Repeatability and reproducibility of the ultrasonic attenuation coefficient and backscatter coefficient measured in the right lobe of the liver in adults with known or suspected nonalcoholic fatty liver disease

Objectives—To assess the repeatability and reproducibility of the ultrasonic attenuation coefficient (AC) and backscatter coefficient (BSC) measured in the livers of adults with known or suspected nonalcoholic fatty liver disease (NAFLD). Methods—The Institutional Review Board approved this Health Insurance Portability and Accountability Act–compliant prospective study; informed consent was obtained. Forty-one research participants with known or suspected NAFLD were recruited and underwent same-day ultrasound examinations of the right liver lobe with a clinical scanner by a clinical sonographer. Each participant underwent 2 scanning trials, with participant repositioning between trials. Two transducers were used in each trial. For each transducer, machine settings were optimized by the sonographer but then kept constant while 3 data acquisitions were obtained from the liver without participant repositioning and then from an external calibrated phantom. Raw RF echo data were recorded. The AC and BSC were measured within 2.6 to 3.0 MHz from a user-defined hepatic field of interest from each acquisition. The repeatability and reproducibility were analyzed by random-effects models. Results—The mean AC and log-transformed BSC (logBSC) were 0.94 dB/cm- MHz and –27.0 dB, respectively. Intraclass correlation coefficients were 0.88 to 0.94 for the AC and 0.87 to 0.95 for the logBSC acquired without participant repositioning. For between-trial repeated scans with participant repositioning, the intraclass correlation coefficients were 0.80 to 0.84 for the AC and 0.69 to 0.82 for the logBSC after averaging results from 3 within-trial images. The variability introduced by the transducer was less than the repeatability error. Conclusions—Hepatic AC and BSC measures using a reference phantom technique on a clinical scanner are repeatable and reproducible between transducers in adults with known or suspected NAFLD.