Proton MR Spectroscopyを用いた脳腫瘍の診断—正常脳とグリオーマの定量値の比較

Diagnosis of Brain Tumor with Proton MR Spectroscopy : the Quantification of Gliomas Compared with Normal Brain

I．はじめに

　臨床用MRI装置におけるproton MR spectro-scopy（MRS）は1990年頃より施行されるようになり，臨床的有用性を強調する報告も少なくない^{1,3,5,6,9,13）}．しかし臨床の場においては限られた施設でしか使用されておらず，広く臨床に役立っているとは思われない．この理由としてMRSはMRI以上に高い精度で磁場の均一性が要求されることや測定法の煩雑さがあげられているが，MRSのデータ解釈にも問題点があると思われる．

　われわれは内在性の組織水を基準物質としたMRSによる脳内代謝物質の相対的定量を行い，正常脳と脳腫瘍の代謝物質の濃度を比較，検討した．

We conducted quantification of proton MR spectroscopy (MRS) using water signal as an internal stan-dard, in order to quantify the concentrations of metabolites in normal adult brains and in gliomas in vivo. Single-voxel spectra were acquired using a point-resolved spectroscopic (PRESS) pulse sequence as part of the Probe. P spectroscopy package on a GE Signs Horizon Hispeed LX1.5T scanner (TR/TE/Ave=3000msec/30msec/64). The volume of interest (VOI) varied from 15.0×15.0×15.0mm³ to 20.0×20.0×20.0mm³ for the brain. The present study included 26 healthy volunteers and 12 patients with gliomas, whose diagnoses were verified by histologic examination. The calculated concentrations of N-acetyl-aspar-tate (NAA), creatine (Cre) and choline (Cho) in normal hemispheric white matter were 23.66±1.94mM (mean±SD), 12.97±1.44mM, and 4.38±0.60mM, respectively. We found they were not necessarily uni-form in different parts of the brain, for example, in the pons and basal ganglia. The concentrations of NAA and Cre decreased in all gliomas (p＜0.001). Cho concentration also decreased in the glioma (p＜0.005). The NAA/Cre, NAA/Cho, and Cre/Cho ratios can distinguish normal brain from gliomas, and NAA/Cho ratio can distinguish low-grade astrocytoma from the high-grade group. The results indicate that this noninvasive method offers reasonable estimation of metabolite concentrations in the brain in vivo and therefore is useful in diagnoses of gliomas.