Biomedical subjects

Y Korogi

Publications and source records attributed to Y Korogi.

At least 145 records · Page 8Linked to original sources

PubMedDate not supplied

Methylmercury poisoning in common marmosets--a study of selective vulnerability within the cerebral cortex.

Neuropathological lesions found in chronic human Minamata disease tend to be localized in the calcarine cortex of occipital lobes, the pre- and postcentral lobuli, and the temporal gyri. The mechanism for the selective vulnerability is still not clear, though several hypotheses have been proposed. One hypothesis is vascular and postulates that the lesions are the result of ischemia secondary to compression of sulcal arteries from methylmercury-induced cerebral edema. To test this hypothesis, we studied common marmosets because the cerebrum of marmosets has 2 distinct deep sulci, the calcarine and Sylvian fissures. MRI analysis, mercury assays of tissue specimens, histologic and histochemical studies of the brain are reported and discussed. Brains sacrificed early after exposure to methylmercury showed high contents of methylmercury and edema of the cerebral white matter. These results may explain the selective cortical degeneration along the deep cerebral fissures or sulci.

Animals↗

PubMedDate not supplied

MR angiography of the persistent trigeminal artery variant.

OBJECTIVE: To evaluate the MR angiographic findings of the persistent trigeminal artery variant (PTAV) and to discuss its clinical implications. MATERIALS AND METHODS: We reviewed time-of-flight MR angiography including individual source imaging in three patients with PTAV, which had been recognized as an incidental finding on conventional arteriography. In all cases, MR angiography was performed at 1.5 T. RESULTS: MR angiography demonstrated the PTAVs as hyperintense structures originating from the precavernous portion of the internal carotid artery, running within or very close to the Meckel cave and near the trigeminal nerve root, and reaching the posterior fossa (cerebellar arteries) without joining the basilar artery. Spin echo imaging failed to demonstrate the PTAVs. CONCLUSION: Source imaging of MR angiography helped demonstrate PTAV and its adjacent structure. Knowledge of the presence and course of this anomalous vessel is useful for various treatment strategies.

Adolescent↗

PubMedDate not supplied

Evaluation of vascular compression in trigeminal neuralgia by 3D time-of-flight MRA.

OBJECTIVE: Our goal was to assess the usefulness of 3D images in the preoperative evaluation of 16 patients with surgically confirmed trigeminal neuralgia. MATERIALS AND METHODS: The axial source images from 3D TOF MRA were evaluated for a total of 32 sides by two observers in a blinded manner, focusing on the presence of the neurovascular compression and the identification of compressing vessels. All 3D images including coronal orientation and gadolinium-enhanced images were reviewed retrospectively by another two observers together with the surgical findings. RESULTS: In the blinded study with axial 3D images, the sensitivity was 75 and 75% with a specificity of 75 and 69% for observers A and B, respectively. By reviewing the coronal images, the relationship between trigeminal nerve and vessels became clearer, especially in sandwich-type compression. With gadolinium-enhanced images, three vessels that were not shown in the nonenhanced images could be identified. On the asymptomatic side, vascular compression could not be excluded retrospectively in five cases. CONCLUSION: Nonenhanced axial images may not display small arteries or veins that are compressing the trigeminal nerve. Gadolinium enhancement will be necessary for those patients without demonstrable compression on nonenhanced examination. Coronal images are also helpful in the evaluation of vascular compression.

Adult↗

PubMedDate not supplied

Chordomas of the skull base: dynamic MRI.

OBJECTIVE: To investigate the role of dynamic MRI in the diagnosis of chordomas at the skull base. MATERIALS AND METHODS: Six patients with surgically proven chordomas of the skull base were examined with spin-echo technique (repetition time/echo time 200 ms/15 ms). Serial imaging was performed every 30 s for 240 s after a rapid injection of gadopenetate dimeglumine (0.1 mmol/kg). The contrast material enhancement ratio (CER) was analyzed. The CER was obtained for each region of interest as follows (Sn - So) x 100/Smax - So, where Sn indicates signal intensity at each dynamic phase; So, signal intensity on the image obtained before administration of contrast material; and Smax, maximum signal intensity of all dynamic imaging. RESULTS: All chordomas showed very slow but steady increase of contrast enhancement with no peak within 240 s. The CERs of six cases at 30 s are 13 to 40 (mean value +/- standard deviation: 22.8 +/- 10.2). CONCLUSION: Dynamic MRI may be helpful in differentiating between chordomas and other tumors of the skull base.

Adult↗

PubMedDate not supplied

Contrast-enhanced CISS MRI of vestibular schwannomas: phantom and clinical studies.

