Taichi Kin

Prediction of surgical view of neurovascular decompression using interactive computer graphics.

OBJECTIVETo assess the value of an interactive visualization method for detecting the offending vessels in neurovascular compression syndrome in patients with facial spasm and trigeminal neuralgia. Computer graphics models are created by fusion of fast imaging employing steady-state acquisition and magnetic resonance angiography. METHODSHigh-resolution magnetic resonance angiography and fast imaging employing steady-state acquisition were performed preoperatively in 17 patients with neurovascular compression syndromes (facial spasm, n = 10; trigeminal neuralgia, n = 7) using a 3.0-T magnetic resonance imaging scanner. Computer graphics models were created with computer software and observed interactively for detection of offending vessels by rotation, enlargement, reduction, and retraction on a graphic workstation. Two-dimensional images were reviewed by 2 radiologists blinded to the clinical details, and 2 neurosurgeons predicted the offending vessel with the interactive visualization method before surgery. Predictions from the 2 imaging approaches were compared with surgical findings. The vessels identified during surgery were assumed to be the true offending vessels. RESULTSOffending vessels were identified correctly in 16 of 17 patients (94%) using the interactive visualization method and in 10 of 17 patients using 2-dimensional images. These data demonstrated a significant difference (P = 0.015 by Fishers exact method). CONCLUSIONThe interactive visualization method data corresponded well with surgical findings (surgical field, offending vessels, and nerves). Virtual reality 3-dimensional computer graphics using fusion magnetic resonance angiography and fast imaging employing steady-state acquisition may be helpful for preoperative simulation.

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.

Intraoperative monitoring of cortically recorded visual response for posterior visual pathway

OBJECT Intraoperative monitoring of visual evoked potentials (VEPs) has been regarded as having limited significance for the preservation of visual function during neurosurgical procedures, mainly due to its poor spatial resolution and signal-to-noise ratio. The authors evaluated the usefulness of cortically recorded VEPs, instead of the usual scalp VEPs, as intraoperative monitoring focusing on the posterior visual pathway. METHODS In 17 consecutive patients who underwent microsurgical procedures for lesions near the posterior visual pathway, cortical responses were recorded using 1-Hz flashing light-emitting diodes and subdural strip electrodes after induction of general anesthesia with sevoflurane or propofol. The detectability and waveform of the initial response, stability, and changes during microsurgical manipulations were analyzed in association with the position of electrodes and postoperative changes in visual function. RESULTS Initial VEPs were detected in 82% of all patients. The VEPs were detected in 94% of patients without total hemianopia in whom electrodes were placed sufficiently near the occipital pole; in these cases the recordings were not significantly affected by anesthesia. The detectability rates of the negative peak before 100 msec (N1), positive peak approximately 100 msec (P100), and negative peak after 100 msec (N2) were 36, 50, and 100%, respectively. The mean latencies and amplitudes of N1, P100, and N2 were 90.0 +/- 15.9 msec and 61.0 +/- 64.0 microV, 103.9 +/- 13.5 msec and 34.3 +/- 38.6 microV, and 125.7 +/- 12.2 msec and 44.9 +/- 48.9 microV, respectively, showing great variability. In 11 patients, the initial waveforms of VEP remained stable during microsurgical procedures, and the visual status did not change postoperatively, while it disappeared in 2 patients who presented with postoperative hemianopia. CONCLUSIONS Direct recording from the visual cortices under general anesthesia achieved satisfactory detectability of the visual response to a light-emitting diode flashing light. Although the initial waveforms varied greatly among patients, they were stable during microsurgical procedures, and the changes were consistent with postoperative visual function. Intraoperative cortical VEP monitoring is a potentially useful procedure to monitor the functional integrity of the posterior visual pathway.

Impact of multiorgan fusion imaging and interactive 3-dimensional visualization for intraventricular neuroendoscopic surgery.

