Choreographing Couch and Collimator in Volumetric Modulated Arc Therapy

Yang, Yingli; Zhang, Pengpeng; Happersett, Laura; Xiong, Jianping; Yang, Jie; Chan, M; Beal, Kathryn; Mageras, G.; Hunt, Margie

doi:10.1016/j.ijrobp.2010.10.016

Cited by 64 publications

(122 citation statements)

References 36 publications

(37 reference statements)

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“…Technically, however, it is already possible to realize arbitrary noncoplanar irradiation trajectories through simultaneous rotation of couch and gantry with a conventional linear accelerator (which may require access to a research mode of operation). 45 For step&shoot IMRT, it has been established that such noncoplanar irradiation fields may allow for substantial dose reductions in OARs, especially if the OARs are close to irregularly shaped target volumes that are located asymmetrically within the body. [46][47][48][49] Leaving potential issues regarding patient immobilization on a robotic couch aside, the first treatment planning studies investigating noncoplanar VMAT have reconfirmed a benefit of noncoplanar irradiation with regard to OAR sparing.…”

Section: E Noncoplanar Generalizations Of Vmatmentioning

confidence: 99%

“…[46][47][48][49] Leaving potential issues regarding patient immobilization on a robotic couch aside, the first treatment planning studies investigating noncoplanar VMAT have reconfirmed a benefit of noncoplanar irradiation with regard to OAR sparing. 33,45,47,[50][51][52][53] From the mathematical and technical side, the optimization of an irradiation trajectory shares the known issues of beam angle optimization (BAO) for step&shoot IMRT. When viewed as a continuous optimization problem, BAO is highly nonconvex.…”

Section: E Noncoplanar Generalizations Of Vmatmentioning

confidence: 99%

“…For the second step, all VMAT methods discussed in this paper can be applied with minor adjustments. The trajectories used for the above treatment planning studies were either found through inspection by a human planner, [50][51][52] using geometric heuristics, 45,53 or exhaustive search considering nine different couch tilts. 47 Wild et al 33 use a noncoplanar beam ensemble which was optimized with a genetic algorithm 49 for step&shoot IMRT to construct a noncoplanar VMAT trajectory.…”

Section: E Noncoplanar Generalizations Of Vmatmentioning

confidence: 99%

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Optimization approaches to volumetric modulated arc therapy planning

et al. 2015

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Volumetric modulated arc therapy (VMAT) has found widespread clinical application in recent years. A large number of treatment planning studies have evaluated the potential for VMAT for different disease sites based on the currently available commercial implementations of VMAT planning. In contrast, literature on the underlying mathematical optimization methods used in treatment planning is scarce. VMAT planning represents a challenging large scale optimization problem. In contrast to fluence map optimization in intensity-modulated radiotherapy planning for static beams, VMAT planning represents a nonconvex optimization problem. In this paper, the authors review the state-of-the-art in VMAT planning from an algorithmic perspective. Different approaches to VMAT optimization, including arc sequencing methods, extensions of direct aperture optimization, and direct optimization of leaf trajectories are reviewed. Their advantages and limitations are outlined and recommendations for improvements are discussed. C 2015 American Association of Physicists in Medicine. [http://dx

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Section: E Noncoplanar Generalizations Of Vmatmentioning

confidence: 99%

Section: E Noncoplanar Generalizations Of Vmatmentioning

confidence: 99%

Section: E Noncoplanar Generalizations Of Vmatmentioning

confidence: 99%

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Optimization approaches to volumetric modulated arc therapy planning

et al. 2015

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“…With the exception of Yang et al (2011), all trajectories were user-defined and therefore notionally 'arbitrary'. Yang et al identified optimal individual source positions using a beam's eye view volumetrics technique , Myrianthopoulos et al 1992, McShan et al 1995.…”

Section: Introductionmentioning

confidence: 99%

Trajectory optimization for dynamic couch rotation during volumetric modulated arc radiotherapy

