Biomedical subjects

Yoshifumi Saijo

Publications and source records attributed to Yoshifumi Saijo.

At least 19 recordsLinked to original sources

PubMed2006

Non-mineralized fibrocartilage shows the lowest elastic modulus in the rabbit supraspinatus tendon insertion: measurement with scanning acoustic microscopy.

The acoustic properties of rabbit supraspinatus tendon insertions were measured by scanning acoustic microscopy. After cutting parallel to the supraspinatus tendon fibers, specimens were fixed with 10% neutralized formalin, embedded in paraffin, and sectioned. Both the sound speed and the attenuation constant were measured at the insertion site. The 2-dimensional distribution of the sound speed and that of the attenuation constant were displayed with color-coded scales. The acoustic properties reflected both the histologic architecture and the collagen type. In the tendon proper and the non-mineralized fibrocartilage, the sound speed and attenuation constant gradually decreased as the predominant collagen type changed from I to II. In the mineralized fibrocartilage, they increased markedly with the mineralization of the fibrocartilaginous tissue. These results indicate that the non-mineralized fibrocartilage shows the lowest elastic modulus among 4 zones at the insertion site, which could be interpreted as an adaptation to various types of biomechanical stress.

Adaptation, Physiological↗

PubMed2006

Intravascular two-dimensional tissue strain imaging.

Our goal is to achieve the precise quantitative imaging of tissue elasticity in clinical settings. In the present study, we measured basic ultrasonic characteristics of atherosclerosis by two-dimensional (2D) intravascular tissue velocity imaging. Radio-frequency (RF) signal from a clinically used IVUS apparatus was digitized at 500 MSa/s and stored in a workstation. First, the correlation coefficient between two consecutive frames was calculated in the rotational direction and the rotational disuniformity was corrected to obtain the maximum correlation coefficient. Then, the polar coordinate images were converted into rectangular coordinate images and the images were divided into 64 by 64 square shaped regions of interest (ROIs). The correlation and displacement of the ROIs between the consecutive two frames were calculated by template matching method. Two-dimensional tissue velocity was defined as the vectors of displacement of ROI with 0.7 and more correlation. IVUS studies were performed in directional coronary atherectomy (DCA) procedures. The specimens excised by DCA were stained with Elastica-Masson's trichrome staining and CD68 immunochemical staining. Eleven cases (including two no re-flow cases and one perforation case) were intraoperatively observed by IVUS and the specimens obtained by DCA were observed by optical microscopy. The specimen from homogeneous 2D strain was collagen dominant fibrosis and the specimen from a lesion with complex vectors contained CD68 positive cells and degenerated collagen fibers, which indicated the plaque was vulnerable.

Algorithms↗

PubMed2006

Ultrasonic speed microscopy for imaging of coronary artery.

We have been developing a scanning acoustic microscope (SAM) system for medicine and biology featuring quantitative measurement of ultrasonic speed and attenuation of soft tissues. In the present study, we will propose a new concept ultrasonic speed microscopy that can measure the thickness and ultrasonic speed using fast Fourier transform of a single pulsed wave instead of continuous waves used in conventional SAM systems. Six coronary arteries were frozen and sectioned approximately 10 microm in thickness. They were mounted on glass slides without cover slips. The scanning time of a frame with 300 x 300 pixels was 121 s and two-dimensional distribution of ultrasonic speed was obtained. The ultrasonic speed was 1720 m/s in the thickened intima with collagen fiber, 1520 m/s in lipid deposition underlying fibrous cap and 1830 m/s in calcified lesion in the intima. These basic measurements will help understanding echogenecity in intravascular ultrasound (IVUS) images. Imaging of coronary artery with the ultrasonic speed microscopy provides important information for study of IVUS coronary imaging.

Algorithms↗

PubMed2006

Does decalcification alter the tissue sound speed of rabbit supraspinatus tendon insertion? In vitro measurement using scanning acoustic microscopy.

