Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.17106/jbr.37.44

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.17106/jbr.37.64

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

in press

DOI： 10.11239/jsmbe.60.149

CiNii Books

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Other Link： https://search.jamas.or.jp/link/ui/2023127141

Language：English   Publishing type：Research paper (scientific journal)  

There are no small-diameter, long artificial vascular grafts for below-knee bypass surgery in chronic limb-threatening ischemia. We have developed tissue-engineered vascular grafts called "Biotubes®" using a completely autologous approach called in-body tissue architecture (iBTA). This study aimed at pre-implantation evaluation of Biotube and its in vivo preparation device, Biotube Maker, for use in below-knee bypass surgery. Forty nine makers were subcutaneously embedded into 17 goats for predetermined periods (1, 2, or 3 months). All makers produced Biotubes as designed without inflammation over all periods, with the exception of a few cases with minor defects (success rate: 94%). Small hole formation occurred in only a few cases. All Biotubes obtained had an inner diameter of 4 mm and a length of 51 to 52 cm with a wall thickness of 594 ± 97 μm. All Biotubes did not kink when completely bent under an internal pressure of 100 mmHg and did not leak without any deformation under a water pressure of 200 mmHg. Their burst strength was 2409 ± 473 mmHg, and suture retention strength was 1.75 ± 0.27 N, regardless of the embedding period, whereas tensile strength increased from 7.5 ± 1.3 N at 1 month to 9.7 ± 2.0 N at 3 months with the embedding period. The amount of water leakage from the needle holes prepared in the Biotube wall was approximately 1/7th of that in expanded polytetrafluoroethylene vascular grafts. The Biotubes could be easily connected to each other without cutting or anastomosis leaks. They could be stored for at least 1 year at room temperature. This study confirmed that even Biotubes formed 1 month after embedding of Biotube Makers had properties comparable to arteries.

DOI： 10.1002/jbm.b.35084

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

Objective: There is a need for small diameter vascular substitutes in the absence of available autologous material. A small diameter, long tissue engineered vascular graft was developed using a completely autologous approach called "in body tissue architecture technology (iBTA)". The aim of this pilot study was to evaluate "Biotubes", iBTA induced autologous collagenous tubes, for their potential use as small diameter vascular bypass conduits. Methods: Biotubes (internal diameter 4 mm, length 50 cm, wall thickness 0.85 mm) were prepared by subcutaneous embedding of plastic moulds (Biotube Maker) in three goats for approximately two months. Allogenic Biotubes (length 10 cm [n = 2], 15 cm [n = 2], 22 cm [n = 2]) were bypassed to both carotid arteries by end to side anastomosis with their ligation between the anastomoses in another three goats. Residual Biotubes were examined for their mechanical properties. After four weeks, the harvested Biotubes were evaluated histologically. Results: All Biotubes had sufficient pressure resistance, approximately 3000 mmHg. Although wall thickening occurred at two proximal anastomosis sites, all six grafts were patent without luminal thrombus formation, stenosis, or aneurysm deformation throughout the implantation period. Endothelial cells covered both anastomosis sites almost completely, with partial covering in the central portion of the grafts. Furthermore, α smooth muscle actin positive cells infiltrated the middle layer along almost the entire graft length. Conclusion: This preliminary study showed that small diameter, long, tissue engineered Biotubes could function properly as arterial bypass conduits in a large animal for one month without any abnormal change in vascular shape. Thus, small diameter, long Biotubes are potentially viable conduits, which are biocompatible and labour non-intensive, and therefore, suitable for clinical practice. Additionally, Biotubes can start the regeneration process in a short period of time.

DOI： 10.1016/j.ejvsvf.2022.01.004

PubMed

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Authorship：Corresponding author   Language：English   Publisher：Japanese Society for Medical and Biological Engineering  

In our previous study, we developed heart valve-like tissue (Biovalve), which was fabricated by employing the technique of in-body tissue architecture (iBTA). We fabricated Biovalve so that it can closely mimic the functionalities of the native mitral valve, papillary muscles, and chordae tendineae. However, owing to its complex structure, Biovalve has not yet been implemented. Hence, the objective of this study is to develop a novel artificial atrioventricular valve by incorporating a sheet of autologous tissue (Biosheet) through iBTA. Since a period of approximately two months is required for obtaining Biosheet, it is unsuited for developing the aforementioned artificial valve. Hence, we fabricated an experimental model by employing a polyurethane sheet, which has comparable mechanical properties as Biosheet. To validate the experimental model, the valve functions of the actual model and experimental model were compared by using Biosheet and the polyurethane sheet, respectively. Furthermore, to determine the optimal shape of the valve cusps, the amount of sheet overhanging from the stent, sheet suture angle, and sheet thickness were varied as experimental parameters. A model of the valve cusps with mechanical anisotropy was fabricated by sandwiching Ni-Ti alloy wires between two polyurethane sheets and thermally welding them. Subsequently, an isotropic model and the fabricated anisotropic model were compared. The experiment was conducted by incorporating our fabricated <i>in-vitro</i> simulator under the physiological conditions of a healthy adult human. The valve function was evaluated on the basis of the ISO 5840-1 and ISO 5840-2 international standards for artificial valves. The obtained results indicate that the valve functions of the actual model and experimental model are nearly identical, which confirms the validity of the experimental model. Furthermore, in the case of the anisotropic model, it is found that when the sheet thickness is 200µm, sheet overhang is 3mm, and suture angle is 0 deg. , the pressure drop reduces by approximately 25%and the regurgitant fraction decreases by approximately 90%, as compared to the isotropic model of the same shape. These results suggest that anisotropic valve cusps can improve both valve opening and closing functionalities.

DOI： 10.11239/jsmbe.59.146

CiNii Books

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Other Link： http://id.ndl.go.jp/bib/031983181

Publishing type：Research paper (scientific journal)  

DOI： 10.3390/kidneydial1010002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

BACKGROUND: Pancreatic juice reflux to the common bile duct and gallbladder is observed in the pancreaticobiliary maljunction (PBM), and various pathological conditions occur in the biliary tract. However, the mechanism of pancreatic juice reflux has not been discussed yet. This study aimed to investigate the mechanism of this phenomenon from the perspective of the fluid dynamics theory. METHODS: A fluid dynamics model of PBM without biliary dilatation having gallbladder function and of the pressure of sphincter of Oddi was developed. Water (as bile juice and pancreatic juice) was flowed to these models with a flow rate similar to that in humans. Pancreatic and bile juice flow and bile duct pressure were observed in three phases of gallbladder function. Moreover, the same experiment was performed in the PBM without biliary dilatation model without gallbladder. RESULTS: Pancreatic juice reflux could be observed when the gallbladder was passively expanded with the pressure in the bile duct lower than that in the sphincter of Oddi. However, pancreatic juice reflux was not observed in the model without gallbladder. CONCLUSIONS: Gallbladder function may be strongly involved in pancreatic juice reflux in PBM without biliary dilatation. Cholecystectomy may be able to stop the reflux of pancreatic juice.

DOI： 10.1002/jhbp.714

PubMed

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/jhbp.714

Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Biorheology  

DOI： 10.17106/jbr.34.47

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.17106/jbr.32.20

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

The treatment of large or wide-necked cerebral aneurysms is extremely difficult, and carries a high risk of rupture, even when surgical or endovascular methods are available. We are developing novel honeycomb microporous covered stents for treating such aneurysms. In this study, 3 experimental animal models were designed and evaluated quantitatively before preclinical study. The stents were prepared using specially designed balloon-expandable stents (diameter 3.5-5.0 mm, length 16-28 mm) by dip-coating to completely cover their struts with polyurethane film (thickness 20 mu m) and microprocessing to form the honeycomb pattern after expansion. (1) In an internal carotid artery canine model (n = 4), all stents mounted on the delivery catheter passed smoothly through the tortuous vessel with minimal arterial damage. (2) In an the large, wide-necked, outer-side-wall aneurysm canine model, almost all parts of the aneurysms had embolized immediately after stenting (n = 4), and histological examination at 2 months revealed neointimal formation with complete endothelialization at all stented segments and entirely organized aneurysms. (3) In a perforating artery rabbit model, all lumbar arteries remained patent (n = 3), with minimal change in the vascular flow pattern for over 1 year, even after placement of a second, overlapping stent (n = 3). At 2 months after stenting, the luminal surface was covered with complete thin neointimal formation. Excellent embolization performance of the honeycomb microporous covered stents without disturbing branching flow was confirmed at the aneurysms in this proof-of-concept study.

