ABSTRACT
The increased technological capabilities, and complexity of multi detector row computed tomography (MDCT) as a diagnostic imaging tool has created a need for more accurate calculation tools to estimate the absorbed dose and radiological risk from CT examinations.1 An estimate of the effective dose to a patient undergoing a CT examination requires knowledge of the absorbed dose to each radiosensitive organ. Direct measurement of CT organ doses is not possible, and conventional dose estimates are dif cult due to the complexity of modern, MDCT scanning protocols. Several approaches have been developed to approximate the behavior of current MDCT scanners such as those employed by imaging performance assessment of CT (ImPACT) in their dose calculation spreadsheet.2 The ImPACT CT dose spreadsheet is based on the simulations performed by the National Radiological Protection Board (NRPB) and the dose estimates for MDCT scan protocols are approximated from contiguous axial scan data and are not derived directly from helical acquisition simulations.3-5 In addition, the dose estimates are based upon the medical internal radiation dose, version V (MIRD-V) geometry model and do not account for patient-speci c size variations.
