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Biomedical subjects

Rainer A Leitgeb

Publications and source records attributed to Rainer A Leitgeb.

4 recordsLinked to original sources

Three-dimensional ultrahigh-resolution optical coherence tomography of macular diseases.

PURPOSE: To demonstrate a new generation of three-dimensional (3-D) ultrahigh-resolution optical coherence tomography (UHR OCT) technology for visualization of macular diseases. METHODS: One hundred forty eyes with a distinct disease in each of the posterior pole compartments were examined with 3-D UHR OCT. 3-D imaging was performed with a high axial resolution of 3 mum with a compact, commercially available, ultra-broad-bandwidth (160 nm) titanium:sapphire laser at a video rate of up to 25 B-scans/s. Each tomogram consisted of 1024 x 1024 pixels, resulting in 25 megavoxels/s. RESULTS: 3-D UHR OCT offers high-precision 3-D visualization of macular diseases at all structural levels. The UHR modality allows identification of the contour of the hyaloid membrane, tractive forces of epiretinal membranes, and changes within the inner limiting membrane. The system provides quality 3-D images of the topographic dynamics of traction lines from the retinal surface down to the level of the photoreceptor segments. Intraretinal diseases are identified by their specific location in different layers of the neurosensory ultrastructure. Photoreceptor inner and outer segments are clearly delineated in configuration and size, with a characteristic peak in the subfoveal area. The microarchitecture of choroidal neovascularization is distinctly imaged, related leakage can be identified, and the volume can be quantified. CONCLUSIONS: High-speed UHR OCT offers unprecedented, realistic, 3-D imaging of ocular diseases at all epi-, intra- and subretinal levels. A complete 3-D data set of the macular layers allows a comprehensive analysis of focal and diffuse diseases, as well as identification of dynamic pathomechanisms.

Diagnostic Techniques, Ophthalmological↗

Real-time measurement of in vitro flow by Fourier-domain color Doppler optical coherence tomography.

The possibility of measuring a full Doppler flow depth profile in parallel by use of frequency-domain optical coherence tomography is demonstrated. The method is based on a local phase analysis of the backscattered signal and allows for imaging of bidirectional Doppler flow. The Doppler frequency limit is 5 kHz for the presented measurements and is set by half of the frame rate of the CCD detector array. We measured the flow of 0.3-microm microspheres suspended in distilled water at controlled flow rates and in vitro human blood flow through a 200-microm capillary with a real-time color-encoded Doppler tomogram rate of 2-3/s.

Blood Cells↗

Phase-shifting algorithm to achieve high-speed long-depth-range probing by frequency-domain optical coherence tomography.

Standard Fourier-domain optical coherence tomography (FDOCT) suffers from the presence of autocorrelation terms that obscure the object information and degrade the sensitivity and signal-to-noise ratio. By exploiting the phase information of the recorded interferograms, it is possible to remove those autocorrelation terms and to double the measurement range. However, standard phase-retrieval algorithms need three to five interferograms. We present a novel technique that shows all the features of complex FDOCT with only two recorded interferograms.

Algorithms↗

Dual-color total internal reflection fluorescence cross-correlation spectroscopy.

We present the development and first application of a novel dual-color total internal reflection (TIR) fluorescence system for single-molecule coincidence analysis and fluorescence cross-correlation spectroscopy (FCCS). As a performance analysis, we measured a synthetic DNA-binding assay, demonstrating this dual-color TIR-FCCS approach to be a suitable method for measuring coincidence assays such as biochemical binding, fusion, or signal transduction at solid/liquid interfaces. Due to the very high numerical aperture of the epi-illumination configuration, our setup provides a very high fluorescence collection efficiency resulting in a two- to three-fold increase in molecular brightness compared to conventional confocal FCCS. Further improvements have been achieved through global analysis of the spectroscopic data.

DNA↗