Diagnostic Radiography

X-rays!

Light penetrates through some materials but not others and in varying amounts. X-rays are similar, but they can penetrate a different range of substances including many that light cannot pass through. It is possible to detect x-rays on film or digitally (similar to photography. As x-rays penetrate the body there is a minor risk of them doing damage, so intensifying screens or digital image capture are used to minimise exposures.

A large chest mass

Bones and teeth

Radiography is commonly thought of as being used to view fractured bones and teh internal structure of teeth. There is a lot of contrast between mineralised tissues (normal bones and teeth) and soft tissues, making it easy to see teeth and most skeletal structures, including joints, and their abnormalities. Radiography is oftenused to monitor treatment (as in the series of images below) and assess healing as well as for initial diagnosis.

Soft tissues

Because most solid soft tissues are largely composed of water, they have similar densities making it difficult to distinguish between them unless there are structures if higher (dense fibrous tissue, teeth, bone) or lower density (fat and air filled structures) between them. When there is insufficient contrast then use of a contast medium can help.

Barium contrast medium in the oesophagus

Injected contrast medium draining from kidneys to bladder

Movement is a problem

Movement during exposure leads to blurring of images. To minimise this and eliminate the need for manual restraint (as well as eliminating pain from movement of sore areas) many x-ray images are taken under sedation or general anaesthesia. When this is inappropriate the time involved is often greater and the cost higher.