Development and evaluation of limitation including error and reproducibility on assessment method of cerebral function using MRI

本研究的目的是评估磁共振灌注成像和质子磁共振波谱(Proton MRS)成像的可能性和问题，包括误差和重复性。选择不同的FIRE反转时间，并与SPECT脑血流灌注进行比较。在SPECT研究中，计算不同TIS(1600ms和800ms)的两幅图像的信号比(SR16/8)，并通过注射乙酰唑胺后脑血流储备(CFR)比值的增加来评价脑血流储备(CFR)。SR和CFR之间呈线性负相关(r=0.75)，说明脑血流储备会影响FIRE图像与TI变化的差异。在质子MRS上，3T强磁场仪器对频域数据进行曲线拟合后的精度有所提高，误差控制在10%以内。通过对3T MRS数据的LC模型分析，对谷氨酸和谷氨酰胺复合体的峰进行了评估，并可单独对谷氨酸的浓度进行定量。用LC模型计算GLX的标准偏差小于15%，谷氨酸的标准偏差小于25%，并将超高压序列制成3Tesla MRI，频率选择性180°脉冲，用于检测γ-氨基丁酸(GABA)的峰值。根据这一序列，在3.01ppm处将GABA与其他主要代谢物分离，并用LC模型对GABA的浓度进行定量。GABA的SD值在25%以下，其量化值与文献值基本一致，表明了新的脑血流灌注参数，提高了3T强磁场质子磁共振成像的准确性和重复性。

The purpose of this study is to evaluate the possibility and problem including error and reproducibility on the perfusion MRI and proton MR spectroscopy (proton MRS).On perfusion MRI, flow sensitive alternating inversion recovery (FAIR) sequence was made and installed into our clinical MRI instrument. The different inversion times on FAIR were selected and compared with the cerebral blood perfusion using SPECT. The signal ratio (SR16/8) of two images with different TIs (1600ms and 800ms) was calculated and the cerebral blood flow reserve (CFR) was evaluated by the increase in the ratio of cerebral perfusion after administration of acetazolamide in the SPECT study. A reversed linear correlation (r=0.75) was found between SR and CFR, indicating that differences of FAIR images with changes of TI will be affected by cerebral flow reserve.On proton MRS, the accuracy after curve-fitting of frequency domain data was increased by high magnetic field instrument at 3 Tesla, and the error was limited under 10%. The peak of glutamate and glutamine complex was also evaluated and the concentration of glutamate alone could be quantified with LCModel analysis on 3T MRS data. The value of SD of Glx by LCModel was under 15% and that of glutamate was under 25%.Furthermore, the sequence of MEGA-PRESS was made into 3 Tesla MRI with frequency selective 180° pulses to detect peak of gamma amino-butyric acid (GABA). By this sequence, GABA was separated from other major metabolites at 3.01 ppm and the concentration of GABA was quantified with LCModel. The SD value of GABA was under 25% and its quantified value was agreed with the literature value.The results indicates the new parameter of cerebral perfusion and the improvement of accuracy and reproducibility on proton MRS by high magnetic field at 3 Tesla.