DOI： 10.1007/s10047-015-0879-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Objectives: To evaluate the functionality of an autologous heart valve with stent (Stent-biovalve or SBV) after implantation in the pulmonic valve position in beagle dogs.
Animals: Five beagle dogs.
Methods: A mold with an aperture of a tri-leaflet structure was constructed from a pair of concave and convex rods to which a nitinol (NiTi) stent was mounted. This mold was embedded in a dorsal subcutaneous pouch in beagle dogs for 4 weeks. At the time of the removal, the surfaces of the molds were completely covered with connective tissues, tri-leaflet valves were formed and the NiTi stent was tightly connected to the structure.
Results: The mean burst strength of the SBV leaflet was 2710 mmHg (range 2280-3116 mmHg), which was approximately equal to that of the native pulimonic valve leaflet. After implantation in the pulmonary position, the SBV showed good functionality as a pulmonic valve. At 84 days after implantation, the SBV was replaced with autologous fibroblasts and collagenous tissues, and showed organization similar to that of native heart valves.
Conclusion: Stent-Biovalves achieved good valvular function with laminar flow in the pulmonic valve position of beagle dogs. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jvc.2014.12.003

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Authorship：Corresponding author   Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

An erythrocyte can be deformed very easily by even very small amounts of stress, enabling it to flow smoothly through approximately 3 µm diameter microvessels despite its larger size of 8 µm in diameter and 2 µm in thickness. Reduction of erythrocyte deformability leads to poor circulation particularly in microvessels, which may result in hypertension and various circulatory diseases. To clarify blood microcirculatory properties, it is very important to understand the deformability of erythrocytes. However, a standard method for quantitative evaluation of erythrocyte deformability has not yet been established. In this study, an apparent Young's modulus and a time constant for the recovery of erythrocyte shape following uniaxial stretching are proposed as deformability indices. When an erythrocyte was pulled horizontally on opposite ends using two micropipettes, tensile stress and strain were measured, and an apparent Young's modulus was calculated based on Hooke's law. On returning to its initial shape after the erythrocyte was released from stretching, the elapsed time and strain were measured, and a time constant for shape recovery was calculated based on the Kelvin model. The average apparent Young's modulus was 16.0Pa, and the average time constant was 113.4ms, with a slight tendency toward an inverse relation between the two physical quantities.

DOI： 10.11239/jsmbe.53.1

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Other Link： http://hdl.handle.net/10112/8962

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

In-body tissue architecturea novel and practical regeneration medicine technologycan be used to prepare a completely autologous heart valve, based on the shape of a mold. In this study, a three-dimensional (3D) printer was used to produce the molds. A 3D printer can easily reproduce the 3D-shape and size of native heart valves within several processing hours. For a tri-leaflet, valved conduit with a sinus of Valsalva (Biovalve type VII), the mold was assembled using two conduit parts and three sinus parts produced by the 3D printer. Biovalves were generated from completely autologous connective tissue, containing collagen and fibroblasts, within 2 months following the subcutaneous embedding of the molds (success rate, 27/30). In vitro evaluation, using a pulsatile circulation circuit, showed excellent valvular function with a durability of at least 10 days. Interposed between two expanded polytetrafluoroethylene grafts, the Biovalves (N=3) were implanted in goats through an apico-aortic bypass procedure. Postoperative echocardiography showed smooth movement of the leaflets with minimal regurgitation under systemic circulation. After 1 month of implantation, smooth white leaflets were observed with minimal thrombus formation. Functional, autologous, 3D-shaped heart valves with clinical application potential were formed following in-body embedding of specially designed molds that were created within several hours by 3D printer. (c) 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1-11, 2015.

DOI： 10.1002/jbm.b.33186

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publisher：The Visualization Society of Japan  

Erythrocyte is the major cellular component in human blood. Its deformability affects the hemo-dynamical performance in microcirculation. So measurement and evaluation of its deformability is really important to understand and diagnose microangiopathy. The author tried to evaluate the deformability of each erythrocyte by measuring the time constant of shape recovery just after the erythrocyte left the micro-channels under the micro visualization. The artificially stiffer the cell membrane and thinner hemoglobin solution was using glutaraldehyde and hypotonic saline solution, the shorter the time constant for relaxation became compared to healthy erythrocytes.. And the time constant distribution of each donor showed the lognormal distribution. These result indicates that the shape recovery process is able to be modeled by the Kelvin model and the deformability of individual erythrocytes can be quantitated by the time constant for relaxation measured by this techniques. Finally, this paper introduce the relationship between the time constant and blood test results of various diabetic subject.

DOI： 10.3154/jvs.34.134_16

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Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

An “active” ultra sound Doppler (USD) method was newly developed for the direct, easy and quantitative discrimination of emboli from micro bubbles in blood flow. This method is based on the measurement of the sound axial velocity of the two induced by using acoustic radiation force of ultra sound wave. This force depends on the difference of characteristic acoustic impedances between ambient fluid and emboli or micro bubbles. In the case of a micro bubble, the change of the moving velocity is larger because of a much larger difference between the characteristic acoustic impedances of the two. In order to prove the availability of active USD method, an <i>in-vitro</i> experiment on discrimination of emboli from micro bubbles was performed in a flow modeled after human's middle cerebral arterial flow. As model emboli, blood clot and alginate gel particle were used, and as working fluid, calcium chlorite aqueous solution and bovine blood. In the experiment, model emboli and micro bubbles were irradiated from the downstream side by ultra sound wave from commercial ultrasound diagnostic equipment being used at clinical sites. It was found that there were obvious differences of moving acceleration in the sound axial direction between micro bubbles and model emboli in the modeled blood flow which was caused by the acoustic radiation force, and that this “active” USD method had high availability for a medical diagnosis system to directly, easily and quantitatively discriminate emboli from micro bubbles flowing in human vessel.

DOI： 10.11239/jsmbe.51.397

CiNii Books

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Other Link： http://id.ndl.go.jp/bib/025346140

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/bioengineering11060598

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese   Publisher：一般社団法人 日本人工臓器学会  

DOI： 10.11392/jsao.52.189

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Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

In recent years, the number of hemodialysis patients is increasing due to population aging and lifestyle-related diseases, and hemodialysis lowers patients’ quality of life. The technique of hemodialysis was developed based on hemolysis, and it is thought that hemolysis in hemodialysis is induced during discharge by the peristaltic pump. However, studies have not investigated in detail whether hemolysis is instantaneously induced either by the pump or the accumulation of mechanical damage to erythrocytes. In this study, the deformability and degree of hemolysis of erythrocytes in extracorporeal circulation during hemodialysis were measured quantitatively, based on the mechanics of an in vitro model experiment using commercially available blood. In this experiment, the influence of drug administration to patients could be ignored. In the experiment, blood was circulated in a hemodialysis circuit model in which the parameters of flow rate and circulation time were set with reference to hemodialysis conditions in clinical settings. Blood for measurement was sampled from the circuit. The deformability of the sampled erythrocytes was evaluated based on the time constant of shape recovery, which was measured using two methods;the micro-channel and uni-axial stretching methods. Hemolysis was quantified based on absorbance measured using a spectrometer. The results showed that the deformability of erythrocytes remained nearly unchanged over time of hemodialysis when measured by both methods, whereas hemolysis increased in all conditions. These findings indicate that hemolysis is induced instantaneously by the peristaltic pump in the hemodialysis system.

DOI： 10.11239/jsmbe.58.230

CiNii Books

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Other Link： http://id.ndl.go.jp/bib/031339462

Publishing type：Research paper (scientific journal)  

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Language：English  

DOI： 10.5963/BER0203002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER JAPAN KK  

Using simple, safe, and economical in-body tissue engineering, autologous valved conduits (biovalves) with the sinus of Valsalva and without any artificial support materials were developed in animal recipients' bodies. In this study, the feasibility of the biovalve as an aortic valve was evaluated in a goat model. Biovalves were prepared by 2-month embedding of the molds, assembled using two types of specially designed plastic rods, in the dorsal subcutaneous spaces of goats. One rod had three projections, resembling the protrusions of the sinus of Valsalva. Completely autologous connective tissue biovalves (type VI) with three leaflets in the inner side of the conduit with the sinus of Valsalva were obtained after removing the molds from both terminals of the harvested implants with complete encapsulation. The biovalve leaflets had appropriate strength and elastic characteristics similar to those of native aortic valves; thus, a robust conduit was formed. Tight valvular coaptation and a sufficient open orifice area were observed in vitro. Biovalves (n = 3) were implanted in the specially designed apico-aortic bypass for 2 months as a pilot study. Postoperative echocardiography showed smooth movement of the leaflets with little regurgitation under systemic circulation (2.6 +/- A 1.1 l/min). alpha-SMA-positive cells appeared significantly with rich angiogenesis in the conduit and expanded toward the leaflet tip. At the sinus portions, marked elastic fibers were formed. The luminal surface was covered with thin pseudointima without thrombus formation. Completely autologous biovalves with robust and elastic characteristics satisfied the higher requirements of the systemic circulation in goats for 2 months with the potential for valvular tissue regeneration.

