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T Nitatori

Publications and source records attributed to T Nitatori.

At least 19 recordsLinked to original sources
PubMed2006

Visualization of cervical nerve roots and their distal nerve fibers by diffusion-weighted scanning using parallel imaging.

PURPOSE: To report a technique developed for visualizing cervical nerve roots and distal nerve fibers using diffusion-weighted magnetic resonance imaging employing parallel imaging. MATERIAL AND METHODS: We performed maximum intensity projection for a stack of isotropic axial diffusion-weighted images obtained with parallel imaging applying a motion-probing gradient in six directions with a b-value of 500 s/mm2 in a preliminary series of 13 subjects. RESULTS: This method worked well for visualizing the spinal cord and most of the nerve roots, the dorsal root ganglia, and proximal peripheral nerves. CONCLUSION: Although the technique remains limited in depicting the brachial plexus and distal nerves, the ability to visualize the proximal peripheral nervous system at the cervical level is promising.

Adult↗
PubMed2000

Quantitative evaluation of coronary stenosis by coronary magnetic resonance angiography.

Coronary magnetic resonance angiography (coronary MRA) can detect, noninvasively, a high proportion of severe stenotic lesions found on coronary angiograms. However, quantitative evaluation of coronary artery stenosis by coronary MRA has been performed only in a small number of patients. This study was designed to determine whether coronary MRA can assess the degree of stenosis using the two-dimensional segmented turbo-FLASH method (2D method). We studied 108 patients with technically adequate coronary MRA images. The blood flow signal intensity on coronary MRA was classified as markedly decreased, moderately decreased, or normal. The severity of coronary artery stenosis was determined by the caliper method, and coronary stenosis was rated using a seven-point scale (0%, 25%, 50%, 75%, 90%, 99%, and 100%) in accordance with the American Heart Association classification system. Patients were classified into three groups: normal coronary artery (0%-25% stenosis), moderate stenosis (50%-75% stenosis), and severe stenosis (90%-100% stenosis). The degree of stenosis on coronary angiography and the decrease in coronary MRA signal intensity were compared. The right coronary artery was evaluated in 64 patients and the left coronary artery in 73 patients. When a marked or moderate decrease in coronary MRA blood flow signal intensity was defined as indicating stenosis, the sensitivity and specificity of coronary MRA for detecting angiographically severe stenosis were 85% and 80%, respectively. A moderate decrease in coronary MRA blood flow signal intensity detected angiographically moderate stenoses with a sensitivity of 38% and a specificity of 83%. Coronary MRA can detect a high proportion of severe stenoses but only a low proportion of moderate stenoses. Technical improvements are required before coronary MRA can be used clinically.

Adult↗
PubMed2000

Reduction of heparin dose is not beneficial to platelet function.

BACKGROUND: To clarify the effects of the reduction of heparin dose on platelets, we conducted a prospective trial on patients undergoing cardiopulmonary bypass. METHODS: Twenty-three patients undergoing coronary artery bypass grafting were studied. The systemic heparin dose was 300 IU/kg in the control group (n = 11) and 200 IU/kg in the low-dose group (n = 12). Heparin-coated cardiopulmonary bypass equipment was used for both the groups. Platelet counts, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) concentrations were measured and the arterial filters in the circuits were observed by electron microscopy. RESULTS: Platelet counts were higher in the low-dose group than in the control group (p < 0.01). No significant differences were found in the platelet release reaction (beta-TG and PF4). Electron microscopy demonstrated that cell adhesion on the arterial filters in the control group was significantly more marked than in the low-dose group (p < 0.01) and that most of the cells on the filters were neutrophils. CONCLUSIONS: We conclude that the reduction of heparin dose with the use of heparin-coated equipment reduces platelet loss, but does not suppress the platelet release reaction. Furthermore, the reduction of heparin dose reduces adherence of leukocytes to the filter surface.

Anticoagulants↗
PubMed1999

Exogenous microglia enter the brain and migrate into ischaemic hippocampal lesions.

