Evaluation of the role of computed tomography in radiotherapy treatment planning.

The role of computed tomography (CT) in radiotherapy treatment planning was assessed in a series of 231 patients in whom treatment was planned with radical intent. For each patient, a treatment plan was produced by the best conventional techniques in use at the Middlesex Hospital. Each patient then underwent a CT scan in which the treatment conditions were closely simulated. As a result of the CT scan images, alteration was made to the planned treatment in 47% of 198 assessable patients. Large differences were seen in the usefulness of CT treatment planning for tumours in different sites, with the greatest contribution made to treatment of tumours of the sinuses and nasopharynx and of the bladder. Although its unit cost is high, computed tomography can be a very useful tool in radiotherapy treatment planning and can contribute uniquely to improved patient management for adequately selected patients.