HOCM remain used for gastrointestinal and cystourethral administration, including the following agents:ĭiatrizoate sodium/meglumine (Gastrografin, MD-Gastroview, Cystografin) As the first generation of iodinated contrast agents, HOCM were associated with high rates of adverse events and fell out of favor in the 1990s for intravascular and intrathecal purposes. High osmolality contrast media (HOCM) are approximately five to eight times the osmolality of serum. In general, HOCM are ionic compounds that include a benzene ring with three iodine atoms and a side chain containing a carboxylic acid (-COOH) group. Water-soluble iodinated contrast media is usefully classified by osmolality: High osmolality contrast media Myasthenia gravis: caution is advised, as reports suggest a clear risk of exacerbation of respiratory symptoms 6,13,14 Risk factors for adverse reactions to iodinated contrast media Milder previous reactions to iodinated contrast media/excipients Material decomposition techniques allows the creation of virtual images in which iodine is preferentially increased in intensity ( iodine map) or removed altogether ( virtual non-contrast), which can hold additional diagnostic value.ĭocumented previous severe reaction to iodinated contrast media, including anaphylaxis, angioedema and bronchospasm
When the incident x-ray energy is closer to the k-edge of the atom it encounters, photoelectric absorption is more likely to occur.ĭifferences in photoelectric absorption across different x-ray energies is harnessed in dual-energy CT, in which patients are scanned with two different x-ray spectra. Iodine has a particular advantage as a contrast agent because the k-shell binding energy ( k-edge) is 33.2 keV, similar to the average energy of x-rays used in diagnostic radiography 1. As iodine has a high atomic number, 53, compared to most tissues in the body, the administration of iodinated material produces image contrast due to differential photoelectric absorption. Both these interactions depend upon physical density, but the latter also depends upon atomic number of the matter. The ability to distinguish between tissues of different x-ray attenuation (image contrast) depends upon two types of interactions between photons and matter: Compton scattering and photoelectric absorption.
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