Kenji Ino

The motor-evoked potential threshold evaluated by tractography and electrical stimulation

OBJECT To validate the corticospinal tract (CST) illustrated by diffusion tensor imaging, the authors used tractography-integrated neuronavigation and direct fiber stimulation with monopolar electric currents. METHODS Forty patients with brain lesions adjacent to the CST were studied. During the operation, the motor responses (motor evoked potential [MEP]) elicited at the hand by the cortical stimulation to the hand motor area were continuously monitored, maintaining the consistent stimulus intensity (mean 15.1 +/- 2.21 mA). During lesion resection, direct fiber stimulation was applied to elicit MEP (referred to as fiber MEP) to identify the CST functionally. The threshold intensity for the fiber MEP was determined by searching for the best stimulus point and changing the stimulus intensity. The minimum distance between the resection border and illustrated CST was measured on postoperative isotropic images. RESULTS Direct fiber stimulation demonstrated that tractography accurately reflected anatomical CST functioning. There were strong correlations between stimulus intensity for the fiber MEP and the distance between the CST and the stimulus points. The results indicate that the minimum stimulus intensity of 20, 15, 10, and 5 mA had stimulus points approximately 16, 13.2, 9.6, and 4.8 mm from the CST, respectively. The convergent calculation formulated 1.8 mA as the electrical threshold of the CST for the fiber MEP, which was much smaller than that of the hand motor area. CONCLUSIONS The investigators found that diffusion tensor imaging-based tractography is a reliable way to map the white matter connections in the entire brain in clinical and basic neuroscience applications. By combining these techniques, investigating the cortical-subcortical connections in the human CNS could contribute to elucidating the neural networks of the human brain and shed light on higher brain functions.

Functional Monitoring for Visual Pathway Using Real-time Visual Evoked Potentials and Optic-radiation Tractography

OBJECTIVE: It has been difficult to obtain anatomic and functional information about the visual pathway during neurosurgical operations. The aim of this study was to combine the information of the visual evoked potentials (VEPs) and the anatomic navigation of the optic radiation by diffusion tensor imaging-based tractography for functional monitoring of the visual pathway. METHODS: The subjects were two patients with brain lesions adjacent to the visual pathway. Diffusion tensor imaging-based tractography of the optic radiation was performed by selecting appropriate regions of interest and by fractional anisotropy. During surgery, cortical VEPs were recorded continuously under general anesthesia with sevoflurane. In Patient 2, the results of optic radiation tractography were imported to a neuronavigation system to better understand the spatial relationships between the lesions and the visual pathway (functional neuronavigation). RESULTS: In Patient 1, the lesion did not seem to be attached to the optic radiation, and VEP profiles remained stable during resection. In Patient 2, who had a lesion adjacent to the posterior horn of the lateral ventricle, VEPs suddenly diminished when resection reached the optic radiation as illustrated on the neuronavigation system. As a result, complete left hemianopia developed after surgery in Patient 2. CONCLUSION: We confirmed functional correlations of the results of diffusion tensor imaging-based tractography by monitoring intraoperative VEPs. The combination of continuous VEP and optic-radiation tractography is reliable to monitor the visual function and is helpful in performing neurosurgical planning near the visual pathway.

Four-Dimensional Measurement of the Displacement of Internal Fiducial Markers During 320-Multislice Computed Tomography Scanning of Thoracic Esophageal Cancer

PURPOSE To investigate the three-dimensional movement of internal fiducial markers placed near esophageal cancers using 320-multislice CT. METHODS AND MATERIALS This study examined 22 metal markers in the esophageal wall near the primary tumors of 12 patients treated with external-beam photon radiotherapy. Motion assessment was analyzed in 41 respiratory phases during 20 s of cine CT in the radiotherapy position. RESULTS Motion in the cranial-caudal (CC) direction showed a strong correlation (R(2) > 0.4) with the respiratory curve in most markers (73%). The average absolute amplitude of the marker movement was 1.5 ± 1.6 mm, 1.6 ± 1.7 mm, and 3.3 ± 3.3 mm in the left-right (LR), anterior-posterior (AP), and CC directions, respectively. The average marker displacements in the CC direction between peak exhalation and inhalation for the 22 clips were 1.1 mm (maximum, 5.5 mm), 3.0 mm (14.5 mm), and 5.1 mm (16.3 mm) for the upper, middle, and lower thoracic esophagus, respectively. CONCLUSIONS Motion in primary esophagus tumor was evaluated with 320-multislice CT. According to this study, 4.3 mm CC, 1.5 mm AP, and 2.0 mm LR in the upper, 7.4 mm CC, 3.0 mm AP, and 2.4 mm LR in the middle, and 13.8 mm CC, 6.6 mm AP, and 6.8 mm LR in the lower thoracic esophagus provided coverage of tumor motion in 95% of the cases in our study population.

