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Biomedical subjects

T Shiota

Publications and source records attributed to T Shiota.

At least 127 records · Page 7Linked to original sources
PubMed1994

Doppler echocardiographic evaluation of left ventricular output and left ventricular diastolic filling changes in the first day of life.

The aim of this study was to evaluate the changes in Doppler transmitral flow patterns during the 1st d of life. Doppler echocardiography of the ascending aorta and mitral valve was performed serially in 20 normal neonates at 2, 12, and 24 h of age. A computer-interfaced digitizer pad was used to measure the following: ascending aorta flow velocity-time integral, total diastolic filling flow velocity-time integral, flow velocity-time integral of early diastolic filling, and flow velocity-time integral of atrial contraction. The inner diameter of the ductus arteriosus was 4.2 +/- 0.6 mm at 2 h of age, 2.3 +/- 0.5 mm at 12 h of age, and had closed in 17 of 20 neonates (85%) by 24 h of age. The ascending aorta flow velocity-time integral and total diastolic filling flow velocity-time integral, which were high at 2 h of age, decreased significantly at 12 h of age [12.2 +/- 2.1 cm versus 9.6 +/- 1.7 cm (p < 0.001) and 8.0 +/- 1.1 versus 7.1 +/- 1.4 (p < 0.01), respectively] but remained constant thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed1993

Effects of adjacent surfaces of different shapes on regurgitant jet sizes: an in vitro study using color Doppler imaging and laser-illuminated dye visualization.

OBJECTIVES: The present study was designed to estimate the influence of different-shaped adjacent surfaces on regurgitant jets as assessed by color Doppler imaging and laser-illuminated dye optical visualization. BACKGROUND: Because color Doppler techniques provide real-time two-dimensional imaging of flow, the evaluation of valvular regurgitation by analysis of variance-encoded regurgitant jets by this method has been widely used in clinical studies. However, recent studies have demonstrated that color Doppler jet sizes are affected not only by several hemodynamic factors and instrument settings but also by the interaction between jets and adjacent wall surfaces. In clinical conditions, jets may interact with adjacent walls of variable shapes that might have different effects on the jet size. METHODS: An in vitro model was constructed consisting of a rigid, optically clear receiving chamber that had no outlet resistance and had a pulsatile pump ejecting through 1.5, 2.3 and 3.1 mm2 inflow orifices into the chamber. The surfaces were flat or smoothly and equally curved, convex and concave aluminum positioned at 0, 2 and 4 mm from and to the side of the inflow orifices. The pump was run with stroke volumes from 0.5 to 3.0 ml and with a pulse frequency of 70 beats/min. The echocardiographic and laser beams were aimed at the inflow orifice imaging jets perpendicular to the surfaces (vertical view) through the central plane of the jet flows. Maximal jet areas were measured by both color Doppler techniques and laser-illuminated dye visualization. RESULTS: Color Doppler study showed fair correlation between the jet areas and the stroke volumes (r = 0.83 to 0.99), but the jet sizes under different surface conditions were variable. All the surface jet areas at a jet-surface distance of 0 and 2 mm were smaller than free jet areas at the same stroke volume for both flat and convex surfaces (p < 0.001). Flow constraint by the concave surface resulted in the smallest jet areas (p < 0.001). The color Doppler jet areas on the curved surfaces were significantly smaller than the laser-illuminated dye visualization jet areas (p < 0.01 to 0.0001). However, at intermediate jet-surface distances (4 mm and sometimes 2 mm with higher velocity flows), jet interaction with the flat and especially with the convex surface resulted in larger jets. This effect was most pronounced on dye fluorescence studies because flow around these jets consisted mainly of low velocity vortical events with only partial surface adherence and these low velocity swirling flows were not well imaged by color Doppler technique. CONCLUSIONS: Our study suggests that the different-shaped adjacent surfaces with different degrees of flow alterations resulted in variable decreases in jet size and that color Doppler imaging could not encode and image the angled and low velocity swirling events well when jets flowed along the curved surfaces. These effects need to be taken into account when interpreting color Doppler images.

