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Biomedical subjects

T Okudera

Publications and source records attributed to T Okudera.

At least 37 records · Page 2Linked to original sources
PubMed1997

MRI of acute cerebral infarction: a comparison of FLAIR and T2-weighted fast spin-echo imaging.

Fluid-attenuated inversion-recovery (FLAIR) sequences have been reported to provide high sensitivity to a wide range of central nervous system diseases. To our knowledge, however, FLAIR sequences have not been used to study patients with acute cerebral infarcts. We evaluated the usefulness of FLAIR sequences in this context. FLAIR sequences were acquired on a 0.5 T superconducting unit within 8 h of the onset in 19 patients (aged 26-80 years) with a total of 23 ischaemic lesions. The images were reviewed retrospectively by three neuroradiologists, and the FLAIR images were compared with T2-weighted fast spin-echo images. All but one of the ischaemic lesions involving grey matter was clearly demonstrated on FLAIR images as increased signal intensity in cortical or central grey matter. FLAIR images were particularly useful for detecting the hyperacute cortical infarcts within 3 h of onset, which were not readily detected on the spin-echo images. In 9 of 11 patients with complete proximal occlusion, the distal portion of the cerebral artery was visible as an area of high signal intensity on FLAIR images.

Acute Disease↗
PubMed1997

Filling defect sign in CT diagnosis of ruptured aneurysm.

We have encountered a ruptured aneurysm as a filling defect in cisternal blood on CT in patients with acute subarachnoid haemorrhage (SAH), as high-attenuation blood can act as a contrast medium. We term this finding the "filling defect sign". To evaluate the usefulness of the sign in the diagnosis of a ruptured aneurysm, we retrospectively analysed CT with 10-mm-thick slices obtained within 2 days of onset of SAH in 100 consecutive patients. The sign was observed in 30 of the 100 patients, and in 13 (68%) of 19 patients with a ruptured aneurysm more than 10 mm in diameter. The filling defect sign is useful in predicting the site of rupture.

Acute Disease↗
PubMed1997

Subacute and chronic subarachnoid hemorrhage: diagnosis with fluid-attenuated inversion-recovery MR imaging.

PURPOSE: To evaluate fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) imaging in the detection of subacute and chronic subarachnoid hemorrhage. MATERIALS AND METHODS: The authors performed 19 FLAIR MR imaging examinations at 0.5 T in 14 adult patients with subarachnoid hemorrhage 3-45 days after the ictus and 22 FLAIR examinations in 22 adult control subjects. The detection of subacute and chronic subarachnoid hemorrhage on FLAIR images was compared with the detection on conventional spin-echo MR and computed tomographic (CT) images. RESULTS: In the detection of subacute subarachnoid hemorrhage, FLAIR (100% detection) was significantly superior to T1-weighted imaging (36% detection, P < .01), T2-weighted imaging (0% detection, P < .02), and CT (45% detection, P < .02 [Fisher exact test]). Although FLAIR imaging (63% detection) was superior in chronic subarachnoid hemorrhage detection, there were no statistically significant differences between modalities. FLAIR imaging demonstrated all subarachnoid hemorrhage areas as high-signal-intensity areas within 18 days and up to a maximum of 45 days after the ictus. In a blind comparison, no FLAIR images acquired in control subjects were confused with those acquired in patients. CONCLUSION: FLAIR diagnostic images are superior to conventional MR or CT images in patients with subacute subarachnoid hemorrhage.

Acute Disease↗
PubMed1997

Secondary thalamic degeneration after cerebral infarction in the middle cerebral artery distribution: evaluation with MR imaging.

