Repeatability and Reproducibility of a Clinically Based QUS Phantom Study and Methodologies.

The purpose of this study is to evaluate the repeatability and reproducibility (R&R) of quantitative ultrasound (QUS) estimates, specifically attenuation coefficient (AC) and backscatter coefficient (BSC), using the same Siemens 3000 clinical ultrasound scanner. Additionally, the purpose of this work is to detail the measurement and analysis methodology. Repeatability is closeness of agreement between measures obtained with the same method under same conditions (same sonographer and same transducer) and reproducibility is closeness of agreement between measures obtained with the same method under different conditions (different sonographers and/or different transducers). Calibrated phantoms were scanned by two sonographers using two transducers in each session for multiple sessions over a period of four months. The phantom scans occurred as part of a clinical QUS liver study in human research participants spanning a spectrum of obesity and liver disease severity. The scanner was adjusted in each participant to obtain the highest quality liver B-mode images prior to acquiring data from the phantoms for which no scanner adjustments were made. The R&R were analyzed and estimated using the unweighted sums of squares ANOVA approach by applying two random effect models. The measurement variance caused by repeatability and reproducibility is small (AC: 2.4- 3.2×10-4 [dB/cm-MHz]2; 10log10BSC: 0.23-0.27 dB2 ). The reproducibility variance is statistically significantly lower than the repeatability variance. The total R&R was not influenced by phantom properties over a wide range representing those found in liver in vivo.