Stereotactic radiotherapy for choroidal melanoma: Analysis of eye movement during treatment, eye simulator design and automated monitoring system development

Abstract

Malignant choroidal melanoma is a choroidal tumor arising in the layer of blood vessels located beneath the retina. It is a rare occurrence, affecting five to every million inhabitants and rapidly evolving into metastasis. The stereotactic radiotherapy is one of the possible treatments for the disease, it consists in the application of small photon beams directed to the PTV, the prescribed dose is delivered in multiple sessions. The success of treatment depends directly, among others biomedical factors, on the precision of the application and how the treatment method can hold still the patient’s eye. This study aims: (a) to analyze the eye’s movement during the treatment for choroidal melanoma and the non-invasive method for fixating the patient’s eye; (b) to develop a monitoring software for patient eye gaze; (c) design a mechanical eye to verify the monitoring system. As a result, it is expected that the system will be improved, raising the precision and accuracy of application and reducing the damage to healthy tissues and side effects. After analyzing the positions of the iris center and calculating its displacements relative to the orthophoria point the standard deviation values of 0.368 mm and 0.364 mm were found for the X-axis and Y-axis, respectively. The LED lamp is enough for a noninvasive fixation of the patient’s eye during treatment. The mechanical eye now is able to verify the monitoring system software, as both work with resolutions within the limit given by the eye movement analyzes.