Sonographers should follow a standard imaging protocol. Studies are often unilateral (evaluating the non-dominant arm) but may be bilateral if the radial artery is inadequate, if the palmar arch is incomplete, or by physician request. Additional physiologic testing can evaluate digital perfusion with radial artery compression.

Throughout each examination, the sonographer or examiner should:

• Observe the sonographic characteristics of normal and abnormal tissues, structures, and blood flow to allow the necessary adjustment to optimize exam quality
• Analyze segmental pressure and waveform findings to ensure that sufficient data is provided to the physician
• 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 and physiologic findings to ensure that sufficient data is provided to the physician to direct patient management and render a final diagnosis

Duplex Imaging Protocol:

B-Mode and color Doppler imaging of the upper extremity arteries should be performed. Diameter measurements of the radial artery should be taken in a transverse plane. Longitudinal grayscale and color Doppler images should be documented for each arterial segment and in areas of stenosis 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.

Transverse B-Mode images must include diameter measurements from the:

• Proximal, mid and distal radial artery

Longitudinal B-mode< and/or color Doppler images should include the following:

• Brachial artery
• Radial and Ulnar arteries
  • Early takeoff of the radial artery in the upper arm and/or other anatomical variants should be noted.
  • Identify areas of stenosis or calcification.
  • A normal ulnar artery is essential if the radial artery is to be harvested.

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 the 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 should include:

• Brachial artery
• Radial and Ulnar arteries
  • Ulnar artery with and without radial artery compression
  • Palmar arch artery with and without radial artery compression

Physiologic Testing Protocol:

Physiologic evaluation involves the use of photoplethysmography waveforms/pulse volume recording, continuous wave (CW) Doppler and segmental pressures of the upper extremities and digits to detect significant upper extremity arterial disease.

Continuous wave (CW) Doppler and segmental pressures of upper extremities:

• At least three representative CW Doppler waveforms are recorded from the brachial, radial and ulnar arteries atan angle that optimizes the visual and audible signal.
  • Gain settings are optimized to display waveform characteristics.
  • Audio interpretation of the CW Doppler signals should attempt to classify the signals as triphasic, biphasic (unidirectional or bidirectional), or monophasic.
• Blood pressure cuffs are placed at the upper arm, mid forearm and wrist. CW Doppler is used to obtain segmental pressures at each level using the brachial, radial and ulnar arteries respectively.
• A wrist brachial index (WBI) is calculated by dividing the highest wrist pressure from each limb by the highest brachial pressure.

Digit PVR/ PPG Waveforms and Pressures:

Evaluation of digit perfusion can be obtained with volume pulse recording (VPR) or photoplethysmography (PPG) based on laboratory’s protocol.

• PVR waveforms are obtained by placing the pressure cuff on the digit and inflating it to a predetermined pressure to evaluate changes in blood volume.
  • At least three representative waveforms are recorded.
• PPG waveforms and pressures are obtained by placing the PPG sensor and digital pressure cuff at the base of the thumb/index finger and fifth digit.
  • At least 3 PPG waveforms are recorded.
  • The cuff is inflated to a supra-systolic pressure and then deflated slowly until the waveform re-appears. Obtain and record the systolic pressure.
  • A digit brachial index (DBI) is obtained by taking the digit pressure divided by the highest brachial pressure.

Allen Test

The Allen Test is performed to assess the patency of the palmar arch and evaluate digital perfusion in the hand. This can be performed with physiologic testing or duplex imaging.

• Use a slow speed and adjust the PPG scale and gain controls at similar amplitudes.
• Resting PPG waveforms are obtained at the 1st, 2nd and 5th digit.
  • At least 3 PPG waveforms are recorded.
• The radial artery is compressed and tracings are captured. Next, the ulnar artery is compressed and tracings are captured.
  • Little or no change in PPG waveforms when either artery is compressed indicates a complete palmar arch.
  • Obliteration of PPG waveforms when either artery is compressed indicates incomplete palmar arch.
• Perform compression maneuvers for each digit examined.
• If the palmar arch is incomplete, assess the other extremity

• Obtain spectral Doppler waveforms in the ulnar artery with and without radial artery compression
  • Normally, a >20% increase in ulnar PSV with radial compression
• Obtain spectral Doppler waveforms within the palmar arch artery/terminal radial artery with and without radial artery compression
  • Normally, a reversal of flow with radial artery compression