Sonographers should follow a standard imaging protocol. A complete evaluation includes B-mode imaging, spectral Doppler analysis, and color Doppler imaging of all accessible portions of the extracranial carotid arteries. Bilateral evaluations are essential for a complete evaluation; however, post-operative studies may be unilateral based on laboratory-specific protocols.

Throughout each examination, the sonographer or examiner should:

• Observe sonographic characteristics of normal and abnormal tissues, structures, and blood flow, allowing necessary adjustments to optimize exam quality.
• Assess and monitor the patient’s physical and mental status, allowing modifications to the procedure plan according to the patient’s clinical status.
• Analyze sonographic findings to ensure that sufficient data is provided to the physician to direct patient management and render a final diagnosis.
• Accurately annotate B-mode, color and spectral Doppler images.

B-mode imaging of the extracranial carotid arteries should be performed in longitudinal and transverse planes utilizing anterior, lateral and posterior-lateral probe positions. Optimize the gain to depict vessel walls, plaque and any other abnormalities.

• B-mode images should include the following:
  • Longitudinal image of the common carotid artery (CCA)
  • Transverse image of the carotid artery bifurcation
  • Longitudinal image of the internal carotid artery (ICA)
  • Longitudinal image of the external carotid artery (ECA)
    • The location, severity and characteristics of plaque should be documented in transverse and longitudinal planes.
    • Any other abnormalities should be documented.
  • When present, carotid artery stent including proximal and distal ends.

Color Doppler may be used to depict areas of abnormal flow or significant stenosis. Power Doppler is useful to confirm areas of possible vessel occlusion or low flow states.

• Color Doppler images may include the following:
  • Longitudinal image of the CCA
  • Transverse image of the carotid artery bifurcation
  • Longitudinal image of the ICA
  • Longitudinal image of the ECA
  • Longitudinal image of the vertebral artery

Velocity measurements should be obtained from a longitudinal plane at an angle of 60° parallel to the direction of the blood flow/vessel walls. Maintain a Doppler angle between 45° and 60° whenever possible. Angles greater than 60° must be avoided. Doppler angles less than 45° may be necessary due to patient anatomy. To obtain peak velocity, utilize color Doppler to note areas of concern and “walk” the spectral Doppler cursor throughout these areas. Post stenotic turbulence should be documented when present.

• Spectral Doppler images should include the following:
  • Proximal CCA
  • Mid to distal CCA
  • Proximal ICA
  • Distal ICA
  • Proximal ECA
  • Vertebral artery
  • Subclavian artery (when appropriate)
    • Typically evaluated in the presence of brachial artery pressure asymmetry, greater than 10 - 20mmHg, and/or flow characteristic changes or flow reversal in the vertebral artery
• In the presence of pathology, spectral waveforms should be recorded proximal to, within, and distal to the lesion.
• Documentation of sites of vascular intervention (i.e., endarterectomy) should include representative waveforms and velocity measurements proximal to the intervention site, within the intervention site, and distal to the intervention site. In the presence of stents, documentation should include:
  • Native artery at the proximal end of the stent
  • Proximal, mid and distal stent
  • Native artery at the distal end of the stent
• Any other abnormalities should be documented.