Institute of Forensic Medicine, Department of Biomedical Engineering, University of Basel, Basel, Switzerland.
Institute of Forensic Medicine, Health Department Basel-Stadt, Basel, Switzerland.
Magn Reson Med. 2025 Jan;93(1):213-227. doi: 10.1002/mrm.30264. Epub 2024 Sep 9.
To compare postmortem in situ with ex situ MRI parameters, including volumetry, diffusion tensor imaging (DTI), and relaxometry for assessing methodology-induced alterations, which is a crucial prerequisite when performing MRI biomarker validation.
MRI whole-brain scans of five deceased patients with amyotrophic lateral sclerosis were performed at 3 T. In situ scans were conducted within 32 h after death (SD 18 h), and ex situ scans after brain extraction and 3 months of formalin fixation. The imaging protocol included MP2RAGE, DTI, and multi-contrast spin-echo and multi-echo gradient-echo sequences. Volumetry, fractional anisotropy, mean diffusivity, T, T, and have been assessed for specific brain regions.
When comparing ex situ to in situ values, the following results were obtained. Deep gray matter as well as the thalamus and the hippocampus showed a reduced volume. Fractional anisotropy was reduced in the cortex and the whole brain. Mean diffusivity was decreased in white matter and deep gray matter. T and T were reduced in all investigated structures, whereas was increased in the cortex.
The results of this study show that the volumes and MRI parameters of several brain regions are potentially affected by tissue extraction and subsequent formalin fixation, suggesting that methodological alterations are present in ex situ MRI. To avoid overlap of indistinguishable methodological and disease-related changes, we recommend performing in situ postmortem MRI as an additional intermediate step for in vivo MRI biomarker validation.
比较死后原位与离体 MRI 参数，包括容积测量、弥散张量成像（DTI）和弛豫测量，以评估方法引起的改变，这是进行 MRI 生物标志物验证的关键前提。
对 5 名肌萎缩侧索硬化症死亡患者的大脑进行 3T 的全脑 MRI 扫描。原位扫描在死后 32 小时内进行（SD 18 小时），离体扫描在大脑提取后和 3 个月福尔马林固定后进行。成像协议包括 MP2RAGE、DTI 以及多对比度自旋回波和多回波梯度回波序列。评估了特定脑区的容积、各向异性分数、平均弥散系数、T1、T2 和。
将离体值与原位值进行比较，得到以下结果。深部灰质以及丘脑和海马的体积减小。皮质和整个大脑的各向异性分数降低。白质和深部灰质的平均弥散系数降低。所有研究结构的 T1 和 T2 降低，而皮质的 增加。
本研究结果表明，几个脑区的体积和 MRI 参数可能受到组织提取和随后的福尔马林固定的影响，这表明离体 MRI 存在方法学改变。为了避免无法区分的方法学和与疾病相关的变化的重叠，我们建议进行原位死后 MRI 作为体内 MRI 生物标志物验证的附加中间步骤。