PURPOSE: The purpose of this work was to assess the changes of signal intensity on constructive interference in steady state (CISS) 3D Fourier transformation (3DFT) MRI after administration of Gd-DTPA and to evaluate the efficacy of contrast-enhanced CISS-3DFT MRI to depict the seventh and eighth cranial nerves affected by vestibular schwannomas. METHOD: All scans were carried out on a 1.5 T MR unit. First, an experimental study was conducted to evaluate the changes in signal intensity of the CISS-3DFT sequence in relation to the concentration of contrast medium. Second, nine consecutive patients with 11 vestibular schwannomas underwent CISS-3DFT imaging before and after contrast agent administration. Signal intensities of the tumors and nerves were measured and compared between the pre- and postcontrast images. Visualization of the facial and cochlear nerves was rated on pre- and postcontrast CISS imaging independently. RESULTS: On the phantom study, the CISS-3DFT sequence showed a constant increase in signal intensity as the concentration of Gd-DTPA increased. The contrast between the nerves and tumors significantly increased after contrast agent administration (from 0.1 to 9.0 as mean contrast-to-noise ratio). The ability to depict the nerves was also significantly higher for postcontrast CISS-3DFT imaging than for precontrast. CONCLUSION: Although the CISS-3DFT sequence offers similar contrast as other heavily T2-weighted sequences, the signal intensity of contrast-enhanced tumors increased on CISS-3DFT imaging. Contrast-enhanced CISS imaging was valuable for evaluating the seventh and eighth cranial nerves affected by vestibular schwannomas.

Adult↗

PubMedDate not supplied

Perfusion-sensitive MRI of cerebral lymphomas: a preliminary report.

PURPOSE: To date, there have been no systematic reports examining cerebral lymphomas with perfusion-sensitive MRI. We sought to determine the characteristics of perfusion-sensitive MRI of these tumors. METHOD: Five primary and three secondary cerebral lymphomas were analyzed. None of the patients had a history of AIDS. Various areas of relative cerebral blood volume (rCBV) within tumor were analyzed, and maximum CBV ratios (CBV[tumor/contralateral]) were identified for evaluation. RESULTS: In three primary and three secondary cerebral lymphomas, maximum CBV ratios were <2.5 (mean 1.50). In others, maximum CBV ratios were markedly higher than those of the white matter (5.38 and 5.42). Mean maximum rCBV ratios of primary and secondary cerebral lymphomas were 2.93 and 1.43, respectively. There was no significant difference between the two groups. CONCLUSION: Cerebral lymphomas had a tendency to have low rCBV values. This information may be helpful in diagnosing these tumors.

Adult↗

PubMedDate not supplied

Hyperintensities of the optic radiation on T2-weighted MR images of elderly subjects.

BACKGROUND AND PURPOSE: Although abnormal hyperintensities are frequently observed at or around the optic radiation in elderly subjects, no previous reports have mentioned the clinical significance and pathologic changes of these hyperintensities. We evaluated the hyperintensity patterns of the optic radiation and its surrounding structures on T2-weighted MR images and compared these findings with pathologic observations and visual field measurements. METHODS: High-resolution coronal T2-weighted MR images of 102 consecutive patients (51-84 years old) were evaluated retrospectively for the presence and morphology of hyperintensities of the optic radiation (204 sides) and its surrounding structures. Pathologic specimens were obtained from 25 other patients (60-91 years old) who had died of nonneurologic causes. The histopathologic changes of the optic radiation and its surrounding structures were evaluated and correlated with the MR findings. Finally, MR findings and visual field measurements were correlated in 46 elderly volunteers (70-91 years old). RESULTS: Hyperintensities of the optic radiation or its surrounding structures or both were observed on 125 sides (93%) of 67 patients (61%), and linear/laminar hyperintensity of the optic radiation and the tapetum was the characteristic finding. Eleven (44%) of 25 pathologic specimens exhibited pallor of three anatomic layers (the external sagittal stratum or the optic radiation, the internal sagittal stratum, and the tapetum). No subjects with hyperintensity of the optic radiation had visual field abnormalities. CONCLUSION: Linear/laminar hyperintensity of the optic radiation and tapetum on T2-weighted images is common in elderly subjects, and may reflect differences in the internal structures and in the water content of three anatomic structures. Hyperintensities of this region did not cause visual field abnormalities in a group of elderly volunteers.

Aged↗

PubMedDate not supplied

Intraarterial catheter thrombolytic therapy for acute peripheral arterial occlusions.

