Abstract
Fourteen patients (17 cases) were treated with the whole brain irradiation. Physiological changes in white matter were measured by in vivo 1H magnetic resonance spectroscopy (1H-MRS). Phantom examination proved the accuracy of our 1H-MRS method to be valid. The measurement was performed 2 or 3 times in each case at the radiation doses ranged from 0 to 40Gy with 2Gy daily fractionation. For the measurement of 1H-MRS, 1.5T whole body MR system was used and stimulated echo aquisition mode (STEAM) with chemical shift selective (CHESS) pulse was applied. Volume of the interest (VOI) was 2.5×2.5×2.5cm3, and the repetiton time and echo time were, 2, 000ms and 272ms, respectively. The acute radiation damage of brain was evaluated by the change of peak area ratio (PAR) of choline, creatine and N-acetyl aspartate (NAA). 1H-MRS spectra before irradiation were different from those observed during irradiation. There were statistically significant (p<0.01) in the choline/creatine ratio between the irradiated group and preirradiated group. Noteworthy, the change of choline/creatine ratio showed good correlation with irradiated dose (correlation coefficient=0.91). As PAR seems to correlate with irradiated dose, it is suggested that choline/creatine ratio might be a useful indicator which reflects the acute radiation damage of brain. 1H-MRS is a powerful modality, detecting the subtle physiological change which is difficult to evaluate with conventional images.
