Abstract
Abstract: :
Purpose:To assess the performance of the Stratus OCTTM system in extracting specific features of given objects, such as shape and volume, a concern that does not appear to have been investigated so far. Methods: The performance of the commercially available Stratus OCTTM system was investigated by scanning different custom–built test objects containing specific enclosed geometric gaps of known size. Measurements were made by filling the gaps with an aqueous suspension containing regular or irregular objects suspended in distilled, deoinized water inside the gaps. The same scanning process was used to test the performance of the Stratus OCTTM system in situations in which the reflected OCT signal was somewhat degraded and boundaries were less well defined. OCT raw data was exported for subsequent analysis using custom software written in MATLAB software platform. An active contour model was used to outline the boundaries of the regular and irregular features on OCT images of the custom–built test objects. The OCT scanning protocol used was radial lines, which usually records 6 radial scans through a common central axis. The scanning area consists of a central disc of 1 mm, and an inner and outer ring, each divided into four quadrants, with outer diameters of 3 and 6 mm, respectively. Images provided by the OCT system were analyzed with the custom software and later compared with the actual geometric parameters of the custom–built test objects. Results: Absolute quantification of volume measurements for irregular objects seems difficult due to the sampling density of the OCT system. Near the center of the scan area the sampling density is quite good with this scanning pattern; however, towards the periphery of the scanned area gross averaging is necessary, causing poor azimutal resolution. Such sampling problem caused poor volume measurements of irregular objects extending beyond the outer ring of the OCT scanning pattern. Conclusions:The custom–built test objects provide an easy and reproducible method of verifying the accuracy and precision of specific features in the images retrieved by the Stratus OCTTM system. Since it is not certainly known whether the directional reflectance of these specific features can cause significant variation of the reflected intensity, an extension of this work will be the creation of new custom–built test objects. Therefore, we can examine the sensitivity of the Stratus OCTTM system to specific features in these objects when the direction of the illumination is changed.
Keywords: image processing • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • optical properties