Attenuation-based Automatic Tube Voltage Selection and Tube Current Modulation for Dose Reduction at Contrast-enhanced Liver CT

PURPOSE: To retrospectively determine whether the combined use of automatic tube voltage selection (ATVS) and automatic tube current modulation (ATCM) can effectively reduce radiation dose at contrast material-enhanced liver computed tomography (CT) while maintaining acceptable image quality compared with the use of ATCM alone. MATERIALS AND METHODS: This study was approved by an institutional review board, and informed consent was waived. Three hundred fourteen consecutive patients suspected of having liver disease were divided into three groups. In two groups, both ATVS and ATCM were used (group A1, n=97; group A2, n=101) but with different contrast gain settings; in one group, only ATCM with a fixed tube potential of 120 kV (group B, n=116) was used. Weighted volume CT dose index and dose-length product, contrast-to-noise ratios (CNRs), and mean image noise were assessed. Qualitative analysis was performed by two board-certified radiologists and one radiology resident. Statistical analysis was performed by using the one-way analysis of variance test, two-tailed paired t test, Kruskal-Wallis test, and noninferiority test. RESULTS: In groups A1 and A2, a significant dose reduction was obtained compared with that in group B (P<.0001). The mean dose reduction was 20% in group A1 and 31% in group A2. Furthermore, CNRs were significantly higher in groups A1 and A2 than in group B (P<.0001). Despite the higher image noise in groups A1 and A2, the overall image quality was acceptable. CONCLUSION: Compared with the use of ATCM alone, the combined use of ATVS and ATCM allowed reduction of radiation exposure while maintaining good image quality at contrast-enhanced liver CT.