Jorge João, Gretsch Frédéric, Najdenovska Elena, Tuleasca Constantin, Levivier Marc, Maeder Philippe, Gallichan Daniel, Marques José P, Bach Cuadra Meritxell
Medical Image Analysis Laboratory, Center for Biomedical Imaging (CIBM), University of Lausanne, Lausanne, Switzerland.
Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Magn Reson Med. 2020 Sep;84(3):1218-1234. doi: 10.1002/mrm.28197. Epub 2020 Feb 12.
The thalamus is an important brain structure and neurosurgical target, but its constituting nuclei are challenging to image non-invasively. Recently, susceptibility-weighted imaging (SWI) at ultra-high field has shown promising capabilities for thalamic nuclei mapping. In this work, several methodological improvements were explored to enhance SWI quality and contrast, and specifically its ability for thalamic imaging.
High-resolution SWI was performed at 7T in healthy participants, and the following techniques were applied: (a) monitoring and retrospective correction of head motion and B perturbations using integrated MR navigators, (b) segmentation and removal of venous vessels on the SWI data using vessel enhancement filtering, and (c) contrast enhancement by tuning the parameters of the SWI phase-magnitude combination. The resulting improvements were evaluated with quantitative metrics of image quality, and by comparison to anatomo-histological thalamic atlases.
Even with sub-millimeter motion and natural breathing, motion and field correction produced clear improvements in both magnitude and phase data quality (76% and 41%, respectively). The improvements were stronger in cases of larger motion/field deviations, mitigating the dependence of image quality on subject performance. Optimizing the SWI phase-magnitude combination yielded substantial improvements in image contrast, particularly in the thalamus, well beyond previously reported SWI results. The atlas comparisons provided compelling evidence of anatomical correspondence between SWI features and several thalamic nuclei, for example, the ventral intermediate nucleus. Vein detection performed favorably inside the thalamus, and vein removal further improved visualization.
Altogether, the proposed developments substantially improve high-resolution SWI, particularly for thalamic nuclei imaging.
丘脑是重要的脑结构和神经外科靶点，但其构成核团的无创成像具有挑战性。最近，超高场的磁敏感加权成像（SWI）在丘脑核团图谱绘制方面显示出了良好的潜力。在这项研究中，探索了几种方法改进措施以提高SWI的质量和对比度，特别是其对丘脑成像的能力。
在7T对健康受试者进行高分辨率SWI，并应用以下技术：（a）使用集成的磁共振导航仪监测并回顾性校正头部运动和B场扰动；（b）使用血管增强滤波对SWI数据进行静脉血管分割和去除；（c）通过调整SWI相位-幅度组合的参数增强对比度。通过图像质量的定量指标以及与解剖组织学丘脑图谱进行比较来评估所取得的改进效果。
即使存在亚毫米级的运动和自然呼吸，运动和场校正也使幅度和相位数据质量都有明显改善（分别提高了76%和41%）。在运动/场偏差较大的情况下，改进更为显著，减轻了图像质量对受试者表现的依赖。优化SWI相位-幅度组合显著提高了图像对比度，特别是在丘脑中，远超先前报道的SWI结果。图谱比较提供了令人信服的证据，证明SWI特征与几个丘脑核团（例如腹中间核）之间存在解剖学对应关系。在丘脑内部静脉检测效果良好，去除静脉进一步改善了可视化效果。
总体而言，所提出的改进措施显著提高了高分辨率SWI，特别是在丘脑核团成像方面。
