Nonalcoholic fatty liver disease (NAFLD) is a common cause of liver disease worldwide. It is associated with obesity, type 2 diabetes mellitus, and hypertriglyiceridemia. Due to their high risk for disease progression to cirrhosis, patients with advanced fibrosis need to be identified, monitored, and receive therapy.
The gold standard for diagnosing advanced fibrosis is biopsy, but a demand for accurate, non-invasive testing has spurred investigation and commercial development of such imaging techniques as ultrasound and magnetic resonance elastography (MRE).
Researches affiliated with the NAFLD Research Center at the University of California at San Diego conducted a prospective study to compare the accuracy of 2D-MRE with 3D-MRE. They determined that the technically undemanding diagnostic performance of 2D-MRE was similar to that of 3D wave field MRE, and that both were highly accurate. This 100 patient prospective study, published in the American Journal of Gastroenterology, supports the use of this non-invasive method of diagnosing or ruling out advanced fibrosis in NAFLD patients.
The cross-sectional analysis enrolled consecutive patients with biopsy-proven NAFLD who underwent MRE. The mean time interval between the two procedures was 44 days.
MRE utilizes shear waves to characterize liver fibrosis. 2D-MRE and 3D-MRE, which can evaluate a larger volume of the liver, were performed using the standard shear wave frequency of 60 Hz. 3D-MRE was also performed separate at 40 Hz. A prototype 3D-MRE implementation developed at the Mayo Clinic was used to acquire the 3D-MRE images and a prototype 3D direct inversion algorithm with characteristics similar to the commercial 2D algorithm was used for image processing.
Lead author Rohit Loomba, MD, director of the NAFLD Research Center; lead radiology author Claude Sirlin, MD, director of the liver imaging group; and Richard Ehman, principal inventor of MRE technology; reported that the area under the receive operator characteristic for diagnosing advanced fibrosis was 0.921 for 2D-MRE and 0.927 for 3D-MRE at 60 Hz. 3D-MRE at 40 Hz had the highest diagnostic accuracy, at 0.981. In addition to advanced fibrosis, both 2D-MRE and 3D-MRE were highly accurate for diagnosing NAFLD-associated cirrhosis. 3D-MRE allowed for improved assessment of spatial patterns of hepatic fibrosis and focal lesions.
The authors suggest that 3D-MRE may provide additional diagnostic utility in patients with indeterminate clinical prediction rule scores. They noted that clinical prediction rules are less accurate than MRE, and said multicenter studies are needed to evaluate 2D-MRE and 3D-MRE for monitoring longitudinal changes in liver fibrosis. They also recommended assessments of the cost-effectiveness of utilizing 3D-MRE compared with 2D-MRE, and MRE compared with biopsy, so that comprehensive, cost-efficient screening strategies for NAFLD-associated advanced fibrosis can be developed.
MRE: Diagnosing advanced fibrosis in NAFLD noninvasively. Appl Radiol.