Universiteit Leiden

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Lecture

MCBIM Colloquium

  • Dr. Freek Ariese (Biophotonics & Medical Imaging, VU University Amsterdam)
  • Dr. Miriam J.B. Moester (Biophotonics & Medical Imaging, VU University Amsterdam)
Date
Thursday 14 January 2016
Time
Location
Gorlaeus Building
Einsteinweg 55
2333 CC Leiden
Room
Havinga Lecture Hall

Dr. Freek Ariese - Depth analysis of non-transparent samples using Time-Resolved Raman Spectroscopy

Raman spectroscopy offers a high degree of molecular specificity for non-invasive sample characterization, including tissue diagnosis, forensics, and in the near future even planetary exploration. Some background knowledge of the method and examples of conventional Raman and resonance Raman applications will be given.
However, in the case of non-transparent samples, classical focusing into deeper layers is not possible due to the scattering nature of the material. In such cases, Raman spectra of the subsurface can still be obtained using Time Resolved Raman Spectroscopy (TRRS). The approach is based on picosecond laser excitation and a fast gated intensified CCD camera. By optimizing the detector delay in a backscatter geometry one can achieve selectivity for deeper layers over the normally much stronger signals from the surface. In addition, the time-gated detector helps to suppress background fluorescence. Several recent applications of TRRS will be discussed.

Dr. Miriam J.B. Moester - Biomedical imaging with Stimulated Raman Scattering microscopy

We demonstrate our shot noise limited set-up for Stimulated Raman Scattering (SRS) microscopy. In SRS, two different colored laser beams are incident on a sample. If the energy difference between them matches a molecular vibration of a molecule, energy is transferred from one beam to the other. By applying amplitude modulation to one of the beams, the modulation transfer to the other beam can be measured. The efficiency of this process is a direct measure for the number of molecules of interest in the focal volume. Combined with laser scanning microscopy, this technique allows for fast and sensitive imaging with sub-micrometer resolution. Recent technological advances have shown an improvement of the sensitivity of SRS applications, but few show shot noise limited detection.

We present a basic SRS set-up with mainly commercial components and a custom built trans impedance amplifier that reaches shot noise limited detection from 0.45 mW to 60 mW of total power on the sample, which corresponds to biologically acceptable intensities. In this talk, we will show some of the results on biomedical imaging projects with this SRS set-up, including research on adipocyte development in zebrafish.

Biophotonics & Medical Imaging group

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