Simultaneous multifrequency ultrasonography.
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概要
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Existing ultrasonography is limited by the slow velocity of sound in the body, namely the product of twice the scan depth, the number of scan lines and the frame rate could not exceed the speed of sound in the body, which is only about 1500 meters per second. If the scan depth is 20 centimeters and the frame rate is 30per second, the number of scan lines per frame is limited to about 120. In order to break through the barrier caused by the slowness of sound, we had devised a new technique, named simultaneous multifrequency ultrasonography in which we can treat two or more ultrasonic beams perfectly simultaneously. This is equivalent to making the sound velocity several times faster.In simultaneous multifrequency ultrasonography, one of the most important things to solve is how to extract one signal from other signals by labels added at transmitting stage to avoid the crosstalk in the body. We examined three labeling methods, namely, pseudo random code modulation, chirp modulation and simple burst pulse, through computer simulation and an experimental circuit in simultaneous 2 beams model. To evaluate the three methods, we used both normalized signal to crosstalk ratio as a figure of merit and images which are obtained through the circuit. About 1MHz frequency separation was found to be almost enough to obtain usable normalized signal to crosstalk ratio—about -40--30dB in each method. After total evaluation, the simple burst pulse was judged to be the best method. At last, the outline of some applications of simultaneous multifrequency ultrasonography, realtime compounded dual B-mode images, realtime cross-sectional dual B-mode images and simultaneous B-mode and Doppler measurement, are introduced, which are obtained through a medical evaluating system in which the simple burst pulse method is adopted.
- 一般社団法人 日本生体医工学会の論文
一般社団法人 日本生体医工学会 | 論文
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