Search PubMed⌕ Search

Biomedical subjects

T Ota

Publications and source records attributed to T Ota.

425 records · Page 24Linked to original sources
PubMedDate not supplied

CT and MR imaging of pancreatic cancer.

Recent improvements in imaging techniques have made it possible to improve the diagnostic accuracy for detection, staging, and indicating surgical resectability of pancreatic cancer. The latest advance in the computed tomography technique, is the introduction of subsecond multislice helical scanning that improves z-axis resolution in the reformatted images and three-dimensional rendering with a large volume data. Magnetic resonance imaging provides versatile information including magnetic resonance cholangiopancreatography that allows noninvasive delineation of the pancreatic and biliary duct systems. The presence of pancreatic cancer may best be evaluated by dynamic computed tomography or dynamic magnetic resonance imaging with administration of intravenous contrast material. Both computed tomography and magnetic resonance imaging are valuable for the preoperative assessment of local invasion and vascular involvement. Multislice helical computed tomography is currently considered as the best single modality for the diagnosis of pancreatic cancer as it provides excellent image quality. When advanced magnetic resonance imaging equipment is used as a primary modality, in the future, it may have a possibility to replace other imaging modalities.

Adenocarcinoma↗
PubMedDate not supplied

Multi-directional positron imaging: evaluation of cancer detection with 2-(F-18)-fluoro-2-deoxy-D-glucose.

We developed a multi-directional positron imaging system for the whole body in order to evaluate the spatial distribution of radiopharmaceuticals. A positron emission tomography (PET) scanner with ring detectors was modified to provide 54 directional planar images with a three-dimensional appearance by using cinematic display. The initial clinical evaluation was performed on two normal volunteers and 17 cancer patients with 32 foci. Images were obtained approximately one hour after the intravenous administration of 2-(F-18)-fluoro-2-deoxy-D-glucose. In all 19 subjects, good quality images with a three-dimensional appearance were obtained. We were able to visualize 16 of 20 (80%) lesions that were three centimeters or more in greatest diameter. In contrast, only seven of 12 (58%) lesions less than three centimeters in greatest diameter were identified. The overall detectability of lesions was 72%. These results suggest that this system will be useful for tumor detection.

Aged↗
PubMedDate not supplied

Hemodynamics of 21 and 23 mm Medtronic Hall valves by Doppler echocardiography.

To evaluate the in vivo hemodynamics of smaller-sized (21 mm and 23 mm) Medtronic Hall (MH) valves in the aortic position, we measured the maximal pressure gradients (maxPG) at rest and during dobutamine (DOB) administration by continuous-wave Doppler echocardiography in 20 patients with aortic valve replacement. Their body surface areas (BSA) averaged 1.54 m2 in MH21 (n = 10) and 1.57 m2 in MH23 (n = 10). For comparison, the same study was performed in 18 patients who underwent replacement with 21 mm and 23 mm Björk-Shiley (BS) convexo-concave valves [BSA averaged 1.52 m2 in BS21 (n = 9) and 1.58 m2 in BS23 (n = 9)] and in 10 patients with 19 mm St. Jude Medical (SJM) valves (BSA averaged 1.43 m2). The maxPG was calculated as 4 Vmax2 (V = peak velocity) by means of a simplified Bernoulli equation. Cardiac output (CO) was obtained from a simultaneously recorded M-mode echocardiogram by Gibson's formula. A significant correlation, revealed as a second-degree polynomial regression equation, was found between CO and maxPG at rest and during DOB administration in each type or size of prosthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMedDate not supplied

New quantitative method for evaluating tricuspid regurgitation.

