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T Yoshiura

Publications and source records attributed to T Yoshiura.

At least 19 recordsLinked to original sources
PubMed2001

Highly diffusion-sensitized MRI of brain: dissociation of gray and white matter.

The brains of six healthy volunteers were scanned with a full tensor diffusion MRI technique to study the effect of a high b value on diffusion-weighted images (DWIs). The b values ranged from 500 to 5000 s/mm(2). Isotropic DWIs, trace apparent diffusion coefficient (ADC) maps, and fractional anisotropy (FA) maps were created for each b value. As the b value increased, ADC decreased in both the gray and white matter. Furthermore, ADC of the white matter became lower than that of the gray matter, and, as a result, the white matter became brighter than the gray matter in the isotropic DWIs. Quantitative analysis showed that these changes were due to nonmonoexponential diffusion signal decay of the brain tissue, which was more prominent in white matter than in gray matter. There was no significant change in relation to the b value in the FA maps. High b value appears to have a dissociating effect on gray and white matter in DWIs.

Adult↗
PubMed2001

[Clinical applications of functional magnetic resonance imaging].

Despite its immediate success as a tool for basic research, the clinical application of functional MRI(fMRI) is still limited. FMRI has proven useful for presurgical functional mapping of the eloquent cortices. Localization of the sensorimotor cortex by fMRI may be of relatively limited value because the sensorimotor cortex can often be readily localized by means of anatomical methods. In contrast, the language cortices may not be localized anatomically and the language dominant hemisphere has been determined by invasive Wada test. Previous reports have shown that fMRI can be a promising alternative to the Wada test. A recent clinical trial has suggested that fMRI can be used to diagnose Alzheimer's disease in its earliest stage, detecting subclinical deterioration of the memory function. FMRI may be useful to predict the future decline of memory in people with genetic risks. Monitoring of the functional recovery of post-stroke brains may be another promising clinical application of fMRI. FMRI has demonstrated functional reorganization of the brain that may be related to the restoration of motor and language functions.

Brain Diseases↗
PubMed2001

[Multiple focal cortical dysplasias presenting with intractable epilepsy: case report].

A 14-year-old female, who had intractable epilepsy associated with multiple focal cortical dysplasias (FCD), was reported. She developed intractable epilepsy at the age of 7 and was diagnosed as having frontal lobe epilepsy based on the seizure semiology and interictal EEG. MRI revealed multiple lesions in the right frontal, bilateral occipital and left parietal lobes. EEG demonstrated that ictal discharge was preceded by spike on the right frontal region and FDG-PET showed hypometabolic area in the right frontal lobe. Chronic subdural electrode recordings from the right frontal lobe indicated that ictal onset zone was located around the right frontal lesion, especially frontal tip and base, and these areas including the lesion were resected. Postoperatively, residual seizure was noted although seizure frequency was decreased. It is well known that, postoperatively, satisfactory seizure outcome can be obtained in patients with FCD. However, further investigation in terms of surgical indication and strategies for multiple FCD should be needed.

Adolescent↗
PubMed2001

[Clinical trial of bradykinin-enhancing chemotherapy for a recurrent malignant glioma: a case report].

Patients with malignant glioma undergo a combined treatment with surgical resection, radiotherapy, and chemotherapy. Although those treatments usually show some restraining effects on the tumor, a relapse occurs in most of the patients within a few years. We have investigated the feasibility and safety of intra-arterial chemotherapy for malignant brain tumors by enhancing vascular permeability using intra-arterial bradykinin infusion. In 2001, The Committee of Ethics in Kyushu University approved our clinical trial of the bradykinin-enhancing chemotherapy for recurrent malignant gliomas. We here report the first case of our clinical trial. A 31-year-old man, who had undergone surgical resection followed by chemotherapy and irradiation for malignant progression of the left frontal astrocytoma over a period of 2 years, had a relapse of the tumor in the bilateral frontal lobes. After obtaining informed consent, bradykinin and carboplatin were infused through a microcatheter at the left A1 portion under general anesthesia. By dose escalation of bradykinin, the enhanced lesion in the bilateral frontal lobes diminished on magnetic resonance imaging after 3 trials with 3-week intervals, regardless of new lesions outside of the treated area. No neurological or physiological complication including myelosuppression was noted. Bradykinin-enhancing chemotherapy appeared to be effective and safe for malignant glioma. Because it was able to increase drug delivery to the tumor, it was possible to reduce the size of the dose of chemotherapeutic agent, which resulted in minimum complication.