Intraarterial thrombolytic therapy was performed in 36 patients with acute arterial occlusions of the extremities. Intraarterial thrombolytic therapy was effective in 19 of 24 patients (79.2%) with embolic occlusions. However, the results were poor in patients who had multiple arterial occlusions including those at sites other than the extremities. Only four of 12 patients (33.3%) with thrombotic occlusions had good initial technical results. Six patients died shortly after the thrombolytic procedure, and seven patients underwent amputation. The long-term patency rate of 21 patients who were treated successfully was 92.7% after one year and 74.6% after five years. Intraarterial catheter thrombolytic therapy was effective for embolic occlusion even when more than six hours had elapsed from the onset of symptoms. The indications for thrombotic occlusions may be limited, since associated marked atherosclerotic change was often present.

Acute Disease↗

PubMedDate not supplied

Increased conspicuity of intraventricular lesions revealed by three-dimensional constructive interference in steady state sequences.

We describe our preliminary experience with the three-dimensional constructive interference in steady state (3D-CISS) sequence for the evaluation of intraventricular lesions. Cyst walls, extent and margins of tumors, and intratumoral cystic structures were clearly depicted on 3D-CISS images. The 3D-CISS sequence can offer additional information to conventional MR studies to define intraventricular lesions better.

Adult↗

PubMedDate not supplied

Light and electron microscopic observations in atherosclerotic rabbits following experimental transluminal angioplasty.

Light and scanning electron microscopy were used to assess the morphologic changes in atherosclerotic lesions in rabbits following percutaneous transluminal angioplasty. Histologic changes observed by light microscopy, i.e. fracture or separation of the plaque and overdistension of the media, were correlated with different balloon sizes. In atherosclerotic rabbits, progressive changes were observed in the vessel wall with increasing size of the balloon. Scanning electron microscopy showed denudation of the endothelial cells, exposure of the subintimal layer, and adhesion of the platelets. In addition, compression of the atheroma, circumferential endothelial rupture, flattening of the intimal fold, and undulation of the intimal fold were observed. Morphometric analysis of histologic sections of the dilated and non-dilated aortas disclosed significant differences in the thickness to width ratio of the plaque. These findings demonstrated that compression of the atherosclerotic plaque could occur.

Angioplasty, Balloon↗

PubMedDate not supplied

Percutaneous transluminal angioplasty of the ilio-femoro-popliteal arteries: initial and long-term results.

Percutaneous transluminal angioplasty has been widely used for dilatation and recanalization of occluded or stenosed vessels, but clinical experience in Japan is not extensive. Follow-ups of 78 ilio-femoro-popliteal angioplasties were performed for up to 51 months to assess the initial and long-term results. The initial technical success rate was 91%. The three-year cumulative patency rate was 75%. This study demonstrates that the long-term results of PTA of ilio-femoro-popliteal arterial lesions are competitive with reconstructive surgery. PTA should be the treatment of choice in patients with atherosclerotic narrowing or occlusion of the lower extremities.

Aged↗

PubMedDate not supplied

Rectangular field of view for dynamic MR imaging of sellar and parasellar regions.

The effectiveness and quality of a rectangular field of view (R-FOV) were compared with those of a square FOV (S-FOV) in dynamic MR study of sellar regions. Cranial nerves in the cavernous sinus were identified more clearly with R-FOV. The image quality grading of R-FOV was significantly superior to that of S-FOV.

Cavernous Sinus↗

PubMedDate not supplied

MR imaging of minamata disease: qualitative and quantitative analysis.

Minamata disease (MD), a result of methylmercury poisoning, is a neurological illness caused by ingestion of contaminated seafood. We evaluated MR findings of patients with MD qualitatively and quantitatively. Magnetic resonance imaging at 1.5 Tesla was performed in seven patients with MD and in eight control subjects. All of our patients showed typical neurological findings like sensory disturbance, constriction of the visual fields, and ataxia. In the quantitative image analysis, inferior and middle parts of the cerebellar vermis and cerebellar hemispheres were significantly atrophic in comparison with the normal controls. There were no significant differences in measurements of the basis pontis, middle cerebellar peduncles, corpus callosum, or cerebral hemispheres between MD and the normal controls. The calcarine sulci and central sulci were significantly dilated, reflecting atrophy of the visual cortex and postcentral cortex, respectively. The lesions located in the calcarine area, cerebellum, and postcentral gyri were related to three characteristic manifestations of this disease, constriction of the visual fields, ataxia, and sensory disturbance, respectively. MR imaging has proved to be useful in evaluating the CNS abnormalities of methylmercury poisoning.

Ataxia↗

PubMedDate not supplied

Iotrolan: a blood-isotonic nonionic dimer contrast agent for peripheral angiography.

