Sievering Clinic

Competence Centre for Minimally Invasive Medical Services

Diagnosis

Non-invasive Diagnosis Methods

Ultrasound Investigation

Imaging Studies

The goal of imaging studies is to identify and map all areas of acute or chronic obstruction and all areas of reflux within the deep and superficial venous systems.

Ultrasound

Successful imaging of the deep venous system requires a thorough knowledge of venous anatomy and physiology and a meticulous attention to detail.

The most useful modalities available for venous imaging are contrast venography, magnetic resonance imaging (MRI), and colour-flow duplex ultrasonography.

Two-dimensional ultrasonography
Two-dimensional ultrasonography forms an anatomic picture based on the time delay of ultrasonic pulses reflected from deep structures. Structures that absorb, transmit, or scatter ultrasonic waves appear as dark areas; structures that reflect the waves back to the transducer appear as white areas in the image. Vessel walls reflect ultrasound; blood flowing in a vessel absorbs and scatters ultrasound in all directions. The normal vessel appears as a dark-filled white-walled structure.
Duplex ultrasonography
Duplex ultrasonography is a combination of anatomic imaging by 2-dimensional ultrasound and flow detection by Doppler-shift. With duplex ultrasonography, after the 2-dimensional anatomic image is displayed, a particular spot in the image can be selected for Doppler-shift measurement of flow direction and velocity.
Colour-flow imaging
Colour-flow imaging (sometimes called triplex ultrasonography) is a special type of 2-dimensional ultrasonography that uses Doppler flow information to colorize areas of the image in which flow has been detected. Vessels in which blood is flowing are coloured red for flow in one direction and blue for flow in the other, with a graduated colour scale to reflect the speed of the flow. Modern colour-flow duplex ultrasonography equipment can provide flow information in conjunction with surprisingly high-resolution views of both deep and superficial venous systems. Structural details that can be observed include the most delicate venous valves, small perforating veins, reticular veins as small as 1 mm in diameter, and (using special 13-MHz probes) even tiny lymphatic channels.
Magnetic resonance venography (MRV)
MRV is the most sensitive and most specific test for deep and superficial venous disease in the lower legs and in the pelvis, where other modalities cannot reach. MRV is particularly useful because unsuspected nonvascular causes for leg pain and oedema may often be observed on the MRV scan when the clinical presentation erroneously suggests venous insufficiency or venous obstruction.
Direct contrast venography
Direct contrast venography is the most labour-intensive and invasive imaging technique. In most centres it has been replaced by duplex ultrasonography for routine evaluation of venous disease, but the technique remains extremely useful for difficult or confusing cases.
An intravenous catheter is placed in a dorsal vein of the foot, and radiographic contrast material is infused into the vein. If deep vein imaging is desired, a superficial tourniquet is placed around the leg to occlude the superficial veins and force contrast into the deep veins more quickly.
Assessment of reflux by direct contrast venography
Assessment of reflux by direct contrast venography is a difficult procedure that requires passing a catheter from ankle to groin with selective introduction of contrast material into each vein segment.
Nearly 15% of patients undergoing venography for detection of deep venous thrombosis (DVT) develop new thrombosis after contrast venography. The incidence of contrast-induced DVT in patients who undergo venography for diagnosis and mapping of varicose veins is not known.