Program Information
Experimental Validation of Radimetrics Estimated Organ Doses in Computed Tomography Examinations Using Metal-Oxide-Semiconductor Field-Effect Transistor Detector in Phantom Measurements
S Zhang*, B Peng , S Jambawalikar , A Einstein , T Lin , M Liu , S Trattner , R Al-Senan , Columbia University New York Presbyterian Hospital, New York, NY
Presentations
SU-K-201-8 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 201
Purpose: To evaluate the accuracy of organ doses estimated by Radimetrics in pediatric CT scans through comparison with measurements in an anthropomorphic phantom using MOSFET detectors.
Methods: In-phantom dose measurements were performed with a Toshiba Aquilion One 320-detector CT scanner using pediatric abdomen and head protocols. A total of 22 calibrated MOSFET detectors were placed at appropriately-selected locations inside a five-year old ATOM® phantom to assess doses to critical organs. Doses to lower lungs, liver, spleen, kidneys, stomach, large intestines, small intestines, and gonads were recorded using abdomen protocol (100 kV / 140 mAs / helical), whilst doses to brain, thyroid and thymus were recorded using head protocol (120 kV / 200 mAs / volume). Five consecutive measurements were made for each protocols and the mean MOSFET voltage was converted to dose in organ. All scans were sent to Radimetrics to generate estimated organ doses using Monte Carlo simulations.
Results: Preliminary results showed good agreement between estimated organ doses from abdomen scan with MOSFETs and those calculated by Radimetrics (12%). Dose to brain (from head scan), however, was 51% higher in Radimetrics compared to MOSFET measurements (47 vs. 31 mGy). For all measured vs. calculated doses, paired t-test showed no statistical significant difference (p = 0.3). If brain is excluded then the p-value becomes 0.6.
Conclusion: With the exception of the brain, preliminary results demonstrated agreement of estimated dose by Radimetrics. Further investigation will be carried out for possible reasons of this higher dose to brain calculated by Radimetrics which also exceeded the CTDIvol of the study (43 mGy). Future work is aimed at extending this approach to investigate the accuracy of estimated adult organ dose across different CT scanners, as well as to compare measured point doses inside anthropomorphic phantom between MOSFET and other dosimeters, e.g. Gafchromic film.
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