A new quantitative method for evaluating regurgitation (TR) is proposed in order to select the most suitable treatment for functional TR associated with acquired valvular heart disease. The regurgitant volume per beat (VTR) is calculated using two-dimensional color Doppler and continuous-wave Doppler echocardiographies. In a study of 48 patients, preoperative VTR showed a significant correlation with tricuspid annular diameter at end-diastole, right atrial mean pressure and right ventricular end-diastolic pressure. Patients were classified into 3 groups according to preoperative VTR: Group I, VTR less than 10 cc (no. 18); Group II, VTR = 10-20 cc (no. 18); Group III, VTR greater than or equal to 20 cc (no. 12). This classification correlated well with the intraoperative findings of TR. In all Group I patients, VTR decreased without any tricuspid valve repair. In Group II, 17 of 18 patients underwent tricuspid annuloplasty, and showed a decrease in VTR to below 10 cc after surgery. In Group III, 10 underwent tricuspid annuloplasty and 2 tricuspid valve replacement. Three of the 10 with tricuspid annuloplasty showed a significant degree of postoperative VTR (10-20 cc). These 3 patients as well as the 2 with tricuspid valve replacement showed a preoperative peak-to-peak pressure difference across the tricuspid valve during the ejection phase (RVsp-TAv) of less than or equal to 20 mmHg and tricuspid annular diameter at end-diastole of greater than or equal to 50 mm. In conclusion, no tricuspid valve repair was required in Group I (TR I). For group II (TR II) patients, tricuspid annuloplasty was necessary and adequate for TR correction. For Group II (TR III) patients, a more substantial procedure like tricuspid valve replacement should be performed, especially when the preoperative RVsp-RAv is less than or equal to 20 mmHg and tricuspid annular diameter at end-diastole is greater than or equal to 50 mm.

Adult↗
PubMedDate not supplied

Stereoselective formation of glucuronides in metabolism of hexobarbital enantiomers in vivo: isolation and quantitation of glucuronides in rabbit urine.

An improved column-chromatographic method was described for isolation and purification on preparative scale of a glucuronide from urine of rabbits administered (RS)-hexobarbital. The analytically pure preparation obtained was found to be a mixture of two glucuronides of diastereomeric 3'-hydroxyhexobarbitals. Rates of hydrolysis of the glucuronides were dependent on the enzyme preparations used as well as on the configuration of the substrate. For quantitative determination, the glucuronides were hydrolyzed completely by beta-glucuronidases from either Escherichia coli or abalone entrails under the conditions used. In vivo studies on the metabolism of (R)-(-)- and (S)-(+)-hexobarbital in the rabbit showed that the glucuronides excreted in 24-hr urine accounted for about 30% of the dose of each enantiomer, and that conjugation of the hydroxy isomers with glucuronic acid was so stereoselective that the isomers with S-configuration at the 3'-position were preferentially conjugated. There were almost no differences in the urinary metabolite profile between normal an PB-treated rabbits; however, a noticeable change was observed in recovery of unchanged (S)-hexobarbital after phenobarbital treatment.

Animals↗
PubMedDate not supplied

Treatment of ilio-femoral venous occlusion.

During the past thirteen and a half years, 222 cases of iliofemoral venous occlusion were treated. Diagnosis was based mainly on clinical symptoms and phlebography. Surgery, injury, malignancy and heavy muscular exercise were the chief etiologic factors of this disease. As therapeutic maneuvres: (1) thrombectomy, (2) Palma's operation, (3) conservative procedures, (4) extirpation of a tumor, and (5) removal of secondary varicose veins were performed. Long-term results of treatment were reviewed. Thrombectomy and Palma's operation obtained good results in 59% and in 42% of cases respectively, while conservative procedures showed a favorable outcome in 36% of cases where followed. Results of thrombectomy were statistically better than those of conservative procedures (p less than 0.05).

Adolescent↗
PubMedDate not supplied

CD44 participates in tumor cell adhesion to endothelial cells in the experimental metastatic process in B16BL6 melanoma cells.

