Certain
radiological exams require a special medication called as “dye” or “contrast agents”.
These are “Imaging-related medications”
and are designated as “prescription
drugs” in accordance with Food and Drug Administration (FDA).
Contrast
helps certain areas to show up better and highlight tissues and organs that
would not be visible otherwise. This allows the radiologist to distinguish normal from
abnormal conditions.
A simple example would be: difference between a color and black &white picture. A color picture has more details and much more information can be extracted (see fig. 1 a and 1 b).
A simple example would be: difference between a color and black &white picture. A color picture has more details and much more information can be extracted (see fig. 1 a and 1 b).
Fig. 1a: B& W picture of sunset Fig. 1b: Color picture of sunset
Similarly, when introduced into the body
prior to an imaging exam, contrast materials make certain structures or tissues
in the body appear different on the images, then they would appear, if no contrast
material had been administered. Fig. 2 b shows, a tumor in the abdomen (red arrow). It is easily identified after giving contrast during a CT scan if compared to fig. 2 a.
Administration of dye, causes organs and tissues to show up better and allowing them to stand out. Thus "contrast selected areas" of the body are easily distinguished form other surrounding tissues. This leads to improved visibility of specific organs, blood vessels or tissues. This helps a radiologist diagnose medical conditions so that treatment can be started early by your physician. You foresee a problem, before it manifests!
There are different types of contrast agents used for various imaging procedures like:
1. Barium
is used for study of intestine like in barium follow through for small
intestine.
2. Iodinated contrast agents
administered for IVP (intra venous
pyelography) or CT scan.
3. Paramagnetic agents
like gadolinium administered during
MRI.
These
contrast agents can be given through different routes like:
1. Orally
or rectally for barium procedures.
2. Injected
through a vein or artery.
3. Injected
into a body cavity under image guidance.
Contrast
Radiography helps answer important questions about the health and functioning
of vital organs. The phenomenon of present-day radiologic
imaging would be lacking without these agents.
References:
3. Jill
M. Widmark, Imaging-related medications: a class overview. proc (bayl univ med cent). oct 2007; 20(4): 408–417. pmcid: pmc2014815.