ULTRASONIC DOPPLER BLOOD FLOWMETER AND MEASUREMENT OF BLOOD FLOW

摘要

PURPOSE:To detect blood flow at a speed higher than a conventional one, by performing the orthogonal detection of an echo signal using a plurality of orthogonal reference signals different in frequency and obtaining Doppler data from the phase difference of the orthogonal detection signals. CONSTITUTION:A transmission circuit 5 outputs a transmission pulse ST having center frequency in the vicinity of the middle between the frequencies of two orthogonal reference signals at a time (to) in synchronous relation to a repeated pulse P. A probe 6 converts the transmission pulse ST to a sonic wave to transmit the same to a living body. The echo signal SR from a reflecting body being an object is delayed a propagation delay time td in receiving. 4 gate generator 7 generates a gate signal G at the time (td) and turns a receiving circuit 8 ON to extract an echo signal SR. The echo signal SR is respectively detected by the first orthogonal detectors 9aY, 9aX and the second orthogonal detectors 9bX, 9bY. A phase difference operator 10 calculates the phase angle difference between the phase angle represented by the first orthogonal detection signals xa, ya outputted from the orthogonal detectors 9aX, 9aY and the phase angle represented by the second orthogonal detection signals xb, yb.