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)

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

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.

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

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.

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

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.

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.

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

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.

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)

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.)

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.

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.

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

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

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)

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)

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

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.

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.

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

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%.

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

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

‘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.  

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

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

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)

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

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.

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

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

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

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)

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...

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

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

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

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.

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)

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

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.

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

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

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

Target tracking using DMLC for volumetric modulated arc therapy: A simulation study

Energy Technology Data Exchange (ETDEWEB)

Sun Baozhou; Rangaraj, Dharanipathy; Papiez, Lech; Oddiraju, Swetha; Yang Deshan; Li, H. Harold [Department of Radiation Oncology, School of Medicine, Washington University, 4921 Parkview Place, St. Louis, Missouri 63110 (United States); Department of Radiation Oncology, Southwestern Medical Center, University of Texas, Dallas, Texas 75390 (United States); Department of Radiation Oncology, School of Medicine, Washington University, 4921 Parkview Place, St. Louis, Missouri 63110 (United States)

2010-12-15

Purpose: Target tracking using dynamic multileaf collimator (DMLC) is a promising approach for intrafraction motion management in radiation therapy. The purpose of this work is to develop a DMLC tracking algorithm capable of delivering volumetric-modulated arc therapy (VMAT) to the targets that experience two-dimensional (2D) rigid motion in the beam's eye view. Methods: The problem of VMAT delivery to moving targets is formulated as a control problem with constraints. The relationships between gantry speed, gantry acceleration, MLC leaf-velocity, dose rate, and target motion are derived. An iterative search algorithm is developed to find numerical solutions for efficient delivery of a specific VMAT plan to the moving target using 2D DMLC tracking. The delivery of five VMAT lung plans is simulated. The planned and delivered fluence maps in the target-reference frame are calculated and compared. Results: The simulation demonstrates that the 2D tracking algorithm is capable of delivering the VMAT plan to a moving target fast and accurately without violating the machine constraints and the integrity of the treatment plan. The average delivery time is only 29 s longer than that of no-tracking delivery, 101 versus 72 s, respectively. The fluence maps are normalized to 200 MU and the average root-mean-square error between the desired and the delivered fluence is 2.1 MU, compared to 14.8 MU for no-tracking and 3.6 MU for one-dimensional tracking. Conclusions: A locally optimal MLC tracking algorithm for VMAT delivery is proposed, aiming at shortest delivery time while maintaining treatment plan invariant. The inconsequential increase of treatment time due to DMLC tracking is clinically desirable, which makes VMAT with DMLC tracking attractive in treating moving tumors.

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.

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.

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

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

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

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

Usefulness of Guided Breathing for Dose Rate-Regulated Tracking

International Nuclear Information System (INIS)

Han-Oh, Sarah; Yi, Byong Yong; Berman, Barry L.; Lerma, Fritz; Yu, Cedric

2009-01-01

Purpose: To evaluate the usefulness of guided breathing for dose rate-regulated tracking (DRRT), a new technique to compensate for intrafraction tumor motion. Methods and Materials: DRRT uses a preprogrammed multileaf collimator sequence that tracks the tumor motion derived from four-dimensional computed tomography and the corresponding breathing signals measured before treatment. Because the multileaf collimator speed can be controlled by adjusting the dose rate, the multileaf collimator positions are adjusted in real time during treatment by dose rate regulation, thereby maintaining synchrony with the tumor motion. DRRT treatment was simulated with free, audio-guided, and audiovisual-guided breathing signals acquired from 23 lung cancer patients. The tracking error and duty cycle for each patient were determined as a function of the system time delay (range, 0-1.0 s). Results: The tracking error and duty cycle averaged for all 23 patients was 1.9 ± 0.8 mm and 92% ± 5%, 1.9 ± 1.0 mm and 93% ± 6%, and 1.8 ± 0.7 mm and 92% ± 6% for the free, audio-guided, and audiovisual-guided breathing, respectively, for a time delay of 0.35 s. The small differences in both the tracking error and the duty cycle with guided breathing were not statistically significant. Conclusion: DRRT by its nature adapts well to variations in breathing frequency, which is also the motivation for guided-breathing techniques. Because of this redundancy, guided breathing does not result in significant improvements for either the tracking error or the duty cycle when DRRT is used for real-time tumor tracking

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)

The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

DEFF Research Database (Denmark)

Falk, Marianne; Larsson, Tobias; Keall, P.

2012-01-01

Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced......-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system. The dosimetric results were evaluated using gamma index evaluation with static target measurements as reference. Results: The plan quality...

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.

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.

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

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.

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

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

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

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

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

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.

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)

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.

IMRT delivery to a moving target by dynamic MLC tracking: delivery for targets moving in two dimensions in the beam's eye view

International Nuclear Information System (INIS)

McQuaid, D; Webb, S

2006-01-01

A new modification of the dynamic multileaf collimator (dMLC) delivery technique for intensity-modulated therapy (IMRT) is outlined. This technique enables the tracking of a target moving through rigid-body translations in a 2D trajectory in the beam's eye view. The accuracy of the delivery versus that of deliveries with no tracking and of 1D tracking techniques is quantified with clinically derived intensity-modulated beams (IMBs). Leaf trajectories calculated in the target-reference frame were iteratively synchronized assuming regular target motion. This allowed the leaves defined in the lab-reference frame to simultaneously follow the target motion and to deliver the required IMB without violation of the leaf maximum-velocity constraint. The leaves are synchronized until the gradient of the leaf position at every instant is less than a calculated maximum. The delivered fluence in the target-reference frame was calculated with a simple primary-fluence model. The new 2D tracking technique was compared with the delivered fluence produced by no-tracking deliveries and by 1D tracking deliveries for 33 clinical IMBs. For the clinical IMBs normalized to a maximum fluence of 200 MUs, the rms difference between the desired and the delivered IMB was 15.6 ± 3.3 MU for the case of a no-tracking delivery, 7.9 ± 1.6 MU for the case where only the primary component of motion was corrected and 5.1 ± 1.1 MU for the 2D tracking delivery. The residual error is due to interpolation and sampling effects. The 2D tracking delivery technique requires an increase in the delivery time evaluated as between 0 and 50% of the unsynchronized delivery time for each beam with a mean increase of 13% for the IMBs tested. The 2D tracking dMLC delivery technique allows an optimized IMB to be delivered to moving targets with increased accuracy and with acceptable increases in delivery time. When combined with real-time knowledge of the target motion at delivery time, this technique facilitates

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.

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)

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

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...

Motion management during IMAT treatment of mobile lung tumors-A comparison of MLC tracking and gated delivery

DEFF Research Database (Denmark)

Falk, Marianne; Pommer, Tobias; Keall, Paul

2014-01-01

Purpose:To compare real-time dynamic multileaf collimator (MLC) tracking, respiratory amplitude and phase gating, and no compensation for intrafraction motion management during intensity modulated arc therapy (IMAT). Methods: Motion management with MLC tracking and gating was evaluated for four...... tracking reduced the effects of the target movements, although the gated delivery showed a better dosimetric accuracy and enabled a larger reduction of the margins in some cases. MLC tracking did not prolong the treatment time compared to delivery with no motion compensation while gating had a considerably...... of the dosimetric error contributions showed that the gated delivery mainly had errors in target localization, while MLC tracking also had contributions from MLC leaf fitting and leaf adjustment. The average treatment time was about three times longer with gating compared to delivery with MLC tracking (that did...

Real-Time Dynamic MLC Tracking for Intensity Modulated Arc Therapy

DEFF Research Database (Denmark)

Falk, Marianne

Motion management of intra-fraction tumour motion during radiotherapy treatment can be a challenging task in order to achieve tumour control as well as minimizing the dose to the surrounding healthy tissue. Real-time dynamic multileaf collimator (MLC) tracking is a novel method for intra-fraction...

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.

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

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

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

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

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

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

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)

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.

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

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)

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

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)

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

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

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.

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

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

Optical Tracking Technology in Stereotactic Radiation Therapy

International Nuclear Information System (INIS)

Wagner, Thomas H.; Meeks, Sanford L.; Bova, Frank J.; Friedman, William A.; Willoughby, Twyla R.; Kupelian, Patrick A.; Tome, Wolfgang

2007-01-01

The last decade has seen the introduction of advanced technologies that have enabled much more precise application of therapeutic radiation. These relatively new technologies include multileaf collimators, 3-dimensional conformal radiotherapy planning, and intensity modulated radiotherapy in radiotherapy. Therapeutic dose distributions have become more conformal to volumes of disease, sometimes utilizing sharp dose gradients to deliver high doses to target volumes while sparing nearby radiosensitive structures. Thus, accurate patient positioning has become even more important, so that the treatment delivered to the patient matches the virtual treatment plan in the computer treatment planning system. Optical and image-guided radiation therapy systems offer the potential to improve the precision of patient treatment by providing a more robust fiducial system than is typically used in conventional radiotherapy. The ability to accurately position internal targets relative to the linac isocenter and to provide real-time patient tracking theoretically enables significant reductions in the amount of normal tissue irradiated. This report reviews the concepts, technology, and clinical applications of optical tracking systems currently in use for stereotactic radiation therapy. Applications of radiotherapy optical tracking technology to respiratory gating and the monitoring of implanted fiducial markers are also discussed

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.

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

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

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

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)

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

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.

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

The impact of leaf width and plan complexity on DMLC tracking of prostate intensity modulated arc therapy

DEFF Research Database (Denmark)

Pommer, Tobias; Falk, Marianne; Poulsen, Per Rugaard

2013-01-01

Purpose: Intensity modulated arc therapy (IMAT) is commonly used to treat prostate cancer. The purpose of this study was to evaluate the impact of leaf width and plan complexity on dynamic multileaf collimator (DMLC) tracking for prostate motion management during IMAT treatments.Methods: Prostate...... IMAT plans were delivered with either a high-definition MLC (HDMLC) or a Millennium MLC (M-MLC) (0.25 and 0.50 cm central leaf width, respectively), with and without DMLC tracking, to a dosimetric phantom that reproduced four prostate motion traces. The plan complexity was varied by applying leaf....... The corresponding pass rates without tracking were 87.6% (range 76.2%-94.7%) and 91.1% (range 81.4%-97.6%), respectively. Decreased plan complexity improved the pass rate when static target measurements were used as reference, but not with the planned dose as reference. The main cause of tracking errors was leaf...

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.

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.

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

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)

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

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

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

Management of three-dimensional intrafraction motion through real-time DMLC tracking

International Nuclear Information System (INIS)

Sawant, Amit; Venkat, Raghu; Srivastava, Vikram; Carlson, David; Povzner, Sergey; Cattell, Herb; Keall, Paul

2008-01-01

Tumor tracking using a dynamic multileaf collimator (DMLC) represents a promising approach for intrafraction motion management in thoracic and abdominal cancer radiotherapy. In this work, we develop, empirically demonstrate, and characterize a novel 3D tracking algorithm for real-time, conformal, intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT)-based radiation delivery to targets moving in three dimensions. The algorithm obtains real-time information of target location from an independent position monitoring system and dynamically calculates MLC leaf positions to account for changes in target position. Initial studies were performed to evaluate the geometric accuracy of DMLC tracking of 3D target motion. In addition, dosimetric studies were performed on a clinical linac to evaluate the impact of real-time DMLC tracking for conformal, step-and-shoot (S-IMRT), dynamic (D-IMRT), and VMAT deliveries to a moving target. The efficiency of conformal and IMRT delivery in the presence of tracking was determined. Results show that submillimeter geometric accuracy in all three dimensions is achievable with DMLC tracking. Significant dosimetric improvements were observed in the presence of tracking for conformal and IMRT deliveries to moving targets. A gamma index evaluation with a 3%-3 mm criterion showed that deliveries without DMLC tracking exhibit between 1.7 (S-IMRT) and 4.8 (D-IMRT) times more dose points that fail the evaluation compared to corresponding deliveries with tracking. The efficiency of IMRT delivery, as measured in the lab, was observed to be significantly lower in case of tracking target motion perpendicular to MLC leaf travel compared to motion parallel to leaf travel. Nevertheless, these early results indicate that accurate, real-time DMLC tracking of 3D tumor motion is feasible and can potentially result in significant geometric and dosimetric advantages leading to more effective management of intrafraction motion

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

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)

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.

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.

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.

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.

Experimental investigation of a moving averaging algorithm for motion perpendicular to the leaf travel direction in dynamic MLC target tracking

Energy Technology Data Exchange (ETDEWEB)

Yoon, Jai-Woong; Sawant, Amit; Suh, Yelin; Cho, Byung-Chul; Suh, Tae-Suk; Keall, Paul [Department of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul, Korea 131-700 and Research Institute of Biomedical Engineering, Catholic University of Korea, Seoul, 131-700 (Korea, Republic of); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States) and Department of Radiation Oncology, Asan Medical Center, Seoul, 138-736 (Korea, Republic of); Department of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul, 131-700 and Research Institute of Biomedical Engineering, Catholic University of Korea, Seoul, 131-700 (Korea, Republic of); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States) and Radiation Physics Laboratory, Sydney Medical School, University of Sydney, 2006 (Australia)

2011-07-15

Purpose: In dynamic multileaf collimator (MLC) motion tracking with complex intensity-modulated radiation therapy (IMRT) fields, target motion perpendicular to the MLC leaf travel direction can cause beam holds, which increase beam delivery time by up to a factor of 4. As a means to balance delivery efficiency and accuracy, a moving average algorithm was incorporated into a dynamic MLC motion tracking system (i.e., moving average tracking) to account for target motion perpendicular to the MLC leaf travel direction. The experimental investigation of the moving average algorithm compared with real-time tracking and no compensation beam delivery is described. Methods: The properties of the moving average algorithm were measured and compared with those of real-time tracking (dynamic MLC motion tracking accounting for both target motion parallel and perpendicular to the leaf travel direction) and no compensation beam delivery. The algorithm was investigated using a synthetic motion trace with a baseline drift and four patient-measured 3D tumor motion traces representing regular and irregular motions with varying baseline drifts. Each motion trace was reproduced by a moving platform. The delivery efficiency, geometric accuracy, and dosimetric accuracy were evaluated for conformal, step-and-shoot IMRT, and dynamic sliding window IMRT treatment plans using the synthetic and patient motion traces. The dosimetric accuracy was quantified via a {gamma}-test with a 3%/3 mm criterion. Results: The delivery efficiency ranged from 89 to 100% for moving average tracking, 26%-100% for real-time tracking, and 100% (by definition) for no compensation. The root-mean-square geometric error ranged from 3.2 to 4.0 mm for moving average tracking, 0.7-1.1 mm for real-time tracking, and 3.7-7.2 mm for no compensation. The percentage of dosimetric points failing the {gamma}-test ranged from 4 to 30% for moving average tracking, 0%-23% for real-time tracking, and 10%-47% for no compensation

Experimental investigation of a moving averaging algorithm for motion perpendicular to the leaf travel direction in dynamic MLC target tracking.

Science.gov (United States)

Yoon, Jai-Woong; Sawant, Amit; Suh, Yelin; Cho, Byung-Chul; Suh, Tae-Suk; Keall, Paul

2011-07-01

In dynamic multileaf collimator (MLC) motion tracking with complex intensity-modulated radiation therapy (IMRT) fields, target motion perpendicular to the MLC leaf travel direction can cause beam holds, which increase beam delivery time by up to a factor of 4. As a means to balance delivery efficiency and accuracy, a moving average algorithm was incorporated into a dynamic MLC motion tracking system (i.e., moving average tracking) to account for target motion perpendicular to the MLC leaf travel direction. The experimental investigation of the moving average algorithm compared with real-time tracking and no compensation beam delivery is described. The properties of the moving average algorithm were measured and compared with those of real-time tracking (dynamic MLC motion tracking accounting for both target motion parallel and perpendicular to the leaf travel direction) and no compensation beam delivery. The algorithm was investigated using a synthetic motion trace with a baseline drift and four patient-measured 3D tumor motion traces representing regular and irregular motions with varying baseline drifts. Each motion trace was reproduced by a moving platform. The delivery efficiency, geometric accuracy, and dosimetric accuracy were evaluated for conformal, step-and-shoot IMRT, and dynamic sliding window IMRT treatment plans using the synthetic and patient motion traces. The dosimetric accuracy was quantified via a tgamma-test with a 3%/3 mm criterion. The delivery efficiency ranged from 89 to 100% for moving average tracking, 26%-100% for real-time tracking, and 100% (by definition) for no compensation. The root-mean-square geometric error ranged from 3.2 to 4.0 mm for moving average tracking, 0.7-1.1 mm for real-time tracking, and 3.7-7.2 mm for no compensation. The percentage of dosimetric points failing the gamma-test ranged from 4 to 30% for moving average tracking, 0%-23% for real-time tracking, and 10%-47% for no compensation. The delivery efficiency of

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.

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

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

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

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.

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.

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

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.

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

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

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

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

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

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

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

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

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

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.

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.

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

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

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

Solar concentrator with integrated tracking and light delivery system with collimation

Science.gov (United States)

Maxey, Lonnie Curt

2015-06-09

A solar light distribution system includes a solar light concentrator that is affixed externally to a light transfer tube. Solar light waves are processed by the concentrator into a collimated beam of light, which is then transferred through a light receiving port and into the light transfer tube. A reflector directs the collimated beam of light through the tube to a light distribution port. The interior surface of the light transfer tube is highly reflective so that the light transfers through the tube with minimal losses. An interchangeable luminaire is attached to the light distribution port and distributes light inside of a structure. A sun tracking device rotates the concentrator and the light transfer tube to optimize the receiving of solar light by the concentrator throughout the day. The system provides interior lighting, uses only renewable energy sources, and releases no carbon dioxide emissions into the atmosphere.

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.

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

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

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.

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

SU-G-BRA-16: Target Dose Comparison for Dynamic MLC Tracking and Mid- Ventilation Planning in Lung Radiotherapy Subject to Intrafractional Baseline Drifts

Energy Technology Data Exchange (ETDEWEB)

Menten, MJ; Fast, MF; Nill, S; Oelfke, U [Joint Department of Physics at The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London (United Kingdom)

2016-06-15

Purpose: Lung tumor motion during radiotherapy can be accounted for by expanded treatment margins, for example using a mid-ventilation planning approach, or by localizing the tumor in real-time and adapting the treatment beam with multileaf collimator (MLC) tracking. This study evaluates the effect of intrafractional changes in the average tumor position (baseline drifts) on these two treatment techniques. Methods: Lung stereotactic treatment plans (9-beam IMRT, 54Gy/3 fractions, mean treatment time: 9.63min) were generated for three patients: either for delivery with MLC tracking (isotropic GTV-to-PTV margin: 2.6mm) or planned with a mid-ventilation approach and delivered without online motion compensation (GTV-to-PTV margin: 4.4-6.3mm). Delivery to a breathing patient was simulated using DynaTrack, our in-house tracking and delivery software. Baseline drifts in cranial and posterior direction were simulated at a rate of 0.5, 1.0 or 1.5mm/min. For dose reconstruction, the corresponding 4DCT phase was selected for each time point of the delivery. Baseline drifts were accounted for by rigidly shifting the CT to ensure correct relative beam-to-target positioning. Afterwards, the doses delivered to each 4DCT phase were accumulated deformably on the mid-ventilation phase using research RayStation v4.6 and dose coverage of the GTV was evaluated. Results: When using the mid-ventilation planning approach, dose coverage of the tumor deteriorated substantially in the presence of baseline drifts. The reduction in D98% coverage of the GTV in a single fraction ranged from 0.4-1.2, 0.6-3.3 and 4.5-6.2Gy, respectively, for the different drift rates. With MLC tracking the GTV D98% coverage remained unchanged (+/− 0.1Gy) regardless of drift. Conclusion: Intrafractional baseline drifts reduce the tumor dose in treatments based on mid-ventilation planning. In rare, large target baseline drifts tumor dose coverage may drop below the prescription, potentially affecting clinical

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

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.

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.

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

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

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

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

Lung tumor tracking in fluoroscopic video based on optical flow

International Nuclear Information System (INIS)

Xu Qianyi; Hamilton, Russell J.; Schowengerdt, Robert A.; Alexander, Brian; Jiang, Steve B.

2008-01-01

Respiratory gating and tumor tracking for dynamic multileaf collimator delivery require accurate and real-time localization of the lung tumor position during treatment. Deriving tumor position from external surrogates such as abdominal surface motion may have large uncertainties due to the intra- and interfraction variations of the correlation between the external surrogates and internal tumor motion. Implanted fiducial markers can be used to track tumors fluoroscopically in real time with sufficient accuracy. However, it may not be a practical procedure when implanting fiducials bronchoscopically. In this work, a method is presented to track the lung tumor mass or relevant anatomic features projected in fluoroscopic images without implanted fiducial markers based on an optical flow algorithm. The algorithm generates the centroid position of the tracked target and ignores shape changes of the tumor mass shadow. The tracking starts with a segmented tumor projection in an initial image frame. Then, the optical flow between this and all incoming frames acquired during treatment delivery is computed as initial estimations of tumor centroid displacements. The tumor contour in the initial frame is transferred to the incoming frames based on the average of the motion vectors, and its positions in the incoming frames are determined by fine-tuning the contour positions using a template matching algorithm with a small search range. The tracking results were validated by comparing with clinician determined contours on each frame. The position difference in 95% of the frames was found to be less than 1.4 pixels (∼0.7 mm) in the best case and 2.8 pixels (∼1.4 mm) in the worst case for the five patients studied.

Whole brain radiotherapy for brain metastases: The technique of irradiation influences the dose to parotid glands

International Nuclear Information System (INIS)

Loos, G.; Paulon, R.; Verrelle, P.; Lapeyre, M.

2012-01-01

In the treatment of brain metastases, whole brain radiotherapy can be carried out according two distinct methods: one using multi-leaf collimator for field shaping and protection of organs at risk, and a second one is to make a rotation of the field to avoid the eyes. The aim of the study was to compare for 10 patients the dose distributions at organs at risk for each method. Patients received 30 Gy in 10 fractions. Except for parotid glands, the dose received by organs at risk and the planning target volume was the same with each method. For whole brain radiotherapy, excluding the cisterna cerebellomedullaris, the mean parotid dose was 9.63 Gy using the multi-leaf collimator versus 12.32 Gy using the field rotation (P = 0.04). For whole brain radiotherapy including the cisterna cerebellomedullaris, the mean parotid dose was 11.12 Gy using the multi-leaf collimator versus 20.06 Gy using field rotation (P < 0.001). Using the multi-leaf collimator seems recommended for whole brain radiotherapy, to reduce the dose to the parotids. (authors)

Real-Time Motion Management of Prostate Cancer Radiotherapy

DEFF Research Database (Denmark)

Pommer, Tobias

of this thesis is to manage prostate motion in real-time by aligning the radiation beam to the prostate using the novel dynamic multileaf collimator (DMLC) tracking method. Specifically, the delivered dose with tracking was compared to the planned dose, and the impact of treatment plan complexity and limitations...

The dosimetric impact of inversely optimized arc radiotherapy plan modulation for real-time dynamic MLC tracking delivery

International Nuclear Information System (INIS)

Falk, Marianne; Larsson, Tobias; Keall, Paul; Chul Cho, Byung; Aznar, Marianne; Korreman, Stine; Poulsen, Per; Munck af Rosenschoeld, Per

2012-01-01

Purpose: Real-time dynamic multileaf collimator (MLC) tracking for management of intrafraction tumor motion can be challenging for highly modulated beams, as the leaves need to travel far to adjust for target motion perpendicular to the leaf travel direction. The plan modulation can be reduced by using a leaf position constraint (LPC) that reduces the difference in the position of adjacent MLC leaves in the plan. The purpose of this study was to investigate the impact of the LPC on the quality of inversely optimized arc radiotherapy plans and the effect of the MLC motion pattern on the dosimetric accuracy of MLC tracking delivery. Specifically, the possibility of predicting the accuracy of MLC tracking delivery based on the plan modulation was investigated. Methods: Inversely optimized arc radiotherapy plans were created on CT-data of three lung cancer patients. For each case, five plans with a single 358 deg. arc were generated with LPC priorities of 0 (no LPC), 0.25, 0.5, 0.75, and 1 (highest possible LPC), respectively. All the plans had a prescribed dose of 2 Gy x 30, used 6 MV, a maximum dose rate of 600 MU/min and a collimator angle of 45 deg. or 315 deg. To quantify the plan modulation, an average adjacent leaf distance (ALD) was calculated by averaging the mean adjacent leaf distance for each control point. The linear relationship between the plan quality [i.e., the calculated dose distributions and the number of monitor units (MU)] and the LPC was investigated, and the linear regression coefficient as well as a two tailed confidence level of 95% was used in the evaluation. The effect of the plan modulation on the performance of MLC tracking was tested by delivering the plans to a cylindrical diode array phantom moving with sinusoidal motion in the superior-inferior direction with a peak-to-peak displacement of 2 cm and a cycle time of 6 s. The delivery was adjusted to the target motion using MLC tracking, guided in real-time by an infrared optical system

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

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

A new type industrial total station based on target automatic collimation

Science.gov (United States)

Lao, Dabao; Zhou, Weihu; Ji, Rongyi; Dong, Dengfeng; Xiong, Zhi; Wei, Jiang

2018-01-01

In the case of industrial field measurement, the present measuring instruments work with manual operation and collimation, which give rise to low efficiency for field measurement. In order to solve the problem, a new type industrial total station is presented in this paper. The new instrument can identify and trace cooperative target automatically, in the mean time, coordinate of the target is measured in real time. For realizing the system, key technology including high precision absolutely distance measurement, small high accuracy angle measurement, target automatic collimation with vision, and quick precise controlling should be worked out. After customized system assemblage and adjustment, the new type industrial total station will be established. As the experiments demonstrated, the coordinate accuracy of the instrument is under 15ppm in the distance of 60m, which proved that the measuring system is feasible. The result showed that the total station can satisfy most industrial field measurement requirements.

Fast regional readout CMOS Image Sensor for dynamic MLC tracking

Science.gov (United States)

Zin, H.; Harris, E.; Osmond, J.; Evans, P.

