Advanced pencil beam scanning Bragg peak FLASH-RT delivery technique can enhance lung cancer planning treatment outcomes compared to conventional multiple-energy proton PBS techniques

Wei, Shouyi; Lin, Haibo; Choi, J. Isabelle; Shi, Chengyu; Simone, Charles B.; Kang, Minglei

doi:10.1016/j.radonc.2022.08.005

Cited by 17 publications

(21 citation statements)

References 54 publications

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“…While it does offer certain advantages over traditional delivery methods, the benefits it provides for cancer treatment are relatively limited. The standard of care in PBS proton therapy [20][21][22] and the single-energy Bragg peak FLASH technique [23][24][25][26] already enable the delivery of highly conformal and precise radiation doses to tumors, which diminishes the significance of proton arc RT for future applications.…”

Section: Opening Statementsmentioning

confidence: 99%

FLASH instead of proton arc therapy is a more promising advancement for the next generation proton radiotherapy

Kang

Ding²,

Rong

2023

J Applied Clin Med Phys

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Section: Opening Statementsmentioning

confidence: 99%

FLASH instead of proton arc therapy is a more promising advancement for the next generation proton radiotherapy

Kang

Ding²,

Rong

2023

J Applied Clin Med Phys

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“…25 To maximize the potential of BPs for FLASH-RT, studies have explored the use of customized range compensators and uniform range shifters (RSs) to align the single-energy BPs to the distal edge of the target, indicating excellent OAR sparing with sufficient FLASH dose rate coverage. [26][27][28] Another avenue of exploration involves the implementation of pin-shaped RFs, 29,30 also known as 3D range-modulators, 31 to produce a uniform single-energy SOBP that conforms to the target along each pencil beam direction (PBD). This approach has demonstrated feasibility for FLASH therapy accounting for dose and dose rate coverage as well as LET effect simultaneously.…”

Section: Introductionmentioning

confidence: 99%

Streamlined pin‐ridge‐filter design for single‐energy proton FLASH planning

Ma,

Zhou,

Chang

et al. 2024

Medical Physics

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BackgroundFLASH radiotherapy (FLASH‐RT) with ultra‐high dose rate has yielded promising results in reducing normal tissue toxicity while maintaining tumor control. Planning with single‐energy proton beams modulated by ridge filters (RFs) has been demonstrated feasible for FLASH‐RT.PurposeThis study explored the feasibility of a streamlined pin‐shaped RF (pin‐RF) design, characterized by coarse resolution and sparsely distributed ridge pins, for single‐energy proton FLASH planning.MethodsAn inverse planning framework integrated within a treatment planning system was established to design streamlined pin RFs for single‐energy FLASH planning. The framework involves generating a multi‐energy proton beam plan using intensity‐modulated proton therapy (IMPT) planning based on downstream energy modulation strategy (IMPT‐DS), followed by a nested pencil‐beam‐direction‐based (PBD‐based) spot reduction process to iteratively reduce the total number of PBDs and energy layers along each PBD for the IMPT‐DS plan. The IMPT‐DS plan is then translated into the pin‐RFs and the single‐energy beam configurations for IMPT planning with pin‐RFs (IMPT‐RF). This framework was validated on three lung cases, quantifying the FLASH dose of the IMPT‐RF plan using the FLASH effectiveness model. The FLASH dose was then compared to the reference dose of a conventional IMPT plan to measure the clinical benefit of the FLASH planning technique.ResultsThe IMPT‐RF plans closely matched the corresponding IMPT‐DS plans in high dose conformity (conformity index of <1.2), with minimal changes in V7Gy and V7.4 Gy for the lung (<3%) and small increases in maximum doses (Dmax) for other normal structures (<3.4 Gy). Comparing the FLASH doses to the doses of corresponding IMPT‐RF plans, drastic reductions of up to nearly 33% were observed in Dmax for the normal structures situated in the high‐to‐moderate‐dose regions, while negligible changes were found in Dmax for normal structures in low‐dose regions. Positive clinical benefits were seen in comparing the FLASH doses to the reference doses, with notable reductions of 21.4%–33.0% in Dmax for healthy tissues in the high‐dose regions. However, in the moderate‐to‐low‐dose regions, only marginal positive or even negative clinical benefit for normal tissues were observed, such as increased lung V7Gy and V7.4 Gy (up to 17.6%).ConclusionsA streamlined pin‐RF design was developed and its effectiveness for single‐energy proton FLASH planning was validated, revealing positive clinical benefits for the normal tissues in the high dose regions. The coarsened design of the pin‐RF demonstrates potential advantages, including cost efficiency and ease of adjustability, making it a promising option for efficient production.

