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Sample records for multileaf collimator hd-mlc

  1. Multileaf collimator in radiotherapy

    International Nuclear Information System (INIS)

    Jeraj, M.; Robar, V.

    2004-01-01

    Background. Basic goal of radiotherapy treatment is the irradiation of a target volume while minimizing the amount of radiation absorbed in healthy tissue. Shaping the beam is an important way of minimizing the absorbed dose in healthy tissue and critical structures. Conventional collimator jaws are used for shaping a rectangular treatment field; but, as usually treatment volume is not rectangular, additional shaping is required. On a linear accelerator, lead blocks or individually made Cerroben TM blocks are attached onto the treatment head under standard collimating system. Another option is the use of multileaf collimator (MLC). Conclusions. Multileaf collimator is becoming the main tool for beam shaping on the linear accelerator. It is a simple and useful system in the preparation and performance of radiotherapy treatment. Multileaf collimators are reliable, as their manufacturers developed various mechanisms for their precision, control and reliability, together with reduction of leakage and transmission of radiation between and through the leaves. Multileaf collimator is known today as a very useful clinical system for simple field shaping, but its use is getting even more important in dynamic radiotherapy, with the leaves moving during irradiation. This enables a precise dose delivery on any part of a treated volume. Intensity modulated radiotherapy (IMRT), the therapy of the future, is based on the dynamic use of MLC. (author)

  2. Multileaf collimator and related apparatus

    International Nuclear Information System (INIS)

    Brown, K.J.

    1989-01-01

    In radiotherapy apparatus using a multileaf collimator, the adjustment positions of the individual leaves can be determined optically by means of a video camera which observes the leaves via a radiation transparent mirror in the beam path. In order to overcome problems of low contrast and varying object brightness, the improvement comprises adding retroreflectors to the collimator leaves whose positions are known relative to the inner edge of the respective leaf. The retroreflectors can extend along the length of the leaf or they can be small. For setting up, corresponding manually adjustable optical diaphragm leaves can be used to project an optical simulation of the treatment area onto the patient, retroreflectors being similarly located relative to the shadow-casting edge of the leaves. (author)

  3. Characterization of a multileaf collimator system

    International Nuclear Information System (INIS)

    Galvin, J.M.; Smith, A.R.; Lally, B.

    1993-01-01

    Commissioning measurements for a multileaf collimator installed on a dual energy accelerator with 6 and 15 MV photons are described. Detailed dosimetric characterization of the multileaf collimator is a requirement for modeling the collimator with treatment planning software. Measurements include a determination of the penumbra width, leaf transmission, between-leaf leakage, and localization of the leaf ends and sides. Standard radiographic film was used for the penumbra measurements, and separate experiments using radiochromic film and thermoluminescent dosimeters were performed to verify that distortions of the dose distribution at an edge due to changing energy sensitivity of silver bromide film are negligible. Films were analyzed with a scanning laser densitometer with a 210 micron spot. Little change in the penumbra edge distribution was noted for different positions of a leaf in the field. Experiments localizing the physical end of the leaves showed less than 1 mm deviation from the 50% decrement line. This small difference is attributed to the shaped end on the leaves. One side of a single leaf corresponded to the 50% decrement line, but the opposite face was aligned with a lower value. This difference is due to the tongue and groove used to decrease between-leaf leakage. For both energies, approximately 2% of photons incident on the multileaf collimator are transmitted and an additional 0.5% leakage occurs between the leaves. Alignment of the leaves to form a straight edge results in a penumbra profile which compares favorably with the standard technique of using alloy blocks. When the edge is stepped, the isodose lines follow the leaf pattern and the boundary is poorly defined compared to divergent blocks. 19 refs., 13 figs

  4. Dynamic and quasi-dynamic multileaf collimation

    International Nuclear Information System (INIS)

    Bortfeld, T.

    1995-01-01

    Several recent investigations deal with the problem of how to produce arbitrary two-dimensional x-ray fluence distributions by means of a multileaf collimator (MLC), an approach, which could be called multileaf modulation. The goal of this approach is to facilitate the delivery of compensated or intensity-modulated fields. The present work gives an overview of these developments. The hardware requirements on MLCs for this special application are specified. Most commercially available MLCs fulfill these requirement sufficiently, however, the MLC control software is generally not capable of controlling an MLC dynamically. There is also the question of how to verify the dynamic movement of the leaves. Some minimum requirements on a control software suitable for application in clinical practice are therefore specified. An alternative, the stepwise or 'quasi-dynamic' movement of the MLC-leaves, is also discussed with respect to practicality. In this case the control is easier, but the demands on the stability of the accelerator for small dose deliveries are higher. Nevertheless, it can be expected that, for reasons of ease of control and verification, the quasi-dynamic technique will become the method of choice in the near future, while the slightly more effective fully dynamic technique will become available later in the future. In any case, multileaf modulation is an interesting and important alternative to the tomotherapy-concept

  5. Leaf sequencing algorithms for segmented multileaf collimation

    International Nuclear Information System (INIS)

    Kamath, Srijit; Sahni, Sartaj; Li, Jonathan; Palta, Jatinder; Ranka, Sanjay

    2003-01-01

    The delivery of intensity-modulated radiation therapy (IMRT) with a multileaf collimator (MLC) requires the conversion of a radiation fluence map into a leaf sequence file that controls the movement of the MLC during radiation delivery. It is imperative that the fluence map delivered using the leaf sequence file is as close as possible to the fluence map generated by the dose optimization algorithm, while satisfying hardware constraints of the delivery system. Optimization of the leaf sequencing algorithm has been the subject of several recent investigations. In this work, we present a systematic study of the optimization of leaf sequencing algorithms for segmental multileaf collimator beam delivery and provide rigorous mathematical proofs of optimized leaf sequence settings in terms of monitor unit (MU) efficiency under most common leaf movement constraints that include minimum leaf separation constraint and leaf interdigitation constraint. Our analytical analysis shows that leaf sequencing based on unidirectional movement of the MLC leaves is as MU efficient as bidirectional movement of the MLC leaves

  6. Leaf sequencing algorithms for segmented multileaf collimation

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, Srijit [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States); Sahni, Sartaj [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States); Li, Jonathan [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Palta, Jatinder [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Ranka, Sanjay [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States)

    2003-02-07

    The delivery of intensity-modulated radiation therapy (IMRT) with a multileaf collimator (MLC) requires the conversion of a radiation fluence map into a leaf sequence file that controls the movement of the MLC during radiation delivery. It is imperative that the fluence map delivered using the leaf sequence file is as close as possible to the fluence map generated by the dose optimization algorithm, while satisfying hardware constraints of the delivery system. Optimization of the leaf sequencing algorithm has been the subject of several recent investigations. In this work, we present a systematic study of the optimization of leaf sequencing algorithms for segmental multileaf collimator beam delivery and provide rigorous mathematical proofs of optimized leaf sequence settings in terms of monitor unit (MU) efficiency under most common leaf movement constraints that include minimum leaf separation constraint and leaf interdigitation constraint. Our analytical analysis shows that leaf sequencing based on unidirectional movement of the MLC leaves is as MU efficient as bidirectional movement of the MLC leaves.

  7. A multileaf collimator field prescription preparation system for conventional radiotherapy

    International Nuclear Information System (INIS)

    Du, M.N.; Yu, C. X.; Symons, M.; Yan, D.; Taylor, R.; Matter, R.C.; Gustafson, G.; Martinez, A.; Wong, J.W.

    1995-01-01

    Purpose: The purpose of this work is to develop a prescription preparation system for efficient field shaping using a multileaf collimator that can be used in community settings as well as research institutions. The efficiency advantage of the computer-controlled multileaf collimator, over cerrobend blocks, to shape radiation fields has been shown in conformal treatments, which typically require complete volumetric computerized tomographic data for three-dimensional radiation treatment planning--a utility not readily available to the general community. As a result, most patients today are treated with conventional radiation therapy. Therefore, we believe that it is very important to fully use the same efficiency advantage of multileaf collimator as a block replacement in conventional practice. Methods and Material: The multileaf collimator prescription preparation system developed by us acquires prescription images from different sources, including film scanner and radiation treatment planning systems. The multileaf collimator angle and leaf positions are set from the desired field contour defined on the prescription image, by minimizing the area discrepancies. Interactive graphical tools include manual adjustment of collimator angle and leaf positions, and definition of portions of the field edges that require maximal conformation. Data files of the final leaf positions are transferred to the multileaf collimator controller via a dedicated communication link. Results: We have implemented the field prescription preparation system and a network model for integrating the multileaf collimator and other radiotherapy modalities for routine treatments. For routine plan evaluation, isodose contours measured with film in solid water phantom at prescription depth are overlaid on the prescription image. Preliminary study indicates that the efficiency advantage of the MLC over cerrobend blocks in conformal therapy also holds true for conventional treatments. Conclusion: Our

  8. Segmented abutting fields irradiation using multileaf collimators

    International Nuclear Information System (INIS)

    Nishimura, Tetsuo

    1998-01-01

    The object of this study is to evaluate the clinical feasibility of segmented abutting fields irradiation (SAFI) using multileaf collimators (MLCs), in which the target volume is divided into several segments to create complex irregular field without use of alloy blocks. A linear accelerator with 26 pairs of roundly ended MLCs of 1 cm in width was tested in this study. In SAFI, radiation leakage occurs at the abutment sites with these MLCs. Film dosimetry was used to determine the optimal length of the MLC overlap to minimize dose profile variation in abutting fields. A mantle field was investigated as a clinical application. Without overlapping the MLCs, radiation leakage at the abutments appeared as a peak of the dose profile. With more overlapping, the profile exhibited a minimized variation with a two-peak pattern. With excessive overlapping, the peak was reversed due to decreased dose. Variation of the profile was minimized with an overlap of 2.0-2.2 mm. The level of variation and the optimal length of overlap were found to be independent of the sites of measurement. Reproducibility was confirmed by repeated measurements. With the mantle field, SAFI using MLCs revealed an profile equivalent to use of alloy blocking fields in all respects other than the variations at the abutting sites. If the length of the MLC abutment overlap differs by site, clinical application of SAFI using MLCs would be quite complicated. The optimal length of the overlap was found to be 2.0 mm and to be independent of the sites of abutment. Therefore, we conclude that SAFI using MLCs of 1 cm in width is feasible for clinical use. (author)

  9. Implementation of intensity modulation with dynamic multileaf collimation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, J W; Yu, C; Jaffray, D [William Beaumont Hospital, Royal Oak, MI (United States)

    1995-12-01

    The computer-controlled multileaf collimator (MLC) marks one of the most important advances in radiation therapy. The device efficiently replaces manual blocking to shape fields and can be used to modulate beam intensity. The results of a research programme at William Beaumont Hospital, aimed at bringing dynamic intensity modulation into clinical use, are discussed.

  10. Evaluation of the penumbras of a Philips multileaf collimator

    International Nuclear Information System (INIS)

    Lafay, F.; Malet, C.; Mombard, C.; Ginestet, C.; Blondel, E.; Desfarges, Y.; Dupin, G.

    1995-01-01

    Since January 1995, a Philips SL20 linear accelerator which is connected to a multileaf collimator has been used. Computer-controlled multileaf collimators open up the opportunity to practice conformal radiotherapy. Its aim is to adjust as well as possible the Planning Target Volume (PTV) to the effective treated volume with an homogeneous dose distribution in the PTV, and to protect healthy tissues and delicate organs. This is possible by means of a multileaf collimator by increasing the number of complex fields with different incidences during a same session. Moreover, the Beam's Eye View function of the three-dimensional treatment planning system allows to define the shape of complex fields. For rectangular fields, the penumbra is defined by the distance between the 80% and 20% isodoses relative to the beam axis. In addition, the distances between, respectively, the 95% and 50% isodoses, the 90% and 50% isodoses, the 50% and 20% isodoses relative to the beam axis have been analysed. Different penumbras were evaluated. The result of this work will enable to adjust the reference isodose to the PTV either by integrating this result into dosimetry software, or by taking it into account for drawing the PTV

  11. Algorithms for optimal sequencing of dynamic multileaf collimators

    International Nuclear Information System (INIS)

    Kamath, Srijit; Sahni, Sartaj; Palta, Jatinder; Ranka, Sanjay

    2004-01-01

    Dynamic multileaf collimator (DMLC) intensity modulated radiation therapy (IMRT) is used to deliver intensity modulated beams using a multileaf collimator (MLC), with the leaves in motion. DMLC-IMRT requires the conversion of a radiation intensity map into a leaf sequence file that controls the movement of the MLC while the beam is on. It is imperative that the intensity map delivered using the leaf sequence file be as close as possible to the intensity map generated by the dose optimization algorithm, while satisfying hardware constraints of the delivery system. Optimization of the leaf-sequencing algorithm has been the subject of several recent investigations. In this work, we present a systematic study of the optimization of leaf-sequencing algorithms for dynamic multileaf collimator beam delivery and provide rigorous mathematical proofs of optimized leaf sequence settings in terms of monitor unit (MU) efficiency under the most common leaf movement constraints that include leaf interdigitation constraint. Our analytical analysis shows that leaf sequencing based on unidirectional movement of the MLC leaves is as MU efficient as bi-directional movement of the MLC leaves

  12. Clinical use of a simulation-multileaf collimator

    International Nuclear Information System (INIS)

    Marx, M.; Vacha, P.; Riis, B.; Feyerabend, T.; Richter, E.

    1998-01-01

    Background: At the University of Luebeck, radiotherapy is delivered by a 6/18-MV linear accelerator. Using the integrated multileaf collimator, irradiation of individually shaped treatment fields is possible in place of alloy blocks. Due to unsatisfactory pretherapeutic review of the radiation-field-specific multileaf collimator (MLC) configuration, we developed a simulation-multileaf collimator (SMLC) and assessed its feasibility at different tumor sites. Material and Methods: The SMLC is made of a perspex carrier with 52 horizontal sliding leaves. The position of each leaf is calculated by a 3D treatment-planning computer. The technician manually adjusts the leaves according to the beams-eye-view plot of the planning computer. Consequently, the SMLC is mounted on the therapy simulator at a distance of 64.8 cm from the focus. The treatment fields and the position of the leaves are documented by X-ray films. Results: Using the SMLC, radiation oncologists are able to review exactly the leaf configuration of each MLC-shaped radiation field and to correlate the MLC-shaped radiation field with the treated volume, the organs at risk and the port films acquired by the Portal Vision trademark system. Conclusion: The SMLC is a new tool to review radiation planning that uses an MLC in daily routine. The use of the SMLC improves the documentation and the quality assurance. It accelerates the treatment field review at the linear accelerator by comparing the SMLC simulator films with the portal images. (orig.) [de

  13. Algorithms for optimal sequencing of dynamic multileaf collimators

    Energy Technology Data Exchange (ETDEWEB)

    Kamath, Srijit [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States); Sahni, Sartaj [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States); Palta, Jatinder [Department of Radiation Oncology, University of Florida, Gainesville, FL (United States); Ranka, Sanjay [Department of Computer and Information Science and Engineering, University of Florida, Gainesville, FL (United States)

    2004-01-07

    Dynamic multileaf collimator (DMLC) intensity modulated radiation therapy (IMRT) is used to deliver intensity modulated beams using a multileaf collimator (MLC), with the leaves in motion. DMLC-IMRT requires the conversion of a radiation intensity map into a leaf sequence file that controls the movement of the MLC while the beam is on. It is imperative that the intensity map delivered using the leaf sequence file be as close as possible to the intensity map generated by the dose optimization algorithm, while satisfying hardware constraints of the delivery system. Optimization of the leaf-sequencing algorithm has been the subject of several recent investigations. In this work, we present a systematic study of the optimization of leaf-sequencing algorithms for dynamic multileaf collimator beam delivery and provide rigorous mathematical proofs of optimized leaf sequence settings in terms of monitor unit (MU) efficiency under the most common leaf movement constraints that include leaf interdigitation constraint. Our analytical analysis shows that leaf sequencing based on unidirectional movement of the MLC leaves is as MU efficient as bi-directional movement of the MLC leaves.

  14. Evaluation of the penumbras of a Philips multileaf collimator

    Energy Technology Data Exchange (ETDEWEB)

    Lafay, F; Malet, C; Mombard, C; Ginestet, C [Centre de Lutte Contre le Cancer Leon-Berard, 69 - Lyon (France); Blondel, E [Isotec, Saint-Quentin (France); Desfarges, Y; Dupin, G [Philips Medical System, Lyon (France)

    1995-12-01

    Since January 1995, a Philips SL20 linear accelerator which is connected to a multileaf collimator has been used. Computer-controlled multileaf collimators open up the opportunity to practice conformal radiotherapy. Its aim is to adjust as well as possible the Planning Target Volume (PTV) to the effective treated volume with an homogeneous dose distribution in the PTV, and to protect healthy tissues and delicate organs. This is possible by means of a multileaf collimator by increasing the number of complex fields with different incidences during a same session. Moreover, the Beam`s Eye View function of the three-dimensional treatment planning system allows to define the shape of complex fields. For rectangular fields, the penumbra is defined by the distance between the 80% and 20% isodoses relative to the beam axis. In addition, the distances between, respectively, the 95% and 50% isodoses, the 90% and 50% isodoses, the 50% and 20% isodoses relative to the beam axis have been analysed. Different penumbras were evaluated. The result of this work will enable to adjust the reference isodose to the PTV either by integrating this result into dosimetry software, or by taking it into account for drawing the PTV.

  15. Independent checks of linear accelerators equipped with multileaf collimators

    International Nuclear Information System (INIS)

    Pavlikova, I.; Ekendahl, D.; Horakova, I.

    2005-01-01

    National Radiation Protection Institute (NRPI) provides independent checks of therapeutic equipment as a part of state supervision. In the end of 2003, the audit was broaden for linear accelerators equipped with multileaf collimators (MLC). NRPI provides TLD postal audits and on-site independent checks. This contribution describes tests for multileaf collimators and intensity modulated radiation therapy (IMRT) technique that are accomplished within the independent on-site check of linear accelerators. The character and type of tests that are necessary to pursue for multileaf collimator depends on application technique. There are three basic application of the MLC. The first we call 'static MLC' and it serves for replacing conventional blocking or for adjusting the field shape to match the beam's-eye view projection of a planning target volume during an arc rotation of the x-ray beam. This procedure is called conformal radiotherapy. The most advanced technique with MLC is intensity modulated radiation therapy. The dose can be delivered to the patient with IMRT in various different ways: dynamic MLC, segmented MLC and IMRT arc therapy. Independent audits represent an important instrument of quality assurance. Methodology for independent check of static MLC was successfully verified on two types of accelerators: Varian and Elekta. Results from pilot measurements with dynamic MLC imply that the methodology is applicable for Varian accelerators. In the future, the experience with other types of linear accelerators will contribute to renovation, modification, and broaden independent checks methodology. (authors)

  16. Clinical use of a simulation-multileaf collimator

    Energy Technology Data Exchange (ETDEWEB)

    Marx, M; Vacha, P; Riis, B; Feyerabend, T; Richter, E [Medizinische Univ., Luebeck (Germany). Klinik fuer Strahlentherapie und Nuklearmedizin

    1998-07-01

    Background: At the University of Luebeck, radiotherapy is delivered by a 6/18-MV linear accelerator. Using the integrated multileaf collimator, irradiation of individually shaped treatment fields is possible in place of alloy blocks. Due to unsatisfactory pretherapeutic review of the radiation-field-specific multileaf collimator (MLC) configuration, we developed a simulation-multileaf collimator (SMLC) and assessed its feasibility at different tumor sites. Material and Methods: The SMLC is made of a perspex carrier with 52 horizontal sliding leaves. The position of each leaf is calculated by a 3D treatment-planning computer. The technician manually adjusts the leaves according to the beams-eye-view plot of the planning computer. Consequently, the SMLC is mounted on the therapy simulator at a distance of 64.8 cm from the focus. The treatment fields and the position of the leaves are documented by X-ray films. Results: Using the SMLC, radiation oncologists are able to review exactly the leaf configuration of each MLC-shaped radiation field and to correlate the MLC-shaped radiation field with the treated volume, the organs at risk and the port films acquired by the Portal Vision {sup trademark} system. Conclusion: The SMLC is a new tool to review radiation planning that uses an MLC in daily routine. The use of the SMLC improves the documentation and the quality assurance. It accelerates the treatment field review at the linear accelerator by comparing the SMLC simulator films with the portal images. (orig.) [Deutsch] Hintergrund: Seit 1994 werden Patienten an der Luebecker Universitaetsklinik fuer Strahlentherapie und Nuklearmedizin an einem Linearbeschleuniger bestrahlt, der mit einem Multileaf-Kollimator ausgeruestet ist. Dieser ermoeglicht die Bestrahlung individuell geformter Zielvolumina ohne gegossene Individualsatelliten. Wegen der unzureichenden praetherapeutischen Kontrolle der Lamellenkonfiguration des Multileaf-Kollimators wurde ein Simulations-Multileaf

  17. Execution of mantle field with multileaf collimator: A simple approach

    Directory of Open Access Journals (Sweden)

    Prabhakar Ramachandran

    2008-01-01

    Full Text Available Background: Until very recently mantle field radiotherapy remained the gold standard for the treatment of favorable early-stage Hodgkin′s lymphoma. The classic mantle includes all the major lymph nodes above the diaphragm and extends from the inferior portion of the mandible to the level of the insertion of the diaphragm. Aims: To describe a simple technique that has been devised to treat the mantle field with the help of multileaf collimator and using computed tomography (CT-based treatment planning. Materials and Methods: CT scan was performed with the patient in the supine position and the datasets were transferred to the Eclipse™ treatment planning system. Elekta Precise™ linear accelerator equipped with 40 pairs of multileaf collimator (MLC was used for the execution of the mantle field. The MLC′s shapes were designed to take the shape of the conventional customized blocks used for treatment of mantle field. The anterior mantle field was divided into three separate MLC segments with the collimator kept at 0°. The first MLC segment was shaped to cover the neck, clavicular regions, and mediastinum. The second and the third MLC segments covered the right and left axilla, respectively. The posterior fields were opposed to the anterior subfields in a similar fashion. The dose was prescribed at the midplane, using reference points. Results and Conclusion: The technique described in this study is very simple, easy to implement, and avoids unnecessary delay in the execution of the mantle field. The mantle field can be easily shaped with the multileaf collimators, without any collimator rotation.

  18. Clinical significance of multi-leaf collimator calibration errors

    International Nuclear Information System (INIS)

    Norvill, Craig; Jenetsky, Guy

    2016-01-01

    This planning study investigates the clinical impact of multi-leaf collimator (MLC) calibration errors on three common treatment sites; head and neck (H&N), prostate and stereotactic body radiotherapy (SBRT) for lung. All plans used using either volumetric modulated adaptive therapy or dynamic MLC techniques. Five patient plans were retrospectively selected from each treatment site, and MLC errors intentionally introduced. MLC errors of 0.7, 0.4 and 0.2 mm were sufficient to cause major violations in the PTV planning criteria for the H&N, prostate and SBRT lung plans. Mean PTV dose followed a linear trend with MLC error, increasing at rates of 3.2–5.9 % per millimeter depending on treatment site. The results indicate that an MLC quality assurance program that provides sub-millimeter accuracy is an important component of intensity modulated radiotherapy delivery techniques.

  19. A proposal for quality assurance of multi-leaf collimators

    International Nuclear Information System (INIS)

    Hounsell, A R; Jordan, T J; Williams, P C

    1995-01-01

    Multi-leaf collimators (MLC's) are rapidly entering clinical service in many Institutes through-out the World. Commercial MLC's are reliable but highly complex devices that have new and sometimes complex maintenance and quality assurance (QA) requirements. The experience gained from installing the prototype Philips MLC and from using and maintaining two production model Philips MLC's - one four years old, one six months old - will be used to define the requirements of a QA schedule for MLC's. Problems specific to MLC's such as leaf positioning and radiation leakage between the leaves will be discussed and methods for measuring these problems presented. Recommendations for the frequency for performing these checks based on our experiences will be made. Preventative maintenance times, machine down times due to the MLC and planned Quality Control down times will be reported

  20. Optimized procedure for calibration and verification multileaf collimator from Elekta Synergy accelerator

    International Nuclear Information System (INIS)

    Castel Millan, A.; Perellezo Mazon, A.; Fernandez Ibiza, J.; Arnalte Olloquequi, M.; Armengol Martinez, S.; Rodriguez Rey, A.; Guedea Edo, F.

    2011-01-01

    The objective of this work is to design an optimized procedure for calibration and verification of a multileaf collimator used so as to allow the EPID and the image plate in a complementary way, using different processing systems. With this procedure we have two equivalent alternative as the same parameters obtained for the calibration of multileaf Elekta Synergy accelerator.

  1. Quality control program of multi-leaf collimation based EPID for teams with Rapidarc

    International Nuclear Information System (INIS)

    Pujades Claumarchirant, M. C.; Richart Sancho, J.; Gimeno Olmos, J.; Lliso Valverde, F.; Carmona Mesenguer, V.; Garcia Martinez, M. T.; Palomo Llinares, R.; Ballester Pallares, F.; Perez Calatayud, J.

    2013-01-01

    The objective of this work is to show a collection of different recommendations on the control of quality of collimation multi-leaf system and present the selection of tests based on the electronic imaging device (EPID) portal that have decided to establish in our Center, where in addition to the requirements of quality assurance generic for collimation multi-leaf system quality control methods have been included for RapidArc. (Author)

  2. Optimized dose conformation of multi-leaf collimator fields

    International Nuclear Information System (INIS)

    Serago, Christopher F.; Buskirk, Steven J.; Foo, May L.; McLaughlin, Mark P.

    1996-01-01

    Purpose/Objective: Current commercially available multi-leaf collimators (MLC) have leaf widths of about 1 cm. These leaf widths may produce stepped dose gradients at the fields edges at the 50% dose level. Small local perturbations of the dose distribution from the prescribed/expected dose distribution may not be acceptable for some clinical applications. Improvements to the conformation of the MLC dose distribution may be achieved using multiple exposures per MLC field, with either shifting the table/patient position, or rotating the orientation of the MLC jaws between exposures. Material and Methods: Dose distributions for MLC, primary jaws only, and lead alloy block fields were measured with film dosimetry for 6 and 20 MV photon beams in a solid water phantom. Square, circular, and typical clinical prostate, brain, lung, esophagus, and head and neck fields were measured. MLC field shapes were produced using a commercial MLC with a leaf width of 1 cm at the treatment isocenter. The dose per MLC field was delivered in either single (conventional) or multiple exposures. The table(patient) position or the collimator rotation was shifted between exposures when multiple exposure MLC fields were used. Differences in the dose distribution were evaluated at the 90% and 50% isodose level. Displacements of the measured 50% isodose from the prescribed/expected 50% isodose were measured at 5 degree intervals. Results: Measurements of the penumbra at a 10 cm depth for square fields show that using double exposure MLC fields with .5 cm table index decreases the effective penumbra by 1 mm. For clinical shaped fields, displacements between the prescribed/expected 50% isodose and the measured 50% isodose for conventional single exposure MLC fields are measured to be as great as 9 mm, and discrepancies on the order of 5 to 6 mm are common. In contrast, the maximum displacement errors measured with multiple exposure MLC fields are less than 5 mm and rarely more than 4 mm. In some

  3. Multileaf Collimator Characteristics and Reliability Requirements for IMRT Elekta System

    International Nuclear Information System (INIS)

    Liu, Chihray; Simon, Thomas A.; Fox, Christopher; Li, Jonathan; Palta, Jatinder R.

    2008-01-01

    Understanding the characteristics of a multileaf collimator (MLC) system, modeling MLC in a treatment planning system, and maintaining the mechanical accuracy of the linear accelerator gantry head system are important factors in the safe implementation of an intensity-modulated radiotherapy program. We review the characteristics of an Elekta MLC system, discuss the necessary MLC modeling parameters for a treatment planning system, and provide a novel method to establish an MLC leaf position quality assurance program. To perform quality assurance on 40 pairs of individual MLC leaves is a time-consuming and difficult task. In this report, an effective routine MLC quality assurance method based on the field edge of a backup jaw as referenced in conjunction with a diode array as a radiation detector system is discussed. The sensitivity of this test for determining the relative leaf positions was observed to be better than 0.1 mm. The Elekta MLC leaf position accuracy measured with this system has been better than 0.3 mm

  4. Multileaf collimator characteristics and reliability requirements for IMRT Elekta system.

    Science.gov (United States)

    Liu, Chihray; Simon, Thomas A; Fox, Christopher; Li, Jonathan; Palta, Jatinder R

    2008-01-01

    Understanding the characteristics of a multileaf collimator (MLC) system, modeling MLC in a treatment planning system, and maintaining the mechanical accuracy of the linear accelerator gantry head system are important factors in the safe implementation of an intensity-modulated radiotherapy program. We review the characteristics of an Elekta MLC system, discuss the necessary MLC modeling parameters for a treatment planning system, and provide a novel method to establish an MLC leaf position quality assurance program. To perform quality assurance on 40 pairs of individual MLC leaves is a time-consuming and difficult task. In this report, an effective routine MLC quality assurance method based on the field edge of a backup jaw as referenced in conjunction with a diode array as a radiation detector system is discussed. The sensitivity of this test for determining the relative leaf positions was observed to be better than 0.1 mm. The Elekta MLC leaf position accuracy measured with this system has been better than 0.3 mm.

  5. Methodology for Multileaf Collimator Quality Assurance in clinical conditions

    International Nuclear Information System (INIS)

    Diaz M, R. M.; Rodriguez Z, M.; Juarez D, A.; Romero R, R.

    2013-01-01

    Multileaf Collimators (MLCs) have become an important technological advance as part of clinical linear accelerators (linacs) for radiotherapy. Treatment planning and delivery were substantially modified after these devices. However, it was needed to develop Quality Assurance (QA) methodologies related to the performance of these developments. The most common methods for QA of MLC are made in basic conditions that hardly cover all possible difficulties in clinical practice. Diaz et. el. developed a methodology based upon volumetric detectors bidimensional arrays that can be extended to more demanding situations. In this work, the Auril methodology of Diaz et. al. was implemented to the irradiation with the linac gantry in horizontal position. A mathematical procedure was developed to ease the dosimetric centering of the device with the Auril centering tool. System calibration was made as in the typical Auril methodology. Patterns with leaf misplacements in known positions were irradiated. the method allowed the detection of leafs' misplacements with a minimum number of false positives. We concluded that Auril methodology can be applied in clinical conditions. (Author)

  6. High-resolution field shaping utilizing a masked multileaf collimator.

    Science.gov (United States)

    Williams, P C; Cooper, P

    2000-08-01

    Multileaf collimators (MLCs) have become an important tool in the modern radiotherapy department. However, the current limit of resolution (1 cm at isocentre) can be too coarse for acceptable shielding of all fields. A number of mini- and micro-MLCs have been developed, with thinner leaves to achieve approved resolution. Currently however, such devices are limited to modest field sizes and stereotactic applications. This paper proposes a new method of high-resolution beam collimation by use of a tertiary grid collimator situated below the conventional MLC. The width of each slit in the grid is a submultiple of the MLC width. A composite shaped field is thus built up from a series of subfields, with the main MLC defining the length of each strip within each subfield. Presented here are initial findings using a prototype device. The beam uniformity achievable with such a device was examined by measuring transmission profiles through the grid using a diode. Profiles thus measured were then copied and superposed to generate composite beams, from which the uniformity achievable could be assessed. With the average dose across the profile normalized to 100%, hot spots up to 5.0% and troughs of 3% were identified for a composite beam of 2 x 5.0 mm grids, as measured at Dmax for a 6 MV beam. For a beam composed from 4 x 2.5 mm grids, the maximum across the profile was 3.0% above the average, and the minimum 2.5% below. Actual composite profiles were also formed using the integrating properties of film, with the subfield indexing performed using an engineering positioning stage. The beam uniformity for these fields compared well with that achieved in theory using the diode measurements. Finally sine wave patterns were generated to demonstrate the potential improvements in field shaping and conformity using this device as opposed to the conventional MLC alone. The scalloping effect on the field edge commonly seen on MLC fields was appreciably reduced by use of 2 x 5.0 mm

  7. Testing of dynamic multileaf collimator by dynamic log file

    International Nuclear Information System (INIS)

    Ono, Kaoru; Nakamura, Tetsuji; Yamato, Shinichirou; Miyazawa, Masanori

    2007-01-01

    Intensity-modulated radiation therapy (IMRT) represents one of the most significant technical advances in radiation therapy. In the dynamic multileaf collimator (MLC) method of IMRT delivery, because of the relatively small gaps between opposed leaves and because most regions are shielded by leaves most of the time, the delivered dose is very sensitive to MLC leaf positional accuracy. A variation of ±0.2 mm in the gap width can result in a dose variation of ±3% for each clinical dynamic MLC field. Most often the effects of leaf motion are inferred from dose deviations on film or from variations in ionization measurements. These techniques provide dosimetric information but do not provide detailed information for diagnosing delivery problems. Therefore, a dynamic log file (Dynalog file) was used to verify dynamic MLC leaf positional accuracy. Measuring for narrow gaps using the thickness gauge could detect a log file accuracy of approximately 0.1 mm. The accuracy of dynamic MLC delivery depends on the accuracy with which the velocity of each leaf is controlled. We studied the relationship between leaf positional accuracy and leaf velocity. Leaf velocity of 0.7 cm/sec caused approximately 0.2 mm leaf positional variation. We then analyzed leaf positional accuracy for the clinical dynamic MLC field using Dynalog File Viewer (Varian Medical Systems, Inc., Palo Alto, California (CA)), and developed a new program that can analyze more detailed leaf motions. Using this program, we can obtain more detailed information, and therefore can determine the source of dose uncertainties for the dynamic MLC field. (author)

  8. Modification of a three-dimensional treatment planning system for the use of multi-leaf collimators in conformation radiotherapy

    International Nuclear Information System (INIS)

    Boesecke, R.; Becker, G.; Alandt, K.; Pastyr, O.; Doll, J.; Schlegel, W.; Lorenz, W.J.

    1991-01-01

    The multi-leaf collimator of the DKFZ is designed as a low cost add-on device for conventional linear accelerators for radiotherapy. The technical specification of the computer controlled collimator is briefly described . A major limitation in the use of the wide capabilities of multi-leaf collimators in the clinic is still an appropriate treatment planning system. This paper describes treatment planning and dose calculation techniques for multi-leaf collimators and shows examples where the capabilities of the collimators are used extensively. (author). 18 refs.; 8 figs.; 2 tabs

  9. Technology assessment of multileaf collimation: a North American users survey

    International Nuclear Information System (INIS)

    Klein, Eric E.; Tepper, Joel; Sontag, Mark; Franklin, Michael; Ling, Clifton; Kubo, Dale

    1999-01-01

    Purpose: The American Association of Physicists in Medicine (AAPM) initiated an Assessment of Technology Subcommittee (ATS) to help the radiotherapy community evaluate emerging technologies. The ATS decided to first address multileaf collimation (MLC) by means of a North American users survey. The survey attempted to address issues such as MLC utility, efficacy, cost-effectiveness, and customer satisfaction. Methods and Materials: The survey was designed with 38 questions, with cross-tabulation set up to decipher a particular clinic's perception of MLC. The surveys were coded according to MLC types, which were narrowed to four: Elekta, Siemens, Varian 52-leaf, and Varian 80-leaf. A 40% return rate was desired. Results: A 44% (108 of 250) return was achieved. On an MLC machine, 76.5% of photon patients are being treated with MLC. The main reasons for not using MLC were stair stepping, field size limitation, and physician objection. The most common sites in which MLC is being used are lung, pelvis, and prostate. The least used sites are head and neck and mantle fields. Of the facilities, 31% claimed an increase in number of patients being treated since MLC was installed, and 44% claimed an increase in the number of fields. Though the staffing for block cutting has decreased, therapist staffing has not. However, 91% of the facilities claimed a decreased workload for the therapists, despite the increase in daily treated patients and fields. Of the facilities that justified MLC purchase for more daily patients, 63% are actually treating more patients. Only 26% of the facilities that justified an MLC purchase for intensity-modulated radiotherapy (IMRT) are currently using it for that purpose. The satisfaction rating (1 = low to 5 = high) for department groups averaged 4.0. Therapists ranked MLC as 4.6. Conclusions: Our survey shows that most users have successfully introduced MLC into the clinic as a block replacement. Most have found MLC to be cost-effective and

  10. Pitfalls of tungsten multileaf collimator in proton beam therapy

    Energy Technology Data Exchange (ETDEWEB)

    Moskvin, Vadim; Cheng, Chee-Wai; Das, Indra J. [Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202 (United States) and Indiana University Health Proton Therapy Center (Formerly Midwest Proton Radiotherapy Institute), Bloomington, Indiana 47408 (United States)

    2011-12-15

    Purpose: Particle beam therapy is associated with significant startup and operational cost. Multileaf collimator (MLC) provides an attractive option to improve the efficiency and reduce the treatment cost. A direct transfer of the MLC technology from external beam radiation therapy is intuitively straightforward to proton therapy. However, activation, neutron production, and the associated secondary cancer risk in proton beam should be an important consideration which is evaluated. Methods: Monte Carlo simulation with FLUKA particle transport code was applied in this study for a number of treatment models. The authors have performed a detailed study of the neutron generation, ambient dose equivalent [H*(10)], and activation of a typical tungsten MLC and compared with those obtained from a brass aperture used in a typical proton therapy system. Brass aperture and tungsten MLC were modeled by absorber blocks in this study, representing worst-case scenario of a fully closed collimator. Results: With a tungsten MLC, the secondary neutron dose to the patient is at least 1.5 times higher than that from a brass aperture. The H*(10) from a tungsten MLC at 10 cm downstream is about 22.3 mSv/Gy delivered to water phantom by noncollimated 200 MeV beam of 20 cm diameter compared to 14 mSv/Gy for the brass aperture. For a 30-fraction treatment course, the activity per unit volume in brass aperture reaches 5.3 x 10{sup 4} Bq cm{sup -3} at the end of the last treatment. The activity in brass decreases by a factor of 380 after 24 h, additional 6.2 times after 40 days of cooling, and is reduced to background level after 1 yr. Initial activity in tungsten after 30 days of treating 30 patients per day is about 3.4 times higher than in brass that decreases only by a factor of 2 after 40 days and accumulates to 1.2 x 10{sup 6} Bq cm{sup -3} after a full year of operation. The daily utilization of the MLC leads to buildup of activity with time. The overall activity continues to increase

  11. Multileaf collimator intercomparison for intensity modulated radiation therapy implementation

    International Nuclear Information System (INIS)

    Viteri, Juan Fernando Delgado

    2006-01-01

    In this work a dosimetric comparison between three multileaf collimator systems is presented: a Varian Millennium with 120 leaves, Brainlab mMLC m3 and Varian Mark II both with 52 leaves. The width projection at isocenter level in field's central region are: 0,5 cm; 0,35 cm and 1,0 cm respectively. Common dosimetric characteristics for the three systems in static mode and dynamic capabilities for the two first were compared. In dynamic mode, tests validating proper MLC function through film irradiation were done, such MLC stability, MU linearity, treatment interruptions sensitivity, stability of MLC in dynamic mode, leaf speed stability, were found within ±3% deviation in all cases. Dose rate linearity showed differences when this parameter decreases in dynamic mode. Average dose errors for fixed width gaps moving at constant speed were found to be proportional to gap errors and inversely proportional to the gap width. Output factors differences delivered through a sweeping gap were found less than ±1% when the gantry was in a lateral position. For the three MLC systems, when comparing beam profiles for the same field was observed that for mMLC presents the sharpest dose gradient region. In the output factors small differences where observed in every MLC system. Dosimetric leaf gap was determined for MLC 120, mMLC and MLC 52, obtained values for a 6 MV beam are: (0,202 ± 0,054) cm; (0,157 ± 0,070) cm and (0,189 ± 0,081) cm respectively. The transmission showed an increase with depth and field width for 6 MV in all the three systems. Average values obtained with ionization chamber for this energy were: (1,630 ± 0,018)% for MLC 120; (1,291 ± 0,029)% for mMLC and (1,638 ± 0,010)% for MLC 52. When obtained through film irradiation, inter and intra leaf transmission showed an off axis dependent behavior for MLC 120 and mMLC. Scatter produced by MLC as a 6 MV open reference field ratio was: (0,297 ± 0,024)% for MLC 120; (0,239 ± 0,052)% for mMLC and (0,202 ± 0

  12. Dose distributions of x-ray fields as shaped with multileaf collimators

    International Nuclear Information System (INIS)

    Zhu, Y.; Boyer, A.L.; Desobry, G.E.

    1992-01-01

    Multileaf collimators (MLC) with various blade widths were simulated using standard cerrobend blocks, and three-dimensional dose computations were carried out to study the resultant radiation field edges. The study suggests that multileaf collimation to the outside of the desired field edge will lead to overdose outside the field, whereas multileaf collimation to the inside of the desired field edge will lead to underdose inside the field. When the direction of travel of the leaves with respect to the field edge is near 45 o , the 50% isodose of a multileaf-collimated beam will fall close to the desired edge with no underdose when the leaf corners are allowed to insert into the desired field edge by 1.2 mm for 6 MV x-rays and 1.4 mm for 18 MV x-rays using a 1 cm wide leaf. These blade offsets account for the scattering of photons and electrons in the medium within the penumbral region. (author)

  13. Peripheral dose in photon beams from a linear accelerator with a multileaf collimator

    International Nuclear Information System (INIS)

    Lope Lope, R.; Lozano Flores, F.; Gracia Sorrosal, J.; Font Gomez, J.A.; Hernandez Vitoria, A.

    2001-01-01

    Radiation doses outside the radiotherapy treatment field are of radiation protection interest when anatomical structures with very low dose tolerances might be involved. One of the major sources of peripheral dose, scatter from secondary collimators, depends on the configuration of the collimator. In this study, peripheral dose was measured at two depths for 6 and 18 MV photons from a linac Primus (Siemens) with a multileaf collimator (MLC). Comparative measurements were made both with leaves and with the upper jaw positioned at the field edge near to the detector. Configuring the MLC leaves at the field edge yielded a reduction in peripheral dose. (author)

  14. Lateral Penumbra Modelling Based Leaf End Shape Optimization for Multileaf Collimator in Radiotherapy

    Directory of Open Access Journals (Sweden)

    Dong Zhou

    2016-01-01

    Full Text Available Lateral penumbra of multileaf collimator plays an important role in radiotherapy treatment planning. Growing evidence has revealed that, for a single-focused multileaf collimator, lateral penumbra width is leaf position dependent and largely attributed to the leaf end shape. In our study, an analytical method for leaf end induced lateral penumbra modelling is formulated using Tangent Secant Theory. Compared with Monte Carlo simulation and ray tracing algorithm, our model serves well the purpose of cost-efficient penumbra evaluation. Leaf ends represented in parametric forms of circular arc, elliptical arc, Bézier curve, and B-spline are implemented. With biobjective function of penumbra mean and variance introduced, genetic algorithm is carried out for approximating the Pareto frontier. Results show that for circular arc leaf end objective function is convex and convergence to optimal solution is guaranteed using gradient based iterative method. It is found that optimal leaf end in the shape of Bézier curve achieves minimal standard deviation, while using B-spline minimum of penumbra mean is obtained. For treatment modalities in clinical application, optimized leaf ends are in close agreement with actual shapes. Taken together, the method that we propose can provide insight into leaf end shape design of multileaf collimator.

  15. Development and validation of a BEAMnrc component module for a miniature multileaf collimator

    Science.gov (United States)

    Doerner, E.; Hartmann, G. H.

    2012-05-01

    A new component module (CM) named mini multileaf collimator (mMLC) was developed for the Monte Carlo code BEAMnrc. It models the geometry of the add-on miniature multileaf collimator ModuLeaf (MRC Systems GmbH, Heidelberg, Germany, now part of Siemens, Erlangen, Germany). The new CM is partly based on the existing CM called DYNVMLC. The development was performed using a modified EGSnrc platform which enables us to work in the Microsoft Visual Studio environment. In order to validate the new CM, the PRIMUS linac with 6 MV x-rays (Siemens OCS, Concord, CA, USA) equipped with the ModuLeaf mMLC was modelled. Validation was performed by two methods: (a) a ray-tracing method to check the correct geometry of the multileaf collimator (MLC) and (b) a comparison of calculated and measured results of the following dosimetrical parameters: output factors, dose profiles, field edge position penumbra, MLC interleaf leakage and transmission values. Excellent agreement was found for all parameters. It was, in particular, found that the relationship between leaf position and field edge depending on the shape of the leaf ends can be investigated with a higher accuracy by this new CM than by measurements demonstrating the usefulness of the new CM.

  16. Lateral Penumbra Modelling Based Leaf End Shape Optimization for Multileaf Collimator in Radiotherapy.

    Science.gov (United States)

    Zhou, Dong; Zhang, Hui; Ye, Peiqing

    2016-01-01

    Lateral penumbra of multileaf collimator plays an important role in radiotherapy treatment planning. Growing evidence has revealed that, for a single-focused multileaf collimator, lateral penumbra width is leaf position dependent and largely attributed to the leaf end shape. In our study, an analytical method for leaf end induced lateral penumbra modelling is formulated using Tangent Secant Theory. Compared with Monte Carlo simulation and ray tracing algorithm, our model serves well the purpose of cost-efficient penumbra evaluation. Leaf ends represented in parametric forms of circular arc, elliptical arc, Bézier curve, and B-spline are implemented. With biobjective function of penumbra mean and variance introduced, genetic algorithm is carried out for approximating the Pareto frontier. Results show that for circular arc leaf end objective function is convex and convergence to optimal solution is guaranteed using gradient based iterative method. It is found that optimal leaf end in the shape of Bézier curve achieves minimal standard deviation, while using B-spline minimum of penumbra mean is obtained. For treatment modalities in clinical application, optimized leaf ends are in close agreement with actual shapes. Taken together, the method that we propose can provide insight into leaf end shape design of multileaf collimator.

  17. Lateral Penumbra Modelling Based Leaf End Shape Optimization for Multileaf Collimator in Radiotherapy

    Science.gov (United States)

    Zhou, Dong; Zhang, Hui; Ye, Peiqing

    2016-01-01

    Lateral penumbra of multileaf collimator plays an important role in radiotherapy treatment planning. Growing evidence has revealed that, for a single-focused multileaf collimator, lateral penumbra width is leaf position dependent and largely attributed to the leaf end shape. In our study, an analytical method for leaf end induced lateral penumbra modelling is formulated using Tangent Secant Theory. Compared with Monte Carlo simulation and ray tracing algorithm, our model serves well the purpose of cost-efficient penumbra evaluation. Leaf ends represented in parametric forms of circular arc, elliptical arc, Bézier curve, and B-spline are implemented. With biobjective function of penumbra mean and variance introduced, genetic algorithm is carried out for approximating the Pareto frontier. Results show that for circular arc leaf end objective function is convex and convergence to optimal solution is guaranteed using gradient based iterative method. It is found that optimal leaf end in the shape of Bézier curve achieves minimal standard deviation, while using B-spline minimum of penumbra mean is obtained. For treatment modalities in clinical application, optimized leaf ends are in close agreement with actual shapes. Taken together, the method that we propose can provide insight into leaf end shape design of multileaf collimator. PMID:27110274

  18. Development and validation of a BEAMnrc component module for a miniature multileaf collimator

    International Nuclear Information System (INIS)

    Doerner, E; Hartmann, G H

    2012-01-01

    A new component module (CM) named mini multileaf collimator (mMLC) was developed for the Monte Carlo code BEAMnrc. It models the geometry of the add-on miniature multileaf collimator ModuLeaf (MRC Systems GmbH, Heidelberg, Germany, now part of Siemens, Erlangen, Germany). The new CM is partly based on the existing CM called DYNVMLC. The development was performed using a modified EGSnrc platform which enables us to work in the Microsoft Visual Studio environment. In order to validate the new CM, the PRIMUS linac with 6 MV x-rays (Siemens OCS, Concord, CA, USA) equipped with the ModuLeaf mMLC was modelled. Validation was performed by two methods: (a) a ray-tracing method to check the correct geometry of the multileaf collimator (MLC) and (b) a comparison of calculated and measured results of the following dosimetrical parameters: output factors, dose profiles, field edge position penumbra, MLC interleaf leakage and transmission values. Excellent agreement was found for all parameters. It was, in particular, found that the relationship between leaf position and field edge depending on the shape of the leaf ends can be investigated with a higher accuracy by this new CM than by measurements demonstrating the usefulness of the new CM. (paper)

  19. Technical Note: Modeling a complex micro-multileaf collimator using the standard BEAMnrc distribution

    International Nuclear Information System (INIS)

    Kairn, T.; Kenny, J.; Crowe, S. B.; Fielding, A. L.; Franich, R. D.; Johnston, P. N.; Knight, R. T.; Langton, C. M.; Schlect, D.; Trapp, J. V.

    2010-01-01

    Purpose: The component modules in the standard BEAMnrc distribution may appear to be insufficient to model micro-multileaf collimators that have trifaceted leaf ends and complex leaf profiles. This note indicates, however, that accurate Monte Carlo simulations of radiotherapy beams defined by a complex collimation device can be completed using BEAMnrc's standard VARMLC component module. Methods: That this simple collimator model can produce spatially and dosimetrically accurate microcollimated fields is illustrated using comparisons with ion chamber and film measurements of the dose deposited by square and irregular fields incident on planar, homogeneous water phantoms. Results: Monte Carlo dose calculations for on-axis and off-axis fields are shown to produce good agreement with experimental values, even on close examination of the penumbrae. Conclusions: The use of a VARMLC model of the micro-multileaf collimator, along with a commissioned model of the associated linear accelerator, is therefore recommended as an alternative to the development or use of in-house or third-party component modules for simulating stereotactic radiotherapy and radiosurgery treatments. Simulation parameters for the VARMLC model are provided which should allow other researchers to adapt and use this model to study clinical stereotactic radiotherapy treatments.

  20. Dose Distribution and Characterization for Radiation Fields of Multileaf Collimator System

    International Nuclear Information System (INIS)

    Chu, Sung Sil; Kim, Gwi Eon

    1996-01-01

    Purpose : Multileaf collimator(MLC) is very suitable tool for conformal radiotherapy and commissioning measurements for a multileaf collimator installed on a dual energy accelerator with 6 and 10MV photons are required. For modeling the collimator with treatment planning software, detailed dosimetric characterization of the multileaf collimator including the penumbra width, leaf transmission between leaf leakage and localization of the leaf ends and sides is an essential requirement. Measurement of characteristic data of the MLC with 26 pair block leaves installed on CLINAC 2100C linear accelerator was performed. Low sensitive radiographic film(X-omatV) was used for the penumbra measurement and separate experiments using radiographic film and thermoluminescent dosimeters were performed to verify the dose distribution, Measured films were analyzed with a photo densitometer of WP700i scanner. For 6 and 10 MV x-ray energies, approximately 2.0% of photons incident on the multileaf collimator were transmitted and an additional 0.5% leakage occurs between the leaves. Localizing the physical end of the leaves showed less than 1mm deviation from the 50% decrement line and this difference is attributed to the curved shaped end on the leaves. One side of a single leaf corresponded to the 50% decrement line, but the opposite face was aligned with a lower value. this difference is due to the tongue and groove used to decrease between leaf leakage. Alignment of the leaves to form a straight edge resulted larger penumbra at far position from isocenter as compare with divergent alloy blocks. When the MLC edge is stepped by sloping field, the isodose lines follow the leaf pattern and produce scalloping isodose curves in tissue. The effective penumbra by 45 degree stepped MLC is about 10mm at 10cm depth for 6MV x-ray. The difference of effective penumbra in deep tissue between MLC and divergent alloy blocks is small (5mm). Using the characteristic data of MLC, the MLC has the

  1. Segmental and dynamic intensity-modulated radiotherapy delivery techniques for micro-multileaf collimator

    International Nuclear Information System (INIS)

    Agazaryan, Nzhde; Solberg, Timothy D.

    2003-01-01

    A leaf sequencing algorithm has been implemented to deliver segmental and dynamic multileaf collimated intensity-modulated radiotherapy (SMLC-IMRT and DMLC-IMRT, respectively) using a linear accelerator equipped with a micro-multileaf collimator (mMLC). The implementation extends a previously published algorithm for the SMLC-IMRT to include the dynamic MLC-IMRT method and several dosimetric considerations. The algorithm has been extended to account for the transmitted radiation and minimize the leakage between opposing and neighboring leaves. The underdosage problem associated with the tongue-and-groove design of the MLC is significantly reduced by synchronizing the MLC leaf movements. The workings of the leaf sequencing parameters have been investigated and the results of the planar dosimetric investigations show that the sequencing parameters affect the measured dose distributions as intended. Investigations of clinical cases suggest that SMLC and DMLC delivery methods produce comparable results with leaf sequences obtained by root-mean-square (RMS) errors specification of 1.5% and lower, approximately corresponding to 20 or more segments. For SMLC-IMRT, there is little to be gained by using an RMS error specification smaller than 2%, approximately corresponding to 15 segments; however, more segments directly translate to longer treatment time and more strain on the MLC. The implemented leaf synchronization method does not increase the required monitor units while it reduces the measured TG underdoses from a maximum of 12% to a maximum of 3% observed with single field measurements of representative clinical cases studied

  2. Penumbra characteristics of square photon beams delimited by a GEMS multi-leaf collimator

    Energy Technology Data Exchange (ETDEWEB)

    Briot, E; Julia, F [Centre de Lutte Contre le Cancer Gustave-Roussy, 94 - Villejuif (France)

    1995-12-01

    A multi-leaf collimator (MLC) has been designed to replace directly the standard collimator of a SATURNE IV Series linac. It consists of 2 x 32 tungsten leaves and one set of upper block jaws. Isodose curves and dose profiles were measured for symmetric fields at the depth of the maximum and the reference depths for 6 MV, 10 MV, 18 MV photon beams. The penumbra (80%-20%) corresponding to the face and the side of the leaves have been compared with the standard collimators. Along with the X direction, the field delimitation is performed primarily with the leaves which are continuously variable in position. Along the Y direction, the field is initially approximated by the closure of opposite leaf pairs; then the Y upper jaws produce the exact size of the required field. As the leaves move linearly the penumbra (80%-20%) corresponding to the leaf ends is minimized and held constant at all positions by curvature of their faces. Penumbra obtained with the superposition of leaves and Y jaws depend on their relative position. The penumbra is minimum when the leaf side and the Y jaw edge coincide and the comparison of the measurement values with the conventional collimator shows that the differences are within 1 mm. When the leaves delineating the field are not entirely covered by the Y block upper jaws, the penumbra increases, and the junction of the opposing leaves, a width increase up to 3.5 mm has been measured.

  3. Use of an amorphous silicon electronic portal imaging device for multileaf collimator quality control and calibration

    International Nuclear Information System (INIS)

    Baker, S J K; Budgell, G J; MacKay, R I

    2005-01-01

    Multileaf collimator (MLC) calibration and quality control is a time-consuming procedure typically involving the processing, scanning and analysis of films to measure leaf and collimator positions. Faster and more reliable calibration procedures are required for these tasks, especially with the introduction of intensity modulated radiotherapy which requires more frequent checking and finer positional leaf tolerances than previously. A routine quality control (QC) technique to measure MLC leaf bank gain and offset, as well as minor offsets (individual leaf position relative to a reference leaf), using an amorphous silicon electronic portal imaging device (EPID) has been developed. The technique also tests the calibration of the primary and back-up collimators. A detailed comparison between film and EPID measurements has been performed for six linear accelerators (linacs) equipped with MLC and amorphous silicon EPIDs. Measurements of field size from 4 to 24 cm with the EPID were systematically smaller than film measurements over all field sizes by 0.4 mm for leaves/back-up collimators and by 0.2 mm for conventional collimators. This effect is due to the gain calibration correction applied by the EPID, resulting in a 'flattening' of primary beam profiles. Linac dependent systematic differences of up to 0.5 mm in individual leaf/collimator positions were also found between EPID and film measurements due to the difference between the mechanical and radiation axes of rotation. When corrections for these systematic differences were applied, the residual random differences between EPID and film were 0.23 mm and 0.26 mm (1 standard deviation) for field size and individual leaf/back-up collimator position, respectively. Measured gains (over a distance of 220 mm) always agreed within 0.4 mm with a standard deviation of 0.17 mm. Minor offset measurements gave a mean agreement between EPID and film of 0.01 ± 0.10 mm (1 standard deviation) after correction for the tilt of the

  4. Evaluation of the vidar`s VXR-12 digitizer performances for film dosimetry of beams delimited by multileaf collimator

    Energy Technology Data Exchange (ETDEWEB)

    Julia, F [Centre de Lutte Contre le Cancer Gustave-Roussy, 94 - Villejuif (France); Briot, E

    1995-12-01

    The development of new irradiation techniques such as conformal radiotherapy increasingly implies the use of a multileaf collimator. The measurement of dose gradients in the penumbra region, and of dose distributions at the edge of complex shaped fields defined by multileaf collimators requires a high definition dosimetric method. Nowadays film digitizers have been notably improved and allow the film dosimetry to be faster, more accurate, presenting a sensitivity and high spatial resolution. To be able to perform the study of physical and dosimetric specifications of a multileaf collimator, we have evaluated the performances of the Vidar VCR-12 digitizer, with respect to its sensitivity, linearity, optical density range and the resolution. These performances were compared with the performances of different systems already in use in our department, either manual or automatic, using specific patterns. The main limitation for dosimetric use is the detection threshold that can introduce errors in isodose calculation, especially for the lowest values. The result of the intercomparisons have allowed corrections to be added, taking into account this Vidar problem. The results obtained after correction for the dose profiles of squared fields are in good agreement with ionization chamber measurements in a water phantom. It is concluded that Vidar digitizer is suitable for the use of film dosimetry for the dose distributions in fields defined by multileaf collimator.

  5. Study on the tongue and groove effect of the elekta multileaf collimator using Monte Carlo simulation and film dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Haryanto, F.; Fippel, M.; Bakai, A.; Nuesslin, F. [Dept. of Medical Physics, Radiooncologic Univ. Clinic, Tuebingen (Germany)

    2004-01-01

    Background: nowadays, multileaf collimation of the treatment fields from medical linear accelerators is a common option. Due to the design of the leaf sides, the tongue and groove effect occurs for certain multileaf collimator applications such as the abutment of fields where the beam edges are defined by the sides of the leaves. Material and methods: in this study, the tongue and groove effect was measured for two pairs of irregular multileaf collimator fields that were matched along leaf sides in two steps. Measurements were made at 10 cm depth in a polystyrene phantom using Kodak EDR2 films for a photon beam energy of 6 MV on an elekta sli-plus accelerator. To verify the measurements, full Monte Carlo simulations were done. In the simulations, the design of the leaf sides was taken into account and one component module of BEAM code was modified to correctly simulate the elekta multileaf collimator. Results and conclusion: the results of measurements and simulations are in good agreement and within the tolerance of film dosimetry. (orig.)

  6. Intensity-modulated stereotactic radiosurgery using dynamic micro-multileaf collimation

    International Nuclear Information System (INIS)

    Benedict, Stanley H.; Cardinale, Robert M.; Wu Qiuwen; Zwicker, Robert D.; Broaddus, William C.; Mohan, Radhe

    2001-01-01

    Purpose: The implementation of dynamic leaf motion on a micro-multileaf collimator system provides the capability for intensity-modulated stereotactic radiosurgery (IMSRS), and the consequent potential for improved dose distributions for irregularly shaped tumor volumes adjacent to critical organs. This study explores the use of IMSRS to provide improved tumor coverage and normal tissue sparing for small cranial tumors relative to plans based on multiple fixed uniform-intensity beams or traditional circular collimator arc-based stereotactic techniques. Methods and Materials: Four patient cases involving small brain lesions are presented and analyzed. The cases were chosen to include a representative selection of target shapes, number of targets, and adjacent critical areas. Patient plans generated for these comparisons include standard arcs with multiple circular collimators, and fixed noncoplanar static fields with uniform-intensity beams and IMSRS. Parameters used for evaluation of the plans include the percentage of irradiated volume to tumor volume (PITV), normal tissue dose-volume histograms, and dose-homogeneity ratios. All IMSRS plans were computed using previously established IMRT techniques adapted for use with the BrainLAB M3 micro-multileaf collimator. The algorithms comprising the IMRT system for optimization of intensity distributions and conversion into leaf trajectories of the BrainLab M3 were developed at our institution. The ADAC Pinnacle 3 radiation treatment-planning system was used for dose calculations and for input of contours for target volumes and normal critical structures. Results: For all cases, the IMSRS plans showed a high degree of conformity of the dose distribution with the target shape. The IMSRS plans provided either (1) a smaller volume of normal tissue irradiated to significant dose levels, generally taken as doses greater than 50% of the prescription, or (2) a lower dose to an important adjacent critical organ. The reduction in

  7. Independent monitor unit calculation for intensity modulated radiotherapy using the MIMiC multileaf collimator

    International Nuclear Information System (INIS)

    Chen Zhe; Xing Lei; Nath, Ravinder

    2002-01-01

    A self-consistent monitor unit (MU) and isocenter point-dose calculation method has been developed that provides an independent verification of the MU for intensity modulated radiotherapy (IMRT) using the MIMiC (Nomos Corporation) multileaf collimator. The method takes into account two unique features of IMRT using the MIMiC: namely the gantry-dynamic arc delivery of intensity modulated photon beams and the slice-by-slice dose delivery for large tumor volumes. The method converts the nonuniform beam intensity planned at discrete gantry angles of 5 deg. or 10 deg. into conventional nonmodulated beam intensity apertures of elemental arc segments of 1 deg. This approach more closely simulates the actual gantry-dynamic arc delivery by MIMiC. Because each elemental arc segment is of uniform intensity, the MU calculation for an IMRT arc is made equivalent to a conventional arc with gantry-angle dependent beam apertures. The dose to the isocenter from each 1 deg. elemental arc segment is calculated by using the Clarkson scatter summation technique based on measured tissue-maximum-ratio and output factors, independent of the dose calculation model used in the IMRT planning system. For treatments requiring multiple treatment slices, the MU for the arc at each treatment slice takes into account the MU, leakage and scatter doses from other slices. This is achieved by solving a set of coupled linear equations for the MUs of all involved treatment slices. All input dosimetry data for the independent MU/isocenter point-dose calculation are measured directly. Comparison of the MU and isocenter point dose calculated by the independent program to those calculated by the Corvus planning system and to direct measurements has shown good agreement with relative difference less than ±3%. The program can be used as an independent initial MU verification for IMRT plans using the MIMiC multileaf collimators

  8. Implementation of multileaf collimator in a LINAC MCNP5 simulation coupled with the radiation treatment planing system PLUNC

    International Nuclear Information System (INIS)

    Abella, Vicente; Miro, Rafael; Juste, Belen; Verdu, Gumersindo

    2010-01-01

    Multileaf collimators are used on linear accelerators to provide conformal shaping of radiotherapy treatment beams, being an important tool for radiation therapy dose delivery. In this work, a multileaf collimator has been designed and implemented in the MCNP model of an Elekta Precise Linear Accelerator and introduced in PLUNC, a set of software tools for radiotherapy treatment planning (RTP) which was coupled in previous works with MCNP5 (Monte Carlo N-Particle transport code), with the purpose of comparing its effect on deterministic and Monte Carlo dose calculations. A 3D Shepp-Logan phantom was utilized as the patient model for validation purposes. Once the multileaf collimator model is implemented in the PLUNC LINAC model, a series of Matlab interfaces extract phantom and beam information created with PLUNC during the treatment plan and write it in MCNP5 input deck format. After the Monte Carlo simulation is performed, results are input back again in PLUNC in order to continue with the plan evaluation. The comparison is made via mapping of dose distribution inside the phantom with different field sizes, utilizing the MCNP5 tool EMESH, superimposed mesh tally, which allows registering the results over the problem geometry. This work follows a valid methodology for multileaf LINAC MC calculations during radiation treatment plans. (author)

  9. SU-F-T-629: Effect of Multi-Leaf Collimator (MLC) Width On Plan Quality of Single-Isocenter VMAT Intracranial Stereotactic Radiosurgery for Multiple Metastases

    International Nuclear Information System (INIS)

    Kraus, J; Thomas, E; Wu, X; Fiveash, J; Popple, R

    2016-01-01

    Purpose: Single-isocenter VMAT has been shown able to create high quality plans for complex intracranial multiple metastasis SRS cases. Linacs capable of the technique are typically outfitted with an MLC that consists of a combination of 5 mm and 10 mm leaves (standard) or 2.5 mm and 5 mm leaves (high-definition). In this study, we test the hypothesis that thinner collimator leaves are associated with improved plan quality. Methods: Ten multiple metastasis cases were identified and planned for VMAT SRS using a 10 MV flattening filter free beam. Plans were created for a standard (std) and a high-definition (HD) MLC. Published values for leaf transmission factor and dosimetric leaf gap were utilized. All other parameters were invariant. Conformity (plan and individual target), moderate isodose spill (V50%), and low isodose spill (mean brain dose) were selected for analysis. Results: Compared to standard MLC, HD-MLC improved overall plan conformity (median: Paddick CI-HD = 0.83, Paddick CI-std = 0.79; p = 0.004 and median: RTOG CI-HD =1.18, RTOG CI-std =1.24; p = 0.01 ), improved individual lesion conformity (median: Paddick CI-HD,i =0.77, Paddick CI-std,i =0.72; p < 0.001 and median: RTOG CI-HD,i = 1.28, RTOG CI-std,i =1.35; p < 0.001), improved moderate isodose spill (median: V50%-HD = 37.0 cc, V50%-std = 45.7 cc; p = 0.002), and improved low dose spill (median: dmean-HD = 2.90 Gy, dmean-std = 3.19 Gy; p = 0.002). Conclusion: For the single-isocenter VMAT SRS of multiple metastasis plans examined, use of HD-MLC modestly improved conformity, moderate isodose, and low isodose spill compared to standard MLC. However, in all cases we were able to generate clinically acceptable plans with the standard MLC. More work is need to further quantify the difference in cases with higher numbers of small targets and to better understand any potential clinical significance. This research was supported in part by Varian Medical Systems.

  10. SU-F-T-629: Effect of Multi-Leaf Collimator (MLC) Width On Plan Quality of Single-Isocenter VMAT Intracranial Stereotactic Radiosurgery for Multiple Metastases

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, J; Thomas, E; Wu, X; Fiveash, J; Popple, R [University Alabama Birmingham, Birmingham, AL (United States)

    2016-06-15

    Purpose: Single-isocenter VMAT has been shown able to create high quality plans for complex intracranial multiple metastasis SRS cases. Linacs capable of the technique are typically outfitted with an MLC that consists of a combination of 5 mm and 10 mm leaves (standard) or 2.5 mm and 5 mm leaves (high-definition). In this study, we test the hypothesis that thinner collimator leaves are associated with improved plan quality. Methods: Ten multiple metastasis cases were identified and planned for VMAT SRS using a 10 MV flattening filter free beam. Plans were created for a standard (std) and a high-definition (HD) MLC. Published values for leaf transmission factor and dosimetric leaf gap were utilized. All other parameters were invariant. Conformity (plan and individual target), moderate isodose spill (V50%), and low isodose spill (mean brain dose) were selected for analysis. Results: Compared to standard MLC, HD-MLC improved overall plan conformity (median: Paddick CI-HD = 0.83, Paddick CI-std = 0.79; p = 0.004 and median: RTOG CI-HD =1.18, RTOG CI-std =1.24; p = 0.01 ), improved individual lesion conformity (median: Paddick CI-HD,i =0.77, Paddick CI-std,i =0.72; p < 0.001 and median: RTOG CI-HD,i = 1.28, RTOG CI-std,i =1.35; p < 0.001), improved moderate isodose spill (median: V50%-HD = 37.0 cc, V50%-std = 45.7 cc; p = 0.002), and improved low dose spill (median: dmean-HD = 2.90 Gy, dmean-std = 3.19 Gy; p = 0.002). Conclusion: For the single-isocenter VMAT SRS of multiple metastasis plans examined, use of HD-MLC modestly improved conformity, moderate isodose, and low isodose spill compared to standard MLC. However, in all cases we were able to generate clinically acceptable plans with the standard MLC. More work is need to further quantify the difference in cases with higher numbers of small targets and to better understand any potential clinical significance. This research was supported in part by Varian Medical Systems.

  11. Leakage of the Siemens 160 MLC multileaf collimator on a dual energy linear accelerator

    International Nuclear Information System (INIS)

    Klueter, Sebastian; Sroka-Perez, Gabriele; Schubert, Kai; Debus, Juergen

    2011-01-01

    Multileaf collimators (MLCs) have been in clinical use for many years and meanwhile are commonly used to deliver intensity-modulated radiotherapy (IMRT) beams. For this purpose it is important to know their dosimetric properties precisely, one of them being inter- and intraleaf leakage. The Siemens 160 MLC features a single focus design with flat-sided and tilted leaves instead of tongue-and-groove. The leakage performance of the 160 MLC was investigated on a dual energy linear accelerator Siemens ARTISTE with 6 MV and 18 MV photon energies. While the intraleaf leakage amounted to nearly the same dose for 6 and for 18 MV, a much higher interleaf leakage for 6 MV was measured. It could be reduced by simply rotating the collimator, and also by changing the voltage applied to the beam steering coils. The leakage of the 160 MLC is shown to be sensitive to beam alignment. This is of special interest for dual energy accelerators, as the two focal spots of both energies, neither in position nor in shape, do not necessarily always coincide. As a consequence of that, a higher leakage can be expected for one out of two energies for the 160 MLC. (note)

  12. Delivery of modulated electron beams with conventional photon multi-leaf collimators

    International Nuclear Information System (INIS)

    Klein, Eric E; Mamalui-Hunter, Maria; Low, Daniel A

    2009-01-01

    Electron beam radiotherapy is an accepted method to treat shallow tumors. However, modulation of electrons to customize dose distributions has not readily been achieved. Studies of bolus and tertiary collimation systems have been met with limitations. We pursue the use of photon multi-leaf collimators (MLC) for modulated electron radiotherapy (MERT) to achieve customized distributions for potential clinical use. As commercial planning systems do not support the use of MLC with electrons, planning was conducted using Monte Carlo calculations. Segmented and dynamic modulated delivery of multiple electron segments was configured, calculated and delivered for validation. Delivery of electrons with segmented or dynamic leaf motion was conducted. A phantom possessing an idealized stepped target was planned and optimized with subsequent validation by measurements. Finally, clinical treatment plans were conducted for post-mastectomy and cutaneous lymphoma of the scalp using forward optimization techniques. Comparison of calculations and measurements was successful with agreement of ±2%/2 mm for the energies, segment sizes, depths tested for delivered segments for the dynamic and segmented delivery. Clinical treatment plans performed provided optimal dose coverage of the target while sparing distal organs at risk. Execution of plans using an anthropomorphic phantom to ensure safe and efficient delivery was conducted. Our study validates that MERT is not only possible using the photon MLC, but the efficient and safe delivery inherent with the dynamic delivery provides an ideal technique for shallow tumor treatment.

  13. A study of inverse planning by simulated annealing for photon beams modulated by a multileaf collimator

    International Nuclear Information System (INIS)

    Grant, Walter; Carol, Mark; Geis, Paul; Boyer, Arthur L.

    1995-01-01

    Purpose/Objective: To demonstrate the feasibility of inverse planning for multiple fixed-field conformal therapy with a prototype simulated annealing technique and to deliver the treatment plan with an engineering prototype dynamic multileaf collimator. Methods and Materials: A version of the NOMOS inverse-planning algorithm was used to compute weighting distributions over the areas of multiple fixed-gantry fields. The algorithm uses simulated annealing and a cost function based on physical dose. The algorithm is a modification of a NOMOS Peacock planning implementation being used clinically. The computed weighting distributions represented the relative intensities over small 0.5 cm x 1.0 cm areas of the fields. The inverse planning was carried out using a Sun Model 20 computer using four processors. Between five and nine fixed-gantry beams were used in the plans. The weighting distributions were rendered into leaf-setting sequences using an algorithm developed for use with a Varian experimental dynamic-multileaf collimator. The sequences were saved as computer files in a format that was used to drive the Varian control system. X-ray fields having 6-MV and 18-MV energies were planned and delivered using tumor target and sensitive structure volumes segmented from clinical CT scans. Results: The resulting beam-modulation sequences could be loaded into the accelerator control systems and initiated. Each fixed-gantry angle beam was delivered in 30 s to 50 s. The resulting dose distributions were measured in quasi-anatomical phantoms using film. Dose distributions that could achieve significant tissue-sparing were demonstrated. There was good agreement between the delivered dose distributions and the planned distributions. Conclusion: The prototype inverse-planning system under development by NOMOS can be integrated with the prototype dynamic-delivery system being developed by Varian Associates. Should these commercial entities chose to offer compatible FDA

  14. Characterization of a commercial multileaf collimator used for intensity modulated radiation therapy

    International Nuclear Information System (INIS)

    Low, Daniel A.; Sohn, Jason W.; Klein, Eric E.; Markman, Jerry; Mutic, Sasa; Dempsey, James F.

    2001-01-01

    The characteristics of a commercial multileaf collimator (MLC) to deliver static and dynamic multileaf collimation (SMLC and DMLC, respectively) were investigated to determine their influence on intensity modulated radiation therapy (IMRT) treatment planning and quality assurance. The influence of MLC leaf positioning accuracy on sequentially abutted SMLC fields was measured by creating abutting fields with selected gaps and overlaps. These data were also used to measure static leaf positioning precision. The characteristics of high leaf-velocity DMLC delivery were measured with constant velocity leaf sequences starting with an open field and closing a single leaf bank. A range of 1-72 monitor units (MU) was used providing a range of leaf velocities. The field abutment measurements yielded dose errors (as a percentage of the open field max dose) of 16.7±0.7% mm-1 and 12.8±0.7% mm-1 for 6 MV and 18 MV photon beams, respectively. The MLC leaf positioning precision was 0.080±0.018 mm (single standard deviation) highlighting the excellent delivery hardware tolerances for the tested beam delivery geometry. The high leaf-velocity DMLC measurements showed delivery artifacts when the leaf sequence and selected monitor units caused the linear accelerator to move the leaves at their maximum velocity while modulating the accelerator dose rate to deliver the desired leaf and MU sequence (termed leaf-velocity limited delivery). According to the vendor, a unique feature to their linear accelerator and MLC is that the dose rate is reduced to provide the correct cm MU-1 leaf velocity when the delivery is leaf-velocity limited. However, it was found that the system delivered roughly 1 MU per pulse when the delivery was leaf-velocity limited causing dose profiles to exhibit discrete steps rather than a smooth dose gradient. The root mean square difference between the steps and desired linear gradient was less than 3% when more than 4 MU were used. The average dose per MU was

  15. An effective method for smoothing the staggered dose distribution of multi-leaf collimator field edge

    International Nuclear Information System (INIS)

    Hwang, I.-M.; Lin, S.-Y.; Lee, M.-S.; Wang, C.-J.; Chuang, K.-S.; Ding, H.-J.