2014-03-01

Advanced radiotherapy techniques such as volumetric modulated arc therapy (VMAT) require verification of the complex beam delivery including tracking of multileaf collimators (MLC) and monitoring the dose rate. This work explores the feasibility of a prototype Complementary metal-oxide semiconductor Image Sensor (CIS) for tracking these complex treatments by utilising fast, region of interest (ROI) read out functionality. An automatic edge tracking algorithm was used to locate the MLC leaves edges moving at various speeds (from a moving triangle field shape) and imaged with various sensor frame rates. The CIS demonstrates successful edge detection of the dynamic MLC motion within accuracy of 1.0 mm. This demonstrates the feasibility of the sensor to verify treatment delivery involving dynamic MLC up to ~400 frames per second (equivalent to the linac pulse rate), which is superior to any current techniques such as using electronic portal imaging devices (EPID). CIS provides the basis to an essential real-time verification tool, useful in accessing accurate delivery of complex high energy radiation to the tumour and ultimately to achieve better cure rates for cancer patients.

Fast regional readout CMOS image sensor for dynamic MLC tracking

International Nuclear Information System (INIS)

Zin, H; Harris, E; Osmond, J; Evans, P

2014-01-01

Advanced radiotherapy techniques such as volumetric modulated arc therapy (VMAT) require verification of the complex beam delivery including tracking of multileaf collimators (MLC) and monitoring the dose rate. This work explores the feasibility of a prototype Complementary metal-oxide semiconductor Image Sensor (CIS) for tracking these complex treatments by utilising fast, region of interest (ROI) read out functionality. An automatic edge tracking algorithm was used to locate the MLC leaves edges moving at various speeds (from a moving triangle field shape) and imaged with various sensor frame rates. The CIS demonstrates successful edge detection of the dynamic MLC motion within accuracy of 1.0 mm. This demonstrates the feasibility of the sensor to verify treatment delivery involving dynamic MLC up to ∼400 frames per second (equivalent to the linac pulse rate), which is superior to any current techniques such as using electronic portal imaging devices (EPID). CIS provides the basis to an essential real-time verification tool, useful in accessing accurate delivery of complex high energy radiation to the tumour and ultimately to achieve better cure rates for cancer patients.

Collimated proton acceleration in light sail regime with a tailored pinhole target

Energy Technology Data Exchange (ETDEWEB)

Wang, H. Y.; Zepf, M. [Helmholtz Institute Jena, Fröbelstieg 3, 07743 Jena (Germany); Yan, X. Q. [State Key Laboratory of Nuclear Physics and Technology and Key Lab of High Energy Density Physics Simulation, CAPT, Peking University, Beijing 100871 (China)

2014-06-15

A scheme for producing collimated protons from laser interactions with a diamond-like-carbon + pinhole target is proposed. The process is based on radiation pressure acceleration in the multi-species light-sail regime [B. Qiao et al., Phys. Rev. Lett. 105, 155002 (2010); T. P. Yu et al., Phys. Rev. Lett. 105, 065002 (2010)]. Particle-in-cell simulations demonstrate that transverse quasistatic electric field at TV/m level can be generated in the pinhole. The transverse electric field suppresses the transverse expansion of protons effectively, resulting in a higher density and more collimated proton beam compared with a single foil target. The dependence of the proton beam divergence on the parameters of the pinhole is also investigated.

Collimated proton acceleration in light sail regime with a tailored pinhole target

International Nuclear Information System (INIS)

Wang, H. Y.; Zepf, M.; Yan, X. Q.

2014-01-01

A scheme for producing collimated protons from laser interactions with a diamond-like-carbon + pinhole target is proposed. The process is based on radiation pressure acceleration in the multi-species light-sail regime [B. Qiao et al., Phys. Rev. Lett. 105, 155002 (2010); T. P. Yu et al., Phys. Rev. Lett. 105, 065002 (2010)]. Particle-in-cell simulations demonstrate that transverse quasistatic electric field at TV/m level can be generated in the pinhole. The transverse electric field suppresses the transverse expansion of protons effectively, resulting in a higher density and more collimated proton beam compared with a single foil target. The dependence of the proton beam divergence on the parameters of the pinhole is also investigated

Magnetic collimation of fast electrons in specially engineered targets irradiated by ultraintense laser pulses

International Nuclear Information System (INIS)

Cai Hongbo; Zhu Shaoping; Wu Sizhong; Chen Mo; Zhou Cangtao; He, X. T.; Yu Wei; Nagatomo, Hideo

2011-01-01

The efficient magnetic collimation of fast electron flow transporting in overdense plasmas is investigated with two-dimensional collisional particle-in-cell numerical simulations. It is found that the specially engineered targets exhibiting either high-resistivity-core-low-resistivity-cladding structure or low-density-core-high-density-cladding structure can collimate fast electrons. Two main mechanisms to generate collimating magnetic fields are found. In high-resistivity-core-low-resistivity-cladding structure targets, the magnetic field at the interfaces is generated by the gradients of the resistivity and fast electron current, while in low-density-core-high-density-cladding structure targets, the magnetic field is generated by the rapid changing of the flow velocity of the background electrons in transverse direction (perpendicular to the flow velocity) caused by the density jump. The dependences of the maximal magnetic field on the incident laser intensity and plasma density, which are studied by numerical simulations, are supported by our analytical calculations.

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

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

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.

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.

Dosimetric effects of sectional adjustments of collimator angles on volumetric modulated arc therapy for irregularly-shaped targets.

Directory of Open Access Journals (Sweden)

Beom Seok Ahn

Full Text Available To calculate an optimal collimator angle at each of sectional arcs in a full-arc volumetric modulated arc therapy (VMAT plan and evaluate dosimetric quality of these VMAT plans comparing full-arc VMAT plans with a fixed collimator angle.Seventeen patients who had irregularly-shaped target in abdominal, head and neck, and chest cases were selected retrospectively. To calculate an optimal collimator angle at each of sectional arcs in VMAT, integrated MLC apertures which could cover all shapes of target determined by beam's-eye view (BEV within angular sections were obtained for each VMAT plan. The angular sections were 40°, 60°, 90° and 120°. When the collimator settings were rotated at intervals of 2°, we obtained the optimal collimator angle to minimize area size difference between the integrated MLC aperture and collimator settings with 5 mm-margins to the integrated MLC aperture. The VMAT plans with the optimal collimator angles (Colli-VMAT were generated in the EclipseTM. For comparison purposes, one full-arc VMAT plans with a fixed collimator angles (Std-VMAT were generated. The dose-volumetric parameters and total MUs were evaluated.The mean dose-volumetric parameters for target volume of Colli-VMAT were comparable to Std-VMAT. Colli-VMAT improved sparing of most normal organs but for brain stem, compared to Std-VMAT for all cases. There were decreasing tendencies in mean total MUs with decreasing angular section. The mean total MUs for Colli-VMAT with the angular section of 40° (434 ± 95 MU, 317 ± 81 MU, and 371 ± 43 MU for abdominal, head and neck, and chest cases, respectively were lower than those for Std-VMAT (654 ± 182 MU, 517 ± 116 MU, and 533 ± 25 MU, respectively.For an irregularly-shaped target, Colli-VMAT with the angular section of 40° reduced total MUs and improved sparing of normal organs, compared to Std-VMAT.

TH-AB-202-03: A Novel Tool for Computing Deliverable Doses in Dynamic MLC Tracking Treatments

Energy Technology Data Exchange (ETDEWEB)

Fast, M; Kamerling, C; Menten, M; Nill, S; Oelfke, U [The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London (United Kingdom); Crijns, S; Raaymakers, B [University Medical Center Utrecht, Utrecht (Netherlands)

2016-06-15

Purpose: In tracked dynamic multi-leaf collimator (MLC) treatments, segments are continuously adapted to the target centroid motion in beams-eye-view. On-the-fly segment adaptation, however, potentially induces dosimetric errors due to the finite MLC leaf width and non-rigid target motion. In this study, we outline a novel tool for computing the 4d dose of lung SBRT plans delivered with MLC tracking. Methods: The following automated workflow was developed: A) centroid tracking, where the initial segments are morphed to each 4dCT phase based on the beams-eye-view GTV shift (followed by a dose calculation on each phase); B) re-optimized tracking, in which all morphed initial plans from (A) are further optimised (“warm-started”) in each 4dCT phase using the initial optimisation parameters but phase-specific volume definitions. Finally, both dose sets are accumulated to the reference phase using deformable image registration. Initial plans were generated according to the RTOG-1021 guideline (54Gy, 3-Fx, equidistant 9-beam IMRT) on the peak-exhale (reference) phase of a phase-binned 4dCT. Treatment planning and delivery simulations were performed in RayStation (research v4.6) using our in-house segment-morphing algorithm, which directly links to RayStation through a native C++ interface. Results: Computing the tracking plans and 4d dose distributions via the in-house interface takes 5 and 8 minutes respectively for centroid and re-optimized tracking. For a sample lung SBRT patient with 14mm peak-to-peak motion in sup-inf direction, mainly perpendicular leaf motion (0-collimator) resulted in small dose changes for PTV-D95 (−13cGy) and GTV-D98 (+18cGy) for the centroid tracking case compared to the initial plan. Modest reductions of OAR doses (e.g. spinal cord D2: −11cGy) were achieved in the idealized tracking case. Conclusion: This study presents an automated “1-click” workflow for computing deliverable MLC tracking doses in RayStation. Adding a non

TH-AB-202-03: A Novel Tool for Computing Deliverable Doses in Dynamic MLC Tracking Treatments

International Nuclear Information System (INIS)

Fast, M; Kamerling, C; Menten, M; Nill, S; Oelfke, U; Crijns, S; Raaymakers, B

2016-01-01

Purpose: In tracked dynamic multi-leaf collimator (MLC) treatments, segments are continuously adapted to the target centroid motion in beams-eye-view. On-the-fly segment adaptation, however, potentially induces dosimetric errors due to the finite MLC leaf width and non-rigid target motion. In this study, we outline a novel tool for computing the 4d dose of lung SBRT plans delivered with MLC tracking. Methods: The following automated workflow was developed: A) centroid tracking, where the initial segments are morphed to each 4dCT phase based on the beams-eye-view GTV shift (followed by a dose calculation on each phase); B) re-optimized tracking, in which all morphed initial plans from (A) are further optimised (“warm-started”) in each 4dCT phase using the initial optimisation parameters but phase-specific volume definitions. Finally, both dose sets are accumulated to the reference phase using deformable image registration. Initial plans were generated according to the RTOG-1021 guideline (54Gy, 3-Fx, equidistant 9-beam IMRT) on the peak-exhale (reference) phase of a phase-binned 4dCT. Treatment planning and delivery simulations were performed in RayStation (research v4.6) using our in-house segment-morphing algorithm, which directly links to RayStation through a native C++ interface. Results: Computing the tracking plans and 4d dose distributions via the in-house interface takes 5 and 8 minutes respectively for centroid and re-optimized tracking. For a sample lung SBRT patient with 14mm peak-to-peak motion in sup-inf direction, mainly perpendicular leaf motion (0-collimator) resulted in small dose changes for PTV-D95 (−13cGy) and GTV-D98 (+18cGy) for the centroid tracking case compared to the initial plan. Modest reductions of OAR doses (e.g. spinal cord D2: −11cGy) were achieved in the idealized tracking case. Conclusion: This study presents an automated “1-click” workflow for computing deliverable MLC tracking doses in RayStation. Adding a non

Heavy-ion collimation at the Large Hadron Collider. Simulations and measurements

Energy Technology Data Exchange (ETDEWEB)

Hermes, Pascal Dominik

2016-12-19

The CERN Large Hadron Collider (LHC) stores and collides proton and {sup 208}Pb{sup 82+} beams of unprecedented energy and intensity. Thousands of superconducting magnets, operated at 1.9 K, guide the very intense and energetic particle beams, which have a large potential for destruction. This implies the demand for a multi-stage collimation system to provide protection from beam-induced quenches or even hardware damage. In heavy-ion operation, ion fragments with significant rigidity offsets can still scatter out of the collimation system. When they irradiate the superconducting LHC magnets, the latter risk to quench (lose their superconducting property). These secondary collimation losses can potentially impose a limitation for the stored heavy-ion beam energy. Therefore, their distribution in the LHC needs to be understood by sophisticated simulations. Such simulation tools must accurately simulate the particle motion of many different nuclides in the magnetic LHC lattice and simulate their interaction with the collimators. Previous simulation tools used simplified models for the simulation of particle-matter interaction and showed discrepancies compared to the measured loss patterns. This thesis describes the development and application of improved heavy-ion collimation simulation tools. Two different approaches are presented to provide these functionalities. In the first presented tool, called STIER, fragmentation at the primary collimator is simulated with the Monte-Carlo event generator FLUKA. The ion fragments scattered out of the primary collimator are subsequently tracked as protons with ion-equivalent rigidities in the existing proton tracking tool SixTrack. This approach was used to prepare the collimator settings for the 2015 LHC heavy-ion run and its predictions allowed reducing undesired losses. More accurate simulation results are obtained with the second presented simulation tool, in which SixTrack is extended to track arbitrary heavy ions. This new

Heavy-ion collimation at the Large Hadron Collider. Simulations and measurements

International Nuclear Information System (INIS)

Hermes, Pascal Dominik

2016-01-01

The CERN Large Hadron Collider (LHC) stores and collides proton and 208 Pb 82+ beams of unprecedented energy and intensity. Thousands of superconducting magnets, operated at 1.9 K, guide the very intense and energetic particle beams, which have a large potential for destruction. This implies the demand for a multi-stage collimation system to provide protection from beam-induced quenches or even hardware damage. In heavy-ion operation, ion fragments with significant rigidity offsets can still scatter out of the collimation system. When they irradiate the superconducting LHC magnets, the latter risk to quench (lose their superconducting property). These secondary collimation losses can potentially impose a limitation for the stored heavy-ion beam energy. Therefore, their distribution in the LHC needs to be understood by sophisticated simulations. Such simulation tools must accurately simulate the particle motion of many different nuclides in the magnetic LHC lattice and simulate their interaction with the collimators. Previous simulation tools used simplified models for the simulation of particle-matter interaction and showed discrepancies compared to the measured loss patterns. This thesis describes the development and application of improved heavy-ion collimation simulation tools. Two different approaches are presented to provide these functionalities. In the first presented tool, called STIER, fragmentation at the primary collimator is simulated with the Monte-Carlo event generator FLUKA. The ion fragments scattered out of the primary collimator are subsequently tracked as protons with ion-equivalent rigidities in the existing proton tracking tool SixTrack. This approach was used to prepare the collimator settings for the 2015 LHC heavy-ion run and its predictions allowed reducing undesired losses. More accurate simulation results are obtained with the second presented simulation tool, in which SixTrack is extended to track arbitrary heavy ions. This new tracking

Toward improved target conformity for two spot scanning proton therapy delivery systems using dynamic collimation

Science.gov (United States)

Moignier, Alexandra; Gelover, Edgar; Smith, Blake R.; Wang, Dongxu; Flynn, Ryan T.; Kirk, Maura L.; Lin, Liyong; Solberg, Timothy D.; Lin, Alexander; Hyer, Daniel E.

2016-01-01

Purpose: To quantify improvement in target conformity in brain and head and neck tumor treatments resulting from the use of a dynamic collimation system (DCS) with two spot scanning proton therapy delivery systems (universal nozzle, UN, and dedicated nozzle, DN) with median spot sizes of 5.2 and 3.2 mm over a range of energies from 100 to 230 MeV. Methods: Uncollimated and collimated plans were calculated with both UN and DN beam models implemented within our in-house treatment planning system for five brain and ten head and neck datasets in patients previously treated with spot scanning proton therapy. The prescription dose and beam angles from the clinical plans were used for both the UN and DN plans. The average reduction of the mean dose to the 10-mm ring surrounding the target between the uncollimated and collimated plans was calculated for the UN and the DN. Target conformity was analyzed using the mean dose to 1-mm thickness rings surrounding the target at increasing distances ranging from 1 to 10 mm. Results: The average reductions of the 10-mm ring mean dose for the UN and DN plans were 13.7% (95% CI: 11.6%–15.7%; p < 0.0001) and 11.5% (95% CI: 9.5%–13.5%; p < 0.0001) across all brain cases and 7.1% (95% CI: 4.4%–9.8%; p < 0.001) and 6.3% (95% CI: 3.7%–9.0%; p < 0.001), respectively, across all head and neck cases. The collimated UN plans were either more conformal (all brain cases and 60% of the head and neck cases) than or equivalent (40% of the head and neck cases) to the uncollimated DN plans. The collimated DN plans offered the highest conformity. Conclusions: The DCS added either to the UN or DN improved the target conformity. The DCS may be of particular interest for sites with UN systems looking for a more economical solution than upgrading the nozzle to improve the target conformity of their spot scanning proton therapy system. PMID:26936726

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

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

Symplectic Tracking of Multi-Isotopic Heavy-Ion Beams in SixTrack

CERN Document Server

Hermes, Pascal; De Maria, Riccardo

2016-01-01

The software SixTrack provides symplectic proton tracking over a large number of turns. The code is used for the tracking of beam halo particles and the simulation of their interaction with the collimators to study the efficiency of the LHC collimation system. Tracking simulations for heavy-ion beams require taking into account the mass to charge ratio of each particle because heavy ions can be subject to fragmentation at their passage through the collimators. In this paper we present the derivation of a Hamiltonian for multi-isotopic heavy-ion beams and symplectic tracking maps derived from it. The resulting tracking maps were implemented in the tracking software SixTrack. With this modification, SixTrack can be used to natively track heavy-ion beams of multiple isotopes through a magnetic accelerator lattice.

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

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

An experimental comparison of conventional two-bank and novel four-bank dynamic MLC tracking

International Nuclear Information System (INIS)

Davies, G A; Clowes, P; McQuaid, D; Evans, P M; Webb, S; Poludniowski, G

2013-01-01

The AccuLeaf mMLC featuring four multileaf-collimator (MLC) banks has been used for the first time for an experimental comparison of conventional two-bank with novel four-bank dynamic MLC tracking of a two-dimensional sinusoidal respiratory motion. This comparison was performed for a square aperture, and for three conformal treatment apertures from clinical radiotherapy lung cancer patients. The system latency of this prototype tracking system was evaluated and found to be 1.0 s and the frequency at which MLC positions could be updated, 1 Hz, and therefore accurate MLC tracking of irregular patient motion would be difficult with the system in its current form. The MLC leaf velocity required for two-bank-MLC and four-bank-MLC tracking was evaluated for the apertures studied and a substantial decrease was found in the maximum MLC velocity required when four-banks were used for tracking rather than two. A dosimetric comparison of the two techniques was also performed and minimal difference was found between two-bank-MLC and four-bank-MLC tracking. The use of four MLC banks for dynamic MLC tracking is shown to be potentially advantageous for increasing the delivery efficiency compared with two-bank-MLC tracking where difficulties are encountered if large leaf shifts are required to track motion perpendicular to the direction of leaf travel. (paper)

Dosimetric benefit of DMLC tracking for conventional and sub-volume boosted prostate intensity-modulated arc radiotherapy

Science.gov (United States)

Pommer, Tobias; Falk, Marianne; Poulsen, Per R.; Keall, Paul J.; O'Brien, Ricky T.; Meidahl Petersen, Peter; Rosenschöld, Per Munck af

2013-04-01

This study investigated the dosimetric impact of uncompensated motion and motion compensation with dynamic multileaf collimator (DMLC) tracking for prostate intensity modulated arc therapy. Two treatment approaches were investigated; a conventional approach with a uniform radiation dose to the target volume and an intraprostatic lesion (IPL) boosted approach with an increased dose to a subvolume of the prostate. The impact on plan quality of optimizations with a leaf position constraint, which limited the distance between neighbouring adjacent MLC leaves, was also investigated. Deliveries were done with and without DMLC tracking on a linear acceleration with a high-resolution MLC. A cylindrical phantom containing two orthogonal diode arrays was used for dosimetry. A motion platform reproduced six patient-derived prostate motion traces, with the average displacement ranging from 1.0 to 8.9 mm during the first 75 s. A research DMLC tracking system was used for real-time motion compensation with optical monitoring for position input. The gamma index was used for evaluation, with measurements with a static phantom or the planned dose as reference, using 2% and 2 mm gamma criteria. The average pass rate with DMLC tracking was 99.9% (range 98.7-100%, measurement as reference), whereas the pass rate for untracked deliveries decreased distinctly as the average displacement increased, with an average pass rate of 61.3% (range 32.7-99.3%). Dose-volume histograms showed that DMLC tracking maintained the planned dose distributions in the presence of motion whereas traces with >3 mm average displacement caused clear plan degradation for untracked deliveries. The dose to the rectum and bladder had an evident dependence on the motion direction and amplitude for untracked deliveries, and the dose to the rectum was slightly increased for IPL boosted plans compared to conventional plans for anterior motion with large amplitude. In conclusion, optimization using a leaf position

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)

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.

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.

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.

Investigations of effect of target thickness and detector collimation on 662 keV multiply backscattered gamma photons

International Nuclear Information System (INIS)

Sabharwal, Arvind D.; Sandhu, B.S.; Singh, Bhajan

2009-01-01

The present studies aimed to investigate the effects of detector collimation and target thickness on multiply backscattered gamma photons. The numbers of multiply backscattered events, having energy the same as in singly scattered distribution, are found to be increasing with target thickness, and saturate for a particular thickness known as saturation thickness. The saturation thickness is not altered by the variation in the collimator opening. The number and energy albedos, characterizing the reflection probability of a material, are also evaluated. Monte Carlo calculations support the present experimental work.

Method for dose-reduced 3D catheter tracking on a scanning-beam digital x-ray system using dynamic electronic collimation

Science.gov (United States)

Dunkerley, David A. P.; Funk, Tobias; Speidel, Michael A.

2016-03-01

Scanning-beam digital x-ray (SBDX) is an inverse geometry x-ray fluoroscopy system capable of tomosynthesis-based 3D catheter tracking. This work proposes a method of dose-reduced 3D tracking using dynamic electronic collimation (DEC) of the SBDX scanning x-ray tube. Positions in the 2D focal spot array are selectively activated to create a regionof- interest (ROI) x-ray field around the tracked catheter. The ROI position is updated for each frame based on a motion vector calculated from the two most recent 3D tracking results. The technique was evaluated with SBDX data acquired as a catheter tip inside a chest phantom was pulled along a 3D trajectory. DEC scans were retrospectively generated from the detector images stored for each focal spot position. DEC imaging of a catheter tip in a volume measuring 11.4 cm across at isocenter required 340 active focal spots per frame, versus 4473 spots in full-FOV mode. The dose-area-product (DAP) and peak skin dose (PSD) for DEC versus full field-of-view (FOV) scanning were calculated using an SBDX Monte Carlo simulation code. DAP was reduced to 7.4% to 8.4% of the full-FOV value, consistent with the relative number of active focal spots (7.6%). For image sequences with a moving catheter, PSD was 33.6% to 34.8% of the full-FOV value. The root-mean-squared-deviation between DEC-based 3D tracking coordinates and full-FOV 3D tracking coordinates was less than 0.1 mm. The 3D distance between the tracked tip and the sheath centerline averaged 0.75 mm. Dynamic electronic collimation can reduce dose with minimal change in tracking performance.

Optimization of radiotherapy to target volumes with concave outlines: target-dose homogenization and selective sparing of critical structures by constrained matrix inversion

Energy Technology Data Exchange (ETDEWEB)

Colle, C; Van den Berge, D; De Wagter, C; Fortan, L; Van Duyse, B; De Neve, W

1995-12-01

The design of 3D-conformal dose distributions for targets with concave outlines is a technical challenge in conformal radiotherapy. For these targets, it is impossible to find beam incidences for which the target volume can be isolated from the tissues at risk. Commonly occurring examples are most thyroid cancers and the targets located at the lower neck and upper mediastinal levels related to some head and neck. A solution to this problem was developed, using beam intensity modulation executed with a multileaf collimator by applying a static beam-segmentation technique. The method includes the definition of beam incidences and beam segments of specific shape as well as the calculation of segment weights. Tests on Sherouse`s GRATISTM planning system allowed to escalate the dose to these targets to 65-70 Gy without exceeding spinal cord tolerance. Further optimization by constrained matrix inversion was investigated to explore the possibility of further dose escalation.

Detailed analysis of latencies in image-based dynamic MLC tracking

International Nuclear Information System (INIS)

Poulsen, Per Rugaard; Cho, Byungchul; Sawant, Amit; Ruan, Dan; Keall, Paul J.

2010-01-01

Purpose: Previous measurements of the accuracy of image-based real-time dynamic multileaf collimator (DMLC) tracking show that the major contributor to errors is latency, i.e., the delay between target motion and MLC response. Therefore the purpose of this work was to develop a method for detailed analysis of latency contributions during image-based DMLC tracking. Methods: A prototype DMLC tracking system integrated with a linear accelerator was used for tracking a phantom with an embedded fiducial marker during treatment delivery. The phantom performed a sinusoidal motion. Real-time target localization was based on x-ray images acquired either with a portal imager or a kV imager mounted orthogonal to the treatment beam. Each image was stored in a file on the imaging workstation. A marker segmentation program opened the image file, determined the marker position in the image, and transferred it to the DMLC tracking program. This program estimated the three-dimensional target position by a single-imager method and adjusted the MLC aperture to the target position. Imaging intervals ΔT image from 150 to 1000 ms were investigated for both kV and MV imaging. After the experiments, the recorded images were synchronized with MLC log files generated by the MLC controller and tracking log files generated by the tracking program. This synchronization allowed temporal analysis of the information flow for each individual image from acquisition to completed MLC adjustment. The synchronization also allowed investigation of the MLC adjustment dynamics on a considerably finer time scale than the 50 ms time resolution of the MLC log files. Results: For ΔT image =150 ms, the total time from image acquisition to completed MLC adjustment was 380±9 ms for MV and 420±12 ms for kV images. The main part of this time was from image acquisition to completed image file writing (272 ms for MV and 309 ms for kV). Image file opening (38 ms), marker segmentation (4 ms), MLC position

Detailed analysis of latencies in image-based dynamic MLC tracking

Energy Technology Data Exchange (ETDEWEB)

Poulsen, Per Rugaard; Cho, Byungchul; Sawant, Amit; Ruan, Dan; Keall, Paul J. [Department of Radiation Oncology, Stanford University, Stanford, California 94305 and Department of Oncology and Department of Medical Physics, Aarhus University Hospital, 8000 Aarhus (Denmark); Department of Radiation Oncology, Stanford University, Stanford, California 94305 and Department of Radiation Oncology, Asan Medical Center, Seoul 138-736 (Korea, Republic of); Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States)

2010-09-15

Purpose: Previous measurements of the accuracy of image-based real-time dynamic multileaf collimator (DMLC) tracking show that the major contributor to errors is latency, i.e., the delay between target motion and MLC response. Therefore the purpose of this work was to develop a method for detailed analysis of latency contributions during image-based DMLC tracking. Methods: A prototype DMLC tracking system integrated with a linear accelerator was used for tracking a phantom with an embedded fiducial marker during treatment delivery. The phantom performed a sinusoidal motion. Real-time target localization was based on x-ray images acquired either with a portal imager or a kV imager mounted orthogonal to the treatment beam. Each image was stored in a file on the imaging workstation. A marker segmentation program opened the image file, determined the marker position in the image, and transferred it to the DMLC tracking program. This program estimated the three-dimensional target position by a single-imager method and adjusted the MLC aperture to the target position. Imaging intervals {Delta}T{sub image} from 150 to 1000 ms were investigated for both kV and MV imaging. After the experiments, the recorded images were synchronized with MLC log files generated by the MLC controller and tracking log files generated by the tracking program. This synchronization allowed temporal analysis of the information flow for each individual image from acquisition to completed MLC adjustment. The synchronization also allowed investigation of the MLC adjustment dynamics on a considerably finer time scale than the 50 ms time resolution of the MLC log files. Results: For {Delta}T{sub image}=150 ms, the total time from image acquisition to completed MLC adjustment was 380{+-}9 ms for MV and 420{+-}12 ms for kV images. The main part of this time was from image acquisition to completed image file writing (272 ms for MV and 309 ms for kV). Image file opening (38 ms), marker segmentation (4 ms

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.

