The best thing since sliced people? CT (computed tomography or computed axial tomography) is a way of scanning the whole body, or part of the body, slice by slice, using the principles of X-ray.

A CT scan uses large two-dimensional X-rays to form a three-dimensional image. Multiple images are processed by sophisticated computer software to create a cross-section view of the body.

CT scans offer far more detailed images of lungs, bones, blood vessels and other body tissues than a conventional X-ray. This is because a CT can differentiate between different types of tissue.

They can be used to screen for cancer, tumours and blood clots, and also investigate heart disease.

How does it work?

The CT machine has an X-ray tube and X-ray detectors on opposite sides of a ring that rotates around the platform the patient lies on. This platform also slides through the ring. The ring can also move around, so the X-ray beams can follow a spiral path.

Some CT scanner machines have two X-ray beams and two scanners to create higher resolution images. Recently, this type of CT scanner was installed in Christchurch – its cost was approximately $2.2 million.

    Published 23 July 2007