Parmar Hemant, Lim Tchoyoson C C, Yin Hong, Chua Violet, Khin Lay-Wai, Raidy Tom, Hui Francis
Department of Neuroradiology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
Eur J Radiol. 2005 Sep;55(3):401-8. doi: 10.1016/j.ejrad.2005.01.002.
Compared to single voxel methods, MR spectroscopic imaging (MRSI) of the brain provides metabolic information with improved anatomical coverage and spectral resolution, but may be difficult to perform in the clinical setting. We evaluate the factors influencing spectral quality in MRSI using a semi-automated method, focussing on lipid contamination, and phase correction errors related to magnetic field inhomogeneity.
We retrospectively analysed MRSI studies planned by radiologists and radiographers. Two-dimensional MRSI studies using point-resolved spectroscopy (PRESS) localisation, at long echo time (135 or 144 ms) were acquired on a 1.5 T scanner. Studies that contained lipid contamination and abnormally inverted spectra were reviewed and the latter correlated with anatomic location at the base of skull, and with the area of the region of interest (ROI) studied.
Of 128 consecutive MRSI studies, six showed abnormal inverted spectra, of which four were acquired at the base of skull. Multivariate logistic regression analysis showed that study location at the base of skull, but not larger ROI, was a significant predictor for the risk of being affected by inverted spectra (RR for base of skull: 11.76, 95% CI: 1.86-74.18, P=0.009. RR for area of ROI: 3.68, 95% CI: 0.57-23.67, P=0.170). Seven studies showed lipid contamination; all were in close proximity to the overlying scalp.
Using a semi-automated acquisition and post-processing method, MRSI can be successfully applied in the clinical setting. However, care should be taken to avoid regions of high magnetic field inhomogeneity at the base of skull, and lipid contamination in voxels prescribed near the scalp.
与单体素方法相比，脑部磁共振波谱成像（MRSI）能提供代谢信息，且具有更好的解剖覆盖范围和光谱分辨率，但在临床环境中可能难以实施。我们使用一种半自动方法评估影响MRSI光谱质量的因素，重点关注脂质污染以及与磁场不均匀性相关的相位校正误差。
我们回顾性分析了由放射科医生和放射技师计划的MRSI研究。在1.5T扫描仪上进行了二维MRSI研究，采用点分辨光谱法（PRESS）定位，长回波时间（135或144毫秒）。对包含脂质污染和异常反转光谱的研究进行了审查，并将后者与颅底的解剖位置以及所研究的感兴趣区域（ROI）面积相关联。
在128项连续的MRSI研究中，六项显示出异常反转光谱，其中四项是在颅底采集的。多变量逻辑回归分析表明，颅底的研究位置，而非较大的ROI，是受反转光谱影响风险的显著预测因素（颅底的相对危险度：11.76，95%置信区间：1.86 - 74.18，P = 0.009。ROI面积的相对危险度：3.68，95%置信区间：0.57 - 23.67，P = 0.170）。七项研究显示有脂质污染；所有这些都紧邻上方头皮。
使用半自动采集和后处理方法，MRSI可以成功应用于临床环境。然而，应注意避免颅底高磁场不均匀区域以及头皮附近体素中的脂质污染。
