Diffusion-weighted MR shows potential to displace liver biopsy

The sale of MR scanners is inextricably linked to the continuing growth in demand for MR procedures and, by extension, new applications for MRI. Among the associated growth opportunities in the eyes of vendors is diffusion-weighted imaging. Now research conducted at New York University Medical Center documents that DWI may be a useful indicator of moderate to severe chronic liver disease.

The need for such a capability is being driven by the increased incidence of chronic hepatitis in the U.S., particularly hepatitis C, the diagnosis of which now depends on liver biopsy. This technique is not only invasive but limited by interobserver variability and sampling error, according to Dr. Bachir Taouli, an assistant professor of radiology at NYU and lead author of the study, which appears in the October issue of the American Journal of Roentgenology.

"DWI appears promising in that purpose, although it needs validation in a larger series," Taouli said.

The NYU study included 30 subjects: 23 patients with chronic hepatitis and seven healthy individuals who were a control group. Taouli and colleagues distinguished between disease and healthy states using apparent diffusion coefficients (ADCs), defined by the quantification of water diffusion in tissue found through diffusion-weighted MR. They compared patients who had liver fibrosis at stage two or greater versus those who were at stage one. They also compared fibrosis patients who were at stage three or greater versus those who were at stage two.

The study showed that hepatic ADC was a significant indicator of liver fibrosis at stage two or greater and stage three or greater.

Taouli noted that the method remains experimental, pending validation through more extensive testing. Future research should compare DWI with other methods such as FibroTest (a score based on a combination of basic serum markers) or FibroScan (an ultrasound-based method to measure liver stiffness), according to Taouli.

"However, diffusion imaging does show potential for decreasing the number of biopsies and decreasing the number of antifibrogenic drug trials," he said.