Analysis of Variance↗
PubMed1993

Determination of most appropriate Nyquist velocity for applying hemispherical flow convergence equation to calculate flow rate using the transorifice pressure gradient: digital computer analysis of Doppler color flow convergence region.

Nyquist velocity and transorifice pressure gradient dramatically influence color aliasing shape and accuracy of simple hemispherical flow convergence equation for calculation of flow rate. The present in vitro study was performed to determine whether the value of Nyquist velocity, at which the shape of proximal isovelocity surface is best fit for a given shape assumption in different orifice size, and the flow rate may be a determinable and orifice size independent function of clinically measurable peak velocity or transorifice pressure gradient. Steady flow was driven through circular discrete orifices with diameter of 3.8 mm, 5.5 mm and 10 mm and flow rate ranging from 2.88 L/min to 8.28 L/min. For every flow rate, Doppler color encoded M-mode images through the center of flow convergence region were transferred into the microcomputer in their original digital format. The continuous wave Doppler traces of maximal velocity through the orifice were performed for the calculation of pressure gradient. Direct numerical spatial velocity measure using color pixel intensity was obtained from the transferred color encoded M-mode images with computer software. The shape of isovelocity surface was determined by the ratio of calculated flow rate with hemispherical flow convergence equation to the actual flow rate. Both the flow rate and orifice size influence the position of the velocity profile curve. The shape of isovelocity surface is not constant and changes with the velocities used for the calculation of flow rates for a given flow rate and orifice size or pressure gradient and also changes with the flow rate or transorifice pressure gradients for a constant Nyquist velocity and orifice size.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1993

Accuracy of flow convergence estimates of mitral regurgitant flow rates obtained by use of multiple color flow Doppler M-mode aliasing boundaries: an experimental animal study.

The proximal flow convergence method of multiplying color Doppler aliasing velocity by flow convergence surface area has yielded a new means of quantifying flow rate by noninvasively derived measurements. Unlike previous methods of visualizing the turbulent jet of mitral regurgitation on color flow Doppler mapping, flow convergence methods are less influenced by machine factors because of the systematic structure of the laminar flow convergence region. However, recent studies have demonstrated that the flow rate calculated from the first aliasing boundary of color flow Doppler imaging is dependent on orifice size, flow rate, aliasing velocity and therefore on the distance from the orifice chosen for measurement. In this study we calculated the regurgitant flow rates acquired by use of multiple proximal aliasing boundaries on color Doppler M-mode traces and assessed the effect of distances of measurement and aliasing velocities on the calculated regurgitant flow rate. Six sheep with surgically induced mitral regurgitation were studied. The distances from the mitral valve leaflet M-mode line to the first, second, and third sequential aliasing boundaries on color Doppler M-mode traces were measured and converted to the regurgitant flow rates calculated by applying the hemispheric flow equation and averaging instantaneous flow rates throughout systole. The flow rates that were calculated from the first, second, and third aliasing boundaries correlated well with the actual regurgitant flow rates (r = 0.91 to 0.96). The mean percentage error from the actual flow rates were 151% for the first aliasing boundary, 7% for the second aliasing boundary, and -43% for the third aliasing boundary; and the association between aliasing velocities and calculated flow rates indicates an inverse relationship, which suggests that in this model, there were limited velocity-distance combinations that fit with a hemispheric assumption for flow convergence geometry. The second aliasing boundary with an aliasing velocity, of 102 cm/sec, (which was achieved by use of a 4 kHz pulse repetition frequency, a 3.75 MHz transducer, and no color baseline shift), provided the closest fit to the actual regurgitant flow rates (r = 0.99; y = 0.95x + 0.07). The averaged calculated flow rates from all aliasing velocities also resulted in excellent correlation (r = 0.97; y = 0.99x + 0.5). A hemispheric flow convergence method that is based on color Doppler M-mode echocardiography is a feasible and automatable method for quantifying mitral regurgitant rate.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Determination of the most appropriate velocity threshold for applying hemispheric flow convergence equations to calculate flow rate: selected according to the transorifice pressure gradient. Digital computer analysis of the Doppler color flow convergence region.

