Radiology: Volume 257: Number 2-November 2010
John Damilakis, PhD Kostas Perisinakis, PhD Antonis Tzedakis, PhD Antonios E. Papadakis, PhD Apostolos Karantanas, MD
Purpose: To develop a method for estimating the radiation dose to the conceptus from multidetector computed tomography (CT) of the abdomen and pelvis in pregnant patients dur¬ing the first 7 weeks of gestation.
Materials and methods: This study was approved by the institutional review board and informed consent was obtained. A CT simulation soft-ware package was used to (a) develop voxelized models on the basis of image data from 117 nonpregnant patients who underwent abdominal and pelvic multidetector CT and (b) calculate dose at a position of the uterus assumed to be the position of the conceptus in case of pregnancy during the first 7 weeks of gestation. Regression analysis was carried out to establish the relationship among con¬ceptus dose, patient body size, and distance from the con¬ceptus to the anterior skin surface.
Results: Normalized conceptus doses calculated by using the soft¬ware package ranged from 0.335 to 0.785 mGy per ab¬sorbed dose to air. Conceptus dose showed a significant correlation with maternal body size and conceptus depth (R2 = 0.793, P < .001). A multivariable correlation of con-ceptus dose normalized to the free-in-air CT dose index (CTDIF) with conceptus depth and patient perimeter was produced for estimating conceptus dose from abdominal and pelvic multidetector CT. Conceptus dose data pro¬vided for a specific scanner can be applied to other scan¬ners by using correction factors based on ratios between the weighted CT dose index and CTDIF, resulting in inac¬curacies in the estimation of conceptus dose of less than 12%.
Conclusion: The radiation dose to the conceptus from abdominal and pelvic multidetector CT can be estimated with a method that allows for variations in maternal body size and con-ceptus position.