Multi-camera optical tracking and fringe pattern analysis for eye surface profilometry in ocular proton therapy

Background and purpose: An optical tracking system for high-precision measurement of eye position and orien-tation during proton irradiation of intraocular tumors was designed. The system performed three-dimensional (3D) topography of the anterior eye segment using fringe pattern analysis based on Fourier Transform Method (FTM).Materials and methods: The system consisted of four optical cameras and two projectors. The design and modi-fications to the FTM pipeline were optimized for the realization of a reliable measurement system. Of note, phase-to-physical coordinate mapping was achieved through the combination of stereo triangulation and fringe pattern analysis. A comprehensive pre-clinical validation was carried out. Then, the system was set to acquire the eye surface of patients undergoing proton therapy. Topographies of the eye were compared to manual contouring on MRI.Results: Pre-clinical results demonstrated that 3D topography could achieve sub-millimetric accuracy (me-dian:0.58 mm) and precision (RMSE:0.61 mm) in the clinical setup. The absolute median discrepancy between MRI and FTM-based anterior eye segment surface reconstruction was 0.43 mm (IQR:0.65 mm)Conclusions: The system complied with the requirement of precision and accuracy for image guidance in ocular proton therapy radiation and is expected to be clinically tested soon to evaluate its performance against the current standard.