Adult↗
PubMed2000

Correlation between proton magnetic resonance spectroscopic lactate measurements and vascular reactivity in chronic occlusive cerebrovascular disease: a comparison with positron emission tomography.

The purpose of this study is to investigate the correlation between lactate levels and cerebral vascular reactivity (VR) in regions outside an area of chronic cerebral infarction. Multivoxel proton magnetic resonance spectroscopy ((1)H-MRS) and positron emission tomography (PET) were performed in 11 patients who suffered chronic cerebral infarction. Of these 11 patients, 4 were examined before and after bypass surgery. Two regions-of-interests (ROIs) were placed outside the area of chronic infarction. One ROI was placed within a control region on the contralateral side. A lactate peak area was obtained in all ROIs. An N-acetyl aspartate (NAA) peak area was obtained in the ROI within the control region. The ratio of the lactate peak area and NAA peak area (Lct/NAA) was calculated for normalization of the lactate level, and was found to be 0.13 +/- 0. 10 (range, 0 to 0.43). The VR was recorded at 13.3 +/- 20.7% (range, - 44.3 to 68.9%), utilizing PET and administering acetazolamide. A significant negative correlation was observed between the Lct/NAA ratio and VR (r = - 0.709, p < 0.0001). These results suggest that lactate levels and VR are closely related in regions outside areas of chronic cerebral infarction.

Adolescent↗
PubMed2000

Efficacy of targeted CT angiography in evaluation of intracranial internal carotid artery disease.

RATIONALE AND OBJECTIVES: This study evaluated the efficacy of targeted computed tomographic (CT) angiography in the diagnosis of intracranial internal carotid artery (ICA) disease and compared the results of routine and targeted CT angiography. MATERIALS AND METHODS: Fifty-four patients (24 male and 30 female patients aged 2 months to 87 years) were examined with CT angiography. Digital subtraction angiography (DSA) was performed in 42. CT angiograms were reconstructed with the maximum-intensity projection (MIP) algorithm. Targeted CT angiography was performed by individually reconstructing a single ICA territory. Each ICA was divided into four segments, and findings of routine MIP CT angiography, routine MIP plus targeted CT angiography, and DSA were reviewed independently by two neuroradiologists for vascular lesions involving each segment. Routine and targeted CT angiograms were also evaluated to determine how well both ICAs were visualized. RESULTS: Routine CT angiography was rated good or excellent for ICA visualization in 64% of cases, compared with 81% for targeted CT angiography (P = .0005). The overall agreement between routine CT angiography and DSA and between routine plus targeted CT angiography and DSA was 92% and 94%, respectively. There was no statistically significant difference between the percentages of vascular lesions detected with routine CT angiography alone and with routine plus targeted CT angiography. Both methods tended to show false-positive findings of steno-occlusive disease, but targeted CT angiography showed details of aneurysms and stenotic lesions that were easily overlooked with routine CT angiography alone. CONCLUSION: Routine plus targeted CT angiography, while providing superior image quality, did not have much clinical effect; further assessment may be needed.

Adolescent↗
PubMed2000

Heschl and superior temporal gyri: low signal intensity of the cortex on T2-weighted MR images of the normal brain.

PURPOSE: To study the normal signal intensity pattern in the primary auditory cortex (first Heschl gyrus [HG]) and the surrounding cortices in the superior temporal gyrus (STG) and middle temporal gyrus (MTG) on T2-weighted magnetic resonance (MR) images. MATERIALS AND METHODS: Coronal T2-weighted fast spin-echo MR images in 30 neurologically normal patients (60 hemispheres) were retrospectively analyzed. Two raters evaluated the cortical signal intensity of the first HG and the neighboring STG and compared them with those of the MTG and the subcortical white matter. The cortical signal intensities between the first HG and the STG were also directly compared. Coronal MR images, which included images of the anterior and posterior halves of the first HG, were evaluated separately. RESULTS: All first HGs were hypointense to the MTG and were either iso- or hypointense to the STG. Cortical hypointensity was especially prominent in the posterior half; the first HG was isointense to the white matter in 33 (55%) hemispheres. The STG was hypointense to the MTG in 54 (90%) hemispheres and in the anterior halves of 36 (60%) hemispheres. CONCLUSION: These findings demonstrate lower signal intensity of the cortex on T2-weighted images in the first HG and surrounding STG compared with that of the MTG.