Simulation and Measurements of Beam Losses on LHC Collimators During Beam Abort Failures

CERN Document Server

Lari, L; Bruce, R; Goddard, B; Redaelli, S; Salvachua, B; Valentino, G; Faus-Golfe, A

2013-01-01

One of the main purposes of tracking simulations for collimation studies is to produce loss maps along the LHC ring, in order to identify the level of local beam losses during nominal and abnormal operation scenarios. The SixTrack program is the standard tracking tool used at CERN to perform these studies. Recently, it was expanded in order to evaluate the proton load on different collimators in case of fast beam failures. Simulations are compared with beam measurements at 4 TeV. Combined failures are assumed which provide worst-case scenarios of the load on tungsten tertiary collimators.

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.

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.

Betatron-collimation Studies for Heavy Ions in the FCC-hh

CERN Multimedia

Logothetis Agaliotis, Efstathios

2018-01-01

One of the biggest challenges in the design of the FCC-hh is the collimation system. From LHC experience it is known that a collimation system optimized for proton cleaning has a significantly reduced efficiency for heavy ions. The study presented in this contribution evaluates the betatron-collimation efficiency for the heavy-ion operation with lead nuclei at a beam energy of 50 Z TeV in the system designed for proton operation. The fragmentation processes of the main beam particles in the primary collimator are simulated with FLUKA and fragments are individually tracked with SixTrack until being lost in the downstream aperture. In this way a first-impact loss-map is obtained, identifying locations where high energy deposition are to be expected. This provides a first-level assessment of feasibility and allows to include countermeasures in the conceptual accelerator design.

Present and future prospects of external radiation cancer treatment

International Nuclear Information System (INIS)

Valuckas, K. P.; Aleknavicius, E.; Grybauskas, M.

2004-01-01

Radiotherapy is the most applicable method in the treatment of cancer patients. Rapid advances in radiotherapy and imaging techniques allow improvement in definition of target margins, volumes, and organs at risk. Conformal radiotherapy using multileaf collimator was introduced towards the end of the 1980s. Further improvements in dose distribution were possible through intensity modulation radiation therapy based on the use of computer-controlled multileaf collimators for creating the desired dose variation inside a radiation field. The dose of definite radiotherapy is limited by dose tolerance of organs or tissues at risk near the target. In the last 50 years radiotherapy modalities achieved rapid developments, particularly in field of treatment planning and dose distribution. The main goal of that development is to apply definite radiotherapy dose to target and minimize normal tissue irradiation, leaving the patient free of treatment related morbidity. (author)

Experimental Comparison of Knife-Edge and Multi-Parallel Slit Collimators for Prompt Gamma Imaging of Proton Pencil Beams.

Science.gov (United States)

Smeets, Julien; Roellinghoff, Frauke; Janssens, Guillaume; Perali, Irene; Celani, Andrea; Fiorini, Carlo; Freud, Nicolas; Testa, Etienne; Prieels, Damien

2016-01-01

More and more camera concepts are being investigated to try and seize the opportunity of instantaneous range verification of proton therapy treatments offered by prompt gammas emitted along the proton tracks. Focusing on one-dimensional imaging with a passive collimator, the present study experimentally compared in combination with the first, clinically compatible, dedicated camera device the performances of instances of the two main options: a knife-edge slit (KES) and a multi-parallel slit (MPS) design. These two options were experimentally assessed in this specific context as they were previously demonstrated through analytical and numerical studies to allow similar performances in terms of Bragg peak retrieval precision and spatial resolution in a general context. Both collimators were prototyped according to the conclusions of Monte Carlo optimization studies under constraints of equal weight (40 mm tungsten alloy equivalent thickness) and of the specificities of the camera device under consideration (in particular 4 mm segmentation along beam axis and no time-of-flight discrimination, both of which less favorable to the MPS performance than to the KES one). Acquisitions of proton pencil beams of 100, 160, and 230 MeV in a PMMA target revealed that, in order to reach a given level of statistical precision on Bragg peak depth retrieval, the KES collimator requires only half the dose the present MPS collimator needs, making the KES collimator a preferred option for a compact camera device aimed at imaging only the Bragg peak position. On the other hand, the present MPS collimator proves more effective at retrieving the entrance of the beam in the target in the context of an extended camera device aimed at imaging the whole proton track within the patient.

Experimental Comparison of Knife-Edge and Multi-Parallel Slit Collimators for Prompt Gamma Imaging of Proton Pencil Beams

Science.gov (United States)

Smeets, Julien; Roellinghoff, Frauke; Janssens, Guillaume; Perali, Irene; Celani, Andrea; Fiorini, Carlo; Freud, Nicolas; Testa, Etienne; Prieels, Damien

2016-01-01

More and more camera concepts are being investigated to try and seize the opportunity of instantaneous range verification of proton therapy treatments offered by prompt gammas emitted along the proton tracks. Focusing on one-dimensional imaging with a passive collimator, the present study experimentally compared in combination with the first, clinically compatible, dedicated camera device the performances of instances of the two main options: a knife-edge slit (KES) and a multi-parallel slit (MPS) design. These two options were experimentally assessed in this specific context as they were previously demonstrated through analytical and numerical studies to allow similar performances in terms of Bragg peak retrieval precision and spatial resolution in a general context. Both collimators were prototyped according to the conclusions of Monte Carlo optimization studies under constraints of equal weight (40 mm tungsten alloy equivalent thickness) and of the specificities of the camera device under consideration (in particular 4 mm segmentation along beam axis and no time-of-flight discrimination, both of which less favorable to the MPS performance than to the KES one). Acquisitions of proton pencil beams of 100, 160, and 230 MeV in a PMMA target revealed that, in order to reach a given level of statistical precision on Bragg peak depth retrieval, the KES collimator requires only half the dose the present MPS collimator needs, making the KES collimator a preferred option for a compact camera device aimed at imaging only the Bragg peak position. On the other hand, the present MPS collimator proves more effective at retrieving the entrance of the beam in the target in the context of an extended camera device aimed at imaging the whole proton track within the patient. PMID:27446802

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.

Hypersonic sliding target tracking in near space

Directory of Open Access Journals (Sweden)

Xiang-yu Zhang

2015-12-01

Full Text Available To improve the tracking accuracy of hypersonic sliding target in near space, the influence of target hypersonic movement on radar detection and tracking is analyzed, and an IMM tracking algorithm is proposed based on radial velocity compensating and cancellation processing of high dynamic biases under the earth centered earth fixed (ECEF coordinate. Based on the analysis of effect of target hypersonic movement, a measurement model is constructed to reduce the filter divergence which is caused by the model mismatch. The high dynamic biases due to the target hypersonic movement are approximately compensated through radial velocity estimation to achieve the hypersonic target tracking at low systematic biases in near space. The high dynamic biases are further eliminated by the cancellation processing of different radars, in which the track association problem can be solved when the dynamic biases are low. An IMM algorithm based on constant acceleration (CA, constant turning (CT and Singer models is used to achieve the hypersonic sliding target tracking in near space. Simulation results show that the target tracking in near space can be achieved more effectively by using the proposed algorithm.

Exploiting target amplitude information to improve multi-target tracking

Science.gov (United States)

Ehrman, Lisa M.; Blair, W. Dale

2006-05-01

Closely-spaced (but resolved) targets pose a challenge for measurement-to-track data association algorithms. Since the Mahalanobis distances between measurements collected on closely-spaced targets and tracks are similar, several elements of the corresponding kinematic measurement-to-track cost matrix are also similar. Lacking any other information on which to base assignments, it is not surprising that data association algorithms make mistakes. One ad hoc approach for mitigating this problem is to multiply the kinematic measurement-to-track likelihoods by amplitude likelihoods. However, this can actually be detrimental to the measurement-to-track association process. With that in mind, this paper pursues a rigorous treatment of the hypothesis probabilities for kinematic measurements and features. Three simple scenarios are used to demonstrate the impact of basing data association decisions on these hypothesis probabilities for Rayleigh, fixed-amplitude, and Rician targets. The first scenario assumes that the tracker carries two tracks but only one measurement is collected. This provides insight into more complex scenarios in which there are fewer measurements than tracks. The second scenario includes two measurements and one track. This extends naturally to the case with more measurements than tracks. Two measurements and two tracks are present in the third scenario, which provides insight into the performance of this method when the number of measurements equals the number of tracks. In all cases, basing data association decisions on the hypothesis probabilities leads to good results.

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.

Underwater Acoustic Target Tracking: A Review

Science.gov (United States)

Han, Ying; Fan, Liying

2018-01-01

Advances in acoustic technology and instrumentation now make it possible to explore marine resources. As a significant component of ocean exploration, underwater acoustic target tracking has aroused wide attention both in military and civil fields. Due to the complexity of the marine environment, numerous techniques have been proposed to obtain better tracking performance. In this paper, we survey over 100 papers ranging from innovative papers to the state-of-the-art in this field to present underwater tracking technologies. Not only the related knowledge of acoustic tracking instrument and tracking progress is clarified in detail, but also a novel taxonomy method is proposed. In this paper, algorithms for underwater acoustic target tracking are classified based on the methods used as: (1) instrument-assisted methods; (2) mode-based methods; (3) tracking optimization methods. These algorithms are compared and analyzed in the aspect of dimensions, numbers, and maneuvering of the tracking target, which is different from other survey papers. Meanwhile, challenges, countermeasures, and lessons learned are illustrated in this paper. PMID:29301318

Practical using of TXRF spectrometers with slitless collimators for the trace analysis of targets surfaces

International Nuclear Information System (INIS)

Egorov, V.K.; Zuev, A.P.; Kondratiev, O.S.; Egorov, E.V.

2000-01-01

TXRF spectrometer with the slitless collimator used for a formation of the x-ray excitating beam (TXRF-SC spectrometer) is a new variety of an instrument been destined for the trace analysis of surfaces by x-ray fluorescence method at the total reflection of the x-ray incident beam. Some theoretical concepts are introduced for a characterization of the x-ray optics been unique to the TXRF-SC spectrometer. The principle design of the TXRF-SC spectrometer used for the trace quantitative analysis of a surface are discussed. Spectra of a secondary x-ray radiation yield for typical targets been collected by using of the TXRF-SC spectrometer and calculation of surface trace elements concentrations are presented. The analytical and operating parameters of the TXRF-SC spectrometer and one characterized by standard optical scheme are compared. The slitless collimator of the x-ray radiation is formed by two quartz polished plates mated together. Lengths of the plates are not equal. The target is placed on the surface of the long quartz plate and produces the continuation of the initial slitless collimator. Target orientation problem vanishes but problem of the surface contact effect appears. The secondary x-ray radiation excitated in a surface of the target is led out across the hole in the long quartz plate. The radiation is registered by a standard Si (Li) semiconductor detector and is collected by a multi-channel analyzer. The fundamental difference of the x-ray optical scheme been unique to TXRF-SC spectrometer from the standard one is the excitation of a studied surface by a flared x-ray beam with angle ΔΘ = 2Θ c , where Θ c is the critical angle of the total reflection. The vital peculiarity of a x-ray slitless collimation is the absence of a radiation monochromatism in output of the collimator. The sensible divergence of the x-ray excitating beam and the availability in it of monochromatic and white radiation alike allow to get in the surface layer of target the

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.

Technical Note: A novel leaf sequencing optimization algorithm which considers previous underdose and overdose events for MLC tracking radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Wisotzky, Eric, E-mail: eric.wisotzky@charite.de, E-mail: eric.wisotzky@ipk.fraunhofer.de; O’Brien, Ricky; Keall, Paul J., E-mail: paul.keall@sydney.edu.au [Radiation Physics Laboratory, Sydney Medical School, University of Sydney, Sydney, NSW 2006 (Australia)

2016-01-15

Purpose: Multileaf collimator (MLC) tracking radiotherapy is complex as the beam pattern needs to be modified due to the planned intensity modulation as well as the real-time target motion. The target motion cannot be planned; therefore, the modified beam pattern differs from the original plan and the MLC sequence needs to be recomputed online. Current MLC tracking algorithms use a greedy heuristic in that they optimize for a given time, but ignore past errors. To overcome this problem, the authors have developed and improved an algorithm that minimizes large underdose and overdose regions. Additionally, previous underdose and overdose events are taken into account to avoid regions with high quantity of dose events. Methods: The authors improved the existing MLC motion control algorithm by introducing a cumulative underdose/overdose map. This map represents the actual projection of the planned tumor shape and logs occurring dose events at each specific regions. These events have an impact on the dose cost calculation and reduce recurrence of dose events at each region. The authors studied the improvement of the new temporal optimization algorithm in terms of the L1-norm minimization of the sum of overdose and underdose compared to not accounting for previous dose events. For evaluation, the authors simulated the delivery of 5 conformal and 14 intensity-modulated radiotherapy (IMRT)-plans with 7 3D patient measured tumor motion traces. Results: Simulations with conformal shapes showed an improvement of L1-norm up to 8.5% after 100 MLC modification steps. Experiments showed comparable improvements with the same type of treatment plans. Conclusions: A novel leaf sequencing optimization algorithm which considers previous dose events for MLC tracking radiotherapy has been developed and investigated. Reductions in underdose/overdose are observed for conformal and IMRT delivery.

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%.

IFE Target Injection Tracking and Position Prediction Update

International Nuclear Information System (INIS)

Petzoldt, Ronald W.; Jonestrask, Kevin

2005-01-01

To achieve high gain in an inertial fusion energy power plant, driver beams must hit direct drive targets with ±20 μm accuracy (±100 μm for indirect drive). Targets will have to be tracked with even greater accuracy. The conceptual design for our tracking system, which predicts target arrival position and timing based on position measurements outside of the reaction chamber was previously described. The system has been built and has begun tracking targets at the first detector station. Additional detector stations are being modified for increased field of view. After three tracking stations are operational, position predictions at the final station will be compared to position measurements at that station as a measure of target position prediction accuracy.The as-installed design will be described together with initial target tracking and position prediction accuracy results. Design modifications that allow for improved accuracy and/or in-chamber target tracking will also be presented

On the suitability of Elekta’s Agility 160 MLC for tracked radiation delivery: closed-loop machine performance

International Nuclear Information System (INIS)

Glitzner, M; Crijns, S P M; De Senneville, B Denis; Lagendijk, J J W; Raaymakers, B W

2015-01-01

For motion adaptive radiotherapy, dynamic multileaf collimator tracking can be employed to reduce treatment margins by steering the beam according to the organ motion. The Elekta Agility 160 MLC has hitherto not been evaluated for its tracking suitability. Both dosimetric performance and latency are key figures and need to be assessed generically, independent of the used motion sensor. In this paper, we propose the use of harmonic functions directly fed to the MLC to determine its latency during continuous motion. Furthermore, a control variable is extracted from a camera system and fed to the MLC. Using this setup, film dosimetry and subsequent γ statistics are performed, evaluating the response when tracking (MRI)-based physiologic motion in a closed-loop. The delay attributed to the MLC itself was shown to be a minor contributor to the overall feedback chain as compared to the impact of imaging components such as MRI sequences. Delay showed a linear phase behaviour of the MLC employed in continuously dynamic applications, which enables a general MLC-characterization. Using the exemplary feedback chain, dosimetry showed a vast increase in pass rate employing γ statistics. In this early stage, the tracking performance of the Agility using the test bench yielded promising results, making the technique eligible for translation to tracking using clinical imaging modalities. (paper)

Design, simulation and manufacture of a multi leaf collimator to confirm the target volumes in intensity modulated radiation therapy

International Nuclear Information System (INIS)

Kamali-Asl, A.; Batooli, A. H.; Harriri, S.; Salman-Rezaee, F.; Shahmardan, F.; Yavari, L.

2010-01-01

Intensity modulated radiation therapy is one of the cancer treatment methods. It is important to selectively aim at the target in this way, which can be performed using a multi leaf collimator. Materials and Methods: In order to specifically irradiate the target volume in radiotherapy to reduce the patient absorbed dose, the use of multi leaf collimator has been investigated in this work. Design and simulation of an multi leaf collimator was performed by a Monte Carlo method and the optimum material for manufacturing the leaves was determined using MCNP4C. After image processing (CT or MRI) in this system, the tumor configuration is determined. Then the linear accelerator is switched on and the beam irradiates the cancerous cells. When the multi leaf collimator leaves receive a command from the micro controller, they start to move and absorb the radiation and modulate its intensity. Consequently, the tumor receives maximum intensity of radiation but minimum intensity is delivered to healthy tissues. Results: According to the simulations and calculations, the best material to manufacture the leaves from is tungsten alloy containing copper and nickel which absorbs a large amount of the radiation; by using a 8.65 cm thickness of alloy, 10.55% of radiation will transmit through the leaves. Discussion and Conclusion: Lead blocks are conventionally used in radiotherapy. However, they have some problems like cost, storage and manufacture for every patient. Certainly, the multi leaf collimator is the most efficient device to specifically irradiate the tumor in Intensity modulated radiation therapy. Furthermore, it facilitates treating the target in different views by rotation around the patient. Thus the patient's absorbed dose will decrease and the tumor will receive maximum dose.

Technical Note: Motion-perturbation method applied to dosimetry of dynamic MLC target tracking—A proof-of-concept

Energy Technology Data Exchange (ETDEWEB)

Feygelman, Vladimir, E-mail: vladimir.feygelman@moffitt.org; Tonner, Brian; Hunt, Dylan; Zhang, Geoffrey; Moros, Eduardo [Department of Radiation Oncology, Moffitt Cancer Center, Tampa, Florida 33612 (United States); Stambaugh, Cassandra [Department of Physics, University of South Florida, Tampa, Florida 33612 (United States); Nelms, Benjamin E. [Canis Lupus LLC, Merrimac, Wisconsin 53561 (United States)

2015-11-15

Purpose: Previous studies show that dose to a moving target can be estimated using 4D measurement-guided dose reconstruction based on a process called virtual motion simulation, or VMS. A potential extension of VMS is to estimate dose during dynamic multileaf collimator (MLC)-tracking treatments. The authors introduce a modified VMS method and quantify its performance as proof-of-concept for tracking applications. Methods: Direct measurements with a moving biplanar diode array were used to verify accuracy of the VMS dose estimates. A tracking environment for variably sized circular MLC apertures was simulated by sending preprogrammed control points to the MLC while simultaneously moving the accelerator treatment table. Sensitivity of the method to simulated tracking latency (0–700 ms) was also studied. Potential applicability of VMS to fast changing beam apertures was evaluated by modeling, based on the demonstrated dependence of the cumulative dose on the temporal dose gradient. Results: When physical and virtual latencies were matched, the agreement rates (2% global/2 mm gamma) between the VMS and the biplanar dosimeter were above 96%. When compared to their own reference dose (0 induced latency), the agreement rates for VMS and biplanar array track closely up to 200 ms of induced latency with 10% low-dose cutoff threshold and 300 ms with 50% cutoff. Time-resolved measurements suggest that even in the modulated beams, the error in the cumulative dose introduced by the 200 ms VMS time resolution is not likely to exceed 0.5%. Conclusions: Based on current results and prior benchmarks of VMS accuracy, the authors postulate that this approach should be applicable to any MLC-tracking treatments where leaf speeds do not exceed those of the current Varian accelerators.

Technical Note: Motion-perturbation method applied to dosimetry of dynamic MLC target tracking—A proof-of-concept

International Nuclear Information System (INIS)

Feygelman, Vladimir; Tonner, Brian; Hunt, Dylan; Zhang, Geoffrey; Moros, Eduardo; Stambaugh, Cassandra; Nelms, Benjamin E.

2015-01-01

Purpose: Previous studies show that dose to a moving target can be estimated using 4D measurement-guided dose reconstruction based on a process called virtual motion simulation, or VMS. A potential extension of VMS is to estimate dose during dynamic multileaf collimator (MLC)-tracking treatments. The authors introduce a modified VMS method and quantify its performance as proof-of-concept for tracking applications. Methods: Direct measurements with a moving biplanar diode array were used to verify accuracy of the VMS dose estimates. A tracking environment for variably sized circular MLC apertures was simulated by sending preprogrammed control points to the MLC while simultaneously moving the accelerator treatment table. Sensitivity of the method to simulated tracking latency (0–700 ms) was also studied. Potential applicability of VMS to fast changing beam apertures was evaluated by modeling, based on the demonstrated dependence of the cumulative dose on the temporal dose gradient. Results: When physical and virtual latencies were matched, the agreement rates (2% global/2 mm gamma) between the VMS and the biplanar dosimeter were above 96%. When compared to their own reference dose (0 induced latency), the agreement rates for VMS and biplanar array track closely up to 200 ms of induced latency with 10% low-dose cutoff threshold and 300 ms with 50% cutoff. Time-resolved measurements suggest that even in the modulated beams, the error in the cumulative dose introduced by the 200 ms VMS time resolution is not likely to exceed 0.5%. Conclusions: Based on current results and prior benchmarks of VMS accuracy, the authors postulate that this approach should be applicable to any MLC-tracking treatments where leaf speeds do not exceed those of the current Varian accelerators

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.

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.

Computer-aided target tracking in motion analysis studies

Science.gov (United States)

Burdick, Dominic C.; Marcuse, M. L.; Mislan, J. D.

1990-08-01

Motion analysis studies require the precise tracking of reference objects in sequential scenes. In a typical situation, events of interest are captured at high frame rates using special cameras, and selected objects or targets are tracked on a frame by frame basis to provide necessary data for motion reconstruction. Tracking is usually done using manual methods which are slow and prone to error. A computer based image analysis system has been developed that performs tracking automatically. The objective of this work was to eliminate the bottleneck due to manual methods in high volume tracking applications such as the analysis of crash test films for the automotive industry. The system has proven to be successful in tracking standard fiducial targets and other objects in crash test scenes. Over 95 percent of target positions which could be located using manual methods can be tracked by the system, with a significant improvement in throughput over manual methods. Future work will focus on the tracking of clusters of targets and on tracking deformable objects such as airbags.

SU-E-J-57: First Development of Adapting to Intrafraction Relative Motion Between Prostate and Pelvic Lymph Nodes Targets

Energy Technology Data Exchange (ETDEWEB)

Ge, Y; Colvill, E; O’Brien, R; Keall, P [Radiation Physics Laboratory, University of Sydney, NSW (Australia); Booth, J [Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW (Australia)

2015-06-15

Purpose Large intrafraction relative motion of multiple targets is common in advanced head and neck, lung, abdominal, gynaecological and urological cancer, jeopardizing the treatment outcomes. The objective of this study is to develop a real-time adaptation strategy, for the first time, to accurately correct for the relative motion of multiple targets by reshaping the treatment field using the multi-leaf collimator (MLC). Methods The principle of tracking the simultaneously treated but differentially moving tumor targets is to determine the new aperture shape that conforms to the shifted targets. Three dimensional volumes representing the individual targets are projected to the beam’s eye view. The leaf openings falling inside each 2D projection will be shifted according to the measured motion of each target to form the new aperture shape. Based on the updated beam shape, new leaf positions will be determined with optimized trade-off between the target underdose and healthy tissue overdose, and considerations of the physical constraints of the MLC. Taking a prostate cancer patient with pelvic lymph node involvement as an example, a preliminary dosimetric study was conducted to demonstrate the potential treatment improvement compared to the state-of- art adaptation technique which shifts the whole beam to track only one target. Results The world-first intrafraction adaptation system capable of reshaping the beam to correct for the relative motion of multiple targets has been developed. The dose in the static nodes and small bowel are closer to the planned distribution and the V45 of small bowel is decreased from 110cc to 75cc, corresponding to a 30% reduction by this technique compared to the state-of-art adaptation technique. Conclusion The developed adaptation system to correct for intrafraction relative motion of multiple targets will guarantee the tumour coverage and thus enable PTV margin reduction to minimize the high target dose to the adjacent organs

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.

Tracking a convoy of multiple targets using acoustic sensor data

Science.gov (United States)

Damarla, T. R.

2003-08-01

In this paper we present an algorithm to track a convoy of several targets in a scene using acoustic sensor array data. The tracking algorithm is based on template of the direction of arrival (DOA) angles for the leading target. Often the first target is the closest target to the sensor array and hence the loudest with good signal to noise ratio. Several steps were used to generate a template of the DOA angle for the leading target, namely, (a) the angle at the present instant should be close to the angle at the previous instant and (b) the angle at the present instant should be within error bounds of the predicted value based on the previous values. Once the template of the DOA angles of the leading target is developed, it is used to predict the DOA angle tracks of the remaining targets. In order to generate the tracks for the remaining targets, a track is established if the angles correspond to the initial track values of the first target. Second the time delay between the first track and the remaining tracks are estimated at the highest correlation points between the first track and the remaining tracks. As the vehicles move at different speeds the tracks either compress or expand depending on whether a target is moving fast or slow compared to the first target. The expansion and compression ratios are estimated and used to estimate the predicted DOA angle values of the remaining targets. Based on these predicted DOA angles of the remaining targets the DOA angles obtained from the MVDR or Incoherent MUSIC will be appropriately assigned to proper tracks. Several other rules were developed to avoid mixing the tracks. The algorithm is tested on data collected at Aberdeen Proving Ground with a convoy of 3, 4 and 5 vehicles. Some of the vehicles are tracked and some are wheeled vehicles. The tracking algorithm results are found to be good. The results will be presented at the conference and in the paper.

