Beyond Confounders: Addressing Source of Measurement Variability and Error in Shear Wave Elastography

Liver disease and cirrhosis are important causes of morbidity and mortality in the United States and are a major public health problem with 40,000 deaths and more than 1.4 billion dollars spent on medical services. Hepatic fibrosis is the final common pathway for many different liver insults and is known to be a dynamic process, which is reversible if diagnosed early and treated. If untreated, fibrosis eventually progresses to cirrhosis, which is irreversible. The diagnosis of fibrosis relies on liver biopsy (the gold standard) however, is an invasive procedure with risks and sampling errors. Indirect biomarkers of fibrogenesis can measure some of these components to determine categories of fibrosis, with a sensitivity and specificity of 47% and 90% respectively.It is shown in the literature that, fat content of liver is related with fibrosis development. Biopsy is accepted as the most accurate technique to assess liver fat and fibrosis amount. Fibrotic livers demonstrate increased stiffness, a property that can be measured using technology named Ultrasound Elastography or sonoelastography (SWE). SWE is performed by insonating the patient with a low energy, amplitude, and frequency shear wave created by a vibrating probe. The propagated wave travels faster with increasing fibrosis: the stiffer the tissue, the faster the shear wave propagates. A pulse-echo ultrasound acquisition allows measurement of the wave velocity and the results are presented as kilopascals (kPa). Prior reports have described sensitivity and specificity for liver fibrosis detection of 80% and 97% respectively for SWE. The benefits of SWE are that it is inexpensive, reproducible, painless, rapid (\< 10 min), easy to perform, and can be used for diagnosis, prognosis and monitoring disease progression. The objective of this study is to compare the variation in elastography values and study the factors that might cause these variations. The proposed investigation is a cross-sectional study using ultrasound elastography. The investigators are planning to enroll 30 subjects 18 years old and older in whom diffuse liver disease is suspected, and who have undergone non-focal liver biopsy in the past 6 months or are scheduled to undergo biopsy within 3 months of enrollment, as part of their routine clinical care. All subjects will be required to come to the MGH main campus for 2 study visits within 60 days of each other. In addition, subjects will need to fast for at least 4 hours prior to study visits There will be two visits in this study and maximum 60 days time frame between the visits is anticipated. Two operators will perform the ultrasound examination. Reproducibility and repeatability of the ultrasound devices will be estimated. Ultrasound examination including sonoelastography will be performed using four FDA-approved ultrasound units; Both operators will perform; * Median Elastograpy (10 measurements) on regular and variable map at a depth(in the area between 2cm from capsule and 6.5cm from skin) * Median SWE value with active/free breath(10measurements) * Median SWE value with less number of acquisitions(3measurements) These measurements will be collected in subgroups using specific systems. In second visit, all measurements will be repeated with the same operators.