 - Vandoeuvre-les-Nancy (France); Hasle, E.; Carrere, M.O. [Centre de Lutte Contre le Cancer Leon-Berard, GRESAC, UMR 5823 du CNRS, 69 - Lyon (France); Dubois, J.B.; Ailleres, N. [Centre Regional de Lutte Contre le Cancer Paul Lamarque, Service de Radiotherapie, 34 - Montpellier (France); Maigon, P.; Naudy, S. [Centre de Lutte Contre le Cancer Georges-Francois-Leclerc, Service de Radiotherapie, 21 - Dijon (France); Bensadoun, R.J.; Marcie, S.; Gerard, J.P. [Centre Antoine-Lacassagne, Service de Radiotherapie, 06 - Nice (France); Le Prise, E.; Manens, J.P. [Centre Eugene-Marquis, Service de Radiotherapie, 35 - Rennes (France); Lartigau, E.; Mazurier, J. [Centre de Lutte Contre le Cancer Oscar-Lambret, Service de Radiotherapie, 59 - Lille (France); Carrie, C.; Ginestet, C.; Pommier, P. [Centre de Lutte Contre le Cancer Leon-Berard, Service de Radiotherapie, 69 - Lyon (France); Dubray, B.; Chauvin, F. [Centre de Lutte Contre le Cancer Leon-Berard, Dept. de Sante Publique, 69 - Lyon (France)

2004-11-01

Introduction. - Between May 2002 and May 2004, eight French comprehensive cancer centres did a prospective non-randomized study including 200 patients, 100 with cancer of the prostate and 100 with head and neck cancers. Half of each patient group was treated by IMRT and the others by RTC 3D. This clinical study was associated with an economic study and a physics study. We report here the first results. Patients and methods. - For the clinical study, the analysis of the data of the first 88 patients irradiated for a prostatic cancer shows that 39 received RTC and 49 IMRT with a mean dose of 78 Gy at the ICRU point at 2 Gy per fraction. For H and N tumours, the preliminary analysis was done on the 87 first patients with a mean follow-up of 11.5 months (2 to 25 months) and a median of 8.4 months for the IMRT groups and 13,2 months for the RTC group. The economic study was done on the first 157 patients included during the first 18 months: 71 treated by RTC (35 for H and N and 36 for prostate) and 86 treated by IMRT (38 for H and N and 48 for prostate). The assessment of the direct costs was realized y a micro-costing technique. The physical study compared dose distributions for both techniques and has created quality control recommendations. Results. - Clinical studies of the acute reactions do not show any difference between groups, but we want to point out the short follow-up and the relatively high dose delivered to cancers of the prostate. The physics study demonstrates that IMRT is technically feasible in good clinical conditions with high quality assurance, a good reproducibility and precision. Dosimetric data show that IMRT could certainly spare organs at risk more than RTC for H and N tumours. The direct costs of 'routine' treatments for H and N tumours were 4922 euros for IMRT versus 1899 euros for RTC and for the prostatic cancers 4911 euros for IMRT versus 2357 for RTC. (authors)

Assessing the effectiveness of climate adaptation

Energy Technology Data Exchange (ETDEWEB)

Anderson, Simon

2011-10-15

As governments and other agencies spend more money on adaptation to climate change they want to know that their investments are effective — that adaptation will keep development on track, that there is a fair distribution of costs and benefits, and that climate resilience is being built. But monitoring and evaluating adaptation policy and practice is not easy. Some approaches are unhelpful because they fail to integrate adaptation and development, use purely quantitative methods and do not include the perspectives of climate-vulnerable groups in their assessments. Enabling countries and organisations to effectively evaluate adaptation requires an inclusive approach built on sharing knowledge among all stakeholders — one that can capture behavioural and institutional changes and that answers to the needs of the climate-vulnerable poor.

Implementation of dosimetric quality control on IMRT and VMAT treatments in radiotherapy using diodes

International Nuclear Information System (INIS)

Gonzales, A.; Garcia, B.; Ramirez, J.; Marquina, J.

2014-08-01

To implement quality control of IMRT and VMAT treatments Rapid Arc radiotherapy using diode array. Were tested 90 patients with IMRT and VMAT Rapid Arc, comparing the planned dose to the dose administered, used the Map-Check-2 and Arc-Check of Sun Nuclear, they using the gamma factor for calculating and using comparison parameters 3% / 3m m. The statistic shows that the quality controls of the 90 patients analyzed, presented a percentage of diodes that pass the test between 96,7% and 100,0% of the irradiated diodes. Implemented in Clinical ALIADA Oncologia Integral, the method for quality control of IMRT and VMAT treatments Rapid Arc radiotherapy using diode array. (Author)

SU-E-T-365: Dosimetric Impact of Dental Amalgam CT Image Artifacts On IMRT and VMAT Head and Neck Plans

Energy Technology Data Exchange (ETDEWEB)

Cao, N; Young, L; Parvathaneni, U; Liao, J; Richard, P; Ford, E; Sandison, G [University of Washington, Department of Radiation Oncology, Seattle, WA (United States)

2014-06-01

Purpose: The presence of high density dental amalgam in patient CT image data sets causes dose calculation errors for head and neck (HN) treatment planning. This study assesses and compares dosimetric variations in IMRT and VMAT treatment plans due to dental artifacts. Methods: Sixteen HN patients with similar treatment sites (oropharynx), tumor volume and extensive dental artifacts were divided into two groups: IMRT (n=8, 6 to 9 beams) and VMAT (n=8, 2 arcs with 352° rotation). All cases were planned with the Pinnacle 9.2 treatment planning software using the collapsed cone convolution superposition algorithm and a range of prescription dose from 60 to 72Gy. Two different treatment plans were produced, each based on one of two image sets: (a)uncorrected; (b)dental artifacts density overridden (set to 1.0g/cm{sup 3}). Differences between the two treatment plans for each of the IMRT and VMAT techniques were quantified by the following dosimetric parameters: maximum point dose, maximum spinal cord and brainstem dose, mean left and right parotid dose, and PTV coverage (V95%Rx). Average differences generated for these dosimetric parameters were compared between IMRT and VMAT plans. Results: The average absolute dose differences (plan a minus plan b) for the VMAT and IMRT techniques, respectively, caused by dental artifacts were: 2.2±3.3cGy vs. 37.6±57.5cGy (maximum point dose, P=0.15); 1.2±0.9cGy vs. 7.9±6.7cGy (maximum spinal cord dose, P=0.026); 2.2±2.4cGy vs. 12.1±13.0cGy (maximum brainstem dose, P=0.077); 0.9±1.1cGy vs. 4.1±3.5cGy (mean left parotid dose, P=0.038); 0.9±0.8cGy vs. 7.8±11.9cGy (mean right parotid dose, P=0.136); 0.021%±0.014% vs. 0.803%±1.44% (PTV coverage, P=0.17). Conclusion: For the HN plans studied, dental artifacts demonstrated a greater dose calculation error for IMRT plans compared to VMAT plans. Rotational arcs appear on the average to compensate dose calculation errors induced by dental artifacts. Thus, compared to VMAT, density

Walking adaptability after a stroke and its assessment in clinical settings.

Science.gov (United States)

Balasubramanian, Chitralakshmi K; Clark, David J; Fox, Emily J

2014-01-01

Control of walking has been described by a tripartite model consisting of stepping, equilibrium, and adaptability. This review focuses on walking adaptability, which is defined as the ability to modify walking to meet task goals and environmental demands. Walking adaptability is crucial to safe ambulation in the home and community environments and is often severely compromised after a stroke. Yet quantification of walking adaptability after stroke has received relatively little attention in the clinical setting. The objectives of this review were to examine the conceptual challenges for clinical measurement of walking adaptability and summarize the current state of clinical assessment for walking adaptability. We created nine domains of walking adaptability from dimensions of community mobility to address the conceptual challenges in measurement and reviewed performance-based clinical assessments of walking to determine if the assessments measure walking adaptability in these domains. Our literature review suggests the lack of a comprehensive well-tested clinical assessment tool for measuring walking adaptability. Accordingly, recommendations for the development of a comprehensive clinical assessment of walking adaptability after stroke have been presented. Such a clinical assessment will be essential for gauging recovery of walking adaptability with rehabilitation and for motivating novel strategies to enhance recovery of walking adaptability after stroke.

Prostate Dose Escalation by Innovative Inverse Planning-Driven IMRT

National Research Council Canada - National Science Library

Xing, Lei

2005-01-01

.... Because of the tacit ignorance of intra-structural tradeoff, the IMRT plans generated by these systems for prostate treatment are, at best, sub-optimal and our endeavor of providing the best possible...

GPU-Monte Carlo based fast IMRT plan optimization

Directory of Open Access Journals (Sweden)

Yongbao Li

2014-03-01

Full Text Available Purpose: Intensity-modulated radiation treatment (IMRT plan optimization needs pre-calculated beamlet dose distribution. Pencil-beam or superposition/convolution type algorithms are typically used because of high computation speed. However, inaccurate beamlet dose distributions, particularly in cases with high levels of inhomogeneity, may mislead optimization, hindering the resulting plan quality. It is desire to use Monte Carlo (MC methods for beamlet dose calculations. Yet, the long computational time from repeated dose calculations for a number of beamlets prevents this application. It is our objective to integrate a GPU-based MC dose engine in lung IMRT optimization using a novel two-steps workflow.Methods: A GPU-based MC code gDPM is used. Each particle is tagged with an index of a beamlet where the source particle is from. Deposit dose are stored separately for beamlets based on the index. Due to limited GPU memory size, a pyramid space is allocated for each beamlet, and dose outside the space is neglected. A two-steps optimization workflow is proposed for fast MC-based optimization. At first step, a rough dose calculation is conducted with only a few number of particle per beamlet. Plan optimization is followed to get an approximated fluence map. In the second step, more accurate beamlet doses are calculated, where sampled number of particles for a beamlet is proportional to the intensity determined previously. A second-round optimization is conducted, yielding the final result.Results: For a lung case with 5317 beamlets, 105 particles per beamlet in the first round, and 108 particles per beam in the second round are enough to get a good plan quality. The total simulation time is 96.4 sec.Conclusion: A fast GPU-based MC dose calculation method along with a novel two-step optimization workflow are developed. The high efficiency allows the use of MC for IMRT optimizations.--------------------------------Cite this article as: Li Y, Tian Z

Conformal intensity-modulated radiotherapy (IMRT) delivered by robotic linac-conformality versus efficiency of dose delivery

International Nuclear Information System (INIS)

Webb, Steve

2000-01-01

Intensity-modulated radiotherapy (IMRT) may be delivered with a high-energy-photon linac mounted on a robotic gantry and executing a complex trajectory. In a previous paper an inverse-planning technique was developed for such an application. Here the work is extended to demonstrate the dependence of conformality on the size of the elemental pencil beam, on the complexity of the trajectory and on the sampling of azimuth and elevation of the collimated source. The improved conformality of complex trajectories is demonstrated and benchmarked relative to simpler trajectories, more representative of existing non-robotic IMRT techniques. Specifically, by choosing a very fine pencil beam, exquisitely conformal dose distributions have been obtained. Important sampling considerations have been determined. Expressions have been derived for the dosimetry and monitor-unit efficiency of robotic IMRT. Equivalent trajectories were computed for executing the complex robotic trajectories instead by using a conventional linac. The work benchmarks an ideal in IMRT against which more practical and more common techniques may be measured. (author)

In silico biology of bone modelling and remodelling: adaptation.

Science.gov (United States)

Gerhard, Friederike A; Webster, Duncan J; van Lenthe, G Harry; Müller, Ralph

2009-05-28

Modelling and remodelling are the processes by which bone adapts its shape and internal structure to external influences. However, the cellular mechanisms triggering osteoclastic resorption and osteoblastic formation are still unknown. In order to investigate current biological theories, in silico models can be applied. In the past, most of these models were based on the continuum assumption, but some questions related to bone adaptation can be addressed better by models incorporating the trabecular microstructure. In this paper, existing simulation models are reviewed and one of the microstructural models is extended to test the hypothesis that bone adaptation can be simulated without particular knowledge of the local strain distribution in the bone. Validation using an experimental murine loading model showed that this is possible. Furthermore, the experimental model revealed that bone formation cannot be attributed only to an increase in trabecular thickness but also to structural reorganization including the growth of new trabeculae. How these new trabeculae arise is still an unresolved issue and might be better addressed by incorporating other levels of hierarchy, especially the cellular level. The cellular level sheds light on the activity and interplay between the different cell types, leading to the effective change in the whole bone. For this reason, hierarchical multi-scale simulations might help in the future to better understand the biomathematical laws behind bone adaptation.

The clinical impact of the couch top and rails on IMRT and arc therapy

International Nuclear Information System (INIS)

Pulliam, Kiley B; Howell, Rebecca M; Followill, David; Luo, Dershan; Kry, Stephen F; White, R Allen

2011-01-01

The clinical impact of the Varian Exact Couch on dose, volume coverage to targets and critical structures, and tumor control probability (TCP) has not been described. Thus, we examined their effects on IMRT and arc therapy. Five clinical prostate patients were planned with both 6 MV eight-field IMRT and 6 MV two-arc RapidArc techniques using the Eclipse treatment planning system. These plans neglected treatment couch attenuation, as is a common clinical practice. Dose distributions were then recalculated in Eclipse with the inclusion of the Varian Exact Couch (imaging couch top) and the rails in varying configurations. The changes in dose and coverage were evaluated using the dose-volume histograms from each plan iteration. We used a TCP model to calculate losses in tumor control resulting from not accounting for the couch top and rails. We also verified dose measurements in a phantom. Failure to account for the treatment couch and rails resulted in clinically unacceptable dose and volume coverage losses to the targets for both IMRT and RapidArc. The couch caused average prescription dose losses (relative to plans that ignored the couch) to the prostate of 4.2% and 2.0% for IMRT with the rails out and in, respectively, and 3.2% and 2.9% for RapidArc with the rails out and in, respectively. On average, the percentage of the target covered by the prescribed dose dropped to 35% and 84% for IMRT (rails out and in, respectively) and to 18% and 17% for RapidArc (rails out and in, respectively). The TCP was also reduced by as much as 10.5% (6.3% on average). Dose and volume coverage losses for IMRT plans were primarily due to the rails, while the imaging couch top contributed most to losses for RapidArc. Both the couch top and rails contribute to dose and coverage losses that can render plans clinically unacceptable. A follow-up study we performed found that the less attenuating unipanel mesh couch top available with the Varian Exact couch does not cause a clinically

Towards Computerized Adaptive Assessment Based on Structured Tasks

NARCIS (Netherlands)

Tvarožek, Jozef; Kravcik, Milos; Bieliková, Mária

2008-01-01

Tvarožek, J., Kravčík, M., & Bieliková, M. (2008). Towards Computerized Adaptive Assessment Based on Structured Tasks. In W. Nejdl et al. (Eds.), Adaptive Hypermedia and Adaptive Web-Based Systems (pp. 224-234). Springer Berlin / Heidelberg.

Online adaptation and verification of VMAT

Energy Technology Data Exchange (ETDEWEB)

Crijns, Wouter, E-mail: wouter.crijns@uzleuven.be [KU Leuven Department of Oncology, Laboratory of Experimental Radiotherapy, Herestraat 49, Leuven 3000, Belgium and KU Leuven Medical Imaging Research Center, Herestraat 49, Leuven 3000 (Belgium); Defraene, Gilles; Depuydt, Tom; Haustermans, Karin [KU Leuven Department of Oncology, Laboratory of Experimental Radiotherapy, Herestraat 49, Leuven 3000 (Belgium); Van Herck, Hans [KU Leuven Medical Imaging Research Center, Herestraat 49, Leuven 3000, Belgium and KU Leuven Department of Electrical Engineering (ESAT), PSI, Center for Processing Speech and Images, Leuven 3000 (Belgium); Maes, Frederik [KU Leuven Department of Electrical Engineering (ESAT), PSI, Center for Processing Speech and Images, Leuven 3000, Belgium and KU Leuven iMinds - Medical IT Department, Leuven 3000 (Belgium); Van den Heuvel, Frank [Department of Oncology, MRC-CR-UK Gray Institute of Radiation Oncology and Biology, University of Oxford, Oxford OX1 2JD (United Kingdom)

2015-07-15

Purpose: This work presents a method for fast volumetric modulated arc therapy (VMAT) adaptation in response to interfraction anatomical variations. Additionally, plan parameters extracted from the adapted plans are used to verify the quality of these plans. The methods were tested as a prostate class solution and compared to replanning and to their current clinical practice. Methods: The proposed VMAT adaptation is an extension of their previous intensity modulated radiotherapy (IMRT) adaptation. It follows a direct (forward) planning approach: the multileaf collimator (MLC) apertures are corrected in the beam’s eye view (BEV) and the monitor units (MUs) are corrected using point dose calculations. All MLC and MU corrections are driven by the positions of four fiducial points only, without need for a full contour set. Quality assurance (QA) of the adapted plans is performed using plan parameters that can be calculated online and that have a relation to the delivered dose or the plan quality. Five potential parameters are studied for this purpose: the number of MU, the equivalent field size (EqFS), the modulation complexity score (MCS), and the components of the MCS: the aperture area variability (AAV) and the leaf sequence variability (LSV). The full adaptation and its separate steps were evaluated in simulation experiments involving a prostate phantom subjected to various interfraction transformations. The efficacy of the current VMAT adaptation was scored by target mean dose (CTV{sub mean}), conformity (CI{sub 95%}), tumor control probability (TCP), and normal tissue complication probability (NTCP). The impact of the adaptation on the plan parameters (QA) was assessed by comparison with prediction intervals (PI) derived from a statistical model of the typical variation of these parameters in a population of VMAT prostate plans (n = 63). These prediction intervals are the adaptation equivalent of the tolerance tables for couch shifts in the current clinical

Online adaptation and verification of VMAT

International Nuclear Information System (INIS)

Crijns, Wouter; Defraene, Gilles; Depuydt, Tom; Haustermans, Karin; Van Herck, Hans; Maes, Frederik; Van den Heuvel, Frank

2015-01-01

Purpose: This work presents a method for fast volumetric modulated arc therapy (VMAT) adaptation in response to interfraction anatomical variations. Additionally, plan parameters extracted from the adapted plans are used to verify the quality of these plans. The methods were tested as a prostate class solution and compared to replanning and to their current clinical practice. Methods: The proposed VMAT adaptation is an extension of their previous intensity modulated radiotherapy (IMRT) adaptation. It follows a direct (forward) planning approach: the multileaf collimator (MLC) apertures are corrected in the beam’s eye view (BEV) and the monitor units (MUs) are corrected using point dose calculations. All MLC and MU corrections are driven by the positions of four fiducial points only, without need for a full contour set. Quality assurance (QA) of the adapted plans is performed using plan parameters that can be calculated online and that have a relation to the delivered dose or the plan quality. Five potential parameters are studied for this purpose: the number of MU, the equivalent field size (EqFS), the modulation complexity score (MCS), and the components of the MCS: the aperture area variability (AAV) and the leaf sequence variability (LSV). The full adaptation and its separate steps were evaluated in simulation experiments involving a prostate phantom subjected to various interfraction transformations. The efficacy of the current VMAT adaptation was scored by target mean dose (CTV mean ), conformity (CI 95% ), tumor control probability (TCP), and normal tissue complication probability (NTCP). The impact of the adaptation on the plan parameters (QA) was assessed by comparison with prediction intervals (PI) derived from a statistical model of the typical variation of these parameters in a population of VMAT prostate plans (n = 63). These prediction intervals are the adaptation equivalent of the tolerance tables for couch shifts in the current clinical practice

Adaptation in integrated assessment modeling: where do we stand?

OpenAIRE

Patt, A.; van Vuuren, D.P.; Berkhout, F.G.H.; Aaheim, A.; Hof, A.F.; Isaac, M.; Mechler, R.

2010-01-01

Adaptation is an important element on the climate change policy agenda. Integrated assessment models, which are key tools to assess climate change policies, have begun to address adaptation, either by including it implicitly in damage cost estimates, or by making it an explicit control variable. We analyze how modelers have chosen to describe adaptation within an integrated framework, and suggest many ways they could improve the treatment of adaptation by considering more of its bottom-up cha...

Treatment accuracy of hypofractionated spine and other highly conformal IMRT treatments

International Nuclear Information System (INIS)

Sutherland, B.; Hanlon, P.; Charles, P.

2011-01-01

Full text: Spinal cord metastases pose difficult challenges for radiation treatment due to tight dose constraints and a concave PTY. This project aimed to thoroughly test the treatment accuracy of the Eclipse Treatment Planning System (TPS) for highly modulated IMRT treatments, in particular of the thoracic spine, using an Elekta Synergy Linear Accelerator. The increased understanding obtained through different quality assurance techniques allowed recommendations to be made for treatment site commissioning with improved accuracy at the Princess Alexandra Hospital (PAH). Three thoracic spine IMRT plans at the PAH were used for data collection. Complex phantom models were built using CT data, and fields simulated using Monte Carlo modelling. The simulated dose distributions were compared with the TPS using gamma analysis and DYH comparison. High resolution QA was done for all fields using the MatriXX ion chamber array, MapCHECK2 diode array shifted, and the EPlD to determine a procedure for commissioning new treatment sites. Basic spine simulations found the TPS overestimated absorbed dose to bone, however within spinal cord there was good agreement. High resolution QA found the average gamma pass rate of the fields to be 99.1 % for MatriXX, 96.5% for MapCHECK2 shifted and 97.7% for EPlD. Preliminary results indicate agreement between the TPS and delivered dose distributions higher than previously believed for the investigated IMRT plans. The poor resolution of the MatriXX, and normalisation issues with MapCHECK2 leads to probable recommendation of EPlD for future IMRT commissioning due to the high resolution and minimal setup required.