DOI： 10.1007/s10047-012-0679-8

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The authors have been developing a microporous covered stent as a newly device for cerebral aneurysm treatment. This stent has a porous film to control both embolization and rapid neointimal formation. According to previous study, it is expected that the neointimal formation becomes earlier by using much larger pores. But there is a possibility that the covered stent with large pare cannot embolize by increasing inflow from the parent vessel. The purpose of this study is estimation of stent embolization and optimization of pore design to ensure compatibility between reliable embolization and controlling early neointimal formation, in-vitro experiment under the steady flow condition based on flow similarity law has been conducted by using a two dimensional parent vessel model with a saccular aneurysm model and simplified micro-porous film models. The PIV results show that mean shear rate in the aneurysm model after stenting, of which pore diameter is &lt
300μm and porosity is 60%, was decreased to less than 1/10 of before stenting. According to flow visualization, it is considered that viscous shear force caused by shear flow in the vicinity of the parent vessel wall drives the blood in the aneurysm cavity passing through the micro-pores on the film. As the result of the driving force estimating, it is suggested that ratio of the viscous shear force to rotational moment of the blood in the aneurysm cavity is one of the important hydrodynamical parameter to estimate the flow pattern in aneurysm and the stent embolization. © 2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaib.79.992

Scopus

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Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-25670628/

Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

Pathology of aortic valve sclerosis is very similar to that of atherosclerosis and it seems to be one of inflammatory changes caused by damage to endothelium of the aortic valve. However, stress factors of the damage have not been clarified yet. This study focused on both aging and hypertension as the highest risk factor of the valve sclerosis and supposed that local mechanical strain on the valvular surface occurred by valve opening and closing behavior with heartbeat is one of the mechanical trigger for inflammatory. So, in order to clarify the pathogenic mechanism, in vitro experiment using a realistic aortic valve model and a cardiovascular flow simulator was conducted and spatial-temporal distribution of the strain on the leaflet was measured by 3D shape measuring technique. As the result, the areas at the centre of the leaflet and the boundary between the leaflet and Valsalva sinus strained locally much larger than the other area during diastole. And tensile strain on the whole leaflet enlarged with increasing pressure load on the valve. On the other hand, the areas in the vicinity of the boundary with the sinus including valve commissures were bent locally during systole and then the bending strain at the area was almost constant. These results indicated that either tensile strain or bending strain is continuously occurred on the valvular surface during a cardiac period. And these high strain areas on the leaflet model were very similar to the place where lipid deposition as a stage prior to sclerosis by the hyper-cholesterol loaded animal experiment using a rabbit of the normal blood pressure. Therefore, this result suggests the local high strain is one of the important mechanical stress for the valve sclerosis occurring.

DOI： 10.11239/jsmbe.51.52

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Other Link： http://search.jamas.or.jp/link/ui/2013308582

Publisher：循環器病研究の進歩  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s12573-012-0052-9

DOI： 10.1007/s12573-012-0054-7

Scopus

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI PUBLISHING CORPORATION  

A miniaturized fiber-optic laser Doppler velocimetry sensor has been developed to measure the local blood velocity in vivo. The laser beam emitted from the sensor tip can be focused at any distance between 0.1 and 0.5mm from the tip. Consequently, the sensor has a sufficiently high signal-to-noise ratio to measure the local velocity in almost any opaque fluid, including blood. The sensor head is inserted in an injection needle or a catheter tube. In the former case, it is inserted at an angle to the wall of a vessel and is scanned across the vessel to measure the velocity distribution. In the latter case, it is aligned parallel with the flow in a vessel. For all flows of whole human blood, whole caprine blood, and 69% hematocrit of bovine blood, the velocity distribution across the vessel could be measured very accurately. The insertion angle of the fiber into the flow significantly affects the measurement accuracy; an angle of about 50. is suitable when an injection needle is used. When a catheter is employed, an insertion direction opposite to the flow direction is better than parallel to the flow due to the generation of a wake behind the fiber.

DOI： 10.1155/2012/426476

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Other Link： https://dblp.uni-trier.de/db/journals/js/js2012.html#TajikawaIKO12

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

In-body tissue, architecture technology represents a promising approach for the development of living heart valve replacements and preparation of a series of biovalves. To reduce the degree of regurgitation and increase the orifice ratio, we designed a novel mold for a type VI biovalve. The mold had an outer diameter of 14 mm for implantation in beagles, and it was prepared by assembling two silicone rods with a small aperture (1 mm) between them. One rod had three protrusions of the sinus of Valsalva, whereas the other was almost cylindrical. When the molds were embedded in the subcutaneous pouches of beagles for 1 month, the native connective tissues that subsequently developed covered the entire outer surface of the molds and migrated into the aperture between the rods. The mold from both sides of the harvested cylindrical implant was removed, and homogenous well-balanced trileaflets were found to be separately formed in the open form with a small aperture at the three commissure parts inside the developed conduit, which had a thick homogenous wall even in the sinus of Valsalva. Exposure of the obtained biovalves to physiological aortic valve flow in beagles revealed proper opening motion with a wide orifice area. The closure dynamics were suboptimal, probably due to the reduction in the size of the sinus of Valsalva. The mechanical behavior of this biovalve might allow its use as a living aortic valve replacement. (C) 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 99B: 135-141, 2011.

DOI： 10.1002/jbm.b.31880

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Language：English   Publishing type：Research paper (scientific journal)  

A novel autologous valved conduit with the sinus of Valsalva-defined as a type IV biovalve-was created in rabbits by "in-body tissue-architecture" technology with a specially designed mold for the valve leaflets and the sinus of Valsalva and a microporous tubular scaffold for the conduit. The mold included 2 rods composed of silicone substrates. One was concave shaped, with 3 projections resembling the sinus of Valsalva; the other was convex shaped. The connection between the rods was designed to resemble the closed form of a trileaflet valve. The 2 rods were connected with a small aperture of 500-800 microm, which bound membranous connective tissue obtained from the dorsal subcutaneous layer of a rabbit. The rods were placed in a polyurethane scaffold that had many windows in its center. Both ends of the scaffold were tied with thread for fixation, and this assembly was embedded for 1 month in a subcutaneous pouch in the same Japanese white rabbit from which the connective tissue was obtained. After 1 month, all the surfaces of the implant were found to be completely covered with newly developed connective tissue. The substrates were removed from both sides of the harvested cylindrical implant, and homogenous well-balanced trileaflet-shaped membranous tissue was found inside the developed conduit with 3 protrusions resembling the sinus of Valsalva. The trileaflet valve closed and opened rapidly in synchrony with the backward and forward flow of a pulsatile flow circuit in vitro.

DOI： 10.1007/s10047-010-0491-2

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Language：Japanese   Publisher：Japan Society of Mechanical Engineers  

It is particularly important to know the deformation behavior of the erythrocyte passing through a micro channel (MC) like the blood capillary. In this paper, the deformation behavior of an erythrocyte passing through the pseudo MC was calculated and observed by a two-dimensional numerical simulation of blood flow. The pseudo MC wall was created by assuming that the wall was one of the fluids which had no velocity at all times. The erythrocyte's movement and deformation were calculated by using an immersed boundary method. The following results were obtained by the simulation. An erythrocyte smoothly deformed and passed through the pseudo MC. In the pseudo MC, its shape changed to bullet-like shape and its moving velocity was almost constant. In addition, a narrow layer of only blood plasma, what we call the plasma layer, was formed between pseudo MC's wall surface and the erythrocyte membrane. It was possible that the plasma layer puts the erythrocyte into fluid lubrication. On the other hand, in our previous researches the deformation behavior of the erythrocyte passing through the MC was observed by experiments. The simulation results had good agreement particularly on an erythrocyte's deformed shape and process in MC with the experimental results.

DOI： 10.1299/kikaib.76.772_2111

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Other Link： https://www.jstage.jst.go.jp/article/kikaib1979/76/772/76_KJ00006813222/_pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-LISS  

The aim of this study was to prepare completely autologous heart-valve-shaped constructs without using any artificial scaffold materials by in-body tissue architecture technology, which is a practical concept of regenerative medicine based on the biological defense mechanism against foreign bodies. Silicone rods were used as molds to achieve the tubular shape of the arteries, which were implanted in the subcutaneous spaces of rabbits. After 2 weeks of primary in-body tissue incubation, the silicone rods were completely encapsulated within a thin membranous connective tissue mainly consisting of collagen and having a thickness of similar to 100 mu m. To achieve the trileaflet shape of the valve, the cylindrical tissues obtained were rolled up with polyurethane belts cut in the shape of three semi-ovals. The assembled tissues were reimplanted for 2 weeks for secondary incubation. The resulting tissues were over-encapsulated with the newly developed membranous connective tissue having a thickness of similar to 200-400 mu m. The newly formed membranes were completely fused to the previously developed inner membrane. After the removal of the two artificial materials, tubular constructs with trileaflet-shaped internal surface were obtained. By controlling the formation of the encapsulating tissue in the two-step in-body tissue incubation process, we were able to develop completely autologous trileaflet valve-shaped constructs. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 91B: 813-818, 2009

DOI： 10.1002/jbm.b.31460

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Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

An “active” ultrasound Doppler method was newly developed in order to directly and easily discriminate emboli from micro bubbles flowing in blood vessel. The principle of this method is based on measuring the induced velocities of an embolus and a micro bubble by acoustic radiation force of ultrasound wave. This force is mainly influenced by the difference in characteristic acoustic impedances between emboli or bubbles and ambient fluid. In order to prove the availability of this new discrimination method, micro bubbles, model emboli and the other particles were irradiated by ultrasound wave from a commercial ultrasound diagnostic equipment. Every motion was observed by a high speed video camera and their velocities along sound axis were measured. As a result, it was found that micro bubbles were strongly moved with a velocity along the axis in steady flow while model emboli were hardly moved, and that this “active” ultrasound Doppler method had high availability for a medical diagnosis system to discriminate emboli from micro bubbles flowing in human vessel.

