Role of intra-ventricular vortex in left ventricular ejection elucidated by echo-dynamography.

Purpose: From the correlation between the blood flow dynamics and wall dynamics in the left ventriocle (LV) analyzed using echo-dynamography, the ejection mechanisms and role of the intra-ventricular vortex in the LV were elucidated in detail during the pre-ejection transitional period (pre-ETP), the very short period preceding LV ejection.

Methods: The study included 10 healthy volunteers. Flow structure was analyzed using echo-dynamography, and LV wall dynamics were measured using both high-frame-rate two-dimensional echocardiography and a phase difference tracking method we developed.

Deformability of the pulsating left ventricular wall: A new aspect elucidated by high resolution ultrasonic methods.

Background: Although the deformability of the left ventricular (LV) wall appears to be important in maintaining effective cardiac performance, this has not been debated by anyone, probably owing to the difficulties of the investigation.

Objectives: This study applies a new technology to demonstrate how the LV wall deforms so as to adjust for optimum cardiac performance.

Subjects And Methods: Ten healthy volunteers were the subjects.

Non-uniform distribution of the contraction/extension (C-E) in the left ventricular myocardium related to the myocardial function.

Objective: We attempted to disclose the microscopic characteristics of the non-uniform distribution of the contraction and extension (C-E) of the left ventricular (LV) myocardium using a new methodology (echo-dynamography).

Methods: The distributions of the "axial strain rate" (aSR) and the intra-mural velocity in the local areas of the free wall including the posterior wall (PW) and interventricular septum (IVS) were microscopically obtained using echo-dynamography with a high accuracy of 821 μm in the spatial resolution. The results were shown by the color M-mode echocardiogram or curvilinear graph.

New concept of the contraction-extension property of the left ventricular myocardium.

Objectives: Using newly developed ultrasonic technology, we attempted to disclose the characteristics of the left ventricular (LV) contraction-extension (C-E) property, which has an important relationship to LV function.

Methods: Strain rate (SR) distribution within the posterior wall and interventricular septum was microscopically measured with a high accuracy of 821μm in spatial resolution by using the phase difference tracking method. The subjects were 10 healthy men (aged 30-50 years).

Physiological basis and clinical significance of left ventricular suction studied using echo-dynamography.

Background: The existence as well as the exact genesis of left ventricular suction during rapid filling phase have been controversial. In the present study, we aimed at resolution of this problem using noninvasive and sophisticated ultrasonic methods. The clinical meaning was also documented.

Location of flow axis line in the left ventricle and its interaction with local myocardial motion.

Background: The interaction between local myocardial motion and blood flow dynamics should be assessed to evaluate left ventricular pump function.

Methods: The contour map of the absolute value of blood flow velocity in the left ventricle (LV) was drawn. The ridgeline of the contour was defined as the "flow axis line".

Spiral systolic blood flow in the ascending aorta and aortic arch analyzed by echo-dynamography.

Using echo-dynamography, systolic blood flow structure in the ascending aorta and aortic arch was investigated in 10 healthy volunteers. The blood flow structure was analyzed based on the two-dimensional (2D) and 1D velocity vector distributions, changing acceleration of flow direction (CAFD), vorticity distribution, and Doppler pressure distribution. To justify the results obtained in humans, in vitro experiments were done using straight and curved tube models of 20mm diameter.

A new echocardiographic method for identifying vortex flow in the left ventricle: numerical validation.

A new mathematical method for estimating velocity vectors from color Doppler datasets is proposed to image blood flow dynamics; this method has been called echodynamography or vector flow mapping (VFM). In this method, the concept of stream function is exploited to expand a 2-D distribution of radial velocities in polar coordinates, observed with color Doppler, to a 2-D distribution of velocity vectors. This study was designed to validate VFM using 3-D numerical flow models.

Blood flow structure and dynamics, and ejection mechanism in the left ventricle: analysis using echo-dynamography.

Using our "echo-dynamography", blood flow structure and flow dynamics during ventricular systole were investigated in 10 normal volunteers. The velocity vector distribution demonstrated blood flow during ejection was laminar along the ventricular septum. The characteristic flow structure was observed in each cardiac phases, early, mid- and late systole and was generated depending on the wall dynamic events such as peristaltic squeezing, hinge-like movement of the mitral ring plane, bellows action of the ventricle and dimensional changes in the funnel shape of the basal part of the ventricle, which were disclosed macroscopically by using the new technology of high speed scanning echo-tomography and microscopically by the strain rate distribution measured by phase tracking method.

Ultrasonic tissue characterization of atherosclerosis by a speed-of-sound microscanning system.

We have been developing a scanning acoustic microscope (SAM) system for medicine and biology featuring quantitative measurement of ultrasonic parameters of soft tissues. In the present study, we propose a new concept sound speed microscopy that can measure the thickness and speed of sound in the tissue using fast Fourier transform of a single pulsed wave instead of burst waves used in conventional SAM systems. Two coronary arteries were frozen and sectioned approximately 10 microm in thickness.

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.

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.

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.

Doppler pressure field deduced from the Doppler velocity field in an observation plane in a fluid.

A new method is developed for a nondisturbing and quantitative measurement of the pressure at an arbitrary point in a flowing fluid in three-dimensional (3-D) space. In this method, after measuring the velocity field in the observation plane (scanning plane) using the pulsed Doppler technique, the velocity component orthogonal to the Doppler velocity is deduced, taking the law of conservation of mass (the equation of continuity) into consideration. Then, the pressure, "Doppler pressure," is calculated from the acceleration.

Influence of tissue preparation on the acoustic properties of tissue sections at high frequencies.

The purpose of the present study was to clarify the influence of tissue preparation on the high-frequency acoustic properties by comparing the acoustic properties of the formalin-fixed, paraffin-embedded, deparaffinized sections and formalin-fixed, frozen sections for two types of fat-containing renal cancer and fat-free renal oncocytoma using a SAM. There was no significant difference for the sound speed among the clear cell, granular cell renal cancer and oncocytoma in either groups, but the attenuation constant was significantly higher for the frozen than for that of the paraffin section in fat-containing renal cancer. In fat-free oncocytoma, there was no significant difference for the attenuation constant in either group.