Comparing different methods for estimating radiation dose to the conceptus.

Purpose: To compare different methods available in the literature for estimating radiation dose to the conceptus (D) against a patient-specific Monte Carlo (MC) simulation and a commercial software package (CSP).

Method: Eight voxel models from abdominopelvic CT exams of pregnant patients were generated. D was calculated with an MC framework including patient-specific longitudinal tube current modulation (TCM). For the same patients, dose to the uterus, D, was calculated as an alternative for D, with a CSP that uses a standard-size, non-pregnant phantom and a generic TCM curve. The percentage error between D and D was studied. Dose to the conceptus and percent error with respect to D was also estimated for three methods in the literature.

Results: The percentage error ranged from -15.9% to 40.0% when comparing MC to CSP. When comparing the TCM profiles with the generic TCM profile from the CSP, differences were observed due to patient habitus and conceptus position. For the other methods, the percentage error ranged from -30.1% to 13.5% but applicability was limited.

Conclusions: Estimating an accurate D requires a patient-specific approach that the CSP investigated cannot provide. Available methods in the literature can provide a better estimation if applicable to patient-specific cases.

Key Points: • A patient's internal anatomy affects the dose to the conceptus. • Conceptus position has an influence on its dose estimation. • Patient anatomy and specific TCM must be considered for accurate conceptus dosimetry. • D to a standard-size phantom should not be used as D .