DOI： 10.11239/jsmbe.47.28

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Other Link： http://id.ndl.go.jp/bib/10225996

Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Kansai University  

CiNii Books

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Authorship：Corresponding author   Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

The sinuses of Valsalva are known to contribute to the normal function. Therefore, the Valsalva graft is being widely used in the aortic root replacement. On the other hand, the artificial valve is developed by the regenerative medical techniques in some research groups. These devices are artificial internal organs. It is desirable for the device to equip long-term durability. In this study, we computed the stress and the displacement in the sinus and the valvular leaflet by commercial software, which is composed by finite element method, in order to clear the between shape parameters and durability. As a result, deformations of the sinuses and leaflets are very small against the pressure loading on a model with sinus of Valsalva. And the rupture part of our developing artificial valve overlapped with very high stress region of the computational model. However, we could minimize the stress by fixing the leaflet shapes.

DOI： 10.11239/jsmbe.47.36

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Other Link： http://id.ndl.go.jp/bib/10226007

Language：English   Publisher：SPRINGER TOKYO  

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Authorship：Lead author,　Corresponding author   Language：English   Publisher：The Japan Society of Mechanical Engineers  

A new miniaturized fiber-optic laser Doppler velocimetry (LDV) sensor has been developed, which is capable of measuring the local velocity in various semi-opaque and opaque fluid flows, particularly whole blood velocity in vessels. The sensor has a convex lens-like fiber tip as a pickup and an improved optical transmission system with markedly decreased stray light. This paper describes methods for fabricating fiber tips like concave and convex lens and the characteristics of the optical sensor system equipped with the fabricated fiber tip. Conventional fiber-optic LDV sensors developed up to now have not been capable of measuring such opaque fluids because scattered light from scattering particles as erythrocytes has very low intensity, which makes signal-to-noise ratio of Doppler signal received by a sensor pickup significantly decreased. To overcome these problems, convex lens-like fiber tips have been fabricated by chemical etching, in which quartz fibers of multimode graded refractive index have been etched in aqueous solutions of hydrogen fluoride and ammonium fluoride under the appropriately controlled condition of the concentration of the solution, the etching duration time and the etchant temperature to obtain the desired curvature radius of the lens-like surface of the fiber tip. In this fiber-optic sensor, a laser beam emitted from the fiber tip can be focused at any position from about 0.1 to 0.5 mm distant from the fiber tip according to its curvature radius. The convex lens-like etched tip totally reduced the intensity of undesired reflecting light at the fiber end by 1/2 to 1/6 compared with normal cut fiber tip. Consequently, this fiber-optic LDV sensor system is capable of measuring the local flow velocity in semi-opaque and opaque fluids, whose turbidity was about five times higher than by any kinds of previous sensors.

DOI： 10.1299/jfst.4.62

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-LISS  

As a practical concept of regenerative medicine, we have focused on in vivo tissue engineering utilizing the foreign body reaction. Plastic substrates for valvular leaflet organization, consisting of two pieces assembled with a small aperture were inserted into a microporous polyurethane conduit scaffold. The assembly was placed in the subcutaneous spaces of Japanese white rabbits for 1 month. After the substrates were pulled out from the harvested implant, valve leaflet-shaped membranous tissue was formed inside the tubular scaffold as designed. The valve leaflet was composed of the same collagen-rich tissue, with the absence of any elastic fiber, as that which had ingrown or covered the scaffold. No abnormal collection or infiltration of inflammatory cells in the leaflet and the scaffold could be demonstrated. According to the immunohistochemical staining, the leaflet was comprised of numerous vimentin- or alpha-SMA-positive cells, corresponding to fibroblasts or myofibroblats, but contained no desmin-positive cells. The analysis of the video data of the valve movement showed that, in synchronization with the backward flow in the diastolic phase, the valve closed rapidly and tightly and, in the transition phase of the flow direction, the valve opened smoothly without flapping or hitting the scaffold wall. Using mold designs, consisting of two different plastic substrates and the tubular scaffold, in conjunction with "in body tissue architecture," the complex 3-dimensional autologous conduit-typed Biovalve was developed for the first time. (C) 2007 Wiley Periodicals, Inc.

DOI： 10.1002/jbm.b.30981

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PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：LIPPINCOTT WILLIAMS & WILKINS  

"In body tissue architecture" technology is a practical concept of regenerative medicine that uses the living recipient body's reaction to a foreign object as a reactor for autologous tissue organization. A novel autologous valved conduit was produced by creating a specially designed conduit-mold composite and elastomeric scaffold for this unique in vivo tissue engineering. Methods: Convex and concave plastic molds assembled with a small aperture of 500-800 pm were inserted into a microporous elastomeric conduit scaffold. The assembly was placed in a subcutaneous pocket of Japanese white rabbits for 1 month. The molds were pulled out from the edge of the harvested implant to obtain the valved conduit. Results: Homogenous and well-balanced trileaflet of membranous tissue was developed in the optimized aperture of molds. The valve leaflet closed and opened rapidly in synchronization with the backward and forward flow of the pulsatile flow circuit in vitro. Conclusions: A tissue-engineered conduit incorporated with a functional autologous trileaflet valve was developed in an in vivo reactor by optimizing the microstructures of conduit scaffolds and newly designing the composite molds. The method holds promise for a safe, biocompatible, and economical heart valve prosthesis.

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Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

For measurement of local blood velocity, a less invasive miniaturized fiber-optic LDV (laser Doppler velocimetry) sensor which was directly inserted into a blood vessel was developed as a monitoring device for clinical use and in vitro testing equipment. By using the process of a chemical etching with a HF-NH4F buffer solution, a convex lens-like surface was formed on the fiber tip having a core of 50 μm. Laser beam emitted from the fiber tip was focused and formed measuring volume. In the authors' previous studies, the local velocity of a steady blood flow was successfully measured using a same type of the present fiber-optic LDV sensor. In order to measure local velocity in a pulsatile flow, the optical system and the curvature of the fiber sensor tip were improved. The fiber sensor was inserted at an insertion angle of 120 deg. through an injection needle into a flow duct of an acrylic pipe in which an opaque fluid as a model of whole blood was pulsatingly flowing. The waveform of the flow rate was modeled after the human middle cerebral arterial flow. In this experiment, the local flow velocity and velocity profile across the duct were measured in a pulsatile flow of a dense suspension of a white pigment. The results measured by this sensor were compared both with that by a fringe-mode LDV and with that calculated on the basis of Womersley's oscillatory flow theory. As a result, it was found that the local velocity and its profile across the duct in the pulsatile flow were successfully measured by the present fiber-optic LDV sensor, which proved the capability of the sensor as a diagnostic device.

DOI： 10.11239/jsmbe.45.298

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Language：Japanese   Publisher：サーキュレーション アップトゥデート  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

One of the well known cures for the annuloaortic ectasia is a vascular grafting surgery using a composite graft as an artificial ascending aorta and an artificial valve. Although, almost all conventional grafts do not have Valsalva sinus at the aortic root, the influence of omitting the Valsalva sinus have not yet been clarified. In order to understand the effect of the Valsalva sinuses at aortic root on the valve characteristics and flow field around the valve and furthermore the coronary blood flow, the authors have fabricated some realistic models of aortic valve using three-dimensional modeling machine, and have investigated the effect of the sinus existence by particle image velocimetry (PIV). As the result, the fluctuation of flow rate at coronary artery in the case of the straight wall model was larger than the Valsalva sinus model. The valve leaflets were pulled to the left ventricle, which could cause a diastolic regurgitant flow from the aorta into the left ventricle. The leaflet suction in the Valsalva sinus model was weaker than the straight wall model. Flow visualization results showed that vortex flow occurred in the Valsalva sinus due to jet flow through the valve leaflets during systole. At early diastole, flow into coronary artery around the Valsalva sinus was smoothly than the straight wall model. Consequently it was concluded from a standpoint of flow and valve characteristics that the Valsalva sinus had an important role for the aortic valve and the inlet of the coronary circulation.