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%).

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)

Autonomous Vehicles Navigation with Visual Target Tracking: Technical Approaches

Directory of Open Access Journals (Sweden)

Zhen Jia

2008-12-01

Full Text Available This paper surveys the developments of last 10 years in the area of vision based target tracking for autonomous vehicles navigation. First, the motivations and applications of using vision based target tracking for autonomous vehicles navigation are presented in the introduction section. It can be concluded that it is very necessary to develop robust visual target tracking based navigation algorithms for the broad applications of autonomous vehicles. Then this paper reviews the recent techniques in three different categories: vision based target tracking for the applications of land, underwater and aerial vehicles navigation. Next, the increasing trends of using data fusion for visual target tracking based autonomous vehicles navigation are discussed. Through data fusion the tracking performance is improved and becomes more robust. Based on the review, the remaining research challenges are summarized and future research directions are investigated.

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

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.

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.

SU-G-JeP1-05: Clinical Impact of MLC Tracking for Lung SABR

Energy Technology Data Exchange (ETDEWEB)

Caillet, V; Colvill, E [Faculty of Medecine, The University of Sydney, Sydney, NSW (Australia); Royal North Shore Hospital, Sydney, NSW (Australia); Szymura, K; Stevens, M; Booth, J [Royal North Shore Hospital, Sydney, NSW (Australia); Keall, P [Faculty of Medecine, The University of Sydney, Sydney, NSW (Australia)

2016-06-15

Purpose: The objective of this study was to investigate the dosimetric benefits of multi-leaf collimator (MLC) tracking for lung SABR treatments in end-to-end clinically realistic planning and delivery scenarios. Methods: The clinical benefits of MLC tracking were assessed using previously delivered treatment plans and physical experiments. The 10 most recent single lesion lung SABR patients were re-planned following a 4D-GTV-based real-time adaptive protocol (PTV defined as the end-of-exhalation GTV plus 5.0 mm margins). The plans were delivered on a Trilogy Varian linac. Electromagnetic transponders (Calypso, Varian Medical Systems, USA) were embedded into a programmable moving phantom (HexaMotion platform) tracked with the Varian Calypso system. For each physical experiment, the MLC positions were collected and used as input for dose reconstruction. For both planned and physical experiments, the OAR dose metrics from the conventional and real-time adaptive SABR plans (Mean Lung Dose (MLD), V20 for lung, and near-maximum dose (D2%) for spine and heart) were statistically compared. The Wilcoxon test was used to compare plan and physical experiment dose metrics. Results: While maintaining target coverage, percentage reductions in dose metrics to the OARs were observed for both planned and physical experiments. Comparing the two plans showed MLD percentage reduction (MLDr) of 25.4% (absolute differences of 1.41 Gy) and 28.9% (1.29%) for the V20r. D2% percentage reduction for spine and heart were respectively 27.9% (0.3 Gy) and 20.2% (0.3 Gy). For the physical experiments, MLDr was 23.9% (1.3 Gy), and V20r 37.4% (1.6%). D2% reduction for spine and heart were respectively 27.3% (0.3 Gy) and 19.6% (0.3 Gy). For both plans and physical experiments, significant OAR dose differences (p<0.05) were found between the conventional SABR and real-time adaptive plans. Conclusion: Application of MLC tracking for lung SABR patients has the potential to reduce the dose to OARs

Virtual target tracking (VTT) as applied to mobile satellite communication networks

Science.gov (United States)

Amoozegar, Farid

1999-08-01

Traditionally, target tracking has been used for aerospace applications, such as, tracking highly maneuvering targets in a cluttered environment for missile-to-target intercept scenarios. Although the speed and maneuvering capability of current aerospace targets demand more efficient algorithms, many complex techniques have already been proposed in the literature, which primarily cover the defense applications of tracking methods. On the other hand, the rapid growth of Global Communication Systems, Global Information Systems (GIS), and Global Positioning Systems (GPS) is creating new and more diverse challenges for multi-target tracking applications. Mobile communication and computing can very well appreciate a huge market for Cellular Communication and Tracking Devices (CCTD), which will be tracking networked devices at the cellular level. The objective of this paper is to introduce a new concept, i.e., Virtual Target Tracking (VTT) for commercial applications of multi-target tracking algorithms and techniques as applied to mobile satellite communication networks. It would be discussed how Virtual Target Tracking would bring more diversity to target tracking research.

Research on infrared small-target tracking technology under complex background

Science.gov (United States)

Liu, Lei; Wang, Xin; Chen, Jilu; Pan, Tao

2012-10-01

In this paper, some basic principles and the implementing flow charts of a series of algorithms for target tracking are described. On the foundation of above works, a moving target tracking software base on the OpenCV is developed by the software developing platform MFC. Three kinds of tracking algorithms are integrated in this software. These two tracking algorithms are Kalman Filter tracking method and Camshift tracking method. In order to explain the software clearly, the framework and the function are described in this paper. At last, the implementing processes and results are analyzed, and those algorithms for tracking targets are evaluated from the two aspects of subjective and objective. This paper is very significant in the application of the infrared target tracking technology.

Eye tracking a self-moved target with complex hand-target dynamics

Science.gov (United States)

Landelle, Caroline; Montagnini, Anna; Madelain, Laurent

2016-01-01

Previous work has shown that the ability to track with the eye a moving target is substantially improved when the target is self-moved by the subject's hand compared with when being externally moved. Here, we explored a situation in which the mapping between hand movement and target motion was perturbed by simulating an elastic relationship between the hand and target. Our objective was to determine whether the predictive mechanisms driving eye-hand coordination could be updated to accommodate this complex hand-target dynamics. To fully appreciate the behavioral effects of this perturbation, we compared eye tracking performance when self-moving a target with a rigid mapping (simple) and a spring mapping as well as when the subject tracked target trajectories that he/she had previously generated when using the rigid or spring mapping. Concerning the rigid mapping, our results confirmed that smooth pursuit was more accurate when the target was self-moved than externally moved. In contrast, with the spring mapping, eye tracking had initially similar low spatial accuracy (though shorter temporal lag) in the self versus externally moved conditions. However, within ∼5 min of practice, smooth pursuit improved in the self-moved spring condition, up to a level similar to the self-moved rigid condition. Subsequently, when the mapping unexpectedly switched from spring to rigid, the eye initially followed the expected target trajectory and not the real one, thereby suggesting that subjects used an internal representation of the new hand-target dynamics. Overall, these results emphasize the stunning adaptability of smooth pursuit when self-maneuvering objects with complex dynamics. PMID:27466129

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

Moving Target Detection and Active Tracking with a Multicamera Network

Directory of Open Access Journals (Sweden)

Long Zhao

2014-01-01

Full Text Available We propose a systematic framework for Intelligence Video Surveillance System (IVSS with a multicamera network. The proposed framework consists of low-cost static and PTZ cameras, target detection and tracking algorithms, and a low-cost PTZ camera feedback control algorithm based on target information. The target detection and tracking is realized by fixed cameras using a moving target detection and tracking algorithm; the PTZ camera is manoeuvred to actively track the target from the tracking results of the static camera. The experiments are carried out using practical surveillance system data, and the experimental results show that the systematic framework and algorithms presented in this paper are efficient.

Straight-Line Target Tracking for Unmanned Surface Vehicles

Directory of Open Access Journals (Sweden)

Morten Breivik

2008-10-01

Full Text Available This paper considers the subject of straight-line target tracking for unmanned surface vehicles (USVs. Target-tracking represents motion control scenarios where no information about the target behavior is known in advance, i.e., the path that the target traverses is not defined apriori. Specifically, this work presents the design of a motion control system which enables an underactuated USV to track a target that moves in a straight line at high speed. The motion control system employs a guidance principle originally developed for interceptor missiles, as well as a novel velocity controller inspired by maneuverability and agility concepts found in fighter aircraft literature. The performance of the suggested design is illustrated through full-scale USV experiments in the Trondheimsfjord.

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

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

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

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

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.

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

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

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

Real-time tracking of tumor motions and deformations along the leaf travel direction with the aid of a synchronized dynamic MLC leaf sequencer

International Nuclear Information System (INIS)

Tacke, Martin; Nill, Simeon; Oelfke, Uwe

2007-01-01

Advanced radiotherapeutical techniques like intensity-modulated radiation therapy (IMRT) are based on an accurate knowledge of the location of the radiation target. An accurate dose delivery, therefore, requires a method to account for the inter- and intrafractional target motion and the target deformation occurring during the course of treatment. A method to compensate in real time for changes in the position and shape of the target is the use of a dynamic multileaf collimator (MLC) technique which can be devised to automatically arrange the treatment field according to real-time image information. So far, various approaches proposed for leaf sequencers have had to rely on a priori known target motion data and have aimed to optimize the overall treatment time. Since for a real-time dose delivery the target motion is not known a priori, the velocity range of the leading leaves is restricted by a safety margin to c x v max while the following leaves can travel with an additional maximum speed to compensate for the respective target movements. Another aspect to be considered is the tongue and groove effect. A uniform radiation field can only be achieved if the leaf movements are synchronized. The method presented in this note is the first to combine a synchronizing sequencer and real-time tracking with a dynamic MLC. The newly developed algorithm is capable of online optimizing the leaf velocities by minimizing the overall treatment time while at the same time it synchronizes the leaf trajectories in order to avoid the tongue and groove effect. The simultaneous synchronization is performed with the help of an online-calculated mid-time leaf trajectory which is common for all leaf pairs and which takes into account the real-time target motion and deformation information. (note)

Real-time tracking of tumor motions and deformations along the leaf travel direction with the aid of a synchronized dynamic MLC leaf sequencer.

Science.gov (United States)

Tacke, Martin; Nill, Simeon; Oelfke, Uwe

2007-11-21

Advanced radiotherapeutical techniques like intensity-modulated radiation therapy (IMRT) are based on an accurate knowledge of the location of the radiation target. An accurate dose delivery, therefore, requires a method to account for the inter- and intrafractional target motion and the target deformation occurring during the course of treatment. A method to compensate in real time for changes in the position and shape of the target is the use of a dynamic multileaf collimator (MLC) technique which can be devised to automatically arrange the treatment field according to real-time image information. So far, various approaches proposed for leaf sequencers have had to rely on a priori known target motion data and have aimed to optimize the overall treatment time. Since for a real-time dose delivery the target motion is not known a priori, the velocity range of the leading leaves is restricted by a safety margin to c x v(max) while the following leaves can travel with an additional maximum speed to compensate for the respective target movements. Another aspect to be considered is the tongue and groove effect. A uniform radiation field can only be achieved if the leaf movements are synchronized. The method presented in this note is the first to combine a synchronizing sequencer and real-time tracking with a dynamic MLC. The newly developed algorithm is capable of online optimizing the leaf velocities by minimizing the overall treatment time while at the same time it synchronizes the leaf trajectories in order to avoid the tongue and groove effect. The simultaneous synchronization is performed with the help of an online-calculated mid-time leaf trajectory which is common for all leaf pairs and which takes into account the real-time target motion and deformation information.

TH-AB-202-02: Real-Time Verification and Error Detection for MLC Tracking Deliveries Using An Electronic Portal Imaging Device

International Nuclear Information System (INIS)

J Zwan, B; Colvill, E; Booth, J; J O’Connor, D; Keall, P; B Greer, P

2016-01-01

Purpose: The added complexity of the real-time adaptive multi-leaf collimator (MLC) tracking increases the likelihood of undetected MLC delivery errors. In this work we develop and test a system for real-time delivery verification and error detection for MLC tracking radiotherapy using an electronic portal imaging device (EPID). Methods: The delivery verification system relies on acquisition and real-time analysis of transit EPID image frames acquired at 8.41 fps. In-house software was developed to extract the MLC positions from each image frame. Three comparison metrics were used to verify the MLC positions in real-time: (1) field size, (2) field location and, (3) field shape. The delivery verification system was tested for 8 VMAT MLC tracking deliveries (4 prostate and 4 lung) where real patient target motion was reproduced using a Hexamotion motion stage and a Calypso system. Sensitivity and detection delay was quantified for various types of MLC and system errors. Results: For both the prostate and lung test deliveries the MLC-defined field size was measured with an accuracy of 1.25 cm 2 (1 SD). The field location was measured with an accuracy of 0.6 mm and 0.8 mm (1 SD) for lung and prostate respectively. Field location errors (i.e. tracking in wrong direction) with a magnitude of 3 mm were detected within 0.4 s of occurrence in the X direction and 0.8 s in the Y direction. Systematic MLC gap errors were detected as small as 3 mm. The method was not found to be sensitive to random MLC errors and individual MLC calibration errors up to 5 mm. Conclusion: EPID imaging may be used for independent real-time verification of MLC trajectories during MLC tracking deliveries. Thresholds have been determined for error detection and the system has been shown to be sensitive to a range of delivery errors.

Active Multimodal Sensor System for Target Recognition and Tracking.

Science.gov (United States)

Qu, Yufu; Zhang, Guirong; Zou, Zhaofan; Liu, Ziyue; Mao, Jiansen

2017-06-28

High accuracy target recognition and tracking systems using a single sensor or a passive multisensor set are susceptible to external interferences and exhibit environmental dependencies. These difficulties stem mainly from limitations to the available imaging frequency bands, and a general lack of coherent diversity of the available target-related data. This paper proposes an active multimodal sensor system for target recognition and tracking, consisting of a visible, an infrared, and a hyperspectral sensor. The system makes full use of its multisensor information collection abilities; furthermore, it can actively control different sensors to collect additional data, according to the needs of the real-time target recognition and tracking processes. This level of integration between hardware collection control and data processing is experimentally shown to effectively improve the accuracy and robustness of the target recognition and tracking system.

Target tracking system based on preliminary and precise two-stage compound cameras

Science.gov (United States)

Shen, Yiyan; Hu, Ruolan; She, Jun; Luo, Yiming; Zhou, Jie

2018-02-01

Early detection of goals and high-precision of target tracking is two important performance indicators which need to be balanced in actual target search tracking system. This paper proposed a target tracking system with preliminary and precise two - stage compound. This system using a large field of view to achieve the target search. After the target was searched and confirmed, switch into a small field of view for two field of view target tracking. In this system, an appropriate filed switching strategy is the key to achieve tracking. At the same time, two groups PID parameters are add into the system to reduce tracking error. This combination way with preliminary and precise two-stage compound can extend the scope of the target and improve the target tracking accuracy and this method has practical value.

COMPARISON OF THE PERIPHERAL DOSES FROM DIFFERENT IMRT TECHNIQUES FOR PEDIATRIC HEAD AND NECK RADIATION THERAPY.

Science.gov (United States)

Toyota, Masahiko; Saigo, Yasumasa; Higuchi, Kenta; Fujimura, Takuya; Koriyama, Chihaya; Yoshiura, Takashi; Akiba, Suminori

2017-11-01

Intensity-modulated radiation therapy (IMRT) can deliver high and homogeneous doses to the target area while limiting doses to organs at risk. We used a pediatric phantom to simulate the treatment of a head and neck tumor in a child. The peripheral doses were examined for three different IMRT techniques [dynamic multileaf collimator (DMLC), segmental multileaf collimator (SMLC) and volumetric modulated arc therapy (VMAT)]. Peripheral doses were evaluated taking thyroid, breast, ovary and testis as the points of interest. Doses were determined using a radio-photoluminescence glass dosemeter, and the COMPASS system was used for three-dimensional dose evaluation. VMAT achieved the lowest peripheral doses because it had the highest monitor unit efficiency. However, doses in the vicinity of the irradiated field, i.e. the thyroid, could be relatively high, depending on the VMAT collimator angle. DMLC and SMLC had a large area of relatively high peripheral doses in the breast region. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Bayesian target tracking based on particle filter

Institute of Scientific and Technical Information of China (English)

无

2005-01-01

For being able to deal with the nonlinear or non-Gaussian problems, particle filters have been studied by many researchers. Based on particle filter, the extended Kalman filter (EKF) proposal function is applied to Bayesian target tracking. Markov chain Monte Carlo (MCMC) method, the resampling step, etc novel techniques are also introduced into Bayesian target tracking. And the simulation results confirm the improved particle filter with these techniques outperforms the basic one.

Target-type probability combining algorithms for multisensor tracking

Science.gov (United States)

Wigren, Torbjorn

2001-08-01

Algorithms for the handing of target type information in an operational multi-sensor tracking system are presented. The paper discusses recursive target type estimation, computation of crosses from passive data (strobe track triangulation), as well as the computation of the quality of the crosses for deghosting purposes. The focus is on Bayesian algorithms that operate in the discrete target type probability space, and on the approximations introduced for computational complexity reduction. The centralized algorithms are able to fuse discrete data from a variety of sensors and information sources, including IFF equipment, ESM's, IRST's as well as flight envelopes estimated from track data. All algorithms are asynchronous and can be tuned to handle clutter, erroneous associations as well as missed and erroneous detections. A key to obtain this ability is the inclusion of data forgetting by a procedure for propagation of target type probability states between measurement time instances. Other important properties of the algorithms are their abilities to handle ambiguous data and scenarios. The above aspects are illustrated in a simulations study. The simulation setup includes 46 air targets of 6 different types that are tracked by 5 airborne sensor platforms using ESM's and IRST's as data sources.

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.

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

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

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

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

Adaptive block online learning target tracking based on super pixel segmentation

Science.gov (United States)

Cheng, Yue; Li, Jianzeng

2018-04-01

Video target tracking technology under the unremitting exploration of predecessors has made big progress, but there are still lots of problems not solved. This paper proposed a new algorithm of target tracking based on image segmentation technology. Firstly we divide the selected region using simple linear iterative clustering (SLIC) algorithm, after that, we block the area with the improved density-based spatial clustering of applications with noise (DBSCAN) clustering algorithm. Each sub-block independently trained classifier and tracked, then the algorithm ignore the failed tracking sub-block while reintegrate the rest of the sub-blocks into tracking box to complete the target tracking. The experimental results show that our algorithm can work effectively under occlusion interference, rotation change, scale change and many other problems in target tracking compared with the current mainstream algorithms.

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...

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

A dynamic collimation system for penumbra reduction in spot-scanning proton therapy: Proof of concept

Energy Technology Data Exchange (ETDEWEB)

Hyer, Daniel E., E-mail: daniel-hyer@uiowa.edu; Hill, Patrick M.; Wang, Dongxu; Smith, Blake R.; Flynn, Ryan T. [Department of Radiation Oncology, University of Iowa, 200 Hawkins Drive, Iowa City, Iowa 52242 (United States)

2014-09-15

Purpose: In the absence of a collimation system the lateral penumbra of spot scanning (SS) dose distributions delivered by low energy proton beams is highly dependent on the spot size. For current commercial equipment, spot size increases with decreasing proton energy thereby reducing the benefit of the SS technique. This paper presents a dynamic collimation system (DCS) for sharpening the lateral penumbra of proton therapy dose distributions delivered by SS. Methods: The collimation system presented here exploits the property that a proton pencil beam used for SS requires collimation only when it is near the target edge, enabling the use of trimmers that are in motion at times when the pencil beam is away from the target edge. The device consists of two pairs of parallel nickel trimmer blades of 2 cm thickness and dimensions of 2 cm × 18 cm in the beam's eye view. The two pairs of trimmer blades are rotated 90° relative to each other to form a rectangular shape. Each trimmer blade is capable of rapid motion in the direction perpendicular to the central beam axis by means of a linear motor, with maximum velocity and acceleration of 2.5 m/s and 19.6 m/s{sup 2}, respectively. The blades travel on curved tracks to match the divergence of the proton source. An algorithm for selecting blade positions is developed to minimize the dose delivered outside of the target, and treatment plans are created both with and without the DCS. Results: The snout of the DCS has outer dimensions of 22.6 × 22.6 cm{sup 2} and is capable of delivering a minimum treatment field size of 15 × 15 cm{sup 2}. Using currently available components, the constructed system would weigh less than 20 kg. For irregularly shaped fields, the use of the DCS reduces the mean dose outside of a 2D target of 46.6 cm{sup 2} by approximately 40% as compared to an identical plan without collimation. The use of the DCS increased treatment time by 1–3 s per energy layer. Conclusions: The spread of

A dynamic collimation system for penumbra reduction in spot-scanning proton therapy: Proof of concept

International Nuclear Information System (INIS)

Hyer, Daniel E.; Hill, Patrick M.; Wang, Dongxu; Smith, Blake R.; Flynn, Ryan T.

2014-01-01

Purpose: In the absence of a collimation system the lateral penumbra of spot scanning (SS) dose distributions delivered by low energy proton beams is highly dependent on the spot size. For current commercial equipment, spot size increases with decreasing proton energy thereby reducing the benefit of the SS technique. This paper presents a dynamic collimation system (DCS) for sharpening the lateral penumbra of proton therapy dose distributions delivered by SS. Methods: The collimation system presented here exploits the property that a proton pencil beam used for SS requires collimation only when it is near the target edge, enabling the use of trimmers that are in motion at times when the pencil beam is away from the target edge. The device consists of two pairs of parallel nickel trimmer blades of 2 cm thickness and dimensions of 2 cm × 18 cm in the beam's eye view. The two pairs of trimmer blades are rotated 90° relative to each other to form a rectangular shape. Each trimmer blade is capable of rapid motion in the direction perpendicular to the central beam axis by means of a linear motor, with maximum velocity and acceleration of 2.5 m/s and 19.6 m/s 2 , respectively. The blades travel on curved tracks to match the divergence of the proton source. An algorithm for selecting blade positions is developed to minimize the dose delivered outside of the target, and treatment plans are created both with and without the DCS. Results: The snout of the DCS has outer dimensions of 22.6 × 22.6 cm 2 and is capable of delivering a minimum treatment field size of 15 × 15 cm 2 . Using currently available components, the constructed system would weigh less than 20 kg. For irregularly shaped fields, the use of the DCS reduces the mean dose outside of a 2D target of 46.6 cm 2 by approximately 40% as compared to an identical plan without collimation. The use of the DCS increased treatment time by 1–3 s per energy layer. Conclusions: The spread of the lateral

Collaborative In-Network Processing for Target Tracking

Directory of Open Access Journals (Sweden)

Juan Liu

2003-03-01

Full Text Available This paper presents a class of signal processing techniques for collaborative signal processing in ad hoc sensor networks, focusing on a vehicle tracking application. In particular, we study two types of commonly used sensors—acoustic-amplitude sensors for target distance estimation and direction-of-arrival sensors for bearing estimation—and investigate how networks of such sensors can collaborate to extract useful information with minimal resource usage. The information-driven sensor collaboration has several advantages: tracking is distributed, and the network is energy-efficient, activated only on a when-needed basis. We demonstrate the effectiveness of the approach to target tracking using both simulation and field data.

Approach the National Quality Audit System for Radiotherapy in Latvia

OpenAIRE

Dehtjars, J; Popovs, S; Plaude, S

2008-01-01

It is very important to make National Quality Audit to ensure accurate conformal RT delivery. It is necessary to develop an Audit system to inspect all Conformal RT and IMRT delivery chain including the Quality checks of linear accelerator, Multileaf Collimator (MLC), Computer Tomography (CT) scanner or simulator, target and tissue delineation, plan evaluation, and delivery.

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.

Fusion-based multi-target tracking and localization for intelligent surveillance systems

Science.gov (United States)

Rababaah, Haroun; Shirkhodaie, Amir

2008-04-01

In this paper, we have presented two approaches addressing visual target tracking and localization in complex urban environment. The two techniques presented in this paper are: fusion-based multi-target visual tracking, and multi-target localization via camera calibration. For multi-target tracking, the data fusion concepts of hypothesis generation/evaluation/selection, target-to-target registration, and association are employed. An association matrix is implemented using RGB histograms for associated tracking of multi-targets of interests. Motion segmentation of targets of interest (TOI) from the background was achieved by a Gaussian Mixture Model. Foreground segmentation, on other hand, was achieved by the Connected Components Analysis (CCA) technique. The tracking of individual targets was estimated by fusing two sources of information, the centroid with the spatial gating, and the RGB histogram association matrix. The localization problem is addressed through an effective camera calibration technique using edge modeling for grid mapping (EMGM). A two-stage image pixel to world coordinates mapping technique is introduced that performs coarse and fine location estimation of moving TOIs. In coarse estimation, an approximate neighborhood of the target position is estimated based on nearest 4-neighbor method, and in fine estimation, we use Euclidean interpolation to localize the position within the estimated four neighbors. Both techniques were tested and shown reliable results for tracking and localization of Targets of interests in complex urban environment.

Robust Target Tracking with Multi-Static Sensors under Insufficient TDOA Information.

Science.gov (United States)

Shin, Hyunhak; Ku, Bonhwa; Nelson, Jill K; Ko, Hanseok

2018-05-08

This paper focuses on underwater target tracking based on a multi-static sonar network composed of passive sonobuoys and an active ping. In the multi-static sonar network, the location of the target can be estimated using TDOA (Time Difference of Arrival) measurements. However, since the sensor network may obtain insufficient and inaccurate TDOA measurements due to ambient noise and other harsh underwater conditions, target tracking performance can be significantly degraded. We propose a robust target tracking algorithm designed to operate in such a scenario. First, track management with track splitting is applied to reduce performance degradation caused by insufficient measurements. Second, a target location is estimated by a fusion of multiple TDOA measurements using a Gaussian Mixture Model (GMM). In addition, the target trajectory is refined by conducting a stack-based data association method based on multiple-frames measurements in order to more accurately estimate target trajectory. The effectiveness of the proposed method is verified through simulations.

