A new approach to the noninvasive measurement of cardiac output using an annular array Doppler technique--I. Theoretical considerations and ultrasonic fields.
This paper describes the development of a Doppler flowmeter capable of measuring blood volume flow rate without the need to measure the vessel lumen area or beam-vessel angle. It requires the production of a uniform wide ultrasound beam to encompass the whole vessel and thus to produce a Doppler spectrum which corresponds to all the flowing blood, and a narrow reference beam placed within the lumen to compensate for various unknown quantities, such as tissue attenuation. The general definition of volume flow rate is described and applied to a new flowmeter, which allows an absolute value of volume flow rate to be measured independently of vessel size, beam-vessel angle, and tissue attenuation. By electronically apodising an annular array transducer in transmission and reception, a uniform wide beam and a narrow reference reception beam are produced. Theory to predict these beam patterns is developed and a computer simulation is made. The ultrasonic fields obtained from an annular array transducer in water are compared with the theoretical fields.
Evans
J M
JM
Department of Medical Physics, Bristol General Hospital, England.
Skidmore
R
R
Luckman
N P
NP
Wells
P N
PN
D000328:Adult; D001011:Aorta / Q000502:physiology; D001783:Blood Flow Velocity; D001808:Blood Vessels / Q000033:anatomy & histology; D002302:Cardiac Output; D003198:Computer Simulation; D006801:Humans; D008838:Microcomputers; D008954:Models, Biological; D012212:Rheology; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods*