There are two main limitations of using
conventional x-rays to examine internal structures of the body. Firstly
superimpositions of the 3-dimensional information onto a single plane make
diagnosis confusing and often difficult. Secondly the photographic film usually
used for making radiographs has a limited dynamic range and therefore only
object that have large variation in the x-ray absorption relative to their
surroundings will cause sufficient contrast differences on the film to be
distinguished by the eye. Thus the details of bony structures can be seen, it
is difficult to discern the shape and composition of soft tissue organ
accurately.
CT uses special x-ray equipment to
obtain image data from different angles around a body and then shows a cross
section of body tissues and organs. i.e., it can show several types of
tissue-lung, bone, soft tissue and blood vessel with great clarity. CT of the body
is a patient friendly exam that involves little radiation exposure
CT
scanner is a large square machine with a hole in the centre, something like a
doughnut. The patient lies still on a table that can move up/down and slide in
to and out from the centre of hole. With in the machine an X-ray tube on a
rotating gantry moves around the patient’s body to produce the images.
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