Absolute quantitation of brain metabolites with respect to heterogeneous tissue compositions in 1H-MR spectroscopic volumes
Absolute quantitation of brain metabolites with respect to heterogeneous tissue compositions in 1H-MR spectroscopic volumes
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DOI：
10.1007/s10334-012-0305-z
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发表时间：
2012-10-01
影响因子：
2.3
通讯作者：
Reichenbach, Jurgen R.
中科院分区：
文献类型：
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作者：
Gussew, Alexander;Erdtel, Marko;Reichenbach, Jurgen R.
参考代谢物强度与组织水强度通常用于从体内H-1-MRS脑数据确定代谢物浓度。然而，由于灰质、白质和脑脊液（CSF）之间的水浓度和弛豫特性不同，因此必须在MRS体素中考虑这些隔室的体积分数。通过在含有不同NAA和水浓度溶液的体素中进行幻像测量，以及分析不同体素组成获得的体内H-1-MRS脑数据，验证了部分体积校正的影响。幻影测量表明，当假设体素组成均匀时，NAA浓度被严重低估，特别是对于含有溶液的体素，模拟CSF（误差：千分之一货币符号92%）。通过考虑体素组成（误差：千分之一货币符号10%），这种偏差大大减少了。在体内研究中，组织校正将量化代谢物的总体变化减少了35%，并揭示了不同脑组织之间预期的代谢差异。组织组成影响代谢物浓度的提取，并且在比较不同体素大小进行的测量时可能导致误解。通过对光谱和成像数据的综合分析，考虑不同的组织类型，可以减少这种差异。
Referencing metabolite intensities to the tissue water intensity is commonly applied to determine metabolite concentrations from in vivo H-1-MRS brain data. However, since the water concentration and relaxation properties differ between grey matter, white matter and cerebrospinal fluid (CSF), the volume fractions of these compartments have to be considered in MRS voxels.The impact of partial volume correction was validated by phantom measurements in voxels containing mixtures of solutions with different NAA and water concentrations as well as by analyzing in vivo H-1-MRS brain data acquired with various voxel compositions.Phantom measurements indicated substantial underestimation of NAA concentrations when assuming homogeneously composed voxels, especially for voxels containing solution, which simulated CSF (error: a parts per thousand currency sign92%). This bias was substantially reduced by taking into account voxel composition (error: a parts per thousand currency sign10%). In the in vivo study, tissue correction reduced the overall variation of quantified metabolites by up to 35% and revealed the expected metabolic differences between various brain tissues.Tissue composition affects extraction of metabolite concentrations and may cause misinterpretations when comparing measurements performed with different voxel sizes. This variation can be reduced by considering the different tissue types by means of combined analysis of spectroscopic and imaging data.