Research Vision

Our current research activities revolve around multimodal imaging enabling detection of relevant biomarkers for disease, by combining Optical Coherence Tomography (OCT), Two-Photon Excitation Fluorescence Microscopy (TPEFM), Three-Photon Excitation Fluorescence Microscopy, and lightsheet microscopy.

OCT for morphology and optical properties

Optical coherence tomography (OCT) provides 2D or 3D scans of biological tissue in situ. OCT is already established as the gold standard in ophthalmic imaging. Other applications are emerging taking full advantage of high-speed frequency-domain OCT (FD-OCT), e.g., intravascular OCT, dermatologic OCT and OCT for endoscopy.

Our current research aims at combining OCT with TPEFM, see below. An important aspect of our current activities concerns light-tissue interactions and extraction of optical properties from OCT images. This can be seen as a novel, functional imaging modality that can dramatically improve diagnosis of disease. Recent results indicate that we can diagnose melanoma with 96% specificity and 97% sensitivity (compared to 72%/73% with current standard methods).

Two-photon excitation fluorescence microscopy for metabolic information

Two-photon excitation fluorescence image of fixed BPAE cells

Two-photon excitation fluorescence microscopy (TPEFM) provides molecular and biochemical information arising from endogenous or exogenous fluorophores. Assessment of metabolites, such as NADPH, allows direct insight into the metabolic state of cells. Because the wavelength of the ultrashort pulse required for excitation is in the NIR region, where tissue scatters significantly less, the penetration depth is improved compared to light in the visible spectrum. Moreover, TPEFM can probe second-harmonic generation (SHG) that provides additional structural information.

Three-photon fluorescence microscopy using near-infrared light (1200 – 1500 nm) for excitation offers great promise to improve both the imaging depth and the signal to noise ratio in respect to single- and two-photon excited fluorescence microscopy and has been shown to be able to image in vivo brain tissue down to a depth of 1.2 mm. The added benefit of this excitation scheme is the simultaneous presence of second harmonic (SH), third harmonic (TH), two-photon fluorescence, and three-photon fluorescence signals from different fluorophores and structures.

Our current research aims at combining TPEFM with OCT/OCM on a microscope platform to investigate biomarkers relevant for bladder cancer. In vivo examination of bladder cancer requires developing novel light delivery probes, which would fit within existing endoscopes. Current efforts entail MEMS-based scanning probes and specialised delivery fibres for in-fibre dispersion compensation.

Our future research activities aim at deploying novel short pulsed fibre lasers for 2PM/3PM imaging applied to small animals studying brain function in vivo.

Single plane illumination microscopy for speed

Two-photon Airy lightsheet microscopy image of fixed rat brain slice, axons labelled with Alexa flzor 568 NCAM-immunolabelling

(Image reproduced from "Integrated single- and two-photon light sheet microscopy using accelerating beams" by Piksarv et al., Sci. Rep. 2017)

Single plane illumination microscopy (SPIM), also known as lightsheet microscopy, overcomes the speed limitation in conventional TPEFM point-scanning techniques. In addition, since only the plane of interest is illuminated at each time point, risk of photo-toxicity is significantly reduced.

In our current research, we aim at implementing TPEF Single Plane Illumination Microscopy (TPEF-SPIM) into endoscopes, both using miniaturised phase masks and all-fibre solutions.

Contact

Peter Eskil Andersen
Groupleader, Senior Researcher
DTU Health Tech
+45 22 45 45 57

Contact

Lars René Lindvold
Senior Scientist
DTU Health Tech
+45 46 77 49 69