3 - Vascular Investigations
Published online by Cambridge University Press: 12 August 2009
Summary
THE VASCULAR LABORATORY
WHAT IS A VASCULAR LABORATORY?
A vascular laboratory is a hospital department in which non-invasive vascular assessments (NIVA) are carried out. These are mainly advanced ultrasound techniques using colour duplex and Doppler ultrasound. Other tests include plethysmography and segmental pressure measurements. In recent years the equipment has become more advanced making the investigations more accurate, safer and more cost effective (see Figure 3.1.1).
Ultrasound (conventional)
This provides anatomical information of the vessel being examined. An example of use is the monitoring and measurement of aortic aneurysms.
High frequency sound waves created by passing a current through a piezoelectric element are transmitted via a transducer into tissue and the reflected sound is used to form an image, based on a time base, which can be displayed on a monitor (Figure 3.1.2).
Doppler ultrasound
This is used to measure the direction and velocity of flow within a vessel. It can also be used to measure the volume of flow within a vessel.
Doppler ultrasound takes its name from the Austrian physicist Christian Doppler (1803–1853) who was the first person to identify the effect on sound as the wavelength changes, i.e. Doppler effect. The Doppler effect can be heard frequently in our daily lives. An example being the apparent change in pitch of an emergency vehicle as it approaches. This is because as the vehicle moves towards you the frequency of the sound waves reaching you is increased resulting in a change in tone of the signal.
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- Vascular DiseaseA Handbook for Nurses, pp. 101 - 120Publisher: Cambridge University PressPrint publication year: 2005