A transcutaneous ultrasonic blood velocity meter

transcutaneous ultrasonic blood-velocity meter. J ’. Appl. Physiol. 21(2): 707--7’1. I g66.-An ultrasonic flowmeter has been developed for continuously indicating instantaneous arterial or venous blood flow velocity in vessels under intact skin or even deep within the body. This flowmeter is based on the Doppler principle that continuous wave ultrasonic energy backscattered from moving blood is altered in frequency. The difference in frequency between transmitted sound and sound backscattered from blood is within the audible range. Mean frequency of the sound spectrum appears to be directly related to mean flow velocity. This signal may also be analyzed by differentiation to inscribe on a standard strip chart re-corder the change of blood velocity with time. If the angles between ultrasonic beams and the vascular channel are known, it is possible to record blood flow velocity. In it