Department of Radiology, University of California San Francisco, Box 0628, L-307, 505 Parnassus Ave, San Francisco, CA 94143-0628, USA.
Radiographics. 2009 Oct;29(6):1653-64. doi: 10.1148/rg.296095520.
Magnetic resonance (MR) spectroscopy allows the demonstration of relative tissue metabolite concentrations along a two- or three-dimensional spectrum based on the chemical shift phenomenon. An MR spectrum is a plot of the signal intensity and frequency of a chemical or metabolite within a given voxel. At proton MR spectroscopy, the frequency at which a chemical or compound occurs depends on the configuration of the protons within the structure of that chemical. At in vivo proton MR spectroscopy, the frequency location of water is used as the standard of reference to identify a chemical. The frequency shift or location of chemicals relative to that of water allows generation of qualitative and quantitative information about the chemicals that occur within tissues, forming the basis of tissue characterization by MR spectroscopy. MR spectroscopy also may be used to quantify liver fat by measuring lipid peaks and to diagnose malignancy, usually by measuring the choline peak. Interpretation of MR spectroscopic data requires specialized postprocessing software and is subject to technical limitations including low signal-to-noise ratio, masking of metabolite peaks by dominant water and lipid peaks, partial-volume averaging from other tissue within the voxel, and phase and frequency shifts from motion. MR spectroscopy of the liver is an evolving technology with potential for improving the diagnostic accuracy of tissue characterization when spectra are interpreted in conjunction with MR images.
磁共振（MR）波谱学基于化学位移现象，允许在二维或三维光谱中展示相对组织代谢物浓度。MR 光谱是给定体素中化学物质或代谢物的信号强度和频率的图。在质子 MR 波谱学中，化学物质或化合物出现的频率取决于该化学物质结构中质子的构型。在体内质子 MR 波谱学中，水的频率位置被用作参考标准，以识别化学物质。化学物质相对于水的频率位移或位置允许生成有关组织中发生的化学物质的定性和定量信息，从而构成 MR 波谱学进行组织特征描述的基础。MR 波谱学还可用于通过测量脂质峰来定量肝脏脂肪，并通过测量胆碱峰来诊断恶性肿瘤。解释 MR 波谱数据需要专门的后处理软件，并且受到技术限制的影响，包括低信噪比、代谢物峰被主导的水和脂质峰掩盖、体素内其他组织的部分容积平均、以及来自运动的相位和频率偏移。肝脏的 MR 波谱学是一项不断发展的技术，当与 MR 图像结合使用时，有可能提高组织特征描述的诊断准确性。
