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Evaluation of jaws-only intensity modulated radiation therapy treatment plans using Octavius 4D system. POLISH JOURNAL OF MEDICAL PHYSICS AND ENGINEERING 2018. [DOI: 10.2478/pjmpe-2018-0010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Abstract
Introduction: Jaws-Only Intensity modulated radiation therapy (JO-IMRT) is a technique uses the collimator jaws of the linear accelerator (LINAC) to delivery of complex intensity patterns. In previous studies, pretreatment patient specific quality assurance for those JO-IMRT were also performed using ionization chamber, MapCHECK2, and Octavius 4D and good agreements were shown. The aim of this study is to further verify JO-IMRT plans in 2 different cases: one with the gantry angle set equal to beam angle as in the plans and the other with gantry angle set to zero degree.
Materials and Methods: Twenty-five JO-IMRT, previously verified, were executed twice for each plan. The first one used a real gantry angle, and the second one used a 0° gantry angle. Measurements were performed using Octavius 4D 1500.
Results: The results were analyzed using Verisoft software. The results show that the Gamma average was 97.32 ± 2.21% for IMRT with a 0° gantry angle and 94.72 ± 2.67% for IMRT with a true gantry angle.
Conclusion: In both cases, gamma index of more than 90% were found for all of our 25 JO-IMRT treatment plans.
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2
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Quality assurance of the jaws only-intensity modulated radiation therapy plans for head-and-neck cancer. Phys Med 2017; 38:148-152. [PMID: 28571708 DOI: 10.1016/j.ejmp.2017.05.059] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 04/29/2017] [Accepted: 05/18/2017] [Indexed: 11/20/2022] Open
Abstract
Intensity-modulated radiation therapy (IMRT) is a treatment technique which has become routine in developed countries. In most centers this technique is delivered with multi-leaf collimators (MLCs). However, the use of MLCs is not mandatory. Several oncology centres in developing countries are still using linear accelerators (LINAC) without MLCs, and can potentially deliver IMRT plans with the use of collimator jaws. In this report, we present the results of quality assurance of this Jaws-Only-IMRT (JO-IMRT) technique in treating nasopharyngeal carcinoma (NPC) patients. Twenty-five plans of nasopharyngeal patients were randomly chosen. For each patient, a JO-IMRT plan was generated and a series of pre-treatment verification measurements was performed including (1) point dose measurement with an ionization chamber, (2) planar dose measurement with a 2D-array detector and (3) 3-dimensional dose measurement using a rotatable phantom with a 2D-array detector. The average differences between the measured and TPS-calculated point doses were found to be 1.26±0.77%, which is within the institution's dose constraint limits. For the planar dose and 3D dose measurements, the average gamma index based on 3%/3mm criteria were 96.77±2.33% and 94.72±2.67%, respectively. Our measurements showed that the JO-IMRT treatment plans applied to the H&N patients were accurate for the treatment delivery based on our established pass criteria.
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Nguyen D, Ruan D, O'Connor D, Woods K, Low DA, Boucher S, Sheng K. A novel software and conceptual design of the hardware platform for intensity modulated radiation therapy. Med Phys 2016; 43:917-29. [PMID: 26843252 DOI: 10.1118/1.4940353] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
PURPOSE To deliver high quality intensity modulated radiotherapy (IMRT) using a novel generalized sparse orthogonal collimators (SOCs), the authors introduce a novel direct aperture optimization (DAO) approach based on discrete rectangular representation. METHODS A total of seven patients-two glioblastoma multiforme, three head & neck (including one with three prescription doses), and two lung-were included. 20 noncoplanar beams were selected using a column generation and pricing optimization method. The SOC is a generalized conventional orthogonal collimators with N leaves in each collimator bank, where N = 1, 2, or 4. SOC degenerates to conventional jaws when N = 1. For SOC-based IMRT, rectangular aperture optimization (RAO) was performed to optimize the fluence maps using rectangular representation, producing fluence maps that can be directly converted into a set of deliverable rectangular apertures. In order to optimize the dose distribution and minimize the number of apertures used, the overall objective was formulated to incorporate an L2 penalty reflecting the difference between the prescription and the projected doses, and an L1 sparsity regularization term to encourage a low number of nonzero rectangular basis coefficients. The optimization problem was solved using the Chambolle-Pock algorithm, a first-order primal-dual algorithm. Performance of RAO was compared to conventional two-step IMRT optimization including fluence map optimization and direct stratification for multileaf collimator (MLC) segmentation (DMS) using the same number of segments. For the RAO plans, segment travel time for SOC delivery was evaluated for the N = 1, N = 2, and N = 4 SOC designs to characterize the improvement in delivery efficiency as a function of N. RESULTS Comparable PTV dose homogeneity and coverage were observed between the RAO and the DMS plans. The RAO plans were slightly superior to the DMS plans in sparing critical structures. On average, the maximum and mean critical organ doses were reduced by 1.94% and 1.44% of the prescription dose. The average number of delivery segments was 12.68 segments per beam for both the RAO and DMS plans. The N = 2 and N = 4 SOC designs were, on average, 1.56 and 1.80 times more efficient than the N = 1 SOC design to deliver. The mean aperture size produced by the RAO plans was 3.9 times larger than that of the DMS plans. CONCLUSIONS The DAO and dose domain optimization approach enabled high quality IMRT plans using a low-complexity collimator setup. The dosimetric quality is comparable or slightly superior to conventional MLC-based IMRT plans using the same number of delivery segments. The SOC IMRT delivery efficiency can be significantly improved by increasing the leaf numbers, but the number is still significantly lower than the number of leaves in a typical MLC.