BACKGROUND: Imaging technologies have evolved to meet the demand for improved presurgical simulations, particularly with the introduction of endoscopic surgery in the neurosurgical field. OBJECTIVE: To evaluate the effectiveness of a 3-dimensional interactive visualization method with a computer graphics model, which was created using hybrid rendering and multimodal fusion methods for neuroendoscopic surgery, and to assess whether the 2-dimensional interactive visualization method could effectively represent the microsurgical anatomical information necessary for endoscopic surgery compared with conventional 3-dimensional computer graphics models. METHODS: Ten patients scheduled for neuroendoscopic surgery for intraventricular lesions were included in the study. For the 3-dimensional interactive visualization method, a hybrid model of volume and surface rendering was created from magnetic resonance images combined with computed tomography and positron emission tomography. Preoperative radiographic images were fused with the normalized mutual information method. Visibility of anatomic structures was compared between the multifusion models and nonfusion models created from only heavy-T2-weighted images that rely solely on the surface rendering method. RESULTS: The average visibility score of the multifusion models was 97.5% (range, 95.6% to 100%), which was significantly higher than that for nonfusion models (35.9% to 64.1%; P = .002). The multifusion model represents an improved visualization method for preoperative virtual simulation for neuroendoscopic intraventricular surgery. CONCLUSION: Our 3-dimensional imaging method is superior to conventional methods and will greatly improve the safety and effectiveness of neuroendoscopic surgical procedures for complex intraventricular lesions.

Improved preservation of function during acoustic neuroma surgery

OBJECT Restoration of cranial nerve functions during acoustic neuroma (AN) surgery is crucial for good outcome. The effects of minimizing the injury period and maximizing the recuperation period were investigated in 89 patients who consecutively underwent retrosigmoid unilateral AN surgery. METHODS Cochlear nerve and facial nerve functions were evaluated during AN surgery by use of continuous auditory evoked dorsal cochlear nucleus action potential monitoring and facial nerve root exit zone-elicited compound muscle action potential monitoring, respectively. Factors affecting preservation of function at the same (preoperative) grade were analyzed. RESULTS A total of 23 patients underwent standard treatment and investigation of the monitoring threshold for preservation of function; another 66 patients underwent extended recuperation treatment and assessment of its effect on recovery of nerve function. Both types of final action potential monitoring response and extended recuperation treatment were associated with preservation of function at the same grade. CONCLUSIONS Preservation of function was significantly better for patients who received extended recuperation treatment.

Angiographic Classification of Tumor Attachment of Meningiomas at the Cerebellopontine Angle

OBJECTIVE To present an angiographic classification of attachment of meningiomas at the cerebellopontine angle (CPA) based on tumor feeding and to validate the utility of this classification in predicting meningioma attachments at the CPA. METHODS The authors retrospectively analyzed 34 consecutive patients with meningioma at the CPA. Based on operative findings, tumors were classified into four types: the petroclival type, in which the trigeminal nerve is displaced laterally; the tentorial type, in which the center of tumor attachment is located at the medial tentorium; the anterior petrous type, in which the center of tumor attachment is located anterior to the meatus; and the posterior petrous type, in which the center of tumor attachment is located posterior to the meatus. Magnetic resonance imaging (MRI) was sufficient to confirm attachment of the posterior petrous type. Another 26 cases were analyzed angiographically and classified into three types: abnormal ipsilateral tentorial artery type (type A); bilateral internal carotid artery (ICA) type (type B); and nontentorial, non-ICA type (type N). This angiographic classification was validated by comparison with the attachment classification. RESULTS Angiographic types A, B, and N corresponded to tentorial, petroclival, and anterior petrous types of attachment. Observed agreement was very high, particularly for tumors greater than 30 mm in diameter (κ statistic 0.83; 95% confidence interval [CI] 0.62-1.0). Angiographic type in this paired attachment typing offered high sensitivity and specificity greater than 0.80 in tumors larger than 30 mm. CONCLUSIONS This angiographic classification seems to be useful in predicting meningioma attachments at the CPA. The existence of an abnormally developed tentorial artery seems highly indicative of tumor attachment to the tentorium.

