Implemetation Of High-field Intraoperative MRI In Evaluation Of Brain Shift And PyramidalTract Shift

Objective:The objective of this study is to evaluate subcortical and pyramidal tract(PT) shift in neurosurgery with intraoperative Magnetic Resonance Imaging(iMRI) and multimodal neuronavigation.Methods: The first part was designed to estimate the PT which reconstructedbased on intraoperative diffusion tensor imaging (DTI). We evaluated theimpairment of PT in insular lesions based on pre-, intra-operative and follow upDTI. After reconstruction of PT, fractional anisotropy (FA) was measured by useof the mask of PT, and compared FA values in different time and differentprognosis. In the second part, patients with Parkinson’s disease who underwentdeep brain stimulation (DBS) surgery during were included. After the electrodewas implanted, we acquired the intraoperative MR imaging and evaluate theaccuracy of the targeting. If the further adjustment is needed, the secondintraoperative MR imaging is used to confirm the location of the implantation.Record and analyze if the trajectory involved the ventricle could decrease theaccuracy of implanting electrode. In the third part, we collected patients withgliomas who underwent intraoperative scan more than once and ventricles wereopened between intraoperative scans during surgeries. Anatomical MRI anddiffusion tensor based tractography of PT were applied for both preoperative andintraoperative assessment of the shift of PT and brain cortex.Results: In the first part, population included89patients who had undergoneresection of insular lesions. These patients were divided into three groupsaccording to their motor function examination results. Repeated measure analysisof variance demonstrated significantly difference in both changes ratio ofintraoperative normalized FA value between transient deficits group andlong-term deficits group (F=22.080，P=0.000), different stages (F=4.544，P=0.041)and group-stages(F＝12.392，P=0.001). In the second part,61patients wereincluded. MR scans performed72times,11leads (10patients) need adjustmentafter the first MR scans.15leads of122leads trajectories involved the lateralventricle, the mean distance between the target and electrode was1.9±1.2mm, and the other was1.1±0.8mm(P=0.000).There was no statistic significant betweentargeting error and gender, age, course, cortical brain shift. Paired-t test showedsignificant between the first location of leads error (2.6±0.5mm) and the finalerror (0.8±0.6mm). We divided all these patients into3groups according to thedistance between the target and the electrode. The Fisher’s exact test showed thattargeting error was relevant to trajectory involved the lateral ventricle (P=0.000).In the third part, fourteen adult patients (six female and eight male; mean age,44years; age range,25–64years) with tumors located in the frontal lobe and adjacentto the ventricles from581patients were included. Patients presented with WHOgrade Ⅱ gliomas in11cases, WHO grade Ⅲ in two cases and WHO grade Ⅳ in1case. The mean tumor volume was58.3±37.1cm3, the mean ventricular volumewas33.9±14.2ml and the mean distance between tumor and CST was11.8±6.4mm.Paired t-test showed significant differences between the variation ofventricles, the PT posterior displacementand the displacement of posterior marginof tumor. The distances of lateral-median displacement of CST, midline shift anddisplacement of median margin of tumor was not significant. Spearmancorrelation analysis demonstrated positive correlations between ventricularvolume and PT displacement.Conclusion:PT could reconstructed based on the intraoperative DTI,fractionalanisotropy values of corticospinal tracts base on intraoperative can be used as aprognostic indicator of predict motor function outcome. Electrode trajectoryinvolved the lateral ventricle could decrease the accuracy of targeting duringplacement for DBS. During the resections of tumors adjacent to PT, opening thelateral ventricles intraoperative often leads to posterior displacement of PT and themargin of the tumor. With the high-field MRI and update navigation system,tumor remnants and PT could be relocalized precisely during surgeries, and it isconduce to extend resection and motor function protection.