Technical Note: A treatment plan comparison between dynamic collimation and a fixed aperture during spot scanning proton therapy for brain treatment

Smith, Blake; Gelover, Edgar; Moignier, A.; Wang, Dongxu; Flynn, R; Lin, Liyong; Kirk, Maura; Solberg, Timothy D.; Hyer, Daniel E.

doi:10.1118/1.4955117

Cited by 31 publications

(51 citation statements)

References 15 publications

(20 reference statements)

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“…The critical structure avoidance and normal tissue sparing achieved in the works of Moignier and Smith were accomplished through the TSA method which optimized the energy‐layer specific collimation for an entire treatment plan. Specifically, the original TSA approach used a simple selection criteria which maximized the dose contribution of an individual beam spot to the target while minimizing the degree of healthy tissue irradiated by the same beamlet at the Bragg peak radiological depth.…”

Section: Discussionmentioning

confidence: 99%

“…A novel optimization algorithm was designed and implemented using an in‐house treatment planning system . The treatment planning system was executed in MATLAB ® (version R2017b and R2018a) using parallelized CPU calculations within MATLAB’s parallel computing toolbox.…”

Section: Methodsmentioning

confidence: 99%

“…Three intracranial treatment plans, which were used during the investigations of Moignier et al . and Smith et al ,. were replanned with an in‐house TPS, RDX, using the asymmetric beamlet model for the IBA Universal Nozzle system .…”

Section: Methodsmentioning

confidence: 99%

“…The work of Smith et al. directly compared DCPT with a DCS against aperture‐based treatments and found that the healthy tissue sparing was nearly doubled when using the DCS . It is clear from these studies that the DCS technology can increase the healthy tissue sparing and target conformity.…”

Section: Introductionmentioning

confidence: 99%

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Technical Note: Optimization of spot and trimmer position during dynamically collimated proton therapy

et al. 2019

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Purpose: To demonstrate a novel theoretical optimization design which considers beam spot and trimmer positioning in addition to beamlet weighting for dynamically collimated proton therapy (DCPT) treatments. Prior to this, the previous methods of plan optimization used to study this emerging technology relied upon an intuitive selection criterion to fix the trimmers blades for a uniform grid of beam spots before determining the individual beamlet weights. To evaluate the potential benefit from this new optimization design, a treatment planning optimization study was performed in order to compare the algorithm’s functionality against the existing methods of plan optimization. Materials and methods: A direct parameter optimization (DPO) method was developed to determine beam spot and trimmer positions cohesively with beamlet weighting for DCPT treatment plans. Gradients were numerically determined from applying small adjustments to the aforementioned parameters and quantifying the resulting impact on an objective function. This technique was compared to the conventional trimmer selection algorithm (TSA) which does not optimize spot position concurrently with trimmer position. Both planning methods were used to optimize a set of brain treatment plans, and the resulting dose distributions were compared with dose–volume histogram quantities in addition to target coverage, homogeneity, and conformity metrics. Results: An overall improvement to the target conformity and healthy tissue sparing was achieved with DPO over TSA while maintaining an equivalent planning target volume (PTV) coverage index for the three brain patients evaluated in this study. On average, the conformity index improved by 5.5% when utilizing DPO. A similar improvement in reducing the dose to several organs at risk was also noted. Conclusion: Both the TSA and DPO planning methods can achieve highly conformal treatments with the dynamic collimation system (DCS) technology. However, an improvement in the target conformity and healthy tissue sparing was achieved by simultaneously optimizing beam spot position, trimmer location, and beamlet weights using DPO in comparison to the TSA technique.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Technical Note: Optimization of spot and trimmer position during dynamically collimated proton therapy

et al. 2019

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“…There exists a substantial amount of literature that focuses on the potential benefits of the DCS device among head and neck and intracranial treatments delivered with both the IBA Universal and Dedicated Nozzle systems [2][3][4] and also in comparison to single-field aperture collimated treatments. 5 These computational studies have utilized an asymmetric beamlet model from Gelover et al 6 to perform efficient dose calculations. The difficulty in modeling asymmetric proton beamlets is reflected in the complexity of the model, which was parameterized from linearly regressing numerous polynomials over energy-dependent Gaussian parameters to approximate Monte Carlo-simulated beamlet profiles.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Monte Carlo characterization of a dynamic collimation system prototype for pencil beam scanning proton therapy

et al. 2020

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There has been a growing interest in the development of energy-specific collimators for low-energy pencil beam scanning (PBS) to reduce the lateral penumbra. One particular device that has been the focus of several recent published works is the dynamic collimation system (DCS), which provides energy-specific collimation by intercepting the scanned proton beam as it nears to target edge with a set of orthogonal trimmer blades. While several computational studies have shown that this dynamic collimator can provide additional healthy tissue sparing, there has not been any rigorous experimental work to benchmark the theoretical models used in these initial studies. Therefore, it was the purpose of this work to demonstrate an experimental method that could integrate an experimental prototype with a clinical PBS system and benchmark the Monte Carlo methods that have been used to model the DCS. Methods: An experimental DCS prototype was designed and built in house to actively collimate individual proton beamlets during PBS within a well-characterized experimental setup. Monte Carlo methods were initially used to assess construction tolerances and later benchmarked against measurements, including integral depth dose and lateral asymmetric beamlet profiles. The experimental apparatus and measurement geometry were modeled using MCNP6 benchmarked from measurements performed at the Northwestern Chicago Proton Center. Results: Gamma analysis tests were used to evaluate the agreement between the measured and simulated profiles with a strict 1 mm/1% criteria and 5% dose threshold. Excellent agreement was observed between the simulated and measured profiles, which included 1 mm/1% gamma analysis pass rates of at least 100% and 95% for the integral depth dose (IDD) profiles and lateral profiles, respectively. Differences in the relative profile shape were observed experimentally between beamlets collimated on-and off-axis, which was attributed to the partial transmission of the beam through an unfocused collimator. Exposure rates resulting from the activation of the device were monitored with survey meter measurements and were found to agree with Monte Carlo estimates of the exposure rate to within 20%. Conclusion: A DCS prototype was constructed and integrated into a clinical dose delivery system. While the results of this work are not exhaustive, they demonstrate the effects of beam source divergence, device activation, and beamlet deflection during scanning, which were found to be successfully modeled using Monte Carlo methods and experimentally benchmarked. Excellent agreement was achieved between the simulated and measured lateral spot profiles of collimated beamlets delivered on-and off-axis in PBS. The Monte Carlo models adequately predicted the measured elevated plateau region in the integral depth-dose profiles from the low-energy scatter off the collimators.

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Proton therapy needs further technological development to fulfill the promise of becoming a superior treatment modality (compared to photon therapy)

Hyer

Ding

Rong

2021

J Applied Clin Med Phys

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Technical Note: A treatment plan comparison between dynamic collimation and a fixed aperture during spot scanning proton therapy for brain treatment

Abstract: The ability of the DCS to provide collimation to each energy layer yielded better conformity in comparison to fixed aperture plans.

Cited by 31 publications

References 15 publications

Technical Note: Optimization of spot and trimmer position during dynamically collimated proton therapy

Technical Note: Optimization of spot and trimmer position during dynamically collimated proton therapy

Experimental and Monte Carlo characterization of a dynamic collimation system prototype for pencil beam scanning proton therapy

Proton therapy needs further technological development to fulfill the promise of becoming a superior treatment modality (compared to photon therapy)

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