    2002-01-01

    Purpose: To smooth the staggered dose distribution that occurs in stepped leaves defined by a multi-leaf collimator (MLC). Materials and methods: The MLC Shaper program controlled the stepped leaves, which were shifted in a traveling range, the pattern of shift was from the position of out-bound to in-bound with a one-segment (cross-bound), three-segment, and five-segment shifts. Film was placed at a depth of 1.5 cm and irradiated with the same irradiation dose used for the cerrobend block experiment. Four field edges with the MLC defining at 15 deg., 30 deg., 45 deg., 60 deg. angels relative to the jaw edge were performed, respectively, in this study. For the field edge defined by the multi-segment technique, the amplitude of the isodose lines for 50% isodose line and both the 80% and 20% isodose lines were measured. The effective penumbra widths with 90-10% and 80-20% distances for different irradiations were determined at four field edges with the MLC defining at 15 deg., 30 deg., 45 deg., 60 deg. angels relative to the jaw edge. Results: Use of the five-segment technique for multi-leaf collimation at the 60 deg. angle field edge smoothes each isodose line into an effectively straight line, similar to the pattern achieved using a cerrobend block. The separation of these lines is also important. The 80-20% effective penumbra width with five-segment techniques (8.23 mm) at 60 deg. angle relative to the jaw edge is little wider (1.9 times) than the penumbra of cerrobend block field edge (4.23 mm). We also found that the 90-10% effective penumbra width with five-segment techniques (12.68 mm) at 60 deg. angle relative to the jaw edge is little wider (1.28 times) than the penumbra of cerrobend block field edge (9.89 mm). Conclusion: The multi-segment technique is effective in smoothing the MLC staggered field edge. The effective penumbra width with more segment techniques at larger degree angles relative to the field edge is little wider than the penumbra for a

  16. [A review of progress of real-time tumor tracking radiotherapy technology based on dynamic multi-leaf collimator].

    Science.gov (United States)

    Liu, Fubo; Li, Guangjun; Shen, Jiuling; Li, Ligin; Bai, Sen

    2017-02-01

    While radiation treatment to patients with tumors in thorax and abdomen is being performed, further improvement of radiation accuracy is restricted by the tumor intra-fractional motion due to respiration. Real-time tumor tracking radiation is an optimal solution to tumor intra-fractional motion. A review of the progress of real-time dynamic multi-leaf collimator(DMLC) tracking is provided in the present review, including DMLC tracking method, time lag of DMLC tracking system, and dosimetric verification.

  17. Lens sparing technique using multi-leaf collimators in irradiation of the unilateral retro-orbital space for benign disease

    International Nuclear Information System (INIS)

    Middleton, Mark; Medwell, Stephen; Bennie, David; Fogarty, Gerald

    2005-01-01

    The authors present a case of a 30-year-old woman with pseudolymphoma of the left medial rectus muscle. A multi-field technique was planned for irradiating the unilateral retro-orbital space to 20 Gray (GY) in 15 fractions while keeping the average dose to the lens of 8 Gy and the peak dose to the lens of 11 Gy using multi-leaf collimators is described. Copyright (2005) Australian Institute of Radiography

  18. Characterization of an extendable multi-leaf collimator for clinical electron beams

    Science.gov (United States)

    O'Shea, Tuathan P.; Ge, Yuanyuan; Foley, Mark J.; Faddegon, Bruce A.

    2011-12-01

    An extendable x-ray multi-leaf collimator (eMLC) is investigated for collimation of electron beams on a linear accelerator. The conventional method of collimation using an electron applicator is impractical for conformal, modulated and mixed beam therapy techniques. An eMLC would allow faster, more complex treatments with potential for reduction in dose to organs-at-risk and critical structures. The add-on eMLC was modelled using the EGSnrc Monte Carlo code and validated against dose measurements at 6-21 MeV with the eMLC mounted on a Siemens Oncor linear accelerator at 71.6 and 81.6 cm source-to-collimator distances. Measurements and simulations at 8.4-18.4 cm airgaps showed agreement of 2%/2 mm. The eMLC dose profiles and percentage depth dose curves were compared with standard electron applicator parameters. The primary differences were a wider penumbra and up to 4.2% reduction in the build-up dose at 0.5 cm depth, with dose normalized on the central axis. At 90 cm source-to-surface distance (SSD)--relevant to isocentric delivery--the applicator and eMLC penumbrae agreed to 0.3 cm. The eMLC leaves, which were 7 cm thick, contributed up to 6.3% scattered electron dose at the depth of maximum dose for a 10 × 10 cm2 field, with the thick leaves effectively eliminating bremsstrahlung leakage. A Monte Carlo calculated wedge shaped dose distribution generated with all six beam energies matched across the maximum available eMLC field width demonstrated a therapeutic (80% of maximum dose) depth range of 2.1-6.8 cm. Field matching was particularly challenging at lower beam energies (6-12 MeV) due to the wider penumbrae and angular distribution of electron scattering. An eMLC isocentric electron breast boost was planned and compared with the conventional applicator fixed SSD plan, showing similar target coverage and dose to critical structures. The mean dose to the target differed by less than 2%. The low bremsstrahlung dose from the 7 cm thick MLC leaves had the added

  19. Sensitivity of 3D Dose Verification to Multileaf Collimator Misalignments in Stereotactic Body Radiation Therapy of Spinal Tumor.

    Science.gov (United States)

    Xin-Ye, Ni; Ren, Lei; Yan, Hui; Yin, Fang-Fang

    2016-12-01

    This study aimed to detect the sensitivity of Delt 4 on ordinary field multileaf collimator misalignments, system misalignments, random misalignments, and misalignments caused by gravity of the multileaf collimator in stereotactic body radiation therapy. (1) Two field sizes, including 2.00 cm (X) × 6.00 cm (Y) and 7.00 cm (X) × 6.00 cm (Y), were set. The leaves of X1 and X2 in the multileaf collimator were simultaneously opened. (2) Three cases of stereotactic body radiation therapy of spinal tumor were used. The dose of the planning target volume was 1800 cGy with 3 fractions. The 4 types to be simulated included (1) the leaves of X1 and X2 in the multileaf collimator were simultaneously opened, (2) only X1 of the multileaf collimator and the unilateral leaf were opened, (3) the leaves of X1 and X2 in the multileaf collimator were randomly opened, and (4) gravity effect was simulated. The leaves of X1 and X2 in the multileaf collimator shifted to the same direction. The difference between the corresponding 3-dimensional dose distribution measured by Delt 4 and the dose distribution in the original plan made in the treatment planning system was analyzed with γ index criteria of 3.0 mm/3.0%, 2.5 mm/2.5%, 2.0 mm/2.0%, 2.5 mm/1.5%, and 1.0 mm/1.0%. (1) In the field size of 2.00 cm (X) × 6.00 cm (Y), the γ pass rate of the original was 100% with 2.5 mm/2.5% as the statistical standard. The pass rate decreased to 95.9% and 89.4% when the X1 and X2 directions of the multileaf collimator were opened within 0.3 and 0.5 mm, respectively. In the field size of 7.00 (X) cm × 6.00 (Y) cm with 1.5 mm/1.5% as the statistical standard, the pass rate of the original was 96.5%. After X1 and X2 of the multileaf collimator were opened within 0.3 mm, the pass rate decreased to lower than 95%. The pass rate was higher than 90% within the 3 mm opening. (2) For spinal tumor, the change in the planning target volume V 18 under various modes calculated using treatment planning system

  20. Variable Circular Collimator in Robotic Radiosurgery: A Time-Efficient Alternative to a Mini-Multileaf Collimator?

    International Nuclear Information System (INIS)

    Water, Steven van de; Hoogeman, Mischa S.; Breedveld, Sebastiaan; Nuyttens, Joost J.M.E.; Schaart, Dennis R.; Heijmen, Ben J.M.

    2011-01-01

    Purpose: Compared with many small circular beams used in CyberKnife treatments, beam's eye view-shaped fields are generally more time-efficient for dose delivery. However, beam's eye view-shaping devices, such as a mini-multileaf collimator (mMLC), are not presently available for CyberKnife, although a variable-aperture collimator (Iris, 12 field diameters; 5-60 mm) is available. We investigated whether the Iris can mimic noncoplanar mMLC treatments using a limited set of principal beam orientations (nodes) to produce time-efficient treatment plans. Methods and Materials: The data from 10 lung cancer patients and the beam-orientation optimization algorithm 'Cycle' were used to generate stereotactic treatment plans (3 x 20 Gy) for a CyberKnife virtually equipped with a mMLC. Typically, 10-16 favorable beam orientations were selected from 117 available robot node positions using beam's eye view-shaped fields with uniform fluence. Second, intensity-modulated Iris plans were generated by inverse optimization of nonisocentric circular candidate beams targeted from the same nodes selected in the mMLC plans. The plans were evaluated using the mean lung dose, lung volume receiving ≥20 Gy, conformality index, number of nodes, beams, and monitor units, and estimated treatment time. Results: The mMLC plans contained an average of 12 nodes and 11,690 monitor units. For a comparable mean lung dose, the Iris plans contained 12 nodes, 64 beams, and 21,990 monitor units. The estimated fraction duration was 12.2 min (range, 10.8-13.5) for the mMLC plans and 18.4 min (range, 12.9-28.5) for the Iris plans. In contrast to the mMLC plans, the treatment time for the Iris plans increased with an increasing target volume. The Iris plans were, on average, 40% longer than the corresponding mMLC plans for small targets ( 3 ) and ≤121% longer for larger targets. For a comparable conformality index, similar results were obtained. Conclusion: For stereotactic lung irradiation, time

  1. Verification of multileaf collimator leaf positions using an electronic portal imaging device

    International Nuclear Information System (INIS)

    Samant, Sanjiv S.; Zheng Wei; Parra, Nestor Andres; Chandler, Jason; Gopal, Arun; Wu Jian; Jain Jinesh; Zhu Yunping; Sontag, Marc

    2002-01-01

    An automated method is presented for determining individual leaf positions of the Siemens dual focus multileaf collimator (MLC) using the Siemens BEAMVIEW(PLUS) electronic portal imaging device (EPID). Leaf positions are computed with an error of 0.6 mm at one standard deviation (σ) using separate computations of pixel dimensions, image distortion, and radiation center. The pixel dimensions are calculated by superimposing the film image of a graticule with the corresponding EPID image. A spatial correction is used to compensate for the optical distortions of the EPID, reducing the mean distortion from 3.5 pixels (uncorrected) per localized x-ray marker to 2 pixels (1 mm) for a rigid rotation and 1 pixel for a third degree polynomial warp. A correction for a nonuniform dosimetric response across the field of view of the EPID images is not necessary due to the sharp intensity gradients across leaf edges. The radiation center, calculated from the average of the geometric centers of a square field at 0 deg. and 180 deg. collimator angles, is independent of graticule placement error. Its measured location on the EPID image was stable to within 1 pixel based on 3 weeks of repeated extensions/retractions of the EPID. The MLC leaf positions determined from the EPID images agreed to within a pixel of the corresponding values measured using film and ionization chamber. Several edge detection algorithms were tested: contour, Sobel, Roberts, Prewitt, Laplace, morphological, and Canny. These agreed with each other to within ≤1.2 pixels for the in-air EPID images. Using a test pattern, individual MLC leaves were found to be typically within 1 mm of the corresponding record-and-verify values, with a maximum difference of 1.8 mm, and standard deviations of <0.3 mm in the daily reproducibility. This method presents a fast, automatic, and accurate alternative to using film or a light field for the verification and calibration of the MLC

  2. Analysis of Radiation Field and Block Pattern for Optimal Size in Multileaf Collimator

    International Nuclear Information System (INIS)

    Ahn, Seoung Do; Yang, Kwang Mo; Yi, Byong Yong; Choi, Eun Kyong; Chang, Hye Sook

    1994-01-01

    The patterns of the conventional radiation treatment fields and their shielding blocks are analysed to determine the optimal dimension of the MultiLeaf Collimator (MLC) which is considered as an essential tool for conformal therapy. Total 1169 radiation fields from 303 patients (203 from Asan Medical center, 50 from Baek Hosp and 50 from Hanyang Univ. Hosp.) were analysed for this study. Weighted case selection treatment site (from The Korean Society of Therapeutic Radiology 1003). Ninety one percent of total fields have shielding blocks. Y axis is defined as leaf movement direction and it is assumed that MLC is installed on the cranial-caudal direction. The length of X axis were distributed from 4cm to 40cm (less than 21cm for 95% of cases), and Y axis from 5cm to 38cm (less than 22cm for 95% of cases). The shielding blocks extended to less than 6cm from center of the filed for 95% of the cases. Start length for ninety five percent of block is less than 10cm for X axis and 11cm for Y axis. Seventy six percent of shielding blocks could be placed by either X or Y axis direction, 7.9% only by Y axis, 5.1% only by X axis and it is reasonable to install MLC for Y direction. Ninety five percent of patients can be treated with coplanar rotation therapy without changing the collimator angle. Eleven percent of cases of cases were impossible to replace with MLC. Futher study of shielding should be larger than 21cm X 22cm. The MLC should be designed as a pair of 21 leaves with 1cm wide for an acceptable resolution and 17cm long to enable the leaf to overtravel at least 6cm from the treatment field center

  3. Initiation of conformal radiotherapy with a multileaf-collimator - An approach to clinical routine

    International Nuclear Information System (INIS)

    Bannach, B.; Doll, Th.; Pape, H.; Schmitt, G.

    1995-01-01

    The implementation of a three-dimensional conformal radiotherapy facility in the radiotherapy department of the Heinrich Heine University is described. Complex radiotherapy techniques with commercially available networked systems are introduced to improve clinical work. Over 18 month we have gained clinical experience with a PHILIPS Multileaf Collimator (MLC) mounted on a SL 25 linear accelerator. For a limited period the MLC was used as a conventional blocking device. The standard MLC-shapes are controlled with a stand-alone computer system. In addition, a three-dimensional treatment planning system (3-D-TPS / TMS-Radix, Helax AB) based on convolution/superposition algorithms was recently installed. Treatment optimization is achieved using static field arrangements with complete volumetric computerized tomographic patient data for 3-D-TPS. Conformal adaptation of the 95%-isodose to the Planning Target Volume (PTV, ICRU 50) results in MLC-field-shaping concerning size, position and contour to PTV-projection in beams-eye-view (BEV). Field prescription with defined leaf positions of the MLC-setting for geometrical beam shaping is transferred from TPS via TCP/IP. Patient treatment with complex coplanar and non-coplanar field arrangements is performed with an automatic set-up for gantry and collimator angle position contolled by a verification system. Quality assurance for treatment set-up is gained with a mega-voltage imaging device (MVI / PHILIPS SRI 100). Actual treatment outcome and accurate dose delivery for conformal therapy is verified by intercomparison of geometrical field matching of MVI and digitally reconstructed radiographs (DRR) for each delivered beam in BEV

  4. SU-F-T-540: Comprehensive Fluence Delivery Optimization with Multileaf Collimation

    Energy Technology Data Exchange (ETDEWEB)

    Weppler, S; Villarreal-Barajas, J [Department of Physics and Astronomy, University of Calgary, Calgary, Alberta (Canada); Department of Medical Physics, Tom Baker Cancer Center, Calgary, Alberta (Canada); McGeachy, P [Department of Medical Physics, CancerCare Manitoba, Winnipeg, Manitoba (Canada); Khan, R [Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO (United States)

    2016-06-15

    Purpose: Multileaf collimator (MLC) leaf sequencing is performed via commercial black-box implementations, on which a user has limited to no access. We have developed an explicit, generic MLC sequencing model to serve as a tool for future investigations of fluence map optimization, fluence delivery optimization, and rotational collimator delivery methods. Methods: We have developed a novel, comprehensive model to effectively account for a variety of transmission and penumbra effects previously treated on an ad hoc basis in the literature. As the model is capable of quantifying a variety of effects, we utilize the asymmetric leakage intensity across each leaf to deliver fluence maps with pixel size smaller than the narrowest leaf width. Developed using linear programming and mixed integer programming formulations, the model is implemented using state of the art open-source solvers. To demonstrate the versatility of the algorithm, a graphical user interface (GUI) was developed in MATLAB capable of accepting custom leaf specifications and transmission parameters. As a preliminary proof-ofconcept, we have sequenced the leaves of a Varian 120 Leaf Millennium MLC for five prostate cancer patient fields and one head and neck field. Predetermined fluence maps have been processed by data smoothing methods to obtain pixel sizes of 2.5 cm{sup 2}. The quality of output was analyzed using computer simulations. Results: For the prostate fields, an average root mean squared error (RMSE) of 0.82 and gamma (0.5mm/0.5%) of 91.4% were observed compared to RMSE and gamma (0.5mm/0.5%) values of 7.04 and 34.0% when the leakage considerations were omitted. Similar results were observed for the head and neck case. Conclusion: A model to sequence MLC leaves to optimality has been proposed. Future work will involve extensive testing and evaluation of the method on clinical MLCs and comparison with black-box leaf sequencing algorithms currently used by commercial treatment planning systems.

  5. Multileaf collimator-based linear accelerator radiosurgery: five-year efficiency analysis.

    Science.gov (United States)

    Lawson, Joshua D; Fox, Tim; Waller, Anthony F; Davis, Lawrence; Crocker, Ian

    2009-03-01

    In 1989, Emory University initiated a linear accelerator (linac) radiosurgery program using circular collimators. In 2001, the program converted to a multileaf collimator. Since then, the treatment parameters of each patient have been stored in the record-and-verify system. Three major changes have occurred in the radiosurgery program in the past 6 years: in 2002, treatment was changed from static conformal beams to dynamic conformal arc (DCA) therapy, and all patients were imaged before treatment. Beginning in 2005, a linac was used, with the opportunity to treat at higher dose rates (600-1,000 monitor units/min). The aim of this study was to analyze the time required to deliver radiosurgery and the factors affecting treatment delivery. Benchmark data are provided for centers contemplating initiating linac radiosurgery programs. Custom software was developed to mine the record-and-verify system database and automatically perform a chart review on patients who underwent stereotactic radiosurgery from March 2001 to October 2006. The software extracted 510 patients who underwent stereotactic radiosurgery, and the following information was recorded for each patient: treatment technique, treatment time (from initiation of imaging, if done, to completion of therapy), number of isocenters, number of fields, total monitor units, and dose rate. Of the 510 patients, 395 were treated with DCA therapy and 115 with static conformal beams. The average number of isocenters treated was 1.06 (range, 1-4). The average times to deliver treatment were 24.1 minutes for patients who underwent DCA therapy and 19.3 minutes for those treated with static conformal beams, reflecting the lack of imaging in the latter patients. Eighty percent of patients were treated in question the need for a dedicated radiosurgery unit for even busy treatment centers.

  6. Monte Carlo simulation of a multi-leaf collimator design for telecobalt machine using BEAMnrc code

    Directory of Open Access Journals (Sweden)

    Ayyangar Komanduri

    2010-01-01

    Full Text Available This investigation aims to design a practical multi-leaf collimator (MLC system for the cobalt teletherapy machine and check its radiation properties using the Monte Carlo (MC method. The cobalt machine was modeled using the BEAMnrc Omega-Beam MC system, which could be freely downloaded from the website of the National Research Council (NRC, Canada. Comparison with standard depth dose data tables and the theoretically modeled beam showed good agreement within 2%. An MLC design with low melting point alloy (LMPA was tested for leakage properties of leaves. The LMPA leaves with a width of 7 mm and height of 6 cm, with tongue and groove of size 2 mm wide by 4 cm height, produced only 4% extra leakage compared to 10 cm height tungsten leaves. With finite 60 Co source size, the interleaf leakage was insignificant. This analysis helped to design a prototype MLC as an accessory mount on a cobalt machine. The complete details of the simulation process and analysis of results are discussed.

  7. Postoperative modified stereotactic radiotherapy using a micro-multileaf collimator in patients with malignant glioma.

    Science.gov (United States)

    Isaka, Toshihiko; Nishiyama, Kinji; Nakagawa, Hidemitsu; Suzuki, Tsuyoshi; Wada, Kouichi

    2002-06-01

    To achieve local control of malignant glioma, we designed a postoperative stereotactic radiotherapy using a micro-multileaf collimator (micro-MLC). The purpose of this study was to clarify the feasibility of this treatment. The treatment was performed in six patients who met the following eligibility criteria: (1) supratentorial tumor, (2) residual tumor volume or = 70. The three planning target volumes (PTVs), which consisted of restricted PTV (RPTV), intermediate PTV (IPTV), and extended PTV (EPTV), defined as the residual tumor plus a 1 cm, 2 cm, and 3 cm margins, respectively, and total dose delivery of 60-68 Gy, 52-60 Gy, and 44-52 Gy to the isocenters of RPTV, IPTV, and EPTV, respectively, in 4 Gy per fraction at five fractions per week, were established. The beam arrangement and the conformal blockade with a micro-MLC for the optimal treatment plan were designed. The treatment plans showed the high dose conformation to EPTV, the appropriate dose gradients in the three PTVs with the high dose homogeneity to RPTV, and the tolerated dose to critical structures. Following the plans, treatment was performed. The clinical findings more than 12 months after the treatment supported its possible use. We conclude that this treatment is feasible at least in selected patients.

  8. Analytical model of the binary multileaf collimator of tomotherapy for Monte Carlo simulations

    International Nuclear Information System (INIS)

    Sterpin, E; Vynckier, S; Salvat, F; Olivera, G H

    2008-01-01

    Helical Tomotherapy (HT) delivers intensity-modulated radiotherapy by the means of many configurations of the binary multi-leaf collimator (MLC). The aim of the present study was to devise a method, which we call the 'transfer function' (TF) method, to perform the transport of particles through the MLC much faster than the time consuming Monte Carlo (MC) simulation and with no significant loss of accuracy. The TF method consists of calculating, for each photon in the phase-space file, the attenuation factor for each leaf (up to three) that the photon passes, assuming straight propagation through closed leaves, and storing these factors in a modified phase-space file. To account for the transport through the MLC in a given configuration, the weight of a photon is simply multiplied by the attenuation factors of the leaves that are intersected by the photon ray and are closed. The TF method was combined with the PENELOPE MC code, and validated with measurements for the three static field sizes available (40x5, 40x2.5 and 40x1 cm 2 ) and for some MLC patterns. The TF method allows a large reduction in computation time, without introducing appreciable deviations from the result of full MC simulations

  9. Modeling Monte Carlo of multileaf collimators using the code GEANT4

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Alex C.H.; Lima, Fernando R.A., E-mail: oliveira.ach@yahoo.com, E-mail: falima@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Lima, Luciano S.; Vieira, Jose W., E-mail: lusoulima@yahoo.com.br [Instituto Federal de Educacao, Ciencia e Tecnologia de Pernambuco (IFPE), Recife, PE (Brazil)

    2014-07-01

    Radiotherapy uses various techniques and equipment for local treatment of cancer. The equipment most often used in radiotherapy to the patient irradiation is linear accelerator (Linac). Among the many algorithms developed for evaluation of dose distributions in radiotherapy planning, the algorithms based on Monte Carlo (MC) methods have proven to be very promising in terms of accuracy by providing more realistic results. The MC simulations for applications in radiotherapy are divided into two parts. In the first, the simulation of the production of the radiation beam by the Linac is performed and then the phase space is generated. The phase space contains information such as energy, position, direction, etc. of millions of particles (photons, electrons, positrons). In the second part the simulation of the transport of particles (sampled phase space) in certain configurations of irradiation field is performed to assess the dose distribution in the patient (or phantom). Accurate modeling of the Linac head is of particular interest in the calculation of dose distributions for intensity modulated radiation therapy (IMRT), where complex intensity distributions are delivered using a multileaf collimator (MLC). The objective of this work is to describe a methodology for modeling MC of MLCs using code Geant4. To exemplify this methodology, the Varian Millennium 120-leaf MLC was modeled, whose physical description is available in BEAMnrc Users Manual (20 11). The dosimetric characteristics (i.e., penumbra, leakage, and tongue-and-groove effect) of this MLC were evaluated. The results agreed with data published in the literature concerning the same MLC. (author)

  10. Monte Carlo simulation of a multi-leaf collimator design for telecobalt machine using BEAMnrc code

    International Nuclear Information System (INIS)

    Ayyangar, Komanduri M.; Narayan, Pradush; Jesuraj, Fenedit; Raju, M.R.; Dinesh Kumar, M.

    2010-01-01

    This investigation aims to design a practical multi-leaf collimator (MLC) system for the cobalt teletherapy machine and check its radiation properties using the Monte Carlo (MC) method. The cobalt machine was modeled using the BEAMnrc Omega-Beam MC system, which could be freely downloaded from the website of the National Research Council (NRC), Canada. Comparison with standard depth dose data tables and the theoretically modeled beam showed good agreement within 2%. An MLC design with low melting point alloy (LMPA) was tested for leakage properties of leaves. The LMPA leaves with a width of 7 mm and height of 6 cm, with tongue and groove of size 2 mm wide by 4 cm height, produced only 4% extra leakage compared to 10 cm height tungsten leaves. With finite 60 Co source size, the interleaf leakage was insignificant. This analysis helped to design a prototype MLC as an accessory mount on a cobalt machine. The complete details of the simulation process and analysis of results are discussed. (author)

  11. Manual multi-leaf collimator for electron beam shaping - a feasibility study

    International Nuclear Information System (INIS)

    Ravindran, B Paul; Singh, I Rabi Raja; Brindha, S; Sathyan, S

    2002-01-01

    In electron beam therapy, lead or low melting point alloy (LMA) sheet cutouts of sufficient thickness are commonly used to shape the beam. In order to avoid making cutouts for each patient, an attempt has been made to develop a manual multi-leaf collimator for electron beams (eMLC). The eMLC has been developed using LMA for a 15x15 cm 2 applicator. Electron beam characteristics such as depth dose, beam profiles, surface dose, output factors and virtual source position with the eMLC have been studied and compared with those of an applicator electron beam. The interleaf leakage radiation has also been measured with film dosimetry. Depth dose values obtained using the eMLC were found to be identical to those with the applicator for depths larger than D max . However, a decrease in the size of the beam penumbra with the eMLC and increase in the values of surface dose, output factors and virtual source position with eMLC were observed. The leakage between the leaves was less than 5% and the leakage between the opposing leaves was 15%, which could be minimized further by careful positioning of the leaves. It is observed that it is feasible to use such a manual eMLC for patients and eliminate the fabrication of cutouts for each patient

  12. Modification of a 3D-planning system for use with a multileaf collimator

    Energy Technology Data Exchange (ETDEWEB)

    Van Duyse, B [Ghent Rijksuniversiteit (Belgium). Kliniek voor Radiotherapie en Kerngeneeskunde; Colle, C; De Wagter, C; De Neve, W

    1995-12-01

    Recently, the Philips SL25 linear accelerator of the Radiotherapy Department at the University Hospital of Gent was retro-fitted with a multileaf collimator (MLC). To allow treatment planning with the MLC, the currently use GRATISTM 3D-planning system (developed by G. Sherouse) needed some adaptations, using the C source code. The virtual Simulator section was extended so that the leaves are graphically set in the Beams Eye View. The leaves can be set manually or automatically, based on a previously defined margin around the target. Once the leaves are set, a data file is created for each beam, containing the leaf settings. This file is finally transferred to the MLC computer over the network or by disk. The entire process does not require any manual transfer of leaf settings, not only adding a time-saving but also an error preventing factor to the GRATISTM 3D-planning system. Measurements to verify the accuracy of the adaptations to the planning system are addressed.

  13. A multileaf collimator phantom for the quality assurance of radiation therapy planning systems and CT simulators

    International Nuclear Information System (INIS)

    McNiven, Andrea; Kron, Tomas; Van Dyk, Jake

    2004-01-01

    Purpose: The evolution of three-dimensional conformal radiation treatment has led to the use of multileaf collimators (MLCs) in intensity-modulated radiation therapy (IMRT) and other treatment techniques to increase the conformity of the dose distribution. A new quality assurance (QA) phantom has been designed to check the handling of MLC settings in treatment planning and delivery. Methods and materials: The phantom consists of a Perspex block with stepped edges that can be rotated in all planes. The design allows for the assessment of several MLC and micro-MLC types from various manufacturers, and is therefore applicable to most radiation therapy institutions employing MLCs. The phantom is computed tomography (CT) scanned as is a patient, and QA assessments can be made of field edge display for a variety of shapes and orientations on both radiation treatment planning systems (RTPS) and computed tomography simulators. Results: The dimensions of the phantom were verified to be physically correct within an uncertainty range of 0-0.7 mm. Errors in leaf position larger than 1 mm were easily identified by multiple observers. Conclusions: The MLC geometry phantom is a useful tool in the QA of radiation therapy with application to RTPS, CT simulators, and virtual simulation packages with MLC display capabilities

  14. Modification of a 3D-planning system for use with a multileaf collimator

    International Nuclear Information System (INIS)

    Van Duyse, B.; Colle, C.; De Wagter, C.; De Neve, W.

    1995-01-01

    Recently, the Philips SL25 linear accelerator of the Radiotherapy Department at the University Hospital of Gent was retro-fitted with a multileaf collimator (MLC). To allow treatment planning with the MLC, the currently use GRATISTM 3D-planning system (developed by G. Sherouse) needed some adaptations, using the C source code. The virtual Simulator section was extended so that the leaves are graphically set in the Beams Eye View. The leaves can be set manually or automatically, based on a previously defined margin around the target. Once the leaves are set, a data file is created for each beam, containing the leaf settings. This file is finally transferred to the MLC computer over the network or by disk. The entire process does not require any manual transfer of leaf settings, not only adding a time-saving but also an error preventing factor to the GRATISTM 3D-planning system. Measurements to verify the accuracy of the adaptations to the planning system are addressed

  15. Assessment of diagnostic multileaf collimator for cephalometric exposure reduction using optically stimulated luminescent dosemeters

    International Nuclear Information System (INIS)

    Han, Su Chul; Kim, Kum Bae; Jung, Haijo; Ji, YoungHoon; Park, Seungwoo

    2017-01-01

    A diagnostic multileaf collimator (MLC) was developed for diagnostic radiography dose reduction. Optically stimulated luminescent dosemeters (OSLDs) were used to evaluate the efficacy of this device for dental radiography cephalometric exposure reduction. The OSLD dosimetric characteristics for 80 kVp cephalometric exposure were first obtained. The batch homogeneity and reproducibility were 1.67 % and 0.18-1.58, respectively. Good linearity was obtained between the OSLD dose and response, and the angular dependence was within ±4 %. The equivalent organ doses for the left eye, right eye and thyroid were 41.20±6.58, 178.86±1.71 and 171.12±8.78 mSv and 36.80±0.33, 156.63±0.22 and 22.04±0.13 mSv for the open and MLC fields, respectively. The MLC-induced dose reductions for the left and right eyes of in field were 10.67±16.78 and 12.42±8.84 %, respectively, and that of the thyroid gland of out of field was 87±8.82 %, considering combined uncertainty. Therefore, use of diagnostic MLC for dose reduction during dental radiography cephalometric exposure is both feasible and effective. (authors)

  16. Feasibility of replacing patient specific cutouts with a computer-controlled electron multileaf collimator

    International Nuclear Information System (INIS)

    Eldib, Ahmed; Jin Lihui; Li Jinsheng; Ma, C-M Charlie

    2013-01-01

    A motorized electron multileaf collimator (eMLC) was developed as an add-on device to the Varian linac for delivery of advanced electron beam therapy. It has previously been shown that electron beams collimated by an eMLC have very similar penumbra to those collimated by applicators and cutouts. Thus, manufacturing patient specific cutouts would no longer be necessary, resulting in the reduction of time taken in the cutout fabrication process. Moreover, cutout construction involves handling of toxic materials and exposure to toxic fumes that are usually generated during the process, while the eMLC will be a pollution-free device. However, undulation of the isodose lines is expected due to the finite size of the eMLC. Hence, the provided planned target volume (PTV) shape will not exactly follow the beam's-eye-view of the PTV, but instead will make a stepped approximation to the PTV shape. This may be a problem when the field edge is close to a critical structure. Therefore, in this study the capability of the eMLC to achieve the same clinical outcome as an applicator/cutout combination was investigated based on real patient computed tomographies (CTs). An in-house Monte Carlo based treatment planning system was used for dose calculation using ten patient CTs. For each patient, two plans were generated; one with electron beams collimated using the applicator/cutout combination; and the other plan with beams collimated by the eMLC. Treatment plan quality was compared for each patient based on dose distribution and dose–volume histogram. In order to determine the optimal position of the leaves, the impact of the different leaf positioning strategies was investigated. All plans with both eMLC and cutouts were generated such that 100% of the target volume receives at least 90% of the prescribed dose. Then the percentage difference in dose between both delivery techniques was calculated for all the cases. The difference in the dose received by 10% of the volume of the

  17. Feasibility of replacing patient specific cutouts with a computer-controlled electron multileaf collimator

    Science.gov (United States)

    Eldib, Ahmed; Jin, Lihui; Li, Jinsheng; Ma, C.-M. Charlie

    2013-08-01

    A motorized electron multileaf collimator (eMLC) was developed as an add-on device to the Varian linac for delivery of advanced electron beam therapy. It has previously been shown that electron beams collimated by an eMLC have very similar penumbra to those collimated by applicators and cutouts. Thus, manufacturing patient specific cutouts would no longer be necessary, resulting in the reduction of time taken in the cutout fabrication process. Moreover, cutout construction involves handling of toxic materials and exposure to toxic fumes that are usually generated during the process, while the eMLC will be a pollution-free device. However, undulation of the isodose lines is expected due to the finite size of the eMLC. Hence, the provided planned target volume (PTV) shape will not exactly follow the beam's-eye-view of the PTV, but instead will make a stepped approximation to the PTV shape. This may be a problem when the field edge is close to a critical structure. Therefore, in this study the capability of the eMLC to achieve the same clinical outcome as an applicator/cutout combination was investigated based on real patient computed tomographies (CTs). An in-house Monte Carlo based treatment planning system was used for dose calculation using ten patient CTs. For each patient, two plans were generated; one with electron beams collimated using the applicator/cutout combination; and the other plan with beams collimated by the eMLC. Treatment plan quality was compared for each patient based on dose distribution and dose-volume histogram. In order to determine the optimal position of the leaves, the impact of the different leaf positioning strategies was investigated. All plans with both eMLC and cutouts were generated such that 100% of the target volume receives at least 90% of the prescribed dose. Then the percentage difference in dose between both delivery techniques was calculated for all the cases. The difference in the dose received by 10% of the volume of the

  18. Dose deviations caused by positional inaccuracy of multileaf collimator in intensity modulated radiotherapy

    International Nuclear Information System (INIS)

    Wang, H.C.; Chui, C.S.; Tsai, H.Y.; Chen, C.H.; Tsai, L.F.

    2008-01-01

    Introduction: Multileaf collimator (MLC) is currently a widely used system in the delivery of intensity modulated radiotherapy (IMRT). The accuracy of the multileaf position plays an important role in the final outcome of the radiation treatment. According to ICRU recommendation, a dose inaccuracy over than 5% of prescribed dose affects treatment results. In order to quantify the influence of leaf positional errors on dose distribution, we set different MLC positional inaccuracy from 0 to 6 mm for step-and-shoot IMRT in clinical cases. Two-dimensional dose distributions of radiotherapy plans with different leaf displacements generated with a commercial treatment planning system. And verification films were used to measure two-dimensional dose distributions. Then a computerized dose comparison system will be introduced to analyze the dose deviations. Materials/methods: We assumed MLC positional inaccuracy from 0 to 6 mm for step-and-shoot IMRT in clinical cases by simulating the different leaf displacements with a commercial treatment planning system. Then we transferred the treatment plans with different leaf offset that may be happened in clinical situation to linear accelerator. Verification films (Kodat EDR2) were well positioned within solid water phantoms to be irradiated by the simulated plans. The films were scanned to display two-dimensional dose distributions. Finally, we compared with the dose distributions with MLC positional inaccuracy by a two-dimensional dose comparison software to analyze the deviations in Gamma indexes and normalized agreement test (NAT) values. Results: In general, the data show that larger leaf positional error induces larger dose error. More fields used for treatment generate lesser errors. Besides, leaf position relative to a field influences the degree of dose error. A leaf lying close to the border of a field leads to a more significant dose deviation than a leaf in the center. Algorithms for intensity modulation also affect

  19. Characterization of an add-on multileaf collimator for electron beam therapy

    International Nuclear Information System (INIS)

    Gauer, T; Sokoll, J; Cremers, F; Schmidt, R; Harmansa, R; Luzzara, M

    2008-01-01

    An add-on multileaf collimator for electrons (eMLC) has been developed that provides computer-controlled beam collimation and isocentric dose delivery. The design parameters result from the design study by Gauer et al (2006 Phys. Med. Biol. 51 5987-6003) and were configured such that a compact and light-weight eMLC with motorized leaves can be industrially manufactured and stably mounted on a conventional linear accelerator. In the present study, the efficiency of an initial computer-controlled prototype was examined according to the design goals and the performance of energy- and intensity-modulated treatment techniques. This study concentrates on the attachment and gantry stability as well as the dosimetric characteristics of central-axis and off-axis dose, field size dependence, collimator scatter, field abutment, radiation leakage and the setting of the accelerator jaws. To provide isocentric irradiation, the eMLC can be placed either 16 or 28 cm above the isocentre through interchangeable holders. The mechanical implementation of this feature results in a maximum field displacement of less than 0.6 mm at 90 0 and 270 0 gantry angles. Compared to a 10 x 10 cm applicator at 6-14 MeV, the beam penumbra of the eMLC at a 16 cm collimator-to-isocentre distance is 0.8-0.4 cm greater and the depth-dose curves show a larger build-up effect. Due to the loss in energy dependence of the therapeutic range and the much lower dose output at small beam sizes, a minimum beam size of 3 x 3 cm is necessary to avoid suboptimal dose delivery. Dose output and beam symmetry are not affected by collimator scatter when the central axis is blocked. As a consequence of the broader beam penumbra, uniform dose distributions were measured in the junction region of adjacent beams at perpendicular and oblique beam incidence. However, adjacent beams with a high difference in a beam energy of 6 to 14 MeV generate cold and hot spots of approximately 15% in the abutting region. In order to

  20. Characterization of an add-on multileaf collimator for electron beam therapy

    Energy Technology Data Exchange (ETDEWEB)

    Gauer, T; Sokoll, J; Cremers, F; Schmidt, R [Department of Radiotherapy and Radio-Oncology, University Medical Center Hamburg-Eppendorf, Hamburg (Germany); Harmansa, R [3D Line, Schwarzenbruck (Germany); Luzzara, M [3D Line, Milan (Italy)], E-mail: t.gauer@uke.uni-hamburg.de

    2008-02-21

    An add-on multileaf collimator for electrons (eMLC) has been developed that provides computer-controlled beam collimation and isocentric dose delivery. The design parameters result from the design study by Gauer et al (2006 Phys. Med. Biol. 51 5987-6003) and were configured such that a compact and light-weight eMLC with motorized leaves can be industrially manufactured and stably mounted on a conventional linear accelerator. In the present study, the efficiency of an initial computer-controlled prototype was examined according to the design goals and the performance of energy- and intensity-modulated treatment techniques. This study concentrates on the attachment and gantry stability as well as the dosimetric characteristics of central-axis and off-axis dose, field size dependence, collimator scatter, field abutment, radiation leakage and the setting of the accelerator jaws. To provide isocentric irradiation, the eMLC can be placed either 16 or 28 cm above the isocentre through interchangeable holders. The mechanical implementation of this feature results in a maximum field displacement of less than 0.6 mm at 90{sup 0} and 270{sup 0} gantry angles. Compared to a 10 x 10 cm applicator at 6-14 MeV, the beam penumbra of the eMLC at a 16 cm collimator-to-isocentre distance is 0.8-0.4 cm greater and the depth-dose curves show a larger build-up effect. Due to the loss in energy dependence of the therapeutic range and the much lower dose output at small beam sizes, a minimum beam size of 3 x 3 cm is necessary to avoid suboptimal dose delivery. Dose output and beam symmetry are not affected by collimator scatter when the central axis is blocked. As a consequence of the broader beam penumbra, uniform dose distributions were measured in the junction region of adjacent beams at perpendicular and oblique beam incidence. However, adjacent beams with a high difference in a beam energy of 6 to 14 MeV generate cold and hot spots of approximately 15% in the abutting region. In

  1. Intensity modulation of therapeutic photon beams using a rotating multileaf collimator

    International Nuclear Information System (INIS)

    Otto, Karl

    2004-01-01

    The thesis describes the development and implementation of a novel method of delivering intensity modulated radiation therapy (IMRT) that provides greater accuracy and spatial resolution than currently available methods. Through improvements in multileaf collimator (MLC) based fluence generation, a dose distribution may be generated that conforms more closely to the tumour target volume. Healthy tissue surrounding the target volume will therefore receive less dose, reducing the probability of side effects and allowing the physician to increase the prescribed tumor dose (dose escalation). As a preamble to the description of the IMRT delivery method a new model for evaluating the spatial resolution capabilities of dose delivery techniques is presented. Flexibility and complexity in patient treatment due to advances in radiotherapy techniques necessitates a simple method for evaluating spatial resolution capabilities of the dose delivery device. The model is based on linear systems theory and is analogous to methods used to describe resolution degradation in imaging systems. The spatial resolution capabilities of different delivery components can be quantified separately, providing a simple method for comparing different treatment machine characteristics. Also, the model provides the ability to evaluate spatial resolution changes independent of the tumor that is being treated, providing a means of comparing delivery techniques that is not biased by the characteristics of any particular treatment volume. MLC based IMRT techniques are well established but suffer several physical limitations. Dosimetric spatial resolution is limited by the MLC leaf width, interleaf leakage and tongue-and-groove effects degrade dosimetric accuracy and the range of leaf motion limits the maximum deliverable field size. Based on observations from the linear systems model it is hypothesized that, by rotating the entire MLC between each sub-field, improvements will be obtained in spatial

  2. A machine learning approach to the accurate prediction of multi-leaf collimator positional errors

    Science.gov (United States)

    Carlson, Joel N. K.; Park, Jong Min; Park, So-Yeon; In Park, Jong; Choi, Yunseok; Ye, Sung-Joon

    2016-03-01

    Discrepancies between planned and delivered movements of multi-leaf collimators (MLCs) are an important source of errors in dose distributions during radiotherapy. In this work we used machine learning techniques to train models to predict these discrepancies, assessed the accuracy of the model predictions, and examined the impact these errors have on quality assurance (QA) procedures and dosimetry. Predictive leaf motion parameters for the models were calculated from the plan files, such as leaf position and velocity, whether the leaf was moving towards or away from the isocenter of the MLC, and many others. Differences in positions between synchronized DICOM-RT planning files and DynaLog files reported during QA delivery were used as a target response for training of the models. The final model is capable of predicting MLC positions during delivery to a high degree of accuracy. For moving MLC leaves, predicted positions were shown to be significantly closer to delivered positions than were planned positions. By incorporating predicted positions into dose calculations in the TPS, increases were shown in gamma passing rates against measured dose distributions recorded during QA delivery. For instance, head and neck plans with 1%/2 mm gamma criteria had an average increase in passing rate of 4.17% (SD  =  1.54%). This indicates that the inclusion of predictions during dose calculation leads to a more realistic representation of plan delivery. To assess impact on the patient, dose volumetric histograms (DVH) using delivered positions were calculated for comparison with planned and predicted DVHs. In all cases, predicted dose volumetric parameters were in closer agreement to the delivered parameters than were the planned parameters, particularly for organs at risk on the periphery of the treatment area. By incorporating the predicted positions into the TPS, the treatment planner is given a more realistic view of the dose distribution as it will truly be

  3. Incorporating multi-leaf collimator leaf sequencing into iterative IMRT optimization

    International Nuclear Information System (INIS)

    Siebers, Jeffrey V.; Lauterbach, Marc; Keall, Paul J.; Mohan, Radhe

    2002-01-01

    Intensity modulated radiation therapy (IMRT) treatment planning typically considers beam optimization and beam delivery as separate tasks. Following optimization, a multi-leaf collimator (MLC) or other beam delivery device is used to generate fluence patterns for patient treatment delivery. Due to limitations and characteristics of the MLC, the deliverable intensity distributions often differ from those produced by the optimizer, leading to differences between the delivered and the optimized doses. Objective function parameters are then adjusted empirically, and the plan is reoptimized to achieve a desired deliverable dose distribution. The resulting plan, though usually acceptable, may not be the best achievable. A method has been developed to incorporate the MLC restrictions into the optimization process. Our in-house IMRT system has been modified to include the calculation of the deliverable intensity into the optimizer. In this process, prior to dose calculation, the MLC leaf sequencer is used to convert intensities to dynamic MLC sequences, from which the deliverable intensities are then determined. All other optimization steps remain the same. To evaluate the effectiveness of deliverable-based optimization, 17 patient cases have been studied. Compared with standard optimization plus conversion to deliverable beams, deliverable-based optimization results show improved isodose coverage and a reduced dose to critical structures. Deliverable-based optimization results are close to the original nondeliverable optimization results, suggesting that IMRT can overcome the MLC limitations by adjusting individual beamlets. The use of deliverable-based optimization may reduce the need for empirical adjustment of objective function parameters and reoptimization of a plan to achieve desired results

  4. Monte Carlo simulation based study of a proposed multileaf collimator for a telecobalt machine

    International Nuclear Information System (INIS)

    Sahani, G.; Dash Sharma, P. K.; Hussain, S. A.; Dutt Sharma, Sunil; Sharma, D. N.

    2013-01-01

    Purpose: The objective of the present work was to propose a design of a secondary multileaf collimator (MLC) for a telecobalt machine and optimize its design features through Monte Carlo simulation. Methods: The proposed MLC design consists of 72 leaves (36 leaf pairs) with additional jaws perpendicular to leaf motion having the capability of shaping a maximum square field size of 35 × 35 cm 2 . The projected widths at isocenter of each of the central 34 leaf pairs and 2 peripheral leaf pairs are 10 and 5 mm, respectively. The ends of the leaves and the x-jaws were optimized to obtain acceptable values of dosimetric and leakage parameters. Monte Carlo N-Particle code was used for generating beam profiles and depth dose curves and estimating the leakage radiation through the MLC. A water phantom of dimension 50 × 50 × 40 cm 3 with an array of voxels (4 × 0.3 × 0.6 cm 3 = 0.72 cm 3 ) was used for the study of dosimetric and leakage characteristics of the MLC. Output files generated for beam profiles were exported to the PTW radiation field analyzer software through locally developed software for analysis of beam profiles in order to evaluate radiation field width, beam flatness, symmetry, and beam penumbra. Results: The optimized version of the MLC can define radiation fields of up to 35 × 35 cm 2 within the prescribed tolerance values of 2 mm. The flatness and symmetry were found to be well within the acceptable tolerance value of 3%. The penumbra for a 10 × 10 cm 2 field size is 10.7 mm which is less than the generally acceptable value of 12 mm for a telecobalt machine. The maximum and average radiation leakage through the MLC were found to be 0.74% and 0.41% which are well below the International Electrotechnical Commission recommended tolerance values of 2% and 0.75%, respectively. The maximum leakage through the leaf ends in closed condition was observed to be 8.6% which is less than the values reported for other MLCs designed for medical linear

  5. Characteristics and performance of the first commercial multileaf collimator for a robotic radiosurgery system

    Energy Technology Data Exchange (ETDEWEB)

    Fürweger, Christoph, E-mail: christoph.fuerweger@cyber-knife.net [Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam 3075 EA, The Netherlands and European CyberKnife Center Munich, Munich 81377 (Germany); Prins, Paulette; Coskan, Harun; Heijmen, Ben J. M. [Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam 3075 EA (Netherlands)

    2016-05-15

    Purpose: The “InCise™ multileaf-collimator (MLC)” is the first commercial MLC to be mounted on a robotic SRS/SBRT platform (CyberKnife). The authors assessed characteristics and performance of this novel device in a preclinical five months test period. Methods: Commissioning beam data were acquired with unshielded diodes. EBT3 radiochromic films were employed for measurement of transmission, leaf/bank position accuracy (garden fence) before and after exercising the MLC, for end-to-end testing and further characterization of the beam. The robot workspace with MLC was assessed analytically by transformation to an Euler geometry (“plane,” “gantry,” and “collimator” angles) and by measuring pointing accuracy at each node. Stability over time was evaluated in picket fence and adapted Winston–Lutz tests (AQA). Results: Beam penumbrae (80%–20%, with 100% = 2 × dose at inflection point for field sizes ≥ 50 × 50 mm{sup 2}) were 2.2–3.7 mm for square fields in reference condition (source-axis-distance 800 mm, depth 15 mm) and depended on field size and off-axis position. Transmission and leakage did not exceed 0.5%. Accessible clinical workspace with MLC covered non-coplanar gantry angles of [−113°; +112°] and collimator angles of [−100°; +107°], with an average robot pointing accuracy of 0.12 ± 0.09 mm. For vertical beams, garden fence tests exhibited an average leaf positioning error of ≤0.2 mm, which increased by 0.25 and 0.30 mm (banks X1 and X2) with leaves traveling parallel to gravity. After execution of a leaf motion stress routine, garden fence tests showed slightly increased jaggedness and allowed to identify one malfunctioning leaf motor. Total system accuracy with MLC was 0.38 ± 0.05 mm in nine end-to-end tests. Picket fence and AQA tests displayed stable results over the test period. Conclusions: The InCise™ MLC for CyberKnife showed high accuracy and adequate characteristics for SRS/SBRT applications. MLC performance

  6. Dosimetric assessment of the field abutment region in head and neck treatments using a multileaf collimator

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Hakim, K.; Nishimura, T.; Sakahara, H. [Dept. of Radiology, Hamamatsu Univ. School of Medicine, Hamamatsu (Japan); Takaih, M.; Suzuki, S. [Dept. of Informatics, Hamamatsu Univ. School of Medicine, Hamamatsu (Japan)

    2003-05-01

    Background and Purpose: The use of conventional asymmetric collimators for junctioning of abutted fields can lead to significant dose inhomogeneity, due to jaw misalignment. However, recent technologic advances enable us to fabricate much finer leaf-positioning accuracy. Consequently, it is anticipated that the use of multileaf collimator (MLC) will potentially improve dose homogeneity at the junction of abutted fields. In this work, we evaluated the dose inhomogeneities at the match-plane in monoisocentric three-field head and neck setups, using MLC for field abutment. Material and Methods: To define either the anterior or the lateral fields, the MLC was used with either the longitudinal (0 angle) or the transverse (90 angle) settings. For 0 setting, each leaf moves in a direction perpendicular to the gantry rotation axis, hence the ''tongue and groove'' (T and G) design can effect matching-area dose at the side of the leaf (Figure 1a). For 90 setting, the rounded shape of the leaf produces its effect at the leaf end. Four combinations of abutted anterior field and abutted lateral field defined by MLC, i.e., abutted using MLC side-by-side, side-by-end, end-by-side and end-by-end, were compared. Dose inhomogeneity was measured at the junction of the two abutted fields with films in a solid water phantom. The effect of jaw settings as a backup diaphragm on the dose distribution was also studied. Reproducibility of the results was confirmed by repeated measurements over a 1-year period. Results: Abutted fields using MLC side-by-side caused underdose of approximately 15%. Abutted fields using MLC side-by-end produced > 10% overdose that could be improved to {+-} 1% for 0.5 mm overlap of the leaf end from the lateral portals. When using end-by-side, an overdose of approximately 15% was observed. However, the dose improved to a homogeneous dose for 0.8 mm overlap of leaf end from the anterior portal. End-by-end showed an overdose of > 20%. This

  7. Dosimetric assessment of the field abutment region in head and neck treatments using a multileaf collimator

    International Nuclear Information System (INIS)

    Abdel-Hakim, K.; Nishimura, T.; Sakahara, H.; Takaih, M.; Suzuki, S.

    2003-01-01

    Background and Purpose: The use of conventional asymmetric collimators for junctioning of abutted fields can lead to significant dose inhomogeneity, due to jaw misalignment. However, recent technologic advances enable us to fabricate much finer leaf-positioning accuracy. Consequently, it is anticipated that the use of multileaf collimator (MLC) will potentially improve dose homogeneity at the junction of abutted fields. In this work, we evaluated the dose inhomogeneities at the match-plane in monoisocentric three-field head and neck setups, using MLC for field abutment. Material and Methods: To define either the anterior or the lateral fields, the MLC was used with either the longitudinal (0 angle) or the transverse (90 angle) settings. For 0 setting, each leaf moves in a direction perpendicular to the gantry rotation axis, hence the ''tongue and groove'' (T and G) design can effect matching-area dose at the side of the leaf (Figure 1a). For 90 setting, the rounded shape of the leaf produces its effect at the leaf end. Four combinations of abutted anterior field and abutted lateral field defined by MLC, i.e., abutted using MLC side-by-side, side-by-end, end-by-side and end-by-end, were compared. Dose inhomogeneity was measured at the junction of the two abutted fields with films in a solid water phantom. The effect of jaw settings as a backup diaphragm on the dose distribution was also studied. Reproducibility of the results was confirmed by repeated measurements over a 1-year period. Results: Abutted fields using MLC side-by-side caused underdose of approximately 15%. Abutted fields using MLC side-by-end produced > 10% overdose that could be improved to ± 1% for 0.5 mm overlap of the leaf end from the lateral portals. When using end-by-side, an overdose of approximately 15% was observed. However, the dose improved to a homogeneous dose for 0.8 mm overlap of leaf end from the anterior portal. End-by-end showed an overdose of > 20%. This overdose could be smoothed

  8. Characteristics and performance of the first commercial multileaf collimator for a robotic radiosurgery system

    International Nuclear Information System (INIS)

    Fürweger, Christoph; Prins, Paulette; Coskan, Harun; Heijmen, Ben J. M.

    2016-01-01

    Purpose: The “InCise™ multileaf-collimator (MLC)” is the first commercial MLC to be mounted on a robotic SRS/SBRT platform (CyberKnife). The authors assessed characteristics and performance of this novel device in a preclinical five months test period. Methods: Commissioning beam data were acquired with unshielded diodes. EBT3 radiochromic films were employed for measurement of transmission, leaf/bank position accuracy (garden fence) before and after exercising the MLC, for end-to-end testing and further characterization of the beam. The robot workspace with MLC was assessed analytically by transformation to an Euler geometry (“plane,” “gantry,” and “collimator” angles) and by measuring pointing accuracy at each node. Stability over time was evaluated in picket fence and adapted Winston–Lutz tests (AQA). Results: Beam penumbrae (80%–20%, with 100% = 2 × dose at inflection point for field sizes ≥ 50 × 50 mm"2) were 2.2–3.7 mm for square fields in reference condition (source-axis-distance 800 mm, depth 15 mm) and depended on field size and off-axis position. Transmission and leakage did not exceed 0.5%. Accessible clinical workspace with MLC covered non-coplanar gantry angles of [−113°; +112°] and collimator angles of [−100°; +107°], with an average robot pointing accuracy of 0.12 ± 0.09 mm. For vertical beams, garden fence tests exhibited an average leaf positioning error of ≤0.2 mm, which increased by 0.25 and 0.30 mm (banks X1 and X2) with leaves traveling parallel to gravity. After execution of a leaf motion stress routine, garden fence tests showed slightly increased jaggedness and allowed to identify one malfunctioning leaf motor. Total system accuracy with MLC was 0.38 ± 0.05 mm in nine end-to-end tests. Picket fence and AQA tests displayed stable results over the test period. Conclusions: The InCise™ MLC for CyberKnife showed high accuracy and adequate characteristics for SRS/SBRT applications. MLC performance after

  9. Characterization of an extendable multi-leaf collimator for clinical electron beams

    International Nuclear Information System (INIS)

    O'Shea, Tuathan P; Foley, Mark J; Ge Yuanyuan; Faddegon, Bruce A

    2011-01-01

    An extendable x-ray multi-leaf collimator (eMLC) is investigated for collimation of electron beams on a linear accelerator. The conventional method of collimation using an electron applicator is impractical for conformal, modulated and mixed beam therapy techniques. An eMLC would allow faster, more complex treatments with potential for reduction in dose to organs-at-risk and critical structures. The add-on eMLC was modelled using the EGSnrc Monte Carlo code and validated against dose measurements at 6–21 MeV with the eMLC mounted on a Siemens Oncor linear accelerator at 71.6 and 81.6 cm source-to-collimator distances. Measurements and simulations at 8.4–18.4 cm airgaps showed agreement of 2%/2 mm. The eMLC dose profiles and percentage depth dose curves were compared with standard electron applicator parameters. The primary differences were a wider penumbra and up to 4.2% reduction in the build-up dose at 0.5 cm depth, with dose normalized on the central axis. At 90 cm source-to-surface distance (SSD)-–relevant to isocentric delivery-–the applicator and eMLC penumbrae agreed to 0.3 cm. The eMLC leaves, which were 7 cm thick, contributed up to 6.3% scattered electron dose at the depth of maximum dose for a 10 × 10 cm 2 field, with the thick leaves effectively eliminating bremsstrahlung leakage. A Monte Carlo calculated wedge shaped dose distribution generated with all six beam energies matched across the maximum available eMLC field width demonstrated a therapeutic (80% of maximum dose) depth range of 2.1–6.8 cm. Field matching was particularly challenging at lower beam energies (6–12 MeV) due to the wider penumbrae and angular distribution of electron scattering. An eMLC isocentric electron breast boost was planned and compared with the conventional applicator fixed SSD plan, showing similar target coverage and dose to critical structures. The mean dose to the target differed by less than 2%. The low bremsstrahlung dose from the 7 cm thick MLC leaves

  10. Results of daily monitoring of positioning MLC multileaf collimator for Siemens 160 with an array of cameras

    International Nuclear Information System (INIS)

    Lopez Fernandez, A.; Rodriguez Rodriguez, C.; Martin Martin, G.; Saez Beltran, M.

    2011-01-01

    Modern techniques of radiotherapy, and in particular the intensity-modulated radiotherapy (IMRT), require sub-millimeter accuracy in the positioning of multileaf collimators to ensure that patients receive the prescribed dose. It is difficult to include checks of positioning accuracy as high on the agendas of regular monitoring of the accelerators of a hospital. This paper presents the results of a method that enables rapid verification of the position of the sheets with an accuracy of tenths of a millimeter by using an ionization chamber array. The procedure has been applied to the daily control of the two accelerators of our service for 12 months.

  11. 6 MV dosimetric characterization of the 160 MLC, the new Siemens multileaf collimator

    International Nuclear Information System (INIS)

    Tacke, Martin B.; Nill, Simeon; Haering, Peter; Oelfke, Uwe

    2008-01-01

    New technical developments constantly aim at improving the outcome of radiation therapy. With the use of a computer-controlled multileaf collimator (MLC), the quality of the treatment and the efficiency in patient throughput is significantly increased. New MLC designs aim to further enhance the advantages. In this article, we present the first detailed experimental investigation of the new 160 MLC TM , Siemens Medical Solutions. The assessment included the experimental investigation of typical MLC characteristics such as leakage, tongue-and-groove effect, penumbra, leaf speed, and leaf positioning accuracy with a 6 MV treatment beam. The leakage is remarkably low with an average of 0.37% due to a new design principle of slightly tilted leaves instead of the common tongue-and-groove design. But due to the tilt, the triangular tongue-and-groove effect occurs. Its magnitude of approximately 19% is similar to the dose defect measured for MLCs with the common tongue-and-groove design. The average longitudinal penumbra measured at depth d max =15 mm with standard 100x100 mm 2 fields is 4.1±0.5 mm for the central range and increases to 4.9±1.3 mm for the entire field range of 400x400 mm 2 . The increase is partly due to the single-focusing design and the large distance between the MLC and the isocenter enabling a large patient clearance. Regarding the leaf speed, different velocity tests were performed. The positions of the moving leaves were continuously recorded with the kilovoltage-imaging panel. The maximum leaf velocities measured were 42.9±0.6 mm/s. In addition, several typical intensity-modulated radiation therapy treatments were performed and the delivery times compared to the Siemens OPTIFOCUS MLC. An average decrease of 11% in delivery time was observed. The experimental results presented in this article indicate that the dosimetric characteristics of the 160 MLC are capable of improving the quality of dose delivery with respect to precision and dose

  12. Dosimetric performance of the new high-definition multileaf collimator for intracranial stereotactic radiosurgery.

    Science.gov (United States)

    Dhabaan, Anees; Elder, Eric; Schreibmann, Eduard; Crocker, Ian; Curran, Walter J; Oyesiku, Nelson M; Shu, Hui-Kuo; Fox, Tim

    2010-06-21

    The objective was to evaluate the performance of a high-definition multileaf collimator (MLC) of 2.5 mm leaf width (MLC2.5) and compare to standard 5 mm leaf width MLC (MLC5) for the treatment of intracranial lesions using dynamic conformal arcs (DCA) technique with a dedicated radiosurgery linear accelerator. Simulated cases of spherical targets were created to study solely the effect of target volume size on the performance of the two MLC systems independent of target shape complexity. In addition, 43 patients previously treated for intracranial lesions in our institution were retrospectively planned using DCA technique with MLC2.5 and MLC5 systems. The gross tumor volume ranged from 0.07 to 40.57 cm3 with an average volume of 5.9 cm3. All treatment parameters were kept the same for both MLC-based plans. The plan evaluation was performed using figures of merits (FOM) for a rapid and objective assessment on the quality of the two treatment plans for MLC2.5 and MLC5. The prescription isodose surface was selected as the greatest isodose surface covering >or= 95% of the target volume and delivering 95% of the prescription dose to 99% of target volume. A Conformity Index (CI) and conformity distance index (CDI) were used to quantifying the dose conformity to a target volume. To assess normal tissue sparing, a normal tissue difference (NTD) was defined as the difference between the volume of normal tissue receiving a certain dose utilizing MLC5 and the volume receiving the same dose using MLC2.5. The CI and normal tissue sparing for the simulated spherical targets were better with the MLC2.5 as compared to MLC5. For the clinical patients, the CI and CDI results indicated that the MLC2.5 provides better treatment conformity than MLC5 even at large target volumes. The CI's range was 1.15 to 2.44 with a median of 1.59 for MLC2.5 compared to 1.60-2.85 with a median of 1.71 for MLC5. Improved normal tissue sparing was also observed for MLC2.5 over MLC5, with the NTD always

  13. Quality assurance for multileaf collimator with radiographic film exposed by slit beam

    International Nuclear Information System (INIS)

    Ma Jinli; Jiang Guoliang; Fu Xiaolong; Liao Yuan; Wu Kailiang; Zhou Lijun

    2004-01-01

    Objective: To evaluate the role of Kodak X-OMAT-V film exposed by slit beam in the check of various leaf positions of multileaf collimator(MLC), and to check the status of Varian 26 leaf pairs MLC in the Department of Radiation Oncology in Shanghai Cancer Hospital affiliated to Fudan University. Methods: At first, some position errors of different sizes were produced for different leaves so as to determine the minimal leaf position error that could be seen on film. Then, exposure conditions including the exposure dose and source to film distance were changed to find the optimal one. Finally, a Kodak X-OMAT-V film was exposed with a leaf sequence file which was designated randomly by a physicist with leaf position errors of different sizes. After the film was developed, two doctors and two physicists were invited to observe, on blind basis, in order to determine the sensitivity and specificity of the film in the check of leaf positions. Ultimately, leaf positions of the Varian 26 leaf pairs MLC were checked, in which way, the leaf motor status and the carriage stability were checked indirectly. Results: Leaf position errors no less than 0.2 mm could be found using Kodak X-OMAT-V film under the following conditions: source to film distance 100 cm, exposure dose 25 MU, which had been considered as the optimal exposure conditions. The sensitivity and specificity of this method were 73.4% and 96.4%. Any MLC leaf position errors more than 0.2 mm could not be detected. Thus, it was deemed that all leaf motors of the Varian 26 leaf pairs MLC were well in gear and the carriages were stable. Conclusions: MLC leaf position errors can be detected by Kodak X-OMAT-V film exposed by slit beam with high accuracy, but the ability to find leaf position errors with the naked eye may vary from person to person. It is proposed that the Kodak X-OMAT-V film exposed by slit beam be used to check the MLC leaf positions, i. e. the leaf motor status and carriage stability, at regular

  14. Characterization of megavoltage electron beams delivered through a photon multi-leaf collimator (pMLC)

    Energy Technology Data Exchange (ETDEWEB)

    Plessis, F C P du; Leal, A; Stathakis, S; Xiong, W; Ma, C-M [Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111 (United States)

    2006-04-21

    A study is presented that characterizes megavoltage electron beams delivered through an existing double-focused photon multi-leaf collimator (pMLC) using film measurements in a solid water phantom. Machine output stability and linearity were evaluated as well as the effect of source-to-surface distance (SSD) and field size on the penumbra for electron energies between 6 and 18 MeV over an SSD range of 60-100 cm. Penumbra variations as a function of field size, depth of measurement and the influence of the jaws were also studied. Field abutment, field flatness and target coverage for segmented beams were also addressed. The measured field size for electrons transported through the pMLC was the same as that for an x-ray beam up to SSDs of 70 cm. At larger SSD, the lower energy electron fields deviated from the projected field. Penumbra data indicated that 60 cm SSD was the most favourable treatment distance. Backprojection of P{sub 20-80} penumbra data yielded a virtual source position located at 98.9 cm from the surface for 18 MeV electrons. For 6 MeV electrons, the virtual source position was at a distance of 82.6 cm. Penumbra values were smaller for small beam slits and reached a near-constant value for field widths larger than 5 cm. The influence of the jaws had a small effect on the penumbra. The R{sub 90} values ranged from 1.4 to 4.8 cm between 6 and 21 MeV as measured at 60 cm SSD for a 9 x 9 cm{sup 2} field. Uniformity and penumbra improvement could be demonstrated using weighted abutted fields especially useful for small segments. No detectable electron leakage through the pMLC was observed. Bremsstrahlung measurements taken at 60 cm SSD for a 9 x 9 cm{sup 2} field as shaped by the pMLC compared within 1% to bremsstrahlung measurements taken at 100 cm SSD for a 10 x 10 cm{sup 2} electron applicator field at 100 cm SSD.

  15. A method for photon beam Monte Carlo multileaf collimator particle transport

    Science.gov (United States)

    Siebers, Jeffrey V.; Keall, Paul J.; Kim, Jong Oh; Mohan, Radhe

    2002-09-01

    Monte Carlo (MC) algorithms are recognized as the most accurate methodology for patient dose assessment. For intensity-modulated radiation therapy (IMRT) delivered with dynamic multileaf collimators (DMLCs), accurate dose calculation, even with MC, is challenging. Accurate IMRT MC dose calculations require inclusion of the moving MLC in the MC simulation. Due to its complex geometry, full transport through the MLC can be time consuming. The aim of this work was to develop an MLC model for photon beam MC IMRT dose computations. The basis of the MC MLC model is that the complex MLC geometry can be separated into simple geometric regions, each of which readily lends itself to simplified radiation transport. For photons, only attenuation and first Compton scatter interactions are considered. The amount of attenuation material an individual particle encounters while traversing the entire MLC is determined by adding the individual amounts from each of the simplified geometric regions. Compton scatter is sampled based upon the total thickness traversed. Pair production and electron interactions (scattering and bremsstrahlung) within the MLC are ignored. The MLC model was tested for 6 MV and 18 MV photon beams by comparing it with measurements and MC simulations that incorporate the full physics and geometry for fields blocked by the MLC and with measurements for fields with the maximum possible tongue-and-groove and tongue-or-groove effects, for static test cases and for sliding windows of various widths. The MLC model predicts the field size dependence of the MLC leakage radiation within 0.1% of the open-field dose. The entrance dose and beam hardening behind a closed MLC are predicted within +/-1% or 1 mm. Dose undulations due to differences in inter- and intra-leaf leakage are also correctly predicted. The MC MLC model predicts leaf-edge tongue-and-groove dose effect within +/-1% or 1 mm for 95% of the points compared at 6 MV and 88% of the points compared at 18 MV

  16. A method for photon beam Monte Carlo multileaf collimator particle transport

    Energy Technology Data Exchange (ETDEWEB)

    Siebers, Jeffrey V. [Department of Radiation Oncology, Medical College of Virginia Hospitals, Virginia Commonwealth University, Richmond, VA (United States)]. E-mail: jsiebers@vcu.edu; Keall, Paul J.; Kim, Jong Oh; Mohan, Radhe [Department of Radiation Oncology, Medical College of Virginia Hospitals, Virginia Commonwealth University, Richmond, VA (United States)

    2002-09-07

    Monte Carlo (MC) algorithms are recognized as the most accurate methodology for patient dose assessment. For intensity-modulated radiation therapy (IMRT) delivered with dynamic multileaf collimators (DMLCs), accurate dose calculation, even with MC, is challenging. Accurate IMRT MC dose calculations require inclusion of the moving MLC in the MC simulation. Due to its complex geometry, full transport through the MLC can be time consuming. The aim of this work was to develop an MLC model for photon beam MC IMRT dose computations. The basis of the MC MLC model is that the complex MLC geometry can be separated into simple geometric regions, each of which readily lends itself to simplified radiation transport. For photons, only attenuation and first Compton scatter interactions are considered. The amount of attenuation material an individual particle encounters while traversing the entire MLC is determined by adding the individual amounts from each of the simplified geometric regions. Compton scatter is sampled based upon the total thickness traversed. Pair production and electron interactions (scattering and bremsstrahlung) within the MLC are ignored. The MLC model was tested for 6 MV and 18 MV photon beams by comparing it with measurements and MC simulations that incorporate the full physics and geometry for fields blocked by the MLC and with measurements for fields with the maximum possible tongue-and-groove and tongue-or-groove effects, for static test cases and for sliding windows of various widths. The MLC model predicts the field size dependence of the MLC leakage radiation within 0.1% of the open-field dose. The entrance dose and beam hardening behind a closed MLC are predicted within {+-}1% or 1 mm. Dose undulations due to differences in inter- and intra-leaf leakage are also correctly predicted. The MC MLC model predicts leaf-edge tongue-and-groove dose effect within {+-}1% or 1 mm for 95% of the points compared at 6 MV and 88% of the points compared at 18 MV

  17. Cost-minimization analysis: radiation treatment with and without a multi-leaf collimator

    International Nuclear Information System (INIS)

    Foroudi, Farshad; Lapsley, Helen; Manderson, Christine; Yeghiaian-Alvandi, Roland

    2000-01-01

    Purpose: To compare the costs of radiation treatment on a linear accelerator with a multileaf collimator (MLC) versus treatment on a linear accelerator without an MLC. The study was designed to determine whether the increased throughput of fields and decreased block cutting made the MLC cost effective from an institutional perspective. Methods and Materials: The number of fields, basic treatment equivalent, equivalent simple treatment visits, and blocks were prospectively collected for the four linear accelerators. Building, equipment, staffing, and service costs were all obtained in 1999 Australian dollars from the manufacturers and hospital department heads. The Joint Radiation Oncology Centre at Westmead and Nepean Hospitals, which are Australian public hospitals, runs as one unit, with the same staff, and currently operates five linear accelerators. Currently, four of the linear accelerators are used for general radiotherapy, operating for exactly the same hours; the final machine operates more limited hours and is used for specialized radiotherapy techniques and emergency cases. Results: The two machines with MLCs, on average, treated 5,169 fields each, while the two machines without MLCs treated 4,543 fields in a 3-month period, a 12% increase in throughput. The two non-MLC machines required 155 premounted trays (PMTs) in total, while the MLC machines required 17 PMTs. Linear accelerators with MLCs were demonstrably more efficient, and while their capital costs were higher, the reduction in labor costs associated with block cutting and, particularly the increased throughput, more than offset these initial costs. The total cost of a radiation field with an MLC was found to be $A101.69 compared to $A106.98 without an MLC. A multiway sensitivity analysis showed the results to be robust. The worst-case scenario was a departmental savings of $A168,000 per year; the best-case scenario was a savings of $A680,000 per year. Conclusion: Under the conditions pertaining

  18. Dosimetric and qualitative analysis of kinetic properties of millennium 80 multileaf collimator system for dynamic intensity modulated radiotherapy treatments

    Directory of Open Access Journals (Sweden)

    Bhardwaj Anup

    2007-01-01

    Full Text Available The aim of this paper is to analyze the positional accuracy, kinetic properties of the dynamic multileaf collimator (MLC and dosimetric evaluation of fractional dose delivery for the intensity modulated radiotherapy (IMRT for step and shoot and sliding window (dynamic techniques of Varian multileaf collimator millennium 80. Various quality assurance tests such as accuracy in leaf positioning and speed, stability of dynamic MLC output, inter and intra leaf transmission, dosimetric leaf separation and multiple carriage field verification were performed. Evaluation of standard field patterns as pyramid, peaks, wedge, chair, garden fence test, picket fence test and sweeping gap output was done. Patient dose quality assurance procedure consists of an absolute dose measurement for all fields at 5 cm depth on solid water phantom using 0.6cc water proof ion chamber and relative dose verification using Kodak EDR-2 films for all treatment fields along transverse and coronal direction using IMRT phantom. The relative dose verification was performed using Omni Pro IMRT film verification software. The tests performed showed acceptable results for commissioning the millennium 80 MLC and Clinac DHX for dynamic and step and shoot IMRT treatments.