PURPOSE: To evaluate secondary degeneration of the ipsilateral thalamus after cerebral infarction in the middle cerebral artery (MCA) distribution by using magnetic resonance (MR) imaging. MATERIALS AND METHODS: Thirty patients (17 men, 13 women; aged 30-85 years) with embolic cerebral infarction in the MCA distribution underwent serial MR imaging 2 hours to 12 months after a stroke. In 23 of the 30 patients, the authors evaluated cerebral blood flow with single photon emission computed tomography (SPECT). RESULTS: T2-weighted spin-echo images disclosed a hyperintense area in the ipsilateral thalamus in 14 patients (47%) 1-12 months after stroke. The hyperintense area was confined to the dorsomedial or anterior and dorsomedial nuclei of the thalamus in nine of the 14 patients; it extended from the dorsomedial or anterior and dorsomedial nuclei to the ventral lateral nucleus or pulvinar in the remaining five patients. Hypoperfusion of the ipsilateral thalamus was observed in 21 of the 23 patients who underwent SPECT. Twelve of the 21 patients also showed a hyperintense area in the ipsilateral thalamus on the MR images. CONCLUSION: MR imaging is useful in evaluating secondary thalamic degeneration after cerebral infarction. In clinical practice, this secondary degeneration should not be mistaken for other lesions such as further cerebral infarction.

Adult↗
PubMed1997

Degeneration of the ipsilateral substantia nigra after striatal infarction: evaluation with MR imaging.

PURPOSE: To evaluate the degeneration of the ipsilateral substantia nigra after striatal infarction by using magnetic resonance (MR) imaging. MATERIALS AND METHODS: Twenty-five adult patients with embolic cerebral infarction of the middle cerebral artery distribution underwent MR imaging 0-4, 5-9, 12-15, and 27-29 days after the stroke. Sixteen of them also underwent follow-up MR imaging 2-12 months after the stroke. RESULTS: Ten patients had an infarct in the striatum with or without a cortical infarct (striatal infarction group); the other 15 patients had an infarct in the cerebral cortex of the middle cerebral artery distribution without a striatal infarct (cortical infarction group). In all 10 patients with striatal infarction, a hyperintense spot appeared in the ipsilateral substantia nigra on T2-weighted fast spin-echo images 7-12 days after the onset. This area became less intense and smaller 3 months later. In the cortical infarction group, no hyperintense spot in the ipsilateral substantia nigra was observed at any time. CONCLUSION: Degeneration of the substantia nigra ipsilateral to the striatal infarction was clearly demonstrated at MR imaging. This finding should not be mistaken for further cerebral infarction.

Aged↗
PubMed1997

Subcortical hypoperfusion associated with asymptomatic white matter lesions on magnetic resonance imaging.

BACKGROUND AND PURPOSE: We examined whether hemodynamic and metabolic abnormalities in the cerebral white matter, basal ganglia, and thalamus are associated with asymptomatic white matter lesions (WML) depicted on MR images. METHODS: A positron emission tomographic study with H2(15)O, C15O, and 15O2 was performed in eight normal control subjects without any WML (mean +/- 1 SD age, 68.5 +/- 10.2 years) and in 15 asymptomatic subjects with WML (71.3 +/- 8.5 years) to measure regional cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and oxygen metabolic rate. RESULTS: In the cerebral white matter in the asymptomatic subjects with WML, significantly lower CBF (20.3 +/- 3.9 mL/100 mL per minute; P < .05) and significantly higher OEF (0.43 +/- 0.08; P < .05) were found compared with those for control subjects (23.5 +/- 2.6 mL/100 mL per minute and 0.37 +/- 0.06, respectively). The severity of WML was not related to the magnitude of hypoperfusion. In the basal ganglia, significantly lower CBF (44.9 +/- 6.9 mL/100 mL per minute; P < .01) and significantly higher OEF (0.54 +/- 0.08; P < .01) were found in the WML group than in control subjects (70.1 +/- 12.0 mL/100 mL/min and 0.39 +/- 0.03, respectively). In the thalamus, there was no significant difference in CBF and OEF between the control and WML groups. CONCLUSIONS: Hypoperfusion of the cerebral white matter and basal ganglia in asymptomatic WML subjects may be induced by the arteriosclerosis of long penetrating medullary arteries and lenticulostriate arteries but may not be directly related to the production of WML. The role of hypoperfusion in the production of WML and acceleration of its development remains to be elucidated.

Aged↗
PubMed1997

Arterial supply to the hippocampal formation.

Arterial supply of hippocampal formation in humans has been studied by many investigators in the past. More recently, investigation of correlation of complex partial seizure with mesial temporal sclerosis has brought a resurgence of interest in studying the hippocampus. This article discusses arterial architecture of the hippocampal formation.

