Figure 1-12. Demonstrated barium impaction following an upper GI.
1-23. WATER-SOLUBLE RADIOPAQUES
a. Introduction. The largest, most versatile, group of contrast media is the
water-soluble radiopaques. Made of iodine compounds, this type of media can be used
in radiographic studies of the urinary system, the cardiovascular system, joint spaces,
and connective structures, as well as many other radiographic examinations. There are
two types of water-soluble contrasts, injectable and noninjectable.
b. Water-Soluble Injectables. The water-soluble injectables are categorized
into two groups according to their weight-by-volume concentration. Although the
dividing line in practice is somewhat vague, those media of lower concentrations are
used for general purposes while those of higher concentration are normally reserved for
examination of the heart and great vessels. Weight-by-volume concentration does not
refer to the iodine content of a particular medium, but to the concentration of the iodine
compound. For example, in 100cc (cubic centimeter) of Renografin 60 percent, 60
percent of the weight is the compound methylglucamine diatrizate and 40 percent of the
weight is sterile water. On the other hand, the iodine content of this medium is
approximately 29 percent.
(1) In 1984, a new generation of contrast media was introduced in the U.S.
that also contains iodine as needed for opacity but contains no positive-charged ions,
thus called non-ionic contrast. These new contrasts have a low osmolality and fewer
severe contrast reactions are experienced. A common non-ionic contrast used is
Isovue 300 (Iopamidol Inj 61 percent I.V.).