Duplex ultrasonography is a form of medical ultrasonography

Medical ultrasonography

Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...

 that incorporates two elements:

• 1) Grayscale Ultrasound to visualize the structure or architecture of the body part. No motion or bloodflow is assessed. This is the way plaque is directly imaged in a blood vessel, with the reader typically commenting on crossectional narrowing (greater than 70% is typically considered worthy of treatment).

• 2) Color-doppler Ultrasound to visualize the flow or movement of a structure, typically used to image blood within an artery. We see blood flow velocities increase through a region of narrowing, like a finger pressing up against the end of a running garden hose. Increased velocities indicate a region of narrowing or resistance (velocities greater than 250 cm/sec typically considered worthy of treatment).

Both displays are presented on the same screen ("duplex") to facilitate interpretation.

Vascular ultrasonography

Vascular ultrasonography is the main branch of radiology that uses duplex. Vascular ultrasonography, a subspeciality within ultrasonography, helps determine multiple factors within the circulatory system. It can evaluate central (abdominal) and peripheral arteries

Artery

Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

 and vein

Vein

In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

s; it helps determine the amount of vascular stenosis

Stenosis

A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....

 (narrowing) or occlusion

Vascular occlusion

Vascular occlusion is a sudden blockage of a blood vessel, usually with a clot. It differs from thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major vein, it can, in some cases, cause deep vein thrombosis. The condition is...

 (complete blockage) within an artery; it assists in ruling out aneurysmal disease

Aneurysm

An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...

; and it is the main aid to rule out thrombotic events. Duplex is an inexpensive, non-invasive way to determine pathology

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

. Duplex evaluation is usually done prior to any invasive testing or surgical procedure

Surgery

Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

. Ultrasound duplex scanning can provide additional information that may guide therapeutic decisions. The location and severity of arterial narrowings and occlusions can be identified. The vascular technologist can map disease in lower-extremity segments with great accuracy — though duplex scanning is more time-consuming than other lower-extremity arterial studies.