Adaptation level as the basic health status characteristics: possibilitics of its assessment and forecasting of desadaptation violations

Directory of Open Access Journals (Sweden)

Vysochyna I.L.

2015-09-01

Full Text Available On the basis of comprehensive survey with integrative assessment of health state (medical history data, physical examination, anthropometry, battery of psychological tests (Eysenck, Shmishek’s Personality Inventory (teen version, tapping - test by E.P. Ilyin, children's questionnaire of neuroses; test for rapid assessment of health, activity and mood, anxiety diagnosis by Spielberg - Khanin; Luscher test, color relations test level of adaptation was defined in 236 children from orphanages aged from 4 to 18 years. The manifestations of maladjustment were registered both on psychological level (neuroticism, high anxiety, decreased performance, activity and psychological endurance, sleep disturbance, presence of accentuation and neurotic disorders and somatic level (recurrent acute respiratory infections, poor physical development, exacerbation of chronic foci of infection and burdened biological history; this summarizes conclusions on a low level of health status of children in orphanages. The author has developed mathematical models of adaptation assessment and prediction of desadaptation, which allowed to identify children at risk for the development of adaptation disorders and children with maladjustment; according to the level and severity of maladaptive disorders correction programs are designed.

SU-F-T-295: MLCs Performance and Patient-Specific IMRT QA Using Log File Analysis

Energy Technology Data Exchange (ETDEWEB)

Osman, A [King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); American University of Biuret Medical Center, Biuret (Lebanon); Maalej, N [King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia); Jayesh, K; Abdel-Rahman, W [King Fahad Specialist Hospital-Dammam, Eastern Province (Saudi Arabia)

2016-06-15

Purpose: To analyze the performance of the multi-leaf collimators (MLCs) from the log files recorded during the intensity modulated radiotherapy (IMRT) treatment and to construct the relative fluence maps and do the gamma analysis to compare the planned and executed MLCs movement. Methods: We developed a program to extract and analyze the data from dynamic log files (dynalog files) generated from sliding window IMRT delivery treatments. The program extracts the planned and executed (actual or delivered) MLCs movement, calculates and compares the relative planned and executed fluences. The fluence maps were used to perform the gamma analysis (with 3% dose difference and 3 mm distance to agreement) for 3 IMR patients. We compared our gamma analysis results with those obtained from portal dose image prediction (PDIP) algorithm performed using the EPID. Results: For 3 different IMRT patient treatments, the maximum difference between the planned and the executed MCLs positions was 1.2 mm. The gamma analysis results of the planned and delivered fluences were in good agreement with the gamma analysis from portal dosimetry. The maximum difference for number of pixels passing the gamma criteria (3%/3mm) was 0.19% with respect to portal dosimetry results. Conclusion: MLC log files can be used to verify the performance of the MLCs. Patientspecific IMRT QA based on MLC movement log files gives similar results to EPID dosimetry results. This promising method for patient-specific IMRT QA is fast, does not require dose measurements in a phantom, can be done before the treatment and for every fraction, and significantly reduces the IMRT workload. The author would like to thank King Fahd University of petroleum and Minerals for the support.

Carcinoma of the anal canal: Intensity modulated radiation therapy (IMRT) versus three-dimensional conformal radiation therapy (3DCRT)

Science.gov (United States)

Sale, Charlotte; Moloney, Phillip; Mathlum, Maitham

2013-01-01

Introduction Patients with anal canal carcinoma treated with standard conformal radiotherapy frequently experience severe acute and late toxicity reactions to the treatment area. Roohipour et al. (Dis Colon Rectum 2008; 51: 147–53) stated a patient's tolerance of chemoradiation to be an important prediction of treatment success. A new intensity modulated radiation therapy (IMRT) technique for anal carcinoma cases has been developed at the Andrew Love Cancer Centre aimed at reducing radiation to surrounding healthy tissue. Methods A same-subject repeated measures design was used for this study, where five anal carcinoma cases at the Andrew Love Cancer Centre were selected. Conformal and IMRT plans were generated and dosimetric evaluations were performed. Each plan was prescribed a total of 54 Gray (Gy) over a course of 30 fractions to the primary site. Results The IMRT plans resulted in improved dosimetry to the planning target volume (PTV) and reduction in radiation to the critical structures (bladder, external genitalia and femoral heads). Statistically there was no difference between the IMRT and conformal plans in the dose to the small and large bowel; however, the bowel IMRT dose–volume histogram (DVH) doses were consistently lower. Conclusion The IMRT plans were superior to the conformal plans with improved dose conformity and reduced radiation to the surrounding healthy tissue. Anecdotally it was found that patients tolerated the IMRT treatment better than the three-dimensional (3D) conformal radiation therapy. This study describes and compares the planning techniques. PMID:26229623

Carcinoma of the anal canal: Intensity modulated radiation therapy (IMRT) versus three-dimensional conformal radiation therapy (3DCRT)

International Nuclear Information System (INIS)

Sale, Charlotte; Moloney, Phillip; Mathlum, Maitham

2013-01-01

Patients with anal canal carcinoma treated with standard conformal radiotherapy frequently experience severe acute and late toxicity reactions to the treatment area. Roohipour et al. (Dis Colon Rectum 2008; 51: 147–53) stated a patient's tolerance of chemoradiation to be an important prediction of treatment success. A new intensity modulated radiation therapy (IMRT) technique for anal carcinoma cases has been developed at the Andrew Love Cancer Centre aimed at reducing radiation to surrounding healthy tissue. A same-subject repeated measures design was used for this study, where five anal carcinoma cases at the Andrew Love Cancer Centre were selected. Conformal and IMRT plans were generated and dosimetric evaluations were performed. Each plan was prescribed a total of 54 Gray (Gy) over a course of 30 fractions to the primary site. The IMRT plans resulted in improved dosimetry to the planning target volume (PTV) and reduction in radiation to the critical structures (bladder, external genitalia and femoral heads). Statistically there was no difference between the IMRT and conformal plans in the dose to the small and large bowel; however, the bowel IMRT dose–volume histogram (DVH) doses were consistently lower. The IMRT plans were superior to the conformal plans with improved dose conformity and reduced radiation to the surrounding healthy tissue. Anecdotally it was found that patients tolerated the IMRT treatment better than the three-dimensional (3D) conformal radiation therapy. This study describes and compares the planning techniques

Carcinoma of the anal canal: Intensity modulated radiation therapy (IMRT) versus three-dimensional conformal radiation therapy (3DCRT).

Science.gov (United States)

Sale, Charlotte; Moloney, Phillip; Mathlum, Maitham

2013-12-01

Patients with anal canal carcinoma treated with standard conformal radiotherapy frequently experience severe acute and late toxicity reactions to the treatment area. Roohipour et al. (Dis Colon Rectum 2008; 51: 147-53) stated a patient's tolerance of chemoradiation to be an important prediction of treatment success. A new intensity modulated radiation therapy (IMRT) technique for anal carcinoma cases has been developed at the Andrew Love Cancer Centre aimed at reducing radiation to surrounding healthy tissue. A same-subject repeated measures design was used for this study, where five anal carcinoma cases at the Andrew Love Cancer Centre were selected. Conformal and IMRT plans were generated and dosimetric evaluations were performed. Each plan was prescribed a total of 54 Gray (Gy) over a course of 30 fractions to the primary site. The IMRT plans resulted in improved dosimetry to the planning target volume (PTV) and reduction in radiation to the critical structures (bladder, external genitalia and femoral heads). Statistically there was no difference between the IMRT and conformal plans in the dose to the small and large bowel; however, the bowel IMRT dose-volume histogram (DVH) doses were consistently lower. The IMRT plans were superior to the conformal plans with improved dose conformity and reduced radiation to the surrounding healthy tissue. Anecdotally it was found that patients tolerated the IMRT treatment better than the three-dimensional (3D) conformal radiation therapy. This study describes and compares the planning techniques.

Carcinoma of the anal canal: Intensity modulated radiation therapy (IMRT) versus three-dimensional conformal radiation therapy (3DCRT)

Energy Technology Data Exchange (ETDEWEB)

Sale, Charlotte; Moloney, Phillip; Mathlum, Maitham [Andrew Love Cancer Centre, Geelong Hospital, Geelong, Victoria (Australia)

2013-12-15

Patients with anal canal carcinoma treated with standard conformal radiotherapy frequently experience severe acute and late toxicity reactions to the treatment area. Roohipour et al. (Dis Colon Rectum 2008; 51: 147–53) stated a patient's tolerance of chemoradiation to be an important prediction of treatment success. A new intensity modulated radiation therapy (IMRT) technique for anal carcinoma cases has been developed at the Andrew Love Cancer Centre aimed at reducing radiation to surrounding healthy tissue. A same-subject repeated measures design was used for this study, where five anal carcinoma cases at the Andrew Love Cancer Centre were selected. Conformal and IMRT plans were generated and dosimetric evaluations were performed. Each plan was prescribed a total of 54 Gray (Gy) over a course of 30 fractions to the primary site. The IMRT plans resulted in improved dosimetry to the planning target volume (PTV) and reduction in radiation to the critical structures (bladder, external genitalia and femoral heads). Statistically there was no difference between the IMRT and conformal plans in the dose to the small and large bowel; however, the bowel IMRT dose–volume histogram (DVH) doses were consistently lower. The IMRT plans were superior to the conformal plans with improved dose conformity and reduced radiation to the surrounding healthy tissue. Anecdotally it was found that patients tolerated the IMRT treatment better than the three-dimensional (3D) conformal radiation therapy. This study describes and compares the planning techniques.

Hematologic Toxicity in RTOG 0418: A Phase 2 Study of Postoperative IMRT for Gynecologic Cancer

International Nuclear Information System (INIS)

Klopp, Ann H.; Moughan, Jennifer; Portelance, Lorraine; Miller, Brigitte E.; Salehpour, Mohammad R.; Hildebrandt, Evangeline; Nuanjing, Jenny; D'Souza, David; Souhami, Luis; Small, William; Gaur, Rakesh; Jhingran, Anuja

2013-01-01

Purpose: Intensity modulated radiation therapy (IMRT), compared with conventional 4-field treatment, can reduce the volume of bone marrow irradiated. Pelvic bone marrow sparing has produced a clinically significant reduction in hematologic toxicity (HT). This analysis investigated HT in Radiation Therapy Oncology Group (RTOG) 0418, a prospective study to test the feasibility of delivering postoperative IMRT for cervical and endometrial cancer in a multiinstitutional setting. Methods and Materials: Patients in the RTOG 0418 study were treated with postoperative IMRT to 50.4 Gy to the pelvic lymphatics and vagina. Endometrial cancer patients received IMRT alone, whereas patients with cervical cancer received IMRT and weekly cisplatin (40 mg/m 2 ). Pelvic bone marrow was defined within the treatment field by using a computed tomography density-based autocontouring algorithm. The volume of bone marrow receiving 10, 20, 30, and 40 Gy and the median dose to bone marrow were correlated with HT, graded by Common Terminology Criteria for Adverse Events, version 3.0, criteria. Results: Eighty-three patients were eligible for analysis (43 with endometrial cancer and 40 with cervical cancer). Patients with cervical cancer treated with weekly cisplatin and pelvic IMRT had grades 1-5 HT (23%, 33%, 25%, 0%, and 0% of patients, respectively). Among patients with cervical cancer, 83% received 5 or more cycles of cisplatin, and 90% received at least 4 cycles of cisplatin. The median percentage volume of bone marrow receiving 10, 20, 30, and 40 Gy in all 83 patients, respectively, was 96%, 84%, 61%, and 37%. Among cervical cancer patients with a V40 >37%, 75% had grade 2 or higher HT compared with 40% of patients with a V40 less than or equal to 37% (P =.025). Cervical cancer patients with a median bone marrow dose of >34.2 Gy also had higher rates of grade ≥2 HT than did those with a dose of ≤34.2 Gy (74% vs 43%, P=.049). Conclusions: Pelvic IMRT with weekly cisplatin is

Hematologic Toxicity in RTOG 0418: A Phase 2 Study of Postoperative IMRT for Gynecologic Cancer

Energy Technology Data Exchange (ETDEWEB)

Klopp, Ann H., E-mail: aklopp@mdanderson.org [The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Moughan, Jennifer [RTOG Statistical Center, Philadelphia, Pennsylvania (United States); Portelance, Lorraine [Sylvester Comprehensive Cancer Center, Miami, Florida (United States); Miller, Brigitte E. [Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina (United States); Salehpour, Mohammad R.; Hildebrandt, Evangeline; Nuanjing, Jenny [The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); D' Souza, David [London Regional Cancer Center, University of Western Ontario, London, Ontario (Canada); Souhami, Luis [Sylvester Comprehensive Cancer Center, Miami, Florida (United States); Small, William [Northwestern Memorial Hospital, Chicago, Illinois (United States); Gaur, Rakesh [St. Luke' s Cancer Institute, Kansas City, Missouri (United States); Jhingran, Anuja [The University of Texas MD Anderson Cancer Center, Houston, Texas (United States)

2013-05-01

Purpose: Intensity modulated radiation therapy (IMRT), compared with conventional 4-field treatment, can reduce the volume of bone marrow irradiated. Pelvic bone marrow sparing has produced a clinically significant reduction in hematologic toxicity (HT). This analysis investigated HT in Radiation Therapy Oncology Group (RTOG) 0418, a prospective study to test the feasibility of delivering postoperative IMRT for cervical and endometrial cancer in a multiinstitutional setting. Methods and Materials: Patients in the RTOG 0418 study were treated with postoperative IMRT to 50.4 Gy to the pelvic lymphatics and vagina. Endometrial cancer patients received IMRT alone, whereas patients with cervical cancer received IMRT and weekly cisplatin (40 mg/m{sup 2}). Pelvic bone marrow was defined within the treatment field by using a computed tomography density-based autocontouring algorithm. The volume of bone marrow receiving 10, 20, 30, and 40 Gy and the median dose to bone marrow were correlated with HT, graded by Common Terminology Criteria for Adverse Events, version 3.0, criteria. Results: Eighty-three patients were eligible for analysis (43 with endometrial cancer and 40 with cervical cancer). Patients with cervical cancer treated with weekly cisplatin and pelvic IMRT had grades 1-5 HT (23%, 33%, 25%, 0%, and 0% of patients, respectively). Among patients with cervical cancer, 83% received 5 or more cycles of cisplatin, and 90% received at least 4 cycles of cisplatin. The median percentage volume of bone marrow receiving 10, 20, 30, and 40 Gy in all 83 patients, respectively, was 96%, 84%, 61%, and 37%. Among cervical cancer patients with a V40 >37%, 75% had grade 2 or higher HT compared with 40% of patients with a V40 less than or equal to 37% (P =.025). Cervical cancer patients with a median bone marrow dose of >34.2 Gy also had higher rates of grade ≥2 HT than did those with a dose of ≤34.2 Gy (74% vs 43%, P=.049). Conclusions: Pelvic IMRT with weekly cisplatin is

Use of plan quality degradation to evaluate tradeoffs in delivery efficiency and clinical plan metrics arising from IMRT optimizer and sequencer compromises

Science.gov (United States)

Wilkie, Joel R.; Matuszak, Martha M.; Feng, Mary; Moran, Jean M.; Fraass, Benedick A.

2013-01-01

Purpose: Plan degradation resulting from compromises made to enhance delivery efficiency is an important consideration for intensity modulated radiation therapy (IMRT) treatment plans. IMRT optimization and/or multileaf collimator (MLC) sequencing schemes can be modified to generate more efficient treatment delivery, but the effect those modifications have on plan quality is often difficult to quantify. In this work, the authors present a method for quantitative assessment of overall plan quality degradation due to tradeoffs between delivery efficiency and treatment plan quality, illustrated using comparisons between plans developed allowing different numbers of intensity levels in IMRT optimization and/or MLC sequencing for static segmental MLC IMRT plans. Methods: A plan quality degradation method to evaluate delivery efficiency and plan quality tradeoffs was developed and used to assess planning for 14 prostate and 12 head and neck patients treated with static IMRT. Plan quality was evaluated using a physician's predetermined “quality degradation” factors for relevant clinical plan metrics associated with the plan optimization strategy. Delivery efficiency and plan quality were assessed for a range of optimization and sequencing limitations. The “optimal” (baseline) plan for each case was derived using a clinical cost function with an unlimited number of intensity levels. These plans were sequenced with a clinical MLC leaf sequencer which uses >100 segments, assuring delivered intensities to be within 1% of the optimized intensity pattern. Each patient's optimal plan was also sequenced limiting the number of intensity levels (20, 10, and 5), and then separately optimized with these same numbers of intensity levels. Delivery time was measured for all plans, and direct evaluation of the tradeoffs between delivery time and plan degradation was performed. Results: When considering tradeoffs, the optimal number of intensity levels depends on the treatment

Intensity modulated radiotherapy (IMRT) in France: the boost of the national funding for the new expensive innovative technologies (STIC 2001 and 2002)

International Nuclear Information System (INIS)

Marchal, C.; Lapeyre, M.; Bensadoun, R.J.; Gerard, J.P.; Hasle, E.; Carrere, M.O.

2003-01-01

The STIC 2001 and STIC 2002 projects intend to allow the implementation and the assessment of Intensity Modulated Radiation Therapy in France. IMRT is an innovative technique in which the high-dose radiation volume conforms to an accurately defined target volume with less morbidity to the surrounding normal tissues. The main medical objectives of the projects are (1) to improve the therapeutic index while decreasing acute toxicity and late sequelae (mainly xerostomia and acute mucite for head and neck tumors), which allows an increase in the radiation dose to the tumor and then a better tumor control; (2) to propose a salvage treatment to patients who locally recurred in previously irradiated sites; (3) to determine the optimal treatment guidelines for a safe use of the technique in clinical routine. Our projects also aim at comparing IMRT and 3D conformal treatments on the one hand (STIC 2001), and IMRT and conventional treatments on the other hand (STIC 2002), with regard to costs. As a matter of fact, the use of IMRT is presently limited in France because its implementation requires high investment and personnel costs. The seventeen French Regional Cancer Centres involved in the two projects intend to study the additional cost of the use IMRT in comparison with the use of standard techniques, which appears to be a step for a wide use of this technique in France. Each of the studies is two-year prospective, and includes patients with head and neck tumors treated with a curative intend (post operative or exclusive treatments for STIC 2002 and STIC 2002), and patients with a prostate cancer (STIC 2001). (author)

Does IGRT ensure target dose coverage of head and neck IMRT patients?

International Nuclear Information System (INIS)

Graff, Pierre; Hu Weigang; Yom, Sue S.; Pouliot, Jean

2012-01-01

Purpose: To determine if image-guided radiotherapy (IGRT) ensures dose coverage to the target, and to assess the dosimetric impact of anatomic changes using megavoltage cone-beam CT (MVCBCT) for patient positioning during head and neck IMRT. Methods and materials: Forty-eight MVCBCT from 10 head and neck IMRT/IGRT patients were analyzed off-line. Target volumes and organs at risk (OARs) contours delineated on CT were transferred and adjusted on MVCBCT images. Each MVCBCT was processed to allow dose recalculation, resulting in 469 dose–volume histograms (DVHs). The concept of dosimetric latitude was introduced to provide a clinical perspective. Results: MVCBCT target DVHs showed a moderate level of difference in D95 (dose to ⩾95% of volume), generally less than a 5% difference from the planned dose. Delivered-dose increases to the spinal cord and brainstem showed no apparent time trend. The 4 mm margin around OARs was a useful precaution to prevent exceeding critical dose thresholds. The parotid glands showed progressive increases in mean dose related to shrinkage of the external contours. Conclusion: IGRT repositioning ensured target volume coverage, but significant dose variations were observed for OARs. The dosimetric impact of anatomic changes during radiotherapy was of lesser importance than the effects of IGRT repositioning.

