| 摘要 |
<p>PURPOSE:To enable better detection of a weak fast blood flow signal by providing a lower-order high pass-filter section which is higher in cutoff frequency than a high pass filter section while allowing the suppression of a slow blood flow signal to make a signal intensity of the weak fast blood flow signal higher relatively. CONSTITUTION:A blood flow filter section 7 is provided at a front stage of a frequency analysis section 5 in the rear of a wall echo filter section 4. A filter characteristic of the wall echo filter section 4 has a cut off frequency at a part of a low frequency and first, a wall echo signal C1 with a very low frequency and a large amplitude is removed with the wall echo filter section 4. Then, the filter characteristic of the blood flow filter section 7 gives a curve in which a slow blood flow signal is checked at a frequency area higher than the cut of frequency of the echo filter section 4 and hence, with the blood flow filter section 7, a slow blood flow signal C3 which could not be removed with the wall echo filter section 4 can be checked to a low level as shown by a curve C3'. Thus, the signal intensity of a weak fast blood flow signal C2 becomes higher relatively thereby enabling better detection thereof.</p> |
