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 lower extremity arteries. Studies may be unilateral or limited 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.

Physiological testing, such as an ankle brachial index (ABI), segmental pressures, pulse volume recordings and Doppler waveform analysis, is often performed to identify significant arterial disease and determine if further imaging is warranted. These studies are not equivalent to arterial Duplex imaging. An initial ABI is typically obtained, in conjunction with Duplex imaging, to support sonographic findings and avoid discrepancies.

B-Mode and color Doppler imaging of the lower extremity arteries should be performed in a longitudinal plane. Transverse imaging may be helpful. Longitudinal grayscale and color Doppler images should be documented for each normal arterial segment and in areas of stenosis, previous intervention or other abnormality. Color Doppler is used to localize areas of flow disturbance and stenosis. Power Doppler is useful to confirm possible vessel occlusion or low flow states.

• Longitudinal B-mode and/or color Doppler images include the following:
  • Common femoral artery (CFA)
  • Proximal deep/profunda femoral artery (DFA/PFA)
  • Proximal, mid and distal Superficial femoral artery (SFA)
  • Popliteal artery (PopA)
  • Tibial and peroneal arteries (where adequately visualized)
  • Aorta, common and external iliac arteries (when indicated)
  • Areas of previous angioplasty or stenting
  • Bypass graft evaluations include B-mode and color Doppler images from:
    • Proximal and distal anastomoses
  • Abnormalities require additional images when present
    • The location, severity and characteristics of plaque should be documented in transverse and longitudinal planes

Doppler spectral analysis is used to quantify disease severity. Spectral Doppler waveforms should be obtained in a longitudinal plane at an angle of 60° and parallel to the direction of blood flow/vessel walls. Maintain Doppler angles between 45° and 60° whenever possible. Angles greater than 60° must be avoided.

Peak systolic velocities should be documented for each normal arterial segment and in areas of stenosis, previous intervention or other abnormality. Spectral Doppler waveforms and velocity measurements should be obtained 1-4cm proximal to, at and distal to sites of suspected stenosis, obstruction or in areas of previous intervention.

• Spectral Doppler waveforms and velocity measures include:
  • Common femoral artery
  • Proximal deep/profunda femoral artery
  • Proximal, mid and distal portions of the superficial femoral artery
  • Popliteal artery
  • The tibial/peroneal trunk (when adequately visualized)
  • The tibial and peroneal arteries (where adequately visualized)
  • Aorta, common iliac and external iliac arteries (when indicated)
  • Areas of previous endovascular intervention (angioplasty, stenting)
    • Spectral waveforms proximal to the intervention site, within the intervention site, and distal to the intervention site.
  • Bypass graft evaluations include waveforms and velocities from:
    • Inflow and outflow arteries
    • Proximal and distal anastomoses
    • Proximal, mid and distal portions of the bypass graft
  • Abnormalities require additional images when present
    • In the presence of pathology, spectral waveforms should be recorded proximal to, within, and distal to the lesion.