Fetal dose in pregnant CT patients: a comparison of four software packages.

Objectives: To compare the fetal dose (FD) as calculated by four different software packages for pregnant women who have undergone CT acquisitions directly exposing the whole fetus to X-rays.

Materials and methods: Pregnant women who underwent CT abdomen-pelvis and/or thorax-abdomen-pelvis acquisitions from February 2018 to May 2024 and for whom the uterine dose and/or FD was calculated by a medical physicist were retrospectively included. FDs were computed per CT acquisition with VirtualDose-CT™ (VDCT), Duke Organ Dose (DOD), fetaldose.org, and COnceptus Dose Estimation (CODE) software, using phantoms taking the stage of pregnancy into account. FDs calculated by each software package were then compared.

Results: A total of 51 pregnant women with a mean age of 30.2 ± 5.7 years at 17.5 ± 10.0 weeks of pregnancy were included. The mean number of CT acquisitions per pregnant patient was 1.4 ± 0.7 with a mean CTDI_vol of 6.77 ± 3.04 [2.34-15.64] mGy, and FDs were computed for a total of 69 acquisitions. For all CT acquisitions, the median FD was 8.6 (6.8; 10.3) mGy for VDCT, 7.7 (6.1; 9.7) mGy for DOD, 6.3 (4.9; 7.6) mGy for fetaldose.org, and 7.1 (4.6; 8.8) mGy for CODE. Differences between each software package were significant (p < 0.01), except between VDCT and DOD (p = 0.025) and between CODE and fetaldose.org (p = 0.15). The concordance of calculated FD values between the software packages was poor (ICC < 0.50), except between VDCT and CODE and between fetaldose.org and CODE.

Conclusion: The choice of software used affects the calculation of the FD.

Key points: Question Differences between calculation software in terms of morphologies and types of phantoms used have an impact on FD calculations? Findings Software choice has an impact on calculated FD, but is not expected to alter patient management except for extreme cases with multiple CT exams. Clinical relevance The FD limit of 100 mGy, defined by the International Commission on Radiological Protection, cannot be reached with a single CT examination, and may only be of concern in cases where the patient undergoes multiple exams with the whole fetus exposed.