³¹P Magnetic Resonance Spectroscopy a Useful Tool for Evaluating Early Acute Hepatic Radiation Injury

A Chinese research team investigated whether changes of ³¹P magnetic resonance spectroscopy (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 significant phosphorylated metabolite for detecting acute hepatic injury.

Acute hepatic radiation injury could lead to necrosis of hepatocytes, fatty degeneration, and hepatic fibrosis. At the present, the gold standard test is liver biopsy. However, this procedure is invasive, uncomfortable for the patients and sometimes results in serious complications. ³¹P MRS has been used to study liver metabolism in vivo for several years.

In the study, a research team led by Dr. Jian-Shan Mao from Zhejiang University (China) studied 30 rabbits that received different radiation doses (ranging 5-20 Gy), which were used to establish acute hepatic injury models. Blood biochemical tests, ³¹P MRS, and pathological examinations were carried out 24 hours after irradiation. The level of injury was evaluated according to LDS and pathology. Ten healthy rabbits served as controls. The MR examination was performed on a 1.5 T imager using a ¹H/³¹P surface coil by the two-dimensional (2D) chemical shift imaging technique. The relative quantities of phosphomonoesters (PME), phosphodiesters (PDE), inorganic phosphate (Pi), and adenosine triphosphate (ATP) were measured.

The investigators, who published their study on June 14, 2009 in the World Journal of Gastroenterology, discovered 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 pathologic grading, respectively, and it decreased progressively with the increased degree of injury (r = -0.723, p = 0.000).

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 pathologic grading, respectively. There were no significant differences among groups according to LDS grading, and no significant differences between the control group and experimental groups according to pathologic grading. Significant differences were only found in PDE/ATP between the moderate injured group, the severe injured group, the control group, and the mild injured group. No significant difference was found in other ratios of relative quantification of phosphorus metabolites.

These results, according to the investigators, indicate that ³¹P MRS is a useful technique to evaluate early acute hepatic radiation injury. The relative quantification of hepatic ATP levels, which can reflect the pathologic severity of acute hepatic radiation injury, is correlated with LDS. This study may be especially useful for allowing clinical identification of early acute hepatic injury with ³¹P MRS in the future.

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