Duplex sonography of the extremities is a non-invasive and valuable tool in detecting diseases in the blood vessels of the arms and legs. In this post we’ll go over the basic evaluation of the extremity arterial systems.
1. Detection of stenosis or occlusions in segments of the peripheral arteries.
2. Monitoring of sites of previous surgical interventions, including sites of previous bypass.
3. Monitoring of sites of various percutaneous interventions.
4. Follow-up of previously diagnosed disease.
5. Evaluation of arterial integrity in the setting of trauma.
Having a well rounded working knowledge of the arterial anatomy helps immensely when performing these exams. Let’s begin with the upper system.
Aorta and its branches
The Aorta is the main artery of the body arising from the outflow tract of the Left Ventricle. It is shaped like an umbrella handle or a candy cane. The first portion is the Ascending Aorta which then curves to become the Arch, here 3 consecutive vessels arise. The first is the Brachiocephalic or Innonimate Artery which further bifurcates into Right Subclavian Artery and Common Carotid Artery. Next is the Left Common Carotid followed immediately by the Left Subclavian Artery.
The Subclavian Artery arises from the Brachiocephalic Artery on the Right and off of the Aortic Arch in the Left. This artery further divides into the Axillary, Brachial, Radial, Ulnar, Palmar and Digital arteries respectively.
After the three Aortic Arch vessels the Aorta dips down and becomes the Descending Thoracic Aorta. Once it pierces the diaphragm it transforms into the Abdominal Aorta.
The Aorta continues to travel down giving off branches to the intestines and abdominal viscera finally terminating in a bifurcation. These two vessels are known as the Common Iliac Arteries.
The Iliac Arteries bifurcate into External and Internal Iliac Arteries. The External Iliac artery continues caudally turning into the Common Femoral Artery which further bifurcates into Superficial Femoral and Deep Femoral Artery (aka Profunda Femoris). The SFA then converts into the Popliteal Artery which gives rise to the Tibioperoneal Trunk that consists of Anterior and Posterior arteries and the Peroneal artery. The Anterior Tibial Artery then becomes the Dorsalis Pedis Artery.
Taking technically superior images not only looks aesthetically pleasing, it is important in that is provides accurate data to render a correct diagnosis. A few parameters you may want to tweak are the Doppler scale or pulse repetition frequency PRF and gain for both color and spectral doppler.
Too low of a scale and you’ll get aliasing which makes getting a proper velocity impossible.
Other parameters to consider are sweep speed, wall filters, color box size and orientation, sample box size and whether you’re color scale is inverted to name a few.
Many people have trouble on how to set the color box. A quick way to get it right is to make sure the steered ultrasound beam and vessel meet an acute angle 60° or less.
Upper Arterial Duplex
Lower Extremity Duplex