Does a combined real-time cross-sectional imaging and Doppler velocimeter system allow for accurate placement of the Doppler sample volume and measurement of blood flow velocities in normal subjects?
A newly developed combined ultrasound imaging and Doppler system demonstrates the feasibility of accurately locating sample volumes for noninvasive blood flow measurement in humans.
An ultrasound instrument has been developed that combines a real-time cross-sectional imaging system and a spectrum analyzer-based Doppler velocimeter. This combination allows the Doppler sample volume to be superimposed on the cross-sectional image of the heart so that the sample volume can be located accurately. The same 2.2 MHz transducer utilized for cross-sectional imaging is stopped mechanically and quickly switched to transmit and receive the Doppler ultrasound signal. Preliminary experience in 20 young and adult normal subjects indicates that it is possible to place the Doppler sample volume in the proximal main pulmonary artery at a point where the sound beam and blood flow stream are parallel. Measurement of the distance from transducer to the sample volume and the peak blood flow velocities in the main pulmonary artery of normal subjects indicates that these quantities are within the measurement capabilities of the system. The ultimate goal of this device is to make measurements of volume blood flow in man noninvasively.
Griffith et al. (Mon,) studied this question.