Hepatic artery: Variability in measurement of resistive index and systolic acceleration time in healthy volunteers

PURPOSE: To determine the intrinsic sampling variability of measurements of hepatic artery resistive index and systolic acceleration time in healthy subjects and to estimate the components of variability attributable to the sonographer, individual measurement, and subject. MATERIALS AND METHODS: In a randomized, controlled (blinded) fashion, nine sonographers measured hepatic artery resistive index and systolic acceleration time in five healthy subjects by using Doppler ultrasound (US). Analysis of variance was used to estimate the contribution of several factors to the observed variability in measurements. RESULTS: The standard deviation for a single measurement was 0.08 for resistive index and 39 msec for systolic acceleration time. For resistive index, the estimated variance components were 0.0012 (18%), 0.0004 (6%), and 0.0050 (76%) for the subject, sonographer, and intrinsic variability, respectively. For systolic acceleration time, the estimated variance components were 59 msec (4%), 264 msec (17%), and 1,250 msec (79%) for the subject, sonographer, and intrinsic variability, respectively. CONCLUSION: Because of substantial variability in hepatic arterial measures, caution is indicated when interpreting small changes in the measurement of these Doppler US indexes.