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Biomedical subjects

Nobuyuki Taniguchi

Publications and source records attributed to Nobuyuki Taniguchi.

At least 19 recordsLinked to original sources
PubMed2006

Sentinel node detection in breast cancer using contrast-enhanced sonography with 25% albumin--Initial clinical experience.

PURPOSE: To determine the clinical usefulness of a sentinel lymph node (SLN) identification technique using contrast-enhanced sonography (CEUS) with 25% albumin. METHODS: The subjects were 23 women with breast cancer. Each was injected subcutaneously with 5 ml of 25% albumin solution as a negative contrast agent directly superficial to the breast tumor. The area was massaged, and the inferior axillary hairline was examined continuously using gray-scale sonography with a 7.5- or 10-MHz transducer. Any contrast-enhanced lymph node was considered a CEUS-detected SLN, was differentiated from other level I and II nodes, and was resected and pathologically assessed. RESULTS: In all 23 patients, 1 or 2 CEUS-detected SLNs (mean, 1.3 SLNs) were identified. Their sizes ranged from 5 mm to 25 mm (mean, 11.3 mm), and their depths (from the skin surface) ranged from 5mm to 20 mm (mean, 12.6 mm). Pathologic examination revealed a metastasis in 5 of the 23 patients, all in CEUS-detected SLNs. CONCLUSION: In a clinical study using CEUS with 25% albumin, contrast-enhanced nodes were identified in all subjects. The pathologic findings suggested that any metastatic nodes observed were SLNs, indicating that this technique may represent a new modality for SLN identification.

Adult↗
PubMed2005

The effects of Levovist and DD-723 in activating platelets and damaging hepatic cells of rats.

OBJECTIVE: The purpose of this study was to compare platelet activation and hepatic cell damage produced by 2 ultrasonographic contrast agents with flow cytometric and ultrastructural analysis. METHODS: Suspension samples were made by mixing Levovist (SH U508A; Schering AG, Berlin, Germany) or DD-723 (Nycomed; Amersham Health, Princeton, NJ) with whole blood. The final concentrations of Levovist in citrated whole blood were 0, 15, and 75 mg/mL, and those of DD-723 were 0, 5, and 50 microL/mL. After exposure to ultrasound in vitro, flow cytometric analysis was performed to determine the concentration of the CD62P activation-specific antigen. To compare the hepatic cell damage associated with these 2 agents, we divided 15 rats into 5 groups as follows: group 1, sham operation; group 2, Levovist injection only; group 3, DD-723 injection only; group 4, Levovist injection (contrast agent) and ultrasound exposure; and group 5, DD-723 injection and ultrasound exposure. The ultrasonographic contrast agents Levovist and DD-723 were administered through the femoral vein and sonicated continuously for the first minute; this was followed by sweeping for 5 minutes 10 seconds after the contrast agent was injected. The rats were perfused via the heart with a fixative solution immediately after the sweeping, and then the liver was excised; the specimens were studied with electron and light microscopy. RESULTS: The percentage of CD62P-expressing platelets increased in both contrast agent-ultrasound exposure groups, and the percentage of CD62P-expressing platelets was greater in the Levovist group. We observed vacuolation and round deposits in the hepatocytes in both contrast agent-ultrasound exposure groups. Microbubbles were observed in the rat Kupffer cells, and a few hepatocytes were seen unexpectedly in the DD-723 group but were found in neither the Kupffer cells nor the hepatocytes in the Levovist group. CONCLUSIONS: Both contrast agents, Levovist and DD-723, produced platelet activation and structural change in the rat hepatic cells, but only the microbubbles of DD-723 were taken up by the Kupffer cells and a few hepatocytes.

Animals↗
PubMed2004

Underlying mechanism of numerical instability in large-eddy simulation of turbulent flows.

This paper extends our recent theoretical work concerning the feasibility of stable and accurate computation of turbulence using a large eddy simulation [Phys. Rev. E 68, 036705 (2003)]]. In our previous paper, it was shown, based on a simple assumption regarding the instantaneous streamwise velocity, that the application of the Gaussian filter to the incompressible Navier-Stokes equations can result in the appearance of a numerically unstable term that can be decomposed into positive and negative viscosities. That result raises the question as to whether an accurate solution can be achieved by a numerically stable subgrid-scale model. In the present paper, based on assumptions regarding the statistically averaged velocity, we present similar theoretical investigations to show that in several situations, the shears appearing in the statistically averaged velocity field numerically destabilize the fluctuation components because of the derivation of a numerically unstable term that represents negative diffusion in a fixed direction. This finding can explain the problematic numerical instability that has been encountered in large eddy simulations of wall-bounded flows. The present result suggests that this numerical problem is universal in large eddy simulations, and that if there is no failure in modeling, the resulting subgrid-scale model can still have unstable characteristics; that is, the known instability problems of several existing subgrid-scale models are not something that one may remove simply by an artificial technique, but must be taken seriously so as to treat them accurately.

