Question

Contrasting agents and their applications for X-ray imaging?

Answer 1

The contrasting agents are used in X - ray imaging techniques to increase the visibility of internal structures providing clarity to locate the abnormalities or defects. The contrast agents commonly used in radio imaging studies include iodine, barium, microbubbles, CO₂ and air. Some agents are less frequently used and these include high atomic number nanoarticles like gold, bismuth, ytterbium and tantalum. The contrast agents absorb the X - rays in more or less concentrations than the body tissues. Absorption of more X - rays provide dark or raiolucent images. The absorption of less X - rays provide white or radio opaque images. These are described as negative and positive images respectively. The agents like iodine,barium water and oil suspensions absorb less X - rays producing positive X - ray contrast media appearing brighter than the surrounding media. In contrast, the CO₂ and air produce negative contrast media and appear dark due to absorption of more X rays than the body structures. The difference in the concentration of contrast agent molecules and density of tissues provide the X ray imaging. The iodinated contrast agents are water soluble and exist in organic (non-ionic) and inorganic (ionic) forms.The iodine agents are used for visualization of circulatory tissues and introduced into body intravascularly. Barium sulfate is oldest X ray contrasting agent used for observation of digestive tract of the body. It is insoluble in water and produces radio opaque and bright images. The air is used as contrasting agent to view digestive system and joint cavities. The CO₂ is used for angiography and microbubbles to detect the thyroid dysfunction or renal impairement. The oil based contrasting agents are used for myelography. The nanoparticles are used for imaging of blood circulation.