| 摘要 |
<p>With a correlation detection type ultrasound blood flowmeter (201), for measuring speed of flowing blood which is passing across two sample volumes (SV21, SV22) which are positioned at equal distances from the blood flowmeter along respective sound-beams (B1, B2) provided by the blood flowmeter (201), the speed of flowing blood is measured by cross correlation time-difference detection, and the detection is performed by using sample and hold voltages obtained from echo signals (C1(t), C2(t) ) reflected from the flowing blood which is passing across the two sample volumes (SV21, SV22). In the blood flowmeter (201), two quadrature detection circuits (401, 402) are provided for selecting echo signals arising from reflection by the flowing blood from echo signals arising from reflection by all bodies or substances located along the two sound-beams (B1, B2), by eliminating echo signals arising from fixed bodies or substances located along the two sound-beams. Two range gate circuits (43A, 43B) are applied to each quadrature detection circuit for extending the range of each sound (sample) volume, for enabling measurement of the speed of flowing blood which passes across the two sample volumes (SV21, SV22) not perpendicularly but aslant with respect to a center line made by the directions of the two sound-beams (B1, B2). </p> |
