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Biomedical subjects

Akira Furukawa

Publications and source records attributed to Akira Furukawa.

At least 19 recordsLinked to original sources
PubMed2007

Magnetic resonance voiding cystourethrography for vesicoureteral reflux.

PURPOSE: To assess the feasibility of magnetic resonance voiding cystourethrography (MRVCUG) using MR fluoroscopy for evaluation of vesicoureteral reflux (VUR), and its use as a noninvasive alternative to standard VCUG. MATERIALS AND METHODS: A total of 22 MR studies of 16 patients (five months to 41 years old) with primary VUR diagnosed by standard VCUG were evaluated. Six patients underwent MR studies and standard VCUG pre- and postoperatively. MR fluoroscopy was executed with a non-enhanced heavily T2-weighted single-shot fast spin-echo (FSE) sequence. The MR findings were correlated with those obtained by the gold standard, standard VCUG. RESULTS: Of the 44 kidney-ureter units, 20 were refluxing on MRVCUG and 21 were refluxing on standard VCUG. There were one false-positive and two false-negative units. MRVCUG was 90% sensitive with a specificity of 96% for detecting VURs that were calculated based on kidney-ureter units. Two false-negative units were found in mild cases (grade I and II). For the units of grade III, IV, and V (high-grade reflux), MRVCUG detected all of the refluxing renal collecting systems. CONCLUSION: MRVCUG can demonstrate high-grade reflux without ionizing radiation or catheterization.

Adolescent↗
PubMed2006

Violation of the incompressibility of liquid by simple shear flow.

In standard fluid dynamics, the density change associated with flow is often assumed to be negligible, implying that the fluid is incompressible. For example, this has been established for simple shear flows, where no pressure change is associated with flow: there is no volume deformation due to viscous stress and inertial effects can be neglected. Accordingly, any flow-induced instabilities (such as cavitation) are unexpected for simple shear flows. Here we demonstrate that the incompressibility condition can be violated even for simple shear flows, by taking into account the coupling between the flow and density fluctuations, which arises owing to the density dependence of the viscosity. We show that a liquid can become mechanically unstable above a critical shear rate that is given by the inverse of the derivative of viscosity with respect to pressure. Our model predicts that, for very viscous liquids, this shear-induced instability should occur at moderate shear rates that are experimentally accessible. Our results explain the unusual shear-induced instability observed in viscous lubricants, and may illuminate other poorly understood phenomena associated with mechanical instability of liquids at low Reynolds number; for example, shear-induced cavitation and bubble growth, and shear-banding of very viscous liquids such as metallic glasses and the Earth's mantle.

Journal Article↗
PubMed2006

Pluronic F127: application in arterial embolization.

PURPOSE: Pluronic is a substance that is widely used in medical and pharmaceutical fields. In particular, 20% Pluronic F127 solution is a unique substance that is liquid at less than 15 degrees C and gelatinous at 25 to 60 degrees C. In this study, the authors took advantage of the gelation property of Pluronic F127 at human body temperature to simulate embolization and dissolution of the embolism in the renal artery and the superior mesenteric artery (SMA) using a rabbit model. MATERIALS AND METHODS: Four female Japanese rabbits (weight, 2.5-3 kg each) were used. The renal artery was fitted with a 4-F cobra-type catheter and embolized with a 20% Pluronic F127 solution at a temperature of 20 degrees C. The embolic effect was evaluated by angiography immediately after the initial injection and every 15 minutes for 2.5 hours after embolization. After 24 hours, pathologic changes of the renal parenchyma were also evaluated. The embolic effect for SMA and ischemic changes of the intestine were evaluated in the same manner. RESULTS: Angiographic findings showed that Pluronic F127 caused embolization immediately after injection and dissolved in the renal artery and the SMA after 90 to 120 minutes. The pathologic findings showed no ischemic change in the renal parenchyma. Necrosis was not found in the intestine, but focal hemorrhagic changes were extensively present when the gel had dissolved. This suggested that Pluronic F127 dissolved before severe tissue damage could occur. CONCLUSION: Pluronic F127 can potentially be used as a temporary embolic material.

Angiography↗
PubMed2005

Analysis of interaction between DNA and Deinococcus radiodurans PprA protein by atomic force microscopy.

