Abstract:

Objective  To compare differences of reconstruction with filtered back projection (FBP), iDose1, iDose3, and iDose5 on the quality of CT images of upper abdomen between low-dose CT scan and routine-dose CT scan. Methods  According to the examination order, 60 patients underwent the contrast-enhanced routine-dose CT scan of upper abdomen and another 60 patients underwent the low-dose CT scan of upper abdomen. The automatic tube current technique was adopted and the mAs reference value of portal venous phase of the low-dose group was 20% lower than that of the routine-dose group. CT images of portal venous phase of two groups were reconstructed by filtered back projection, iDose1, iDose3, and iDose5. The noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of images were calculated. The subjective quality (noise, diagnostic acceptability, artifacts, and sharpness) of images was evaluated by 2 radiologists with work experience of more than 5 years. Patients of routine-dose group and low-dose group were divided into two subgroups according to the gender. Volume CT dose index (CTDIvol) and dose length product (DLP) were recorded and effective dose (ED) were calculated. Results  Low-dose CT scan combined with iDose reconstruction could satisfy the diagnostic demand. Compared with the routine-dose group, CTDIvol, DLP, and ED of male patients of the low-dose group decreased 26.39%, 26.71%, and 26.71%, respectively, while those of female patients of the low-dose group decreased 24.52%, 25.27%, and 25.27%, respectively. Conclusion  Low-dose CT scan combined with iDose iterative technique can effectively reduce the radiation dose while meeting the diagnostic quality of images.

Key words: upper abdominal computed tomography, iDose iterative reconstruction algorithm, FBP reconstruction algorithm, radiation dose, image quality