DOI： 10.1299/kikaib.73.231

DOI： 10.1143/jjap.48.017002_references_DOI_NXnIust42sG6TfUhpBwZ5SN6nAE

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Other Link： http://id.ndl.go.jp/bib/8663747

Authorship：Corresponding author   Language：Japanese   Publisher：Kansai University  

Kansai University the Academic Frontier project of ”Creation of the Realistic Model of Human Tissues/Organs using Nano / Sub-Micro Technology and their Development to Artificial Tissues/Organ” 20030401-20080331

DOI： 10.1299/kikaib.72.1702

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Language：Japanese   Publisher：The Visualization Society of Japan  

One of the well known cures for the aortic regurgitateon is a vascular grafting surgery using a composite graft as an artificial ascending aorta and an artificial valve. Although, almost all conventional grafts do not have Valsalva sinus at the aortic root, the influence of omitting the sinus have not yet been clarified. In order to understand the effect of the sinuses at aortic root on the valve characteristics and flow field around the valve and furthermore the coronary blood flow, the authors have fabricated some realistic models of aortic valve using 3D modeling machine, and have investigated the effect of the sinus existence by PIV. As the result, flow into coronary artery around the Valsalva sinus was smoothly than the straight wall model at early diastole. Consequently it was concluded from a standpoint of flow and valve characteristics that the sinus had an important role for the aortic valve and the inlet of the coronary circulation.

DOI： 10.3154/jvs.26.supplement2_93

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I8857670

Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：The Visualization Society of Japan  

the Grant-in-Aid for Young Scientists (B) 20030401-20050331

DOI： 10.3154/tvsj.25.84

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Japanese Society for Medical and Biological Engineering  

Kansai University the Academic Frontier project of ”Creation of the Realistic Model of Human Tissues/Organs using Nano / Sub-Micro Technology and their Development to Artificial Tissues/Organ”” 20030401-20080331

DOI： 10.11239/jsmbe.43.638

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Other Link： http://search.jamas.or.jp/link/ui/2006156902

Authorship：Corresponding author   Language：Japanese   Publisher：Japan Society of Mechanical Engineers  

A miniaturized fiber-optic laser Doppler velocimetry (LDV) sensor has been newly developed, which is capable of measuring the local velocity in various semi-opaque and opaque fluid flows, particularly local blood velocity in blood vessel. The developed sensor has a convex lens-like fiber tip as a pickup and an improved optical transmission system of remarkably decreased stray light. The present paper describes a method of fabricating a fiber tip and the characteristics of the sensor optical system provided with the fabricated fiber tip. Any fiber-optic LDV sensors up to now developed have not been capable of measuring such opaque fluids because of very low light intensity scattered from the fluid and received by the sensor pickup and of low signal-to-noise ratio. In order to overcome these problems, convex and/or concave lens-like fiber tips have been fabricated by chemical etching, in which quartz fibers have been etched in aqueous solution of hydrogen fluoride. The curvature of the lens-like surface of the fiber tip has depended on the refractive index distribution across the fiber cross section, the concentration of HF-NH4F solution and the etching time. In the present fiber-optic sensor, laser beam emitted from the fiber tip can be focused at any position from about 0.1 to 0.5 mm distant from the fiber tip. Consequently the present sensor is capable of measuring the local velocity in almost all semi-opaque and opaque fluids including blood.

DOI： 10.1299/kikaib.71.2092

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Japan Society of Mechanical Engineers  

It is important to understand an interaction between deformable surface and flow field surrounding it. In order to clarify this interaction, we had made some detailed experiments using several kinds of cylinder models having elasto-flexible surface in uniform water flow, and had found that on the surface were excited three different kinds of traveling waves, i.e. a continuously occurring wave, a periodically occurring wave and a randomly occurring wave. The present experiments were made to elucidate the mechanism of the wave generation and its propagation. The results showed that a relative frequency of the wave generation to that of the Karman vortex pair emission was linearly proportional to the power of 2/3 of the Reynolds number. This dependency is similar to the dependency of the wave propagation speed of Kelvin-Helmholtz instability in free shear layer on the Reynolds number. The traveling velocities of the waves were found to be about 65% of the main flow velocities regardless of the model diameter. Small vortices observed in the vicinity of the wave were found to move with same velocities as the wave propagating velocities. The velocity distribution in the shear layer of the separated flow around the cylinder was measured. The velocity at the inflexion point of the distribution was found to be same as the wave propagation velocity and the moving velocity of the small vortices. We concluded from the above results that the traveling waves were generated by the flow instability of the shear layer in the separated flow around the cylinder.

DOI： 10.1299/kikaib.69.2431

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Other Link： http://www.jstage.jst.go.jp/article/kikaib1979/69/687/69_687_2431/_pdf

Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Japan Society of Mechanical Engineers  

It is important to bio-fluidmechanics to understand the interaction among deformable surface, its surrounding flow field and hydrodynamical forces. In order to clarify this interaction, we have been using cylinder models having an elasto-flexible surface in uniform water flow. The laser light sheet method was used to visualize the deformation of the surface and the flow field around it. The experimental result showed that there were three different kinds of traveling wave generated on the surface, namely, a continuously-occurring wave, a periodically-occurring wave and a randomly occurring wave. In the case of the periodical and continuous waves, the frequencies of the waves were 6 to 9 times higher than that of the Karman vortex pair shedding from the rigid cylinder. Their wavelengths were about 1/8 compared with the theoretical wavelength of the Karman vortex street behind the rigid cylinder. It is indicated that generation of the wave was not caused by large pressure variation from the vortex shedding. The visualization results suggest that local pressure decrease flow separation from the surface and by the generation and moement of the small vortex were responsible for the apperarance and the propagation of the transient wave.

DOI： 10.1299/kikaib.67.67

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Other Link： http://www.jstage.jst.go.jp/article/kikaib1979/67/653/67_653_67/_pdf

Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Japan Society of Mechanical Engineers  

It is important to fluid mechanics and bio-fluid mechanics to understand an interaction among deformable surface, its surface, its surrounding flow field and hydrodynamical forces. In order to clarify this interaction by experiments, we have been using several cylinder models having an elasto-flexible surface in uniform water flow. The hydrodynamic forces were measured by a three-component force balance. The deformation of the surface and the flow field around it were visualized using a laser light sheet method simultaneously. 'The experimental results showed that the time-averaged hydrodynamical drag was approximately 20% lower than that of the rigid cylinder when the continuously occurring wave appeared on the surface. In the case of the drag reduction occurrence, the power spectra of the lift fluctuation were broadened and had several peaks. In particular, the prominent frequency of power spectrum was about 45% lower than the frequency in the cases of the rigid cylinder and of no drag reduction occurring. The visualization results suggested that the strength of the Karman vortex shed from the cylinder was decreased compared with that from the rigid cylinder and this decrease was responsible for the above mentioned drag reduction.

DOI： 10.1299/kikaib.67.1338

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Other Link： http://id.ndl.go.jp/bib/5817652

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Other Link： http://id.ndl.go.jp/bib/029199074

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Language：Japanese   Publisher：吹田 : 関西大学先端科学技術推進機構  

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Other Link： http://id.ndl.go.jp/bib/031603739

Language：Japanese   Publisher：吹田 : 関西大学先端科学技術推進機構  

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Other Link： http://id.ndl.go.jp/bib/030539135

Language：Japanese   Publisher：吹田 : 関西大学先端科学技術推進機構  

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Other Link： http://id.ndl.go.jp/bib/029841009

Language：Japanese   Publisher：吹田 : 関西大学先端科学技術推進機構  

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Other Link： http://id.ndl.go.jp/bib/029199074

Language：Japanese   Publisher：関西大学先端科学技術推進機構  

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Language：Japanese   Publisher：特定非営利活動法人 日本バイオレオロジー学会  

DOI： 10.11262/jpnbr.30.3_156

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Language：Japanese   Publisher：特定非営利活動法人 日本バイオレオロジー学会  

DOI： 10.11262/jpnbr.30.3_153

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J-GLOBAL

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Language：Japanese   Publisher：関西大学先端科学技術推進機構  

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Language：Japanese   Publisher：一般社団法人日本機械学会  

DOI： 10.1299/jsmemag.117.1146_286_2

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Language：Japanese   Publisher：特定非営利活動法人 日本バイオレオロジー学会  

DOI： 10.11262/jpnbr.28.3_148

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J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：The Visualization Society of Japan  

DOI： 10.3154/jvs.33.6

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Language：Japanese   Publisher：関西大学  

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J-GLOBAL

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J-GLOBAL

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Publisher：生体医工学  

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J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：Japanese Society of Biorheology  

DOI： 10.11262/jpnbr.24.1_3

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J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：一般社団法人 日本機械学会  

DOI： 10.1299/jsmemag.111.1074_388_6

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J-GLOBAL

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J-GLOBAL

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It is the first step to proper appreciation of human cardiovascular system to clarify the microcirculatory blood flow. Especially, because of red blood cell (RBC) play an indispensable role in mass and gas transfer in capillary vessel, it is important to make clear the behavior of RBC in capillary. And it is well know that RBC passes through capillary whose diameter is smaller than that of RBC with small pressure gradients. In this study, new micro-channel array devices which are able to adapt to evaluating both the throughput of whole blood and the deformability of RBC are developed. As a result of observing RBC in micro channel, deformation of RBC can observed clearly. And 3 kinds of typical deformation were observed. In the case of bullet-shaped deformation, the RBC was not deformed as the well known parachute-shape in narrowest capillary vessel whose diameter was smaller than RBC diameter.