A lightweight target-tracking scheme using wireless sensor network

International Nuclear Information System (INIS)

Kuang, Xing-hong; Shao, Hui-he; Feng, Rui

2008-01-01

This paper describes a lightweight target-tracking scheme using wireless sensor network, where randomly distributed sensor nodes take responsibility for tracking the moving target based on the acoustic sensing signal. At every localization interval, a backoff timer algorithm is performed to elect the leader node and determine the transmission order of the localization nodes. An adaptive active region size algorithm based on the node density is proposed to select the optimal nodes taking part in localization. An improved particle filter algorithm performed by the leader node estimates the target state based on the selected nodes' acoustic energy measurements. Some refinements such as optimal linear combination algorithm, residual resampling algorithm, Markov chain Monte Carlo method are introduced in the scheme to improve the tracking performance. Simulation results validate the efficiency of the proposed tracking scheme

Double lens collimator solar feedback sensor and master slave configuration: Development of compact and low cost two axis solar tracking system for CPV applications

KAUST Repository

Burhan, Muhammad

2016-08-31

The conventional CPV systems, as big unit design, are only suitable to be installed in the open regions, like desert areas. This gigantic system design restricts their use on the rooftop of commercial and residential buildings, unlike the conventional PV systems. This paper proposes a compact but highly accurate and cheap two axis solar tracking system, designed for CPV system field operation. The proposed system is designed and verified for tracking accuracy requirement of 0.3 degrees, and has maximum capability of as high as 0.1 degrees tracking accuracy. High tracking accuracy is ensured using in-house built double lens collimator solar feedback sensor, within a fraction of the cost of commercial solar tracking sensors. A hybrid tracking algorithm is developed in C-programming using astronomical and optical solar tracking methods. As compact CPV system design demands larger number of tracking units, for same power capacity of system. Therefore, a master slave control configuration is also proposed for the CPV field operation. Only master tracker will be equipped with the expensive tracking devices, while the required tracking information will be sent to all of the slave trackers using wireless communication through ZigBee devices. With detailed optical design, simulation and control strategy, a prototype of the proposed CPV tracking system is developed, experimentally investigated and verified for tracking accuracy for outdoor operation at the rooftop. (C) 2016 Elsevier Ltd. All rights reserved.

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

Beam collimation and transport of quasineutral laser-accelerated protons by a solenoid field

International Nuclear Information System (INIS)

Harres, K.; Alber, I.; Guenther, M.; Nuernberg, F.; Otten, A.; Schuetrumpf, J.; Roth, M.; Tauschwitz, A.; Bagnoud, V.; Daido, H.; Tampo, M.; Schollmeier, M.

2010-01-01

This article reports about controlling laser-accelerated proton beams with respect to beam divergence and energy. The particles are captured by a pulsed high field solenoid with a magnetic field strength of 8.6 T directly behind a flat target foil that is irradiated by a high intensity laser pulse. Proton beams with energies around 2.3 MeV and particle numbers of 10 12 could be collimated and transported over a distance of more than 300 mm. In contrast to the protons the comoving electrons are strongly deflected by the solenoid field. They propagate at a submillimeter gyroradius around the solenoid's axis which could be experimentally verified. The originated high flux electron beam produces a high space charge resulting in a stronger focusing of the proton beam than expected by tracking results. Leadoff particle-in-cell simulations show qualitatively that this effect is caused by space charge attraction due to the comoving electrons. The collimation and transport of laser-accelerated protons is the first step to provide these unique beams for further applications such as postacceleration by conventional accelerator structures.

Volume of interest CBCT and tube current modulation for image guidance using dynamic kV collimation

Energy Technology Data Exchange (ETDEWEB)

Parsons, David, E-mail: david.parsons@dal.ca, E-mail: james.robar@nshealth.ca [Department of Physics and Atmospheric Science, Dalhousie University, 5820 University Avenue, Halifax, Nova Scotia B3H 1V7 (Canada); Robar, James L., E-mail: david.parsons@dal.ca, E-mail: james.robar@nshealth.ca [Department of Radiation Oncology and Department of Physics and Atmospheric Science, Dalhousie University, 5820 University Avenue, Halifax, Nova Scotia B3H 1V7 (Canada)

2016-04-15

Purpose: The focus of this work is the development of a novel blade collimation system enabling volume of interest (VOI) CBCT with tube current modulation using the kV image guidance source on a linear accelerator. Advantages of the system are assessed, particularly with regard to reduction and localization of dose and improvement of image quality. Methods: A four blade dynamic kV collimator was developed to track a VOI during a CBCT acquisition. The current prototype is capable of tracking an arbitrary volume defined by the treatment planner for subsequent CBCT guidance. During gantry rotation, the collimator tracks the VOI with adjustment of position and dimension. CBCT image quality was investigated as a function of collimator dimension, while maintaining the same dose to the VOI, for a 22.2 cm diameter cylindrical water phantom with a 9 mm diameter bone insert centered on isocenter. Dose distributions were modeled using a dynamic BEAMnrc library and DOSXYZnrc. The resulting VOI dose distributions were compared to full-field CBCT distributions to quantify dose reduction and localization to the target volume. A novel method of optimizing x-ray tube current during CBCT acquisition was developed and assessed with regard to contrast-to-noise ratio (CNR) and imaging dose. Results: Measurements show that the VOI CBCT method using the dynamic blade system yields an increase in contrast-to-noise ratio by a factor of approximately 2.2. Depending upon the anatomical site, dose was reduced to 15%–80% of the full-field CBCT value along the central axis plane and down to less than 1% out of plane. The use of tube current modulation allowed for specification of a desired SNR within projection data. For approximately the same dose to the VOI, CNR was further increased by a factor of 1.2 for modulated VOI CBCT, giving a combined improvement of 2.6 compared to full-field CBCT. Conclusions: The present dynamic blade system provides significant improvements in CNR for the same

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.

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.

INSPTRAX - The Inspection Targeting, Planning and Tracking Database

Data.gov (United States)

U.S. Environmental Protection Agency — The INSPTRAX System tracks Air, RCRA, and Water inspection targeting, planning and tracking information. It is used by the the Air, RCRA, and Water programs to input...

Studies on heavy ion losses from collimation cleaning at the LHC

CERN Document Server

Hermes, P D; Jowett, J M; Redaelli, S; Salvachua, B M; Valentino, G; Wollmann, D

2015-01-01

The LHC collimation system protects superconducting magnets from beam losses. By design, it was optimized for the high-intensity proton challenges but so far provided adequate protection also during the LHC heavy-ion runs with 208Pb82+ ions up to a beam energy of 4 Z TeV. Ion beam cleaning brings specific challenges due to different physical interactions with the collimator materials and might require further improvements for operation at 7 Z TeV. In this article, we study heavy-ion beam losses leaking out of the LHC collimation system, both in measurement and simulations. The simulations are carried out using both ICOSIM, with a simplified ion physics model implemented, and SixTrack, including more detailed starting conditions from FLUKA but without including online scattering in subsequent collimator hits. The results agree well with measurements overall, although some discrepancies are present. The reasons for the discrepancies are investigated and, on this basis, the requirements for an improved simulatio...

Data fusion for target tracking and classification with wireless sensor network

Science.gov (United States)

Pannetier, Benjamin; Doumerc, Robin; Moras, Julien; Dezert, Jean; Canevet, Loic

2016-10-01

In this paper, we address the problem of multiple ground target tracking and classification with information obtained from a unattended wireless sensor network. A multiple target tracking (MTT) algorithm, taking into account road and vegetation information, is proposed based on a centralized architecture. One of the key issue is how to adapt classical MTT approach to satisfy embedded processing. Based on track statistics, the classification algorithm uses estimated location, velocity and acceleration to help to classify targets. The algorithms enables tracking human and vehicles driving both on and off road. We integrate road or trail width and vegetation cover, as constraints in target motion models to improve performance of tracking under constraint with classification fusion. Our algorithm also presents different dynamic models, to palliate the maneuvers of targets. The tracking and classification algorithms are integrated into an operational platform (the fusion node). In order to handle realistic ground target tracking scenarios, we use an autonomous smart computer deposited in the surveillance area. After the calibration step of the heterogeneous sensor network, our system is able to handle real data from a wireless ground sensor network. The performance of system is evaluated in a real exercise for intelligence operation ("hunter hunt" scenario).

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.)

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.

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

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

Fast IMRT with narrow high energy scanned photon beams

Energy Technology Data Exchange (ETDEWEB)

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

2011-08-15

Purpose: Since the first publications on intensity modulated radiation therapy (IMRT) in the early 1980s almost all efforts have been focused on fairly time consuming dynamic or segmental multileaf collimation. With narrow fast scanned photon beams, the flexibility and accuracy in beam shaping increases, not least in combination with fast penumbra trimming multileaf collimators. Previously, experiments have been performed with full range targets, generating a broad bremsstrahlung beam, in combination with multileaf collimators or material compensators. In the present publication, the first measurements with fast narrow high energy (50 MV) scanned photon beams are presented indicating an interesting performance increase even though some of the hardware used were suboptimal. Methods: Inverse therapy planning was used to calculate optimal scanning patterns to generate dose distributions with interesting properties for fast IMRT. To fully utilize the dose distributional advantages with scanned beams, it is necessary to use narrow high energy beams from a thin bremsstrahlung target and a powerful purging magnet capable of deflecting the transmitted electron beam away from the generated photons onto a dedicated electron collector. During the present measurements the scanning system, purging magnet, and electron collimator in the treatment head of the MM50 racetrack accelerator was used with 3-6 mm thick bremsstrahlung targets of beryllium. The dose distributions were measured with diodes in water and with EDR2 film in PMMA. Monte Carlo simulations with geant4 were used to study the influence of the electrons transmitted through the target on the photon pencil beam kernel. Results: The full width at half-maximum (FWHM) of the scanned photon beam was 34 mm measured at isocenter, below 9.5 cm of water, 1 m from the 3 mm Be bremsstrahlung target. To generate a homogeneous dose distribution in a 10 x 10 cm{sup 2} field, the authors used a spot matrix of 100 equal intensity

Research on target tracking in coal mine based on optical flow method

Science.gov (United States)

Xue, Hongye; Xiao, Qingwei

2015-03-01

To recognize, track and count the bolting machine in coal mine video images, a real-time target tracking method based on the Lucas-Kanade sparse optical flow is proposed in this paper. In the method, we judge whether the moving target deviate from its trajectory, predicate and correct the position of the moving target. The method solves the problem of failure to track the target or lose the target because of the weak light, uneven illumination and blocking. Using the VC++ platform and Opencv lib we complete the recognition and tracking. The validity of the method is verified by the result of the experiment.

Group Targets Tracking Using Multiple Models GGIW-CPHD Based on Best-Fitting Gaussian Approximation and Strong Tracking Filter

Directory of Open Access Journals (Sweden)

Yun Wang

2016-01-01

Full Text Available Gamma Gaussian inverse Wishart cardinalized probability hypothesis density (GGIW-CPHD algorithm was always used to track group targets in the presence of cluttered measurements and missing detections. A multiple models GGIW-CPHD algorithm based on best-fitting Gaussian approximation method (BFG and strong tracking filter (STF is proposed aiming at the defect that the tracking error of GGIW-CPHD algorithm will increase when the group targets are maneuvering. The best-fitting Gaussian approximation method is proposed to implement the fusion of multiple models using the strong tracking filter to correct the predicted covariance matrix of the GGIW component. The corresponding likelihood functions are deduced to update the probability of multiple tracking models. From the simulation results we can see that the proposed tracking algorithm MM-GGIW-CPHD can effectively deal with the combination/spawning of groups and the tracking error of group targets in the maneuvering stage is decreased.

Moving target tracking through distributed clustering in directional sensor networks.

Science.gov (United States)

Enayet, Asma; Razzaque, Md Abdur; Hassan, Mohammad Mehedi; Almogren, Ahmad; Alamri, Atif

2014-12-18

The problem of moving target tracking in directional sensor networks (DSNs) introduces new research challenges, including optimal selection of sensing and communication sectors of the directional sensor nodes, determination of the precise location of the target and an energy-efficient data collection mechanism. Existing solutions allow individual sensor nodes to detect the target's location through collaboration among neighboring nodes, where most of the sensors are activated and communicate with the sink. Therefore, they incur much overhead, loss of energy and reduced target tracking accuracy. In this paper, we have proposed a clustering algorithm, where distributed cluster heads coordinate their member nodes in optimizing the active sensing and communication directions of the nodes, precisely determining the target location by aggregating reported sensing data from multiple nodes and transferring the resultant location information to the sink. Thus, the proposed target tracking mechanism minimizes the sensing redundancy and maximizes the number of sleeping nodes in the network. We have also investigated the dynamic approach of activating sleeping nodes on-demand so that the moving target tracking accuracy can be enhanced while maximizing the network lifetime. We have carried out our extensive simulations in ns-3, and the results show that the proposed mechanism achieves higher performance compared to the state-of-the-art works.

Through-Wall Multiple Targets Vital Signs Tracking Based on VMD Algorithm

Directory of Open Access Journals (Sweden)

Jiaming Yan

2016-08-01

Full Text Available Targets located at the same distance are easily neglected in most through-wall multiple targets detecting applications which use the single-input single-output (SISO ultra-wideband (UWB radar system. In this paper, a novel multiple targets vital signs tracking algorithm for through-wall detection using SISO UWB radar has been proposed. Taking advantage of the high-resolution decomposition of the Variational Mode Decomposition (VMD based algorithm, the respiration signals of different targets can be decomposed into different sub-signals, and then, we can track the time-varying respiration signals accurately when human targets located in the same distance. Intensive evaluation has been conducted to show the effectiveness of our scheme with a 0.15 m thick concrete brick wall. Constant, piecewise-constant and time-varying vital signs could be separated and tracked successfully with the proposed VMD based algorithm for two targets, even up to three targets. For the multiple targets’ vital signs tracking issues like urban search and rescue missions, our algorithm has superior capability in most detection applications.

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

A game theory approach to target tracking in sensor networks.

Science.gov (United States)

Gu, Dongbing

2011-02-01

In this paper, we investigate a moving-target tracking problem with sensor networks. Each sensor node has a sensor to observe the target and a processor to estimate the target position. It also has wireless communication capability but with limited range and can only communicate with neighbors. The moving target is assumed to be an intelligent agent, which is "smart" enough to escape from the detection by maximizing the estimation error. This adversary behavior makes the target tracking problem more difficult. We formulate this target estimation problem as a zero-sum game in this paper and use a minimax filter to estimate the target position. The minimax filter is a robust filter that minimizes the estimation error by considering the worst case noise. Furthermore, we develop a distributed version of the minimax filter for multiple sensor nodes. The distributed computation is implemented via modeling the information received from neighbors as measurements in the minimax filter. The simulation results show that the target tracking algorithm proposed in this paper provides a satisfactory result.

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)

The Bering Target Tracking Instrumentation

DEFF Research Database (Denmark)

Denver, Troelz; Jørgensen, John Leif; Betto, Maurizio

2003-01-01

The key science instrument on the Bering satellite mission is a relative small telescope with an entrance aperture of 300 mm and a focal length between 500 and 1000 mm. The detection of potential targets is performed by one of the target scanning advanced stellar compasses (ASCs). This procedure...... results in a simple prioritized list of right ascension, declination, proper motion and intensity of each prospective target. The telescope itself has a dedicated ASC Camera Head Unit (CHU) mounted on the secondary mirror, largely co-aligned with the telescope. This CHU accurately determines the telescope......'s pointing direction. To achieve fast tracking over a large solid angle, the telescope pointing is achieved by means of a folding mirror in the optical pathway. When a prospective target approaches the telescope FOV, the ASC on the secondary will guide the folding mirror into position such that the target...

A Novel Loss Recovery and Tracking Scheme for Maneuvering Target in Hybrid WSNs.

Science.gov (United States)

Qian, Hanwang; Fu, Pengcheng; Li, Baoqing; Liu, Jianpo; Yuan, Xiaobing

2018-01-25

Tracking a mobile target, which aims to timely monitor the invasion of specific target, is one of the most prominent applications in wireless sensor networks (WSNs). Traditional tracking methods in WSNs only based on static sensor nodes (SNs) have several critical problems. For example, to void the loss of mobile target, many SNs must be active to track the target in all possible directions, resulting in excessive energy consumption. Additionally, when entering coverage holes in the monitoring area, the mobile target may be missing and then its state is unknown during this period. To tackle these problems, in this paper, a few mobile sensor nodes (MNs) are introduced to cooperate with SNs to form a hybrid WSN due to their stronger abilities and less constrained energy. Then, we propose a valid target tracking scheme for hybrid WSNs to dynamically schedule the MNs and SNs. Moreover, a novel loss recovery mechanism is proposed to find the lost target and recover the tracking with fewer SNs awakened. Furthermore, to improve the robustness and accuracy of the recovery mechanism, an adaptive unscented Kalman filter (AUKF) algorithm is raised to dynamically adjust the process noise covariance. Simulation results demonstrate that our tracking scheme for maneuvering target in hybrid WSNs can not only track the target effectively even if the target is lost but also maintain an excellent accuracy and robustness with fewer activated nodes.

Improving Global Multi-target Tracking with Local Updates

DEFF Research Database (Denmark)

Milan, Anton; Gade, Rikke; Dick, Anthony

2014-01-01

-target tracker, if they result in a reduction in the global cost function. Since tracking failures typically arise when targets become occluded, we propose a local data association scheme to maintain the target identities in these situations. We demonstrate a reduction of up to 50% in the global cost function...

Moving Target Tracking through Distributed Clustering in Directional Sensor Networks

Directory of Open Access Journals (Sweden)

Asma Enayet

2014-12-01

Full Text Available The problem of moving target tracking in directional sensor networks (DSNs introduces new research challenges, including optimal selection of sensing and communication sectors of the directional sensor nodes, determination of the precise location of the target and an energy-efficient data collection mechanism. Existing solutions allow individual sensor nodes to detect the target’s location through collaboration among neighboring nodes, where most of the sensors are activated and communicate with the sink. Therefore, they incur much overhead, loss of energy and reduced target tracking accuracy. In this paper, we have proposed a clustering algorithm, where distributed cluster heads coordinate their member nodes in optimizing the active sensing and communication directions of the nodes, precisely determining the target location by aggregating reported sensing data from multiple nodes and transferring the resultant location information to the sink. Thus, the proposed target tracking mechanism minimizes the sensing redundancy and maximizes the number of sleeping nodes in the network. We have also investigated the dynamic approach of activating sleeping nodes on-demand so that the moving target tracking accuracy can be enhanced while maximizing the network lifetime. We have carried out our extensive simulations in ns-3, and the results show that the proposed mechanism achieves higher performance compared to the state-of-the-art works.

Real-time Non-linear Target Tracking Control of Wheeled Mobile Robots

Institute of Scientific and Technical Information of China (English)

YU Wenyong

2006-01-01

A control strategy for real-time target tracking for wheeled mobile robots is presented. Using a modified Kalman filter for environment perception, a novel tracking control law derived from Lyapunov stability theory is introduced. Tuning of linear velocity and angular velocity with mechanical constraints is applied. The proposed control system can simultaneously solve the target trajectory prediction, real-time tracking, and posture regulation problems of a wheeled mobile robot. Experimental results illustrate the effectiveness of the proposed tracking control laws.

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

PMHT Approach for Multi-Target Multi-Sensor Sonar Tracking in Clutter.

Science.gov (United States)

Li, Xiaohua; Li, Yaan; Yu, Jing; Chen, Xiao; Dai, Miao

2015-11-06

Multi-sensor sonar tracking has many advantages, such as the potential to reduce the overall measurement uncertainty and the possibility to hide the receiver. However, the use of multi-target multi-sensor sonar tracking is challenging because of the complexity of the underwater environment, especially the low target detection probability and extremely large number of false alarms caused by reverberation. In this work, to solve the problem of multi-target multi-sensor sonar tracking in the presence of clutter, a novel probabilistic multi-hypothesis tracker (PMHT) approach based on the extended Kalman filter (EKF) and unscented Kalman filter (UKF) is proposed. The PMHT can efficiently handle the unknown measurements-to-targets and measurements-to-transmitters data association ambiguity. The EKF and UKF are used to deal with the high degree of nonlinearity in the measurement model. The simulation results show that the proposed algorithm can improve the target tracking performance in a cluttered environment greatly, and its computational load is low.

SU-G-IeP4-04: DD-Neutron Source Collimation for Neutron Stimulated Emission Computed Tomography: A Monte Carlo Simulation Study

Energy Technology Data Exchange (ETDEWEB)

Fong, G; Kapadia, A [Carl E Ravin Advanced Imaging Laboratories, Durham, North Carolina (United States)

2016-06-15

Purpose: To optimize collimation and shielding for a deuterium-deuterium (DD) neutron generator for an inexpensive and compact clinical neutron imaging system. The envisioned application is cancer diagnosis through Neutron Stimulated Emission Computed Tomography (NSECT). Methods: Collimator designs were tested with an isotropic 2.5 MeV neutron source through GEANT4 simulations. The collimator is a 52×52×52 cm{sup 3} polyethylene block coupled with a 1 cm lead sheet in sequence. Composite opening was modeled into the collimator to permit passage of neutrons. The opening varied in shape (cylindrical vs. tapered), size (1–5 cm source-side and target-side openings) and aperture placements (13–39 cm from source-side). Spatial and energy distribution of neutrons and gammas were tracked from each collimator design. Parameters analyzed were primary beam width (FWHM), divergence, and efficiency (percent transmission) for different configurations of the collimator. Select resultant outputs were then used for simulated NSECT imaging of a virtual breast phantom containing a 2.5 cm diameter tumor to assess the effect of the collimator on spatial resolution, noise, and scan time. Finally, composite shielding enclosure made of polyethylene and lead was designed and evaluated to block 99.99% of neutron and gamma radiation generated in the system. Results: Analysis of primary beam indicated the beam-width is linear to the aperture size. Increasing source-side opening allowed at least 20% more neutron throughput for all designs relative to the cylindrical openings. Maximum throughput for all designs was 364% relative to cylindrical openings. Conclusion: The work indicates potential for collimating and shielding a DD neutron generator for use in a clinical NSECT system. The proposed collimator designs produced a well-defined collimated neutron beam that can be used to image samples of interest with millimeter resolution. Balance in output efficiency, noise reduction, and scan

SU-G-IeP4-04: DD-Neutron Source Collimation for Neutron Stimulated Emission Computed Tomography: A Monte Carlo Simulation Study

International Nuclear Information System (INIS)

Fong, G; Kapadia, A

2016-01-01

Purpose: To optimize collimation and shielding for a deuterium-deuterium (DD) neutron generator for an inexpensive and compact clinical neutron imaging system. The envisioned application is cancer diagnosis through Neutron Stimulated Emission Computed Tomography (NSECT). Methods: Collimator designs were tested with an isotropic 2.5 MeV neutron source through GEANT4 simulations. The collimator is a 52×52×52 cm"3 polyethylene block coupled with a 1 cm lead sheet in sequence. Composite opening was modeled into the collimator to permit passage of neutrons. The opening varied in shape (cylindrical vs. tapered), size (1–5 cm source-side and target-side openings) and aperture placements (13–39 cm from source-side). Spatial and energy distribution of neutrons and gammas were tracked from each collimator design. Parameters analyzed were primary beam width (FWHM), divergence, and efficiency (percent transmission) for different configurations of the collimator. Select resultant outputs were then used for simulated NSECT imaging of a virtual breast phantom containing a 2.5 cm diameter tumor to assess the effect of the collimator on spatial resolution, noise, and scan time. Finally, composite shielding enclosure made of polyethylene and lead was designed and evaluated to block 99.99% of neutron and gamma radiation generated in the system. Results: Analysis of primary beam indicated the beam-width is linear to the aperture size. Increasing source-side opening allowed at least 20% more neutron throughput for all designs relative to the cylindrical openings. Maximum throughput for all designs was 364% relative to cylindrical openings. Conclusion: The work indicates potential for collimating and shielding a DD neutron generator for use in a clinical NSECT system. The proposed collimator designs produced a well-defined collimated neutron beam that can be used to image samples of interest with millimeter resolution. Balance in output efficiency, noise reduction, and scan time

First evaluation of the feasibility of MLC tracking using ultrasound motion estimation

Energy Technology Data Exchange (ETDEWEB)

Fast, Martin F., E-mail: martin.fast@icr.ac.uk; O’Shea, Tuathan P., E-mail: tuathan.oshea@nhs.net; Nill, Simeon; Oelfke, Uwe; Harris, Emma J. [Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London SM2 5NG (United Kingdom)

2016-08-15

Purpose: To quantify the performance of the Clarity ultrasound (US) imaging system (Elekta AB, Stockholm, Sweden) for real-time dynamic multileaf collimator (MLC) tracking. Methods: The Clarity calibration and quality assurance phantom was mounted on a motion platform moving with a periodic sine wave trajectory. The detected position of a 30 mm hypoechogenic sphere within the phantom was continuously reported via Clarity’s real-time streaming interface to an in-house tracking and delivery software and subsequently used to adapt the MLC aperture. A portal imager measured MV treatment field/MLC apertures and motion platform positions throughout each experiment to independently quantify system latency and geometric error. Based on the measured range of latency values, a prostate stereotactic body radiation therapy (SBRT) delivery was performed with three realistic motion trajectories. The dosimetric impact of system latency on MLC tracking was directly measured using a 3D dosimeter mounted on the motion platform. Results: For 2D US imaging, the overall system latency, including all delay times from the imaging and delivery chain, ranged from 392 to 424 ms depending on the lateral sector size. For 3D US imaging, the latency ranged from 566 to 1031 ms depending on the elevational sweep. The latency-corrected geometric root-mean squared error was below 0.75 mm (2D US) and below 1.75 mm (3D US). For the prostate SBRT delivery, the impact of a range of system latencies (400–1000 ms) on the MLC tracking performance was minimal in terms of gamma failure rate. Conclusions: Real-time MLC tracking based on a noninvasive US input is technologically feasible. Current system latencies are higher than those for x-ray imaging systems, but US can provide full volumetric image data and the impact of system latency was measured to be small for a prostate SBRT case when using a US-like motion input.

First evaluation of the feasibility of MLC tracking using ultrasound motion estimation

International Nuclear Information System (INIS)

Fast, Martin F.; O’Shea, Tuathan P.; Nill, Simeon; Oelfke, Uwe; Harris, Emma J.

2016-01-01

Purpose: To quantify the performance of the Clarity ultrasound (US) imaging system (Elekta AB, Stockholm, Sweden) for real-time dynamic multileaf collimator (MLC) tracking. Methods: The Clarity calibration and quality assurance phantom was mounted on a motion platform moving with a periodic sine wave trajectory. The detected position of a 30 mm hypoechogenic sphere within the phantom was continuously reported via Clarity’s real-time streaming interface to an in-house tracking and delivery software and subsequently used to adapt the MLC aperture. A portal imager measured MV treatment field/MLC apertures and motion platform positions throughout each experiment to independently quantify system latency and geometric error. Based on the measured range of latency values, a prostate stereotactic body radiation therapy (SBRT) delivery was performed with three realistic motion trajectories. The dosimetric impact of system latency on MLC tracking was directly measured using a 3D dosimeter mounted on the motion platform. Results: For 2D US imaging, the overall system latency, including all delay times from the imaging and delivery chain, ranged from 392 to 424 ms depending on the lateral sector size. For 3D US imaging, the latency ranged from 566 to 1031 ms depending on the elevational sweep. The latency-corrected geometric root-mean squared error was below 0.75 mm (2D US) and below 1.75 mm (3D US). For the prostate SBRT delivery, the impact of a range of system latencies (400–1000 ms) on the MLC tracking performance was minimal in terms of gamma failure rate. Conclusions: Real-time MLC tracking based on a noninvasive US input is technologically feasible. Current system latencies are higher than those for x-ray imaging systems, but US can provide full volumetric image data and the impact of system latency was measured to be small for a prostate SBRT case when using a US-like motion input.

