Walker Matthew R, Zhong Jidan, Waspe Adam C, Looi Thomas, Piorkowska Karolina, Hawkins Cynthia, Drake James M, Hodaie Mojgan
Institute of Medical Science, University of Toronto, Toronto, ON, Canada.
Division of Brain, Imaging and Behaviour - Systems Neuroscience, Krembil Research Institute, University Health Network, Toronto, ON, Canada.
Front Neurol. 2019 Oct 15;10:1069. doi: 10.3389/fneur.2019.01069. eCollection 2019.
The application of magnetic resonance-guided focused ultrasound (MRgFUS) for the treatment of neurological conditions has been of increasing interest. Conventional MR imaging can provide structural information about the effect of MRgFUS, where differences in ablated tissue can be seen, but it lacks information about the status of the cellular environment or neural microstructure. We investigate acute changes in water diffusion and white matter tracts in the brain of a piglet model after MRgFUS treatment using diffusion-weighted imaging (DWI) with histological verification of treatment-related changes. MRgFUS was used to treat the anterior body of the fornix in four piglets. T1 and diffusion-weighted images were collected before and after treatment. Mean diffusion-weighted imaging (MDWI) images were generated to measure lesion volumes via signal intensity thresholds. Histological data were collected for volume comparison and assessment of treatment effect. DWI metric maps of fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) were generated for quantitative assessment. Fornix-related fiber tracts were generated before and after treatment for qualitative assessment. The volume of treated tissue measured via MDWI did not differ significantly from histological measurements, and both were significantly larger than the treatment cell volume. Diffusion metrics in the treatment region were significantly decreased following MRgFUS treatment, with the peak change seen at the lesion core and decreasing radially. Histological analysis confirmed an area of coagulative necrosis in the targeted region with sharp demarcation zone with surrounding brain. Tractography from the lesion core and the fornix revealed fiber disruptions following treatment. Diffusion maps and fiber tractography are an effective method for assessing lesion volumes and microstructural changes following MRgFUS treatment. This study demonstrates that DWI has the potential to advance MRgFUS by providing convenient microstructural lesion and fiber tractography assessment after treatment.
磁共振引导聚焦超声(MRgFUS)在神经疾病治疗中的应用越来越受到关注。传统的磁共振成像可以提供有关MRgFUS治疗效果的结构信息,能够看到消融组织的差异,但它缺乏关于细胞环境或神经微结构状态的信息。我们使用扩散加权成像(DWI)并结合治疗相关变化的组织学验证,研究了MRgFUS治疗后仔猪模型大脑中水分扩散和白质束的急性变化。MRgFUS用于治疗四只仔猪的穹窿前体。在治疗前后采集T1和扩散加权图像。生成平均扩散加权成像(MDWI)图像,通过信号强度阈值测量病变体积。收集组织学数据用于体积比较和治疗效果评估。生成分数各向异性(FA)、表观扩散系数(ADC)、轴向扩散率(AD)、径向扩散率(RD)和平均扩散率(MD)的DWI指标图进行定量评估。在治疗前后生成与穹窿相关的纤维束进行定性评估。通过MDWI测量的治疗组织体积与组织学测量结果无显著差异,且两者均显著大于治疗单元体积。MRgFUS治疗后,治疗区域的扩散指标显著降低,病变核心处变化最为明显,并呈径向递减。组织学分析证实了靶向区域存在凝固性坏死,与周围脑组织有清晰的分界区。病变核心和穹窿的纤维束成像显示治疗后纤维中断。扩散图和纤维束成像术是评估MRgFUS治疗后病变体积和微结构变化的有效方法。本研究表明,DWI有潜力通过在治疗后提供便捷的微结构病变和纤维束成像评估来推动MRgFUS的发展。