Radiocontrast agents are preparations that are distinguished by their ability to absorb X-rays from biological tissues. They are used to visualize the structures of organs and systems that are not detected or poorly examined by conventional radiography, CT and fluoroscopy.
The essence of such research
A necessary condition for radiographic examination of pathological changes in organs is the presence of a sufficient degree of radiopaque substances in organs and systems. The passage of rays through the tissues of the body is accompanied by the absorption of one or another part of the radiation.
If the level of X-ray absorption by the tissues of the organ is the same, then the image will also be uniform, that is, structureless. With conventional fluoroscopy and radiography, the outlines of bones and metallic foreign bodies are visible. Bones, due to their phosphoric acid content, absorb rays much more strongly and therefore appear denser (darker on screen) than the surrounding muscles, blood vessels, ligaments, etc.
The lungs when inhaled, in which there is a large amount of air, weakly absorb X-rays and, therefore, are less pronounced in the picture than the dense tissue of organs and vessels.
Gastrointestinal organs, vessels, muscles and tissues of many organs absorb radiation almost equally. The use of certain contrast agents changes the degree of absorption of X-rays by organs and systems, that is, it becomes possible to make them visible during the examination.
Basic requirements
Radiocontrast agents must meet the following requirements:
- harmlessness, that is, low toxicity (there should be no pronounced local and general reactions as a result of the introduction of a contrast solution);
- isotonicity in relation to liquid media with which they must mix well, which is especially important when they are introduced into the bloodstream;
- easy and complete removal of the contrast agent from the body unchanged;
- the ability, if necessary, to partially accumulate, and then be removed in a short time by certain organs and systems;
- relative ease of manufacture, storage and use in medical research.
Types of radiopaque compounds
Substances that can form a contrast image on an x-ray are divided into several types:
- Substances with a low atomic mass - gaseous substances that reduce the absorption of x-rays. They are usually introduced to determinecontouring anatomical structures into hollow organs or body cavities.
- Substances with a large atomic weight - compounds that absorb X-rays. Depending on the composition, radiopaque agents are divided into iodine-containing and iodine-free preparations.
The following low atomic weight radiopaque agents are used in veterinary practice: nitric oxide, carbon dioxide, oxygen and room air.
Contraindications for contrast enhancement
This type of study is not recommended for those who have individual iodine intolerance, previously diagnosed renal failure, diabetes mellitus or thyrotoxicosis. X-ray contrast examination of the gastrointestinal tract is prohibited if the patient has a suspicion of perforation. This is due to the fact that free barium is an active irritant to the peritoneal organs, while water-soluble contrast is less irritating.
Relative contraindications to a study using a contrast agent are acute liver and kidney disease, active tuberculosis and a tendency to allergies.
Methods of X-ray contrast studies
Radiocontrast diagnostics can be positive, negative and double. Positive studies involve the administration of a high atomic mass X-ray positive contrast agent, while negative studies involve the use of a negative low atomic mass contrast agent.mass. Dual diagnostics are carried out with the introduction of both positive and negative drugs at the same time.
Composition of contrast agents
Today there are radiopaque agents such as:
- water mixture based on barium sulfate (activators - tannin, sorbitol, gelatin, sodium citrate);
- solutions containing iodine (iodized oils, gases).
For diagnostics, special substances are used that contain polarized atoms with an increased reflective property. These drugs are administered intravenously.
Preparation for the study
Research areas such as the skull, brain, paranasal sinuses, temporal lobes and chest organs do not require special preparation of patients for X-rays. Before injecting a radiopaque substance to examine bones and joints, pelvic and abdominal organs, kidneys, pancreas, vertebrae and intervertebral discs, it is necessary to prepare a person.
The patient must inform the medical staff about previous illnesses, recent surgical interventions, and the presence of foreign bodies in the study area. Before the day of intravenous administration of radiopaque agents, it is advisable for patients to limit themselves to a light breakfast. For constipation, it is worth taking a laxative the day before, for example, Regulax or Senade.
Stages of X-ray recognition
X-ray examinations are carried out in specially equipped rooms in a clinic or diagnostic centers. You can get pictures, that is, the result of the examination, using a special apparatus. X-ray studies begin with the identification of deviations in the areas under study. The next stage is a contrast polypositional study, that is, a combination of radiography and fluoroscopy. Of great importance in the study of organs and tissues is the diagnosis of the general appearance of the contrasted area.
Any injection of a radiopaque substance must be carried out under the strict indication of the attending physician. Before the procedure, the medical staff must explain to the patient the purpose of the diagnosis and the algorithm for conducting the study.
Medical kit for the introduction of radiopaque substances includes:
- intravenous contrast device;
- syringes and containers for radiopaque solutions.
The volume of syringes can range from 50 to 200 ml. In each case, a set for the introduction of contrast before diagnosis is selected individually. Contrast syringes must be fully compatible with the auto injector.
