An Assessment of Uncertainties in Pediatric CT Organ Dosimetry When Scan Parameters and Individual Body Morphometry Are Unknown
C Kofler1*, E Olguin2, E Stepusin3, D Long4, M Kwan5, D Miglioretti6, R Smith-bindman7, W Bolch8, (1) University of Florida, Gainesville, FL, (2) University of Flordia, Gainesville, FL, (3) Chicago, IL, (4) Memorial Sloan Kettering Cancer Center, New York, NY, (5) Kiser Permanente Northern California, Oakland, CA, (6) University of California Davis, Davis, CA, (7) University of California San Francisco, San Francisco , CA, (8) University of Florida, Gainesville, Florida
Presentations
WE-D-TRACK 3-2 (Wednesday, 7/28/2021) 2:00 PM - 3:00 PM [Eastern Time (GMT-4)]
Purpose: In many epidemiology studies of patient CT exposures, details regarding patient-specific body morphometry and/or exam-specific technique factors are typically absent, and thus various assumptions are employed during organ dose reconstruction. The purpose of this study is to highlight the importance of these parameter sets in estimating effective and organ doses from a CT scan.
Methods: The University of Florida/National Cancer Institute (UF/NCI) computational phantom library (12 reference phantoms and 351 non-reference phantoms) were used to compute organ doses within a population of 2,815 American pediatric patients undergoing CT imaging from 1998 to 2013 in which both patient height/weight and exam-specific scan lengths were available. Next, patient morphometry and scan length data were incrementally removed and replaced with various estimates to assess uncertainties in CT dosimetry when these data are unavailable.
Results: Using the effective diameter of the patient to estimate height and weight resulted in up to an 82% overestimation of the effective dose. Matching to a reference phantom resulted in up to a 54% overestimation of effective dose. Estimating height based on patient age and weight based on effective diameter resulted in effective dose being underestimated by a maximum of 8% and overestimated by a maximum of 10%. Estimating height and weight based on patient age resulted in effective dose being underestimated by a maximum of 25% and overestimated by a maximum of 12%. Using a default scan length in place of a patient-specific scan length resulted in up to a >200% overestimate or a 51% underestimate of the effective dose.
Conclusion: The differences in organ and effective doses found in this study highlight the need for patient- and exam-specific information when estimating organ and effective doses from CT imaging in pediatric patient populations.
Funding Support, Disclosures, and Conflict of Interest: Funding for this study was provided by NIH/NCI Grant R01 CA185687.
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