Digital subtraction angiography

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Digital subtraction angiography
Example of iodine-based contrast in cerebral angiography
MeSHD015901

Digital subtraction angiography (DSA) is a fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a "pre-contrast image" or mask from subsequent images, once the contrast medium has been introduced into a structure. Hence the term "digital subtraction angiography.[1][2] Subtraction angiography was first described in 1935 and in English sources in 1962 as a manual technique. Digital technology made DSA practical starting in the 1970s.[3][4]

Procedure

DSA and fluoroscopy

In traditional angiography, images are acquired by exposing an area of interest with time-controlled x-rays while injecting a contrast medium into the blood vessels. The image obtained includes the blood vessels, together with all overlying and underlying structures.[3] The images are useful for determining anatomical position and variations, but unhelpful for visualizing blood vessels accurately.

In order to remove the 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 X-ray image intensifier, which then keeps producing images of the same area at a set rate (1 to 7.5 frames per second). Each subsequent image gets the original "mask" image subtracted out. (Mathematically, the incoming image is divided by the 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.[5]

Neuro Coiling Procedure

Intravenous digital subtraction angiography

Intravenous digital subtraction angiography (IV-DSA) is a form of angiography which was first developed in the late 1970s.

IV-DSA is a computer technique that compares an X-ray image of a region of the body before and after radiopaque iodine based dye has been injected intravenously into the body. Tissues and blood vessels on the first image are digitally subtracted from the second image, leaving a clear picture of the artery which can then be studied independently and in isolation from the rest of the body.

Some limited studies have indicated that IV-DSA is not suitable for patients with

diabetes or kidney failure because the dye load is significantly higher than that used in arteriography.[6] However, IV-DSA has been used successfully to study the vessels of the brain and heart and has helped detect carotid artery obstruction and to map patterns of cerebral blood flow. It also helps detect and diagnose lesions in the carotid arteries, a potential cause of strokes.[7][8][9]

IV-DSA has also been useful in assessing patients prior to surgery and after

transplant
operations.

Applications

DSA is primarily used to image blood vessels. It is useful in the diagnosis and treatment of arterial and venous occlusions, including

cerebral aneurysms and arteriovenous malformations
(AVM).

The future

DSA is done less routinely in imaging departments. It is being replaced by

nephrotoxic contrast agents.[13]

See also

References

  1. ^ Glick, Yair. "Digital subtraction angiography | Radiology Reference Article | Radiopaedia.org". Radiopaedia. Retrieved 2021-09-29.
  2. ISBN 9780199687817
    .
  3. ^
    PMID 2185864
    .
  4. PMID 13952459
    .
  5. ISBN 9781428923348
    .
  6. doi:10.1148/radiol.2392050413
    .
  7. PMID 2334014
    .
  8. PMID 3895593
    .
  9. PMID 3900078
    .
  10. ISBN 978-1405183239
    .
  11. doi:10.1111/j.1468-1331.2004.00878.x. Archived from the original
    (PDF) on 5 December 2013. Retrieved 26 June 2013.
  12. ^ Newton, Carter (11 May 2010). "Comparing CTA and MRA". Diagnostic and Interventional Cardiology. Scranton Gillette Communications. Retrieved 6 January 2017.
  13. PMID 21388544
    .

Further reading
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