BACKGROUND: While flow convergence methods have been promising for calculating volume flows from color Doppler images, it appears that the velocity threshold used and the transorifice pressure gradient dramatically influence the accuracy of application of the simple hemispheric flow convergence equation for calculation of flow rate. The present in vitro study was performed to determine whether the value of velocity threshold at which the shape of proximal isovelocity surface best fits given shape assumptions with different orifice sizes and flow rates is predictable as a function independent of orifice size from clinically measurable peak velocity or transorifice pressure gradient information. METHODS AND RESULTS: In an in vitro model built to facilitate ultrasound imaging, steady flow was driven through circular discrete orifices with diameters of 3.8, 5.5, and 10 mm. Flow rates ranged from 2.88 to 8.28 L/min with corresponding driving pressure gradients from 14 to 263 mm Hg. At each flow rate, Doppler color-encoded M-mode images through the center of the flow convergence region were obtained and transferred into the microcomputer (Macintosh IIci) in their original digital format. Then, the continuous wave Doppler traces of maximal velocity through the orifice were derived for the calculation of driving pressure gradient. Direct numerical spatial velocity measurements were obtained from the digital color encoded M-mode velocities with computer software. For each flow rate, we could calculate flow volume from any number of velocity distance combinations with a number of assumptions and use the results to assess expected flow convergence shape based on a priori knowledge of the progression from oblate hemispheroid to hemisphere to prolate hemispheroid changes observed previously. Our results showed that for a given ratio of calculated flow rate to actual flow rate (0.7 and 1), the velocity threshold that could be used for the calculation of flow rate with a hemispheric flow convergence equation correlated well with the pressure gradient for a given orifice size, and the differences in velocity threshold that could be used this way among different orifice sizes once they were adjusted for the covariate pressure gradients were not statistically significant (P = .79 for ratio = 0.7, and P = .81 for ratio = 1). CONCLUSIONS: Our present study provides an orifice size-independent quantitative method that can be used to select the most suitable velocity threshold for applying a simple hemispheric flow convergence equation based on clinically predictable pressure gradients ranging from 40 to 200 mm Hg, and it offers a correction factor that can be applied to the hemispheric flow convergence equation when the pressure gradient is less than 40 mm Hg.

Blood Flow Velocity↗
PubMed1993

Gene analysis of pulmonary pseudolymphoma.

The value of gene analysis was assessed in patients with pulmonary pseudolymphoma. Two patients with histopathologic evidence of pseudolymphoma took part in the study. High molecular weight DNA was extracted from resected specimens and digested with restriction enzymes, followed by southern blotting. Gene rearrangement of immunoglobulins and T-cell receptors was investigated using DNA probes against heavy chain (H chain), kappa chain, and lambda chain of immunoglobulin genes and that against the beta-chain of T-cell receptor genes. Both patients with pseudolymphoma showed rearranged bands for the H chain; B-cell lymphoma was diagnosed from the gene analysis. Gene analysis is a valuable method when it is difficult to judge whether the tumor cells are of T-cell origin or B-cell origin in phenotype analysis by immunohistologic studies and when it should be judged whether or not the lymphoid hyperplasia is tumor related.

Adult↗
PubMed1993

Hemostasis of gastric variceal hemorrhage by transileocoecal and transhepatic obliteration.

