Technical note: Delivery benefit and dosimetric implication of synchrotron‐based proton pencil beam scanning using continuous scanning mode

Liang, Xiaoying; Beltran, Chris; Liu, Chunbo; Shen, Jiajian; Li, Heng; Furutani, Keith M.

doi:10.1002/mp.16434

Cited by 4 publications

(13 citation statements)

References 23 publications

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“…DDCS when compared with DSS (Liang et al 2022). In this present study, a comparison between DSS and DDCS irradiation duty factor and BDTs were also conducted, and our results align with previously published work (Liang et al 2022(Liang et al , 2023. The substantial improvement in the irradiation duty factor within DDCS can be attributed to two factors.…”

Section: Discussionsupporting

confidence: 89%

“…DDCS, through the elimination of beam-offs between spots, holds the potential of improving irradiation duty factor and reducing BDT. Previous research has demonstrated that DDCS substantially improves the irradiation duty factor (range, 11%-41%) compared to DSS (range, 4%-14%) (Liang et al 2023). In our earlier study encompassing 36 clinical plans for 6 treatment sites, an average reduction of 10% in BDT was observed for a BDT is the total beam delivery time, defined as from the instance that the irradiation started to the instance that the last spot finished irradiation.…”

Section: Discussionmentioning

confidence: 87%

“…While DSS remains the predominant scanning mode in proton PBS (Pedroni et al 1995, Smith et al 2009, recent advancements, such as the Hitachi particle system, have made DDCS available for proton therapy. In preparing our upcoming Hitachi particle therapy system, in which the DDCS mode will be available, we conducted a series of in-silico simulations to gain better understanding of the DDCS (Liang et al 2022(Liang et al , 2023. Our work manifested that DDCS offers potential benefits, including improved beam irradiation duty factor, and shortened beam delivery time (BDT) (Liang et al 2022(Liang et al , 2023.…”

Section: Introductionmentioning

confidence: 99%

“…In preparing our upcoming Hitachi particle therapy system, in which the DDCS mode will be available, we conducted a series of in-silico simulations to gain better understanding of the DDCS (Liang et al 2022(Liang et al , 2023. Our work manifested that DDCS offers potential benefits, including improved beam irradiation duty factor, and shortened beam delivery time (BDT) (Liang et al 2022(Liang et al , 2023. However, the existing commercially available treatment planning systems (TPS) are only able to handle discrete spot plans and do not model the dose between spots during continuous beam delivery (hereafter referred to as move dose).…”

Section: Introductionmentioning

confidence: 99%

“…However, the existing commercially available treatment planning systems (TPS) are only able to handle discrete spot plans and do not model the dose between spots during continuous beam delivery (hereafter referred to as move dose). Consequently, for DDCS, there is a discrepancy between the planned dose calculated by the TPS and the DDCS dose due to the TPS's inability to account for move dose (Liang et al 2023). To address this dose discrepancy, one approach is to optimize the scan path to minimize the dose delivered between spots.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of scan path optimization in improving proton pencil beam scanning continuous delivery

Liu,

Beltran,

Shen

et al. 2023

Phys. Med. Biol.

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Objective. To investigate the impact of scan path optimization on the dose accuracy and beam delivery time (BDT) of proton pencil beam scanning in the dose-driven continuous scanning (DDCS). Approach. A diverse set of six clinical plans, representing various spot patterns and treatment sites, was used to evaluate the effectiveness of scan time optimization and scan length optimization. The DDCS dose discrepancy and BDT with optimized scan paths was compared to the default serpentine scan path. Main results. Both scan time optimization and scan path optimization were able to reduce the DDCS dose discrepancy compared to the default serpentine scan path. All plans, except for the layer repainting lung plan, achieved a 2%/2 mm gamma pass rate of over 99% and less than 1% PTV DVH root mean square error (RMSE) through scan path optimization. In the case of the layer repainting lung plan, when compared to the default serpentine scan path, the 2%/2 mm gamma pass rate showed improvements from 91.3% to 93.1% and 95.8%, while the PTV DVH RMSE decreased from 2.1% to 1.7% and 1.1% for scan time optimization and scan length optimization, respectively. Although scan time optimization resulted in shorter total scan times for all plans compared to the default scan path and scan length optimization tended to have longer total scan times. However, due to the short total scan times and their minimal contribution to the total BDT, the impact of scan path optimization on the total BDT was practically negligible. Significance. Both scan time optimization and scan length optimization proved to be effective in minimizing DDCS dose discrepancy. No definitive winner can be determined between these two optimization approaches. Both scan time and scan length optimization had minimal effect on the total BDT.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Investigation of scan path optimization in improving proton pencil beam scanning continuous delivery

Liu,

Beltran,

Shen

et al. 2023

Phys. Med. Biol.

