正常人脑不同区域^1H磁共振波谱研究

Localized proton 1 H MR spectroscopy in different regions of the human brain

目的：应用１Ｈ磁共振波谱技术研究正常人脑内化合物的含量和分布。材料和方法：应用１．５Ｔ磁共振仪对１８例正常人脑进行１Ｈ波谱测试，测量的感兴趣区包括大脑皮层、白质、丘脑和小脑，所用序列为激励回波探测序列（ｓｔｉｍｕｌａｔｅｄｅｃｈｏａｑｕｉｓｉｔｉｏｎｍｏｄｅ，ＳＴＥＡＭ）。结果：１Ｈ磁共振波谱可以检测出脑内许多化合物，如Ｎ－乙酰门冬氨酸（ＮＡＡ）、含胆碱类化合物（Ｃｈｏ）、肌酸和磷酸肌酸（Ｃｒ＋Ｐｃｒ）、谷氨酸和谷氨酰胺（Ｇｌｕ＋Ｇｌｎ）、脂质、乳酸等。各化合物的浓度在脑的不同区域存在着差异。ＮＡＡ／Ｃｈｏ比值在灰质最高，小脑最低。Ｃｒ／Ｃｈｏ比值在小脑最高、白质最低。设定肌酸的浓度在灰质和小脑为１０ｍｍｏｌ／Ｌ，在白质和丘脑为１１ｍｍｏｌ／Ｌ，计算ＮＡＡ的绝对浓度为１３～２３ｍｍｏｌ／Ｌ，并且灰质的含量高于小脑和丘脑。结论：１Ｈ磁共振波谱技术可无创性检测出脑组织中与能量代谢、氨基酸、脂肪酸及神经递质有关的化合物，并可定量测定，有助于研究生理和疾病时脑生化改变。

Purpose: To study the 1 H MR spectrum of normal human brain and the concentration and distribution of main metabolites using 1 H MR spectroscopy. Materials and methods: Eighteen health human brains were examined by conventional 1.5T MRI system. Volume of interest (VOI) included temporal lobe (mainly gray matter), thalamus, cerebellum as well as white matter. Results: Proton MR spectroscopy can detect a variety of metabolites in human brain in vivo. The main detectable metabolites were N acetyl aspartate (NAA: at 2.02ppm), cholinecontaining compounds (Cho: at 3.2ppm), phosphocreatine and creatine (PCr+Cr: at 3.0ppm), glutamine and glutamate (Gln+Glu: at 2.34-2.45ppm), lipids (Lip: at 1.0ppm) and lactate (Lac: at 1.3ppm). The metabolite concentration varied in different parts of the brain. The relative signal intensity calculation showed that: NAA/Cho ratio is the highest in gray matter and lowest in cerebellun. Cr/Cho is the highest in cerebellum and lowest in white matter. The assumed creatine concentration is 10mmol/L for gray matter and cerebellum, 11 mmol/L for white matter and thalamus, the absolute concentration of NAA in the brain is about 13-23 mmol/L, and is higher in gray matter than in cerebellum and thalamus. Conclusion: Proton MR spectroscopy is a new noninvasive method which can be used to detect a number of chemical compounds pertaining to energy metabolism, free amino acids, fatty acids and neurotransmitters in the brain. It is useful to assess the cerebral biochemical changes in vivo both in healthy subjects and in patients with various brain disease.