Vascular anatomy and physiology lend themselves readily to the modality of ultrasound. Ultrasound’s ability to assess velocity of moving fluid allows for real-time evaluation of the speed and direction with which blood is flowing through a vessel. This provides for a dynamic assessment of the vascular tree. In addition the ability of ultrasound to measure distances allows it to be a very effective method for screening for dilated blood vessels. The ease of use, relatively low cost of the devices, and speed of the tests allow ultrasound to be the lowest-cost method next to physical examination to assess the vascular beds. These unique properties of ultrasound allow for the accredited Vascular Laboratories, with the appropriately credentialed and trained physician, the technologist, and a program of continuous quality assurance, to obtain results that are comparable to much more expensive imaging techniques.
The clinical indications that call for ultrasound are from the head to the toes: temporal arteritis: carotid disease – stenosis, dissection, and aneurysm; vertebral artery stenosis; subclavian disease – steal, stenosis, and aneurysm; brachial artery stenosis; fibromuscular dysplasia of the carotid, brachial, and renal arteries; abdominal aortic – aneurysm, stenosis, dissection, and occlusion; visceral and renal artery – stenosis, aneurysm; iliac artery – aneurysm, stenosis, and dissection; common femoral – aneurysm; pseudoaneurysm, venous fistula; superficial femoral and popliteal artery – stenosis, aneurysm, and occlusion, and venous thrombosis of the deep and superficial veins of the leg; chronic venous insufficiency – obstructive and reflux based; and evaluation of arteriovenous – fistulas and graft. Ultrasound can be used for the preoperative assessment of vein conduits, and the intraoperative completion sonogram can be used to assess the adequacy of plaque removal during endarterectomy, as well as the quality of distal anastomoses. Air is a profound limitation to the transmission of ultrasound; therefore, diagnosis of intrathoracic pathology requires the use of specific ultrasound technologies and techniques such as intravascular ultrasound or transesophageal ultrasound, which can diagnose thoracic aortic plaques, aortic dissections, and aneurysms.
The Doppler capabilities unique to ultrasound make it of remarkable usefulness in assessing the severity of patients’ peripheral arterial disease. By adding peak continuous wave Doppler occlusion pressure ratios between the upper and lower extremities one has the ability to determine the severity of blood flow restriction in the lower extremity.
The ultrasound device we use in assessing vascular anatomy is better known as the duplex scanner.1,2 This device combines a pulsed Doppler system with a real-time B-mode (brightness-mode) imaging system. This device also has the ability to color encode the directional data found in the flowing blood vessel.3 Scanners currently obtain Doppler signals from a whole region simultaneously, then the linear array transducer technology is used to create a grid of insonation. Both magnitude and direction of motion are obtained this way, and an arbitrary color is assigned to that magnitude and direction of flow. This technology can show helical or complex flow patterns ...