An analysis of stabilisation for head and neck image guided IMRT

International Nuclear Information System (INIS)

Middleton, Mark; Nguyen, Huong; Plank, Ashley; Jones, Mark; Shannon, Debbie; Sisson, Toni

2014-01-01

Aims: Daily IGRT using kV imaging has allowed an enhanced field of view for head and neck IMRT patients. This has allowed the treating radiation therapists to note set-up error beyond traditional spatial or translational and include angular error. This study compares two stabilisation methods for head and neck IGRT and compares spatial and angular error between them. Methods and materials: 9 patients were assessed using a CIVCO S-board and generic Silverman head rest and another 9 patients were assessed using a CIVCO S-board with a CIVCO S-type vac-fix bag. Daily IGRT was undertaken and pre-intervention set-up error collected. This was inclusive of error in the lateral, longitudinal and vertical plans and angular discrepancy between cervical spine 1 and cervical spine 7. Results: The vac-fix solution provided a significant reduction in the systematic yaw position (anterior–posterior) (p = 0.04). It also reduced the mean resultant systematic angular error significantly (p = 0.01). The lateral systematic spatial error was decreased significantly by the vac-fix (p = 0.03) whilst the longitudinal and vertical systematic errors were not. The differences in random error between the two stabilisation solutions were not significant. Conclusion: kV IGRT has allowed treating radiation therapists to note angular error in the head and neck region. This can be difficult to deal with using only IGRT. Stabilisation solutions in the head and neck region must be able to manage both spatial and angular set-up error. The vac-fix solution has improved the management of angular error for head and neck IMRT patients

Evaluation of atlas based auto-segmentation for head and neck target volume delineation in adaptive/replan IMRT

International Nuclear Information System (INIS)

Speight, R; Lindsay, R; Harding, R; Sykes, J; Karakaya, E; Prestwich, R; Sen, M

2014-01-01

IMRT for head and neck patients requires clinicians to delineate clinical target volumes (CTV) on a planning-CT (>2hrs/patient). When patients require a replan-CT, CTVs must be re-delineated. This work assesses the performance of atlas-based autosegmentation (ABAS), which uses deformable image registration between planning and replan-CTs to auto-segment CTVs on the replan-CT, based on the planning contours. Fifteen patients with planning-CT and replan-CTs were selected. One clinician delineated CTVs on the planning-CTs and up to three clinicians delineated CTVs on the replan-CTs. Replan-CT volumes were auto-segmented using ABAS using the manual CTVs from the planning-CT as an atlas. ABAS CTVs were edited manually to make them clinically acceptable. Clinicians were timed to estimate savings using ABAS. CTVs were compared using dice similarity coefficient (DSC) and mean distance to agreement (MDA). Mean inter-observer variability (DSC>0.79 and MDA<2.1mm) was found to be greater than intra-observer variability (DSC>0.91 and MDA<1.5mm). Comparing ABAS to manual CTVs gave DSC=0.86 and MDA=2.07mm. Once edited, ABAS volumes agreed more closely with the manual CTVs (DSC=0.87 and MDA=1.87mm). The mean clinician time required to produce CTVs reduced from 169min to 57min when using ABAS. ABAS segments volumes with accuracy close to inter-observer variability however the volumes require some editing before clinical use. Using ABAS reduces contouring time by a factor of three.

Acute toxicity of postoperative IMRT and chemotherapy for endometrial cancer

International Nuclear Information System (INIS)

Tierney, R.M.; Powell, M.A.; Mutch, D.G.; Gibb, R.K.; Rader, J.S.; Grigsby, P.W.

2007-01-01

The aim of this study was to determine the acute toxicity of postoperative intensity-modulated radiotherapy (IMRT) with and without chemotherapy in patients with endometrial cancer. A total of 19 patients with stages IB-IVB endometrial cancer who underwent surgery and postoperative IMRT were reviewed. The treatment planning goal was to cover the tissue at risk and minimize the dose to the bladder, bowel, and bone marrow. Median dose was 50.4 Gy (range 49.6-51.2 Gy). Altogether, 14 patients underwent chemotherapy; most were given carboplatin and paclitaxel. Toxicity was scored according to the Common Terminology Criteria for Adverse Events version 3.0 (CTCAE). The prescribed radiation treatment was completed in all patients. The prescribed cycles of chemotherapy were completed in all 14 patients, except one who received five of six cycles limited by prolonged thrombocytopenia. Chemotherapy was delayed in two patients (14%). Three patients required growth factor support during chemotherapy, and one patient required a blood transfusion. Acute grades 3-4 hematological toxicity occurred in 9 of the 14 patients (64%) who underwent chemotherapy. None experienced acute grade 3 or 4 genitourinary or gastrointestinal toxicity. Adjuvant IMRT and chemotherapy following surgery in patients with endometrial cancer is well tolerated and did not lead to treatment modification in most patients. (author)

Intensity modulated radiation therapy (IMRT: differences in target volumes and improvement in clinically relevant doses to small bowel in rectal carcinoma

Directory of Open Access Journals (Sweden)

Delclos Marc E

2011-06-01

Full Text Available Abstract Background A strong dose-volume relationship exists between the amount of small bowel receiving low- to intermediate-doses of radiation and the rates of acute, severe gastrointestinal toxicity, principally diarrhea. There is considerable interest in the application of highly conformal treatment approaches, such as intensity-modulated radiation therapy (IMRT, to reduce dose to adjacent organs-at-risk in the treatment of carcinoma of the rectum. Therefore, we performed a comprehensive dosimetric evaluation of IMRT compared to 3-dimensional conformal radiation therapy (3DCRT in standard, preoperative treatment for rectal cancer. Methods Using RTOG consensus anorectal contouring guidelines, treatment volumes were generated for ten patients treated preoperatively at our institution for rectal carcinoma, with IMRT plans compared to plans derived from classic anatomic landmarks, as well as 3DCRT plans treating the RTOG consensus volume. The patients were all T3, were node-negative (N = 1 or node-positive (N = 9, and were planned to a total dose of 45-Gy. Pairwise comparisons were made between IMRT and 3DCRT plans with respect to dose-volume histogram parameters. Results IMRT plans had superior PTV coverage, dose homogeneity, and conformality in treatment of the gross disease and at-risk nodal volume, in comparison to 3DCRT. Additionally, in comparison to the 3DCRT plans, IMRT achieved a concomitant reduction in doses to the bowel (small bowel mean dose: 18.6-Gy IMRT versus 25.2-Gy 3DCRT; p = 0.005, bladder (V40Gy: 56.8% IMRT versus 75.4% 3DCRT; p = 0.005, pelvic bones (V40Gy: 47.0% IMRT versus 56.9% 3DCRT; p = 0.005, and femoral heads (V40Gy: 3.4% IMRT versus 9.1% 3DCRT; p = 0.005, with an improvement in absolute volumes of small bowel receiving dose levels known to induce clinically-relevant acute toxicity (small bowel V15Gy: 138-cc IMRT versus 157-cc 3DCRT; p = 0.005. We found that the IMRT treatment volumes were typically larger than that

Long-term disease control and toxicity outcomes following surgery and intensity modulated radiation therapy (IMRT) in pediatric craniopharyngioma.

Science.gov (United States)

Greenfield, Brad J; Okcu, Mehmet F; Baxter, Patricia A; Chintagumpala, Murali; Teh, Bin S; Dauser, Robert C; Su, Jack; Desai, Snehal S; Paulino, Arnold C

2015-02-01

To report long-term progression-free survival (PFS) and late-toxicity outcomes in pediatric craniopharyngioma patients treated with IMRT. Twenty-four children were treated with IMRT to a median dose of 50.4Gy (range, 49.8-54Gy). The clinical target volume (CTV) was the gross tumor volume (GTV) with a 1cm margin. The planning target volume (PTV) was the CTV with a 3-5mm margin. Median follow-up was 107.3months. The 5- and 10-year PFS rates were 65.8% and 60.7%. The 5- and 10-year cystic PFS rates were 70.2% and 65.2% while the 5- and 10-year solid PFS were the same at 90.7%. Endocrinopathy was seen in 42% at initial diagnosis and in 74% after surgical intervention, prior to IMRT. Hypothalamic dysfunction and visual deficits were associated with increasing PTV and number of surgical interventions. IMRT is a viable treatment option for pediatric craniopharyngioma. Despite the use of IMRT, majority of the craniopharyngioma patients experienced long-term toxicity, many of which present prior to radiotherapy. Limitations of retrospective analyses on small patient cohort elicit the need for a prospective multi-institutional study to determine the absolute benefit of IMRT in pediatric craniopharyngioma. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Long-term disease control and toxicity outcomes following surgery and intensity modulated radiation therapy (IMRT) in pediatric craniopharyngioma

International Nuclear Information System (INIS)

Greenfield, Brad J.; Okcu, Mehmet F.; Baxter, Patricia A.; Chintagumpala, Murali; Teh, Bin S.; Dauser, Robert C.; Su, Jack; Desai, Snehal S.; Paulino, Arnold C.

2015-01-01

Purpose: To report long-term progression-free survival (PFS) and late-toxicity outcomes in pediatric craniopharyngioma patients treated with IMRT. Patients and methods: Twenty-four children were treated with IMRT to a median dose of 50.4 Gy (range, 49.8–54 Gy). The clinical target volume (CTV) was the gross tumor volume (GTV) with a 1 cm margin. The planning target volume (PTV) was the CTV with a 3–5 mm margin. Median follow-up was 107.3 months. Results: The 5- and 10-year PFS rates were 65.8% and 60.7%. The 5- and 10-year cystic PFS rates were 70.2% and 65.2% while the 5- and 10-year solid PFS were the same at 90.7%. Endocrinopathy was seen in 42% at initial diagnosis and in 74% after surgical intervention, prior to IMRT. Hypothalamic dysfunction and visual deficits were associated with increasing PTV and number of surgical interventions. Conclusions: IMRT is a viable treatment option for pediatric craniopharyngioma. Despite the use of IMRT, majority of the craniopharyngioma patients experienced long-term toxicity, many of which present prior to radiotherapy. Limitations of retrospective analyses on small patient cohort elicit the need for a prospective multi-institutional study to determine the absolute benefit of IMRT in pediatric craniopharyngioma

Adaptive Assessment of Young Children with Visual Impairment

Science.gov (United States)

Ruiter, Selma; Nakken, Han; Janssen, Marleen; Van Der Meulen, Bieuwe; Looijestijn, Paul

2011-01-01

The aim of this study was to assess the effect of adaptations for children with low vision of the Bayley Scales, a standardized developmental instrument widely used to assess development in young children. Low vision adaptations were made to the procedures, item instructions and play material of the Dutch version of the Bayley Scales of Infant…

An Approach for Practical Multiobjective IMRT Treatment Planning

International Nuclear Information System (INIS)

Craft, David; Halabi, Tarek; Shih, Helen A.; Bortfeld, Thomas

2007-01-01

Purpose: To introduce and demonstrate a practical multiobjective treatment planning procedure for intensity-modulated radiation therapy (IMRT) planning. Methods and Materials: The creation of a database of Pareto optimal treatment plans proceeds in two steps. The first step solves an optimization problem that finds a single treatment plan which is close to a set of clinical aspirations. This plan provides an example of what is feasible, and is then used to determine mutually satisfiable hard constraints for the subsequent generation of the plan database. All optimizations are done using linear programming. Results: The two-step procedure is applied to a brain, a prostate, and a lung case. The plan databases created allow for the selection of a final treatment plan based on the observed tradeoffs between the various organs involved. Conclusions: The proposed method reduces the human iteration time common in IMRT treatment planning. Additionally, the database of plans, when properly viewed, allows the decision maker to make an informed final plan selection

Dosimetric comparison of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in total scalp irradiation: a single institutional experience

International Nuclear Information System (INIS)

Ostheimer, Christian; Huebsch, Patrick; Janich, Martin; Gerlach, Reinhard; Vordermark, Dirk

2016-01-01

Total scalp irradiation (TSI) is a rare but challenging indication. We previously reported that non-coplanar intensity-modulated radiotherapy (IMRT) was superior to coplanar IMRT in organ-at-risk (OAR) protection and target dose distribution. This consecutive treatment planning study compared IMRT with volumetric-modulated arc therapy (VMAT). A retrospective treatment plan databank search was performed and 5 patient cases were randomly selected. Cranial imaging was restored from the initial planning computed tomography (CT) and target volumes and OAR were redelineated. For each patients, three treatment plans were calculated (coplanar/non-coplanar IMRT, VMAT; prescribed dose 50 Gy, single dose 2 Gy). Conformity, homogeneity and dose volume histograms were used for plan. VMAT featured the lowest monitor units and the sharpest dose gradient (1.6 Gy/mm). Planning target volume (PTV) coverage and homogeneity was better in VMAT (coverage, 0.95; homogeneity index [HI], 0.118) compared to IMRT (coverage, 0.94; HI, 0.119) but coplanar IMRT produced the most conformal plans (conformity index [CI], 0.43). Minimum PTV dose range was 66.8% –88.4% in coplanar, 77.5%–88.2% in non-coplanar IMRT and 82.8%–90.3% in VMAT. Mean dose to the brain, brain stem, optic system (maximum dose) and lenses were 18.6, 13.2, 9.1, and 5.2 Gy for VMAT, 21.9, 13.4, 14.5, and 6.3 Gy for non-coplanar and 22.8, 16.5, 11.5, and 5.9 Gy for coplanar IMRT. Maximum optic chiasm dose was 7.7, 8.4, and 11.1 Gy (non-coplanar IMRT, VMAT, and coplanar IMRT). Target coverage, homogeneity and OAR protection, was slightly superior in VMAT plans which also produced the sharpest dose gradient towards healthy tissue

Dosimetric comparison of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in total scalp irradiation: a single institutional experience

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Ostheimer, Christian; Huebsch, Patrick; Janich, Martin; Gerlach, Reinhard; Vordermark, Dirk [Dept. of Radiation Oncology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, Halle (Germany)

2016-12-15

Total scalp irradiation (TSI) is a rare but challenging indication. We previously reported that non-coplanar intensity-modulated radiotherapy (IMRT) was superior to coplanar IMRT in organ-at-risk (OAR) protection and target dose distribution. This consecutive treatment planning study compared IMRT with volumetric-modulated arc therapy (VMAT). A retrospective treatment plan databank search was performed and 5 patient cases were randomly selected. Cranial imaging was restored from the initial planning computed tomography (CT) and target volumes and OAR were redelineated. For each patients, three treatment plans were calculated (coplanar/non-coplanar IMRT, VMAT; prescribed dose 50 Gy, single dose 2 Gy). Conformity, homogeneity and dose volume histograms were used for plan. VMAT featured the lowest monitor units and the sharpest dose gradient (1.6 Gy/mm). Planning target volume (PTV) coverage and homogeneity was better in VMAT (coverage, 0.95; homogeneity index [HI], 0.118) compared to IMRT (coverage, 0.94; HI, 0.119) but coplanar IMRT produced the most conformal plans (conformity index [CI], 0.43). Minimum PTV dose range was 66.8% –88.4% in coplanar, 77.5%–88.2% in non-coplanar IMRT and 82.8%–90.3% in VMAT. Mean dose to the brain, brain stem, optic system (maximum dose) and lenses were 18.6, 13.2, 9.1, and 5.2 Gy for VMAT, 21.9, 13.4, 14.5, and 6.3 Gy for non-coplanar and 22.8, 16.5, 11.5, and 5.9 Gy for coplanar IMRT. Maximum optic chiasm dose was 7.7, 8.4, and 11.1 Gy (non-coplanar IMRT, VMAT, and coplanar IMRT). Target coverage, homogeneity and OAR protection, was slightly superior in VMAT plans which also produced the sharpest dose gradient towards healthy tissue.

Impact of Salivary Gland Dosimetry on Post-IMRT Recovery of Saliva Output and Xerostomia Grade for Head-and-Neck Cancer Patients Treated With or Without Contralateral Submandibular Gland Sparing: A Longitudinal Study

International Nuclear Information System (INIS)

Wang Zhonghe; Yan Chao; Zhang Zhiyuan; Zhang Chenping; Hu Haisheng; Tu Wenyong; Kirwan, Jessica; Mendenhall, William M.

2011-01-01

Purpose: To observe the recovery of saliva output and effect on xerostomia grade after intensity-modulated radiotherapy (IMRT) with or without contralateral submandibular gland (cSMG) sparing and to assess the impact of salivary gland dosimetry on this recovery among patients with head-and-neck cancer. Methods and Materials: Between May 2007 and May 2008, 52 patients with head-and-neck cancer received definitive (n = 5 patients) and postoperative (n = 47 patients) IMRT at our institution, with at least one parotid gland spared. Of these patients, 26 patients with a low risk of recurrence in the cSMG region underwent IMRT and had their cSMGs spared (cSMG-sparing group). The remaining 26 high-risk patients had no cSMGs spared (cSMG-unspared group). Xerostomia grades and salivary flow rates were monitored at five time points (before IMRT and at 2, 6, 12, and 18 months after IMRT). Results: Average mean doses and mean volumes receiving 30 Gy (V30) of the cSMGs were lower in the cSMG-sparing group than in the cSMG-unspared group (mean dose, 20.4 Gy vs. 57.4 Gy; mean V30, 14.7% vs. 99.8%, respectively). Xerostomia grades at 2 and 6 months post-IMRT were also significantly lower among patients in the cSMG-sparing group than in the cSMG-unspared group, but differences were not significant at 12 and 18 months after IMRT. Patients in the cSMG-sparing group had significantly better mean unstimulated salivary flow rates at each time point post- IMRT as well as better mean stimulated salivary flow rates at 2 months post-IMRT. Conclusions: Recovery of saliva output and grade of xerostomia post-IMRT in patients whose cSMGs were spared were much better than in patients whose cSMGs were not spared. The influence of the mean doses to the cSMG and parotid gland on the recovery of saliva output was equivalent to that of the mean V30 to the glands.

Impact of Salivary Gland Dosimetry on Post-IMRT Recovery of Saliva Output and Xerostomia Grade for Head-and-Neck Cancer Patients Treated With or Without Contralateral Submandibular Gland Sparing: A Longitudinal Study

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Wang Zhonghe; Yan Chao [Division of Radiation Oncology, the Shanghai Ninth Peoples Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai (China); Zhang Zhiyuan; Zhang Chenping [Department of Oral and Maxillofacial Surgery, the Shanghai Ninth Peoples Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai (China); Hu Haisheng; Tu Wenyong [Division of Radiation Oncology, the Shanghai Ninth Peoples Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai (China); Kirwan, Jessica [Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida (United States); Mendenhall, William M., E-mail: mendwm@shands.ufl.edu [Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida (United States)

2011-12-01

Purpose: To observe the recovery of saliva output and effect on xerostomia grade after intensity-modulated radiotherapy (IMRT) with or without contralateral submandibular gland (cSMG) sparing and to assess the impact of salivary gland dosimetry on this recovery among patients with head-and-neck cancer. Methods and Materials: Between May 2007 and May 2008, 52 patients with head-and-neck cancer received definitive (n = 5 patients) and postoperative (n = 47 patients) IMRT at our institution, with at least one parotid gland spared. Of these patients, 26 patients with a low risk of recurrence in the cSMG region underwent IMRT and had their cSMGs spared (cSMG-sparing group). The remaining 26 high-risk patients had no cSMGs spared (cSMG-unspared group). Xerostomia grades and salivary flow rates were monitored at five time points (before IMRT and at 2, 6, 12, and 18 months after IMRT). Results: Average mean doses and mean volumes receiving 30 Gy (V30) of the cSMGs were lower in the cSMG-sparing group than in the cSMG-unspared group (mean dose, 20.4 Gy vs. 57.4 Gy; mean V30, 14.7% vs. 99.8%, respectively). Xerostomia grades at 2 and 6 months post-IMRT were also significantly lower among patients in the cSMG-sparing group than in the cSMG-unspared group, but differences were not significant at 12 and 18 months after IMRT. Patients in the cSMG-sparing group had significantly better mean unstimulated salivary flow rates at each time point post- IMRT as well as better mean stimulated salivary flow rates at 2 months post-IMRT. Conclusions: Recovery of saliva output and grade of xerostomia post-IMRT in patients whose cSMGs were spared were much better than in patients whose cSMGs were not spared. The influence of the mean doses to the cSMG and parotid gland on the recovery of saliva output was equivalent to that of the mean V30 to the glands.

Hypofractionated IMRT of the Prostate Bed After Radical Prostatectomy: Acute Toxicity in the PRIAMOS-1 Trial

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Katayama, Sonja, E-mail: sonja.katayama@med.uni-heidelberg.de [Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld, Heidelberg (Germany); Striecker, Thorbjoern; Kessel, Kerstin [Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld, Heidelberg (Germany); Sterzing, Florian [Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld, Heidelberg (Germany); Department of Radiation Oncology, German Cancer Research Center, Im Neuenheimer Feld, Heidelberg (Germany); Habl, Gregor [Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld, Heidelberg (Germany); Edler, Lutz [Department of Biostatistics, German Cancer Research Center, Im Neuenheimer Feld, Heidelberg (Germany); Debus, Juergen [Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld, Heidelberg (Germany); Department of Radiation Oncology, German Cancer Research Center, Im Neuenheimer Feld, Heidelberg (Germany); Herfarth, Klaus [Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld, Heidelberg (Germany)

2014-11-15

Purpose: Hypofractionated radiation therapy as primary treatment for prostate cancer is currently being investigated in large phase 3 trials. However, there are few data on postoperative hypofractionation. The Radiation therapy for the Prostate Bed With or Without the Pelvic Lymph Nodes (PRIAMOS 1) trial was initiated as a prospective phase 2 trial to assess treatment safety and toxicity of a hypofractionated intensity modulated radiation therapy (IMRT) of the prostate bed. Methods and Materials: From February to September 2012, 40 patients with indications for adjuvant or salvage radiation therapy were enrolled. One patient dropped out before treatment. Patients received 54 Gy in 18 fractions to the prostate bed with IMRT and daily image guidance. Gastrointestinal (GI) and genitourinary (GU) toxicities (according to National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0) were recorded weekly during treatment and 10 weeks after radiation therapy. Results: Overall acute toxicity was favorable, with no recorded adverse events grade ≥3. Acute GI toxicity rates were 56.4% (grade 1) and 17.9% (grade 2). Acute GU toxicity was recorded in 35.9% of patients (maximum grade 1). Urinary stress incontinence was not influenced by radiation therapy. The incidence of grade 1 urinary urge incontinence increased from 2.6% before to 23.1% 10 weeks after therapy, but grade 2 urge incontinence remained unchanged. Conclusions: Postoperative hypofractionated IMRT of the prostate bed is tolerated well, with no severe acute side effects.

