[Computer-assisted placement for after-loading procedures with iridium 192].

Extremely high precision is needed to place radiation sources in the after-loading technique, but localisation techniques so far described do not offer the required accuracy. We used the computer-assisted surgery (CAS) localising system for the placement of after-loading probes in patients with head and neck carcinoma. Surgical instruments can be positioned without visual control using the CAS system. Since 1989 after-loading tubes have been placed using the CAS method. We evaluated the accuracy to be better than 1 mm. Ten after-loading treatments with iridium 192 of head and neck carcinomas were carried out between August 1989 and February 1991 with exact placement of the after-loading tubes in the nasopharynx. It seems feasible to treat cerebral tumours as well as tumours of the pelvic region by computer-assisted after-loading brachytherapy.