MR spectroscopy could replace liver biopsy for assessing radiation injury

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While liver biopsy is the gold-standard test for early acute hepatic injury--which includes the risk of hepatocytes' necrosis, fatty degeneration and hepatic fibrosis--31P MR spectroscopy (MRS) could offer a non-invasive alternative, according to research published June 14 in the World Journal of Gastroenterology.

A research team led by Jian-Shan Mao from the department of internal medicine at Zhejiang University in China investigated whether changes of 31P MRS in the liver with early acute radiation injury were related to the liver damage score (LDS) and pathologic changes. They also determined the value of 31P MRS in detecting early acute hepatic radiation injury, and identified the most valuable phosphorylated metabolite for detecting acute hepatic injury.

In the study, 30 rabbits which received different radiation doses (ranging 5-20 Gy) were used to establish acute hepatic injury models. Blood biochemical tests, 31P MRS and pathological examinations were carried out 24 h after irradiation. The degree of injury was evaluated according to the LDS and pathology. Ten healthy rabbits served as controls. The MRS exam was performed on a 1.5T scanner using a 1H/31P surface coil by the 2D chemical shift imaging technique. The relative quantities of phosphomonoesters (PME), phosphodiesters (PDE), inorganic phosphate (Pi) and adenosine triphosphate (ATP) were measured.

They found that there were significant differences of ATP relative quantification among control group, mild injured group, moderate injured group and severe injured group according to both LDS grading and pathological grading, respectively, and it decreased progressively with the increased degree of injury (r = -0.723).

The relative quantification of PME and Pi decreased significantly in the severe injured group, and the difference between the control group and severe injured group was significant (P < 0.05) according to LDS grading and pathological grading, respectively. There were no significant differences among groups according to LDS grading, and no significant differences between the control group and experimental groups, based on the pathological grading. Significant differences were only found in PDE/ATP between the moderate injured group, the severe injured group and the control group, the mild injured group. No significant difference was found in other ratios of relative quantification of phosphorus metabolites.

Already, it has been reported that 31P MRS not only complements liver biopsy but also is a possible replacement, and furthermore, 31P MRS has particular value in assessing disease progression, Mao and colleagues noted.

"The relative quantification of hepatic ATP levels, which can reflect the pathological severity of acute hepatic radiation injury, is correlated with LDS. This study may be particularly useful for allowing clinical detection of early acute hepatic injury with 31P MRS in the future," according to the authors.