A DNA repair-promoting protein, PprA, was isolated from a radiation resistant bacterium, Deinococcus radiodurans [I. Narumi, K. Sato, S. Cui, T. Funayama, S. Kitayama, H. Watanabe, PprA: a novel protein from Deinococcus radiodurans that stimulates DNA ligation, Mol. Microbiol. 54 (2004) 278-285]. Despite several studies, however, the function of PprA is not still clear. We used atomic force microscopy (AFM) to elucidate the role of this protein in the DNA repair pathway. In the present study, interaction between the linear DNA and PprA protein was imaged and analyzed by AFM without any fixation or staining. Though both end-bound and internally bound PprA was observed, the affinity of the end-bound protein was greater considering the proportion of features of binding analyzed by AFM. In some conditions, looping forms of the DNA-PprA complex were observed. Gel filtration high performance liquid chromatography (HPLC) was also conducted to estimate the molecular weight of this protein. The result of the HPLC analysis suggested that PprA formed multimers in buffer solution without DNA.

Bacterial Proteins↗
PubMed2005

Budd-Chiari syndrome: a case with a combination of hepatic vein and superior vena cava occlusion.

We here report a recent, rare case of Budd-Chiari syndrome, associated with a combination of hepatic vein and superior vena cava occlusion. A young female, who had been in good health, was admitted to our hospital because of massive ascites. The patient had used no oral contraceptives. Tests for coagulation disorders, hematological disorders, and antiphospholipid syndrome were all negative. Budd-Chiari syndrome was diagnosed by radiographic examination. The patient was suffering from a combination of hepatic vein and superior vena cava occlusion. In particular, the venous flow returned from the liver mainly through a right accessory hepatic vein, and stenosis was recognized at the orifice of this collateral vein into the vena cava. Subsequently, the patient underwent percutaneous balloon dilatation therapy for this stenosis. After this treatment, the massive ascites was gradually reduced, and she was discharged from our hospital. It has now been one year since discharge, and the patient has been doing well. If deteriorating liver function or intractable ascites occur again, a liver transplantation may be anticipated. This is the first case report of Budd-Chiari syndrome associated with a superior vena cava occlusion.

Adult↗
PubMed2005

MR imaging of the normal appendix and acute appendicitis.

PURPOSE: To describe the MR appearance of the normal appendix and the MR imaging characteristics of acute appendicitis with correlation to pathological severity. MATERIALS AND METHODS: A total of 20 volunteers participated in this study to demonstrate normal appendices by MR imaging. A total of 37 consecutive patients with clinically diagnosed acute appendicitis were also scanned. T1-weighted (T1WI) spin-echo images, T2-weighted (T2WI) fast spin-echo, and fat-suppressed spectral presaturation inversion recovery T2-weighted (T2SPIR) fast spin-echo images were obtained. The MR criteria for considering acute appendicitis were as follows: 1) thickening of the appendiceal wall with high intensity on T2WI or T2SPIR; 2) dilated lumen filled with high intensity material on T2WI or T2SPIR; and 3) increased intensity of periappendiceal tissue on T2WI or T2SPIR. RESULTS: The visibility of a normal appendix on MR imaging was 90% (18/20). It appeared as a cord-like structure of medium intensity without fluid collection in the lumen. A total of 30 cases with clinically diagnosed acute appendicitis had positive MR findings and all except one were pathologically proven. The one had cecal diverticulitis. These cases demonstrated filled lumen, with a hypointense wall on T1WI and slightly hyperintense on T2WI or T2SPIR. MR findings correlated well with pathological severity, especially a thicker wall, periappendiceal high intensity, and ascites were useful for suspecting severe appendicitis. CONCLUSION: Correct diagnosis of acute appendicitis was obtained with MRI, and correlated well with its pathological severity. MRI is a powerful alternative for diagnosing acute appendicitis especially for the patients in whom the radiation is major concern.

Acute Disease↗
PubMed2005

Percutaneous transluminal angioplasty for Brescia-Cimino hemodialysis fistula dysfunction: technical success rate, patency rate and factors that influence the results.

