Abstract
PURPOSE Objective determination of the orbital volume is important in the diagnostic process and in evaluating the efficacy of medical and/or surgical treatment of orbital diseases. Tools designed to measure orbital volume with computed tomography (CT) often cannot be used with cone beam CT (CBCT) because of inferior tissue representation, although CBCT has the benefit of greater availability and lower patient radiation exposure. Therefore, a model-based segmentation technique is presented as a new method for measuring orbital volume and compared to alternative techniques. METHODS Both eyes from thirty subjects with no known orbital pathology who had undergone CBCT as a part of routine care were evaluated ([Formula: see text] eyes). Orbital volume was measured with manual, atlas-based, and model-based segmentation methods. Volume measurements, volume determination time, and usability were compared between the three methods. Differences in means were tested for statistical significance using two-tailed Student's t tests. RESULTS Neither atlas-based [Formula: see text] nor model-based [Formula: see text] measurements were significantly different from manual volume measurements [Formula: see text]. However, the time required to determine orbital volume was significantly longer for manual measurements ([Formula: see text] min) than for atlas-based ([Formula: see text] min, [Formula: see text]) or model-based ([Formula: see text] min, [Formula: see text]) measurements. CONCLUSION All three orbital volume measurement methods examined can accurately measure orbital volume, although atlas-based and model-based methods seem to be more user-friendly and less time-consuming. The new model-based technique achieves fully automated segmentation results, whereas all atlas-based segmentations at least required manipulations to the anterior closing. Additionally, model-based segmentation can provide reliable orbital volume measurements when CT image quality is poor.
Wagner, Maximilian E H