Fast film dosimetry calibration method for IMRT treatment plan verification

International Nuclear Information System (INIS)

Schwob, N.; Wygoda, A.

2004-01-01

Intensity-Modulated Radiation Therapy (IMRT) treatments are delivered dynamically and as so, require routinely performed verification measurements [1]. Radiographic film dosimetry is a well-adapted method for integral measurements of dynamic treatments fields, with some drawbacks related to the known problems of dose calibration of films. Classically, several films are exposed to increasing doses, and a Net Optical Density (N.O.D) vs. dose sensitometric curve (S.C.) is generated. In order to speed up the process, some authors have developed a method based on the irradiation of a single film with a non-uniform pattern of O.D., delivered with a dynamic MLC. However, this curve still needs to be calibrated to dose by the means of measurements in a water phantom. It is recommended to make a new calibration for every series of measurements, in order to avoid the processing quality dependence of the film response. These frequent measurements are very time consuming. We developed a simple method for quick dose calibration of films, including a check of the accuracy of the calibration curve obtained

A comparative planning study of step-and-shoot IMRT versus helical tomotherapy for whole-pelvis irradiation in cervical cancer

International Nuclear Information System (INIS)

Chitapanarux, Imjai; Tharavichitkul, Ekkasit; Nobnop, Wannapa; Wanwilairat, Somsak; Vongtama, Roy; Traisathit, Patrinee

2015-01-01

The aim of this study was to compare the dosimetric parameters of whole-pelvis radiotherapy (WPRT) for cervical cancer between step-and-shoot IMRT (SaS-IMRT) and Helical Tomotherapy TM (HT). Retrospective analysis was performed on 20 cervical cancer patients who received WPRT in our center between January 2011 and January 2014. SaS-IMRT and HT treatment plans were generated for each patient. The dosimetric values for target coverage and organ-at-risk (OAR) sparing were compared according to the criteria of the International Commission on Radiation Units and Measurements 83 (ICRU 83) guidelines. Differences in beam-on time (BOT) were also compared. All the PTV dosimetric parameters (D5%, D50% and D95%) for the HT plan were (statistically significantly) of better quality than those for the SaS-IMRT plan (P-value < 0.001 in all respects). HT was also significantly more accurate than SaS-IMRT with respect to the D98% and Dmean of the CTV (P-values of 0.008 and <0.001, respectively). The median Conformity Index (CI) did not differ between the two plans (P-value = 0.057). However, the Uniformity Index for HT was significantly better than that for SaS-IMRT (P-value < 0.001). The median of D50% for the bladder, rectum and small bowel were significantly lower in HT planning than SaS-IMRT (P-value < 0.001). For D2%, we found that HT provided better sparing to the rectum and bladder (P-value < 0.001). However, the median of D2% for the small bowel was comparable for both plans. The median of Dmax of the head of the left femur was significantly lower in the HT plan, but this did not apply for the head of the right femur. BOT for HT was significantly shorter than for SaS-IMRT (P-value < 0.001). HT provided highly accurate plans, with more homogeneous PTV coverage and superior sparing of OARs than SaS-IMRT. In addition, HT enabled a shorter delivery time than SaS-IMRT. (author)

Whole brain radiotherapy with adjuvant or concomitant boost in brain metastasis: dosimetric comparison between helical and volumetric IMRT technique.

Science.gov (United States)

Borghetti, Paolo; Pedretti, Sara; Spiazzi, Luigi; Avitabile, Rossella; Urpis, Mauro; Foscarini, Federica; Tesini, Giulia; Trevisan, Francesca; Ghirardelli, Paolo; Pandini, Sara Angela; Triggiani, Luca; Magrini, Stefano Maria; Buglione, Michela

2016-04-19

To compare and evaluate the possible advantages related to the use of VMAT and helical IMRT and two different modalities of boost delivering, adjuvant stereotactic boost (SRS) or simultaneous integrated boost (SIB), in the treatment of brain metastasis (BM) in RPA classes I-II patients. Ten patients were treated with helical IMRT, 5 of them with SRS after whole brain radiotherapy (WBRT) and 5 with SIB. MRI co-registration with planning CT was mandatory and prescribed doses were 30 Gy in 10 fractions (fr) for WBRT and 15Gy/1fr or 45Gy/10fr in SRS or SIB, respectively. For each patient, 4 "treatment plans" (VMAT SRS and SIB, helical IMRT SRS and SIB) were calculated and accepted if PTV boost was included in 95 % isodose and dose constraints of the main organs at risk were respected without major deviations. Homogeneity Index (HI), Conformal Index (CI) and Conformal Number (CN) were considered to compare the different plans. Moreover, time of treatment delivery was calculated and considered in the analysis. Volume of brain metastasis ranged between 1.43 and 51.01 cc (mean 12.89 ± 6.37 ml) and 3 patients had double lesions. V95% resulted over 95 % in the average for each kind of technique, but the "target coverage" was inadequate for VMAT planning with two sites. The HI resulted close to the ideal value of zero in all cases; VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS showed mean CI of 2.15, 2.10, 2.44 and 1.66, respectively (optimal range: 1.5-2.0). Helical IMRT-SRS was related to the best and reliable finding of CN (0.66). The mean of treatment time was 210 s, 467 s, 440 s, 1598 s, respectively, for VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS. This dosimetric comparison show that helical IMRT obtain better target coverage and respect of CI and CN; VMAT could be acceptable in solitary metastasis. SIB modality can be considered as a good choice for clinical and logistic compliance; literature's preliminary data are confirming also a

Effects of intra-fraction motion on IMRT dose delivery: statistical analysis and simulation

International Nuclear Information System (INIS)

Bortfeld, Thomas; Jokivarsi, Kimmo; Goitein, Michael; Kung, Jong; Jiang, Steve B.

2002-01-01

There has been some concern that organ motion, especially intra-fraction organ motion due to breathing, can negate the potential merit of intensity-modulated radiotherapy (IMRT). We wanted to find out whether this concern is justified. Specifically, we wanted to investigate whether IMRT delivery techniques with moving parts, e.g., with a multileaf collimator (MLC), are particularly sensitive to organ motion due to the interplay between organ motion and leaf motion. We also wanted to know if, and by how much, fractionation of the treatment can reduce the effects. We performed a statistical analysis and calculated the expected dose values and dose variances for volume elements of organs that move during the delivery of the IMRT. We looked at the overall influence of organ motion during the course of a fractionated treatment. A linear-quadratic model was used to consider fractionation effects. Furthermore, we developed software to simulate motion effects for IMRT delivery with an MLC, with compensators, and with a scanning beam. For the simulation we assumed a sinusoidal motion in an isocentric plane. We found that the expected dose value is independent of the treatment technique. It is just a weighted average over the path of motion of the dose distribution without motion. If the treatment is delivered in several fractions, the distribution of the dose around the expected value is close to a Gaussian. For a typical treatment with 30 fractions, the standard deviation is generally within 1% of the expected value for MLC delivery if one assumes a typical motion amplitude of 5 mm (1 cm peak to peak). The standard deviation is generally even smaller for the compensator but bigger for scanning beam delivery. For the latter it can be reduced through multiple deliveries ('paintings') of the same field. In conclusion, the main effect of organ motion in IMRT is an averaging of the dose distribution without motion over the path of the motion. This is the same as for treatments

SU-E-J-20: Adaptive Aperture Morphing for Online Correction for Prostate Cancer Radiotherapy

International Nuclear Information System (INIS)

Sandhu, R; Qin, A; Yan, D

2014-01-01

Purpose: Online adaptive aperture morphing is desirable over translational couch shifts to accommodate not only the target position variation but also anatomic changes (rotation, deformation, and relation of target to organ-atrisks). We proposed quick and reliable method for adapting segment aperture leaves for IMRT treatment of prostate. Methods: The proposed method consists of following steps: (1) delineate the contours of prostate, SV, bladder and rectum on kV-CBCT; (2) determine prostate displacement from the rigid body registration of the contoured prostate manifested on the reference CT and the CBCT; (3) adapt the MLC segment apertures obtained from the pre-treatment IMRT planning to accommodate the shifts as well as anatomic changes. The MLC aperture adaptive algorithm involves two steps; first move the whole aperture according to prostate translational/rotational shifts, and secondly fine-tune the aperture shape to maintain the spatial relationship between the planning target contour and the MLC aperture to the daily target contour. Feasibility of this method was evaluated retrospectively on a seven-field IMRT treatment of prostate cancer patient by comparing dose volume histograms of the original plan and the aperture-adjusted plan, with/without additional segments weight optimization (SWO), on two daily treatment CBCTs selected with relative large motion and rotation. Results: For first daily treatment, the prostate rotation was significant (12degree around lateral-axis). With apertureadjusted plan, the D95 to the target was improved 25% and rectum dose (D30, D40) was reduced 20% relative to original plan on daily volumes. For second treatment-fraction, (lateral shift = 6.7mm), after adjustment target D95 improved by 3% and bladder dose (D30, maximum dose) was reduced by 1%. For both cases, extra SWO did not provide significant improvement. Conclusion: The proposed method of adapting segment apertures is promising in treatment position correction

SU-E-J-20: Adaptive Aperture Morphing for Online Correction for Prostate Cancer Radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Sandhu, R; Qin, A; Yan, D [William Beaumont Hospital, Royal Oak, MI (United States)

2014-06-01

Purpose: Online adaptive aperture morphing is desirable over translational couch shifts to accommodate not only the target position variation but also anatomic changes (rotation, deformation, and relation of target to organ-atrisks). We proposed quick and reliable method for adapting segment aperture leaves for IMRT treatment of prostate. Methods: The proposed method consists of following steps: (1) delineate the contours of prostate, SV, bladder and rectum on kV-CBCT; (2) determine prostate displacement from the rigid body registration of the contoured prostate manifested on the reference CT and the CBCT; (3) adapt the MLC segment apertures obtained from the pre-treatment IMRT planning to accommodate the shifts as well as anatomic changes. The MLC aperture adaptive algorithm involves two steps; first move the whole aperture according to prostate translational/rotational shifts, and secondly fine-tune the aperture shape to maintain the spatial relationship between the planning target contour and the MLC aperture to the daily target contour. Feasibility of this method was evaluated retrospectively on a seven-field IMRT treatment of prostate cancer patient by comparing dose volume histograms of the original plan and the aperture-adjusted plan, with/without additional segments weight optimization (SWO), on two daily treatment CBCTs selected with relative large motion and rotation. Results: For first daily treatment, the prostate rotation was significant (12degree around lateral-axis). With apertureadjusted plan, the D95 to the target was improved 25% and rectum dose (D30, D40) was reduced 20% relative to original plan on daily volumes. For second treatment-fraction, (lateral shift = 6.7mm), after adjustment target D95 improved by 3% and bladder dose (D30, maximum dose) was reduced by 1%. For both cases, extra SWO did not provide significant improvement. Conclusion: The proposed method of adapting segment apertures is promising in treatment position correction

A hybrid electron and photon IMRT planning technique that lowers normal tissue integral patient dose using standard hardware.

Science.gov (United States)

Rosca, Florin

2012-06-01

To present a mixed electron and photon IMRT planning technique using electron beams with an energy range of 6-22 MeV and standard hardware that minimizes integral dose to patients for targets as deep as 7.5 cm. Ten brain cases, two lung, a thyroid, an abdominal, and a parotid case were planned using two planning techniques: a photon-only IMRT (IMRT) versus a mixed modality treatment (E+IMRT) that includes an enface electron beam and a photon IMRT portion that ensures a uniform target coverage. The electron beam is delivered using a regular cutout placed in an electron cone. The electron energy was chosen to provide a good trade-off between minimizing integral dose and generating a uniform, deliverable plan. The authors choose electron energies that cover the deepest part of PTV with the 65%-70% isodose line. The normal tissue integral dose, the dose for ring structures around the PTV, and the volumes of the 75%, 50%, and 25% isosurfaces were used to compare the dose distributions generated by the two planning techniques. The normal tissue integral dose was lowered by about 20% by the E+IMRT plans compared to the photon-only IMRT ones for most studied cases. With the exception of lungs, the dose reduction associated to the E+IMRT plans was more pronounced further away from the target. The average dose ratio delivered to the 0-2 cm and the 2-4 cm ring structures for brain patients for the two planning techniques were 89.6% and 70.8%, respectively. The enhanced dose sparing away from the target for the brain patients can also be observed in the ratio of the 75%, 50%, and 25% isodose line volumes for the two techniques, which decreases from 85.5% to 72.6% and further to 65.1%, respectively. For lungs, the lateral electron beams used in the E+IMRT plans were perpendicular to the mostly anterior/posterior photon beams, generating much more conformal plans. The authors proved that even using the existing electron delivery hardware, a mixed electron/photon planning

IMRT and radiation protection in the prostate cancer therapy

International Nuclear Information System (INIS)

Santos, Helena C.; Silva, Andre R.M.; Oliveira, Claudia F.M.

2015-01-01

This study aims to specify the technological advances that IMRT presents relative to other traditional radiotherapy, particularly to conformal radiotherapy three dimensional (3D-TCR) and benefits compared to the side effects caused by from treatment of radiotherapy

Importance of the initial volume of parotid glands in xerostomia for patients with head and neck cancers treated with IMRT

International Nuclear Information System (INIS)

Nishimura, Yasumasa; Nakamatsu, Kiyoshi; Shibata, Toru; Kanamori, Shuichi; Koike, Ryuta; Okumura, Masahiko; Suzuki, Minoru

2005-01-01

Our aim was to evaluate predictors of xerostomia in patients with head and neck cancers treated with intensity-modulated radiation therapy (IMRT). Thirty-three patients with pharyngeal cancer were evaluated for xerostomia after having been treated with IMRT. All patients were treated with whole-neck irradiation of 46-50 Gy by IMRT, followed by boost IMRT to the high-risk clinical target volume to a total dose of 56-70 Gy in 28-35 fractions (median, 68 Gy). For boost IMRT, a second computed tomography (CT-2) scan was done in the third to fourth week of IMRT. Xerostomia was scored 3-4 months after the start of IMRT. The mean doses to the contralateral and ipsilateral parotid glands were 24.0±6.2 and 30.3±6.6 Gy, respectively. Among the 33 patients, xerostomia of grades 0, 1, 2 and 3 was noted in one, 18, 12 and two patients, respectively. Although the mean dose to the parotid glands was not correlated with the grade of xerostomia, the initial volume of the parotid glands was correlated with the grade of xerostomia (P=0.04). Of 17 patients with small parotid glands (≤38.8 ml) on initial CT (CT-1), 11 (65%) showed grade 2 or grade 3 xerostomia, whereas only three (19%) of 16 patients with larger parotid glands showed grade 2 xerostomia (P<0.05). The mean volume of the parotid glands on CT-1 was 43.1±15.2 ml, but decreased significantly to 32.0±11.4 ml (74%) on CT-2 (P<0.0001). Initial volumes of the parotid glands are significantly correlated with the grade of xerostomia in patients treated with IMRT. The volume of the parotid glands decreased significantly during the course of IMRT. (author)

Investigation of effective decision criteria for multiobjective optimization in IMRT.

Science.gov (United States)

Holdsworth, Clay; Stewart, Robert D; Kim, Minsun; Liao, Jay; Phillips, Mark H

2011-06-01

To investigate how using different sets of decision criteria impacts the quality of intensity modulated radiation therapy (IMRT) plans obtained by multiobjective optimization. A multiobjective optimization evolutionary algorithm (MOEA) was used to produce sets of IMRT plans. The MOEA consisted of two interacting algorithms: (i) a deterministic inverse planning optimization of beamlet intensities that minimizes a weighted sum of quadratic penalty objectives to generate IMRT plans and (ii) an evolutionary algorithm that selects the superior IMRT plans using decision criteria and uses those plans to determine the new weights and penalty objectives of each new plan. Plans resulting from the deterministic algorithm were evaluated by the evolutionary algorithm using a set of decision criteria for both targets and organs at risk (OARs). Decision criteria used included variation in the target dose distribution, mean dose, maximum dose, generalized equivalent uniform dose (gEUD), an equivalent uniform dose (EUD(alpha,beta) formula derived from the linear-quadratic survival model, and points on dose volume histograms (DVHs). In order to quantatively compare results from trials using different decision criteria, a neutral set of comparison metrics was used. For each set of decision criteria investigated, IMRT plans were calculated for four different cases: two simple prostate cases, one complex prostate Case, and one complex head and neck Case. When smaller numbers of decision criteria, more descriptive decision criteria, or less anti-correlated decision criteria were used to characterize plan quality during multiobjective optimization, dose to OARs and target dose variation were reduced in the final population of plans. Mean OAR dose and gEUD (a = 4) decision criteria were comparable. Using maximum dose decision criteria for OARs near targets resulted in inferior populations that focused solely on low target variance at the expense of high OAR dose. Target dose range, (D

SU-E-T-643: Pure Alanine Dosimeter for Verification Dosimetry in IMRT

International Nuclear Information System (INIS)

Al-Karmi, Anan M.; Zraiqat, Fadi

2015-01-01

Purpose: The objective of this study was evaluation of accuracy of pure alanine dosimeters measuring intensity-modulated radiation therapy (IMRT) dose distributions in a thorax phantom. Methods: Alanine dosimeters were prepared in the form of 110 mg pure L-α-alanine powder filled into clear tissue-equivalent polymethylmethacrylate (PMMA) plastic tubes with the dimensions 25 mm length, 3 mm inner diameter, and 1 mm wall thickness. A dose-response calibration curve was established for the alanine by placing the dosimeters at 1.5 cm depth in a 30×30×30 cm 3 solid water phantom and then irradiating on a linac with 6 MV photon beam at 10×10 cm 2 field size to doses ranging from 1 to 5 Gy. Electron paramagnetic resonance (EPR) spectroscopy was used to determine the absorbed dose in alanine. An IMRT treatment plan was designed for a commercial heterogeneous CIRS thorax phantom and the dose values were calculated at three different points located in tissue, lung, and bone equivalent materials. A set of dose measurements was carried out to compare measured and calculated dose values by placing the alanine dosimeters at those selected locations inside the thorax phantom and delivering the IMRT to the phantom. Results: The alanine dose measurements and the IMRT plan dose calculations were found to be in agreement within ±2%. Specifically, the deviations were −0.5%, 1.3%, and −1.7% for tissue, lung, and bone; respectively. The slightly large deviations observed for lung and bone may be attributed to tissue inhomogeneity, steep dose gradients in these regions, and uncontrollable changes in spectrometer conditions. Conclusion: The results described herein confirmed that pure alanine dosimeter was suitable for in-phantom dosimetry of IMRT beams because of its high sensitivity and acceptable accuracy. This makes the dosimeter a promising option for quality control of the therapeutic beams, complementing the commonly used ionization chambers, TLDs, and films

Development of an IMRT quality assurance program using an amorphous silicon electronic portal imaging device

International Nuclear Information System (INIS)

Hunt, P.; Oliver, L.; Mallik, A.

2000-01-01

Full text: Quality Assurance (QA) for an intensity modulated radiotherapy (IMRT) megavoltage beam is a complex task. The positional accuracy of the MLC; its radiation leakage; the overall distribution of the dose delivered as compared to the treatment plan and; the accuracy of the calculated monitor units to deliver this dose, are all important parameters to clinically monitor. We are presently assessing the Varian version 6 software package with CadPlan, Helios with IMRT and inverse planning, VARiS Vision and the linear accelerator DMLC controller. Whilst conventional QA tools such as ionisation chamber and film measurements are used, these methods are inconvenient for directly monitoring an IMRT patient treatment. Varian Medical Systems has developed an improved electronic portal imaging device (EPID) with an amorphous silicon (a-Si) detector array. The A-Si has a sensitive area of 40x30cm and an improved image resolution of 512x384 pixels. Images are recorded at approximately 7-10 frames per second for an exposure rate of 100-600 MU/minute. Although the A-Si was designed as an EPID for a static treatment field, this new device could be a valuable IMRT QA tool for a range of different tests. Measurements taken on the RNSH and Varian prototype A-Si EPI devices showed a linear dose response for 6-18MeV X-ray energy. In addition to the Varian IAS2 internal software handlers, we have developed some image data handling programs to view and analyse these images in more detail. The software is primarily used to view the images; measure the reading in a region of interest or profile; or merge, overlay, add or subtract images during the analysis. The small pixel resolution provides a reliable, highly accurate means of measuring beam size, leaf position, MLC radiation leakage or profile intensity curves with a positional accuracy of 0.8mm. The images produced by an IMRT exposure is clearly discernible and appears consistent with the result expected. Step wedge images

Impact of 18FDG-PET/CT on biological target volume (BTV) definition for treatment planning for non-small cell lung cancer patients

International Nuclear Information System (INIS)

Devic, Slobodan; Tomic, Nada; Faria, Sergio; Dean, Geoffrey; Lisbona, Robert; Parker, William; Kaufman, Chris; Podgorsak, Ervin B.

