avb
For the
digestive system barium sulphate is used. It is the barium that makes it
opaque to X-rays. Barium belongs to the Calcium group of elements and is much
“heavier”, with an atomic mass of 137. (Do not worry, I shall not ask the
atomic mass in an exam!) Barium
sulphate is insoluble in water and hydrochloric acid. This is important,
because this property makes it nonabsorbable even in the strong acidic
environment of the stomach. It is mixed with water to form a suspension which
the patient is given to drink. This is called a ‘barium meal’. For studying
the oesophagus, a spoonful of barium paste is given (called a barium
swallow).
In either
case the radiographer watches the progress of the barium on a screen. At
appropriate moments, films are exposed.
The
barium stays in the stomach (a little spills into the duodenum) for a while. A
study of these structures is a “stomach-duodenum” study. It is then passed on
to the small intestine and the colon. A study of the small intestine and the
colon is also called a “follow-through”. In a follow-through the barium is
spread out and diluted by intestinal fluids. For a clearer view of the colon,
barium is given through the rectum as an enema.
Contrast Media - 1
Key
Points : See next slide.