Angiography↗
PubMed1997

Venous architecture of cerebral hemispheric white matter and comments on pathogenesis of medullary venous and other cerebral vascular malformations.

The parenchymal veins, especially the deep medullary veins, of the cerebral hemispheres were studied in detail by analyzing the stereoroentgenograms of multiple brain slices of postmortem injected brain specimens (injected into the internal carotid arteries in 17 cases and into the jugular veins in 12 cases). The presence of four zones--the first (or outer), the second (or candelabra), the third (or palmate) and the fourth (or subependymal) zone--of venous convergence was confirmed within the centrum semiovale, particularly in the frontoparietal area. Other venous convergences such as those related to the optic radiation in the para-atrial area were also found. Arterial branching zones were also observed in the areas similar to those of the medullary veins. It appears that these converging zones are created by rapidly growing crossing nerve fiber tracts, i.e., projection, commissural, and association fibers which grow rapidly during intrauterine and postnatal life. Pathogenesis of medullary venous malformation is also discussed from anatomical viewpoint, venoarchitecture of the pial, parenchymal, and subependymal veins and of the dural venous sinuses. The possibility of a similar mechanism (partial, mild, repetitive venoocclusive disease developing over a long period with fluctuating venous pressure) leading to formation of most (if not all) cases of medullary venous malformation and in some, if not many, cases of cerebral vascular malformations [aside from gene abnormality (chromosome 7) in familial cavernous angiomatosis, particularly in Hispanic American or other familial hereditary conditions] has been postulated.

Cerebral Cortex↗
PubMed1997

[Radiological anatomy of the vein of Labbé].

The development and radiology of the vein of Labbé (VL) were investigated using the brains of 19 aborted human fetuses and 6 normal adults injected at autopsy with radiopaque material through the venous system. Carotid angiograms taken in stereoscopic pairs (110 cases, 167 hemispheres) were also analyzed in detail. Developmental alterations of the cerebral structures, particularly those of the opercula and cerebral sulci, are reflected in our classification of the pial veins of the lateral cerebral convexity into the superior, middle and inferior groups. The anastomotic veins of Trolard and Labbé were already recognizable at the fetal age of 6 to 7 months, as development of the opercula and resultant depression of the insula became advanced. In our series, superficial draining veins opening into the VL were 14 to 20 mm (average 16.8 mm) in length. Anastomoses among the superior, middle and inferior groups were analyzed angiographically: single anastomosis was found in 23 percent of cases, while double and triple anastomoses were found in 32 and 45 percent, respectively. A majority of the veins at the sites of anastomosis were found to have calibers of less than 1 mm. The VL, therefore, should be considered in most cases as an independent major superficial draining venous channel of the cerebral convexity with insignificant connections with the superior and middle groups.

Adult↗
PubMed1996

Anatomic study of anterior frontal cortical bridging veins with special reference to the frontopolar vein.

Anatomic variations of the frontopolar vein were investigated in 21 cadaver brains to improve the preservation rate of this vein in interhemispheric surgery for anterior communicating aneurysms. Most of the frontopolar vein has been considered to drain the outer convex side of the frontal lobe, but in reality, the area of its venous drainage was found to cover a large part of the frontal lobe, including its medial and basal surfaces. This observation suggests that sacrifice of the vein during surgery carries a risk of venous infarction. Therefore, care must be taken to not injure the vein during surgery. The mean distance between the frontopolar vein and the most anterior point of the frontal lobe was 31.1 mm. Although the vein became smaller close to the frontal tip, the mean diameter of the vein was 1.9 mm. Morphologically, approximately two-thirds of the frontopolar veins was found to have a "main trunk." The frontopolar vein can be spared during surgery by using a flexible surgical technique incorporating vein dissection or additional craniotomy.

Aged↗
PubMed1996

Subarachnoid hemorrhage caused by previously diagnosed, previously unruptured intracranial aneurysms: a retrospective analysis of 25 cases.

