Attenuation-Based Automatic Kilovolt Selection in Abdominal Computed Tomography Effects on Radiation Exposure and Image Quality

Objectives: Dose reduction has become a major issue in computed tomography (CT). The benefit of kilovolt (kV) reduction has been demonstrated in CT angiography. We sought to evaluate an attenuation-based fully automated kV-selection and milliampere second-adaption algorithm for CT and to assess radiation dose and image quality in comparison with a standard 120 kV protocol in contrast-enhanced (CE) portal-venous thoracoabdominal imaging. Materials and Methods: One hundred patients (mean age, 58.4 +/- 5.7 years; mean body mass index [BMI], 26.1 +/- 5.1 kg/m(2)) underwent CE CT using automated selection of the tube potential (80-140 kV) with milliampere second adaption based on the attenuation profile of the scout scan. The estimated CT dose index was recorded for the proposed scan setting and standard 120-kV protocol. Regions of interest measurements were performed at different locations for objective assessment of image quality. Signal-to-noise ratio and contrast-to-noise ratio (CNR) were calculated. The subjective image quality was assessed by 2 observers with a 4-point scale using previous CT examinations with the 120-kV standard protocol as the reference for comparison. Results: The kV-selection algorithm could be applied in all examinations without problems. Image quality was high, and there were no significant differences compared with previous examinations of the patients performed at 120 kV. Eighty kilovolts was used in 9% of examinations (mean BMI, 22.8 +/- 2.8 kg/m(2)); 100 kV, in 75% (mean BMI, 23.7 +/- 4.7 kg/m(2)); 120 kV, in 16% (mean BMI, 30 +/- 3.3 kg/m(2)); and 140 kV, in a single case (BMI, 49.4 kg/m(2)). The average estimated CT dose index reduction was 25.3% in the 80-kV group, 14.5% in the 100-kV group, and 11.4% overall. The CNR did not differ significantly, whereas the signal-to-noise ratio was significantly higher in the 80- and 100-kV examinations. Conclusion: The attenuation-based kV-selection algorithm was demonstrated to be applicable in clinical routine of CE thoracoabdominal CT, to keep CNR constant, and to result in a significant dose reduction while preserving image quality.