et al. 2013

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Abstract. Non-coplanar radiation beams are often used in three-dimensional conformal and intensity modulated radiotherapy to reduce dose to organs at risk (OAR) by geometric avoidance. In volumetric modulated arc radiotherapy (VMAT) non-coplanar geometries are generally achieved by applying patient couch rotations to single or multiple full or partial arcs. This paper presents a trajectory optimization method for a non-coplanar technique, dynamic couch rotation during VMAT (DCR-VMAT), which combines ray tracing with a graph search algorithm. Four clinical test cases (partial breast, brain, prostate only, and prostate and pelvic nodes) were used to evaluate the potential OAR sparing for trajectory optimized DCR-VMAT plans, compared with standard coplanar VMAT. In each case, ray tracing was performed and a cost map reflecting the number of OAR voxels intersected for each potential source position was generated. The least-cost path through the cost map, corresponding to an optimal DCR-VMAT trajectory, was determined using Dijkstra's algorithm. Results show that trajectory optimization can reduce dose to specified OARs for plans otherwise comparable to conventional coplanar VMAT techniques. For the partial breast case, the mean heart dose was reduced by 53%. In the brain case, the maximum lens doses were reduced by 61% (left) and 77% (right) and the globes by 37% (left) and 40% (right). Bowel mean dose was reduced by 15% in the prostate only case. For the prostate and pelvic nodes case, the bowel V 50Gy and V 60Gy were reduced by 9% and 45% respectively. Future work will involve further development of the algorithm and assessment of its performance over a larger number of cases in site specific cohorts.

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“…Different combinations of collimator and couch angles will result in different tracking complexity which affects the delivery performance. Therefore, optimization of collimator and couch trajectories may reduce the possibility of having plans running at the mechanical limits of the linac, which can improve the treatment efficiency and robustness 36, 37. In most published studies on VMAT plans with motion tracking, collimator, and couch angles for plans were set at 90° and 0°, respectively, which has been shown to be favorable for MLC tracking because the MLC leaf motion direction is parallel to target motion in superior‐inferior (SI) direction 30, 32, 34, 35.…”

Section: Introductionmentioning

confidence: 99%

Effects of collimator angle, couch angle, and starting phase on motion‐tracking dynamic conformal arc therapy (4D DCAT)

Yao

Podgorsak

et al. 2017

J Applied Clin Med Phys

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PurposeThe aim of this study was to find an optimized configuration of collimator angle, couch angle, and starting tracking phase to improve the delivery performance in terms of MLC position errors, maximal MLC leaf speed, and total beam‐on time of DCAT plans with motion tracking (4D DCAT).Method and materialsNontracking conformal arc plans were first created based on a single phase (maximal exhalation phase) of a respiratory motion phantom with a spherical target. An ideal model was used to simulate the target motion in superior‐inferior (SI), anterior‐posterior (AP), and left‐right (LR) dimensions. The motion was decomposed to the MLC leaf position coordinates for motion compensation and generating 4D DCAT plans. The plans were studied with collimator angle ranged from 0° to 90°; couch angle ranged from 350°(−10°) to 10°; and starting tracking phases at maximal inhalation (θ=π/2) and exhalation (θ=0) phases. Plan performance score (PPS) evaluates the plan complexity including the variability in MLC leaf positions, degree of irregularity in field shape and area. PPS ranges from 0 to 1, where low PPS indicates a plan with high complexity. The 4D DCAT plans with the maximal and the minimal PPS were selected and delivered on a Varian TrueBeam linear accelerator. Gafchromic‐EBT3 dosimetry films were used to measure the dose delivered to the target in the phantom. Gamma analysis for film measurements with 90% passing rate threshold using 3%/3 mm criteria and trajectory log files were analyzed for plan delivery accuracy evaluation.ResultsThe maximal PPS of all the plans was 0.554, achieved with collimator angle at 87°, couch angle at 350°, and starting phase at maximal inhalation (θ=π/2). The maximal MLC leaf speed, MLC leaf errors, total leaf travel distance, and beam‐on time were 20 mm/s, 0.39 ± 0.16 mm, 1385 cm, and 157 s, respectively. The starting phase, whether at maximal inhalation or exhalation had a relatively small contribution to PPS (0.01 ± 0.05).ConclusionsBy selecting collimator angle, couch angle, and starting tracking phase, 4D DCAT plans with the maximal PPS demonstrated less MLC leaf position errors, lower maximal MLC leaf speed, and shorter beam‐on time which improved the performance of 4D motion‐tracking DCAT delivery.

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Choreographing Couch and Collimator in Volumetric Modulated Arc Therapy

Cited by 64 publications

References 36 publications

Optimization approaches to volumetric modulated arc therapy planning

Optimization approaches to volumetric modulated arc therapy planning

Trajectory optimization for dynamic couch rotation during volumetric modulated arc radiotherapy

Effects of collimator angle, couch angle, and starting phase on motion‐tracking dynamic conformal arc therapy (4D DCAT)

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