Yoshimitsu Kikuchi

Early Cancer Diagnosis through Ultrasonics

We succeeded in obtaining ultrasonic echoes from human intracranial ventricles and brain tumors, not only through the dura mater during surgical operation, but also through the skull at preoperative and postoperative examinations. In these experiments, we used 1–5 megacycle ultrasound and A‐Scope presentation. We found, among other things, that an echo from the ventricle wall pulsates slowly and rhythmically with synchronization to each heartbeat. Furthermore, we succeeded in detecting echoes from various abdominal organs and tumors through the skin, and found that the echoes reflected from the bowel move in correlation to bowel peristalsis. As the echoes are so clearly perceptible, we are now engaged in developing an “ultrasono‐tomography” for a horizontal section of the human head or abdomen by plan‐position indication; such a tomograph cannot be obtained by any other penetration‐method including x‐ray. In thoracic examination also, we have made achievements not only in ultrasonic diagnosis of breast tu...

Physical Structure of DC Diode Sputtered ZnO Films and its Influence on the Effective Electromechanical Coupling Factors

A number of ZnO polycrystalline films with various degrees of structural ordering of the crystallites were obtained by dc diode sputtering. A quantitative description was obtained by rocking curve studies and pole-figure analysis for the spatial distribution of c-axis orientations of the crystallites in the deposited films. The distribution was found to be expressed by a Gaussian distribution for most of the specimens. The physical structure of the films can be represented by a mean m (an inclination angle of mean c-axis orientation) and a standard deviation σ. Measurements of the effective electromechanical coupling factors kt (m=0°~6°) and ks (m=7°~12°) were made for the films of σ=2°~8°. It was found that the coupling factors kt and ks were not affected remarkably by the standard deviation until σ=6°.

On the Variation of Acoustic Radiation Resistance in Water under Ultrasonic Cavitation

The variation of acoustic radiation resistance of ultrasonic radiation in a cavitating liquid is studied as a function of acoustic intensity, and the pulse width of the radiation. Intensities up to 1.75 w/cm2 are employed and pulse widths down to 3 msec.

Magnetostrictive materials and applications

The dynamic magnetostrictive properties of materials and their applications will be reviewed. The order of presentation is to first discuss the various dynamic magnetostriction contents K (defined by Smith), λ and γ (defined by Butterworth and Smith), and Γ (defined by the present author). Next, the application of the magnetic domain theory to dynamic magnetostriction will be presented. The ΔE-effect, a useful material criterion, will then be examined. Experimental results of the electromechanical coupling factor at an optimum bias are then shown. The second section of the paper will present the magnetostrictive characteristics of Ni, Ni-Fe alloys, Fe-Al alloys, other metals, cobalt rondel, and the ferrites. Much of the emphasis will be placed on the effects of cold reduction, hysteresis phenomena, and the effects of oxide films. Empirical formulas which describe these properties are presented. Large amplitude ferrite vibrators are described. The third part of the study is devoted to a phenomological method of predicting the magnetostrictive characteristics of polycrystalline metals. Experimental data for iron which agrees with the model is presented. The effect of anisotropic grain growth is discussed in terms of the model. The last section is devoted to the mechanical power limitations of magnetostrictive vibrators both from the theoretical and the experimental points of view.

A New Ultrasonic Amplifier Device of CdS Crystal with Integrated Diffusion-Layer Transducers

It has been accomplished to embed a pair of CdS diffusion-layer transducers in a photoconductive CdS crystal for ultrasonic amplification. That is, a pair of transducer layers and conductive layers, and an amplifying part are integrated in a single piece of CdS crystal. The conductive layers are formed by heating the crystal in cadmium vapor, and they act as both a pair of electrodes for applying drift field voltage and the electrodes for transducer layers. A fabricated sample shows that the effective resistance of the conductive layer, which is considered to be in series with the equivalent electric impedance of the transducer, is lower than the impedance of the transducer itself. Upon application of the drift field, ultrasonic wave was amplified by 35 dB at 54 Mc compared with that of no drift field.

Magnetostrictive Metals and Piezomagnetic Ceramics as Transducer Materials

Magnetostrictive materials have been studied and developed during the last 40 years mainly for the generation and detection of ultrasonic waves. More recently some resonator applications have been introduced. We shall give a few examples of practical magnetostrictive transducers for both generators and detectors as well as electric wave filter applications.

Influence of Dislocations in CdS Crystal on Its Electromechanical Coupling Factors

The electromechanical coupling factors are measured in the frequency range from 100 kHz to 260 MHz for CdS single crystals with various dislocation densities. These measurements show that each of the electromechanical coupling factors kt, k15, and k31 begins to decrease in a steep slope as the density of dislocation which terminates at c surface of the crystal exceeds an amount around 106 cm−2. However, these coupling factors come back toward the normal values when the density of dislocation is decreased by means of the annealing of the crystals in a sulfur vapor. No appreciable change of the elastic constants and the dielectric constants is observed. Therefore, the observed variation of the electromechanical coupling factors is attributable to the dependence of the corresponding piezoelectric constants on the dislocation density.

Present Aspects of “Ultrasonotomography” for Medical Diagnostics

The beginning of research on the use of ultrasound for medical diagnostics was not so old as that on the use of ultrasonic energy for medical purpose. In 1942,1 Dussik in Austria reported the possibility of diagnostic use, and in 19472a, he made public a sort of ultrasonic image of some brain tumors, which he named “hyperphonogram” (Figure 1). The upper picture is for normal, and the lower is for Astrocytoma, a sort of brain tumor. Although the images are obscure in comparison to current ultrasonotomograms, the historical significance is sharply dominant2b. Dussik obtained these images by using ultrasonic beams of l.2 to 1.5 MHz, which penetrated the human brain and showed varied attenuation, route-by-route, to reach the receiving transducer that is placed at the corresponding opposite side of the head. The dark patterns are for good penetration, and a simple pattern in the normal brain is the ultrasonic projection of the intracranial ventricle. In 1950,3 Ballantine and Bolt, in the United States, made public a similar experiment with knowledge of ultrasonic attenuation in biological tissues. In 1951,4 they made the instrumentation of this penetration method and named it “ultrasonic ventriculography.”

Ultrasono-Cardio-Tomography

In obtaining ultrasonic tomograms of the heart and great vessels, there are, unlike other organs, some particular conditions: The pulsation of movement of all the echo sources, and the anatomical situation that the heart is covered by the lung and the costa. The positions of the echo sources repeatedly vary with time in the thoracic cavity. To obtain the stationary tomograms of the living heart at various cardiac phases, there have been proposed several methods. To overcome the pulsation movement, a synchronization method, a high speed scanning method and a tomo-kymographic method have been introduced. To solve the anatomical situation, an intra-cardiac, intra-esophagal, intra-tracheal and transthoracic methods have been developed. Those methods will be described in this paper, by placing some emphasis on the methods which the present authors have developed within the present clinical routine.

Bragg Condition of Light Diffraction by Ultrasonic Waves in Anisotropic Crystals

The whole characteristics of the Bragg condition in anisotropic crystals are graphically discussed. Typical Bragg angles are investigated qualitatively for several crystal planes where both the ultrasonic waves and the light waves propagate. Numerical calculations are made for an α-quartz crystal for the same crystal planes and the Bragg angles observed experimentally agree well with the calculated values.