Failure of the tendon or ligament insertions is one of the most common injuries in the Orthopaedic field. To elucidate the pathogenesis of those injuries, the authors had attempted to measure the tissue sound speed that could be correlated to its elasticity using scanning acoustic microscopy (SAM). For the application of SAM to tendon or ligament insertions, it was necessary to determine the role of decalcification in SAM measurements since mineralized tissues including bone or mineralized fibrocartilage were present at the insertion site. To assess whether decalcification alters the tissue sound speed or not, supraspinatus tendon insertion of six Japanese white rabbits were measured with SAM operating in the frequency range of 50-150 MHz. Right supraspinatus tendons attached to the humeral head were cut into two pieces at the center of the tendon. Then, they were fixed with 10% neutralized formalin for 12 h. In each specimen, medial half was not decalcified, while lateral half was decalcified with ethylene-diamine-tetra-acetic acid (EDTA). After embedding in paraffin, 5 microm thick specimens were prepared for the measurement using SAM. The mean sound speed in each histologic zone was evaluated, and subsequently compared to that measured in the undecalcified and the decalcified specimens. Mean sound speed of non-mineralized fibrocartilage was 1544 m/s in the undecalcified specimens, while the value of 1541 m/s was determined in the decalcified ones. On the other hand, it decreased 2-3% after decalcification in the mineralized tissue including mineralized fibrocartilage and bone (mineralized fibrocartilage: undecalcified = 1648 m/s, decalcified = 1604 m/s; bone: undecalcified = 1716 m/s, decalcified = 1677 m/s). However, no significant differences were found between the undecalcified and the decalcified specimens (non-mineralized fibrocartilage: p = 0.84, mineralized fibrocartilage: p = 0.35, bone: p = 0.28). These results indicate that SAM could be applied to determine the properties of the tendon or the ligament insertions after decalcification with EDTA. Although SAM is applicable only for in vitro experimental study, it is expected that these data will contribute to better understanding concerning the biomechanics of tendon or ligament insertions as well as the pathogenesis of their failure at a microscopic level.

Animals↗

PubMed2006

Impact of type A behavior on brachial-ankle pulse wave velocity in Japanese.

Pulse wave velocity (PWV) is the velocity of a pulse wave traveling a given distance between 2 sites in the arterial system, and is a well-known indicator of arteriosclerosis. Brachial-ankle PWV (baPWV) is a parameter more simple to obtain, compared with the conventional PWV, and is an easy and effective means of evaluating arteriosclerosis. BaPWV can be obtained by only wrapping the four extremities with blood pressure cuffs, and it can be easily used to screen a large number of subjects. Type A behavior has been confirmed as an independent risk factor for the development of coronary heart disease. To examine the relationship between Type A behavior and arteriosclerosis, 307 normal Japanese subjects were classified into either a Type A group (n = 90) or a non-Type A group (n = 217) by using Maeda's Type A Scale. BaPWV was evaluated using a PWV diagnosis device. The baPWV in the Type A group was significantly higher than that obtained in the non-Type A group. The baPWV showed a positive correlation with age both in the Type A group and in the non-Type A group; however, the straight-line regression slope of baPWV versus age in the Type A group was significantly larger than that in the non-Type A group. Therefore, our results suggest that arteriosclerosis might be promoted earlier in subjects expressing the Type A behavior pattern. Type A behavior pattern is confirmed as a risk factor for arteriosclerosis, and may increase the risk of the cardiovascular disease related to arteriosclerosis.

Adult↗

PubMed2005

Fundamental study of ultrasonic-measurement-integrated simulation of real blood flow in the aorta.

Acquisition of detailed information on the velocity and pressure fields of the blood flow is essential to achieve accurate diagnosis or treatment for serious circulatory diseases such as aortic aneurysms. A possible way to obtain such information is integration of numerical simulation and color Doppler ultrasonography in the framework of a flow observer. This methodology, namely, Ultrasonic-Measurement-Integrated (UMI) Simulation, consists of the following processes. At each time step of numerical simulation, the difference between the measurable output signal and the signal indicated by numerical simulation is evaluated. Feedback signals are generated from the difference, and numerical simulation is updated applying the feedback signal to compensate for the difference. This paper deals with a numerical study on the fundamental characteristics of UMI simulation using a simple two-dimensional model problem for the blood flow in an aorta with an aneurysm. The effect of the number of feedback points and the feedback formula are investigated systematically. It is revealed that the result of UMI simulation in the feedback domain rapidly converges to the standard solution, even with usually inevitable incorrect upstream boundary conditions. Finally, an example of UMI simulation with feedback from real color Doppler measurement also shows a good agreement with measurement.