Obliteration for gastric or duodenal variceal hemorrhage was performed via transileocoecal or transhepatic portal catheterization in 8 patients with portal hypertension. The patients were 6 men and 2 women, whose average age was 59 years. All of the patients had cirrhosis of the liver. The obliteration was performed as an emergency procedure in 6 cases, and 2 patients were electively treated. Transileocoecal obliteration (TIO) and transhepatic obliteration (PTO) were selected for 6, and 2 patients, respectively. Variceal bleeding was successfully controlled in all patients after completion of the therapy. One patient died after 3 months when duodenal variceal bleeding recurred. Elective surgical operations were performed on 2 patients after the initial therapy, because the vein feeding toward the varices remained. Six of the patients have survived to date without bleeding. Transient oliguria and jaundice after the therapy were noticed in 2 patients. Histological examination revealed cast formation of polymerized cyanoacrylate in the obliterated gastric varices of 2 patients. TIO and PTO seem to be safe, effective procedures to stop bleeding from ectopic varices, gastric or duodenal. This therapy is useful either to obtain accurate information about the varices or to obliterate the collateral veins in patients with ruptured ectopic varices.

Adult↗
PubMed1992

Treatment of hepatocellular carcinoma by transcatheter hepatic arterial injection of radioactive iodized oil solution.

After 12 days of culture, VX2 carcinoma cells were inoculated into the liver of 16 rabbits; 14 days later, 131I-labeled iodized oil ([131I]-Lp) suspended in lipiodol was injected into the hepatic artery. Selective accumulation of the contrast material in the tumor for an extended time was evident on X-rays and hepatic scintiphotographs. The antitumor effect was remarkable. [131I]-Lp agents warrant further examination for their clinical usefulness. Internal radiation therapy by transcatheter hepatic arterial injection of [131I]-Lp (group A) was evaluated in 9 patients with hepatocellular carcinoma (HCC, tumor stage III or IV) associated with liver cirrhosis (LC) and compared with combination therapy of Lp-TAE (group B) in 18 patients with HCC (tumor stage III or IV) associated with LC. In group A, serum AFP levels dropped rapidly in eight of the nine patients who had an elevated initial level of more than 500 ng/ml. The average reduction in tumor size was 50% in eight cases as determined by computed tomography. Histological examination of one resected liver specimen at 3 months after the third injection of [131I]-Lp revealed microscopic features highly suggestive of a radiation effect in the [131I]-Lp-containing area. The 1-year survival value for patients with HCC was estimated at 49.0% using the Kaplan-Meier method. The survival of patients treated with internal radiation therapy tended to be better than that of those treated with Lp-TAE (P = 0.119).

Aged↗
PubMed1992

Effectivity and safety of mannitol treatment for acute hepatic failure in rats.

In rats with D-galactosamine-induced hepatic failure, 14C-D-mannitol transport into the brain was accelerated through an increase of vesicular transport via the blood-brain barrier and thus brain mannitol contents increased. However, the osmolarity of the brain tissue changed little and the mortality was decreased by mannitol infusion to acute hepatic-failure rats. Experimental data indicate the effectivity and safety of hypertonic mannitol therapy for cerebral edema in acute hepatic failure.

Animals↗
PubMed1992

Lifetime data analysis of disease and aging by the Weibull probability distribution.

We applied the Weibull distribution to the life-table and age-patterns of diseases in Japan. The life-table follows a composite Weibull distribution composed of initial failure and two stage wear-out failure periods. The extension of lifespan during the past century is manifested as increases in the scale parameters in all three periods and the shape parameters in the wear-out periods with female predominancy. The shape parameters of diseases show time-independent sex-dependent specific values. When consistent changes are observed, such as increases in the shape parameters of tuberculosis and pneumonia, legitimate causes such as prevention and repair at the societal and medical level are present. Cancer and arteriosclerosis share a common range of shape parameters suggesting analogous underlying biological processes. An analysis of the epidemiology of human aging and disease by the Weibull distribution discloses intrinsic properties of man as a biological organization as well as a societal presence.

Adolescent↗
PubMed1992

Experimental studies to define the geometry of the flow convergence region. Laser Doppler particle tracking and color Doppler imaging.

