Proposal and validation of weighting factors for the weighted computed tomography dose index in dual-energy computed...

This study aimed to propose and validate optimal weighting factors for weighted computed tomography dose index (CTDI_w) in dual-energy computed tomography (DECT) to improve average dose estimation in the central cross-sectional plane of a CTDI phantom. CTDI₁₀₀measurements were acquired at 13 points in a CTDI phantom with a diameter of 32 cm using five dual-energy tube voltage combinations ranging from 70/Sn150 to 100/Sn150 kV. The average doses across the cross-sectional plane were calculated by integrating the dose profiles. After calculating the average dose profiles, the weighting factors were optimised using a Python-based search algorithm to minimise the relative error to within 1%, while selecting the smallest possible integers to maintain accuracy and simplicity. The percentage difference (PD) between the average dose and the CTDI_wwas then evaluated for the proposed weighting factors and those derived from two previously reported methods. The proposed weighting factors were derived as 2/5 for the centre and 3/5 for the periphery. Applying these factors reduced the PD between the CTDI_wand the average cross-sectional dose to a maximum of 0.5%. Compared with the currently used standard weighting factors and two previously reported weighting factors, the proposed factors provided the most accurate estimation of the average dose in the CTDI phantom across all tube voltages in DECT, with a maximum deviation of only 0.5%. In contrast, previously reported factors showed deviations of up to 2.5%. These findings demonstrated that the proposed weighting factors provided a more accurate estimation of CTDI_wunder DECT compared with both the currently used and previously reported factors.