  19. 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

  20. Multibeam tomotherapy: A new treatment unit devised for multileaf collimation, intensity-modulated radiation therapy

    International Nuclear Information System (INIS)

    Achterberg, Nils; Mueller, Reinhold G.

    2007-01-01

    A fully integrated system for treatment planning, application, and verification for automated multileaf collimator (MLC) based, intensity-modulated, image-guided, and adaptive radiation therapy (IMRT, IGRT and ART, respectively) is proposed. Patient comfort, which was the major development goal, will be achieved through a new unit design and short treatment times. Our device for photon beam therapy will consist of a new dual energy linac with five fixed treatment heads positioned evenly along one plane but one electron beam generator only. A minimum of moving parts increases technical reliability and reduces motion times to a minimum. Motion is allowed solely for the MLCs, the robotic patient table, and the small angle gantry rotation of ±36 deg. . Besides sophisticated electron beam guidance, this compact setup can be built using existing modules. The flattening-filter-free treatment heads are characterized by reduced beam-on time and contain apertures restricted in one dimension to the area of maximum primary fluence output. In the case of longer targets, this leads to a topographic intensity modulation, thanks to the combination of ''step and shoot'' MLC delivery and discrete patient couch motion. Owing to the limited number of beam directions, this multislice cone beam serial tomotherapy is referred to as ''multibeam tomotherapy.'' Every patient slice is irradiated by one treatment head at any given moment but for one subfield only. The electron beam is then guided to the next head ready for delivery, while the other heads are preparing their leaves for the next segment. The ''Multifocal MLC-positioning'' algorithm was programmed to enable treatment planning and optimize treatment time. We developed an overlap strategy for the longitudinally adjacent fields of every beam direction, in doing so minimizing the field match problem and the effects of possible table step errors. Clinical case studies show for the same or better planning target volume coverage

  1. Toward the development of intrafraction tumor deformation tracking using a dynamic multi-leaf collimator

    Energy Technology Data Exchange (ETDEWEB)

    Ge, Yuanyuan; O’Brien, Ricky T.; Shieh, Chun-Chien; Keall, Paul J., E-mail: paul.keall@sydney.edu.au [Radiation Physics Laboratory, University of Sydney, NSW 2006 (Australia); Booth, Jeremy T. [Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW 2065 (Australia)

    2014-06-15

    Purpose: Intrafraction deformation limits targeting accuracy in radiotherapy. Studies show tumor deformation of over 10 mm for both single tumor deformation and system deformation (due to differential motion between primary tumors and involved lymph nodes). Such deformation cannot be adapted to with current radiotherapy methods. The objective of this study was to develop and experimentally investigate the ability of a dynamic multi-leaf collimator (DMLC) tracking system to account for tumor deformation. Methods: To compensate for tumor deformation, the DMLC tracking strategy is to warp the planned beam aperture directly to conform to the new tumor shape based on real time tumor deformation input. Two deformable phantoms that correspond to a single tumor and a tumor system were developed. The planar deformations derived from the phantom images in beam's eye view were used to guide the aperture warping. An in-house deformable image registration software was developed to automatically trigger the registration once new target image was acquired and send the computed deformation to the DMLC tracking software. Because the registration speed is not fast enough to implement the experiment in real-time manner, the phantom deformation only proceeded to the next position until registration of the current deformation position was completed. The deformation tracking accuracy was evaluated by a geometric target coverage metric defined as the sum of the area incorrectly outside and inside the ideal aperture. The individual contributions from the deformable registration algorithm and the finite leaf width to the tracking uncertainty were analyzed. Clinical proof-of-principle experiment of deformation tracking using previously acquired MR images of a lung cancer patient was implemented to represent the MRI-Linac environment. Intensity-modulated radiation therapy (IMRT) treatment delivered with enabled deformation tracking was simulated and demonstrated. Results: The first

  2. Multileaf collimator performance monitoring and improvement using semiautomated quality control testing and statistical process control

    International Nuclear Information System (INIS)

    Létourneau, Daniel; McNiven, Andrea; Keller, Harald; Wang, An; Amin, Md Nurul; Pearce, Jim; Norrlinger, Bernhard; Jaffray, David A.

    2014-01-01

    Purpose: High-quality radiation therapy using highly conformal dose distributions and image-guided techniques requires optimum machine delivery performance. In this work, a monitoring system for multileaf collimator (MLC) performance, integrating semiautomated MLC quality control (QC) tests and statistical process control tools, was developed. The MLC performance monitoring system was used for almost a year on two commercially available MLC models. Control charts were used to establish MLC performance and assess test frequency required to achieve a given level of performance. MLC-related interlocks and servicing events were recorded during the monitoring period and were investigated as indicators of MLC performance variations. Methods: The QC test developed as part of the MLC performance monitoring system uses 2D megavoltage images (acquired using an electronic portal imaging device) of 23 fields to determine the location of the leaves with respect to the radiation isocenter. The precision of the MLC performance monitoring QC test and the MLC itself was assessed by detecting the MLC leaf positions on 127 megavoltage images of a static field. After initial calibration, the MLC performance monitoring QC test was performed 3–4 times/week over a period of 10–11 months to monitor positional accuracy of individual leaves for two different MLC models. Analysis of test results was performed using individuals control charts per leaf with control limits computed based on the measurements as well as two sets of specifications of ±0.5 and ±1 mm. Out-of-specification and out-of-control leaves were automatically flagged by the monitoring system and reviewed monthly by physicists. MLC-related interlocks reported by the linear accelerator and servicing events were recorded to help identify potential causes of nonrandom MLC leaf positioning variations. Results: The precision of the MLC performance monitoring QC test and the MLC itself was within ±0.22 mm for most MLC leaves

  3. Multileaf collimator performance monitoring and improvement using semiautomated quality control testing and statistical process control.

    Science.gov (United States)

    Létourneau, Daniel; Wang, An; Amin, Md Nurul; Pearce, Jim; McNiven, Andrea; Keller, Harald; Norrlinger, Bernhard; Jaffray, David A

    2014-12-01

    High-quality radiation therapy using highly conformal dose distributions and image-guided techniques requires optimum machine delivery performance. In this work, a monitoring system for multileaf collimator (MLC) performance, integrating semiautomated MLC quality control (QC) tests and statistical process control tools, was developed. The MLC performance monitoring system was used for almost a year on two commercially available MLC models. Control charts were used to establish MLC performance and assess test frequency required to achieve a given level of performance. MLC-related interlocks and servicing events were recorded during the monitoring period and were investigated as indicators of MLC performance variations. The QC test developed as part of the MLC performance monitoring system uses 2D megavoltage images (acquired using an electronic portal imaging device) of 23 fields to determine the location of the leaves with respect to the radiation isocenter. The precision of the MLC performance monitoring QC test and the MLC itself was assessed by detecting the MLC leaf positions on 127 megavoltage images of a static field. After initial calibration, the MLC performance monitoring QC test was performed 3-4 times/week over a period of 10-11 months to monitor positional accuracy of individual leaves for two different MLC models. Analysis of test results was performed using individuals control charts per leaf with control limits computed based on the measurements as well as two sets of specifications of ± 0.5 and ± 1 mm. Out-of-specification and out-of-control leaves were automatically flagged by the monitoring system and reviewed monthly by physicists. MLC-related interlocks reported by the linear accelerator and servicing events were recorded to help identify potential causes of nonrandom MLC leaf positioning variations. The precision of the MLC performance monitoring QC test and the MLC itself was within ± 0.22 mm for most MLC leaves and the majority of the

  4. Dosimetric effect of multileaf collimator leaf width on volumetric modulated arc stereotactic radiotherapy for spine tumors

    Energy Technology Data Exchange (ETDEWEB)

    Amoush, Ahmad, E-mail: aamoush@augusta.edu [Augusta University, 1120 15th St, Augusta, GA 30912 (United States); Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195 (United States); Long, Huang [University of Utah, 1950 Circle of Hope, Salt Lake City, UT 84112 (United States); Subedi, Laxmi [Cleveland State University, 2121 Euclid Ave., Cleveland, OH 44115 (United States); Qi, Peng; Djemil, Toufik; Xia, Ping [Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195 (United States)

    2017-07-01

    This work aimed to study the dosimetric effect of multileaf collimator (MLC) leaf widths in treatment plans for patients receiving volumetric modulated arc therapy (VMAT) for spine stereotactic body radiation therapy (SBRT). Thirteen patients treated with spine SBRT were retrospectively selected for this study. The patients were treated following the protocol of the Radiation Therapy Oncology Group 0631 (RTOG 0631) for spine metastasis. The prescription dose was 16 Gy in 1 fraction to 90% of the target volume (V16 > 90%). The maximum spinal cord dose of 14 Gy and 10% of the spinal cord receiving < 10 Gy (V10) were the acceptable tolerance doses. For the purpose of this study, 2 dual-arc VMAT plans were created for each patient using 3 different MLC leaf widths: 2.5 mm, 4 mm, and 5 mm. The compliance with the RTOG 0631 protocol, conformity index (CI), dose gradient index (DGI), and number of monitor units (MUs) were compared. The average V16Gy of the targets was 91.8 ± 1.2%, 92.2 ± 2.1%, and 91.7 ± 2.3% for 2.5-mm, 4-mm, and 5-mm leaf widths, respectively (p = 0.78). Accordingly, the average CI was 1.45 ± 0.4, 1.47 ± 0.29, and 1.47 ± 0.31 (p = 0.98), respectively. The average DGI was 0.22 ± 0.04, 0.20 ± 0.06, and 0.22 ± 0.05, respectively (p = 0.77). The average maximum dose to the spinal cord was 12.45 ± 1.0 Gy, 12.80 ± 1.0 Gy, and 12.48 ± 1.1 (p = 0.62) and V10% of the spinal cord was 3.6 ± 2.1%, 5.6 ± 2.8%, and 5.5 ± 3.0% (p = 0.11) for 2.5-mm, 4-mm, and 5-mm leaf widths, respectively. Accordingly, the average number of MUs was 4341 ± 500 MU, 5019 ± 834 MU, and 4606 ± 691 MU, respectively (p = 0.053). The use of 2.5-mm, 4-mm, and 5-mm MLCs achieved similar VMAT plan quality as recommended by the RTOG 0631. The dosimetric parameters were also comparable for the 3 MLCs. In general, any of these leaf widths can be used for spine

  5. Sensitivity of volumetric modulated arc therapy patient specific QA results to multileaf collimator errors and correlation to dose volume histogram based metrics.

    LENUS (Irish Health Repository)

    Coleman, Linda

    2013-11-01

    This study investigates the impact of systematic multileaf collimator (MLC) positional errors on gamma analysis results used for quality assurance (QA) of Rapidarc treatments. In addition, this study evaluates the relationship of these gamma analysis results and clinical dose volume histogram metrics (DVH) for Rapidarc treatment plans.

  6. Geometrical and dosimetrical characterization of the photon source using a micro-multileaf collimator for stereotactic radiosurgery

    International Nuclear Information System (INIS)

    Treuer, H; Hoevels, M; Luyken, K; Hunsche, S; Kocher, M; Mueller, R-P; Sturm, V

    2003-01-01

    A micro-multileaf collimator (μMLC) for stereotactic radiosurgery is used for determination of the spatial intensity distribution of the photon source of a linear accelerator. The method is based on grid field dose measurements using film dosimetry and is easy to perform. Since the μMLC does not allow 'direct' imaging of the photon source, special software has been developed to analyse grid field measurements. Besides the source-density function, grid field analysis yields the position of the focal spot in the room laser coordinate system of the linear accelerator and the position of the treatment head rotation axis and the inclination angle of the leaf bank. Thus the method can be used for base dosimetry and for quality assurance in radiosurgery using a μMLC

  7. A strategy to minimize errors from differential intrafraction organ motion using a single configuration for a 'breathing' multileaf collimator

    International Nuclear Information System (INIS)

    Webb, S; Binnie, D M

    2006-01-01

    Intensity-modulated radiation therapy (IMRT) can be delivered by the 'sliding-leaves' dynamic multileaf collimator (DMLC) technique. Intrafraction organ motion can be accommodated by arranging an identical tracking motion for 'breathing leaves'. However, this is only possible for very specific circumstances such as regular, mathematically parameterizable, rigid-body, density-conserving, one-dimensional translations. In this paper, we investigate what happens when planes of tissue in the line of sight of the MLC have differential motion with respect to the moving leaves. In this situation, there is no solution to the problem and a perfect tracking motion cannot be arranged. However, an iterative minimization-of-errors 'solution' (or strategy) can be found and the technique is presented for this. From this, under certain mathematically simple differential motions it is possible to obtain some elegant algebraic solutions which are presented. In general, however, a lengthy computational minimization is required and results of examples of these are presented

  8. Determination of Tongue and Groove parameters for multileaf collimators; Determinaco de parametros de Tongue and Groove de colimadores de multilaminas

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Aluisio; Almeida, Carlos E. de, E-mail: alu_neto@hotmail.com [Universidade Estadual do Rio de Janeiro (UERJ), RJ (Brazil). Laboratorio de Ciencias Radiologicas; Nguyen, Bihn [Prowess Inc., Concord, CA (United States)

    2012-08-15

    The Tongue and Groove effect (TandG) is characterized by an additional attenuation between adjacent and opposing leaves on multileaf collimators (MLCs) in adjacent or complementary fields. This is a typical situation in of intensity-modulated radiotherapy treatments. The aim of this study was to measure the width and transmission of TandG effect for two commercial MLCs: Varian Millennium 120 (6 MV and 16 MV beams) and BrainLab m3 (only for 6 MV). The methodology used was based on the creation of MLC shapes that emphasizes TandG effect, the irradiation of these fields on radiochromic film and the sensitometric evaluation of the films in order to determine the TandG width and transmission. The results for TandG width for studied MLCs were 2.5, 1.8 and 2 mm, respectively, whit transmission TandG values of 87, 90 and 85%. (author)

  9. A comparison of arc-based and static mini-multileaf collimator-based radiosurgery treatment plans

    International Nuclear Information System (INIS)

    Kubo, Hideo Dale; Pappas, Conrad T.E.; Wilder, Richard B.

    1997-01-01

    Background: The purpose of this study is to compare arc-based and mini-multileaf collimator (mMLC)-based radiosurgery treatment plans using isodose distributions and dose-volume histograms. Methods: Of 11 patients who underwent conventional arc-based radiosurgery for intracranial malignancies, four were treated with one isocenter, four were treated with two isocenters and three were treated with three isocenters. The same cases were re-planned using a test version of mMLC-based radiosurgery software for multiple static non-coplanar fields. Results and conclusion: For non-spherical targets, treatment planning is relatively intuitive with mMLC-based radiosurgery, reducing the amount of time required for planning. Moreover, a lower dose of radiation is delivered to normal tissue with mMLC-based radiosurgery than with arc-based radiosurgery, which theoretically should lead to a reduced risk of complications

  10. Geometrical and dosimetrical characterization of the photon source using a micro-multileaf collimator for stereotactic radiosurgery

    Energy Technology Data Exchange (ETDEWEB)

    Treuer, H [Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Cologne (Germany); Hoevels, M [Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Cologne (Germany); Luyken, K [Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Cologne (Germany); Hunsche, S [Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Cologne (Germany); Kocher, M [Department of Radiotherapy, University of Cologne, Cologne (Germany); Mueller, R-P [Department of Radiotherapy, University of Cologne, Cologne (Germany); Sturm, V [Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Cologne (Germany)

    2003-08-07

    A micro-multileaf collimator ({mu}MLC) for stereotactic radiosurgery is used for determination of the spatial intensity distribution of the photon source of a linear accelerator. The method is based on grid field dose measurements using film dosimetry and is easy to perform. Since the {mu}MLC does not allow 'direct' imaging of the photon source, special software has been developed to analyse grid field measurements. Besides the source-density function, grid field analysis yields the position of the focal spot in the room laser coordinate system of the linear accelerator and the position of the treatment head rotation axis and the inclination angle of the leaf bank. Thus the method can be used for base dosimetry and for quality assurance in radiosurgery using a {mu}MLC.

  11. ‘Inverted Y’ field radiotherapy planning with multi-leaf collimator: A single isocentric technique using multiple fields

    Directory of Open Access Journals (Sweden)

    Puja Sahai

    2015-01-01

    Full Text Available The purpose of our study is to describe a planning technique using multi-leaf collimator and asymmetric fields for irradiating an ‘inverted Y’ shaped geometry in a patient with testicular seminoma. The entire target area covering the para-aortic, pelvic, and inguinal nodal regions was split into three fields. Single isocenter half-beam block technique was employed. The fields were planned with antero-posterior and postero-anterior portals with a differential weightage. The dose was prescribed at the respective reference points of the fields. A uniform dose distribution for the entire portal was achieved without any under- or over-dosing at the field junctions.  

  12. Adverse impact of multileaf collimator field shaping on lens dose in children with acute leukemia receiving cranial irradiation

    International Nuclear Information System (INIS)

    Kalapurakal, John A.; Sathiaseelan, Vythialingam; Bista, Tomasz C.; Marymont, Maryanne H.

    2000-01-01

    Purpose: This study was designed to investigate the impact of multileaf collimator (MLC) on lens dose in children with leukemia undergoing cranial irradiation. Methods and Materials: This is a prospective study utilizing three common cranial irradiation techniques. Technique A uses a half-beam, nondivergent radiation field. Technique B has the anterior divergent field edge at the lateral bony canthus. Technique C is similar to B, but with a field collimator angle. Thermoluminescent dosimeter (TLD) lens dose measurements were obtained in children and phantom with all three techniques. Results: Seventeen children were studied. Lens dose measurements were obtained in 14 children with technique A using MLC and blocks. In 7 of 14 children, dose measurements were obtained with MLC only. One child was treated with technique B and 2 children were treated with C, with MLC ± blocks. In all 3 techniques, with MLC alone, the lens dose increased by 64%, 119%, and 72%, respectively. Similar results were obtained in phantom. Conclusion: This study demonstrates that independent of irradiation technique, additional custom blocking is required to maximally protect the lens with MLC shaped fields. This is due to the lack of conformity between MLC and the desired field edge at the lateral bony canthus

  13. The application in detection the position accuracy of the multi-leaf collimator of Varian linear accelerator with dynamic therapy log files

    International Nuclear Information System (INIS)

    Li Changhu; Xu Liming; Teng Jianjian; Ge Wei; Zhang Jun; Ma Guangdong

    2010-01-01

    Objective: To explorer the application in detection the position accuracy of the multileaf collimator of Varian accelerator with dynamic therapy log files. Methods: A pre-designed MLC format files named PMLC for two Varian accelerators, the dynamic treatment log files were recorded 10 times on a different date, and be converted into the MLC format files named DMLC, compared with the original plan PMLC, so we can analysis two files for each leaf position deviation. In addition, we analysis the repeatability of MLC leaves position accuracy between 10 dynalog files of two accelerators. Results: No statistically significant difference between the average position of the 10 times leaf position of the two accelerators,their were 0.29 -0.29 and 0.29 -0.30 (z = -0.77, P=0.442). About 40%, 30%, 20% and 10% of the leaf position deviation was at ≤0.2 mm, 0.3 mm, 0.5 mm and 0.4 mm, respectively. the maximum value was 0.5 mm. More than 86% of the leaf position are completely coincident between 10 dynamic treatment files of two accelerators. The rate of position deviation no more 0. 05 mm was 96. 6% and 97.3%, respectively. And the maximum value was 0.09 mm. Conclusions: Dynamic treatment log file is a splendid tool in testing the actual position of multi-leaf collimator. The multi-leaf collimator of two accelerators be detected are precise and stabilized. (authors)

  14. Measurement of back-scattered radiation from micro multileaf collimator into the beam monitor chamber from a dual energy linear accelerator

    Directory of Open Access Journals (Sweden)

    Muralidhar K

    2007-01-01

    Full Text Available Measurements designed to find the collimator backscatter into the beam monitor chamber from Micro Multileaf collimator of 6 MV photon beams of the Siemens Primus linear accelerator were made with the help of dose rate feedback control. The photons and electrons backscattered from the upper and lower secondary collimator jaws give rise to a significant increase in the ion charge measured by monitor chamber. This increase varies between the different accelerators. The output measurements were carried out in air at the isocenter. The effect of collimator backscatter was investigated by measuring the pulse width, number of beam pulses per monitor unit, monitor unit rate and dose for different mMLC openings. These measurements were made with and without dose rate feedback control, i.e., with constant electron beam current in the accelerator. Monitor unit rate (MU/min was almost constant for all field sizes. The maximum variation between the open and the closed feedback control circuits was 2.5%. There was no difference in pulse width and negligible difference in pulse frequency. Maximum value of backscattered radiation from the micro Multileaf collimator into the beam monitor chamber was found to be 0.5%.

  15. SU-E-T-467: Implementation of Monte Carlo Dose Calculation for a Multileaf Collimator Equipped Robotic Radiotherapy System

    Energy Technology Data Exchange (ETDEWEB)

    Li, JS; Fan, J; Ma, C-M [Fox Chase Cancer Center, Philadelphia, PA (United States)

    2015-06-15

    Purpose: To improve the treatment efficiency and capabilities for full-body treatment, a robotic radiosurgery system has equipped with a multileaf collimator (MLC) to extend its accuracy and precision to radiation therapy. To model the MLC and include it in the Monte Carlo patient dose calculation is the goal of this work. Methods: The radiation source and the MLC were carefully modeled to consider the effects of the source size, collimator scattering, leaf transmission and leaf end shape. A source model was built based on the output factors, percentage depth dose curves and lateral dose profiles measured in a water phantom. MLC leaf shape, leaf end design and leaf tilt for minimizing the interleaf leakage and their effects on beam fluence and energy spectrum were all considered in the calculation. Transmission/leakage was added to the fluence based on the transmission factors of the leaf and the leaf end. The transmitted photon energy was tuned to consider the beam hardening effects. The calculated results with the Monte Carlo implementation was compared with measurements in homogeneous water phantom and inhomogeneous phantoms with slab lung or bone material for 4 square fields and 9 irregularly shaped fields. Results: The calculated output factors are compared with the measured ones and the difference is within 1% for different field sizes. The calculated dose distributions in the phantoms show good agreement with measurements using diode detector and films. The dose difference is within 2% inside the field and the distance to agreement is within 2mm in the penumbra region. The gamma passing rate is more than 95% with 2%/2mm criteria for all the test cases. Conclusion: Implementation of Monte Carlo dose calculation for a MLC equipped robotic radiosurgery system is completed successfully. The accuracy of Monte Carlo dose calculation with MLC is clinically acceptable. This work was supported by Accuray Inc.

  16. An analytical approach for optimizing the leaf design of a multi-leaf collimator in a linear accelerator

    International Nuclear Information System (INIS)

    Topolnjak, R; Heide, U A van der

    2008-01-01

    In this study, we present an analytical approach for optimizing the leaf design of a multi-leaf collimator (MLC) in a linear accelerator. Because leaf designs vary between vendors, our goal is to characterize and quantify the effects of different compromises which have to be made between performance parameters. Subsequently, an optimal leaf design for an earlier proposed six-bank MLC which combines a high-resolution field-shaping ability with a large field size is determined. To this end a model of the linac is created that includes the following parameters: the source size, the maximum field size, the distance between source and isocenter, and the leaf's design parameters. First, the optimal radius of the leaf tip was found. This optimum was defined by the requirement that the fluence intensity should fall from 80% of the maximum value to 20% in a minimal distance, defining the width of the fluence penumbra. A second requirement was that this penumbra width should be constant when a leaf moves from one side of the field to the other. The geometric, transmission and total penumbra width (80-20%) were calculated depending on the design parameters. The analytical model is in agreement with Elekta, Varian and Siemens collimator designs. For leaves thinner than 4 cm, the transmission penumbra becomes dominant, and for leaves close to the source the geometric penumbra plays a role. Finally, by choosing the leaf thickness of 3.5 cm, 4 cm and 5 cm from the lowest to the highest bank, respectively, an optimal leaf design for a six-bank MLC is achieved

  17. SU-E-T-247: Multi-Leaf Collimator Model Adjustments Improve Small Field Dosimetry in VMAT Plans

    Energy Technology Data Exchange (ETDEWEB)

    Young, L; Yang, F [University of Washington, Seattle, WA (United States)

    2014-06-01

    Purpose: The Elekta beam modulator linac employs a 4-mm micro multileaf collimator (MLC) backed by a fixed jaw. Out-of-field dose discrepancies between treatment planning system (TPS) calculations and output water phantom measurements are caused by the 1-mm leaf gap required for all moving MLCs in a VMAT arc. In this study, MLC parameters are optimized to improve TPS out-of-field dose approximations. Methods: Static 2.4 cm square fields were created with a 1-mm leaf gap for MLCs that would normally park behind the jaw. Doses in the open field and leaf gap were measured with an A16 micro ion chamber and EDR2 film for comparison with corresponding point doses in the Pinnacle TPS. The MLC offset table and tip radius were adjusted until TPS point doses agreed with photon measurements. Improvements to the beam models were tested using static arcs consisting of square fields ranging from 1.6 to 14.0 cm, with 45° collimator rotation, and 1-mm leaf gap to replicate VMAT conditions. Gamma values for the 3-mm distance, 3% dose difference criteria were evaluated using standard QA procedures with a cylindrical detector array. Results: The best agreement in point doses within the leaf gap and open field was achieved by offsetting the default rounded leaf end table by 0.1 cm and adjusting the leaf tip radius to 13 cm. Improvements in TPS models for 6 and 10 MV photon beams were more significant for smaller field sizes 3.6 cm or less where the initial gamma factors progressively increased as field size decreased, i.e. for a 1.6cm field size, the Gamma increased from 56.1% to 98.8%. Conclusion: The MLC optimization techniques developed will achieve greater dosimetric accuracy in small field VMAT treatment plans for fixed jaw linear accelerators. Accurate predictions of dose to organs at risk may reduce adverse effects of radiotherapy.

  18. SU-E-T-467: Implementation of Monte Carlo Dose Calculation for a Multileaf Collimator Equipped Robotic Radiotherapy System

    International Nuclear Information System (INIS)

    Li, JS; Fan, J; Ma, C-M

    2015-01-01

    Purpose: To improve the treatment efficiency and capabilities for full-body treatment, a robotic radiosurgery system has equipped with a multileaf collimator (MLC) to extend its accuracy and precision to radiation therapy. To model the MLC and include it in the Monte Carlo patient dose calculation is the goal of this work. Methods: The radiation source and the MLC were carefully modeled to consider the effects of the source size, collimator scattering, leaf transmission and leaf end shape. A source model was built based on the output factors, percentage depth dose curves and lateral dose profiles measured in a water phantom. MLC leaf shape, leaf end design and leaf tilt for minimizing the interleaf leakage and their effects on beam fluence and energy spectrum were all considered in the calculation. Transmission/leakage was added to the fluence based on the transmission factors of the leaf and the leaf end. The transmitted photon energy was tuned to consider the beam hardening effects. The calculated results with the Monte Carlo implementation was compared with measurements in homogeneous water phantom and inhomogeneous phantoms with slab lung or bone material for 4 square fields and 9 irregularly shaped fields. Results: The calculated output factors are compared with the measured ones and the difference is within 1% for different field sizes. The calculated dose distributions in the phantoms show good agreement with measurements using diode detector and films. The dose difference is within 2% inside the field and the distance to agreement is within 2mm in the penumbra region. The gamma passing rate is more than 95% with 2%/2mm criteria for all the test cases. Conclusion: Implementation of Monte Carlo dose calculation for a MLC equipped robotic radiosurgery system is completed successfully. The accuracy of Monte Carlo dose calculation with MLC is clinically acceptable. This work was supported by Accuray Inc

  19. SU-F-T-527: A Novel Dynamic Multileaf Collimator Leaf-Sequencing Algorithm in Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Jing, J; Lin, H [Hefei University of Technology, Hefei, Anhui (China); Chow, J [Princess Margaret Cancer Centre, Toronto, ON (Canada)

    2016-06-15

    Purpose: A novel leaf-sequencing algorithm is developed for generating arbitrary beam intensity profiles in discrete levels using dynamic multileaf collimator (MLC). The efficiency of this dynamic MLC leaf-sequencing method was evaluated using external beam treatment plans delivered by intensity modulated radiation therapy technique. Methods: To qualify and validate this algorithm, integral test for the beam segment of MLC generated by the CORVUS treatment planning system was performed with clinical intensity map experiments. The treatment plans were optimized and the fluence maps for all photon beams were determined. This algorithm started with the algebraic expression for the area under the beam profile. The coefficients in the expression can be transformed into the specifications for the leaf-setting sequence. The leaf optimization procedure was then applied and analyzed for clinical relevant intensity profiles in cancer treatment. Results: The macrophysical effect of this method can be described by volumetric plan evaluation tools such as dose-volume histograms (DVHs). The DVH results are in good agreement compared to those from the CORVUS treatment planning system. Conclusion: We developed a dynamic MLC method to examine the stability of leaf speed including effects of acceleration and deceleration of leaf motion in order to make sure the stability of leaf speed did not affect the intensity profile generated. It was found that the mechanical requirements were better satisfied using this method. The Project is sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry.

  20. An alternative effective method for verifying the multileaf collimator leaves speed by using a digital-video imaging system

    International Nuclear Information System (INIS)

    Hwang, Ing-Ming; Wu, Jay; Chuang, Keh-Shih; Ding, Hueisch-Jy

    2010-01-01

    We present an alternative effective method for verifying the multileaf collimator (MLC) leaves speed using a digital-video imaging system in daily dynamic conformal radiation therapy (DCRT) and intensity-modulation radiation therapy (IMRT) in achieving increased convenience and shorter treatment times. The horizontal leaves speed measured was within 1.76-2.08 cm/s. The mean full range of traveling time was 20 s. The initial speed-up time was within 1.5-2.0 s, and the slowing-down time was within 2.0-2.5 s. Due to gravity the maximum speed-up effect in the X1 bank was +0.10 cm/s, but the lagging effect in the X2 bank was -0.20 cm/s. This technique offered an alternative method with electronic portal imaging device (EPID), charged coupled device (CCD) or a light field for the measurement of MLC leaves speed. When time taken on the linac was kept to a minimum, the image could be processed off-line.

  1. Rounded leaf end effect of multileaf collimator on penumbra width and radiation field offset: an analytical and numerical study

    International Nuclear Information System (INIS)

    Zhou, Dong; Zhang, Hui; Ye, Peiqing

    2015-01-01

    Penumbra characteristics play a significant role in dose delivery accuracy for radiation therapy. For treatment planning, penumbra width and radiation field offset strongly influence target dose conformity and organ at risk sparing. In this study, we present an analytical and numerical approach for evaluation of the rounded leaf end effect on penumbra characteristics. Based on the rule of half-value layer, algorithms for leaf position calculation and radiation field offset correction were developed, which were advantageous particularly in dealing with large radius leaf end. Computer simulation was performed based on the Monte Carlo codes of EGSnrc/BEAMnrc, with groups of leaf end radii and source sizes. Data processing technique of curve fitting was employed for deriving penumbra width and radiation field offset. Results showed that penumbra width increased with source size. Penumbra width curves for large radius leaf end were U-shaped. This observation was probably related to the fact that radiation beams penetrated through the proximal and distal leaf sides. In contrast, source size had negligible impact on radiation field offset. Radiation field offsets were found to be constant both for analytical method and numerical simulation. However, the overall resulting values of radiation field offset obtained by analytical method were slightly smaller compared with Monte Carlo simulation. The method we proposed could provide insight into the investigation of rounded leaf end effects on penumbra characteristics. Penumbra width and radiation field offset calibration should be carefully performed to commission multileaf collimator for intensity modulated radiotherapy

  2. SU-F-T-527: A Novel Dynamic Multileaf Collimator Leaf-Sequencing Algorithm in Radiation Therapy

    International Nuclear Information System (INIS)

    Jing, J; Lin, H; Chow, J

    2016-01-01

    Purpose: A novel leaf-sequencing algorithm is developed for generating arbitrary beam intensity profiles in discrete levels using dynamic multileaf collimator (MLC). The efficiency of this dynamic MLC leaf-sequencing method was evaluated using external beam treatment plans delivered by intensity modulated radiation therapy technique. Methods: To qualify and validate this algorithm, integral test for the beam segment of MLC generated by the CORVUS treatment planning system was performed with clinical intensity map experiments. The treatment plans were optimized and the fluence maps for all photon beams were determined. This algorithm started with the algebraic expression for the area under the beam profile. The coefficients in the expression can be transformed into the specifications for the leaf-setting sequence. The leaf optimization procedure was then applied and analyzed for clinical relevant intensity profiles in cancer treatment. Results: The macrophysical effect of this method can be described by volumetric plan evaluation tools such as dose-volume histograms (DVHs). The DVH results are in good agreement compared to those from the CORVUS treatment planning system. Conclusion: We developed a dynamic MLC method to examine the stability of leaf speed including effects of acceleration and deceleration of leaf motion in order to make sure the stability of leaf speed did not affect the intensity profile generated. It was found that the mechanical requirements were better satisfied using this method. The Project is sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry.

  3. Dosimetric verification and evaluation of segmental multileaf collimator (SMLC)-IMRT for quality assurance. The second report. Absolute dose

    International Nuclear Information System (INIS)

    Tateoka, Kunihiko; Hareyama, Masato; Oouchi, Atsushi; Nakata, Kensei; Nagase, Daiki; Saikawa, Tsunehiko; Shimizume, Kazunari; Sugimoto, Harumi; Waka, Masaaki

    2003-01-01

    Intensity-modulated radiation therapy (IMRT) was developed to irradiate the target are more conformally, sparing organs at risk (OARs). Since the beams are sequentially delivered by many, small, irregular, and off-center fields in IMRT, dosimetric quality assurance (QA) is an extremely important issue. QA is performed by verifying both the dose distribution and doses at arbitrary points. In this work, we describe the verification of doses at arbitrary points in our hospital for Segmental multileaf collimator (SMLC)-IMRT. In general, verification of the absolute doses for IMRT is performed by comparison between the calculated doses using Radiation Treatment Planning Systems (RTP) and the measured doses using an ionization chamber with a small volume at arbitrary points in relatively flat regions of the dose gradients. However, no clear definitions of the dose gradients and the flat regions have yet been reported. We carried out verification by comparison of the measured doses with the average dose and the central point dose in a virtual Farmer type ionization chamber (V-F) and a virtual PinPoint ionization chamber (V-P) equal to the Farmer-type ionization chamber volume and PinPoint ionization chamber volumes using the RTP. Furthermore, we defined the dose gradients as the deviation of the maximum dose from the minimum dose in the virtual ionization chamber volume. In IMRT, the dose gradients may be as high as 80% or more in the virtual ionization chamber volume. Therefore, it is thought that the effective center of the ionization chamber varies by segment for IMRT fields (i.e., the variation of the ionization chamber replacement effect). Additionally, in regions with a higher dose gradient, uncertainty in the measured doses is influenced by the variations in the ionization chamber replacement effect and the ionization chamber positioning error. We more objectively examined the verification method for the absolute dose in IMRT using the virtual ionization chamber

  4. Multileaf collimator leaf position verification and analysis for adaptive radiation therapy using a video-optical method

    Science.gov (United States)

    Sethna, Sohrab B.

    External beam radiation therapy is commonly used to eliminate and control cancerous tumors. High-energy beams are shaped to match the patient's specific tumor volume, whereby maximizing radiation dose to malignant cells and limiting dose to normal tissue. A multileaf collimator (MLC) consisting of multiple pairs of tungsten leaves is used to conform the radiation beam to the desired treatment field. Advanced treatment methods utilize dynamic MLC settings to conform to multiple treatment fields and provide intensity modulated radiation therapy (IMRT). Future methods would further increase conformity by actively tracking tumor motion caused by patient cardiac and respiratory motion. Leaf position quality assurance for a dynamic MLC is critical as variation between the planned and actual leaf positions could induce significant errors in radiation dose. The goal of this research project is to prototype a video-optical quality assurance system for MLC leaf positions. The system captures light-field images of MLC leaf sequences during dynamic therapy. Image acquisition and analysis software was developed to determine leaf edge positions. The mean absolute difference between QA prototype predicted and caliper measured leaf positions was found to be 0.6 mm with an uncertainty of +/- 0.3 mm. Maximum errors in predicted positions were below 1.0 mm for static fields. The prototype served as a proof of concept for quality assurance of future tumor tracking methods. Specifically, a lung tumor phantom was created to mimic a lung tumor's motion from respiration. The lung tumor video images were superimposed on MLC field video images for visualization and analysis. The toolbox is capable of displaying leaf position, leaf velocity, tumor position, and determining errors between planned and actual treatment fields for dynamic radiation therapy.

  5. Impact of Multileaf Collimator Configuration Parameters on the Dosimetric Accuracy of 6-MV Intensity-Modulated Radiation Therapy Treatment Plans.

    Science.gov (United States)

    Petersen, Nick; Perrin, David; Newhauser, Wayne; Zhang, Rui

    2017-01-01

    The purpose of this study was to evaluate the impact of selected configuration parameters that govern multileaf collimator (MLC) transmission and rounded leaf offset in a commercial treatment planning system (TPS) (Pinnacle 3 , Philips Medical Systems, Andover, MA, USA) on the accuracy of intensity-modulated radiation therapy (IMRT) dose calculation. The MLC leaf transmission factor was modified based on measurements made with ionization chambers. The table of parameters containing rounded-leaf-end offset values was modified by measuring the radiation field edge as a function of leaf bank position with an ionization chamber in a scanning water-tank dosimetry system and comparing the locations to those predicted by the TPS. The modified parameter values were validated by performing IMRT quality assurance (QA) measurements on 19 gantry-static IMRT plans. Planar dose measurements were performed with radiographic film and a diode array (MapCHECK2) and compared to TPS calculated dose distributions using default and modified configuration parameters. Based on measurements, the leaf transmission factor was changed from a default value of 0.001 to 0.005. Surprisingly, this modification resulted in a small but statistically significant worsening of IMRT QA gamma-index passing rate, which revealed that the overall dosimetric accuracy of the TPS depends on multiple configuration parameters in a manner that is coupled and not intuitive because of the commissioning protocol used in our clinic. The rounded leaf offset table had little room for improvement, with the average difference between the default and modified offset values being -0.2 ± 0.7 mm. While our results depend on the current clinical protocols, treatment unit and TPS used, the methodology used in this study is generally applicable. Different clinics could potentially obtain different results and improve their dosimetric accuracy using our approach.

  6. Impact of multileaf collimator configuration parameters on the dosimetric accuracy of 6-MV Intensity-Modulated radiation therapy treatment plans

    Directory of Open Access Journals (Sweden)

    Nick Petersen

    2017-01-01

    Full Text Available The purpose of this study was to evaluate the impact of selected configuration parameters that govern multileaf collimator (MLC transmission and rounded leaf offset in a commercial treatment planning system (TPS (Pinnacle3, Philips Medical Systems, Andover, MA, USA on the accuracy of intensity-modulated radiation therapy (IMRT dose calculation. The MLC leaf transmission factor was modified based on measurements made with ionization chambers. The table of parameters containing rounded-leaf-end offset values was modified by measuring the radiation field edge as a function of leaf bank position with an ionization chamber in a scanning water-tank dosimetry system and comparing the locations to those predicted by the TPS. The modified parameter values were validated by performing IMRT quality assurance (QA measurements on 19 gantry-static IMRT plans. Planar dose measurements were performed with radiographic film and a diode array (MapCHECK2 and compared to TPS calculated dose distributions using default and modified configuration parameters. Based on measurements, the leaf transmission factor was changed from a default value of 0.001 to 0.005. Surprisingly, this modification resulted in a small but statistically significant worsening of IMRT QA gamma-index passing rate, which revealed that the overall dosimetric accuracy of the TPS depends on multiple configuration parameters in a manner that is coupled and not intuitive because of the commissioning protocol used in our clinic. The rounded leaf offset table had little room for improvement, with the average difference between the default and modified offset values being −0.2 ± 0.7 mm. While our results depend on the current clinical protocols, treatment unit and TPS used, the methodology used in this study is generally applicable. Different clinics could potentially obtain different results and improve their dosimetric accuracy using our approach.

  7. Evaluation of Kodak EDR2 film for dose verification of intensity modulated radiation therapy delivered by a static multileaf collimator.

    Science.gov (United States)

    Zhu, X R; Jursinic, P A; Grimm, D F; Lopez, F; Rownd, J J; Gillin, M T

    2002-08-01

    A new type of radiographic film, Kodak EDR2 film, was evaluated for dose verification of intensity modulated radiation therapy (IMRT) delivered by a static multileaf collimator (SMLC). A sensitometric curve of EDR2 film irradiated by a 6 MV x-ray beam was compared with that of Kodak X-OMAT V (XV) film. The effects of field size, depth and dose rate on the sensitometric curve were also studied. It is found that EDR2 film is much less sensitive than XV film. In high-energy x-ray beams, the double hit process is the dominant mechanism that renders the grains on EDR2 films developable. As a result, in the dose range that is commonly used for film dosimetry for IMRT and conventional external beam therapy, the sensitometric curves of EDR2 films cannot be approximated as a linear function, OD = c * D. Within experimental uncertainty, the film sensitivity does not depend on the dose rate (50 vs 300 MU/min) or dose per pulse (from 1.0 x 10(-4) to 4.21 x 10(-4) Gy/pulse). Field sizes and depths (up to field size of 10 x 10 cm2 and depth = 10 cm) have little effect on the sensitometric curves. Percent depth doses (PDDs) for both 6 and 23 MV x rays were measured with both EDR2 and XV films and compared with ion chamber data. Film data are within 2.5% of the ion chamber results. Dose profiles measured with EDR2 film are consistent with those measured with an ion chamber. Examples of measured IMRT isodose distributions versus calculated isodoses are presented. We have used EDR2 films for verification of all IMRT patients treated by SMLC in our clinic. In most cases, with EDR2 film, actual clinical daily fraction doses can be used for verification of composite isodose distributions of SMLC-based IMRT.

  8. TH-AB-BRA-01: A Novel Doubly-Focused Multileaf Collimator Design for MR-Guided Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Li, H; Mutic, S; Green, O [Washington University School of Medicine, St. Louis, MO (United States); Low, D [UCLA, Los Angeles, CA (United States); Fought, G; Kawrakow, I; Sharma, A; Shvartsman, S; Dempsey, J [ViewRay, Inc., Oakwood Village, OH (United States)

    2016-06-15

    Purpose: To describe the physical and dosimetric properties of a novel double-stack multileaf collimator (MLC). Methods: One of the compromises made in the MLC design has been to employ linear-motion singly-divergent shapes. Because the MLC leading edge moves linearly, it is rounded to provide a consistent, albeit compromised penumbra. The MLC employed in the new linac-based MR-IGRT unit is designed to be doubly focused in that each leaf moves in an arc centered at the source, and the sides of the leaves are machined such that they lie parallel to a line between the leaf edge and the source. The curvature of the MLC keeps motors and encoders in lower magnetic field. However, high spatial-resolution leaves are difficult to manufacture to sufficiently tight tolerances and difficult to move due to restricted space on the gantry. Wider leaves alleviate this problem with less moving parts but the coarse resolution disallows treating very small lesions. This compromise has been overcome by splitting the MLC leaf bank into two sets, stacked one upon the other and offset half of a leaf width. The dosimetry has been simulated using Monte-Carlo and a 6 MV linac in a 0.35 T magnetic field. Results: The combined MLC leaf set has a spatial resolution of effectively half of the leaf width, 4mm here. The dosimetry resolution and conformality are consistent with 4mm wide MLC assisted by inverse fluence modulation. Also, because each leaf junction is backed up by the stacked leaf that lies over the junction, the problem of tongue-and-groove dosimetry has been greatly reduced. The novel MLC design allows the use of more powerful leaf motors than would be otherwise possible if a single MLC bank is employed. Conclusions: The stacked MLC will provide highly conformal dose distributions suitable for stereotactic radiation therapy of small lesions. The research was funded by ViewRay, Inc.

  9. First Demonstration of Combined kV/MV Image-Guided Real-Time Dynamic Multileaf-Collimator Target Tracking

    International Nuclear Information System (INIS)

    Cho, Byungchul; Poulsen, Per R.; Sloutsky, Alex; Sawant, Amit; Keall, Paul J.

    2009-01-01

    Purpose: For intrafraction motion management, a real-time tracking system was developed by combining fiducial marker-based tracking via simultaneous kilovoltage (kV) and megavoltage (MV) imaging and a dynamic multileaf collimator (DMLC) beam-tracking system. Methods and Materials: The integrated tracking system employed a Varian Trilogy system equipped with kV/MV imaging systems and a Millennium 120-leaf MLC. A gold marker in elliptical motion (2-cm superior-inferior, 1-cm left-right, 10 cycles/min) was simultaneously imaged by the kV and MV imagers at 6.7 Hz and segmented in real time. With these two-dimensional projections, the tracking software triangulated the three-dimensional marker position and repositioned the MLC leaves to follow the motion. Phantom studies were performed to evaluate time delay from image acquisition to MLC adjustment, tracking error, and dosimetric impact of target motion with and without tracking. Results: The time delay of the integrated tracking system was ∼450 ms. The tracking error using a prediction algorithm was 0.9 ± 0.5 mm for the elliptical motion. The dose distribution with tracking showed better target coverage and less dose to surrounding region over no tracking. The failure rate of the gamma test (3%/3-mm criteria) was 22.5% without tracking but was reduced to 0.2% with tracking. Conclusion: For the first time, a complete tracking system combining kV/MV image-guided target tracking and DMLC beam tracking was demonstrated. The average geometric error was less than 1 mm, and the dosimetric error was negligible. This system is a promising method for intrafraction motion management.

  10. TH-AB-BRA-01: A Novel Doubly-Focused Multileaf Collimator Design for MR-Guided Radiation Therapy

    International Nuclear Information System (INIS)

    Li, H; Mutic, S; Green, O; Low, D; Fought, G; Kawrakow, I; Sharma, A; Shvartsman, S; Dempsey, J

    2016-01-01

    Purpose: To describe the physical and dosimetric properties of a novel double-stack multileaf collimator (MLC). Methods: One of the compromises made in the MLC design has been to employ linear-motion singly-divergent shapes. Because the MLC leading edge moves linearly, it is rounded to provide a consistent, albeit compromised penumbra. The MLC employed in the new linac-based MR-IGRT unit is designed to be doubly focused in that each leaf moves in an arc centered at the source, and the sides of the leaves are machined such that they lie parallel to a line between the leaf edge and the source. The curvature of the MLC keeps motors and encoders in lower magnetic field. However, high spatial-resolution leaves are difficult to manufacture to sufficiently tight tolerances and difficult to move due to restricted space on the gantry. Wider leaves alleviate this problem with less moving parts but the coarse resolution disallows treating very small lesions. This compromise has been overcome by splitting the MLC leaf bank into two sets, stacked one upon the other and offset half of a leaf width. The dosimetry has been simulated using Monte-Carlo and a 6 MV linac in a 0.35 T magnetic field. Results: The combined MLC leaf set has a spatial resolution of effectively half of the leaf width, 4mm here. The dosimetry resolution and conformality are consistent with 4mm wide MLC assisted by inverse fluence modulation. Also, because each leaf junction is backed up by the stacked leaf that lies over the junction, the problem of tongue-and-groove dosimetry has been greatly reduced. The novel MLC design allows the use of more powerful leaf motors than would be otherwise possible if a single MLC bank is employed. Conclusions: The stacked MLC will provide highly conformal dose distributions suitable for stereotactic radiation therapy of small lesions. The research was funded by ViewRay, Inc.

  11. Minimizing the number of segments in a delivery sequence for intensity-modulated radiation therapy with a multileaf collimator

    International Nuclear Information System (INIS)

    Dai Jianrong; Zhu Yunping

    2001-01-01

    This paper proposes a sequencing algorithm for intensity-modulated radiation therapy with a multileaf collimator in the static mode. The algorithm aims to minimize the number of segments in a delivery sequence. For a machine with a long verification and recording overhead time (e.g., 15 s per segment), minimizing the number of segments is equivalent to minimizing the delivery time. The proposed new algorithm is based on checking numerous candidates for a segment and selecting the candidate that results in a residual intensity matrix with the least complexity. When there is more than one candidate resulting in the same complexity, the candidate with the largest size is selected. The complexity of an intensity matrix is measured in the new algorithm in terms of the number of segments in the delivery sequence obtained by using a published algorithm. The beam delivery efficiency of the proposed algorithm and the influence of different published algorithms used to calculate the complexity of an intensity matrix were tested with clinical intensity-modulated beams. The results show that no matter which published algorithm is used to calculate the complexity of an intensity matrix, the sequence generated by the algorithm proposed here is always more efficient than that generated by the published algorithm itself. The results also show that the algorithm used to calculate the complexity of an intensity matrix affects the efficiency of beam delivery. The delivery sequences are frequently most efficient when the algorithm of Bortfeld et al. is used to calculate the complexity of an intensity matrix. Because no single variation is most efficient for all beams tested, we suggest implementing multiple variations of our algorithm

  12. Monitor Unit Calculation for the Multileaf Intensity Modulating Collimator (MIMiCTM) in the PeacockTM Plan System

    International Nuclear Information System (INIS)

    Kania, Aleksander A.; Bleier, Alan R.; Carol, Mark P.

    1995-01-01

    A finite-size pencil beam method has been chosen for dose modelling in conformal radiotherapy when the Multileaf Intensity Modulating Collimator (MIMiC) is used to deliver the treatment. The MIMiC has two rows of 20 tungsten leaves which retract toward or away from the accelerator gantry, producing two intensity-modulated transaxial treatment slices which are 20 cm x 1 or 2 cm at isocenter. The treatment field is thus a fan beam made up of 40 sub-beams or finite-size pencil beams, leading to the choice of the model. Rotational treatments with the MIMiC are modelled in Peacock Plan as a set of ports spaced at gantry angle increments of 5 deg. to 10 deg. . The fractional time spent by the leaf in the beam during the gantry angle increment determines the intensity. The intensities from each leaf for each port are optimized in Peacock Plan, one treatment slice at a time, and then the dose from all slices is combined. The treatment planning system uses a two-dimensional measured pencil beam profile from one leaf at a selected reference depth along with measured open field, broad beam profiles at several depths. This makes beam data collection simple and dosimetrically flexible. The nature of the measured data imposes some conditions on calculation of Monitor Units (MU). The calculation must also take into consideration that two independent slices are delivered at the same time, and that multiple slices may be used to treat targets which are longer in the inferior-superior direction than the field produced by two slices. The MU calculation method is derived and presented as an enhancement of the traditional method of MU determination for treatments based on static ports. Experimental results indicative of the validity and limitations of the model will be demonstrated

  13. Using the volumetric effect of a finite-sized detector for routine quality assurance of multileaf collimator leaf positioning

    International Nuclear Information System (INIS)

    Yang Yong; Xing Lei

    2003-01-01

    Intensity modulated radiation therapy (IMRT) is an advanced form of radiation therapy and promises to improve dose conformation while reducing the irradiation to the sensitive structures. The modality is, however, more complicated than conventional treatment and requires much more stringent quality assurance (QA) to ensure what has been planned can be achieved accurately. One of the main QA tasks is the assurance of positioning accuracy of multileaf collimator (MLC) leaves during IMRT delivery. Currently, the routine quality assurance of MLC in most clinics is being done using radiographic films with specially designed MLC leaf sequences. Besides being time consuming, the results of film measurements are difficult to quantify and interpret. In this work, we propose a new and effective technique for routine MLC leaf positioning QA. The technique utilizes the fact that, when a finite-sized detector is placed under a leaf, the relative output of the detector will depend on the relative fractional volume irradiated. A small error in leaf positioning would change the fractional volume irradiated and lead to a deviation of the relative output from the normal reading. For a given MLC and detector system, the relation between the relative output and the leaf displacement can be easily established through experimental measurements and used subsequently as a quantitative means for detecting possible leaf positional errors. The method was tested using a linear accelerator with an 80-leaf MLC. Three different locations, including two locations on central plane (X1=X2=0) and one point on an off-central plane location (X1=-7.5, X=7.5), were studied. Our results indicated that the method could accurately detect a leaf positional change of ∼0.1 mm. The method was also used to monitor the stability of MLC leaf positioning for five consecutive weeks. In this test, we intentionally introduced two positional errors in the testing MLC leaf sequences: -0.2 mm and 1.2 mm. The technique

  14. SU-E-T-610: Comparison of Treatment Times Between the MLCi and Agility Multileaf Collimators

    International Nuclear Information System (INIS)

    Ramsey, C; Bowling, J

    2014-01-01

    Purpose: The Agility is a new 160-leaf MLC developed by Elekta for use in their Infinity and Versa HD linacs. As compared to the MLCi, the Agility increased the maximum leaf speed from 2 cm/s to 3.5 cm/s, and the maximum primary collimator speed from 1.5 cm/s to 9.0 cm/s. The purpose of this study was to determine if the Agility MLC resulted in improved plan quality and/or shorter treatment times. Methods: An Elekta Infinity that was originally equipped with a 80 leaf MLCi was upgraded to an 160 leaf Agility. Treatment plan quality was evaluated using the Pinnacle planning system with SmartArc. Optimization was performed once for the MLCi and once for the Agility beam models using the same optimization parameters and the same number of iterations. Patient treatment times were measured for all IMRT, VMAT, and SBRT patients treated on the Infinity with the MLCi and Agility MLCs. Treatment times were extracted from the EMR and measured from when the patient first walked into the treatment room until exiting the treatment room. Results: 11,380 delivery times were measured for patients treated with the MLCi, and 1,827 measurements have been made for the Agility MLC. The average treatment times were 19.1 minutes for the MLCi and 20.8 minutes for the Agility. Using a t-test analysis, there was no difference between the two groups (t = 0.22). The dose differences between patients planned with the MLCi and the Agility MLC were minimal. For example, the dose difference for the PTV, GTV, and cord for a head and neck patient planned using Pinnacle were effectively equivalent. However, the dose to the parotid glands was slightly worse with the Agility MLC. Conclusion: There was no statistical difference in treatment time, or any significant dosimetric difference between the Agility MLC and the MLCi

  15. Dosimetric evaluation of the conformation of the multileaf collimator to irregularly shaped fields

    International Nuclear Information System (INIS)

    Frazier, Arthur; Du, Maria; Wong, John; Vicini, Frank; Taylor, Roy; Yu, Cedric; Matter, Richard; Martinez, Alvaro; Yan Di

    1995-01-01

    Purpose: The goal of this study was to evaluate the dosimetric characteristics of geometric MLC prescription strategies and compare them to those of conventional shielding block. Methods and Materials: Circular fields, square fields, and 12 irregular fields for patients with cancer of the head and neck, lung, and pelvis were included in this study. All fields were shaped using the MLC and conventional blocks. A geometric criterion was defined as the amount of area discrepancy between the MLC and the prescription outline. The 'least area discrepancy' (LAD) of the MLC conformation was searched by selecting the collimator angle, meanwhile keeping a preselected position along the width of the leaf into the prescribed field. Five LAD conventions were studied. These included the LAD-0, LAD-(1(3)), LAD-(1(2)), and LAD-(2(3)) that inserted the leaves at the 0, (1(3)), (1(2)), and (2(3)) of the leaf end into the prescription field, respectively. In addition, the LAD optimization was applied to the transecting (TRN) approach for leaf conformation that prescribed an equal area of overblocking and underblocking under each leaf. Film dosimetry was performed in a 20 cm polystyrene phantom at 10 cm depth 100 cm from source to axis distance (SAD) for both 6 and 18 MV photons with each of the above MLC conformations and conventional blocks. The field penumbra width, defined as the mean of the separation between the 20% and 80% isodose lines along the normal of the prescription field edge, was calculated using both the MLC and conventional block film dosimetry and compared. In a similar way, the d20 is defined as the mean separation between the 20% isodose line and the prescription field edge, and the d80 is defined as the mean separation between the 80% isodose line and the prescription field edge. Results: The field penumbra width for all MLC conventions was approximately 2 mm larger than that of the conventional block. However, there was a larger variation of the separation

  16. Dosimetric comparison of different multileaf collimator leaves in treatment planning of intensity-modulated radiotherapy for cervical cancer

    International Nuclear Information System (INIS)

    Wang, Shichao; Ai, Ping; Xie, Li; Xu, Qingfeng; Bai, Sen; Lu, You; Li, Ping; Chen, Nianyong

    2013-01-01

    To study the effect of multileaf collimator (MLC) leaf widths (standard MLC [sMLC] width of 10 mm and micro-MLC [mMLC] width of 4 mm) on intensity-modulated radiotherapy (IMRT) for cervical cancer. Between January 2010 and August 2010, a retrospective analysis was conducted on 12 patients with cervical cancer. The treatment plans for all patients were generated with the same machine setup parameters and optimization methods in a treatment planning system (TPS) based on 2 commercial Elekta MLC devices. The dose distribution for the planning tumor volume (PTV), the dose sparing for organs at risk (OARs), the monitor units (MUs), and the number of IMRT segments were evaluated. For the delivery efficiency, the MUs were significantly higher in the sMLC-IMRT plan than in the mMLC-IMRT plan (802 ± 56.9 vs 702 ± 56.7; p 0.05). For the planning quality, the conformity index (CI) between the 2 paired IMRT plans with the mMLC and the sMLC did not differ significantly (average: 0.817 ± 0.024 vs 0.810 ± 0.028; p > 0.05). The differences of the homogeneity index (HI) between the 2 paired plans were statistically significant (average: 1.122 ± 0.010 vs 1.132 ± 0.014; p 10 , V 20 , V 30 , and V 40 , percentage of contoured OAR volumes receiving 10, 20, 30, and 40 Gy, respectively, and the mean dose (D mean ) received. The IMRT plans with the mMLC protected the OARs better than the plans with the sMLC. There were significant differences (p 30 and V 40 of the rectum and V 10 , V 20 , V 40 , and D mean of the bladder. IMRT plans with the mMLC showed advantages over the plans with the sMLC in dose homogeneity for targets, dose sparing of OARs, and fewer MUs in cervical cancer

  17. SU-E-T-766: Treatment Planning Comparison Study On Two Different Multileaf Collimators Delivered with Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Zhang, R; Xiaomei, F; Bai, W; Zhang, X; Gao, Y

    2015-01-01

    Purpose: To compare and evaluate the performance of two different multileaf collimators(MLCi2 and Agility) delivery with volumetric modulated arc therapy techniques. Methods: Treatment plans were graded four (Low, Moderate, Moderate-High and High complexity) accorrding to the complexity. This includes 1 Low complexity(brain metastasis), 2 Moderate complexity(Lung and Liver), 1 Moderate-High complexity(prostate) and 1 High complexity ( head and neck) cases. Total dose of 60 Gy was given for all the plans. All cases were desigined two VMAT plans, one with MLCi2(group A) and the other with Agility(group B). All plans were done on Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X-rays for both Plan A and Plan B. Plans were evaluated based on the ability to meet the dose volume histogram, radiation conformity index, estimated radiation delivery time, dose homogeneity index(HI) and monitor units(MU) needed to deliver the prescribed dose. Results: Plans of group B achieved the best HI (HI = 1.05 Vs. 1.06) at the Low complexity cases while plans of group A were slightly better at the high complexity cases (HI = 1.12 Vs. 1.14). Faster VMAT plan delivery with Agility than with MLCi2 as plan complexity increased (Low complexity:52s Vs.52s, Moderate complexity:58s Vs. 55s, Moderate-High complexity: 171s Vs.152s, High complexity : 326s Vs. 202s ), especially for the most complex paradigms delivered time can be decresed 38%. No Significant changes were observed between the group B and group A plans in terms of the healthy tissue mean dose and MU. Both plans respected the planning objective for all organs at risk. Conclusion: The study concludes that VMAT plans with the novel Agility MLC can significant decrease the delivering time at the high complexity cases, while a slight compromise in the dose homogeneity index should be noted. This work was supported by The Medical Science Foundation of The health department of Hebei Province (No

  18. SU-E-T-766: Treatment Planning Comparison Study On Two Different Multileaf Collimators Delivered with Volumetric Modulated Arc Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, R; Xiaomei, F; Bai, W [The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei (China); Zhang, X [The First Hospital of Hebei Medical University, Shijiazhuang, Hebei (China); Gao, Y [Hebei General Hospital, Shijiazhuang, Hebei (China)

    2015-06-15

    Purpose: To compare and evaluate the performance of two different multileaf collimators(MLCi2 and Agility) delivery with volumetric modulated arc therapy techniques. Methods: Treatment plans were graded four (Low, Moderate, Moderate-High and High complexity) accorrding to the complexity. This includes 1 Low complexity(brain metastasis), 2 Moderate complexity(Lung and Liver), 1 Moderate-High complexity(prostate) and 1 High complexity ( head and neck) cases. Total dose of 60 Gy was given for all the plans. All cases were desigined two VMAT plans, one with MLCi2(group A) and the other with Agility(group B). All plans were done on Elekta VMAT with Monaco treatment planning system. All plans were generated with 6 MV X-rays for both Plan A and Plan B. Plans were evaluated based on the ability to meet the dose volume histogram, radiation conformity index, estimated radiation delivery time, dose homogeneity index(HI) and monitor units(MU) needed to deliver the prescribed dose. Results: Plans of group B achieved the best HI (HI = 1.05 Vs. 1.06) at the Low complexity cases while plans of group A were slightly better at the high complexity cases (HI = 1.12 Vs. 1.14). Faster VMAT plan delivery with Agility than with MLCi2 as plan complexity increased (Low complexity:52s Vs.52s, Moderate complexity:58s Vs. 55s, Moderate-High complexity: 171s Vs.152s, High complexity : 326s Vs. 202s ), especially for the most complex paradigms delivered time can be decresed 38%. No Significant changes were observed between the group B and group A plans in terms of the healthy tissue mean dose and MU. Both plans respected the planning objective for all organs at risk. Conclusion: The study concludes that VMAT plans with the novel Agility MLC can significant decrease the delivering time at the high complexity cases, while a slight compromise in the dose homogeneity index should be noted. This work was supported by The Medical Science Foundation of The health department of Hebei Province (No

  19. SU-E-T-646: Quality Assurance of Truebeam Multi-Leaf Collimator Using a MLC QA Phantom

    International Nuclear Information System (INIS)

    Zhang, J; Lu, J; Hong, D

    2015-01-01

    Purpose: To perform a routine quality assurance procedure for Truebeam multi-leaf collimator (MLC) using MLC QA phantom, verify the stability and reliability of MLC during the treatment. Methods: MLC QA phantom is a specialized phantom for MLC quality assurance (QA), and contains five radio-opaque spheres that are embedded in an “L” shape. The phantom was placed isocentrically on the Truebeam treatment couch for the tests. A quality assurance plan was setted up in the Eclipse v10.0, the fields that need to be delivered in order to acquire the necessary images, the MLC shapes can then be obtained by the images. The images acquired by the electronic portal imaging device (EPID), and imported into the PIPSpro software for the analysis. The tests were delivered twelve weeks (once a week) to verify consistency of the delivery, and the images are acquired in the same manner each time. Results: For the Leaf position test, the average position error was 0.23mm±0.02mm (range: 0.18mm∼0.25mm). The Leaf width was measured at the isocenter, the average error was 0.06mm±0.02mm (range: 0.02mm∼0.08mm) for the Leaf width test. Multi-Port test showed the dynamic leaf shift error, the average error was 0.28mm±0.03mm (range: 0.2mm∼0.35mm). For the leaf transmission test, the average inter-leaf leakage value was 1.0%±0.17% (range: 0.8%∼1.3%) and the average inter-bank leakage value was 32.6%±2.1% (range: 30.2%∼36.1%). Conclusion: By the test of 12 weeks, the MLC system of the Truebeam is running in a good condition and the MLC system can be steadily and reliably carried out during the treatment. The MLC QA phantom is a useful test tool for the MLC QA

  20. Neutron dosimetry in organs of an adult human phantom using linacs with multileaf collimator in radiotherapy treatments

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Ovalle, S. A.; Barquero, R.; Gomez-Ros, J. M.; Lallena, A. M. [Grupo de Fisica Nuclear Aplicada y Simulacion, Universidad Pedagogica y Tecnologica de Colombia, Tunja 15001000 (Colombia); Servicio de Proteccion Radiologica, Hospital Clinico Universitario, E-47012 Valladolid (Spain) and Departamento de Radiologia, Universidad de Valladolid, Valladolid E-47071 (Spain); CIEMAT, Avda. Complutense 40, Madrid, E-28040 (Spain); Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, Granada E-18071 (Spain)

    2012-05-15

    Purpose: To calculate absorbed doses due to neutrons in 87 organs/tissues for anthropomorphic phantoms, irradiated in position supine (head first into the gantry) with orientations anteroposterior (AP) and right-left (RLAT) with a 18 MV accelerator. Conversion factors from monitor units to {mu}Gy per neutron in organs, equivalent doses in organs/tissues, and effective doses, which permit to quantify stochastic risks, are estimated. Methods: MAX06 and FAX06 phantoms were modeled with MCNPX and irradiated with a 18 MV Varian Clinac 2100C/D accelerator whose geometry included a multileaf collimator. Two actual fields of a pelvic treatment were simulated using electron-photon-neutron coupled transport. Absorbed doses due to neutrons were estimated from kerma. Equivalent doses were estimated using the radiation weighting factor corresponding to an average incident neutron energy 0.47 MeV. Statistical uncertainties associated to absorbed doses, as calculated by MCNPX, were also obtained. Results: Largest doses were absorbed in shallowest (with respect to the neutron pathway) organs. In {mu}GyMU{sup -1}, values of 2.66 (for penis) and 2.33 (for testes) were found in MAX06, and 1.68 (for breasts), 1.05 (for lenses of eyes), and 0.94 (for sublingual salivary glands) in FAX06, in AP orientation. In RLAT, the largest doses were found for bone tissues (leg) just at the entrance of the beam in the body (right side in our case). Values, in {mu}GyMU{sup -1}, of 1.09 in upper leg bone right spongiosa, for MAX06, and 0.63 in mandible spongiosa, for FAX06, were found. Except for gonads, liver, and stomach wall, equivalent doses found for FAX06 were, in both orientations, higher than for MAX06. Equivalent doses in AP are higher than in RLAT for all organs/tissues other than brain and liver. Effective doses of 12.6 and 4.1 {mu}SvMU{sup -1} were found for AP and RLAT, respectively. The organs/tissues with larger relative contributions to the effective dose were testes and breasts, in

  1. An automatic CT-guided adaptive radiation therapy technique by online modification of multileaf collimator leaf positions for prostate cancer

    International Nuclear Information System (INIS)

    Court, Laurence E.; Dong Lei; Lee, Andrew K.; Cheung, Rex; Bonnen, Mark D.; O'Daniel, Jennifer; Wang He; Mohan, Radhe; Kuban, Deborah

    2005-01-01

    Purpose: To propose and evaluate online adaptive radiation therapy (ART) using in-room computed tomography (CT) imaging that detects changes in the target position and shape of the prostate and seminal vesicles (SVs) and then automatically modifies the multileaf collimator (MLC) leaf pairs in a slice-by-slice fashion. Methods and materials: For intensity-modulated radiation therapy (IMRT) using a coplanar beam arrangement, each MLC leaf pair projects onto a specific anatomic slice. The proposed strategy assumes that shape deformation is a function of only the superior-inferior (SI) position. That is, there is no shape change within a CT slice, but each slice can be displaced in the anteroposterior (AP) or right-left (RL) direction relative to adjacent slices. First, global shifts (in SI, AP, and RL directions) were calculated by three-dimensional (3D) registration of the bulk of the prostate in the treatment planning CT images with the daily CT images taken immediately before treatment. Local shifts in the AP direction were then found using slice-by-slice registration, in which the CT slices were individually registered. The translational shift within a slice could then be projected to a translational shift in the position of the corresponding MLC leaf pair for each treatment segment for each gantry angle. Global shifts in the SI direction were accounted for by moving the open portal superiorly or inferiorly by an integral number of leaf pairs. The proposed slice-by-slice registration technique was tested by using daily CT images from 46 CT image sets (23 each from 2 patients) taken before the standard delivery of IMRT for prostate cancer. A dosimetric evaluation was carried out by using an 8-field IMRT plan. Results: The shifts and shape change of the prostate and SVs could be separated into 3D global shifts in the RL, AP, and SI directions, plus local shifts in the AP direction, which were different for each CT slice. The MLC leaf positions were successfully

  2. Planning, delivery, and quality assurance of treatment with dynamic multileaf collimator for prostate: a strategy for large scale implementation

    International Nuclear Information System (INIS)

    Burman, Chandra; Chen, Chui; Kutcher, Gerald; Leibel, Steven; Zelefsky, Michael; LoSasso, Thomas; Spirou, Spiridon; Wu Qiuwen; Stein, Jorge; Mohan, Radhe; Ling, C. Clifton; Fuks, Zvi

    1996-01-01

    Purpose: In an attempt to improve tumor control of patients treated for the adenocarcinoma of the prostate, we have implemented a technique to deliver a prescribed dose of 81 Gy. At such high doses, the surrounding normal organs such as the rectum, bladder, and femur impose challenging constraints. We present a method to plan and deliver intensity modulated fields with dynamic multileaf collimators (DMLCs) in an effort to meet the difficult constraints. While the planning technique which uses inverse planning has been described in the literature, safe delivery with DMLC is a new and challenging problem. We will describe in detail our procedures with the emphasis on the delivery problems and chosen solutions. Procedures for the quality assurance of DMLC will be described. Methods and Materials: Using a recently developed and modified inverse planning algorithm, we have developed a 5-field intensity modulated plan that is delivered using DMLC. The planner specifies the target, normal organs, and the desired doses for these tissues and for the overlap regions. The planning system designs the desired intensity profiles to meet the specified criteria. To deliver the dose DMLCs provide a practical and convenient method. A procedure has been developed for the dose delivery. A scheme has been designed to determine the leaf motion to produce the required intensity pattern based on the prescribed dose and the dose rate. In order to ensure that the dose is delivered as planned, we have instituted the following procedures: (1) verification of the aperture shape on a localization port film, (2) an additional dose calculation, which uses the delivered leaf motion, and compares the difference between the planned and delivered doses, (3) comparison of the machine log files, generated during the actual dose delivery, with the planned leaf motions, (4) comparison of the measured dose profile in a flat phantom with the calculated dose distribution using the prescribed treatment

  3. Matching extended-SSD electron beams to multileaf collimated photon beams in the treatment of head and neck cancer

    Energy Technology Data Exchange (ETDEWEB)

    Steel, Jared; Stewart, Allan; Satory, Philip [Auckland Regional Blood and Cancer Service, Auckland City Hospital, 2 Park Road, Grafton, Auckland 1023 (New Zealand)

    2009-09-15

    Purpose: Matching the penumbra of a 6 MeV electron beam to the penumbra of a 6 MV photon beam is a dose optimization challenge, especially when the electron beam is applied from an extended source-to-surface distance (SSD), as in the case of some head and neck treatments. Traditionally low melting point alloy blocks have been used to define the photon beam shielding over the spinal cord region. However, these are inherently time consuming to construct and employ in the clinical situation. Multileaf collimators (MLCs) provide a fast and reproducible shielding option but generate geometrically nonconformal approximations to the desired beam edge definition. The effects of substituting Cerrobend for the MLC shielding mode in the context of beam matching with extended-SSD electron beams are the subject of this investigation. Methods: Relative dose beam data from a Varian EX 2100 linear accelerator were acquired in a water tank under the 6 MeV electron beam at both standard and extended-SSD and under the 6 MV photon beam defined by Cerrobend and a number of MLC stepping regimes. The effect of increasing the electron beam SSD on the beam penumbra was assessed. MLC stepping was also assessed in terms of the effects on both the mean photon beam penumbra and the intraleaf dose-profile nonuniformity relative to the MLC midleaf. Computational techniques were used to combine the beam data so as to simulate composite relative dosimetry in the water tank, allowing fine control of beam abutment gap variation. Idealized volumetric dosimetry was generated based on the percentage depth-dose data for the beam modes and the abutment geometries involved. Comparison was made between each composite dosimetry dataset and the relevant ideal dosimetry dataset by way of subtraction. Results: Weighted dose-difference volume histograms (DDVHs) were produced, and these, in turn, summed to provide an overall dosimetry score for each abutment and shielding type/angle combination. Increasing the

  4. Matching extended-SSD electron beams to multileaf collimated photon beams in the treatment of head and neck cancer

    International Nuclear Information System (INIS)

    Steel, Jared; Stewart, Allan; Satory, Philip

    2009-01-01

    Purpose: Matching the penumbra of a 6 MeV electron beam to the penumbra of a 6 MV photon beam is a dose optimization challenge, especially when the electron beam is applied from an extended source-to-surface distance (SSD), as in the case of some head and neck treatments. Traditionally low melting point alloy blocks have been used to define the photon beam shielding over the spinal cord region. However, these are inherently time consuming to construct and employ in the clinical situation. Multileaf collimators (MLCs) provide a fast and reproducible shielding option but generate geometrically nonconformal approximations to the desired beam edge definition. The effects of substituting Cerrobend for the MLC shielding mode in the context of beam matching with extended-SSD electron beams are the subject of this investigation. Methods: Relative dose beam data from a Varian EX 2100 linear accelerator were acquired in a water tank under the 6 MeV electron beam at both standard and extended-SSD and under the 6 MV photon beam defined by Cerrobend and a number of MLC stepping regimes. The effect of increasing the electron beam SSD on the beam penumbra was assessed. MLC stepping was also assessed in terms of the effects on both the mean photon beam penumbra and the intraleaf dose-profile nonuniformity relative to the MLC midleaf. Computational techniques were used to combine the beam data so as to simulate composite relative dosimetry in the water tank, allowing fine control of beam abutment gap variation. Idealized volumetric dosimetry was generated based on the percentage depth-dose data for the beam modes and the abutment geometries involved. Comparison was made between each composite dosimetry dataset and the relevant ideal dosimetry dataset by way of subtraction. Results: Weighted dose-difference volume histograms (DDVHs) were produced, and these, in turn, summed to provide an overall dosimetry score for each abutment and shielding type/angle combination. Increasing the

  5. Matching extended-SSD electron beams to multileaf collimated photon beams in the treatment of head and neck cancer.

    Science.gov (United States)

    Steel, Jared; Stewart, Allan; Satory, Philip

    2009-09-01

    Matching the penumbra of a 6 MeV electron beam to the penumbra of a 6 MV photon beam is a dose optimization challenge, especially when the electron beam is applied from an extended source-to-surface distance (SSD), as in the case of some head and neck treatments. Traditionally low melting point alloy blocks have been used to define the photon beam shielding over the spinal cord region. However, these are inherently time consuming to construct and employ in the clinical situation. Multileaf collimators (MLCs) provide a fast and reproducible shielding option but generate geometrically nonconformal approximations to the desired beam edge definition. The effects of substituting Cerrobend for the MLC shielding mode in the context of beam matching with extended-SSD electron beams are the subject of this investigation. Relative dose beam data from a Varian EX 2100 linear accelerator were acquired in a water tank under the 6 MeV electron beam at both standard and extended-SSD and under the 6 MV photon beam defined by Cerrobend and a number of MLC stepping regimes. The effect of increasing the electron beam SSD on the beam penumbra was assessed. MLC stepping was also assessed in terms of the effects on both the mean photon beam penumbra and the intraleaf dose-profile nonuniformity relative to the MLC midleaf. Computational techniques were used to combine the beam data so as to simulate composite relative dosimetry in the water tank, allowing fine control of beam abutment gap variation. Idealized volumetric dosimetry was generated based on the percentage depth-dose data for the beam modes and the abutment geometries involved. Comparison was made between each composite dosimetry dataset and the relevant ideal dosimetry dataset by way of subtraction. Weighted dose-difference volume histograms (DDVHs) were produced, and these, in turn, summed to provide an overall dosimetry score for each abutment and shielding type/angle combination. Increasing the electron beam SSD increased

  6. The effect on IMRT conformality of elastic tissue movement and a practical suggestion for movement compensation via the modified dynamic multileaf collimator (dMLC) technique

    International Nuclear Information System (INIS)

    Webb, S

    2005-01-01

    A major remaining problem in delivering radiotherapy, specifically intensity-modulated radiation therapy (IMRT), is the need to accommodate and correct for intrafraction movement. The developing availability of 4D computed tomographic images can potentially form the basis of the new field of image-guided IMRT. It is important to understand the effects on delivered dose of the patient breathing during IMRT and this paper models the effect which applies whether there is or is not a time component to the IMRT delivery method. It then goes on to suggest a practical correction strategy. The 'stretch-and-shift-the-planned-modulations' strategy is proposed and a practical method to deliver this is explained. This practical strategy is based on a modification of the dynamic multileaf collimator IMRT method whereby the leaves are arranged to 'breath' in tandem with the breathing of the patient. Some examples are also given from a study of mismatching the patient and leaf-correction motions

  7. Collimators

    CERN Document Server

    Wronka, Slawomir

    2013-01-01

    The collimator system of a particle accelerator must efficiently remove stray particles and provide protection against uncontrolled losses. In this article, the basic design concepts of collimators and some realizations are presented.