The color flow convergence method for calculating volume flow through regurgitant or forward flow restrictive orifices has gained significant interest and a number of in vitro studies have suggested that this method is accurate, even in pulsatile models. Clinical application of the method over a wide range of conditions will require improved understanding of the effect of orifice size, flow geometry, and flow rate on the flow convergence geometry. In this study, we performed laser particle tracking investigations to allow visualization of streamlines into stenotic orifices. These streamlines are theoretically perpendicular to the isovelocity surfaces used for flow convergence calculations. We compared those observations to color flow map, flow convergence images obtained with a Toshiba 160A for orifices 5 to 15 mm 2 with flow rates of 1.5 to 9.7 L/min. Our results show that for large orifices, low flow rates, and/or low pressure gradients, more oblique streamlines in the velocity of the orifice correspond to nonhemispherical, but more elliptical, flow convergence geometries. This can be corrected for by using lower Nyquist limits and calculating flow convergence at greater distances from the orifice. Under high flow and high gradient conditions, increased Nyquist limits and shorter aliasing radii are more suitable. Our studies yield insights into flow convergence geometry and yield corrective procedures to improve volume flow calculation.

Blood Flow Velocity↗
PubMed1992

Intraluminal ultrasound imaging through a balloon dilation catheter in an animal model of coarctation of the aorta.

BACKGROUND: Controversy still exists over the optimal balloon size, extent of vascular disruption, and long-term results of balloon dilation therapy for coarctation of the aorta. Intravascular ultrasound imaging has been used in patients with coronary artery disease to provide further insight into the anatomy of atherosclerotic lesions and the results of angioplasty and atherectomy. Initial observations of the results of balloon dilation of coarctations with intravascular ultrasound imaging have shown prominent dissections of the inner vascular layers that are often not detected by angiography. The purpose of this study was to test a new transballoon catheter ultrasonic imaging system capable of on-line direct visualization of lumen diameter and vessel wall structure for imaging before, during, and after dilation in an acute animal model of aortic coarctation. METHODS AND RESULTS: Abdominal aortic coarctations were created surgically in three 14-19-kg mongrel dogs by using Teflon gauze ties. The 6.8F ultrasound balloon catheter was placed percutaneously in the right femoral artery through a 9F sheath. Ultrasound imaging allowed measurement of the coarctation diameter, characterization of the vessel wall structure, localization of the stenosis, and placement of the midportion of the balloon at the narrowest area. Imaging through the balloon was performed through several dilations (five to eight per animal), and after balloon deflation, it provided information on postdilation diameter, intimal tears, long-segment dissections, and intramural thrombi, findings that were confirmed at postmortem examination. CONCLUSIONS: The results of this study demonstrate that imaging with a new intraballoon ultrasound device is feasible during inflation to therapeutic dilation pressures; it allows visualization of the changes in diameter and vascular wall structure after serial dilations without having to recross the obstructed area. Adaptation to larger balloon sizes and lower frequencies should make this system applicable to interventional catheterizations in patients with congenital cardiac and vascular lesions.

Animals↗
PubMed1992

Transesophageal echocardiography in infants and children with congenital heart disease.

TEE applications for children and infants with congenital heart disease are now clinically established and TEE is being used in most major pediatric cardiovascular centers. This technology has evolved to the point that it is capable of providing diagnostic quality imaging, even for small infants. With expanding technology and increasing experience, new and more sophisticated applications will be found for pediatric TEE.

Child↗
PubMed1992

Rat liver nodules induced by 2-acetylaminofluorene lose an ability to take up indocyanine green in the process of hepatocarcinogenesis.