Random Scenario Generation for a Multiple Target Tracking Environment Evaluation

DEFF Research Database (Denmark)

Hussain, Dil Muhammad Akbar

2006-01-01

, which were normally crossing targets, was to test the efficiency of the track splitting algorithm for different situations. However this approach only gives a measure of performance for a specific, possibly unrealistic, scenario and it was felt appropriate to develop procedures that would enable a more...... general performance assessment. Therefore, a random target motion scenario is adopted. Its implementation in particular for testing the track splitting algorithm using Kalman filters is used and a couple of tracking performance parameters are computed to investigate such random scenarios....

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

Tracking target objects orbiting earth using satellite-based telescopes

Science.gov (United States)

De Vries, Willem H; Olivier, Scot S; Pertica, Alexander J

2014-10-14

A system for tracking objects that are in earth orbit via a constellation or network of satellites having imaging devices is provided. An object tracking system includes a ground controller and, for each satellite in the constellation, an onboard controller. The ground controller receives ephemeris information for a target object and directs that ephemeris information be transmitted to the satellites. Each onboard controller receives ephemeris information for a target object, collects images of the target object based on the expected location of the target object at an expected time, identifies actual locations of the target object from the collected images, and identifies a next expected location at a next expected time based on the identified actual locations of the target object. The onboard controller processes the collected image to identify the actual location of the target object and transmits the actual location information to the ground controller.

Computationally Efficient Automatic Coast Mode Target Tracking Based on Occlusion Awareness in Infrared Images.

Science.gov (United States)

Kim, Sohyun; Jang, Gwang-Il; Kim, Sungho; Kim, Junmo

2018-03-27

This paper proposes the automatic coast mode tracking of centroid trackers for infrared images to overcome the target occlusion status. The centroid tracking method, using only the brightness information of an image, is still widely used in infrared imaging tracking systems because it is difficult to extract meaningful features from infrared images. However, centroid trackers are likely to lose the track because they are highly vulnerable to screened status by the clutter or background. Coast mode, one of the tracking modes, maintains the servo slew rate with the tracking rate right before the loss of track. The proposed automatic coast mode tracking method makes decisions regarding entering coast mode by the prediction of target occlusion and tries to re-lock the target and resume the tracking after blind time. This algorithm comprises three steps. The first step is the prediction process of the occlusion by checking both matters which have target-likelihood brightness and which may screen the target despite different brightness. The second step is the process making inertial tracking commands to the servo. The last step is the process of re-locking a target based on the target modeling of histogram ratio. The effectiveness of the proposed algorithm is addressed by presenting experimental results based on computer simulation with various test imagery sequences compared to published tracking algorithms. The proposed algorithm is tested under a real environment with a naval electro-optical tracking system (EOTS) and airborne EO/IR system.

Computationally Efficient Automatic Coast Mode Target Tracking Based on Occlusion Awareness in Infrared Images

Directory of Open Access Journals (Sweden)

Sohyun Kim

2018-03-01

Full Text Available This paper proposes the automatic coast mode tracking of centroid trackers for infrared images to overcome the target occlusion status. The centroid tracking method, using only the brightness information of an image, is still widely used in infrared imaging tracking systems because it is difficult to extract meaningful features from infrared images. However, centroid trackers are likely to lose the track because they are highly vulnerable to screened status by the clutter or background. Coast mode, one of the tracking modes, maintains the servo slew rate with the tracking rate right before the loss of track. The proposed automatic coast mode tracking method makes decisions regarding entering coast mode by the prediction of target occlusion and tries to re-lock the target and resume the tracking after blind time. This algorithm comprises three steps. The first step is the prediction process of the occlusion by checking both matters which have target-likelihood brightness and which may screen the target despite different brightness. The second step is the process making inertial tracking commands to the servo. The last step is the process of re-locking a target based on the target modeling of histogram ratio. The effectiveness of the proposed algorithm is addressed by presenting experimental results based on computer simulation with various test imagery sequences compared to published tracking algorithms. The proposed algorithm is tested under a real environment with a naval electro-optical tracking system (EOTS and airborne EO/IR system.

TRUSTWORTHY OPTIMIZED CLUSTERING BASED TARGET DETECTION AND TRACKING FOR WIRELESS SENSOR NETWORK

Directory of Open Access Journals (Sweden)

C. Jehan

2016-06-01

Full Text Available In this paper, an efficient approach is proposed to address the problem of target tracking in wireless sensor network (WSN. The problem being tackled here uses adaptive dynamic clustering scheme for tracking the target. It is a specific problem in object tracking. The proposed adaptive dynamic clustering target tracking scheme uses three steps for target tracking. The first step deals with the identification of clusters and cluster heads using OGSAFCM. Here, kernel fuzzy c-means (KFCM and gravitational search algorithm (GSA are combined to create clusters. At first, oppositional gravitational search algorithm (OGSA is used to optimize the initial clustering center and then the KFCM algorithm is availed to guide the classification and the cluster formation process. In the OGSA, the concept of the opposition based population initialization in the basic GSA to improve the convergence profile. The identified clusters are changed dynamically. The second step deals with the data transmission to the cluster heads. The third step deals with the transmission of aggregated data to the base station as well as the detection of target. From the experimental results, the proposed scheme efficiently and efficiently identifies the target. As a result the tracking error is minimized.

An Integral Model for Target Tracking Based on the Use of a WSN

Directory of Open Access Journals (Sweden)

Pietro Manzoni

2013-06-01

Full Text Available The use of wireless sensor networks (WSN in tracking applications is growing at a fast pace. In these applications, the sensor nodes discover, monitor and track an event or target object. A significant number of proposals relating the use of WSNs for target tracking have been published to date. However, they either focus on the tracking algorithm or on the communication protocol, and none of them address the problem integrally. In this paper, a comprehensive proposal for target detection and tracking is discussed. We introduce a tracking algorithm to detect and estimate a target location. Moreover, we introduce a low-overhead routing protocol to be used along with our tracking algorithm. The proposed algorithm has low computational complexity and has been designed considering the use of a mobile sink while generating minimal delay and packet loss. We also discuss the results of the evaluation of the proposed algorithms.

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

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

EXPERIMENTAL TARGET INJECTION AND TRACKING SYSTEM CONSTRUCTION AND SINGLE SHOT TESTING

International Nuclear Information System (INIS)

PETZOLDT, R.W.; ALEXANDER, N.B.; DRAKE, T.J.; GOODIN, D.T; JONESTRACK, K; VERMILLION, B.A

2003-01-01

Targets must be injected into an IFE power plant at a rate of approximately 5 to 10 Hz. Targets must be tracked very accurately to allow driver beams to be aligned with defined points on the targets with accuracy ± 150 (micro)m for indirect drive and ± 20 (micro)m for direct drive. An experimental target injection and tracking system has been constructed at General Atomics. The injector system will be used as a tool for testing the survivability of various target designs and provide feedback to the target designers. Helium gas propels the targets down an 8 m gun barrel up to 400 m/s. Direct-drive targets are protected in the barrel by sabots that are spring loaded to separate into two halves after acceleration. A sabot deflector directs the sabot halves away from the target injection path. Targets will be optically tracked with laser beams and line-scan cameras. Target position and arrival time will be predicted in real time based on early target position measurements. The system installation will be described. System testing to overcome excessive projectile wear and debris in the gun barrel is presented

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.

A ground moving target emergency tracking method for catastrophe rescue

Science.gov (United States)

Zhou, X.; Li, D.; Li, G.

2014-11-01

In recent years, great disasters happen now and then. Disaster management test the emergency operation ability of the government and society all over the world. Immediately after the occurrence of a great disaster (e.g., earthquake), a massive nationwide rescue and relief operation need to be kicked off instantly. In order to improve the organizations efficiency of the emergency rescue, the organizers need to take charge of the information of the rescuer teams, including the real time location, the equipment with the team, the technical skills of the rescuers, and so on. One of the key factors for the success of emergency operations is the real time location of the rescuers dynamically. Real time tracking methods are used to track the professional rescuer teams now. But volunteers' participation play more and more important roles in great disasters. However, real time tracking of the volunteers will cause many problems, e.g., privacy leakage, expensive data consumption, etc. These problems may reduce the enthusiasm of volunteers' participation for catastrophe rescue. In fact, the great disaster is just small probability event, it is not necessary to track the volunteers (even rescuer teams) every time every day. In order to solve this problem, a ground moving target emergency tracking method for catastrophe rescue is presented in this paper. In this method, the handheld devices using GPS technology to provide the location of the users, e.g., smart phone, is used as the positioning equipment; an emergency tracking information database including the ID of the ground moving target (including the rescuer teams and volunteers), the communication number of the handheld devices with the moving target, and the usually living region, etc., is built in advance by registration; when catastrophe happens, the ground moving targets that living close to the disaster area will be filtered by the usually living region; then the activation short message will be sent to the selected

Microstrip silicon detectors in a bent crystal based collimation system: The UA9 experiment

International Nuclear Information System (INIS)

Bolognini, D.

2010-01-01

In a hadron accelerator like Lhc, a collimation system needs to be developed to protect the accelerator itself from the beam loss damage, increasing the beam luminosity. At present, a classical robust multi-stage collimation system (based on amorphous jaws) allows to protect Lhc, but limits the luminosity to the 40% of the nominal value. In order to solve this problem, a series of low-impedance collimation systems is being developed for the second Lhc collimation phase: among these, a key role could be played by bent crystals. In a bent crystal, in fact, charged particles can be deviated in a given direction with a high efficiency, reducing the impedance and increasing the luminosity. After the satisfactory results on extracted beams, it was decided to test bent crystals on a circular accelerator (the Super Proton Synchrotron Sps at CERN): the UA9 experiment was born. In order to qualify the crystal behavior, a tracking system has been developed: the system is based on microstrip silicon detectors readout by self-triggering ASICs with a spatial resolution of the order of 5 μm; the system, completely remotely controlled and based on the optical fiber transmission, would be able to measure the beam halo phase space x - x 1 . This paper, after a brief introduction of the UA9 experiment, will describe the tracking system and the first results obtained in the commissioning phase and data takings with a detector prototype.

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.

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

Ballistic target tracking algorithm based on improved particle filtering

Science.gov (United States)

Ning, Xiao-lei; Chen, Zhan-qi; Li, Xiao-yang

2015-10-01

Tracking ballistic re-entry target is a typical nonlinear filtering problem. In order to track the ballistic re-entry target in the nonlinear and non-Gaussian complex environment, a novel chaos map particle filter (CMPF) is used to estimate the target state. CMPF has better performance in application to estimate the state and parameter of nonlinear and non-Gassuian system. The Monte Carlo simulation results show that, this method can effectively solve particle degeneracy and particle impoverishment problem by improving the efficiency of particle sampling to obtain the better particles to part in estimation. Meanwhile CMPF can improve the state estimation precision and convergence velocity compared with EKF, UKF and the ordinary particle filter.

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...

Failure mode and effect analysis-based quality assurance for dynamic MLC tracking systems

Energy Technology Data Exchange (ETDEWEB)

Sawant, Amit; Dieterich, Sonja; Svatos, Michelle; Keall, Paul [Stanford University, Stanford, California 94394 (United States); Varian Medical Systems, Palo Alto, California 94304 (United States); Stanford University, Stanford, California 94394 (United States)

2010-12-15

Purpose: To develop and implement a failure mode and effect analysis (FMEA)-based commissioning and quality assurance framework for dynamic multileaf collimator (DMLC) tumor tracking systems. Methods: A systematic failure mode and effect analysis was performed for a prototype real-time tumor tracking system that uses implanted electromagnetic transponders for tumor position monitoring and a DMLC for real-time beam adaptation. A detailed process tree of DMLC tracking delivery was created and potential tracking-specific failure modes were identified. For each failure mode, a risk probability number (RPN) was calculated from the product of the probability of occurrence, the severity of effect, and the detectibility of the failure. Based on the insights obtained from the FMEA, commissioning and QA procedures were developed to check (i) the accuracy of coordinate system transformation, (ii) system latency, (iii) spatial and dosimetric delivery accuracy, (iv) delivery efficiency, and (v) accuracy and consistency of system response to error conditions. The frequency of testing for each failure mode was determined from the RPN value. Results: Failures modes with RPN{>=}125 were recommended to be tested monthly. Failure modes with RPN<125 were assigned to be tested during comprehensive evaluations, e.g., during commissioning, annual quality assurance, and after major software/hardware upgrades. System latency was determined to be {approx}193 ms. The system showed consistent and accurate response to erroneous conditions. Tracking accuracy was within 3%-3 mm gamma (100% pass rate) for sinusoidal as well as a wide variety of patient-derived respiratory motions. The total time taken for monthly QA was {approx}35 min, while that taken for comprehensive testing was {approx}3.5 h. Conclusions: FMEA proved to be a powerful and flexible tool to develop and implement a quality management (QM) framework for DMLC tracking. The authors conclude that the use of FMEA-based QM ensures

Failure mode and effect analysis-based quality assurance for dynamic MLC tracking systems.

Science.gov (United States)

Sawant, Amit; Dieterich, Sonja; Svatos, Michelle; Keall, Paul

2010-12-01

To develop and implement a failure mode and effect analysis (FMEA)-based commissioning and quality assurance framework for dynamic multileaf collimator (DMLC) tumor tracking systems. A systematic failure mode and effect analysis was performed for a prototype real-time tumor tracking system that uses implanted electromagnetic transponders for tumor position monitoring and a DMLC for real-time beam adaptation. A detailed process tree of DMLC tracking delivery was created and potential tracking-specific failure modes were identified. For each failure mode, a risk probability number (RPN) was calculated from the product of the probability of occurrence, the severity of effect, and the detectibility of the failure. Based on the insights obtained from the FMEA, commissioning and QA procedures were developed to check (i) the accuracy of coordinate system transformation, (ii) system latency, (iii) spatial and dosimetric delivery accuracy, (iv) delivery efficiency, and (v) accuracy and consistency of system response to error conditions. The frequency of testing for each failure mode was determined from the RPN value. Failures modes with RPN > or = 125 were recommended to be tested monthly. Failure modes with RPN < 125 were assigned to be tested during comprehensive evaluations, e.g., during commissioning, annual quality assurance, and after major software/hardware upgrades. System latency was determined to be approximately 193 ms. The system showed consistent and accurate response to erroneous conditions. Tracking accuracy was within 3%-3 mm gamma (100% pass rate) for sinusoidal as well as a wide variety of patient-derived respiratory motions. The total time taken for monthly QA was approximately 35 min, while that taken for comprehensive testing was approximately 3.5 h. FMEA proved to be a powerful and flexible tool to develop and implement a quality management (QM) framework for DMLC tracking. The authors conclude that the use of FMEA-based QM ensures efficient allocation

Failure mode and effect analysis-based quality assurance for dynamic MLC tracking systems

International Nuclear Information System (INIS)

Sawant, Amit; Dieterich, Sonja; Svatos, Michelle; Keall, Paul

2010-01-01

Purpose: To develop and implement a failure mode and effect analysis (FMEA)-based commissioning and quality assurance framework for dynamic multileaf collimator (DMLC) tumor tracking systems. Methods: A systematic failure mode and effect analysis was performed for a prototype real-time tumor tracking system that uses implanted electromagnetic transponders for tumor position monitoring and a DMLC for real-time beam adaptation. A detailed process tree of DMLC tracking delivery was created and potential tracking-specific failure modes were identified. For each failure mode, a risk probability number (RPN) was calculated from the product of the probability of occurrence, the severity of effect, and the detectibility of the failure. Based on the insights obtained from the FMEA, commissioning and QA procedures were developed to check (i) the accuracy of coordinate system transformation, (ii) system latency, (iii) spatial and dosimetric delivery accuracy, (iv) delivery efficiency, and (v) accuracy and consistency of system response to error conditions. The frequency of testing for each failure mode was determined from the RPN value. Results: Failures modes with RPN≥125 were recommended to be tested monthly. Failure modes with RPN<125 were assigned to be tested during comprehensive evaluations, e.g., during commissioning, annual quality assurance, and after major software/hardware upgrades. System latency was determined to be ∼193 ms. The system showed consistent and accurate response to erroneous conditions. Tracking accuracy was within 3%-3 mm gamma (100% pass rate) for sinusoidal as well as a wide variety of patient-derived respiratory motions. The total time taken for monthly QA was ∼35 min, while that taken for comprehensive testing was ∼3.5 h. Conclusions: FMEA proved to be a powerful and flexible tool to develop and implement a quality management (QM) framework for DMLC tracking. The authors conclude that the use of FMEA-based QM ensures efficient allocation

Analysis of LFM-waveform Libraries for Cognitive Tracking Maneuvering Targets

Directory of Open Access Journals (Sweden)

Wang Hongyan

2016-01-01

Full Text Available Based on the idea of the waveform agility in cognitive radars，the waveform libraries for maneuvering target tracking are discussed. LFM-waveform libraries are designed according to different combinations of chirp parameters and FrFT rotation angles. By applying the interact multiple model (IMM algorithm in tracking maneuvering targets, transmitted waveform is called real time from the LFM-waveform libraries. The waveforms are selected from the library according to the criterion of maximum mutual information between the current state of knowledge of the model and the measurement. Simulation results show that waveform library containing certain amount LFM-waveforms can improve the performance of cognitive tracking radar.

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

A Bayesian solution to multi-target tracking problems with mixed labelling

NARCIS (Netherlands)

Aoki, E.H.; Boers, Y.; Svensson, Lennart; Mandal, Pranab K.; Bagchi, Arunabha

In Multi-Target Tracking (MTT), the problem of assigning labels to tracks (track labelling) is vastly covered in literature and has been previously formulated using Bayesian recursion. However, the existing literature lacks an appropriate measure of uncertainty related to the assigned labels which

A Single Unexpected Change in Target- but Not Distractor Motion Impairs Multiple Object Tracking

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Hauke S. Meyerhoff

2013-02-01

Full Text Available Recent research addresses the question whether motion information of multiple objects contributes to maintaining a selection of objects across a period of motion. Here, we investigate whether target and/or distractor motion information is used during attentive tracking. We asked participants to track four objects and changed either the motion direction of targets, the motion direction of distractors, neither, or both during a brief flash in the middle of a tracking interval. We observed that a single direction change of targets is sufficient to impair tracking performance. In contrast, changing the motion direction of distractors had no effect on performance. This indicates that target- but not distractor motion information is evaluated during tracking.

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.

Study of the IMRT interplay effect using a 4DCT Monte Carlo dose calculation.

Science.gov (United States)

Jensen, Michael D; Abdellatif, Ady; Chen, Jeff; Wong, Eugene

2012-04-21

Respiratory motion may lead to dose errors when treating thoracic and abdominal tumours with radiotherapy. The interplay between complex multileaf collimator patterns and patient respiratory motion could result in unintuitive dose changes. We have developed a treatment reconstruction simulation computer code that accounts for interplay effects by combining multileaf collimator controller log files, respiratory trace log files, 4DCT images and a Monte Carlo dose calculator. Two three-dimensional (3D) IMRT step-and-shoot plans, a concave target and integrated boost were delivered to a 1D rigid motion phantom. Three sets of experiments were performed with 100%, 50% and 25% duty cycle gating. The log files were collected, and five simulation types were performed on each data set: continuous isocentre shift, discrete isocentre shift, 4DCT, 4DCT delivery average and 4DCT plan average. Analysis was performed using 3D gamma analysis with passing criteria of 2%, 2 mm. The simulation framework was able to demonstrate that a single fraction of the integrated boost plan was more sensitive to interplay effects than the concave target. Gating was shown to reduce the interplay effects. We have developed a 4DCT Monte Carlo simulation method that accounts for IMRT interplay effects with respiratory motion by utilizing delivery log files.

Models and Algorithms for Tracking Target with Coordinated Turn Motion

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Xianghui Yuan

2014-01-01

Full Text Available Tracking target with coordinated turn (CT motion is highly dependent on the models and algorithms. First, the widely used models are compared in this paper—coordinated turn (CT model with known turn rate, augmented coordinated turn (ACT model with Cartesian velocity, ACT model with polar velocity, CT model using a kinematic constraint, and maneuver centered circular motion model. Then, in the single model tracking framework, the tracking algorithms for the last four models are compared and the suggestions on the choice of models for different practical target tracking problems are given. Finally, in the multiple models (MM framework, the algorithm based on expectation maximization (EM algorithm is derived, including both the batch form and the recursive form. Compared with the widely used interacting multiple model (IMM algorithm, the EM algorithm shows its effectiveness.

Modeling of beam-induced damage of the LHC tertiary collimators

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E. Quaranta

2017-09-01

Full Text Available Modern hadron machines with high beam intensity may suffer from material damage in the case of large beam losses and even beam-intercepting devices, such as collimators, can be harmed. A systematic method to evaluate thresholds of damage owing to the impact of high energy particles is therefore crucial for safe operation and for predicting possible limitations in the overall machine performance. For this, a three-step simulation approach is presented, based on tracking simulations followed by calculations of energy deposited in the impacted material and hydrodynamic simulations to predict the thermomechanical effect of the impact. This approach is applied to metallic collimators at the CERN Large Hadron Collider (LHC, which in standard operation intercept halo protons, but risk to be damaged in the case of extraction kicker malfunction. In particular, tertiary collimators protect the aperture bottlenecks, their settings constrain the reach in β^{*} and hence the achievable luminosity at the LHC experiments. Our calculated damage levels provide a very important input on how close to the beam these collimators can be operated without risk of damage. The results of this approach have been used already to push further the performance of the present machine. The risk of damage is even higher in the upgraded high-luminosity LHC with higher beam intensity, for which we quantify existing margins before equipment damage for the proposed baseline settings.

Modeling of beam-induced damage of the LHC tertiary collimators

Science.gov (United States)

Quaranta, E.; Bertarelli, A.; Bruce, R.; Carra, F.; Cerutti, F.; Lechner, A.; Redaelli, S.; Skordis, E.; Gradassi, P.

2017-09-01

Modern hadron machines with high beam intensity may suffer from material damage in the case of large beam losses and even beam-intercepting devices, such as collimators, can be harmed. A systematic method to evaluate thresholds of damage owing to the impact of high energy particles is therefore crucial for safe operation and for predicting possible limitations in the overall machine performance. For this, a three-step simulation approach is presented, based on tracking simulations followed by calculations of energy deposited in the impacted material and hydrodynamic simulations to predict the thermomechanical effect of the impact. This approach is applied to metallic collimators at the CERN Large Hadron Collider (LHC), which in standard operation intercept halo protons, but risk to be damaged in the case of extraction kicker malfunction. In particular, tertiary collimators protect the aperture bottlenecks, their settings constrain the reach in β* and hence the achievable luminosity at the LHC experiments. Our calculated damage levels provide a very important input on how close to the beam these collimators can be operated without risk of damage. The results of this approach have been used already to push further the performance of the present machine. The risk of damage is even higher in the upgraded high-luminosity LHC with higher beam intensity, for which we quantify existing margins before equipment damage for the proposed baseline settings.

A proton beam delivery system for conformal therapy and intensity modulated therapy

International Nuclear Information System (INIS)

Yu Qingchang

2001-01-01

A scattering proton beam delivery system for conformal therapy and intensity modulated therapy is described. The beam is laterally spread out by a dual-ring double scattering system and collimated by a program-controlled multileaf collimator and patient specific fixed collimators. The proton range is adjusted and modulated by a program controlled binary filter and ridge filters

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.

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

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)

Optimizing Laser-accelerated Ion Beams for a Collimated Neutron Source

International Nuclear Information System (INIS)

Ellison, C.L.; Fuchs, J.

2010-01-01

High-flux neutrons for imaging and materials analysis applications have typically been provided by accelerator- and reactor-based neutron sources. A novel approach is to use ultraintense (>1018W/cm2) lasers to generate picosecond, collimated neutrons from a dual target configuration. In this article, the production capabilities of present and upcoming laser facilities are estimated while independently maximizing neutron yields and minimizing beam divergence. A Monte-Carlo code calculates angular and energy distributions of neutrons generated by D-D fusion events occurring within a deuterated target for a given incident beam of D+ ions. Tailoring of the incident distribution via laser parameters and microlens focusing modifies the emerging neutrons. Projected neutron yields and distributions are compared to conventional sources, yielding comparable on-target fluxes per discharge, shorter time resolution, larger neutron energies and greater collimation.

Multiple Maneuvering Target Tracking by Improved Particle Filter Based on Multiscan JPDA

Directory of Open Access Journals (Sweden)

Jing Liu

2012-01-01

Full Text Available The multiple maneuvering target tracking algorithm based on a particle filter is addressed. The equivalent-noise approach is adopted, which uses a simple dynamic model consisting of target state and equivalent noise which accounts for the combined effects of the process noise and maneuvers. The equivalent-noise approach converts the problem of maneuvering target tracking to that of state estimation in the presence of nonstationary process noise with unknown statistics. A novel method for identifying the nonstationary process noise is proposed in the particle filter framework. Furthermore, a particle filter based multiscan Joint Probability Data Association (JPDA filter is proposed to deal with the data association problem in a multiple maneuvering target tracking. In the proposed multiscan JPDA algorithm, the distributions of interest are the marginal filtering distributions for each of the targets, and these distributions are approximated with particles. The multiscan JPDA algorithm examines the joint association events in a multiscan sliding window and calculates the marginal posterior probability based on the multiscan joint association events. The proposed algorithm is illustrated via an example involving the tracking of two highly maneuvering, at times closely spaced and crossed, targets, based on resolved measurements.

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

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

Efficient and Adaptive Node Selection for Target Tracking in Wireless Sensor Network

Directory of Open Access Journals (Sweden)

Juan Feng

2016-01-01

Full Text Available In target tracking wireless sensor network, choosing the proper working nodes can not only minimize the number of active nodes, but also satisfy the tracking reliability requirement. However, most existing works focus on selecting sensor nodes which are the nearest to the target for tracking missions and they did not consider the correlation of the location of the sensor nodes so that these approaches can not meet all the goals of the network. This work proposes an efficient and adaptive node selection approach for tracking a target in a distributed wireless sensor network. The proposed approach combines the distance-based node selection strategy and particle filter prediction considering the spatial correlation of the different sensing nodes. Moreover, a joint distance weighted measurement is proposed to estimate the information utility of sensing nodes. Experimental results show that EANS outperformed the state-of-the-art approaches by reducing the energy cost and computational complexity as well as guaranteeing the tracking accuracy.

