Ultra-fast, high spatial resolution single-pulse scintillation imaging of synchrocyclotron pencil beam scanning proton delivery.
Physics in medicine and biology
OBJECTIVE: To demonstrates the ability of an ultra-fast imaging system to measure high resolution spatial and temporal beam characteristics of a synchrocyclotron proton pencil beam scanning (PBS) system.
APPROACH: An ultra-fast (1kHz frame rate), intensified CMOS camera was triggered by a scintillation sheet coupled to a remote trigger unit (RTU) for beam on detection. The camera was calibrated using the linear (R2>0.9922) dose response of a single spot beam to varying currents. Film taken for the single spot beam was used to produce a scintillation intensity to absolute dose calibration.
MAIN RESULTS: Spatial alignment was confirmed with the film, where the x and y-profiles of the single spot cumulative image agreed within 1mm. A sample brain patient plan was analyzed to demonstrate dose and temporal accuracy for a clinically-relevant plan, through agreement within 1mm to the planned and delivered spot locations. The cumulative dose agreed with the planned dose with a gamma passing rate of 97.5% (2mm/3%, 10% dose threshold).
SIGNIFICANCE: This is the first system able to capture single-pulse spatial and temporal information for the unique pulse structure of a synchrocyclotron PBS systems at conventional dose rates, enabled by the ultra-fast sampling frame rate of this camera. This study indicates that, with continued camera development and testing, target applications in clinical and FLASH proton beam characterization and validation are possible.
Clark MA, Ding X, Zhao L, Pogue BW, Gladstone D, Rahman M, et al. Ultra-fast, high spatial resolution single-pulse scintillation imaging of synchrocyclotron pencil beam scanning proton delivery. Phys Med Biol. 2023 Feb 17;68(4):045016. doi: 10.1088/1361-6560/acb753. PMID: 36716492.