Department of Diagnostic and Interventional Neuroradiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.
Department of Diagnostic and Interventional Radiology, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.
NMR Biomed. 2022 Dec;35(12):e4805. doi: 10.1002/nbm.4805. Epub 2022 Aug 15.
The main pathologies in the muscles of patients with neuromuscular diseases (NMD) are fatty infiltration and edema. Recently, quantitative magnetic resonance (MR) imaging for determination of the MR biomarkers proton density fat fraction (PDFF) and water T (T ) has been advanced. Biophysical effects or pathology can have different effects on MR biomarkers. Thus, for heterogeneously affected muscles, the routinely performed mean or median value analyses of MR biomarkers are questionable. Our work presents a voxel-based histogram analysis of PDFF and T images to point out potential quantification errors. In 12 patients with NMD, chemical-shift encoding-based water-fat imaging for PDFF and T mapping with spectral adiabatic inversion recovery (SPAIR) for T determination was performed. Segmentation of nine thigh muscles was performed bilaterally (n = 216). PDFF and T maps were coregistered. A voxel-based comparison of PDFF and T showed a decreased T with increasing PDFF. Mean T and mean T (PDFF < 10%) show good agreement, whereas standard deviation (σ) T and σ T show increasing difference with increasing values of σ. Thereby two subgroups can be observed, referring to muscles in which the exclusion of fatty voxels has a negligible influence versus muscles in which a strong dependency of the T value distribution on the exclusion of fatty voxels is present. Because of the two opposite effects that influence T in a voxel, namely, (i) a pathophysiologically increased water mobility leading to T elevation, and (ii) a dependency of T on the PDFF leading to decreased T , the T distribution within a muscle might be heterogenous and the routine mean or median analysis can lead to a misinterpretation of the muscle health. It was concluded that muscle T mean values can wrongly suggest healthy muscle tissue. A deeper analysis of the underlying value distribution is necessary. Therefore, a quantitative analysis of T histograms is a potential alternative.
肌肉磁共振质子密度脂肪分数（PDFF）和水 T （T ）定量成像的磁振造影生物标志物在神经肌肉疾病（NMD）患者的肌肉中，主要的病变是脂肪浸润和水肿。最近，已经提出了用于确定磁共振生物标志物的定量磁共振（MR）成像。生物物理效应或病理学对 MR 生物标志物可能有不同的影响。因此，对于不均匀受影响的肌肉，常规进行的 MR 生物标志物的平均值或中位数分析是值得怀疑的。我们的工作提出了一种基于体素的 PDFF 和 T 图像直方图分析，以指出潜在的量化错误。在 12 名 NMD 患者中，进行了基于化学位移编码的水脂成像以进行 PDFF 和 T 映射，并用光谱绝热反转恢复（SPAIR）进行 T 确定。双侧进行了 9 个大腿肌肉的分割（n=216）。PDFF 和 T 图进行了配准。基于体素的 PDFF 和 T 的比较显示，随着 PDFF 的增加，T 降低。平均 T 和平均 T （PDFF <10%）显示出良好的一致性，而标准偏差（σ）T 和 σ T 显示出随着 σ 值的增加而差异增加。由此可以观察到两个亚组，一个是指排除脂肪体素对 T 值分布的影响可以忽略不计的肌肉，另一个是指排除脂肪体素对 T 值分布有很强依赖性的肌肉。由于影响体素中 T 的两种相反的效应，即（i）病理上增加的水流动性导致 T 升高，和（ii）T 对 PDFF 的依赖性导致 T 降低，肌肉内的 T 分布可能是不均匀的，常规的平均值或中位数分析可能导致对肌肉健康的误解。结论是，肌肉 T 的平均值可能错误地提示健康的肌肉组织。需要对基础值分布进行更深入的分析。因此，T 直方图的定量分析是一种潜在的替代方法。