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Affiliation(s)
- Dan Nguyen
- Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California 90024
| | - Dan Ruan
- Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California 90024
| | - Daniel O'Connor
- Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California 90024
| | - Kaley Woods
- Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California 90024
| | - Daniel A Low
- Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California 90024
| | | | - Ke Sheng
- Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California 90024
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Jensen MD, Hrinivich WT, Jung JA, Holdsworth DW, Drangova M, Chen J, Wong E. Implementation and commissioning of an integrated micro-CT/RT system with computerized independent jaw collimation. Med Phys 2013; 40:081706. [DOI: 10.1118/1.4812422] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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5
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Webb S. The fish (IMRT) needs a bicycle (MLC)? The bicycle factories seem flourishing; not so the goldfish-bowl factories. Phys Med 2011; 27:177-80. [DOI: 10.1016/j.ejmp.2010.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 12/21/2010] [Indexed: 10/18/2022] Open
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6
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Salari E, Men C, Romeijn HE. Accounting for the tongue-and-groove effect using a robust direct aperture optimization approach. Med Phys 2011; 38:1266-79. [PMID: 21520839 DOI: 10.1118/1.3547722] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Traditionally, the tongue-and-groove effect due to the multileaf collimator architecture in intensity-modulated radiation therapy (IMRT) has typically been deferred to the leaf sequencing stage. The authors propose a new direct aperture optimization method for IMRT treatment planning that explicitly incorporates dose calculation inaccuracies due to the tongue-and-groove effect into the treatment plan optimization stage. METHODS The authors avoid having to accurately estimate the dosimetric effects of the tongue-and-groove architecture by using lower and upper bounds on the dose distribution delivered to the patient. They then develop a model that yields a treatment plan that is robust with respect to the corresponding dose calculation inaccuracies. RESULTS Tests on a set of ten clinical head-and-neck cancer cases demonstrate the effectiveness of the new method in developing robust treatment plans with tight dose distributions in targets and critical structures. This is contrasted with the very loose bounds on the dose distribution that are obtained by solving a traditional treatment plan optimization model that ignores tongue-and-groove effects in the treatment planning stage. CONCLUSIONS A robust direct aperture optimization approach is proposed to account for the dosimetric inaccuracies caused by the tongue-and-groove effect. The experiments validate the ability of the proposed approach in designing robust treatment plans regardless of the exact consequences of the tongue-and-groove architecture.
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Affiliation(s)
- Ehsan Salari
- Department of Industrial and Systems Engineering, University of Florida, Gainesville, Florida 32611-6595, USA.
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7
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Webb S, Poludniowski G. Intensity-modulated radiation therapy (IMRT) by a dynamic-jaws-only (DJO) technique in rotate-translate mode. Phys Med Biol 2010; 55:N495-506. [PMID: 20938068 DOI: 10.1088/0031-9155/55/21/n01] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In this note it is shown how the use of a rotate-translate methodology employing only jaws, which move dynamically with the beam continuously on, can lead to a delivery of a two-dimensional intensity-modulated beam wherein the modulation is spatially slowly varying. All that is necessary is that a pair of jaws sweep across the face of an accelerator with the aperture between them suitably varying in width and defined by a position-time trajectory function for each jaw. This is then repeated, at the same gantry angle, with the jaws rotated to a different head twist and with a different jaw-pair trajectory for a number of sequential head twists. The result of superposing the individual beams at the same gantry angle is a two-dimensional variation of fluence at this gantry angle. A powerful theorem is developed which shows that there is an infinity of jaw trajectories for some specified number of head twists, each of which corresponds to the same delivered two-dimensional modulated beam.
