Journal of radiosurgery and SBRT · 2026
Transition from passive scattering to pencil beam scanning: Physics commissioning of a proton radiosurgery system.
СтатьяНазвание и аннотация: Перевод пока не подготовлен
Обработка статьи · этапы, ошибки и управление
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Ошибки и ограничения
История · было → стало
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Daartz Juliane, Verburg Joost M, Depauw Nicolas, Kooy Hanne M, Chapman Paul H, Shih Helen A, Bussière Marc R
Аннотация
BACKGROUND: Our institution has provided proton stereotactic radiosurgery (PSRS) since 1961 using passive scattering (PS). A recent transition to pencil beam scanning with a new treatment planning system required extensive validation, particularly for small field applications.
PURPOSE: This study details the clinical adaptation of our PSRS program to pencil beam scanning (PBS), emphasizing small field dosimetry and treatment delivery accuracy.Methods: Patient alignment via implanted fiducials was validated using a head phantom. Test fields were created to span clinically relevant parameters including distal target depth (3.4-17.9 cm), target thickness (1.0-3.0 cm), aperture diameter (0.9-3.0 cm), and aperture aspect ratios (1.0-3.0). Dosimetric validation of the in-house, vendor co-developed planning system included: (1) central axis depth-dose measurements in water with a micro-diamond detector; (2) absolute point dose measurements in solid water; and (3) two-dimensional relative dose distributions with Gafchromic film. Validation was supplemented by a commercial high-resolution ion chamber array.
RESULTS: End-to-end alignment using a hidden target approach showed a mean deviation of 0.6 ± 0.3 mm. Agreement with the treatment planning system (TPS) for 90% distal and proximal central axis depths was within 0.1 ± 0.7 mm and 0.7 ± 0.5 mm, respectively. Absolute isocenter dose agreement in water was within 1.6%. Gamma analysis (2%/1 mm, 10% threshold) yielded a 97.6% average pass rate. A patient-specific QA protocol for small fields was established and validated.
CONCLUSIONS: We successfully transitioned our PSRS program to PBS, achieving high geometric and dosimetric accuracy suitable for small field proton radiosurgery.
PURPOSE: This study details the clinical adaptation of our PSRS program to pencil beam scanning (PBS), emphasizing small field dosimetry and treatment delivery accuracy.Methods: Patient alignment via implanted fiducials was validated using a head phantom. Test fields were created to span clinically relevant parameters including distal target depth (3.4-17.9 cm), target thickness (1.0-3.0 cm), aperture diameter (0.9-3.0 cm), and aperture aspect ratios (1.0-3.0). Dosimetric validation of the in-house, vendor co-developed planning system included: (1) central axis depth-dose measurements in water with a micro-diamond detector; (2) absolute point dose measurements in solid water; and (3) two-dimensional relative dose distributions with Gafchromic film. Validation was supplemented by a commercial high-resolution ion chamber array.
RESULTS: End-to-end alignment using a hidden target approach showed a mean deviation of 0.6 ± 0.3 mm. Agreement with the treatment planning system (TPS) for 90% distal and proximal central axis depths was within 0.1 ± 0.7 mm and 0.7 ± 0.5 mm, respectively. Absolute isocenter dose agreement in water was within 1.6%. Gamma analysis (2%/1 mm, 10% threshold) yielded a 97.6% average pass rate. A patient-specific QA protocol for small fields was established and validated.
CONCLUSIONS: We successfully transitioned our PSRS program to PBS, achieving high geometric and dosimetric accuracy suitable for small field proton radiosurgery.