Aortic Aneurysm, Thoracic↗

PubMed2005

Influence of aging on cardiac function examined by echocardiography.

We assessed the influence of aging on cardiac function by means of parameters measured by echocardiography. The study group consisted of 494 normal subjects aged 13 to 87 years. We measured the ratio of early filling (E) and atrial contraction (A) transmitral flow velocities (E/A) of left and right ventricular inflow (LV E/A and RV E/A) for assessment of diastolic function. We also measured left ventricular ejection fraction (LVEF), and the ratio of pre-ejection period (PEP) and ejection time (ET) of the left ventricle (PEP/ET) for assessment of systolic function. Both LV E/A and RV E/A decreased significantly with aging while LVEF and PEP/ET remained normal range. The decline rate as aging was greater in LV E/A than in RV E/A. These results showed that both left and right ventricular diastolic function deteriorated with aging while left ventricular systolic function was not noticeably affected by aging. We suggest that indexes of diastolic function are more sensitive than those of systolic function when the natural course is studied in a large population.

Adolescent↗

PubMed2005

Comparison of brachial-ankle pulse wave velocity in Japanese and Russians.

Pulse wave velocity (PWV) is a well-known indicator of arterial stiffness and a marker of the presence of vascular lesions. Cardiovascular mortality in Russia has become the highest in the world. The Japanese are enjoying long lives, and the mortality caused by cardiovascular diseases has thus far remained at lower levels than that in Russia. In this study, we focused on brachial-ankle pulse wave velocity (baPWV) obtained from normal human subjects in Russia as well as in Japan, and compared their respective cardiovascular risks. We evaluated baPWV in 337 Japanese and 138 Russian healthy subjects. The baPWV was recorded using a PWV diagnosis device. BaPWV was measured between 2 locations of the arterial tree. The baPWV in the Russian group was significantly higher than that obtained in the Japanese of two groups categorized by age (40-59 years and 60- years). Further, body mass index (BMI), systolic blood pressure (SBP) and diastolic blood pressure in the Russian group were significantly higher than those obtained in Japanese in three age groups (under 39 years, 40-59 years, and 60- years). Moreover, the baPWV indicated a positive correlation with age, BMI and SBP in both Japanese and Russians, although the increasing trend of the baPWV against age of the Russian group had a larger value than that of the Japanese. Therefore, we suggest that arterial stiffness might be promoted earlier in the Russian group, which might be the main cause of the increased cardiovascular risk in Russia.

Adult↗

PubMed2005

Sound speed scanning acoustic microscopy for biomedical applications.

Since 1985, we have been developing a scanning acoustic microscope (SAM) system for biomedical use and have been investigating the acoustic properties of various organs and disease states by using this SAM system. In biomedicine, SAM is useful for intraoperative pathological examination, study of low-frequency ultrasonic images, and assessment of biomechanics at a microscopic level. Recently, we have proposed a new concept -- acoustic microscopy -- using a single pulsed wave instead of continuous waves used in conventional SAM systems. In the present study, we compared two systems by measuring the same biological material. The sound speed image obtained by sound speed microscopy corresponded well to that obtained using a conventional SAM system. Lesions with hyaline degeneration showed a lower sound speed when compared with that of normal myocardium. Frequency domain analysis of amplitude and phase by both methods also showed similar characteristics. Although the data acquisition time of one frame was greater than that in conventional SAM, the total time required for calculation was significantly shorter. The SAM system can be applied to intraoperative pathological examination.

Animals↗

PubMed2005

Detection and correction of aliasing in ultrasonic measurement of blood flows with Ultrasonic-Measurement-Integrated simulation.

Detailed information of real blood flows is essential to develop an accurate diagnosis or treatment for serious circulatory diseases such as aortic aneurysms. Ultrasonic-Measurement-Integrated (UMI) simulation, in which feedback signals from the ultrasonic measurement make the simulation converge to the real blood flow, is a key to solving this problem. However, aliasing in the ultrasonic blood velocity measurement causes UMI simulation to converge to an erroneous result. In this paper, we have investigated the detection and the correction of aliasing in UMI simulation. The artificial force in the feedback of UMI simulation can be used as an index to detect the aliasing. We have proposed two ways for the correction of the aliasing. Correction A, in which measurement velocity is replaced with the computational one at the monitoring point where the aliasing is detected, substantially improves the accuracy of UMI simulation. Correction B, in which measurement velocity is replaced with an estimated Doppler velocity, can provide exactly the same result as that of UMI simulation using the nonaliased standard solution. Although correction B gives the most accurate result, correction A seems more robust and, therefore, a beneficial choice considering the other artifacts in the measurement.