DOI： 10.3154/jvs.24.supplement1_21

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Other Link： https://ndlsearch.ndl.go.jp/books/R000000004-I7706915

Language：Japanese   Publisher：関西大学  

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Language：Japanese   Publisher：The Visualization Society of Japan  

In order to clarify the influence of an interaction between defomiable surface and its surrounding flow field, this study has been carried out using cylinder models having an elasto-flexible surface which simulates the skin of dolphins. The deformation of the surface and the flow field around the model were observed using a laser light sheet visualization method. The visualization result showed that there were three different kinds of travelling waves generated on the surface, namely, continuously-occurring wave, unstable-wave occurring at high-speed stream, periodically-occuning wave. Especially, in the third case, the traveling waves (TW) were observed to occur as every Karman vortex is shed from the cylinders. When silicon oil whose viscosity was about 20 times higher than the water's one is contained in the cylinder, the domain of the appearance of the continuously-occurring waves pattern was shifted and extended high ratio of the models sectional area. It is suggested that generation of the traveling wave is caused by flow separation on the surface of cylinder. And wavelength of TW is 20% shorter and traveling velocity of TW is slower than the case of water contained.

DOI： 10.3154/jvs.19.supplement2_237

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Other Link： http://id.ndl.go.jp/bib/4871017

Language：Japanese   Publisher：The Visualization Society of Japan  

The purpose of this study is to clarify the influence of interaction between deformable surface and flow field. Generally speaking, Dolphin could swim fast because of oscillated stomach skin. Cylinder models having an elasto-flexible surface were used to simulate the skin of marine animal. These cylinders were placed in water tunnel, and using laser light sheet method to visualize deformation of its cross sectional form, pattern of vortex shedding from the model, flow separation point. Vorticity and hydrodynamical forces were measured. As a result, three different patterns of travelling wave generation on the surface of elasto-flexible cylinder were observed. Separation points moved to downward more compared with the rigid one. And streak line in the vicinity of the wave is broken by new generated wave and small vortexes shed simultaneously from the surface. Distribution of vorticity around the cylinder was clearly different from that of the rigid one. The cylinder, on which travelling waves appear on the surface, has shown about 10% smaller hydrodynamical drag than the rigid cylinder.

DOI： 10.3154/jvs.18.supplement2_47

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Other Link： http://id.ndl.go.jp/bib/4571899

Event date： 2022

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Event date： 2021

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Event date： 2021

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We have been developing heart valve-like tissues (Biovalve) using in-body tissue architecture. Previously, we fabricated a novel prosthetic valve with a membranous tissue (Biosheet) as a valve cusp and an elliptical valve annulus. Because of isotropic mechanical properties of the valve, it was difficult to satisfy the performance of both opening and closing. The purpose of this study is to clarify the influence of mechanical property of anisotropic cusp on valve performance.The valve models were fabricated from a combination of polyurethane sheets and Ni-Ti wires. In-Vitro simulation was performed to evaluate valve performance and to observe its opening-closing behavior. The experimental conditions were set at the physiological condition of healthy adult male. According to ISO5840, temporal waveform of left atrial pressure, left ventricular pressure and mitral regurgitation were measured, and regurgitation rate, mean pressure gradient and effective orifice area were calculated to evaluate the valve performance.

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Event date： 2020.12

Language：Japanese  

In recent years, the number of hemodialysis patients is increasing due to population aging and lifestyle-related diseases, and hemodialysis lowers patients’ quality of life. The technique of hemodialysis was developed based on hemolysis, and it is thought that hemolysis in hemodialysis is induced during discharge by the peristaltic pump. However, studies have not investigated in detail whether hemolysis is instantaneously induced either by the pump or the accumulation of mechanical damage to erythrocytes. In this study, the deformability and degree of hemolysis of erythrocytes in extracorporeal circulation during hemodialysis were measured quantitatively, based on the mechanics of an in vitro model experiment using commercially available blood. In this experiment, the influence of drug administration to patients could be ignored. In the experiment, blood was circulated in a hemodialysis circuit model in which the parameters of flow rate and circulation time were set with reference to hemodialysis conditions in clinical settings. Blood for measurement was sampled from the circuit. The deformability of the sampled erythrocytes was evaluated based on the time constant of shape recovery, which was measured using two methods;the micro-channel and uni-axial stretching methods. Hemolysis was quantified based on absorbance measured using a spectrometer. The results showed that the deformability of erythrocytes remained nearly unchanged over time of hemodialysis when measured by both methods, whereas hemolysis increased in all conditions. These findings indicate that hemolysis is induced instantaneously by the peristaltic pump in the hemodialysis system.

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Other Link： http://id.ndl.go.jp/bib/031339462

Event date： 2020

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Event date： 2020

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We have developed a microporous covered stent (CS) for the endovascular embolization treatment of intracranial aneurysm (IA). This stent promotes progressive thrombosis by flow diversion and facilitates IA embolization treatment by clotting of whole blood in the IA. Because it is difficult to quantitatively evaluate in vivo embolization performance of CS, we have been developing a model blood which can produce clot like red thrombus by using hyper-coagulable skim milk. In this study, the embolization device performances were evaluated by using our developed model blood. The saccular IA model was placed at the outer wall of a U-bend vessel model of which curvature was almost same as that of human internal carotid siphon. The IA opening position at the U-bend vessel model was located at θ = 60, 90 and 120 deg. Reynolds number of the flow in the U-bend vessel model was set at 580, which was mean Reynolds number in the human internal carotid siphon. FD model (pore diameter: 74μm, aperture ratio: 53%) was placed at opening of IA model. The model blood clot forming and growing process was visualized by colored die injecting and clotting volume in the IA was measured by image processing of the time tracking color-die images. As a result, model blood clot was formed locally caused by flow diversion caused by FD model stenting. These results suggest that the embolization performance is able to be evaluated quantitatively.

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Event date： 2020

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Event date： 2020

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We have been developing BioValve as an artificial hearts valve by using iBTA. Because atrioventricular valve has a complicated structure consisting of both leaflet and tendinous cords, and its performance is affected by the cord length, BioValve have not been applied to atrioventricular valve. The purpose of this study is a simple shape artificial atrioventricular valve developing. Newly developed valve consists of a metal annulus and a BioSheet. Because a BioSheet is fixed on a beam of the annulus, the sheet can open and close with flow change like a mechanical butterfly-valve. The valve performance, such as regurgitation-ratio, EOA and pressure-drop was measured by using arterial circulation simulator under the typical physiological conditions. To apply to optimal design, we had fabricated a valve model by using polyurethane sheet, of which mechanical bending properties were same as the BioSheet, and the influence of shape change of the leaflet was investigated.

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Event date： 2019.1

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Other Link： http://id.ndl.go.jp/bib/030658804

Event date： 2019

Language：Japanese  

Recently, number of veterinary disease for mitral valve insufficiency in is increasing. Because there are not adequate artificial mitral valves yet, mitral reconstructive surgery is performed. Therefore, there is a tremendous need for small size artificial atrioventricular valves. We have been developing “Bio-valve” fabricated by IBTA. This study was developed membrane-type biological valves such as Jellyfish type and Butterfly type were prepared by sewing membrane-like connective tissue with metal made valve ring. The valve function and its opening-closing behavior was evaluated by using in-vitro simulator. As a result, Butterfly type model with a Bio-sheet as leaflet showed good valve closing performance. But the effective orifice area as valve opening performance was not achieved to the ISO requirement.

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Event date： 2019

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Event date： 2019

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Event date： 2019

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We have developed a novel microporous covered stent (MCS) for the endovascular embolization treatment of intracranial aneurysm (IA). This stent promotes progressive thrombosis by flow divertion and facilitates IA embolization treatment by clotting of whole blood in the IA. However, difference of geometric configuration of each aneurysms affects the performance. In this study, we investigated intra-aneurysmal flow with various aneurysm position at a curved parent vessel by using in-vitro flow simulator. The IA models were placed at the outer-sidewall at the U-bend parent vessel, of which curvature was as same as that of human carotid siphon. The IA opening position on U-bend vessel was located at <i>θ_a</i> = 30, 60, 90, 120, 150 and 180 deg. Reynolds number of the parent vessel flow was set at 190 - 970 to simulate CCA blood flow. Microporous sheet (pore diameter: 100μm, aperture ratio: 30%) was placed as a model of a MCS at opening of IA. Flow velocity field at the IA model were measured by PIV. As the results, by MCS stenting, volumetric mean share rate (VMSR) in IA model became about 15 times smaller than before stenting. Dimensionless VMSR was increased proportionally by dimensionless IA in-coming/out-going flow rate increasing. These results suggest that our developed MCS has one of the best embolization device for IA therapy and is expected high embolic effects due to obstruction of direction flow in aneurysm.

