Purpose: The purpose of this study was to determine how the characteristics of the data-acquisition (DAQ) electronics of a Compton camera (CC) affect the quality of the recorded prompt gamma (PG) interaction data and the reconstructed PG images, during clinical proton beam delivery.
Methods: We used the Monte-Carlo-plus-Detector-Effect (MCDE) model to simulate the delivery of a 150 MeV clinical proton pencil beam to a tissue-equivalent plastic phantom at a low dose rate of 1.0 × 103 p+/sec, representing a rate at which only one gamma is estimated to interact in the CC at a time, and clinical dose rates from 1.0 × 109 p+/s up to 1.0 × 1010 p+/s. We studied how the recorded PG interaction data, at each dose rate, changed as two characteristics of the DAQ electronics of a CC were changed: (1) the number of data readout channels; and (2) the active charge collection, readout, and reset time.
Results: As the dose rate increased, the number of recorded PG single-, double-, and triple-scatter events recorded decreased by a factor of 45x for the current CC DAQ configuration. However, as the DAQ readout channels increased and the readout/reset timing decreased, the number of recorded events decreased by <5× at the highest clinical dose rate. The increased readout channels and reduced readout/reset timing also resulted in a higher percentage of the recorded double- and triple-scatters being “true” events (caused by a single incident gamma) and not “false” events (caused by multiple incident gammas).
Conclusion: The increase in the number and the quality of recorded double- and triple-scatter events resulted in a significant improvement to the reconstructed PG images, especially at the highest clinical dose rates.
Funding Support, Disclosures, and Conflict of Interest: The research reported in this publication was supported by the National Institutes of Health National Cancer Institute under award number R01CA187416. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Protons, In Vivo Dosimetry, Treatment Verification
IM- Particle (e.g., Proton) CT: Detector development & evaluation