Digital subtraction angiography
The digital subtraction angiography (DSA) is a form of angiography , that is the study of blood vessels . Their advantage over so-called conventional sheet film angiography is that "disruptive" image aspects are invisible due to the subtraction. DSA is a projection radiography procedure that competes with magnetic resonance angiography , computed tomography angiography and sonography .
Here, several X-ray images following one another in time are created of the body part to be examined, for example the brain. During the acquisition sequence, a contrast agent is injected into blood vessels. The result is an X-ray image without contrast agent , also known as a mask, and further X-ray images with contrast agent distribution. The digital mask image is subtracted from the subsequent images. Only those parts of the image that differ, i.e. exactly the (perfused) blood vessels remain. By creating several images at different times that follow a mask image, film-like image sequences can be created. A color-coded representation is also possible in that the gray value curves for the image pixels are mapped onto color values.
The necessary justification (med .: indication) for the preference of intra-arterial DSA for the targeted representation of body arteries, which is associated with a higher risk for the patient, prior to an MR or CT angiography, in addition to the greater diagnostic significance, is the possibility of direct Intervention in cases of narrowing or aneurysmal vascular changes and bleeding.
The contrast agent used here is usually iodine-containing (since iodine contrasts very well due to its high radiation density); however, a “negative contrast agent” can also be used in patients with renal insufficiency . Isotonic saline solution is only less dense than blood, but it does contrast. There is even a method in which CO 2 (about 10–20 ml in gaseous form) is given into the arterial vascular access (usually the femoral artery ) or into the catheter that has been advanced into the examination / intervention area. In this way, the vessels are shown very clearly hypodense .
- K. Meyne: Handbook of arterial occlusive diseases. Schlütersche, 2003, ISBN 3-87706-694-1 , p. 77. (online)
- E. Nagel: Cardiovascular magnetic resonance imaging. Springer, 2002, ISBN 3-7985-1285-X , p. 107. (online)
- M. Reiser, FP Kuhn, J. Debus: Radiology. (= Dual row ). 3. Edition. Thieme, Stuttgart 2011, ISBN 978-3-13-125323-1 , p. 394.
- M.-M. Barbey et al: Digital subtraction angiography with carbon dioxide - basics, technology and clinical application. In: VASA. Volume 28, Issue 4, Verlag Hans Huber, Bern 1999, pp. 243-249. ( online ( Memento from August 20, 2008 in the Internet Archive ))