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The groupCurrently, radiation to diagnose various diseases of internal organs using x-ray beams of magnetic resonance and ultrasound. The ability of any of these types of diagnosis has increased in the use of contrast media, which can be divided into three groups :
1) means rentgencontrastnye (RAC);
2) magnitno-rezonansnye contrast media (MRKS);
3) ultrasound contrast media (UOS).
While the history of workers began almost immediately after the opening VK Röntgen rays in 1895 MRKS and offered the medicine only a few decades. But it is among the products of these groups contrast in recent years the most visible progress Although continue to appear and more new products to a number of workers who remain most peremenaemami means to radiation diagnostics.
According to P. B. Sergeyev, the RCU are divided into two groups : rentgenonegativee which receives x-ray beams, and rentgenopozitivee delayed them. The first group includes carbon dioxide, nitrogen, oxygen, xenon and other gases Second-yozameshchenne and do not contain iodine substance.
Rentgenpozitivee medicines have a higher density than the soft tissue and bone. Density is defined molecular weight. The atomic mass elements of the workers, resulting in more contrastirovania internal organs. Density soft tissue is about the density of water (0,92-1,06 g / cm ^ 3), the density of iodine-4.94 g / cm ^ 3 and barium - 3.51 g / cm ^ 3.
The elements will be included in sex, the most acceptable to iodine and barium. Anti barium (sulfate) for a half used to contrastirovania blood, their main advantage-pharmacological inertia, but they do not fit for contrastirovania closed cavities or vascular entities.
For the purposes of the angiography, urografii, holetsistografii, mielografii and other varieties of these methods since the 1950s, growing organic iodized workers.
Among them are now available ionic and non-ionic and monomernye dimernye iodized workers. Under existing dokliniceski and clinical research ionic workers compared with calculations have more security and better tolerance.
Embedded in medical practice until 1969, iodized organic workers are salt dissocerute in aqueous solutions. Ion their nature, and hence giperosmolarnosti (5 times higher osmoticnosti blood) makes a number of spin-off effects : tissues, nefropatiu, increased capillary permeability, pressure pain, nausea, vomiting, etc. Therefore, a marked step towards improving WAN Time was the creation neih preparations osmoticnosti are 2-3 times lower than in the metal workers. The first such product was metrizamid (amipak), which because of the instability is not yet widespread. Since the 1880s have been established and implemented stable triyodirovanne monomernye ionic WAN (iogexol, iopromid, etc.) give the best guarantee radiologists in the diagnostic efficacy and safety. Despite lower toxicity and improved portability, ionic workers because of the high cost of Russia and some other countries have not yet fully replaced ion sex.
All organic triyozameshchenne workers classified as follows :
- derivatives of benzoic acid (diatrizoat, ioksitalamat, yotalamat, metrizoat, yodamid)
- derivatives ариламиноацетиламино добензойной acid (yoksaglat)
polimetilenove - dimers triyodbensana acid (yodipamid, yodoksamat, yotroksat).
1. Monomernye (iopamidol, yopromid, iohexol).
2. Dimernye (iotrolan, yodiksanol).
WAN used to holegrafii and angiography are different pharmacokinetic characteristics, and are either inside or intravenously or vnutriarterialno.
Intravenous holetsistograficskie substances penetrate cell membranes active secretiruyutza liver and diffundiruut in jelchne floodplain. They excretiruyutza liver in an unmodified form.
Some holegraficskih yodsoderjath workers out from the body with the urine, this should be taken into account when Ray study of patients with severe kidney conditions.
Among angiourograficskih pharmacokinetics is the circulation in sossoudistom away with the protein and the high (in the) speed their excretion kidneys (subject to the normal functioning of urinary system). They excretiruyutza kidneys usually unaltered.
Based on an examination of the transport workers, their interaction with plasma protein, formennami elements of the blood, membrannami structures liver and kidney formulated theory organotroponosti sex, which is the existence of holetsistograficskih WAN transport systems in the cell membranes operating on the principle of molecular "brand" " and for urograficskih sex-specific mechanisms secreta and concentration in the renal bone.
Adverse reactions to the introduction of vnutrisosudistoe angiourograficskih metal worker is about 12% of cases, some of them require emergency resuscitation activities. Despite the creation in the last decade new, less toxic sex, the problem of security for their use remains relevant.
All the side effects caused by workers shared on hemotoksicskie and atopicescie (anaphylactoidnye and allergic).
Atopicescie reaction inducyruemye workers due gistamina release, and other mediators. They occur more frequently in patients prone to allergic diseases, and the primary risk in the clinical use of sex. Hemotoksicskie effects are almost always explained osmoticescoy activity WAN (gematokrita decline owing to the normal vascular tissue fluid and water from the blood cells; osmoticski diurezom after falling molecules workers in renal clearance Channel), their lipophilicity, electric charge the ability to interact with biomacromolekulami etc. In some areas, there is no central GEB, for example in the area postrema, with its trigger zone, a defining nausea and vomiting. Direct effect of contrast for these zones (it is the better, The higher osmoticnosti WAN), and may be the cause of these side effects.
To reduce the risk of anaphylactoidnykh reactions should apply premedikatia (antihistamines preparations glukokortikoida, adrenomimetiki, etc.) and hemotokscheskih reactions (especially true for the metal vsokoosmotichnykh WAN), protivorvotnye funds (metoclopramide).
Several vehicles used in the MR and ultrasound studies. For example, gadolini-soderjaschie some compounds (Magnevist) enhance image contrast and tissue pathology areas in the central nervous system and other internal organs during magnetic resonance imaging, mikronizirovannaya D-galactoza (Levovist) increases (implicitly) the intensity of the reflected Eho-signala in ultrasonic diagnosis.