2007-01-01

This work represents our effort to test feasibility of FDG-based PET/CT on target volume delineation in radiotherapy treatment planning of NSCLC patients. Different methods have been developed to enable more precise target outlining using PET: Qualitative Visual Method, CTV=2.5 SUV units, linear SUV threshold function method, and CTV=40% Iso of Maximum Uptake Value. We are proposing reconstruction of three biological target volumes: necrotic BTV (same as PTV created by radiation oncologist using CT data), proliferating BTV (based on PET signal to background ratio 1:3) and hypoxic BTV (based on PET signal to background ratio of 1:19). Two IMRT plans were created and compared to the conventional treatment plan: 'conservative' IMRT plan delivers 52.5 Gy to the necrotic BTV and 65 Gy to the hypoxic BTV; 'radical' IMRT plan delivers 30 Gy to necrotic BTV, 52.5 Gy to proliferating BTV and 65 Gy to hypoxic BTV. Use of BTVs in IMRT plans is attractive because it increases dose to targets considered to need higher doses. It reduces considerably dose to heart and spinal cord, organs considered to limit dose escalation approaches in NSCLC treatment. 'Conservative' IMRT approach can be understood as a PET/CT-based concomitant boost to the tumor expressing the highest FDG uptake. 'Radical' plan implies deviation from the traditional uniform dose target coverage approach, with the intention of achieving better surrounding tissue sparing and ultimately allowing for dose escalation protocols relying on biologically based treatment planning

Six years of experience in the planning and verification of the IMRT dynamics with portal dosimetry

International Nuclear Information System (INIS)

Molina Lopez, M. Y.; Pardo Perez, E.; Ruiz Maqueda, S.; Castro Novais, J.; Diaz Gavela, A. A.

2013-01-01

The objective of this study is the make a review of the method of verification of the IMRT throughout the 6 years of functioning of the service of-radiophysics and radiology protection, analyzing the parameters of each field evaluation to the 718 made IMRT during this period. (Author)

Comparison of 3DCRT,VMAT and IMRT techniques in metastatic vertebra radiotherapy: A phantom Study

Directory of Open Access Journals (Sweden)

Gedik Sonay

2017-01-01

Full Text Available Vertebra metastases can be seen during the prognosis of cancer patients. Treatment ways of the metastasis are radiotherapy, chemotherapy and surgery. Three-dimensional conformal therapy (3D-CRT is widely used in the treatment of vertebra metastases. Also, Intensity Modulated Radiotherapy (IMRT and Volumetric Arc Therapy (VMAT are used too. The aim of this study is to examine the advantages and disadvantages of the different radiotherapy techniques. In the aspect of this goal, it is studied with a randophantom in Uludag University Medicine Faculty, Radiation Oncology Department. By using a computerized tomography image of the phantom, one 3DCRT plan, two VMAT and three IMRT plans for servical vertebra and three different 3DCRT plans, two VMAT and two IMRT plans for lomber vertebra are calculated. To calculate 3DCRT plans, CMS XiO Treatment System is used and to calculate VMAT and IMRT plans Monaco Treatment Planning System is used in the department. The study concludes with the dosimetric comparison of the treatment plans in the spect of critical organ doses, homogeneity and conformity index. As a result of this study, all critical organ doses are suitable for QUANTEC Dose Limit Report and critical organ doses depend on the techniques which used in radiotherapy. According to homogeneity and conformity indices, VMAT and IMRT plans are better than one in 3DCRT plans in servical and lomber vertebra radiotherapy plans.

Toxicities Affecting Quality of Life After Chemo-IMRT of Oropharyngeal Cancer: Prospective Study of Patient-Reported, Observer-Rated, and Objective Outcomes

International Nuclear Information System (INIS)

Hunter, Klaudia U.; Schipper, Matthew; Feng, Felix Y.; Lyden, Teresa; Haxer, Mark; Murdoch-Kinch, Carol-Anne; Cornwall, Benjamin; Lee, Connie S.Y.; Chepeha, Douglas B.; Eisbruch, Avraham

2013-01-01

Purpose: To test the hypothesis that intensity modulated radiation therapy (IMRT) aiming to spare the salivary glands and swallowing structures would reduce or eliminate the effects of xerostomia and dysphagia on quality of life (QOL). Methods and Materials: In this prospective, longitudinal study, 72 patients with stage III-IV oropharyngeal cancer were treated uniformly with definitive chemo-IMRT sparing the salivary glands and swallowing structures. Overall QOL was assessed by summary scores of the Head Neck QOL (HNQOL) and University of Washington QOL (UWQOL) questionnaires, as well as the HNQOL “Overall Bother” question. Quality of life, observer-rated toxicities (Common Toxicity Criteria Adverse Effects scale, version 2), and objective evaluations (videofluoroscopy assessing dysphagia and saliva flow rates assessing xerostomia) were recorded from before therapy through 2 years after therapy. Correlations between toxicities/objective evaluations and overall QOL were assessed using longitudinal repeated measures of analysis and Pearson correlations. Results: All observer-rated toxicities and QOL scores worsened 1-3 months after therapy and improved through 12 months, with minor further improvements through 24 months. At 12 months, dysphagia grades 0-1, 2, and 3, were observed in 95%, 4%, and 1% of patients, respectively. Using all posttherapy observations, observer-rated dysphagia was highly correlated with all overall QOL measures (P<.0001), whereas xerostomia and mucosal and voice toxicities were significantly correlated with some, but not all, overall QOL measures, with lower correlation coefficients than dysphagia. Late overall QOL (≥6 or ≥12 months after therapy) was primarily associated with observer-rated dysphagia, and to a lesser extent with xerostomia. Videofluoroscopy scores, but not salivary flows, were significantly correlated with some of the overall QOL measures. Conclusion: After chemo-IMRT, although late dysphagia was on average mild

Toxicities Affecting Quality of Life After Chemo-IMRT of Oropharyngeal Cancer: Prospective Study of Patient-Reported, Observer-Rated, and Objective Outcomes

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Hunter, Klaudia U. [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Schipper, Matthew [Department of Biostatistics, University of Michigan, Ann Arbor, Michigan (United States); Feng, Felix Y. [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States); Lyden, Teresa; Haxer, Mark [Department of Speech-Language Pathology, University of Michigan, Ann Arbor, Michigan (United States); Murdoch-Kinch, Carol-Anne; Cornwall, Benjamin [Department of Hospital Dentistry, University of Michigan, Ann Arbor, Michigan (United States); Lee, Connie S.Y. [Department of Biostatistics, University of Michigan, Ann Arbor, Michigan (United States); Chepeha, Douglas B. [Department of Otolaryngology-Head Neck Surgery, University of Michigan, Ann Arbor, Michigan (United States); Eisbruch, Avraham, E-mail: Eisbruch@umich.edu [Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan (United States)

2013-03-15

Purpose: To test the hypothesis that intensity modulated radiation therapy (IMRT) aiming to spare the salivary glands and swallowing structures would reduce or eliminate the effects of xerostomia and dysphagia on quality of life (QOL). Methods and Materials: In this prospective, longitudinal study, 72 patients with stage III-IV oropharyngeal cancer were treated uniformly with definitive chemo-IMRT sparing the salivary glands and swallowing structures. Overall QOL was assessed by summary scores of the Head Neck QOL (HNQOL) and University of Washington QOL (UWQOL) questionnaires, as well as the HNQOL “Overall Bother” question. Quality of life, observer-rated toxicities (Common Toxicity Criteria Adverse Effects scale, version 2), and objective evaluations (videofluoroscopy assessing dysphagia and saliva flow rates assessing xerostomia) were recorded from before therapy through 2 years after therapy. Correlations between toxicities/objective evaluations and overall QOL were assessed using longitudinal repeated measures of analysis and Pearson correlations. Results: All observer-rated toxicities and QOL scores worsened 1-3 months after therapy and improved through 12 months, with minor further improvements through 24 months. At 12 months, dysphagia grades 0-1, 2, and 3, were observed in 95%, 4%, and 1% of patients, respectively. Using all posttherapy observations, observer-rated dysphagia was highly correlated with all overall QOL measures (P<.0001), whereas xerostomia and mucosal and voice toxicities were significantly correlated with some, but not all, overall QOL measures, with lower correlation coefficients than dysphagia. Late overall QOL (≥6 or ≥12 months after therapy) was primarily associated with observer-rated dysphagia, and to a lesser extent with xerostomia. Videofluoroscopy scores, but not salivary flows, were significantly correlated with some of the overall QOL measures. Conclusion: After chemo-IMRT, although late dysphagia was on average mild

Density variation of parotid glands during IMRT for head–neck cancer: Correlation with treatment and anatomical parameters

International Nuclear Information System (INIS)

Fiorino, Claudio; Rizzo, Giovanna; Scalco, Elisa; Broggi, Sara; Belli, Maria Luisa; Dell’Oca, Italo; Dinapoli, Nicola; Ricchetti, Francesco; Rodriguez, Aldo Mejia; Di Muzio, Nadia; Calandrino, Riccardo; Sanguineti, Giuseppe; Valentini, Vincenzo; Cattaneo, Giovanni Mauro

2012-01-01

Purpose: Measuring parotid density changes in patients treated with IMRT for head–neck cancer (HNC) and assessing correlation with treatment-related parameters. Patients and materials: Data of 84 patients treated with IMRT for different HNC were pooled from three institutions. Parotid deformation and average Hounsfield number changes (ΔHU) were evaluated through MVCT (with Helical Tomotherapy) or diagnostic kVCT images taken at the treatment start/end. Parotids were delineated in the first image and propagated to the last using a previously validated algorithm based on elastic registration. The correlation between ΔHU and several treatment-related parameters was tested; then, logistic uni- and multi-variate analyses taking “large” ΔHU as end-point were carried out. Due to the better image quality, analyses were repeated considering only kVCT data. Results: ΔHU was negative in 116/168 parotids (69%; for kVCT patients: 72/92, 78%). The average ΔHU was significantly different from zero (−7.3, 0.20–0.25 HU/fraction, p m ean), and with neck thickness variation; these correlations were much stronger for kVCT data. Logistic analyses considering ΔHU m ean < 0.68) and initial neck thickness to be the most predictive variables (p < 0.0005, AUC = 0.683; AUC = 0.776 for kVCT); the odd ratio of large vs moderate/small parotid deformation was 3.8 and 8.0 for the whole and the kVCT population respectively. Conclusions: Parotid density reduced in most patients during IMRT and this phenomenon was highly correlated with parotid deformation. The individual assessment of density changes was highly reliable just with diagnostic KvCT. Density changes should be considered as an additional objective measurement of early parotid radiation-induced modifications; further research is warranted.

Comparative study between IMRT planning and RapidArc® sliding window for head and neck tumors; Estudo comparativo de planejamento entre IMRT sliding window e RapidArc® para tumores de cabeca e pescoco

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Pirani, Luiz F.; Silva, Leonardo P.; Lima, Marilia B.; Bittencourt, Guilherme R.; Ferreira, Anne Caroline M.; Batista, Delano V.S., E-mail: nando_lfp@yahoo.com.br [Instituto Nacional de Cancer (INCA), Rio de Janeiro, RJ (Brazil)

2012-12-15

This study aims to evaluate the RapidArc (RA) technique in the treatment of head and neck tumors and compare the results of treatments with intensity modulated radiation therapy (IMRT) in the National Cancer Institute (INCA). Head and neck carcinomas have a natural history with relative expansion to others regions, especially in advanced levels. Faster treatments, with better coverage of the Planning Target Volume (PTV) and sparing more risks organs (ROs) are necessary and bring a better clinical impact. Ten patients with head and neck cancer, planned with IMRT technique were replanned using the RA technique. Some dosimetric indexes were calculated for both techniques, with the intention of verifying which of them, at the same time, would promote greater coverage of the PTV and preserve more healthy tissue. In terms of coverage, both indexes were similar. The RA technique was more efficient for delivered doses to ROs. The number of monitor units (MU), number of fields and treatments time estimated were lower than IMRT technique. Finally, the results have showed that the RA technique clearly reduces the treatment time, reducing the average and maximum dose to ROs and conforming the target as IMRT technique. (author)

Phase II Study of Long-Term Androgen Suppression With Bevacizumab and Intensity-Modulated Radiation Therapy (IMRT) in High-Risk Prostate Cancer

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Vuky, Jacqueline, E-mail: vukyja@ohsu.edu [Section of Community Hematology/Oncology, Knight Cancer Institute, Oregon Health Sciences University, Portland, OR (United States); Pham, Huong T. [Section of Hematology/Oncology and Radiation Oncology, Virginia Mason Medical Center, Seattle, WA (United States); Warren, Sarah; Douglass, Erika [Benaroya Research Institute, Virginia Mason Medical Center, Seattle, WA (United States); Badiozamani, Kasra [Section of Hematology/Oncology and Radiation Oncology, Virginia Mason Medical Center, Seattle, WA (United States); Madsen, Berit; Hsi, Alex [Peninsula Cancer Center, Poulsbo, WA (United States); Song Guobin [Section of Hematology/Oncology and Radiation Oncology, Virginia Mason Medical Center, Seattle, WA (United States)

2012-03-15

Purpose: We report a Phase II trial assessing the acute and late toxicities of intensity-modulated radiation therapy (IMRT), long-term androgen suppression (LTAS), and bevacizumab in patients with high-risk localized prostate cancer. Methods and Materials: We treated 18 patients with LTAS with bicalutamide and goserelin in combination with bevacizumab and IMRT. Bevacizumab (10 mg/kg every 2 weeks) was administered for the first 16 weeks, and 15 mg/kg was then given every 3 weeks for 12 additional weeks, with an IMRT dose of 77.9 Gy to the prostate, 64.6 Gy to the seminal vesicles, and 57 Gy to the pelvic lymph nodes. Patients were eligible if they had clinical stage T2b to T4, a Gleason sum score of 8 to 10, or a prostate- specific antigen level of 20ng/mL or greater. The primary endpoint of the study was evaluation of acute and late toxicities. Results: The median age was 69 years, with a median pretreatment prostate-specific antigen level of 12.5 ng/mL and Gleason score of 8. The pretreatment clinical stage was T1c in 4 patients, T2 in 11, and T3 in 3. All patients completed IMRT with median follow-up of 34 months (range, 28-40 months) The most common Grade 2 or higher toxicities were hypertension (61% of patients with Grade 2 and 11% with Grade 3), proteinuria (28% with Grade 2 and 6% with Grade 3), and leucopenia (28% with Grade 2). No Grade 4 or higher acute toxicities were reported. Late toxicities included proctitis (6% of patients with Grade 2 and 11% with Grade 3), rectal bleeding (6% with Grade 2 and 11% with Grade 3), hematuria (6% with Grade 2), proteinuria (17% with Grade 2), hyponatremia (6% with Grade 3), cystitis (6% with Grade 3), and urinary retention (6% with Grade 2 and 11% with Grade 3). Grade 4 prostatitis occurred in 1 patient (6%). Conclusions: Bevacizumab does not appear to exacerbate the acute effects of IMRT. Late toxicities may have been worsened with this regimen. Further investigations of bevacizumab with LTAS and IMRT should be

Phase II Study of Long-Term Androgen Suppression With Bevacizumab and Intensity-Modulated Radiation Therapy (IMRT) in High-Risk Prostate Cancer

International Nuclear Information System (INIS)

Vuky, Jacqueline; Pham, Huong T.; Warren, Sarah; Douglass, Erika; Badiozamani, Kasra; Madsen, Berit; Hsi, Alex; Song Guobin

2012-01-01

Purpose: We report a Phase II trial assessing the acute and late toxicities of intensity-modulated radiation therapy (IMRT), long-term androgen suppression (LTAS), and bevacizumab in patients with high-risk localized prostate cancer. Methods and Materials: We treated 18 patients with LTAS with bicalutamide and goserelin in combination with bevacizumab and IMRT. Bevacizumab (10 mg/kg every 2 weeks) was administered for the first 16 weeks, and 15 mg/kg was then given every 3 weeks for 12 additional weeks, with an IMRT dose of 77.9 Gy to the prostate, 64.6 Gy to the seminal vesicles, and 57 Gy to the pelvic lymph nodes. Patients were eligible if they had clinical stage T2b to T4, a Gleason sum score of 8 to 10, or a prostate- specific antigen level of 20ng/mL or greater. The primary endpoint of the study was evaluation of acute and late toxicities. Results: The median age was 69 years, with a median pretreatment prostate-specific antigen level of 12.5 ng/mL and Gleason score of 8. The pretreatment clinical stage was T1c in 4 patients, T2 in 11, and T3 in 3. All patients completed IMRT with median follow-up of 34 months (range, 28–40 months) The most common Grade 2 or higher toxicities were hypertension (61% of patients with Grade 2 and 11% with Grade 3), proteinuria (28% with Grade 2 and 6% with Grade 3), and leucopenia (28% with Grade 2). No Grade 4 or higher acute toxicities were reported. Late toxicities included proctitis (6% of patients with Grade 2 and 11% with Grade 3), rectal bleeding (6% with Grade 2 and 11% with Grade 3), hematuria (6% with Grade 2), proteinuria (17% with Grade 2), hyponatremia (6% with Grade 3), cystitis (6% with Grade 3), and urinary retention (6% with Grade 2 and 11% with Grade 3). Grade 4 prostatitis occurred in 1 patient (6%). Conclusions: Bevacizumab does not appear to exacerbate the acute effects of IMRT. Late toxicities may have been worsened with this regimen. Further investigations of bevacizumab with LTAS and IMRT should be

Evaluation of delivered monitor unit accuracy of gated step-and-shoot IMRT using a two-dimensional detector array

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Cheong, Kwang-Ho; Kang, Sei-Kwon; Lee, MeYeon; Kim, Su SSan; Park, SoAh; Hwang, Tae-Jin; Kim, Kyoung Ju; Oh, Do Hoon; Bae, Hoonsik; Suh, Tae-Suk [Department of Radiation Oncology, Hallym University College of Medicine, Seoul, 431070 (Korea, Republic of) and Department of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 137701 (Korea, Republic of); Department of Radiation Oncology, Hallym University College of Medicine, Seoul 431070 (Korea, Republic of); Department of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul 137701 (Korea, Republic of)

2010-03-15

Purpose: To overcome the problem of organ motion in intensity-modulated radiation therapy (IMRT), gated IMRT is often used for the treatment of lung cancer. In this study, the authors investigated the accuracy of the delivered monitor units (MUs) from each segment during gated IMRT using a two-dimensional detector array for user-specific verification purpose. Methods: The authors planned a 6 MV photon, seven-port step-and-shoot lung IMRT delivery. The respiration signals for gated IMRT delivery were obtained from the one-dimensional moving phantom using the real-time position management (RPM) system (Varian Medical Systems, Palo Alto, CA). The beams were delivered using a Clinac iX (Varian Medical Systems, Palo Alto, CA) with the Millennium 120 MLC. The MatriXX (IBA Dosimetry GmbH, Germany) was validated through consistency and reproducibility tests as well as comparison with measurements from a Farmer-type ion chamber. The authors delivered beams with varying dose rates and duty cycles and analyzed the MatriXX data to evaluate MU delivery accuracy. Results: There was quite good agreement between the planned segment MUs and the MUs computed from the MatriXX within {+-}2% error. The beam-on times computed from the MatriXX data were almost identical for all cases, and they matched well with the RPM beam-on and beam-off signals. A slight difference was observed between them, but it was less than 40 ms. The gated IMRT delivery demonstrated an MU delivery accuracy that was equivalent to ungated IMRT, and the delivered MUs with a gating signal agreed with the planned MUs within {+-}0.5 MU regardless of dose rate and duty cycle. Conclusions: The authors can conclude that gated IMRT is able to deliver an accurate dose to a patient during a procedure. The authors believe that the methodology and results can be transferred to other vendors' devices, particularly those that do not provide MLC log data for a verification purpose.

Assessing Working Memory in Spanish-Speaking Children: Automated Working Memory Assessment Battery Adaptation

Science.gov (United States)

Injoque-Ricle, Irene; Calero, Alejandra D.; Alloway, Tracy P.; Burin, Debora I.

2011-01-01

The Automated Working Memory Assessment battery was designed to assess verbal and visuospatial passive and active working memory processing in children and adolescents. The aim of this paper is to present the adaptation and validation of the AWMA battery to Argentinean Spanish-speaking children aged 6 to 11 years. Verbal subtests were adapted and…

Adaptation in integrated assessment modeling: where do we stand?

