Evaluation of acute radiation damage of the normal brain using 31P-MR spectroscopy

The authors evaluated the effect of radiotherapy on the normal brain in patients with brain tumor. 31P-magnetic resonance spectroscopy (31P-MRS) was used to determine the cerebral energy levels, phospholipid metabolism, and intracellular pH. The five patients with glioma and one patient with a metastatic brain tumor included in the study were treated with conventional radiation. 31P-MRS was studied before, during, and after radiotherapy. The measurements were performed three to six times on each patient. The acute radiation damage of the normal brain was evaluated by the change of ratios of the peak area (%) of phosphomonoesters (PME), inorganic phosphate (Pi), phosphodiesters (PDE), phosphocreatine (PCr), and β-ATP to the total areas of the phosphorus peak. After radiotherapy, the normal brain 31-spectrum exhibited transient elevation and reduction of % Pi. The % PDE showed a transient reduction during radiation therapy. On the other hand, the intracellular pH was transiently elevated during radiotherapy. It can be concluded that 31P-MRS appears to be very useful approach for evaluating the acute radiation damage of the normal human brain. Such an evaluation is difficult with the other conventional imaging procedures. (author)