Journal Article↗
PubMed2004

A new system for in vivo assessment of the degree of nonlinear generation using the second harmonic component in echo signals.

To assess the feasibility of a new system that uses the finite amplitude method and makes possible the assessment of the degree of nonlinear generation in vivo we adopted a method for agar-gel phantoms, using varying lipid concentrations and human livers in vivo. Instead of calculating the nonlinearity parameter B/A value, we evaluated the h value, which is determined by plotting the measured values of the ratio of the amplitude of the second harmonic component to that of the fundamental component. The agar-gel phantoms of various lipid concentrations and 20 cases of normal and 21 cases of fatty liver were studied in this investigation. There was an almost linear agreement between the h value and the lipid concentration of the phantom. The h value (mean +/- SD) was 0.25 +/- 0.03 in normal liver and 0.35 +/- 0.05 in fatty liver. A statistically significant difference was found between them (p < 0.0001). This new system was considered to be usable for evaluating h in vivo as an indicator of the lipid content of the liver.

Fatty Liver↗
PubMed2004

Endothelial cell injury and platelet aggregation induced by contrast ultrasonography in the rat hepatic sinusoid.

OBJECTIVE: To determine whether contrast ultrasonography can affect the sinusoidal cells and platelets of the liver by using ultrastructural analysis in vivo. METHODS: Fifteen Wistar rats were placed into the following 5 groups of 3 rats each: 3 control groups comprising a sham operation group, a contrast agent injection-alone group, and an ultrasound exposure-alone group; and 2 contrast agent injection with ultrasound exposure groups, split according to excision time. After a dose of an echo contrast agent (100 mg/kg of body weight) was administered through the femoral vein, the rats that received injections were subjected to ultrasound for the first minute, no ultrasound for the next 4 minutes, and then ultrasound sweep scanning for 10 seconds. The rats were perfused via the heart with cold physiologic saline containing 2% paraformaldehyde and 2.5% glutaraldehyde solution buffered with 0.1-mol/L phosphate. The livers of the rats in 4 of the groups were excised immediately. The livers of the rats in 1 of the 2 contrast agent with ultrasound exposure groups were excised by the same procedure 5 hours after they received the injections. All specimens were studied with light and electron microscopy. RESULTS: Platelet aggregation and injury to endothelial cells were more severe in the contrast agent injection and ultrasound exposure groups than in the other groups. CONCLUSIONS: Contrast ultrasonography can cause platelet aggregation and endothelial cell damage in the rat hepatic sinusoid.

Animals↗
PubMed2003

Can a numerically stable subgrid-scale model for turbulent flow computation be ideally accurate?: a preliminary theoretical study for the Gaussian filtered Navier-Stokes equations.

This paper introduces a candidate for the origin of the numerical instabilities in large eddy simulation repeatedly observed in academic and practical industrial flow computations. Without resorting to any subgrid-scale modeling, but based on a simple assumption regarding the streamwise component of flow velocity, it is shown theoretically that in a channel-flow computation, the application of the Gaussian filtering to the incompressible Navier-Stokes equations yields a numerically unstable term, a cross-derivative term, which is similar to one appearing in the Gaussian filtered Vlasov equation derived by Klimas [J. Comput. Phys. 68, 202 (1987)] and also to one derived recently by Kobayashi and Shimomura [Phys. Fluids 15, L29 (2003)] from the tensor-diffusivity subgrid-scale term in a dynamic mixed model. The present result predicts that not only the numerical methods and the subgrid-scale models employed but also only the applied filtering process can be a seed of this numerical instability. An investigation concerning the relationship between the turbulent energy scattering and the unstable term shows that the instability of the term does not necessarily represent the backscatter of kinetic energy which has been considered a possible origin of numerical instabilities in large eddy simulation. The present findings raise the question whether a numerically stable subgrid-scale model can be ideally accurate.

Journal Article↗
PubMed2003

Sonographic diagnosis and successful nonoperative management of sealed perforated duodenal ulcer.

We encountered a case of sealed perforated duodenal ulcer in a 75-year-old woman with rheumatoid arthritis and chronic renal failure. Abdominal sonography showed a bright linear echo within the thickened anterior wall of the duodenal bulb and the presence of free air at the anterior surface of the liver. We found no signs of direct communication between the duodenal lumen and the peritoneal cavity or any free fluid. On follow-up sonography performed every 2 days during the first week of the patient's hospitalization, no free fluid was found in the abdomen. The use of sonography to diagnose this patient's sealed perforated duodenal ulcer and to monitor the ulcer for the appearance of free fluid allowed us to provide successful nonsurgical management to this patient. We believe that the use of abdominal sonography in all patients suspected of having a perforated duodenal ulcer may help increase the diagnostic accuracy of this modality and may reduce the need for surgery in such patients.

