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Proton Range Measurements Using a Geometrically Calibrated Liquid Scintillator Detector

C Hui

C Hui*, D Robertson , F Alsanea , S Beddar , UT MD Anderson Cancer Center, Houston, TX


SU-E-T-641 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: The purpose of this work is to develop a geometric calibration method to accurately calculate physical distances within a liquid scintillator detector and to assess the accuracy, consistency, and robustness of proton beam range measurements when using a liquid scintillator detector system with the proposed geometric calibration process.

Methods: We developed a geometric calibration procedure to accurately convert pixel locations in the camera frame into physical locations in the scintillator frame. To ensure accuracy, the geometric calibration was performed before each experiment. The liquid scintillator was irradiated with spot scanning proton beams of 94 energies in two deliveries. A CCD camera was used to capture the two-dimensional scintillation light profile of each of the proton energies. An algorithm was developed to automatically calculate the proton range from the acquired images. The measured range was compared to the nominal range to assess the accuracy of the detector. To evaluate the robustness of the detector between each setup, the experiments were repeated on three different days. To evaluate the consistency of the measurements between deliveries, three sets of measurements were acquired for each experiment.

Results: Using this geometric calibration procedure, the proton beam ranges measured using the liquid scintillator system were all within 0.3mm of the nominal range. The average difference between the measured and nominal ranges was -0.20mm. The delivery-to-delivery standard deviation of the proton range measurement was 0.04mm, and the setup-to-setup standard deviation of the measurement was 0.10mm.

Conclusion: The liquid scintillator system can measure the range of all 94 beams in just two deliveries. With the proposed geometric calibration, it can measure proton range with sub-millimeter accuracy, and the measurements were shown to be consistent between deliveries and setups. Therefore, we conclude that the liquid scintillator system provides a reliable and convenient tool for proton range measurement.

Funding Support, Disclosures, and Conflict of Interest: This project was supported in part by award number CA182450 from the National Cancer Institute.

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