Dynamic collimator trajectory algorithm for multiple metastases dynamic conformal arc treatment planning

MacDonald, R. Lee; Thomas, Christopher G.; Syme, Alasdair

doi:10.1002/mp.12648

Cited by 15 publications

(42 citation statements)

References 12 publications

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“…Another approach is including table rotation in the beam arrangements either at different static gantry angles or with a dynamic gantry rotation . Instead of including the table rotation also the collimator rotation can be taken into account to additionally increase the number of degrees of freedom . A further step, which is also the aim of this work, is to include both collimator and table rotation during beam delivery …”

Section: Introductionmentioning

confidence: 99%

Part 1: Optimization and evaluation of dynamic trajectory radiotherapy

et al. 2018

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Section: Introductionmentioning

confidence: 99%

Part 1: Optimization and evaluation of dynamic trajectory radiotherapy

et al. 2018

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“…Selection of dynamic collimator angles for arc therapy based on patient anatomy has suggested previously, for example, by alignment of the MLC with the spinal cord for paraspinal treatments or based on conformance of the MLC to the target for treatments of multiple metastatic brain tumors . Our method, in contrast, is based on two tractable algorithms: convex fluence map optimization (FMO) followed by a linear network flow model to select a trajectory of collimator rotations.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Improving VMAT delivery efficiency by optimizing the dynamic collimator trajectory

2019

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Purpose To provide a method for optimizing the multileaf collimator angle trajectory in volumetric modulated arc therapy (VMAT) in order to make VMAT delivery and planning more efficient. Methods Static fluence maps are optimized at a 10‐degree spacing around the patient. Sliding window delivery time of each of these fields is computed for a large set of possible collimator orientations. An optimal trajectory, which selects a collimator angle for each field and assures that the collimator angles do not differ excessively between adjacent fields, is computed by solving a network flow model of a shortest path problem. Results For four clinical cases (two brains, an anal, and a spine), we demonstrate time reductions from 6% to 32% (average: 24%) for the optimal static angle vs the worst static angle. Further reductions from 3% to 17% (average 9%) are achievable when dynamic collimator trajectories are allowed. Conclusions Dynamic collimator trajectories, which can be computed with an efficient linear programming formulation, can improve the efficiency of VMAT delivery.

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“…: a statistically significant decrease of 34% in MUs (increase in MU efficiency) when compared to VMAT plans, and a statistically significant improvement of 14% in target coverage accuracy when compared to optimized DCA. A previous study by this group has demonstrated the potential advantages of collimator optimization in DCA treatments of multiple metastases. However, that study focused on single prescription multiple metastases cases.…”

Section: Discussionmentioning

confidence: 99%

“…The optimizer then computes the objective function by approximating total dose as the sum of all dose matrices. While this method ignores the presence of nontarget anatomy between targets that may be present in the final MLC apertures (potentially unavoidable due to relative target orientation, or potentially caused by mechanical constraints on collimator motions), the optimization of the collimator angle through dynamic collimator rotation minimizes discrepancies caused by this approximation . By computing this sum, the optimization does not require recalculation of dose with each modification to the aperture, as there are only two possible positions for the aperture: completely closed (zero) or set conformally (one).…”

Section: Discussionmentioning

confidence: 99%

Intra‐arc binary collimation algorithm for the optimization of stereotactic radiotherapy treatment of multiple metastases with multiple prescriptions

et al. 2018

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Purpose To design and implement a novel treatment planning algorithm based on a modification of dynamic conformal arc (DCA) therapy for the treatment of multiple cranial metastases with variable prescription doses. Methods A workflow was developed in which separate dose matrices were calculated for each target at each control point (i.e., the multileaf collimator (MLC) was fit conformally to that single target). A cost function was used to quantify the relative contributions of each dose matrix in the plan to the overall plan objectives. Simulated annealing was used to allow for the inclusion or exclusion of individual dose matrices at each control point. The exclusion of individual targets at a given control point is termed intra‐arc binary collimation (iABC) in this work and is accomplished by closing the MLCs over the target for a duration specified by simulated annealing optimization. Dynamic collimator motions were employed to minimize the variation between the idealized dose matrices (i.e., perfectly collimated targets) and actual dose matrices (i.e., MLC apertures that include quantities of nontarget tissue due to the relative orientations of targets in the field). An additional simulated annealing optimization was performed to weight the relative contributions of dose at each control point [referred to as the monitor unit distribution (MUD)] to improve compliance with plan objectives. The algorithm was tested on seven previously treated multiple metastases patients and plans were compared to the clinically treated VMAT plans. Results Treatment plans generated with iABC used an average of 2716 (34%) fewer MU in the total plan than VMAT (P = 0.01). All normal tissue metrics for all plans and all patients were clinically acceptable. There were no statistically significant differences in any normal tissue dose metrics. Normalized prescription target coverage accuracy for all targets was 3% better on average for VMAT plans when compared to iABC (P = 0.07), and 14% better on average for iABC when compared to optimized DCA (P = 0.03). Conclusion A novel method of aperture and dose distribution design has been developed to significantly increase the MU efficiency of single isocenter treatment of multiple metastases with variable prescription doses when compared to VMAT, and which improves target coverage accuracy significantly when compared to optimized DCA. By applying a DCA approach to subsets of targets across control points, a hybrid method of treatment delivery has been developed that combines the efficiency of dynamic conformal treatments and the dosimetric flexibility of VMAT.

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Dynamic collimator trajectory algorithm for multiple metastases dynamic conformal arc treatment planning

Cited by 15 publications

References 12 publications

Part 1: Optimization and evaluation of dynamic trajectory radiotherapy

Part 1: Optimization and evaluation of dynamic trajectory radiotherapy

Technical Note: Improving VMAT delivery efficiency by optimizing the dynamic collimator trajectory

Intra‐arc binary collimation algorithm for the optimization of stereotactic radiotherapy treatment of multiple metastases with multiple prescriptions

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