NARCIS (Netherlands)

Patt, A.; van Vuuren, D.P.; Berkhout, F.G.H.; Aaheim, A.; Hof, A.F.; Isaac, M.; Mechler, R.

2010-01-01

Adaptation is an important element on the climate change policy agenda. Integrated assessment models, which are key tools to assess climate change policies, have begun to address adaptation, either by including it implicitly in damage cost estimates, or by making it an explicit control variable. We

Comparison of radiotherapy dosimetry for 3D-CRT, IMRT, and SBRT based on electron density calibration

International Nuclear Information System (INIS)

Kartutik, K; Pawiro, S A; Wibowo, W E

2016-01-01

Accurate calculation of dose distribution affected by inhomogeneity tissue is required in radiotherapy planning. This study was performed to determine the ratio between radiotherapy planning using 3D-CRT, IMRT, and SBRT based on a calibrated curve of CT-number in the lung for different target's shape in 3D-CRT, IMRT, and spinal cord for SBRT. Calibration curves of CT-number were generated under measurement basis and introduced into TPS, then planning was performed for 3D-CRT, IMRT, and SBRT with 7, and 15 radiation fields. Afterwards, planning evaluation was performed by comparing the DVH curve, HI, and CI. 3D-CRT and IMRT produced the lowest HI at calibration curve of CIRS 002LFC with the value 0.24 and 10. Whereas SBRT produced the lowest HI on a linear calibration curve with a value of 0.361. The highest CI in IMRT and SBRT technique achieved using a linear calibration curve was 0.97 and 1.77 respectively. For 3D-CRT, the highest CI was obtained by using calibration curve of CIRS 062M with the value of 0.45. From the results of CI and HI, it is concluded that the calibration curve of CT-number does not significantly differ with Schneider's calibrated curve, and inverse planning gives a better result than forward planning. (paper)

Conventional patient specific IMRT QA and 3DVH verification of dose distribution for helical tomotherapy

International Nuclear Information System (INIS)

Sharma, Prabhat Krishna; Joshi, Kishore; Epili, D.; Gavake, Umesh; Paul, Siji; Reena, Ph.; Jamema, S.V.

2016-01-01

In recent years, patient-specific IMRT QA has transitioned from point dose measurements by ion chambers to films to 2D array measurements. 3DVH software has taken this transition a step further by estimating the 3D dose delivered to the patient volume from 2D diode measurements using a planned dose perturbation (PDP) algorithm. This algorithm was developed to determine, if the conventional IMRT QA though sensitive at detecting errors, has any predictive power in detecting dose errors of clinical significance related to dose to the target volume and organs at risk (OAR). The aim of this study is to compare the conventional IMRT patient specific QA and 3DVH dose distribution for patients treated with helical tomotherapy (HT)

Volumetric modulated arc therapy: IMRT in a single gantry arc

International Nuclear Information System (INIS)

Otto, Karl

2008-01-01

In this work a novel plan optimization platform is presented where treatment is delivered efficiently and accurately in a single dynamically modulated arc. Improvements in patient care achieved through image-guided positioning and plan adaptation have resulted in an increase in overall treatment times. Intensity-modulated radiation therapy (IMRT) has also increased treatment time by requiring a larger number of beam directions, increased monitor units (MU), and, in the case of tomotherapy, a slice-by-slice delivery. In order to maintain a similar level of patient throughput it will be necessary to increase the efficiency of treatment delivery. The solution proposed here is a novel aperture-based algorithm for treatment plan optimization where dose is delivered during a single gantry arc of up to 360 deg. The technique is similar to tomotherapy in that a full 360 deg. of beam directions are available for optimization but is fundamentally different in that the entire dose volume is delivered in a single source rotation. The new technique is referred to as volumetric modulated arc therapy (VMAT). Multileaf collimator (MLC) leaf motion and number of MU per degree of gantry rotation is restricted during the optimization so that gantry rotation speed, leaf translation speed, and dose rate maxima do not excessively limit the delivery efficiency. During planning, investigators model continuous gantry motion by a coarse sampling of static gantry positions and fluence maps or MLC aperture shapes. The technique presented here is unique in that gantry and MLC position sampling is progressively increased throughout the optimization. Using the full gantry range will theoretically provide increased flexibility in generating highly conformal treatment plans. In practice, the additional flexibility is somewhat negated by the additional constraints placed on the amount of MLC leaf motion between gantry samples. A series of studies are performed that characterize the relationship

Dysphagia and trismus after concomitant chemo-Intensity-Modulated Radiation Therapy (chemo-IMRT) in advanced head and neck cancer; dose-effect relationships for swallowing and mastication structures

NARCIS (Netherlands)

van der Molen, Lisette; Heemsbergen, Wilma D.; de Jong, Rianne; van Rossum, Maya A.; Smeele, Ludi E.; Rasch, Coen R. N.; Hilgers, Frans J. M.

2013-01-01

Prospective assessment of dysphagia and trismus in chemo-IMRT head and neck cancer patients in relation to dose-parameters of structures involved in swallowing and mastication. Assessment of 55 patients before, 10-weeks (N=49) and 1-year post-treatment (N=37). Calculation of dose-volume parameters

Dysphagia and trismus after concomitant chemo-Intensity-Modulated Radiation Therapy (chemo-IMRT) in advanced head and neck cancer; dose-effect relationships for swallowing and mastication structures

NARCIS (Netherlands)

van der Molen, L.; Heemsbergen, W.D.; de Jong, R.; van Rossum, M.A.; Smeele, L.E.; Rasch, C.R.N.; Hilgers, F.J.M.

2013-01-01

Background and purpose: Prospective assessment of dysphagia and trismus in chemo-IMRT head and neck cancer patients in relation to dose-parameters of structures involved in swallowing and mastication. Material and methods: Assessment of 55 patients before, 10-weeks (N=49) and 1-year post-treatment

A retrospective planning analysis comparing intensity modulated radiation therapy (IMRT) to volumetric modulated arc therapy (VMAT) using two optimization algorithms for the treatment of early-stage prostate cancer

International Nuclear Information System (INIS)

Elith, Craig A; Dempsey, Shane E; Warren-Forward, Helen M

2013-01-01

The primary aim of this study is to compare intensity modulated radiation therapy (IMRT) to volumetric modulated arc therapy (VMAT) for the radical treatment of prostate cancer using version 10.0 (v10.0) of Varian Medical Systems, RapidArc radiation oncology system. Particular focus was placed on plan quality and the implications on departmental resources. The secondary objective was to compare the results in v10.0 to the preceding version 8.6 (v8.6). Twenty prostate cancer cases were retrospectively planned using v10.0 of Varian's Eclipse and RapidArc software. Three planning techniques were performed: a 5-field IMRT, VMAT using one arc (VMAT-1A), and VMAT with two arcs (VMAT-2A). Plan quality was assessed by examining homogeneity, conformity, the number of monitor units (MUs) utilized, and dose to the organs at risk (OAR). Resource implications were assessed by examining planning and treatment times. The results obtained using v10.0 were also compared to those previously reported by our group for v8.6. In v10.0, each technique was able to produce a dose distribution that achieved the departmental planning guidelines. The IMRT plans were produced faster than VMAT plans and displayed improved homogeneity. The VMAT plans provided better conformity to the target volume, improved dose to the OAR, and required fewer MUs. Treatments using VMAT-1A were significantly faster than both IMRT and VMAT-2A. Comparison between versions 8.6 and 10.0 revealed that in the newer version, VMAT planning was significantly faster and the quality of the VMAT dose distributions produced were of a better quality. VMAT (v10.0) using one or two arcs provides an acceptable alternative to IMRT for the treatment of prostate cancer. VMAT-1A has the greatest impact on reducing treatment time

Whole brain radiotherapy with adjuvant or concomitant boost in brain metastasis: dosimetric comparison between helical and volumetric IMRT technique

International Nuclear Information System (INIS)

Borghetti, Paolo; Pedretti, Sara; Spiazzi, Luigi; Avitabile, Rossella; Urpis, Mauro; Foscarini, Federica; Tesini, Giulia; Trevisan, Francesca; Ghirardelli, Paolo; Pandini, Sara Angela; Triggiani, Luca; Magrini, Stefano Maria; Buglione, Michela

2016-01-01

To compare and evaluate the possible advantages related to the use of VMAT and helical IMRT and two different modalities of boost delivering, adjuvant stereotactic boost (SRS) or simultaneous integrated boost (SIB), in the treatment of brain metastasis (BM) in RPA classes I-II patients. Ten patients were treated with helical IMRT, 5 of them with SRS after whole brain radiotherapy (WBRT) and 5 with SIB. MRI co-registration with planning CT was mandatory and prescribed doses were 30 Gy in 10 fractions (fr) for WBRT and 15Gy/1fr or 45Gy/10fr in SRS or SIB, respectively. For each patient, 4 “treatment plans” (VMAT SRS and SIB, helical IMRT SRS and SIB) were calculated and accepted if PTV boost was included in 95 % isodose and dose constraints of the main organs at risk were respected without major deviations. Homogeneity Index (HI), Conformal Index (CI) and Conformal Number (CN) were considered to compare the different plans. Moreover, time of treatment delivery was calculated and considered in the analysis. Volume of brain metastasis ranged between 1.43 and 51.01 cc (mean 12.89 ± 6.37 ml) and 3 patients had double lesions. V95% resulted over 95 % in the average for each kind of technique, but the “target coverage” was inadequate for VMAT planning with two sites. The HI resulted close to the ideal value of zero in all cases; VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS showed mean CI of 2.15, 2.10, 2.44 and 1.66, respectively (optimal range: 1.5–2.0). Helical IMRT-SRS was related to the best and reliable finding of CN (0.66). The mean of treatment time was 210 s, 467 s, 440 s, 1598 s, respectively, for VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS. This dosimetric comparison show that helical IMRT obtain better target coverage and respect of CI and CN; VMAT could be acceptable in solitary metastasis. SIB modality can be considered as a good choice for clinical and logistic compliance; literature’s preliminary data are confirming

Method to account for dose fractionation in analysis of IMRT plans: Modified equivalent uniform dose

International Nuclear Information System (INIS)

Park, Clinton S.; Kim, Yongbok; Lee, Nancy; Bucci, Kara M.; Quivey, Jeanne M.; Verhey, Lynn J.; Xia Ping

2005-01-01

Purpose: To propose a modified equivalent uniform dose (mEUD) to account for dose fractionation using the biologically effective dose without losing the advantages of the generalized equivalent uniform dose (gEUD) and to report the calculated mEUD and gEUD in clinically used intensity-modulated radiotherapy (IMRT) plans. Methods and Materials: The proposed mEUD replaces the dose to each voxel in the gEUD formulation by a biologically effective dose with a normalization factor. We propose to use the term mEUD D o /n o that includes the total dose (D o ) and number of fractions (n o ) and to use the term mEUD o that includes the same total dose but a standard fraction size of 2 Gy. A total of 41 IMRT plans for patients with nasopharyngeal cancer treated at our institution between October 1997 and March 2002 were selected for the study. The gEUD and mEUD were calculated for the planning gross tumor volume (pGTV), planning clinical tumor volume (pCTV), parotid glands, and spinal cord. The prescription dose for these patients was 70 Gy to >95% of the pGTV and 59.4 Gy to >95% of the pCTV in 33 fractions. Results: The calculated average gEUD was 72.2 ± 2.4 Gy for the pGTV, 54.2 ± 7.1 Gy for the pCTV, 26.7 ± 4.2 Gy for the parotid glands, and 34.1 ± 6.8 Gy for the spinal cord. The calculated average mEUD D o /n o using 33 fractions was 71.7 ± 3.5 Gy for mEUD 70/33 of the pGTV, 49.9 ± 7.9 Gy for mEUD 59.5/33 of the pCTV, 27.6 ± 4.8 Gy for mEUD 26/33 of the parotid glands, and 32.7 ± 7.8 Gy for mEUD 45/33 of the spinal cord. Conclusion: The proposed mEUD, combining the gEUD with the biologically effective dose, preserves all advantages of the gEUD while reflecting the fractionation effects and linear and quadratic survival characteristics

Monte Carlo investigation of collapsed versus rotated IMRT plan verification.

Science.gov (United States)

Conneely, Elaine; Alexander, Andrew; Ruo, Russell; Chung, Eunah; Seuntjens, Jan; Foley, Mark J

2014-05-08

IMRT QA requires, among other tests, a time-consuming process of measuring the absorbed dose, at least to a point, in a high-dose, low-dose-gradient region. Some clinics use a technique of measuring this dose with all beams delivered at a single gantry angle (collapsed delivery), as opposed to the beams delivered at the planned gantry angle (rotated delivery). We examined, established, and optimized Monte Carlo simulations of the dosimetry for IMRT verification of treatment plans for these two different delivery modes (collapsed versus rotated). The results of the simulations were compared to the treatment planning system dose calculations for the two delivery modes, as well as to measurements taken. This was done in order to investigate the validity of the use of a collapsed delivery technique for IMRT QA. The BEAMnrc, DOSXYZnrc, and egs_chamber codes were utilized for the Monte Carlo simulations along with the MMCTP system. A number of different plan complexity metrics were also used in the analysis of the dose distributions in a bid to qualify why verification in a collapsed delivery may or may not be optimal for IMRT QA. Following the Alfonso et al. formalism, the kfclin,frefQclin,Q correction factor was calculated to correct the deviation of small fields from the reference conditions used for beam calibration. We report on the results obtained for a cohort of 20 patients. The plan complexity was investigated for each plan using the complexity metrics of homogeneity index, conformity index, modulation complexity score, and the fraction of beams from a particular plan that intersect the chamber when performing the QA. Rotated QA gives more consistent results than the collapsed QA technique. The kfclin,frefQclin,Qfactor deviates less from 1 for rotated QA than for collapsed QA. If the homogeneity index is less than 0.05 then the kfclin,frefQclin,Q factor does not deviate from unity by more than 1%. A value this low for the homogeneity index can only be obtained

IMRT treatment planning-A comparative inter-system and inter-centre planning exercise of the ESTRO QUASIMODO group

International Nuclear Information System (INIS)

Bohsung, Joerg; Gillis, Sofie; Arrans, Rafael; Bakai, Annemarie; De Wagter, Carlos; Knoeoes, Tommy; Mijnheer, Ben J.; Paiusco, Marta; Perrin, Bruce A.; Welleweerd, Hans; Williams, Peter

2005-01-01

Background and purpose: The purpose of this work was a comparison of realistic IMRT plans based on the same CT-image data set and a common predefined set of dose objectives for the planning target volume and the organs at risk. This work was part of the larger European QUASIMODO IMRT verification project. Materials and methods: Eleven IMRT plans were produced by nine different European groups, each applying a representative set of clinically used IMRT treatment planning systems. The plans produced were to be deliverable in a clinically acceptable treatment time with the local technical equipment. All plans were characterized using a set of different quality measures such as dose-volume histograms, number of monitor units and treatment time. Results: Only one plan was able to fulfil all dose objectives strictly; six plans failed some of the objectives but were still considered to be clinically acceptable; four plans were not able to reach the objectives. Additional quality scores such as the number of monitor units and treatment time showed large variations, which mainly depend on the delivery technique. Conclusion: The presented planning study showed that with nearly all presently available IMRT planning and delivery systems comparable dose distributions could be achieved if the planning goals are clearly defined in advance

Impact of MLC leaf position errors on simple and complex IMRT plans for head and neck cancer

International Nuclear Information System (INIS)

Mu, G; Ludlum, E; Xia, P

2008-01-01

The dosimetric impact of random and systematic multi-leaf collimator (MLC) leaf position errors is relatively unknown for head and neck intensity-modulated radiotherapy (IMRT) patients. In this report we studied 17 head and neck IMRT patients, including 12 treated with simple plans ( 100 segments). Random errors (-2 to +2 mm) and systematic errors (±0.5 mm and ±1 mm) in MLC leaf positions were introduced into the clinical plans and the resultant dose distributions were analyzed based on defined endpoint doses. The dosimetric effect was insignificant for random MLC leaf position errors up to 2 mm for both simple and complex plans. However, for systematic MLC leaf position errors, we found significant dosimetric differences between the simple and complex IMRT plans. For 1 mm systematic error, the average changes in D 95% were 4% in simple plans versus 8% in complex plans. The average changes in D 0.1cc of the spinal cord and brain stem were 4% in simple plans versus 12% in complex plans. The average changes in parotid glands were 9% in simple plans versus 13% for the complex plans. Overall, simple IMRT plans are less sensitive to leaf position errors than complex IMRT plans

SU-F-T-391: Comparative Study of Treatment Planning Between IMRT and IMAT for Malignant Pleural Mesothelioma

International Nuclear Information System (INIS)

Duan, J

2016-01-01

Purpose: The purpose of this study was to compare the dosimetric differences between intensitymodulated radiation therapy (IMRT) and intensity modulated arc therapy (IMAT) for malignant pleural mesothelioma (MPM) patients with regard to the sparing effect on organs at risk (OARs), plan quality, and delivery efficiency. Methods: Ten MPM patients were recruited in this study. To avoid the inter-operator variability, IMRT and IMAT plans for each patient were performed by one experienced dosimetrist. The treatment planning optimization process was carried out using the Eclipse 13.0 software. For a fair comparison, the planning target volume (PTV) coverage of the two plans was normalized to the same level. The treatment plans were evaluated on the following dosimetric variables: conformity index (CI) and homogeneity index (HI) for PTV, OARs dose, and the delivery efficiency for each plan. Results: All plans satisfied clinical requirements. The IMAT plans gained better CI and HI. The IMRT plans performed better sparing for heart and lung. Less MUs and control points were found in the IMAT plans. IMAT shortened delivery time compared with IMRT. Conclusion: For MPM, IMAT gains better conformity and homogeneity for PTV with IMRT, but increases the irradiation dose for OARs. IMAT shows an advantage in delivery efficiency.

SU-F-T-391: Comparative Study of Treatment Planning Between IMRT and IMAT for Malignant Pleural Mesothelioma

Energy Technology Data Exchange (ETDEWEB)

Duan, J [Shandong Cancer Hospital and Institute, Jinan, Shandong province (China)

2016-06-15

Purpose: The purpose of this study was to compare the dosimetric differences between intensitymodulated radiation therapy (IMRT) and intensity modulated arc therapy (IMAT) for malignant pleural mesothelioma (MPM) patients with regard to the sparing effect on organs at risk (OARs), plan quality, and delivery efficiency. Methods: Ten MPM patients were recruited in this study. To avoid the inter-operator variability, IMRT and IMAT plans for each patient were performed by one experienced dosimetrist. The treatment planning optimization process was carried out using the Eclipse 13.0 software. For a fair comparison, the planning target volume (PTV) coverage of the two plans was normalized to the same level. The treatment plans were evaluated on the following dosimetric variables: conformity index (CI) and homogeneity index (HI) for PTV, OARs dose, and the delivery efficiency for each plan. Results: All plans satisfied clinical requirements. The IMAT plans gained better CI and HI. The IMRT plans performed better sparing for heart and lung. Less MUs and control points were found in the IMAT plans. IMAT shortened delivery time compared with IMRT. Conclusion: For MPM, IMAT gains better conformity and homogeneity for PTV with IMRT, but increases the irradiation dose for OARs. IMAT shows an advantage in delivery efficiency.

Soft-Rt: software for IMRT simulations based on MCNPX

International Nuclear Information System (INIS)

Ferreira F, T. C.; Campos, T.

