Computer aided patient positioning in proton therapy of eye tumours

Purpose To improve and accelerate patient positioning during proton treatment of eye tumours using an automated monitoring procedure Methods and Materials Proton therapy of eye tumours requires positioning in the sub millimetre range. For this purpose, small tantalum clips sutured to the eye globe serve as landmarks. While the patient is immobilised in the treatment chair and keeps looking at a fixation light, clip and eye positions can be determined with a digital X amp; 64979;ray system providing orthogonal images. The clip projections derived from the treatment plan are superimposed with the present X ray images for position control. By the correction of chair and fixation light coordinates the patient is repositioned until both actual and target clip projections match with each other. In order to avoid a time consuming trial and error correction approach, a novel procedure has been implemented in the image processing software that compares both projections with each other. By automatically calculating the necessary corrections of chair and light coordinates it is aimed to facilitate adjustment to the final treatment position. Results Perpendicular X ray views provided precise patient positioning with an accuracy of below 0.3 mm. By use of the automated procedure, the mean positioning time could be reduced. Discussion and Conclusions To date, the installation of an on amp; 64979;site digital X ray system for patient positioning is unique in proton therapy. Reduced positioning time due to the use of image processing to full capacity makes therapy more tolerable for the patient and may result in higher patient throughput