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Event date： 2019

Language：Japanese  

Half crushed collapsible tube occur to self-excited oscillation in fluid is flowing in tube but cause of oscillation is unidentified．We aim to explore the cause of oscillation．We measure flowrate, headstream and downstream pressure and cross-sectional area on condition that tube external pressure decreasing and increasing under the constant upper tank pressure．The result of this study is that oscillation began to expand in z=10-25mm and began to close in z=30-50mm．

We expected that oscillation begin to close throughout the tube．This result suggests an influence of flow in tube.

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Event date： 2019

Language：Japanese  

The Blalock-Taussing shunt (BTS) operation is a cornerstone as initial palliative surgery for congenitial heart disease with severely reduced pulmonary blood flow. But BTS is difficult to manage the postoperative blood flow rate. The pourpose of this study is to develop a novel artificial blood vessel device capable of controlling bypass blood flow by BTS. Pressure loss by shunt was measured and estimated by using theory of fluid engineering. As the result, our proposed estimating method, which was including not only viscus friction loss but also pressure loss caused by flow separation, showed good agreement with experimental measured data.

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Event date： 2019

Language：Japanese  

It is well known that RBC deformability is influenced by not only hemodialysis induced by hemolysis but also pH of blood. In order to investigate relationship among RBC deformability, hemolysis and dialysis treatment, time constant of shape recovery of RBC and absorbance of blood plasma as hemolytic index were measured by using MC technique and spectrophotometer. As a result, dialysis treatment affected not the time constant as RBC deformability but hemolysis occurring. On the other hand, RBC deformability became higher when the suspension of RBC was alkaline.

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Event date： 2018.1

Language：Japanese  

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Other Link： http://id.ndl.go.jp/bib/029314879

Event date： 2018

Language：Japanese  

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Event date： 2018

Language：Japanese  

The purpose of study is developing modeled blood, which is able to produce thrombus formation caused by flow stagnation of blood flow, and evaluating therapeutic performance of embolic device such as intravascular treatment. This study was employed hyper-coagulable skim milk as an agglutinable modeled of blood, a uniform shear was applied by using a cone plate type viscometer. Rheological characteristics of human blood and hyper-coagulable skim milk during red thrombus / milk cot formation were measured. As a result, by changing constituents of hyper-coagulable skim milk such as concentration of skim milk, calcium chloride and rennet, it was able to model agglutination of blood caused by flow stagnation same as red thrombus formation. And the rheological specification of the modeled blood was almost same as the viscosity before agglutination and the first yield viscosity of human blood.

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Event date： 2018

Language：Japanese  

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Event date： 2018

Language：Japanese  

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Event date： 2017

Language：Japanese  

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Event date： 2017

Language：Japanese  

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Event date： 2017

Language：Japanese  

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Event date： 2016.6

Venue：東京  

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Event date： 2016.6

Venue：東京  

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Event date： 2016.4

Venue：富山  

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Event date： 2016.4

Language：Japanese  

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Event date： 2016.3

Venue：寝屋川  

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Event date： 2016.3

Language：Japanese  

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Event date： 2016.1

Venue：東京  

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Event date： 2016.1

Language：Japanese  

We have been developing microporous covered stents (MCSs) for the treatment of giant and wide neck intracranial aneurysms (IAs). By shielding IA neck with the microporous cover film, blood flow in IA was stagnated immediately. Subsequently, IA embolization is occurred by thrombus formation with a remarkable decrease of shear rate in IA flow. So, flow reduction performance of device placing is closely related to capability of IA embolization. In this study, we compared the flow reduction performance between MCS and flow diverter (FD), a another type stent for the IA treatment. IA flow was visualized by using in vitro flow simulator and evaluated by particle image velocimetry (PIV). Two-dimensional sidewall IA model was made from acrylic resin. Aneurysm depth, Dome size and neck width of IA model were 9.1 mm, 10.0 mm, 7.1 mm respectively. FD or MCS models were placed at the neck of the aneurysm model. Distributions of flow velocity and shear rate in IA were measured. Before stenting, high shear rate regions spread throughout IA cavity. After stenting, flow velocities in IA model stagnated remarkably. Area mean shear rate in IA flow became about 9 % by FD and 3 % by MCS. Flow reduction performance of MCS was about 3 times higher than the FD.

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Event date： 2016

Language：Japanese  

<p>In order to clarify the property of blood microcirculation, it is very important to comprehend the deformability of erythrocytes which occupy about 45 % of the blood volume. By tensile test to an erythrocyte using micropipettes in the microscope, an apparent Young's modulus was calculated based on Hooke's low and a time constant of an erythrocyte's shape recovering process was calculated based on Kelvin model as an index of its deformability. In this study, the influence of inner viscosity of erythrocytes to the physical quantities was confirmed experimentally with erythrocyte ghost of inner viscosity adjusted by using isotonic solution of dextran and so on. As a result, it was found that apparent Young's modulus was not changed by the change of inner viscosity of erythrocytes, while time constant of shape recovering was decreased, which had a good agreement with Kelvin model in changing trend of physical quantities.</p>

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Event date： 2016

Language：Japanese  

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Event date： 2015.11

Presentation type：Poster presentation  

Venue：東京  

第52回日本人工臓器学会大会 萌芽研究ポスター発表優秀賞 受賞
https://www.jsao.org/files/magazine/44_1/44_22.pdf

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Event date： 2015.11

Venue：東京  

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Event date： 2015.11

Venue：Orlando, USA  

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Event date： 2015.10

Venue：京都  

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Event date： 2015.9

Venue：Saporo, Japan  

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Event date： 2015.9

Venue：札幌  

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Event date： 2015.9

Language：Japanese  

We have been developing microporous covered stents for a treatment of intracranial aneurysm (IA). This device promotes flow reduction and induces progressive thrombosis in IA. In this study, we investigated intra-aneurysmal flow with various curvature ratios of parent vessel by using in vitro flow simulator. Two-dimensional sidewall IA models were fabricated from acrylic plastic. Parent vessels shape were designed on a straight and U-bend shape (curvature ratio: 0, 0.125, 0.250, 0.500, 0.667) models. Reynolds number in the parent vessel flow was set between 160 and 980 in steady flow. Microporous stainless-steel sheet (pore diameter: 100 μm, porosity: 30 %) was prepared as a stent model. Distributions of velocity and shear rate of intra-aneurysmal flow were measured by particle image velocimetry. As the result, faster intra-aneurysmal flow was observed in the case of sharper bended vessel model. Area mean shear rates in the case of the U-bend vessel model (curvature ratio: 0.500) was about 5 times higher than the case of straight vessel model. After stenting, the area mean shear rates at the all IA models were decreased to about 12 % of before stenting. It is suggested that our developing microporous covered stent has a good embolization performance, if the aneurysm is created at such curved vessel.

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Event date： 2015.9

Venue：Leuven, Belgian  

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Event date： 2015.8 - 2015.9

Venue：London, UK  

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Event date： 2015.6

Venue：東京  

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Event date： 2015.6

Venue：東京  

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Event date： 2015.3

Venue：京都  

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Event date： 2015.3

Venue：京都  

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Event date： 2015.3

Venue：京都  

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Event date： 2015.2

Language：Japanese  

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Event date： 2015.1

Venue：新潟  

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Event date： 2015.1

Venue：新潟  

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Event date： 2015.1

Venue：新潟  

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Event date： 2015.1

Language：Japanese  

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Event date： 2015.1

Language：Japanese  

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Event date： 2015.1

Language：Japanese  

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Other Link： http://id.ndl.go.jp/bib/027679831

