[Application of brain diffusion-weighted imaging performed using readout segmentation of long variable echo trains].

We report the preliminary use of the readout segmentation of long variable echo trains(RESOLVE)sequence, a novel magnetic resonance(MR)scanning technique based on a readout segmented echo planar imaging(EPI)strategy. RESOLVE enables high-resolution diffusion-weighted imaging(DWI)by minimizing susceptibility distortions and T2* blurring. The software for this sequence was provided by Siemens AG, Germany. Previously, we determined appropriate sequence parameters to obtain sufficiently high-resolution images through phantom studies. Then, we applied the sequence to some clinical cases with neurological disorders and analyzed the RESOLVE-DWI data with diffusion tensor imaging(DTI)techniques. In this article, we report clinical application of the RESOLVE sequence in two cases, one with cerebellar infarction and one with an intracranial epidermoid cyst. In both cases, RESOLVE-DWI clearly exposed structures that were obscured or severely distorted by artifacts on usual single-shot EPI-DWI. DTI analyses for RESOLVE-DWI data provided detailed information about fiber tracts and cranial nerves.

[Depiction of the trigeminal nerve deviated by a tumor lesion, using probabilistic diffusion tensor tractography].

We attempted presurgical visualization of the trigeminal nerve deviated by tumor compression using the probabilistic diffusion tractography (PDT) technique, which is used to analyze diffusion tensor imaging (DTI) data. We acquired DTI data of 3 patients with a tumor lesion around the trigeminal nerve (2 patients with trigeminal neurinomas and 1 with epidermoid) using the 3T magnetic resonance imaging system. The DTI data was analyzed by PDT using the Diffusion Toolbox, and the software of FMRIB (FDT; www.fmrib.ox.ac.uk/fsl). In all 3 patients, PDT allowed successful visualization of the trigeminal nerve which is further distal to the trigeminal ganglion, even when heavy T2-weighted imaging and conventional fiber-tracking analysis of the DTI data revealed only the cisternal segment of the nerves. Especially in 2 cases with the tumor mainly located in the Meckel's cave, the location of the nerve was determined only by PDT. All these findings obtained by PDT were concordant with the intraoperative observation of the actual nerves. In conclusion, PDT is a useful technique for visualization of the trigeminal nerve even when it is severely deviated by tumor compression, and this technique could have potential for evaluating other cranial nerves in surgical cases with a tumor in the skull base.

[Depiction of the cranial nerves around the cavernous sinus by 3D reversed FISP with diffusion weighted imaging (3D PSIF-DWI)].

To evaluate the anatomy of cranial nerves running in and around the cavernous sinus, we employed three-dimensional reversed fast imaging with steady-state precession (FISP) with diffusion weighted imaging (3D PSIF-DWI) on 3-T magnetic resonance (MR) system. After determining the proper parameters to obtain sufficient resolution of 3D PSIF-DWI, we collected imaging data of 20-side cavernous regions in 10 normal subjects. 3D PSIF-DWI provided high contrast between the cranial nerves and other soft tissues, fluid, and blood in all subjects. We also created volume-rendered images of 3D PSIF-DWI and anatomically evaluated the reliability of visualizing optic, oculomotor, trochlear, trigeminal, and abducens nerves on 3D PSIF-DWI. All 20 sets of cranial nerves were visualized and 12 trochlear nerves and 6 abducens nerves were partially identified. We also presented preliminary clinical experiences in two cases with pituitary adenomas. The anatomical relationship between the tumor and cranial nerves running in and around the cavernous sinus could be three-dimensionally comprehended by 3D PSIF-DWI and the volume-rendered images. In conclusion, 3D PSIF-DWI has great potential to provide high resolution "cranial nerve imaging", which visualizes the whole length of the cranial nerves including the parts in the blood flow as in the cavernous sinus region.

[The utility of presurgical simulation of microvascular decompression by MR virtual endoscopy].

OBJECTIVE: We conducted the present study to assess the utility of virtual endoscopy (VE) created by volume rendering of MR images in presurgical simulation for trigeminal neuralgia (TN) and hemifacial spasm (HFS). METHODS: In 12 patients (six with TN and six with HFS), we presurgically evaluated the anatomy of the cerebellopontine angle (CPA) region and simulated an appropriate surgical approach by VE of heavy T2-weighted imaging and MR angiography. RESULTS: The three-dimensional (3-D) relations of neurovascular structures in the CPA region were compatible between on-VE and on-the-intraoperative view in all patients. The compression sites and the major offending vessels were correctly depicted, except for two small branches as the offending vessel. The other important structures affecting the surgical procedure were identified as major petrosal veins in all patients with TN, a vertebral artery in three with HFS, and a large cerebellar flocculus in three with HFS. Transposition of the offending vessels was performed as simulated in all patients with TN and in three patients with HFS. All patients had an excellent surgical outcome. CONCLUSIONS: Presurgical simulation by VE in patients with TN and HFS is a novel method that provides excellent visualization of the 3-D relations of neurovascular structures in the CPA region and allows us to accomplish successful and safe surgery.

