Junichi Makita

Microanatomy of the cerebellopontine angle and internal auditory canal: study with new magnetic resonance imaging technique using three-dimensional fast spin echo.

OBJECTIVE We report a new magnetic resonance imaging technique that uses three-dimensional fast spin echo and the minimum intensity projection method. Using this technique, detailed images of the cerebellopontine angle (CPA) and internal auditory canal (IAC) were obtained in normal volunteers and in patients with acoustic neuromas or hemifacial spasm. METHODS Ten normal volunteers, 44 patients with acoustic neuromas, and 31 patients with hemifacial spasm were studied using the three-dimensional fast spin echo magnetic resonance imaging protocol. The CPA and IAC were scanned by using a 1-mm slice thickness in the axial and parasagittal planes. RESULTS Normal anatomy was as follows. 1) The vestibulocochlear nerve was ovoid near the brain stem and changed to a slightly crescentic configuration (C shape) as it traveled laterally. 2) Separation of the cochlear and vestibular nerves was observed near the central part of the IAC. 3) Discrimination between the superior and inferior vestibular nerves was also possible near the fundus of the IAC. 4) The facial nerve was easily identifiable as a discrete nerve at the anterior aspect of the vestibulocochlear nerve. 5) The meatal loop of the cerebellar artery was located medial to the porus in 44% of 95 CPAs and reached the porus or protruded into the porus in 56%. Acoustic neuromas were as follows. 1) In a patient with a very small intracanalicular tumor, the nerve on which the tumor was located could be identified. 2) In 22 of 44 acoustic neuromas, cerebrospinal fluid was present between the tumor and the fundus of the IAC. Hemifacial spasm was as follows. The relationship between the responsible artery and the facial nerve could be precisely observed. CONCLUSION The three-dimensional fast spin echo method offers ultrahigh-resolution images, which are extremely useful in understanding the surgical anatomy of the CPA and IAC.

Radio-frequency magnetic field regulating apparatus for magnetic resonance imaging

Between at least one of a transmitting coil and a receiving coil and a subject to be examined is interposed a member containing a high molecular compound such as a molded sheet of nonconductive fiber or rubber, a PVA gel sheet or a PAR gel sheet. Thereby, the radio-frequency magnetic field distribution can be regulated with ease without adjusting hardware or software of a magnetic resonance diagnostic apparatus, thus permitting diagnosises to be made with high accuracy.

Intracranial Cerebrospinal Fluid Distribution and its Postoperative Changes in Normal Pressure Hydrocephalus

Summary Background. This study was conducted to investigate the usefulness of intracranial cerebrospinal fluid (CSF) volume measurement using MR-based methods in the management of patients with normal pressure hydrocephalus (NPH). Methods. The study group comprised 19 patients with NPH who showed a favorable outcome after ventricular shunting, 15 normal volunteers (NV), and 15 patients with cerebrovascular disease (CVD). A 3D-fast asymmetric spin echo MR imaging sequence and the region-growing method were used to extract the CSF space from MR images. Ventricular volume (VV) and intracranial CSF volume (ICV) were measured and the VV/ICV ratio was calculated in each case. In NPH patients, the CSF volume was measured again after shunting. Findings. The mean VV and VV/ICV ratio in the NPH group (91.1 mL and 45.2%, respectively) were significantly (p<0.01) higher than those in the NV group (26.5 mL and 13.7%) and in the CVD group (44.5 mL and 17.8%). On the other hand, mean ICV values were not significantly different among the three groups. The VV was markedly decreased postoperatively (mean −40.7%), whereas the ICV was unchanged, resulting in a marked reduction in the VV/ICV ratio (mean −39.3%). Interpretation. These results suggest that patients with NPH have a unique intracranial CSF distribution, with an enlarged VV and a slightly increased ICV, resulting in a high VV/ICV ratio. Shunting led to dramatic improvement in our patients. It is likely that CSF measurement can provide valuable information in the management of patients with NPH.

Evaluation of noninvasive cerebrospinal fluid volume measurement method with 3D-FASE MRI

Hydrocephalus and cerebral atrophy are pathologies characterized by an abnormal increase in intracranial cerebrospinal fluid (CSF) volume accompanied by dilation of the cerebral ventricles and fissures. Measurements of the CSF volume are necessary to accurately assess the clinical course of such patients. A noninvasive and rapid CSF volume measurement method has been developed using heavily T2-weighted 3D-FASE MRI, which can selectively visualize the CSF with high signal intensities, and a region-growing method for extracting the CSF region. Volume measurement requires about 30 minutes, and the segmentation results of CSF are also used to create 3D displays showing the relevant anatomical information. The error in measured volumes was within 10% in phantom experiments. Intracranial and ventricular CSF volumes of normal volunteers ranged between 100 and 150 ml and between 10 and 20 ml, respectively, which agree with the values obtained by conventional methods. Increased intracranial and/or ventricular CSF volumes were observed in patients with hydrocephalus and patients with cerebral atrophy. The results suggest that the ratio of intracranial and ventricular CSF volumes could be useful for the evaluation of patients with neurological diseases.