![]() ![]() None of the four chemical types of contrast media have marked pharmacological actions. 4 Their osmolality and viscosity appear in Figs. 5 All four are tri-iodo benzene ring derivatives with three atoms of iodine at 2,4,6 positions in monomers and six atoms of iodine per molecule of the ring atom in dimers they are very hydrophilic have low lipid solubility, low toxicity, low binding affinities for protein, receptors or membranes and have molecular weights less than 2000. Since the 1950s, four chemical varieties of iodine-based contrast media in clinical use have been introduced. Organic carriers of iodine will probably remain the basis of all intravascular contrast media for the foreseeable future. 4 Some agents can even be administered into the cerebrospinal fluid without causing major problems. brain, heart, kidneys) in the very large amounts required to produce adequate radiopacity. 3 The problem has always been how to pack the iodine so it may be delivered safely into very sensitive arterial systems (e.g. 2 The iodine provides the radiopacity the other elements of the contrast medium molecule provide no radiopacity but act as carriers of the iodine, greatly increasing the solubility and markedly reducing the toxicity of the molecule. Iodine (atomic number 53 and atomic weight of 127) is the only element that is proved satisfactory for general use as an intravascular contrast medium for radiography including angiography and CT. peritonitis through perforation ( Table 2-1). Side effects include barium causing or exacerbating constipation, worsening ulcerative colitis inflammation, e.g. Leakage into the vasculature is life threatening and it is therefore important to be aware of this during the study, so treatment can be initiated immediately. 1 Therefore, when one suspects aspiration, a fistula between the oesophagus and lungs, or perforation of the gastrointestinal tract, the use of barium sulphate should be avoided. It may overflow into the lungs and leak into the mediastinum, the tissue around the rectum or intraperitoneal cavity causing granuloma and occasional fatal reactions. Barium sulphate is normally not absorbed during passage through the digestive tract. The gastrointestinal tract is most frequently studied with very poorly soluble barium sulphate, BaSO 4, which is administered orally or rectally, in a finely divided aqueous suspension with 0.3 to 1 g dry weight per millilitre. blueberry juice, pineapple juice, can be used as contrast media, but their use is beyond the scope of this chapter. Products like air, carbon dioxide, tap water, and juices containing manganese, e.g. Barium products or iodine-based oral agents stay in the intact gastrointestinal tract. Hepatobiliary gadolinium-based agents are partially excreted via the hepatobiliary system, whereas the ion manganese is excreted solely by the liver. Iron-based agents enter the natural circulation like any other iron ion. It may take weeks before the agent is out of the body if the patient has severely reduced renal function. Most of the agents are out of the body within 24 hours if the patient has normal renal function. Acute non-renal adverse reactions are the same for all types of contrast media, whereas there are differences regarding acute renal adverse reactions, late reactions and very late reactions. Serious reactions requiring treatment are infrequent. metal taste and/or feeling of warmth, is frequent. Almost all agents cause discomfort and adverse reactions to some degree. It should leave the body as soon as possible-after it has enhanced the structures in question-in unchanged form and without causing any harm to the body, including adverse reactions. It should be possible to inject the ideal agent fast or drink it. ![]() The ideal contrast medium does not exist. Various types of contrast media exist for each technique, and their applications depend on the chemical and physical properties of the agents. They may be used in radiological procedures such as radiography, fluoroscopy, angiography, computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound. Contrast media are commonly used for imaging to enhance the differences of structures or fluids within the body tissue. ![]()
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