  8. Collimator

    International Nuclear Information System (INIS)

    1976-01-01

    A collimator, to be used in conjunction with a scintiscanner containing a detector and an optical or electronic means of producing and analyzing signals is discussed in this patent. The author gives a tomograph as an example. The collimator consists of parallel lamellae which can shield the gamma radiation which intersect with each other each along a single straight perpendicular line as opposed to the normal multi-hole collimator. The benefits of this new collimator are better signal to noise ratio, a shorter exposure time is needed, smaller radiation doses may be used and by placing the lamellae closer to each other, the separation ability of the collimator is increased

  9. SU-E-T-515: Field-In-Field Compensation Technique Using Multi-Leaf Collimator to Deliver Total Body Irradiation (TBI) Dose

    Energy Technology Data Exchange (ETDEWEB)

    Lakeman, T [The State University of New York at Buffalo (United States); Wang, IZ [The State University of New York at Buffalo (United States); Roswell Park Cancer Institute, Buffalo, NY (United States)

    2014-06-01

    Purpose: Total body irradiation (TBI) uses large parallel-opposed radiation fields to suppress the patient's immune system and eradicate the residual cancer cells in preparation of recipient for bone marrow transplant. The manual placement of lead compensators has been used conventionally to compensate for the varying thickness through the entire body in large-field TBI. The goal of this study is to pursue utilizing the modern field-in-field (FIF) technique with the multi-leaf collimator (MLC) to more accurately and efficiently deliver dose to patients in need of TBI. Method: Treatment plans utilizing the FIF technique to deliver a total body dose were created retrospectively for patients for whom CT data had been previously acquired. Treatment fields include one pair of opposed open large fields (collimator=45°) with a specific weighting and a succession of smaller fields (collimator=90°) each with their own weighting. The smaller fields are shaped by moving MLC to block the sections of the patient which have already received close to 100% of the prescribed dose. The weighting factors for each of these fields were calculated using the attenuation coefficient of the initial lead compensators and the separation of the patient in different positions in the axial plane. Results: Dose-volume histograms (DVH) were calculated for evaluating the FIF compensation technique. The maximum body doses calculated from the DVH were reduced from the non-compensated 179.3% to 148.2% in the FIF plans, indicating a more uniform dose with the FIF compensation. All calculated monitor units were well within clinically acceptable limits and exceeded those of the original lead compensation plan by less than 50 MU (only ~1.1% increase). Conclusion: MLC FIF technique for TBI will not significantly increase the beam on time while it can substantially reduce the compensator setup time and the potential risk of errors in manually placing lead compensators.

  10. Dosimetric advantage and clinical implication of a micro-multileaf collimator in the treatment of prostate with intensity-modulated radiotherapy

    International Nuclear Information System (INIS)

    Wang Lu; Hoban, Peter; Paskalev, Kamen; Yang Jie; Li Jinsheng; Chen Lili; Xiong Weijun; Ma, Charlie

    2005-01-01

    This paper investigates the dosimetric benefits of a micro-multileaf (4-mm leaf width) collimator (mMLC) for intensity-modulated radiation therapy (IMRT) treatment planning of the prostate cancer and its potential application for dose escalation and hypofractionation. We compared treatment plans for IMRT delivery using 2 different multileaf collimator (MLC) leaf widths (4 vs. 10 mm) for 10 patients with prostate cancer. Treatment planning was performed on the XknifeRT2 treatment planning system. All beams and optimization parameters were identical for the mMLC and MLC plans. All of the plans were normalized to ensure that 95% of the planning target volume (PTV) received 100% of the prescribed dose (74 Gy). The differences in dose distribution between the 2 groups of plans using the mMLC and the MLC were assessed by dose-volume histogram (DVH) analysis of the target and critical organs. Significant reductions in the volume of rectum receiving medium to higher doses were achieved using the mMLC. The average decrease in the volume of the rectum receiving 40, 50, and 60 Gy using the mMLC plans was 40.2%, 33.4%, and 17.7%, respectively, with p-values less than 0.0001 for V 40 and V 50 and 0.012 for V 60 . The mean dose reductions for D 17 and D 35 for the rectum were 20.0% (p 0.78). Because of the reduction of rectal volume receiving medium to higher doses, dose to the prostate target can be escalated by about 20 Gy to over 74 Gy, while keeping the rectal dose (either denoted by D 17 or D 35 ) the same as those with the use of the MLC. The maximum achievable dose, derived when the rectum is allowed to reach the tolerance level, was found to be in the range of 113-172 Gy (using the tolerance value of D 17 ). We conclude that the use of the mMLC for IMRT of the prostate may facilitate dose hypofractionation due to its dosimetric advantage in significantly improving the DVH parameters of the prostate and critical organs. When used for conventional fractionation scheme, m

  11. Electronic compensation using multileaf collimation for involved field radiation to the neck and mediastinum in non-Hodgkin's lymphoma and Hodgkin's lymphoma

    International Nuclear Information System (INIS)

    MacDonald, Shelly; Bernard, Shelley; Balogh, Alex; Spencer, David; Sawchuk, Stephen

    2005-01-01

    An efficient procedure is required for the preparation, planning, and delivery of radiation therapy for involved field radiation to the neck and mediastinum. This technique must reduce tissue complications while maintaining dose uniformity. An elegant intensity-modulated radiation therapy (IMRT) treatment that is forward planned has been developed. Both static fields and static subfields shaped by multileaf collimators (MLCs) and asymmetric jaws are used. Patients receiving involved field radiation to the neck and mediastinum are planned in 3 dimensions (3D), where 3D dose compensation is provided using subfields consisting of MLC or asymmetric jaws instead of physical compensators or wedges. Forward planning is performed, usually generating 2 pairs of parallel-opposed fields, with at least 1 of them consisting of subfields to eliminate elevated dose regions. Efficiency in the preparation, planning, and delivery of treatment has been achieved for more than 10 patients. Verification of treatment setup, target anatomy, and MLC configuration is quick when using an electronic portal imaging device. Thermoluminescent dosimeters (TLDs) have verified point-dose uniformity noticeably to ± 5%. An efficient technique using forward planning for simple IMRT consisting of static MLC and asymmetric jaws has been developed

  12. Can cost make a difference dosimetrically? Volumetric modulated arc therapy study for multileaf collimators of various widths for head and neck and prostate cancers

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Jong-Han, E-mail: jonghanho@gmail.com; Hagler, Shane; Lujano, Carrie; Seng, Sopaul; Starks, Christine; Perrin, Kelly; Turner, Lehendrick; Court, Laurence

    2017-04-01

    Cancer is a global health issue that disproportionately kills based on stage of disease, cellular pathology, and genetics, to name a few. Another variable to consider in this ongoing fight is treatment machine complexity that leads to elevated development and purchasing cost, leading to a reduced use. Reducing the complexity (in hopes of lowering costs) would benefit underdeveloped, low- and middle-income countries by introducing newer treatment technology, as their currently accepted standards do not meet standards of more advanced, developed countries. In this study, unilateral head and neck (H&N), and prostate cases using volumetric modulated arc therapy (VMAT) were tested with multiple segment widths of 5, 10, 15, and 20 mm to create treatable plans. Pinnacle 9.10v was used for planning purposes. A total of 12 cases were planned with varying multileaf collimator (MLC) widths. Treatment plans were evaluated retrospectively. Results show that altering the MLC widths from 5 through 20 mm produces both comparable and treatable plans up to 99% and 98% target coverage for H&N and prostate, respectively, albeit clinically significant hot spots were shown to increase with increasing segment width. Furthermore, the results show that increasing widths can produce comparable treatment plans as measured against our current Food and Drug Administration (FDA)–approved treatment devices—leading to an increase in treatment efficacy in economically underdeveloped countries.

  13. SU-G-JeP1-12: Head-To-Head Performance Characterization of Two Multileaf Collimator Tracking Algorithms for Radiotherapy

    International Nuclear Information System (INIS)

    Caillet, V; Colvill, E; O’Brien, R; Keall, P; Poulsen, P; Moore, D; Booth, J; Sawant, A

    2016-01-01

    Purpose: Multi-leaf collimator (MLC) tracking is being clinically pioneered to continuously compensate for thoracic and abdominal motion during radiotherapy. The purpose of this work is to characterize the performance of two MLC tracking algorithms for cancer radiotherapy, based on a direct optimization and a piecewise leaf fitting approach respectively. Methods: To test the algorithms, both physical and in silico experiments were performed. Previously published high and low modulation VMAT plans for lung and prostate cancer cases were used along with eight patient-measured organ-specific trajectories. For both MLC tracking algorithm, the plans were run with their corresponding patient trajectories. The physical experiments were performed on a Trilogy Varian linac and a programmable phantom (HexaMotion platform). For each MLC tracking algorithm, plan and patient trajectory, the tracking accuracy was quantified as the difference in aperture area between ideal and fitted MLC. To compare algorithms, the average cumulative tracking error area for each experiment was calculated. The two-sample Kolmogorov-Smirnov (KS) test was used to evaluate the cumulative tracking errors between algorithms. Results: Comparison of tracking errors for the physical and in silico experiments showed minor differences between the two algorithms. The KS D-statistics for the physical experiments were below 0.05 denoting no significant differences between the two distributions pattern and the average error area (direct optimization/piecewise leaf-fitting) were comparable (66.64 cm2/65.65 cm2). For the in silico experiments, the KS D-statistics were below 0.05 and the average errors area were also equivalent (49.38 cm2/48.98 cm2). Conclusion: The comparison between the two leaf fittings algorithms demonstrated no significant differences in tracking errors, neither in a clinically realistic environment nor in silico. The similarities in the two independent algorithms give confidence in the use

  14. Dosimetric evaluation of multi-pattern spatially fractionated radiation therapy using a multi-leaf collimator and collapsed cone convolution superposition dose calculation algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Stathakis, Sotirios [Department of Radiation Oncology, University of Texas Health Science Center San Antonio, 7979 Wurzbach Rd, San Antonio, TX 78229 (United States)], E-mail: stathakis@uthscsa.edu; Esquivel, Carlos; Gutierrez, Alonso N.; Shi, ChengYu; Papanikolaou, Niko [Department of Radiation Oncology, University of Texas Health Science Center San Antonio, 7979 Wurzbach Rd, San Antonio, TX 78229 (United States)

    2009-10-15

    Purpose: In this paper, we present an alternative to the originally proposed technique for the delivery of spatially fractionated radiation therapy (GRID) using multi-leaf collimator (MLC) shaped fields. We employ the MLC to deliver various pattern GRID treatments to large solid tumors and dosimetrically characterize the GRID fields. Methods and materials: The GRID fields were created with different open to blocked area ratios and with variable separation between the openings using a MLC. GRID designs were introduced into the Pinnacle{sup 3} treatment planning system, and the dose was calculated in a water phantom. Ionization chamber and film measurements using both Kodak EDR2 and Gafchromic EBT film were performed in a SolidWater phantom to determine the relative output of each GRID design as well as its spatial dosimetric characteristics. Results: Agreement within 5.0% was observed between the Pinnacle{sup 3} predicted dose distributions and the measurements for the majority of experiments performed. A higher magnitude of discrepancy (15%) was observed using a high photon beam energy (18 MV) and small GRID opening. Skin dose at the GRID openings was higher than the corresponding open field by a factor as high as three for both photon energies and was found to be independent of the open-to-blocked area ratio. Conclusion: In summary, we reaffirm that the MLC can be used to deliver spatially fractionated GRID therapy and show that various GRID patterns may be generated. The Pinnacle{sup 3} TPS can accurately calculate the dose of the different GRID patterns in our study to within 5% for the majority of the cases based on film and ion chamber measurements. Disadvantages of MLC-based GRID therapy are longer treatment times and higher surface doses.

  15. SU-G-JeP1-12: Head-To-Head Performance Characterization of Two Multileaf Collimator Tracking Algorithms for Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Caillet, V; Colvill, E [School of Medecine, The University of Sydney, Sydney, NSW (Australia); Royal North Shore Hospital, St Leonards, Sydney (Australia); O’Brien, R; Keall, P [School of Medecine, The University of Sydney, Sydney, NSW (Australia); Poulsen, P [Aarhus University Hospital, Aarhus (Denmark); Moore, D [UT Southwestern Medical Center, Dallas, TX (United States); University of Maryland School of Medicine, Baltimore, MD (United States); Booth, J [Royal North Shore Hospital, St Leonards, Sydney (Australia); Sawant, A [University of Maryland School of Medicine, Baltimore, MD (United States)

    2016-06-15

    Purpose: Multi-leaf collimator (MLC) tracking is being clinically pioneered to continuously compensate for thoracic and abdominal motion during radiotherapy. The purpose of this work is to characterize the performance of two MLC tracking algorithms for cancer radiotherapy, based on a direct optimization and a piecewise leaf fitting approach respectively. Methods: To test the algorithms, both physical and in silico experiments were performed. Previously published high and low modulation VMAT plans for lung and prostate cancer cases were used along with eight patient-measured organ-specific trajectories. For both MLC tracking algorithm, the plans were run with their corresponding patient trajectories. The physical experiments were performed on a Trilogy Varian linac and a programmable phantom (HexaMotion platform). For each MLC tracking algorithm, plan and patient trajectory, the tracking accuracy was quantified as the difference in aperture area between ideal and fitted MLC. To compare algorithms, the average cumulative tracking error area for each experiment was calculated. The two-sample Kolmogorov-Smirnov (KS) test was used to evaluate the cumulative tracking errors between algorithms. Results: Comparison of tracking errors for the physical and in silico experiments showed minor differences between the two algorithms. The KS D-statistics for the physical experiments were below 0.05 denoting no significant differences between the two distributions pattern and the average error area (direct optimization/piecewise leaf-fitting) were comparable (66.64 cm2/65.65 cm2). For the in silico experiments, the KS D-statistics were below 0.05 and the average errors area were also equivalent (49.38 cm2/48.98 cm2). Conclusion: The comparison between the two leaf fittings algorithms demonstrated no significant differences in tracking errors, neither in a clinically realistic environment nor in silico. The similarities in the two independent algorithms give confidence in the use

  16. SU-E-T-214: Intensity Modulated Proton Therapy (IMPT) Based On Passively Scattered Protons and Multi-Leaf Collimation: Prototype TPS and Dosimetry Study

    International Nuclear Information System (INIS)

    Sanchez-Parcerisa, D; Carabe-Fernandez, A

    2014-01-01

    Purpose. Intensity-modulated proton therapy is usually implemented with multi-field optimization of pencil-beam scanning (PBS) proton fields. However, at the view of the experience with photon-IMRT, proton facilities equipped with double-scattering (DS) delivery and multi-leaf collimation (MLC) could produce highly conformal dose distributions (and possibly eliminate the need for patient-specific compensators) with a clever use of their MLC field shaping, provided that an optimal inverse TPS is developed. Methods. A prototype TPS was developed in MATLAB. The dose calculation process was based on a fluence-dose algorithm on an adaptive divergent grid. A database of dose kernels was precalculated in order to allow for fast variations of the field range and modulation during optimization. The inverse planning process was based on the adaptive simulated annealing approach, with direct aperture optimization of the MLC leaves. A dosimetry study was performed on a phantom formed by three concentrical semicylinders separated by 5 mm, of which the inner-most and outer-most were regarded as organs at risk (OARs), and the middle one as the PTV. We chose a concave target (which is not treatable with conventional DS fields) to show the potential of our technique. The optimizer was configured to minimize the mean dose to the OARs while keeping a good coverage of the target. Results. The plan produced by the prototype TPS achieved a conformity index of 1.34, with the mean doses to the OARs below 78% of the prescribed dose. This Result is hardly achievable with traditional conformal DS technique with compensators, and it compares to what can be obtained with PBS. Conclusion. It is certainly feasible to produce IMPT fields with MLC passive scattering fields. With a fully developed treatment planning system, the produced plans can be superior to traditional DS plans in terms of plan conformity and dose to organs at risk

  17. Dose linearity and uniformity of a linear accelerator designed for implementation of multileaf collimation system-based intensity modulated radiation therapy

    International Nuclear Information System (INIS)

    Saw, Cheng B.; Li Sicong; Ayyangar, Komanduri M.; Yoe-Sein, Maung; Pillai, Susha; Enke, Charles A.; Celi, Juan C.

    2003-01-01

    The dose linearity and uniformity of a linear accelerator designed for multileaf collimation system- (MLC) based IMRT was studied as a part of commissioning and also in response to recently published data. The linear accelerator is equipped with a PRIMEVIEW, a graphical interface and a SIMTEC IM-MAXX, which is an enhanced autofield sequencer. The SIMTEC IM-MAXX sequencer permits the radiation beam to be 'ON' continuously while delivering intensity modulated radiation therapy subfields at a defined gantry angle. The dose delivery is inhibited when the electron beam in the linear accelerator is forced out of phase with the microwave power while the MLC configures the field shape of a subfield. This beam switching mechanism reduces the overhead time and hence shortens the patient treatment time. The dose linearity, reproducibility, and uniformity were assessed for this type of dose delivery mechanism. The subfields with monitor units ranged from 1 MU to 100 MU were delivered using 6 MV and 23 MV photon beams. The doses were computed and converted to dose per monitor unit. The dose linearity was found to vary within 2% for both 6 MV and 23 MV photon beam using high dose rate setting (300 MU/min) except below 2 MU. The dose uniformity was assessed by delivering 4 subfields to a Kodak X-OMAT TL film using identical low monitor units. The optical density was converted to dose and found to show small variation within 3%. Our results indicate that this linear accelerator with SIMTEC IM-MAXX sequencer has better dose linearity, reproducibility, and uniformity than had been reported

  18. SU-G-TeP4-03: A Multileaf Collimator Calibration and Quality Assurance Technique Using An Electronic Portal Imaging Device

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-06-15

    Purpose: To develop an accurate and quick multileaf collimator (MLC) calibration and quality assurance technique using an electronic portal imaging device (EPID) Methods: The MLC models used include the MLCi and Agility (Elekta Ltd). This technique consists of two 22(L)x10(W) cm{sup 2} fields with 0{sup 0} and 180{sup 0} collimator angles centered to an offset EPID. The MLC opening is estimated by calculating the profile at the image’s center in the image’s horizontal direction. Scans in the image’s vertical direction were calculated every 20 pixels in the inner 70% of estimated MLC opening. The profiles’ edges were fitted with linear equations to determine the image’s rotation angle. Then, crossline profiles were scanned at the center of each leaf taking into account the leaf’s width at isocenter and the rotation angle. The profiles’ edges determine the location of the leaves’ edges and these were subtracted from the reference leaf’s position in order to determine the relative leaf offsets. The edge location of all profiles was determined by using the parameterized gradient of the penumbra region. The technique was tested against an established diode array-based method, and for different MLC systems, patterns, gantry angles, days, energies, beam modalities and MLC openings. Results: The differences between the proposed and established methods were 0.26±0.19mm. The leaf offsets’ deviation was <0.3mm (5 months period). For pattern fields, the differences between predetermined and calculated offsets were 0.18±0.18mm. The leaf offset deviation of measurements with different energies and MLC openings were <0.1mm and <0.3mm, respectively. The differences between offsets of FF and FFF beams were 0.01±0.02mm (<0.07mm). The differences between the offsets at different gantry angles were 0.08±0.15mm. Conclusion: The proposed method proved to be accurate and efficient in calculating the relative leaf offsets. Parameterized field edge is essential to

  19. 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

  20. Non-dosimetric quality assurance for the three-dimensional radiation treatment planning systems using a multi-leaf collimator phantom

    International Nuclear Information System (INIS)

    Tateoka, Kunihiko; Nagase, Daiki; Sato, Takahito; Shimizume, Kazunari; Ouchi, Atsushi; Nakata, Kensei; Hareyama, Masato

    2008-01-01

    Evaluation of errors and limitations in simulation software for three-dimensional radiation treatment systems (3D-RTPS) is an important issue. Non-dosimetric quality assurance (QA) of the simulation software of 3D-RTPS was evaluated by graphical displays of JAW and multi-leaf collimator (MLC) settings in a 3D-RTPS. The influence of observations made using the phantom depends on human errors and several parameters of the CT scan set, such as slice thickness and spacing, pixel size, partial volume effects and the reconstructed image orientation. We explored the methods that were minimally influenced by these errors and parameters. The QA phantom (MLC phantom) has been designed for checking a JAW and MLC settings in a 3D-RTPS is used for non-dosimetric QA. We analyzed the CT value of the boundary the structures of the MLC phantom. The relative CT value for thickness 1 mm slice in border of each structure body of MLC phantom respectively shows a decrease of about 2%, 4%, 10% by 2 mm, 3 mm and 5 mm. In case of thickness 5 mm slice, the mean deference of border of virtual radiation beams and phantom was 0.8 mm, and standard deviation of them was 0.6 mm. And the mean difference of border of a DRR image and phantom was 0.08 mm and the standard deviation of them 0.6 mm. In case of thickness 2 mm slice, the mean deference of border of virtual radiation beams and phantom was -0.18 mm, and standard deviation of them was 0.32 mm. And the mean difference of border of a DRR image and phantom was 0.87 mm and the standard deviation of them 0.54 mm. The result of the study is useful for improvement in a precision of non-dosimetric QA. Our method of non-dosimetric QA can minimize human error and influence of several parameters of the CT scan set. The MLC phantom is a useful tool in the QA of radiation therapy with application to 3D-RTPS, CT simulators, and virtual simulation packages with MLC display capabilities. (author)

  1. SU-F-T-481: Physics Evaluation of a Newly Released InCise™ Multileaf Collimator for CyberKnife M6™ System

    Energy Technology Data Exchange (ETDEWEB)

    Wang, L; Chin, E; Lo, A [Stanford University Cancer Center, Stanford, CA (United States)

    2016-06-15

    Purpose: This work reports the results of the physics evaluation of a newly released InCise™2 Multileaf Collimator (MLC) installed in our institution. Methods: Beam property data was measured with unshielded diode and EBT2 films. The measurements included MLC leaf transmission, beam profiles, output factors and tissue-phantom ratios. MLC performance was evaluated for one month after commissioning. Weekly Garden Fence tests were performed for leaf / bank positioning in standard (A/P) and clinically relevant non-standard positions, before and after MLC driving exercises of 10+ minutes. Daily Picket Fence test and AQA test, End-to-End tests and dosimetric quality assurance were performed to evaluate the overall system performance. Results: All measurements including beam energy, flatness and symmetry, were within manufacture specifications. Leaf transmission was 0.4% <0.5% specification. The values of output factors ranged from 0.825 (7.6 mm × 7.5 mm) to 1.026 (115.0 mm × 100.1 mm). Average beam penumbra at 10 cm depth ranged from 2.7mm/2.7mm(7.6 mm × 7.5 mm) to 6.0 mm/6.2mm(84.6 mm × 84.7 mm). Slight penumbra difference (<10% from average penumbra for fields >20 mm) was observed in the direction perpendicular to leaf motion due to the tilting of the leaf housing. Mean leaf position offsets was −0.08±0.07mm and −0.13 ± 0.08 for X1 and X2 leaf banks in 13 Garden Fence tests. No significant difference on average leaf positioning offsets was observed between different leaf orientations and before/after MLC driving exercises. Six End-to-End tests showed 0.43±0.23mm overall targeting accuracy. Picket-Fence and AQA showed stable performance of MLC during the test period. Dosimetric point dose measurements for test cases agreed with calculation within 3%. All film measurements on relative dose had Gamma (2%, 2mm) passing rate of >95%. Conclusion: The Incise™2 MLC for CyberKnife M6™ was proven to be accurate and reliable, and it is currently in clinical use

  2. SU-E-T-428: Dosimetric Impact of Multileaf Collimator Leaf Width On Single and multiple Isocenter Stereotactic IMRT Treatment Plans for multiple Brain Tumors

    International Nuclear Information System (INIS)

    Giem, J; Algan, O; Ahmad, S; Ali, I; Young, J; Hossain, S

    2014-01-01

    Purpose: To assess the impacts that multileaf collimator (MLC) leaf width has on the dose conformity and normal brain tissue doses of single and multiple isocenter stereotactic IMRT (SRT) plans for multiple intracranial tumors. Methods: Fourteen patients with 2–3 targets were studied retrospectively. Patients treated with multiple isocenter treatment plans using 9 to 12 non-coplanar beams per lesion underwent repeat planning using single isocenter and 10 to 12 non-coplanar beams with 2.5mm, 3mm and 5mm MLC leaf widths. Brainlab iPlan treatment planning system for delivery with the 2.5mm MLC served as reference. Identical contour sets and dose-volume constraints were applied. The prescribed dose to each target was 25 Gy to be delivered over 5 fractions with a minimum of 99% dose to cover ≥ 95% of the target volume. Results: The lesions and normal brains ranged in size from 0.11 to 51.67cc (median, 2.75cc) and 1090 to 1641cc (median, 1401cc), respectively. The Paddick conformity index for single and multiple isocenter (2.5mm vs. 3mm and 5mm MLCs) was (0.79±0.08 vs. 0.79±0.07 and 0.77±0.08) and (0.79±0.09 vs. 0.77±0.09 and 0.76±0.08), respectively. The average normal brain volumes receiving 15 Gy for single and multiple isocenter (2.5mm vs. 3mm and 5mm MLCs) were (3.65% vs. 3.95% and 4.09%) and (2.89% vs. 2.91% and 2.92%), respectively. Conclusion: The average dose conformity observed for the different leaf width for single and multiple isocenter plans were similar, throughout. However, the average normal brain volumes receiving 2.5 to 15 Gy were consistently lower for the 2.5mm MLC leaf width, especially for single isocenter plans. The clinical consequences of these integral normal brain tissue doses are still unknown, but employing the use of the 2.5mm MLC option is desirable at sparing normal brain tissue for both single and multiple isocenter cases

  3. Multileaf collimator for radiotherapy machines

    International Nuclear Information System (INIS)

    Nunan, C.S.

    1989-01-01

    This patent describes an apparatus for radiotherapy treatment of a patient. It comprises: an electron linear accelerator means for generating x-rays at an x-ray source target; a set of four moveable jaws mounted on a jaw frame between the x-ray source target and the patient. The set of jaws defining a rectangular x-ray field; mounting means for mounting a leaf means on the jaw frame; the mounting means including a main leaf support frame; a pair of subframes, each of which is linearly movable mounted from the frame. The subframes being coplanar; a multiplicity of leaves of material substantially opaque to x-rays. The leaves provided with means to make them linearly movable relative to each subframe, each leaf being capable of extension beyond a field mid-line, the length of each leaf being shorter than half of a maximum field length capability of the jaws measured in the direction and plane of the leaves; leaf drive means; and computer control means for controlling the subframe drive means and the leaf drive means to provide a dynamically changing radiation field shape during the course of radiation treatment of the patient

  4. Multileaf collimator intercomparison for intensity modulated radiation therapy implementation; Intercomparacao de colimadores de multiplas laminas para implementacao de terapia de feixes de intensidade modulada

    Energy Technology Data Exchange (ETDEWEB)

    Viteri, Juan Fernando Delgado

    2006-07-01

    In this work a dosimetric comparison between three multileaf collimator systems is presented: a Varian Millennium with 120 leaves, Brainlab mMLC m3 and Varian Mark II both with 52 leaves. The width projection at isocenter level in field's central region are: 0,5 cm; 0,35 cm and 1,0 cm respectively. Common dosimetric characteristics for the three systems in static mode and dynamic capabilities for the two first were compared. In dynamic mode, tests validating proper MLC function through film irradiation were done, such MLC stability, MU linearity, treatment interruptions sensitivity, stability of MLC in dynamic mode, leaf speed stability, were found within {+-}3% deviation in all cases. Dose rate linearity showed differences when this parameter decreases in dynamic mode. Average dose errors for fixed width gaps moving at constant speed were found to be proportional to gap errors and inversely proportional to the gap width. Output factors differences delivered through a sweeping gap were found less than {+-}1% when the gantry was in a lateral position. For the three MLC systems, when comparing beam profiles for the same field was observed that for mMLC presents the sharpest dose gradient region. In the output factors small differences where observed in every MLC system. Dosimetric leaf gap was determined for MLC 120, mMLC and MLC 52, obtained values for a 6 MV beam are: (0,202 {+-} 0,054) cm; (0,157 {+-} 0,070) cm and (0,189 {+-} 0,081) cm respectively. The transmission showed an increase with depth and field width for 6 MV in all the three systems. Average values obtained with ionization chamber for this energy were: (1,630 {+-} 0,018)% for MLC 120; (1,291 {+-} 0,029)% for mMLC and (1,638 {+-} 0,010)% for MLC 52. When obtained through film irradiation, inter and intra leaf transmission showed an off axis dependent behavior for MLC 120 and mMLC. Scatter produced by MLC as a 6 MV open reference field ratio was: (0,297 {+-} 0,024)% for MLC 120; (0,239 {+-} 0

  5. Multileaf collimator intercomparison for intensity modulated radiation therapy implementation; Intercomparacao de colimadores de multiplas laminas para implementacao de terapia de feixes de intensidade modulada

    Energy Technology Data Exchange (ETDEWEB)

    Viteri, Juan Fernando Delgado

    2006-07-01

    In this work a dosimetric comparison between three multileaf collimator systems is presented: a Varian Millennium with 120 leaves, Brainlab mMLC m3 and Varian Mark II both with 52 leaves. The width projection at isocenter level in field's central region are: 0,5 cm; 0,35 cm and 1,0 cm respectively. Common dosimetric characteristics for the three systems in static mode and dynamic capabilities for the two first were compared. In dynamic mode, tests validating proper MLC function through film irradiation were done, such MLC stability, MU linearity, treatment interruptions sensitivity, stability of MLC in dynamic mode, leaf speed stability, were found within {+-}3% deviation in all cases. Dose rate linearity showed differences when this parameter decreases in dynamic mode. Average dose errors for fixed width gaps moving at constant speed were found to be proportional to gap errors and inversely proportional to the gap width. Output factors differences delivered through a sweeping gap were found less than {+-}1% when the gantry was in a lateral position. For the three MLC systems, when comparing beam profiles for the same field was observed that for mMLC presents the sharpest dose gradient region. In the output factors small differences where observed in every MLC system. Dosimetric leaf gap was determined for MLC 120, mMLC and MLC 52, obtained values for a 6 MV beam are: (0,202 {+-} 0,054) cm; (0,157 {+-} 0,070) cm and (0,189 {+-} 0,081) cm respectively. The transmission showed an increase with depth and field width for 6 MV in all the three systems. Average values obtained with ionization chamber for this energy were: (1,630 {+-} 0,018)% for MLC 120; (1,291 {+-} 0,029)% for mMLC and (1,638 {+-} 0,010)% for MLC 52. When obtained through film irradiation, inter and intra leaf transmission showed an off axis dependent behavior for MLC 120 and mMLC. Scatter produced by MLC as a 6 MV open reference field ratio was: (0,297 {+-} 0,024)% for MLC 120; (0,239 {+-} 0,052)% for

  6. Electronic tissue compensation achieved with both dynamic and static multileaf collimator in eclipse treatment planning system for Clinac 6 EX and 2100 CD Varian linear accelerators: Feasibility and dosimetric study

    Directory of Open Access Journals (Sweden)

    Kinhikar Rajesh

    2007-01-01

    Full Text Available Dynamic multileaf collimator (DMLC and static multileaf collimator (SMLC, along with three-dimensional treatment planning system (3-D TPS, open the possibility of tissue compensation. A method using electronic tissue compensator (ETC has been implemented in Eclipse 3-D TPS (V 7.3, Varian Medical Systems, Palo Alto, USA at our center. The ETC was tested for head and neck conformal radiotherapy planning. The purpose of this study was to verify the feasibility of DMLC and SMLC in head and neck field irradiation for delivering homogeneous dose in the midplane at a pre-defined depth. In addition, emphasis was given to the dosimetric aspects in commissioning ETC in Eclipse. A Head and Neck Phantom (The Phantom Laboratory, USA was used for the dosimetric verification. Planning was carried out for both DMLC and SMLC ETC plans. The dose calculated at central axis by eclipse with DMLC and SMLC was noted. This was compared with the doses measured on machine with ion chamber and thermoluminescence dosimetry (TLD. The calculated isodose curves and profiles were compared with the measured ones. The dose profiles along the two major axes from Eclipse were also compared with the profiles obtained from Amorphous Silicon (AS500 Electronic portal imaging device (EPID on Clinac 6 EX machine. In uniform dose regions, measured dose values agreed with the calculated doses within 3%. Agreement between calculated and measured isodoses in the dose gradient zone was within 3 mm. The isodose curves and the profiles were found to be in good agreement with the measured curves and profiles. The measured and the calculated dose profiles along the two major axes were flat for both DMLC and SMLC. The dosimetric verification of ETC for both the linacs demonstrated the feasibility and the accuracy of the ETC treatment modality for achieving uniform dose distributions. Therefore, ETC can be used as a tool in head and neck treatment planning optimization for improved dose uniformity.

  7. SU-E-T-88: Acceptance Testing and Commissioning Measurements of a Newly Released InCiseâ„¢ Multileaf Collimator for CyberKnife M6â„¢ System

    Energy Technology Data Exchange (ETDEWEB)

    Huq, M Saiful; Ozhasoglu, C; Jang, S; Hwang, M; Heron, D; Lalonde, R [UPMC CancerCenter, Pittsburgh, PA (United States)

    2015-06-15

    Purpose: Accuray recently released a new collimator, the InCise™ Multileaf Collimator (MLC), for clinical use with the CyberKnife M6™ System. This work reports the results of acceptance testing and commissioning measurements for this collimator. Methods: The MLC consists of 41 pairs of 2.5 mm wide leaves projecting a clinical maximum field size of 110 mm x 97.5 mm at 800 mm SAD. The leaves are made of tungsten, 90 mm in height and tilted by 0.5 degree. The manufacturer stated leaf positioning accuracy and reproducibility are 0.5 mm and 0.4 mm respectively at 800 mm SAD. The leaf over-travel is 100% with full interdigitation capability. Acceptance testing included, but are not limited to, the verification of the specifications of various parameters described above, leakage measurements and end-to-end tests. Dosimetric measurements included, but not limited to, measurements of output factors, open beam profiles, tissue-phantom ratios, beam flatness and symmetry, and patient specific QA. Results: All measurements were well within the manufacturer specifications. The values of output factors ranged from 0.804 (smallest field size of 7.6 mm x 7.5 mm) to 1.018 (largest field size of 110.0 mm x 97.5 mm). End-to-end test results for the various tracking modes are: Skull (0.27mm), fiducial (0.16mm), Xsight Spine (0.4mm), Xsight Lung (0.93 mm) and Synchrony (0.43mm). Measured maximum and average leakage was 0.37% and 0.3%, respectively. Patient-specific QA measurements with chamber were all within 5% absolute dose agreement, and film measurements all passed 2%/2mm gamma evaluation for more than 95% of measurement points. Conclusion: The presented results are the first set of data reported on the InCise™ MLC. The MLC proved to be very reliable and is currently in clinical use.

  8. Planning and delivering high doses to targets surrounding the spinal cord at the lower neck and upper mediastinal levels: static beam-segmentation technique executed by a multileaf collimator

    International Nuclear Information System (INIS)

    Schelfhout, J.; Derycke, S.; Fortan, L.; Van Duyse, B.; Colle, C.; De Wagter, C.; De Neve, W.

    1995-01-01

    The possibility to plan and deliver beam intensity modulated radiotherapy using a general purpose 3D-planning system (Sherouse's GRATISTM) and a linear accelerator equipped with a standard multileaf collimator (MLC) was investigated in view of limiting the dose at the spinal cord below tolerance. During the planning process, dose homogenization at the target is obtained by the calculation of the weights, given to beam segments of a specific predetermined geometry. This specific geometry maximizes the area of each segment and thus reduces the number of segments. With a virtual patient in supine position, a first planning using a single isocenter, with gantry positions of -60, -30, 0, 30 and 60 degrees was performed. Medial edges of all segments were located tangential to the spinal cord. The resulting dose distribution allowed to encompass the target by an isodose surface of 66-70 Gy without exceeding spinal cord tolerance but required 42 segments distributed over 5 gantry angles. Therefore, dose-volume histogram analysis were performed for those cases where: 1) for some gantry positions, all beam segments could be omitted; 2) at the remaining gantry angles, segments could be omitted; 3) at least 2 segments could be traded off against 1 additional gantry angle. This procedure resulted in a final plan containing 22 segments spread over 8 gantry angles. Preliminary dosimetric results on a RANDO phantom support the robustness of the method. The first clinical applications have been planned. Although up to 99 beam segments can be programmed on the Philips SL25 linear accelerator, it remained impossible to use these segments synchronized with the MLC. From a clinical viewpoint, the proposed treatment for irradiating lower neck and upper mediastinal targets could be used as a standard against which other solutions might be tested

  9. Planning and delivering high doses to targets surrounding the spinal cord at the lower neck and upper mediastinal levels: static beam-segmentation technique executed with a multileaf collimator

    International Nuclear Information System (INIS)

    Neve, W. de; Wagter, C. de; Jaeger, K. de; Thienpont, M.; Colle, C.; Derycke, S.; Schelfhout, J.

    1996-01-01

    Background and purpose. It remains a technical challenge to limit the dose to the spinal cord below tolerance if, in head and neck or thyroid cancer, the planning target volume reaches to a level below the shoulders. In order to avoid these dose limitations, we developed a standard plan involving Beam Intensity Modulation (BIM) executed by a static technique of beam segmentation. In this standard plan, many machine parameters (gantry angles, couch position, relative beam and segment weights) as well as the beam segmentation rules were identical for all patients. Materials and methods. The standard plan involved: the use of static beams with a single isocenter; BIM by field segmentation executable with a standard Philips multileaf collimator; virtual simulation and dose computation on a general 3D-planning system (Sherouse's GRATIS[reg]); heuristic computation of segment intensities and optimization (improving the dose distribution and reducing the execution time) by human intelligence. The standard plan used 20 segments spread over 8 gantry angles plus 2 non-segmented wedged beams (2 gantry angles). Results. The dose that could be achieved at the lowest target voxel, without exceeding tolerance of the spinal cord (50 Gy at highest voxel) was 70-80 Gy. The in-target 3D dose-inhomogeneity was ∼25%. The shortest time of execution of a treatment (22 segments) on a patient (unpublished) was 25 min. Conclusions. A heuristic model has been developed and investigated to obtain a 3D concave dose distribution applicable to irradiate targets in the lower neck and upper mediastinal regions. The technique spares efficiently the spinal cord and allows the delivery of higher target doses than with conventional techniques. It can be planned as a standard plan using conventional 3D-planning technology. The routine clinical implementation is performed with commercially available equipment, however, at the expense of extended execution times

  10. SU-E-T-604: Penumbra Characteristics of a New InCiseâ„¢ Multileaf Collimator of CyberKnife M6â„¢ System

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, M; Jang, S; Ozhasoglu, C; Lalonde, R; Heron, D; Huq, M [University of Pittsburgh Medical Center, Pittsburgh, PA (United States)

    2015-06-15

    Purpose: The InCise™ Multileaf Collimator (MLC) of CyberKnife M6™ System has been released recently. The purpose of this study was to explore the dosimetric characteristics of the new MLC. In particular, the penumbra characteristics of MLC fields at varying locations are evaluated. Methods: EBT3-based film measurements were performed with varying MLC fields ranging from 7.5 mm to 27.5 mm. Seventeen regions of interests (ROIs) were identified for irradiation. These are regions located at the central area (denoted as reference field), at the left/right edge areas of reference open field, at an intermediate location between central and edge area. Single beam treatment plans were designed by using the MultiPlan and was delivered using the Blue Phantom. Gafchromic films were irradiated at 1.5 cm depth in the Blue Phantom and analyzed using the Film Pro software. Variation of maximum dose, penumbra of MLC-defined fields, and symmetry/flatness were calculated as a function of locations of MLC fields. Results: The InCise™ MLC System showed relatively consistent dose distribution and penumbra size with varying locations of MLC fields. The measured maximum dose varied within 5 % at different locations compared to that at the central location and agreed with the calculated data well within 2%. The measured penumbrae were in the range of 2.9 mm and 3.7 mm and were relatively consistent regardless of locations. However, dose profiles in the out-of-field and in-field regions varied with locations and field sizes. Strong variation was seen for all fields located at 55 mm away from the central field. The MLC leakage map showed that the leakage is dependent on position. Conclusion: The size of penumbra and normalized maximum dose for MLC-defined fields were consistent in different regions of MLC. However, dose profiles in the out-field region varied with locations and field sizes.

  11. SU-E-T-604: Penumbra Characteristics of a New InCiseâ„¢ Multileaf Collimator of CyberKnife M6â„¢ System

    International Nuclear Information System (INIS)

    Hwang, M; Jang, S; Ozhasoglu, C; Lalonde, R; Heron, D; Huq, M

    2015-01-01

    Purpose: The InCise™ Multileaf Collimator (MLC) of CyberKnife M6™ System has been released recently. The purpose of this study was to explore the dosimetric characteristics of the new MLC. In particular, the penumbra characteristics of MLC fields at varying locations are evaluated. Methods: EBT3-based film measurements were performed with varying MLC fields ranging from 7.5 mm to 27.5 mm. Seventeen regions of interests (ROIs) were identified for irradiation. These are regions located at the central area (denoted as reference field), at the left/right edge areas of reference open field, at an intermediate location between central and edge area. Single beam treatment plans were designed by using the MultiPlan and was delivered using the Blue Phantom. Gafchromic films were irradiated at 1.5 cm depth in the Blue Phantom and analyzed using the Film Pro software. Variation of maximum dose, penumbra of MLC-defined fields, and symmetry/flatness were calculated as a function of locations of MLC fields. Results: The InCise™ MLC System showed relatively consistent dose distribution and penumbra size with varying locations of MLC fields. The measured maximum dose varied within 5 % at different locations compared to that at the central location and agreed with the calculated data well within 2%. The measured penumbrae were in the range of 2.9 mm and 3.7 mm and were relatively consistent regardless of locations. However, dose profiles in the out-of-field and in-field regions varied with locations and field sizes. Strong variation was seen for all fields located at 55 mm away from the central field. The MLC leakage map showed that the leakage is dependent on position. Conclusion: The size of penumbra and normalized maximum dose for MLC-defined fields were consistent in different regions of MLC. However, dose profiles in the out-field region varied with locations and field sizes

  12. Planning and delivering high doses to targets surrounding the spinal cord at the lower neck and upper mediastinal levels: static beam-segmentation technique executed by a multileaf collimator

    Energy Technology Data Exchange (ETDEWEB)

    Schelfhout, J; Derycke, S; Fortan, L; Van Duyse, B; Colle, C; De Wagter, C; De Neve, W [Ghent Rijksuniversiteit (Belgium). Kliniek voor Radiotherapie en Kerngeneeskunde

    1995-12-01

    The possibility to plan and deliver beam intensity modulated radiotherapy using a general purpose 3D-planning system (Sherouse`s GRATISTM) and a linear accelerator equipped with a standard multileaf collimator (MLC) was investigated in view of limiting the dose at the spinal cord below tolerance. During the planning process, dose homogenization at the target is obtained by the calculation of the weights, given to beam segments of a specific predetermined geometry. This specific geometry maximizes the area of each segment and thus reduces the number of segments. With a virtual patient in supine position, a first planning using a single isocenter, with gantry positions of -60, -30, 0, 30 and 60 degrees was performed. Medial edges of all segments were located tangential to the spinal cord. The resulting dose distribution allowed to encompass the target by an isodose surface of 66-70 Gy without exceeding spinal cord tolerance but required 42 segments distributed over 5 gantry angles. Therefore, dose-volume histogram analysis were performed for those cases where: (1) for some gantry positions, all beam segments could be omitted; (2) at the remaining gantry angles, segments could be omitted; (3) at least 2 segments could be traded off against 1 additional gantry angle. This procedure resulted in a final plan containing 22 segments spread over 8 gantry angles. Preliminary dosimetric results on a RANDO phantom support the robustness of the method. The first clinical applications have been planned. Although up to 99 beam segments can be programmed on the Philips SL25 linear accelerator, it remained impossible to use these segments synchronized with the MLC. From a clinical viewpoint, the proposed treatment for irradiating lower neck and upper mediastinal targets could be used as a standard against which other solutions might be tested.

  13. SU-E-T-225: Correction Matrix for PinPoint Ionization Chamber for Dosimetric Measurements in the Newly Released Incise™ Multileaf Collimator Shaped Small Field for CyberKnife M6™ Machine

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y; Li, T; Heron, D; Huq, M [University of Pittsburgh Cancer Institute and UPMC CancerCenter, Pittsburgh, PA (United States)

    2015-06-15

    Purpose: For small field dosimetry, such as measurements of output factors for cones or MLC-shaped irregular small fields, ion chambers often Result in an underestimation of the dose, due to both the volume averaging effect and the lack of lateral charged particle equilibrium. This work presents a mathematical model for correction matrix for a PTW PinPoint ionization chamber for dosimetric measurements made in the newly released Incise™ Multileaf collimator fields of the CyberKnife M6™ machine. Methods: A correction matrix for a PTW 0.015cc PinPoint ionization chamber was developed by modeling its 3D dose response in twelve cone-shaped circular fields created using the 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 50mm, 60mm cones in a CyberKnife M6™ machine. For each field size, hundreds of readings were recorded for every 2mm chamber shift in the horizontal plane. The contribution of each dose pixel to a measurement point depended on the radial distance and the angle to the chamber axis. These readings were then compared with the theoretical dose as obtained with Monte Carlo calculation. A penalized least-square optimization algorithm was developed to generate the correction matrix. After the parameter fitting, the mathematical model was validated for MLC-shaped irregular fields. Results: The optimization algorithm used for parameter fitting was stable and the resulted response factors were smooth in spatial domain. After correction with the mathematical model, the chamber reading matched with the calculation for all the tested fields to within 2%. Conclusion: A novel mathematical model has been developed for PinPoint chamber for dosimetric measurements in small MLC-shaped irregular fields. The correction matrix is dependent on detector, treatment unit and the geometry of setup. The model can be applied to non-standard composite fields and provides an access to IMRT point dose validation.

  14. SU-E-T-225: Correction Matrix for PinPoint Ionization Chamber for Dosimetric Measurements in the Newly Released Incise™ Multileaf Collimator Shaped Small Field for CyberKnife M6™ Machine

    International Nuclear Information System (INIS)

    Zhang, Y; Li, T; Heron, D; Huq, M

    2015-01-01

    Purpose: For small field dosimetry, such as measurements of output factors for cones or MLC-shaped irregular small fields, ion chambers often Result in an underestimation of the dose, due to both the volume averaging effect and the lack of lateral charged particle equilibrium. This work presents a mathematical model for correction matrix for a PTW PinPoint ionization chamber for dosimetric measurements made in the newly released Incise™ Multileaf collimator fields of the CyberKnife M6™ machine. Methods: A correction matrix for a PTW 0.015cc PinPoint ionization chamber was developed by modeling its 3D dose response in twelve cone-shaped circular fields created using the 5mm, 7.5mm, 10mm, 12.5mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 50mm, 60mm cones in a CyberKnife M6™ machine. For each field size, hundreds of readings were recorded for every 2mm chamber shift in the horizontal plane. The contribution of each dose pixel to a measurement point depended on the radial distance and the angle to the chamber axis. These readings were then compared with the theoretical dose as obtained with Monte Carlo calculation. A penalized least-square optimization algorithm was developed to generate the correction matrix. After the parameter fitting, the mathematical model was validated for MLC-shaped irregular fields. Results: The optimization algorithm used for parameter fitting was stable and the resulted response factors were smooth in spatial domain. After correction with the mathematical model, the chamber reading matched with the calculation for all the tested fields to within 2%. Conclusion: A novel mathematical model has been developed for PinPoint chamber for dosimetric measurements in small MLC-shaped irregular fields. The correction matrix is dependent on detector, treatment unit and the geometry of setup. The model can be applied to non-standard composite fields and provides an access to IMRT point dose validation

  15. Computer controlled multi-leaf conformation radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, T [Tokyo Metropolitan Komagome Hospital (Japan); Inamura, K

    1981-10-01

    A conformation radiotherapy system with 5-split collimators of which openings can be controlled symmetrically by computerized techniques during rotational irradiation by a linear accelerator has been developed. Outline of the system performance and its clinical applications are described as follows. 1. Profile of the system: The hardware is composed of three parts, namely, the multi-split collimator, the electronic data processor, and the interface between those two parts. 1) The multi-leaf collimator is composed of 5 pairs (10 leaves) diaphragms. It can be mounted to the X-ray head of a linear accelerator when used, and can be dismounted after its use. 2) The electronic data processor sends control signal to the collimator according to the 5-leaf target volume data which can be stored into a minifloppy disc through the curve digitizer previously. This part is composed of a) dedicated micro processor, b) I/O expansion unit, c) color CRT display with key board, d) dual mini-floppy disc unit, e) curve digitizer and f) digital plotter for recording and verification of resulted accuracy. 2. Performance of the system: 1) Maximum field size: 15 cm x 15 cm at isocenter. 2) Maximum elongation ratio of the target volume: 3 : 1 when the longer diameter is 15 cm. 3) Control accuracy: Within +-3 mm deviation from planned beam focus at isocenter. 3. Clinical application: The method of treatment planning and clinical advantages of this irradiation method are explained by raising clinical experiences such as treating brain tumor and rectal cancer.

  16. Computer controlled multi-leaf conformation radiotherapy

    International Nuclear Information System (INIS)

    Matsuda, Tadayoshi; Inamura, Kiyonari.

    1981-01-01

    A conformation radiotherapy system with 5-split collimators of which openings can be controlled symmetrically by computerized techniques during rotational irradiation by a linear accelerator has been developed. Outline of the system performance and its clinical applications are described as follows. 1. Profile of the system: The hardware is composed of three parts, namely, the multi-split collimator, the electronic data processor, and the interface between those two parts. 1) The multi-leaf collimator is composed of 5 pairs (10 leaves) diaphragms. It can be mounted to the X-ray head of a linear accelerator when used, and can be dismounted after its use. 2) The electronic data processor sends control signal to the collimator according to the 5-leaf target volume data which can be stored into a minifloppy disc through the curve digitizer previously. This part is composed of a) dedicated micro processor, b) I/O expansion unit, c) color CRT display with key board, d) dual mini-floppy disc unit, e) curve digitizer and f) digital plotter for recording and verification of resulted accuracy. 2. Performance of the system: 1) Maximum field size: 15 cm x 15 cm at isocenter. 2) Maximum elongation ratio of the target volume: 3 : 1 when the longer diameter is 15 cm. 3) Control accuracy: Within +-3 mm deviation from planned beam focus at isocenter. 3. Clinical application: The method of treatment planning and clinical advantages of this irradiation method are explained by raising clinical experiences such as treating brain tumor and rectal cancer. (author)

  17. Collimator kit

    International Nuclear Information System (INIS)

    Jonker, R.R.

    1976-01-01

    A collimator kit having a number of parts which may be assembled in various combinations to provide focusing collimators with different performance characteristics for radioisotope imaging apparatus is described

  18. Development of a Multileaf Collimator for Proton Radiotherapy

    Science.gov (United States)

    2010-06-01

    the oxygen fraction would be underestimated by the MGH calibration, and the carbon fraction would be overestimated. The differences are likely due...the Roberts Proton Therapy Center. Our long term goal is to simulate and measure proton-induced positron isotope distributions at different time...Dr. Mayer has considerable experience extending from medical physics to image-processing. Ms. Kathleen Noel and Ms. Jean Petrov, both research nurses

  19. Development of a Multileaf Collimator for Proton Therapy

    Science.gov (United States)

    2012-11-01

    in 3.3 mm thick waterproof PMMA sleeves within a 30_30_30 cm water phantom with 0.5 cm thick PMMA walls at an SSD of 100 cm, with the xray beam...machines located at WRAMC connected to Internet2 were isolated from those on the WRAMC LAN, with the ‘‘tennis shoe network’’ (thumb drives) used to

  20. Variable collimator

    International Nuclear Information System (INIS)

    Richey, J.B.; McBride, T.R.; Covic, J.

    1981-01-01

    A CAT scanning device has two collimators, one on the beam side of the scanned object, and the other on the detector side. Both have adjustable apertures for shaping the beam, and varying the aperture of one collimator automatically produces a corresponding change in the aperture of the other

  1. Variable collimator

    International Nuclear Information System (INIS)

    Richey, J.B.; McBride, T.R.; Covic, J.

    1979-01-01

    This invention describes an automatic variable collimator which controls the width and thickness of X-ray beams in X-ray diagnostic medical equipment, and which is particularly adapted for use with computerized axial tomographic scanners. A two-part collimator is provided which shapes an X-ray beam both prior to its entering an object subject to radiographic analysis and after the attenuated beam has passed through the object. Interposed between a source of radiation and the object subject to radiographic analysis is a first or source collimator. The source collimator causes the X-ray beam emitted by the source of radiation to be split into a plurality of generally rectangular shaped beams. Disposed within the source collimator is a movable aperture plate which may be used to selectively vary the thickness of the plurality of generally rectangular shaped beams transmitted through the source collimator. A second or receiver collimator is interposed between the object subject to radiographic analysis and a series of radiation detectors. The receiver collimator is disposed to receive the attenuated X-ray beams passing through the object subject to radiographic analysis. Located within the receiver collimator are a plurality of movable aperture plates adapted to be displaced relative to a plurality of fixed aperture plates for the purpose of varying the width and thickness of the attenuated X-ray beams transmitted through the object subject to radiographic analysis. The movable aperture plates of the source and receiver collimators are automatically controlled by circuitry which is provided to allow remote operation of the movable aperture plates

  2. Impact of collimator leaf width on stereotactic radiosurgery and 3D conformal radiotherapy treatment plans

    International Nuclear Information System (INIS)

    Kubo, H. Dale; Wilder, Richard B.; Pappas, Conrad T.E.

    1999-01-01

    Purpose: The authors undertook a study to analyze the impact of collimator leaf width on stereotactic radiosurgery and 3D conformal radiotherapy treatment plans. Methods and Materials: Twelve cases involving primary brain tumors, metastases, or arteriovenous malformations that had been planned with BrainLAB's conventional circular collimator-based radiosurgery system were re-planned using a β-version of BrainLAB's treatment planning software that is compatible with MRC Systems' and BrainLAB's micro-multileaf collimators. These collimators have a minimum leaf width of 1.7 mm and 3.0 mm, respectively, at isocenter. The clinical target volumes ranged from 2.7-26.1 cc and the number of static fields ranged from 3-5. In addition, for 4 prostate cancer cases, 2 separate clinical target volumes were planned using MRC Systems' and BrainLAB's micro-multileaf collimators and Varian's multileaf collimator: the smaller clinical target volume consisted of the prostate gland and the larger clinical target volume consisted of the prostate and seminal vesicles. For the prostate cancer cases, treatment plans were generated using either 6 or 7 static fields. A 'PITV ratio', which the Radiation Therapy Oncology Group defines as the volume encompassed by the prescription isodose surface divided by the clinical target volume, was used as a measure of the quality of treatment plans (a PITV ratio of 1.0-2.0 is desirable). Bladder and rectal volumes encompassed by the prescription isodose surface, isodose distributions and dose volume histograms were also analyzed for the prostate cancer patients. Results: In 75% of the cases treated with radiosurgery, a PITV ratio between 1.0-2.0 could be achieved using a micro-multileaf collimator with a leaf width of 1.7-3.0 mm at isocenter and 3-5 static fields. When the clinical target volume consisted of the prostate gland, the micro-multileaf collimator with a minimum leaf width of 3.0 mm allowed one to decrease the median volume of bladder and

  3. VMAT optimization with dynamic collimator rotation.

    Science.gov (United States)

    Lyu, Qihui; O'Connor, Daniel; Ruan, Dan; Yu, Victoria; Nguyen, Dan; Sheng, Ke

    2018-04-16

    Although collimator rotation is an optimization variable that can be exploited for dosimetric advantages, existing Volumetric Modulated Arc Therapy (VMAT) optimization uses a fixed collimator angle in each arc and only rotates the collimator between arcs. In this study, we develop a novel integrated optimization method for VMAT, accounting for dynamic collimator angles during the arc motion. Direct Aperture Optimization (DAO) for Dynamic Collimator in VMAT (DC-VMAT) was achieved by adding to the existing dose fidelity objective an anisotropic total variation term for regulating the fluence smoothness, a binary variable for forming simple apertures, and a group sparsity term for controlling collimator rotation. The optimal collimator angle for each beam angle was selected using the Dijkstra's algorithm, where the node costs depend on the estimated fluence map at the current iteration and the edge costs account for the mechanical constraints of multi-leaf collimator (MLC). An alternating optimization strategy was implemented to solve the DAO and collimator angle selection (CAS). Feasibility of DC-VMAT using one full-arc with dynamic collimator rotation was tested on a phantom with two small spherical targets, a brain, a lung and a prostate cancer patient. The plan was compared against a static collimator VMAT (SC-VMAT) plan using three full arcs with 60 degrees of collimator angle separation in patient studies. With the same target coverage, DC-VMAT achieved 20.3% reduction of R50 in the phantom study, and reduced the average max and mean OAR dose by 4.49% and 2.53% of the prescription dose in patient studies, as compared with SC-VMAT. The collimator rotation co-ordinated with the gantry rotation in DC-VMAT plans for deliverability. There were 13 beam angles in the single-arc DC-VMAT plan in patient studies that requires slower gantry rotation to accommodate multiple collimator angles. The novel DC-VMAT approach utilizes the dynamic collimator rotation during arc

  4. Adjustable collimator

    International Nuclear Information System (INIS)

    Carlson, R.W.; Covic, J.; Leininger, G.

    1981-01-01

    In a rotating fan beam tomographic scanner there is included an adjustable collimator and shutter assembly. The assembly includes a fan angle collimation cylinder having a plurality of different length slots through which the beam may pass for adjusting the fan angle of the beam. It also includes a beam thickness cylinder having a plurality of slots of different widths for adjusting the thickness of the beam. Further, some of the slots have filter materials mounted therein so that the operator may select from a plurality of filters. Also disclosed is a servo motor system which allows the operator to select the desired fan angle, beam thickness and filter from a remote location. An additional feature is a failsafe shutter assembly which includes a spring biased shutter cylinder mounted in the collimation cylinders. The servo motor control circuit checks several system conditions before the shutter is rendered openable. Further, the circuit cuts off the radiation if the shutter fails to open or close properly. A still further feature is a reference radiation intensity monitor which includes a tuning-fork shaped light conducting element having a scintillation crystal mounted on each tine. The monitor is placed adjacent the collimator between it and the source with the pair of crystals to either side of the fan beam

  5. Independent collimators are sufficient to conform and combine adjacent fields?; Os colimadores independentes sao suficientes para conformar e combinar campos adjacentes?

    Energy Technology Data Exchange (ETDEWEB)

    Andrade Neto, Enock de A. [Hospital Sirio Libanes, Sao Paulo, SP (Brazil). Sociedade Beneficente de Senhoras. Servico de Radioterapia; Santos Neto, Geraldo [Grupo COI, Rio de Janeiro, RJ (Brazil). Servico de Radioterapia; Sant' Anna, Marcelo C., E-mail: enock92@gmail.com [RADCLIN Centro de Oncologia, Volta Redonda, RJ (Brazil). Servico de Radioterapia

    2014-12-15

    Consider a radiotherapy treatment in which the tumor is located in the region of head and neck. In general, isocentric technique combined with three tangents half-beam fields are used. How these fields must be collimated? We show that the combination of independent collimators and multi-leaf results in a uniform dose in the region which these fields touch each other. Moreover, we recommend a setup that minimizes the heterogeneity for LINAC's that doesn't possess a multi-leaf collimator. (author)

  6. Measuring the wobble of radiation field centers during gantry rotation and collimator movement on a linear accelerator

    International Nuclear Information System (INIS)

    Du, Weiliang; Gao, Song

    2011-01-01

    Purpose: The isocenter accuracy of a linear accelerator is often assessed with star-shot films. This approach is limited in its ability to quantify three dimensional wobble of radiation field centers (RFCs). The authors report a Winston-Lutz based method to measure the 3D wobble of RFCs during gantry rotation, collimator rotation, and collimator field size change. Methods: A stationary ball-bearing phantom was imaged using multileaf collimator-shaped radiation fields at various gantry angles, collimator angles, and field sizes. The center of the ball-bearing served as a reference point, to which all RFCs were localized using a computer algorithm with subpixel accuracy. Then, the gantry rotation isocenter and the collimator rotation axis were derived from the coordinates of these RFCs. Finally, the deviation or wobble of the individual RFC from the derived isocenter or rotation axis was quantified. Results: The results showed that the RFCs were stable as the field size of the multileaf collimator was varied. The wobble of RFCs depended on the gantry angle and the collimator angle and was reproducible, indicating that the mechanical imperfections of the linac were mostly systematic and quantifiable. It was found that the 3D wobble of RFCs during gantry rotation was reduced after compensating for a constant misalignment of the multileaf collimator. Conclusions: The 3D wobble of RFCs can be measured with submillimeter precision using the proposed method. This method provides a useful tool for checking and adjusting the radiation isocenter tightness of a linac.

  7. Measuring the wobble of radiation field centers during gantry rotation and collimator movement on a linear accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Du, Weiliang; Gao, Song [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas, 77030 (United States)

    2011-08-15

    Purpose: The isocenter accuracy of a linear accelerator is often assessed with star-shot films. This approach is limited in its ability to quantify three dimensional wobble of radiation field centers (RFCs). The authors report a Winston-Lutz based method to measure the 3D wobble of RFCs during gantry rotation, collimator rotation, and collimator field size change. Methods: A stationary ball-bearing phantom was imaged using multileaf collimator-shaped radiation fields at various gantry angles, collimator angles, and field sizes. The center of the ball-bearing served as a reference point, to which all RFCs were localized using a computer algorithm with subpixel accuracy. Then, the gantry rotation isocenter and the collimator rotation axis were derived from the coordinates of these RFCs. Finally, the deviation or wobble of the individual RFC from the derived isocenter or rotation axis was quantified. Results: The results showed that the RFCs were stable as the field size of the multileaf collimator was varied. The wobble of RFCs depended on the gantry angle and the collimator angle and was reproducible, indicating that the mechanical imperfections of the linac were mostly systematic and quantifiable. It was found that the 3D wobble of RFCs during gantry rotation was reduced after compensating for a constant misalignment of the multileaf collimator. Conclusions: The 3D wobble of RFCs can be measured with submillimeter precision using the proposed method. This method provides a useful tool for checking and adjusting the radiation isocenter tightness of a linac.

  8. The ARCS radial collimator

    International Nuclear Information System (INIS)

    Stone, M.B.; Abernathy, D.L.; Niedziela, J.L.; Overbay, M.A.

    2015-01-01

    We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. The collimator is composed of collimating blades (or septa). The septa are 12 micron thick Kapton foils coated on each side with 39 microns of enriched boron carbide ( 10 B 4 C with 10 B > 96%) in an ultra-high vacuum compatible binder. The collimator blades represent an additional 22 m 2 of surface area. In the article we present collimator's design and performance and methodologies for its effective use

  9. Penumbra measurements of BeamModulatorTM multi leaf collimator

    International Nuclear Information System (INIS)

    Lu Xiaoguang; Wang Yunlai; Huo Xiaoqing; Sha Xiangyan; Miao Xiongfei

    2010-01-01

    Objective: To evaluate the penumbra of a new multileaf collimator equipped with Elekta Synergy accelerator. Methods: The penumbra were derived from beam profiles measured in air and water using PinPoint ion chamber with PTW MP3 water phantom. Variations of penumbra with X-ray beam energy, depth in water, and leaf position were investigated. Results: The penumbra in air for 6 MV X-ray was 2 mm less than that at depth of maximal dose in water. The penumbra of leaf side was 1 mm less than that of the leaf end. The penumbra had close relationship with beam energy, depth in water and leaf position. penumbra increased with beam quality and water depth. The leaf position had great influence on the penumbra. Conclusions: The penumbra of the multileaf collimator is related to its original design and radiation delivery technique. Special considerations should be taken into during treatment planning. Regular measurement should be performed to guarantee the delivery quality. (authors)

  10. IMRT sequencing for a six-bank multi-leaf system

    International Nuclear Information System (INIS)

    Topolnjak, R; Heide, U A van der; Lagendijk, J J W

    2005-01-01

    In this study, we present a sequencer for delivering step-and-shoot IMRT using a six-bank multi-leaf system. Such a system was proposed earlier and combines a high-resolution field-shaping ability with a large field size. It consists of three layers of two opposing leaf banks with 1 cm leaves. The layers are rotated relative to each other at 60 0 . A low-resolution mode of sequencing is achieved by using one layer of leaves as primary MLC, while the other two are used to improve back-up collimation. For high-resolution sequencing, an algorithm is presented that creates segments shaped by all six banks. Compared to a hypothetical mini-MLC with 0.4 cm leaves, a similar performance can be achieved, but a trade-off has to be made between accuracy and the number of segments

  11. Characterization of Embedded BPM Collimators

    CERN Document Server

    VALENTINO, Gianluca

    2015-01-01

    During LS1, 16 tertiary collimators (TCTs) and 2 secondary collimators (TCSGs) in IR6 were replaced by new embedded BPM collimators. The BPM functionality allows the possibility to align the collimators more quickly and therefore be able to respond faster to machine configuration changes, as well as a direct monitoring of the beam orbit at the collimators. Following an initial commissioning phase, an MD was carried out to test the new collimators and acquisition electronics with beam in the LHC.

  12. The multi leaf collimator for fast neutron therapy at louvain-la-Neuve

    International Nuclear Information System (INIS)

    Denis, J.M.; Richard, F.; Vynckier, S.; Wambersie, A.; Meulders, J.P.; Lannoye, E.; Longree, Y.; Ryckewaert, G.

    1996-01-01

    The multi-leaf collimator of the fast neutron therapy facility at Louvain-la-Neuve is described, as well as some of the physics experiments performed in order to evaluate the attenuation of neutron beams in different materials and thus optimize the composition of collimator leaves. The multi-leaf collimator consists of two sets of 22 leaves each, which can be moved independently. They are made of iron and their thickness is 95 cm. Seven borated polyethylene disks are located in the distal part of the leaves in order to absorb more efficiently the low-energy component of the neutron spectrum. The width of the leaves is 1 cm at their distal part. The leaves can more 11 cm outwards and 6 cm inwards from their reference position, and field size up to 25.7 x 24.8 cm as well as irregular field shapes, can be obtained. The inner part of the leaves and their two sides are always focused on the target. The complete multi-leaf collimator can rotate around the beam axis, from -90 deg to + 90 deg from the reference position. The width of the penumbra (80 - 20 % isodoses) is 0.64 cm and 1.17 cm at the depth of the maximum buildup and at 10 cm in depth respectively, for a 10 x 10 cm field size. The collimator is adequate for the energy of the p(65)+Be neutron beam of Louvain-la-Neuve and has been adapted to the fixed vertical beam. It has been designed following the original plans of Scanditronix, adjusted and fully assembled at the workshop of the Centre de Recherches du Cyclotron (CRC). Systematic measurements were performed in order to optimize the design and the composition of the leaves. In particular the attenuations of the actual beam and of monoenergetic neutron beams were measured in different materials such as iron and polyethylene. Above (upstream) the multi-leaf collimator, a fixed pre-collimator (iron thickness 50 cm; section 1 x 1 m) defines a conical aperture aligned on the largest opening of the leaves. It contains the two transmission chambers and a 2 cm thick

  13. Megavoltage CT imaging as a by-product of multileaf collimator leakage

    International Nuclear Information System (INIS)

    Ruchala, K.J.; Kapatoes, J.M.; Olivera, G.H.; Schloesser, E.A.; Reckwerdt, P.J.; Mackie, T.R.

    2000-01-01

    In addition to their potential for the delivery of highly conformal radiation therapy treatments, tomotherapeutic treatments also feature increased potential for verification. For example, megavoltage CT allows one to use the megavoltage linac to generate tomographic images of the patient in the treatment position. This is typically done before or after radiation therapy treatments. However, it is also possible to collect MVCT images entirely during the treatment itself. This process utilizes the leakage radiation through the closed leaves of the Nomos MIMiC MLC, along with slight inefficiencies in treatment delivery, to generate MVCT images during treatment that require neither additional time nor dose. The image quality is limited, yet sufficient to see a patient's external boundary, density differences over 8% for 25.0 mm objects and resolutions of 3.0 mm for high-contrast objects. Such images can potentially be viewed during treatment, used to flag additional CT immediately after the treatment and provide a representation of the patient's exact position during treatment for use with dose reconstruction. (author)

  14. Linear accelerator based stereotactic radiosurgery with micro multi-leaf collimator : technological advancement in precision radiotherapy

    International Nuclear Information System (INIS)

    Dayananda, S.; Kinhikar, R.A.; Saju, Sherley; Deshpande, D.D.; Jalali, R.; Sarin, R.; Shrivastava, S.K.; Dinshaw, K.A.

    2003-01-01

    Stereotactic Radiosurgery (SRS) is an advancement on precision radiotherapy, in which stereo tactically guided localized high dose is delivered to the lesion (target) in a single fraction, while sparing the surrounding normal tissue. Radiosurgery has been used to treat variety of benign and malignant lesions as well as functional disorders in brain such as arteriovenous malformation (AVM), acoustic neuroma, solitary primary brain tumor, single metastasis, pituitary adenoma etc

  15. Electromagnetic guided couch and multileaf collimator tracking on a TrueBeam accelerator

    DEFF Research Database (Denmark)

    Hansen, Rune; Ravkilde, Thomas; Worm, Esben Schjødt

    2016-01-01

    Purpose: Couch and MLC tracking are two promising methods for real-time motion compensation during radiation therapy. So far, couch and MLC tracking experiments have mainly been performed by different research groups, and no direct comparison of couch and MLC tracking of volumetric modulated arc...... to characterize the geometric and dosimetric performance of electromagnetic guided couch and MLC tracking on a TrueBeam accelerator equipped with a Millennium MLC. The tracking system latency was determined without motion prediction as the time lag between sinusoidal target motion and the compensating motion...

  16. Treatment planning for conformation therapy using a multi-leaf collimator

    International Nuclear Information System (INIS)

    Boesecke, R.; Doll, J.; Bauer, B.; Schlegel, W.; Pastyr, O.; Lorenz, W.J.

    1988-01-01

    In high energy photon therapy an optimum dose distribution is achieved with an irradiation from several directions, thus adapting the field shape to the target volume. Some methods of irradiation planning using these techniques are presented. The result of such a treatment planning is demonstrated. (orig.) [de

  17. Conformal radiotherapy using multileaf collimation: quality assurance and in vivo dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Aletti, P [Centre A. Vautrin, Nancy (France)

    1995-12-01

    The application of quality assurance principles in three dimensional conformal therapy is discussed.Critical requirements in three dimensional radiotherapy are the patient immobilization, the location, and the delivered dose. General recommendations with respect to the equipment for conformal radiotherapy and personnel are made.