Adolescent↗
PubMed2000

[Small epidermoid induced trigeminal neuralgia unrecognized by conventional CT and MRI for over 25 years].

A 65-year-old woman had been conservatively treated as idiopathic trigeminal neuralgia for over 25 years, because conventional computed tomography (CT) and magnetic resonance imaging(MRI) showed no abnormality in the cerebello-pontine(CP) angle cistern. She received a detailed MRI by constructive interference in steady state and diffusion weighted image(DWI) sequences. Those sequences on MRI well demonstrated a epidermoid tumor in the CP angle cistern, and the removal of the tumor completely resolved the neuralgia. Since a small epidermoid in the CP angle cistern seems to be unrecognized by conventional CT and MRI, detailed evaluation by DWI sequence, which has been widespread recently, is required for patients with trigeminal neuralgia.

Aged↗
PubMed1999

Functional MRI study of auditory and visual oddball tasks.

To seek neural sources of endogenous event-related potentials, brain activations related to rare target stimuli detection in auditory and visual oddball tasks were imaged using a high temporal resolution functional MRI technique. There were multiple modality specific and modality non-specific activations. Auditory specific activations were seen in the bilateral transverse temporal gyri and posterior superior temporal planes while visual specific activations were seen in the bilateral occipital lobes and their junctions with the temporal lobes. Modality non-specific activations were seen in multiple areas including the bilateral parietal and temporal association areas, bilateral prefrontal cortex, bilateral premotor areas, bilateral supplementary motor areas and anterior cingulate gyrus. Results were consistent with previous intracranial evoked potential recording studies, and supported the multiple generator theory of the endogenous event-related potentials.

Acoustic Stimulation↗
PubMed1999

Advanced MR techniques: diffusion MR imaging, perfusion MR imaging, and spectroscopy.

Recent technical advances in MR imaging have enabled the authors to investigate early physiological changes in acute ischemic stroke lesion. Diffusion and perfusion MR imaging can provide clinically useful information not only for early detection of ischemia, but also for prediction of tissue outcome. MR spectroscopy is a potentially powerful tool to study acute stroke, but its clinical value has been limited due to long examination time and low spatial resolution.

Brain↗
PubMed1998

Magnetic source imaging of the sensory cortex on the surface anatomy MR scanning.

Surgery for lesions either within or close to the central sulcus of the brain always carries the risk of inducing iatrogenic motor or sensory deficits. We performed advanced magnetic source imaging (MSI) of the somatosensory cortex combined with 3-dimensional (3-D) surface anatomy scanning (SAS) of magnetic resonance imaging on 9 patients who had peri-Rolandic lesions, including 7 tumor cases, 1 arteriovenous malformation and 1 focal cortical dysplasia. 3-D MSI mapped out the entire somatosensory homunculus and localized the lesion on a cortical surface image. The results were then used for developing an appropriate surgical strategy and also as a reference in the operating room. This relationship and deduced localization were both confirmed by a cortical recording of the somatosensory evoked potentials at the time of surgery. Case histories of selected patients are briefly reported to demonstrate how the method can be used to improve the safety of surgical excisions of peri-Rolandic lesions. MSI on SAS including the cortical veins, was thus found to provide a readily interpretable presurgical road map of the cortical surface which compares favorably to that of intraoperative brain mapping.

Adolescent↗
PubMed1998

Perirolandic cortex in infants: signal intensity on MR images as a landmark of the sensorimotor cortex.

PURPOSE: To correlate the perirolandic low signal intensity seen on T2-weighted magnetic resonance (MR) images in neonates and infants with the anatomically located sensorimotor cortex. MATERIALS AND METHODS: Axial T2-weighted MR images of 146 consecutive patients less than 6 months old were reviewed. The sensorimotor cortex was located by identifying the central sulcus. Two independent readers attempted to identify the central sulcus using two anatomic methods independently and in combination. The location of the central sulcus was compared with that of the perirolandic low signal intensity. RESULTS: Seventy-two normal hemispheres in 36 patients and 91 abnormal hemispheres in 47 patients showed clear perirolandic low signal intensity. The central sulcus was located anatomically in 70 and 72 normal hemispheres (97% and 100%, respectively) and 90 and 91 abnormal hemispheres (99% and 100%, respectively). In all normal hemispheres, the identified central sulcus correlated with the perirolandic low signal intensity. In contrast, an apparent mismatch was found in two hemispheres in a patient with Dandy-Walker syndrome. CONCLUSION: The perirolandic low signal intensity seen on T2-weighted MR images is located exactly in the anatomic sensorimotor cortex in normal brains, whereas a mismatch can occur in abnormal brains.

