Carotid doppler study

Carotid doppler evaluation is one of the easiest doppler to record and at the same time, quite difficult to interpret (and sometimes even identifying vessels!). Position the patient's head in slight hyperextension and rotate 45 degrees away from the side being examined. Perform a complete gray scale survey, which means a longutidinal and axial survey along neck, caudal angulation in supraclavicular region and cephalic angulation of transducer at level of mandible. Color doppler is done to look for any hemodynamic abnormality and then proceed to pulse wave doppler. Due to tortuous/non-linear course of vessels, correct angle is vital to the study. Don't align the angle with the vessel as we always tend to do, but align with the velocity vector. Avoid color aliasing artefact by setting an optimum color scale (not too low nor too high). Identification of vessels is done as
a) Common carotid artery is easily located, and then follow it superiorly to locate 2 vessels beyond bifurcation. Sometimes, bifurcation is pretty high-up and difficult to identify. ECA is identified by presence of its multiple branches in neck. Another method is tapping on superficial temporal artery and looking for reflected flow in ECA. Normally, ICA shows some color during diastole while ECA doesn't.
b) Identification of the vertebral artery is achieved by locating the CCA in sagittal view and sweeping the tranducer laterally to the transverse processes of cervical spine.

Checklist
1. Intima media thickness, plaque measurement and characterization
2. Area reduction
3. ICA PSV, ICA:CCA PSV ratio
4. Near complete/complete occlusion
5. Vertebral steal (Complete or partial)

1. Intima media thickness: Intima media thickness means measuring from inner wall (echogenic) till the hypoechoic media layer. It is normally less than 1 mm.
2. Plaque morphology: Check if plaque is homogenous or heterogenous, echogenic or hypoechoic. Hypoechoic and heterogenous plaques are more ominous.
3. Area reduction: Area reduction >50% is significant stenosis.
4. ICA PSV and ICA:CCA PSV ratio: ICA PSV is normally less than 125 cm/sec. More than 230 cm/sec PSV is very significant stenosis. ICA:CCA PSV ratio should be less than 2.0. If it is more than 4.0, its quite significant. Normal flow in CCA is 45-120 cm/sec.
A suggested format is given below.