Combined use of diffusion tensor tractography and multifused contrast-enhanced FIESTA for predicting facial and cochlear nerve positions in relation to vestibular schwannoma

OBJECT The authors assessed whether the combined use of diffusion tensor tractography (DTT) and contrast-enhanced (CE) fast imaging employing steady-state acquisition (FIESTA) could improve the accuracy of predicting the courses of the facial and cochlear nerves before surgery. METHODS The population was composed of 22 patients with vestibular schwannoma in whom both the facial and cochlear nerves could be identified during surgery. According to DTT, depicted fibers running from the internal auditory canal to the brainstem were judged to represent the facial or vestibulocochlear nerve. With regard to imaging, the authors investigated multifused CE-FIESTA scans, in which all 3D vessel models were shown simultaneously, from various angles. The low-intensity areas running along the tumor from brainstem to the internal auditory canal were judged to represent the facial or vestibulocochlear nerve. RESULTS For all 22 patients, the rate of fibers depicted by DTT coinciding with the facial nerve was 13.6% (3/22), and that of fibers depicted by DTT coinciding with the cochlear nerve was 63.6% (14/22). The rate of candidates for nerves predicted by multifused CE-FIESTA coinciding with the facial nerve was 59.1% (13/22), and that of candidates for nerves predicted by multifused CE-FIESTA coinciding with the cochlear nerve was 4.5% (1/22). The rate of candidates for nerves predicted by combined DTT and multifused CE-FIESTA coinciding with the facial nerve was 63.6% (14/22), and that of candidates for nerves predicted by combined DTT and multifused CE-FIESTA coinciding with the cochlear nerve was 63.6% (14/22). The rate of candidates predicted by DTT coinciding with both facial and cochlear nerves was 0.0% (0/22), that of candidates predicted by multifused CE-FIESTA coinciding with both facial and cochlear nerves was 4.5% (1/22), and that of candidates predicted by combined DTT and multifused CE-FIESTA coinciding with both the facial and cochlear nerves was 45.5% (10/22). CONCLUSIONS By using a combination of DTT and multifused CE-FIESTA, the authors were able to increase the number of vestibular schwannoma patients for whom predicted results corresponded with the courses of both the facial and cochlear nerves, a result that has been considered difficult to achieve by use of a single modality only. Although the 3D image including these prediction results helped with comprehension of the 3D operative anatomy, the reliability of prediction remains to be established.

A high-resolution method with increased matrix size can characterize small arteries around a giant aneurysm in three dimensions.

Visualization of the small arteries around a giant intracranial aneurysm remains challenging, even with three-dimensional (3D) rotational angiography. Here we present a new method with the increased matrix size to visualize three-dimensional course of the anterior choroidal artery around a giant aneurysm to help estimate the risk of intraoperative complications.

Ptosis as Partial Oculomotor Nerve Palsy Due to Compression by Infundibular Dilatation of Posterior Communicating Artery, Visualized with Three-Dimensional Computer Graphics: Case Report

Oculomotor nerve palsy (ONP) due to internal carotid-posterior communicating artery (PcomA) aneurysm generally manifests as partial nerve palsy including pupillary dysfunction. In contrast, infundibular dilatation (ID) of the PcomA has no pathogenic significance, and mechanical compression of the cranial nerve is extremely rare. We describe a 60-year-old woman who presented with progressive ptosis due to mechanical compression of the oculomotor nerve by an ID of the PcomA. Three-dimensional computer graphics (3DCG) accurately visualized the mechanical compression by the ID, and her ptosis was improved after clipping of the ID. ID of the PcomA may cause ONP by mechanical compression and is treatable surgically. 3DCG are effective for the diagnosis and preoperative simulation.

Surgical Simulation of Cerebrovascular Disease With Multimodal Fusion 3-Dimensional Computer Graphics

Although recent advancements in medical imaging technology have allowed detailed preoperative examinations, neurosurgeons still have to interpret large amounts of medical imaging data. In various modalities such as computed tomography (CT), magnetic resonance imaging (MRI), and angiography, there are multiple sequences and 3-dimensional (3-D) images, and it is not uncommon for there to be several hundred to several thousand section images per case. Clinicians have to interpret each of these multimodalities/sequences individually and consolidate this information in their heads to form a 3-D image that can be used in preoperative planning. From the perspectives of accuracy, reproducibility, and sharing information with other people, it is hard to ensure sufficient precision. Furthermore, the spatial resolution of the 3-D images used in today’s clinical settings is inferior to that in 2-dimensional (2-D) imaging because the processing methods are limited. Consequently, ascertaining detailed findings from 3-D images alone is unsatisfactory; clinicians must additionally interpret 2-D section images of the same site. In this report, we describe the fusion of all image data required for preoperative examination and the construction of 3-D computer graphics (3-DCG) with a high spatial resolution using our own image processing technique. We then apply this to surgical strategies in cerebral vascular disease and report our experience and the usefulness of the technique.