OBJECTIVE: To evaluate the initial clinical success and long-term patency rates of percutaneous transluminal angioplasty (PTA) using a venous approach for dysfunctional Brescia-Cimino fistula and to identify factors that may affect initial success and long-term patency. MATERIALS AND METHODS: A total of 99 PTA procedures were performed in retrograde fassion for 60 mature Brescia-Cimino shunts with dysfunction caused by anastomotic or peripheral outflow vein stenosis or occlusion. The initial clinical success rates were compared between stenosis and occlusion using Fisher's exact test. The Kaplan-Meier method was used to calculate the primary and secondary cumulative patency rates, and the log-rank test was used for comparison. Relative risks of patency loss according to clinical characteristics were determined with multivariate Cox models. RESULTS: The initial clinical success rate of all interventions was 92%, and the rates for stenosis and occlusion were 99 and 65%, respectively (P < 0.0001). The primary and secondary cumulative patency rates for fistulas (excluding initial failure) at 12 months were 53 and 84%, respectively. The relative risks were 5.2 (P = 0.004) for longer lesions and 4.5 (P = 0.007) for younger fistulas. The primary cumulative patency rate of four patients with a younger fistula and a longer stenosis at 4 months was 0%. CONCLUSION: Favorable primary and secondary cumulative patency rates are obtained in most patients. Long lesion length and younger age of fistulas were the two factors that reduced the patency rate after PTA.

Adult↗
PubMed2005

The first trial of phase contrast imaging for digital full-field mammography using a practical molybdenum x-ray tube.

RATIONALE AND OBJECTIVES: The image quality of a newly developed full-field digital phase contrast mammography (PCM) system and of a conventional screen-film (SF) mammography system were compared via images of a phantom and receiver operating characteristic (ROC) analysis of clinical images. METHODS: Magnified (1.75X) PCM images were scanned (sampling rate, 43.75 microm) and then reduced to original-sized, 25-micron pixel images printed on photothermographic film. Along with corresponding SF images, the phantom images were evaluated subjectively, and the clinical images of 38 patients were subjected to ROC analysis of mass and microcalcification. RESULTS: In the image quality of a phantom, the PCM exceeded the SF. In both mass and microcalcification, the ROC analysis Az values of the PCM clinical images surpassed those of the SF images. CONCLUSION: The PCM provides better images than the SF. Clinical trials suggest superior detection of both mass and microcalcification by full-field digital PCM over conventional SF mammography.

Breast Diseases↗
PubMed2004

Viscoelastic phase separation in shear flow.

We numerically investigate viscoelastic phase separation in polymer solutions under shear using a time-dependent Ginzburg-Landau model. The gross variables in our model are the polymer volume fraction and a conformation tensor. The latter represents chain deformations and relaxes slowly on the rheological time giving rise to a large viscoelastic stress. The polymer and the solvent obey two-fluid dynamics in which the viscoelastic stress acts asymmetrically on the polymer and, as a result, the stress and the diffusion are dynamically coupled. Below the coexistence curve, interfaces appear with increasing the quench depth and the solvent regions act as a lubricant. In these cases the composition heterogeneity causes more enhanced viscoelastic heterogeneity and the macroscopic stress is decreased at fixed applied shear rate. We find steady two-phase states composed of the polymer-rich and solvent-rich regions, where the characteristic domain size is inversely proportional to the average shear stress for various shear rates. The deviatoric stress components exhibit large temporal fluctuations. The normal stress difference can take negative values transiently at weak shear.

Journal Article↗
PubMed2004

Microrheology of entangled polymer solutions.

Microrheology of semidilute polymer solutions is investigated. In this paper we calculate a response function of a probe particle embedded in a semidilute polymer solution by analyzing the two-fluid model. We find that when the size of the probe particle is comparable to the viscoelastic length, the response from the longitudinal compression modes becomes more important than that of the transverse shear modes. As a result, depending on the circumstances, the obtained complex shear modulus cannot be well approximated by that measured in macroscopic rheology experiments. The present results are due to the dynamical asymmetry coupling and the existence of the cooperative dynamics, which are intrinsic to entangled polymer solutions.

Journal Article↗
PubMed2004

Role of combined CT hepatic angiography and CT during arterial portography in the management of patients with hepatocellular carcinomas and liver metastases.

