Takaki Shimura

Ultrasound medium characteristics measuring apparatus

An apparatus for measuring acoustic characteristic values of a medium by sending ultrasound pulses into the medium and analyzing the reflected waves from the medium. Medium characteristic values are extracted from the reflected waves, and spectrum scalloping is eliminated. The present invention executes the nonlinear filtering process, for example, the median filtering process to the spectrums, applies a model spectrum to the filtered result and thereby facilitates measurement of supressing fluctuation even when a small number of space average samples one used, by obtaining β from such model spectrum.

Ultrasonic equipment and its catheter-type ultrasonic probe

An Ultrasonic Equipment and its Catheter-type Ultrasonic Probe can be inserted in capillaries such as blood vessels, and comprises a catheter-type ultrasonic probe for generating ultrasonic waves by a piezoelectric transducer arrayed at its tip. A plurality of the piezoelectric transducer segments are arrayed on a two-dimensional plane, perpendicular or approximately perpendicular to the insertion direction of the probe into a capillary with their ultrasonic wave emitting surface faced in the insertion direction. A part of the plane is cut out to provide a guide unit for passing a treating catheter or a guide wire in the insertion direction.

Validation of transthoracic myocardial ultrasonic tissue characterization: comparison of transthoracic and open-chest measurements of integrated backscatter

To investigate whether myocardial integrated backscatter (IB) can be measured through the chest wall, myocardial IB parameters were measured in five adult mongrel dogs with a newly developed IB imaging system capable of measurements of myocardial IB relative to backscatter from the blood. There was no significant difference in the calibrated myocardial IB between the closed chest and the open chest conditions either in the septum or in the posterior wall if a 2.5- or 3.5-MHz frequency transducer was used. There was no significant difference in the magnitude of cyclic variation in IB between the closed chest and the open chest conditions independent of the frequency of the transducer used. These data suggest that we can accurately measure not only the magnitude of cyclic variation in IB but also the calibrated myocardial IB through the chest wall with a 2.5- or 3.5-MHz frequency transducer. Such data may validate measurements of myocardial IB parameters through the chest wall even in humans.

Nonlinear parameter tomography system using counter-propagating probe and pump waves

In this paper, a novel tomographic system for imaging the nonlinear parameter (B/A) of biological objects is described. This parameter is closely related to the detailed properties of tissue, and may well provide a new powerful tool for ultrasonic tissue characterization. In our new system, an impulsive, relatively high power (10 mW/cm2), low frequency pump wave is applied from the opposite direction of a cw low intensity probe wave of high frequency (5 MHz) so that the phase of the probe wave is modulated sequentially by the product of the nonlinear parameter (B/A) along the beam (x axis) and the pressure of the impulsive pump wave. This modulated probe wave is detected and demodulated to derive the distribution of (B/A) along the x axis. Many responses are averaged to increase the S/N ratio. Inverse or other filtering operations are applied to widen the frequency bandwidth of the pump wave. The entire system is realized in hardware. The counterbeam orientation makes the imaging system compact, with easy access to many parts of the human body. Its resolution is two times that of the perpendicular system proposed previously by us and the attenuation of the pump wave can also be compensated for easily. A practical system aimed at breast and liver diagnosis is described. The principle of the method and the system construction are described. B/A images of several objects are given.

Method of displaying stream lines of an inhomogeneous flowing medium and a device therefor

A method and device to display in real time a stream line of an inhomogeneous flowing medium such as blood flow in a heart, is disclosed. The object is scanned several times by ultrasonic beam pulses. Echoes appearing within a predetermined time interval at each point of the object are combined to produce an image of speckles formed by the flow. The process is repeated several times, to obtain the motion of the speckles. Differences between the images of spatially correlated speckles obtained within the time interval, produce the segments of the stream lines. Differences between successive frames or successive lines can be used to produce the speckle and several methods of scanning are disclosed to produce the differences between the images to produce the stream lines.

Ultrasonic diagnosis apparatus for tissue characterization

A diagnosis apparatus for discriminating a property of the tissue to be observed from the reflected ultrasonic wave uses the nature of the fine structure of the tissue, and more practically uses the interval of small reflecting bodies dispersely distributed in the tissue as the parameters. The intervals flucatuate. Therefore, an average value and/or a degree of fluctuation is calculated and is displayed. For obtaining the average interval, a method of using the cepstrum of the received signal or a method of using the self-correlation of the received signal can be used.

Apparatus for measuring the characteristics of an ultrasonic wave medium

The present invention relates to an apparatus which determines the distribution of the attenuation slope coefficient on a real-time basis using the center frequency shift. In one embodiment, the phase difference between a received signal and a reference signal is determined using EXCLUSIVE OR gates or an inverse trigonometric relation stored in a ROM. The phase difference is input to a differentiator which outputs the center frequency shift of the received signal on a real-time basis. The center frequency shift is input to another differentiator which outputs the attenuation slope coefficient. In other embodiments, the received signal is distributed into received signal bands, having different center frequencies, and signal characteristics of the received signal bands are averaged to remove virtually all effects of spectrum scalloping in the time domain. Thus, the attenuation slope coefficient is obtained without the effects of spectrum scalloping using simple hardware and without Fourier transformation.

Electro-sound transducer eliminating acoustic multi-reflection, and ultrasonic diagnostic apparatus applying it

An ultrasonic diagnostic apparatus protected from multi-reflection of sound echoes. Multi-reflection is avoided by eliminating the reflection from the surface of an electro-sound transducer. This invention eliminates the surface reflection of the transducer by following three methods: (a) changing a direction of each surface of an array of transducer elements to direct the reflected sound wave away from the main direction of the sound beam; (b) applying an acoustic matching layer to a surface of a piezo-electric device of the transducer to cancel out phases of sound waves reflected by the surfaces of the layer and the device; and (c) providing an acoustic matching surface on a front or back face of the piezo-electric device to cancel out phases of sound waves reflected by the surface of the device.

A measurement method for absolute value of integrated backscatter

The usefulness of measuring integrated backscatter in diagnosing ischemic heart disease remains to be determined due to the adverse effect of tissue attenuation on measurement accuracy. The measurement of the absolute value of integrated backscatter using as a reference the backscatter power from blood flow near the region of interest is discussed. The method eliminates the adaptive interval clutter component, enabling one to accurately calculate the backscatter power from the Doppler spectrum.<<ETX>>

Effect of saw-cut depth on characteristics of array transducer

The authors suggest that saw-cut depth affects the electroacoustic conversion characteristics of an array transducer. To investigate this, they made several samples and measured the impedance of the sawed part of the backing. The results indicate that this impedance is less than that of the solid backing because the acoustic velocity of the sawed part is decreased. Assuming that the sawed part acts as a pseudolayer between the PZT (lead zinc titanate) elements and backing, the authors calculated transducer conversion characteristics by computer simulation. On the basis of the simulation, they built transducers and measured their characteristics. Excellent agreement between the simulation and experiment supports the pseudolayer theory. It is concluded that by making good use of the saw-cut-depth effect, high-efficiency broad-bandwidth transducers can be made.<<ETX>>