Contrast agents

A contrast agent (synonym radiopaque contrast agent) - various chemical substances and compounds used for artificial contrasting such bodies, which under normal chest x-ray does not give sufficient density shadows and therefore poorly differentiated from surrounding organs and tissues.
A necessary condition for x-ray detection of pathological changes in organs and tissues is sufficient contrast between the separate parts of the studied object, and between the object and the surrounding background against which this object is allocated. The passage of x-rays through the investigated object is accompanied by a takeover of one or another part of the radiation in the object itself, and x-ray image is created that part of the energy of x-ray radiation, which, passing an object that acts on the screen or film. If the rate of absorption of x-rays of various tissues studied object will be the same, the image it will also be homogeneous, that is unstructured. The necessary degree of structure and contrast can be achieved only if the different degree of energy absorption of x-ray radiation of various tissues of the object.
Under normal fluoroscopy and radiography clearly differentiate the bones, lungs, calcification and metallic foreign body. Bones due to the content of phosphate of lime stronger than soft fabric, absorbs x-rays and, therefore, are more dense (dark)than the surrounding muscles, ligaments, blood vessels and so on, Light, containing air, on the contrary, poorly absorb x-ray radiation and therefore appear lighter than the dense fabric of the chest and the shadow of the heart and blood vessels.
Gastro-intestinal tract, blood vessels, muscles, and most of the internal organs absorb x-ray radiation is almost equally and give the radiological examination homogeneous, non-contrast images. The application of appropriate contrast agents alters the degree of absorption of x-ray radiation invisible bodies, that is, creates the necessary conditions contrast and makes them visible and available to x-ray study.
The absorption of x-ray radiation with various substances, increases in direct proportion to the fourth degree of their atomic numbers. On this basis (depending on the extent of absorption) all contrast agents are divided into light and heavy (nizkoatomnye and vysokostatusnye) or, otherwise, on the negative, absorb x-ray radiation in less than fabrics of an organism, and positive, therefore, more likely than body tissues and absorptive capacity.
Negative contrast agents are gases (air, oxygen, nitrous oxide, carbon dioxide), against which the monitoring bodies are more dense.
Positive contrast agents are oil and water-soluble iodine compounds (order of iodine 53), barium sulfate and other vysokostatusnye connection and probes and catheters, strongly absorb x-ray radiation.
Along with contrast substance that, when introduced directly in certain Organs, contrast them (for example, yodolipola used bronhografii or fistulografii), there are also such, the application of which is based on the properties of a number of bodies accumulate them and highlight. These contrast agents used in the study of urinary system (Sergazin, tritryst) or gallbladder and biliary tract (bilitrast, bilignost).
The basic requirements to all contrast agents:
1) harmlessness, the minimal toxicity to the body (should not be expressed in the local and General reactions, side effects and complications in the process of introduction and further);
2) izotonichnost in relation to liquid environments of an organism with which they must blend well, which is especially important with the introduction of those or other contrast agents in the bloodstream; 3) easy and complete withdrawal from the body in an unmodified form; 4) ability in necessary cases selectively accumulated and allocated to certain organs and systems (gall bladder, urinary system); 5) the relative ease of manufacture, storage and use.
In medical practice it is allowed to use a contrast agent approved by the Pharmacological Committee of the Ministry of health of the Russian Federation and provided with the relevant guidance and guidelines on their application. The use of other contrast agents should be justified in each individual case. Contraindicated containing iodine contrast medium with individual intolerance or sensitivity to iodine. The diagnostic application of a range of contrast agents should be preceded by a test for tolerance: 1-2 days before the proposed research intravenous 2 ml of contrast and then carefully observe patients. Signs of yodizma (conjunctivitis, rhinitis, urticaria, diarrhoea phenomenon, heart disorder) is an absolute contraindication to the use of contrast agents.
The most frequently used contrast agents: barium sulphate (see) in the study of the gastrointestinal tract; negative contrast medium (air and other gases)used as yourself (with the pneumoperitoneum, pneumotachography, pneumoencephalography and ventrikulografii)and in combination with some positive contrast substances (so-called methods of double contrast study, often used in the study of the stomach and intestines); Sergazin (see)applied to the investigation of urogenital system; yodolipola (see) and propyliodone (see) - bronhografii, myelography, hysterosalpingography and others; gepac, urographine, cardiotest (see), tritryst (see) - when angiocardiography; bilitrast (see) and bilignost (see), used in the study of the gallbladder and biliary tract (cholecystography, holografia).