Lober Robert M, Guzman Raphael, Cheshier Samuel H, Fredrick Douglas R, Edwards Michael S B, Yeom Kristen W
Departments of Neurosurger, Division of Pediatric NeurosurgeryStanford University School of Medicine, Stanford, California 94305-5327, USA.
J Neurosurg Pediatr. 2012 Oct;10(4):273-80. doi: 10.3171/2012.7.PEDS1270. Epub 2012 Aug 17.
Magnetic resonance imaging is commonly used in diagnosis and surveillance for optic pathway glioma (OPG). The authors investigated the role of diffusion tensor (DT) tractography in assessing the location of visual pathway fibers in the presence of tumor.
Data in 10 children with OPG were acquired using a 3T MRI generalized autocalibrating parallel acquisitions DT-echo planar imaging sequence (25 isotropic directions with a b value of 1000 seconds/mm(2), slice thickness 3 mm). Fiber tractography was performed, with seed regions placed within the optic chiasm and bilateral nerves on the coronal plane, including the tumor and surrounding normal-appearing tissue. Tracking was performed with a curvature threshold of 30°.
For prechiasmatic lesions, fibers either stopped abruptly at the tumor or traversed abnormally dilated nerve segments. Similar findings were seen with chiasmatic lesions, with an additional arrangement in which fibers diverged around the tumor. For each patient, DT tractography provided additional information about visual fiber arrangement in relation to the tumor that was not evident by using conventional MRI methods. Retrospective reconstruction of visual fibers in 1 patient with new postoperative hemianopia revealed an unexpected superior displacement of the optic tract that might have been helpful information had it been applied to preoperative planning or surgical navigation.
Optic pathway DT tractography is feasible in patients with OPG and provides new information about the arrangement of visual fibers in relation to tumors that could be incorporated into surgical navigation for tumor biopsy or debulking procedures.
磁共振成像常用于视神经通路胶质瘤（OPG）的诊断和监测。作者研究了扩散张量（DT）纤维束成像在评估肿瘤存在时视觉通路纤维位置方面的作用。
对10例OPG患儿的数据采用3T MRI广义自校准并行采集DT回波平面成像序列（25个各向同性方向，b值为1000秒/毫米²，层厚3毫米）进行采集。进行纤维束成像，在冠状面上将种子区域置于视交叉和双侧神经内，包括肿瘤及周围外观正常的组织。以30°的曲率阈值进行追踪。
对于视交叉前病变，纤维要么在肿瘤处突然中断，要么穿过异常扩张的神经节段。视交叉病变也有类似发现，另外还有纤维在肿瘤周围发散的排列方式。对于每位患者，DT纤维束成像提供了有关视觉纤维相对于肿瘤排列的额外信息，这是使用传统MRI方法无法发现的。对1例术后出现新的偏盲患者的视觉纤维进行回顾性重建发现，视束意外向上移位，若将其应用于术前规划或手术导航，可能会提供有用信息。
视神经通路DT纤维束成像在OPG患者中是可行的，并提供了有关视觉纤维相对于肿瘤排列的新信息，这些信息可纳入肿瘤活检或减瘤手术的手术导航中。
