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Computerised tomography

Computerised tomography - or computerised axial tomography (CT ot CAT scan) - is an X-ray imaging technique which allows the assessment of soft tissues as well as bones.

If X-rays are taken from different angles around the body, a computer can analyse the image and construct a three-dimensional representation of it. As there is no way to print a three-dimensional image, the computer can then be instructed to ‘slice’ this reconstruction into thin two-dimensional ‘slices’ and present these on X-ray film in sequence, allowing the trained doctor to reconstruct the structures again in his mind in three dimensions.

Using CT soft tissue as well as bony interfaces can be clearly seen, allowing the evaluation of tendons, ligaments, cartilage and menisci, all more-or-less invisible on ordinary X-ray.

When CT was first introduced, it seemed like a miracle being able to ‘see’ soft tissues, but it was soon more-or-less supplanted by MRI scanning.