| 摘要 |
PURPOSE:To reduce a measurement error in a low speed area by providing a first phase difference detecting means for adding a phase difference vector and calculating its deflection angle, a second phase difference detecting means for correcting an average phase difference obtained by adding a phase difference, and a selecting means for selecting one of the detecting means by whether a speed is high or low. CONSTITUTION:First of all, a phase vector is inputted to a (phase difference detector) 701, and complex multiplication of the phase vector and plural conjugate vectors of a vector of one time before is performed. A speed arithmetic part 7 consists of speed arithmetic parts (707, 708, 709, 713 and 714) by a phase difference averaging method and a selector 709 and obtains a result output of a deflection angle by inputting a phase vector to an ATAN memory 707. By a phase difference detector 713, a difference output of the present and the deflection angle of one time before is obtained. A centroid computing element 13 brings each phase difference and its amplitude to sum-of-products operation, and divides it by the sum total of an amplitude value. In the selector 709, a blood flow speed is selected by using a deflection angle (average phase difference), an angle dispersion, and reflection strength obtained by a power computing element 706 as parameters. |
