Purpose: To retrospectively determine whether routine utilization of the combined use of automatic tube voltage selection (ATVS) and automatic tube current modulation (ATCM) can effectively reduce radiation dose while maintaining acceptable image quality compared with the use of ATCM alone.
Materials and Methods: Post contrast abdominal CT studies performed using both ATVS and ATCM (Somatom Drive Dual Source; Siemens Medical Solutions, Forchheim, Germany) (Group 1) were collected and compared to studies performed using ATCM with a fixed tube voltage of 120 kV (Philips Brilliance iCT, Philips Medical Systems, Best, Netherlands) (Group 2) in terms of radiation exposure and image quality. Volume CT dose index (CTDIvol) and dose-length product (DLP), contrast-to-noise ratios (CNRs) and mean image noise were assessed. Quantitative and qualitative evaluation of image quality were performed by two radiologists and one radiologist, respectively. Qualitative evaluation included assessment of image noise, visibility of small anatomical structures, and artifacts.Demographic data of the patients including BMI was collected.
Results: The final study population included 108 consecutive patients (53 in Group 1 and 55 in Group 2) who underwent CT with the defined protocol. No significant differences in age, sex and BMI were observed between the two patient groups (p> 0.05).
Mean CTDIvol was 12.94 ±9.6 mGy in Group 1 and 16.85 ±5.33 mGy in Group 2 with a decrease of 23% (<0.05). Mean DLP was 645.78±530.03 mGy*cm in Group 1 and 982.14±361.39 mGy*cm in Group 2 with a decrease of 34% (<0.05). There was no significant difference in mean image noise between two groups (9.28±2.35 in Group 1 and 10.08±2.51 in Group 2) (p=0.087). CNR of the aorta, liver and portal vein were significantly higher for the Group 1 studies (p<0.05). Analysis of qualitative evaluation demonstrated a significant difference between the two groups (p<0.05) in all assessed parameters, with Group 1 possessing the advantage except in regards to artifacts. However, not one of the CT studies had a non-diagnostic degree of artifacts.
Conclusions: Combined use of ATVS and ATCM results in significant dose reduction while maintaining diagnostic image quality.
