Biomedical scientists are dreaming of a technique showing the distribution of all the biomolecular constituents that make up biological tissue in high-resolution, three-dimensional maps. Such a visualization tool does not currently exist. Whereas fluorescence and refraction based techniques will never be able to identify an arbitrary molecular compound in tissue, vibrational imaging techniques offer much more promise.
They work label-free and non-invasively and they are able to identify many important groups.
The conventional vibrational imaging technique is Raman microscopy. Practical limitations have so far prevented Raman microscopy from reaching its full potential. The most important limitation is speed. The intrinsically weak Raman signals severely limit the achievable image acquisition rate. The development of coherent Raman scattering (CRS) microscopy techniques over the last decade has resulted in important steps toward resolving the speed issue.
In a feature article, Eric O. Potma and a team of scientists at the University of California (Irvine, USA) discuss several ways in which the improved speed of CRS microscopy has transformed the biomedical imaging field and touch on some of the challenges that lie ahead in moving towards the realization of a more generally applicable visualization technique.
Stronger signals are obtained because in CRS the molecules are driven coherently, which makes them radiate in unison. The resulting signal is coherently amplified through constructive interference in a well-defined, phase-matched direction which enables efficient detection of the Raman response.
For instance, when the microscopic focal volume is filled with lipids, the number of detected photons in coherent anti-Stokes Raman scattering (CARS), generated from the CH2 stretching mode, can easily exceed 102 per microsecond at 10 mW of illumination. With such high signal levels, real-time Raman imaging of biological tissues becomes feasible.
An important application of high speed CRS imaging is the visualization of large tissue segments. For example, neural injuries and myelination disorders in live spinal tissues have been mapped as well as atherosclerotic plaques in aortas. Tissue maps were generated that cover up to several centimeters in lateral and hundreds of microns in axial distance, while preserving the (sub-)micrometer resolution offered by the high numerical aperture objective.
The intrinsic movement of the tissue, due to pulsation of blood vessels, breathing, or positional adjustments by the subject, poses a challenge when imaging living tissues. Imaging at video-rate enables image acquisition in which the individual frames show minimal blurring due to movements. Another advantage of fast imaging is the reduction of possible photodamage in living tissues. Besides live tissue imaging in small animal models, CRS imaging has already been applied to the examination of human skin in vivo.
In addition, the fast imaging modalities enable a time- and space-resolved view of dynamic processes of biological relevance. Water diffusion in neutrophile cells, the dynamics of intracellular droplets, and the diffusion of pharmaceutically relevant agents through skin are examples of dynamic processes that have been visualized.
Single frequency CARS and SRS have already proven indispensable in the study of lipids and lipid metabolism in live tissues and cells. Because of its imaging speed and chemical contrast, CRS has pushed the concept of label-free and noninvasive chemical imaging closer to clinical biomedical applications. The challenge ahead is to marry the speed qualities of single frequency scanning with the superior spectral information of broadband Raman spectroscopy. Recent developments suggest several approaches by which this could occur and provide a glimpse toward the ideal of clinically relevant, real-time chemical inspection of live tissues.(Text contributed by K. Maedefessel-Herrmann)
Regina Hagen | WILEY-VCH Verlag
Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel
Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Life Sciences
26.04.2017 | Physics and Astronomy
26.04.2017 | Earth Sciences