![]() Therefore, efforts have been directed towards increasing temporal acquisition rates by using MHz-rate swept sources, implementing cylindrical lenses for line field illumination, multiplexing cameras to quadruple the acquisition rate, full field implementation and bidirectional scanning. This kind of approach benefits from frequent revisitation of the structures, which minimizes intraframe distortions, in turn improving registration accuracy. This has resulted in a new sub-field of research that develops algorithms and methods dedicated to motion correction and volumetric motion correction. Careful post-processing is then required to accurately register each volume prior to making any quantitative measures of that structure. Most research systems, with a few exceptions, direct their efforts to track a structure over time by imaging an entire volume sequence to ensure that the structures of interest are captured frequently so that their position can be registered onto a reference volume. Acquiring a sequence of B-scans (single retinal cross-section images) from a fixed location over any length of time in a human eye, for example, is extremely challenging due to the lack of spatial references in the dimension perpendicular to the scanning direction which impedes accurate registration of the B-scans. For commercial OCT systems and many clinical applications, this is generally acceptable however, for high resolution and/or research-application OCT systems, these errors remain problematic. ![]() Most modern commercial systems now employ some form of active tracking to mitigate these artifacts, but these trackers are relatively slow and have limited accuracy so that most clinical data, upon close inspection, still contain artifacts caused by motion. However, even during fixation, OCT images are subject to motion artifacts caused by ever-present ocular movements. OCT has been valuable clinically for its functional imaging techniques to evaluate the vasculature via angiography and functional cellular changes in the retina. Technological development of OCT has been directed towards improving its sensitivity, in turn allowing high-speed imaging improving its axial resolution and incorporating adaptive optics (AO) for lateral resolution improvement. Due to OCT’s high volumetric resolution and rapid acquisition speeds, it has become a standard ophthalmic instrument for diagnostics and it is becoming standard-of-care in other disciplines such as dermatology, cardiology and pulmonology. Optical coherence tomography (OCT) is a non-invasive interferometric imaging technique that can record three-dimensional images of biological tissue. ![]() This system enables spatially targeted retinal imaging as well as volume averaging over multiple imaging sessions with minimal correction of motion in post processing. The use of a high-quality reference frame for eye tracking increases revisitation accuracy between successive imaging sessions, allowing to collect several volumes from the same area. The AOOCT system features an independent focus adjustment that allows focusing on different retinal layers while maintaining the AOSLO focus on the photoreceptor mosaic for high fidelity active motion correction. We describe the system design and quantify its performance. Correction of ocular aberrations and of retinal motion is provided by an adaptive optics scanning laser ophthalmoscope (AOSLO) that is optically and electronically combined with the AOOCT system. Here, an adaptive optics optical coherence tomography (AOOCT) system with real-time active eye motion correction is presented. One of the main obstacles in high-resolution 3-D retinal imaging is eye motion, which causes blur and distortion artifacts that require extensive post-processing to be corrected.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |