Periorbital Doppler is a continuous wave Doppler examination, determining the amplitude, flow direction, and compression effect of the frontal or supraorbital arteries in the periorbital region.

See also Acoustic Window, and Cerebrovascular Ultrasonography.

Cerebrovascular ultrasonography is the best screening tool for the detection of carotid artery stenosis. Transcranial sonography is used in the evaluation of patients with suspected cerebrovascular disease, but a common problem is the attenuation of the ultrasound signal by the skull.
Contrast enhanced ultrasound play a particularly important role in the visualization of the intracranial vessels, and thus improves the accuracy of transcranial Doppler and increases the potential of this technique. The use of microbubbles is helpful for classification of stenosis and for plaque evaluation in patients with poor initial examination. Ultrasound contrast agents avoid misdiagnosing a subtotal stenosis, which is a very important clinical issue.

See also Adventitia, Intima, Periorbital Doppler, and Acoustic Window.

(CWD) Continuous wave (CW) Doppler is an ultrasound imaging mode, which records blood flow velocities along the length of the beam. Continuous wave Doppler uses different crystals to send and receive the signal. The transducer operating in continuous wave mode utilizes one half of the elements and is continuously sending sound waves of a single frequency while the other half is continuously receiving the reflected signals.
The advantages of a continuous wave transducer are a high sensitivity and no Nyquist limit. CW Doppler does not alias but has no depth precision and large gate. The beat frequency is the Doppler shift. CW Doppler echocardiography employs this technique to record the flow of blood through the cardiovascular system.

See also Cross Talk, Periorbital Doppler, and Mirror Artifact.