Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy.
Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy; IRCCS Fondazione Don Carlo Gnocchi ONLUS, Milan, Italy.
Neuroimage. 2023 Sep;278:120272. doi: 10.1016/j.neuroimage.2023.120272. Epub 2023 Jul 10.
Quantitative Susceptibility Mapping (QSM) is a recent MRI-technique able to quantify the bulk magnetic susceptibility of myelin, iron, and calcium in the brain. Its variability across different acquisition parameters has prompted the need for standardisation across multiple centres and MRI vendors. However, a high level of agreement between repeated imaging acquisitions is equally important. With this study we aimed to assess the inter-scan repeatability of an optimised multi-echo GRE sequence in 28 healthy volunteers. We extracted and compared the susceptibility measures from the scan and rescan acquisitions across 7 bilateral brain regions (i.e., 14 regions of interest (ROIs)) relevant for neurodegeneration. Repeatability was first assessed while reconstructing QSM with a fixed number of echo times (i.e., 8). Excellent inter-scan repeatability was found for putamen, globus pallidus and caudate nucleus, while good performance characterised the remaining structures. An increased variability was instead noted for small ROIs like red nucleus and substantia nigra. Secondly, we assessed the impact exerted on repeatability by the number of echoes used to derive QSM maps. Results were impacted by this parameter, especially in smaller regions. Larger brain structures, on the other hand, showed more consistent performance. Nevertheless, with either 8 or 7 echoes we managed to obtain good inter-scan repeatability on almost all ROIs. These findings indicate that the designed acquisition/reconstruction protocol has wide applicability, particularly in clinical or research settings involving longitudinal acquisitions (e.g. rehabilitation studies).
定量磁敏感图（QSM）是一种最近的 MRI 技术，能够定量测量脑内髓鞘、铁和钙的总体磁化率。其在不同采集参数下的可变性促使需要在多个中心和 MRI 供应商之间进行标准化。然而，重复成像采集之间具有高度一致性同样重要。通过这项研究，我们旨在评估 28 名健康志愿者中优化的多回波 GRE 序列的扫描间可重复性。我们从扫描和重扫采集中提取并比较了与神经退行性变相关的 7 个双侧脑区（即 14 个感兴趣区（ROI））的磁化率测量值。首先，我们在使用固定数量的回波时间（即 8 个回波）重建 QSM 时评估了可重复性。在壳核、苍白球和尾状核中发现了极好的扫描间可重复性，而其余结构的性能则较好。而在红核和黑质等较小的 ROI 中则存在更大的可变性。其次，我们评估了用于导出 QSM 图的回波数量对可重复性的影响。结果受此参数的影响，特别是在较小的区域。另一方面，较大的脑结构表现出更一致的性能。然而，使用 8 个或 7 个回波，我们几乎可以在所有 ROI 上获得良好的扫描间可重复性。这些发现表明，所设计的采集/重建方案具有广泛的适用性，特别是在涉及纵向采集的临床或研究环境中（例如康复研究）。