Indocyanine green (ICG) was injected into rat liver nodules induced by 2-acetylaminofluorene (2-AAF) via portal vein. The relationship between ICG staining and cell atypism of liver nodules was examined by means of histology and DNA flow cytometry. After 2-AAF administration, many small nodules appeared on the liver surface. All hyperplastic nodules were ICG stained until 10 weeks after the administration, but some nodules were not stained after 14 weeks. ICG-stained nodules histologically consisted of benign tissues and borderline lesions, and many of them showed "diploidy" in DNA cytometry. ICG-unstained nodules consisted of hepatocellular carcinoma (HCCs) and borderline lesions, and many of them showed "aneuploidy". In this way, it has been suggested that HCC could derive from hyperplastic nodules and that they might lose an ability to take up ICG in the process of hepatocarcinogenesis. Immunohistochemical staining for glutathione-S-transferase alpha (GST-alpha), a carrier protein of ICG in hepatocytes, was well correlated with ICG staining in the nodules, suggesting that the loss of ICG uptake in HCC was partly due to the decrease of GST-alpha. Moreover, the appearance of ICG unstained and aneuploid nodules was significantly inhibited in rats which were fed on diet containing Syosaiko-to after the administration of 2-AAF. Chemopreventive effect of Syo-saiko-to on hepatocarcinogenesis was identified.

2-Acetylaminofluorene↗
PubMed1992

Prognostic assessment of fulminant hepatitis from indication criteria for liver transplantation.

The clinical outcome in 15 patients with fulminant hepatitis was predicted by the indication criteria for liver transplantation used in five different transplantation centers. Fifty-four to 100% of 13 fulminant hepatitis patients died who were fulfilled with these criteria for transplantation. Most of the patients died within five to nine days after the decision of liver transplantation was made. Takahashi's score of prognostic assessment for fulminant hepatitis decreased rapidly during the time when all the different criteria in transplantation centers were fulfilled. However, two survival cases with the acute type of fulminant hepatitis were incorrectly judged to be transplanted by the two criteria. The Cambridge's criterion for liver transplantation predicted the prognosis of fulminant hepatitis most correctly; sensitivity was 84.6% and specificity 100%.

Acute Disease↗
PubMed1992

Multiple organ failure in patients with fulminant hepatitis and in post-operative patients with liver cirrhosis.

Multiple organ failure (MOF) appeared during the course of nine cases with fulminant hepatitis, and it was compared with that of seven cirrhotic patients with post-operative hepatic failure. The number of organs failed was 4.9 and 3.6 on average in fulminant hepatitis and post-operative cirrhosis, respectively. All the patients died in less than nine days following the occurrence of MOF. Gastrointestinal bleeding was more frequently observed in fulminant hepatitis cases than in cirrhotic patients. In post-operative cirrhotics, hepatic failure occurred later and the elevation of serum total bilirubin was mild and slow. Renal failure and/or gastrointestinal bleeding was observed prior to death in fulminant hepatitis cases, and cardiac failure and hepatic failure in post-operative cirrhotics. These organ failures resulted in death, although extensive and multimodal treatments were carried out in both groups of patients.

Adult↗
PubMed1992

Cerebral edema during hepatic encephalopathy in fulminant hepatic failure.

Thirteen out of 18 patients with fulminant hepatitis developed cerebral edema macroscopically confirmed at autopsy. Cerebral bleeding and herniation were also observed in 38 and 8% of edema cases, respectively. No significant difference was found in the clinical backgrounds (age, sex, laboratory data) of patients with and without cerebral edema. Respiratory distress (100% of edema cases, p less than 0.05), abnormal pupils (89%, p less than 0.10), convulsions (61%) and tachycardia unrelated to fever (60%) were more frequently observed in cerebral edema cases than in those without edema. The frequency of convulsions increased as hepatic encephalopathy progressed, and the frequency of respiratory distress and abnormal pupils in edema cases was significantly higher at the coma grade V of hepatic encephalopathy. Tachycardia was detected early, even at the mild grades of hepatic encephalopathy. These results suggest that symptoms due to cerebral edema such as convulsions, abnormal pupils and respiratory distress should be distinguished from those due to hepatic encephalopathy in fulminant hepatitis patients.

Adult↗