Detection of the phase of an optical wave is the basis of holography. It allows loss-less computational image reconstruction and liberates imaging from constraints of optical components. It also provides additional information on the sample giving unique quantitative contrast. Recently, we realized volumetric tomography of the living human retina, based on optical coherence tomography (OCT) and gained access to the full optical phases, despite continuous motion of the retinal tissue. This enabled three major new applications with high scientific and clinical potential. First, we were able to correct the imaging errors (aberrations) of the eye and resolve single photoreceptor cells, solely by computer post-processing. Second, we measured pressure waves caused by blood pulsation, which provide unique information on hemodynamics and mechanical properties of the vascular system. And finally, we reliably measured retinal photoreceptor function for the first time in human cones.Today, scanning Fourier domain optical coherence tomography (FD-OCT) cannot fully utilize the possibilities of holographic tomographic imaging. Sample motion destroys the lateral phase stability. In contrast, holographic imaging by full-field swept-source OCT (FF-SS-OCT) keeps the phase relations and has great potential in retinal imaging. In this research project, we want to demonstrate theoretically and experimentally that holographic tomography provides additional information when imaging the human retina. It involves general investigations about phase stability of scattered light, motion correction, reconstruction of the object structure, limits by the achievable signal-to-noise ratio as well as improvements of FF-SS-OCT imaging itself. In three work packages, we want to answer following scientific questions. 1. How does motion and diffusion degrade phase stability and what is the final limit?2. How can the effect of motion on the phases be compensated? 3. Can numerical filtering increase contrast or visualize otherwise invisible structures? Can new processing techniques based on the full phase information increase image quality? 4. Can we improve axial and lateral resolution of FF-SS-OCT and which additional information does this provide?5. What is the origin of the optical path length changes of the photoreceptor outer segments that we observed after optical stimulation?6. Can functioning of neuronal retinal tissue be visualized by changes of the optical phase? 7. Can we measure biomechanical parameters of retinal tissue? By answering these questions we expect to foster the understanding of the potential and limitations of holographic OCT. Achieved results shall be applied to measure biomechanical parameters of retinal tissue and to identify the origin of intrinsic optical signals (IOSs). This research project will demonstrate future applications for retinal imaging, which make use of the full phase of scattered light.
|Effective start/end date||01.01.17 → …|
Research Areas and Centers
- Academic Focus: Biomedical Engineering
DFG Research Classification Scheme
- 205-32 Biomedical Engineering and Medical Physics
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