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Affiliation(s)
- S Webb
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM25PT, UK
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8
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Webb S, Poludniowski G. Delivery of two-dimensional spatially-slowly-varying intensity-modulated beams by jaws only (JO) in rotate-translate mode. Phys Med Biol 2010; 55:L21-7. [PMID: 20348607 DOI: 10.1088/0031-9155/55/8/l01] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
IMRT can be delivered by jaws only (JO) provided some compromises are accepted. In this letter it is shown how the use of a rotate-translate methodology (ROTJO), also employing only jaws, can lead to the delivery of a two-dimensional intensity-modulated beam wherein the modulation is spatially slowly varying.
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9
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Mu G, Xia P. A feasibility study of using conventional jaws to deliver complex IMRT plans for head and neck cancer. Phys Med Biol 2009; 54:5613-23. [DOI: 10.1088/0031-9155/54/18/017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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10
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Zhang Y, Hu Y, Ma L, Dai J. Dynamic delivery of IMRT using an independent collimator: a model study. Phys Med Biol 2009; 54:2527-39. [DOI: 10.1088/0031-9155/54/8/018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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11
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Men C, Romeijn HE, Taşkın ZC, Dempsey JF. An exact approach to direct aperture optimization in IMRT treatment planning. Phys Med Biol 2007; 52:7333-52. [DOI: 10.1088/0031-9155/52/24/009] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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12
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Kim Y, Verhey LJ, Xia P. A feasibility study of using conventional jaws to deliver IMRT plans in the treatment of prostate cancer. Phys Med Biol 2007; 52:2147-56. [PMID: 17404460 DOI: 10.1088/0031-9155/52/8/007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The aim of this study is to investigate the feasibility of using conventional jaws to deliver inverse planned intensity-modulated radiotherapy (IMRT) plans for patients with prostate cancer. For ten patients, each had one three-dimensional conformal plan (3D plan) and seven inverse IMRT plans using direct aperture optimization. For IMRT plans using conventional jaws (JO plans), the number of apertures per beam angle was set from two to seven while three apertures per beam angle were set for the multi-leaf collimator (MLC) plans. To evaluate each planning method, we compared average dose volume histograms (DVH), the conformal index (COIN), total number of segments and total number of monitor units. Among the JO plans with the number of apertures per beam angle varying from two to seven, no difference was observed in the average DVHs, and the plan conformal index became saturated after four apertures per beam angle. Subsequently, JO plans with four apertures per beam angle (JO-4A) were compared with 3D and MLC plans. Based on the average DVHs, no difference was found among 3D, JO-4A and MLC plans with regard to the planning target volume and rectum, but the DVHs for the bladder and penile bulb were significantly better with inverse IMRT plans than those with 3D plans. When compared with the plan conformity, the average COIN values for 3D, JO-4A and MLC plans were 0.61 +/- 0.07, 0.73 +/- 0.05 and 0.83 +/- 0.05, respectively. In conclusion, inverse IMRT plans using conventional jaws are clinically feasible, achieving better plan quality than 3D-CRT plans.