The purpose of this study was to evaluate the role of combined CT hepatic angiography (CTHA) and CT during arterial portography (CTAP) in the diagnosis and management of patients with hepatocellular carcinomas (HCC) and liver metastases. Fifty patients with HCC and 19 patients with liver metastases were referred for CTHA and CTAP prior to surgery or interventional therapy. Diagnosis was established by either surgery or clinical observation. Alterations of diagnosis and management resulting from CTHA and CTAP information were recorded. In patients with HCC, diagnosis was altered either by number, location or extent of lesions in 46% of patients and was 78% correct. Alterations of management were performed in 32% of the patients in total, and were correct in all but one. In patients with liver metastases, diagnosis was altered regarding either number, location or extent of lesions in 21% of patients and were 50% correct. Management was not altered after CTHA and CTAP in the patients with liver metastases. We conclude that CTHA and CTAP provide valuable clinical information for patients with HCC and significantly corrected their previous diagnosis and plans of management. CTHA and CTAP should be performed in patients with HCC when either surgical or interventional therapy is the treatment option.

Journal Article↗
PubMed2003

CT diagnosis of small bowel obstruction: scanning technique, interpretation and role in the diagnosis.

Intestinal obstruction is a relatively common condition with diagnosis based on the clinical signs, patient history, and radiographical findings. Once suspected, its presence should be determined and if present, the site and cause of obstruction, and presence of strangulation should be assessed for the appropriate patient management. With the recent technological developments, the role of computed tomography (CT) in the diagnosis of bowel obstruction has expanded. The examination should be performed with intravenous contrast administration and thinner sections and multi-planner image reformation are recommended to evaluate a site of particular interest. CT is reported to have a sensitivity refer to detection of a small bowel obstruction at over 90% for complete or high-grade obstruction and to disclose causes of obstruction in 70% to 95% of cases. CT also provides characteristic findings indicating the presence of closed-loop obstruction and intestinal ischemia, which leads to appropriate and timely management for these emergent cases.

Diagnosis, Differential↗
PubMed2003

Estimation of cerebral perfusion reserve by blood oxygenation level-dependent imaging: comparison with single-photon emission computed tomography.

Measurement of cerebrovascular reserve capacity predicts the risk of ischemic insult in patients with major vessel occlusion. Blood oxygenation level-dependent (BOLD) imaging has the potential to estimate reserve capacity of the cerebral circulation noninvasively based on changes in the signal that reflect differences in the magnetic susceptibility of intravascular oxyhemoglobin and deoxyhemoglobin. The authors examined the feasibility of using the BOLD technique to assess cerebrovascular reserve capacity in patients with cerebrovascular occlusive disease by comparing results with an established method of measuring CBF. Ten patients with severe or complete occlusion of the internal carotid artery were compared with 17 healthy subjects to evaluate regional differences and identify variables that indicate a change in the BOLD signal. Dilation of cerebral vessels was induced by breath holding, and the R2* change was examined with gradient-echo, echo-planar imaging. Before measuring the regional change in the BOLD signal, actual timing of "activated" and "rest" periods was corrected by shifting the phase of a sine-wave template to obtain the largest correlation coefficient. Percent signal change was calculated on a pixel-by-pixel basis and was compared with CBF measured by single-photon emission computed tomography (SPECT) before and after acetazolamide challenge. The degree of impairment and the distribution of impaired areas detected by the BOLD study correlated with the results of SPECT. Overall sensitivity and specificity of the BOLD technique by visual inspection were 100% and 98.4%, respectively. A negative response (decreased CBF) frequently was observed in areas of exhausted reserve capacity, suggesting that a "steal" phenomenon exists. The percent change and the (Delta)CBF were well correlated (P < 0.01). The mean percent change in most areas of impaired reserve capacity was more than 2 SD below the mean values in healthy subjects. The present method of semiquantitative BOLD analysis can be used to create a map of the cerebral hemodynamic state. Furthermore, the development of reliable, generally accessible techniques for evaluating cerebral hemodynamics opens the door for clinical studies to monitor and treat patients with compromised reserve. This study is an attempt to develop such analysis.

