高场强磁共振系统点分辨波谱技术探讨

目的研究单体素点分辨波谱技术 (PRESS) 中不同参数对结果的影响,并对优化技术参数进行探讨.方法运用GE 3.0 T signa excite 核磁共振扫描仪对四组无明显临床脑神经系统疾患者分别行单体素PRESS扫描.每组在其他参数不变的条件下,分别改变不同的TR, NAV, NEX以及在静注造影剂前后扫描.记录NAA/Cr, Cho/Cr, mI/Cr和SNR值,并进行统计学分析.如数据属正态分布,则进行配对t检验;否则进行Wilcoxon检验.结果各组中NAA/Cr, Cho/Cr和mI/Cr均没有显著性差异.TR为 2000 ms时,信噪比(SNR)明显高于TR 为1500 ms和1200 ms时.NAV为128时,SNR明显高于NAV为64和32时.但NAV为128和96,NEX为 8和2以及静注造影剂前后SNR没有显著性差异.结论在PRESS序列参数的选择上,考虑到SNR、测量值及扫描时间,最佳参数为TR 1500 ms,TE 35 ms,NAV 96和NEX 2.在某些特定情况下,参数可做相应调整.

Evaluation of MR spectroscopy with PRESS sequence on 3.0 T

Objective To study the effect of parameters on results of single voxel MR spectroscopy with point resolved spectroscopy (PRESS), and optimization of the parameters. Methods Four groups of persons without evidence of neurological diseases were included. All the examinations were performed with GE 3.0 T Signa Excite MR scanner. In each group, one parameter was evaluated with other parameters remaining constant. The parameters are TR, NAV, NEX and contrast medium respectively. Then the values of NAA/Cr, Cho/Cr, mI/Cr, and SNR (signal noise ratio) were recorded and analyzed. If the data were in normalized distribution, paired t-test was used; If not, Wilcoxon test was used. Results There was no significant difference in the values of NAA/Cr, Cho/Cr, and mI/Cr with different TR, NAV, NEX and before and after injection of contrast medium. The SNRs were statistically higher with TR 2000 ms than those with TR 1500 ms and 1200 ms. And the SNRs were higher with NAV 128 than those with NAV 64 and 32. But there was no significant difference in SNRs with NAV 128 and 96. And the SNRs were not significantly different with NEX 8 and 2, as well as before and after injection of contrast medium. Conclusion Taking SNR, values measured and scan time into account, the parameters as TR 1500ms,TE 35 ms, NAV 96 and NEX 2 are recommended. In some circumstance, if a certain aspect was emphasized, the parameters should be adjusted accordingly.