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Affiliation(s)
- Yongbok Kim
- Department of Radiation Oncology, University of California, San Francisco, Comprehensive Cancer Center, 1600 Divisadero Street, Suite H1031, San Francisco, CA 94143-1708, USA
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13
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Fenwick JD, Tomé WA, Soisson ET, Mehta MP, Rock Mackie T. Tomotherapy and other innovative IMRT delivery systems. Semin Radiat Oncol 2007; 16:199-208. [PMID: 17010902 DOI: 10.1016/j.semradonc.2006.04.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Fixed-field treatments, delivered using conventional clinical linear accelerators fitted with multileaf collimators, have rapidly become the standard form of intensity-modulated radiotherapy (IMRT). Several innovative nonstandard alternatives also exist, for which delivery and treatment planning systems are now commercially available. Three of these nonstandard IMRT approaches are reviewed here: tomotherapy, robotic linear accelerators (CyberKnife, Accuray Inc., Sunnyvale, CA), and standard linear accelerators modulated by jaws alone or by their jaws acting together with a tertiary beam-masking device. Rationales for the nonstandard IMRT approaches are discussed, and elements of their delivery system designs are briefly described. Differences between fixed-field IMRT dose distributions and the distributions that can be delivered by using the nonstandard technologies are outlined. Because conventional linear accelerators are finely honed machines, innovative design enhancement of one aspect of system performance often limits another facet of machine capability. Consequently the various delivery systems may prove optimal for different types of treatment, with specific machine designs excelling for disease sites with specific target volume and normal structure topologies. However it is likely that the delivery systems will be distinguished not just by the optimality of the dose distributions they deliver, but also by factors such as the efficiency of their treatment process, the integration of their onboard imaging systems into that process, and their ability to measure and minimize or compensate for target movement, including the effects of respiratory motion.
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Affiliation(s)
- John D Fenwick
- Department of Medical Physics, Clatterbridge Centre for Oncology, Wirral, United Kingdom.
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14
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Earl MA, Afghan MKN, Yu CX, Jiang Z, Shepard DM. Jaws-only IMRT using direct aperture optimization. Med Phys 2006; 34:307-14. [PMID: 17278516 DOI: 10.1118/1.2403966] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Using direct aperture optimization, we have developed an inverse planning approach that is capable of producing efficient intensity modulated radiotherapy (IMRT) treatment plans that can be delivered without a multileaf collimator. This "jaws-only" approach to IMRT uses a series of rectangular field shapes to achieve a high degree of intensity modulation from each beam direction. Direct aperture optimization is used to directly optimize the jaw positions and the relative weights assigned to each aperture. Because the constraints imposed by the jaws are incorporated into the optimization, the need for leaf sequencing is eliminated. Results are shown for five patient cases covering three treatment sites: pancreas, breast, and prostate. For these cases, between 15 and 20 jaws-only apertures were required per beam direction in order to obtain conformal IMRT treatment plans. Each plan was delivered to a phantom, and absolute and relative dose measurements were recorded. The typical treatment time to deliver these plans was 18 min. The jaws-only approach provides an additional IMRT delivery option for clinics without a multileaf collimator.
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Affiliation(s)
- M A Earl
- University of Maryland School of Medicine, Department of Radiation Oncology, 22 South Greene St., Baltimore, Maryland 21201-1595, USA.
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15
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Sasaki K, Obata Y. Dosimetric characteristics of a cubic-block-piled compensator for intensity-modulated radiation therapy in the Pinnacle radiotherapy treatment planning system. J Appl Clin Med Phys 2006; 8:85-100. [PMID: 17592450 PMCID: PMC5722403 DOI: 10.1120/jacmp.v8i1.2323] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 11/23/2006] [Accepted: 12/31/1969] [Indexed: 11/24/2022] Open
Abstract
We examined the dose distributions generated by Pinnacle3 (Philips Radiation Oncology Systems, Milpitas, CA) for intensity‐modulated radiotherapy (IMRT) plans using a cubic‐block‐piled compensator as the intensity modulator for 4‐MV and 10‐MV photon beams. The Pinnacle treatment planning system (TPS) uses an algorithm in which only the physical density of the absorber is required for calculating the characteristics of the modulator. The intensity modulator consists of cubic blocks (attenuator) of a tungsten alloy, plus cubic blocks of polyethylene resin foam that fill the spaces between the attenuator blocks and polymethyl methacrylate (PMMA) boards that act as the platform for the modulator. By measuring the transmission for various thicknesses of attenuator and by deriving values for the total physical density of the modulator, we determined the optimal effective density by comparing the curves fitted for the actual transmission data with the transmission calculated by the TPS. Using these effective densities, we examined the accuracy of Pinnacle3 for dose profiles of specific geometric patterns. The levels of consistency between the measurements and the calculations were within a tolerance of 3% of the dose difference and had a 3‐mm distance to agreement for the ladder‐, stairstep‐, and pyramid‐shaped test patterns, except in the high dose gradient region. In this modulator assembly, leakage occurred from the slits between the cubic blocks. This leakage was about 1.6% at maximum, and its influence on dose distribution was not crucial. In the TPS, in which physical density was the only user‐controllable parameter, we used the effective density of the absorber deduced from the effective mass attenuation coefficient. We conclude that the intensity modulation compensator system, together with a piled cubic attenuator, is clinically applicable, with an acceptable tolerance level. For the intensity map of the IMRT plan, measurements in treatment fields met 3% and 3‐mm criteria, excluding some regions of high gradient, which had a discrepancy of less than 5% and 4 mm. PACS numbers: 87.53.Mr, 87.53.Tf
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Affiliation(s)
- Koji Sasaki
- Department of Radiological and Medical Sciences, Nagoya University Graduate School of Medicine, Daiko-Minami, Higashi-ku, Nagoya, Japan.
