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CONTRAST AGENTS

CONTRAST AGENTS. 3 rd Radiopharmaceuticals 3 rd Year Pharmacy 2016-2017. Radiography and Computed Tomography.

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CONTRAST AGENTS

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  1. CONTRAST AGENTS 3rd Radiopharmaceuticals 3rd Year Pharmacy 2016-2017

  2. Radiography and Computed Tomography • A photographic film containing a radiographic image is properly called a radiograph, although it is commonly referred to as an x-ray or a film. The relative difference between the light and dark areas on a radiographic image reflects what is called radiographic contrast.

  3. Contrast media • Any agent or compound administered to a patient to improve the visualization of an organ or tissue is called a contrast agent.

  4. Contrast agents can be classified as negative or positive. Air and other gases are negative contrast agents because they render a structure, such as the gut, more translucent. An agent that increases the radiographic opacity of an organ or tissue is a positive contrast agent. • Most contrast agents used in diagnostic radiology are positive contrast agents.

  5. An ideal radiographic contrast agent should have the following properties • (a) readily available, • (b) inexpensive, • (c) excellent x-ray absorption characteristics at the x-ray energies used in diagnostic radiology, • (d) minimal toxicity, • (e) patient acceptance, • (f) chemical stability, • (g) high-water solubility with low viscosity and no significant osmotic effects, and • (h) the ability to be administered for selective tissue uptake and excretion

  6. Barium Sulfate BaSO4 • Barium sulfate is a nearly ideal contrast agent for oral and rectal studies of the GI tract. It produces a metal-like density on radiological studies, is inexpensive, and when properly utilized, has minimal patient morbidity and mortality. While various water-soluble barium compounds are quite toxic, barium sulfate is an insoluble white power that is a colloidal suspension in water.

  7. Magnetic Resonance Imaging • Many contrast agents used for MRI are extracellular paramagnetic agents. The primary paramagnetic metal ion used is gadolinium, a rare earth element. Gadolinium ions (Gd+3) form when prepared in 0.05 M hydrochloric acid and are extremely effective for enhancing water proton relaxation rates.

  8. All intravenous gadolinium complexes are hypertonic when compared with plasma. The most common side effects are headache, nausea, dizziness, taste perversions, and vasodilation.

  9. ULTRASOUND CONTRAST AGENTS • Contrast agents are not used for most diagnostic ultrasound examinations. Because ultrasound relies on the detection of sound waves reflected from tissue interfaces, gases can create prominent acoustic interfaces near body tissues and can be adapted for use as contrast agents.

  10. Perflutren • octafluoropropane • is a volatile gas that efficiently reflects sound waves. This gas is encapsulated as a protein or lipid microsphere that is generated when a solution of protein or lipids is agitated with the gas immediately prior to use for cardiac.

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