  18. An accurate calibration method of the multileaf collimator valid for conformal and intensity modulated radiation treatments

    Energy Technology Data Exchange (ETDEWEB)

    Sastre-Padro, Maria; Heide, Uulke A van der; Welleweerd, Hans [Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht (Netherlands)

    2004-06-21

    Because for IMRT treatments the required accuracy on leaf positioning is high, conventional calibration methods may not be appropriate. The aim of this study was to develop the tools for an accurate MLC calibration valid for conventional and IMRT treatments and to investigate the stability of the MLC. A strip test consisting of nine adjacent segments 2 cm wide, separated by 1 mm and exposed on Kodak X-Omat V films at D{sub max} depth, was used for detecting leaf-positioning errors. Dose profiles along the leaf-axis were taken for each leaf-pair. We measured the dose variation on each abutment to quantify the relative positioning error (RPE) and the absolute position of the abutment to quantify the absolute positioning error (APE). The accuracy of determining the APE and RPE was 0.15 and 0.04 mm, respectively. Using the RPE and the APE the MLC calibration parameters were calculated in order to obtain a flat profile on the abutment at the correct position. A conventionally calibrated Elekta MLC was re-calibrated using the strip test. The stability of the MLC and leaf-positioning reproducibility was investigated exposing films with 25 adjacent segments 1 cm wide during three months and measuring the standard deviation of the RPE values. A maximum shift over the three months of 0.27 mm was observed and the standard deviation of the RPE values was 0.11 mm.

  19. An accurate calibration method of the multileaf collimator valid for conformal and intensity modulated radiation treatments

    International Nuclear Information System (INIS)

    Sastre-Padro, Maria; Heide, Uulke A van der; Welleweerd, Hans

    2004-01-01

    Because for IMRT treatments the required accuracy on leaf positioning is high, conventional calibration methods may not be appropriate. The aim of this study was to develop the tools for an accurate MLC calibration valid for conventional and IMRT treatments and to investigate the stability of the MLC. A strip test consisting of nine adjacent segments 2 cm wide, separated by 1 mm and exposed on Kodak X-Omat V films at D max depth, was used for detecting leaf-positioning errors. Dose profiles along the leaf-axis were taken for each leaf-pair. We measured the dose variation on each abutment to quantify the relative positioning error (RPE) and the absolute position of the abutment to quantify the absolute positioning error (APE). The accuracy of determining the APE and RPE was 0.15 and 0.04 mm, respectively. Using the RPE and the APE the MLC calibration parameters were calculated in order to obtain a flat profile on the abutment at the correct position. A conventionally calibrated Elekta MLC was re-calibrated using the strip test. The stability of the MLC and leaf-positioning reproducibility was investigated exposing films with 25 adjacent segments 1 cm wide during three months and measuring the standard deviation of the RPE values. A maximum shift over the three months of 0.27 mm was observed and the standard deviation of the RPE values was 0.11 mm

  20. A modified method of planning and delivery for dynamic multileaf collimator intensity-modulated radiation therapy

    International Nuclear Information System (INIS)

    Dogan, Nesrin; Leybovich, Leonid B.; Sethi, Anil; Krasin, Matthew; Emami, Bahman

    2000-01-01

    Purpose: To develop a modified planning and delivery technique that reduces dose nonuniformity for tomographic delivery of intensity-modulated radiation therapy (IMRT). Methods and Materials: The NOMOS-CORVUS system delivers IMRT in a tomographic paradigm. This type of delivery is prone to create multiple dose nonuniformity regions at the arc abutment regions. The modified technique was based on the cyclical behavior of arc positions as a function of a target length. With the modified technique, two plans are developed for the same patient, one with the original target and the second with a slightly increased target length and the abutment regions shifted by ∼5 mm compared to the first plan. Each plan is designed to deliver half of the target prescription dose delivered on alternate days, resulting in periodic shifts of abutment regions. This method was experimentally tested in phantoms with and without intentionally introduced errors in couch indexing. Results: With the modified technique, the degree of dose nonuniformity was reduced. For example, with 1 mm error in couch indexing, the degree of dose nonuniformity changed from ∼25% to ∼12%. Conclusion: Use of the modified technique reduces dose nonuniformity due to periodic shifts of abutment regions during treatment delivery

  1. 'Tongue-and-groove' effect in intensity modulated radiotherapy with static multileaf collimator fields

    International Nuclear Information System (INIS)

    Que, W; Kung, J; Dai, J

    2004-01-01

    The 'tongue-and-groove problem' in step-and-shoot delivery of intensity modulated radiotherapy is investigated. A 'tongue-and-groove' index (TGI) is introduced to quantify the 'tongue-and-groove' effect in step-and-shoot delivery. Four different types of leaf sequencing methods are compared. The sliding window method and the reducing level method use the same number of field segments to deliver the same intensity map, but the TGI is much less for the reducing level method. The leaf synchronization method of Van Santvoort and Heijmen fails in step-and-shoot delivery, but a new method inspired by the method of Van Santvoort and Heijmen is shown to eliminate 'tongue-and-groove' underdosage completely

  2. Modulated electron radiotherapy treatment planning using a photon multileaf collimator for post-mastectomized chest walls

    International Nuclear Information System (INIS)

    Salguero, Francisco Javier; Palma, Bianey; Arrans, Rafael; Rosello, Joan; Leal, Antonio

    2009-01-01

    Background and purpose: To evaluate the feasibility of using a photon MLC (xMLC) for modulated electron radiotherapy treatment (MERT) as an alternative to conventional post-mastectomy chest wall (CW) irradiation. A Monte Carlo (MC) based planning system was developed to overcome the inaccuracy of the 'pencil beam' algorithm. MC techniques are known to accurately calculate the dose distributions of electron beams, allowing the explicit simulation of electron interactions within the MLC. Materials and methods: Four real clinical CW cases were planned using MERT which were compared with the conventional electron treatments based on blocks and by a straightforward approach using the MLC, and not the blocks (as an intermediate step to MERT) to shape the same segments with SSD between 60 and 70 cm depending on PTV size. MC calculations were verified with an array of ionization chambers and radiochromic films in a solid water phantom. Results: Tests based on gamma analysis between MC dose distributions and radiochromic film measurements showed an excellent agreement. Differences in the absolute dose measured with a plane-parallel chamber at a reference point were below 3% for all cases. MERT solution showed a better PTV coverage and a significant reduction of the doses to the organs at risk (OARs). Conclusion: MERT can effectively improve the current electron treatments by obtaining a better PTV coverage and sparing healthy tissues. More directly, block-shaped treatments could be replaced by MLC-shaped non-modulated segments providing similar results.

  3. Conformity of LINAC-Based Stereotactic Radiosurgery Using Dynamic Conformal Arcs and Micro-Multileaf Collimator

    International Nuclear Information System (INIS)

    Hazard, Lisa J.; Wang, Brian; Skidmore, Thomas B.; Chern, Shyh-Shi; Salter, Bill J.; Jensen, Randy L.; Shrieve, Dennis C.

    2009-01-01

    Purpose: To assess the conformity of dynamic conformal arc linear accelerator-based stereotactic radiosurgery and to describe a standardized method of isodose surface (IDS) selection. Methods and Materials: In 174 targets, the conformity index (CI) at the prescription IDS used for treatment was calculated as CI = (PIV/PVTV)/(PVTV/TV), where TV is the target volume, PIV (prescription isodose volume) is the total volume encompassed by the prescription IDS, and PVTV is the TV encompassed by the IDS. In addition, a 'standardized' prescription IDS (sIDS) was chosen according to the following criteria: 95% of the TV was encompassed by the PIV and 99% of TV was covered by 95% of the prescription dose. The CIs at the sIDS were also calculated. Results: The median CI at the prescription IDS and sIDS was 1.63 and 1.47, respectively (p < 0.001). In 132 of 174 cases, the volume of normal tissue in the PIV was reduced by the prescription to the sIDS compared with the prescription IDS, in 20 cases it remained unchanged, and in 22 cases it was increased. Conclusion: The CIs obtained with linear accelerator-based stereotactic radiosurgery are comparable to those previously reported for gamma knife stereotactic radiosurgery. Using a uniform method to select the sIDS, adequate target coverage was usually achievable with prescription to an IDS greater than that chosen by the treating physician (prescription IDS), providing sparing of normal tissue. Thus, the sIDS might aid physicians in identifying a prescription IDS that balances coverage and conformity

  4. Conformal radiotherapy using multileaf collimation: quality assurance and in vivo dosimetry

    International Nuclear Information System (INIS)

    Aletti, P.

    1995-01-01

    The application of quality assurance principles in three dimensional conformal therapy is discussed.Critical requirements in three dimensional radiotherapy are the patient immobilization, the location, and the delivered dose. General recommendations with respect to the equipment for conformal radiotherapy and personnel are made

  5. The LHC collimators

    CERN Document Server

    Bertarelli, A

    2004-01-01

    In the framework of the LHC Collimator project, TS department has been assigned the task to design the series collimators and to manufacture prototypes to be tested in summer 2004. Their concept must comply with a very demanding specification, entailing a temperature on the collimating jaws not exceeding 50ºC in steady conditions and an unparalleled overall geometrical stability of 25 micro m on a 1200 mm span, meeting, at the same time, the challenging deadlines required by the project schedule. To respond to these tough and sometimes conflicting constraints, the chosen design appeals to a mixture of traditional and innovative technologies, largely drawing from LEP collimator experience. The specification imposes a low-Z material for the collimator jaws, directing the design towards graphite or such novel materials as 2-D and 3-D Carbon/Carbon composites. An accurate mechanical design has allowed to considerably reduce the mechanical play and to optimize the geometrical stability. The mechanical lay-out a...

  6. Cleaning Insertions and Collimation Challenges

    Science.gov (United States)

    Redaelli, S.; Appleby, R. B.; Bertarelli, A.; Bruce, R.; Jowett, J. M.; Lechner, A.; Losito, R.

    High-performance collimation systems are essential for operating efficiently modern hadron machine with large beam intensities. In particular, at the LHC the collimation system ensures a clean disposal of beam halos in the superconducting environment. The challenges of the HL-LHC study pose various demanding requests for beam collimation. In this paper we review the present collimation system and its performance during the LHC Run 1 in 2010-2013. Various collimation solutions under study to address the HL-LHC requirements are then reviewed, identifying the main upgrade baseline and pointing out advanced collimation concept for further enhancement of the performance.

  7. 3-D dosimetric evaluation of 2.5 mm HD120 multileaf system for intensity modulated stereotactic radiosurgery using optical CT based polymer gel dosimetry

    International Nuclear Information System (INIS)

    Wuu, C-S; Kessel, Jack; Xu, Y

    2009-01-01

    A Trilogy TX equipped with a 2.5 mm HD120 multileaf collimator system is available for the treatment of radiosurgery and IMRT. In this study, we evaluated the 3-D dosimetric impact of leaf width on an IMRT radiosurgery plan by comparing the target coverage and the dose gradient around the target, produced from both a 2.5 mm HD120 high-definition MLC system and a 5mm-leaf-width millennium 120 MLC system, using an optical CT based polymer gel dosimetry system. The 2.5 mm MLC improves target conformity and surrounding tissue sparing when compared to that of 5 mm MLC.

  8. Collimation Cleaning at the LHC with Advanced Secondary Collimator Materials

    CERN Document Server

    AUTHOR|(CDS)2085459; Bruce, Roderik; Mereghetti, Alessio; Redaelli, Stefano; Rossi, A

    2015-01-01

    The LHC collimation system must ensure efficient beam halo cleaning in all machine conditions. The first run in 2010-2013 showed that the LHC performance may be limited by collimator material-related concerns, such as the contribution from the present carbon-based secondary collimators to the machine impedance and, consequently, to the beam instability. Novel materials based on composites are currently under development for the next generation of LHC collimators to address these limitations. Particle tracking simulations of collimation efficiency were performed using the Sixtrack code and a material database updated to model these composites. In this paper, the simulation results will be presented with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.

  9. Beam Cleaning and Collimation Systems

    CERN Document Server

    Redaelli, S

    2016-01-01

    Collimation systems in particle accelerators are designed to dispose of unavoidable losses safely and efficiently during beam operation. Different roles are required for different types of accelerator. The present state of the art in beam collimation is exemplified in high-intensity, high-energy superconducting hadron colliders, like the CERN Large Hadron Collider (LHC), where stored beam energies reach levels up to several orders of magnitude higher than the tiny energies required to quench cold magnets. Collimation systems are essential systems for the daily operation of these modern machines. In this document, the design of a multistage collimation system is reviewed, taking the LHC as an example case study. In this case, unprecedented cleaning performance has been achieved, together with a system complexity comparable to no other accelerator. Aspects related to collimator design and operational challenges of large collimation systems are also addressed.

  10. Choreographing Couch and Collimator in Volumetric Modulated Arc Therapy

    International Nuclear Information System (INIS)

    Yang Yingli; Zhang Pengpeng; Happersett, Laura; Xiong Jianping; Yang Jie; Chan, Maria; Beal, Kathryn; Mageras, Gig; Hunt, Margie

    2011-01-01

    Purpose: To design and optimize trajectory-based, noncoplanar subarcs for volumetric modulated arc therapy (VMAT) deliverable on both Varian TrueBEAM system and traditional accelerators; and to investigate their potential advantages for treating central nervous system (CNS) tumors. Methods and Materials: To guide the computerized selection of beam trajectories consisting of simultaneous couch, gantry, and collimator motion, a score function was implemented to estimate the geometric overlap between targets and organs at risk for each couch/gantry angle combination. An initial set of beam orientations is obtained as a function of couch and gantry angle, according to a minimum search of the score function excluding zones of collision. This set is grouped into multiple continuous and extended subarcs subject to mechanical limitations using a hierarchical clustering algorithm. After determination of couch/gantry trajectories, a principal component analysis finds the collimator angle at each beam orientation that minimizes residual target-organ at risk overlaps. An in-house VMAT optimization algorithm determines the optimal multileaf collimator position and monitor units for control points within each subarc. A retrospective study of 10 CNS patients compares the proposed method of VMAT trajectory with dynamic gantry, leaves, couch, and collimator motion (Tra-VMAT); a standard noncoplanar VMAT with no couch/collimator motion within subarcs (Std-VMAT); and noncoplanar intensity-modulated radiotherapy (IMRT) plans that were clinically used. Results: Tra-VMAT provided improved target dose conformality and lowered maximum dose to brainstem, optic nerves, and chiasm by 7.7%, 1.1%, 2.3%, and 1.7%, respectively, compared with Std-VMAT. Tra-VMAT provided higher planning target volume minimum dose and reduced maximum dose to chiasm, optic nerves, and cochlea by 6.2%, 1.3%, 6.3%, and 8.4%, respectively, and reduced cochlea mean dose by 8.7%, compared with IMRT. Tra-VMAT averaged

  11. Collimator changer for scintillation camera

    International Nuclear Information System (INIS)

    Jupa, E.C.; Meeder, R.L.; Richter, E.K.

    1976-01-01

    A collimator changing assembly mounted on the support structure of a scintillation camera is described. A vertical support column positioned proximate the detector support column with a plurality of support arms mounted thereon in a rotatable cantilevered manner at separate vertical positions. Each support arm is adapted to carry one of the plurality of collimators which are interchangeably mountable on the underside of the detector and to transport the collimator between a store position remote from the detector and a change position underneath said detector

  12. Collimation: a silicon solution

    CERN Multimedia

    2007-01-01

    Silicon crystals could be used very efficiently to deflect high-energy beams. Testing at CERN has produced conclusive results, which could pave the way for a new generation of collimators. The set of five crystals used to test the reflection of the beams. The crystals are 0.75 mm wide and their alignment is adjusted with extreme precision. This figure shows the deflection of a beam by channelling and by reflection in the block of five crystals. Depending on the orientation of the crystals: 1) The beam passes without "seeing" the crystals and is not deflected 2) The beam is deflected by channelling (with an angle of around 100 μrad) 3) The beam is reflected (with an angle of around 50 μrad). The intensity of the deflected beam is illustrated by the intensity of the spot. The spot of the reflected beam is clearly more intense than that one of the channelled beam, demonstrating the efficiency of t...

  13. Wakefields in SLAC linac collimators

    Directory of Open Access Journals (Sweden)

    A. Novokhatski

    2014-12-01

    Full Text Available When a beam travels near collimator jaws, it gets an energy loss and a transverse kick due to the backreaction of the beam field diffracted from the jaws. The effect becomes very important for an intense short bunch when a tight collimation of the background beam halo is required. In the Linac Coherent Light Source at SLAC a collimation system is used to protect the undulators from radiation due to particles in the beam halo. The halo is most likely formed from gun dark current or dark current in some of the accelerating sections. However, collimators are also responsible for the generation of wake fields. The wake field effect from the collimators not only brings an additional energy jitter and change in the trajectory of the beam, but it also rotates the beam on the phase plane, which consequently leads to a degradation of the performance of the Free Electron Laser at the Linac Coherent Light Source. In this paper, we describe a model of the wake field radiation in the SLAC linac collimators. We use the results of a numerical simulation to illustrate the model. Based on the model, we derive simple formulas for the bunch energy loss and the average kick. We also present results from experimental measurements that confirm our model.

  14. Dosimetric comparison using different multileaf collimeters in intensity-modulated radiotherapy for upper thoracic esophageal cancer

    Directory of Open Access Journals (Sweden)

    Fu Yuchuan

    2010-07-01

    Full Text Available Abstract Purpose To study the impacts of multileaf collimators (MLC width [standard MLC width of 10 mm (sMLC and micro-MLC width of 4 mm (mMLC] in the intensity-modulated radiotherapy (IMRT planning for the upper thoracic esophageal cancer (UTEC. Methods and materials 10 patients with UTEC were retrospectively planned with the sMLC and the mMLC. The monitor unites (MUs and dose volume histogram-based parameters [conformity index (CI and homogeneous index (HI] were compared between the IMRT plans with sMLC and with mMLC. Results The IMRT plans with the mMLC were more efficient (average MUs: 703.1 ± 68.3 than plans with the sMLC (average MUs: 833.4 ± 73.8 (p p 5 (3260.3 ± 374.0 vs 3404.5 ± 374.4/gEUD (1815.1 ± 281.7 vs 1849.2 ± 297.6 of the spinal cord, the V10 (33.2 ± 6.5 vs 34.0 ± 6.7, V20 (16.0 ± 4.6 vs 16.6 ± 4.7, MLD (866.2 ± 174.1 vs 887.9 ± 172.1 and gEUD (938.6 ± 175.2 vs 956.8 ± 171.0 of the lungs were observed in the plans with the mMLC, respectively (p Conclusions Comparing to the sMLC, the mMLC not only demonstrated higher efficiencies and more optimal target coverage, but also considerably improved the dose sparing of OARs in the IMRT planning for UTEC.

  15. SU-E-T-11: A Dosimetric Comparison of Robotic Prostatic Radiosugery Using Multi- Leaf Collimation Vs Circular Collimators

    Energy Technology Data Exchange (ETDEWEB)

    Feng, J; Yang, J; Lamond, J; Lavere, N; Laciano, R; Ding, W; Arrigo, S; Brady, L [Philadelphia Cyberknife, Philadelphia, PA (United States)

    2014-06-01

    Purpose: The study compared the dosimetry plans of Stereotatic Body Radiotherapy (SBRT) prostate cancer patients using the M6 Cyberknife with Multi-leaf Collimation (MLC) compared with the plans using G4 Cyberknife with circular collimators. Methods: Eight previously treated prostate cancer patients' SBRT plans using circular collimators, designed with Multiplan v3.5.3, were used as a benchmark. The CT, contours and the optimization scripts were imported into Multiplan v5.0 system and replanned with MLC. The same planning objectives were used: more than 95% of PTV received 36.25Gy, 90% of prostate received 40Gy and maximum dose <45Gy, in five fractions. For organs at risk, less than 1cc of rectum received 36Gy and less than 10cc of bladder received 37Gy. Plans were evaluated on parameters derived from dose volume. The beam number, MU and delivery time were recorded to compare the treatment efficiency. Results: The mean CTV volume was 41.3cc (27.5∼57.6cc) and mean PTV volume was 76.77cc (59.1∼99.7cc). The mean PTV coverage was comparable between MLC (98.87%) and cone (98.74%). MLC plans had a slightly more favorable homogeneity index (1.22) and conformity index (1.17), than the cone (1.24 and 1.15). The mean rectum volume of 36 Gy (0.52cc) of MLC plans was slightly larger than cone (0.38cc) and the mean bladder volume of 37 Gy was smaller in MLC (1.82cc) than in cone plans (3.09cc). The mean number of nodes and beams were 65.9 and 80.5 in MLC vs 65.9 and 203.6 in cone. The mean MUs were significantly less for MLC plans (24,228MUs) than cone (32,347MUs). The total delivery time (which included 5 minutes for setup) was less, 29.6min (26∼32min) for MLC vs 45min (35∼55min) for cone. Conclusion: While the differences in the dosimetry between the MLC and circular collimator plans were rather minor, the MLC plans were much more efficient and required significantly less treatment time.

  16. Fermilab Recycler Collimation System Design

    Energy Technology Data Exchange (ETDEWEB)

    Brown, B. C. [Fermilab; Adamson, P. [Fermilab; Ainsworth, R. [Fermilab; Capista, D. [Fermilab; Hazelwood, K. [Fermilab; Kourbanis, I. [Fermilab; Mokhov, N. V. [Fermilab; Morris, D. K. [Fermilab; Murphy, M. [Fermilab; Sidorov, V. [Fermilab; Stern, E. [Fermilab; Tropin, I. [Fermilab; Yang, M-J. [Fermilab

    2016-10-04

    To provide 700 kW proton beams for neutrino production in the NuMI facility, we employ slip stacking in the Recycler with transfer to the Main Injector for recapture and acceleration. Slip stacking with 12 Booster batches per 1.33 sec cycle of the Main Injector has been implemented and briefly tested while extensive operation with 8 batches and 10 batches per MI cycle has been demonstrated. Operation in this mode since 2013 shows that loss localization is an essential component for long term operation. Beam loss in the Recycler will be localized in a collimation region with design capability for absorbing up to 2 kW of lost protons in a pair of 20-Ton collimators (absorbers). This system will employ a two stage collimation with a thin molybdenum scattering foil to define the bottom edge of both the injected and decelerated-for-slipping beams. Optimization and engineering design of the collimator components and radiation shielding are based on comprehensive MARS15 simulations predicting high collimation efficiency as well as tolerable levels of prompt and residual radiation. The system installation during the Fermilab 2016 facility shutdown will permit commissioning in the subsequent operating period.

  17. Requirements for the LHC collimation system

    CERN Document Server

    Assmann, R W; Brugger, M; Bruno, L; Burkhardt, H; Burtin, G; Dehning, Bernd; Fischer, C; Goddard, B; Gschwendtner, E; Hayes, M; Jeanneret, J B; Jung, R; Kain, V; Kaltchev, D I; Lamont, M; Schmidt, R; Vossenberg, Eugène B; Weisse, E; Wenninger, J

    2002-01-01

    The LHC requires efficient collimation during all phases of the beam cycle. Collimation plays important roles in prevention of magnet quenches from regular beam diffusion, detection of abnormal beam loss and subsequent beam abort, radiation protection, and passive protection of the superconducting magnets in case of failures. The different roles of collimation and the high beam power in the LHC impose many challenges for the design of the collimation system. In particular, the collimators must be able to withstand the expected particle losses. The requirements for the LHC collimation system are presented.

  18. Automatic Angular alignment of LHC Collimators

    CERN Document Server

    Azzopardi, Gabriella; Salvachua Ferrando, Belen Maria; Mereghetti, Alessio; Bruce, Roderik; Redaelli, Stefano; CERN. Geneva. ATS Department

    2017-01-01

    The LHC is equipped with a complex collimation system to protect sensitive equipment from unavoidable beam losses. Collimators are positioned close to the beam using an alignment procedure. Until now they have always been aligned assuming no tilt between the collimator and the beam, however, tank misalignments or beam envelope angles at large-divergence locations could introduce a tilt limiting the collimation performance. Three different algorithms were implemented to automatically align a chosen collimator at various angles. The implementation was tested on a number of collimators during this MD and no human intervention was required.

  19. Movable collimator for positron annihilation imaging device

    International Nuclear Information System (INIS)

    Thompson, C.J.

    1981-01-01

    A positron annihilation imaging device having two circular arrays of detectors disposed in spaced apart parallel planes wherein axially movable annular collimator rings are generally disposed in a pair of opposite planes outside the associated planes of the collimators to each collimator being movable toward the opposite collimator and a central collimator of annular configuration generally disposed between the two rows of detectors but being split into two rings which may be separated, the outer and inner collimators serving to enhance data readout and imaging

  20. The six-bank multi-leaf system : A large field size, high resolution collimator for advanced

    NARCIS (Netherlands)

    Topolnjak, R.

    2006-01-01

    A linear accelerator (linac) is the most commonly used device for treatment of patients with cancer in external beam radiotherapy (EBRT). The Linac delivers a high-energy ionizing radiation (photons or electrons) to the region of the patient's tumor. The absorption of radiation in the treated area

  1. Multileaf Collimator Tracking Improves Dose Delivery for Prostate Cancer Radiation Therapy: Results of the First Clinical Trial

    DEFF Research Database (Denmark)

    Colvill, Emma; Booth, Jeremy T; O'Brien, Ricky T

    2015-01-01

    was tested for each dose-volume value via analysis of variance using the F test. RESULTS: Of the 513 fractions delivered, 475 (93%) were suitable for analysis. The mean difference and standard deviation between the planned and treated MLC tracking doses and the planned and without-MLC tracking doses for all...... 475 fractions were, respectively, PTV D99% -0.8% ± 1.1% versus -2.1% ± 2.7%; CTV D99% -0.6% ± 0.8% versus -0.6% ± 1.1%; rectum V65% 1.6% ± 7.9% versus -1.2% ± 18%; and bladder V65% 0.5% ± 4.4% versus -0.0% ± 9.2% (P

  2. Field factors for asymmetric collimators

    International Nuclear Information System (INIS)

    Turner, J.R.; Butler, A.P.H.

    1996-01-01

    In recent years manufacturers have been supplying linear accelerators with either a single pair or a dual pair of collimators. The use of a model to relate off-axis field factors to on-axis field factors obviates the need for repeat measurements whenever the asymmetric collimators are employed. We have investigated the variation of collimator scatter Sc, with distance of the central ray x from the central axis for a variety of non square field sizes. Collimator scatter was measured by in-air measurements with a build-up cap. The Primaty-Off-Centre-Ratio (POCR) was measured in-air by scanning orthogonally across the beam with an ionization chamber. The result of the investigation is the useful prediction of off-axis field factors for a range of rectangular asymmetric fields using the simple product of the on-axis field factor and the POCR in air. The effect of asymmetry on the quality of the beam and hence the percent depth dose will be discussed. (author)

  3. Radiation leakage dose from Elekta electron collimation system.

    Science.gov (United States)

    Pitcher, Garrett M; Hogstrom, Kenneth R; Carver, Robert L

    2016-09-08

    This study provided baseline data required for a greater project, whose objective was to design a new Elekta electron collimation system having significantly lighter electron applicators with equally low out-of field leakage dose. Specifically, off-axis dose profiles for the electron collimation system of our uniquely configured Elekta Infinity accelerator with the MLCi2 treatment head were measured and calculated for two primary purposes: 1) to evaluate and document the out-of-field leakage dose in the patient plane and 2) to validate the dose distributions calculated using a BEAMnrc Monte Carlo (MC) model for out-of-field dose profiles. Off-axis dose profiles were measured in a water phantom at 100 cm SSD for 1 and 2 cm depths along the in-plane, cross-plane, and both diagonal axes using a cylindrical ionization chamber with the 10 × 10 and 20 × 20 cm2 applicators and 7, 13, and 20 MeV beams. Dose distributions were calculated using a previously developed BEAMnrc MC model of the Elekta Infinity accelerator for the same beam energies and applicator sizes and compared with measurements. Measured results showed that the in-field beam flatness met our acceptance criteria (± 3% on major and ±4% on diagonal axes) and that out-of-field mean and maximum percent leakage doses in the patient plane met acceptance criteria as specified by the International Electrotechnical Commission (IEC). Cross-plane out-of-field dose profiles showed greater leakage dose than in-plane profiles, attributed to the curved edges of the upper X-ray jaws and multileaf collimator. Mean leakage doses increased with beam energy, being 0.93% and 0.85% of maximum central axis dose for the 10 × 10 and 20 × 20 cm2 applicators, respectively, at 20 MeV. MC calculations predicted the measured dose to within 0.1% in most profiles outside the radiation field; however, excluding model-ing of nontrimmer applicator components led to calculations exceeding measured data by as much as 0.2% for some regions

  4. Crystal collimator systems for high energy frontier

    CERN Document Server

    AUTHOR|(CDS)2100516; Tikhomirov, Viktor; Lobko, Alexander

    2017-01-01

    Crystalline collimators can potentially considerably improve the cleaning performance of the presently used collimator systems using amorphous collimators. A crystal-based collimation scheme which relies on the channeling particle deflection in bent crystals has been proposed and extensively studied both theoretically and experimentally. However, since the efficiency of particle capture into the channeling regime does not exceed ninety percent, this collimation scheme partly suffers from the same leakage problems as the schemes using amorphous collimators. To improve further the cleaning efficiency of the crystal-based collimation system to meet the requirements of the FCC, we suggest here a double crystal-based collimation scheme, to which the second crystal is introduced to enhance the deflection of the particles escaping the capture to the channeling regime in its first crystal. The application of the effect of multiple volume reflection in one bent crystal and of the same in a sequence of crystals is simu...

  5. Effect of MLC leaf position, collimator rotation angle, and gantry rotation angle errors on intensity-modulated radiotherapy plans for nasopharyngeal carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Sen; Li, Guangjun; Wang, Maojie; Jiang, Qinfeng; Zhang, Yingjie [State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan (China); Wei, Yuquan, E-mail: yuquawei@vip.sina.com [State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan (China)

    2013-07-01

    The purpose of this study was to investigate the effect of multileaf collimator (MLC) leaf position, collimator rotation angle, and accelerator gantry rotation angle errors on intensity-modulated radiotherapy plans for nasopharyngeal carcinoma. To compare dosimetric differences between the simulating plans and the clinical plans with evaluation parameters, 6 patients with nasopharyngeal carcinoma were selected for simulation of systematic and random MLC leaf position errors, collimator rotation angle errors, and accelerator gantry rotation angle errors. There was a high sensitivity to dose distribution for systematic MLC leaf position errors in response to field size. When the systematic MLC position errors were 0.5, 1, and 2 mm, respectively, the maximum values of the mean dose deviation, observed in parotid glands, were 4.63%, 8.69%, and 18.32%, respectively. The dosimetric effect was comparatively small for systematic MLC shift errors. For random MLC errors up to 2 mm and collimator and gantry rotation angle errors up to 0.5°, the dosimetric effect was negligible. We suggest that quality control be regularly conducted for MLC leaves, so as to ensure that systematic MLC leaf position errors are within 0.5 mm. Because the dosimetric effect of 0.5° collimator and gantry rotation angle errors is negligible, it can be concluded that setting a proper threshold for allowed errors of collimator and gantry rotation angle may increase treatment efficacy and reduce treatment time.

  6. Development of tungsten collimators for industrial radiography

    International Nuclear Information System (INIS)

    Varkey, P.A.; Verma, P.B.; Jayakumar, T.K.; Mammachan, M.K.

    2001-01-01

    Collimators are essential components of industrial radiography set up as it provides radiation safety to persons involved in the radiography work. A collimator with optimum design features also helps in reducing the scattered radiation which in turn results in radiographs having better sensitivity. This papers describes the salient design features of the tungsten collimators developed by the BRIT, for industrial radiography. (author)

  7. Optimizing Collimator Margins for Isotoxically Dose-Escalated Conformal Radiation Therapy of Non-Small Cell Lung Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Samantha, E-mail: Samantha.warren@oncology.ox.ac.uk [Department of Oncology, Gray Institute of Radiation Oncology and Biology, University of Oxford, Oxford (United Kingdom); Oxford Cancer Centre, Oxford University Hospitals, Oxford (United Kingdom); Panettieri, Vanessa [William Buckland Radiotherapy Centre, Alfred Hospital, Commercial Road, Melbourne (Australia); Panakis, Niki; Bates, Nicholas [Oxford Cancer Centre, Oxford University Hospitals, Oxford (United Kingdom); Lester, Jason F. [Velindre Cancer Centre, Velindre Road, Whitchurch, Cardiff (United Kingdom); Jain, Pooja [Clatterbridge Cancer Centre, Clatterbridge Road, Wirral (United Kingdom); Landau, David B. [Department of Radiotherapy, Guy' s and St. Thomas' NHS Foundation Trust, London (United Kingdom); Nahum, Alan E.; Mayles, W. Philip M. [Clatterbridge Cancer Centre, Clatterbridge Road, Wirral (United Kingdom); Fenwick, John D. [Department of Oncology, Gray Institute of Radiation Oncology and Biology, University of Oxford, Oxford (United Kingdom); Oxford Cancer Centre, Oxford University Hospitals, Oxford (United Kingdom)

    2014-04-01

    Purpose: Isotoxic dose escalation schedules such as IDEAL-CRT [isotoxic dose escalation and acceleration in lung cancer chemoradiation therapy] (ISRCTN12155469) individualize doses prescribed to lung tumors, generating a fixed modeled risk of radiation pneumonitis. Because the beam penumbra is broadened in lung, the choice of collimator margin is an important element of the optimization of isotoxic conformal radiation therapy for lung cancer. Methods and Materials: Twelve patients with stage I-III non-small cell lung cancer (NSCLC) were replanned retrospectively using a range of collimator margins. For each plan, the prescribed dose was calculated according to the IDEAL-CRT isotoxic prescription method, and the absolute dose (D{sub 99}) delivered to 99% of the planning target volume (PTV) was determined. Results: Reducing the multileaf collimator margin from the widely used 7 mm to a value of 2 mm produced gains of 2.1 to 15.6 Gy in absolute PTV D{sub 99}, with a mean gain ± 1 standard error of the mean of 6.2 ± 1.1 Gy (2-sided P<.001). Conclusions: For NSCLC patients treated with conformal radiation therapy and an isotoxic dose prescription, absolute doses in the PTV may be increased by using smaller collimator margins, reductions in relative coverage being offset by increases in prescribed dose.

  8. Positron annihilation imaging device having movable collimator

    International Nuclear Information System (INIS)

    Thompson, C.J.

    1981-01-01

    This patent application relates to a positron annihilation imaging device comprising two circular arrays of detectors disposed in spaced apart parallel planes and circumferentially offset by half the detector spacing, axially movable annular outer collimator rings, generally disposed in a pair of opposite planes outside the associated planes of the detectors, each collimator being movable toward the opposite collimator. An inner collimator of annular configuration is disposed between the two rows of detectors and is formed in two rings which may be separated axially. The outer and inner collimators serve to enhance data readout and imaging. (author)

  9. The design and construction of modulation collimators

    International Nuclear Information System (INIS)

    Oda, M.; Muranaka, N.; Matsuoka, M.; Miyamoto, S.; Ogawara, Y.

    1976-01-01

    The technique of the modulation collimator is reviewed as a device to provide seemingly conflicting properties: high angular resolution, wide aperture and large brightness. The method of synthesizing a two-dimensional image of a source from several one-dimensional scans is discussed. Several methods of achieving angular resolution higher than the FWHM of the transmission window of the collimator are presented. The source structure may be reconstructed by means of one or more bigrid modulation collimators. Design problems of modulation collimators are discussed in relation to the collimator constructed for a balloon experiment under the collaboration of the UCSD group and the Tokyo group. (Auth.)

  10. Digital chest radiography: collimation and dose reduction

    DEFF Research Database (Denmark)

    Debess, Jeanne; Johnsen, Karen Kirstine; Vejle-Sørensen, Jens Kristian

    ,3 mAs and SID SID of 180 centimetres using a phantom and lithium fluoride thermo luminescence dosimeter (TLD). Dose to risk organs mamma, thyroid and colon are measured at different collimations with one-centimetre steps. TLD results are used to estimate dose reduction for different collimations...... at the conference. Conclusion: Collimation improvement in basic chest radiography can reduce the radiation to female patients at chest x-ray examinations....

  11. Collimator trans-axial tomographic scintillation camera

    International Nuclear Information System (INIS)

    Jaszczak, R.J.

    1977-01-01

    A collimator is provided for a scintillation camera system in which a detector precesses in an orbit about a patient. The collimator is designed to have high resolution and lower sensitivity with respect to radiation traveling in paths laying wholly within planes perpendicular to the cranial-caudal axis of the patient. The collimator has high sensitivity and lower resolution to radiation traveling in other planes. Variances in resolution and sensitivity are achieved by altering the length, spacing or thickness of the septa of the collimator

  12. Computer technique for evaluating collimator performance

    International Nuclear Information System (INIS)

    Rollo, F.D.

    1975-01-01

    A computer program has been developed to theoretically evaluate the overall performance of collimators used with radioisotope scanners and γ cameras. The first step of the program involves the determination of the line spread function (LSF) and geometrical efficiency from the fundamental parameters of the collimator being evaluated. The working equations can be applied to any plane of interest. The resulting LSF is applied to subroutine computer programs which compute corresponding modulation transfer function and contrast efficiency functions. The latter function is then combined with appropriate geometrical efficiency data to determine the performance index function. The overall computer program allows one to predict from the physical parameters of the collimator alone how well the collimator will reproduce various sized spherical voids of activity in the image plane. The collimator performance program can be used to compare the performance of various collimator types, to study the effects of source depth on collimator performance, and to assist in the design of collimators. The theory of the collimator performance equation is discussed, a comparison between the experimental and theoretical LSF values is made, and examples of the application of the technique are presented

  13. WE-AB-BRB-10: Filmless QA of CyberKnife MLC-Collimated and Iris-Collimated Fields

    International Nuclear Information System (INIS)

    Gersh, J

    2015-01-01

    Purpose: Current methods of CK field shape QA is based on the use of radiochromic film. Though accurate results can be attained, these methods are prone to error, time consuming, and expensive. The techniques described herein perform similar QA using the FOIL Detector (Field, Output, and Image Localization). A key feature of this in-house QA solution, and central to this study, is an aSi flat-panel detector which provides the user with the means to perform accurate, immediate, and quantitative field analysis. Methods: The FOIL detector is automatically aligned in the CK beam using fiducial markers implanted within the detector case. Once the system is aligned, a treatment plan is delivered which irradiates the flat-panel imager using the field being tested. The current study tests each of the clinically-used fields shaped using the Iris variable-aperture collimation system using a plan which takes 6 minutes to deliver. The user is immediately provided with field diameter and beam profile, as well as a comparison to baseline values. Additionally, the detector is used to acquire and analyze leaf positions of the InCise multi-leaf collimation system. Results: Using a 6-minute plan consisting of 11 beams of 25MU-per-beam, the FOIL detector provided the user with a quantitative analysis of all clinically-used field shapes. The FOIL detector was also able to clearly resolve field edge junctions in a picket fence test, including slight over-travel of individual leaves as well as inter-leaf leakage. Conclusion: The FOIL system provided comparable field diameter and profile data when compared to methods using film; providing results much faster and with 5% of the MU used for film. When used with the MLC system, the FOIL detector provided the means for immediate quantification of the performance of the system through analysis of leaf positions in a picket fence test field. Author is the President/Owner of Spectrum Medical Physics, LLC, a company which maintains contracts

  14. WE-AB-BRB-10: Filmless QA of CyberKnife MLC-Collimated and Iris-Collimated Fields

    Energy Technology Data Exchange (ETDEWEB)

    Gersh, J [Gibbs Cancer Center and Research Institute - Pelham, Greer, SC (United States); Spectrum Medical Physics, LLC, Greenville, SC (United States)

    2015-06-15

    Purpose: Current methods of CK field shape QA is based on the use of radiochromic film. Though accurate results can be attained, these methods are prone to error, time consuming, and expensive. The techniques described herein perform similar QA using the FOIL Detector (Field, Output, and Image Localization). A key feature of this in-house QA solution, and central to this study, is an aSi flat-panel detector which provides the user with the means to perform accurate, immediate, and quantitative field analysis. Methods: The FOIL detector is automatically aligned in the CK beam using fiducial markers implanted within the detector case. Once the system is aligned, a treatment plan is delivered which irradiates the flat-panel imager using the field being tested. The current study tests each of the clinically-used fields shaped using the Iris variable-aperture collimation system using a plan which takes 6 minutes to deliver. The user is immediately provided with field diameter and beam profile, as well as a comparison to baseline values. Additionally, the detector is used to acquire and analyze leaf positions of the InCise multi-leaf collimation system. Results: Using a 6-minute plan consisting of 11 beams of 25MU-per-beam, the FOIL detector provided the user with a quantitative analysis of all clinically-used field shapes. The FOIL detector was also able to clearly resolve field edge junctions in a picket fence test, including slight over-travel of individual leaves as well as inter-leaf leakage. Conclusion: The FOIL system provided comparable field diameter and profile data when compared to methods using film; providing results much faster and with 5% of the MU used for film. When used with the MLC system, the FOIL detector provided the means for immediate quantification of the performance of the system through analysis of leaf positions in a picket fence test field. Author is the President/Owner of Spectrum Medical Physics, LLC, a company which maintains contracts

  15. Some new insights into collimator design

    International Nuclear Information System (INIS)

    Metz, C.E.; Atkins, F.B.; Tsui, B.M.W.; Beck, R.N.

    1978-01-01

    Relationships among collimator design parameters, physical properties of the resulting images, and human observer performance are discussed. The insight provided by these relationships hopefully will prove useful to the individual who must design or select a collimator for a particular imaging task

  16. Construction and Bench Testing of a Rotatable Collimator for the LHC Collimation Upgrade

    International Nuclear Information System (INIS)

    Smith, Jeffrey

    2010-01-01

    The Phase II upgrade to the LHC collimation system calls for complementing the 30 high robust Phase I graphite secondary collimators with 30 high Z Phase II collimators. The Phase II collimators must be robust in various operating conditions and accident scenarios. This paper reports on the final construction and testing of the prototype collimator to be installed in the SPS (Super Proton Synchrotron) at CERN. Bench-top measurements will demonstrate that the device is fully operational and has the mechanical and vacuum characteristics acceptable for installation in the SPS.

  17. Photon caliper to achieve submillimeter positioning accuracy

    Science.gov (United States)

    Gallagher, Kyle J.; Wong, Jennifer; Zhang, Junan

    2017-09-01

    The purpose of this study was to demonstrate the feasibility of using a commercial two-dimensional (2D) detector array with an inherent detector spacing of 5 mm to achieve submillimeter accuracy in localizing the radiation isocenter. This was accomplished by delivering the Vernier ‘dose’ caliper to a 2D detector array where the nominal scale was the 2D detector array and the non-nominal Vernier scale was the radiation dose strips produced by the high-definition (HD) multileaf collimators (MLCs) of the linear accelerator. Because the HD MLC sequence was similar to the picket fence test, we called this procedure the Vernier picket fence (VPF) test. We confirmed the accuracy of the VPF test by offsetting the HD MLC bank by known increments and comparing the known offset with the VPF test result. The VPF test was able to determine the known offset within 0.02 mm. We also cross-validated the accuracy of the VPF test in an evaluation of couch hysteresis. This was done by using both the VPF test and the ExacTrac optical tracking system to evaluate the couch position. We showed that the VPF test was in agreement with the ExacTrac optical tracking system within a root-mean-square value of 0.07 mm for both the lateral and longitudinal directions. In conclusion, we demonstrated the VPF test can determine the offset between a 2D detector array and the radiation isocenter with submillimeter accuracy. Until now, no method to locate the radiation isocenter using a 2D detector array has been able to achieve such accuracy.

  18. Electron beam collimation with a photon MLC for standard electron treatments

    Science.gov (United States)

    Mueller, S.; Fix, M. K.; Henzen, D.; Frei, D.; Frauchiger, D.; Loessl, K.; Stampanoni, M. F. M.; Manser, P.

    2018-01-01

    Standard electron treatments are currently still performed using standard or molded patient-specific cut-outs placed in the electron applicator. Replacing cut-outs and electron applicators with a photon multileaf collimator (pMLC) for electron beam collimation would make standard electron treatments more efficient and would facilitate advanced treatment techniques like modulated electron radiotherapy (MERT) and mixed beam radiotherapy (MBRT). In this work, a multiple source Monte Carlo beam model for pMLC shaped electron beams commissioned at a source-to-surface distance (SSD) of 70 cm is extended for SSDs of up to 100 cm and validated for several Varian treatment units with field sizes typically used for standard electron treatments. Measurements and dose calculations agree generally within 3% of the maximal dose or 2 mm distance to agreement. To evaluate the dosimetric consequences of using pMLC collimated electron beams for standard electron treatments, pMLC-based and cut-out-based treatment plans are created for a left and a right breast boost, a sternum, a testis and a parotid gland case. The treatment plans consist of a single electron field, either alone (1E) or in combination with two 3D conformal tangential photon fields (1E2X). For each case, a pMLC plan with similar treatment plan quality in terms of dose homogeneity to the target and absolute mean dose values to the organs at risk (OARs) compared to a cut-out plan is found. The absolute mean dose to an OAR is slightly increased for pMLC-based compared to cut-out-based 1E plans if the OAR is located laterally close to the target with respect to beam direction, or if a 6 MeV electron beam is used at an extended SSD. In conclusion, treatment plans using cut-out collimation can be replaced by plans of similar treatment plan quality using pMLC collimation with accurately calculated dose distributions.

  19. A study of RHIC crystal collimation

    International Nuclear Information System (INIS)

    Trbojevic, D.; Harrison, M.; Parker, B.; Thompson, P.; Stevens, A.; Biryukov, V.; Mokhov, N.; Drozhdin, A.

    1998-01-01

    The Relativistic Heavy Ion Collider (RHIC) will experience increasing longitudinal and transverse heavy ion emittances, mostly due to intra-beam scattering (IBS). The experiments in RHIC are expected to not only have reduced luminosities due to IBS but also background caused by beam halo. Primary betatron collimators will be used to remove the large amplitude particles. The efficiency of the primary collimator in RHIC strongly depends on the alignment of the jaws which needs to be within about ten micro-radians for the optimum conditions. As proposed by V. biryukov bent crystals could be used to improve the efficiency of an existing collimation system by installing them upstream of the collimator jaws. Bent crystals have been successfully used in SPS, Protvino and Fermilab for extraction of the beam particles channeled through them. This study examines possible improvements of the primary collimator system for heavy ions at RHIC by use of bent crystals. Bent crystals will reduce the collimator jaws alignment requirement and will increase collimator efficiency thereby reducing detector background

  20. Spike Pattern Recognition for Automatic Collimation Alignment

    CERN Document Server

    Azzopardi, Gabriella; Salvachua Ferrando, Belen Maria; Mereghetti, Alessio; Redaelli, Stefano; CERN. Geneva. ATS Department

    2017-01-01

    The LHC makes use of a collimation system to protect its sensitive equipment by intercepting potentially dangerous beam halo particles. The appropriate collimator settings to protect the machine against beam losses relies on a very precise alignment of all the collimators with respect to the beam. The beam center at each collimator is then found by touching the beam halo using an alignment procedure. Until now, in order to determine whether a collimator is aligned with the beam or not, a user is required to follow the collimator’s BLM loss data and detect spikes. A machine learning (ML) model was trained in order to automatically recognize spikes when a collimator is aligned. The model was loosely integrated with the alignment implementation to determine the classification performance and reliability, without effecting the alignment process itself. The model was tested on a number of collimators during this MD and the machine learning was able to output the classifications in real-time.

  1. Collimator for the SPS extracted beam

    CERN Multimedia

    CERN PhotoLab

    1976-01-01

    This is a water cooled copper collimator (TCSA) which has exactly the shape of the cross section of the downstream magnetic beam splitter. Parts of the blown up primary proton beam pass above/below and left through this collimator. A small part of the protons is absorbed in the thin copper wedges. In this way the downstream magnetic splitter of the same cross section receives already a beam where its magnetic wedges are no longer hit by protons. The upstream, water cooled collimator, more resistant to protons, has cast a 'shadow' onto the downstream magnetic splitter, less resistant to protons. Gualtero Del Torre stands on the left.

  2. Freeform lens design for LED collimating illumination.

    Science.gov (United States)

    Chen, Jin-Jia; Wang, Te-Yuan; Huang, Kuang-Lung; Liu, Te-Shu; Tsai, Ming-Da; Lin, Chin-Tang

    2012-05-07

    We present a simple freeform lens design method for an application to LED collimating illumination. The method is derived from a basic geometric-optics analysis and construction approach. By using this method, a highly collimating lens with LED chip size of 1.0 mm × 1.0 mm and optical simulation efficiency of 86.5% under a view angle of ± 5 deg is constructed. To verify the practical performance of the lens, a prototype of the collimator lens is also made, and an optical efficiency of 90.3% with a beam angle of 4.75 deg is measured.

  3. The Mechanical Design for the LHC Collimators

    CERN Document Server

    Bertarelli, A; Assmann, R W; Chiaveri, Enrico; Kurtyka, T; Mayer, M; Perret, R; Sievers, P

    2004-01-01

    The design of the LHC collimators must comply with the very demanding specifications entailed by the highly energetic beam handled in the LHC: these requirements impose a temperature on the collimating jaws not exceeding 50ºC in steady operations and an unparalleled overall geometrical stability of 25 micro-m on a 1200 mm span. At the same time, the design phase must meet the challenging deadlines required by the general time schedule. To respond to these tough and sometimes conflicting constraints, the chosen design appeals to a mixture of traditional and innovative technologies, largely drawing from LEP collimator experience. The specifications impose a low-Z material for the collimator jaws, directing the design towards such graphite or such novel materials as 3-d Carbon/carbon composites. An accurate mechanical design has allowed to considerably reduce mechanical play and optimize geometrical stability. Finally, all mechanical studies were supported by in-depth thermo-mechanical analysis concerning tempe...

  4. Loss Control and Collimation for the LHC

    Science.gov (United States)

    Burkhardt, H.

    2005-06-01

    The total energy stored in the LHC is expected to reach 360 Mega Joule, which is about two orders of magnitude higher than in HERA or the Tevatron. Damage and quench protection in the LHC require a highly efficient and at the same time very robust collimation system. The currently planned system, the status of the project and the expected performance of the collimation system from injection up to operation with colliding beams will be presented.

  5. Loss Control and Collimation for the LHC

    International Nuclear Information System (INIS)

    Burkhardt, H.

    2005-01-01

    The total energy stored in the LHC is expected to reach 360 Mega Joule, which is about two orders of magnitude higher than in HERA or the Tevatron. Damage and quench protection in the LHC require a highly efficient and at the same time very robust collimation system. The currently planned system, the status of the project and the expected performance of the collimation system from injection up to operation with colliding beams will be presented

  6. Crystal collimator systems for high energy frontier

    Science.gov (United States)

    Sytov, A. I.; Tikhomirov, V. V.; Lobko, A. S.

    2017-07-01

    Crystalline collimators can potentially considerably improve the cleaning performance of the presently used collimator systems using amorphous collimators. A crystal-based collimation scheme which relies on the channeling particle deflection in bent crystals has been proposed and extensively studied both theoretically and experimentally. However, since the efficiency of particle capture into the channeling regime does not exceed ninety percent, this collimation scheme partly suffers from the same leakage problems as the schemes using amorphous collimators. To improve further the cleaning efficiency of the crystal-based collimation system to meet the requirements of the FCC, we suggest here a double crystal-based collimation scheme, to which the second crystal is introduced to enhance the deflection of the particles escaping the capture to the channeling regime in its first crystal. The application of the effect of multiple volume reflection in one bent crystal and of the same in a sequence of crystals is simulated and compared for different crystal numbers and materials at the energy of 50 TeV. To enhance also the efficiency of use of the first crystal of the suggested double crystal-based scheme, we propose: the method of increase of the probability of particle capture into the channeling regime at the first crystal passage by means of fabrication of a crystal cut and the method of the amplification of nonchanneled particle deflection through the multiple volume reflection in one bent crystal, accompanying the particle channeling by a skew plane. We simulate both of these methods for the 50 TeV FCC energy.

  7. Collimator setting optimization in intensity modulated radiotherapy

    International Nuclear Information System (INIS)

    Williams, M.; Hoban, P.

    2001-01-01

    Full text: The aim of this study was to investigate the role of collimator angle and bixel size settings in IMRT when using the step and shoot method of delivery. Of particular interest is minimisation of the total monitor units delivered. Beam intensity maps with bixel size 10 x 10 mm were segmented into MLC leaf sequences and the collimator angle optimised to minimise the total number of MU's. The monitor units were estimated from the maximum sum of positive-gradient intensity changes along the direction of leaf motion. To investigate the use of low resolution maps at optimum collimator angles, several high resolution maps with bixel size 5 x 5 mm were generated. These were resampled into bixel sizes, 5 x 10 mm and 10 x 10 mm and the collimator angle optimised to minimise the RMS error between the original and resampled map. Finally, a clinical IMRT case was investigated with the collimator angle optimised. Both the dose distribution and dose-volume histograms were compared between the standard IMRT plan and the optimised plan. For the 10 x 10 mm bixel maps there was a variation of 5% - 40% in monitor units at the different collimator angles. The maps with a high degree of radial symmetry showed little variation. For the resampled 5 x 5 mm maps, a small RMS error was achievable with a 5 x 10 mm bixel size at particular collimator positions. This was most noticeable for maps with an elongated intensity distribution. A comparison between the 5 x 5 mm bixel plan and the 5 x 10 mm showed no significant difference in dose distribution. The monitor units required to deliver an intensity modulated field can be reduced by rotating the collimator and aligning the direction of leaf motion with the axis of the fluence map that has the least intensity. Copyright (2001) Australasian College of Physical Scientists and Engineers in Medicine

  8. A variable angle slant-hole collimator

    International Nuclear Information System (INIS)

    Moore, R.H.; Alpert, N.M.; Strauss, H.W.

    1983-01-01

    A variable-angle slant-hole (VASH) collimator was constructed to show the feasibility of using multiple sliding plates to achieve a range of collimator channel inclinations. One hundred and sixty tungsten plates, 0.125 mm thick and 14 cm square, were photoetched to produce 3025 1.5-mm2 holes in each plate, separated by 0.8-mm septa. Along with the collimator holes, registration holes and positioning grooves were also etched. The plates were placed in a holder and stacked to form a collimator 2.0 cm high. The holder permitted the plates to be sheared to achieve viewing angles from 0 to 40 degrees from the vertical. Resolution and sensitivity were determined both across and along the shear directions. Resolution of a thin /sup 99m/Tc source, 1.24 mm diam and 7 cm long, located 5 cm from the collimator face in air, was 1.1 cm FWHM at 0 degree shear and remained unchanged with increasing slant. The resolution was similar both across and along the shear plane. Sensitivity was determined with a point source placed 7 cm from the collimator face. At 0 degree slant the sensitivity was 169 cps/MBq (6.24 csp/mu Ci). A general all purpose (GAP) collimator had a FWHM of 1 cm for the line source in air at 5 cm, and a sensitivity of 205 cps/MBq (7.58 cps/mu Ci) for the point source at 7 cm. The data suggest that a variable-angle slant-hole collimator can be constructed of laminated plates

  9. Soller collimators for small angle neutron scattering

    International Nuclear Information System (INIS)

    Crawford, R.K.; Epperson, J.E.; Thiyagarajan, P.

    1989-01-01

    The neutron beam transmitted through the soller collimators on the SAD (Small Angle Diffractometer) instrument at IPNS (Intense Pulsed Neutron Source) showed wings about the main beam. These wings were quite weak, but were sufficient to interfere with the low-Q scattering data. General considerations of the theory of reflection from homogeneous absorbing media, combined with the results from a Monte Carlo simulation, suggested that these wings were due to specular reflection of neutrons from the absorbing material on the surfaces of the collimator blades. The simulations showed that roughness of the surface was extremely important, with wing background variations of three orders of magnitude being observed with the range of roughness values used in the simulations. Based on the results of these simulations, new collimators for SAD were produced with a much rougher 10 B-binder surface coating on the blades. These new collimators were determined to be significantly better than the original SAD collimators. This work suggests that any soller collimators designed for use with long wavelengths should be fabricated with such a rough surface coating, in order to eliminate (or at least minimize) the undesirable reflection effects which otherwise seem certain to occur. 4 refs., 6 figs

  10. Apparatus and method for variable angle slant hole collimator

    Science.gov (United States)

    Lee, Seung Joon; Kross, Brian J.; McKisson, John E.

    2017-07-18

    A variable angle slant hole (VASH) collimator for providing collimation of high energy photons such as gamma rays during radiological imaging of humans. The VASH collimator includes a stack of multiple collimator leaves and a means of quickly aligning each leaf to provide various projection angles. Rather than rotate the detector around the subject, the VASH collimator enables the detector to remain stationary while the projection angle of the collimator is varied for tomographic acquisition. High collimator efficiency is achieved by maintaining the leaves in accurate alignment through the various projection angles. Individual leaves include unique angled cuts to maintain a precise target collimation angle. Matching wedge blocks driven by two actuators with twin-lead screws accurately position each leaf in the stack resulting in the precise target collimation angle. A computer interface with the actuators enables precise control of the projection angle of the collimator.

  11. Embedded Collimator Beam Position Monitors

    CERN Document Server

    Bertarelli, A; Dallocchio, A; Gasior, M; Gentini, L; Nosych, A

    2011-01-01

    The LHC col­li­ma­tion sys­tem is cru­cial for safe and re­li­able op­er­a­tion of pro­ton beams with 350 MJ stored en­er­gy. Cur­rent­ly the col­li­ma­tor set-up is per­formed by ob­serv­ing beam loss­es when ap­proach­ing the colli­ma­tor jaws to the beam. For all 100 LHC mov­able col­li­ma­tors the pro­ce­dure may take sev­er­al hours and since it has to be re­peat­ed whenev­er the beam con­fig­u­ra­tion changes sig­nif­i­cant­ly, the col­li­ma­tor setup has an im­por­tant im­pact on the over­all ma­chine op­er­a­tion efficien­cy. To re­duce the col­li­ma­tor setup time by two or­ders of magni­tude the next gen­er­a­tion of the LHC col­li­ma­tors will be equipped with but­ton beam po­si­tion mon­i­tors (BPMs) em­bed­ded into the collimator jaws. This paper de­scribes the BPM de­sign and pre­sents proto­type re­sults ob­tained with beam in the CERN-SPS.

  12. Parasternal lymphoscintigraphy using the bilateral collimator

    International Nuclear Information System (INIS)

    Ohtake, Eiji; Iio, Masahiro; Toyama, Hinako; Kawaguchi, Shinichiro; Murata, Hajime

    1981-01-01

    A new method for measuring the depth of the parasternal lymph node was studied. The bilateral collimator used in this study consisted of two arrays of parallel holes which were slanted at +-30 degrees, respectively, to the vertical line. When the collimator was set to image the object in both sides of the field, the object and the dual images formed a regular triangle. The distance (D) from the image (crystal) plane to the object can be expressed by the equation: D = 1/2.L.cot30 0 = 0.866.L where L is the interval between the dual images calibrated to the real length. The distance from the collimator surface to the object is obtained by subtracting the effective thickness (T) between the image plane and the collimator surface from D. T was experimentally measured by the above equation, placing point sources on the collimator surface. The principle was applied to measure the depth of the parasternal lymph node. The parasternal lymphoscintigram was obtained four hours after bilateral subcostal injection of sup(99m)Tc-sulfur colloid and the image was taken by a Searle Pho/Gamma LFOV camera equipped with the bilateral collimator. When the scintigraphic image was made, radioactive markers were placed at the body surface to measure the distance from the collimator surface to the body surface Nineteen patients were examined. As a result, the lymph nodes were found to be located in the depths ranging widely from 0.4 to 6.5 cm from the anterior surface of the chest wall. These lymph nodes were thought to contain the deeply seated mediastinal nodes, and the superficial nodes located directly beneath the skin. Model studies were also performed to estimate the accuracy of this method and satisfactory results were obtained. (author)

  13. Monte Carlo design and simulation of a grid-type multi-layer pixel collimator for radiotherapy: feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Do-Kun; Jung, Joo-Young; Suh, Tae-Suk [The Catholic University of Korea, Seoul (Korea, Republic of)

    2014-05-15

    In order to confirm the possibility of field application of a different type collimator with a multileaf collimator (MLC), we constructed a grid-type multi-layer pixel collimator (GTPC) by using a Monte Carlo n-particle simulation (MCNPX). In this research, a number of factors related to the performance of the GPTC were evaluated using simulated output data of a basic MLC model. A layer was comprised of a 1024-pixel collimator (5.0 x 5.0 mm{sup 2}) which could operate individually as a grid-type collimator (32 x 32). A 30-layer collimator was constructed for a specific portal form to pass radiation through the opening and closing of each pixel cover. The radiation attenuation level and the leakage were compared between the GTPC modality simulation and MLC modeling (tungsten, 17.50 g/cm{sup 3}, 5.0 x 70.0 x 160.0 mm{sup 3}) currently used for a radiation field. Comparisons of the portal imaging, the lateral dose profile from a virtual water phantom, the dependence of the performance on the increase in the number of layers, the radiation intensity modulation verification, and the geometric error between the GTPC and the MLC were done using the MCNPX simulation data. From the simulation data, the intensity modulation of the GTPC showed a faster response than the MLC's (29.6%). In addition, the agreement between the doses that should be delivered to the target region was measured as 97.0%, and the GTPC system had an error below 0.01%, which is identical to that of MLC. A Monte Carlo simulation of the GTPC could be useful for verification of application possibilities. Because the line artifact is caused by the grid frame and the folded cover, a lineal dose transfer type is chosen for the operation of this system. However, the result of GTPC's performance showed that the methods of effective intensity modulation and the specific geometric beam shaping differed with the MLC modality.

  14. Monte Carlo design and simulation of a grid-type multi-layer pixel collimator for radiotherapy: Feasibility study

    Science.gov (United States)

    Yoon, Do-Kun; Jung, Joo-Young; Suh, Tae Suk

    2014-05-01

    In order to confirm the possibility of field application of a different type collimator with a multileaf collimator (MLC), we constructed a grid-type multi-layer pixel collimator (GTPC) by using a Monte Carlo n-particle simulation (MCNPX). In this research, a number of factors related to the performance of the GPTC were evaluated using simulated output data of a basic MLC model. A layer was comprised of a 1024-pixel collimator (5.0 × 5.0 mm2) which could operate individually as a grid-type collimator (32 × 32). A 30-layer collimator was constructed for a specific portal form to pass radiation through the opening and closing of each pixel cover. The radiation attenuation level and the leakage were compared between the GTPC modality simulation and MLC modeling (tungsten, 17.50 g/cm3, 5.0 × 70.0 × 160.0 mm3) currently used for a radiation field. Comparisons of the portal imaging, the lateral dose profile from a virtual water phantom, the dependence of the performance on the increase in the number of layers, the radiation intensity modulation verification, and the geometric error between the GTPC and the MLC were done using the MCNPX simulation data. From the simulation data, the intensity modulation of the GTPC showed a faster response than the MLC's (29.6%). In addition, the agreement between the doses that should be delivered to the target region was measured as 97.0%, and the GTPC system had an error below 0.01%, which is identical to that of MLC. A Monte Carlo simulation of the GTPC could be useful for verification of application possibilities. Because the line artifact is caused by the grid frame and the folded cover, a lineal dose transfer type is chosen for the operation of this system. However, the result of GTPC's performance showed that the methods of effective intensity modulation and the specific geometric beam shaping differed with the MLC modality.

  15. Monte Carlo design and simulation of a grid-type multi-layer pixel collimator for radiotherapy: feasibility study

    International Nuclear Information System (INIS)

    Yoon, Do-Kun; Jung, Joo-Young; Suh, Tae-Suk

    2014-01-01

    In order to confirm the possibility of field application of a different type collimator with a multileaf collimator (MLC), we constructed a grid-type multi-layer pixel collimator (GTPC) by using a Monte Carlo n-particle simulation (MCNPX). In this research, a number of factors related to the performance of the GPTC were evaluated using simulated output data of a basic MLC model. A layer was comprised of a 1024-pixel collimator (5.0 x 5.0 mm 2 ) which could operate individually as a grid-type collimator (32 x 32). A 30-layer collimator was constructed for a specific portal form to pass radiation through the opening and closing of each pixel cover. The radiation attenuation level and the leakage were compared between the GTPC modality simulation and MLC modeling (tungsten, 17.50 g/cm 3 , 5.0 x 70.0 x 160.0 mm 3 ) currently used for a radiation field. Comparisons of the portal imaging, the lateral dose profile from a virtual water phantom, the dependence of the performance on the increase in the number of layers, the radiation intensity modulation verification, and the geometric error between the GTPC and the MLC were done using the MCNPX simulation data. From the simulation data, the intensity modulation of the GTPC showed a faster response than the MLC's (29.6%). In addition, the agreement between the doses that should be delivered to the target region was measured as 97.0%, and the GTPC system had an error below 0.01%, which is identical to that of MLC. A Monte Carlo simulation of the GTPC could be useful for verification of application possibilities. Because the line artifact is caused by the grid frame and the folded cover, a lineal dose transfer type is chosen for the operation of this system. However, the result of GTPC's performance showed that the methods of effective intensity modulation and the specific geometric beam shaping differed with the MLC modality.

  16. Vol. 31 - Crystal Collimation for LHC

    CERN Document Server

    Mirarchi, Daniele; Scandale, Walter; Hall, Geoffrey

    2015-01-01

    Future upgrades of the CERN Large Hadron Collider (LHC) may demand improved cleaning performance of its collimation system. Very efficient collimation is required during regular operations at high intensities, because even a small amount of energy deposited on superconducting magnets can cause an abrupt loss of superconducting conditions (quench). The present collimation system has accomplished its tasks during the LHC Run I very well, where no quench with circulating beam took place with up to 150 MJ of stored energy at 4 TeV. On the other hand, uncertainty remains on the performance at the design energy of 7 TeV and with 360 MJ of stored energy. In particular, a further increase up to about 700 MJ is expected for the high luminosity upgrade (HL-LHC), where improved cleaning performance may be needed together with a reduction of collimator impedance. The possibility to use a crystal-based collimation system represents an option for improving both cleaning performance and impedance compared to the present s...

  17. Multi-view collimators for scintillation cameras

    International Nuclear Information System (INIS)

    Hatton, J.; Grenier, R.P.

    1982-01-01

    This patent specification describes a collimator for obtaining multiple images of a portion of a body with a scintillation camera comprises a body of radiation-impervious material defining two or more groups of channels each group comprising a plurality of parallel channels having axes intersecting the portion of the body being viewed on one side of the collimator and intersecting the input surface of the camera on the other side of the collimator to produce a single view of said body, a number of different such views of said body being provided by each of said groups of channels, each axis of each channel lying in a plane approximately perpendicular to the plane of the input surface of the camera and all of such planes containing said axes being approximately parallel to each other. (author)

  18. Collimation system for electron arc therapy

    International Nuclear Information System (INIS)

    Brunelli, R.J.; Carter, J.C.

    1984-01-01

    An electron collimation system for electron arc therapy treatments consists of a slit collimation system which is movable with the electron beam applicator and is designed to allow for dose compensation in the sagittal direction and a hoop-and-clamp assembly for final field shaping. By correctly designing the shape of the slit in the former and properly adjusting the components of the latter, it is possible to accomplish quite uniform shielding without causing any weight of the shielding material to rest on the patient. The slit collimation system has a specially shaped aperture for confining the radiation beam. The hoop-and-clamp assembly has hoops and clamps which locate shielding over the patient's body. The shielding locating clamps are adjustably movable radially with respect to the hoops. (author)

  19. Do we really need a collimator upgrade?

    International Nuclear Information System (INIS)

    Redaelli, S.

    2012-01-01

    Several improvements are foreseen for the LHC collimation system during the LS1 and beyond. The changes are matched to the required performance reach during the HL-LHC era. The scenarios for system upgrades are determined based on the present operational experience with the operation at 3.5 TeV, well about the beam stored energy regime of 100 MJ. The present upgrade strategy, and the uncertainties on the performance extrapolation to 7 TeV are presented. The collimation activities in LS1 are outlined and the possible works for LS2 and LS3 are presented. (author)

  20. Multi-view collimator for scintillation cameras

    International Nuclear Information System (INIS)

    Hatton, J.; Grenier, R.P.

    1979-01-01

    A collimator comprises a block or blocks of radiation-impervious material which defines a first plurality of parallel channels, each channel defining a direction of acceptance of radiation from a body. The axes of a second plurality channels define another direction of acceptance of radiation from the body and intersect the same portion of the body as the axes of the first plurality of channels thus producing a second view of the body. Where the collimator is built up as a stack of blocks, each pair of adjacent blocks defines a slice of the body which is viewed from two angles defined by the channels. (UK)

  1. Two-argument total scatter factor for small fields simultaneously collimated by MLC and jaws: application to stereotactic radiosurgery and radiotherapy

    Science.gov (United States)

    Han, Zhaohui; Friesen, Scott; Hacker, Fred; Zygmanski, Piotr

    2018-01-01

    Direct use of the total scatter factor (S tot) for independent monitor unit (MU) calculations can be a good alternative approach to the traditional separate treatment of head/collimator scatter (S c) and phantom scatter (S p), especially for stereotactic small fields under the simultaneous collimation of secondary jaws and tertiary multileaf collimators (MLC). We have carried out the measurement of S tot in water for field sizes down to 0.5  ×  0.5 cm2 on a Varian TrueBeam STx medical linear accelerator (linac) equipped with high definition MLCs. Both the jaw field size (c) and MLC field size (s) significantly impact the linac output factors, especially when c \\gg s and s is small (e.g. s  effectively transforms the measured trapezoidal domain in (c,s) plane to a rectangular domain to facilitate easier two-dimensional interpolation to determine S tot for arbitrary (c,s) combinations. Both the empirical fit and interpolation showed good agreement with experimental validation data.

  2. Parallel hole collimator acceptance tests for SPECT and planar studies

    International Nuclear Information System (INIS)

    Babicheva, R.R.; Bennie, D.N.; Collins, L.T.; Gruenwald, S.M.

    1998-01-01

    Full text: Different kinds of collimator damage can occur either during shipping or from regular use. Imperfections of construction along the strips or their connections give rise to nonperpendicular hole alignments to the crystal face and can produce potential problems such as ring artifacts and image degradation. Gamma camera collimator hole alignments and integrity were compared in four parallel hole high resolution collimators-two new cast and two used foil collimators, one with damage to the protective surface. [1] The point source flood image of the defective collimator was non-circular as were the images of cast collimators. The image of new foil collimator was circular. [2] High count sheet flood did not show any imperfections. [3] Bone mineral densitometer was used to perform collimated X-ray beam. The collimator was placed on the scanning bed with an X-ray cassette placed directly above it. The damaged area was well demonstrated. [4] The COR offset test was taken at two extreme radii. The offset value with the defective collimator is increased by 0.53 pixel or 129% with increase of COR from radius 14 cm to 28cm. [5] The collimator hole alignment test involves performing multiple measurements of COR along the length of the collimator, and checking for variations in COR with both position of source and angle of rotation. The maximum variation in COR of the defective collimator hole alignment was 1.13 mm. Collimators require testing when new and at regular intervals, or following damage. The point source test can be used for foil collimators. The most sensitive tests were collimated X-ray source, COR offset test and collimator hole alignment

  3. TU-H-BRC-09: Validation of a Novel Therapeutic X-Ray Array Source and Collimation System

    International Nuclear Information System (INIS)

    Trovati, S; King, GJ; Loo, BW; Maxim, P; Schueler, E; Wang, J; Wang, L; Borchard, P; Limborg, CG; McCormick, D; Nicolas, LY; Tantawi, S

    2016-01-01

    Purpose: We have experimentally characterized and simulated the dosimetric properties and spatial fidelity of a novel X-ray array source and collimation system called SPHINX that has the potential to generate complex intensity modulated X-ray beams by varying the electron beam intensity only, and without any moving parts like in multi-leaf collimators. Methods: We investigated the spatial fidelity and the X-ray performances of a SPHINX prototype in tungsten, using a Cyber Knife and the experimental high-energy electron beam line at XTA at SLAC National Laboratory. Dose distributions were recorded with gafchromic films, placed at the distal end of SPHINX and at several depths in a solid water phantom. The geometry of SPHINX and of the experimental set-ups was also modeled in Monte Carlo (MC) simulations with the FLUKA code, used to reproduce the experimental results and, after validation, to predict and optimize the performance and design of the SPHINX. Results: The results indicate significant particle leakage through the channels during a single-channel irradiation for high incident energies, followed by a rapid decrease for energies of clinical interest. When the collimator channels are used as target, the photon production increases, however at expense of the beam size that is also enlarged. The illumination of all channels simultaneously shows a fairly even transmission of the beam. Conclusion: With the measurements we have verified the MC models and the uniformity of beam transmission through SPHINX, and we have evaluated the importance of particle leakage through adjacent channels. These results can be used to optimize SPHINX design through the validated MC simulations. Funding: Weston Havens Foundation, Office of the Dean of Medical School and Office of the Provost (Stanford University). Loo, Maxim, Borchard, Tantawi are co-founders of TibaRay Inc. Loo and Tantawi are TibaRay Inc. board members. Loo and Maxim received grants from Varian Medical Systems and

  4. TU-H-BRC-09: Validation of a Novel Therapeutic X-Ray Array Source and Collimation System

    Energy Technology Data Exchange (ETDEWEB)

    Trovati, S; King, GJ; Loo, BW; Maxim, P; Schueler, E; Wang, J; Wang, L [Stanford University School of Medicine, Palo Alto, California (United States); Borchard, P [Tibaray Inc, San Francisco, California (United States); Limborg, CG; McCormick, D; Nicolas, LY; Tantawi, S [Stanford Linear Accelerator, Menlo Park, CA (United States)

    2016-06-15

    Purpose: We have experimentally characterized and simulated the dosimetric properties and spatial fidelity of a novel X-ray array source and collimation system called SPHINX that has the potential to generate complex intensity modulated X-ray beams by varying the electron beam intensity only, and without any moving parts like in multi-leaf collimators. Methods: We investigated the spatial fidelity and the X-ray performances of a SPHINX prototype in tungsten, using a Cyber Knife and the experimental high-energy electron beam line at XTA at SLAC National Laboratory. Dose distributions were recorded with gafchromic films, placed at the distal end of SPHINX and at several depths in a solid water phantom. The geometry of SPHINX and of the experimental set-ups was also modeled in Monte Carlo (MC) simulations with the FLUKA code, used to reproduce the experimental results and, after validation, to predict and optimize the performance and design of the SPHINX. Results: The results indicate significant particle leakage through the channels during a single-channel irradiation for high incident energies, followed by a rapid decrease for energies of clinical interest. When the collimator channels are used as target, the photon production increases, however at expense of the beam size that is also enlarged. The illumination of all channels simultaneously shows a fairly even transmission of the beam. Conclusion: With the measurements we have verified the MC models and the uniformity of beam transmission through SPHINX, and we have evaluated the importance of particle leakage through adjacent channels. These results can be used to optimize SPHINX design through the validated MC simulations. Funding: Weston Havens Foundation, Office of the Dean of Medical School and Office of the Provost (Stanford University). Loo, Maxim, Borchard, Tantawi are co-founders of TibaRay Inc. Loo and Tantawi are TibaRay Inc. board members. Loo and Maxim received grants from Varian Medical Systems and

  5. Method to assist conception of collimators in nuclear medicine

    International Nuclear Information System (INIS)

    Gantet, P.; Esquerre, J.P.; Danet, B.; Roux, G.; Guiraud, R.

