Ex-vivo MRI of human brain hemispheres from patients with globular glial tauopathy and one typical control

Ex vivo whole-hemisphere T2*-weighted MRI of 6 human brain hemispheres, 5 from patients with globular glial tauopathy (GGT) and 1 from a typically aging patient. MRI data is stored as NIFTI files, with one file per hemisphere. Gradient echo times were chosen to be approximately 20 ms to maximize sensitivity to GGT pathology.

Methods
Samples were placed in Fomblin (California Vacuum Technology; Freemont, CA), a proton-free fluid with volume magnetic susceptibility close to that of tissue. Samples were enclosed in either custom-build cylindrical holders or plastic bags, and then left to rest for at least two days to allow air bubbles to escape from the tissue. Depending on their size, samples were scanned using either a custom-built birdcage coil or a custom-modified quadrature birdcage (Varian, Palo Alto, CA, USA) coil. These transmit/receive coils were attached to a two-channel transmit-receive adapter (Stark Contrast, Erlangen, Germany). The smallest coil was chosen that could hold each sample, tuned/matched by hand, and then placed into our whole-body 7 T scanner (MAGNETOM Terra, Siemens Healthineers, Erlangen, Germany) using plastic shims under the coils to position the sample near isocenter.

MRI data were acquired with a 3D-encoded, multi-echo gradient-recalled echo (GRE) sequence with non-selective RF pulses. The final echo was followed by an additional completely rephrased readout to measure frequency drifts. Scans for individual patients were acquired with somewhat different scanning protocols, reflecting the evolution of standard practices at our imaging center. Specific details of the scanning parameters for each patient are listed in the associated journal article:

Clinicoanatomic localization of iron-rich gliosis in aphasic presentations of globular glial tauopathy, Brain Communications, in press

Images were reconstructed using the vendor’s on-scanner reconstruction software which automatically corrected the global frequency drift, combined the signal averages in k-space, and produced magnitude images for each echo.

本数据集包含6例人脑半球的离体全脑T2*加权磁共振成像（T2*-weighted MRI）数据，其中5例来自球状胶质tau蛋白病（globular glial tauopathy, GGT）患者，1例来自正常衰老个体。MRI数据以NIfTI文件格式存储，每个半球对应一个文件。梯度回波时间设置为约20 ms，以最大化对GGT病理的检测灵敏度。

实验方法
标本置于Fomblin（California Vacuum Technology；美国加利福尼亚州弗里蒙特市）中，该液体不含质子，其体积磁化率与人体组织相近。标本被装入定制圆柱形容器或塑料袋中，静置至少两天以排出组织内的气泡。根据标本尺寸，分别使用定制鸟笼线圈或定制改造的正交鸟笼线圈（Varian，美国加利福尼亚州帕洛阿尔托市）进行扫描。上述收发线圈均连接至双通道收发适配器（Stark Contrast，德国埃尔朗根市）。选用尺寸恰好容纳标本的最小线圈，手动完成调谐与匹配，随后将线圈置于全身7特斯拉扫描仪（MAGNETOM Terra，Siemens Healthineers，德国埃尔朗根市）中，通过线圈下方的塑料垫片将标本定位至接近等中心的位置。

MRI数据采用三维编码多回波梯度回波（GRE）序列采集，使用非选择性射频脉冲。最终回波后附加一次完全重聚的读出序列以测量频率漂移。不同患者的扫描参数存在一定差异，这反映了本影像中心标准操作流程的演进。每位患者的具体扫描参数细节已在相关已录用期刊论文中列出：
《球状胶质tau蛋白病失语表现中富铁胶质增生的临床解剖定位》，《脑通讯》，即将刊出

图像采用扫描仪厂商自带的重建软件进行重建，该软件可自动校正整体频率漂移、合并k空间内的信号平均，并生成各回波的幅值图像。