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16
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Anderson JW, Symonds-Tayler R, Webb S. Investigating the fundamentals of IMRT decomposition using ten simple collimator models. Phys Med Biol 2006; 51:2225-36. [PMID: 16625038 DOI: 10.1088/0031-9155/51/9/008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The fundamentals of IMRT collimation have been studied using ten conceptual collimators. Spanning a range of complexities from the LINAC jaws alone to a full multi-leaf collimator (MLC), these collimators were designed with two abilities in mind: (1) to be able to define arbitrary field shapes, and (2) to be able to irradiate multiple, disconnected regions in a single segment. The collimators were tested by finding decompositions of random and clinical intensity-modulated beams (IMBs), and collimator performance was measured using both the number of segments required to complete the IMB and the monitor-unit efficiency of the treatment. The decompositions were run on 10 x 10 IMBs with integer bixel values randomly between 1 and 10, and clinical IMBs of varying sizes from lung, head and neck, and pelvic patients taken from a Pinnacle treatment-planning system. Results confirmed that although treatment performance improves with increased collimator complexity, it is not solely dependent on the number of segment shapes deliverable by the collimator but instead on how well these shapes lend themselves to IMRT delivery.
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Affiliation(s)
- J W Anderson
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT, UK.
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17
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Anderson JW, Symonds-Tayler R, Hartmann G, Echner G, Lang C, Schlegel W, Webb S. Comparative efficiency of the multi-leaf collimator and variable-aperture collimator in intensity-modulated radiotherapy. Phys Med Biol 2006; 51:1725-36. [PMID: 16552100 DOI: 10.1088/0031-9155/51/7/006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The potential of the variable-aperture collimator (VAC) in intensity-modulated radiation therapy (IMRT) has been evaluated by comparing its performance with that of the multi-leaf collimator (MLC). This comparison used a decomposition algorithm to find the series of collimator segments that would treat a given intensity-modulated beam (IMB). Collimator performance was measured using both the number of segments required to complete the IMB and the monitor-unit efficiency of the treatment. The VAC was modelled with aperture sizes from 4 x 4 cm to 20 x 20 cm, and these apertures were allowed to be located anywhere within the IMB. To enable a direct comparison, a similar scanning MLC was modelled at the same range of aperture sizes. Using both collimators, decompositions were run on 10 x 10 and 20 x 20 random IMBs with integer bixel values ranging from 1 to 10. Clinical IMBs from lung, head and neck, and pelvic patients were taken from a Pinnacle treatment-planning system and tested in the same manner. It was found that for all treatment sites, a small, scanning MLC performs as well or better than an equivalent sized VAC in both number of segments and monitor-unit efficiency, and would be an efficient choice for centres looking for a simple collimator for IMRT.
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Affiliation(s)
- J W Anderson
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT, UK.
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Abstract
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 degrees . 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.
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Affiliation(s)
- R Topolnjak
- Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands.
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19
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Wang D, Hill RW, Lam S. A new algorithm for determining collimator angles that favor efficiency in MLC based IMRT delivery. Med Phys 2004; 31:1249-53. [PMID: 15191316 DOI: 10.1118/1.1696708] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A new algorithm to determine collimator angles that favor delivery efficiency of intensity modulated radiotherapy plans was developed. It was found that the number of segments and monitor units (MUs) were largely reduced with the set of collimator angles determined with the new algorithm without compromising plan quality. The improvement of delivery efficiency using the new algorithm depends on the size and shape of the target(s), the number of modulation levels, and the type of leaf-sequencing algorithm. In a typical prostate case, when a sweeping leaf-sequencer is used for Varian 120 leaf (0.5 x 0.5 cm2 beamlet), 80 leaf (1 x 1 cm2 beamlet) and Elekta 40 leaf (1 x 1 cm2 beamlet), the number of segments was reduced by 42%, 29%, and 5%, respectively. The number of MUs was reduced by 41%, 35%, and 10%. For the Siemens MLC (IMFAST leaf sequencer, 1 x 1 cm2 beamlet) the segment reduction was 32% and the MU reduction was 14%. Comparison of the plans using the new and Brahme algorithms, in terms of target conformity index and dose volume histogram of the organs at risk, showed that the quality of the plans using the new algorithm was uncompromised. Similar results were obtained for a set of head and neck treatment plans.