Optic radiation tractography integrated into simulated treatment planning for Gamma Knife surgery

OBJECT No definitive method of preventing visual field deficits after stereotactic radiosurgery for lesions near the optic radiation (OR) has been available so far. The authors report the results of integrating OR tractography based on diffusion tensor (DT) magnetic resonance imaging into simulated treatment planning for Gamma Knife surgery (GKS). METHODS Data from imaging studies performed in 10 patients who underwent GKS for treatment of arteriovenous malformations (AVMs) located adjacent to the OR were used for the simulated treatment planning. Diffusion tensor images performed without the patients head being secured by a stereotactic frame were used for DT tractography, and the OR was visualized by means of software developed by the authors. Data from stereotactic 3D imaging studies performed after frame fixation were coregistered with the data from DT tractography. The combined images were transferred to a GKS treatment-planning workstation. Delivered doses and distances between the treated lesions and the OR were analyzed and correlated with posttreatment neurological changes. RESULTS In patients presenting with migraine with visual aura or occipital lobe epilepsy, the OR was located within 11 mm from AVMs. In a patient who developed new quadrantanopia after GKS, the OR had received 32 Gy. A maximum dose to the OR of less than 12 Gy did not cause new visual field deficits. A maximum dose to the OR of 8 Gy or more was significantly related to neurological change (p < 0.05), including visual field deficits and development or improvement of migraine. CONCLUSIONS Integration of OR tractography into GKS represents a promising tool for preventing GKS-induced visual disturbances and headaches. Single-session irradiation at a dose of 8 Gy or more was associated with neurological change.

A new strategic neurosurgical planning tool for brainstem cavernous malformations using interactive computer graphics with multimodal fusion images

OBJECT In this study, the authors used preoperative simulation employing 3D computer graphics (interactive computer graphics) to fuse all imaging data for brainstem cavernous malformations. The authors evaluated whether interactive computer graphics or 2D imaging correlated better with the actual operative field, particularly in identifying a developmental venous anomaly (DVA). METHODS The study population consisted of 10 patients scheduled for surgical treatment of brainstem cavernous malformations. Data from preoperative imaging (MRI, CT, and 3D rotational angiography) were automatically fused using a normalized mutual information method, and then reconstructed by a hybrid method combining surface rendering and volume rendering methods. With surface rendering, multimodality and multithreshold techniques for 1 tissue were applied. The completed interactive computer graphics were used for simulation of surgical approaches and assumed surgical fields. Preoperative diagnostic rates for a DVA associated with brainstem cavernous malformation were compared between conventional 2D imaging and interactive computer graphics employing receiver operating characteristic (ROC) analysis. RESULTS The time required for reconstruction of 3D images was 3-6 hours for interactive computer graphics. Observation in interactive mode required approximately 15 minutes. Detailed anatomical information for operative procedures, from the craniotomy to microsurgical operations, could be visualized and simulated three-dimensionally as 1 computer graphic using interactive computer graphics. Virtual surgical views were consistent with actual operative views. This technique was very useful for examining various surgical approaches. Mean (±SEM) area under the ROC curve for rate of DVA diagnosis was significantly better for interactive computer graphics (1.000±0.000) than for 2D imaging (0.766±0.091; p<0.001, Mann-Whitney U-test). CONCLUSIONS The authors report a new method for automatic registration of preoperative imaging data from CT, MRI, and 3D rotational angiography for reconstruction into 1 computer graphic. The diagnostic rate of DVA associated with brainstem cavernous malformation was significantly better using interactive computer graphics than with 2D images. Interactive computer graphics was also useful in helping to plan the surgical access corridor.

Outcomes of Diffusion Tensor Tractography–Integrated Stereotactic Radiosurgery

PURPOSE To analyze the effect of use of tractography of the critical brain white matter fibers created from diffusion tensor magnetic resonance imaging on reduction of morbidity associated with radiosurgery. METHODS AND MATERIALS Tractography of the pyramidal tract has been integrated since February 2004 if lesions are adjacent to it, the optic radiation since May 2006, and the arcuate fasciculus since October 2007. By visually confirming the precise location of these fibers, the dose to these fiber tracts was optimized. One hundred forty-four consecutive patients with cerebral arteriovenous malformations who underwent radiosurgery with this technique between February 2004 and December 2009 were analyzed. RESULTS Tractography was prospectively integrated in 71 of 155 treatments for 144 patients. The pyramidal tract was visualized in 45, the optic radiation in 22, and the arcuate fasciculus in 13 (two tracts in 9). During the follow-up period of 3 to 72 months (median, 23 months) after the procedure, 1 patient showed permanent worsening of pre-existing dysesthesia, and another patient exhibited mild transient hemiparesis 12 months later but fully recovered after oral administration of corticosteroid agents. Two patients had transient speech disturbance before starting integration of the arcuate fasciculus tractography, but no patient thereafter. CONCLUSION Integrating tractography helped prevent morbidity of radiosurgery in patients with brain arteriovenous malformations.

