Computed Tomography scanners produce detailed pictures of both bones and soft tissues using multiple X-ray beams
Also known as computerized tomography, computed axial tomography, computed tomography (CT) is a type of diagnostic radiology used to obtain detailed images of various medical disorders. CT scanners were first developed in the early 1970s; today, millions of scans are performed worldwide every year.

How Does a CT Scanner Work?
To produce pictures of the inside of the body, a CT scanner uses the same type of radiation as a conventional X-ray machine. CT scans are more detailed than X-ray films, however, especially in the case of soft tissues. The greater detail is achieved because, while an medical-x-ray machine sends only a single beam of radiation into the body, a CT scanner sends multiple beams from many different angles. A computer is used to interpret the results and produce an image.
As on an X-ray film, the appearance of different tissues on a CT scan depends on how much each tissue blocks the passage of the radiation. Bone, which blocks the most radiation, appears white, while air, which blocks the least, appears black. Other tissues are represented by various shades of grey.

Having a CT Scan
CT scanners were originally designed to take pictures of the brain, and are still important in the diagnosis of brain tumours, aneurysms and other brain disorders. Modern scanners can image any part of the body. CT scans are also invaluable in assessing skeletal injuries, as even very tiny bones are shown clearly.
For some CT scans, a special dye may be injected into a vein before the scan to improve the contrast between different tissues on the images obtained.
During the scan, the patient lies on a bed with the hollow opening of the CT machine placed over the part of the body that is to be imaged. CT scanning is not painful, though it can be distressing for people with severe claustrophobia or those who find it difficult to lie still because of chronic pain. In some cases, a sedative may given before the procedure.

Benefits and Dangers of CT Scans
Unlike X-rays, CT scans show soft tissues as well as bones, so they can be used to diagnose a wide range of disorders. CT images are not as detailed as MRI scans, but, unlike MRI, CT can be used for people who have an implanted device such as a heart pacemaker. The main disadvantage of CT is that it exposes the patient to radiation. CT scanning is generally not recommended for women who are or may become pregnant, and is used for children only when essential.

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