(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: To dosimetrically characterize a 50 MeV preclinical proton irradiator for use in cell and small animal experiments. A process for verifying the dose using cross-calibrated detectors and Monte Carlo (MC) was developed. The film response in the changing LET environment of the proton Bragg peak must be determined for accurate dosimetry of the beams. This study aimed to determine corrections required for characterization of this preclinical beamline.
Methods: Lateral and depth beam profiles were measured using Gafchromic EBT3 film. The film measurements were compared to percentage depth dose curves determined with a microDiamond detector, a microioniziation chamber, and MC simulations in TOPAS. The LET with depth was also determined using MC. Using this, the LET-dependent quenching of the film was found at varying points along the Bragg peak.
Results: Comparisons between the measured and simulated depth dose profiles revealed a 20% under-response of the film in the Bragg peak region. This high LET dependence has been previously reported in the literature. Using the TOPAS calculation of LET along the Bragg peak, the correction for detector response was determined in each LET environment. The lateral profiles from the film and TOPAS model were consistent with each other at the entrance and Bragg Peak of the beam.
Conclusion: A preclinical proton beam was characterized using three detectors and Monte Carlo. With a Bragg Peak depth of 18.3 mm, this beam is useful for cell and small animal studies. The film measurements verified the simulated beam profiles and the LET dependence along the Bragg peak was determined. This allows for LET-specific film corrections for more accurate dosimetry of the beamline.
Keywords
Protons, Radiobiology, Radiochromic Film
Taxonomy
TH- Small Animal RT: Experimental Dosimetry
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