Semiautomatic Regional Segmentation to Measure Orbital Fat Volumes in Thyroid-Associated ophthalmopathy A Validation Study

This study was designed to validate a novel semi-automated segmentation method to measure regional intra-orbital fat tissue volume in. Graves' ophthalmopathy. Twenty-four orbits from 12 patients with Graves' ophthalmopathy, 24 orbits from 12 controls, ten orbits from five study simulations and two orbits front, a digital model, were used. Following manual region of interest definition of the orbital volumes performed by two operators with different levels of expertise, an automated procedure calculated intra-orbital fat tissue volumes (global and regional, with automated definition of four quadrants). In patients with Graves' disease, clinical activity score and degree of exophthalmos were measured and correlated with intra-orbital fat volumes. Operator performance was evaluated and statistical analysis of the measurements was performed. Accurate intra-orbital fat volume measurements were obtained with coefficients of variation, below 5%. The mean operator difference in total fat volume measurements was 0.56%. Patients had significantly higher intra-orbital fat volumes than controls (p<0.001 using Student's t test). Fat volumes and score were significantly correlated (p<0.001). The semi-automated method described here can provide accurate, reproducible antra-orbital fat measurements with low inter-operator variation, and good correlation with clinical data.