Lecocq Angèle, Le Fur Yann, Amadon Alexis, Vignaud Alexandre, Cozzone Patrick J, Guye Maxime, Ranjeva Jean-Philippe
Centre de Résonance Magnétique Biologique et Médicale, CRMBM, UMR 7339, CNRS, Faculté de Médecine de la Timone, Aix-Marseille Université, 23, Boulevard Jean Moulin, 13385, Marseille, Cedex 05, France.
MAGMA. 2015 Feb;28(1):87-100. doi: 10.1007/s10334-014-0451-6. Epub 2014 Jun 8.
To propose a fast and robust acquisition and post-processing pipeline that is time-compatible with clinical explorations to obtain a proton density (ρ) map used as a reference for metabolic map normalization. This allows inter-subject and inter-group comparisons of magnetic resonance spectroscopic imaging (MRSI) data and longitudinal follow-up for single subjects.
A multi-echo T 2 (*) mapping sequence, the XEP sequence for B 1 (+) -mapping and Driven Equilibrium Single Pulse Observation of T 1-an optimized variable flip angle method for T 1 mapping used for both B 1 (-) -mapping and M 0 calculation-were used to determine correction factors leading to quantitative water proton density maps at 3T. Normalized metabolite maps were obtained on a phantom and nine healthy volunteers. To show the potential use of this technique at the individual level, we also explored one patient with low-grade glioma.
Accurate ρ maps were obtained both on phantom and volunteers. After signal normalization with the generated ρ maps, metabolic concentrations determined by the present method differed from theory by <7 % in the phantom and were in agreement with data from the literature for the healthy controls. Using these normalized metabolic values, it was possible to demonstrate in the patient with brain glioma, metabolic abnormalities in normalized N-acetyl aspartate, choline and creatine levels; illustrating the potential for direct use of this technique in clinical studies.
The proposed combination of sequences provides a robust ρ map that can be used to normalize metabolic maps in clinical MRSI studies.
提出一种快速且稳健的采集和后处理流程，该流程在时间上与临床检查兼容，以获取用作代谢图标准化参考的质子密度（ρ）图。这使得能够对磁共振波谱成像（MRSI）数据进行受试者间和组间比较，并对单个受试者进行纵向随访。
使用多回波T2（*）映射序列、用于B1（+）映射的XEP序列以及用于T1映射的驱动平衡单脉冲观测（一种用于B1（-）映射和M0计算的优化可变翻转角方法）来确定校正因子，从而在3T下获得定量水质子密度图。在体模和九名健康志愿者身上获得了归一化代谢图。为了展示该技术在个体层面的潜在应用，我们还对一名低级别胶质瘤患者进行了研究。
在体模和志愿者身上均获得了准确的ρ图。使用生成的ρ图进行信号归一化后，本方法测定的代谢物浓度与体模中的理论值相差<7%，并且与健康对照的文献数据一致。利用这些归一化代谢值，能够在脑胶质瘤患者中证明归一化的N-乙酰天门冬氨酸、胆碱和肌酸水平存在代谢异常；这说明了该技术在临床研究中直接应用的潜力。
所提出的序列组合提供了一种稳健的ρ图，可用于临床MRSI研究中的代谢图标准化。