    1990-01-01

    Designing a collimator should begin by an accurate computation of its performances in order to minimize the usual expensive and time consuming phase of trial and error. The authors briefly describe several methods currently used, and present a method of simulation of the percussional response of collimators. The computation takes into account the attenuation of photons by the collimator septas. An other benefit is its ability to be used whatever the geometric specifications of the collimator. The program computes spatial resolution, geometric efficiency, septal penetration, as well as slice thickness when the collimator is used with a SPECT device. The study presents the results concerning two collimators: a general purpose parallel hole commercially available and a focused parallel one dedicated to a single slice SPECT system. In conclusion, this deterministic method which takes attenuation into account for collimators performances computation should be useful tool to assist conception of new collimators in nuclear medicine [fr

  6. A Simple and Inexpensive Collimator for Neutron Radiography

    DEFF Research Database (Denmark)

    Olsen, J.; Mortensen, L.

    1974-01-01

    A neutron beam collimator was constructed by means of plastic drinking “straws”. The properties of the collimator were investigated, and especially the distribution of the neutrons at different distances....

  7. ON THE USE OF THIN SCRAPERS FOR MOMENTUM COLLIMATION

    International Nuclear Information System (INIS)

    CATALAN-LASHERAS, N.

    2001-01-01

    In transverse collimation systems, thin scrapers are used as primary collimators to interact with the beam halo and increase its impact parameter on the secondary collimators or absorbers. In the same way, placing the primary collimator in a dispersion region is used for momentum collimation. However, the use of scrapers for momentum collimation presents an additional disadvantage when handling medium-low energy beams. The energy lost by ionization is non negligible and the proton can be kicked out of the RF bucket. The material and thickness of the scraper have to be carefully adjusted according to the position of secondary collimators and momentum aperture of the machine. We derive simple analytical expressions for a generic case. The same calculations have been applied to the case of the SNS accumulator ring. After careful considerations, the use of scrapers for momentum collimation was ruled out in favor of a beam in gap kicker system

  8. Grazing function g and collimation angular acceptance

    Directory of Open Access Journals (Sweden)

    Stephen G. Peggs

    2009-11-01

    Full Text Available The grazing function g is introduced—a synchrobetatron optical quantity that is analogous (and closely connected to the Twiss and dispersion functions β, α, η, and η^{′}. It parametrizes the rate of change of total angle with respect to synchrotron amplitude for grazing particles, which just touch the surface of an aperture when their synchrotron and betatron oscillations are simultaneously (in time at their extreme displacements. The grazing function can be important at collimators with limited acceptance angles. For example, it is important in both modes of crystal collimation operation—in channeling and in volume reflection. The grazing function is independent of the collimator type—crystal or amorphous—but can depend strongly on its azimuthal location. The rigorous synchrobetatron condition g=0 is solved, by invoking the close connection between the grazing function and the slope of the normalized dispersion. Propagation of the grazing function is described, through drifts, dipoles, and quadrupoles. Analytic expressions are developed for g in perfectly matched periodic FODO cells, and in the presence of β or η error waves. These analytic approximations are shown to be, in general, in good agreement with realistic numerical examples. The grazing function is shown to scale linearly with FODO cell bend angle, but to be independent of FODO cell length. The ideal value is g=0 at the collimator, but finite nonzero values are acceptable. Practically achievable grazing functions are described and evaluated, for both amorphous and crystal primary collimators, at RHIC, the SPS (UA9, the Tevatron (T-980, and the LHC.

  9. Collimator scatter and 2D dosimetry in small proton beams

    NARCIS (Netherlands)

    van Luijk, P.; van 't Veld, A.A.; Zelle, H.D.; Schippers, J.M.

    Monte Carlo simulations have been performed to determine the influence of collimator-scattered protons from a 150 MeV proton beam on the dose distribution behind a collimator. Slit-shaped collimators with apertures between 2 and 20 mm have been simulated. The Monte Carlo code GEANT 3.21 has been

  10. The usefulness of cardiofocal collimator in static renal imaging

    International Nuclear Information System (INIS)

    Evren, I.; Durak, H.; Degirmenci, B.; Derebek, E.; Oezbilek, E.; Capa, G.

    2001-01-01

    Static renal imaging is best performed using pinhole collimator. But this technique takes too much time and generally parallel hole collimators are preferred for static renal imaging in nuclear medicine departments. The purpose of this study was to investigate the usefulness of the cardio-focal collimator used for myocardial perfusion imaging in static renal scintigraphy

  11. The proton collimation system of HERA

    International Nuclear Information System (INIS)

    Seidel, M.

    1994-06-01

    This thesis is concerned with the two stage collimation system in HERA-p which is supposed to suppress this kind of background. The HERA-p collimation system consists of 12 movable tungsten jaws at three locations in the ring. A manual operation of the system is therefore rather time consuming, but also dangerous in the case of an operational mistake. The development of partially automised controls for the system is therefore an important topic of this thesis as well. In order to control the precise positioning of the jaws at the beam edge the induced hadronic showers are monitored immediately downstream the collimators. Small PIN-diode based shower detectors are used for this purpose. A detailed analysis of these shower rates turned out to be a sensitive source of information on the beam. A large section of the thesis is therefore concerned with the diagnostic possibilities of collimators in a proton machine. A passive method for the determination of the machine acceptance is presented. A second topic is the determination of diffusion rates in the beam halo. A stepwise movement of a beam limiting collimator jaw induces relaxation processes in the beam halo. From an analysis of the transient time evolution of the loss rates after the movement one can determine the diffusion coefficient in the beam halo. A completely new method is the frequency analysis of the halo induced shower rates. If the beam oscillates it scrapes periodically at the collimator which results in a modulation of the measured loss rates. The method allows measurements of slow orbit oscillations in the range of some μm. In the last section of the thesis the diffusion of halo protons as a result of beam-beam interaction is investigated. A little collection of diffusion measurements as a function of particle amplitude is presented. With the help of tracking simulations it is demonstrated that diffusion rates of the observed size can be generated by a certain modulation of the betatron frequency

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

    Science.gov (United States)

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

    2018-06-01

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

  13. A dosimetric comparison of real-time adaptive and non-adaptive radiotherapy: A multi-institutional study encompassing robotic, gimbaled, multileaf collimator and couch tracking

    DEFF Research Database (Denmark)

    Colvill, Emma; Booth, Jeremy; Nill, Simeon

    2016-01-01

    AND MATERIALS: Ten institutions with robotic(2), gimbaled(2), MLC(4) or couch tracking(2) used common materials including CT and structure sets, motion traces and planning protocols to create a lung and a prostate plan. For each motion trace, the plan was delivered twice to a moving dosimeter; with and without...

  14. Sci-Fri PM: Radiation Therapy, Planning, Imaging, and Special Techniques - 02: Feasibility of using multileaf collimation for stereotactic radiosurgery of arteriovenous malformation

    International Nuclear Information System (INIS)

    Lee, Young; Ruschin, Mark; Tsao, May; Schwartz, Michael

    2016-01-01

    SRS using linac and cones offers steep dose fall-off but a tradeoff exists between conformality and treatment time, which depends on the number of isocentres. Purpose of this study is to quantify planning metrics between cones- and MLC-based SRS for arteriovenous malformation(AVM). Seven AVM cases treated with cones were re-planned with MLC on Pinnacle treatment planning system. Planning target volume(PTV) was created with 1mm uniform margin to the AVM to account for MLC positional variation. Clinically-planned prescription dose(15–25Gy) was used. Four plans were generated per case:non-coplanar VMAT(ncV), single-arc VMAT(saV), non-coplanar IMRT(ncI), non-coplanar conformal(ncC). Plans were compared for conformity(CI), heterogeneity(HI) and gradient(GI) indices and brain doses. Estimated treatment times and monitor units(MU) were compared. Cone-based plans required 2–6 isocentres. Though CI-RTOG was similar for plans(median=0.98), CI-Paddick was most favourable for ncV(median=0.86) and worst for cones(0.54). HI for MLC plans(median=1.19–1.27) were lower than cone-based plans(1.43). GI was similar for all plans. For 2/7 ncC had brainstem maximum dose>16.7Gy and therefore were clinically unacceptable. Brain V12Gy,V10Gy,V2Gy were lowest in the cones plan. ncV brain V12Gy,V10Gy,V2Gy were lowest of all MLC-based plans studied. Treatment MUs were similar for MLC-based plans and up to 70% lower than clinically delivered plans. ncV showed best conformality in this study. Of the MLC-based plans, ncV also showed lowest normal tissue dose with reasonable treatment time.

  15. Sci-Fri PM: Radiation Therapy, Planning, Imaging, and Special Techniques - 02: Feasibility of using multileaf collimation for stereotactic radiosurgery of arteriovenous malformation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young; Ruschin, Mark [Department of Medical Physics, Sunnybrook Health Science Centre, University of Toronto (Canada); Tsao, May [Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto (Canada); Schwartz, Michael [Department of Surgery (Neurosurgery), Sunnybrook Health Sciences Centre, University of Toronto (Canada)

    2016-08-15

    SRS using linac and cones offers steep dose fall-off but a tradeoff exists between conformality and treatment time, which depends on the number of isocentres. Purpose of this study is to quantify planning metrics between cones- and MLC-based SRS for arteriovenous malformation(AVM). Seven AVM cases treated with cones were re-planned with MLC on Pinnacle treatment planning system. Planning target volume(PTV) was created with 1mm uniform margin to the AVM to account for MLC positional variation. Clinically-planned prescription dose(15–25Gy) was used. Four plans were generated per case:non-coplanar VMAT(ncV), single-arc VMAT(saV), non-coplanar IMRT(ncI), non-coplanar conformal(ncC). Plans were compared for conformity(CI), heterogeneity(HI) and gradient(GI) indices and brain doses. Estimated treatment times and monitor units(MU) were compared. Cone-based plans required 2–6 isocentres. Though CI-RTOG was similar for plans(median=0.98), CI-Paddick was most favourable for ncV(median=0.86) and worst for cones(0.54). HI for MLC plans(median=1.19–1.27) were lower than cone-based plans(1.43). GI was similar for all plans. For 2/7 ncC had brainstem maximum dose>16.7Gy and therefore were clinically unacceptable. Brain V12Gy,V10Gy,V2Gy were lowest in the cones plan. ncV brain V12Gy,V10Gy,V2Gy were lowest of all MLC-based plans studied. Treatment MUs were similar for MLC-based plans and up to 70% lower than clinically delivered plans. ncV showed best conformality in this study. Of the MLC-based plans, ncV also showed lowest normal tissue dose with reasonable treatment time.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-06-15

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

  17. Collimator settings and performance in 2011 and 2012

    International Nuclear Information System (INIS)

    Bruce, R.; Assmann, R.W.; Burkart, F.; Cauchi, M.; Deboy, D.; Lari, L.; Redaelli, S; Rossi, A.; Salvachua, B.; Valentino, G.; Wollmann, D.

    2012-01-01

    Collimator settings and performance are key parameters for deciding the reach in intensity and β* in order to conclude on possible limits for the 2012 run, a summary is first given of the relevant running experience in 2011 and the collimation-related MDs. These include among others tight collimator settings, a quench test, and aperture measurements. Based on the 2011 experience, we conclude on possible running scenarios for 2012 in terms of collimator settings, intensity and β* from the collimation point of view. (authors)

  18. Collimation settings and performance in 2011 and 2012

    CERN Document Server

    Bruce, R; Burkart, F; Cauchi, M; Deboy, D; Lari, L; Redaelli, S; Rossi, A; Salvachua, B; Valentino, G; Wollmann, D

    2012-01-01

    Collimator settings and available aperture are key parameters for deciding the reach in intensity and β*. In order to conclude on possible limits for the 2012 run, a summary is first given of the relevant running experience in 2011 and the collimation-related MDs. These include among others tight collimator settings, a quench test, and aperture measurements. Based on the 2011 experience, we conclude on possible running scenarios for 2012 in terms of collimator settings, intensity and β* from the collimation point of view.

  19. Collimation settings and performance in 2011 and 2012

    Energy Technology Data Exchange (ETDEWEB)

    Bruce, R; Assmann, R W; Burkart, F; Cauchi, M; Deboy, D; Lari, L; Redaelli, S; Rossi, A; Salvachua, B; Valentino, G; Wollmann, D [European Organization for Nuclear Research, Geneva (Switzerland)

    2012-07-01

    Collimator settings and available aperture are key parameters for deciding the reach in intensity and β*. In order to conclude on possible limits for the 2012 run, a summary is first given of the relevant running experience in 2011 and the collimation-related MDs. These include among others tight collimator settings, a quench test, and aperture measurements. Based on the 2011 experience, we conclude on possible running scenarios for 2012 in terms of collimator settings, intensity and β* from the collimation point of view.

  20. Collimation techniques for dense object flash radiography

    International Nuclear Information System (INIS)

    Mueller, K.H.

    1984-08-01

    In explosively driven experiments, flash radiography can record a wealth of information about material densities and boundaries. Obtaining accurate quantitative data from these radiographs requires careful design of the experiment so that one can control and measure the scattered radiation background that is a part of any experiment. We have used collimators at the x-ray source to match the incident x-ray flux to the transmission of the object, thereby reducing the production of scattered radiation while still preserving a complete view of the object. Multi-hole collimators (at the film plane) with a length-to-diameter ratio of approx. 20:1 have been used to measure the scattered radiation field with several exposure geometries and with various shielding methods

  1. Collimation systems in the next linear collider

    International Nuclear Information System (INIS)

    Merminga, N.; Irwin, J.; Helm, R.; Ruth, R.D.

    1991-02-01

    Experience indicates that beam collimation will be an essential element of the next generation e + E - linear colliders. A proposal for using nonlinear lenses to drive beam tails to large amplitudes was presented in a previous paper. Here we study the optimization of such systems including effects of wakefields and optical aberrations. Protection and design of the scrapers in these systems are discussed. 9 refs., 7 figs

  2. Coronal Jet Collimation by Nonlinear Induced Flows

    Energy Technology Data Exchange (ETDEWEB)

    Vasheghani Farahani, S.; Hejazi, S. M. [Department of Physics, Tafresh University, Tafresh 39518 79611 (Iran, Islamic Republic of)

    2017-08-01

    Our objective is to study the collimation of solar jets by nonlinear forces corresponding to torsional Alfvén waves together with external forces. We consider a straight, initially non-rotating, untwisted magnetic cylinder embedded in a plasma with a straight magnetic field, where a shear between the internal and external flows exists. By implementing magnetohydrodynamic theory and taking into account the second-order thin flux tube approximation, the balance between the internal nonlinear forces is visualized. The nonlinear differential equation containing the ponderomotive, magnetic tension, and centrifugal forces in the presence of the shear flow is obtained. The solution presents the scale of influence of the propagating torsional Alfvén wave on compressive perturbations. Explicit expressions for the compressive perturbations caused by the forces connected to the torsional Alfvén wave show that, in the presence of a shear flow, the magnetic tension and centrifugal forces do not cancel each other’s effects as they did in its absence. This shear flow plays in favor of the magnetic tension force, resulting in a more efficient collimation. Regarding the ponderomotive force, the shear flow has no effect. The phase relations highlight the interplay of the shear flow and the plasma- β . As the shear flow and plasma- β increase, compressive perturbation amplitudes emerge. We conclude that the jet collimation due to the torsional Alfvén wave highly depends on the location of the jet. The shear flow tightens the collimation as the jet elevates up to the solar corona.

  3. Single photon emission computed tomography by using fan beam collimator

    International Nuclear Information System (INIS)

    Akiyama, Yoshihisa

    1992-01-01

    A multislice fan beam collimator which has parallel collimation along the cephalic-caudul axis of a patient and converging collimation within planes that are perpendicular to that axis was designed for a SPECT system with a rotating scintillation camera, and it was constructed by the lead casting method which was developed in recent years. A reconstruction algorithm for fan beam SPECT was formed originally by combining the reconstruction algorithm of the parallel beam SPECT with that of the fan beam X-ray CT. The algorithm for fan beam SPECT was confirmed by means of computer simulation and a head phantom filled with diluted radionuclide. Not only 99m Tc but also 123 I was used as a radionuclide. A SPECT image with the fan beam collimator was compared with that of a parallel hole, low energy, high resolution collimator which was routinely used for clinical and research SPECT studies. Both system resolution and sensitivity of the fan beam collimator were ∼20% better than those of the parallel hole collimator. Comparing SPECT images obtained from fan beam collimator with those of parallel hole collimator, the SPECT images using fan beam collimator had far better resolution. A fan beam collimator is a useful implement for the SPECT study. (author)

  4. A six-bank multi-leaf system for high precision shaping of large fields

    International Nuclear Information System (INIS)

    Topolnjak, R; Heide, U A van der; Raaymakers, B W; Kotte, A N T J; Welleweerd, J; Lagendijk, J J W

    2004-01-01

    In this study, we present the design for an alternative MLC system that allows high precision shaping of large fields. The MLC system consists of three layers of two opposing leaf banks. The layers are rotated 60 deg. relative to each other. The leaves in each bank have a standard width of 1 cm projected at the isocentre. Because of the symmetry of the collimator set-up it is expected that collimator rotation will not be required, thus simplifying the construction considerably. A 3D ray tracing computer program was developed in order to simulate the fluence profile for a given collimator and used to optimize the design and investigate its performance. The simulations show that a six-bank collimator will afford field shaping of fields of about 40 cm diameter with a precision comparable to that of existing mini MLCs with a leaf width of 4 mm

  5. Jet collimation by turbulent viscosity. I

    International Nuclear Information System (INIS)

    Henriksen, R.N.

    1987-01-01

    In this paper it is assumed that the subscale turbulent eddies induced in an ambient medium by the emergence of a (already collimated) jet from a galactic nucleus (VLBI jet) are the source of the viscosity which causes material to be entrained into the large-scale (VLA) jet. New analytic solutions are derived by a generalization of the self-similar Ansatz used in the Landau-Squires solution to include variable density and viscosity. It is shown that such a process of viscous collimation of the VLA jets can account for the observed collimation-luminosity correlation, the magnetic flux, and the inferred mass flux of these jets. Order of magnitude comparisons of velocity and density fields with recently observed emission-line flow regions near radio jets are made. All of the viscosity-dependent observational checks imply roughly the same plausible value for the eddy viscosity. It is emphasized that storing the initial VLBI jet energy in the intermediate scales occupied by the turbulent eddies allows this energy to be largely undetected. 35 references

  6. Collimator trans-axial tomographic scintillation camera

    International Nuclear Information System (INIS)

    Jaszczak, Ronald J.

    1979-01-01

    An improved collimator is provided for a scintillation camera system that employs a detector head for transaxial tomographic scanning. One object of this invention is to significantly reduce the time required to obtain statistically significant data in radioisotope scanning using a scintillation camera. Another is to increase the rate of acceptance of radioactive events to contribute to the positional information obtainable from a radiation source of known strength without sacrificing spatial resolution. A further object is to reduce the necessary scanning time without degrading the images obtained. The collimator described has apertures defined by septa of different radiation transparency. The septa are aligned to provide greater radiation shielding from gamma radiation travelling within planes perpendicular to the cranial-caudal axis and less radiation shielding from gamma radiation travelling within other planes. Septa may also define apertures such that the collimator provides high spatial resolution of gamma rays traveling within planes perpendicular to the cranial-caudal axis and directed at the detector and high radiation sensitivity to gamma radiation travelling other planes and indicated at the detector. (LL)

  7. Hybrid collimation for industrial gamma-ray imaging

    International Nuclear Information System (INIS)

    He, Z.; Knoll, G. F.; Smith, L. E.; Wehe, D. K.

    1999-01-01

    Portable photon imaging devices with a broad energy range of sensitivity, adequate angular resolution and high efficiency are useful in applications such as environmental remediation and industrial surveys. The vast majority of past systems built for these applications have relied on mechanical collimation although a few have used electronic collimation. To our knowledge, no devices have been built that exploit the benefits of both mechanical and electronic collimation in the same system. The combination of a mechanically-collimated camera with an electronically-collimated camera offers both the high efficiency and good angular resolution typical in a mechanically-collimated camera for lower energies and the uncoupling of spatial resolution and efficiency provided by an electronically-collimated camera at higher energies

  8. One primary collimator with optional crystal feature, tested with beam

    CERN Document Server

    EuCARD, Collaboration

    2014-01-01

    The WP8 of EuCARD aims at the design of more advanced materials and collimator concepts for high beam power in particle accelerators like LHC and FAIR. Deliverable 8.3.1 concerned the production and the validation by beam tests of an advanced collimator prototype to improve various aspects of the LHC collimation system, such as the accuracy of the collimator jaw alignment to the circulating beam, the duration of collimator setup time and the overall halo cleaning performance. A collimator prototype was built and installed in the SPS for beam tests in the running period between 2010 and 2012. Crystal collimation aspects were dealt with in a dedicated SPS experiment, which also profited from EuCARD contributions.

  9. Development of collimator insert for linac based stereotactic irradiation

    International Nuclear Information System (INIS)

    Singh, I.R.R.; Brindha, S.; Ravindran, B.P.; Rajshekhar, V.

    1999-01-01

    The aim of this study is to develop collimator inserts of various sizes which are either not commercially available or are expensive to import. The dosimetry parameters such as tissue maximum ratio (TMR), off-axis ratio (OAR) and output factor of the developed collimator insert are compared with that of the commercial collimator insert (Radionics). In order to check the suitability of the collimator insert developed locally for clinical use and to standardize the method of development, a collimator insert of 15 mm identical to the one supplied by Radionics is developed with low-melting alloy (Cerrobend). Moreover for the clinical use of the developed collimator insert, certain acceptance tests are performed which include a collimator concentricity test, beam size check and radiation leakage test. The dose verification is carried out with a thermoluminescent dosimeter ( 7 LiF rods) and an FBX chemical dosimeter in a human-head-shaped Perspex phantom filled with water. The variation between the calculated and measured dose is found to be within +2.4% for 7 LiF rods and -2.0% for the FBX chemical dosimeter thus ensuring the suitability of the developed collimator insert for clinical use. This has encouraged us to standardize the method adapted to develop the collimator insert and to develop collimator inserts of different field sizes. (author)

  10. Dosimetric commissioning and system for stereotactic radiation treatments based on linear accelerators with dynamic micromultilaminas collimators

    International Nuclear Information System (INIS)

    Ascension, Yudy; Alfonso, Rodolfo; Silvestre, Ileana

    2009-01-01

    Once installed and accepted, a system for stereotactic radiosurgery / stereotactic radiotherapy (CERs / RTE) requires, before starting to be used clinically in patients undergoing a process of commissioning dosimetry, which evaluates all geometric parameters, physical, Dosimetric and technical impact on the precision and accuracy of treatment to administer, and therefore its effectiveness. This process includes training and familiarization of the multidisciplinary team (medical physicists, radiation oncologists, neurosurgeons, dosimetrists, biomedical engineers) with the equipment and techniques used, the quality assurance program and special radiation protection standards for this technology. The aim of this work is to prepare the pre-clinical dosimetric conditions to ensure the quality and radiation safety of treatment with CER RTE. Treatment with CER RTE INOR has a linear accelerator equipped with a micro-multileaf collimator dynamic tertiary (dMLC 3Dline). The system aceleradordMLC geometric and dosimetric was calibrated, using ionization chambers miniature, diode and film dosimetry. The immobilization of the patient and location of the lesion is made by both invasive stereotactic frames and relocatable. The computerized planning of the CER / TEN is done with the ERGO system, for which commissioning is designed test cases of increasing complexity, using planes and anthropomorphic dummies, which help assess the accuracy of the dosimetric calculations and accuracy of the system as a whole. We compared the results of the planning system with measurements, showing that the discrepancies are within tolerances, so it is concluded that from the standpoint of physical dosimetry, the system-under-ERGO accelerator MLC is eligible for clinical use. (author)

  11. Properties of a new variable collimator at orthovoltage energies

    International Nuclear Information System (INIS)

    Lee, K.; Butson, M.; Metcalfe, P.; University of Wollongong, Wollongong, NSW

    1996-01-01

    Full text: Beam characteristics of a Therapax DXT 300 Orthovoltage Machine are investigated using fixed collimators or 'cones' and a variable collimator. Previously, fixed collimators have always been used throughout patient treatments. The variable collimator is an optional accessory to the DXT 300 machine and has just been implemented at our centre. The variable collimator mounts to the DXT 300 at the same position as the fixed collimators and produces rectangular field sizes up to 20 x 20 cmm at 50 cm FSD. Surface/near surface charge measurements were performed for the variable collimator and various configurations of cones for a 10 x 10 cm field at 250kVp and a FSD of 50cm in solid water using a Markus Type 329 parallel plate ionisation chamber connected via a shielded triaxial cable to a 2570/1 NE Farmer electrometer. Central axis percentage depth doses and beam profiles were measured using a Scanditronix RK ionisation chamber in a RFA300 water tank for both cones and the variable collimator. This data was then transferred to the Target Series 2 computer planning system for isodose display. Measurements were performed at 250 kVp. Beam profiles were scanned both perpendicular to and along the cathode-anode direction. A change in charge measured at the surface and to 1 mm depth for the variable collimator and the cones was observed. The normal cone and the variable collimator have surface charges of 100% and 98% respectively. Maximum surface charge occurred for the open-end 'lead' cone. A comparison was made between the central axis percentage depth dose produced by the cones and variable collimator for field sizes of 10 x 10cm and 20 x 20 cm. Maximum dose for the cones is deposited at the surface whereas for the variable collimator there is a slight build-up region before maximum dose is deposited at a depth of 1 mm. Upon comparing the beam profiles produced by the variable collimator and the cones, it was observed that the width of the penumbra differed by

  12. Reflection jets and collimation of radio sources

    International Nuclear Information System (INIS)

    Pacholczyk, A.G.

    1983-01-01

    A discussion of the hydrodynamics of jets formed by discrete portions of materials ejected from the parent galaxy through a channel, and reflected back to it as a result of an encounter with the material accumulated at the end of the channel, is the basis of the present descriptive hypothesis for a class of jets in extended radio sources. The model encompasses the view of extended radio sources as the multiple ejection of plasmoids through a channel, as well as the formation of retrojets through the interaction of a plasmon with the dense relic material at the end of a channel, and the collimation of plasmon material in channels. 14 references

  13. Atomic and molecular beams production and collimation

    CERN Document Server

    Lucas, Cyril Bernard

    2013-01-01

    Atomic and molecular beams are employed in physics and chemistry experiments and, to a lesser extent, in the biological sciences. These beams enable atoms to be studied under collision-free conditions and allow the study of their interaction with other atoms, charged particles, radiation, and surfaces. Atomic and Molecular Beams: Production and Collimation explores the latest techniques for producing a beam from any substance as well as from the dissociation of hydrogen, oxygen, nitrogen, and the halogens.The book not only provides the basic expressions essential to beam design but also offers

  14. Preliminary assessment of beam impact consequences on LHC Collimators

    CERN Document Server

    Cauchi, M; Bertarelli, A; Bruce, R; Carra, F; Dallocchio, A; Deboy, D; Mariani, N; Rossi, A; Lari, L; Mollicone, P; Sammut, N

    2011-01-01

    The correct functioning of the LHC collimation system is crucial to attain the desired LHC luminosity performance. However, the requirements to handle high intensity beams can be demanding. In this respect, the robustness of the collimators plays an important role. An accident, which causes the proton beam to hit a collimator, might result in severe beam-induced damage and, in some cases, replacement of the collimator, with consequent downtime for the machine. In this paper, several case studies representing different realistic beam impact scenarios are shown. A preliminary analysis of the thermal response of tertiary collimators to beam impact is presented, from which the most critical cases can be identified. Such work will also help to give an initial insight on the operational constraints of the LHC by taking into account all relevant collimator damage limits.

  15. Gallium-67 imaging with low collimators and energy weighted acquisition

    International Nuclear Information System (INIS)

    Hamill, J.J.; DeVito, R.P.

    1990-01-01

    This paper reports that the medium and high energy collimators used in 67 Ga imaging have poorer resolution than low-energy collimators, such as the LEAP. The low energy collimators could be used for gallium imaging if the background under the 93 and 185 keV peaks could be reduced without degrading the signal-to-noise ratio unacceptably. energy weighted acquisition provides a means of accomplishing this background reduction. The authors have developed weighing functions for gallium imaging through LEAP and high resolution collimators. The resolution of the low energy collimators is realized while the background is comparable to, or better than, the background in normal, energy-window imaging with the medium energy collimator. The pixel noise is somewhat greater than the Poisson noise in normal gallium imaging, and some noise correlations, or noise texture, is introduced

  16. Acoustic measurements in the collimation region of the LHC

    CERN Document Server

    Deboy, D; Baccigalupi, C; Burkart, F; Cauchi, M; Derrez, C S; Lendaro, J; Masi, A; Spiezia, G; Wollmann, D

    2011-01-01

    The LHC accelerator at CERN has the most advanced collimation system ever being installed. The collimators intercept unavoidable particle losses and therefore are essential to avoid beam induced quenches of the superconducting magnets. In addition, they provide passive machine protection against mis-kicked beams. During material robustness tests on a LHC collimator prototype in 2004 and 2006, vibration and acoustic measurements have shown that a beam impact detection system should be feasible using accelerometers and microphones as sensors in the LHC. Recently, such sensors have been installed close to the primary collimators in the LHC tunnel. First analyses of raw data show that the system is sensitive enough to detect beam scraping on collimators. Therefore, the implementation of a sophisticated acousticmonitoring system is under investigation. It may be useful not only to detect beam impacts on primary collimators in case of failure, but also to derive further information on beam losses that occur during ...

  17. Beam Collimation Studies for the ILC Positron Source

    Energy Technology Data Exchange (ETDEWEB)

    Drozhdin, A.; /Fermilab; Nosochkov, Y.; Zhou, F.; /SLAC

    2008-06-26

    Results of the collimation studies for the ILC positron source beam line are presented. The calculations of primary positron beam loss are done using the ELEGANT code. The secondary positron and electron beam loss, the synchrotron radiation along the beam line and the bremsstrahlung radiation in the collimators are simulated using the STRUCT code. The first part of the collimation system, located right after the positron source target (0.125 GeV), is used for protection of the RF Linac sections from heating and radiation. The second part of the system is used for final collimation before the beam injection into the Damping Ring at 5 GeV. The calculated power loss in the collimation region is within 100 W/m, with the loss in the collimators of 0.2-5 kW. The beam transfer efficiency from the target to the Damping Ring is 13.5%.

  18. Mechanical approach to the neutrons spectra collimation and detection

    Energy Technology Data Exchange (ETDEWEB)

    Sadeghi, H.; Roshan, M. V. [Energy Engineering and Physics Department, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

    2014-11-15

    Neutrons spectra from most of known sources require being collimated for numerous applications; among them one is the Neutron Activation Analysis. High energy neutrons are collimated through a mechanical procedure as one of the most promising methods. The output energy of the neutron beam depends on the velocity of the rotating Polyethylene disks. The collimated neutrons are then measured by an innovative detection technique with high accuracy.

  19. SU-F-BRB-12: A Novel Haar Wavelet Based Approach to Deliver Non-Coplanar Intensity Modulated Radiotherapy Using Sparse Orthogonal Collimators

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, D; Ruan, D; Low, D; Sheng, K [Deparment of Radiation Oncology, University of California Los Angeles, Los Angeles, CA (United States); O’Connor, D [Deparment of Mathematics, University of California Los Angeles, Los Angeles, CA (United States); Boucher, S [RadiaBeam Technologies, Santa Monica, CA (United States)

    2015-06-15

    Purpose: Existing efforts to replace complex multileaf collimator (MLC) by simple jaws for intensity modulated radiation therapy (IMRT) resulted in unacceptable compromise in plan quality and delivery efficiency. We introduce a novel fluence map segmentation method based on compressed sensing for plan delivery using a simplified sparse orthogonal collimator (SOC) on the 4π non-coplanar radiotherapy platform. Methods: 4π plans with varying prescription doses were first created by automatically selecting and optimizing 20 non-coplanar beams for 2 GBM, 2 head & neck, and 2 lung patients. To create deliverable 4π plans using SOC, which are two pairs of orthogonal collimators with 1 to 4 leaves in each collimator bank, a Haar Fluence Optimization (HFO) method was used to regulate the number of Haar wavelet coefficients while maximizing the dose fidelity to the ideal prescription. The plans were directly stratified utilizing the optimized Haar wavelet rectangular basis. A matching number of deliverable segments were stratified for the MLC-based plans. Results: Compared to the MLC-based 4π plans, the SOC-based 4π plans increased the average PTV dose homogeneity from 0.811 to 0.913. PTV D98 and D99 were improved by 3.53% and 5.60% of the corresponding prescription doses. The average mean and maximal OAR doses slightly increased by 0.57% and 2.57% of the prescription doses. The average number of segments ranged between 5 and 30 per beam. The collimator travel time to create the segments decreased with increasing leaf numbers in the SOC. The two and four leaf designs were 1.71 and 1.93 times more efficient, on average, than the single leaf design. Conclusion: The innovative dose domain optimization based on compressed sensing enables uncompromised 4π non-coplanar IMRT dose delivery using simple rectangular segments that are deliverable using a sparse orthogonal collimator, which only requires 8 to 16 leaves yet is unlimited in modulation resolution. This work is

  20. Optimization of convergent collimators for pixelated SPECT systems

    International Nuclear Information System (INIS)

    Capote, Ricardo M.; Matela, Nuno; Conceição, Raquel C.; Almeida, Pedro

    2013-01-01

    Purpose: The optimization of the collimator design is essential to obtain the best possible sensitivity in single photon emission computed tomography imaging. The aim of this work is to present a methodology for maximizing the sensitivity of convergent collimators, specifically designed to match the pitch of pixelated detectors, for a fixed spatial resolution value and to present some initial results using this approach. Methods: Given the matched constraint, the optimal collimator design cannot be simply found by allowing the highest level of septal penetration and spatial resolution consistent with the imposed restrictions, as it is done for the optimization of conventional collimators. Therefore, an algorithm that interactively calculates the collimator dimensions, with the maximum sensitivity, which respect the imposed restrictions was developed and used to optimize cone and fan beam collimators with tapered square-shaped holes for low (60–300 keV) and high energy radiation (300–511 keV). The optimal collimator dimensions were locally calculated based on the premise that each hole and septa of the convergent collimator should locally resemble an appropriate optimal matched parallel collimator. Results: The optimal collimator dimensions, calculated for subcentimeter resolutions (3 and 7.5 mm), common pixel sizes (1.6, 2.1, and 2.5 mm), and acceptable septal penetration at 140 keV, were approximately constant throughout the collimator, despite their different hole incidence angles. By using these input parameters and a less strict septal penetration value of 5%, the optimal collimator dimensions and the corresponding mass per detector area were calculated for 511 keV. It is shown that a low value of focal distance leads to improvements in the average sensitivity at a fixed source-collimator distance and resolution. The optimal cone beam performance outperformed that of other optimal collimation geometries (fan and parallel beam) in imaging objects close to

  1. Tests of a silicon wafer based neutron collimator

    International Nuclear Information System (INIS)

    Cussen, L.D.; Vale, C.J.; Anderson, I.S.; Hoeghoj, P.

    2001-01-01

    A Soller slit neutron collimator has been prepared by stacking 160 μm thick single crystal silicon wafers coated on one surface with 4 μm of gadolinium metal. The collimator has an angular width of 20 min full width at half maximum and an effective length of 2.75 cm. The collimator has beam dimensions of 1 cm wide by 5.3 cm high. Tests at neutron wavelengths 7.5A and 1.8A showed a peak transmission of 88% within 2% of the optimum theoretical possibility. The background suppression in the wings is comparable with that of conventional neutron collimators

  2. Tests of a silicon wafer based neutron collimator

    CERN Document Server

    Cussen, L D; Anderson, I S; Hoeghoj, P

    2001-01-01

    A Soller slit neutron collimator has been prepared by stacking 160 mu m thick single crystal silicon wafers coated on one surface with 4 mu m of gadolinium metal. The collimator has an angular width of 20 min full width at half maximum and an effective length of 2.75 cm. The collimator has beam dimensions of 1 cm wide by 5.3 cm high. Tests at neutron wavelengths 7.5A and 1.8A showed a peak transmission of 88% within 2% of the optimum theoretical possibility. The background suppression in the wings is comparable with that of conventional neutron collimators.

  3. Computation of the efficiency distribution of a multichannel focusing collimator

    International Nuclear Information System (INIS)

    Balasubramanian, A.; Venkateswaran, T.V.

    1977-01-01

    This article describes two computer methods of calculating the point source efficiency distribution functions of a focusing collimator with round tapered holes. The first method which computes only the geometric efficiency distribution is adequate for low energy collimators while the second method which computes both geometric and penetration efficiencies can be made use of for medium and high energy collimators. The scatter contribution to the efficiency is not taken into account. In the first method the efficiency distribution of a single cone of the collimator is obtained and the data are used for computing the distribution of the whole collimator. For high energy collimator the entire detector region is imagined to be divided into elemental areas. Efficiency of the elemental area is computed after suitably weighting for the penetration within the collimator septa, which is determined by three dimensional geometric techniques. The method of computing the line source efficiency distribution from point source distribution is also explained. The formulations have been tested by computing the efficiency distribution of several commercial collimators and collimators fabricated by us. (Auth.)

  4. A parabolic mirror x-ray collimator

    Science.gov (United States)

    Franks, A.; Jackson, K.; Yacoot, A.

    2000-05-01

    A robust and stable x-ray collimator has been developed to produce a parallel beam of x-rays by total external reflection from a parabolic mirror. The width of the gold-coated silica mirror varies along its length, which allows it to be bent from a plane surface into a parabolic form by application of unequal bending forces at its ends. A family of parabolas of near constant focal length can be formed by changing the screw-applied bending force, thus allowing the collimator to cater for a range of wavelengths by the turning of a screw. Even with radiation with a wavelength as short as that as Mo Kicons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/> 1 (icons/Journals/Common/lambda" ALT="lambda" ALIGN="TOP"/> = 0.07 nm), a gain in flux by a factor of 5.5 was achieved. The potential gain increases with wavelength, e.g. for Cu Kicons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/> 1 radiation this amounts to over a factor of ten.

  5. A variable-collimation display system

    Science.gov (United States)

    Batchko, Robert; Robinson, Sam; Schmidt, Jack; Graniela, Benito

    2014-03-01

    Two important human depth cues are accommodation and vergence. Normally, the eyes accommodate and converge or diverge in tandem; changes in viewing distance cause the eyes to simultaneously adjust both focus and orientation. However, ambiguity between accommodation and vergence cues is a well-known limitation in many stereoscopic display technologies. This limitation also arises in state-of-the-art full-flight simulator displays. In current full-flight simulators, the out-the-window (OTW) display (i.e., the front cockpit window display) employs a fixed collimated display technology which allows the pilot and copilot to perceive the OTW training scene without angular errors or distortions; however, accommodation and vergence cues are limited to fixed ranges (e.g., ~ 20 m). While this approach works well for long-range, the ambiguity of depth cues at shorter range hinders the pilot's ability to gauge distances in critical maneuvers such as vertical take-off and landing (VTOL). This is the first in a series of papers on a novel, variable-collimation display (VCD) technology that is being developed under NAVY SBIR Topic N121-041 funding. The proposed VCD will integrate with rotary-wing and vertical take-off and landing simulators and provide accurate accommodation and vergence cues for distances ranging from approximately 3 m outside the chin window to ~ 20 m. A display that offers dynamic accommodation and vergence could improve pilot safety and training, and impact other applications presently limited by lack of these depth cues.

  6. Treatment planning systems for external whole brain radiation therapy: With and without MLC (multi leaf collimator) optimization

    Science.gov (United States)

    Budiyono, T.; Budi, W. S.; Hidayanto, E.

    2016-03-01

    Radiation therapy for brain malignancy is done by giving a dose of radiation to a whole volume of the brain (WBRT) followed by a booster at the primary tumor with more advanced techniques. Two external radiation fields given from the right and left side. Because the shape of the head, there will be an unavoidable hotspot radiation dose of greater than 107%. This study aims to optimize planning of radiation therapy using field in field multi-leaf collimator technique. A study of 15 WBRT samples with CT slices is done by adding some segments of radiation in each field of radiation and delivering appropriate dose weighting using a TPS precise plan Elekta R 2.15. Results showed that this optimization a more homogeneous radiation on CTV target volume, lower dose in healthy tissue, and reduced hotspots in CTV target volume. Comparison results of field in field multi segmented MLC technique with standard conventional technique for WBRT are: higher average minimum dose (77.25% ± 0:47%) vs (60% ± 3:35%); lower average maximum dose (110.27% ± 0.26%) vs (114.53% ± 1.56%); lower hotspot volume (5.71% vs 27.43%); and lower dose on eye lenses (right eye: 9.52% vs 18.20%); (left eye: 8.60% vs 16.53%).

  7. Treatment planning systems for external whole brain radiation therapy: With and without MLC (multi leaf collimator) optimization

    International Nuclear Information System (INIS)

    Budiyono, T; Budi, W S; Hidayanto, E

    2016-01-01

    Radiation therapy for brain malignancy is done by giving a dose of radiation to a whole volume of the brain (WBRT) followed by a booster at the primary tumor with more advanced techniques. Two external radiation fields given from the right and left side. Because the shape of the head, there will be an unavoidable hotspot radiation dose of greater than 107%. This study aims to optimize planning of radiation therapy using field in field multi-leaf collimator technique. A study of 15 WBRT samples with CT slices is done by adding some segments of radiation in each field of radiation and delivering appropriate dose weighting using a TPS precise plan Elekta R 2.15. Results showed that this optimization a more homogeneous radiation on CTV target volume, lower dose in healthy tissue, and reduced hotspots in CTV target volume. Comparison results of field in field multi segmented MLC technique with standard conventional technique for WBRT are: higher average minimum dose (77.25% ± 0:47%) vs (60% ± 3:35%); lower average maximum dose (110.27% ± 0.26%) vs (114.53% ± 1.56%); lower hotspot volume (5.71% vs 27.43%); and lower dose on eye lenses (right eye: 9.52% vs 18.20%); (left eye: 8.60% vs 16.53%). (paper)

  8. Collimator optimization studies for the new MIT epithermal neutron beam

    International Nuclear Information System (INIS)

    Riley, K.J.; Ali, S.J.; Harling, O.K.

    2000-01-01

    A patient collimator has been designed for the epithermal neutron facility now being commissioned at MIT. Collimator performance both in and out of field was evaluated using the Monte Carlo code MCNP. A two piece design that can accommodate different circular field sizes will be manufactured using a composite lead, epoxy, boron and lithium mixture. (author)

  9. Collimator performance evaluation by Monte-Carlo techniques

    International Nuclear Information System (INIS)

    Milanesi, L.; Bettinardi, V.; Bellotti, E.; Gilardi, M.C.; Todd-Pokropek, A.; Fazio, F.

    1985-01-01

    A computer program using Monte-Carlo techniques has been developed to simulate gamma camera collimator performance. Input data include hole length, septum thickness, hole size and shape, collimator material, source characteristics, source to collimator distance and medium, radiation energy, total events number. Agreement between Monte-Carlo simulations and experimental measurements was found for commercial hexagonal parallel hole collimators in terms of septal penetration, transfer function and sensitivity. The method was then used to rationalize collimator design for tomographic brain studies. A radius of ration of 15 cm was assumed. By keeping constant resolution at 15 cm (FWHM = 1.3.cm), SPECT response to a point source was obtained in scattering medium for three theoretical collimators. Sensitivity was maximized in the first collimator, uniformity of resolution response in the third, while the second represented a trade-off between the two. The high sensitivity design may be superior in the hot spot and/or low activity situation, while for distributed sources of high activity an uniform resolution response should be preferred. The method can be used to personalize collimator design to different clinical needs in SPECT

  10. Towards Optimum Material Choices for HL-LHC Collimator Upgrade

    CERN Document Server

    Quaranta, E.; Biancacci, N.; Bruce, R.; Carra, F.; Métral, E.; Redaelli, S.; Rossi, A.; Salvant, B.

    2016-01-01

    properties that address different limitations of the present collimation system, solutions have been found to fulfil various upgrade challenges. This paper describes the proposed staged approach to deploy new materials in the upgraded HL-LHC collimation system. Beam tests at the CERN HiRadMat facility were also performed to benchmark simulation methods and constitutive material models.

  11. Efficient Collimation and Machine Protection for the Compact Linear Collider

    CERN Document Server

    Assmann, R W

    2006-01-01

    We present a new approach to machine protection and collimation in CLIC, separating these two functions: If emergency dumps in the linac protect the downstream beam line against drive-beam failures, the energy collimation only needs to clean the beam tails and can be compact. Overall, the length of the beam-delivery system (BDS) is significantly reduced.

  12. Collimated trans-axial tomographic scintillation camera

    International Nuclear Information System (INIS)

    1980-01-01

    The objects of this invention are first to reduce the time required to obtain statistically significant data in trans-axial tomographic radioisotope scanning using a scintillation camera. Secondly, to provide a scintillation camera system to increase the rate of acceptance of radioactive events to contribute to the positional information obtainable from a known radiation source without sacrificing spatial resolution. Thirdly to reduce the scanning time without loss of image clarity. The system described comprises a scintillation camera detector, means for moving this in orbit about a cranial-caudal axis relative to a patient and a collimator having septa defining apertures such that gamma rays perpendicular to the axis are admitted with high spatial resolution, parallel to the axis with low resolution. The septa may be made of strips of lead. Detailed descriptions are given. (U.K.)

  13. Collimated trans-axial tomographic scintillation camera

    International Nuclear Information System (INIS)

    1980-01-01

    The principal problem in trans-axial tomographic radioisotope scanning is the length of time required to obtain meaningful data. Patient movement and radioisotope migration during the scanning period can cause distortion of the image. The object of this invention is to reduce the scanning time without degrading the images obtained. A system is described in which a scintillation camera detector is moved to an orbit about the cranial-caudal axis relative to the patient. A collimator is used in which lead septa are arranged so as to admit gamma rays travelling perpendicular to this axis with high spatial resolution and those travelling in the direction of the axis with low spatial resolution, thus increasing the rate of acceptance of radioactive events to contribute to the positional information obtainable without sacrificing spatial resolution. (author)

  14. Reflection jets and collimation of radio sources

    International Nuclear Information System (INIS)

    Pacholczyk, A.G.

    1983-01-01

    The author proposes a description of only a certain class of jets in extended radio sources by discussing hydrodynamics of jets formed by discrete portions of material ejected from the parent galaxy through a channel and reflected back into it as a result of an encounter with the material accumulated at the end of the channel. The picture presented here combines some older ideas with recent ones. The older ideas consist of modeling of extended radio sources in terms of multiple ejection of plasmons through a channel ploughed by the first few plasmons in the ambient medium with a resupply of energy in plasmons through the conversion of bulk kinetic energy into relativistic electron energy through instability driven turbulence. The recent ideas concern the formation of retro-jets as the result of interaction of a plasmon with the dense relic material at the end of a channel and the collimation of plasmon material in channels. (Auth.)

  15. Ion beam collimating grid to reduce added defects

    Science.gov (United States)

    Lindquist, Walter B.; Kearney, Patrick A.

    2003-01-01

    A collimating grid for an ion source located after the exit grid. The collimating grid collimates the ion beamlets and disallows beam spread and limits the beam divergence during transients and steady state operation. The additional exit or collimating grid prevents beam divergence during turn-on and turn-off and prevents ions from hitting the periphery of the target where there is re-deposited material or from missing the target and hitting the wall of the vessel where there is deposited material, thereby preventing defects from being deposited on a substrate to be coated. Thus, the addition of a collimating grid to an ion source ensures that the ion beam will hit and be confined to a specific target area.

  16. Beam diffusion measurements using collimator scans in the LHC

    Directory of Open Access Journals (Sweden)

    Gianluca Valentino

    2013-02-01

    Full Text Available The time evolution of beam losses during a collimator scan provides information on halo diffusion and population. This is an essential input for machine performance characterization and for the design of collimation systems. Beam halo measurements in the CERN Large Hadron Collider were conducted through collimator scrapings in a dedicated beam study for the first time at 4 TeV. Four scans were performed with two collimators, in the vertical plane for beam 1 and horizontally for beam 2, before and after bringing the beams into collisions. Inward and outward steps were performed. A diffusion model was used to interpret the observed loss rate evolution in response to the collimator steps. With this technique, diffusion coefficients were estimated as a function of betatron oscillation amplitude from approximately 3 to 7 standard deviations of the transverse beam distribution. A comparison of halo diffusion and core emittance growth rates is also presented.

  17. FINAL IMPLEMENTATION AND PERFORMANCE OF THE LHC COLLIMATOR CONTROL SYSTEM

    CERN Document Server

    Redaelli, S; Masi, A; Losito, R

    2009-01-01

    The 2008 collimation system of the CERN Large Hadron Collider (LHC) included 80 movable collimators for a total of 316 degrees of freedom. Before beam operation, the final controls implementation was deployed and commissioned. The control system enabled remote control and appropriate diagnostics of the relevant parameters. The collimator motion is driven with time-functions, synchronized with other accelerator systems, which allows controlling the collimator jaw positions with a micrometer accuracy during all machine phases. The machine protection functionality of the system, which also relies on function-based tolerance windows, was also fully validated. The collimator control challenges are reviewed and the final system architecture is presented. The results of the remote system commissioning and the overall performance are discussed.

  18. Trapped Mode Study in the LHC Rotatable Collimator

    CERN Document Server

    Xiao, L; Smith, J C; Caspers, F

    2010-01-01

    A rotatable collimator is proposed for the LHC phase II collimation upgrade. When the beam crosses the collimator, trapped modes will be excited that result in beam energy loss and collimator power dissipation. Some of the trapped modes can also generate transverse kick on the beam and affect the beam operation. In this paper the parallel eigensolver code Omega3P is used to search for all the trapped modes below 2GHz in the collimator, including longitudinal modes and transverse modes. The loss factors and kick factors of the trapped modes are calculated as function of the jaw positions. The amplitude ratio between transverse and longitudinal trapped mode intensity can be used as a direct measure of the position of the beam. We present simulation results and discuss the results.

  19. Micro-array collimators for X-rays and neutrons

    International Nuclear Information System (INIS)

    Cimmino, A.; Allman, B.E.; Klein, A.G.; Bastie, P.

    1998-08-01

    The authors describe the fabrication techniques of novel, compact optical elements for collimating and/or focusing beams of X-rays or thermal neutrons. These optical elements are solid composite arrays consisting of regular stacks of alternating micro-foils, analogous in action to Soller slit collimators, but up to three orders of magnitude smaller. The arrays are made of alternating metals with suitable refractive indices for reflection and/or absorption of the specific radiation. In one implementation, the arrays are made of stacked micro-foils of transmissive elements (Al, Cu) coated and/or electroplated with absorbing elements (Gd, Cd), which are repeatedly rolled or drawn and restacked to achieve the required collimation parameters. The authors present results of these collimators using both X-rays and neutrons. The performance of the collimating element is limited only by the choice of micro-foil materials and the uniformity of their interfaces

  20. Analysis appliance by gamma tomography with focused collimators

    International Nuclear Information System (INIS)

    Stoddart, H.F.

    1978-01-01

    This invention concerns nuclear medicine and specifically an image-forming appliance providing a very sensitive quantitative determination and the localization in space of the radioactivity of a body organ such as the brain of a patient to whom a substance labelled with radioactive isotopes has been administered. The characteristics of this appliance, which forms an image in a transversal scanning field by means of radioactive isotope radiations, includes several highly focused collimators, placed in line and focused inwards so that they form an arrangement that surrounds a given scanning field. Each collimator is mobile with respect to the adjacent collimator and a system moves the collimators so that the focus of each one uniformly samples at least a half of the total scanning field corresponding to a cross section. The number of detectors is an even one between two and twenty four, and the collimators are twelve in number [fr

  1. Beam diffusion measurements using collimator scans in the LHC

    CERN Document Server

    Valentino, Gianluca; Bruce, Roderik; Burkart, Florian; Previtali, Valentina; Redaelli, Stefano; Salvachua, Belen; Stancari, Giuliov; Valishev, Alexander

    2013-01-01

    The time evolution of beam losses during a collimator scan provides information on halo diffusion and population. This is an essential input for machine performance characterization and for the design of collimation systems. Beam halo measurements in the CERN Large Hadron Collider were conducted through collimator scrapings in a dedicated beam study for the first time at 4 TeV. Four scans were performed with two collimators, in the vertical plane for beam 1 and horizontally for beam 2, before and after bringing the beams into collisions. Inward and outward steps were performed. A diffusion model was used to interpret the observed loss rate evolution in response to the collimator steps. With this technique, diffusion coefficients were estimated as a function of betatron oscillation amplitude from approximately 3 to 7 standard deviations of the transverse beam distribution. A comparison of halo diffusion and core emittance growth rates is also presented.

  2. Optimization of Collimator Jaw Locations for the LHC

    CERN Document Server

    Kaltchev, D I; Servranckx, R V; Jeanneret, J B

    1996-01-01

    A highly effective collimation scheme is required in the LHC to limit heating of the vacuum chamber and superconducting magnets by protons either uncaptured at injection or scattered from the collision points. The proposed system would consist of one set of primary collimators followed by three sets of secondary collimators downstream to clean up protons scattered from the primaries. Each set of collimators would consist of four pairs of jaws - horizontal, vertical, and 45 o and 135 o skew. A study is reported of the optimization of the longitudinal positions of these jaws with the aim of minimizing the maximum betatron amplitudes of protons surviving the collimation system. This is performed using an analytical representation of the action of the jaws and is confirmed by tracking. Significant improvement can be obtained by omitting inactive jaws and adding skew jaws.

  3. Decreasing the LHC impedance with a nonlinear collimation system

    CERN Document Server

    Resta-López, J; Zimmermann, F

    2007-01-01

    A two-stage nonlinear collimation system based on a pair of skew sextupoles is presented for the LHC.We show the details of the optics design and study the halo cleaning efficiency of such a system. This nonlinear collimation system would allow opening up collimator gaps, and thereby reduce the collimator impedance, which presently limits the LHC beam intensity. Assuming the nominal LHC beam at 7 TeV, the transverse coherent tune shifts of rigid-dipole coupled-bunch modes are computed for both the baseline linear collimation system and the proposed nonlinear one. In either case, the tune shifts of the most unstable modes are compared with the stability diagrams for Landau damping.

  4. Multipinhole collimator with 20 apertures for a brain SPECT application

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tzu-Cheng; Ellin, Justin R.; Shrestha, Uttam; Seo, Youngho, E-mail: youngho.seo@ucsf.edu [Physics Research Laboratory, Department of Radiology and Biomedical Imaging, University of California, San Francisco, California 94107 (United States); Huang, Qiu [School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China); Gullberg, Grant T. [Department of Radiotracer Development and Imaging Technology, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94702 (United States)

    2014-11-01

    Purpose: Several new technologies for single photon emission computed tomography (SPECT) instrumentation with parallel-hole collimation have been proposed to improve detector sensitivity and signal collection efficiency. Benefits from improved signal efficiency include shorter acquisition times and lower dose requirements. In this paper, the authors show a possibility of over an order of magnitude enhancement in photon detection efficiency (from 7.6 × 10{sup −5} to 1.6 × 10{sup −3}) for dopamine transporter (DaT) imaging of the striatum over the conventional SPECT parallel-hole collimators by use of custom-designed 20 multipinhole (20-MPH) collimators with apertures of 0.75 cm diameter. Methods: Quantifying specific binding ratio (SBR) of {sup 123}I-ioflupane or {sup 123}I-iometopane’s signal at the striatal region is a common brain imaging method to confirm the diagnosis of the Parkinson’s disease. The authors performed imaging of a striatal phantom filled with aqueous solution of I-123 and compared camera recovery ratios of SBR acquired between low-energy high-resolution (LEHR) parallel-hole collimators and 20-MPH collimators. Results: With only two-thirds of total acquisition time (20 min against 30 min), a comparable camera recovery ratio of SBR was achieved using 20-MPH collimators in comparison to that from the LEHR collimator study. Conclusions: Their systematic analyses showed that the 20-MPH collimator could be a promising alternative for the DaT SPECT imaging for brain over the traditional LEHR collimator, which could give both shorter scan time and improved diagnostic accuracy.

  5. Collimator Layouts for HL-LHC in the Experimental Insertions

    CERN Document Server

    Bruce, R; Esposito, Luigi Salvatore; Jowett, John; Lechner, Anton; Quaranta, Elena; Redaelli, Stefano; Schaumann, Michaela; Skordis, Eleftherios; Eleanor Steele, G; Garcia Morales, H; Kwee-Hinzmann, Regina

    2015-01-01

    This paper presents the layout of collimators for HL-LHC in the experimental insertions. On the incoming beam, we propose to install additional tertiary collimators to protect potential new aperture bottlenecks in cells 4 and 5, which in addition reduce the experimental background. For the outgoing beam, the layout of the present LHC with three physics debris absorbers gives sufficient protection for highluminosity proton operation. However, collisional processes for heavy ions cause localized beam losses with the potential to quench magnets. To alleviate these losses, an installation of dispersion suppressor collimators is proposed.

  6. Characterization of plastic and boron carbide additive manufactured neutron collimators

    Science.gov (United States)

    Stone, M. B.; Siddel, D. H.; Elliott, A. M.; Anderson, D.; Abernathy, D. L.

    2017-12-01

    Additive manufacturing techniques allow for the production of materials with complicated geometries with reduced costs and production time over traditional methods. We have applied this technique to the production of neutron collimators for use in thermal and cold neutron scattering instrumentation directly out of boron carbide. We discuss the design and generation of these collimators. We also provide measurements at neutron scattering beamlines which serve to characterize the performance of these collimators. Additive manufacturing of parts using neutron absorbing material may also find applications in radiography and neutron moderation.

  7. Development of hollow electron beams for proton and ion collimation

    CERN Document Server

    Stancari, G; Kuznetsov, G; Shiltsev, V; Still, D A; Valishev, A; Vorobiev, L G; Assmann, R; Kabantsev, A

    2012-01-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams.

  8. Development of hollow electron beams for proton and ion collimation

    CERN Document Server

    Stancari, G.; Kuznetsov, G.; Shiltsev, V.; Still, D.A.; Valishev, A.; Vorobiev, L.G.; Assmann, R.; Kabantsev, A.

    2010-01-01

    Magnetically confined hollow electron beams for controlled halo removal in high-energy colliders such as the Tevatron or the LHC may extend traditional collimation systems beyond the intensity limits imposed by tolerable material damage. They may also improve collimation performance by suppressing loss spikes due to beam jitter and by increasing capture efficiency. A hollow electron gun was designed and built. Its performance and stability were measured at the Fermilab test stand. The gun will be installed in one of the existing Tevatron electron lenses for preliminary tests of the hollow-beam collimator concept, addressing critical issues such as alignment and instabilities of the overlapping proton and electron beams

  9. Compton backscattered collimated x-ray source

    Science.gov (United States)

    Ruth, R.D.; Huang, Z.

    1998-10-20

    A high-intensity, inexpensive and collimated x-ray source is disclosed for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications. 4 figs.

  10. Reduction of the secondary neutron dose in passively scattered proton radiotherapy, using an optimized pre-collimator/collimator

    International Nuclear Information System (INIS)

    Brenner, David J; Elliston, Carl D; Hall, Eric J; Paganetti, Harald

    2009-01-01

    Proton radiotherapy represents a potential major advance in cancer therapy. Most current proton beams are spread out to cover the tumor using passive scattering and collimation, resulting in an extra whole-body high-energy neutron dose, primarily from proton interactions with the final collimator. There is considerable uncertainty as to the carcinogenic potential of low doses of high-energy neutrons, and thus we investigate whether this neutron dose can be significantly reduced without major modifications to passively scattered proton beam lines. Our goal is to optimize the design features of a patient-specific collimator or pre-collimator/collimator assembly. There are a number of often contradictory design features, in terms of geometry and material, involved in an optimal design. For example, plastic or hybrid plastic/metal collimators have a number of advantages. We quantify these design issues, and investigate the practical balances that can be achieved to significantly reduce the neutron dose without major alterations to the beamline design or function. Given that the majority of proton therapy treatments, at least for the next few years, will use passive scattering techniques, reducing the associated neutron-related risks by simple modifications of the collimator assembly design is a desirable goal.

  11. Mechanical Design for Robustness of the LHC Collimators

    CERN Document Server

    Bertarelli, Alessandro; Assmann, R W; Calatroni, Sergio; Dallocchio, Alessandro; Kurtyka, Tadeusz; Mayer, Manfred; Perret, Roger; Redaelli, Stefano; Robert-Demolaize, Guillaume

    2005-01-01

    The functional specification of the LHC Collimators requires, for the start-up of the machine and the initial luminosity runs (Phase 1), a collimation system with maximum robustness against abnormal beam operating conditions. The most severe cases to be considered in the mechanical design are the asynchronous beam dump at 7 TeV and the 450 GeV injection error. To ensure that the collimator jaws survive such accident scenarios, low-Z materials were chosen, driving the design towards Graphite or Carbon/Carbon composites. Furthermore, in-depth thermo-mechanical simulations, both static and dynamic, were necessary.This paper presents the results of the numerical analyses performed for the 450 GeV accident case, along with the experimental results of the tests conducted on a collimator prototype in Cern TT40 transfer line, impacted by a 450 GeV beam of 3.1·1013

  12. Collimator fast failure losses for various HL-LHC configurations

    CERN Document Server

    Lari, L; Redaelli, S

    2014-01-01

    The upgrade of the Large Hadron Collider (LHC), in terms of beam intensity and energy, implies an increasing risk of severe damage in particular in case of beam losses during fast failures. For this reason, efforts were put in developing simulation tools to allow studies of asynchronous dump accidents, including realistic additional failure scenarios. The scope of these studies is to understand realistic beam loads in different collimators, in order to improve the actual LHC collimation system design, to provide feedbacks on optics design and to elaborate different mitigation actions. Simulations were set up with a modified SixTrack collimation routine able to simulate erroneous firing of a single dump kicker or the simultaneous malfunction of all the 15 kickers. In such a context, results are evaluated from the whole LHC collimation system point of view.

  13. Beam Loss and Beam Shape at the LHC Collimators

    CERN Document Server

    Burkart, Florian

    In this master thesis the beam loss and the beam shape at the LHC collimators was measured, analysed, presented and discussed. Beginning with a short introduction of the LHC, the experiments, the supercon- ducting magnet system, the basics on linear beam dynamics and a describtion of the LHC collimation system are given. This is followed by the presentation of the performance of the LHC collimation sys- tem during 2011. A method to convert the Beam Loss Monitor signal in Gy/s to a proton beam loss rate will be introduced. Also the beam lifetime during the proton physics runs in 2011 will be presented and discussed. Finally, the shape of the LHC beams is analysed by using data obtained by scraping the beam at the LHC primary collimators.

  14. The LHC Collimator Controls Architecture - Design and beam tests

    CERN Document Server

    Redaelli, S; Gander, P; Jonker, M; Lamont, M; Losito, R; Masi, A; Sobczak, M

    2007-01-01

    The LHC collimation system will require simultaneous management by the LHC control system of more than 500 jaw positioning mechanisms in order to ensure the required beam cleaning and machine protection performance in all machine phases, from injection at 450 GeV to collision at 7 TeV. Each jaw positionis a critical parameter for the machine safety. In this paper, the architecture of the LHC collimator controls is presented. The basic design to face the accurate control of the LHC collimators and the interfaces to the other components of LHC Software Application and control infrastructures are described. The full controls system has been tested in a real accelerator environment in the CERN SPS during beam tests with a full scale collimator prototype. The results and the lessons learned are presented.

  15. Collimation issues for the PEP-II B-factory

    International Nuclear Information System (INIS)

    Sullivan, M.

    1997-12-01

    This note describes how beam collimation affects detector backgrounds at the collision point for the PEP-II B-factory, a joint effort of three laboratories: LBNL, LLNL, and SLAC. Beam collimation controls the transverse size as well as the maximum allowed energy spread of the beam. The location of synchrotron radiation masks is determined by the transverse size of the beam in that the masks must prevent radiation generated by beam particles located at large transverse beam positions from directly striking the detector beam pipe. Collimation of the energy spread of the beam is important in the control of backgrounds produced by beam particles that strike a gas molecule (lost beam particles). The author describes some preliminary information from background studies during the first months of commissioning the high energy ring of the PEP-II B-factory and present some model predictions for synchrotron radiation backgrounds when collimators are not present

  16. Magnetized and collimated millimeter scale plasma jets with astrophysical relevance

    International Nuclear Information System (INIS)

    Brady, Parrish C.; Quevedo, Hernan J.; Valanju, Prashant M.; Bengtson, Roger D.; Ditmire, Todd

    2012-01-01

    Magnetized collimated plasma jets are created in the laboratory to extend our understanding of plasma jet acceleration and collimation mechanisms with particular connection to astrophysical jets. In this study, plasma collimated jets are formed from supersonic unmagnetized flows, mimicking a stellar wind, subject to currents and magnetohydrodynamic forces. It is found that an external poloidal magnetic field, like the ones found anchored to accretion disks, is essential to stabilize the jets against current-driven instabilities. The maximum jet length before instabilities develop is proportional to the field strength and the length threshold agrees well with Kruskal-Shafranov theory. The plasma evolution is modeled qualitatively using MHD theory of current-carrying flux tubes showing that jet acceleration and collimation arise as a result of electromagnetic forces.

  17. Beam Loss Patterns at the LHC Collimators Measurements & Simulations

    CERN Document Server

    Böhlen, Till Tobias

    2008-01-01

    The Beam Loss Monitoring (BLM) system of the Large Hadron Collider (LHC) detects particle losses of circulating beams and initiates an emergency extraction of the beam in case that the BLM thresholds are exceeded. This protection is required as energy deposition in the accelerator equipment due to secondary shower particles can reach critical levels; causing damage to the beam-line components and quenches of superconducting magnets. Robust and movable beam line elements, so-called collimators, are the aperture limitations of the LHC. Consequently, they are exposed to the excess of lost beam particles and their showers. Proton loss patterns at LHC collimators have to be determined to interpret the signal of the BLM detectors and to set adequate BLM thresholds for the protection of collimators and other equipment in case of unacceptably increased loss rates. The first part of this work investigates the agreement of BLM detector measurements with simulations for an LHC-like collimation setup. The setup consists ...

  18. LHC collimator controls for a safe LHC operation

    International Nuclear Information System (INIS)

    Redaelli, S.; Assmann, R.; Losito, R.; Donze, M.; Masi, A.

    2012-01-01

    The Large Hadron Collider (LHC) collimation system is designed to protect the machine against beam losses and consists of 108 collimators, 100 of which are movable, located along the 27 km long ring and in the transfer lines. The cleaning performance and machine protection role of the system depend critically on accurate jaw positioning. A fully redundant control system has been developed to ensure that the collimators dynamically follow optimum settings in all phases of the LHC operational cycle. Jaw positions and collimator gaps are interlocked against dump limits defined redundantly as functions of time, beam energy and the β functions, which describe the focusing property of the beams. In this paper, the architectural choices that guarantee a safe LHC operation are presented. Hardware and software implementations that ensure the required performance are described. (authors)

  19. Errors generated with the use of rectangular collimation

    International Nuclear Information System (INIS)

    Parks, E.T.

    1991-01-01

    This study was designed to determine whether various techniques for achieving rectangular collimation generate different numbers and types of errors and remakes and to determine whether operator skill level influences errors and remakes. Eighteen students exposed full-mouth series of radiographs on manikins with the use of six techniques. The students were grouped according to skill level. The radiographs were evaluated for errors and remakes resulting from errors in the following categories: cone cutting, vertical angulation, and film placement. Significant differences were found among the techniques in cone cutting errors and remakes, vertical angulation errors and remakes, and total errors and remakes. Operator skill did not appear to influence the number or types of errors or remakes generated. Rectangular collimation techniques produced more errors than did the round collimation techniques. However, only one rectangular collimation technique generated significantly more remakes than the other techniques

  20. Applications of slant collimators to cardiovascular nuclear medicine

    International Nuclear Information System (INIS)

    Nishimura, Tsunehiko; Uehara, Toshio; Hayashi, Makoto; Kagawa, Masaaki; Kozuka, Takahiro

    1980-01-01

    The RI examination of hearts is attracting increasingly interest as cardiovascular nuclear medicine in recent years. As for the background, there are the development of such radioactive agents with high heart-muscle specificity as 201 TICI and the minicomputer capability of measuring rapid contraction and expansion of hearts. Under the situation, the variety of contrivance in collimators is attempted for higher accuracy in grasping the form and function of hearts. With a 30 deg inclination slant type collimator (made by EDC firm) which became available, its applications as cardiovascular nuclear medicine have been examined in heart-muscle scintigraphy and heart RI angiography. These results are described. In the above connection, a bifocal collimator and a seven pinhole collimator are also explained briefly. (J.P.N.)

  1. COLLIMATORS AND MATERIALS FOR HIGH INTENSITY HEAVY ION SYNCHROTRONS

    CERN Document Server

    Stadlmann, J; Kollmus, H; Spiller, P; Strasik, I; Tahir, N A; Tomut, M; Trautmann, C

    2012-01-01

    The operation of high power high brightness accelerators requires huge efforts for beam cleaning and machine protection. Within the WP 8 (ColMat) of the EU research framework EuCARD[1] we investigate new materials and methods for beam collimation and machine protection. We present an overview of these activities at the GSI Helmholtzzentrum f¨ur Schwerionenforschung, Darmstadt. Simulations of accidental beam losses in LHC and SIS100 have been performed. Scenarios for halo collimation of heavy ions and protons in SIS100 routine operation have been investigated. A prototype of a cryogenic collimator for charge exchange losses during intermediate charge state heavy ion operation in SIS100 has been build and tested with beam. Several candidates of advanced composite materials for collimation system upgrades of present and future high power accelerators have been irradiated and their properties are being characterized. Most deliverables and milestones of the R&D programme were already reached before the end of...

  2. Collimation of particle beams from thick accretion discs

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, M [N. Copernicus Astronomical Center, Warszawa (Poland); Wilson, D B [Cambridge Univ. (UK). Inst. of Astronomy

    1981-11-01

    The acceleration and collimation of particle beams in the funnel of thick accretion discs is studied in the approximation that the flow is optically thin. Such flows can be collimated to within approximately 0.1 radians by sufficiently thick discs. The flow cannot convert more than a small fraction of the disc's (super-Eddington) luminosity into the energy flow of a narrow beam without being optically thick.

  3. Imaging electron flow from collimating contacts in graphene

    Science.gov (United States)

    Bhandari, S.; Lee, G. H.; Watanabe, K.; Taniguchi, T.; Kim, P.; Westervelt, R. M.

    2018-04-01

    The ballistic motion of electrons in graphene opens exciting opportunities for electron-optic devices based on collimated electron beams. We form a collimating contact in a hBN-encapsulated graphene hall bar by adding zigzag contacts on either side of an electron emitter that absorb stray electrons; collimation can be turned off by floating the zig-zag contacts. The electron beam is imaged using a liquid-He cooled scanning gate microscope (SGM). The tip deflects electrons as they pass from the collimating contact to a receiving contact on the opposite side of the channel, and an image of electron flow can be made by displaying the change in transmission as the tip is raster scanned across the sample. The angular half width Δθ of the electron beam is found by applying a perpendicular magnetic field B that bends electron paths into cyclotron orbits. The images reveal that the electron flow from the collimating contact drops quickly at B  =  0.05 T when the electron orbits miss the receiving contact. The flow for the non-collimating case persists longer, up to B  =  0.19 T, due to the broader range of entry angles. Ray-tracing simulations agree well with the experimental images. By fitting the fields B at which the magnitude of electron flow drops in the experimental SGM images, we find Δθ  =  9° for electron flow from the collimating contact, compared with Δθ  =  54° for the non-collimating case.

  4. Mini-beam collimator applications at the Advanced Photon Source

    Energy Technology Data Exchange (ETDEWEB)

    Xu Shenglan, E-mail: sxu@anl.gov [GM/CA CAT, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Keefe, Lisa J.; Mulichak, Anne [IMCA CAT, Argonne National Laboratory, Argonne, IL 60439 (United States); Yan Lifen; Alp, Ercan E.; Zhao Jiyong [X-ray Sciences Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Fischetti, Robert F. [GM/CA CAT, Biosciences Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2011-09-01

    In 2007, the General Medicine and Cancer Institutes Collaborative Access Team (GM/CA CAT, Sector 23, Advanced Photon Source) began providing mini-beam collimators to its users. These collimators contained individual, 5- or 10-{mu}m pinholes and were rapidly exchangeable, thereby allowing users to tailor the beam size to their experimental needs. The use of these collimators provided a reduction in background noise, and thus improved the signal-to-noise ratio . Recent improvements in the collimator design include construction of the device from a monolithic piece of molybdenum with multiple pinholes mounted inside . This allows users to select from various size options from within the beamline control software without the realignment that was previously necessary. In addition, a new, 20-{mu}m pinhole has been added to create a 'quad-collimator', resulting in greater flexibility for the users. The mini-beam collimator is now available at multiple crystallographic beamlines and also is a part of the first Moessbauer Microscopic system at sector 3-ID.