Doppler Effect↗

PubMed2004

Paclitaxel prevents loss of pulmonary endothelial barrier integrity during cold preservation.

BACKGROUND: Cold preservation is the most practical method to maintain the viability of isolated lungs. However, rapid cooling may affect pulmonary endothelial function. We examined the effects of microtubule stabilization with paclitaxel on pulmonary endothelial barrier integrity under cold temperature. METHODS: Human pulmonary arterial endothelial cells were incubated at 4 degrees C for 2 hr in the presence or absence of paclitaxel (2.5 micromol/L). Microtubules was visualized using immunocytochemical techniques. Ultrasonic attenuation was measured with scanning acoustic microscopy. Endothelial barrier integrity was measured as transendothelial electric resistance. In addition, we examined graft function in a rat lung transplantation model, in which the donor lung had been preserved in the presence of paclitaxel (2.5 micromol/L) at 4 degrees C for 12 hr. RESULTS: Low temperature caused a reversible microtubule disassembly, but the structure of microtubules was preserved by paclitaxel. Paclitaxel prevented the cooling-induced decrease in ultrasonic attenuation and transendothelial electric resistance. In a rat transplantation model, we found that preservation with paclitaxel successfully improved the oxygenation performance of the donor lung, which demonstrated only mild congestion and less significant interstitial edema without fluid accumulation in the alveolar spaces. CONCLUSIONS: Our results indicate that microtubule stabilization with paclitaxel may be beneficial to prevent the loss of the endothelial barrier during cold preservation. We conclude that the use of paclitaxel in organ preservation solutions is useful in protecting pulmonary endothelial barrier integrity during cold preservation, thereby reducing the occurrence of early graft failure.

Animals↗

PubMed2004

Development of an ultra-portable echo device connected to USB port.

In practical cardiology, a stethoscope based auscultation has been used to reveal the patient's clinical status. Recently, several hand-held echo devices are going on market and they are expected to play a role as "visible" auscultation instead of stethoscope. We have developed a portable and inexpensive echo device which can be used for screening of cardiac function. Two single element transducers were attached 180 degrees apart to a rotor with 14-mm diameter. The mechanical scanner, integrated circuits for transmitting and receiving ultrasonic signals and an A/D converter were encapsulated in a 150 x 40 mm probe weighing 200 g. The scan was started and the image was displayed on a Windows based personal computer (PC) as soon as the probe was connected to USB 2.0 port of the PC. The central frequency was available between 2.5 and 7.5 MHz, the image depth was 15 cm and the frame rate was 30/s. The estimated price of this ultra-portable ultrasound is about 3000 US dollars with software. For 69 cardiac patients with informed consent, image quality was compared with those obtained with basic range diagnostic echo machines. Left ventricular ejection fraction (EF) derived from normal M-mode image of standard machines (EFm) were compared with visual EF of the ultra-portable ultrasound device (EFv). The image quality was comparable to the basic range diagnostic echo machines although short axis view of aortic root was not clearly visualized because the probe was too large for intercostal approach. EFv agreed well with EFm. The ultra-portable ultrasound may provide useful information on screening and health care.

Echocardiography↗

PubMed2004

Tissue velocity imaging of coronary artery by rotating-type intravascular ultrasound.

