ESTRO 2025 - Abstract Book

S3355

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2025

4537

Digital Poster An Eye-Tracking Device for Uveal Melanoma Stereotactic Radiotherapy Bolshakov Sergey, Fayzullin Rafael Medical Physics, OncoStop, Moscow, Russian Federation

Purpose/Objective: Uveal melanoma is one of the most common primary eye tumours for which stereotactic radiotherapy is a treatment option. In this case, retrobulbar anaesthesia is usually used to achieve adequate eye immobilisation. An alternative, less invasive approach implements online eye position tracking [1]. This paper presents a new pupil tracking device for ensuring reliable eye fixation during stereotactic radiotherapy. Material/Methods: In the device (Fig. 1), a small infrared video camera was used to track the current pupil position utilizing a global thresholding-based algorithm. An infrared light emitting diode (LED) provided an illumination of the eye. Another LED allowed to fixate the patient’s gaze direction. An eye phantom allowing the insertion of radiochromic films was designed to validate the tracking device (Fig. 2).

Fig 1. Appearance of the eye tracking device

Fig 2. Composition and appearance of the eye phantom

Results: Deviations of up to 5 mm of the eye phantom calculated by the device and the CyberKnife system were within the margin of error. The gamma pass rate (1%1mm10%Theshold) was over 90% for all of the EBT3 films inserted into the eye phantom during the test treatment plan delivery. During the 30 minutes of the volunteer’s eye tracking, the algorithm was unable to define the pupil’s contour in almost four percent of the frames mainly due to blinking. In the remaining 96% of cases, the average radial deviation from the initial position was 0.27 mm, with it being less than 0.5 mm and 1 mm in 90.8% and 98.9% of cases respectively.