The most appropriate region-of-interest position for attenuation coefficient measurement in the evaluation of liver steatosis

Purpose Attenuation imaging (ATI) is a new noninvasive ultrasound technique for assessing steatosis grade (S). However, validated region-of-interest (ROI) sampling strategies are not currently available. We investigated the diagnostic performance of various ATI-ROI positions for determining histopathologic S in patients with nonalcoholic fatty liver disease (NAFLD). Methods This retrospective study included 105 patients with biopsy-proven NAFLD. All attenuation coefficient (AC, dB/cm/MHz) measurements were obtained by the same hepatologist using a commercially available ultrasound system on the same day as liver biopsy. Mean (+/- standard deviation) age and body mass index of the patients were 53 (+/- 18) years and 27.1 (+/- 4.1) kg/m(2), respectively. The numbers of patients with steatosis affecting < 5%, 5-33%, 33-66%, and > 66% of hepatocytes were 8, 50, 29, and 18, respectively. The ATI-ROI was placed at three different positions for AC measurement using a dedicated workstation: the upper edge of the area ROI, twice the depth of the liver capsule, and the lower edge of the area ROI. Diagnostic performance was evaluated using the area under the receiver-operating characteristic curve (AUC). Results The AUCs of AC at the three ATI-ROI positions were 0.734 (95% confidence interval [CI]: 0.470-0.998), 0.750 (0.639-0.861), and 0.878 (0.788-0.968) for S >= 1; 0.503 (0.392-0.615), 0.824 (0.741-0.907), and 0.809 (0.724-0.895) for S >= 2; and 0.606 (0.486-0.726), 0.849 (0.767-0.932), and 0.737 (0.626-0.848) for S = 3, respectively. Conclusion For accurate steatosis grade assessment, the ATI-ROI should not be placed at the upper edge of the area ROI.