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Affiliation(s)
- David Wang
- Cancer Care Group, PC, Medical Physics, 950 North Meridian Street, Suite 920, Indianapolis, Indiana 46204, USA
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Webb S, Hartmann G, Echner G, Schlegel W. Intensity-modulated radiation therapy using a variable-aperture collimator. Phys Med Biol 2003; 48:1223-38. [PMID: 12765333 DOI: 10.1088/0031-9155/48/9/310] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This paper extends some earlier concepts of using a tertiary mask plus jaws for delivering IMRT without a multileaf collimator. The new concept is to sweep a variable-aperture collimator (VAC) across the space of the intensity-modulated beam (IMB) to be delivered and to strip this IMB down into multiple-static-field components, each deliverable with the VAC. The stripping algorithm is described and it is shown, for several designs of VAC, that the mean number of field components and mean number of monitor units is less using the VAC than would be required for a jaws-only (JO) decomposition. The VAC would be simpler to construct than several previously suggested jaws-plus-mask (J+M) combinations. As well as describing a simple VAC for the use with jaws, we propose a design concept of a hybrid VAC. We also show that adding the potential to rotate the simple or hybrid VAC for some components relative to the field to be modulated is advantageous.
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Affiliation(s)
- S Webb
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Trust, Downs Road, Sutton, Surrey, SM2 5PT, UK
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Crooks SM, McAven LF, Robinson DF, Xing L. Minimizing delivery time and monitor units in static IMRT by leaf-sequencing. Phys Med Biol 2002; 47:3105-16. [PMID: 12361213 DOI: 10.1088/0031-9155/47/17/305] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Intensity-modulated radiation therapy (IMRT) requires the determination of the appropriate multileaf collimator settings to deliver an intensity map. The purpose of this work was to attempt to reduce the number of segments required for IMRT delivery and the number of monitor units required to deliver an intensity map. An intensity map may be written as a matrix. Leaf sequencing was formulated as a problem of decomposing the matrix into a series of sub-matrices. Sets of random intensity matrices were created and the segmentations produced by applying different algorithms were compared. The number of segments, important if verification and record (VR) overhead is significant, and beam on times were examined. It is shown that reducing the value of the matrix entries by the maximum amount at each stage results in the smallest number of steps. Reducing the 2-norm (sum of the squares) of the matrix entries by the maximum amount at each step results in the smallest beam on time. Three new algorithms are introduced, two of which produce results that are superior to those generated by the algorithms of other researchers. The resulting methods can be expanded upon to include tongue and groove effects and leaf inter-digitization. With square random matrices of the order 15, the reduction in beam time and segmentation is up to 30-40%. Compared to previous algorithms, those presented here have demonstrated a reduction in the beam on time required to deliver an intensity map by 30-40%. Similarly, the number of segments needed to deliver an intensity map is also reduced.
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Affiliation(s)
- S M Crooks
- Department of Radiation Oncology, Stanford Medical Center, Palo Alto, CA, USA
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Abstract
For intensity-modulated radiation therapy (IMRT), a simple technique is described which splits any N x N matrix I of fluences into two mathematically equivalent matrices IA and IB summing to 21, each of which requires considerably fewer segments to deliver IMRT using the jaws-plus-mask technique (Webb 2002b). When IA and IB are delivered alternately at fractions throughout the treatment, the total number of field segments required is between 1/2 and 2/3 that of delivering matrix I when unadjusted.
