gfgdfgFor visualization of organs and anatomical structures that are not discernible on the survey radiographs, an artificial contrast technique is used, in which a contrast medium is introduced into the study region, having the ability to absorb X-ray radiation or reduce its absorption intensively.
Preparations with a small atomic weight are gaseous substances, which reduce the absorption of X-rays. Gases are usually introduced to contour the investigated anatomical structures into hollow organs (for example, into the bladder) or body cavity. Gases are radiopaque substances and look on the roentgenogram in the color of a negative image. Therefore they are called negative radiopaque preparations.
Preparations with a large atomic weight are substances that absorb X-rays. They are divided into iodine-containing preparations and do not contain iodine; they look like a positive image on the X-ray. Therefore they are called positive radiopaque preparations. Iodine-containing preparations contain at least three iodine atoms in their molecule.