DOPPLER BLOOD FLOW APPARATUS AND METHOD USING SPECIAL ZERO FLOW RATE ANALYSIS

摘要

PURPOSE: To measure a flow amount of fluid containing fine particles run through a vessel by comparing an amount of received ultrasonic signal with a specified value and judging the presence of a special case in which a flow amount equals to zero when the former amount being below the specified value. CONSTITUTION: A signal 36 containing Doppler information is treated in order to extract a frequency information expressing a blood flow amount correctly and supplied to a clipper circuit 38, and a maximal amplitude is limited. The signal is supplied to an AGC circuit 40 which offers an automatic gain control, then to a filter 42, and to an analog-digital convertor 44 wherein the signal is digitized. Once the Doppler signal is converted into a digital form by the analog-digital convertor 44, the signal is digitized by means of a computer 46. The digital Doppler signal contains an information as to a flow amount of blood 22 run through a vessel 20, but is contains other information, in particular, noise, also. By a software, past data samples are averaged to determine a correct and stable reading of the flow amount and determine whether a special case, i.e., a flow amount of zero, is present or not.