Lee Seung-Yi, Meyer Briana P, Kurpad Shekar N, Budde Matthew D
Neuroscience Doctoral Program, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
Magn Reson Med. 2021 Aug;86(2):984-994. doi: 10.1002/mrm.28751. Epub 2021 Mar 15.
Diffusion MRI provides unique contrast important for the detection and examination of pathophysiology after acute neurologic insults, including spinal cord injury. Diffusion weighted imaging of the rodent spinal cord has typically been evaluated with axial EPI readout. However, Diffusion weighted imaging is prone to motion artifacts, whereas EPI is prone to susceptibility artifacts. In the context of acute spinal cord injury, diffusion filtering has previously been shown to improve detection of injury by minimizing the confounding effects of edema. We propose a diffusion-preparation module combined with a rapid acquisition with relaxation enhancement readout to minimize artifacts for sagittal imaging.
Sprague-Dawley rats with cervical contusion spinal cord injury were scanned at 9.4 Tesla. The sequence optimization included the evaluation of motion-compensated encoding diffusion gradients, gating strategy, and different spinal cord-specific diffusion-weighting schemes.
A diffusion-prepared rapid acquisition with relaxation enhancement achieved high-quality images free from susceptibility artifacts with both second-order motion-compensated encoding and gating necessary for reduction of motion artifacts. Axial diffusivity obtained from the filtered diffusion-encoding scheme had greater lesion-to-healthy tissue contrast (52%) compared to the similar metric from DTI (25%).
This work demonstrated the feasibility of high-quality diffusion sagittal imaging in the rodent cervical cord with diffusion-prepared relaxation enhancement. The sequence and results are expected to improve injury detection and evaluation in acute spinal cord injury.
扩散磁共振成像（Diffusion MRI）提供了独特的对比度，这对于急性神经损伤（包括脊髓损伤）后的病理生理学检测和检查非常重要。啮齿动物脊髓的扩散加权成像通常采用轴向回波平面成像（EPI）读出进行评估。然而，扩散加权成像容易出现运动伪影，而EPI容易出现磁化率伪影。在急性脊髓损伤的背景下，先前已表明扩散滤波可通过最小化水肿的混杂效应来改善损伤检测。我们提出了一种扩散准备模块，结合具有弛豫增强读出的快速采集，以最小化矢状面成像的伪影。
对患有颈髓挫伤性脊髓损伤的Sprague-Dawley大鼠在9.4特斯拉进行扫描。序列优化包括对运动补偿编码扩散梯度、门控策略和不同的脊髓特异性扩散加权方案的评估。
通过具有弛豫增强的扩散准备快速采集，利用二阶运动补偿编码和减少运动伪影所需的门控，获得了无磁化率伪影的高质量图像。与扩散张量成像（DTI）的类似指标相比，从滤波后的扩散编码方案获得的轴向扩散率具有更高的病变与健康组织对比度（52%对25%）。
这项工作证明了在啮齿动物颈髓中使用扩散准备弛豫增强进行高质量扩散矢状面成像的可行性。该序列和结果有望改善急性脊髓损伤中的损伤检测和评估。
