The emphasis of this tool was given to its dynamic functionality. The tool requires a minimal set of input parameters enabling its use in clinical routine. Of course the tool is associated also with shortcomings which may introduce errors in calculation of fetal doses for individual pregnant patients undergoing CT. The most relevant limitations are as follows:


1.     MC dose calculations were based on a limited number of validated CT source term models, namely the Discovery CT750 HD scanner from GE Healthcare and the SOMATOM Flash scanner from Siemens Healthineers. Uncertainties associated with the generic CT model used for simulations and these two CT scanners were below 7%. Still, there might be differences in radiation dose distributions for other CT vendors and models due to differences in x-ray beam and filtration schemes.


2.     The tool does not take into account the realistic shape and starting angles of tube current modulation employed in the particular CT examination. Currently, CT systems do not capture angle-specific tube current information. The CTDIvol provided by the user for fetal dose assessment is usually calculated based on the averaged tube current data available in the DICOM file. When such averaged information is used to compute organ doses (including the fetal dose), uncertainties might be introduced especially if the structure of interest is located asymmetrically in the body.


3.     Another uncertainty is associated with the unique medical characteristics different from the generalized model used in this tool. This includes individual patients’ anatomy, specific fetus location in the body, and spatial distribution of organs. Additionally, the software tool assumes that patient’s arms are located in the overhead position for CT scans of the body.

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