Acetazolamide↗
PubMed2003

[Urinary continence after radical retropubic prostatectomy: a modification in the technique of apical dissection].

Urinary incontinence impairs the quality of life for patients following radical prostatectomy. We retrospectively reviewed the records of 36 patients who underwent radical retropubic prostatectomy between 1987 and 2002, and achieved the time from operation until urinary continence. A modification in the technique of apical dissection was introduced in 1999 and applied in 12 cases of consecutive radical prostatectomy. The principles for this technique were based on sharp division of the dorsal vein complex, continuous suturing cut edges of lateral pelvic fascia, and anterior anastomotic sutures including lateral pelvic fascia as well as urethra and bladder neck. None of the patients undergoing the new technique used pads at 6 months. With introduction of this technique, the rate of continence at 12 months increased from 58.3 to 100.0%. Our results suggest that the surgical technique of apical dissection is an important factor associated with postprostatectomy in continence.

Aged↗
PubMed2002

Convective heat transport in compressible fluids.

We present hydrodynamic equations of compressible fluids in gravity as a generalization of those in the Boussinesq approximation used for nearly incompressible fluids. They account for adiabatic processes taking place throughout the cell (the piston effect) and those taking place within plumes (the adiabatic temperature gradient effect). Performing two-dimensional numerical analysis, we reveal some unique features of plume generation and convection in transient and steady states of compressible fluids. As the critical point is approached, the overall temperature changes induced by plume arrivals at the boundary walls are amplified, giving rise to overshoot behavior in transient states and significant noise in the temperature in steady states. The velocity field is suggested to assume a logarithmic profile within boundary layers. Random reversal of macroscopic shear flow is examined in a cell with unit aspect ratio. We also present a simple scaling theory for moderate Rayleigh numbers.

Journal Article↗
PubMed2002

Fenestrated stent-graft for traumatic juxtahepatic inferior vena cava injury.

PURPOSE: To report the use of a fenestrated stent-graft to manage a traumatic rupture of the juxtahepatic inferior vena cava (IVC). CASE REPORT: A 62-year-old man was involved in a traffic accident and hospitalized for severe right leg fractures. Computed tomography also uncovered liver contusion and retroperitoneal hematoma. The next day, he became hemodynamically unstable; a huge retroperitoneal hematoma had developed from a rupture of the juxtahepatic IVC. An emergent procedure to implant a self-expanding fenestrated stent-graft was successful in repairing the IVC injury and maintaining hepatic venous return. The patient recovered and continues in good health with a patent endograft 16 months after treatment. CONCLUSIONS: This experience supports the efficacy of fenestrated endograft implantation for emergent repair of IVC injuries, although proper facilities, an experienced interventional team, and an assortment of devices must be available.

Accidents, Traffic↗
PubMedDate not supplied

Neoadjuvant intra-arterial chemotherapy for locally advanced uterine cervical cancer: clinical efficacy and factors influencing response.

PURPOSE: To evaluate the effects of neoadjuvant intra-arterial chemotherapy (NAIC) for locally advanced uterine cervical cancer, and to analyze factors influencing the response to the chemotherapy. METHODS: Thirty-four patients with invasive cervical cancer more than 4 cm in diameter were enrolled in this study. NAIC was performed using cisplatin-based regimens. The response was assessed by magnetic resonance imaging (MRI) and examination of surgical specimens. Pretreatment factors involved in the response to NAIC were evaluated and the relationship between the factors and the prognosis was assessed. RESULTS: Clinical response was achieved in 28 (82%) patients. Thirty-one of 49 invasions in the parametrial halves disappeared. Seventeen of 28 lymph node swellings responded to NAIC. Six of the 14 stage III patients became operable. In the 19 surgical cases, pathologically complete responses were found in four. Twenty-eight of the 38 parametrial halves were free from cancer. No lymph node metastases were found in eight patients. Initial tumor volume was found to be an independent, significant determining factor of the response to NAIC. Patients with initial tumor volumes less than 80 cm3 had a significantly better estimated 5-year disease-free survival rate compared with those with larger tumors. CONCLUSION: NAIC for locally advanced cervical cancer is useful for preoperative tumor reduction. Tumor volume is a significant determining factor for the response to NAIC.

Adenocarcinoma↗