超音波Doppler法による心臓機能検査法
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概要
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When an ultrasonic beam is radiated into the body by a transducer placed on the suface of the chest wall, the motion of the heart causes the so-called Doppler effect on the wave reflected from it. Thus, several kinds of beat tones whose frequencies are proportional to the speed of the heart motion are perceived at the earphones of the receiving apparatus. Designating the frequency of these beat as fd(c/s), the speed of the reflecting area as u_0(cm/sec), the ultrasonic wavelength in the body as λ(cm), the following relation holds between them. u_0=λ/2fd. Since λ is determined by the frequency of the ultrasound which is being used, the knowledge of fd makes it possible to investigate the behaviour of the reflecting region of the heart in motion. In the same way, the minute vibration of the heart surface or of the valvular structures which would be developed by the blood flow would cause the vibrational alterations in the phase of the reflected wave. Hence they can be detected as the vibrational tones of the same kind (in this case, chiefly, heart noises). The principal parts of the apparatus consist of a HF-oscillator, an ultrasonic transducer for the purpose of both transmission and reception, a detector-amplifier, an earphone and a recorder. The transducer is of barium-titanate, 1 cm in diameter. The positive electrode is separated into two concentric parts, the inner disc of 3 mm in diameter being used for transmission and the outer circular ring for reception. The sensitive range proves to be a beam of approximately 1 cm in diameter. Therefore, the investigations of the heart is performed on the distinct parts of this small extension. By supplying a frequency-selecter of bandpass type for the amplifier, it becomes possible to separate and select the movements of the particular parts of the heart. The HF-oscillator is realized by a 6V6 type tube, operating as a self-oscillator. The ultrasonic power output is calculated to be 20 mW/cm^2. In practice, the ultrasonic transducer, attached to the end of a flexible cable, is placed at the various positions on the chest wall, and the Doppler beat due to the movements of the corresponding parts are made audible or recorded. There are three kinds in these tones: 1. Higher Doppler beat. (Movements of the valves) 2. Lower Doppler beat. (Movements of the surface of the heart) 3. Doppler heart noises. (Heart noises)
- 社団法人日本音響学会の論文
- 1957-06-30