OBJECTIVE: We conducted a retrospective analysis of the clinical features of angiographically diagnosed unruptured intracranial aneurysms that were treated conservatively and subsequently ruptured. METHODS: At our center, we reviewed the angiographic and clinical features of 25 patients with subarachnoid hemorrhage caused by previously unruptured aneurysms. RESULTS: Eleven of the 25 patients died, including 1 patient who had undergone surgery. Ten patients had single aneurysms, and 15 had multiple aneurysms. Thus, multiple aneurysms were significantly more common than single aneurysms. The associated disease was cerebral infarction in 12 patients, previous subarachnoid hemorrhage from different aneurysm in 8 patients, intracerebral hemorrhage in 3 patients, and other conditions in 2 patients. Aneurysm size was able to be evaluated after rupture in 20 patients. At initial diagnosis, 16 aneurysms measured less than 5 mm in maximum diameter; the size of most aneurysms had increased by the time of rupture, although the aneurysm size remained less than 5 mm in five patients. No relationship was found between aneurysm rupture and patient age, aneurysm size at initial diagnosis, or time interval from diagnosis to rupture. The incidence of aneurysm rupture in patients with cerebrovascular disease, although higher than the incidence in patients with other underlying disease, was not significant. CONCLUSION: We conclude that small unruptured intracranial aneurysms measuring less than 5 mm are susceptible to the risk of rupture, so that radical treatment or careful follow-up examination should be considered.

Adult↗
PubMed1996

[Positron emission tomographic evaluation for frontal hypertrophic cranial pachymeningitis using 11C-methyl-L-methionine].

A case of frontal hypertrophic cranial pachymeningitis was presented with positron emission tomography (PET) using (11C-methyl)-L-methionine (11C-Met). A 55-year-old male developed right hemiparesis after generalized tonic convulsion one month prior to admission. MR images revealed patchy enhancement extending from the dura mater to the cerebral parenchyma surrounding high T2-weighted signal in the left frontal region. Left carotid angiogram showed atresia of the rostral superior sagittal sinus and obliteration of the cortical veins associated with compensatory venous channels coursing in the frontal deep white matter. PET demonstrated high 11C-Met uptake in the area corresponding to the enhancing lesion on the MR images. The ratio of lesion/normal cortex was 1.58 as an indicator of selective uptake in the lesion. The contralateral temporal gray matter was representative of a normal cortex. In contrast, 11C-Met did not accumulate in the frontal white matter where T2-weighted MR images showed abnormal high intensity lesion. This suggested that the frontal white matter lesion was derived from vasogenic edema due to venous infarction. The patient underwent an uneventful exploratory biopsy. The dura mater had proliferated to a thickness of 3.5mm and was tightly adherent to the left middle frontal gyrus. Microscopically, the thickened dura mater where the tracers had accumulated was composed of abundant collagenous fibers together with diffuse infiltration of inflammatory cells, including predominantly lymphocytes, plasma cells, and neutrocytes. The lymphocytes, which proved positive in both UCHL-1 and L26 staining, had no atypism. Histological findings corresponded to hypertrophic pachymeningitis. Met-PET clearly represented viable and infiltrative zones of inflammatory cells. The patient's neurological symptoms and signs gradually improved. Follow-up MR images three months after the surgery showed the enhancing lesion to be diminished and a marked regression of the vasogenic edema. Spatial determination of viable lesions permitting differentiation from biological inactive or vasogenic edema is an important guideline in selecting an appropriate surgical procedure in the diagnosis and treatment of hypertrophic cranial pachymeningitis. Met-PET would appear useful in delineating inflammatory lesions such as hypertrophic cranial pachymeningitis.

Carbon Radioisotopes↗
PubMed1996

Cerebral aneurysms: evaluation with three-dimensional CT angiography.

