Directional DBS leads show large deviations from their intended implantation orientation

Objective: Lead orientation is a new degree of freedom with directional deep brain stimulation (DBS) leads. We investigated how prevalent deviations from the intended implantation direction are in a large patient cohort. Methods: The Directional Orientation Detection (DiODe) algorithm to determine lead orientation from postoperative CT scans was implemented into the open-source Lead-DBS toolbox. Lead orientation was analyzed in 100 consecutive patients (198 leads). Different anatomical targets and intraoperative setups were compared. Results: Deviations of up to 90 degrees from the intended implantation direction were observed. Deviations of more than 30 degrees were seen in 42% of the leads and deviations of more than 60 degrees in about 11% of the leads. Deviations were independent from the neuroanatomical target and the stereotactic frame but increased depending on which microdrive was used. Discussion: Our results indicate that large deviations from the intended implantation direction are a common phenomenon in directional leads. Postoperative determination of lead orientation is thus mandatory for investigating directional DBS

Diagnostic Accuracy of MR Spectroscopic Imaging and 18 F-FET PET for Identifying Glioma: A Biopsy-Controlled Hybrid PET/MRI Study

Contrast-enhanced MRI is the method of choice for brain tumor diagnostics, despite its low specificity for tumor tissue. This study compared the contribution of MR spectroscopic imaging (MRSI) and amino acid PET to improve the detection of tumor tissue. In 30 untreated patients with suspected glioma, -(2-[ F]fluoroethyl)-l-tyrosine ( F-FET) PET; 3-T MRSI with a short echo time; and fluid-attenuated inversion recovery, T2-weighted, and contrast-enhanced T1-weighted MRI were performed for stereotactic biopsy planning. Serial samples were taken along the needle trajectory, and their masks were projected to the preoperative imaging data. Each sample was individually evaluated neuropathologically. F-FET uptake and the MRSI signals choline (Cho), -acetyl-aspartate (NAA), creatine, myoinositol, and derived ratios were evaluated for each sample and classified using logistic regression. The diagnostic accuracy was evaluated by receiver operating characteristic analysis. On the basis of the neuropathologic evaluation of tissue from 88 stereotactic biopsies, supplemented with F-FET PET and MRSI metrics from 20 areas on the healthy-appearing contralateral hemisphere to balance the glioma/nonglioma groups, F-FET PET identified glioma with the highest accuracy (area under the receiver operating characteristic curve, 0.89; 95% CI, 0.81-0.93; threshold, 1.4 × background uptake). Among the MR spectroscopic metabolites, Cho/NAA normalized to normal brain tissue showed the highest diagnostic accuracy (area under the receiver operating characteristic curve, 0.81; 95% CI, 0.71-0.88; threshold, 2.2). The combination of F-FET PET and normalized Cho/NAA did not improve the diagnostic performance. MRI-based delineation of gliomas should preferably be supplemented by F-FET PET