The Effect of Measurement Depth and Technical Considerations in Performing Liver Attenuation Imaging

Background and objectives: Clinical unmet need in managing nonalcoholic fatty liver disease (NAFLD), a common liver disorder affecting 25-30% of American adults is to develop noninvasive and robust biomarkers. Methods:We re-measured liver AC by placing a region of interest (ROI, 3 cm tall and 3 cm wide) at 4.5 cm, 6 cm, and 7.5 cm from the skin and a large ROI (6.0 cm tall and 7.3 cm wide) on pre-recorded ATI images from 117 participants screened for NAFLD.The difference in AC value at variable ROI depths was tested using one-way ANOVA (analysis of variance).Diagnostic performances of AC at variable depths in determining hepatic steatosis were examined by area under receiver operating characteristic curve (AUC) using MRI-proton density fat fraction (MRI-PDFF) as reference and were compared using paired-sample Z-test.Results: Based on MRI-PDFF, 117 livers were divided to 27 normal livers (MRI-PDFF < 5%) or 90 steatotic livers (MRI-PDFF ≥ 5%).Differences in AUC and AC value at variable depths and size were statistically significant (p < 0.01).The best performance for determining hepatic steatosis was the AC measured at 6 cm from the skin (AUC = 0.92).Sources of errors in performing ATI included reverberation, blank color region, and acoustic shadowing within the measurement ROI.Conclusions: ROI depth significantly influences liver AC estimation.The best ROI depth to measure liver AC in patients with BMI ≥ 30 may be at a depth of 6 cm from the skin.Technical considerations should be taken in performing liver ATI.