Commissioning and Validation of a Synchrocyclotron - Based Ultra-High-Dose-Rate Beamline for FLASH

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Accelerator Technology

Background:

• FLASH radiotherapy utilizes ultra-high dose rates (>40 Gy/s) to potentially reduce normal tissue toxicity while maintaining tumor control.
• IBA's synchrocyclotron proton system can achieve ultra-high dose rate (UHDR) delivery, necessitating integration into treatment planning systems (TPS) for accurate preclinical research.
• Accurate dose calculation and 2D dose profile optimization are critical for advancing spread-out Bragg peak FLASH techniques.

Purpose of the Study:

• To commission and validate a synchrocyclotron-based pencil beam scanning UHDR proton beamline on the IBA ProteusONE system within the RayStation TPS.
• To establish a framework for TPS modeling and validation to support preclinical FLASH radiotherapy studies.
• To enable accurate dose calculations and 2D dose profile optimization for UHDR proton beams.

Main Methods:

• Characterization of the transmission UHDR beamline (228 MeV protons) at gantry 0° using point dose and 2D lateral profile measurements.
• Development of a beam model in RayStation TPS, including virtual source position, spot size, integrated depth dose (IDD), and absolute dose calibration.
• Validation of the TPS model using ionization chambers, film dosimetry, and 2D scintillation detectors, with gamma analysis for accuracy assessment.

Main Results:

• The UHDR beamline achieved dose rates exceeding 40 Gy/s, with validated consistent dose output across multiple detectors.
• The RayStation beam model showed excellent agreement with experimental data, with <2.5% deviation for point doses and >95% gamma passing rates (2%/2 mm) for 2D profiles.
• The TPS facilitated spot pattern optimization for UHDR FLASH beams, aligning with clinical profiles for accurate preclinical comparisons.

Conclusions:

• Successful commissioning and validation of a synchrocyclotron-based UHDR beamline using a reliable TPS model for transmission FLASH applications.
• The established framework provides a foundation for preclinical FLASH-RT research and future clinical integration into existing proton therapy platforms.
• Future work will involve commissioning at all gantry angles and exploring spread-out Bragg peak FLASH for enhanced dose conformity.