Method for Multiple Targets Tracking in Cognitive Radar Based on Compressed Sensing

Directory of Open Access Journals (Sweden)

Yang Jun

2016-02-01

Full Text Available A multiple targets cognitive radar tracking method based on Compressed Sensing (CS is proposed. In this method, the theory of CS is introduced to the case of cognitive radar tracking process in multiple targets scenario. The echo signal is sparsely expressed. The designs of sparse matrix and measurement matrix are accomplished by expressing the echo signal sparsely, and subsequently, the restruction of measurement signal under the down-sampling condition is realized. On the receiving end, after considering that the problems that traditional particle filter suffers from degeneracy, and require a large number of particles, the particle swarm optimization particle filter is used to track the targets. On the transmitting end, the Posterior Cramér-Rao Bounds (PCRB of the tracking accuracy is deduced, and the radar waveform parameters are further cognitively designed using PCRB. Simulation results show that the proposed method can not only reduce the data quantity, but also provide a better tracking performance compared with traditional method.

Collimation method using an image processing technique for an assembling-type antenna

Science.gov (United States)

Okuyama, Toshiyuki; Kimura, Shinichi; Fukase, Yutaro; Ueno, Hiroshi; Harima, Kouichi; Sato, Hitoshi; Yoshida, Tetsuji

1998-10-01

To construct highly precise space structures, such as antennas, it is essential to be able to collimate them with high precision by remote operation. Surveying techniques which are commonly used for collimating ground-based antennas cannot be applied to space systems, since they require relatively sensitive and complex instruments. In this paper, we propose a collimation method that is applied to mark-patterns mounted on an antenna dish for detecting very slight displacements. By calculating a cross- correlation function between the target and reference mark- patterns, and by interpolating this calculated function, we can measure the displacement of the target mark-pattern in sub-pixel precision. We developed a test-bed for the measuring system and evaluated several mark-patterns suitable for our image processing technique. A mark-pattern with which enabled to detect displacement within an RMS error of 1/100 pixels was found. Several tests conducted using this chosen pattern verified the robustness of the method to different light conditions and alignment errors. This collimating method is designed for application to an assembling-type antenna which is being developed by the Communications Research Laboratory.

Analysis and experimental investigation for collimator reflective mirror surface deformation adjustment

Directory of Open Access Journals (Sweden)

Chia-Yen Chan

2017-01-01

Full Text Available Collimator design is essential for meeting the requirements of high-precision telescopes. The collimator diameter should be larger than that of the target for alignment. Special supporting structures are required to reduce the gravitational deformation and control the surface deformation induced by the mounting force when inspecting large-aperture primary mirrors (M1. A ZERODURÂŽ mirror 620 mm in diameter for a collimator was analyzed using the finite element method to obtain the deformation induced by the supporting structures and adjustment mechanism. Zernike polynomials were also adopted to fit the optical surface and separate corresponding aberrations. The computed and measured wavefront aberration configurations for the collimator M1 were obtained complementally. The wavefront aberrations were adjusted using fine adjustment screws using 3D optical path differences map of the mirror surface. Through studies using different boundary conditions and inner ring support positions, it is concluded that the optical performance was excellent under a strong enough supporter. The best adjustment position was attained and applied to the actual collimator M1 to prove the correctness of the simulation results.

Target injection and tracking for inertial fusion energy

Energy Technology Data Exchange (ETDEWEB)

Petzoldt, R.W. [Lawrence Livermore National Lab., CA (United States); Moir, R.W. [Lawrence Livermore National Lab., CA (United States)

1996-11-01

In an inertial fusion power plant, several cryogenic targets must be injected each second into a reaction chamber with speeds of about 100 m s{sup -1}. This speed can be achieved with an acceleration in the range from 1000 to 10 000 m s{sup -2}. The total accuracy of driver beam pointing and target position prediction must be less than {+-}0.6 mm for a 3 mm beam spot radius. A 0.1 {mu}m thick dual membrane supporting the capsule in the hohlraum will allow nearly 2000 m s{sup -2} acceleration. The strength of frozen DT in the capsule is calculated to allow acceleration in excess of 10 000 m s{sup -2} if the DT temperature is less than 17 K. A gas gun is the preferred device for injecting indirect drive targets owing to its simplicity and proven reliability. The amount of gas required for each target (about 10-100 mg) is acceptable. A revolver loading mechanism is recommendced with a cam-operated poppet valve to control the gas flow. Slots near the muzzle of the gun barrel are recommended to vent gas and thereby to improve accuracy and to aid gas pumping. Optical target tracking and electronic timing devices can predict target arrival time with sufficient accuracy. Target steering by electrostatic deflection of the in-flight target is shown to be feasible and would avoid the need to point the beams actively. Calculations show that induced tumble from electrostatically steering the target is not excessive. An experiment has been designed to develop target injection and to verify the predicted accuracy of sequential injection and tracking of multiple targets. (orig.)

Collimator optimization for small animal radiation therapy at a micro-CT

Energy Technology Data Exchange (ETDEWEB)

Felix, Manuela C. [Heidelberg Univ., Mannheim (Germany). Medical Radiation Physics/Radiation Protection; Heidelberg Univ., Mannheim (Germany). Dept. of Radiation Oncology; Glatting, Gerhard [Heidelberg Univ., Mannheim (Germany). Medical Radiation Physics/Radiation Protection; Giordano, Frank A.; Wenz, Frederik; Fleckenstein, Jens [Heidelberg Univ., Mannheim (Germany). Dept. of Radiation Oncology; Brockmann, Marc A. [Heidelberg Univ., Mannheim (Germany). Dept. of Neuroradiology; University Medical Center Mainz (Germany). Dept. of Neuroradiology

2017-05-01

In radiation therapy of small animals treatment depths range from a few millimetres to several centimetres. In order to spare surrounding organs at risk steep dose gradients are necessary. To minimize the treatment time, and therefore the strain to the animals, a high dose rate is required. A description how these parameters can be optimized through an appropriate choice of collimators with different source surface distances (SSD) as well as different materials and geometries is presented. An industrial micro-CT unit (Y.Fox, YXLON GmbH, Hamburg, Germany) was converted into a precision irradiator for small animals. Different collimators of either stainless steel (Fe) with cylindrical bores (SSD = 42 mm) or tungsten (W) with conical bores (SSD = 14 mm) were evaluated. The dosimetry of very small radiation fields presents a challenge and was performed with GafChromic EBT3 films (Ashland, Vayne, KY, USA) in a water phantom. The films were calibrated with an ionization chamber in the uncollimated field. Treatments were performed via a rotation of the objects with a fixed radiation source. As expected, the shorter SSD of the W-collimators resulted in a (4.5 ± 1.6)-fold increase of the dose rates compared to the corresponding Fe-collimators. The ratios of the dose rates at 1 mm and 10 mm depth in the water phantom was (2.6 ± 0.2) for the Fe- and (4.5 ± 0.1) for the W-collimators. For rotational treatments in a cylindrical plastic phantom maximum dose rates of up to 1.2 Gy/min for Fe- and 5.1 Gy/min for W-collimators were measured. Choosing the smallest possible SSD leads to a high dose rate and a high surface dose, which is of advantage for the treatment of superficial target volumes. For larger SSD the dose rate is lower and the depth dose curve is shallower. This leads to a reduction of the surface dose and is best suited for treatments of deeper seated target volumes. Divergent collimator bores have, due to the reduced scatter within the collimators, a steeper

Node Depth Adjustment Based Target Tracking in UWSNs Using Improved Harmony Search

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Meiqin Liu

2017-12-01

Full Text Available Underwater wireless sensor networks (UWSNs can provide a promising solution to underwater target tracking. Due to the limited computation and bandwidth resources, only a small part of nodes are selected to track the target at each interval. How to improve tracking accuracy with a small number of nodes is a key problem. In recent years, a node depth adjustment system has been developed and applied to issues of network deployment and routing protocol. As far as we know, all existing tracking schemes keep underwater nodes static or moving with water flow, and node depth adjustment has not been utilized for underwater target tracking yet. This paper studies node depth adjustment method for target tracking in UWSNs. Firstly, since a Fisher Information Matrix (FIM can quantify the estimation accuracy, its relation to node depth is derived as a metric. Secondly, we formulate the node depth adjustment as an optimization problem to determine moving depth of activated node, under the constraint of moving range, the value of FIM is used as objective function, which is aimed to be minimized over moving distance of nodes. Thirdly, to efficiently solve the optimization problem, an improved Harmony Search (HS algorithm is proposed, in which the generating probability is modified to improve searching speed and accuracy. Finally, simulation results are presented to verify performance of our scheme.

Design and evaluation of two multi-pinhole collimators for brain SPECT.

Science.gov (United States)

Chen, Ling; Tsui, Benjamin M W; Mok, Greta S P

2017-10-01

SPECT is a powerful tool for diagnosing or staging brain diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) but is limited by its inferior resolution and sensitivity. At the same time, pinhole SPECT provides superior resolution and detection efficiency trade-off as compared to the conventional parallel-hole collimator for imaging small field-of-view (FOV), which fits for the case of brain imaging. In this study, we propose to develop and evaluate two multi-pinhole (MPH) collimator designs to improve the imaging of cerebral blood flow and striatum. We set the target resolutions to be 12 and 8 mm, respectively, and the FOV at 200 mm which is large enough to cover the whole brain. The constraints for system optimization include maximum and minimum detector-to-center-of-FOV (CFOV) distances of 344 and 294 mm, respectively, and minimal radius-of-rotation (ROR) of 135 mm to accommodate patients' shoulder. According to the targeted FOV, resolutions, and constraints, we determined the pinhole number, ROR, focal length, aperture acceptance angle, and aperture diameter which maximized the system sensitivity. We then assessed the imaging performance of the proposed MPH and standard low-energy high-resolution (LEHR) collimators using analytical simulations of a digital NCAT brain phantom with 99m Tc-HMPAO/ 99m Tc-TRODAT-1 distributions; Monte Carlo simulations of a hot-rod phantom; and a Defrise phantom using GATE v6.1. Projections were generated over 360° and reconstructed using the 3D MPH/LEHR OS-EM methods with up to 720 updates. The normalized mean square error (NMSE) was calculated over the cerebral and striatal regions extracted from the reconstructed images for 99m Tc-HMPAO and 99m Tc-TRODAT-1 simulations, respectively, and average normalized standard deviation (NSD) based on 20 noise realizations was assessed on selected uniform 3D regions as the noise index. Visual assessment and image profiles were applied to the results of Monte Carlo

Robotics Vision-based Heuristic Reasoning for Underwater Target Tracking and Navigation

OpenAIRE

Kia, Chua; Arshad, Mohd Rizal

2006-01-01

This paper presents a robotics vision-based heuristic reasoning system for underwater target tracking and navigation. This system is introduced to improve the level of automation of underwater Remote Operated Vehicles (ROVs) operations. A prototype which combines computer vision with an underwater robotics system is successfully designed and developed to perform target tracking and intelligent navigation. This study focuses on developing image processing algorithms and fuzzy inference system ...

Wavefront sensing and adaptive control in phased array of fiber collimators

Science.gov (United States)

Lachinova, Svetlana L.; Vorontsov, Mikhail A.

2011-03-01

A new wavefront control approach for mitigation of atmospheric turbulence-induced wavefront phase aberrations in coherent fiber-array-based laser beam projection systems is introduced and analyzed. This approach is based on integration of wavefront sensing capabilities directly into the fiber-array transmitter aperture. In the coherent fiber array considered, we assume that each fiber collimator (subaperture) of the array is capable of precompensation of local (onsubaperture) wavefront phase tip and tilt aberrations using controllable rapid displacement of the tip of the delivery fiber at the collimating lens focal plane. In the technique proposed, this tip and tilt phase aberration control is based on maximization of the optical power received through the same fiber collimator using the stochastic parallel gradient descent (SPGD) technique. The coordinates of the fiber tip after the local tip and tilt aberrations are mitigated correspond to the coordinates of the focal-spot centroid of the optical wave backscattered off the target. Similar to a conventional Shack-Hartmann wavefront sensor, phase function over the entire fiber-array aperture can then be retrieved using the coordinates obtained. The piston phases that are required for coherent combining (phase locking) of the outgoing beams at the target plane can be further calculated from the reconstructed wavefront phase. Results of analysis and numerical simulations are presented. Performance of adaptive precompensation of phase aberrations in this laser beam projection system type is compared for various system configurations characterized by the number of fiber collimators and atmospheric turbulence conditions. The wavefront control concept presented can be effectively applied for long-range laser beam projection scenarios for which the time delay related with the double-pass laser beam propagation to the target and back is compared or even exceeds the characteristic time of the atmospheric turbulence change

Efficient characterization of labeling uncertainty in closely-spaced targets tracking

NARCIS (Netherlands)

Moreno Leon, Carlos; Moreno Leon, Carlos; Driessen, Hans; Mandal, Pranab K.

2016-01-01

In this paper we propose a novel solution to the labeled multi-target tracking problem. The method presented is specially effective in scenarios where the targets have once moved in close proximity. When this is the case, disregarding the labeling uncertainty present in a solution (after the targets

Estimation of Radar Cross Section of a Target under Track

Directory of Open Access Journals (Sweden)

Hong Sun-Mog

2010-01-01

Full Text Available In allocating radar beam for tracking a target, it is attempted to maintain the signal-to-noise ratio (SNR of signal returning from the illuminated target close to an optimum value for efficient track updates. An estimate of the average radar cross section (RCS of the target is required in order to adjust transmitted power based on the estimate such that a desired SNR can be realized. In this paper, a maximum-likelihood (ML approach is presented for estimating the average RCS, and a numerical solution to the approach is proposed based on a generalized expectation maximization (GEM algorithm. Estimation accuracy of the approach is compared to that of a previously reported procedure.

Event-triggered cooperative target tracking in wireless sensor networks

Directory of Open Access Journals (Sweden)

Lu Kelin

2016-10-01

Full Text Available Since the issues of low communication bandwidth supply and limited battery capacity are very crucial for wireless sensor networks, this paper focuses on the problem of event-triggered cooperative target tracking based on set-membership information filtering. We study some fundamental properties of the set-membership information filter with multiple sensor measurements. First, a sufficient condition is derived for the set-membership information filter, under which the boundedness of the outer ellipsoidal approximation set of the estimation means is guaranteed. Second, the equivalence property between the parallel and sequential versions of the set-membership information filter is presented. Finally, the results are applied to a 1D event-triggered target tracking scenario in which the negative information is exploited in the sense that the measurements that do not satisfy the triggering conditions are modelled as set-membership measurements. The tracking performance of the proposed method is validated with extensive Monte Carlo simulations.

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.

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.

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

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.

Interacting with target tracking algorithms in a gaze-enhanced motion video analysis system

Science.gov (United States)

Hild, Jutta; Krüger, Wolfgang; Heinze, Norbert; Peinsipp-Byma, Elisabeth; Beyerer, Jürgen

2016-05-01

Motion video analysis is a challenging task, particularly if real-time analysis is required. It is therefore an important issue how to provide suitable assistance for the human operator. Given that the use of customized video analysis systems is more and more established, one supporting measure is to provide system functions which perform subtasks of the analysis. Recent progress in the development of automated image exploitation algorithms allow, e.g., real-time moving target tracking. Another supporting measure is to provide a user interface which strives to reduce the perceptual, cognitive and motor load of the human operator for example by incorporating the operator's visual focus of attention. A gaze-enhanced user interface is able to help here. This work extends prior work on automated target recognition, segmentation, and tracking algorithms as well as about the benefits of a gaze-enhanced user interface for interaction with moving targets. We also propose a prototypical system design aiming to combine both the qualities of the human observer's perception and the automated algorithms in order to improve the overall performance of a real-time video analysis system. In this contribution, we address two novel issues analyzing gaze-based interaction with target tracking algorithms. The first issue extends the gaze-based triggering of a target tracking process, e.g., investigating how to best relaunch in the case of track loss. The second issue addresses the initialization of tracking algorithms without motion segmentation where the operator has to provide the system with the object's image region in order to start the tracking algorithm.

Development of target-tracking algorithms using neural network

Energy Technology Data Exchange (ETDEWEB)

Park, Dong Sun; Lee, Joon Whaoan; Yoon, Sook; Baek, Seong Hyun; Lee, Myung Jae [Chonbuk National University, Chonjoo (Korea)

1998-04-01

The utilization of remote-control robot system in atomic power plants or nuclear-related facilities grows rapidly, to protect workers form high radiation environments. Such applications require complete stability of the robot system, so that precisely tracking the robot is essential for the whole system. This research is to accomplish the goal by developing appropriate algorithms for remote-control robot systems. A neural network tracking system is designed and experimented to trace a robot Endpoint. This model is aimed to utilized the excellent capabilities of neural networks; nonlinear mapping between inputs and outputs, learning capability, and generalization capability. The neural tracker consists of two networks for position detection and prediction. Tracking algorithms are developed and experimented for the two models. Results of the experiments show that both models are promising as real-time target-tracking systems for remote-control robot systems. (author). 10 refs., 47 figs.

Present and Future Developments in Radiotherapy Treatment Units.

Science.gov (United States)

Boyer

1995-04-01

Technical advances in the design of medical accelerators are making possible the exploration of new treatment techniques. Technology currently available to the radiation oncologist allows the use of internal and dynamic wedges. Multileaf collimators can be used for static treatment ports, and dynamic field shaping and beam modulation using multileaf collimators has been shown to be feasible. Computer interfaces are necessary to transfer the complex treatment sequences that are possible with these devices. Such network interfaces also provide for more efficient conventional treatments. New machines such as X-band linear accelerators and advanced proton accelerators are being developed for applications such as boron neutron capture therapy and proton conformal therapy.

Investigating the impact of treatment delivery uncertainties on treatment effectiveness for lung SABR

DEFF Research Database (Denmark)

Blake, Samuel J.; Arumugam, Sankar; Holloway, Lois

2017-01-01

To quantify the impact of treatment delivery uncertainties on lung stereotactic ablative body radiotherapy (SABR) plans for step-and-shoot intensity-modulated radiotherapy (ssIMRT) and volumetric modulated arc therapy (VMAT). Baseline ssIMRT and VMAT treatment plans were generated for a cohort...... of 18 lung SABR patients. Modified plans were generated for each baseline plan by systematically varying gantry and collimator angles between − 5 and + 5 degrees, as well as multi-leaf collimator (MLC) leaf position errors of magnitude between 1 and 5 mm in both directions (i.e. leaf banks shifted...... either in the same (Type 1) or opposite (Type 2) directions). Planning target volume (PTV), spinal cord and healthy lung dose-volume histogram (DVH) metrics were compared between the modified and baseline plans. Collimator and gantry angle uncertainties did not significantly impact any of the PTV DVH...

Dynamic-MLC leaf control utilizing on-flight intensity calculations: A robust method for real-time IMRT delivery over moving rigid targets

International Nuclear Information System (INIS)

McMahon, Ryan; Papiez, Lech; Rangaraj, Dharanipathy

2007-01-01

An algorithm is presented that allows for the control of multileaf collimation (MLC) leaves based entirely on real-time calculations of the intensity delivered over the target. The algorithm is capable of efficiently correcting generalized delivery errors without requiring the interruption of delivery (self-correcting trajectories), where a generalized delivery error represents anything that causes a discrepancy between the delivered and intended intensity profiles. The intensity actually delivered over the target is continually compared to its intended value. For each pair of leaves, these comparisons are used to guide the control of the following leaf and keep this discrepancy below a user-specified value. To demonstrate the basic principles of the algorithm, results of corrected delivery are shown for a leading leaf positional error during dynamic-MLC (DMLC) IMRT delivery over a rigid moving target. It is then shown that, with slight modifications, the algorithm can be used to track moving targets in real time. The primary results of this article indicate that the algorithm is capable of accurately delivering DMLC IMRT over a rigid moving target whose motion is (1) completely unknown prior to delivery and (2) not faster than the maximum MLC leaf velocity over extended periods of time. These capabilities are demonstrated for clinically derived intensity profiles and actual tumor motion data, including situations when the target moves in some instances faster than the maximum admissible MLC leaf velocity. The results show that using the algorithm while calculating the delivered intensity every 50 ms will provide a good level of accuracy when delivering IMRT over a rigid moving target translating along the direction of MLC leaf travel. When the maximum velocities of the MLC leaves and target were 4 and 4.2 cm/s, respectively, the resulting error in the two intensity profiles used was 0.1±3.1% and -0.5±2.8% relative to the maximum of the intensity profiles. For

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

Location detection and tracking of moving targets by a 2D IR-UWB radar system.

Science.gov (United States)

Nguyen, Van-Han; Pyun, Jae-Young

2015-03-19

In indoor environments, the Global Positioning System (GPS) and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB) technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB) radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF) is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking.

Multi-agent target tracking using particle filters enhanced with context data

CSIR Research Space (South Africa)

Claessens, R

2015-05-01

Full Text Available The proposed framework for Multi-Agent Target Tracking supports i) tracking of objects and ii) search and rescue based on the fusion of very heterogeneous data. The system is based on a novel approach to fusing sensory observations, intelligence...

Passive target tracking using marginalized particle filter

Institute of Scientific and Technical Information of China (English)

无

2007-01-01

A marginalized particle filtering(MPF)approach is proposed for target tracking under the background of passive measurement.Essentially,the MPF is a combination of particle filtering technique and Kalman filter.By making full use of marginalization,the distributions of the tractable linear part of the total state variables are updated analytically using Kalman filter,and only the lower-dimensional nonlinear state variable needs to be dealt with using particle filter.Simulation studies are performed on an illustrative example,and the results show that the MPF method leads to a significant reduction of the tracking errors when compared with the direct particle implementation.Real data test results also validate the effectiveness of the presented method.

Online variational Bayesian filtering-based mobile target tracking in wireless sensor networks.

Science.gov (United States)

Zhou, Bingpeng; Chen, Qingchun; Li, Tiffany Jing; Xiao, Pei

2014-11-11

The received signal strength (RSS)-based online tracking for a mobile node in wireless sensor networks (WSNs) is investigated in this paper. Firstly, a multi-layer dynamic Bayesian network (MDBN) is introduced to characterize the target mobility with either directional or undirected movement. In particular, it is proposed to employ the Wishart distribution to approximate the time-varying RSS measurement precision's randomness due to the target movement. It is shown that the proposed MDBN offers a more general analysis model via incorporating the underlying statistical information of both the target movement and observations, which can be utilized to improve the online tracking capability by exploiting the Bayesian statistics. Secondly, based on the MDBN model, a mean-field variational Bayesian filtering (VBF) algorithm is developed to realize the online tracking of a mobile target in the presence of nonlinear observations and time-varying RSS precision, wherein the traditional Bayesian filtering scheme cannot be directly employed. Thirdly, a joint optimization between the real-time velocity and its prior expectation is proposed to enable online velocity tracking in the proposed online tacking scheme. Finally, the associated Bayesian Cramer-Rao Lower Bound (BCRLB) analysis and numerical simulations are conducted. Our analysis unveils that, by exploiting the potential state information via the general MDBN model, the proposed VBF algorithm provides a promising solution to the online tracking of a mobile node in WSNs. In addition, it is shown that the final tracking accuracy linearly scales with its expectation when the RSS measurement precision is time-varying.

D0 central tracking chamber performance studies

International Nuclear Information System (INIS)

Pizzuto, D.

1991-12-01

The performance of the completed DO central tracking chamber was studied using cosmic rays at the State University of New York at Stony Brook. Also studied was a prototype tracking chamber identical in design to the completed DO tracking chamber. The prototype chamber was exposed to a collimated beam of 150 GeV pions at the Fermilab NWA test facility. Results indicate an RΦ tracking resolution compatible with the limitations imposed by physical considerations, excellent 2 track resolution, and a high track reconstruction efficiency along with a good rejection power against γ → e + e - events

Photon and electron collimator effects on electron output and abutting segments in energy modulated electron therapy

International Nuclear Information System (INIS)

Olofsson, Lennart; Karlsson, Magnus G.; Karlsson, Mikael

2005-01-01

In energy modulated electron therapy a large fraction of the segments will be arranged as abutting segments where inhomogeneities in segment matching regions must be kept as small as possible. Furthermore, the output variation between different segments should be minimized and must in all cases be well predicted. For electron therapy with add-on collimators, both the electron MLC (eMLC) and the photon MLC (xMLC) contribute to these effects when an xMLC tracking technique is utilized to reduce the x-ray induced leakage. Two add-on electron collimator geometries have been analyzed using Monte Carlo simulations: One isocentric eMLC geometry with an isocentric clearance of 35 cm and air or helium in the treatment head, and one conventional proximity geometry with a clearance of 5 cm and air in the treatment head. The electron fluence output for 22.5 MeV electrons is not significantly affected by the xMLC if the shielding margins are larger than 2-3 cm. For small field sizes and 9.6 MeV electrons, the isocentric design with helium in the treatment head or shielding margins larger than 3 cm is needed to avoid a reduced electron output. Dose inhomogeneity in the matching region of electron segments is, in general, small when collimator positions are adjusted to account for divergence in the field. The effect of xMLC tracking on the electron output can be made negligible while still obtaining a substantially reduced x-ray leakage contribution. Collimator scattering effects do not interfere significantly when abutting beam techniques are properly applied

Collimation system for the VUV free-electron laser at the TESLA test facility

International Nuclear Information System (INIS)

Schlarb, H.

2001-11-01

To perform a proof-of-principle experiment for a Free Electron Laser operating at VUV wavelengths an undulator has been installed in the TESLA Test Facility linac phase I. To meet the requirements on the magnetic field quality in the undulator, a hybrid type structure with NdFeB permanent magnets has been chosen. The permanent magnets are sensitive to radiation by high energy particles. In order to perform the various experiments planned at the TESLA Test Facility linac, a collimator section has been installed to protect the undulator from radiation. In this thesis the design, performance and required steps for commissioning the collimator system are presented. To identify potential difficulties for the linac operation, the beam halo and the dark current transport through the entire linac is discussed. Losses of primary electrons caused by technical failures, component misalignments, and operation errors are investigated by tracking simulations, in order to derive a complete understanding of the absorbed dose in the permanent magnets of the undulator. Various topics related to a collimator system such as the removal of secondary particles produced at the collimators, generation and shielding of neutrons, excitation of wake fields, and beam based alignment concepts are important subjects of this thesis. (orig.)