Presurgical simulation with advanced 3-dimensional multifusion volumetric imaging in patients with skull base tumors.

BACKGROUND: Despite recent diagnostic and technical advancements in the field of neurosurgery, surgical treatment for tumors in the skull base region, ie, skull base tumors (SBTs), remains a challenge. OBJECTIVE: To validate the utility of presurgical simulation for the treatment of SBTs by 3-dimensional multifusion volumetric imaging (3D MFVI), including volume rendering and image fusion, to combine data from various imaging modalities. METHODS: We performed presurgical simulation using 3D MFVI for 21 SBTs (acoustic neurinomas, jugular neurinomas, meningiomas, chordomas, and others) in 20 patients. We collected targeted data from computed tomography, magnetic resonance imaging, computed tomography or magnetic resonance angiography, and digital subtraction angiography and combined these data using image-analyzing software. The simulations were used to assess the 3D relationships among the microsurgical anatomical components, the appropriate surgical approach, and the resectable parts of the tumor. Finally, we compared the results of the simulation with the operative results. RESULTS: In all patients, the 3D MFVI techniques enabled adequate visualization of the microsurgical anatomy and facilitated presurgical simulation, thereby allowing the surgeons to determine an appropriate and feasible surgical approach. All procedures to open the bone window were performed in accordance with the simulations, except for the surgical exposure of the acoustic canal for 2 acoustic neurinomas. In 3 of the 21 cases, tumor removal could not be performed according to the simulations because of unexpected bleeding or other restrictions. CONCLUSION: The 3D MFVI technique was of a sufficiently high quality to enable visualization of the 3D microsurgical anatomy. This promising method can facilitate determination of the most appropriate approach and safe and precise surgical procedures for SBTs.

Prediction of the microsurgical window for skull-base tumors by advanced three-dimensional multi-fusion volumetric imaging.

The surgery of skull base tumors (SBTs) is difficult due to the complex and narrow surgical window that is restricted by the cranium and important structures. The utility of three-dimensional multi-fusion volumetric imaging (3-D MFVI) for visualizing the predicted window for SBTs was evaluated. Presurgical simulation using 3-D MFVI was performed in 32 patients with SBTs. Imaging data were collected from computed tomography, magnetic resonance imaging, and digital subtraction angiography. Skull data was processed to imitate actual bone resection and integrated with various structures extracted from appropriate imaging modalities by image-analyzing software. The simulated views were compared with the views obtained during surgery. All craniotomies and bone resections except opening of the acoustic canal in 2 patients were performed as simulated. The simulated window allowed observation of the expected microsurgical anatomies including tumors, vasculatures, and cranial nerves, through the predicted operative window. We could not achieve the planned tumor removal in only 3 patients. 3-D MFVI afforded high quality images of the relevant microsurgical anatomies during the surgery of SBTs. The intraoperative déjà-vu effect of the simulation increased the confidence of the surgeon in the planned surgical procedures.

Three-dimensional visualization of neurovascular compression: presurgical use of virtual endoscopy created from magnetic resonance imaging.

OBJECTIVE: To assess the usefulness of presurgical simulation of microvascular decompression (MVD) by virtual endoscopy (VE), a new tool to analyze three-dimensionally reconstructed magnetic resonance data sets in patients with trigeminal neuralgia or hemifacial spasm (HFS). METHODS: In 17 patients (10 with trigeminal neuralgia and seven with HFS) determined to be candidates for MVD, we performed presurgical simulation of MVD using VE. We used constructive interference in steady-state imaging and magnetic resonance angiography to obtain the original images. VE findings were compared with surgical findings. RESULTS: The three-dimensional relations between visible structures seen on VE were consistent with intraoperative findings in all patients. In total, 20 (91%) of 22 neurovascular compression sites in all 17 patients were correctly delineated on VE, with the exception of two small branches identified as offending vessel in two patients with HFS. Perforators that were not apparent on VE limited our ability to accomplish transpositioning of the offending vessels as simulated. The positions of structures that can affect individual surgical approaches, such as the petrosal vein, cerebellar flocculus, and vertebral artery, were also adequately predicted on VE. All patients had excellent surgical outcomes. CONCLUSION: Presurgical VE in patients with trigeminal neuralgia or HFS is a novel technique that provides excellent visualization of the three-dimensional relations between neurovascular structures and allows simulation of MVD.