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Validation of Size-Specific Dose Estimates (SSDE) in Body CT Studies with Directly Measured Organ Doses in Adult Female Cadaveric Subjects


L Sinclair

L Sinclair1*, A Mench1, T Griglock2, S Bidari1, B Cormack1, M Arreola1, (1) University of Florida, Gainesville, FL, (2) Oregon Health & Science Univ, Portland, OR

MO-D-134-8 Monday 2:00PM - 3:50PM Room: 134

Purpose: To compare directly measured organ doses in cadaveric subjects with calculated size-specific dose estimates (SSDE) for CT studies of the torso.
Methods:: In 2011, the SSDE protocols were introduced by AAPM Task Group 204, which provides a library of conversion factors that can be applied directly to scanner-generated CTDIvol for a CT exam of the torso to generate a patient-specific dose estimate. However, the results of the SSDE formalism have not been compared to actual dose measurements. In this work, several cadaveric subjects of varying body habitus, were utilized to directly measure organ doses which result from CT examinations. Optically-stimulated luminescent dosimeters (OSLDs) were employed to measure dose within the following organs: thyroid, breasts, lungs, liver, stomach, small intestine, colon, ovary, uterus, and skin. Dose measurements were made for a standard Chest Abdomen Pelvis (CAP) protocol. After organ dose measurements were completed for each subject, the anterior-posterior and lateral patient dimensions were measured on the central slice of the study to obtain the corresponding correction factor and SSDE from AAPM 204, which was then compared with the measured organ doses for each cadaver.
Results: A total of four subjects were utilized for this study, with body mass indices (BMIs) ranging from 17.4-43.9. For the subject with a BMI of 17.4, the average organ dose from a CAP exam was 11.8 mGy. The corresponding SSDE for that subject was 12 mGy.
Conclusion:It is observed with this data that the SSDE does accurately describe the average dose absorbed in the body. The SSDE can be effectively used as a patient dose descriptor in the clinic, while organ dose libraries and software that allow for organ dose calculation are still being developed.

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