There are several pieces of evidence suggesting a relationship between CD44 expression and tumor metastasis, but the role of CD44 in the metastatic processes is unclear. We analysed the role of CD44 in the experimental metastatic processes of B16BL6 melanoma cells using anti-CD44 monoclonal antibody (clone IM7). B16BL6 melanoma cells expressed CD44 and these cells treated with anti-CD44 monoclonal antibody increased in the experimental metastatic ability, indicating that CD44 participates in metastatic processes in B16BL6 cells. Furthermore, the adhesiveness of B16BL6 cells to endothelial cells and the retention of these cells in the lung increased by treatment with anti-CD44 monoclonal antibody. These results suggested that the CD44-mediated adhesion of tumor cells to endothelial cells was involved in the experimental metastatic process of B 16BL6 cells.

Animals↗
PubMedDate not supplied

Evaluation of the performance of a whole-body positron imaging system with attenuation correction.

A PET scanner with ring detectors has been modified to accomplish whole-body imaging with attenuation correction. To evaluate the performance of this system, phantom studies and clinical studies were performed in seven patients. The transaxial resolution (FWHM) at the center of the field was 8.6 mm, and the axial resolution was 12.3 mm. The counts on the images with attenuation correction were linearly related to accumulation of the radiopharmaceuticals, and attenuation correction was made accurately. The transmission scan from the top of the head to the thigh, about 110 cm in length, required 36 minutes, and one emission scan required 18 minutes. The total study time for one transmission scan and three sequential emission scans was 1.9 hours. In clinical studies, attenuation correction made the discrimination of organs clearer, and would facilitate the detection of tumors, especially those in the high attenuation organs or matter. The use of this system made it possible to obtain quantitative whole-body positron images with adequate diagnostic quality within a reasonable scanning time.

Aged↗
PubMedDate not supplied

Radiation surface doses to patients and staff during positron emission tomography.

In view of the complexities involved in estimating individual organ doses in positron emission tomography, the present study was undertaken to measure radiation surface doses in 23 patients undergoing PET studies using specially designed CaSO4: Tm TL dosimeters. In patients with brain disorders, the mean radiation surface doses to the chest and gonads were 0.52 mGy and 0.47 mGy, respectively. In patients with cardiac disorders, the mean surface doses to the forehead and gonadals were, respectively, 0.29 mGy and 0.41 mGy. It was possible to measure the radiation surface doses to all the intended sites in patients with liver malignancies, and maximum surface doses of 0.50 mGy and 0.49 mGy were recorded at the chest and gonadals, respectively. The measurement of radiation surface doses enables easy, quick, and reliable intercomparison of radiation load to patients and staff in various PET procedures.

Brain Diseases↗
PubMedDate not supplied

Benzyl-alpha-GalNAc inhibits sialylation of O-glycosidic sugar chains on CD44 and enhances experimental metastatic capacity in B16BL6 melanoma cells.

We examined the effect of benzyl-alpha-N-acetylgalactosamine (benzyl-alpha-GalNAc), which specifically inhibits the synthesis of O-linked oligosaccharides, on the expression of the peanut agglutinin (PNA)-binding sugar chains (Gal beta 1-3GalNAc) of CD44 and on its experimental metastatic ability in B16BL6 melanoma. Benzyl-alpha-GalNAc increased the PNA-binding, but not Concanavalin A (Con A), wheat germ agglutinin (WGA), and leukoagglutinating phytohemaagglutinin (L-PHA)-binding to the cell surface. Benzyl-alpha-GalNAc markedly increased the PNA-binding to CD44 by decreasing the sialylation of these sugar chains. The experimental metastatic ability of B16BL6 cells was enhanced in association with this modulation of the sugar chains. These findings suggested that unsialylated Gal beta 1-3GalNAc sugar chains on the cell surface and/or CD44 are involved in the metastatic process of B16BL6 melanoma cells. On the other hand, the known functions of CD44, such as adhesion to hyaluronate, fibronectin, collagen, and endothelial cells, as well as homotypic aggregation, were not affected by benzyl-alpha-GalNAc regardless of the enhancement of metastatic ability induced by this glycosylation inhibitor. CD44 might have other metastasis related functions that remain to be elucidated.

Acetylgalactosamine↗