Intravascular ultrasound (IVUS) provides not only the dimensions of coronary artery but the information of tissue components. In catheterization laboratory, soft and hard plaques are classified by visual inspection of echo intensity. So-called soft plaque contains lipid core or thrombus and it is believed to be more vulnerable than a hard plaque. However, it is not simple to analyze the echo signals quantitatively. When we look at a reflection signal, the intensity is affected by the distance of the object, the medium between transducer and objects and the fluctuation caused by rotation of IVUS probe. The time of flight is also affected by the sound speed of the medium and Doppler shift caused by tissue motion but usually those can be neglected. Thus, the analysis of RF signal in time domain can be more quantitative than intensity of RF signal. In the present study, a novel imaging technique called "intravascular tissue velocity imaging" was developed for searching a vulnerable plaque. Radio-frequency (RF) signal from a clinically used IVUS apparatus was digitized at 500 MSa/s and stored in a workstation. First, non-uniform rotation was corrected by maximizing the correlation coefficient of circumferential RF signal distribution in two consecutive frames. Then, the correlation and displacement were calculated by analyzing the radial difference of RF signal. Tissue velocity was determined by the displacement and the frame rate. The correlation image of normal and atherosclerotic coronary arteries clearly showed the internal and external borders of arterial wall. Soft plaque with low echo area in the intima showed high velocity while the calcified lesion showed the very low tissue velocity. This technique provides important information on tissue character of coronary artery.

Coronary Artery Disease↗

PubMed2004

Acoustic properties of aortic aneurysm obtained with scanning acoustic microscopy.

In aortic aneurysm tissues, macrophages and their secretion of matrix metalloproteinases (MMPs) are playing important role for tissue degeneration. Some studies have shown that weakening of the mechanical properties of the degenerated tissues may progress the expansion of the aneurysm. However, actual measurement of the mechanical properties has not been investigated at microscopic level. The objective of the present study is to assess the mechanical properties of aortic aneurysm tissues by measuring acoustic properties by scanning acoustic microscopy (SAM). Twenty-one cases of aortic aneurysm including renal and common iliac aneurysm tissues were surgically excised. Each tissue was fixed by 4% formaldehyde and the specimens were treated as (1) picrosirius red staining for normal and polarized light microscopy, (2) CD68 staining for macrophage detection, and (3) no staining for acoustic microscopy. A specially developed SAM system operating in the frequency range of 100-200 MHz, was employed in the measurement. Images of amplitude and phase are obtained in a field of 2x2 mm. The intima was mainly consisted of degenerated collagen without polarization of picrosirius red staining. Macrophages stained by CD68 were observed near the degenerated collagen fibers. The sound speed was 1567 m/s in the intima, 1576 m/s in the media, 1640 m/s in the adventitia, respectively. Infiltration of macrophages showed higher values of attenuation and sound speed than the surrounding tissues. The sound speed of the intima was significantly lower than our previous measurement of atherosclerotic aorta without aneurismal change. As the tissue elasticity is closely correlated with the sound speed, the elasticity of the intima was considered to be lower in aneurysm tissues. This mechanical weakness may contribute to the expansion of the diameter of the aneurysm. Acoustic microscopy provided important data for assessing tissue mechanical properties of abdominal aneurysm.

Acoustics↗

PubMed2004

A Japanese-Russian collaborative study on aging and atherosclerosis.

In Russia, the average life span is decreasing. This phenomenon has not been previously observed in the western hemisphere during periods of relative peace. Although this trend can be attributed to various causes, the available statistics suggest that approximately 55% of the total mortality in Russia at the present time is due to cardiovascular events. Similarly, cardiovascular events are also increasing in Japan and are associated with changes in eating habits. A Japanese-Russian international collaborative study was therefore initiated to investigate this. Data on 102 normal Russian subjects were obtained from a total of 345 patients treated at the Smolensk State Medical Academy outpatients' clinic. The data on the Japanese patients were collected at Tohoku University, Tohoku Rosai Hospital, and Fukuda Denshi Company. Sixty-seven healthy male Japanese volunteers were compared with 44 healthy male Russian patients. In this study, Vasera VS1000 (Fukuda Denshi, Tokyo) was utilized to measure pulse wave velocity (PWV). Linear regression analysis was performed, and the results showed that brachial-ankle PWV (baPWV) was significantly higher in the Russian compared with the Japanese study group. With regard to aging, PWV was found to increase both in the Japanese and Russian subjects, with a significant increase in the latter group during their 40s compared with the Japanese, and with this tendency being carried forward into the 50s. This may be the principal cause for the higher incidence of cardiovascular events reported among Russians. Furthermore, when a straight line regression analysis was performed, the zero axis intercept in both cases showed almost the same value. These results indicated that the PWV may be almost the same in Japanese and Russian populations at the time of birth. In conclusion, at the time of birth, there is no difference in the atherosclerotic status of Japanese and Russian infants. However, over time atherosclerosis becomes more apparent and progresses significantly in the case of Russian subjects. This finding is observed through the analysis of PWV. The present authors intend to continue their study aimed at preventing the further development of atherosclerosis through medical intervention.