Aged↗
PubMed2003

Attenuation coefficient measurement in the thyroid.

OBJECTIVE: To assess the feasibility of a novel method of measuring the attenuation coefficient in the thyroid, which offers less variability of results than the conventional method. METHODS: In our new method, the attenuation coefficient was evaluated on the basis of the following equation with sound field correction: alpha = -1/4[Fc(z)-epsilon(z)] x d/dz[log(M0(z))-tau(z)]. In our system, the attenuation coefficient was also evaluated by the spectral shift central frequency method at the same time. In this study, we used 32 cases of normal thyroid, 26 cases of Graves disease, and 11 cases of Hashimoto thyroiditis in the system. RESULTS: With this novel method, attenuation coefficient values of the thyroid (mean +/- SD) were 1.50 +/- 0.26 dB x cm(-1) x MHz(-1) in the normal group, 0.91 +/- 0.23 dB x cm(-1) x MHz(-1) in the Graves disease group, and 1.10 +/- 0.27 dB x cm(-1) x MHz(-1) in the Hashimoto thyroiditis group. The novel method recorded a statistically significant difference between normal and diseased thyroids (P < .0001) and between Graves disease and Hashimoto thyroiditis groups (P = .0035). Statistical variation of the attenuation coefficient values obtained using the novel method was much smaller than that of those obtained by the spectral shift central frequency method in every group. CONCLUSIONS: This new method is considered usable for evaluating the attenuation coefficient of the thyroid in vivo.

Adolescent↗
PubMed2003

In vitro platelet activation by an echo contrast agent.

OBJECTIVE: We investigated whether an ultrasonic echo contrast agent containing microbubbles (Levovist [SH U 508A]; Schering AG, Berlin, Germany) could in routine use activate platelets. METHODS: Levovist and its main component, galactose, were mixed with separate samples of whole blood (1.5-75 mg/mL) from 5 healthy volunteers to form a 1-mL suspension sample. After in vitro exposure to ultrasound emitted from a commercial ultrasonic scanner at a pulse frequency of 3.5 MHz with a mechanical index of 1.9 and an exposure duration of 5 minutes, 5 microL of the sample was incubated for 20 minutes with the fluorescein isothiocyanate-labeled CD61 antibody, which is a platelet-specific antigen, and the phycoerythrin-labeled CD62P (P-selectin) antibody, an activation-specific antigen, both on the platelet surface. After more than 30 minutes of fixing in 1% paraformaldehyde, flow cytometric analysis was performed. RESULTS: The percentage of CD62P-expressing platelets increased according to the concentrations of Levovist and galactose, which showed almost equal effects. Ultrasound exposure did not enhance the effect except at the highest concentration of Levovist (75 mg/mL). CONCLUSIONS: In vitro, a galactose-based echo contrast agent could not activate the platelets at its routine concentration.

Adult↗
PubMed2003

[Laboratory examinations performed in rural practice].

Graduates from Jichi Medical School are obligated to work at rural clinics or hospitals, where most of them are the only medical doctor in the house. To understand how these graduates actually use laboratory examinations, what examinations they found most important in their practice, and when they were confident of their laboratory techniques, we designed a questionnaire to address these questions. Many respondents reported that their institutions had electrocardiographs, abdominal and/or cardiac ultrasonographs, urinalysis test paper, and portable blood glucose meters, and more than half of them reported having used these instruments without assistance in emergency situations. Moreover, a majority of the respondents said that they considered it important that a physician is able to use these instruments without the help of other staff members. Proficiency in many laboratory techniques was obtained and physicians were confident during their first postgraduate clinical practice. These responses clearly show the importance and usefulness of covering examination techniques and the principles of laboratory medicine in medical education and the first postgraduate clinical practice.

Clinical Competence↗
PubMed2003

[The ultrasound examination of the deep vein thrombosis].

Ultrasonography is very useful for detection of deep vein thrombosis. The purpose of this paper is to show a method for detecting them efficiently by high resolution transducer and color Doppler system. We examined patients in the supine and prone positions. To detect the venous flow easily and differentiate thrombi from simple venous dilatation, some maneuvers are useful; one is pushing the vein area using the transducer on examination, the second is breathing overload, and the last is so-called milking. We can find throombi in the external iliac or femoral veins of patients who have symptoms of lower leg swelling, however, we need to better detect venous thrombi in the lower leg in patients with a history of pulmonary embolism. Because deep venous thrombi are increasing, the role of ultrasound will expand in the future.

