WHAT IS DOPPLER ULTRASONOGRAPHIC FLOW STUDIES (INCLUDES CAROTID DOPPLER, CAROTID ARTERY ECHOGRAPHY, CAROTID ARTERY ULTRASONOGRAPHY, DUPLEX ULTRASONOGRAPHY, TRANSCRANIAL DOPPLER ULTRASONOGRAPHY) TEST?
A noninvasive, hand-held mechanical ultrasonograph that uses a low-frequency (2-2.5 MHz) sector transducer through temporal, orbital, and suboccipital acoustic windows of the skull. Constant-frequency ultrasonic waves are transmitted into the vessel of interest by a transducer in the form of either fixed-wave or pulsed signals. Using the colour and powerful technique of the Doppler signal instead of the frequency shift, it records the anatomy, flow direction, and mean blood flow velocity in real-time imaging. Doppler ultrasonography can display very small quantitative and qualitative volumes, allowing great morphologic detail. Inferences about the presence of an obstruction to blood flow can be made with this procedure. When this technique is combined with a static image of the vessel provided by B-mode imaging ultrasonography, the procedure is referred to as “duplex Doppler ultrasonography.” When a colour image is generated by changes in blood flow, the term colour Doppler” is applied.