We compared migration of systemically injected microglia into normal brain vs. ischaemic brain using a model of ischaemic hippocampal lesion. Microglia were labeled by a fluorescent dye using our standard phagocytosis procedure of microscopic particles and then injected intra-arterially into Mongolian gerbils subjected to ischaemia reperfusion neuronal injury. Delayed death of pyramidal neurons was confirmed by conventional histological analysis and dUTP nick end labeling (TUNEL) method. Clusters of dye-tagged cells migrating into the hippocampal ischaemic lesions were confirmed histochemically to be microglia. Since peripherally injected microglia exhibit specific affinity for ischaemic brain lesions and does not exacerbate ischaemic neuronal injury in the present model, we suggest that microglia may have a potential to be used as a piggy-back ride to deliver therapeutic genes and/or drugs for CNS repair following transitory global ischaemic insult.

Animals↗
PubMed1999

Coronary MR angiography-a clinical experience in Japan.

Magnetic resonance angiography (MRA) has been expected to provide a useful noninvasive means of assessing coronary artery disease as this disease continues to increase due to westernization of life style. Several Japanese investigators have assessed the diagnostic value of two-dimensional (2D) and 3D coronary MRA in clinical patients evaluated for ischemic heart disease. Almost all reports indicate a high correlation between findings on 2D MRA and findings on conventional coronary angiography (CAG) in patients with severe stenosis of proximal arteries. However, in our study involving 153 patients with ischemic heart disease, 2D MRA tended to underestimate lesions in patients with moderate stenotic lesions. Furthermore, this method could not be applied successfully in approximately 15% of our patients due to difficulty with breath-holding. These findings indicate some of the limitations associated with breath-holding in the 2D method. Recently, several reports have described high diagnostic accuracy using respiratory-gated 3D MRA with navigator echo. Effective use of a suitable contrast agent with better spatial and time resolution and better image reconstruction methods will enable 3D MRA to serve a useful role, even in screening for coronary artery disease. J. Magn. Reson. Imaging 1999;10:709-712.

Coronary Disease↗
PubMed1999

Hippocampal neuronal death following deep hypothermic circulatory arrest in dogs: involvement of apoptosis.

This study was undertaken to evaluate the histological nature of brain damage caused by deep hypothermic circulatory arrest during cardiopulmonary bypass. Total body cooling to 15 degrees C and rewarming were performed with a conventional cardiopulmonary bypass technique using the femoral artery and vein. Dogs were assigned to one of three groups. In group 1 (n = 4), cardiopulmonary bypass was maintained in a state of deep hypothermia (15 degrees C) for 90 min, group 2 animals (n = 5) underwent 60 min of deep hypothermic circulatory arrest at 15 degrees C, and group 3 (n = 6) underwent 90 min of deep hypothermic circulatory arrest at 15 degrees C. All dogs were killed by perfusion fixation 72 h after cardiopulmonary bypass. The CA1 regions of the hippocampi were examined by light and electron microscopy. Biotinylated dUTP was used for nick-end labeling of apoptotic cells mediated by terminal deoxytransferase. No morphological change was observed in group 1 dogs, and very little in group 2 dogs. More severe neuronal damage was observed in group 3. The nuclei of many cells were shrunken and showed nick-end labeling. Dense chromatin masses were detected electron microscopically in the nuclei of CA1 pyramidal cells. Neuronal cell death observed in CA1 pyramidal cells 72 h after 90 min of deep hypothermic circulatory arrest at 15 degrees C involves apoptosis. Therefore, according to this model, the maximum duration of deep hypothermic circulatory arrest should not be allowed to exceed 60 min.

Animals↗
PubMed1998

Diffusion-weighted MR imaging with a single-shot echoplanar sequence: detection and characterization of focal hepatic lesions.