Humans↗
PubMed2002

Intussusception induced by villous tumor of the colon: sonographic findings.

We report a case of intussusception caused by a villous tumor of the ascending colon in an 82-year-old man. Abdominal sonography showed intussusception in the ascending colon, with a transverse scan demonstrating a multiple concentric ring sign. Color Doppler sonography showed blood flow signals in a mass, which was considered to be the lead point of the intussusception. A spontaneous reduction of the intussusception occurred during the examination; sonography then showed a mildly echogenic, mass. The graded compression method revealed that the mass was soft and immobile. Colonoscopy confirmed the diagnosis of villous tumor. Sonography helped to make an early diagnosis, allowing successful conservative management of the tumor and the intussusception.

Adenoma, Villous↗
PubMed2002

New method of sentinel node identification with ultrasonography using albumin as contrast agent: a study in pigs.

The purpose of our study was to verify in animals the possibility of using albumin-enhanced ultrasonography as a modality for sentinel node detection. The nine pigs were injected subcutaneously in the neck with albumin, five with 5% solution and four with 25% solution, and then the regional lymph nodes were observed over time. It was found that, where the 5% solution had been injected, the lymph nodes showed no change, but where the 25% solution had been used, a high echo 1 to 5 mm in size was seen at the hilus of the nearest lymph node. Examination of the excised pathologic specimens of lymph nodes demonstrated that this echo was due to albumin accumulated in the efferent lymphatics. This finding suggested that this technique of ultrasonography using albumin as a contrast agent was an effective new method of identifying sentinel nodes.

Albumins↗
PubMed2002

Simultaneous velocity and concentration measurements of a turbulent jet mixing flow.

A method for the simultaneous measurement of velocity and passive scalar concentration fields by means of particle image velocimetry (PIV) and planar laser induced florescence (PLIF) techniques is described here. An application of the combined PIV-PLIF system is demonstrated by performing simultaneous velocity and concentration measurements in the near field of a turbulent jet mixing flow. The distributions of the ensemble-averaged velocity and concentration, turbulent velocity fluctuation, concentration standard deviation, and the correlation terms between the fluctuating velocities and concentration in the near field of the turbulent jet flow are presented as the measurement results of the simultaneous PIV-PLIF system.

Fluorescent Dyes↗
PubMed2002

A new method for attenuation coefficient measurement in the liver: comparison with the spectral shift central frequency method.

OBJECTIVE: To assess the feasibility of a new method of measuring the attenuation coefficient in the liver, which offers less variability of results than the conventional method. METHODS: The attenuation coefficient was evaluated on the basis of the following equation with sound field correction: [log(M0 (z)) - tau(z)]. In our system, the attenuation coefficient was also evaluated by the spectral shift central frequency method at the same time. We used 44 cases of normal liver, 40 cases of fatty liver, and 20 cases of cirrhotic liver in the system. RESULTS: With this new method, attenuation coefficient values were 0.59+/-0.10 dB x cm(-1) x MHz(-1) in normal livers, 0.80+/-0.12 dB x cm(-1) x MHz(-1) in fatty livers, and 0.62+/-0.09 dB x cm(-1) x MHz(-1) in cirrhotic livers. In both methods we recorded a statistically significant difference between normal and fatty livers and between fatty and cirrhotic livers (P < .0001). Only in the fatty liver was any significant difference (P < .0001) found between attenuation coefficients in the new method and those in the spectral shift central frequency method (0.70+/-0.05 dB x cm(-1) x MHz(-1)). CONCLUSIONS: This new method, which was more sensitive in detecting fatty infiltration than the spectral shift central frequency method, was considered usable for evaluating the attenuation coefficient of the liver in vivo.

Adolescent↗
PubMedDate not supplied

Primary linitis plastica carcinoma of the colon accompanied by peritoneal abscess.

We describe the case of a 75-year-old woman with linitis plastica carcinoma of the colon, accompanied by a peritoneal abscess, in which the use of transabdominal sonography enabled prompt detection and diagnosis. Sonographic examinations revealed diffuse wall thickening with blurred layer stratification in the ascending colon. The irregular outer margin of the affected area was surrounded by thickened pericolic fat. A peritoneal abscess covered by the omentum was also found. CT confirmed these findings. We extensively resected the right half of the colon. Histopathologic examination of the excised segment of the colon revealed a poorly differentiated adenocarcinoma with fibrotic infiltration. The patient was discharged 6 weeks postoperatively, and chemotherapy was begun, but she was lost to our follow-up. Although linitis plastica carcinoma of the colon is rare, it must be considered when patients have extensive colonic wall thickening with blurred layer stratification and an irregular outer margin surrounded by thickened pericolic fat. Transabdominal sonography should be considered the imaging modality of choice for the detection and diagnosis of this disease entity.

Abscess↗