Moderator of 1 Session
Presenter of 1 Presentation
FIRST TRIGGERED SINGLE-PULSE SCINTILLATION IMAGING OF SYNCHROCYCLOTRON PENCIL BEAM SCANNING PROTON SYSTEM
Abstract
Background and Aims
To test an improved imaging system for spatial and temporal characterization of a synchrocyclotron proton pencil beam scanning (PBS) system.
Methods
An ultra-fast CMOS camera was externally triggered by a scintillation sheet coupled to a remote trigger unit (RTU) for beam-on detection of single spot beams and of 10×10 cm2 field with 2.5 mm spot spacing. A uniquely high temporal frame rate (1 kHz) coupled with the triggering mechanism allowed for capture of each synchrocyclotron pulse (3 ms rep rate, 0.1% duty cycle, 4 μs pulse width), Figure 1. The full-field images of a scintillation screen produced with the intensified camera were acquired with 0.265 mm image pixel size and processed by correcting for the background, flat, and dark fields. Cumulative image and pixel intensity were used for quantitative assessment of dose and dose rate.
Results
The processed images were calibrated to beam currents across the conventional clinical range, and the linear relationship (R2=0.992) between dose and scintillation intensity was used to validate the expected camera response, Figure 2. Similarly, the spatial profile of the single spot beam agreed within an average of 3%, Figure 3. Preliminary results from the 10×10 cm2 field indicate strong spatial agreement with the planned dose, with a mean spatial percent agreement of within 5%, and demonstrate the camera’s ability to capture each pulse as the spot is scanned, Figure 4.
Conclusions
The temporal pulse structure of a synchrocyclotron produced proton beam, interplayed with delivery via PBS, introduces complicated spatiotemporal dosimetric characteristics, warranting a fast, time-gated, intensified camera for real-time imaging. This study demonstrates the first system able to resolve single pulse characteristics of a synchrocyclotron beam at conventional dose rates. Further camera development and testing will enable the target applications in clinical and FLASH proton beam characterization and validation.