Design a freeform microlens array module for any arbitrary-shape collimated beam shaping and color mixing

Science.gov (United States)

Chen, Enguo; Wu, Rengmao; Guo, Tailiang

2014-06-01

Collimated beam shaping with freeform surface usually employs a predefined mapping to tailor one or multiple freeform surfaces. Limitation on those designs is that the source, the freeform optics and the target are in fixed one-to-one correspondence with each other. To overcome this drawback, this paper presents a kind of freeform microlens array module integrated with an ultra-thin freeform microlens array and a condenser lens to reshape any arbitrary-shape collimated beam into a prescribed uniform rectangular illumination and achieve color mixing. The design theory is explicitly given, and some key issues are addressed. Several different application examples are given, and the target is obtained with high uniformity and energy efficiency. This freeform microlens array module, which shows better flexibility and practicality than the regular designs, can be used not only to reshape any arbitrary-shape collimated beam (or a collimated beam integrated with several sub-collimated beams), but also most importantly to achieve color mixing. With excellent optical performance and ultra-compact volume, this optical module together with the design theory can be further introduced into other applications and will have a huge market potential in the near future.

Target Tracking in 3-D Using Estimation Based Nonlinear Control Laws for UAVs

Directory of Open Access Journals (Sweden)

Mousumi Ahmed

2016-02-01

Full Text Available This paper presents an estimation based backstepping like control law design for an Unmanned Aerial Vehicle (UAV to track a moving target in 3-D space. A ground-based sensor or an onboard seeker antenna provides range, azimuth angle, and elevation angle measurements to a chaser UAV that implements an extended Kalman filter (EKF to estimate the full state of the target. A nonlinear controller then utilizes this estimated target state and the chaser’s state to provide speed, flight path, and course/heading angle commands to the chaser UAV. Tracking performance with respect to measurement uncertainty is evaluated for three cases: (1 stationary white noise; (2 stationary colored noise and (3 non-stationary (range correlated white noise. Furthermore, in an effort to improve tracking performance, the measurement model is made more realistic by taking into consideration range-dependent uncertainties in the measurements, i.e., as the chaser closes in on the target, measurement uncertainties are reduced in the EKF, thus providing the UAV with more accurate control commands. Simulation results for these cases are shown to illustrate target state estimation and trajectory tracking performance.

Location Detection and Tracking of Moving Targets by a 2D IR-UWB Radar System

Directory of Open Access Journals (Sweden)

Van-Han Nguyen

2015-03-01

Full Text Available In indoor environments, the Global Positioning System (GPS and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking.

Image-Based Multi-Target Tracking through Multi-Bernoulli Filtering with Interactive Likelihoods.

Science.gov (United States)

Hoak, Anthony; Medeiros, Henry; Povinelli, Richard J

2017-03-03

We develop an interactive likelihood (ILH) for sequential Monte Carlo (SMC) methods for image-based multiple target tracking applications. The purpose of the ILH is to improve tracking accuracy by reducing the need for data association. In addition, we integrate a recently developed deep neural network for pedestrian detection along with the ILH with a multi-Bernoulli filter. We evaluate the performance of the multi-Bernoulli filter with the ILH and the pedestrian detector in a number of publicly available datasets (2003 PETS INMOVE, Australian Rules Football League (AFL) and TUD-Stadtmitte) using standard, well-known multi-target tracking metrics (optimal sub-pattern assignment (OSPA) and classification of events, activities and relationships for multi-object trackers (CLEAR MOT)). In all datasets, the ILH term increases the tracking accuracy of the multi-Bernoulli filter.

Target Tracking of a Linear Time Invariant System under Irregular Sampling

Directory of Open Access Journals (Sweden)

Jin Xue-Bo

2012-11-01

Full Text Available Due to event-triggered sampling in a system, or maybe with the aim of reducing data storage, tracking many applications will encounter irregular sampling time. By calculating the matrix exponential using an inverse Laplace transform, this paper transforms the irregular sampling tracking problem to the problem of tracking with time-varying parameters of a system. Using the common Kalman filter, the developed method is used to track a target for the simulated trajectory and video tracking. The results of simulation experiments have shown that it can obtain good estimation performance even at a very high irregular rate of measurement sampling time.

Bearings-Only Tracking of Manoeuvring Targets Using Particle Filters

Directory of Open Access Journals (Sweden)

M. Sanjeev Arulampalam

2004-11-01

Full Text Available We investigate the problem of bearings-only tracking of manoeuvring targets using particle filters (PFs. Three different (PFs are proposed for this problem which is formulated as a multiple model tracking problem in a jump Markov system (JMS framework. The proposed filters are (i multiple model PF (MMPF, (ii auxiliary MMPF (AUX-MMPF, and (iii jump Markov system PF (JMS-PF. The performance of these filters is compared with that of standard interacting multiple model (IMM-based trackers such as IMM-EKF and IMM-UKF for three separate cases: (i single-sensor case, (ii multisensor case, and (iii tracking with hard constraints. A conservative CRLB applicable for this problem is also derived and compared with the RMS error performance of the filters. The results confirm the superiority of the PFs for this difficult nonlinear tracking problem.

Postural sway and gaze can track the complex motion of a visual target.

Directory of Open Access Journals (Sweden)

Vassilia Hatzitaki

Full Text Available Variability is an inherent and important feature of human movement. This variability has form exhibiting a chaotic structure. Visual feedback training using regular predictive visual target motions does not take into account this essential characteristic of the human movement, and may result in task specific learning and loss of visuo-motor adaptability. In this study, we asked how well healthy young adults can track visual target cues of varying degree of complexity during whole-body swaying in the Anterior-Posterior (AP and Medio-Lateral (ML direction. Participants were asked to track three visual target motions: a complex (Lorenz attractor, a noise (brown and a periodic (sine moving target while receiving online visual feedback about their performance. Postural sway, gaze and target motion were synchronously recorded and the degree of force-target and gaze-target coupling was quantified using spectral coherence and Cross-Approximate entropy. Analysis revealed that both force-target and gaze-target coupling was sensitive to the complexity of the visual stimuli motions. Postural sway showed a higher degree of coherence with the Lorenz attractor than the brown noise or sinusoidal stimulus motion. Similarly, gaze was more synchronous with the Lorenz attractor than the brown noise and sinusoidal stimulus motion. These results were similar regardless of whether tracking was performed in the AP or ML direction. Based on the theoretical model of optimal movement variability tracking of a complex signal may provide a better stimulus to improve visuo-motor adaptation and learning in postural control.

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

Opportune acquisition and tracking time for the fast-moving targets in a ground-based telescope

Science.gov (United States)

Chen, Juan; Wang, Jianli; Chen, Tao

2004-10-01

Acquisition is defined as identification for a fixed target in the related field of sight (FOS), while tracking means the sway of the telescope's axis of sight (AOS). The automatic acquisition and tracking is a process in which the operating way of the telescope should be switched from guiding to automatic tracking. There are some kinds of method to improve the acquisition and tracking ability for fast moving targets: to extend the acquisition and tracking FOS with memory and storage information of the sensor system; the multimode control to improve the dynamic property of the servo system; to choose an opportune time for acquisition and tracking; to select the control regulator parameter in every working states. If the processor of the CCD sensor can temporarily remember and save the information of the target before it moves out of the FOS, correspondingly, the FOS may be extended. The data forecast technology is used to store the target information. The automatic interception experiments are carried out to verify the control strategy.

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Real-time non-rigid target tracking for ultrasound-guided clinical interventions

Science.gov (United States)

Zachiu, C.; Ries, M.; Ramaekers, P.; Guey, J.-L.; Moonen, C. T. W.; de Senneville, B. Denis

2017-10-01

Biological motion is a problem for non- or mini-invasive interventions when conducted in mobile/deformable organs due to the targeted pathology moving/deforming with the organ. This may lead to high miss rates and/or incomplete treatment of the pathology. Therefore, real-time tracking of the target anatomy during the intervention would be beneficial for such applications. Since the aforementioned interventions are often conducted under B-mode ultrasound (US) guidance, target tracking can be achieved via image registration, by comparing the acquired US images to a separate image established as positional reference. However, such US images are intrinsically altered by speckle noise, introducing incoherent gray-level intensity variations. This may prove problematic for existing intensity-based registration methods. In the current study we address US-based target tracking by employing the recently proposed EVolution registration algorithm. The method is, by construction, robust to transient gray-level intensities. Instead of directly matching image intensities, EVolution aligns similar contrast patterns in the images. Moreover, the displacement is computed by evaluating a matching criterion for image sub-regions rather than on a point-by-point basis, which typically provides more robust motion estimates. However, unlike similar previously published approaches, which assume rigid displacements in the image sub-regions, the EVolution algorithm integrates the matching criterion in a global functional, allowing the estimation of an elastic dense deformation. The approach was validated for soft tissue tracking under free-breathing conditions on the abdomen of seven healthy volunteers. Contact echography was performed on all volunteers, while three of the volunteers also underwent standoff echography. Each of the two modalities is predominantly specific to a particular type of non- or mini-invasive clinical intervention. The method demonstrated on average an accuracy of�

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

Image-Based Multi-Target Tracking through Multi-Bernoulli Filtering with Interactive Likelihoods

Directory of Open Access Journals (Sweden)

Anthony Hoak

2017-03-01

Full Text Available We develop an interactive likelihood (ILH for sequential Monte Carlo (SMC methods for image-based multiple target tracking applications. The purpose of the ILH is to improve tracking accuracy by reducing the need for data association. In addition, we integrate a recently developed deep neural network for pedestrian detection along with the ILH with a multi-Bernoulli filter. We evaluate the performance of the multi-Bernoulli filter with the ILH and the pedestrian detector in a number of publicly available datasets (2003 PETS INMOVE, Australian Rules Football League (AFL and TUD-Stadtmitte using standard, well-known multi-target tracking metrics (optimal sub-pattern assignment (OSPA and classification of events, activities and relationships for multi-object trackers (CLEAR MOT. In all datasets, the ILH term increases the tracking accuracy of the multi-Bernoulli filter.

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

Infrared dim moving target tracking via sparsity-based discriminative classifier and convolutional network

Science.gov (United States)

Qian, Kun; Zhou, Huixin; Wang, Bingjian; Song, Shangzhen; Zhao, Dong

2017-11-01

Infrared dim and small target tracking is a great challenging task. The main challenge for target tracking is to account for appearance change of an object, which submerges in the cluttered background. An efficient appearance model that exploits both the global template and local representation over infrared image sequences is constructed for dim moving target tracking. A Sparsity-based Discriminative Classifier (SDC) and a Convolutional Network-based Generative Model (CNGM) are combined with a prior model. In the SDC model, a sparse representation-based algorithm is adopted to calculate the confidence value that assigns more weights to target templates than negative background templates. In the CNGM model, simple cell feature maps are obtained by calculating the convolution between target templates and fixed filters, which are extracted from the target region at the first frame. These maps measure similarities between each filter and local intensity patterns across the target template, therefore encoding its local structural information. Then, all the maps form a representation, preserving the inner geometric layout of a candidate template. Furthermore, the fixed target template set is processed via an efficient prior model. The same operation is applied to candidate templates in the CNGM model. The online update scheme not only accounts for appearance variations but also alleviates the migration problem. At last, collaborative confidence values of particles are utilized to generate particles' importance weights. Experiments on various infrared sequences have validated the tracking capability of the presented algorithm. Experimental results show that this algorithm runs in real-time and provides a higher accuracy than state of the art algorithms.

On the Impact of Localization and Density Control Algorithms in Target Tracking Applications for Wireless Sensor Networks

Science.gov (United States)

Campos, Andre N.; Souza, Efren L.; Nakamura, Fabiola G.; Nakamura, Eduardo F.; Rodrigues, Joel J. P. C.

2012-01-01

Target tracking is an important application of wireless sensor networks. The networks' ability to locate and track an object is directed linked to the nodes' ability to locate themselves. Consequently, localization systems are essential for target tracking applications. In addition, sensor networks are often deployed in remote or hostile environments. Therefore, density control algorithms are used to increase network lifetime while maintaining its sensing capabilities. In this work, we analyze the impact of localization algorithms (RPE and DPE) and density control algorithms (GAF, A3 and OGDC) on target tracking applications. We adapt the density control algorithms to address the k-coverage problem. In addition, we analyze the impact of network density, residual integration with density control, and k-coverage on both target tracking accuracy and network lifetime. Our results show that DPE is a better choice for target tracking applications than RPE. Moreover, among the evaluated density control algorithms, OGDC is the best option among the three. Although the choice of the density control algorithm has little impact on the tracking precision, OGDC outperforms GAF and A3 in terms of tracking time. PMID:22969329

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...

TU-CD-304-10: Development and Optimization of “Compton Lens” Collimator Design for Increased Dose Rate in SRS

Energy Technology Data Exchange (ETDEWEB)

Shepard, A; Bender, E [The University of Wisconsin-Madison, Madison, WI (United States)

2015-06-15

Purpose: To provide a proof of concept for a new collimator design to increase the dose rate at isocenter for stereotactic radiosurgery (SRS) treatments by taking advantage of off axis Compton scattered photons which are attenuated in current collimators. Methods: A fundamentally new collimator design was developed and optimized by introducing a series of slits to a standard block collimator. The introduction of slits allowed for initially off axis radiation that was scattered in the direction of the target to contribute to the target dose. For optimization, the design was broken into two parts: an upper interaction plate where primary scattering occurs, and a lower “Compton slit” region which allows for scattered photons traveling toward the target to reach isocenter. To optimize the design, a series of simulations were performed using MCNP6 in which several key parameters were adjusted and the output was compared to a standard collimator. Key parameters modified included the collimator material, cone size, and interaction plate thickness. The effects of using energies different than the traditional 6 MV beam were also explored. Results: An optimized collimator design utilizing a solid interaction plate with a Cesium-137 beam and a 4 mm cone size resulted in a dose rate increase on the order of 5% relative to standard collimators in use. Currently, designs incorporating a Cesium-137 source are the most feasible due to necessary size and weight concerns for 6 MV beams. Conclusion: Preliminary designs provide a proof of concept and indicate a potential to improve upon the dose rate of current collimators while not largely compromising the sharp dose falloff inherent to SRS. Further optimization into the geometry and positioning of the interaction plate, as well as slit optimization, will likely lead to further dose rate increases than were observed in this study. Funding for this work was provided by the Wisconsin Alumni Research Foundation (WARF). Authors have

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.

Multi-Target Tracking via Mixed Integer Optimization

Science.gov (United States)

2016-05-13

an easily interpretable global objective function. Furthermore, we propose a greedy heuristic which quickly finds good solutions. We extend both the... heuristic and the MIO model to scenarios with missed detections and false alarms. Index Terms—optimization; multi-target tracking; data asso- ciation...energy in [14] and then again as a minimization of discrete-continuous energy in [15]. These algorithms aim to more accurately represent the nature of the

Optimized swimmer tracking system based on a novel multi-related-targets approach

Science.gov (United States)

Benarab, D.; Napoléon, T.; Alfalou, A.; Verney, A.; Hellard, P.

2017-02-01

Robust tracking is a crucial step in automatic swimmer evaluation from video sequences. We designed a robust swimmer tracking system using a new multi-related-targets approach. The main idea is to consider the swimmer as a bloc of connected subtargets that advance at the same speed. If one of the subtargets is partially or totally occluded, it can be localized by knowing the position of the others. In this paper, we first introduce the two-dimensional direct linear transformation technique that we used to calibrate the videos. Then, we present the classical tracking approach based on dynamic fusion. Next, we highlight the main contribution of our work, which is the multi-related-targets tracking approach. This approach, the classical head-only approach and the ground truth are then compared, through testing on a database of high-level swimmers in training, national and international competitions (French National Championships, Limoges 2015, and World Championships, Kazan 2015). Tracking percentage and the accuracy of the instantaneous speed are evaluated and the findings show that our new appraoach is significantly more accurate than the classical approach.

Measuring coseismic displacements with point-like targets offset tracking

KAUST Repository

Hu, Xie; Wang, Teng; Liao, Mingsheng

2014-01-01

Offset tracking is an important complement to measure large ground displacements in both azimuth and range dimensions where synthetic aperture radar (SAR) interferometry is unfeasible. Subpixel offsets can be obtained by searching for the cross-correlation peak calculated from the match patches uniformly distributed on two SAR images. However, it has its limitations, including redundant computation and incorrect estimations on decorrelated patches. In this letter, we propose a simple strategy that performs offset tracking on detected point-like targets (PT). We first detect image patches within bright PT by using a sinc-like template from a single SAR image and then perform offset tracking on them to obtain the pixel shifts. Compared with the standard method, the application on the 2010 M 7.2 El Mayor-Cucapah earthquake shows that the proposed PT offset tracking can significantly increase the cross-correlation and thus result in both efficiency and reliability improvements. © 2013 IEEE.

Real-time WAMI streaming target tracking in fog

Science.gov (United States)

Chen, Yu; Blasch, Erik; Chen, Ning; Deng, Anna; Ling, Haibin; Chen, Genshe

2016-05-01

Real-time information fusion based on WAMI (Wide-Area Motion Imagery), FMV (Full Motion Video), and Text data is highly desired for many mission critical emergency or security applications. Cloud Computing has been considered promising to achieve big data integration from multi-modal sources. In many mission critical tasks, however, powerful Cloud technology cannot satisfy the tight latency tolerance as the servers are allocated far from the sensing platform, actually there is no guaranteed connection in the emergency situations. Therefore, data processing, information fusion, and decision making are required to be executed on-site (i.e., near the data collection). Fog Computing, a recently proposed extension and complement for Cloud Computing, enables computing on-site without outsourcing jobs to a remote Cloud. In this work, we have investigated the feasibility of processing streaming WAMI in the Fog for real-time, online, uninterrupted target tracking. Using a single target tracking algorithm, we studied the performance of a Fog Computing prototype. The experimental results are very encouraging that validated the effectiveness of our Fog approach to achieve real-time frame rates.

Dazzle camouflage, target tracking, and the confusion effect.

Science.gov (United States)

Hogan, Benedict G; Cuthill, Innes C; Scott-Samuel, Nicholas E

2016-01-01

The influence of coloration on the ecology and evolution of moving animals in groups is poorly understood. Animals in groups benefit from the "confusion effect," where predator attack success is reduced with increasing group size or density. This is thought to be due to a sensory bottleneck: an increase in the difficulty of tracking one object among many. Motion dazzle camouflage has been hypothesized to disrupt accurate perception of the trajectory or speed of an object or animal. The current study investigates the suggestion that dazzle camouflage may enhance the confusion effect. Utilizing a computer game style experiment with human predators, we found that when moving in groups, targets with stripes parallel to the targets' direction of motion interact with the confusion effect to a greater degree, and are harder to track, than those with more conventional background matching patterns. The findings represent empirical evidence that some high-contrast patterns may benefit animals in groups. The results also highlight the possibility that orientation and turning may be more relevant in the mechanisms of dazzle camouflage than previously recognized.

Automatic Prostate Tracking and Motion Assessment in Volumetric Modulated Arc Therapy With an Electronic Portal Imaging Device

International Nuclear Information System (INIS)

Azcona, Juan Diego; Li, Ruijiang; Mok, Edward; Hancock, Steven; Xing, Lei

2013-01-01

Purpose: To assess the prostate intrafraction motion in volumetric modulated arc therapy treatments using cine megavoltage (MV) images acquired with an electronic portal imaging device (EPID). Methods and Materials: Ten prostate cancer patients were treated with volumetric modulated arc therapy using a Varian TrueBeam linear accelerator equipped with an EPID for acquiring cine MV images during treatment. Cine MV images acquisition was scheduled for single or multiple treatment fractions (between 1 and 8). A novel automatic fiducial detection algorithm that can handle irregular multileaf collimator apertures, field edges, fast leaf and gantry movement, and MV image noise and artifacts in patient anatomy was used. All sets of images (approximately 25,000 images in total) were analyzed to measure the positioning accuracy of implanted fiducial markers and assess the prostate movement. Results: Prostate motion can vary greatly in magnitude among different patients. Different motion patterns were identified, showing its unpredictability. The mean displacement and standard deviation of the intrafraction motion was generally less than 2.0 ± 2.0 mm in each of the spatial directions. In certain patients, however, the percentage of the treatment time in which the prostate is displaced more than 5 mm from its planned position in at least 1 spatial direction was 10% or more. The maximum prostate displacement observed was 13.3 mm. Conclusion: Prostate tracking and motion assessment was performed with MV imaging and an EPID. The amount of prostate motion observed suggests that patients will benefit from its real-time monitoring. Megavoltage imaging can provide the basis for real-time prostate tracking using conventional linear accelerators

Fast leaf-fitting with generalized underdose/overdose constraints for real-time MLC tracking

Energy Technology Data Exchange (ETDEWEB)

Moore, Douglas, E-mail: douglas.moore@utsouthwestern.edu; Sawant, Amit [Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, Texas 75390 (United States); Ruan, Dan [Department of Radiation Oncology, University of California, Los Angeles, California 90095 (United States)

2016-01-15

Purpose: Real-time multileaf collimator (MLC) tracking is a promising approach to the management of intrafractional tumor motion during thoracic and abdominal radiotherapy. MLC tracking is typically performed in two steps: transforming a planned MLC aperture in response to patient motion and refitting the leaves to the newly generated aperture. One of the challenges of this approach is the inability to faithfully reproduce the desired motion-adapted aperture. This work presents an optimization-based framework with which to solve this leaf-fitting problem in real-time. Methods: This optimization framework is designed to facilitate the determination of leaf positions in real-time while accounting for the trade-off between coverage of the PTV and avoidance of organs at risk (OARs). Derived within this framework, an algorithm is presented that can account for general linear transformations of the planned MLC aperture, particularly 3D translations and in-plane rotations. This algorithm, together with algorithms presented in Sawant et al. [“Management of three-dimensional intrafraction motion through real-time DMLC tracking,” Med. Phys. 35, 2050–2061 (2008)] and Ruan and Keall [Presented at the 2011 IEEE Power Engineering and Automation Conference (PEAM) (2011) (unpublished)], was applied to apertures derived from eight lung intensity modulated radiotherapy plans subjected to six-degree-of-freedom motion traces acquired from lung cancer patients using the kilovoltage intrafraction monitoring system developed at the University of Sydney. A quality-of-fit metric was defined, and each algorithm was evaluated in terms of quality-of-fit and computation time. Results: This algorithm is shown to perform leaf-fittings of apertures, each with 80 leaf pairs, in 0.226 ms on average as compared to 0.082 and 64.2 ms for the algorithms of Sawant et al., Ruan, and Keall, respectively. The algorithm shows approximately 12% improvement in quality-of-fit over the Sawant et al

Fast leaf-fitting with generalized underdose/overdose constraints for real-time MLC tracking

International Nuclear Information System (INIS)

Moore, Douglas; Sawant, Amit; Ruan, Dan

2016-01-01

Purpose: Real-time multileaf collimator (MLC) tracking is a promising approach to the management of intrafractional tumor motion during thoracic and abdominal radiotherapy. MLC tracking is typically performed in two steps: transforming a planned MLC aperture in response to patient motion and refitting the leaves to the newly generated aperture. One of the challenges of this approach is the inability to faithfully reproduce the desired motion-adapted aperture. This work presents an optimization-based framework with which to solve this leaf-fitting problem in real-time. Methods: This optimization framework is designed to facilitate the determination of leaf positions in real-time while accounting for the trade-off between coverage of the PTV and avoidance of organs at risk (OARs). Derived within this framework, an algorithm is presented that can account for general linear transformations of the planned MLC aperture, particularly 3D translations and in-plane rotations. This algorithm, together with algorithms presented in Sawant et al. [“Management of three-dimensional intrafraction motion through real-time DMLC tracking,” Med. Phys. 35, 2050–2061 (2008)] and Ruan and Keall [Presented at the 2011 IEEE Power Engineering and Automation Conference (PEAM) (2011) (unpublished)], was applied to apertures derived from eight lung intensity modulated radiotherapy plans subjected to six-degree-of-freedom motion traces acquired from lung cancer patients using the kilovoltage intrafraction monitoring system developed at the University of Sydney. A quality-of-fit metric was defined, and each algorithm was evaluated in terms of quality-of-fit and computation time. Results: This algorithm is shown to perform leaf-fittings of apertures, each with 80 leaf pairs, in 0.226 ms on average as compared to 0.082 and 64.2 ms for the algorithms of Sawant et al., Ruan, and Keall, respectively. The algorithm shows approximately 12% improvement in quality-of-fit over the Sawant et al

The pitfalls of dosimetric commissioning for intensity modulated radiation therapy

International Nuclear Information System (INIS)

Tohyama, Naoki; Kodama, Takashi; Hatano, K.

2013-01-01

Intensity modulated radiation therapy (IMRT) allows higher radiation dose to be focused to the target volumes while minimizing the dose to OAR. To start of clinical treatment in IMRTvwe must perform commissioning strictly than 3D-conformal radiotherapy (CRT). In this report, pitfalls of dosimetric commissioning for intensity modulated radiation therapy were reviewed. Multileaf collimator (MLC) offsets and MLC transmissions are important parameters in commissioning of RTPS for IMRT. Correction of depth scaling and fluence scaling is necessary for dose measurement using solid phantom. (author)

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.

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

Reflector automatic acquisition and pointing based on auto-collimation theodolite

Science.gov (United States)

Luo, Jun; Wang, Zhiqian; Wen, Zhuoman; Li, Mingzhu; Liu, Shaojin; Shen, Chengwu

2018-01-01

An auto-collimation theodolite (ACT) for reflector automatic acquisition and pointing is designed based on the principle of autocollimators and theodolites. First, the principle of auto-collimation and theodolites is reviewed, and then the coaxial ACT structure is developed. Subsequently, the acquisition and pointing strategies for reflector measurements are presented, which first quickly acquires the target over a wide range and then points the laser spot to the charge coupled device zero position. Finally, experiments are conducted to verify the acquisition and pointing performance, including the calibration of the ACT, the comparison of the acquisition mode and pointing mode, and the accuracy measurement in horizontal and vertical directions. In both directions, a measurement accuracy of ±3″ is achieved. The presented ACT is suitable for automatic pointing and monitoring the reflector over a small scanning area and can be used in a wide range of applications such as bridge structure monitoring and cooperative target aiming.