Pose estimation of eyes for particle beam treatment of tumors

To assure a correct position and orientation of the patient's eye in radiation treatment, a new approach in image-guided radiotherapy is used to determine the misalignment of the eye and the respective correction for the patient support devices. New methods allow correcting the misalignment of the patient's eye full-automatically. Therefore, metallic clips attached to the patient's eyeball are detected in a CT and in two digital X-ray images. Corresponding pairs of clip positions found in the X-ray images are then transferred into the 3D space of the CT volume via inverse projection and compared to the clips found in the CT slices. If several combinations of correspondences are possible, we use a temporary pre-registration to assure that the correct back-projections will be obtained. A rigid, point-set based 6 degrees of freedom registration of the back-projected clip positions with the CT clips allows determining the misalignment of the eye tumor which consists of three shifts and three rotations. These transformations are transformed into parameters for a treatment chair and an eye fixation designated to control placement and orientation of the eye during treatment.