PURPOSE: To introduce a noninvasive eye fixation and computer-aided eye monitoring system for linear accelerator-based stereotactic radiotherapy for @entity2184 . METHODS AND MATERIALS: At the Department of Radiotherapy and Radiobiology, University of Vienna, stereotactic radiotherapy is offered to @entity1 with @entity2184 considered unsuitable for (106)Ru brachytherapy or local resection. For the present feasibility study, 8 @entity1 were carefully selected according to their ability to fixate a small light source with the diseased eye and whether they had a rather small head to meet the limited geometric space available. A @entity4625 tube was attached to a stereotactic mask system in craniocaudal orientation supporting a 45 degrees mirror, which was placed in front of the diseased eye. At the other end of the tube, the @entity1 was given a small fixation light, and a small camera was positioned beneath, which was shielded for use during MRI. A computer interface calculated and visualized the spatial difference of the actual and a given reference pupil position, which was defined before CT scanning, during the MRI sequences, and during treatment delivery at the linear accelerator. RESULTS: The described system can be attached to a conventional stereotactic mask system with minor modifications. Because of the large distance between the eye and the fixation light, the optical fixation system was well tolerated by all @entity1 , and a stable position of the eye was obtained. The camera system can be used during CT and MRI without interference. Absorption of the 6-MV photon beam by the mirror and the @entity4625 tube was negligible. The computer interface designed to determine the pupil position uses an image-processing algorithm that correlates a template of the reference image with the actual image of the eye. Provided sufficient illumination of the pupil, the correlation function showed a pronounced minimum at the reference position. The precision of the algorithm was tested by phantom measurements. For a given 1 mm or 2 mm displacement, the interface reported a mean shift of 0.96 +/- 0.18 mm or 2.07 +/- 0.11 mm, respectively. CONCLUSION: The results of this study demonstrated the feasibility of a new optical fixation system for linear accelerator-based stereotaxis. The artifact-free application of the camera system during image acquisition and irradiation and the use of the computer interface, which automatically monitored @entity1319 with submillimeter precision, provided large improvements compared with existing techniques. Given well-defined interruption criteria and accelerated image processing, the described system has a high potential to perform automatically gated treatment beam delivery in the near future.

A noninvasive eye fixation and computer-aided eye monitoring system for linear accelerator-based stereotactic radiotherapy of XXXX .

@entity1 :: ('9606', 'Species') :: ['patients', 'patient'] @entity2184 :: ('MESH:C536494', 'Disease') :: ['uveal melanoma'] @entity4625 :: ('MESH:D019904', 'Chemical') :: ['polymethyl methacrylate'] @entity1319 :: ('MESH:D015835', 'Disease') :: ['eye movements']
@entity2184 :: (MESH:C536494,Disease) :: ['uveal melanoma']
