Duplex sonography, background information

Colour-coded duplex sonography is a non-invasive (bloodless) and non-radioactive diagnostic test for evaluating of arteries and veins. It is a combination of the Doppler technique and ultrasound imaging.

At first, with the help of the so-called B-mode method a two-dimensional image of a vessel is produced (see navigation item Sonography. The vascular pattern and the nature of the vascular wall can be well evaluated; and especially the deposits in the vascular wall, such as calcium plaque, can be easily detected. Constant monitoring allows to make conclusions about the progression of the atherosclerotic process.

As a next step, the colour-coded duplex sonography itself takes place. A Doppler blood flow signal occurring in a vessel is converted into a colour. The flow velocity can be measured, thus making it possible to detect the vascular constrictions (stenoses) and to evaluate their extent.

Vein occlusion due to blood clots (thromboses) can be quickly and easily detected with the help of duplex sonography.

As with conventional ultrasound, the gel applied to the skin allows a sonographic contact between the skin and the transducer. The measurements of the blood flow may be accompanied by an audible noise.

During venous examinations, the vessels are slightly pressed together by a transducer, in order to exclude the possibility of a blood clot inside the vessel. It is mostly well tolerated by the patients.

The result of the examination, which lasts only a few minutes, can be immediately reported.

Duplex sonography does not require any preparatory measures to be taken by the patient. In most cases, it is performed in the supine, sometimes in the sitting position or prone position.