Publications de Theo Lasser | EPFL Graph Search

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Fourier Domain OCT proved to be an outstanding tool for measuring 3D retinal structures with high sensitivity, resolution, and speed. We extended the FDOCT concept towards functional imaging by analyzing the spectroscopic tissue properties, polarization contrast and Doppler velocity imaging. Differential spectral contrast FDOCT allows optical staining of retinal tomograms and to contrast tissue of high pigmentation such as the retinal pigment epithelium (RPE). The latter shows strong correlation if compared

Rapid acquisition of volumetric data is a mandatory prerequisite for small animal in vivo imaging. Due to its high sensitivity and capacity to extract the sample depth profile in parallel Fourier Domain Optical Coherence Tomography (FDOCT) complies with this requirement. The absence of labeling further simplifies its use for in vivo application. In order to provide the high spatial resolution necessary to gain biologically relevant insights focusing optics from microscopy are usually employed. The resulting

The theory of compressed sensing (CS) shows that signals can be acquired at sub-Nyquist rates if they are sufficiently sparse or compressible. Since many images bear this property, several acquisition models have been proposed for optical CS. An interestin ...

Fourier domain Optical coherence microscopy (FDOCM) offers excellent sensitivity and high axial resolution to image the structure of biological tissue. The depth information is extracted in parallel and allows very high volume acquisition rates. The present system uses a diffractionless beam, produced with an axicon lens, to achieve high lateral resolution all while maintaining an extended depth of field (xf). The xfOCM signal reveals the spatial distribution of changes of the refractive index in the sample

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 measur ...

Fourier domain optical coherence tomography (FDOCT) is a high speed imaging technique with high axial resolution in the micro-meter-scale range combined with a high sensitivity allowing to probe 3D volumes of weakly back- scattering biological tissues in-vivo. Phase shifting techniques allow the reconstruction of the full complex sample signal which results in an additional suppression of unwanted auto-correlated distortion as well as an extended depth range. Current complex FDOCT realizations introduce the

We demonstrate the use of laser-induced. fluorescence confocal spectroscopy to measure analyte-stimulated enhanced green fluorescent protein (egfp) synthesis by genetically modified Escherichia coli bioreporter cells. Induction is measured in cell lysates ...

A classical technique to monitor dynamical processes at the single-molecule level is fluorescence correlation spectroscopy (FCS). However, FCS requires fluorescent labels that are typically limited by photobleaching and saturation. We present a new method, optical coherence correlation spectroscopy (OCCS), based on noble-metal nanoparticles that overcome those photobleaching and saturation limitations. OCCS is a correlation spectroscopy technique based on dark-field optical coherence microscopy (dfOCM), a F

We present a method for fast calculation of the electromagnetic field near the focus of an objective with a high numerical aperture (NA). Instead of direct integration, the vectorial Debye diffraction integral is evaluated with the fast Fourier transform for calculating the electromagnetic field in the entire focal region. We generalize this concept with the chirp z transform for obtaining a flexible sampling grid and an additional gain in computation speed. Under the conditions for the validity of the Deby

Functional magnetic resonance (fMRI) imaging is the current gold-standard in neuroimaging. fMRI exploits local changes in blood oxygenation to map neuronal activity over the entire brain. However, its spatial resolution is currently limited to a few hundre ...

This paper describes the design and the performance of a new high-speed laser Doppler imaging system for monitoring blood flow over an area of tissue. The new imager delivers high-resolution flow images (256 x 256 pixels) every 2 to 10 seconds, depending o ...

The use of fluorescence light for far-field imaging at the nanometer scale has drawn much attention worldwide. Example techniques include STED microscopy and localization microscopy (PALM, STORM). Typically, nanoscopy approaches have been focused on the manipulation and detection of the intensity of fluorescence light leading to lateral accuracy of a few nanometers. However, three-dimensional nanometer accuracy, in particular axial accuracy of the same order, remains a challenge. The phase of fluorescence l

Quantitative three-dimensional blood flow imaging is a valuable technique to investigate the physiology of the brain. Two-photon microscopy (2PM) allows quantification of the local blood flow velocity with micrometric resolution by performing repeated line ...

To preserve the speed advantage of Fourier Domain detection in Optical Coherence Microscopy (OCM), extended depth of field is needed. With a narrow probing volume that extends over a long axial range, tissue could be measured in vivo and at cellular resolution. To assess and improve the DOF and the lateral resolution, we analyzed the coherent transfer function (CTF) of OCM. Both the illumination and detection optics contribute equally to the overall imaging performance. In the Fourier domain detection, each

We report the design and application of a prism-based detection system for fluorescence (cross) correlation spectroscopy. The system utilizes a single laser wavelength for the simultaneous excitation of several dyes of different emission spectra. Fluoresce ...

A classical technique to monitor dynamical processes at the molecular level is fluorescence correlation spectroscopy (FCS). FCS requires fluorescent labels that are typically limited by photobleaching and saturation. We present a new method that uses noble-metal nanoparticles instead of fluorophores: optical coherence correlation spectroscopy (OCCS). OCCS is a correlation spectroscopy technique based on dark-field optical coherence microscopy, a Fourier domain optical coherence tomography technique. In OCCS

Fluorescence cross-correlation spectroscopy is a powerful method for the study of molecular interactions and dynamics in solution and even in living cells. Usually, in the optical setup, either two laser beams have to be superimposed in their respective co ...

This contribution summarizes first some of our efforts in imaging G-protein-coupled receptor (GPCR) functional inserted into planar tethered lipid bilayer membranes (tBLMs) as a novel platform for biophysical studies. The authors introduced recently a nove ...

Resonant Doppler Fourier Domain Optical Coherence Tomography is a functional imaging modality for quantifying fast tissue flow. The method profits from the effect of interference fringe blurring in spectrometer-based FDOCT in the presence of sample motion. ...

Theo Lasser

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Measurement of retinal physiology using functional Fourier domain OCT concepts

In Vivo extended focus Optical Coherence Microscopy of endocrine islets of Langerhans in mice

Compressed imaging by sparse random convolution

Extended focus optical coherence microscopy and fluorescence lifetime imaging

Dual-color total internal reflection fluorescence cross- correlation spectroscopy

Complex unltrahigh resolution Fourier domain optical coherence tomography

Ultrasensitive reporter protein detection in genetically engineered bacteria

Optical Coherence Correlation Spectroscopy (OCCS)

Fast focus field calculations

Statistical parametric mapping of stimuli evoked changes in total blood flow velocity in the mouse cortex obtained with extended-focus optical coherence microscopy

High-speed laser Doppler perfusion imaging using an integrating CMOS image sensor

Three-dimensional Nano-Localization of Fluroescent Emitters

Quantitative cerebral blood flow imaging with extended-focus optical coherence microscopy

Fast focus field calculations

Coherent transfer functions and extended depth of field

Prism-based multicolor fluorescence correlation spectrometer

Optical Coherence Correlation Spectroscopy (OCCS)

Simultaneous Multicolor Fluorescence Cross-Correlation Spectroscopy to Detect Higher Order Molecular Interactions Using Single Wavelength Laser Excitation

Imaging of G protein-coupled receptors in solid-supported planar lipid membranes

Intensity based quantification of fast retinal blood flow in 3D via high resolution resonant Doppler spectral OCT