Institute of Neuroradiology, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
NMR Biomed. 2023 Jun;36(6):e4717. doi: 10.1002/nbm.4717. Epub 2022 Mar 17.
The objective of the current study was to optimize the postprocessing pipeline of 7 T chemical exchange saturation transfer (CEST) imaging for reproducibility and to prove this optimization for the detection of age differences and differences between patients with Parkinson's disease versus normal subjects. The following 7 T CEST MRI experiments were analyzed: repeated measurements of a healthy subject, subjects of two age cohorts (14 older, seven younger subjects), and measurements of 12 patients with Parkinson's disease. A slab-selective, -homogeneous parallel transmit protocol was used. The postprocessing, consisting of motion correction, smoothing, -correction, normalization, denoising, -correction and Lorentzian fitting, was optimized regarding the intrasubject and intersubject coefficient of variation (CoV) of the amplitudes of the amide pool and the aliphatic relayed nuclear Overhauser effect (rNOE) pool within the brain. Seven "tricks" for postprocessing accomplished an improvement of the mean voxel CoV of the amide pool and the aliphatic rNOE pool amplitudes of less than 5% and 3%, respectively. These postprocessing steps are: motion correction with interpolation of the motion of low-signal offsets (1) using the amide pool frequency offset image as reference (2), normalization of the Z-spectrum using the outermost saturated measurements (3), correction of the Z-spectrum with moderate spline smoothing (4), denoising using principal component analysis preserving the 11 highest intensity components (5), correction using a linear fit (6) and Lorentzian fitting using the five-pool fit model (7). With the optimized postprocessing pipeline, a significant age effect in the amide pool can be detected. Additionally, for the first time, an aliphatic rNOE contrast between subjects with Parkinson's disease and age-matched healthy controls in the substantia nigra is detected. We propose an optimized postprocessing pipeline for CEST multipool evaluation. It is shown that by the use of these seven "tricks", the reproducibility and, thus, the statistical power of a CEST measurement, can be greatly improved and subtle changes can be detected.
本研究的目的是优化 7T 化学交换饱和传递（CEST）成像的后处理管道，以提高可重复性，并证明该优化可用于检测年龄差异和帕金森病患者与正常受试者之间的差异。对以下 7T CEST MRI 实验进行了分析：一位健康受试者的重复测量、两个年龄组（14 位年龄较大的受试者和 7 位年龄较小的受试者）的测量以及 12 位帕金森病患者的测量。采用了一个片状选择、均匀平行传输协议。后处理包括运动校正、平滑、校正、归一化、去噪、校正和洛伦兹拟合，优化了大脑内酰胺池和脂肪relayed 核奥弗豪瑟效应（rNOE）池幅度的受试者内和受试者间系数变化（CoV）。七种“技巧”用于后处理，可以将酰胺池和脂肪 rNOE 池幅度的平均体素 CoV 分别改善小于 5%和 3%。这些后处理步骤包括：（1）使用酰胺池频率偏移图像作为参考，对低信号偏移的运动进行插值的运动校正；（2）使用最外层饱和测量值对 Z 谱进行归一化；（3）使用中等样条平滑对 Z 谱进行校正；（4）使用主成分分析保留最高 11 个强度分量进行去噪；（5）使用线性拟合进行校正；（6）使用洛伦兹拟合使用五池拟合模型进行拟合（7）。使用优化的后处理管道，可以检测到酰胺池的显著年龄效应。此外，首次在帕金森病患者和年龄匹配的健康对照组的黑质中检测到脂肪 rNOE 对比。我们提出了CEST 多池评估的优化后处理管道。结果表明，通过使用这七个“技巧”，可以大大提高 CEST 测量的可重复性，从而提高统计能力，并可以检测到细微的变化。