Aging↗

PubMed2004

Brachio-ankle pulse wave velocity and cardio-ankle vascular index (CAVI).

In order to diagnose arteriosclerosis in any part of the body, pulse wave velocity (PWV) measurement is a useful approach. However, it is considered that the technique of PWV measurement should be simplified. A new method for measuring PWV has therefore been proposed in Japan. The PWV of the brachial artery (ba) and the ankle was measured by applying air pressure with the aid of a volume plethysmograph. Comparisons between the baPWV measurement method and the conventional method are currently being performed. Since satisfactory results have been obtained to date, baPWV has gained popularity throughout Japan. Since this method measures PWV in the arm and foot, it may be said that aortic PWV is not reflected though a large amount of past PWV measurements. BaPWV is influenced by blood pressure. With the baPWV technique, blood pressure compensation is not carried out. Furthermore, the pulse pressure is measured by air pressure; therefore any stimulus that exerts pressure on an artery may influence these results. Due to these reasons, a cardie-ankle vascular index (CAVI) has been proposed in which the pressure wave form indicating the closing of the aortic valve appears in the form of an arterial pressure wave after a fixed delay time. This delay is the time difference between the actual closing of the aortic valve and the measuring point. Prior to the introduction of baPWV, PWV was measured in the carotid artery and foot. As in traditional PWV, baPWV uses the delay time, but between the brachial artery and the ankle artery. However, the carotid artery differs from the brachial artery, and the measured value differs depending on whether the arteriosclerosis is present in the carotid artery or the brachial artery. CAVI is calculated from the ECG, PCG, brachial artery waveform and ankle artery waveform using a special algorithm. This new method represents a breakthrough in the diagnosis of atherosclerosis.

Ankle↗

PubMed2004

Addition of rhythm to non-pulsatile circulation.

The development of a rotary blood pump (RP) is desirable as it can be used as a small ventricular assistance device (VAD). However, a RP does not generate any pulse. It may be physiologically better for the patient if the RP could generate a pulse. We have attempted to develop a device that produces a pulse in the RP. Intra-aortic balloon pumping (IABP) is effective in producing a pulse. However, the IABP cannot be implanted inside the body. Therefore, an attempt was made to develop pulse-generating equipment that was not driven by air pressure. The ball screw motor was considered as a possible candidate. In the future, we plan to apply small shape memory alloys. An electrohydraulic system was adopted, and actuator power output was connected to the diaphragm. The diaphragm was placed outside the ventricle. Most RPs developed throughout the world drain blood from the ventricle. The pulse wave should be generated if a pulse is added by the part from which blood is being drawn. In this study, animal experiments were conducted and the output assistance was tested from outside the ventricle. The device operated effectively in the animal experiment. The RP can easily be equipped with this device at the time of performing the implant operation. For a patient with problems of peripheral circulation and the internal organ function, it may prove to be an effective device.

Animal Experimentation↗

PubMed2003

Artificial myocardium with an artificial baroreflex system using nano technology.

Where is the place which should be helped in a patient with congestive heart failure? The answer may be contraction of the heart. At Tohoku University, development research of "the artificial myocardium" has been conducted, using a ball screw type electromagnetic motor. Furthermore, super-miniaturization is being attempted at present. Thus, a system with shape memory alloy is being developed. The cooling speed problem was solved by the application of the Peltier element. A drive at a speed equal to that of a heartbeat was realized by the application of this system. At present, a ventricular assist device is used for patients waiting for a heart transplant in Japan. An air driven type system disturbs a patient's QOL remarkably because it is connected to the drive device. With our concept, energy is provided by using the electromagnetic force from outside of the body by the use of transcutaneous energy transmission system. Magnetic shielding by amorphous fibers was used at Tohoku University to improve the total efficiency. A natural heart can alter the cardiac output corresponding to the demand. Artificial internal organs must participate in the system of the living body, too. Tohoku University has developed a resistance based artificial heart control algorithm, which simulated a baroreflex system to cope with every demand. Nano level sensing equipment is now under development at Tohoku University. At present, development is being conducted aiming at an "intelligent artificial myocardium".

Baroreflex↗