PURPOSE: To evaluate the usefulness of three-dimensional CT angiography (CTA), in which contrast material is used to create reformations of dynamic scans, in the diagnosis and the preoperative evaluation of cerebral aneurysms. METHODS: We used 3-D CTA to examine 65 patients with suspected or angiographically verified cerebral aneurysms. A blind study was performed to evaluate the diagnostic accuracy of 3-D CTA for cerebral aneurysms with the use of conventional angiography as the reference standard. RESULTS: In 50 patients, conventional angiography revealed 73 cerebral aneurysms ranging from 2 to 32 mm in maximum diameter. Three of the 73 cerebral aneurysms were located outside the imaging volume of 3-D CTA. The sensitivities of the two neuroradiologists for the remaining 70 aneurysms were 67% and 70%, respectively. Although 3-D CTA depicted cerebral aneurysms 5 mm or larger with good accuracy, it was less useful for the detection of smaller aneurysms. For the evaluation of giant aneurysms, this technique elucidated the relationships among the aneurysm, surrounding arteries, and neighboring bone structure. CONCLUSION: Three-dimensional CTA is useful for the diagnosis of cerebral aneurysms with diameters of 5 mm or more. This technique is especially useful in the preoperative evaluation of giant aneurysms.

Adult↗
PubMed1996

Regional cerebral blood flow response in gray matter heterotopia during finger tapping: an activation study with positron emission tomography.

We examined regional cerebral blood flow response in a patient with gray matter heterotopia located beneath the sensorimotor cortex during a finger tapping task. We found regional cerebral blood flow was specifically increased during contralateral finger tapping. This indicated the possibility of functional differentiation of the ectopic neurons despite incomplete migration.

Adult↗
PubMed1995

Regional cerebral blood flow, blood volume, oxygen extraction fraction, and oxygen utilization rate in normal volunteers measured by the autoradiographic technique and the single breath inhalation method.

By means of a high resolution PET scanner, the regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), and metabolic rate of oxygen (rCMRO2) for major cerebral gyri and deep brain structures were studied in eleven normal volunteers during an eye-covered and ear-unplugged resting condition. Regional CBF was measured by the autoradiographic method after intravenous administration of H2(15)O. Regional OEF and rCMRO2 were measured by the single inhalation of 15O2. With MR T1-weighted images as an anatomical reference, thirteen major cerebral gyri, caudate nucleus, lentiform nucleus, thalamus, midbrain, pons, cerebellum and vermis were defined on the CMRO2 images. Values were read by using circular regions of interest 16 mm in diameter. The posterior part of the cingulate gyri had the highest rCBF and rCMRO2 values among brain structures, followed by the lentiform nucleus, the cerebellum, the caudate nucleus, and the thalamus. Parahippocampal gyri had the lowest rCBF and rCMRO2 values among the cortical gyri. Regional OEF for the pontine nuclei (0.34 +/- 0.04), the midbrain (0.35 +/- 0.05), the parahippocampal gyri (0.35 +/- 0.04 for the right and 0.37 +/- 0.05 for the left), and the thalami (0.37 +/- 0.05 for the right and 0.36 +/- 0.04 for the left) were significantly lower than the mean OEF for the cerebral cortices (0.42 +/- 0.04) (p < 0.05 or less). The global CBF and CMRO2 were consistent with those obtained by the Kety-Schmidt method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Acute subarachnoid hemorrhage: MR imaging with fluid-attenuated inversion recovery pulse sequences.

PURPOSE: To evaluate the usefulness of fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging sequences in the detection of acute subarachnoid hemorrhage (SAH). MATERIALS AND METHODS: MR imaging with FLAIR sequences was performed with a 0.5-T superconducting unit in 20 patients (aged 30-72 years) with acute SAH due to a ruptured aneurysm and in 27 control subjects (aged 32-72 years). FLAIR images were obtained 2 hours to 2 days after ictus. Findings were evaluated and compared with computed tomographic (CT) findings. RESULTS: In all patients, acute SAH was clearly demonstrated as an area with signal intensity that was high relative to that of the normal cerebrospinal fluid and surrounding brain parenchyma at FLAIR imaging. This sequence was especially useful in demonstration of acute SAH in the posterior fossa, which was difficult to show at CT because of beam-hardening artifacts. In a double-blind comparison, no FLAIR images acquired in control subjects were confused with those acquired in control subjects were confused with those acquired in patients. CONCLUSION: FLAIR sequences reliably provide diagnostic images in patients with acute SAH.

Acute Disease↗