OBJECTIVE: The purpose of this study was to determine the usefulness of diffusion-weighted MR imaging with single-shot echoplanar imaging in characterizing focal hepatic lesions by apparent diffusion coefficient (ADC) and contrast-to-noise ratio (CNR) measurements. MATERIALS AND METHODS: Diffusion-weighted imaging on a 1.5-T MR unit was performed in 46 patients with 74 known focal hepatic lesions (11 hemangiomas, 15 metastases, and 48 hepatocellular carcinomas [HCCs]). Mean values for ADCs and CNRs of all lesions were calculated. Mean values for CNRs with diffusion-weighted imaging were also compared with those for breath-hold T2-weighted fast spin-echo images. RESULTS: The mean values for ADCs were different for each type of tumor (5.39 x 10(-3) mm2/sec +/- 1.23 in hemangiomas, 2.85 x 10(-3) mm2/sec +/- 0.59 in metastases, and 3.84 x 10(-3) mm2/sec +/- 0.92 in HCCs), and each of them was significantly greater than the mean values for ADCs of the normal liver (2.28 x 10(-3) mm2/sec +/- 1.23 in normal liver [p < .05] except metastasis versus normal liver [p < .1]). Also, the mean values for ADCs were based on differences of ADC values. Only four (6%) of 63 malignant tumors (three HCCs and one metastasis) could not be differentiated from hemangiomas. The mean value for CNRs with diffusion-weighted images (14.4 +/- 8.54 in HCC and 29.0 +/- 6.79 in metastasis) was significantly higher than the mean values for CNRs obtained with T2-weighted fast spin-echo images in both metastases and HCCs (p < .05), whereas no significant difference was seen for hemangiomas. CONCLUSION: Mean values for ADCs differed for the three types of the hepatic lesions and were higher than ADCs of the normal liver. We suggest that diffusion-weighted imaging may be useful for increased detection of HCCs and metastases and in distinguishing these entities from hemangiomas.

Carcinoma, Hepatocellular↗
PubMed1998

Characterization of hepatic lesions by perfusion-weighted MR imaging with an echoplanar sequence.

OBJECTIVE: The purpose of this study was to examine the usefulness of perfusion-weighted MR imaging with a single-shot gradient echoplanar sequence in characterizing hepatic tumors. SUBJECTS AND METHODS: Perfusion-weighted imaging was performed in 61 patients with 91 confirmed hepatic tumors (14 hemangiomas, 19 metastases, and 58 hepatocellular carcinomas). The perfusion-weighted imaging was started at the time of administration of 0.1 mmol/kg of gadolinium, and images were continuously obtained every 2 sec for 88 sec. Time-intensity curves for all the tumors were created for quantitative analysis. Patterns of enhancement were also evaluated. RESULTS: Changes in signal intensity that occurred throughout examination differed in three types of tumor. Transient signal intensity decreases in the perfusion phase significantly differed in three types of tumors (46% in hepatocellular carcinoma, 48% in hemangioma, and 15% in metastasis, p < .05 for hepatocellular carcinoma versus metastasis and for hemangioma versus metastasis). Signal intensity recovered rapidly for hepatocellular carcinoma and metastasis, whereas recovery was slower for hemangioma. Final signal intensity recovery was 94% in hepatocellular carcinoma, 91% in metastasis, and 54% in hemangioma compared with their initial signal intensities. (p < .05 for hepatocellular carcinoma versus hemangioma and for hemangioma versus metastasis.) The enhancement patterns also differed in three types of tumor. CONCLUSION: Perfusion-weighted imaging with a gradient echoplanar sequence provides real-time mapping of many points along the enhancement profile curves because of its excellent temporal resolution. Therefore, it accurately characterizes hepatic tumors based on their different negative-enhancement patterns.

Adult↗
PubMed1998

[Breath-hold MR cholangiopancreatography with 2D and 3D-FASE sequence at 0.5 tesla: evaluation based on measurements of signal intensity ratio and contrast-to-noise ratio].

Single-slice 2D-FASE (more than 2 cm) and 3D-FASE images proved to be reliable techniques by which to create high-resolution MRCP images at 0.5 T. In particular, 3D-FASE sequence can provided MIP and its thin source images with sufficient SIR and CNR of the images, which are useful to evaluate detailed structures. Using 3D-FASE sequence, even the non-dilated pancreatobiliary system can frequently be demonstrated because each source image retains satisfactory SIR and CNR of the images due to 3D acquisition and is not affected by motion artifacts of any kind. The most important problem for 3D-FASE sequence is that view-to view amplitude modulation errors may persist, though gradient moment errors can be reduced because of no actual motion during acquisition, resulting in degraded the MIP images due to the different positions of the source images in a few patients with inconstant respiration.

Biliary Tract↗
PubMed1997

Directed proximal magnetic resonance coronary angiography compared with conventional contrast coronary angiography.

