Use of a simulator with CT option in radiotherapy of macular degeneration.

Abstract

To assess the accuracy of a conventional simulation procedure in radiotherapy of age-related macular degeneration. A computed tomographic (CT) extension attached to the treatment simulator was used to acquire CT images immediately after conventional simulation in 18 patients referred for treatment of age-related macular degeneration. Analysis was performed on 16 one-sided treatment cases for whom images were obtained. Error was estimated by the displacement between the observed treatment isocenter and the intended isocenter based on reconstructed eye geometry. Based on single slice measurements, the mean error amplitude was 2.3 mm (range 0.2-5.6). Based on three-dimensional eye globe reconstruction, the mean error amplitude was 2.8 mm (range 0.8-5.3). An incidental finding previously unreported was the lower image quality at the center of the simulator-CT image acquisition field. Small but significant errors from conventional simulation were noted. The integrated simulation-CT procedure may help correct the errors to improve the accuracy of simulation setup. The lower image quality at the center of image acquisition field requires adaptation of the simulation-CT procedure.