Factors affecting size-specific dose estimates in addition to scanning parameters for chest-abdomen-pelvis computed tomography using automatic tube current modulation at Chiangrai prachanukroh hospital
Keywords:
Arm position, Automatic tube current modulation, Computed tomography, Patient off-centering, Size-specific dose estimatesAbstract
Background: Computed tomography (CT) is a high radiation dose modality in diagnostic radiology. In addition to the scanning parameters, there are other factors affecting patient radiation dose. Objective: To study the factors in addition to scanning parameters that may affect size-specific dose estimates (SSDE). Methods: This study was a retrospective observational cross-sectional design in the patients who underwent Chest-Abdomen-Pelvis CT using automatic tube current modulation between September 2019 and June 2020 at Chiangrai prachanukroh hospital (CRH). Five hundred thirty-five patients were divided into 5 groups based on water-equivalent diameter (Dw) and then patients in each group were divided into 2 subgroups: SSDE being greater than the median and SSDE not being greater than the median. A cut-off value was the median SSDE of each Dw group. The variables of interest (gender, age, effective diameter, scan projection radiography (SPR) view, arm position, presence of foreign bodies or medical devices and patient off-centering) were compared between the group with SSDE being greater than the median and the group with SSDE not being greater than the median. Results: Female, younger than 60 years old and effective diameter were associated with the significantly increased likelihood of SSDE being greater than the median (p-value<0.05). The presence of foreign bodies or medical devices were associated with the borderline significantly increased likelihood of SSDE being greater than the median (p-value=0.050). The likelihood of SSDE being greater than the median, in arm-down position on SPR and then repositioning to be arm up position on the axial images was not statistically significantly different from non-reposition (arm down position on both SPR and axial images), but both of these were statistically significantly associated with the higher likelihood compared with the arm up position on both SPR and axial images. The SPR view and patient off-centering were no statistically significant associations with the SSDE being greater than the median. Conclusions: Female, younger than 60 years-old, effective diameter, presence of the foreign body or medical devices and arm down position on the SPR had an effect on higher SSDE than the median.
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