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Affiliation(s)
- Steve Webb
- Joint Department of Physics, Institute of Cancer Research, Royal Marsden NHS Trust, Sutton, Surrey, UK
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Webb S. Intensity-modulated radiation therapy using only jaws and a mask: II. A simplified concept of relocatable single-bixel attenuators. Phys Med Biol 2002; 47:1869-79. [PMID: 12108772 DOI: 10.1088/0031-9155/47/11/303] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Intensity-modulated radiation therapy (IMRT) can be delivered inefficiently using the movable jaws of a linac. The efficiency can be much improved by delivering IMRT with the movable jaws together with a relocatable mask below the jaws (Webb 2002 Phys. Med. Biol. 47 257-75). This paper extends the modelling work by showing that a much simpler relocatable mask than previously conceptualized can lead to very similar improvements in monitor-unit efficiency and a decrease in the number of field components compared with the use of jaws only (JO). The new concept comprises a set of relocatable single-bixel attenuators (SBAs) which can be moved into the field components otherwise collimated by jaws only. Typically for a 15 x 15 bixel2 2D matrix of fluence with a peak value of Ip = 10 MUs (or equivalently ten stratified fluence levels) and using just four SBAs the MU-efficiency is nearly three times that of the JO technique and the number of field components is reduced to about 0.6 the number required by the JO technique. These gains become greater by using more SBAs or for larger Ip values. Component reordering was achieved to minimize the total delivery time including intersegment deadtimes. Practicalities are discussed.
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Affiliation(s)
- Steve Webb
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Trust, Sutton, Surrey, UK
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Abstract
Intensity-modulated radiation therapy (IMRT) generally requires complex equipment for delivery. Just one study has investigated the use of 'jaws-only' IMRT with not discouraging conclusions. However, the monitor-unit efficiency is still considered to be too low compared with the use of a multileaf collimator (MLC). In this paper a new IMRT delivery technique is proposed which does not require the MLC and is only moderately more complex than the use of jaws alone. In this method a secondary collimator (mask) is employed together with the jaws. This mask may translate parallel to the jaw axes. Two types of mask have been investigated. One is a regular binary-attenuation pattern and the other is a random binary-attenuation pattern. Studies show that the monitor-unit efficiency of this 'jaws-plus-mask' technique, with a random binary mask, is more than double that of the jaws-only technique for typical two-dimensional intensity-modulated beams of size 10 x 10 bixels2 and with a peak value of 10 MU (or quantized into 10 fluence increments). For two-dimensional intensity-modulated beams of size 15 x 15 bixels2 with a peak value of 10 MU (or quantized into 10 fluence increments), the monitor-unit efficiency of the 'jaws-plus-mask' technique with a random binary mask is almost triple that of the jaws-only technique. Some further extensions to this concept are presented showing that some more practical mask arrangements are possible but with somewhat compromised monitor-unit efficiency. Some comments are provided on practicalities and on delivery times.
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Affiliation(s)
- Steve Webb
- Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Trust, Sutton, Surrey, UK
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Langer M, Thai V, Papiez L. Improved leaf sequencing reduces segments or monitor units needed to deliver IMRT using multileaf collimators. Med Phys 2001; 28:2450-8. [PMID: 11797948 DOI: 10.1118/1.1420392] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Leaf sequencing algorithms may use an unnecessary number of monitor units or segments to generate intensity maps for delivery of intensity modulated radiotherapy (IMRT) using multiple static fields. An integer algorithm was devised to generate a sequence with the fewest possible segments when the minimum number of monitor units are used. Special hardware related restrictions on leaf motion can be incorporated. The algorithm was tested using a benchmark map from the literature and clinical examples. Results were compared to sequences given by the routine of Bortfeld that minimizes monitor units by treating each row independently, and the areal or reducing routines that use fewer segments at the price of more monitor units. The Bortfeld algorithm used on average 58% more segments than provided by the integer algorithm with bidirectional motion and 32% more segments than did an integer algorithm admitting only unidirectional sequences. The areal algorithm used 48% more monitor units and the reducing algorithm used 23% more monitor units than did the bidirectional integer algorithm, while the areal and reducing algorithms used 23% more segments than did the integer algorithm. Improved leaf sequencing algorithms can allow more efficient delivery of static field IMRT. The integer algorithm demonstrates the efficiencies possible with an improved routine and opens a new avenue for development.
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Affiliation(s)
- M Langer
- Department of Radiation Oncology, Indiana University Medical School, Indianapolis 46202, USA.
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Dai J, Zhu Y. Minimizing the number of segments in a delivery sequence for intensity-modulated radiation therapy with a multileaf collimator. Med Phys 2001; 28:2113-20. [PMID: 11695773 DOI: 10.1118/1.1406518] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
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.
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Affiliation(s)
- J Dai
- Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-2794, USA.
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