Unravelling the helix--a physician's guide to spiral computed tomography.

The introduction of spiral technology to computed tomography (CT) scanners in the late 1980s has revolutionised the field of CT. Spiral CT offers definite practical benefits over conventional scanners and has expanded the role of CT through the development of new scanning techniques. CT scanning now rivals magnetic resonance imaging in many areas of investigation, and for some situations is the clear investigation of choice. This review is aimed at those clinicians who have access to spiral scanning services but wish to have a greater understanding of the technique and its clinical applications. The concept of spiral CT, and the differences between spiral and conventional scanning are discussed. The various clinical applications of the technique are illustrated.