USE OF A SIMULATOR WITH CT OPTION IN RADIOTHERAPY OF MACULAR DEGENERATION

Purpose: To assess the accuracy of a conventional simulation procedure in radiotherapy of age-related macular degeneration, Methods and Mate rials: A computed tomographic (CT) extension attached to the treatment simulator was used to acquire CT images immediately after conventiona l simulation in 18 patients referred for treatment of age-related macu lar degeneration. Analysis was performed on 16 one-sided treatment cas es for whom images were obtained. Error was estimated by the displacem ent between the observed treatment isocenter and the intended isocente r based on reconstructed eye geometry. Results: Based on single slice measurements, the mean error amplitude was 23 mm (range 0.2-5.6). Base d on three dimensional eye globe reconstruction, the mean error amplit ude was 2.8 mm (range 0.8-5.3). An incidental finding previously unrep orted was the lower image quality at the center of the simulator-CT im age acquisition held. Conclusions: Small but significant errors from c onventional simulation were noted. The integrated simulation-CT proced ure may help correct the errors to improve the accuracy of simulation setup. The lower image quality at the tenter of image acquisition fiel d requires adaptation of the simulation-CT procedure. (C) 1998 Elsevie r Science Inc.