Angiography

What is Angiography?

Angiography is a radiological examination that allows you to view certain vascular districts, in order to study their morphology and course, and reveal any alterations.

Traditional angiography uses X-rays to obtain the representation of the blood and lymphatic vessels for diagnostic purposes.

Since - unlike bones or lungs - the blood has a radio-opacity similar to that of the surrounding tissues, it is necessary to use a special water-soluble contrast agent, to be injected near the circulation that one intends to examine.

Depending on the injection site, angiography takes on particular names, such as ventriculography, aortography, coronary angiography, etc.

The injection of the contrast medium can be performed by direct puncture, or, when the examined district is not directly accessible (think of the coronary arteries of the heart), by catheterization. In the latter case the catheter, an extremely thin and flexible tube, it is made to penetrate the arterial access point and pushed into the vessels until it reaches the vascular district to be examined. Thanks to local anesthesia, performed at the puncture site, the examination is not painful, while the release of the contrast medium can produce a brief and localized sensation of heat or tension.

In the absence of the contrast medium, the radiographic image would not provide any useful information on the state of health of the analyzed district. Together with the high radiopacity, which allows to clearly distinguish the vessel into which it is injected, the contrast medium must have an adequate " water solubility and tolerability Its elimination occurs via the kidney and urine.

At the beginning of its development, angiography was carried out on a special radiological plate, with a limited rate of recovery that allowed to evaluate only the morphology of the vessels.

With the refinement of radiological techniques, new imaging methods have been developed, such as digitized ones that allow to study the circulatory dynamics and appreciate the functionality of the vessels in a less invasive way. Thanks to the ability of the equipment to highlight even poorly opacified vessels, there is now the possibility of reducing the quantity of the contrast medium used, which can also be injected intravenously. Frames and movies are no longer saved on plates or films, but on CD-roms or other storage media.

The digital angiography techniques are based on the computerized radiological reconstruction of the vessel, after having subtracted from the frames - appropriately amplified - the image obtained before the introduction of the contrast medium. In this way the static structures of the image, such as bones and other organs (which appear with the same intensity before and after the introduction of the contrast agent) are eliminated, obtaining a greater sharpness of the blood vessels. This technique, called DSA (Digital Subtraction Angiography), cannot be applied to the study of the heart.

Interventional Angiography and Stent

At the end of the diagnostic part it is possible to intervene with specific endovascular treatments, aimed at resolving the pathological condition identified. An example is the application of stents to restore the patency of an occluded vessel (see angioplasty). In these cases we speak of interventional angiography.

MRI and CT angiography

The angiographic examination can also be conducted by exploiting the potential of magnetic resonance imaging (Angio-MRI) or computed tomography (Angio-CT).

In the first case, non-ionizing radiation is used and the special contrast medium, not always necessary and injected intravenously, has a lower degree of toxicity than that used in traditional X-ray angiography.

The advantages of CT angiography lie in the lower amount of radiation administered and in the less invasiveness of the injection procedure of the contrast medium, which takes place intravenously instead of arterial.

Both techniques produce three-dimensional images and are part of the so-called "non-invasive" imaging methods, which will characterize the near future of radiology.

In fact, we must not forget that angiography, whether traditional or digital, is not free from risks, including non-negligible mortality rates, which is why new imaging techniques have considerably reduced its use.