  5. Mini-beam collimator applications at the Advanced Photon Source

    International Nuclear Information System (INIS)

    Xu Shenglan; Keefe, Lisa J.; Mulichak, Anne; Yan Lifen; Alp, Ercan E.; Zhao Jiyong; Fischetti, Robert F.

    2011-01-01

    In 2007, the General Medicine and Cancer Institutes Collaborative Access Team (GM/CA CAT, Sector 23, Advanced Photon Source) began providing mini-beam collimators to its users. These collimators contained individual, 5- or 10-μm pinholes and were rapidly exchangeable, thereby allowing users to tailor the beam size to their experimental needs. The use of these collimators provided a reduction in background noise, and thus improved the signal-to-noise ratio . Recent improvements in the collimator design include construction of the device from a monolithic piece of molybdenum with multiple pinholes mounted inside . This allows users to select from various size options from within the beamline control software without the realignment that was previously necessary. In addition, a new, 20-μm pinhole has been added to create a 'quad-collimator', resulting in greater flexibility for the users. The mini-beam collimator is now available at multiple crystallographic beamlines and also is a part of the first Moessbauer Microscopic system at sector 3-ID.

  6. Development and deployment of the Collimated Directional Radiation Detection System

    Science.gov (United States)

    Guckes, Amber L.; Barzilov, Alexander

    2017-09-01

    The Collimated Directional Radiation Detection System (CDRDS) is capable of imaging radioactive sources in two dimensions (as a directional detector). The detection medium of the CDRDS is a single Cs2LiYCl6:Ce3+ scintillator cell enriched in 7Li (CLYC-7). The CLYC-7 is surrounded by a heterogeneous high-density polyethylene (HDPE) and lead (Pb) collimator. These materials make-up a coded aperture inlaid in the collimator. The collimator is rotated 360° by a stepper motor which enables time-encoded imaging of a radioactive source. The CDRDS is capable of spectroscopy and pulse shape discrimination (PSD) of photons and fast neutrons. The measurements of a radioactive source are carried out in discrete time steps that correlate to the angular rotation of the collimator. The measurement results are processed using a maximum likelihood expectation (MLEM) algorithm to create an image of the measured radiation. This collimator design allows for the directional detection of photons and fast neutrons simultaneously by utilizing only one CLYC-7 scintillator. Directional detection of thermal neutrons can also be performed by utilizing another suitable scintillator. Moreover, the CDRDS is portable, robust, and user friendly. This unit is capable of utilizing wireless data transfer for possible radiation mapping and network-centric applications. The CDRDS was tested by performing laboratory measurements with various gamma-ray and neutron sources.

  7. Optimization of detector size and collimator for PG-SPECT

    International Nuclear Information System (INIS)

    Ishikawa, M.; Kobayashi, T.; Kanda, K.

    2000-01-01

    A current absorbed dose evaluation method in a Boron Neutron Capture Therapy demands boron reaction rate from a boron concentration of an affected part supposed from a neutron flux and a boron concentration in blood measured by an activation method of a gold wire indirectly and converts it into an absorbed dose. So we devised a PG-SEPCT (Prompt Gamma-ray Single Photon Emission Computed Tomography) system to evaluate an absorbed dose directly by measuring prompt gamma-rays. Ordinary SPECT system uses a big NaI scintillator for detector so that measurement is done in low background gamma-ray environment. However, a conventional detector and collimator system cannot be just applied to PG-SPECT system because a background radiation coexists abundantly (PG-SPECT system is set in irradiation room). Accordingly PG-SPECT system requires a dedicated detector and collimator system. In order to reduce efficiency for background gamma-rays, we arranged detectors in a collimator to shield from background gamma-rays. We examined the most suitable collimator shape. The optimization condition of a dedicated collimator system is as follows: 1) the smallest particle size that can be distinguished is 1 cm. 2) necessary counts at measurement target center is not less than 10,000. (author)

  8. Tissue compensation using dynamic collimation on a linear accelerator

    International Nuclear Information System (INIS)

    Gaballa, Hani E.; Mitev, George; Zwicker, Robert D.; Ting, Joseph Y.; Tercilla, Oscar F.

    1995-01-01

    Purpose: The availability of computer-controlled collimators on some accelerators has led to techniques for dynamic beam modification, mainly to simulate beam wedge filters. This work addresses the practical aspects of dynamic tissue compensation in one dimension using available treatment-planning software. Methods and Materials: Data derived from the treatment-planning program is used with an iterative calculational routine to determine the monitor unit settings needed for the collimator-controlling computer. The method was first tested by simulating a 60 deg. physical wedge. Further studies were carried out on a specially fabricated plastic phantom that modeled the sagittal contour of the upper torso, neck, and lower head regions. Results: Dynamic wedge point doses generated by the planning program agreed within 1% with the values directly measured in a polystyrene phantom. In the patient phantom, dynamic collimation achieved calculated dose uniformity within 0.5% in a reference plane near the phantom midline. A comparison of computer-generated and measured point doses in this case showed agreement within 3%. Conclusions: Dynamic collimation can provide effective compensation for contours that vary primarily along one direction. A conventional treatment-planning program can be used to plan dynamic collimation and deliver a prescribed dose with reliable accuracy

  9. Optimization of planar self-collimating photonic crystals.

    Science.gov (United States)

    Rumpf, Raymond C; Pazos, Javier J

    2013-07-01

    Self-collimation in photonic crystals has received a lot of attention in the literature, partly due to recent interest in silicon photonics, yet no performance metrics have been proposed. This paper proposes a figure of merit (FOM) for self-collimation and outlines a methodical approach for calculating it. Performance metrics include bandwidth, angular acceptance, strength, and an overall FOM. Two key contributions of this work include the performance metrics and identifying that the optimum frequency for self-collimation is not at the inflection point. The FOM is used to optimize a planar photonic crystal composed of a square array of cylinders. Conclusions are drawn about how the refractive indices and fill fraction of the lattice impact each of the performance metrics. The optimization is demonstrated by simulating two spatially variant self-collimating photonic crystals, where one has a high FOM and the other has a low FOM. This work gives optical designers tremendous insight into how to design and optimize robust self-collimating photonic crystals, which promises many applications in silicon photonics and integrated optics.

  10. Plasma tubes becoming collimated as a result of magnetohydrodynamic pumping

    International Nuclear Information System (INIS)

    Yun, Gunsu S.; Bellan, Paul M.

    2010-01-01

    Collimated magnetized plasma structures are commonly observed on galactic, stellar, and laboratory scales. The Caltech plasma gun produces magnetically driven plasma jets bearing a striking resemblance to astrophysical jets and solar coronal loops by imposing boundary conditions analogous to those plasmas. This paper presents experimental observations of gun-produced plasma jets that support a previously proposed magnetohydrodynamic (MHD) pumping model [P. M. Bellan, Phys. Plasmas 10, 1999 (2003)] as a universal collimation mechanism. For any initially flared, magnetized plasma tube with a finite axial current, the model predicts (i) magnetic pumping of plasma particles from a constricted region into a bulged region and (ii) tube collimation if the flow slows down at the bulged region leading to accumulation of mass and thus concentrating the azimuthal magnetic flux frozen in the mass flow (i.e., increasing the pinch force). Time- and space-resolved spectroscopic measurements of gun-produced plasmas have confirmed the highly dynamic nature of the process leading to a collimated state, namely, (i) suprathermal Alfvenic flow (30-50 km/s), (ii) large density amplification from ∼10 17 to ∼10 22 m -3 in an Alfvenic time scale (5-10 μs), and (iii) flow slowing down and mass accumulation at the flow front, the place where the tube collimation occurs according to high-speed camera imaging. These observations are consistent with the predictions of the MHD pumping model, and offer valuable insight into the formation mechanism of laboratory, solar, and astrophysical plasma structures.

  11. An improved scattering routine for collimation tracking studies at LHC

    CERN Document Server

    Tambasco, Claudia; Salvachua Ferrando, Maria Belen; Cavoto, Gianluca

    The present Master thesis work has been carried out at CERN in the framework of the LHC (Large Hadron Collider) Collimation project. The LHC accelerates proton beams up to 7 TeV colliding in the experiment detectors installed in four points of the accelerator ring. The LHC is built to store a energy of 360MJ for each beam. The energy deposition induced by local beam losses could quench the superconducting magnets located around the accelerator beam pipes. To prevent and keep under control dangerous beam losses, an efficient collimation system is required. In addition, the achievable LHC beam intensity is related to the beam loss rate and, consequently, to the cleaning efficiency of the collimation system. Collimation studies at LHC are carried out also by means of simulations by using SixTrack, a dedicated simulation tool that tracks a large numbers of particles for many turns around the ring. The SixTrack code includes a scattering routine to model proton interactions with the material of the collimators j...

  12. Collimated fast electron beam generation in critical density plasma

    Energy Technology Data Exchange (ETDEWEB)

    Iwawaki, T., E-mail: iwawaki-t@eie.eng.osaka-u.ac.jp; Habara, H.; Morita, K.; Tanaka, K. A. [Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871 (Japan); Baton, S.; Fuchs, J.; Chen, S. [LULI, CNRS-Ecole Polytechnique-Université Pierre et Marie Curie-CEA, 91128 Palaiseau (France); Nakatsutsumi, M. [LULI, CNRS-Ecole Polytechnique-Université Pierre et Marie Curie-CEA, 91128 Palaiseau (France); European X-Ray Free-Electron Laser Facility (XFEL) GmbH (Germany); Rousseaux, C. [CEA, DAM, DIF, F-91297 Arpajon (France); Filippi, F. [La SAPIENZA, University of Rome, Dip. SBAI, 00161 Rome (Italy); Nazarov, W. [School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9ST, Scotland (United Kingdom)

    2014-11-15

    Significantly collimated fast electron beam with a divergence angle 10° (FWHM) is observed when an ultra-intense laser pulse (I = 10{sup 14 }W/cm{sup 2}, 300 fs) irradiates a uniform critical density plasma. The uniform plasma is created through the ionization of an ultra-low density (5 mg/c.c.) plastic foam by X-ray burst from the interaction of intense laser (I = 10{sup 14 }W/cm{sup 2}, 600 ps) with a thin Cu foil. 2D Particle-In-Cell (PIC) simulation well reproduces the collimated electron beam with a strong magnetic field in the region of the laser pulse propagation. To understand the physical mechanism of the collimation, we calculate energetic electron motion in the magnetic field obtained from the 2D PIC simulation. As the results, the strong magnetic field (300 MG) collimates electrons with energy over a few MeV. This collimation mechanism may attract attention in many applications such as electron acceleration, electron microscope and fast ignition of laser fusion.

  13. Status report of the baseline collimation system of CLIC. Part I

    CERN Document Server

    Resta-Lopez, J.; Dalena, B.; Fernandez-Hernando, J.L.; Jackson, F.; Schulte, D.; Seryi, A.; Tomas, R.

    2011-01-01

    Important efforts have recently been dedicated to the characterisation and improvement of the design of the post-linac collimation system of the Compact Linear Collider (CLIC). This system consists of two sections: one dedicated to the collimation of off-energy particles and another one for betatron collimation. The energy collimation system is further conceived as protection system against damage by errant beams. In this respect, special attention is paid to the optimisation of the energy collimator design. The material and the physical parameters of the energy collimators are selected to withstand the impact of an entire bunch train. Concerning the betatron collimation section, different aspects of the design have been optimised: the transverse collimation depths have been recalculated in order to reduce the collimator wakefield effects while maintaining a good efficiency in cleaning the undesired beam halo; the geometric design of the spoilers has been reviewed to minimise wakefields; in addition, the opti...

  14. Status report of the baseline collimation system of CLIC. Part II

    CERN Document Server

    Resta-Lopez, J.; Dalena, B.; Fernandez-Hernando, J.L.; Jackson, F.; Schulte, D.; Seryi, A.; Tomas, R.

    2011-01-01

    Important efforts have recently been dedicated to the characterisation and improvement of the design of the post-linac collimation system of the Compact Linear Collider (CLIC). This system consists of two sections: one dedicated to the collimation of off-energy particles and another one for betatron collimation. The energy collimation system is further conceived as protection system against damage by errant beams. In this respect, special attention is paid to the optimisation of the energy collimator design. The material and the physical parameters of the energy collimators are selected to withstand the impact of an entire bunch train. Concerning the betatron collimation section, different aspects of the design have been optimised: the transverse collimation depths have been recalculated in order to reduce the collimator wakefield effects while maintaining a good efficiency in cleaning the undesired beam halo; the geometric design of the spoilers has been reviewed to minimise wakefields; in addition, the opti...

  15. Optical effects on neutron guide tubes produced by collimation

    International Nuclear Information System (INIS)

    Margaca, F.M.A.; Falcao, A.N.; Sequeira, A.D.; Salgado, J.F.

    1991-01-01

    The collimation of a neutron beam carried by a guide tube is shown to procedure extensive regions of umbra and penumbra on the inner walls of the guide tube whenever a diaphragm is used at the exit. The region of umbra renders useless a certain length of the guide-tube end while in the region of penumbra the guide exhibits a faint luminosity. These optical effects are particularly important for stringent collimation. It is shown that these effects render impossible the implementation of the 'equal-flight-paths' design currently used for small-angle neutron scattering instruments, which use guide segments and a diaphragm in the collimation assembly. As a consequence, these operate most of the time in strongly unmatched configurations. It is shown that the optimized design formerly proposed by the authors, in which, whenever possible, the full luminous source area is used, not only avoids the optical effects mentioned but also guarantees the highest detector count rate. (orig.)

  16. Self-collimation-based photonic crystal notch filters

    International Nuclear Information System (INIS)

    Lee, Sun-Goo; Kim, Seong-Han; Kee, Chul-Sik; Kim, Kap-Joong

    2017-01-01

    We introduce a design concept of an optical notch filter (NF) utilizing two perfectly reflecting mirrors and a beam splitter. Based on the new design concept, a photonic crystal (PC)-NF based on the self-collimation phenomenon in a two-dimensional PC is proposed and studied through finite-difference time-domain simulations and experimental measurements in a microwave region. The transmission properties of the self-collimation-based PC-NF were demonstrated to be controlled by adjusting the values of parameters such as the radius of rods in the line-defect beam splitter, distance between the two perfectly reflecting mirrors, and radius of rods on the outermost surface of the perfectly reflecting mirrors. Our results indicate that the proposed design concept could provide a new approach to manipulate light propagation, and the PC-NF could increase the applicability of the self-collimation phenomenon in a PC. (paper)

  17. Reliability review of the LHC collimators low level control system

    International Nuclear Information System (INIS)

    Masi, A.; Donze, M.; Losito, R.

    2011-01-01

    The LHC collimators' low level control system is responsible for the positioning, with an accuracy of a few um, of more than 500 motor axes located around the entire LHC tunnel and synchronized at us level,The collimators' axes position is verified in Real Time, monitoring at 100 Hz more than 700 LVDT positioning sensors. Apart from the challenging requirements of timing and positioning accuracy, the system is characterized by a high level of reliability since the collimators have the crucial function of machine protection. In this paper we focus on the architectural and technical choices adopted to guarantee the level of reliability required by the application. We also present the tools and solutions developed to manage this huge control system making the support easier and faster for its operation. (authors)

  18. Novel Materials for Collimators at LHC and its Upgrades

    CERN Document Server

    AUTHOR|(CDS)2108536; Dallocchio, Alessandro; Garlasche, Marco; Gentini, Luca; Gradassi, Paolo; Guinchard, Michael; Redaelli, Stefano; Rossi, Adriana; Sacristan De Frutos, Oscar; Carra, Federico; Quaranta, Elena

    2015-01-01

    Collimators for last-generation particle accelerators like the LHC, must be designed to withstand the close interaction with intense and energetic particle beams, safely operating over an extended range of temperatures in harsh environments, while minimizing the perturbing effects, such as instabilities induced by RF impedance, on the circulating beam. The choice of materials for collimator active components is of paramount importance to meet these requirements, which are to become even more demanding with the increase of machine performances expected in future upgrades, such as the High Luminosity LHC (HL-LHC). Consequently, a farreaching R&D program has been launched to develop novel materials with excellent thermal shock resistance and high thermal and electrical conductivity, replacing or complementing materials used for present collimators. Molybdenum Carbide - Graphite and Copper-Diamond composites have been so far identified as the most promising materials. The manufacturing methods, properties and...

  19. Advanced materials for future Phase II LHC collimators

    CERN Document Server

    Dallocchio, A; Arnau Izquierdo, G; Artoos, K

    2009-01-01

    Phase I collimators, equipped with Carbon-Carbon jaws, effectively met specifications for the early phase of LHC operation. However, the choice of carbon-based materials is expected to limit the nominal beam intensity mainly because of the high RF impedance and limited efficiency of the collimators. Moreover, C/C may be degraded by high radiation doses. To overcome these limitations, new Phase II secondary collimators will complement the existing system. Their extremely challenging requirements impose a thorough material investigation effort aiming at identifying novel materials combining very diverse properties. Relevant figures of merit have been identified to classify materials: Metal-diamonds composites look a promising choice as they combine good thermal, structural and stability properties. Molybdenum is interesting for its good thermal stability. Ceramics with non-conventional RF performances are also being evaluated. The challenges posed by the development and industrialization of these materials are ...

  20. Modeling skin collimation using the electron pencil beam redefinition algorithm

    International Nuclear Information System (INIS)

    Chi, Pai-Chun M.; Hogstrom, Kenneth R.; Starkschall, George; Antolak, John A.; Boyd, Robert A.

    2005-01-01

    Skin collimation is an important tool for electron beam therapy that is used to minimize the penumbra when treating near critical structures, at extended treatment distances, with bolus, or using arc therapy. It is usually made of lead or lead alloy material that conforms to and is placed on patient surface. Presently, commercially available treatment-planning systems lack the ability to model skin collimation and to accurately calculate dose in its presence. The purpose of the present work was to evaluate the use of the pencil beam redefinition algorithm (PBRA) in calculating dose in the presence of skin collimation. Skin collimation was incorporated into the PBRA by terminating the transport of electrons once they enter the skin collimator. Both fixed- and arced-beam dose calculations for arced-beam geometries were evaluated by comparing them with measured dose distributions for 10- and 15-MeV beams. Fixed-beam dose distributions were measured in water at 88-cm source-to-surface distance with an air gap of 32 cm. The 6x20-cm 2 field (dimensions projected to isocenter) had a 10-mm thick lead collimator placed on the surface of the water with its edge 5 cm inside the field's edge located at +10 cm. Arced-beam dose distributions were measured in a 13.5-cm radius polystyrene circular phantom. The beam was arced 90 deg. (-45 deg. to +45 deg. ), and 10-mm thick lead collimation was placed at ±30 deg. . For the fixed beam at 10 MeV, the PBRA-calculated dose agreed with measured dose to within 2.0-mm distance to agreement (DTA) in the regions of high-dose gradient and 2.0% in regions of low dose gradient. At 15 MeV, the PBRA agreed to within a 2.0-mm DTA in the regions of high-dose gradient; however, the PBRA underestimated the dose by as much as 5.3% over small regions at depths less than 2 cm because it did not model electrons scattered from the edge of the skin collimation. For arced beams at 10 MeV, the agreement was 1-mm DTA in the high-dose gradient regions, and 2

  1. A circular multifocal collimator for 3D SPECT imaging

    International Nuclear Information System (INIS)

    Guillemaud, R.; Grangeat, P.

    1993-01-01

    In order to improve sensitivity of 3D Single Photon Emission Tomography (SPECT) image, a cone-beam collimator can be used. A new circular multifocal collimator is proposed. The multiple focal points are distributed on a transaxial circle which is the trajectory of the focal points during the circular acquisition. This distribution provides a strong focusing at the center of the detector like a cone-beam collimator, with a good sensitivity, and a weak transaxial focusing at the periphery. A solution for an analytical multifocal reconstruction algorithm has been derived. Grangeat algorithm is proposed to use for this purpose in order to reconstruct with a good sensitivity the region of interest. (R.P.) 3 refs

  2. Updated Simulation Studies of Damage Limit of LHC Tertiary Collimators

    CERN Document Server

    AUTHOR|(CDS)2085459; Bertarelli, Alessandro; Bruce, Roderik; Carra, Federico; Cerutti, Francesco; Gradassi, Paolo; Lechner, Anton; Redaelli, Stefano; Skordis, Eleftherios

    2015-01-01

    The tertiary collimators (TCTs) in the LHC, installed in front of the experiments, in standard operation intercept fractions of 10−3 halo particles. However, they risk to be hit by high-intensity primary beams in case of asynchronous beam dump. TCT damage thresholds were initially inferred from results of destructive tests on a TCT jaw, supported by numerical simulations, assuming simplified impact scenarios with one single bunch hitting the jaw with a given impact parameter. In this paper, more realistic failure conditions, including a train of bunches and taking into account the full collimation hierarchy, are used to derive updated damage limits. The results are used to update the margins in the collimation hierarchy and could thus potentially have an influence on the LHC performance.

  3. Impedance Studies for the Phase 2 LHC Collimators

    CERN Document Server

    Métral, E; Grudiev, A; Kroyer, T; Zotter, B; Roncarolo, F; Salvant, B

    2010-01-01

    The LHC phase 2 collimation project aims at gaining a factor ten in cleaning efficiency, robustness and impedance reduction. From the impedance point of view, several ideas emerged during the last year, such as using dielectric collimators, slots or rods in copper plates, or Litz wires. The purpose of this paper is to discuss the possible choices, showing analytical estimates, electromagnetic simulations performed using Maxwell, HFSS and GdFidL, and preliminary bench measurements. The corresponding complex tune shifts are computed for the different cases and compared on the stability diagram defined by the settings of the Landau octupoles available in the LHC at 7 TeV.

  4. A fast algorithm for computer aided collimation gamma camera (CACAO)

    Science.gov (United States)

    Jeanguillaume, C.; Begot, S.; Quartuccio, M.; Douiri, A.; Franck, D.; Pihet, P.; Ballongue, P.

    2000-08-01

    The computer aided collimation gamma camera is aimed at breaking down the resolution sensitivity trade-off of the conventional parallel hole collimator. It uses larger and longer holes, having an added linear movement at the acquisition sequence. A dedicated algorithm including shift and sum, deconvolution, parabolic filtering and rotation is described. Examples of reconstruction are given. This work shows that a simple and fast algorithm, based on a diagonal dominant approximation of the problem can be derived. Its gives a practical solution to the CACAO reconstruction problem.

  5. Interactions of collimation, sampling and filtering on spect spatial resolution

    International Nuclear Information System (INIS)

    Tsui, B.M.W.; Jaszczak, R.J.

    1984-01-01

    The major factors which affect the spatial resolution of single-photon emission computer tomography (SPECT) include collimation, sampling and filtering. A theoretical formulation is presented to describe the relationship between these factors and their effects on the projection data. Numerical calculations were made using commercially available SPECT systems and imaging parameters. The results provide an important guide for proper selection of the collimator-detector design, the imaging and the reconstruction parameters to avoid unnecessary spatial resolution degradation and aliasing artifacts in the reconstructed image. In addition, the understanding will help in the fair evaluation of different SPECT systems under specific imaging conditions

  6. Apparatus and Experimental Procedures to Test Crystal Collimation

    CERN Document Server

    Montesano, S

    2012-01-01

    UA9 is an experimental setup operated in the CERN-SPS in view of investigating the feasibility of halo collimation assisted by bent crystals. The test collimation system is composed of one crystal acting as primary halo deflector in the horizontal plane and an absorber. Different crystals are tested in turn using two-arm goniometers with an angular reproducibility of better than 10 microrad. The performance of the system is assessed through the study of the secondary and tertiary halo in critical areas, by using standard machine instrumentation and few customized equipments. The alignment of the crystal is verified by measuring the loss rate close to the crystal position. The collimation efficiency is computed by intercepting the deflected halo with a massive collimator or with an imaging device installed into a Roman Pot. The leakage of the system is evaluated in the dispersion suppressor by means of movable aperture restrictions. In this contribution the setup and the experimental methods in use are revisit...

  7. The practical Pomeron for high energy proton collimation

    Science.gov (United States)

    Appleby, R. B.; Barlow, R. J.; Molson, J. G.; Serluca, M.; Toader, A.

    2016-10-01

    We present a model which describes proton scattering data from ISR to Tevatron energies, and which can be applied to collimation in high energy accelerators, such as the LHC and FCC. Collimators remove beam halo particles, so that they do not impinge on vulnerable regions of the machine, such as the superconducting magnets and the experimental areas. In simulating the effect of the collimator jaws it is crucial to model the scattering of protons at small momentum transfer t, as these protons can subsequently survive several turns of the ring before being lost. At high energies these soft processes are well described by Pomeron exchange models. We study the behaviour of elastic and single-diffractive dissociation cross sections over a wide range of energy, and show that the model can be used as a global description of the wide variety of high energy elastic and diffractive data presently available. In particular it models low mass diffraction dissociation, where a rich resonance structure is present, and thus predicts the differential and integrated cross sections in the kinematical range appropriate to the LHC. We incorporate the physics of this model into the beam tracking code MERLIN and use it to simulate the resulting loss maps of the beam halo lost in the collimators in the LHC.

  8. The practical Pomeron for high energy proton collimation

    Energy Technology Data Exchange (ETDEWEB)

    Appleby, R.B. [University of Manchester, The Cockcroft Institute, Manchester (United Kingdom); Barlow, R.J.; Toader, A. [The University of Huddersfield, Huddersfield (United Kingdom); Molson, J.G. [Univ. Paris-Sud, CNRS/IN2P3, Universite Paris-Saclay, LAL, Orsay (France); Serluca, M. [CERN, Geneva (Switzerland)

    2016-10-15

    We present a model which describes proton scattering data from ISR to Tevatron energies, and which can be applied to collimation in high energy accelerators, such as the LHC and FCC. Collimators remove beam halo particles, so that they do not impinge on vulnerable regions of the machine, such as the superconducting magnets and the experimental areas. In simulating the effect of the collimator jaws it is crucial to model the scattering of protons at small momentum transfer t, as these protons can subsequently survive several turns of the ring before being lost. At high energies these soft processes are well described by Pomeron exchange models. We study the behaviour of elastic and single-diffractive dissociation cross sections over a wide range of energy, and show that the model can be used as a global description of the wide variety of high energy elastic and diffractive data presently available. In particular it models low mass diffraction dissociation, where a rich resonance structure is present, and thus predicts the differential and integrated cross sections in the kinematical range appropriate to the LHC. We incorporate the physics of this model into the beam tracking code MERLIN and use it to simulate the resulting loss maps of the beam halo lost in the collimators in the LHC. (orig.)

  9. MD1878: Operation with primary collimators at tighter settings

    CERN Document Server

    AUTHOR|(CDS)2078850; Amorim, David; Biancacci, Nicolo; Bruce, Roderik; Buffat, Xavier; Carver, Lee Robert; Fiascaris, Maria; Mereghetti, Alessio; Redaelli, Stefano; Rossi, Roberto; Salvachua Ferrando, Belen Maria; Soderen, Martin; Trad, Georges; CERN. Geneva. ATS Department

    2017-01-01

    Primary (TCP) collimators of the betatron cleaning insertion determine the betatron cut of the LHC beam. During the 2016 they were set at 5.5 nominal beam sigmas at 6.5 TeV (i.e. by using a normalized emittance ε* = 3:5 μm is used). Reducing their settings is a possible way to push the ß* at the LHC, which depends on the collimation hierarchy. This study aims at understanding possible limitations of operating the LHC with tighter settings of the primary collimators. This is a crucial input to the choice of operational configuration in terms of ß* at the LHC as well as at the HL-LHC. This study follows a successful MD done in block 3 to understand limitations from TCP impedance [1]. The outcome of this MD can also have an impact for the design of the FCC collimation system, which is currently based on the present TCP gaps. Studies of beam stability as a function of octupole current, transverse feedback gain (ADT) and transverse separation at the IPs were also carried out.

  10. Collimator design for neutron imaging of laser-fusion targets

    International Nuclear Information System (INIS)

    Sommargren, G.E.; Lerche, R.A.

    1981-01-01

    Several pinhole collimator geometries for use in neutron imaging experiments have been modeled and compared. Point spread functions are shown for a cylinder, hyperbola, intersecting cones, and a five-zone approximation to the intersecting cones. Of the geometries studied, the intersecting cones appear the most promising with respect to neutron efficiency, field of view, and isoplanatism

  11. Tandem collimators for the JET tangential gamma-ray spectrometer

    International Nuclear Information System (INIS)

    Soare, Sorin; Balshaw, Nick; Blanchard, Patrick; Craciunescu, Teddy; Croft, David; Curuia, Marian; Edlington, Trevor; Kiptily, Vasily; Murari, Andrea; Prior, Phil; Sanders, Steven; Syme, Brian; Zoita, Vasile

    2011-01-01

    The tangential gamma-ray spectrometer (TGRS) of the JET tokamak fusion facility is an important diagnostics for investigating the fast particle evolution. A well defined field of view for the TGRS diagnostics is essential for its proper operation and this is to be determined by a rather complex system of collimators and shields both for the neutron and gamma radiations. A conceptual design for this system has been carried out with the main design target set to maximize the signal-to-background ratio at the spectrometer detector, the ratio being defined in terms of the plasma emitted gamma radiation and the gamma-ray background. As a first phase of the TGRS diagnostics upgrade a set of two tandem collimators has been designed with the aim of determining a quasi-tangential field of view through JET tokamak plasmas. A modular design of the tandem system has been developed in order to allow for the construction of different configurations for deuterium and deuterium-tritium discharges. The internal structure of the collimators consists of nuclear grade lead and high density polyethylene slabs arranged in an optimized pattern. The performance of a simplified geometry of the tandem collimator configuration has been evaluated by neutron and photon transport calculations and the numerical results show that the design parameters can be attained.

  12. Improved self-reliance shearing interferometric technique for collimation testing

    Science.gov (United States)

    Zhao, Mingshan; Li, Guohua; Wang, Zhaobing; Jing, Yaling; Li, Yi

    1995-06-01

    Self-reference single plate shearing interferometric technique used for collimation testing of light beams are briefly reviewed. Two improved configurations of this self-reference interferometry with an inclined screen and matched half-field interferograms are described in detail. Sensitivity of these configurations is analyzed and compared with that of the existing ones.

  13. Laser welding of a beryllium/tantalum collimator

    International Nuclear Information System (INIS)

    Lingenfelter, A.C.; Anglin, C.D.

    1985-01-01

    This report describes the methods utilized in the fabrication of a collimator from 0.001 inch thick beryllium and tantalum foil. The laser welding process proved to be an acceptable method for joining the beryllium in a standing edge joint configuration

  14. Improvements in or relating to neutron beam collimators

    International Nuclear Information System (INIS)

    Lundberg, D.A.

    1975-01-01

    Reference is made to collimators suitable for use in neutron therapy equipment. The design of such collimators presents considerable difficulties, since neutrons are very penetrating. Scattering processes are also much more significant with neutrons than with x-rays or γ-rays. A further difficulty is that neutron activation causes some materials to become radioactive, which may present a hazard to users of the equipment. A novel form of collimator is described that overcomes these disadvantages to some extent. It comprises a body containing W for moderating the neutrons by inelastic collision processes, a slow neutron absorbing material intimately mixed with the W for reducing collisions between slow neutrons and the W atoms, a hydrogenous material for further moderating the neutrons to thermal energies by elastic collision processes with H atoms and for absorbing the thermal neutrons by capture processes, and a material having a density of at least 10g/cm 3 for attenuating γ-radiation produced in the hydrogenous material during neutron capture processes. The collimator is of sufficient thickness to be substantially opaque to neutrons of predetermined energy. The slow neutron absorbing material may be B, the hydrogenous material may be polyethylene, and the high density material may be Pb. Alternative methods of using and packing the various materials are described. (U.K.)

  15. Crystal Collimation Cleaning Measurements with Proton Beams in LHC

    CERN Document Server

    Rossi, Roberto; Andreassen, Odd Oyvind; Butcher, Mark; Dionisio Barreto, Cristovao Andre; Masi, Alessandro; Mirarchi, Daniele; Montesano, Simone; Lamas Garcia, Inigo; Redaelli, Stefano; Scandale, Walter; Serrano Galvez, Pablo; Rijllart, Adriaan; Valentino, Gianluca; CERN. Geneva. ATS Department

    2016-01-01

    During this MD, performed on July 29th, 2016, bent silicon crystal were tested with proton beams for a possible usage of crystal-assisted collimation. Tests were performed at both injection energy and flat top using horizontal and vertical crystal. Loss maps with crystals at 6.5 TeV were measured.

  16. DOUBLE-WALL COLLIMATOR DESIGN OF THE SNS PROJECT

    International Nuclear Information System (INIS)

    SIMOS, N.; LUDEWIG, H.; CATALAN-LASHERAS, N.; CRIVELLO, S.

    2001-01-01

    The collimator absorber array of the Spallation Neutron Source (SNS) project is responsible for stopping the 1.0 GeV protons that are in the halo of the beam. It is estimated that 0.1% of the 2 MW beam will be intercepted by the adopted collimating scheme implemented at various sections of the beam transport and accumulation. This paper summarizes the conceptual design of the collimator absorber as well as the supporting detailed analysis that were performed and guided the design process. Key requirement in the design process is the need for the collimator beam tube to minimize beam impedance while closely following its beta function. Due to lack of available experimental data, the long-term behavior of irradiated materials in an environment where they interface with coolant flow becomes an issue. Uncertainties in the long-term behavior prompted a special double-wall design that will enable not only beam halo interception but also the efficient transfer of deposited energy both under normal and off-normal conditions to the coolant flow. The thermo-mechanical response of the double wall beam tube and of a particle bed surrounding it are discussed in detail in the paper

  17. A high-orbit collimating infrared earth simulator

    International Nuclear Information System (INIS)

    Zhang Guoyu; Jiang Huilin; Fang Yang; Yu Huadong; Xu Xiping; Wang, Lingyun; Liu Xuli; Huang Lan; Yue Shixin; Peng Hui

    2007-01-01

    The earth simulator is the most important testing equipment ground-based for the infrared earth sensor, and it is also a key component in the satellite controlling system. for three orbit heights 18000Km, 35786Km and 42000Km, in this paper we adopt a project of collimation and replaceable earth diaphragm and develop a high orbit collimation earth simulator. This simulator can afford three angles 15.19 0 , 17.46 0 and 30.42 0 , resulting simulating the earth on the ground which can be seen in out space by the satellite. In this paper we introduce the components, integer structure, and the earth's field angles testing method of the earth simulator in detail. Germanium collimation lens is the most important component in the earth simulator. According to the optical configuration parameter of Germanium collimation lens, we find the location and size of the earth diaphragm and the hot earth by theoretical analyses and optics calculation, which offer foundation of design in the study of the earth simulator. The earth angle is the index to scale the precision of earth simulator. We test the three angles by experiment and the results indicate that three angles errors are all less than ±0.05 0

  18. Geometric beam coupling impedance of LHC secondary collimators

    Science.gov (United States)

    Frasciello, Oscar; Tomassini, Sandro; Zobov, Mikhail; Salvant, Benoit; Grudiev, Alexej; Mounet, Nicolas

    2016-02-01

    The High Luminosity LHC project is aimed at increasing the LHC luminosity by an order of magnitude. One of the key ingredients to achieve the luminosity goal is the beam intensity increase. In order to keep beam instabilities under control and to avoid excessive power losses a careful design of new vacuum chamber components and an improvement of the present LHC impedance model are required. Collimators are among the major impedance contributors. Measurements with beam have revealed that the betatron coherent tune shifts were higher by about a factor of 2 with respect to the theoretical predictions based on the LHC impedance model up to 2012. In that model the resistive wall impedance has been considered as the dominating impedance contribution for collimators. By carefully simulating also their geometric impedance we have contributed to the update of the LHC impedance model, reaching also a better agreement between the measured and simulated betatron tune shifts. During the just ended LHC Long Shutdown I (LSI), TCS/TCT collimators were replaced by new devices embedding BPMs and TT2-111R ferrite blocks. We present here preliminary estimations of their broad-band impedance, showing that an increase of about 20% is expected in the kick factors with respect to previous collimators without BPMs.

  19. EPICS Controlled Collimator for Controlling Beam Sizes in HIPPO

    Energy Technology Data Exchange (ETDEWEB)

    Napolitano, Arthur Soriano [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vogel, Sven C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-08-03

    Controlling the beam spot size and shape in a diffraction experiment determines the probed sample volume. The HIPPO - High-Pressure-Preferred Orientation– neutron time-offlight diffractometer is located at the Lujan Neutron Scattering Center in Los Alamos National Laboratories. HIPPO characterizes microstructural parameters, such as phase composition, strains, grain size, or texture, of bulk (cm-sized) samples. In the current setup, the beam spot has a 10 mm diameter. Using a collimator, consisting of two pairs of neutron absorbing boron-nitride slabs, horizontal and vertical dimensions of a rectangular beam spot can be defined. Using the HIPPO robotic sample changer for sample motion, the collimator would enable scanning of e.g. cylindrical samples along the cylinder axis by probing slices of such samples. The project presented here describes implementation of such a collimator, in particular the motion control software. We utilized the EPICS (Experimental Physics Interface and Control System) software interface to integrate the collimator control into the HIPPO instrument control system. Using EPICS, commands are sent to commercial stepper motors that move the beam windows.

  20. Vectorial analysis of the collimated beam of a small Gaussian source

    Science.gov (United States)

    Cao, Changqing; Wang, Ting; Zeng, Xiaodong; Feng, Zhejun; Zhang, Wenrui; Zhang, Xiaobing; Chen, Kun

    2018-03-01

    A vectorial analysis method to describe the collimated beam is proposed, the formulas of the intensity distribution and divergence angles represented in terms of Bessel functions are derived, and the propagation properties such as the vectorial structure of the collimated field and the shape of the beam spot are discussed in detail. Omitting the vectorial nature of the collimated beam can cause an error of 7.6% in determining the intensity distribution on the optical axis of the collimated beam.

  1. Evaluation of dual γ-ray imager with active collimator using various types of scintillators.

    Science.gov (United States)

    Lee, Wonho; Lee, Taewoong; Jeong, Manhee; Kim, Ho Kyung

    2011-10-01

    The performance of a specialized dual γ-ray imager using both mechanical and electronic collimation was evaluated by Monte Carlo simulation (MCNP5). The dual imager consisted of an active collimator and a planar detector that were made from scintillators. The active collimator served not only as a coded aperture for mechanical collimation but also as a first detector for electronic collimation. Therefore, a single system contained both mechanical and electronic collimation. Various types of scintillators were tested and compared with each other in terms of their angular resolution, efficiency, and background noise. In general, a BGO active collimator had the best mechanical collimation performance, and an LaCl₃(Ce) active collimator provided the best electronic collimation performance. However, for low radiation energies, the mechanical collimation images made from both scintillators showed the same quality, and, for high radiation energies, electronic collimation images made from both scintillators also show similar quality. Therefore, if mechanical collimation is used to detect low-energy radiation and electronic collimation is applied to reconstruct a high-energy source, either LaCl₃(Ce) or BGO would be appropriate for the active collimator of a dual γ-ray imager. These results broaden the choice of scintillators for the active collimator of the dual γ-ray imager, which makes it possible to consider other factors, such as machinability and cost, in making the imager. As a planar detector, BGO showed better performance than other scintillators since its radiation detection efficiency was highest of all. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Model-Based Normalization of a Fractional-Crystal Collimator for Small-Animal PET Imaging.

    Science.gov (United States)

    Li, Yusheng; Matej, Samuel; Karp, Joel S; Metzler, Scott D

    2017-05-01

    Previously, we proposed to use a coincidence collimator to achieve fractional-crystal resolution in PET imaging. We have designed and fabricated a collimator prototype for a small-animal PET scanner, A-PET. To compensate for imperfections in the fabricated collimator prototype, collimator normalization, as well as scanner normalization, is required to reconstruct quantitative and artifact-free images. In this study, we develop a normalization method for the collimator prototype based on the A-PET normalization using a uniform cylinder phantom. We performed data acquisition without the collimator for scanner normalization first, and then with the collimator from eight different rotation views for collimator normalization. After a reconstruction without correction, we extracted the cylinder parameters from which we generated expected emission sinograms. Single scatter simulation was used to generate the scattered sinograms. We used the least-squares method to generate the normalization coefficient for each LOR based on measured, expected and scattered sinograms. The scanner and collimator normalization coefficients were factorized by performing two normalizations separately. The normalization methods were also verified using experimental data acquired from A-PET with and without the collimator. In summary, we developed a model-base collimator normalization that can significantly reduce variance and produce collimator normalization with adequate statistical quality within feasible scan time.

  3. Evaluation of parathyroid imaging methods with 99mTc-MIBI. The comparison of planar images obtained using a pinhole collimator and a parallel-hole collimator

    International Nuclear Information System (INIS)

    Fujii, Hirofumi; Iwasaki, Ryuichiro; Hashimoto, Jun; Nakamura, Kayoko; Kunieda, Etsuo; Sanmiya, Toshikazu; Kubo, Atsushi; Ogawa, Koichi; Inagaki, Kazutoshi

    1999-01-01

    Parathyroid scintigraphy with 99m Tc-MIBI was performed using two kinds of collimators, namely, a pinhole one and a parallel-hole one, to evaluate which one was more suitable for the detection of hyperfunctioning parathyroid lesions. In the studies using 99m Tc source, the pinhole collimator showed better efficiency and spatial resolution in the distance where the parathyroid scan are actually performed. In the phantom study, the nodular activities modeling parathyroid lesions were visualized better on the images obtained using the pinhole collimator. In clinical studies for 30 patients suspicious of hyperparathyroidism, hyperfunctioning parathyroid nodules were better detected when the pinhole collimator was used. In conclusion, the pinhole collimator was thought to be more suitable for parathyroid scintigraphy with 99m Tc-MIBI than the parallel-hole collimator. (author)

  4. Evaluation of parathyroid imaging methods with {sup 99m}Tc-MIBI. The comparison of planar images obtained using a pinhole collimator and a parallel-hole collimator

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Hirofumi; Iwasaki, Ryuichiro; Hashimoto, Jun; Nakamura, Kayoko; Kunieda, Etsuo; Sanmiya, Toshikazu; Kubo, Atsushi [Keio Univ., Tokyo (Japan). School of Medicine; Ogawa, Koichi; Inagaki, Kazutoshi

    1999-07-01

    Parathyroid scintigraphy with {sup 99m}Tc-MIBI was performed using two kinds of collimators, namely, a pinhole one and a parallel-hole one, to evaluate which one was more suitable for the detection of hyperfunctioning parathyroid lesions. In the studies using {sup 99m}Tc source, the pinhole collimator showed better efficiency and spatial resolution in the distance where the parathyroid scan are actually performed. In the phantom study, the nodular activities modeling parathyroid lesions were visualized better on the images obtained using the pinhole collimator. In clinical studies for 30 patients suspicious of hyperparathyroidism, hyperfunctioning parathyroid nodules were better detected when the pinhole collimator was used. In conclusion, the pinhole collimator was thought to be more suitable for parathyroid scintigraphy with {sup 99m}Tc-MIBI than the parallel-hole collimator. (author)

  5. SU-F-T-402: The Effect of Extremely Narrow MLC Leaf Width On the Plan Quality of VMAT for Prostate Cancer

    International Nuclear Information System (INIS)

    Kim, J; Park, S; Kim, J; Choi, C; Park, J

    2016-01-01

    Purpose: To investigate the effect of multi-leaf collimators (MLCs) with leaf width of 1.25 mm on the plan quality of volumetric modulated arc therapy (VMAT) for prostate cancer. Methods: A total of 20 patients with prostate cancer were retrospectively selected. Using a high definition MLC (HD MLC), primary and boost VMAT plans with two full arcs were generated for each patient (original plan). After that, by shifting patient CT images by 1.25 mm in the cranio-caudal direction between the 1st and the 2nd arc, we simulated fluences made with MLCs with leaf width of 1.25 mm. After shifting, primary and boost plans were generated for each patient (shifted plan). A sum plan was generated by summation of the primary and boost plan for each patient. Dose-volumetric parameters were calculated and compared. Results: Both homogeneity index (HI) and conformity index (CI) of the shifted plans were better than those of the original plans in primary plans (HI = 0.044 vs. 0.040 with p < 0.001 and CI = 1.056 vs. 1.044 with p = 0.006). Similarly, the shifted plans for boost target volume showed better homogeneity and conformity than did the original plans (HI = 0.042 vs. 0.037 with p = 0.006 and CI = 1.015 vs. 1.009 with p < 0.001). The total body volumes of the original plans irradiated by the prescription dose were larger than those of the shifted plans in sum plans (60.9 cc vs. 49.0 cc with p = 0.007). Conclusion: Use of extremely narrow MLCs could increase dose homogeneity and conformity of the target volume for prostate VMAT. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2015R1C1A1A02036331).

  6. Mechanical Engineering and Design of the LHC Phase II Collimators

    CERN Document Server

    Bertarelli, A; Gentini, L; Mariani, N; Perret, R; Timmins, M A

    2010-01-01

    Phase II collimators will complement the existing system to improve the expected high RF impedance and limited efficiency of Phase I jaws. An international collaborative effort has been launched to identify novel advanced materials responding to the very challenging requirements of the new collimators. Complex numerical calculations simulating extreme conditions and experimental tests are in progress. In parallel, an innovative modular design concept of the jaw assembly is being developed to allow fitting in alternative materials, minimizing the thermally induced deformations, withstanding accidents and accepting high radiation doses. Phase II jaw assembly is made up of a molybdenum back-stiffener ensuring high geometrical stability and a modular jaw split in threes sectors. Each sector is equipped with a high-efficiency independent cooling circuit. Beam position monitors (BPM) are embedded in the jaws to fasten setup time and improve beam monitoring. An adjustment system will permit to fine-tune the jaw flat...

  7. Simulator for beam-based LHC collimator alignment

    Science.gov (United States)

    Valentino, Gianluca; Aßmann, Ralph; Redaelli, Stefano; Sammut, Nicholas

    2014-02-01

    In the CERN Large Hadron Collider, collimators need to be set up to form a multistage hierarchy to ensure efficient multiturn cleaning of halo particles. Automatic algorithms were introduced during the first run to reduce the beam time required for beam-based setup, improve the alignment accuracy, and reduce the risk of human errors. Simulating the alignment procedure would allow for off-line tests of alignment policies and algorithms. A simulator was developed based on a diffusion beam model to generate the characteristic beam loss signal spike and decay produced when a collimator jaw touches the beam, which is observed in a beam loss monitor (BLM). Empirical models derived from the available measurement data are used to simulate the steady-state beam loss and crosstalk between multiple BLMs. The simulator design is presented, together with simulation results and comparison to measurement data.

  8. Self-collimated slow sound in sonic crystals

    International Nuclear Information System (INIS)

    Kaya, Olgun Adem; Cicek, Ahmet; Ulug, Bulent

    2012-01-01

    Self-collimated slow-sound propagation in a two-dimensional rectangular sonic crystal composed of elliptical scatterers in air is numerically demonstrated. The group velocity at the centre and the edges of the fourth acoustic band is reduced to 45 m s -1 and 30 m s -1 , corresponding to 1/8 and 1/12 of the speed of sound in air, respectively. Elimination of omni-directional reflections encountered in linear waveguides and the reduction of group-velocity dispersion at the mid-band frequencies lead to preservation of pulse shape and amplitude upon traversal of the sonic crystal. Wave transmission is increased from approximately -20 to -2.5 dB, with almost an order of magnitude enhancement, via injector layers optimized through a pattern search algorithm. Self-collimating performance of the system is not degraded under oblique incidence, except for pulse broadening due to increased effective source width.

  9. Radiation collimator for use with high energy radiation beams

    International Nuclear Information System (INIS)

    Malak, S.P.

    1978-01-01

    A collimator is described for use with a beam of radiation, and in particular, for use in controlling the cross-sectional size and shape of the radiation beam and intercepting undesired off-focus radiation in an x-ray apparatus. The collimator is positioned adjacent to the source of radiation and embodies a plurality longitudinally extending leaves pivotally mounted on and between two supports, the leaves move about their pivots to close overlapping relation to define a hollow cone. The cone defines an aperture at its narrow end which can be adjusted in size and shape by rotation of the two supports which are adaptable to being moved one relative to the other, to cause an expansion or contraction of the hollow cone and correspondingly an increase or decrease of the cross-sectional size and/or shape of the radiation beam passing through the aperture

  10. Collimation in the Transfer Lines to the LHC

    CERN Document Server

    Burkhardt, Helmut; Kadi, Yacine; Kain, Verena; Risselada, Thys; Weterings, Wim

    2005-01-01

    Injection intensities for the LHC are over an order of magnitude above damage level. The TI 2 and TI 8 transfer lines between the SPS and LHC are each about 2.5 km long and comprise many active elements running in pulsed mode. The collimation system in the transfer lines is designed to dilute the beam energy sufficiently in case of accidental beam loss or mis-steered beam. A system using three collimator families spaced by 60 degrees in phase advance, both in the horizontal and the vertical plane has been chosen. We discuss the reasons for this choice, the layout and, the expected performance of the system in terms of maximum amplitudes and energy deposition.

  11. Polarimetric evidence against a collimated outflow in the Horsehead Nebula

    Energy Technology Data Exchange (ETDEWEB)

    Warren-Smith, R F; Gledhill, T M; Scarrott, S M

    1985-08-01

    Imaging polarimetry of the Horsehead Nebula in Orion shows that the 'jaw' region of the nebula, which includes a proposed collimated flow from a highly reddened star B33-6, is illuminated by a distant source, sigma Orionis, and not by B33-6. The polarization pattern also shows features which suggest the presence of magnetically aligned dust grains in the surrounding medium. The possible structure of the aligning field is discussed.

  12. Method of making a low energy gamma ray collimator

    International Nuclear Information System (INIS)

    Muehllehner, Gerd.

    1975-01-01

    Described herein is a method for making a low energy gamma ray collimator which involves corrugating lead foil strips by passing them through pinion wire rollers and gluing corrugated strips between straight strips using an adhesive such as epoxy to build up a honeycomb-like structure. A thin aluminum sheet is glued to both edges of the strips to protect them and to provide a more rigid assembly which may be sawed to a desired shape. (Patent Office Record)

  13. Anti-collimation of ballistic electrons by a potential barrier

    Science.gov (United States)

    Coleridge, P. T.; Taylor, R. P.; Sachrajda, A. S.; Adams, J. A.

    1994-03-01

    A pair of Quantum Point Contacts separated by a continuous barrier have been fabricated using the surface gate technique. Transport measurements for each component of this system and for various combinations have shown both additive and non-additive behaviour. The results are explained by a combination of reflection by the barrier of electrons collimated by the Quantum Point Contacts and transport by diffusion across the barrier.

  14. Fourier correction for spatially variant collimator blurring in SPECT

    International Nuclear Information System (INIS)

    Xia, W.; Lewitt, R.M.; Edholm, P.R.

    1995-01-01

    In single-photon emission computed tomography (SPECT), projection data are acquired by rotating the photon detector around a patient, either in a circular orbit or in a noncircular orbit. The projection data of the desired spatial distribution of emission activity is blurred by the point-response function of the collimator that is used to define the range of directions of gamma-ray photons reaching the detector. The point-response function of the collimator is not spatially stationary, but depends on the distance from the collimator to the point. Conventional methods for deblurring collimator projection data are based on approximating the actual distance-dependent point-response function by a spatially invariant blurring function, so that deconvolution methods can be applied independently to the data at each angle of view. A method is described in this paper for distance-dependent preprocessing of SPECT projection data prior to image reconstruction. Based on the special distance-dependent characteristics of the Fourier coefficients of the sinogram, a spatially variant inverse filter can be developed to process the projection data in all views simultaneously. The algorithm is first derived from fourier analysis of the projection data from the circular orbit geometry. For circular orbit projection data, experimental results from both simulated data and real phantom data indicate the potential of this method. It is shown that the spatial filtering method can be extended to the projection data from the noncircular orbit geometry. Experiments on simulated projection data from an elliptical orbit demonstrate correction of the spatially variant blurring and distortion in the reconstructed image caused by the noncircular orbit geometry

  15. Simulation of the collimator of the residual stress instrument

    International Nuclear Information System (INIS)

    Li, Jian; Wang, Xiaoying; Xie, Chaomei

    2009-04-01

    In order to understand the detailed influence from the collimator system to the main index of the Residual Stress Nertron Diffractometer (RSND) such as the flux at sample position, and the resolution of the spectrometer, the MCStas simulation software is used to build the proper Model of the Collimator system to complete the calculation and simulation. During the simulation, the authors setup the divergence and length of each collimator to check if it had big effect to the whole system. Based on the simulation, the authors obtained an optimized result: When the α 1 =α 2 =30', the horizontal flux at the sample position can be 2.3 x 10 6 n·cm -2 ·s -1 , the vertical flux can be 3.5 x 10 6 n·cm -2 ·s -1 , and when the α 1 =α 2 =10' the best resolution of the spectrometer can be 0.2 degree. This is a valuable result for the RDND. (authors)

  16. Self-collimation in photonic crystals. Applications and opportunities

    International Nuclear Information System (INIS)

    Noori, Mina; Soroosh, Mohammad; Baghban, Hamed

    2018-01-01

    A comprehensive review considering recent advances in self-collimation and its applications in optical integration is covered in the current article. Self-collimation is compared to the conventional technique of photonic bandgap engineering to control the light propagation in photonic crystal-based structures. It is fully discussed how the self-collimation phenomenon can be tailored to be independent of the incident angle and polarization. This adds substantial flexibility to the structure to overcome light coupling challenges and simultaneously aids in the omission of bulk and challenging elements, including polarizers and lenses from optical integrated circuits. Additionally, designed structures have the potential to be rescaled to operate in any desired frequency range thanks to the scalability rule in the field of electromagnetics. Moreover, it is shown that one can boost the coupling efficiency by applying an anti-reflection property to the structure, which provides not only efficient index matching but also the matching between external waves with uniform amplitude and Bloch waves with periodic amplitude. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. First Sub-arcsecond Collimation of Monochromatic Neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Wagh, Apoorva G; Abbas, Sohrab; Treimer, Wolfgang, E-mail: nintsspd@barc.gov.in

    2010-11-01

    We have achieved the tightest collimation to date of a monochromatic neutron beam by diffracting neutrons from a Bragg prism, viz. a single crystal prism operating in the vicinity of Bragg incidence. An optimised silicon {l_brace}111{r_brace} Bragg prism has collimated 5.26A neutrons down to 0.58 arcsecond. In conjunction with a similarly optimised Bragg prism analyser of opposite asymmetry, this ultra-parallel beam yielded a 0.62 arcsecond wide rocking curve. This beam has produced the first SUSANS spectrum in Q {approx} 10{sup -6} A{sup -1} range with a hydroxyapatite casein protein sample and demonstrated the instrument capability of characterising agglomerates upto 150 {mu}m in size. The super-collimation has also enabled recording of the first neutron diffraction pattern from a macroscopic grating of 200 {mu}m period. An analysis of this pattern yielded the beam transverse coherence length of 175 {mu}m (FWHM), the greatest achieved to date for A wavelength neutrons.

  18. A rotating-slit-collimator-based gamma radiation mapper.

    Science.gov (United States)

    Nilsson, Jonas M C; Finck, Robert R; Rääf, Christopher L

    2017-10-01

    For situations with radioactive material out of control where it may be physically difficult or prohibited to access areas close to the source, measurements from distance may be the only way to assess the radiation environment. Using collimated detectors will provide means to locate the direction of the radiation from the source. To investigate the possibilities of mapping gamma emitting radioactive material in a closed non-enterable area, a tentative system for mapping radioactive materials from a distance was built. The system used a computer controlled cylindrical rotating slit collimator with a high purity germanium detector placed in the cylinder. The system could be placed on a car-towed trailer, with the centre of the detector about 1.4 m above ground. Mapping was accomplished by the use of a specially developed image reconstruction algorithm that requires measurements from two or more locations around the area to be investigated. The imaging capability of the system was tested by mapping an area, 25 by 25 m 2 , containing three 330 MBq 137 Cs point sources. Using four locations outside the area with about 20 min measuring time in each location and applying the image reconstruction algorithm on the deconvoluted data, the system indicated the three source locations with an uncertainty of 1-3 m. The results demonstrated the potential of using collimated mobile gamma radiometry combined with image reconstruction to localize gamma sources inside non-accessible areas. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Locating gamma radiation source by self collimating BGO detector system

    Energy Technology Data Exchange (ETDEWEB)

    Orion, I; Pernick, A; Ilzycer, D; Zafrir, H [Israel Atomic Energy Commission, Yavne (Israel). Soreq Nuclear Research Center; Shani, G [Ben-Gurion Univ. of the Negev, Beersheba (Israel)

    1996-12-01

    The need for airborne collimated gamma detector system to estimate the radiation released from a nuclear accident has been established. A BGO detector system has been developed as an array of separate seven cylindrical Bismuth Germanate scintillators, one central detector symmetrically surrounded by six detectors. In such an arrangement, each of the detectors reduced the exposure of other detectors in the array to a radiation incident from a possible specific spatial angle, around file array. This shielding property defined as `self-collimation`, differs the point source response function for each of the detectors. The BGO detector system has a high density and atomic number, and therefore provides efficient self-collimation. Using the response functions of the separate detectors enables locating point sources as well as the direction of a nuclear radioactive plume with satisfactory angular resolution, of about 10 degrees. The detector`s point source response, as function of the source direction, in a horizontal plane, has been predicted by analytical calculation, and was verified by Monte-Carlo simulation using the code EGS4. The detector`s response was tested in a laboratory-scale experiment for several gamma ray energies, and the experimental results validated the theoretical (analytical and Monte-Carlo) results. (authors).

  20. Mechanical Engineering and Design of Novel Collimators for HL-LHC

    CERN Document Server

    Carra, F; Dallocchio, A; Gentini, L; Gradassi, P; Maitrejean, G; Manousos, A; Mariani, N; Mounet, N; Quaranta, E; Redaelli, S; Vlachoudis, V

    2014-01-01

    In view of High Luminosity LHC (HL-LHC) upgrades, collimator materials may become a limit to the machine performance: the high RF impedance of Carbon-Carbon composites used for primary and secondary collimators can lead to beam instabilities, while the Tungsten alloy adopted in tertiary collimators exhibits low robustness in case of beam-induced accidents. An R&D program has been pursued to develop new materials overcoming such limitations. Molybdenum-Graphite, in addition to its outstanding thermal conductivity, can be coated with pure molybdenum, reducing collimator impedance by a factor of 10. A new secondary collimator is being designed around this novel composite. New high-melting materials are also proposed to improve the robustness of tertiary collimators. New collimators will also be equipped with BPMs, significantly enhancing the alignment speed and the beta-star reach. This implies additional constraints of space, as well as detailed static and fatigue calculations on cables and connectors. This...

  1. Optimal Shape of a Gamma-ray Collimator: single vs double knife edge

    Science.gov (United States)

    Metz, Albert; Hogenbirk, Alfred

    2017-09-01

    Gamma-ray collimators in nuclear waste scanners are used for selecting a narrow vertical segment in activity measurements of waste vessels. The system that is used by NRG uses tapered slit collimators of both the single and double knife edge type. The properties of these collimators were investigated by means of Monte Carlo simulations. We found that single knife edge collimators are highly preferable for a conservative estimate of the activity of the waste vessels. These collimators show much less dependence on the angle of incidence of the radiation than double knife edge collimators. This conclusion also applies to cylindrical collimators of the single knife edge type, that are generally used in medical imaging spectroscopy.

  2. LHC Collimators with Embedded Beam Position Monitors: a New Adbanced Mechanical Design

    CERN Document Server

    Dallocchio, A; Boccard, C; Carra, F; Gasior, M; Gentini, L; Timmins, M

    2011-01-01

    The LHC collimation system, ensuring both functions of beam cleaning and machine protection, is potentially submitted to high-energy beam impacts. Currently the collimators setup is performed by monitoring beam losses generated by the collimator jaws when approaching the particle beam. This procedure is applied to all LHC collimators (almost one hundred), taking several hours, and needs to be repeated if beam settings change significantly. Furthermore, during the beam-based alignment, the LHC tertiary collimators are potentially exposed to abnormal losses entailing possible damage to their tungsten jaws. To improve the efficiency of the machine operation and better control the particle beam a new advanced design embedding Beam Position Monitors (BPM) into the movable collimator jaws has been developed. This paper describes the mechanical design of various types of future collimators with embedded BPMs. Experimental measurements performed on a simplified functional prototype installed in the CERN SPS showed th...

  3. LHC Collimators with Embedded Beam Position Monitors: A New Advanced Mechanical Design

    CERN Document Server

    Dallocchio, A; Boccard, C; Carra, F; Gasior, M; Gentini, L; Timmins, M A

    2011-01-01

    The LHC collimation system, ensuring both functions of beam cleaning and machine protection, is potentially submitted to high-energy beam impacts. Currently the collimators setup is performed by monitoring beam losses generated by the collimator jaws when approaching the particle beam. This procedure is applied to all LHC collimators (almost one hundred), taking several hours, and needs to be repeated if beam settings change significantly. Furthermore, during the beam-based alignment, the LHC tertiary collimators are potentially exposed to abnormal losses entailing possible damage to their tungsten jaws. To improve the efficiency of the machine operation and better control the particle beam a new advanced design embedding Beam Position Monitors (BPM) into the movable collimator jaws has been developed. This paper describes the mechanical design of various types of future collimators with embedded BPMs. Experimental measurements performed on a simplified functional prototype installed in the CERN SPS showed th...

  4. LOR-interleaving image reconstruction for PET imaging with fractional-crystal collimation

    International Nuclear Information System (INIS)

    Li, Yusheng; Matej, Samuel; Karp, Joel S; Metzler, Scott D

    2015-01-01

    Positron emission tomography (PET) has become an important modality in medical and molecular imaging. However, in most PET applications, the resolution is still mainly limited by the physical crystal sizes or the detector’s intrinsic spatial resolution. To achieve images with better spatial resolution in a central region of interest (ROI), we have previously proposed using collimation in PET scanners. The collimator is designed to partially mask detector crystals to detect lines of response (LORs) within fractional crystals. A sequence of collimator-encoded LORs is measured with different collimation configurations. This novel collimated scanner geometry makes the reconstruction problem challenging, as both detector and collimator effects need to be modeled to reconstruct high-resolution images from collimated LORs. In this paper, we present a LOR-interleaving (LORI) algorithm, which incorporates these effects and has the advantage of reusing existing reconstruction software, to reconstruct high-resolution images for PET with fractional-crystal collimation. We also develop a 3D ray-tracing model incorporating both the collimator and crystal penetration for simulations and reconstructions of the collimated PET. By registering the collimator-encoded LORs with the collimator configurations, high-resolution LORs are restored based on the modeled transfer matrices using the non-negative least-squares method and EM algorithm. The resolution-enhanced images are then reconstructed from the high-resolution LORs using the MLEM or OSEM algorithm. For validation, we applied the LORI method to a small-animal PET scanner, A-PET, with a specially designed collimator. We demonstrate through simulated reconstructions with a hot-rod phantom and MOBY phantom that the LORI reconstructions can substantially improve spatial resolution and quantification compared to the uncollimated reconstructions. The LORI algorithm is crucial to improve overall image quality of collimated PET, which

  5. Characterization of parallel-hole collimator using Monte Carlo Simulation

    International Nuclear Information System (INIS)

    Pandey, Anil Kumar; Sharma, Sanjay Kumar; Karunanithi, Sellam; Kumar, Praveen; Bal, Chandrasekhar; Kumar, Rakesh

    2015-01-01

    Accuracy of in vivo activity quantification improves after the correction of penetrated and scattered photons. However, accurate assessment is not possible with physical experiment. We have used Monte Carlo Simulation to accurately assess the contribution of penetrated and scattered photons in the photopeak window. Simulations were performed with Simulation of Imaging Nuclear Detectors Monte Carlo Code. The simulations were set up in such a way that it provides geometric, penetration, and scatter components after each simulation and writes binary images to a data file. These components were analyzed graphically using Microsoft Excel (Microsoft Corporation, USA). Each binary image was imported in software (ImageJ) and logarithmic transformation was applied for visual assessment of image quality, plotting profile across the center of the images and calculating full width at half maximum (FWHM) in horizontal and vertical directions. The geometric, penetration, and scatter at 140 keV for low-energy general-purpose were 93.20%, 4.13%, 2.67% respectively. Similarly, geometric, penetration, and scatter at 140 keV for low-energy high-resolution (LEHR), medium-energy general-purpose (MEGP), and high-energy general-purpose (HEGP) collimator were (94.06%, 3.39%, 2.55%), (96.42%, 1.52%, 2.06%), and (96.70%, 1.45%, 1.85%), respectively. For MEGP collimator at 245 keV photon and for HEGP collimator at 364 keV were 89.10%, 7.08%, 3.82% and 67.78%, 18.63%, 13.59%, respectively. Low-energy general-purpose and LEHR collimator is best to image 140 keV photon. HEGP can be used for 245 keV and 364 keV; however, correction for penetration and scatter must be applied if one is interested to quantify the in vivo activity of energy 364 keV. Due to heavy penetration and scattering, 511 keV photons should not be imaged with HEGP collimator

  6. Comparison of fan beam, slit-slat and multi-pinhole collimators for molecular breast tomosynthesis.

    Science.gov (United States)

    van Roosmalen, Jarno; Beekman, Freek J; Goorden, Marlies C

    2018-05-16

    Recently, we proposed and optimized dedicated multi-pinhole molecular breast tomosynthesis (MBT) that images a lightly compressed breast. As MBT may also be performed with other types of collimators, the aim of this paper is to optimize MBT with fan beam and slit-slat collimators and to compare its performance to that of multi-pinhole MBT to arrive at a truly optimized design. Using analytical expressions, we first optimized fan beam and slit-slat collimator parameters to reach maximum sensitivity at a series of given system resolutions. Additionally, we performed full system simulations of a breast phantom containing several tumours for the optimized designs. We found that at equal system resolution the maximum achievable sensitivity increases from pinhole to slit-slat to fan beam collimation with fan beam and slit-slat MBT having on average a 48% and 20% higher sensitivity than multi-pinhole MBT. Furthermore, by inspecting simulated images and applying a tumour-to-background contrast-to-noise (TB-CNR) analysis, we found that slit-slat collimators underperform with respect to the other collimator types. The fan beam collimators obtained a similar TB-CNR as the pinhole collimators, but the optimum was reached at different system resolutions. For fan beam collimators, a 6-8 mm system resolution was optimal in terms of TB-CNR, while with pinhole collimation highest TB-CNR was reached in the 7-10 mm range.

  7. Slit-Slat Collimator Equipped Gamma Camera for Whole-Mouse SPECT-CT Imaging

    Science.gov (United States)

    Cao, Liji; Peter, Jörg

    2012-06-01

    A slit-slat collimator is developed for a gamma camera intended for small-animal imaging (mice). The tungsten housing of a roof-shaped collimator forms a slit opening, and the slats are made of lead foils separated by sparse polyurethane material. Alignment of the collimator with the camera's pixelated crystal is performed by adjusting a micrometer screw while monitoring a Co-57 point source for maximum signal intensity. For SPECT, the collimator forms a cylindrical field-of-view enabling whole mouse imaging with transaxial magnification and constant on-axis sensitivity over the entire axial direction. As the gamma camera is part of a multimodal imaging system incorporating also x-ray CT, five parameters corresponding to the geometric displacements of the collimator as well as to the mechanical co-alignment between the gamma camera and the CT subsystem are estimated by means of bimodal calibration sources. To illustrate the performance of the slit-slat collimator and to compare its performance to a single pinhole collimator, a Derenzo phantom study is performed. Transaxial resolution along the entire long axis is comparable to a pinhole collimator of same pinhole diameter. Axial resolution of the slit-slat collimator is comparable to that of a parallel beam collimator. Additionally, data from an in-vivo mouse study are presented.

  8. Effects of hole tapering on cone-beam collimation for brain SPECT imaging

    International Nuclear Information System (INIS)

    Park, Mi-Ae; Kijewski, Marie Foley; Moore, Stephen C.

    2006-01-01

    New collimator manufacturing technologies, such as photoetching, electrical discharge machining, and stereolithography, expand the range of possible cone-beam collimator configurations. For example, it might now be possible for brain SPECT to make a short-focusing cone-beam collimator with tapered holes that increase in size with distance from the collimator surface; conventional lead-casting techniques produce holes of constant size and, consequently, varying septal thicknesses. Moreover, the changes in hole shape and loss of close packing due to focusing leads to thicker septa in the collimator periphery, especially for shorter focal lengths. We investigated the potential advantages of new cone-beam collimator manufacturing processes, and proposed a new design for very short focal-length collimators for brain SPECT imaging. We compared three cone-beam collimators, a conventional collimator manufactured using casting techniques (CC), a novel collimator with uniform hole sizes on the collimator surface and constant hole size through the collimator thickness (FC), and a novel collimator with uniform hole sizes and tapered holes (TC). We determined the resolution of each collimator analytically for focal lengths ranging from 20-50 cm, and adjusted the entrance hole sizes of FC and TC to equalize resolution of all collimators. Sensitivity was calculated at several locations by Monte Carlo simulation. Sensitivity was higher at all points for TC and FC than for CC, and higher for TC than for FC. The differences in sensitivity were larger for shorter focal lengths. For a point on the focal line at 10 cm in front of the collimator entrance surface, the sensitivity gain for TC compared to CC was 7% and 45% for focal lengths of 50 and 20 cm, respectively. The sensitivity gain for a 20-cm focal length, compared to CC, averaged over all locations, was 44% for TC and 23% for FC. We have shown that the new collimator designs made possible by new manufacturing techniques will

  9. Validity of medium-energy collimator for sentinel lymphoscintigraphy imaging

    International Nuclear Information System (INIS)

    Tsushima, Hiroyuki; Yamanaga, Takashi; Shimonishi, Yoshihiro; Kosakai, Kazuhisa; Takayama, Teruhiko; Kizu, Hiroto; Noguchi, Atsushi; Onoguchi, Masahisa

    2007-01-01

    For lymphoscintigraphy to detect sentinel lymph node (SLN) in the breast cancer, the lead shielding of the injection site is often used to avoid artifacts, but the method tends to cover the neighborhood SLN. To exclude this defect, authors developed ME (medium-energy) method where ME collimator and energy setting shifted to its higher region were employed. This paper described the development and validity evaluation of the ME method. Performed were examinations with 3 acrylic phantoms of the injection site (IS), LN and combination of IS+LN (CB): IS was a cylinder, containing 40 MBq of 99m Tc-pertechnetate and LN, a plate with 30 sealed holes having 0.78-400 kBq. CB phantom consisted from LN-simulating holes (each, 40 kBq) placed linearly around the center of IS in H and S directions. Imaging was conducted with 2 kinds of 2-detector gamma camera, FORTE (ADAGA) and DSX rectangular (Sopha Medical Corp.). CB phantom was found optimally visualized by ME collimator at 146, rather than 141, keV. In clinic, 99m Tc-Sn-colloid 40 MBq was given near the tumor of a patient and imaging was done with or without the lead shield with FORTE equipped with low energy high-resolution or ME collimator for their comparison. The present ME method described above set at 146 keV was found to give the image with excellent contrast and without false positive when compared with the lead shield method hitherto. (R.T.)

  10. Hard X-ray imaging with a slat collimated telescope

    International Nuclear Information System (INIS)

    Lu Zhuguo; Kotov, Yu.D.; Suslov, A.Yu.

    1995-01-01

    Imaging experiments with a slat collimated hard X-ray telescope are described in this paper demonstrating the feasibility of the direct demodulation imaging method used in hard X-ray scanning modulation experiments. On 25 September 1993 an X-ray raster scan observation of Cyg X-1 was performed in a balloon flight with the hard X-ray telescope HAPI-4. An experiment to image radioactive X-ray sources was performed in the laboratory before. In both experiments the expected X-ray images were obtained, confirming the imaging capability of this method. (orig.)

  11. Plume collimation for laser ablation electrospray ionization mass spectrometry

    Science.gov (United States)

    Vertes, Akos; Stolee, Jessica A.

    2014-09-09

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  12. Integrated simulation tools for collimation cleaning in HL-LHC

    CERN Document Server

    Bruce, R; Cerutti, F; Ferrari, A; Lechner, A; Marsili, A; Mirarchi, D; Ortega, P G; Redaelli, S; Rossi, A; Salvachua, B; Sinuela, D P; Tambasco, C; Vlachoudis, V; Mereghetti, A; Assmann, R; Lari, L; Gibson, S M; Nevay, LJ; Appleby, R B; Molson, J; Serluca, M; Barlow, R J; Rafique, H; Toader, A

    2014-01-01

    The Large Hadron Collider is designed to accommodate an unprecedented stored beam energy of 362 MJ in the nominal configuration and about the double in the high-luminosity upgrade HL-LHC that is presently under study. This requires an efficient collimation system to protect the superconducting magnets from quenches. During the design, it is therefore very important to accurately predict the expected beam loss distributions and cleaning efficiency. For this purpose, there are several ongoing efforts in improving the existing simulation tools or developing new ones. This paper gives a brief overview and status of the different available codes.

  13. Characteristic of laser diode beam propagation through a collimating lens.

    Science.gov (United States)

    Xu, Qiang; Han, Yiping; Cui, Zhiwei

    2010-01-20

    A mathematical model of a laser diode beam propagating through a collimating lens is presented. Wave propagation beyond the paraxial approximation is studied. The phase delay of the laser diode wave in passing through the lens is analyzed in detail. The propagation optical field after the lens is obtained from the diffraction integral by the stationary phase method. The model is employed to predict the light intensity at various beam cross sections, and the computed intensity distributions are in a good agreement with the corresponding measurements.