Bacterial Infections↗
PubMed1998

MR imaging of the mamillothalamic tract.

PURPOSE: To demonstrate the normal and abnormal appearance of the mamillothalamic tract (MTT) on cranial magnetic resonance (MR) images. MATERIALS AND METHODS: Two formalin-fixed normal human brain specimens sectioned in axial and coronal planes were used to demonstrate the normal anatomy of the MTT. MR images were obtained in 32 volunteers. Proton-density-weighted coronal and axial pulse sequences were used. The images were evaluated for visualization quality and size and signal intensity of the MTTs in correlation with the specimens. Abnormal MTTs were identified on cranial MR images in two patients, and the imaging findings were analyzed. The clinical history of the patients was also reviewed to determine the effect of these findings on patient care. RESULTS: Normal MTTs were easily identified on MR studies of cadaveric brains and of the brains of the human volunteers. On MR images, normal MTTs were commonly symmetric in appearance, with signal intensity equal to that of other normal fiber tracts. The abnormal MTTs showed high signal intensity on images obtained with a long repetition time or asymmetric volume loss and were associated with atrophy of the ipsilateral mamillary body. CONCLUSION: Normal MTTs are readily visible on conventional MR images. Abnormality of the MTT is a very subtle finding but may be a marker of a limbic system abnormality.

Adult↗
PubMed1997

Increased activity of the ipsilateral motor cortex during a hand motor task in patients with brain tumor and paresis.

PURPOSE: To look for changes in the motor cortex in patients with brain tumors. METHODS: Both cerebral hemispheres in seven patients with brain tumors were examined with functional MR imaging during a motor task performed by the hand opposite the site of tumor. The ratio of the activated area in the motor cortex ipsilateral/contralateral to the tested hand was calculated for each subject. Twenty healthy subjects were also examined in the same manner for comparison. RESULTS: The ratio of the ipsilateral/contralateral activated area was abnormally high in three patients with tumor-related paresis of the tested hand. The ratio was significantly greater in patients with paresis than in healthy subjects. CONCLUSION: This study demonstrated increased activity in the ipsilateral (unaffected) motor area during a hand motor task in patients with brain tumor and paresis, which was thought to reflect compensatory reorganization induced by the functional damage.

Adult↗
PubMed1996

Human middle latency auditory evoked magnetic fields.

The magnetic equivalents of SN10, Po, Na, Pa, Nb and Pb (SN10m, Pom, Nam, Pam, Nbm, and Pbm) in short and middle latency auditory evoked potentials were measured with a 7-channel DC superconducting quantum interference device (SQUID). The sources of Pom, Nam, Pam, Nbm and Pbm responses were estimated to be located in the auditory cortex, while the source of SN10m was considered to be in a deeper part of the brain. In addition, the source of Pam was estimated to be in the vicinity of the moving N100m source. The source of Pbm was considered to be in a separate area, anterior to the source of Pam and N100m, which suggested that source of Pam was located in the primary auditory cortex, while the source of Pbm was located in the secondary auditory cortex. The source of N100m was considered to spread from the primary auditory cortex to the secondary auditory cortex.

Adult↗
PubMed1996

Contrast-enhanced MRI in spinal arteriovenous malformations and fistulae before and after embolisation therapy.

MRI was performed in six cases of spinal arteriovenous malformation (AVM) and arteriovenous fistula (AVF) before and after embolisation. Intramedullary and perimedullary AVMs showed marked vascular enhancement after embolisation. This was thought to reflect feeding vessel occlusion and correlated well with a favourable clinical outcome. In dural AVFs, contrast-enhanced studies were essential for the diagnosis, unenhanced images being nonspecific. After embolisation, enhancement of the spinal cord was reduced, although one case with a poor outcome showed persistent enhancement.

Adult↗