Department of Neuroscience, Georgia Institute of Technology, Atlanta, GA, United States of America; Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States of America.
Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States of America; Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States of America.
Magn Reson Imaging. 2023 Jan;95:59-62. doi: 10.1016/j.mri.2022.10.007. Epub 2022 Oct 20.
The presence of orientation-dependent susceptibility artifacts in magnetic resonance chemical shift thermometry (CST) can confound accurate temperature calculations. Here, we quantify the effect of white matter (WM) tract orientation on CST due to tissue-specific susceptibility.
Twenty-nine healthy volunteers (27 ± 4 years old) were scanned on a 3 T MR scanner with a 32-channel head coil. Diffusion tensor imaging (DTI), T1-weighted imaging, and single voxel spectroscopy (SVS) for CST were acquired. Participants were then asked to rotate their head ∼3-5° (yaw or roll) to alter the orientation of WM tracts relative to the external magnetic field. After head rotation, a second SVS scan and T1-weighted imaging were acquired. The WM-fraction-normalized DTI principal eigenvector (V1) images were used to calculate the length of the x-y component of V1, which was used as a surrogate for WM tracts perpendicular to B. A linear regression model was used to determine the relationship between the perpendicular WM tracts and brain temperature.
Significant temperature differences between post- and pre-head rotation scans were observed for brain (-0.72 °C ± 1.36 °C, p = 0.01) but not body (0.012 °C ± 0.07 °C, p = 0.37) temperatures. The difference in brain temperature was positively associated with the corresponding change in perpendicular WM tracts after head rotation (R = 0.26, p = 0.005).
Our results indicate WM tract orientation affects temperature calculations, suggesting artifacts from orientation-dependent susceptibility may be present in CST.
磁共振化学位移测温（CST）中存在各向异性磁化率伪影，可能会影响温度计算的准确性。本研究旨在量化组织特异性磁化率引起的白质（WM）束方向对 CST 的影响。
29 名健康志愿者（27±4 岁）在 3T 磁共振扫描仪上使用 32 通道头部线圈进行扫描。采集扩散张量成像（DTI）、T1 加权成像和单体素波谱（SVS）进行 CST。然后，要求参与者将头部旋转约 3-5°（偏航或滚动），以改变 WM 束相对于外磁场的方向。头部旋转后，采集第二组 SVS 扫描和 T1 加权成像。使用 WM 分数归一化 DTI 主特征向量（V1）图像计算 V1 的 x-y 分量的长度，该长度用作与 B 垂直的 WM 束的替代指标。采用线性回归模型确定垂直 WM 束与大脑温度之间的关系。
与头部旋转前后的扫描相比，大脑温度存在显著差异（-0.72°C±1.36°C，p=0.01），但身体温度无显著差异（0.012°C±0.07°C，p=0.37）。头部旋转后垂直 WM 束的相应变化与大脑温度的差异呈正相关（R=0.26，p=0.005）。
我们的结果表明 WM 束方向会影响温度计算，表明 CST 中可能存在各向异性磁化率伪影。
