Acquisition-related morphological variability in structural MRI
Acquisition-related morphological variability in structural MRI
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DOI：
10.1016/j.acra.2006.05.001
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发表时间：
2006-09-01
影响因子：
4.8
通讯作者：
Stiehl, Hans-Siegfried
中科院分区：
文献类型：
--
作者：
Littmann, Arne;Jens, Guehring;Stiehl, Hans-Siegfried
理由和目标。在过去的几十年中，已经花费了大量的努力来开发创新的图像处理算法，并在精度，再现性和计算效率方面改进现有的方法，但相对较少的研究进行，以找出在何种程度上的有效性与这些方法所获得的结果是有限的输入图像的固有缺陷。这种观察对于基于磁共振成像（MRI）的形态测量尤其如此，其目的在于精确且高度可重复地确定解剖结构的几何特性，尽管MRI图像是几何失真的。一种用于表征特定部位的几何失真的方法和长期研究的结果，该研究旨在发现数据采集过程中的缺陷在多大程度上限制了用最先进的扫描仪采集的MRI数据中细微形态变化的可靠检测。由于研究的长期性，结果包括有限的硬件稳定性以及患者重新定位的不完善所产生的影响。在我们的体模数据系列中检测到的最大相对形态学变化为1.0 mm位置差异和2.0%体积差异（相对于7600 mm（3）长方体），在与全脑形态测定相关的子体积中。由于扫描期间的运动，人类志愿者数据的形态变异性甚至更大（局部灰质体积高达5%）。自然形态的变异性，以及一个可能不太精确的分割程序。MRI数据采集过程中的不完善以及患者重新定位的实际限制可能会严重混淆对细微形态学变化的研究。
Rationale and Objectives. Significant effort has been spent during the past decades to develop innovative image-processing algorithms and improve existing methods in terms of precision, reproducibility, and computational efficiency, but relatively little research was undertaken to find out the extent to which the validity of results obtained with these methods is limited by inherent imperfections of the input images. This observation is especially true for magnetic resonance imaging (MRI)-based morphometry, which aims at precise and highly reproducible determination of geometric properties of anatomic structures, although MRI images are geometrically distorted.Materials and Methods. A method for characterization of site-specific geometric distortions and results of a long-term study designed to find the extent to which imperfections in the data-acquisition process limit the reliable detection of subtle morphological changes in MRI data acquired with state-of-the-art scanners are presented. Because of the long-term character of the study, results include effects resulting from limited hardware stability, as well as from imperfections in patient repositioning.Results. Maximal relative morphological changes detected in our phantom data series were 1.0 mm positional and 2.0% volumetric difference (relative to a 7600-mm(3) Cuboid) in a subvolume relevant for whole-brain morphometry. Morphological variability was even greater for human volunteer data (up to 5% in local gray matter volume) because of movements during, scan. natural morphological variability, and a presumably less precise segmentation procedure.Conclusion. Imperfections in the MRI data- acquisition process in combination with practical limitations in patient repositioning can substantially confound studies of subtle morphological changes.