Magnetic resonance coronary angiography in 36 patients with proximal 1-vessel disease within 1 week of contrast coronary angiography was performed and the time required to complete the study was 13.4 +/- 4.2 min 13.2 +/- 8.1 minutes for the right and left coronary arteries, respectively. The sensitivity, specificity, positive and negative predictive values, and accuracy of magnetic resonance coronary angiography were 100% for right cronary artery disease, and 83%, 98%, 94%, 94%, and 94%, respectively, for left coronary artery disease.

Aged↗
PubMed1997

Pancreatic ductal adenocarcinoma: preoperative assessment with helical CT versus dynamic MR imaging.

PURPOSE: To compare helical computed tomography (CT) and dynamic, magnetic resonance (MR) imaging in the evaluation of pancreatic ductal adenocarcinoma. MATERIALS AND METHODS: Dynamic MR images obtained with breath holding, 256 phase- and 512 frequency-encoding steps, 5-mm section thickness, phased-array multicoil, and double-dose gadolinium were available from 21 patients. Dynamic MR images were retrospectively compared with helical CT images in the evaluation of tumor detection, local tumor extension, and vascular involvement. RESULTS: Tumors were detected on dynamic MR images of 19 of 21 (90%) patients and on helical CT scans of 16 (76%) patients. Dynamic MR imaging had equal or better sensitivity, accuracy, and agreement of tumor grade than did helical CT in the comparison of imaging findings and histopathologic findings. Dynamic MR imaging also had equal or better specificity than had helical CT in determination of local tumor extension and vascular involvement, except in the factors of duodenal invasion and portal venous system involvement. However, there was no statistically significant difference among any of these measurements. CONCLUSION: Dynamic MR imaging may be better than helical CT in the preoperative detection and evaluation of local tumor extension and of vascular involvement of pancreatic ductal adenocarcinomas.

Adult↗
PubMed1997

Immunocytochemical localization of lysosomal cysteine and aspartic proteinases, and ubiquitin in rat epidermis.

To analyze the degradation system in epidermal cells during their generation, differentiation, and cell death, immunocytochemical localization of lysosomal cysteine and aspartic proteinases, an endogenous cysteine proteinase inhibitor, cystatin beta, and ubiquitin were examined using rat sole skin. By confocal laser microscopy, granular immunodeposits for lysosomal proteinases were well demonstrated in epidermal cells; immunoreactivity for cathepsins B and C was prominent in the lower spinous and basal layers, while that for cathepsins L and D was intense in the upper spinous and granular layers, although immunoreactivity for cathepsin D was also detected in the lower epidermal layers. Immunoreactivity for cathepsin H was weakly detected only in the spinous layer, where there were some intensely immunopositive cells with processes which were also immunopositive for S-100 alpha, indicating that these cells were Langerhans cells. Diffuse immunoreactivity for cystatin beta was intense in the spinous and granular layers and weak in the basal layer. In addition, we also examined the localization of ubiquitin, which is a signal peptide for cytosolic proteolysis; clear-cut granular immunodeposits for ubiquitin were detected in spinous and granular cells, and some were co-localized with cathepsin B immunoreactivity. In the basal layer, mitotic cells were strongly immunopositive for ubiquitin. These results suggest that cysteine and aspartic proteinases are involved in the lysosomal system of the epidermis, showing different distributions in the epidermal layers depending on the enzymes examined. Moreover, ubiquitin may be associated with the cell cycle-dependent degradation in basal cells while it also participates in the non-lysosomal proteolysis and probably, lysosomal proteolysis in the spinous and granular cells.

Animals↗
PubMed1997

Perfusion-weighted MR imaging in the upper abdomen: preliminary clinical experience in 61 patients.