Twenty-four patients undergoing peripheral arteriography with iotrolan 280, a blood-isotonic, nonionic, dimeric contrast medium, were evaluated in a carefully controlled phase III open trial using a variety of objective and subjective tests of discomfort. There was almost no evidence of pain, and the patients reported that they had minimal warm sensation during injection. No abnormalities in blood chemistry or urinalysis were noted in relation to injection of the contrast medium. Opacification of the peripheral arteries was excellent in all patients. Multiple physical examinations, chemical tests, electrocardiograms, and monitoring of the blood pressure showed that iotrolan 280 was a safe and useful contrast agent for peripheral angiography.

Adult↗

PubMedDate not supplied

Correlation of sequential MR imaging of the injured spinal cord with prognosis.

Forty-nine patients with acute spinal cord injuries were studied sequentially with MR imaging by using 0.5 Tesla superconductive units, and sequential MR changes were correlated with the prognosis of the patients. MR images were obtained within one week of the injury and then every two to six months when possible. The Frankel classification of neurologic function was correlated with MR findings. The most frequently observed types of signal intensity patterns on MR imaging were type 0 (isointensity on both T1- and T2-weighted images) and type I (isointensity on T1- and hyperintensity on T2-weighted images). In subsequent subacute and chronic stages, type II (hypointensity on T1 and hyperintensity on T2) was most frequently observed. The evolution of type 0 was to types I and II, whereas type I usually turned into type II or remained as type I. Type III (hyperintensity on T1 and hyper-, iso- or hypointensity on T2 images) patients were few in number. There was a good correlation between MR imaging patterns and neurologic recovery for initial and subsequent MR patterns, in that type 0 showed good recovery, whereas types I and II revealed good improvement or no recovery. In addition, the extent of the high signal intensity area on initial as well as on subsequent T2-weighted images was proportionally correlated to neurologic recovery. The degree of cord compression was also important for predicting recovery of neurologic function. Findings of MR imaging of acutely injured spinal cord suggested the prognosis of spinal cord injury, especially when sequential studies were obtained.

Acute Disease↗

PubMedDate not supplied

MR findings in two presumed cases of mild central pontine myelinolysis.

The authors describe two patients with presumed central pontine myelinolysis whose clinical symptoms were mild despite extensive intrapontine lesions evident on MR imaging. Enhancement of the lesions with Gd-DTPA was not observed in either case. It is suggested that the severity of findings on MR imaging does not necessarily reflect the severity of clinical symptoms of the disease.

Adult↗

PubMedDate not supplied

MR imaging of lingual carcinoma: comparison with surgical staging.

The purpose of this study was to determine the usefulness of magnetic resonance (MR) imaging for the preoperative staging of 18 patients with lingual carcinomas. Tumor stage as determined by MR imaging was compared with pathological stage. Conspicuity of tumors was compared among dynamic MR, T2-weighted, and postcontrast T1-weighted images. The tumor stage was evaluated correctly with MR imaging in 15/18 patients (83.3%). One patient was overstaged and two understaged due to incorrect diagnosis of size. In all T4 cases, tumor extension was diagnosed correctly. Dynamic MR and T2-weighted images were superior to postcontrast T1-weighted images in delineating and showing the extension of carcinomas. However, dynamic MR imaging showed no significant superiority to T2-weighted imaging. We conclude that MR imaging is of great value in the staging of lingual carcinoma. Dynamic study should be performed only when the lesion is undetectable or equivocal on T2-weighted imaging.

Adult↗

PubMedDate not supplied

Representation of the visual field in the striate cortex: comparison of MR findings with visual field deficits in organic mercury poisoning (Minamata disease).

PURPOSE: To compare MR imaging findings of the striate cortex with visual field deficits in patients with Minamata disease and to reestimate the classical Holmes retinotopic map by using the data obtained from comparing visual field abnormalities with degree of visual cortex atrophy. METHODS: MR imaging was performed in eight patients with Minamata disease who had been given a full neuroophthalmic examination, including Goldmann dynamic perimetry. The atrophic portions of the calcarine area were measured in the sagittal plane next to the midsagittal image and represented as a percentage of atrophy of the total length of the calcarine fissure. MR findings were compared with results of a visual field test. RESULTS: The visual field test revealed moderate to severe concentric constriction of the visual fields, with central vision ranging from 7 degrees to 42 degrees (mean, 19 degrees). The ventral portion of the calcarine sulcus was significantly dilated on MR images in all patients. A logarithmic correlation was found between the visual field defect and the extent of dilatation of the calcarine fissure. The central 10 degrees and 30 degrees of vision seemed to fill about 20% and 50% of the total surface area of the calcarine cortex, respectively. CONCLUSION: Visual field deficits in patients with Minamata disease correlated well with MR findings of the striate cortex. Our data were consistent with the classical Holmes retinotopic map.

Atrophy↗