MO‐E‐204B‐05: A Novel Organ Dosimetry in an Anthropomorphic Phantom Using XRQA‐2 Radiochromic Film
Purpose: A novel method to measure organ dose distributions in a phantom of heterogeneous tissue composition was established using radiochromic XRQA‐2 films. Film response accuracy was validated using thermoluminescent dosimeters (TLDs). Method and Materials: Film response accuracy and sensitivity in CT exposure geometry were verified by comparing TLD responses between two CTDI head phantoms. The phantoms were placed end‐to‐end to allow for a uniform scatter environment. TLDs and films were placed between cross‐sectional slabs of a 5‐yr old anthropomorphic phantom's thorax and abdomen regions. Software was written for dosimeter comparison within a complex anthropomorphic phantom. Film accuracy within the anthropomorphic phantom was measured by comparing TLD results within the lung, liver, and kidney organs. Results: Film and TLD dose response differences were measured for CTDI phantom, 45% (SD ± 2%), and for the anthropomorphic phantom in the lung, 28% (SD ± 8%), and liver/kidneys, 15% (SD ± 4%). Due to consistent response differences in low and high organ dose, a tissue specific correction was applied to the film organ responses. Corrected film response agreed to better than 3% (SD ± 2%), for CTDI scans, and 3% (SD ± 3%) for lungs, 5% (SD ± 3%) for liver, and 4% (SD ± 3%) for kidneys. Film measured a heterogeneous dose distribution within the organ volumes; the extent of which was not measured with the TLDs. XRQA film demonstrated an advantage over the TLD method by discovering a 15% greater maximum dose to lung in a region unmeasured by TLDs. Conclusion: XRQA films demonstrated lower sensitivity to absorbed dose measurements due to geometric inefficiencies of measuring dose from a beam situated end‐on to the film. Corrected film responses demonstrated equivalent measurement accuracy as TLD detectors with the added advantage of measuring high‐resolution dose distributions throughout an organ volume. © 2010, American Association of Physicists in Medicine. All rights reserved.
Brady, S; Yoshizumi, T; Toncheva, G; Anderson‐evans, C; Fredrickson, M; Frush, D
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