Masami Kawabuchi

Dependence of the electromechanical coupling coefficient on the width‐to‐thickness ratio of plank‐shaped piezoelectric transducers used for electronically scanned ultrasound diagnostic systems

A finite element analysis method is used to obtain the electromechanical coupling coefficient ke for plank‐shaped piezoelectric transducers with a width W to thickness T ratio of not more than two. Calculation results for typical piezoelectric ceramics show that there exist maximum values of ke at certain values of W/T. For PCM‐5R material the maximum value of ke is 0.69 at a W/T of 0.6. It is shown that only one vibrational mode is very strongly coupled around this value of W/T. This vibrational mode is very useful for application to electronically scanned arrayed transducers.

Arc scan ultrasonic transducer array

A plurality of transducers is arranged successively on a common impedance matching layer of a resilient material. Each transducer comprises an elongated piezoelectric element having a width expansion vibrational mode, a pair of first and second electrodes attached to opposite surfaces of the element across its thickness and an elongated block of an impedance matching material disposed between the second electrode and the common impedance matching layer. The common impedance matching layer is bent to take the shape of an arch to conform to the surface of a frame structure which is convexed in the direction of propagation of ultrasonic energy. The piezoelectric elements are secured to the frame so that they bridge the parallel side members of the frame. The piezoelectric members are divided into a plurality of subgroups, each composed of successively arranged elements. The piezoelectric elements of a given subgroup are selected and energized during each clock interval for transmission of focused ultrasonic energy. The subgroup to be selected is shifted linearly to the next by at least one element in response to successive clock pulses. Becuase of the convex shape of the array, the transmitted energy is successively angulated to provide arc scan.

Piezoelectric ultrasonic probe using an epoxy resin and iron carbonyl acoustic matching layer

An ultrasonic probe for an ultrasonic medical diagnostic apparatus which is composed of a piezoelectric vibrator with electrodes attached onto both surfaces thereof and one or two acoustic matching layers which are provided on the surface of one electrode of the piezoelectric vibrator. One of the acoustic matching layers is made of thermosetting resin such as epoxy resin mixed with magnetic material. A backing load member which is made of ferrite rubber or plastic mixed with tungsten powder is provided on the surface of the other electrode of the piezoelectric vibrator. An acoustic lens which is made of silicone rubber may be disposed on the upper acoustic matching layer. The acoustic matching layers may be formed by pouring the materials, thereby to form the ultrasonic probe without an intermedium of a different kind of material on the piezoelectric vibrator.

Ultrasonic transducer assembly for medical diagnostic examinations

An ultrasonic transducer for medical diagnostic examinations which comprises a transducer element having one surface through ultrasonic waves are emitted, an acoustic impedance matcher, and a contact member brought to contact with an object being examined and formed on the one surface of the ultrasonic transducer element. The contact member includes at least a flat plate or an acoustic lens made of a-4-methylpentene-1-base polymer which has high mechanical strength. Transducer arrays and assemblies using such polymer as a member directly contacted with human body are also described.

Farfield angular radiation pattern generated from arrayed piezoelectric transducers

Farfield angular radiation patterns generated from plank‐shaped and arrayed piezoelectric transducers are obtained by using a finite element analysis method. The calculation and experimental results are obtained for piezoelectric ceramic transducers with typical width W to thickness T ratio of 0.6 and 2.0. At W/T=0.6 the radiation pattern is that of diffraction from a plane aperture, while at W/T=2.0 the pattern is significantly different from the plane aperture theory. This is mainly due to the coupling between the thickness and other modes of vibrations in the piezoelectric transducer.

Design of ultrasound transducers using new piezoelectric ceramic materials.

Abstract Three parameters α, DR and D n ( A ), i.e. the efficiency, the dynamic range and the normalized axial resolution are used to evaluate the performance of ultrasound transducers for diagnostic imaging equipment. These parameters determine optimum conditions for use in the design of high frequency array transducers. A newly-developed piezoelectric ceramic material composed of (Pb,Sr)(Ti,Zr)O 3 or Pb[(Mg 13 , Nb 23 ), Ti,Zr]O 3 which satisfies the above-mentioned conditions was used to fabricate a co-phase array ultrasound transducer. The transducer showed good electrical and acoustic performance in accordance with theoretical considerations.

A Simulation Model for B-Mode Imaging

Ultrasonic B-mode images, as the output of diagnostic ultrasonic imaging systems, are the results caused by acoustic properties inside the human body and a number of acoustic or electrical processings by equipment. In order to estimate a B-mode image and extract useful information for diagnosis, research in the new methods is necessary so that B-mode images can be analyzed quantitatively. For the first step in the development of such new techniques, a simulation model for B-mode imaging was developed. This paper describes the structure of the simulation model studied, and presents some calculated B-mode images.