OBJECTIVE: We quantitatively analyzed the potential usefulness of perfusion-weighted (PW) MR imaging of the upper abdomen performed with a single-shot gradient-recalled echo echoplanar (GRE EP) sequence. SUBJECTS AND METHODS: PW imaging of the upper abdomen with a GRE EP sequence was performed in 61 patients who had suspected liver or pancreatic disease. PW imaging was started at the time of administration of 0.1 mmol/kg of gadopentetate dimeglumine, and images were obtained every 2 sec for 88 sec. Time-intensity curves for the liver, pancreas, spleen, and kidney, and for subgroups of patients with various pathologic conditions, were constructed for quantitative analysis. RESULTS: The signal-intensity changes seen throughout the PW imaging process differed for each abdominal organ and pathologic condition. In the spleen, pancreas, and renal cortex, a transient signal-intensity decrease was seen in the perfusion phase (42%, 39%, and 78%, respectively). In the liver and renal medulla, the maximum signal-intensity decrease occurred in the later phase rather than in the perfusion phase. Signal-intensity recovery in the spleen and pancreas occurred soon after the maximum signal-intensity decrease, whereas such recovery was delayed in the liver and renal cortex. In cirrhotic livers, the signal-intensity change seen throughout the examination was minimal. CONCLUSION: Unlike conventional MR imaging, PW imaging with a GRE EP sequence can provide detailed hemodynamic information about upper abdomen organs and about disorders of these organs because of its excellent temporal resolution and susceptibility to contrast enhancement.

Abdomen↗
PubMed1996

Nonsurgical management of patients with blunt splenic injury: efficacy of transcatheter arterial embolization.

OBJECTIVE: We evaluated the efficacy of nonsurgical management of patients with blunt splenic injury using detailed angiographic examinations and transcatheter arterial embolization. SUBJECTS AND METHODS: We prospectively studied 228 patients who had blunt abdominal injury and for whom CT was performed. When splenic injury was revealed by CT, angiography was performed in all patients except those requiring emergency surgery. Transcatheter arterial embolization was performed when patients had the following angiographic criteria: (1) extravasation of contrast material extending beyond or within the splenic parenchyma, (2) arterial disruption or major arteriovenous fistula, or (3) both. Splenic function was subsequently estimated by 99mTc-sulfur colloid scintigraphy and repeat angiography. RESULTS: Of 228 patients with blunt trauma, 31 patients had CT evidence of splenic injury. In three of these 31 patients, emergency laparotomy was performed before angiography because of an associated injury or unstable circulatory status. In 13 of the 28 remaining patients, transcatheter arterial embolization was not required as these patients did not meet the necessary criteria. They were treated with bed rest. Transcatheter arterial embolization was performed in the remaining 15 patients and was completely successful in 13. Because one of these 13 patients died of a brain contusion, follow-up angiography and scintigraphy were performed in the remaining 12 patients and showed preservation of splenic function. Nonsurgical treatment of splenic injury with angiography was successful in 93% of patients. CONCLUSION: Our success rate for nonsurgical management of patients with blunt splenic injury should encourage more extensive evaluation and use of angiography for splenic injury and the subsequent management of splenic injury without surgery.

Adolescent↗
PubMed1996

[MR imaging for breast cancer].

The potential role of magnetic resonance (MR) imaging in the diagnosis of breast disease has been investigated since the late 1970s. Conventional MR imaging has not been reliable for diagnosis of breast masses, and so contrast MRI using Gd-DTPA has been performed. In particular the gradient echo (GRE) technique combined with administration Gd-DTPA (i.e., dynamic MRI) improves detection and tissue characterization of breast masses. In recent studies, breast MR imaging has shown up to 100% sensitivity in the detection of breast cancer. On the other hand, its specificity varies between 37% and 98% because of the fact that may benign lesions are also enhanced with many contrast media, similar to breast cancer. To improve the specificity of MR imaging, MR-guiding localization and fine needle aspiration biopsy for breast masses will be necessary. Recently breast conserving therapy has been widely accepted in our country, so we deduce that MRI is useful method for detecting multifocal or multicentric breast cancer.

Adult↗
PubMed1995

[Clinical application of magnetic resonance angiography for coronary arteries: correlation with conventional angiography and evaluation of imaging time].

Magnetic resonance angiography (MRA) of the coronary arteries is a particularly difficult task because of the small size of the vessels and cardio-respiratory motion. The authors describe a method of performing of ultrafast MRA of the coronary arteries with a standard MR system and body coil. Each image was obtained within a single breath hold by "segmented Turbo FLASH" sequences using an electrocardiography gate. Clinical application was performed in 20 patients with ischemic heart disease, and a comparison was made with conventional coronary angiography. The imaging time was shortened significantly by our methods. The diagnosis was made by at least two different images to avoid false positives. The results indicated a good correlation between MRA and conventional angiography.

Aged↗