Event date： 2015

Language：Japanese  

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Event date： 2015

Language：Japanese  

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Event date： 2015

Language：Japanese  

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Event date： 2015

Language：Japanese  

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Event date： 2014.11

Venue：Chicago,USA  

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Event date： 2014.11

Venue：Chicago,USA  

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Event date： 2014.10

Venue：札幌  

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Event date： 2014.10

Venue：札幌  

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Event date： 2014.10

Venue：札幌  

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Event date： 2014.10

Venue：札幌  

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Event date： 2014.10

Venue：札幌  

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Event date： 2014.9

Venue：小金井  

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Event date： 2014.9

Venue：Barcerona, Spain  

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Event date： 2014.9

Language：Japanese  

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Event date： 2014.8 - 2014.9

Venue：Barcerona, Spain  

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Event date： 2014.7

Venue：Boston, USA  

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Event date： 2014.6

Venue：埼玉  

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Event date： 2014.6

Venue：埼玉  

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Event date： 2014.4

Venue：Nice, France  

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Event date： 2014.4

Venue：Nice, France  

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Event date： 2014.3

Venue：堺  

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Event date： 2014.3

Venue：堺  

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Event date： 2014.3

Venue：堺  

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Event date： 2014.3

Language：Japanese  

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Event date： 2014.3

Language：Japanese  

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Event date： 2014.3

Language：Japanese  

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Event date： 2014.3

Venue：京都  

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Event date： 2014.3

Venue：京都  

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Event date： 2014.3

Venue：京都  

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Event date： 2014.3

Venue：京都  

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Event date： 2014.3

Venue：京都  

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Event date： 2014.1

Venue：吹田  

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Event date： 2014.1

Venue：吹田  

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Event date： 2014.1

Language：Japanese  

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Event date： 2014.1

Venue：仙台  

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Event date： 2014.1

Venue：仙台  

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Event date： 2014.1

Venue：仙台  

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Event date： 2014.1

Venue：仙台  

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Event date： 2014.1

Venue：仙台  

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Event date： 2014.1

Language：Japanese  

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Event date： 2014.1

Language：Japanese  

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Event date： 2014.1

Language：Japanese  

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Event date： 2014.1

Language：Japanese  

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Event date： 2014

Language：Japanese  

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Event date： 2013.12

Venue：九十九里  

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Event date： 2013.11

Venue：Dalas  

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Event date： 2013.11

Venue：福岡  

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Event date： 2013.11

Language：Japanese  

The purpose of this study is elucidating the mechanism of mosquito's flight. The motion of mosquito's wings consists of three representative motion; flapping, lead-lug and feathering motion. The feathering motion is a rotational movement which is centering on a wing leading edge. The mosquitoes are performing this motion passively produced by fluid forces and so on. In order to build the enlarged model which simulates this motion, we need to measure the stiffness of the mosquito's wings. The bending stiffness of the mosquito's wings were measured by the experiment using a cantilever. The enlarged wing model was designed based on its results. We observed the flapping motion of the enlarged wing model in the very low velocity wind tunnel and verified whether the feathering motion can be simulated.

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Event date： 2013.11

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Event date： 2013.11

Language：English  

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Event date： 2013.9

Venue：横浜  

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Event date： 2013.9

Venue：横浜  

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Event date： 2013.9

Venue：横浜  

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Event date： 2013.9

Venue：横浜  

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Event date： 2013.9

Venue：岐阜  

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Event date： 2013.9

Venue：福岡  

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Event date： 2013.9

Venue：福岡  

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Event date： 2013.9

Venue：福岡  

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Event date： 2013.9

Venue：福岡  

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Event date： 2013.9

Venue：岐阜  

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Event date： 2013.9

Venue：Glasgow  

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Event date： 2013.9

Language：Japanese  

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Event date： 2013.8

Language：Japanese  

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Event date： 2013.6

Venue：Venice  

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Event date： 2013.6

Venue：福岡  

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Event date： 2013.6

Venue：福岡  

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Event date： 2013.3

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Event date： 2013.3

Venue：横浜  

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Event date： 2013.3

Venue：横浜  

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Event date： 2013.2

Language：Japanese  

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Event date： 2013.2

Language：Japanese  

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Event date： 2013.1

Venue：吹田  

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Event date： 2013.1

Language：Japanese  

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Event date： 2013.1

Venue：吹田  

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Event date： 2013.1

Venue：つくば  

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Event date： 2013.1

Venue：つくば  

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Event date： 2013.1

Venue：つくば  

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Event date： 2013.1

Language：Japanese  

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Event date： 2013.1

Language：Japanese  

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Event date： 2013.1

Language：Japanese  

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Event date： 2013

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Event date： 2012.11

Venue：福岡  

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Event date： 2012.11

Venue：福岡  

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Event date： 2012.11

Venue：福岡  

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Event date： 2012.11

Venue：福岡  

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Event date： 2012.11

Language：Japanese  

We have been developing a microporous covered stent as a newly device for cerebral aneurysm treatment.This stent has a porous film to control both embolization and rapid neointimal formation.It is expected that the neointimal formation becomes earlier by using much larger pores,but there is a possibility that the covered stent with large pare cannot embolize by increasing inflow from parent vessel.The purpose of this study is estimation of stent embolization and optimization of pore design to ensure compatibility between reliable embolization and controlling early neointimal formation,in-vitro experiment based on flow similarity low has been conducted by using a 2D parent vessel model with a side wall type aneurysm model.The flow visualization result shows that three kinds of flow pattern in the aneurysm were observed namely,viscous shear induced flow,pressure drop induced flow and those coexistence flow.According to PIV result,mean shear rate in the aneurysm after stenting was decreased to less than 1/10 of before stenting.

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Event date： 2012.11

Language：Japanese  

Recently,pathogenesis of aortic valve sclerosis with aging is increasing with development of the aging of the population in Japan.It has been known that endothelial injury is the first step of valvular cholesterosis and the sclerosis.This study considered that some kinds of mechanical stress caused by blood flow e.g.both wall shear stress and structural tensile/compressive stress are one of the factors of endothelial damage.Therefore,in vitro experiment for blood flow was conducted by using a realistic model of human aortic valve and cardiovascular flow simulator based on wind-kessel model and three-dimensional velocity vector distribution and wall shear stress distribution on the model surface were measured by stereo PIV.As a result,swirling flow in a Valsalva sinus model caused by inflow from a part of the jet flow through the valve opening was observed during systole Large shear stress gradient was observed on the surface of the valve basis with valve deformation at the mid systole.

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Event date： 2012.11

Language：Japanese  

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Event date： 2012.11

Language：Japanese  

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Event date： 2012.11

Language：Japanese  

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Event date： 2012.10

Venue：福岡  

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Event date： 2012.10

Venue：弘前  

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Event date： 2012.10

Venue：弘前  

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Event date： 2012.10

Venue：弘前  

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Event date： 2012.10

Venue：姫路  

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Event date： 2012.10

Language：Japanese  

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Event date： 2012.10

Language：Japanese  

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Event date： 2012.10

Language：Japanese  

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Event date： 2012.10

Venue：大阪  

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Event date： 2012.9

Venue：盛岡  

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Event date： 2012.9

Language：Japanese  

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Event date： 2012.9

Language：Japanese  

We have been developing a micro porous covered stent as a newly device for cerebral aneurysm treatment to adapt large and giant cerebral aneurysm with a broad neck. This stent has a porous film to control among thrombus formation, rapid neointimal formation and intimal hyperplasia. It is expected that the neointimal formation becomes earlier by using much larger pores. But there is a possibility that the covered stent with large pare cannot embolize an aneurysm by increasing inflow from parent vessel. The purpose of this study is optimization of pore design to ensure compatibility between reliable embolization and controlling early neointimal formation, in-vitro experiment based on flow similarity low has been conducted by using a 2D parent vessel model with a side wall type aneurysm model. The flow visualization result shows that three kinds of flow pattern in the aneurysm were observed namely, viscous shear induced flow, pressure drop induced flow and those coexistence flow. According to PIV measurement result, area mean shear rate in the aneurysm after stenting was decreased to less than 1/5 of before stenting. Especially, when the covered stents of which aperture diameter was lower than 200μm and aperture ratio was 60% were installed, shear rate in aneurysm was less than 1 s^<-1> which was a threshold of F-IX activating necessary for venous thrombus formation.

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Event date： 2012.9

Venue：豊中  

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Event date： 2012.9

Venue：豊中  

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Event date： 2012.9

Venue：豊中  

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Event date： 2012.8

Language：Japanese  

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Event date： 2012.8

Language：Japanese  

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Event date： 2012.7

Venue：高槻  

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Event date： 2012.6

Venue：横浜  

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Event date： 2012.6

Venue：横浜  

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Event date： 2012.6

Venue：横浜  

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Event date： 2012.6

Venue：横浜  

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Event date： 2012.6

Venue：埼玉  

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Event date： 2012.6

Language：Japanese  

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Event date： 2012.6

Language：English  

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Event date： 2012.5 - 2012.6

Venue：新潟  

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Event date： 2012.5

Language：Japanese  

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Event date： 2012.5

Language：Japanese  

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Event date： 2012.5

Language：Japanese  

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Event date： 2012.5

Venue：福岡  

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Event date： 2012.3

Language：Japanese  

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Event date： 2012.3

Venue：吹田  

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Event date： 2012.3

Venue：吹田  

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Event date： 2012.3

Venue：吹田  

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Event date： 2012.3

Venue：吹田  

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Event date： 2012.3

Venue：吹田  

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Event date： 2012.3

Venue：吹田  

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Event date： 2012.3

Venue：吹田  

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Event date： 2012.3

Language：Japanese  

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Event date： 2012.3

Language：Japanese  

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Event date： 2012.3

Language：Japanese  

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Event date： 2012.3

Language：Japanese  

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Event date： 2012.3

Language：Japanese  

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Event date： 2012.3

Language：Japanese  

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Event date： 2012.3

Language：Japanese  

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Event date： 2012.1

Venue：吹田  

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Event date： 2012.1

Venue：吹田  

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Event date： 2012.1

Venue：吹田  

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Event date： 2012.1

Language：Japanese  

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Event date： 2012.1

Venue：豊中  

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Event date： 2012.1

Venue：豊中  

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Event date： 2012.1

Venue：豊中  

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Event date： 2012.1

Venue：豊中  

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Event date： 2012.1

Venue：豊中  

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Event date： 2012.1

Language：Japanese  

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Event date： 2012.1

Language：Japanese  

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Event date： 2012.1

Language：Japanese  

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Event date： 2012.1

Language：Japanese  

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Event date： 2012.1

Language：Japanese