2015-10-01

Intensity Modulated Radiation Therapy (IMRT) is an advanced treatment technique, widely used in external radiotherapy. This paper presents the Soft-Rt which allows the simulation of an entire IMRT treatment protocol. The Soft-Rt performs a full three-dimensional rendering of a set of patient images, including the definitions of region of interest with organs in risk, and the target tumor volume and margins (PTV). Thus, a more accurate analysis and planning can be performed, taking into account the features and orientation of the radiation beams. The exposed tissues as well as the amount of absorbed dose is depicted in healthy and/or cancerous tissues. As conclusion, Soft-Rt can predict dose on the PTV accurately, preserving the surrounding healthy tissues. Soft-Rt is coupled with SISCODES code. The SISCODES code is firstly applied to segment the set of CT or MRI patient images in distinct tissues pointing out its respective density and chemical compositions. Later, the voxel model is export to the Soft-Rt IMRT planning module in which a full treatment planning is created. All geometrical parameters are sent to the general purpose Monte Carlo transport code - MCNP - to simulate the interaction of each incident beam towards to the PTV avoiding organs in risk. The normalized dose results are exported to the Soft-Rt out-module, in which the three-dimensional model visualization is shown in a transparent glass procedure adopting gray scale for the dependence on the mass density of the correlated tissue; while, a color scale to depict dose values in a superimpose protocol. (Author)

Soft-Rt: software for IMRT simulations based on MCNPX

Energy Technology Data Exchange (ETDEWEB)

Ferreira F, T. C. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil); Campos, T., E-mail: tcff01@gmail.com [Universidade Federal de Minas Gerais, Departamento de Engenharia Nuclear, Programa de Pos Graduacao em Ciencias e Tecnicas Nucleares, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil)

2015-10-15

Intensity Modulated Radiation Therapy (IMRT) is an advanced treatment technique, widely used in external radiotherapy. This paper presents the Soft-Rt which allows the simulation of an entire IMRT treatment protocol. The Soft-Rt performs a full three-dimensional rendering of a set of patient images, including the definitions of region of interest with organs in risk, and the target tumor volume and margins (PTV). Thus, a more accurate analysis and planning can be performed, taking into account the features and orientation of the radiation beams. The exposed tissues as well as the amount of absorbed dose is depicted in healthy and/or cancerous tissues. As conclusion, Soft-Rt can predict dose on the PTV accurately, preserving the surrounding healthy tissues. Soft-Rt is coupled with SISCODES code. The SISCODES code is firstly applied to segment the set of CT or MRI patient images in distinct tissues pointing out its respective density and chemical compositions. Later, the voxel model is export to the Soft-Rt IMRT planning module in which a full treatment planning is created. All geometrical parameters are sent to the general purpose Monte Carlo transport code - MCNP - to simulate the interaction of each incident beam towards to the PTV avoiding organs in risk. The normalized dose results are exported to the Soft-Rt out-module, in which the three-dimensional model visualization is shown in a transparent glass procedure adopting gray scale for the dependence on the mass density of the correlated tissue; while, a color scale to depict dose values in a superimpose protocol. (Author)

IMRT treatment of anal cancer with a scrotal shield

International Nuclear Information System (INIS)

Hood, Rodney C.; Wu, Q. Jackie; McMahon, Ryan; Czito, Brian; Willett, Christopher

2012-01-01

The risk of sterility in males undergoing radiotherapy in the pelvic region indicates the use of a shielding device, which offers protection to the testes for patients wishing to maintain fertility. The use of such devices in the realm of intensity-modulated radiotherapy (IMRT) in the pelvic region can pose many obstacles during simulation, treatment planning, and delivery of radiotherapy. This work focuses on the development and execution of an IMRT plan for the treatment of anal cancer using a scrotal shielding device on a clinical patient. An IMRT plan was developed using Eclipse treatment planning system (Varian Medical Systems, Palo Alto, CA), using a wide array of gantry angles as well as fixed jaw and fluence editing techniques. When possible, the entire target volume was encompassed by the treatment field. When the beam was incident on the scrotal shield, the jaw was fixed to avoid the device and the collimator rotation optimized to irradiate as much of the target as possible. This technique maximizes genital sparing and allows minimal irradiation of the gonads. When this fixed-jaw technique was found to compromise adequate coverage of the target, manual fluence editing techniques were used to avoid the shielding device. Special procedures for simulation, imaging, and treatment verification were also developed. In vivo dosimetry was used to verify and ensure acceptable dose to the gonads. The combination of these techniques resulted in a highly conformal plan that spares organs and risk and avoids the genitals as well as entrance of primary radiation onto the shielding device.

SU-F-J-124: Reduction in Dosimetric Impact of Motion Using VMAT Compared to IMRT in Hypofractionated Prostate Cancer Patients

Energy Technology Data Exchange (ETDEWEB)

Ravindranath, B; Xiong, J; Happersett, L; Mageras, G; Zhang, P; Hunt, M [Memorial Sloan Kettering Cancer Center, New York, NY (United States)

2016-06-15

Purpose: To quantify and compare the dosimetric impact of motion management correction strategies during VMAT and IMRT for hypofractionated prostate treatment. Methods: Two arc VMAT and 9 field IMRT plans were generated for two prostate cancer patients undergoing hypofractionated radiotherapy (7.5Gy × 5 and 8Gy × 5). 212 motion traces were retrospectively extracted from treatment records of prostate cancer patients with implanted Calypso beacons. Dose to the CTV and normal tissues was reconstructed for each trace and plan taking into account the actual treatment delivery time. Following motion correction scenarios were simulated: (1) VMAT plan – (a) No correction, (b) correction between arcs, (c) correction every 20 degrees of gantry rotation and (2) IMRT plan - (a) No correction,(b) correction between fields. Two mm action threshold for position correction was assumed. The 5–95% confidence interval (CI) range was extracted from the family of DVHs for each correction scenario. Results: Treatment duration for 8Gy plan (VMAT vs IMRT) was 3 vs 12 mins and for 7.5Gy plan was 3 vs 9 mins. In the absence of correction, the VMAT 5–−95% CI dose spread was, on average, less than the IMRT dose spread by 2% for CTVD95, 9% for rectalwall (RW) D1cc and 9% for bladderwall (BW) D53. Further, VMAT b/w arcs correction strategy reduced the spread about the planned value compared to IMRT b/w fields correction by: 1% for CTVD95, 2.6% for RW1cc and 2% for BWD53. VMAT 20 degree strategy led to greater reduction in dose spread compared to IMRT by: 2% for CTVD95, 4.5% for RW1cc and 6.7% for BWD53. Conclusion: In the absence of a correction strategy, the limited motion during VMAT’s shorter delivery times translates into less motion-induced dosimetric degradation than IMRT. Performing limited periodic motion correction during VMAT can yield excellent conformity to planned values that is superior to IMRT. This work was partially supported by Varian Medical Systems.

A dosimetric selectivity intercomparison of HDR brachytherapy, IMRT and helical tomotherapy in prostate cancer radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Hermesse, Johanne; Biver, Sylvie; Jansen, Nicolas; Coucke, Philippe [Dept. of Radiation Oncology, Liege Univ. Hospital (Belgium); Lenaerts, Eric [Dept. of Medical Physics, Liege Univ. Hospital (Belgium); De Patoul, Nathalie; Vynckier, Stefaan [Dept. of Medical Physics, St Luc Univ. Hospital, Brussels (Belgium); Scalliet, Pierre [Dept. of Radiation Oncology, St Luc Univ. Hospital, Brussels (Belgium); Nickers, Philippe [Dept. of Radiation Oncology, Oscar Lambret Center, Lille (France)

2009-11-15

Background and purpose: dose escalation in order to improve the biochemical control in prostate cancer requires the application of irradiation techniques with high conformality. The dosimetric selectivity of three radiation modalities is compared: high-dose-rate brachytherapy (HDR-BT), intensity-modulated radiation radiotherapy (IMRT), and helical tomotherapy (HT). Patients and methods: ten patients with prostate adenocarcinoma treated by a 10-Gy HDR-BT boost after external-beam radiotherapy were investigated. For each patient, HDR-BT, IMRT and HT theoretical treatment plans were realized using common contour sets. A 10-Gy dose was prescribed to the planning target volume (PTV). The PTVs and critical organs' dose-volume histograms obtained were compared using Student's t-test. Results: HDR-BT delivers spontaneously higher mean doses to the PTV with smaller cold spots compared to IMRT and HT. 33% of the rectal volume received a mean HDR-BT dose of 3.86 {+-} 0.3 Gy in comparison with a mean IMRT dose of 6.57 {+-} 0.68 Gy and a mean HT dose of 5.58 {+-} 0.71 Gy (p < 0.0001). HDR-BT also enables to better spare the bladder. The hot spots inside the urethra are greater with HDR-BT. The volume of healthy tissue receiving 10% of the prescribed dose is reduced at least by a factor of 8 with HDR-BT (p < 0.0001). Conclusion: HDR-BT offers better conformality in comparison with HT and IMRT and reduces the volume of healthy tissue receiving a low dose. (orig.)

Poster - Thur Eve - 57: Craniospinal irradiation with jagged-junction IMRT approach without beam edge matching for field junctions.

Science.gov (United States)

Cao, F; Ramaseshan, R; Corns, R; Harrop, S; Nuraney, N; Steiner, P; Aldridge, S; Liu, M; Carolan, H; Agranovich, A; Karva, A

2012-07-01

Craniospinal irradiation were traditionally treated the central nervous system using two or three adjacent field sets. A intensity-modulated radiotherapy (IMRT) plan (Jagged-Junction IMRT) which overcomes problems associated with field junctions and beam edge matching, improves planning and treatment setup efficiencies with homogenous target dose distribution was developed. Jagged-Junction IMRT was retrospectively planned on three patients with prescription of 36 Gy in 20 fractions and compared to conventional treatment plans. Planning target volume (PTV) included the whole brain and spinal canal to the S3 vertebral level. The plan employed three field sets, each with a unique isocentre. One field set with seven fields treated the cranium. Two field sets treated the spine, each set using three fields. Fields from adjacent sets were overlapped and the optimization process smoothly integrated the dose inside the overlapped junction. For the Jagged-Junction IMRT plans vs conventional technique, average homogeneity index equaled 0.08±0.01 vs 0.12±0.02, and conformity number equaled 0.79±0.01 vs 0.47±0.12. The 95% isodose surface covered (99.5±0.3)% of the PTV vs (98.1±2.0)%. Both Jagged-Junction IMRT plans and the conventional plans had good sparing of the organs at risk. Jagged-Junction IMRT planning provided good dose homogeneity and conformity to the target while maintaining a low dose to the organs at risk. Jagged-Junction IMRT optimization smoothly distributed dose in the junction between field sets. Since there was no beam matching, this treatment technique is less likely to produce hot or cold spots at the junction in contrast to conventional techniques. © 2012 American Association of Physicists in Medicine.

Stereotactic intensity-modulated radiation therapy (IMRT) and inverse treatment planning for advanced pleural mesothelioma. Feasibility and initial results

Energy Technology Data Exchange (ETDEWEB)

Muenter, M.W.; Thilmann, C.; Hof, H.; Debus, J. [Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (dkfz), Heidelberg (Germany); Nill, S.; Hoess, A.; Partridge, M. [Dept. of Medical Physics, German Cancer Research Center (dkfz), Heidelberg (Germany); Haering, P. [Dept. of Central Dosimetry, German Cancer Research Center (dkfz), Heidelberg (Germany); Manegold, C. [Dept. of Medical Oncology/Internal Medicine, Thoraxklinik Heidelberg gGmbH, Heidelberg (Germany); Wannenmacher, M. [Dept. of Clinical Radiology, Univ. of Heidelberg, Heidelberg (Germany)

2003-08-01

Background and Purpose: Complex-shaped malignant pleural mesotheliomas (MPMs) with challenging volumes are extremely difficult to treat by conventional radiotherapy due to tolerance doses of the surrounding normal tissue. In a feasibility study, we evaluated if inversely planned stereotactic intensity-modulated radiation therapy (IMRT) could be applied in the treatment of MPM. Patients and Methods: Eight patients with unresectable lesions were treated after failure of chemotherapy. All patients were positioned using noninvasive patient fixation techniques which can be attached to the applied extracranial stereotactic system. Due to craniocaudal extension of the tumor, it was necessary to develop a special software attached to the inverse planning program KonRad, which can connect two inverse treatment plans and consider the applied dose of the first treatment plan in the area of the matchline of the second treatment plan. Results: Except for one patient, in whom radiotherapy was canceled due to abdominal metastasis, treatment could be completed in all patients and was well tolerated. Median survival after diagnosis was 20 months and after IMRT 6.5 months. Therefore, both the 1-year actuarial overall survival from the start of radiotherapy and the 2-year actuarial overall survival since diagnosis were 28%. IMRT did not result in clinically significant acute side effects. By using the described inverse planning software, over- or underdosage in the region of the field matchline could be prevented. Pure treatment time ranged between 10 and 21 min. Conclusion: This study showed that IMRT is feasible in advanced unresectable MPM. The presented possibilities of stereotactic IMRT in the treatment of MPM will justify the evaluation of IMRT in early-stage pleural mesothelioma combined with chemotherapy in a study protocol, in order to improve the outcome of these patients. Furthermore, dose escalation should be possible by using IMRT. (orig.)

Impact of head and neck cancer adaptive radiotherapy to spare the parotid glands and decrease the risk of xerostomia

International Nuclear Information System (INIS)

Castelli, Joel; Simon, Antoine; Louvel, Guillaume; Henry, Olivier; Chajon, Enrique; Nassef, Mohamed; Haigron, Pascal; Cazoulat, Guillaume; Ospina, Juan David; Jegoux, Franck; Benezery, Karen; Crevoisier, Renaud de

2015-01-01

Large anatomical variations occur during the course of intensity-modulated radiation therapy (IMRT) for locally advanced head and neck cancer (LAHNC). The risks are therefore a parotid glands (PG) overdose and a xerostomia increase. The purposes of the study were to estimate: - the PG overdose and the xerostomia risk increase during a “standard” IMRT (IMRT std ); - the benefits of an adaptive IMRT (ART) with weekly replanning to spare the PGs and limit the risk of xerostomia. Fifteen patients received radical IMRT (70 Gy) for LAHNC. Weekly CTs were used to estimate the dose distributions delivered during the treatment, corresponding either to the initial planning (IMRT std ) or to weekly replanning (ART). PGs dose were recalculated at the fraction, from the weekly CTs. PG cumulated doses were then estimated using deformable image registration. The following PG doses were compared: pre-treatment planned dose, per-treatment IMRT std and ART. The corresponding estimated risks of xerostomia were also compared. Correlations between anatomical markers and dose differences were searched. Compared to the initial planning, a PG overdose was observed during IMRT std for 59% of the PGs, with an average increase of 3.7 Gy (10.0 Gy maximum) for the mean dose, and of 8.2% (23.9% maximum) for the risk of xerostomia. Compared to the initial planning, weekly replanning reduced the PG mean dose for all the patients (p < 0.05). In the overirradiated PG group, weekly replanning reduced the mean dose by 5.1 Gy (12.2 Gy maximum) and the absolute risk of xerostomia by 11% (p < 0.01) (30% maximum). The PG overdose and the dosimetric benefit of replanning increased with the tumor shrinkage and the neck thickness reduction (p < 0.001). During the course of LAHNC IMRT, around 60% of the PGs are overdosed of 4 Gy. Weekly replanning decreased the PG mean dose by 5 Gy, and therefore by 11% the xerostomia risk

SU-E-J-193: Feasibility of MRI-Only Based IMRT Planning for Pancreatic Cancer

International Nuclear Information System (INIS)

Prior, P; Botros, M; Chen, X; Paulson, E; Erickson, B; Li, X

2014-01-01

Purpose: With the increasing use of MRI simulation and the advent of MRI-guided delivery, it is desirable to use MRI only for treatment planning. In this study, we assess the dosimetric difference between MRI- and CTbased IMRT planning for pancreatic cancer. Methods: Planning CTs and MRIs acquired for a representative pancreatic cancer patient were used. MRI-based planning utilized forced relative electron density (rED) assignment of organ specific values from IRCU report 46, where rED = 1.029 for PTV and a rED = 1.036 for non-specified tissue (NST). Six IMRT plans were generated with clinical dose-volume (DV) constraints using a research Monaco planning system employing Monte Carlo dose calculation with optional perpendicular magnetic field (MF) of 1.5T. The following five plans were generated and compared with the planning CT: 1.) CT plan with MF and dose recalculation without optimization; 2.) MRI (T2) plan with target and OARs redrawn based on MRI, forced rED, no MF, and recalculation without optimization; 3.) Similar as in 2 but with MF; 4.) MRI plan with MF but without optimization; and 5.) Similar as in 4 but with optimization. Results: Generally, noticeable differences in PTV point doses and DV parameters (DVPs) between the CT-and MRI-based plans with and without the MF were observed. These differences between the optimized plans were generally small, mostly within 2%. Larger differences were observed in point doses and mean doses for certain OARs between the CT and MRI plan, mostly due to differences between image acquisition times. Conclusion: MRI only based IMRT planning for pancreatic cancer is feasible. The differences observed between the optimized CT and MRI plans with or without the MF were practically negligible if excluding the differences between MRI and CT defined structures

Clinical validation of an in-house EPID dosimetry system for IMRT QA at the Prince of Wales Hospital

Science.gov (United States)

Tyler, M.; Vial, P.; Metcalfe, P.; Downes, S.

2013-06-01

In this study a simple method using standard flood-field corrected Electronic Portal Imaging Device (EPID) images for routine Intensity Modulated Radiation Therapy (IMRT) Quality Assurance (QA) was investigated. The EPID QA system was designed and tested on a Siemens Oncor Impression linear accelerator with an OptiVue 1000ST EPID panel (Siemens Medical Solutions USA, Inc, USA) and an Elekta Axesse linear accelerator with an iViewGT EPID (Elekta AB, Sweden) for 6 and 10 MV IMRT fields with Step-and-Shoot and dynamic-MLC delivery. Two different planning systems were used for patient IMRT field generation for comparison with the measured EPID fluences. All measured IMRT plans had >95% agreement to the planning fluences (using 3 cGy / 3 mm Gamma Criteria) and were comparable to the pass-rates calculated using a 2-D diode array dosimeter.

Clinical validation of an in-house EPID dosimetry system for IMRT QA at the Prince of Wales Hospital

International Nuclear Information System (INIS)

Tyler, M; Downes, S; Vial, P; Metcalfe, P

2013-01-01

In this study a simple method using standard flood-field corrected Electronic Portal Imaging Device (EPID) images for routine Intensity Modulated Radiation Therapy (IMRT) Quality Assurance (QA) was investigated. The EPID QA system was designed and tested on a Siemens Oncor Impression linear accelerator with an OptiVue 1000ST EPID panel (Siemens Medical Solutions USA, Inc, USA) and an Elekta Axesse linear accelerator with an iViewGT EPID (Elekta AB, Sweden) for 6 and 10 MV IMRT fields with Step-and-Shoot and dynamic-MLC delivery. Two different planning systems were used for patient IMRT field generation for comparison with the measured EPID fluences. All measured IMRT plans had >95% agreement to the planning fluences (using 3 cGy / 3 mm Gamma Criteria) and were comparable to the pass-rates calculated using a 2-D diode array dosimeter.

IMRT for Sinonasal Tumors Minimizes Severe Late Ocular Toxicity and Preserves Disease Control and Survival

International Nuclear Information System (INIS)

Duprez, Fréderic; Madani, Indira; Morbée, Lieve; Bonte, Katrien; Deron, Philippe; Domján, Vilmos; Boterberg, Tom; De Gersem, Werner; De Neve, Wilfried

2012-01-01

Purpose: To report late ocular (primary endpoint) and other toxicity, disease control, and survival (secondary endpoints) after intensity-modulated radiotherapy (IMRT) for sinonasal tumors. Methods and Materials: Between 1998 and 2009, 130 patients with nonmetastatic sinonasal tumors were treated with IMRT at Ghent University Hospital. Prescription doses were 70 Gy (n = 117) and 60–66 Gy (n = 13) at 2 Gy per fraction over 6–7 weeks. Most patients had adenocarcinoma (n = 82) and squamous cell carcinoma (n = 23). One hundred and one (101) patients were treated postoperatively. Of 17 patients with recurrent tumors, 9 were reirradiated. T-stages were T1–2 (n = 39), T3 (n = 21), T4a (n = 38), and T4b (n = 22). Esthesioneuroblastoma was staged as Kadish A, B, and C in 1, 3, and 6 cases, respectively. Results: Median follow-up was 52, range 15–121 months. There was no radiation-induced blindness in 86 patients available for late toxicity assessment (≥6 month follow-up). We observed late Grade 3 tearing in 10 patients, which reduced to Grade 1–2 in 5 patients and Grade 3 visual impairment because of radiation-induced ipsilateral retinopathy and neovascular glaucoma in 1 patient. There was no severe dry eye syndrome. The worst grade of late ocular toxicity was Grade 3 (n = 11), Grade 2 (n = 31), Grade 1 (n = 33), and Grade 0 (n = 11). Brain necrosis and osteoradionecrosis occurred in 6 and 1 patients, respectively. Actuarial 5-year local control and overall survival were 59% and 52%, respectively. On multivariate analysis local control was negatively affected by cribriform plate and brain invasion (p = 0.044 and 0.029, respectively) and absence of surgery (p = 0.009); overall survival was negatively affected by cribriform plate and orbit invasion (p = 0.04 and <0.001, respectively) and absence of surgery (p = 0.001). Conclusions: IMRT for sinonasal tumors allowed delivering high doses to targets at minimized ocular toxicity, while maintaining disease control and

IMRT for Sinonasal Tumors Minimizes Severe Late Ocular Toxicity and Preserves Disease Control and Survival

Energy Technology Data Exchange (ETDEWEB)

Duprez, Frederic, E-mail: frederic.duprez@ugent.be [Department of Radiotherapy, Ghent University Hospital, Ghent (Belgium); Madani, Indira; Morbee, Lieve [Department of Radiotherapy, Ghent University Hospital, Ghent (Belgium); Bonte, Katrien; Deron, Philippe; Domjan, Vilmos [Department of Head and Neck Surgery, Ghent University Hospital, Ghent (Belgium); Boterberg, Tom; De Gersem, Werner; De Neve, Wilfried [Department of Radiotherapy, Ghent University Hospital, Ghent (Belgium)

