Brain Imaging Center, Goethe University, Frankfurt am Main, Germany.
Department of Neurology, Goethe University, Frankfurt am Main, Germany.
NMR Biomed. 2020 Feb;33(2):e4203. doi: 10.1002/nbm.4203. Epub 2019 Dec 3.
The detection of cortical malformations in conventional MR images can be challenging. Prominent examples are focal cortical dysplasias (FCD), the most common cause of drug-resistant focal epilepsy. The two main MRI hallmarks of cortical malformations are increased cortical thickness and blurring of the gray (GM) and white matter (WM) junction. The purpose of this study was to derive synthetic anatomies from quantitative T1 maps for the improved display of the above imaging characteristics in individual patients. On the basis of a T1 map, a mask comprising pixels with T1 values characteristic for GM is created from which the local cortical extent (CE) is determined. The local smoothness (SM) of the GM-WM junctions is derived from the T1 gradient. For display of cortical malformations, the resulting CE and SM maps serve to enhance local intensities in synthetic double inversion recovery (DIR) images calculated from the T1 map. The resulting CE- and/or SM-enhanced DIR images appear hyperintense at the site of cortical malformations, thus facilitating FCD detection in epilepsy patients. However, false positives may arise in areas with naturally elevated CE and/or SM, such as large GM structures and perivascular spaces. In summary, the proposed method facilitates the detection of cortical abnormalities such as cortical thickening and blurring of the GM-WM junction which are typical FCD markers. Still, subject motion artifacts, perivascular spaces, and large normal GM structures may also yield signal hyperintensity in the enhanced synthetic DIR images, requiring careful comparison with clinical MR images by an experienced neuroradiologist to exclude false positives.
在常规磁共振成像中检测皮质畸形可能具有挑战性。突出的例子是局灶性皮质发育不良（FCD），这是药物难治性局灶性癫痫的最常见原因。皮质畸形的两个主要 MRI 特征是皮质厚度增加和灰质（GM）和白质（WM）交界处模糊。本研究的目的是从定量 T1 图谱中得出合成解剖结构，以改善个体患者上述成像特征的显示。基于 T1 图谱，创建一个包含 T1 值特征为 GM 的像素的掩模，从中确定局部皮质范围（CE）。GM-WM 交界处的局部平滑度（SM）源自 T1 梯度。为了显示皮质畸形，生成的 CE 和 SM 图谱用于增强从 T1 图谱计算得出的合成双反转恢复（DIR）图像中的局部强度。生成的 CE 和/或 SM 增强的 DIR 图像在皮质畸形部位呈高信号，从而有助于癫痫患者 FCD 的检测。然而，在自然 CE 和/或 SM 升高的区域可能会出现假阳性，例如大 GM 结构和血管周围间隙。总之，该方法有助于检测皮质异常，如皮质增厚和 GM-WM 交界处模糊，这是典型的 FCD 标志物。尽管如此，运动伪影、血管周围间隙和大的正常 GM 结构也可能在增强的合成 DIR 图像中产生信号高信号，需要由有经验的神经放射科医生仔细与临床 MR 图像进行比较，以排除假阳性。
