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Biomedical subjects

F Kajiya

Publications and source records attributed to F Kajiya.

At least 91 records · Page 5Linked to original sources
PubMed1986

[Coronary blood flow velocities in humans evaluated during cardiac surgery using a 20 MHz 80 + 1 channel ultrasound pulsed Doppler velocimeter].

We have developed an 80 + 1 channel high resolution pulsed Doppler velocimeter for measuring in detail the blood flow velocities in relatively small human vessels (1-5 mm in diameter). Real time velocity measurements were performed at 80 sample points using a multigated zero-cross method. The Doppler signal in the desired channel was subjected to real time Fourier analysis. This facilitated analyzing in detail the blood flow velocity profile across vessel, as well as the velocity distribution in a sample volume. The sampling volume was pi X 0.5(2) X 0.2 mm3 and the maximum depth was 1.5 cm. When the incidence angle was selected as 60 degrees, the velocity resolution and maximum velocity were 1.5 and 1.9 m/sec, respectively. Blood flow velocities were measured in the coronary artery and in the aorto-coronary bypass graft in patients during cardiac surgery. The blood flow velocities in the normal coronary artery had a predominantly diastolic pattern which is characteristic of coronary artery flow. Comparing with the systolic forward velocities in the left coronary artery, those of the right coronary artery were more prominent. The velocity wave forms in the graft and in the coronary artery distal to the insertion of the graft had a predominantly diastolic pattern when there was sufficient coronary blood flow through the graft. In contrast, during the occlusion of the graft, the blood velocity wave form in the distal coronary artery became predominantly systolic, indicating insufficient myocardial inflow before the bypass graft. Intravenous dipyridamole administration increased the bypass flow by 50% in a patient who had 100% occlusion before the bypass operation. This indicates that the coronary reserve can still be preserved in some cases of total coronary occlusion. With an intra-aortic balloon pumping (IABP) assist (2:1), the velocity wave form in the graft had predominantly diastolic in both IABP-on and -off beats. However, diastolic augmentation and systolic reduction of the velocity wave form were clearly observed in beats with IABP-on. The velocity wave forms in the anterior descending coronary artery in a patient with aortic regurgitation showed a predominantly systolic pattern with a broad velocity spectrum. After aortic valve replacement, the blood velocity pattern became predominantly diastolic, indicating improvement of the coronary perfusion into the myocardium. In conclusion, our velocimeter proved effective for evaluating coronary blood flow velocities in patients during cardiac surgery.

Aortic Valve Insufficiency↗
PubMed1985

Evaluation of phasic blood flow velocity in the great cardiac vein by a laser Doppler method.

In the present study, characteristics of the phasic flow pattern in the great cardiac vein and the mechanism of such pattern formation were investigated using a laser Doppler velocimeter with an optic fiber probe. The laser Doppler velocimeter allowed measurements of venous blood velocity under more physiological conditions than were possible with previous methods. Moreover, venous blood flow measurement in the great cardiac vein mirrors the effects of myocardial contraction on the venous flow more directly than does measurement in the coronary sinus. Thus, our method is considered very useful. Results obtained from the present study are as follows: 1) Measurement of the phasic flow in the great cardiac vein was made in 11 anesthetized dogs using our laser Doppler method. The blood velocity curve obtained in the great cardiac vein was always characterized by a prominent systolic flow wave (SFW). The mean value for the maximum velocities under control conditions in 11 cases was 40 +/- 13 cm/s. The blood velocity increased with the onset of left ventricular ejection and decreased gradually after the peak formation at mid- or late systole.--2) Besides the above SFW, one or two small wave components were frequently observed during the atrial contraction period and/or during the isovolumic contraction phase. On the waveform during the atrial contraction period, two cases showed forward flow, while one case showed reverse flow. The small reverse flow waves during the isovolumic contraction phase were found in seven cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Evaluation of local blood flow velocity in proximal and distal coronary arteries by laser Doppler method.

A high resolution laser Doppler velocimeter using an optical fiber was developed to evaluate detailed characteristics of phasic blood flow in the coronary artery. Local blood flow velocities were measured in the proximal (0.27 +/- 0.05 cm i.d.) and the distal portion (0.09 +/- 0.02 cm i.d.) of the left circumflex coronary artery of anesthetized, open-chest dogs. The velocity waveform in the central axial region of the vessel and the velocity profile across the vascular lumen were compared in the proximal and the distal portions.

Animals↗
PubMed1982

Engineering approaches to the evaluation of cardiac function in future.

The present and future impact of engineering technology on observing and evaluating cardiac function is discussed, with particular reference to the development of cardiac measurements. Several new topics in cardiac imaging, manometers, and blood flow velocity measurements are briefly reviewed. The effectiveness of cardiac models in the evaluation of cardiac function is emphasized, although there are many unsolved basic problems concerning muscle mechanics of the heart. Overall, comprehensive studies in cooperation with clinical cardiology, cardiac physiology, and engineering are necessary to accelerate further progress in the evaluation of cardiac function.

Biomedical Engineering↗
PubMed1981

Measurement of point velocity in the canine coronary artery by laser Doppler velocimeter with optical fiber.

A laser Doppler velocimeter with an optical fiber was developed to investigate point blood velocity in the arteries and was applied to the measurement of blood velocity in the canine coronary artery. Fundamental experiments revealed that the accuracy of this method was satisfactory, since an excellent linear relation was found between the known blood velocity and the Doppler shift frequency (r = 0.998). The fiber tip (0.1 mm diam.) was inserted into the proximal portion of the left circumflex coronary artery and was traversed across the vascular lumen to measure the point velocity at each sampling point. Detailed velocity profiles were than reconstructed sequentially in three dimensional coordinates, i.e., velocity, diameter and time. In general the velocity waveform showed a diastolic dominant pattern which is characteristic of coronary arterial flow. One peak in early systole and two peaks in early and in late diastole were commonly observed in the velocity waveform near the center-line of the vessel. The velocity profiles were flat in the axial region and declined abruptly near the vessel wall. These results indicate that the laser Doppler velocimetry with an optimal fiber proved to be an accurate and feasible method of evaluating the point velocity of coronary artery flow.

Animals↗