Digital subtraction angiography is an imaging procedure that allows blood vessels in the body to be shown with great precision. Using X-rays and a contrast dye, fine vessel structures are made visible by digitally removing the overlapping shadows of bones and tissue.
How does this examination work?
In a digital subtraction angiography, also called DSA, two X-ray images are taken: one before the contrast dye is injected, and one after. The first image shows the normal state, the second shows the vessels filled with contrast dye. A computer then subtracts the first image from the second. This leaves only the blood vessels on the final image, while bones and other structures are removed. Even the smallest changes or narrowings in the vessels can be spotted, which might otherwise be easily missed.
The contrast dye is usually injected through a thin catheter directly into the artery or vein being examined. Common areas include the vessels of the brain, the coronary arteries, and the vessels in the arms and legs. The examination takes place in a specially equipped room called an angiography suite.
When is digital subtraction angiography used?
This method is used whenever a particularly precise image of the blood vessels is needed. This is the case, for example, when there is a suspicion of a narrowed vessel, an aneurysm (a bulge in a vessel wall), a vascular malformation, or a blocked vessel. Digital subtraction angiography can also be very helpful in preparing for or checking the results after certain procedures, such as the treatment of blocked vessels.
Compared to other imaging methods such as ultrasound or computed tomography, DSA offers especially high detail. In particular, in difficult cases, such as unclear circulation problems or when planning surgery, it provides crucial information.
What happens during the examination?
Before the examination begins, an access point is usually placed through which the contrast dye can be introduced into the vascular system. This is often done through the groin or the arm. During the examination, you lie still on a table. The contrast dye may cause a brief feeling of warmth or a slight tingling, which is generally harmless.
The entire examination usually takes between 30 minutes and one hour, depending on how many sections of vessels need to be examined. Once finished, the access point is removed and the puncture site is monitored briefly to prevent any bleeding.
What are the advantages of digital subtraction angiography?
One major advantage is the very precise display of vessels, even in difficult anatomical situations. By digitally removing bones and tissue, even small vessel changes can be detected. The procedure helps to decide clearly whether treatment is needed and, if so, what kind. In addition, a treatment can often be carried out directly during the examination, for example widening a narrowed vessel or inserting a stent.
Are there any risks or side effects?
As with any examination involving X-rays and contrast dye, there are certain risks with digital subtraction angiography. In rare cases, the contrast dye can cause allergic reactions. People with reduced kidney function or certain pre-existing conditions should discuss with their doctor beforehand whether the procedure is suitable for them. Small bruises can occasionally occur at the puncture site. Serious complications such as vessel injuries or infections are very rare.
Overall, digital subtraction angiography is considered a safe and well-established procedure that is carried out routinely in specialist centres.
What happens after the examination?
After the examination, the puncture site is monitored for some time to prevent any bleeding. It is often advisable to rest for a few hours and to drink plenty of fluids so that the contrast dye is flushed out quickly. In most cases, you can go home on the same day, provided no further procedures are planned.
What is the difference from other angiographies?
Unlike conventional angiography, where images are recorded directly onto X-ray film, digital subtraction angiography uses modern computer technology. This means the images can be processed and assessed immediately. The image quality is noticeably better, and the radiation exposure is usually lower. DSA can also display moving images in real time, which is particularly useful during procedures.
When might a different examination be more appropriate?
In some cases, a less involved examination is sufficient, such as a vascular ultrasound or a computed tomography scan with contrast dye. The choice of procedure depends on what question needs to be answered and how well the vessels can be seen on other images. Digital subtraction angiography remains especially important when the highest level of accuracy is required or when a treatment is planned at the same time.
What should be considered before the examination?
Before a DSA, you will usually be asked about allergies, kidney conditions, and your current medication. Certain medicines that affect blood clotting may need to be stopped temporarily. It is a good idea to drink enough beforehand to ease the strain on the kidneys. Anyone with questions or concerns should raise them in advance and ask for a clear explanation of the examination.
Digital subtraction angiography is an important part of modern vascular diagnostics. It allows accurate and safe assessment of vascular conditions and has become an essential tool in medicine today.
