| 摘要 |
The blood flow rate is determined using an ultrasonic Doppler instrument coupled with a spectrum analyser and monitor. The equipment consists of an ultrasonic pulse transmitter (3) and corresponding echo receiver (4) connected to the ultrasonic transformer (1) through a switch (2). The receiver is linked to a fixed target canceller (6), complex demodulator (7), spectrum analyser (8) and information monitor (9,9A). The received echoes give a signal, clarified by high pass filters, which is picked up by the frequency spectrum analyser to calculate the blood flow rate. The process is repeated over a period of time for continuing analysis. It is also used in different positions and at variable points in time.
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