  14. Off-momentum collimation and cleaning in the energy ramp in the LHC

    CERN Document Server

    Quaranta, Elena; Giulini Castiglioni Agosteo, Stefano Luigi Maria

    This Master thesis work has been carried out at CERN in the framework of the LHC (Large Hadron Collider) Collimation project. The LHC is a two-beam proton collider, built to handle a stored energy of 360MJ for each beam. Since the energy deposition from particle losses could quench the superconducting magnets, a system of collimators has been installed in two cleaning insertions in the ring and in the experimental areas. The achievable LHC beam intensity is directly coupled to the beam loss rate and, consequently, to the cleaning eciency of the collimation system. This study analyses the collimation cleaning performance in dierent scenarios inside the accelerator. First, simulations are performed of the transverse losses in the LHC collimation system during the acceleration process. The results are compared with data taken during a dedicated session at the LHC machine. Simulations are also performed to predict the collimation eciency during future operation at higher energy. Furthermore, an investigation of t...

  15. Three-dimensional single-photon emission computed tomography using cone beam collimation (CB-SPECT)

    International Nuclear Information System (INIS)

    Jaszczak, R.J.; Floyd, C.E. Jr.; Manglos, S.H.; Greer, K.L.; Coleman, R.E.

    1986-01-01

    A simple and economically practical method of improving the sensitivity of camera-based SPECT was developed using converging (cone-beam) collimation. This geometry is particularly advantageous for SPECT devices using large field-of-view cameras in imaging smaller, centrally located activity distributions. Geometric sensitivities, spatial resolutions, and fields-of-view of a cone-beam collimator having a focal length of 48 cm and a similarly designed parallel hole collimator were compared analytically. At 15 cm from the collimator surface the point-source sensitivity of the cone-beam collimator was 2.4 times the sensitivity of the parallel-hole collimator. SPECT projection data (simulated using Monte Carlo methodology) were reconstructed using a 3-D filtered backprojection algorithm. Cone-beam emission CT (CB-SPECT) seems potentially useful for animal investigations, pediatric studies, and for brain imaging

  16. Cerrobend collimation effect on electron beams; Efeito de colimacoes de cerrobend em feixes de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Furnari, Laura; Albino, Lucas D.; Ribeiro, Victor A.B.; Santos, Gabriela R., E-mail: laurafurnari@hotmail.com [Universidade de Sao Paulo (InRad/FM/USP), SP (Brazil). Faculdade de Medicina. Hospital das Clinicas. Instituto de Radiologia

    2012-12-15

    The aim of this work was to discuss about the cerrobend collimation effect on clinical electron beams. When a cerrobend collimation is used, both the percentage depth dose (PDD) and the absolute dose that is delivered to the patient changes. It was analyzed how those parameters change and it was evaluated in which cases a correction factor should be applied due to this collimation. It was founded that, when the smallest dimension of the collimation is smaller than the minimum radius to lateral scatter equilibrium, the collimation will change the PDD in such a way that it should take into account in the treatment planning. For one specific collimation usually applied in head and neck treatments, it was found that no correction factor is necessary. (author)

  17. First Design of a Proton Collimation System for 50 TeV FCC-hh

    CERN Document Server

    Fiascaris, Maria; Mirarchi, Daniele; Redaelli, Stefano

    2016-01-01

    We present studies aimed at defining a first conceptual solution for a collimation system for the hadron-hadron option for the Future Circular Collider (FCC-hh). The baseline collimation layout is based on the scaling of the present LHC collimation system to the FCC-hh energy. It currently includes a dedicated betatron cleaning insertion as well as collimators in the experimental insertions to protect the inner triplets. An aperture model for the FCC-hh is defined and the geometrical acceptance is calculated at top energy taking into account mechanical and optics imperfections. Based on these studies the collimator settings needed to protect the machine are defined. The performance of the collimation system is then assessed with particle tracking simulation tools assuming a perfect machine.

  18. Evaluation of the response of a round hole scintillation camera collimator by the Fourier analysis method

    International Nuclear Information System (INIS)

    Hernandez, A.; Millan, S.; Yzuel, M.J.

    1986-01-01

    The Fourier analysis method was used to investigate the response of scintillation camera collimators with parallel holes. This method which takes into account the septal penetration was applied to the case of round hole collimators having a hexagonal distribution. Modulation transfer functions, MTF have been determined to verify the accuracy of the computed Fourier coefficients of the collimator function. Comparisons between the geometric and the penetrating plus geometric transfer function are shown for round and hexagonal holes. (author)

  19. Auxiliary collimating device for obtaining irradiation fields of any shape for high energy radiotherapy apparatus

    International Nuclear Information System (INIS)

    Piret, P.; Fraikin, H.; Hubert, A.

    1976-01-01

    An auxiliary collimator is added to the main collimator of a radiotherapy apparatus and comprises a master-container filled with mercury and a localizing container containing a block of nonabsorbent material having a predetermined shape; means being provided for automatically positioning these containers with respect to the main collimator and for allowing the mercury to enter the localizing container when once it has taken its working position

  20. Dynamic and Stagnating Plasma Flow Leading to Magnetic-Flux-Tube Collimation

    International Nuclear Information System (INIS)

    You, S.; Yun, G.S.; Bellan, P.M.

    2005-01-01

    Highly collimated, plasma-filled magnetic-flux tubes are frequently observed on galactic, stellar, and laboratory scales. We propose that a single, universal magnetohydrodynamic pumping process explains why such collimated, plasma-filled magnetic-flux tubes are ubiquitous. Experimental evidence from carefully diagnosed laboratory simulations of astrophysical jets confirms this assertion and is reported here. The magnetohydrodynamic process pumps plasma into a magnetic-flux tube and the stagnation of the resulting flow causes this flux tube to become collimated

  1. Design and fabrication of multigrid X-ray collimators. [For airborne x-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Acton, L W; Joki, E G; Salmon, R J [Lockheed Missiles and Space Co., Palo Alto, Calif. (USA). Lockheed Palo Alto Research Lab.

    1976-08-01

    Multigrid X-ray collimators continue to find wide application in space research. This paper treats the principles of their design and fabrication and summarizes the experience obtained in making and flying thirteen such collimators ranging in angular resolution from 10 to 0.7 arc min FWHM. Included is a summary of a survey of scientist-users and industrial producers of collimator grids regarding grid materials, precision, plating, hole quality and results of acceptance testing.

  2. Preliminary Comparison of the Response of LHC Tertiary Collimators to Proton and Ion Beam Impacts

    CERN Document Server

    Cauchi, M; Bertarelli, A; Carra, F; Cerutti, F; Lari, L; Mollicone, P; Sammut, N

    2013-01-01

    The CERN Large Hadron Collider is designed to bring into collision protons as well as heavy ions. Accidents involving impacts on collimators can happen for both species. The interaction of lead ions with matter differs to that of protons, thus making this scenario a new interesting case to study as it can result in different damage aspects on the collimator. This paper will present a preliminary comparison of the response of collimators to proton and ion beam impacts.

  3. MERLIN Cleaning Studies with Advanced Collimator Materials for HL-LHC

    CERN Document Server

    Valloni, A.; Mereghetti, A.; Molson, J. G.; Appleby, R.; Bruce, R.; Quaranta, E.; Redaelli, S.

    2016-01-01

    The challenges of the High-Luminosity upgrade of the Large Hadron Collider require improving the beam collimation system. An intense R&D program has started at CERN to explore novel materials for new collimator jaws to improve robustness and reduce impedance. Particle tracking simulations of collimation efficiency are performed using the code MERLIN which has been extended to include new materials based on composites. After presenting two different implementations of composite materials tested in MERLIN, we present simulation studies with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.

  4. Dose characteristics of in-house-built collimators for stereotactic radiotherapy with a linear accelerator

    International Nuclear Information System (INIS)

    Norrgaard, F. Stefan E.; Kulmala, Jarmo A.J.; Minn, Heikki R.I.; Sipilae, Petri M.

    1998-01-01

    Dose characteristics of a stereotactic radiotherapy unit based on a standard Varian Clinac 4/100 4 MV linear accelerator, in-house-built Lipowitz collimators and the SMART stereotactic radiotherapy treatment planning software have been determined. Beam collimation is constituted from the standard collimators of the linear accelerator and a tertiary collimation consisting of a replaceable divergent Lipowitz collimator. Four collimators with isocentre diameters of 15, 25, 35 and 45 mm, respectively, were constructed. Beam characteristics were measured in air, acrylic or water with ionization chamber, photon diode, electron diode, diamond detector and film. Monte Carlo simulation was also applied. The radiation leakage under the collimators was less than 1% at 50 mm depth in water. Specific beam characteristics for each collimator were imported to SMART and dose planning with five non-coplanar converging 140 deg. arcs separated by 36 deg. angles was performed for treatment of a RANDO phantom. Dose verification was made with TLD and radiochromic film. The in-house-built collimators were found to be suitable for stereotactic radiotherapy and patient treatments with this system are in progress. (author)

  5. Cardiac single-photon emission-computed tomography using combined cone-beam/fan-beam collimation

    International Nuclear Information System (INIS)

    Gullberg, Grant T.; Zeng, Gengsheng L.

    2004-01-01

    The objective of this work is to increase system sensitivity in cardiac single-photon emission-computed tomography (SPECT) studies without increasing patient imaging time. For imaging the heart, convergent collimation offers the potential of increased sensitivity over that of parallel-hole collimation. However, if a cone-beam collimated gamma camera is rotated in a planar orbit, the projection data obtained are not complete. Two cone-beam collimators and one fan-beam collimator are used with a three-detector SPECT system. The combined cone-beam/fan-beam collimation provides a complete set of data for image reconstruction. The imaging geometry is evaluated using data acquired from phantom and patient studies. For the Jaszazck cardiac torso phantom experiment, the combined cone-beam/fan-beam collimation provided 1.7 times greater sensitivity than standard parallel-hole collimation (low-energy high-resolution collimators). Also, phantom and patient comparison studies showed improved image quality. The combined cone-beam/fan-beam imaging geometry with appropriate weighting of the two data sets provides improved system sensitivity while measuring sufficient data for artifact free cardiac images

  6. Anatomically shaped cranial collimation (ACC) for lateral cephalometric radiography: a technical report.

    Science.gov (United States)

    Hoogeveen, R C; van der Stelt, P F; Berkhout, W E R

    2014-01-01

    Lateral cephalograms in orthodontic practice display an area cranial of the base of the skull that is not required for diagnostic evaluation. Attempts have been made to reduce the radiation dose to the patient using collimators combining the shielding of the areas above the base of the skull and below the mandible. These so-called "wedge-shaped" collimators have not become standard equipment in orthodontic offices, possibly because these collimators were not designed for today's combination panoramic-cephalometric imaging systems. It also may be that the anatomical variability of the area below the mandible makes this area unsuitable for standardized collimation. In addition, a wedge-shaped collimator shields the cervical vertebrae; therefore, assessment of skeletal maturation, which is based on the stage of development of the cervical vertebrae, cannot be performed. In this report, we describe our investigations into constructing a collimator to be attached to the cephalostat and shield the cranial area of the skull, while allowing the visualization of diagnostically relevant structures and markedly reducing the size of the irradiated area. The shape of the area shielded by this "anatomically shaped cranial collimator" (ACC) was based on mean measurements of cephalometric landmarks of 100 orthodontic patients. It appeared that this collimator reduced the area of irradiation by almost one-third without interfering with the imaging system or affecting the quality of the image. Further research is needed to validate the clinical efficacy of the collimator.

  7. A new approach to evaluate the response functions for conical and cylindrical collimators

    International Nuclear Information System (INIS)

    Gigante, G.E.

    1989-01-01

    A new approach to the evaluation of the conical collimator response function is shown. The basic collimator formulae are reviewed. The collimator response function has been found in a very easy way. An approximate solution has been introduced. Studying the response of a measuring system, the use of this approximation strongly reduces the complexity of the relations to be used; therefore it would provide a useful starting point for a Monte Carlo calculation. The errors introduced are less than 10%. Approximate relations that allow the evaluation of the response of conical and cylindrical collimators to plane and line sources are also given. (orig.)

  8. A collimator optimization method for quantitative imaging: application to Y-90 bremsstrahlung SPECT.

    Science.gov (United States)

    Rong, Xing; Frey, Eric C

    2013-08-01

    Post-therapy quantitative 90Y bremsstrahlung single photon emission computed tomography (SPECT) has shown great potential to provide reliable activity estimates, which are essential for dose verification. Typically 90Y imaging is performed with high- or medium-energy collimators. However, the energy spectrum of 90Y bremsstrahlung photons is substantially different than typical for these collimators. In addition, dosimetry requires quantitative images, and collimators are not typically optimized for such tasks. Optimizing a collimator for 90Y imaging is both novel and potentially important. Conventional optimization methods are not appropriate for 90Y bremsstrahlung photons, which have a continuous and broad energy distribution. In this work, the authors developed a parallel-hole collimator optimization method for quantitative tasks that is particularly applicable to radionuclides with complex emission energy spectra. The authors applied the proposed method to develop an optimal collimator for quantitative 90Y bremsstrahlung SPECT in the context of microsphere radioembolization. To account for the effects of the collimator on both the bias and the variance of the activity estimates, the authors used the root mean squared error (RMSE) of the volume of interest activity estimates as the figure of merit (FOM). In the FOM, the bias due to the null space of the image formation process was taken in account. The RMSE was weighted by the inverse mass to reflect the application to dosimetry; for a different application, more relevant weighting could easily be adopted. The authors proposed a parameterization for the collimator that facilitates the incorporation of the important factors (geometric sensitivity, geometric resolution, and septal penetration fraction) determining collimator performance, while keeping the number of free parameters describing the collimator small (i.e., two parameters). To make the optimization results for quantitative 90Y bremsstrahlung SPECT more

  9. Calibration issues of the TFTR multichannel neutron collimator

    International Nuclear Information System (INIS)

    Goeler, S. von; Johnson, L.C.; Bitter, M.; Efthimion, P.C.; Roquemore, A.L.

    1996-01-01

    The calibration procedures for the detectors in the Neutron Collimator are reviewed. The absolute calibration was performed for the NE451 detectors, in situ, by moving a DT neutron generator in the TFTR vacuum vessel across each sight line. This calibration was transferred to other detectors in the same channel. Four new sight lines have been installed at a different toroidal location, which view the plasma through the vacuum vessel port cover rather than through thinned windows. The new detectors are cross-calibrated to the NE451 detectors with a jog shot procedure, where the plasma is quickly shifted in major radius over a distance of 30 cm. The jog shot procedure shows that scattered neutrons account approximately for 30% of the signal of the new central channels. The neutron source strength from the collimator agrees within 10% with the source strength from global neutron monitors in the TFTR test cell. Detector non-linearity is discussed. Another special issue is the behavior of the detectors during T-puffs, where the DD/DT neutron ratio changes rapidly

  10. X-ray microscopy using collimated and focussed synchrotron radiation

    International Nuclear Information System (INIS)

    Jones, K.W.; Kwiatek, W.M.; Gordon, B.M.

    1987-01-01

    X-ray microscopy is a field that has developed rapidly in recent years. Two different approaches have been used. Zone plates have been employed to produce focused beams with sizes as low as 0.07 μm for x-ray energies below 1 keV. Images of biological materials and elemental maps for major and minor low Z have been produced using above and below absorption edge differences. At higher energies collimators and focusing mirrors have been used to make small diameter beams for excitation of characteristic K- or L-x rays of all elements in the periodic table. The practicality of a single instrument combining all the features of these two approaches is unclear. The use of high-energy x rays for x-ray microscopy has intrinsic value for characterization of thick samples and determination of trace amounts of most elements. A summary of work done on the X-26 beam line at the National Synchrotron Light Source (NSLS) with collimated and focused x rays with energies above 4 keV is given here. 6 refs., 5 figs., 1 tab

  11. Direct fission fragment energy converter - Magnetic collimator option

    International Nuclear Information System (INIS)

    Tsvetkov, P. V.; Hart, R. R.

    2006-01-01

    The present study was focused on developing a technologically feasible power system that is based on direct fission fragment energy conversion utilizing magnetic collimation. The new concept is an attempt to combine several advantageous design solutions, which have been proposed for application in both fission and fusion reactors, into one innovative system that can offer exceptional energy conversion efficiency. The analysis takes into consideration a wide range of operational aspects including fission fragment escape from the fuel, collimation, collection, criticality, long-term performance, energy conversion efficiency, heat removal, and safety characteristics. Specific characteristics of the individual system components and the entire system are evaluated. Analysis and evaluation of the technological feasibility of the concept were achieved using state-of-the-art computer codes that allowed realistic and consistent modeling. In addition to the extensive computational effort, the scaled prototype experimental proof-of-principle program was conducted to validate basic physics of the concept. The program was focused on electromagnetic components and experimental demonstration of performance. This paper summarizes the final results of the 6-years research program including both computational and experimental efforts. Potential future research and development and anticipated applications are discussed. (authors)

  12. Description and benefits of dynamic collimation in digital breast tomosynthesis

    International Nuclear Information System (INIS)

    Popova, Y.; Hersemeule, G.; Klausz, R.; Souchay, H.

    2015-01-01

    X-ray field to image receptor active area alignment is usually tested in mammographic QC. In digital breast tomosynthesis (dBT), the source moves during the acquisition, generating a displacement of the X-ray beam edges relative to the detector, in or out of the detector active area. To minimise unnecessary radiation while maximising the useful field of view, a solution consisting in adjusting the collimation with the source rotation was implemented on the GE SenoClaire dBT system. This solution is described and tested using three different methods based on: (1) images from the detector, (2) a non-screen film and (3) a semiconductor tool providing the X-ray intensity profile. Method 1 demonstrated a maximum positioning error of 0.3 mm. Method 2 was found non-applicable; Method 3 provided measurements within 1.5 mm. Dynamic collimation enables maintaining an X-ray field to detector congruence comparable with 2D. Measuring the position of the X-ray field edges using a dedicated tool makes routine QC possible. (authors)

  13. An energy-optimized collimator design for a CZT-based SPECT camera

    International Nuclear Information System (INIS)

    Weng, Fenghua; Bagchi, Srijeeta; Zan, Yunlong; Huang, Qiu; Seo, Youngho

    2016-01-01

    In single photon emission computed tomography, it is a challenging task to maintain reasonable performance using only one specific collimator for radiotracers over a broad spectrum of diagnostic photon energies, since photon scatter and penetration in a collimator differ with the photon energy. Frequent collimator exchanges are inevitable in daily clinical SPECT imaging, which hinders throughput while subjecting the camera to operational errors and damage. Our objective is to design a collimator, which is independent of the photon energy, performs reasonably well for commonly used radiotracers with low- to medium-energy levels of gamma emissions. Using the Geant4 simulation toolkit, we simulated and evaluated a parallel-hole collimator mounted to a CZT detector. With the pixel-geometry-matching collimation, the pitch of the collimator hole was fixed to match the pixel size of the CZT detector throughout this work. Four variables, hole shape, hole length, hole radius/width and the source-to-collimator distance were carefully studied. Scatter and penetration of the collimator, sensitivity and spatial resolution of the system were assessed for four radionuclides including "5"7Co, "9"9"mTc, "1"2"3I and "1"1"1In, with respect to the aforementioned four variables. An optimal collimator was then decided upon such that it maximized the total relative sensitivity (TRS) for the four considered radionuclides while other performance parameters, such as scatter, penetration and spatial resolution, were benchmarked to prevalent commercial scanners and collimators. Digital phantom studies were also performed to validate the system with the optimal square-hole collimator (23 mm hole length, 1.28 mm hole width, and 0.32 mm septal thickness) in terms of contrast, contrast-to-noise ratio and recovery ratio. This study demonstrates promise of our proposed energy-optimized collimator to be used in a CZT-based gamma camera, with comparable or even better imaging performance versus

  14. Comparing planar image quality of rotating slat and parallel hole collimation: influence of system modeling

    International Nuclear Information System (INIS)

    Holen, Roel van; Vandenberghe, Stefaan; Staelens, Steven; Lemahieu, Ignace

    2008-01-01

    The main remaining challenge for a gamma camera is to overcome the existing trade-off between collimator spatial resolution and system sensitivity. This problem, strongly limiting the performance of parallel hole collimated gamma cameras, can be overcome by applying new collimator designs such as rotating slat (RS) collimators which have a much higher photon collection efficiency. The drawback of a RS collimated gamma camera is that, even for obtaining planar images, image reconstruction is needed, resulting in noise accumulation. However, nowadays iterative reconstruction techniques with accurate system modeling can provide better image quality. Because the impact of this modeling on image quality differs from one system to another, an objective assessment of the image quality obtained with a RS collimator is needed in comparison to classical projection images obtained using a parallel hole (PH) collimator. In this paper, a comparative study of image quality, achieved with system modeling, is presented. RS data are reconstructed to planar images using maximum likelihood expectation maximization (MLEM) with an accurate Monte Carlo derived system matrix while PH projections are deconvolved using a Monte Carlo derived point-spread function. Contrast-to-noise characteristics are used to show image quality for cold and hot spots of varying size. Influence of the object size and contrast is investigated using the optimal contrast-to-noise ratio (CNR o ). For a typical phantom setup, results show that cold spot imaging is slightly better for a PH collimator. For hot spot imaging, the CNR o of the RS images is found to increase with increasing lesion diameter and lesion contrast while it decreases when background dimensions become larger. Only for very large background dimensions in combination with low contrast lesions, the use of a PH collimator could be beneficial for hot spot imaging. In all other cases, the RS collimator scores better. Finally, the simulation of a

  15. Joint optimization of collimator and reconstruction parameters in SPECT imaging for lesion quantification

    International Nuclear Information System (INIS)

    McQuaid, Sarah J; Southekal, Sudeepti; Kijewski, Marie Foley; Moore, Stephen C

    2011-01-01

    Obtaining the best possible task performance using reconstructed SPECT images requires optimization of both the collimator and reconstruction parameters. The goal of this study is to determine how to perform this optimization, namely whether the collimator parameters can be optimized solely from projection data, or whether reconstruction parameters should also be considered. In order to answer this question, and to determine the optimal collimation, a digital phantom representing a human torso with 16 mm diameter hot lesions (activity ratio 8:1) was generated and used to simulate clinical SPECT studies with parallel-hole collimation. Two approaches to optimizing the SPECT system were then compared in a lesion quantification task: sequential optimization, where collimation was optimized on projection data using the Cramer–Rao bound, and joint optimization, which simultaneously optimized collimator and reconstruction parameters. For every condition, quantification performance in reconstructed images was evaluated using the root-mean-squared-error of 400 estimates of lesion activity. Compared to the joint-optimization approach, the sequential-optimization approach favoured a poorer resolution collimator, which, under some conditions, resulted in sub-optimal estimation performance. This implies that inclusion of the reconstruction parameters in the optimization procedure is important in obtaining the best possible task performance; in this study, this was achieved with a collimator resolution similar to that of a general-purpose (LEGP) collimator. This collimator was found to outperform the more commonly used high-resolution (LEHR) collimator, in agreement with other task-based studies, using both quantification and detection tasks.

  16. Improved electron collimation system design for Elekta linear accelerators.

    Science.gov (United States)

    Pitcher, Garrett M; Hogstrom, Kenneth R; Carver, Robert L

    2017-09-01

    Prototype 10 × 10 and 20 × 20-cm 2 electron collimators were designed for the Elekta Infinity accelerator (MLCi2 treatment head), with the goal of reducing the trimmer weight of excessively heavy current applicators while maintaining acceptable beam flatness (±3% major axes, ±4% diagonals) and IEC leakage dose. Prototype applicators were designed initially using tungsten trimmers of constant thickness (1% electron transmission) and cross-sections with inner and outer edges positioned at 95% and 2% off-axis ratios (OARs), respectively, cast by the upstream collimating component. Despite redefining applicator size at isocenter (not 5 cm upstream) and reducing the energy range from 4-22 to 6-20 MeV, the designed 10 × 10 and 20 × 20-cm 2 applicator trimmers weighed 6.87 and 10.49 kg, respectively, exceeding that of the current applicators (5.52 and 8.36 kg, respectively). Subsequently, five design modifications using analytical and/or Monte Carlo (MC) calculations were applied, reducing trimmer weight while maintaining acceptable in-field flatness and mean leakage dose. Design Modification 1 beveled the outer trimmer edges, taking advantage of only low-energy beams scattering primary electrons sufficiently to reach the outer trimmer edge. Design Modification 2 optimized the upper and middle trimmer distances from isocenter for minimal trimmer weights. Design Modification 3 moved inner trimmer edges inward, reducing trimmer weight. Design Modification 4 determined optimal X-ray jaw positions for each energy. Design Modification 5 adjusted middle and lower trimmer shapes and reduced upper trimmer thickness by 50%. Design Modifications 1→5 reduced trimmer weights from 6.87→5.86→5.52→5.87→5.43→3.73 kg for the 10 × 10-cm 2 applicator and 10.49→9.04→8.62→7.73→7.35→5.09 kg for the 20 × 20-cm 2 applicator. MC simulations confirmed these final designs produced acceptable in-field flatness and met IEC-specified leakage dose at 7, 13, and 20 Me

  17. Lumbar spine radiography — poor collimation practices after implementation of digital technology

    DEFF Research Database (Denmark)

    Zetterberg, Lars Gøran; Espeland, Ansgar

    2011-01-01

    Objectives: The transition from analogue to digital radiography may have reduced the motivation to perform proper collimation, as digital techniques have made it possible to mask areas irradiated outside the area of diagnostic interest (ADI). We examined the hypothesis that collimation practices...

  18. Aperture Determination in the LHC Based on an Emittance Blowup Technique with Collimator Position Scan

    CERN Document Server

    Assmann, R W; del Carmen Alabau, M; Giovannozzi, M; Muller, GJ; Redaelli, S; Schmidt, F; Tomas, R; Wenninger, J; Wollmann, D

    2011-01-01

    A new method to determine the LHC aperture was proposed. The new component is a collimator scan technique that refers the globally measured aperture limit to the shadow of the primary collimator, expressed in sigmas of rms beam size. As a by-product the BLM response to beam loss is quantified. The method is described and LHC measurement results are presented.

  19. Review of SPECT collimator selection, optimization, and fabrication for clinical and preclinical imaging

    Energy Technology Data Exchange (ETDEWEB)

    Van Audenhaege, Karen, E-mail: karen.vanaudenhaege@ugent.be; Van Holen, Roel; Vandenberghe, Stefaan; Vanhove, Christian [Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University–iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000 (Belgium); Metzler, Scott D. [Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Moore, Stephen C. [Division of Nuclear Medicine, Department of Radiology, Brigham and Women’s Hospital and Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115 (United States)

    2015-08-15

    In single photon emission computed tomography, the choice of the collimator has a major impact on the sensitivity and resolution of the system. Traditional parallel-hole and fan-beam collimators used in clinical practice, for example, have a relatively poor sensitivity and subcentimeter spatial resolution, while in small-animal imaging, pinhole collimators are used to obtain submillimeter resolution and multiple pinholes are often combined to increase sensitivity. This paper reviews methods for production, sensitivity maximization, and task-based optimization of collimation for both clinical and preclinical imaging applications. New opportunities for improved collimation are now arising primarily because of (i) new collimator-production techniques and (ii) detectors with improved intrinsic spatial resolution that have recently become available. These new technologies are expected to impact the design of collimators in the future. The authors also discuss concepts like septal penetration, high-resolution applications, multiplexing, sampling completeness, and adaptive systems, and the authors conclude with an example of an optimization study for a parallel-hole, fan-beam, cone-beam, and multiple-pinhole collimator for different applications.

  20. Simulation study for high resolution alpha particle spectrometry with mesh type collimator

    International Nuclear Information System (INIS)

    Park, Seunghoon; Kwak, Sungwoo; Kang, Hanbyeol; Shin, Jungki; Park, Iljin

    2014-01-01

    An alpha particle spectrometry with a mesh type collimator plays a crucial role in identifying specific radionuclide in a radioactive source collected from the atmosphere or environment. The energy resolution is degraded without collimation because particles with a high angle have a longer path to travel in the air. Therefore, collision with the background increases. The collimator can cut out particles which traveling at a high angle. As a result, an energy distribution with high resolution can be obtained. Therefore, the mesh type collimator is simulated for high resolution alpha particle spectrometry. In conclusion, the collimator can improve resolution. With collimator, the collimator is a role of cutting out particles with a high angle, so, low energy tail and broadened energy distribution can be reduced. The mesh diameter is found out as an important factor to control resolution and counting efficiency. Therefore, a target particle, for example, 235 U, can be distinguished by a detector with a collimator under a mixture of various nuclides, for example: 232 U, 238 U, and 232 Th

  1. Conceptual Analysis of Fission Fragment Magnetic Collimator Reactors

    International Nuclear Information System (INIS)

    Tsvetkov, Pavel V.; Parish, Theodore A.

    2002-01-01

    As part of the current research work within the US DOE NERI Direct Electricity Conversion (DEC) Project on methods for utilizing direct electricity conversion in nuclear reactors, a detailed study of a Fission Fragment Magnetic Collimator Reactor (FFMCR) has been performed. The FFMCR concept is an advanced DEC system that combines advantageous design solutions proposed for application in both fission and fusion reactors. The present study was focused on determining the electrical efficiency and other important operational aspects of the FFMCR concept. In principle, acceptable characteristics have been demonstrated, and results obtained are presented in the paper. Technological visibility of the FFMCR concept and required further design development are discussed. Preliminary characteristics of the promising design are outlined. (authors)

  2. Faraday cup dosimetry in a proton therapy beam without collimation

    International Nuclear Information System (INIS)

    Grusell, Erik; Isacsson, Ulf; Montelius, Anders; Medin, Joakim

    1995-01-01

    A Faraday cup in a proton beam can give an accurate measurement of the number of protons collected by the cup. It is shown that the collection efficiency with a proper design can be close to unity. To be able to calibrate an ionization chamber from such a measurement, as is recommended in some dosimetry protocols, the energy spectrum of the proton beam must be accurately known. This is normally not the case when the lateral beam extension is defined by collimators. Therefore a method for relating an ionization chamber measurement in an uncollimated beam to the total number of protons in the beam has been developed and is described together with experimental results from calibrating an ionization chamber using this method in the therapeutic beam in Uppsala. This method is applicable to ionization chambers of any shape and the accuracy is estimated to be 1.6% (1 SD). (Author)

  3. Augmented reality aiding collimator exchange at the LHC

    International Nuclear Information System (INIS)

    Martínez, Héctor; Fabry, Thomas; Laukkanen, Seppo; Mattila, Jouni; Tabourot, Laurent

    2014-01-01

    Novel Augmented Reality techniques have the potential to have a large positive impact on the way remote maintenance operations are carried out in hazardous areas, e.g. areas where radiation doses that imply careful planning and optimization of maintenance operations are present. This paper describes an Augmented Reality strategy, system and implementation for aiding the remote collimator exchange in the LHC, currently the world's largest and highest-energy particle accelerator. The proposed system relies on marker detection and multi-modal augmentation in real-time. A database system has been used to ensure flexibility. The system has been tested in a mock-up facility, showing real time performance and great potential for future use in the LHC. The technical-scientific difficulties identified during the development of the system and the proposed solutions described in this paper may help the development of future Augmented Reality systems for remote handling in scientific facilities

  4. Optimizing renal DMSA-scintigraphy with 7-pinhole collimator

    International Nuclear Information System (INIS)

    Botsch, H.; Pottmeyer, A.; Savaser, A.; Lochner, B.; Felix, R.

    1982-01-01

    Multiple pinhole emission tomographic imaging techniques are currently being applied to imaging of organs of a limited size. The purpose of this study was to evaluate the feasibility of this technique in kidney imaging with Tcsup(99m)-DMSA. A 7-pinhole collimator having 4.5 mm. pinhole apertures was used in conjunction with a widefield camera. Left and right kidney were imaged separately. Twelve small renal cysts with a diameter of 1 to 3.5 cm. verified by US or CAT were investigated by 7-pinhole and planar scintigraphy. Eight of 12 renal cysts were identified by 7-pinhole scintigraphy whereas only one cyst was seen by planar scintigraphy. The borderline of cysts detection was 1.5 cm. in 7-pinhole tomography. Basing on these comparative studies and experiences on many patient investigations it seems reasonable to perform renal scintigraphy with 7-pinhole tomography in a routine manner. (orig.)

  5. Beam collimator for a particle accelerator. [German patent

    Energy Technology Data Exchange (ETDEWEB)

    Benedetti, R

    1977-12-01

    The beam collimator for the electron beam coming from an electron accelerator consists of aperture plates and penumbra trimmers aligned parallel to them. To protect the patient from scattered radiation, additional tube plates are arranged between the radiation source and the patient. Continuous matching of the radiation field to the dimensions of a focus is achieved by providing a support plate outside the beam path which holds the tube plates. In this arrangement, the tube plates are aligned parallel to the edges of the aperture plates limiting the beam cone. The tube plates have different widths. They can be moved out of the beam path. Lining the inner walls of the tube plates with acrylic glass prevents the generation of secondary electrons and X-rays.

  6. Adaptive fiber optics collimator based on flexible hinges.

    Science.gov (United States)

    Zhi, Dong; Ma, Yanxing; Ma, Pengfei; Si, Lei; Wang, Xiaolin; Zhou, Pu

    2014-08-20

    In this manuscript, we present a new design for an adaptive fiber optics collimator (AFOC) based on flexible hinges by using piezoelectric stacks actuators for X-Y displacement. Different from traditional AFOC, the new structure is based on flexible hinges to drive the fiber end cap instead of naked fiber. We fabricated a real AFOC based on flexible hinges, and the end cap's deviation and resonance frequency of the device were measured. Experimental results show that this new AFOC can provide fast control of tip-tilt deviation of the laser beam emitting from the end cap. As a result, the fiber end cap can support much higher power than naked fiber, which makes the new structure ideal for tip-tilt controlling in a high-power fiber laser system.

  7. Augmented reality aiding collimator exchange at the LHC

    Energy Technology Data Exchange (ETDEWEB)

    Martínez, Héctor, E-mail: hector.martinez@sensetrix.com [SenseTrix, PL 20 FI-00101 Helsinki (Finland); Fabry, Thomas [European Organization for Nuclear Research, CERN, CH-1211 Genève 23 (Switzerland); Laukkanen, Seppo [SenseTrix, PL 20 FI-00101 Helsinki (Finland); Mattila, Jouni [Tampere University of Technology, PO Box 527, FI-33101 Tampere (Finland); Tabourot, Laurent [SYMME, Université de Savoie, Polytech Annecy-Chambéry, 5 chemin de Bellevue, 74944 Annecy le Vieux (France)

    2014-11-01

    Novel Augmented Reality techniques have the potential to have a large positive impact on the way remote maintenance operations are carried out in hazardous areas, e.g. areas where radiation doses that imply careful planning and optimization of maintenance operations are present. This paper describes an Augmented Reality strategy, system and implementation for aiding the remote collimator exchange in the LHC, currently the world's largest and highest-energy particle accelerator. The proposed system relies on marker detection and multi-modal augmentation in real-time. A database system has been used to ensure flexibility. The system has been tested in a mock-up facility, showing real time performance and great potential for future use in the LHC. The technical-scientific difficulties identified during the development of the system and the proposed solutions described in this paper may help the development of future Augmented Reality systems for remote handling in scientific facilities.

  8. Collimation in the Transfer Lines to the LHC

    CERN Document Server

    Burkhardt, H; Kadi, Y; Kain, V; Weterings, W

    2004-01-01

    The intensities foreseen for injection into the LHC are over an order of magnitude above the expected damage levels. The TI 2 and TI 8 transfer lines between the SPS and LHC are each about 2.5 km long and comprise many magnet families. Despite planned power supply surveillance and interlocks, failure modes exist which could result in uncontrolled beam loss and serious transfer line or LHC equipment damage. We describe the collimation system in the transfer lines that has been designed to provide passive protection against damage at injection. Results of simulations to develop a conceptual design are presented. The optical and physical installation constraints are described, and the resulting element locations and expected system performance presented, in terms of the phase space coverage, local element temperature rises and the characteristics of the beam transmitted into the LHC.

  9. Energy budget in collimated gamma-ray bursts

    International Nuclear Information System (INIS)

    Tudose, Valeriu; Biermann, Peter

    2003-01-01

    There is increasing evidence for the existence of collimation in some, if not most, of the gamma-ray bursts. This would have direct implications, for instance, on the energy budget, the rate of events, but also indirect consequences for the theoretical models because it provides a tool to differentiate between their predictions. We consider the case of a structured jet, i.e. we assume the energy within the jet varies as a power-law, being a function of the angle between the jet axis and an arbitrary direction. We analyze first the situation in which the jet axis and the line of sight have a particular orientation, then we relax this assumption by allowing for an arbitrary viewing angle with respect to the symmetry axis of the jet. A qualitative study of the total energy content of the jet is performed. It turns out that the 'real' energy could be higher than what is inferred from observations. (authors)

  10. Self-collimating photonic crystal polarization beam splitter.

    Science.gov (United States)

    Zabelin, V; Dunbar, L A; Le Thomas, N; Houdré, R; Kotlyar, M V; O'Faolain, L; Krauss, T F

    2007-03-01

    We present theoretical and experimental results of a polarization splitter device that consists of a photonic crystal (PhC) slab, which exhibits a large reflection coefficient for TE and a high transmission coefficient for TM polarization. The slab is embedded in a PhC tile operating in the self-collimation mode. Embedding the polarization-discriminating slab in a PhC with identical lattice symmetry suppresses the in-plane diffraction losses at the PhC-non-PhC interface. The optimization of the PhC-non-PhC interface is thereby decoupled from the optimization of the polarizing function. Transmissions as high as 35% for TM- and 30% for TE-polarized light are reported.

  11. A collimator-converter system for IEC propulsion

    International Nuclear Information System (INIS)

    Momota, Hiromu; Miley, George H.

    2002-01-01

    The collimator-converter system extracts fusion power from D- 3 He fueled IEC devices and provides electricity needed to operate ionic thrusters and other-power components. The whole system is linear and consists of a series of collimator units at the center, magnetic expander units at both sides of the fusion units, followed by direct energy converters at both ends. This system is enclosed in a vacuum chamber with a magnetic channel provided by magnetic solenoids out of respective chambers. The fusion unit consists of an IEC fusion core, a pair of coils anti-parallel to the solenoid coils, and a stabilization coil that stabilizes the position of coil pair coils. The IEC fusion core is installed at the center of the pair coils. After the magnetic expander, velocities of fusion particles from D- 3 He fueled IEC units are directed to the magnetic channel, which guides energetic fusion particles as well as leaking unburned fuel components to a high-efficiency traveling wave direct energy converter (TWDEC). Leaking unburned fuel components are separated with a magnetic separator at the entrance of a direct energy converter and pumped out for further refueling. A TWDEC is made of an array of metallic meshed grids, each of which is connected to every terminal with an external transmission circuit. The transmission line couples to the direct energy converter. Substations for electricity, a cryogenic plant, and various power control systems are outside of the vacuum chamber. The length of the cylindrical system is essentially determined by the proton energy of 14.8 MeV and the radius should be large so as to reduce power flow density. The present system provides 250 MW f fusion power and converting it to 150 MW c electricity. Its size is 150 m(length)x6.6 m(diameter) in size and 185 tons in weight

  12. Dosimetric Characteristics of Dual Photon Energy Using Independent Collimator Jaws

    International Nuclear Information System (INIS)

    Kim, Jeung Kee; Choi, Young Min; Lee, Hyung Sik; Hur, Won Joo

    1996-01-01

    Purpose : The accurate dosimetry of independent collimator equipped for 6MV and 15MV X-ray beam was investigated to search for the optimal correction factor. Methods and Materials : The field size factors, beam quality and dose distribution were measured by using 6MV, 15MV X-ray. Field size factors were measured FROM 3X3cm 2 to 35X35cm 2 by using 0.6cc ion chamber (NE 2571) at Dmax. Beam qualities were measured at different field sizes, off-axis distances and depths. Isodose distributions at different off-axis distance using 10X10cm 2 field were also investigated and compared with symmetric field. Results : 1) Relative field size factors was different along lateral distance with maximum changes in 3.1% for 6MV and 5% for 15MV. But the field size factors of asymmetric fields were identical to the modified central-axis values in symmetric field, which corrected by off-axis ratio at Dmax. 2) The HVL and PDD was decreased by increasing off-axis distance. PDD was also decreased by increasing depth For field size more than 5X5cm 2 and depth less than 15cm, PDD of asymmetric field differs FROM that of symmetric one (0.5∼2% for 6MV and 0.4∼1.4% for 15MV). 3) The measured isodose curves demonstrate divergence effects and reduced doses adjacent to the edge close to the flattening filter center was also observed. Conclusion : When asymmetric collimator is used, calculation of MU must be corrected with off-axis and PDD with a caution of under dose in central axis

  13. Orthovoltage computer planning with a new type of variable collimator

    International Nuclear Information System (INIS)

    Beckham, W.A.; Hill, R.F.; Perez, M.D.

    1996-01-01

    Full text: The Liverpool Hospital Radiation Oncology Department has recently installed and commissioned a Pantak Therapax DXT-300 orthovoltage therapy treatment unit. Purchased with this was a variable collimator capable of producing rectangular fields up to 20 x 20 cm 2 . Occasionally patients who are treated with, for example, mediastinal deep therapy portals go on to have further megavoltage therapy (eg. total body irradiation (TBI)). The orthovoltage dose distribution in lung tissue can be the limiting factor in terms of proceeding with TBI due to the inherent risk of radiation induced pneumonitis. The present work assesses the ability of the Department's Varian Cadplan treatment planning system (TPS) to calculate dosage distribution for orthovoltage radiation fields delineated by the variable collimator. Data was collected using a Scanditronix RFA-300 beam data acquisition system (BDAS). For each of four qualities (0.85, 1.7, 2.6, and 3.8 mm Cu) profile data at five depths and central axis depth dose data were collected for square field sizes of 3, 4, 6, 8, 10, 12, 15 and 20 cm 2 , as input to the TPS. Isodose distributions produced by the TPS were then checked against the BDAS collected isodoses. Good agreement was found under these conditions of irradiation of a homogeneous medium. Work is ongoing to assess the accuracy of the TPS for simple heterogeneities which are introduced to these orthovoltage beams. It is expected that the heterogeneity correction method used by the TPS will be in error when higher atomic number (Z) media are introduced (eg. bone analogues) due to the fact that the algorithm assumes that tissue attenuation is related solely to electron density, which is generally valid for megavoltage photon beams where Compton interactions are predominant. With the increasing contribution from photo-electric interaction processes as the orthovoltage beam quality decreases, preliminary results have shown increasing TPS deviation under these

  14. SU-F-T-671: Effects of Collimator Material On Proton Minibeams

    International Nuclear Information System (INIS)

    Lee, E; Sandison, G; Cao, N; Stewart, R; Meyer, J; Eagle, J; Marsh, S

    2016-01-01

    Purpose: To investigate the dosimetric effects of collimator material on spatially modulated proton minibeams (pMBRT). Methods: pMBRT holds promise to exhibit shallow depth normal-tissue sparing effects similar to synchrotron based microbeams while also retaining potential for uniform dose distributions for tumor targets. TOPAS Monte Carlo simulations were performed for a 5cm thick multislit collimator with 0.3mm slits and 1mm center-to-center spacing for a 50.5MeV proton minibeam while varying collimator material between brass, tungsten, and iron. The collimator was placed both “flush” at the water phantom surface and at 5cm distance to investigate the effects on surface dose, peak-to-valley-dose-ratio (PVDR) and neutron contribution. Results: For flush placement, the neutron dose at the phantom surface for the tungsten collimator was approximately 20% higher than for brass and iron. This was not reflected in the overall surface dose, which was comparable for all materials due to the relatively low neutron contribution of <0.1%. When the collimator was retracted, the overall neutron contribution was essentially identical for all three collimators. Surface dose dropped by ∼40% for all collimator materials with air gap compared to being flush with the phantom surface. This surface dose reduction was at the cost of increase in valley dose for all collimator materials due to increased angular divergence of the mini-beams at the surface and their consequent geometric penumbra at depth. When the collimator was placed at distance from the phantom surface the PVDR decreased. The peak-to-entrance-dose ratio was highest for the iron collimator with 5cm air gap. Conclusion: The dosimetric difference between the collimator materials is minimal despite the relatively higher neutron contribution at the phantom surface for the tungsten collimator when placed flush. The air gap between the collimator and phantom surface strongly influences all dosimetry parameters due to

  15. Magnetic collimation and metal foil filtering for electron range and fluence modulation

    International Nuclear Information System (INIS)

    Phaisangittisakul, N.; D'Souza, W.D.; Ma Lijun

    2004-01-01

    We investigated the use of magnetically collimated electron beams together with metal filters for electron fluence and range modulation. A longitudinal magnetic field collimation method was developed to reduce skin dose and to improve the electron beam penumbra. Thin metal foils were used to adjust the energies of magnetically collimated electrons. The effects for different types of foils such as Al, Be, Cu, Pb, and Ti were studied using Monte Carlo calculations. An empirical pencil beam dose calculation model was developed to calculate electron dose distributions under magnetic collimation and foil modulation. An optimization method was developed to produce conformal dose distributions for simulated targets such as a horseshoe-shaped target. Our results show that it is possible to produce an electron depth dose enhancement peak using similar techniques of producing a spread-out Bragg peak. In conclusion, our study demonstrates new aspects of using magnetic collimation and foil filtration for producing fluence and range modulated electron dose distributions

  16. Calculation of effective dose in whole body in dependence of angle of collimator for photon fields

    International Nuclear Information System (INIS)

    Fuenzalida, M.; Varon, C.; Piriz, G.; Banguero, Y.; Lozano, E.; Mancilla, C.

    2011-01-01

    The objective of this work is to obtain quantifiable data of whole body effective dose for photons fields of 6 MV and 18 MV in function of the collimator angle of a Varian Clinac 21EX lineal accelerator. It has been made a variety of studies which investigate the form to reduce the dose in whole body with photons fields, specially over the potential risks and the influence of the collimator angle, as performed Stanthakis et al. [1] with the Monte Carlo method. As a result of this work, the values of whole body effective doses are higher with a 0 deg collimator than with a 90 deg collimator, and as the field size increases, the effective doses difference in whole body, between 0 deg and 90 deg collimator angle, for both energies, becomes smaller. (author)

  17. [Evaluation of Dose Reduction of the Active Collimator in Multi Detector Row CT].

    Science.gov (United States)

    Ueno, Hiroyuki; Matsubara, Kosuke

    The purpose of this study was to evaluate the performance of active collimator by changing acquisition parameters and obtaining dose profiles in z-axis direction. Dose profiles along z-axis were obtained using XRQA2 Gafchromic film. As a result, the active collimator reduced overranging about 55% compared to that without the active collimator. In addition, by changing the combination of X-ray beam width (32 mm, 40 mm), pitch factor (1.4, 0.6), and the X-ray tube rotation time (0.5 s/rot, 1.0 s/rot), the overranging changed from 19.4 to 34.9 mm. Although the active collimator is effective for reducing overranging, it is necessary to adjust acquisition parameters by taking the properties of the active collimator for acquisition parameters, especially setting beam width, into consideration.

  18. Global and Local Loss Suppression in the UA9 Crystal Collimation Experiment

    CERN Document Server

    Montesano, S

    2012-01-01

    UA9 was operated in the CERN-SPS for some years in view of investigating the feasibility of the halo collimation assisted by bent crystals. Silicon crystals 2 mm long with bending angles of about 150 μrad are used as primary collimators. The crystal collimation process is obtained consistently through channeling with high efficiency. The loss profiles in the area of the crystal collimator setup and in the downstream dispersion suppressor area show a steady reduction of slightly less than one order of magnitude at the onset of the channeling process. This result holds both for protons and for lead ions. The corresponding loss map in the accelerator ring is accordingly reduced. These observations strongly support our expectation that the coherent deflection of the beam halo by a bent crystal should enhance the collimation efficiency in hadron colliders, such as LHC.

  19. Note: Detector collimators for the nanoscale ordered materials diffractometer instrument at the Spallation Neutron Source

    Energy Technology Data Exchange (ETDEWEB)

    Tamalonis, A. [Materials Development, Inc., Arlington Heights, Illinois 60004 (United States); Weber, J. K. R., E-mail: rweber@anl.gov; Alderman, O. L. G. [Materials Development, Inc., Arlington Heights, Illinois 60004 (United States); Argonne National Laboratory, Argonne, Illinois 60439 (United States); Neuefeind, J. C.; Carruth, J. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States); Skinner, L. B. [Materials Development, Inc., Arlington Heights, Illinois 60004 (United States); Argonne National Laboratory, Argonne, Illinois 60439 (United States); Stony Brook University, Stony Brook, New York 11794 (United States); Benmore, C. J. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2015-09-15

    Five neutron collimator designs were constructed and tested at the nanoscale ordered materials diffractometer (NOMAD) instrument. Collimators were made from High Density PolyEthylene (HDPE) or 5% borated HDPE. In all cases, collimators improved the signal to background ratio and reduced detection of secondary scattering. In the Q-range 10-20 Å{sup −1}, signal to background ratio improved by factors of approximately 1.6 and 2.0 for 50 and 100 mm deep collimators, respectively. In the Q-range 40-50 Å{sup −1}, the improvement factors were 1.8 and 2.7. Secondary scattering as measured at Q ∼ 9.5 Å{sup −1} was significantly decreased when the collimators were installed.

  20. Advantage of fan beam collimators for contrast recovery of hyperfixation in clinical SPECT

    International Nuclear Information System (INIS)

    Vera, P.

    1997-01-01

    The influence of the collimator on the contrast recovery of hyperfixation was studied using a dual-headed single photon emission computer tomography (SPECT) system with standard clinical acquisition parameters. Three parallel collimator sets and two fan beam collimator sets were tested with a Jaszczak phantom. The six spheres of the phantom were filled with 99m Tc, and four background levels were progressively obtained by adding radioactivity to the cylinder of the phantom, providing four hyperfixation levels. The effects of angular sampling and reconstruction filters have been tested. The statistical analysis was performed with analysis of variance (ANOVA). This study demonstrates the advantage of ultra-high resolution fan beam collimators for contrast recovery of hyperfixation with SPECT when using 64 projections over 360 degree, in particular when the contrast is low. The authors also demonstrate that fan beam collimators permit smaller size hyperfixation detection

  1. A facility to produce collimated neutron beams at the Legnaro Laboratories

    International Nuclear Information System (INIS)

    Colautti, P.; Talpo, G.; Tornielli, G.

    1988-01-01

    The 7 MV Van de Graaff and the 16 MV Tandem accelerators at the Legnaro National Laboratories can be used to produce fast neutron fluxes of moderate intensity, ranging in energy from 1 MeV to 50 MeV. A W-polyethylene-Pb cylindrical collimator has been constructed in order to produce a collimated neutron beam, with well defined dose and microdose characteristics for radiobiological experiments. The collimator can be assembled in different configurations allowing both for different thicknesses and different beam apertures. Dosimetric measurements have been made with a d(4.5)+Be source. These demonstrate sharp beam edges with attenuation behind the shield of 20% with the 15 cm collimator and 1.5% with the 50 cm collimator. (author)

  2. Calculation of effective dose in whole body in dependence of angle of collimator for photon fields

    Energy Technology Data Exchange (ETDEWEB)

    Fuenzalida, M. [Universidad de la Frontera, Temuco (Chile). Programa de Magister en Fisica Medica; Varon, C.; Piriz, G.; Banguero, Y.; Lozano, E.; Mancilla, C., E-mail: fisicamedica@incancer.c [Instituto Nacional del Cancer, Santiago (Chile). Unidad de Fisica Medica

    2011-07-01

    The objective of this work is to obtain quantifiable data of whole body effective dose for photons fields of 6 MV and 18 MV in function of the collimator angle of a Varian Clinac 21EX lineal accelerator. It has been made a variety of studies which investigate the form to reduce the dose in whole body with photons fields, specially over the potential risks and the influence of the collimator angle, as performed Stanthakis et al. [1] with the Monte Carlo method. As a result of this work, the values of whole body effective doses are higher with a 0 deg collimator than with a 90 deg collimator, and as the field size increases, the effective doses difference in whole body, between 0 deg and 90 deg collimator angle, for both energies, becomes smaller. (author)

  3. Observation of strong leakage reduction in crystal assisted collimation of the SPS beam

    Energy Technology Data Exchange (ETDEWEB)

    Scandale, W. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Laboratoire de l' Accelerateur Lineaire (LAL), Universite Paris Sud Orsay, Orsay (France); INFN Sezione di Roma, Piazzale Aldo Moro 2, 00185 Rome (Italy); Arduini, G.; Butcher, M.; Cerutti, F.; Garattini, M.; Gilardoni, S.; Lechner, A.; Losito, R.; Masi, A.; Mereghetti, A.; Metral, E. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Mirarchi, D. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Imperial College, London (United Kingdom); Montesano, S.; Redaelli, S. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Rossi, R. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); INFN Sezione di Roma, Piazzale Aldo Moro 2, 00185 Rome (Italy); Schoofs, P.; Smirnov, G. [CERN, European Organization for Nuclear Research, CH-1211 Geneva 23 (Switzerland); Bagli, E.; Bandiera, L.; Baricordi, S. [INFN Sezione di Ferrara, Dipartimento di Fisica, Università di Ferrara, Ferrara (Italy); and others

    2015-09-02

    In ideal two-stage collimation systems, the secondary collimator–absorber should have its length sufficient to exclude practically the exit of halo particles with large impact parameters. In the UA9 experiments on the crystal assisted collimation of the SPS beam a 60 cm long tungsten bar is used as a secondary collimator–absorber which is insufficient for the full absorption of the halo protons. Multi-turn simulation studies of the collimation allowed to select the position for the beam loss monitor downstream the collimation area where the contribution of particles deflected by the crystal in channeling regime but emerging from the secondary collimator–absorber is considerably reduced. This allowed observation of a strong leakage reduction of halo protons from the SPS beam collimation area, thereby approaching the case with an ideal absorber.

  4. Compatibility of metal additive manufactured tungsten collimator for SPECT/MRI integration

    Energy Technology Data Exchange (ETDEWEB)

    Samudi, Amine M [INTEC, Ghent University/iMinds, Ghent (Belgium); Van Audenhaege, Karen [ELIS, Ghent University/iMinds, Gent (Belgium); Vermeeren, Gunter; Martens, Luc [INTEC, Ghent University/iMinds, Ghent (Belgium); Van Holen, Roel [ELIS, Ghent University/iMinds, Gent (Belgium); Joseph, Wout [INTEC, Ghent University/iMinds, Ghent (Belgium)

    2015-05-18

    We optimized the MR-compatibility of a novel tungsten collimator, produced with metal additive manufacturing that is part of a microSPECT insert for a preclinical SPECT/MRI scanner. We characterized the current density due to the gradient field and adapted the collimators by smart design to reduce the induced eddy currents. The z-gradient coil and the collimator were modeled with SEMCAD. The gradient strength was 510 mT/m, the gradient efficiency was about 3.4 mT/m/A. The setup was simulated with a working frequency of 10 kHz. The system consists of 7 identical collimators and digital silicon photomultipliers assembled in a ring. We evaluated the global reduction in current density J (reduction) based on the sum of all current densities in the collimator. We applied the following optimizations on the collimator: 1. We reduced the excessive material in the flanges. 2. We applied horizontal slits of 2 mm in the collimator surface. 3. We reduced material in the core; the photons are attenuated before they reach the core. The collimator will need a supporting structure. 4. The supporting structure can be avoided by using two vertical slits in the middle of the collimator. 5. We used a Z-shaped slit instead of the vertical slit. Results of simulations show that smaller flanges reduce the current density with 23%. The horizontal slits reduce the eddy currents with 6%. Using less material in the core or applying vertical slits results in the same reduction of current density. However, the vertical slits are cheaper because a hollow collimator requires supporting structures during production. Both can be combined if z-shaped slits are used to prevent attenuation problems. The reduction is then 27%. Finally, when all previous adaptations are combined, the reduction in eddy currents is about 56.3%.

  5. Automated collimation testing by determining the statistical correlation coefficient of Talbot self-images.

    Science.gov (United States)

    Rana, Santosh; Dhanotia, Jitendra; Bhatia, Vimal; Prakash, Shashi

    2018-04-01

    In this paper, we propose a simple, fast, and accurate technique for detection of collimation position of an optical beam using the self-imaging phenomenon and correlation analysis. Herrera-Fernandez et al. [J. Opt.18, 075608 (2016)JOOPDB0150-536X10.1088/2040-8978/18/7/075608] proposed an experimental arrangement for collimation testing by comparing the period of two different self-images produced by a single diffraction grating. Following their approach, we propose a testing procedure based on correlation coefficient (CC) for efficient detection of variation in the size and fringe width of the Talbot self-images and thereby the collimation position. When the beam is collimated, the physical properties of the self-images of the grating, such as its size and fringe width, do not vary from one Talbot plane to the other and are identical; the CC is maximum in such a situation. For the de-collimated position, the size and fringe width of the self-images vary, and correspondingly the CC decreases. Hence, the magnitude of CC is a measure of degree of collimation. Using the method, we could set the collimation position to a resolution of 1 μm, which relates to ±0.25   μ    radians in terms of collimation angle (for testing a collimating lens of diameter 46 mm and focal length 300 mm). In contrast to most collimation techniques reported to date, the proposed technique does not require a translation/rotation of the grating, use of complicated phase evaluation algorithms, or an intricate method for determination of period of the grating or its self-images. The technique is fully automated and provides high resolution and precision.

  6. Compatibility of metal additive manufactured tungsten collimator for SPECT/MRI integration

    International Nuclear Information System (INIS)

    Samudi, Amine M; Van Audenhaege, Karen; Vermeeren, Gunter; Martens, Luc; Van Holen, Roel; Joseph, Wout

    2015-01-01

    We optimized the MR-compatibility of a novel tungsten collimator, produced with metal additive manufacturing that is part of a microSPECT insert for a preclinical SPECT/MRI scanner. We characterized the current density due to the gradient field and adapted the collimators by smart design to reduce the induced eddy currents. The z-gradient coil and the collimator were modeled with SEMCAD. The gradient strength was 510 mT/m, the gradient efficiency was about 3.4 mT/m/A. The setup was simulated with a working frequency of 10 kHz. The system consists of 7 identical collimators and digital silicon photomultipliers assembled in a ring. We evaluated the global reduction in current density J (reduction) based on the sum of all current densities in the collimator. We applied the following optimizations on the collimator: 1. We reduced the excessive material in the flanges. 2. We applied horizontal slits of 2 mm in the collimator surface. 3. We reduced material in the core; the photons are attenuated before they reach the core. The collimator will need a supporting structure. 4. The supporting structure can be avoided by using two vertical slits in the middle of the collimator. 5. We used a Z-shaped slit instead of the vertical slit. Results of simulations show that smaller flanges reduce the current density with 23%. The horizontal slits reduce the eddy currents with 6%. Using less material in the core or applying vertical slits results in the same reduction of current density. However, the vertical slits are cheaper because a hollow collimator requires supporting structures during production. Both can be combined if z-shaped slits are used to prevent attenuation problems. The reduction is then 27%. Finally, when all previous adaptations are combined, the reduction in eddy currents is about 56.3%.

  7. Sci-Thur PM – Brachytherapy 05: Surface Collimation Applied to Superficial Flap High Dose-Rate Brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Derek; Sabondjian, Eric; Lawrence, Kailin; Sankreacha, Raxa [University of Toronto, Carlo Fidani Peel Regional Cancer Center, Carlo Fidani Peel Regional Cancer Center, University of Toronto (Canada)

    2016-08-15

    Purpose: To apply surface collimation for superficial flap HDR skin brachytherapy utilizing common clinical resources and to demonstrate the potential for OAR dose reduction within a clinically relevant setting. Methods: Two phantom setups were used. 3 mm lead collimation was applied to a solid slab phantom to determine appropriate geometries relating to collimation and dwell activation. The same collimation was applied to the temple of an anthropomorphic head phantom to demonstrate lens dose reduction. Each setup was simulated and planned to deliver 400 cGy to a 3 cm circular target to 3 mm depth. The control and collimated irradiations were sequentially measured using calibrated radiochromic films. Results: Collimation for the slab phantom attenuated the dose beyond the collimator opening, decreasing the fall-off distances by half and reducing the area of healthy skin irradiated. Target coverage can be negatively impacted by a tight collimation margin, with the required margin approximated by the primary beam geometric penumbra. Surface collimation applied to the head phantom similarly attenuated the surrounding normal tissue dose while reducing the lens dose from 84 to 68 cGy. To ensure consistent setup between simulation and treatment, additional QA was performed including collimator markup, accounting for collimator placement uncertainties, standoff distance verification, and in vivo dosimetry. Conclusions: Surface collimation was shown to reduce normal tissue dose without compromising target coverage. Lens dose reduction was demonstrated on an anthropomorphic phantom within a clinical setting. Additional QA is proposed to ensure treatment fidelity.

  8. Sci-Thur PM – Brachytherapy 05: Surface Collimation Applied to Superficial Flap High Dose-Rate Brachytherapy

    International Nuclear Information System (INIS)

    Liu, Derek; Sabondjian, Eric; Lawrence, Kailin; Sankreacha, Raxa

    2016-01-01

    Purpose: To apply surface collimation for superficial flap HDR skin brachytherapy utilizing common clinical resources and to demonstrate the potential for OAR dose reduction within a clinically relevant setting. Methods: Two phantom setups were used. 3 mm lead collimation was applied to a solid slab phantom to determine appropriate geometries relating to collimation and dwell activation. The same collimation was applied to the temple of an anthropomorphic head phantom to demonstrate lens dose reduction. Each setup was simulated and planned to deliver 400 cGy to a 3 cm circular target to 3 mm depth. The control and collimated irradiations were sequentially measured using calibrated radiochromic films. Results: Collimation for the slab phantom attenuated the dose beyond the collimator opening, decreasing the fall-off distances by half and reducing the area of healthy skin irradiated. Target coverage can be negatively impacted by a tight collimation margin, with the required margin approximated by the primary beam geometric penumbra. Surface collimation applied to the head phantom similarly attenuated the surrounding normal tissue dose while reducing the lens dose from 84 to 68 cGy. To ensure consistent setup between simulation and treatment, additional QA was performed including collimator markup, accounting for collimator placement uncertainties, standoff distance verification, and in vivo dosimetry. Conclusions: Surface collimation was shown to reduce normal tissue dose without compromising target coverage. Lens dose reduction was demonstrated on an anthropomorphic phantom within a clinical setting. Additional QA is proposed to ensure treatment fidelity.

  9. Introduction of a novel ultrahigh sensitivity collimator for brain SPECT imaging

    Energy Technology Data Exchange (ETDEWEB)

    Park, Mi-Ae, E-mail: miaepark@bwh.harvard.edu; Kijewski, Marie Foley; Lyon, Morgan C.; Horky, Laura; Moore, Stephen C. [Department of Radiology, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts 02115 (United States); Keijzers, Ronnie; Keijzers, Mark [Nuclear Fields USA, Des Plaines, Illinois 60018 (United States)

    2016-08-15

    Purpose: Noise levels of brain SPECT images are highest in central regions, due to preferential attenuation of photons emitted from deep structures. To address this problem, the authors have designed a novel collimator for brain SPECT imaging that yields greatly increased sensitivity near the center of the brain without loss of resolution. This hybrid collimator consisted of ultrashort cone-beam holes in the central regions and slant-holes in the periphery (USCB). We evaluated this collimator for quantitative brain imaging tasks. Methods: Owing to the uniqueness of the USCB collimation, the hole pattern required substantial variations in collimator parameters. To utilize the lead-casting technique, the authors designed two supporting plates to position about 37 000 hexagonal, slightly tapered pins. The holes in the supporting plates were modeled to yield the desired focal length, hole length, and septal thickness. To determine the properties of the manufactured collimator and to compute the system matrix, the authors prepared an array of point sources that covered the entire detector area. Each point source contained 32 μCi of Tc-99m at the first scan time. The array was imaged for 5 min at each of the 64 shifted locations to yield a 2-mm sampling distance, and hole parameters were calculated. The sensitivity was also measured using a point source placed along the central ray at several distances from the collimator face. High-count projection data from a five-compartment brain phantom were acquired with the three collimators on a dual-head SPECT/CT system. The authors calculated Cramer-Rao bounds on the precision of estimates of striatal and background activity concentration. In order to assess the new collimation system to detect changes in striatal activity, the authors evaluated the precision of measuring a 5% decrease in right putamen activity. The authors also reconstructed images of projection data obtained by summing data from the individual phantom

  10. Installing collimators in the next long shut-down: plans, status and challenges

    CERN Document Server

    Parma, V

    2011-01-01

    The first part of the collimation upgrade plan features the installation of 4 collimators in the 2 DS of point 3, in addition to the upgrade of the existing collimation system. What makes this upgrade so special is that for the first time collimators will be placed within the continuous cryostat of the LHC sectors. For this purpose, 16 main dipoles and 8 main quadrupoles will have to be disconnected and displaced by about 4.5 m, as well as the 2 electrical feedboxes (DFBAs) on either side of the DS, in order to create the space required for installing the additional collimators. The collimators themselves, although remaining of the warm type, feature a design substantially different from the others, mainly imposed by tight space constraints. These collimator modules will have to be complemented by a special bypass cryostat whose function is to preserve the continuity of the technical systems along the arcs (magnet powering, cryogenics and insulation vacuum), while providing cold to warm transitions to the bea...

  11. Studies on the optimal collimation of fast neutrons for neutron therapy

    International Nuclear Information System (INIS)

    Pfister, G.

    1973-08-01

    Optimal dimensions and materials of collimators for the neutron therapy installations under construction in Hamburg and Heidelberg were investigated by computer simulation of clinical irradiations. The neutron transport from the source through collimator and phantom was calculated by numerical solution of the Boltzmann equation by the Ssub(N) method with first collision correction. It was shown that the collimater quantity can be the same for both installations if the same materials are used. With homogeneous distribution of the materials in the collimator, tungsten was found to be most suitable, but almost the same results were achieved with nickel. Alloys of various elements did not improve W/Fe and Fe/(CH 2 )sub(n) distribution significantly improved the collimator quantity. The radiation scattering component is reduced by filters, by smaller beam cross sections, and by longer collimators. The γ quanta which are due to nuclear excitation and by the isotopes produced in the collimator are not dangerous to the patient. Long-term activation of the collimator material should, however, be allowed for in order to ensure radiation protection of the operating personnel. A hardening of the neutron energy spectra on the sides of the useful radiation beam could be determined. (orig./AK) [de

  12. Beam feasibility study of a collimator with in-jaw beam position monitors

    Science.gov (United States)

    Wollmann, Daniel; Nosych, Andriy A.; Valentino, Gianluca; Aberle, Oliver; Aßmann, Ralph W.; Bertarelli, Alessandro; Boccard, Christian; Bruce, Roderik; Burkart, Florian; Calvo, Eva; Cauchi, Marija; Dallocchio, Alessandro; Deboy, Daniel; Gasior, Marek; Jones, Rhodri; Kain, Verena; Lari, Luisella; Redaelli, Stefano; Rossi, Adriana

    2014-12-01

    At present, the beam-based alignment of the LHC collimators is performed by touching the beam halo with both jaws of each collimator. This method requires dedicated fills at low intensities that are done infrequently and makes this procedure time consuming. This limits the operational flexibility, in particular in the case of changes of optics and orbit configuration in the experimental regions. The performance of the LHC collimation system relies on the machine reproducibility and regular loss maps to validate the settings of the collimator jaws. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with jaw-integrated Beam Position Monitors (BPMs) was proposed and successfully tested with a prototype (mock-up) collimator in the CERN SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper, the results of these experiments are discussed. The non-linear response of the BPMs is compared to the predictions from electromagnetic simulations. Finally, the measured alignment accuracy is compared to the one achieved with the present collimators in the LHC.

  13. WE-AB-209-06: Dynamic Collimator Trajectory Algorithm for Use in VMAT Treatment Deliveries

    Energy Technology Data Exchange (ETDEWEB)

    MacDonald, L [Department of Medical Physics, Dalhousie University, Halifax, Nova Scotia, CA (Canada); Thomas, C; Syme, A [Department of Medical Physics, Dalhousie University, Halifax, Nova Scotia, CA (Canada); Department of Radiation Oncology, Dalhousie University, Halifax, Nova Scotia (Canada); Medical Physics, Nova Scotia Cancer Centre, Halifax, Nova Scotia (Canada)

    2016-06-15

    Purpose: To develop advanced dynamic collimator positioning algorithms for optimal beam’s-eye-view (BEV) fitting of targets in VMAT procedures, including multiple metastases stereotactic radiosurgery procedures. Methods: A trajectory algorithm was developed, which can dynamically modify the angle of the collimator as a function of VMAT control point to provide optimized collimation of target volume(s). Central to this algorithm is a concept denoted “whitespace”, defined as area within the jaw-defined BEV field, outside of the PTV, and not shielded by the MLC when fit to the PTV. Calculating whitespace at all collimator angles and every control point, a two-dimensional topographical map depicting the tightness-of-fit of the MLC was generated. A variety of novel searching algorithms identified a number of candidate trajectories of continuous collimator motion. Ranking these candidate trajectories according to their accrued whitespace value produced an optimal solution for navigation of this map. Results: All trajectories were normalized to minimum possible (i.e. calculated without consideration of collimator motion constraints) accrued whitespace. On an acoustic neuroma case, a random walk algorithm generated a trajectory with 151% whitespace; random walk including a mandatory anchor point improved this to 148%; gradient search produced a trajectory with 137%; and bi-directional gradient search generated a trajectory with 130% whitespace. For comparison, a fixed collimator angle of 30° and 330° accumulated 272% and 228% of whitespace, respectively. The algorithm was tested on a clinical case with two metastases (single isocentre) and identified collimator angles that allow for simultaneous irradiation of the PTVs while minimizing normal tissue irradiation. Conclusion: Dynamic collimator trajectories have the potential to improve VMAT deliveries through increased efficiency and reduced normal tissue dose, especially in treatment of multiple cranial metastases

  14. WE-AB-209-06: Dynamic Collimator Trajectory Algorithm for Use in VMAT Treatment Deliveries

    International Nuclear Information System (INIS)

    MacDonald, L; Thomas, C; Syme, A

    2016-01-01

    Purpose: To develop advanced dynamic collimator positioning algorithms for optimal beam’s-eye-view (BEV) fitting of targets in VMAT procedures, including multiple metastases stereotactic radiosurgery procedures. Methods: A trajectory algorithm was developed, which can dynamically modify the angle of the collimator as a function of VMAT control point to provide optimized collimation of target volume(s). Central to this algorithm is a concept denoted “whitespace”, defined as area within the jaw-defined BEV field, outside of the PTV, and not shielded by the MLC when fit to the PTV. Calculating whitespace at all collimator angles and every control point, a two-dimensional topographical map depicting the tightness-of-fit of the MLC was generated. A variety of novel searching algorithms identified a number of candidate trajectories of continuous collimator motion. Ranking these candidate trajectories according to their accrued whitespace value produced an optimal solution for navigation of this map. Results: All trajectories were normalized to minimum possible (i.e. calculated without consideration of collimator motion constraints) accrued whitespace. On an acoustic neuroma case, a random walk algorithm generated a trajectory with 151% whitespace; random walk including a mandatory anchor point improved this to 148%; gradient search produced a trajectory with 137%; and bi-directional gradient search generated a trajectory with 130% whitespace. For comparison, a fixed collimator angle of 30° and 330° accumulated 272% and 228% of whitespace, respectively. The algorithm was tested on a clinical case with two metastases (single isocentre) and identified collimator angles that allow for simultaneous irradiation of the PTVs while minimizing normal tissue irradiation. Conclusion: Dynamic collimator trajectories have the potential to improve VMAT deliveries through increased efficiency and reduced normal tissue dose, especially in treatment of multiple cranial metastases

  15. Design and development of collimator for 9 MeV BARC-ECIL linac

    International Nuclear Information System (INIS)

    Ghodke, S.R.; Barnwal, Rajesh; Mahendra Kumar; Nayak, Susanta; Barje, S.R.; Sinha, A.K.; Mittal, K.C.; Chakravarthy, D.P.; Gantayet, L.M.; Baiswar, Rishabh

    2011-01-01

    High Energy electron beam technology is useful for both fundamental and applied research in the sciences, and also in many technical and industrial fields. It has been estimated that there are approximately 26,000 accelerators worldwide. The collimator is designed to function with a 9 MeV LINAC Test Facility (LTF) at ECIL, Hyderabad. The accelerated electron beam hits a tantalum target and X-Rays generated though the target are fed to the collimator. Thereafter, collimated high energy X-Rays will be used for cargo scanning. The X-ray collimator will complement the existing system at LTF, ECIL to get collimated fan beam. A collaborative effort has been made to identify novel and advanced materials to achieve low coefficient of friction for various lateral and angular movements of collimator plates weighing nearly 5 tons. Complex numerical calculations simulating extreme conditions and experimental tests have been undertaken using Ansys. In parallel, an innovative modular design concept of the assembly has been developed to allow fitting in alternative materials, minimizing the load induced deformations, withstanding accidents and accepting desired radiation doses. The collimator plates are made up of mild steel blocks of IS 2062A grade ensuring high geometrical stability. The assembly structures for the collimator are made up of high stiffness I-beams ISMB 150. Each plate has been machined with high precision Electric Discharge Machining (EDM) and Surface Grinding processes. The plates are also hard chrome plated to provide corrosion resistance and increase surface hardness. A full scale collimator prototype has been manufactured to validate each feature of the new design at the LTF, ECIL, Hyderabad. (author)

  16. Numerical modeling of a fast-neutron collimator for the Alcator A fusion device

    International Nuclear Information System (INIS)

    Fisher, W.A.

    1982-12-01

    A numerical procedure is developed to analyze neutron collimators used for spatial neutron measurements of plasma neutrons. The procedure is based upon Monte-Carlo methods and uses a standard Monte-Carlo code. The specific developments described herein involve a new approach to represent complex spatial details in a method that is conservative of computer time, retains accuracy and required only modest changes in already-developed Monte-Carlo procedures. The procedure was used to model the Alcator A collimator. The collimator consists of 448 cells and has a measured spatial point source response of 0.7 cm. The numerical procedure successfully predicts this response

  17. Simulation a