3 Tesla MRI detects accelerated hippocampal volume reduction in postmenopausal women

To clarify age‐related structural changes specific to hippocampal volume by hierarchizing according to age, gender, and menopausal status. Many studies report the neuroprotective effects of estrogen and age‐related brain volume changes; however, there are no studies regarding age‐related change specific to hippocampal volume in terms of age, gender, and menopausal status.

Adaptive statistical iterative reconstruction for volume-rendered computed tomography portovenography: improvement of image quality

PurposeAdaptive statistical iterative reconstruction (ASIR) is a reconstruction technique for computed tomography (CT) that reduces image noise. The purpose of our study was to investigate whether ASIR improves the quality of volume-rendered (VR) CT portovenography.Materials and methodsInstitutional review board approval, with waived consent, was obtained. A total of 19 patients (12 men, 7 women; mean age 69.0 years; range 25–82 years) suspected of having liver lesions underwent three-phase enhanced CT. VR image sets were prepared with both the conventional method and ASIR. The required time to make VR images was recorded. Two radiologists performed independent qualitative evaluations of the image sets. The Wilcoxon signed-rank test was used for statistical analysis. Contrast-noise ratios (CNRs) of the portal and hepatic vein were also evaluated.ResultsOverall image quality was significantly improved by ASIR (P < 0.0001 and P = 0.0155 for each radiologist). ASIR enhanced CNRs of the portal and hepatic vein significantly (P < 0.0001). The time required to create VR images was significantly shorter with ASIR (84.7 vs. 117.1 s; P = 0.014).ConclusionASIR enhances CNRs and improves image quality in VR CT portovenography. It also shortens the time required to create liver VR CT portovenographs.

Entorhinal cortex volume measured with 3T MRI is positively correlated with the Wechsler Memory Scale-Revised logical/verbal memory score for healthy subjects

IntroductionPrevious studies revealed a correlation between local brain volume and cognitive function. The aim of the present study was to investigate the correlation between local gray matter volume and the Wechsler Memory Scale-Revised (WMS-R) logical/verbal memory (WMS-R-verbal) score in healthy adults using a 3 Tesla magnetic resonance scanner and voxel-based morphometry (VBM).MethodsT1-weighted magnetic resonance images were obtained in 1,169 healthy adults. The T1-weighted images in native space were bias-corrected, spatially normalized, and segmented into gray matter, white matter, and cerebrospinal fluid images with Statistical Parametric Mapping 5. To investigate regionally the specific effects of the WMS-R-verbal score on the gray matter images, simple regression analysis was performed by VBM treating age, total intracranial volume, and gender as confounding covariates. A P value of less than 0.05 corrected with false discovery rate in voxel difference was considered to be statistically significant.ResultsOur study showed a significant positive correlation between the WMS-R-verbal score and the bilateral entorhinal cortex volume. In the right entorhinal, T value is 4.75, and the size of the clusters is 155 voxels. In the left entorhinal, T value is 4.08, and the size of the clusters is 23 voxels. A significant negative correlation was not found.ConclusionTo our knowledge, this is the first VBM study showing that entorhinal cortex volume is positively correlated with the WMS-R-verbal score for healthy subjects. Therefore, in our structural neuroimaging study, we add evidence to the hypothesis that the entorhinal cortex is involved in verbal memory processing.

Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra provides reduced effect of scanner for cortex volumetry with atlas-based method in healthy subjects

IntroductionThis study aimed to investigate whether the effect of scanner for cortex volumetry with atlas-based method is reduced using Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra (DARTEL) normalization compared with standard normalization.MethodsThree-dimensional T1-weighted magnetic resonance images (3D-T1WIs) of 21 healthy subjects were obtained and evaluated for effect of scanner in cortex volumetry. 3D-T1WIs of the 21 subjects were obtained with five MRI systems. Imaging of each subject was performed on each of five different MRI scanners. We used the Voxel-Based Morphometry 8 tool implemented in Statistical Parametric Mapping 8 and WFU PickAtlas software (Talairach brain atlas theory). The following software default settings were used as bilateral region-of-interest labels: “Frontal Lobe,” “Hippocampus,” “Occipital Lobe,” “Orbital Gyrus,” “Parietal Lobe,” “Putamen,” and “Temporal Lobe.”ResultsEffect of scanner for cortex volumetry using the atlas-based method was reduced with DARTEL normalization compared with standard normalization in Frontal Lobe, Occipital Lobe, Orbital Gyrus, Putamen, and Temporal Lobe; was the same in Hippocampus and Parietal Lobe; and showed no increase with DARTEL normalization for any region of interest (ROI).ConclusionDARTEL normalization reduces the effect of scanner, which is a major problem in multicenter studies.