Emulating Clinical Workflow of Scintillator Array Dosimetry for FLASH Pencil-Beam Scanning Proton Therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Imaging Technology

Background:

• Ultra-high dose rate (UHDR) proton therapy, particularly pencil-beam scanning (PBS), is advancing rapidly, necessitating improved in vivo validation systems.
• Current dosimetry tools lack the spatiotemporal resolution required for effective monitoring of clinical FLASH (Focalized Ablative Radiat Therapy) treatments.
• There is a critical need for advanced systems capable of real-time, high-resolution dosimetry during UHDR proton therapy delivery.

Purpose of the Study:

• To demonstrate the capability of a novel scintillation imaging system for monitoring UHDR PBS proton therapy.
• To evaluate the system's accuracy in measuring two-dimensional dose and dose rate maps in an emulated clinical in vivo setting.
• To assess the system's clinical compatibility and impact on workflow for future large animal and human studies.

Main Methods:

• A novel optical dosimetry system featuring a 1 kHz intensified CMOS camera, stereo-vision, and a deformable scintillator array was utilized.
• A conventional lung PBS plan was adapted to simulate FLASH conditions (99 nA, 250 MeV) for end-to-end validation.
• An anthropomorphic chest phantom was used for validation, comparing cumulative dose to film, analyzing spot positions, and verifying dose rate areas.

Main Results:

• Scintillation imaging achieved high gamma passing rates (92.5% at 1%/1 mm) when compared to gafchromic film for cumulative dose distribution.
• Spot monitoring demonstrated submillimeter accuracy with a deviation of 0.32 ± 0.19 mm.
• Excellent agreement was found between planned and measured surface dose rates, with only a 0.71% difference in coverage at 40 Gy/s.

Conclusions:

• This study marks the first practical implementation of scintillator array dosimetry for UHDR PBS proton therapy.
• The developed system enables real-time, high-resolution dose and dose rate monitoring for complex geometries.
• It offers a novel, clinically compatible approach for in vivo treatment validation, providing crucial metrics for UHDR proton beam dynamics.