2012-05-01

Purpose: To report late ocular (primary endpoint) and other toxicity, disease control, and survival (secondary endpoints) after intensity-modulated radiotherapy (IMRT) for sinonasal tumors. Methods and Materials: Between 1998 and 2009, 130 patients with nonmetastatic sinonasal tumors were treated with IMRT at Ghent University Hospital. Prescription doses were 70 Gy (n = 117) and 60-66 Gy (n = 13) at 2 Gy per fraction over 6-7 weeks. Most patients had adenocarcinoma (n = 82) and squamous cell carcinoma (n = 23). One hundred and one (101) patients were treated postoperatively. Of 17 patients with recurrent tumors, 9 were reirradiated. T-stages were T1-2 (n = 39), T3 (n = 21), T4a (n = 38), and T4b (n = 22). Esthesioneuroblastoma was staged as Kadish A, B, and C in 1, 3, and 6 cases, respectively. Results: Median follow-up was 52, range 15-121 months. There was no radiation-induced blindness in 86 patients available for late toxicity assessment ({>=}6 month follow-up). We observed late Grade 3 tearing in 10 patients, which reduced to Grade 1-2 in 5 patients and Grade 3 visual impairment because of radiation-induced ipsilateral retinopathy and neovascular glaucoma in 1 patient. There was no severe dry eye syndrome. The worst grade of late ocular toxicity was Grade 3 (n = 11), Grade 2 (n = 31), Grade 1 (n = 33), and Grade 0 (n = 11). Brain necrosis and osteoradionecrosis occurred in 6 and 1 patients, respectively. Actuarial 5-year local control and overall survival were 59% and 52%, respectively. On multivariate analysis local control was negatively affected by cribriform plate and brain invasion (p = 0.044 and 0.029, respectively) and absence of surgery (p = 0.009); overall survival was negatively affected by cribriform plate and orbit invasion (p = 0.04 and <0.001, respectively) and absence of surgery (p = 0.001). Conclusions: IMRT for sinonasal tumors allowed delivering high doses to targets at minimized ocular toxicity, while maintaining disease control and survival

SU-F-T-378: Evaluation of Dose-Volume Variability and Parameters Between Prostate IMRT and VMAT Plans

Energy Technology Data Exchange (ETDEWEB)

Chow, J [Princess Margaret Cancer Centre, Toronto, ON (Canada); Jiang, R [Grand River Regional Cancer Centre, Kitchener, ON (Canada); Kiciak, A [University of Waterloo, Waterloo, ON (Canada)

2016-06-15

Purpose: This study compared the rectal dose-volume consistency, equivalent uniform dose (EUD) and normal tissue complication probability (NTCP) in prostate intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). Methods: For forty prostate IMRT and fifty VMAT patients treated using the same dose prescription (78 Gy/39 fraction) and dose-volume criteria in inverse planning optimization, the rectal EUD and NTCP were calculated for each patient. The rectal dose-volume consistency, showing the variability of dose-volume histogram (DVH) among patients, was defined and calculated based on the deviation between the mean and corresponding rectal DVH. Results: From both the prostate IMRT and VMAT plans, the rectal EUD and NTCP were found decreasing with the rectal volume. The decrease rates for the IMRT plans (EUD = 0.47 × 10{sup −3} Gy cm{sup −3} and NTCP = 3.94 × 10{sup −2} % cm{sup −3}) were higher than those for the VMAT (EUD = 0.28 × 10{sup −3} Gy cm{sup −3} and NTCP = 2.61 × 10{sup −2} % cm{sup −3}). In addition, the dependences of the rectal EUD and NTCP on the dose-volume consistency were found very similar between the prostate IMRT and VMAT plans. This shows that both delivery techniques have similar variations of the rectal EUD and NTCP on the dose-volume consistency. Conclusion: Dependences of the dose-volume consistency on the rectal EUD and NTCP were compared between the prostate IMRT and VMAT plans. It is concluded that both rectal EUD and NTCP decreased with an increase of the rectal volume. The variation rates of the rectal EUD and NTCP on the rectal volume were higher for the IMRT plans than VMAT. However, variations of the rectal dose-volume consistency on the rectal EUD and NTCP were found not significant for both delivery techniques.

Psychological adaptations for assessing gossip veracity.

Science.gov (United States)

Hess, Nicole H; Hagen, Edward H

2006-09-01

Evolutionary models of human cooperation are increasingly emphasizing the role of reputation and the requisite truthful "gossiping" about reputation-relevant behavior. If resources were allocated among individuals according to their reputations, competition for resources via competition for "good" reputations would have created incentives for exaggerated or deceptive gossip about oneself and one's competitors in ancestral societies. Correspondingly, humans should have psychological adaptations to assess gossip veracity. Using social psychological methods, we explored cues of gossip veracity in four experiments. We found that simple reiteration increased gossip veracity, but only for those who found the gossip relatively uninteresting. Multiple sources of gossip increased its veracity, as did the independence of those sources. Information that suggested alternative, benign interpretations of gossip decreased its veracity. Competition between a gossiper and her target decreased gossip veracity. These results provide preliminary evidence for psychological adaptations for assessing gossip veracity, mechanisms that might be used to assess veracity in other domains involving social exchange of information.

SU-E-T-163: Evaluation of Dose Distributions Recalculated with Per-Field Measurement Data Under the Condition of Respiratory Motion During IMRT for Liver Cancer

Energy Technology Data Exchange (ETDEWEB)

Song, J; Yoon, M; Nam, T; Ahn, S; Chung, W [Chonnam National University Hwasun Hospital, Hwasun-kun, Chonnam (Korea, Republic of)

2014-06-01

Purpose: The dose distributions within the real volumes of tumor targets and critical organs during internal target volume-based intensity-modulated radiation therapy (ITV-IMRT) for liver cancer were recalculated by applying the effects of actual respiratory organ motion, and the dosimetric features were analyzed through comparison with gating IMRT (Gate-IMRT) plan results. Methods: The 4DCT data for 10 patients who had been treated with Gate-IMRT for liver cancer were selected to create ITV-IMRT plans. The ITV was created using MIM software, and a moving phantom was used to simulate respiratory motion. The period and range of respiratory motion were recorded in all patients from 4DCT-generated movie data, and the same period and range were applied when operating the dynamic phantom to realize coincident respiratory conditions in each patient. The doses were recalculated with a 3 dose-volume histogram (3DVH) program based on the per-field data measured with a MapCHECK2 2-dimensional diode detector array and compared with the DVHs calculated for the Gate-IMRT plan. Results: Although a sufficient prescription dose covered the PTV during ITV-IMRT delivery, the dose homogeneity in the PTV was inferior to that with the Gate-IMRT plan. We confirmed that there were higher doses to the organs-at-risk (OARs) with ITV-IMRT, as expected when using an enlarged field, but the increased dose to the spinal cord was not significant and the increased doses to the liver and kidney could be considered as minor when the reinforced constraints were applied during IMRT plan optimization. Conclusion: Because Gate-IMRT cannot always be considered an ideal method with which to correct the respiratory motional effect, given the dosimetric variations in the gating system application and the increased treatment time, a prior analysis for optimal IMRT method selection should be performed while considering the patient's respiratory condition and IMRT plan results.

Evaluation of homogeneity and dose conformity in IMRT planning in prostate radiotherapy; Avaliacao da homogeneidade e conformidade de dose em planejamentos de IMRT de prostata em radioterapia

Energy Technology Data Exchange (ETDEWEB)

Lopes, Juliane S.; Leidens, Matheus; Estacio, Daniela R., E-mail: juliane.lopes@pucrs.br [Hospital Sao Lucas (PUC-RS), Porto Alegre, RS (Brazil). Servico de Radioterapia; Razera, Ricardo A.Z.; Streck, Elaine E.; Silva, Ana M.M. da [Pontificia Universidade Catolica do Rio Grande do Sul (PUC-RS), Porto Alegre, RS (Brazil). Faculdade de Fisica

2015-12-15

The goal of this study was to evaluate the dose distribution homogeneity and conformity of radiation therapy plans of prostate cancer using IMRT. Data from 34 treatment plans of Hospital Sao Lucas of PUCRS, where those plans were executed, were retrospectively analyzed. All of them were done with 6MV X-rays from a linear accelerator CLINAC IX, and the prescription doses varied between 60 and 74 Gy. Analyses showing the homogeneity and conformity indices for the dose distribution of those plans were made. During these analyses, some comparisons with the traditional radiation therapy planning technic, the 3D-CRT, were discussed. The results showed that there is no correlation between the prescribed dose and the homogeneity and conformity indices, indicating that IMRT works very well even for higher doses. Furthermore, a comparison between the results obtained and the recommendations of ICRU 83 was carried out. It has also been observed that the indices were really close to the ideal values. 82.4% of the cases showed a difference below 5% of the ideal value for the index of conformity, and 88.2% showed a difference below 10% for the homogeneity index. Concluding, it is possible to confirm the quality of the analyzed radiation therapy plans of prostate cancer using IMRT. (author)

A dose planning study on applicator guided stereotactic IMRT boost in combination with 3D MRI based brachytherapy in locally advanced cervical cancer

International Nuclear Information System (INIS)

Assenholt, Marianne S.; Petersen, Joergen B.; Nielsen, Soeren K.; Lindegaard, Jacob C.; Tanderup, Kari

2008-01-01

Purpose. Locally advanced cervical cancer is usually treated with external beam radiotherapy followed by brachytherapy (BT). However, if response or tumour topography is unfavourable it may be difficult to reach a sufficient BT dose. The purpose of this study was to explore whether an applicator guided stereotactic IMRT boost could be combined with brachytherapy to improve dose volume parameters. Material and methods. Dose plans of 6 patients with HR CTV volumes of 31-100cc at the time of BT were analysed. MRI was performed with a combined intracavitary (IC)-interstitial (IS) ring applicator in situ. A radiotherapy schedule consisting of 45Gy (1.8Gyx25) IMRT followed by boost of 28Gy (7Gyx4fx) was modelled. Four different boost techniques were evaluated: IC-BT, IC/IS-BT, IC-BT+IMRT and IMRT. Dose plans were optimised for maximal tumour dose (D90) and coverage (V85Gy) while respecting DVH constraints in organs at risk: D2cc <75Gy in rectum and sigmoid and <90Gy in bladder (EQD2). In combined BT+IMRT dose plans, the IMRT plan was optimised on top of the BT dose distribution. Volumes irradiated to more than 60 Gy EQD2 (V60Gy) were evaluated. Results. Median dose coverage in IC plans was 74% [66-93%]. By using IC/IS or IC-BT+IMRT boost, the median coverage was improved to 95% [78-99%], and to 96% [69-99%] respectively. For IMRT alone, a median coverage of 98% [90-100%] was achieved, but V60Gy volumes were significantly increased by a median factor of 2.0 [1.4-2.3] as compared to IC/IS. It depended on the individual tumour topography whether IC/IS-BT or IC-BT+IMRT boost was the most favourable technique. Conclusion. It is technically possible to create dose plans that combine image guided BT and IMRT. In this study the dose coverage could be significantly increased by adding IS-BT or IMRT boost to the intracavitary dose. Using IMRT alone for boost cannot be advocated since this results in a significant increase of the volume irradiated to 60Gy

Cardiac dose-sparing effects of deep-inspiration breath-hold in left breast irradiation. Is IMRT more beneficial than VMAT

Energy Technology Data Exchange (ETDEWEB)

Sakka, Mazen; Grabenbauer, Gerhard G. [Coburg Cancer Center, Department of Radiation Oncology, Coburg (Germany); Friedrich-Alexander University of Erlangen-Nuernberg, Faculty of Medicine, Erlangen (Germany); Kunzelmann, Leonie; Metzger, Martin [Coburg Cancer Center, Department of Radiation Oncology, Coburg (Germany)

2017-10-15

Given the reduction in death from breast cancer, as well as improvements in overall survival, adjuvant radiotherapy is considered the standard treatment for breast cancer. However, left-sided breast irradiation was associated with an increased rate of fatal cardiovascular events due to incidental irradiation of the heart. Recently, considerable efforts have been made to minimize cardiac toxicity of left-sided breast irradiation by new treatment methods such as deep-inspiration breath-hold (DIBH) and new radiation techniques, particularly intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT). The primary aim of this study was to evaluate the effect of DIBH irradiation on cardiac dose compared with free-breathing (FB) irradiation, while the secondary objective was to compare the advantages of IMRT versus VMAT plans in both the FB and the DIBH position for left-sided breast cancer. In all, 25 consecutive left-sided breast cancer patients underwent CT simulation in the FB and DIBH position. Five patients were excluded with no cardiac displacement following DIBH-CT simulation. The other 20 patients were irradiated in the DIBH position using respiratory gating. Four different treatment plans were generated for each patient, an IMRT and a VMAT plan in the DIBH and in the FB position, respectively. The following parameters were used for plan comparison: dose to the heart, left anterior descending coronary artery (mean dose, maximum dose, D25% and D45%), ipsilateral, contralateral lung (mean dose, D20%, D30%) and contralateral breast (mean dose). The percentage in dose reduction for organs at risk achieved by DIBH for both IMRT and VMAT plans was calculated and compared for each patient by each treatment plan. DIBH irradiation significantly reduced mean dose to the heart and left anterior descending coronary artery (LADCA) using both IMRT (heart -20%; p = 0.0002, LADCA -9%; p = 0.001) and VMAT (heart -23%; p = 0.00003, LADCA -16%; p = 0

Dose-volume based ranking of incident beam direction and its utility in facilitating IMRT beam placement

International Nuclear Information System (INIS)

Schreibmann, Eduard; Xing Lei

2005-01-01

Purpose: Beam orientation optimization in intensity-modulated radiation therapy (IMRT) is computationally intensive, and various single beam ranking techniques have been proposed to reduce the search space. Up to this point, none of the existing ranking techniques considers the clinically important dose-volume effects of the involved structures, which may lead to clinically irrelevant angular ranking. The purpose of this work is to develop a clinically sensible angular ranking model with incorporation of dose-volume effects and to show its utility for IMRT beam placement. Methods and Materials: The general consideration in constructing this angular ranking function is that a beamlet/beam is preferable if it can deliver a higher dose to the target without exceeding the tolerance of the sensitive structures located on the path of the beamlet/beam. In the previously proposed dose-based approach, the beamlets are treated independently and, to compute the maximally deliverable dose to the target volume, the intensity of each beamlet is pushed to its maximum intensity without considering the values of other beamlets. When volumetric structures are involved, the complication arises from the fact that there are numerous dose distributions corresponding to the same dose-volume tolerance. In this situation, the beamlets are not independent and an optimization algorithm is required to find the intensity profile that delivers the maximum target dose while satisfying the volumetric constraints. In this study, the behavior of a volumetric organ was modeled by using the equivalent uniform dose (EUD). A constrained sequential quadratic programming algorithm (CFSQP) was used to find the beam profile that delivers the maximum dose to the target volume without violating the EUD constraint or constraints. To assess the utility of the proposed technique, we planned a head-and-neck and abdominal case with and without the guidance of the angular ranking information. The qualities of the

Optimization of dose distributions for adjuvant locoregional radiotherapy of gastric cancer by IMRT

International Nuclear Information System (INIS)

Lohr, F.; Dobler, B.; Mai, S.; Hermann, B.; Tiefenbacher, U.; Wieland, P.; Steil, V.; Wenz, F.

2003-01-01

Background and Purpose: Locoregional relapse is a problem frequently encountered with advanced gastric cancer. Data from the randomized Intergroup trial 116 suggest effectiveness of adjuvant radiochemotherapy, albeit with significant toxicity. The potential of intensity-modulated radiotherapy (IMRT) to reduce toxicity by significantly reducing maximum and median doses to organs at risk while still applying sufficient dose to the target volume in the upper abdomen was studied. Patient and Methods: For a typical configuration of target volumes and organs, a step-and-shoot IMRT plan (eight beam orientations), developed as a class solution for treatment of tumors in the upper abdomen (Figures 1 to 3), a conventional plan, a combination of the conventional plan with a kidney-sparing boost plan, and a conventional plan with noncoplanar ap and pa fields for improved kidney sparing were compared with respect to coverage of target volume and dose to organs at risk with a dose of 45 Gy delivered as the median dose to the target volume. Results: When using the conventional three-dimensionally planned box techniques, the right kidney could be kept below tolerance, but median dose to the left kidney amounted to between 14.8 and 26.9 Gy, depending on the plan. IMRT reduced the median dose to the left kidney to 10.5 Gy, while still keeping the dose to the right kidney 90% of prescription dose were delivered to > 90% of target volume with IMRT (Table 1). Conclusion: IMRT has the potential to deliver efficient doses to target volumes in the upper abdomen, while delivering dose to organs at risk in a more advantageous fashion than a conventional technique. For clinical implementation, the possibility of extensive organ motion in the upper abdomen has to be taken into account for treatment planning and patient positioning. The multitude of potential risks related to its application has to be the subject of thorough follow-up and further studies. (orig.)

Assessment of variable application rates of biological amendment ...

African Journals Online (AJOL)

Assessment of variable application rates of biological amendment substances on establishment and growth characteristics of maize plants. ... Hence, a greenhouse experiment was conducted in 2008 to assess the effects of variable rates (50, 75 and 100% of the recommended rates) of industrial manufactured biological ...

Impact of environmental adaptation on tear film assessments.

Science.gov (United States)

Fagehi, R

2018-03-01

The purpose of this study was to investigate the effect of ocular environmental adaptation on clinical tear film assessment. Thirty subjects (male, mean age 23±2.5) participated in this study. A number of clinical tear film tests were applied, including: fluorescein tear break-up time (FTBUT), Schirmer test and tear prism height test (TPH). The tear physiology of each subject was evaluated twice, once immediately when they arrived from the external environment, and then after 30minutes adaptation in the exam room environment. The mean values were: Schirmer test A (22.1±2.99), Schirmer test B (24.2±2.63), FTBUT A (8.00±1.94), FTBUT B (9.13±2.04), TPH A (0.179±0.026) and TPH B* (0.187±0.023). Statistical testing using Wilcoxon-signed rank test showed a significant difference between the Schirmer test results measured at the different times (P=0.008). Also, the FTBUT and tear prism height test results showed significant differences between the two evaluation times, (P=0.001, 0.011, respectively) (A: tear assessed when the subject comes from the outside environment, B: tear film assessed after 30min adaptation in the clinical environment). This study showed a significant difference between the tear film test results evaluated when the subjects were assessed immediately from the outside environment and after an adaptation time in the clinic environment. Practitioners must consider the effect of differences between external and clinical environment adaptation on clinical tear film physiology. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

GATE Monte Carlo simulation in radiation therapy for complex and dynamic beams in IMRT

International Nuclear Information System (INIS)

Benhalouche, Saadia

2014-01-01

Radiotherapy is one of the three methods of cancer treatment along with surgery and chemotherapy. It has evolved with the development of treatment techniques such as IMRT and VMAT along with IGRT for patient positioning. The aim is to effectively treat tumors while limiting the dose to healthy organs. In our work, we use the GATE Monte Carlo simulation platform to model a LINAC for a 6 MV photon beam. The resulting model is then validated with a dosimetric study by calculating relevant parameters for the beam quality. The LINAC model is then used for simulating clinical IMRT treatment plans in the ORL domain. Simulation results are compared with experimental measurements. We also explored the possibility of modeling the LINAC portal imaging system. This technique referred to as MV-CBCT combine the LINAC source with a flat panel detector to acquire 3D images of the patient. This part was validated first by acquiring 2D projections on patient and anthropomorphic phantom, and by reconstructing 3D volumes. Here again, validation was performed by comparing simulated and actual images. As a second step, a dosimetric validation was done by evaluating the dose deposited by IMRT beams, by means of portal signal only. We show in the present work the ability of GATE to perform complex IMRT treatments and portal images as they are performed routinely for dosimetric quality control. (author) [fr

The Quality Control of Intensity Modulated Radiation Therapy (IMRT for ONCOR Siemens Linear Accelerators Using Film Dosimetry

Directory of Open Access Journals (Sweden)

Keyvan Jabbari

2012-03-01

Full Text Available Introduction Intensity Modulated Radiation Therapy (IMRT has made a significant progress in radiation therapy centers in recent years. In this method, each radiation beam is divided into many subfields that create a field with a modulated intensity. Considering the complexity of this method, the quality control for IMRT is a topic of interest for researchers. This article is about the various steps of planning and quality control of Siemens linear accelerators for IMRT, using film dosimetry. This article in addition to review of the techniques, discusses the details of experiments and possible sources of errors which are not mentioned in the protocols and other references. Materials and Methods This project was carried out in Isfahan Milad hospital which has two Siemens ONCOR linear accelerators. Both accelerators are equipped with Multi-Leaf Collimators (MLC which enables us to perform IMRT delivery in the step-and-shoot method. The quality control consists of various experiments related to the sections of radiation therapy. In these experiments, the accuracy of some components such as treatment planning system, imaging device (CT, MLC, control system of accelerator, and stability of the output are evaluated. The dose verification is performed using film dosimetry method. The films were KODAK-EDR2, which were calibrated before the experiments. One of the important steps is the comparison of the calculated dose with planning system and the measured dose in experiments. Results The results of the experiments in various steps have been acceptable according to the standard protocols. The calibration of MLC and evaluation of the leakage through the leaves of MLC was performed by using the film dosimetry and visual check. In comparison with calculated and measured dose, more that 80% of the points have to be in agreement within 3% of the value. In our experiments, between 85 and 90% of the points had such an agreement with IMRT delivery. Conclusion