DSA, is primarily used to image blood vessels. It is useful in the diagnosis and treatment of:
In order to remove these distracting structures to see the vessels better, first a mask image is acquired. The mask image is simply an image of the same area before the contrast is administered. The radiological equipment used to capture this is usually an image intensifier, which will then keep producing images of the same area at a set rate (1 - 6 frames per second), taking all subsequent images away from the original 'mask' image. The radiologist controls how much contrast media is injected and for how long. Smaller structures require less contrast to fill the vessel than others. Images produced appear with a very pale grey background, which produces a high contrast to the blood vessels, which appear a very dark grey.
The images are all produced in real time by the computer, as the contrast is injected into the blood vessels.
DSA is being used less and less routinely in imaging departments. It is being taken over by Computed Tomography Angiography, which can produce 3D images through a test which is less invasive and stressful for the patient.