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“…Although electron FLASH RT has presented encouraging preclinical outcomes, its clinical utility is currently limited to treating shallow tumors 2,17–20 . FLASH delivery using protons could potentially ensure broader clinical application because of its ability to treat deep‐seated targets, excellent dose conformality, and availability with minimal modifications to existing clinical machines 8,10,12,14,21 . Pencil beam scanning (PBS), which can provide great dose conformity and organs‐at‐risk (OARs) sparing through precise proton beamlet positioning, intensity, and energy modulation, has become the most dominant technology used in the clinic to deliver proton therapy.…”

Section: Introductionmentioning

confidence: 99%

“…2,[17][18][19][20] FLASH delivery using protons could potentially ensure broader clinical application because of its ability to treat deep-seated targets,excellent dose conformality, and availability with minimal modifications to existing clinical machines. 8,10,12,14,21 Pencil beam scanning (PBS), which can provide great dose conformity and organs-at-risk (OARs) sparing through precise proton beamlet positioning, intensity, and energy modulation, has become the most dominant technology used in the clinic to deliver proton therapy. Current PBS planning and treatment require generating multiple-layer spread-out Bragg peaks (SOBP) to cover the tumor volume.…”

Section: Introductionmentioning

confidence: 99%

Implementation of novel measurement‐based patient‐specific QA for pencil beam scanning proton FLASH radiotherapy

et al. 2023

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Background Several studies have shown pencil beam scanning (PBS) proton therapy is a feasible and safe modality to deliver conformal and ultra‐high dose rate (UHDR) FLASH radiation therapy. However, it would be challenging and burdensome to conduct the quality assurance (QA) of the dose rate along with conventional patient‐specific QA (psQA). Purpose To demonstrate a novel measurement‐based psQA program for UHDR PBS proton transmission FLASH radiotherapy (FLASH‐RT) using a high spatiotemporal resolution 2D strip ionization chamber array (SICA). Methods The SICA is a newly designed open‐air strip‐segmented parallel plate ionization chamber, which is capable of measuring spot position and profile through 2 mm‐spacing‐strip electrodes at a 20 kHz sampling rate (50 μs per event) and has been characterized to exhibit excellent dose and dose rate linearity under UHDR conditions. A SICA‐based delivery log was collected for each irradiation containing the measured position, size, dwell time, and delivered MU for each planned spot. Such spot‐level information was compared with the corresponding quantities in the treatment planning system (TPS). The dose and dose rate distributions were reconstructed on patient CT using the measured SICA log and compared to the planned values in volume histograms and 3D gamma analysis. Furthermore, the 2D dose and dose rate measurements were compared with the TPS calculations of the same depth. In addition, simulations using different machine‐delivery uncertainties were performed, and QA tolerances were deduced. Results A transmission proton plan of 250 MeV for a lung lesion was planned and measured in a dedicated ProBeam research beamline (Varian Medical System) with a nozzle beam current between 100 to 215 nA. The worst gamma passing rates for dose and dose rate of the 2D SICA measurements (four fields) compared to TPS prediction (3%/3 mm criterion) were 96.6% and 98.8%, respectively, whereas the SICA‐log reconstructed 3D dose distribution achieved a gamma passing rate of 99.1% (2%/2 mm criterion) compared to TPS. The deviations between SICA measured log, and TPS were within 0.3 ms for spot dwell time with a mean difference of 0.069 ± 0.11 s, within 0.2 mm for spot position with a mean difference of −0.016 ± 0.03 mm in the x‐direction, and −0.036 ± 0.059 mm in the y‐direction, and within 3% for delivered spot MUs. Volume histogram metric of dose (D95) and dose rate (V40Gy/s) showed minimal differences, within less than 1%. Conclusions This work is the first to describe and validate an all‐in‐one measurement‐based psQA framework that can fulfill the goals of validating the dose rate accuracy in addition to dosimetric accuracy for proton PBS transmission FLASH‐RT. The successful implementation of this novel QA program can provide future clinical practice with more confidence in the FLASH application.

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Advanced pencil beam scanning Bragg peak FLASH-RT delivery technique can enhance lung cancer planning treatment outcomes compared to conventional multiple-energy proton PBS techniques

Cited by 17 publications

References 54 publications

FLASH instead of proton arc therapy is a more promising advancement for the next generation proton radiotherapy

FLASH instead of proton arc therapy is a more promising advancement for the next generation proton radiotherapy

Streamlined pin‐ridge‐filter design for single‐energy proton FLASH planning

Implementation of novel measurement‐based patient‐specific QA for pencil beam scanning proton FLASH radiotherapy

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