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Dosimetric study of synchrotron rapid beam off control and skip spot function for high beam intensity proton therapy

Yagi,

Furutani,

Ogata

et al. 2024

Medical Physics

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BackgroundAll Hitachi proton pencil beam scanning facilities currently use discrete spot scanning (DSS). Mayo Clinic Florida (MCF) is installing a Hitachi particle therapy system with advanced technologies, including fast scan speeds, high beam intensity, rapid beam off control (RBOC), a skip spot function, and proton pencil beam scanning using dose driven continuous scanning (DDCS). A potential concern of RBOC is the generation of a shoulder at the end of the normal spot delivery due to a flap spot (FS) with a flap dose (FD), which has been investigated for carbon synchrotron but not for proton delivery. While investigated, for instance, for Hitachi's installation at MCF, this methodology could be applicable for all future high intensity proton deliveries.PurposeNo Hitachi proton facility currently uses the proposed RBOC. This study aimed to understand the dosimetric impact of proton FD at MCF by simulating the FS with a Hitachi proton machine in research mode, reflecting the higher proton intensities expected with RBOC at MCF.MethodExperiments were conducted to simulate MCF RBOC at Kyoto Prefecture University of Medicine (KPUM) in research mode, reducing delay time (Td) from 1.5 ms to 0.1 ms. 5,000 contiguous spots were delivered on the central axis for proton energies of 70.2, 142.5, and 220.0 MeV; at normal, high dose rate (HDR), and ultra‐high dose rate (uHDR) intensities; and at vertical and horizontal gantry angles for different Td. Measurements were taken using a fast oscilloscope and the nozzle's spot position monitor (SPM) and dose monitor (DM). A model was developed to predict FD dependence on beam intensity and assess the dosimetric impact for prostate and brain treatment plans. Two simulation types were planned: a flap DSS plan with FS at every spot and a flap DDCS plan with FS only at the end of each layer.ResultFD was observed for RBOC with Td = 0.1 ms, showing no gantry angle dependence. FD increased with higher delayed dose rate (DDR), that is, beam intensity. The planning study showed dose volume histogram deterioration with increased FD compared to the clinical plan, but it was only significant for uHDR intensities. Deterioration was marginal in flap DSS plans for the HDR intensities planned at MCF, and flap DDCS plans were even less sensitive than flap DSS plans.ConclusionMCF is installing proton DDCS with higher beam intensities, a skip spot function, and fast beam‐off control. The resulting FD had an insignificant impact on dose distribution for two patient plans with both DSS and DDCS at the anticipated MCF intensities. However, significant dependence was observed in the case of uHDR. A method to measure the position and dose of the FS during commissioning is described in addition to recommendations for regular QA and log‐based proton patient‐specific quality assurance.

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Investigation of dosimetric effect of beam current fluctuations in synchrotron-based proton PBS continuous scanning

Liu,

Furutani,

Shen

et al. 2024

Phys. Med. Biol.

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Objective. In proton pencil beam scanning (PBS) continuous delivery, the beam is continuously delivered without interruptions between spots. For synchrotron-based systems, the extracted beam current exhibits a spill structure, and recent publications on beam current measurements have demonstrated significant fluctuations around the nominal values. These fluctuations potentially lead to dose deviations from those calculated assuming a stable beam current. This study investigated the dosimetric implications of such beam current fluctuations during proton PBS continuous scanning. Approach. Using representative clinical proton PBS plans, we performed simulations to mimic a worst-case clinical delivery environment with beam current varies from 50% to 250% of the nominal values. The simulations used the beam delivery parameters optimized for the best beam delivery efficiency of the upcoming particle therapy system at Mayo Clinic Florida. We reconstructed the simulated delivered dose distributions and evaluated the dosimetric impact of beam current fluctuations. Main results. Despite significant beam current fluctuations resulting in deviations at each spot level, the overall dose distributions were nearly identical to those assuming a stable beam current. The 1 mm/1% Gamma passing rate was 100% for all plans. Less than 0.2% root mean square error was observed in the planning target volume dose-volume histogram. Minimal differences were observed in all dosimetric evaluation metrics. Significance. Our findings demonstrate that with our beam delivery system and clinical planning practice, while significant beam current fluctuations may result in large local move monitor unit deviations at each spot level, the overall impact on the dose distribution is minimal.

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Technical note: Delivery benefit and dosimetric implication of synchrotron‐based proton pencil beam scanning using continuous scanning mode

Cited by 4 publications

References 23 publications

Investigation of scan path optimization in improving proton pencil beam scanning continuous delivery

Investigation of scan path optimization in improving proton pencil beam scanning continuous delivery

Dosimetric study of synchrotron rapid beam off control and skip spot function for high beam intensity proton therapy

Investigation of dosimetric effect of beam current fluctuations in synchrotron-based proton PBS continuous scanning

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