Fluorescence spectroscopy

Fluorescence spectroscopy can be used as a diagnostic tool for malignant diseases. The spectroscopy involves detection of tissue autofluorescence as well as characteristic fluorescence emitted from specially designed probes attached to a target. There are several advantages with fluorescence spectroscopy, e.g. it is a non-invasive tool and can be performed in real-time. The ultimate goal is to use the fluorescence measurements as a guiding tool for biopsies. There are mainly four projects concerning fluorescence spectroscopy within the medical group:
  • Development of tools for Fluorescence Mediated Molecular Imaging
  • Development of fluorescence imaging instrumentation within the EC project WWW.BRIGHT.EU
  • Evaluation of fluorescence spectroscopy/imaging for laryngeal lesions
  • Identification of brain tumour boundaries using fluorescence spectroscopy/imaging

Molecular Imaging

Molecular Imaging is a multidisciplinary field that visualizes and quantifies biological processes at cellular and sub cellular levels in living animals. There are different goals with molecular imaging, one to mention could be monitoring of specific molecules and cellular processes in vivo to learn more about the activities in the cells.
Our group is one of the partners in the E.C. Integrated Project "Molecular Imaging" LSHG-CT-2003-503259. Our work within the integrated project is to determine the depth of an embedded object. This object could e.g. be a deep-lying tumor marked with a fluorescent probe. We utilize the concept of forming a ratio of the detected intensities in two fluorescent wavelengths. The ratio becomes depth-dependent if there is a difference in absorption in tissue at these two wavelengths. A difference in absorption will filter the light differently.

The set-up used in the experiments

Fluorescence emitted from meat
and the fluorophore Rhodamine 6G

Reference list
  1. J. Swartling, J. Svensson, D. Bengtsson, K. Terike, and S. Andersson-Engels, "Fluorescence spectra provide information on the depth of fluorescent lesions in tissue," Appl. Opt. 44(10), 1934-1941 (2005)
  2. J. Svensson and S. Andersson-Engels, "Modeling of spectral changes for depth localization of fluorescent inclusion," Opt. Express 13(11), 4263-4274 (2005)

BRIGHT.EU
WWW.BRIGHT.EU is a recently started E.C. project, with the focus on development of new compact high-brightness light sources. We work here mainly in collaboration with the Danish research institute RISØ, where we develop a blue light diode-laser-based source that is going to be used for tissue diagnostics. Our goal within this project is to have a complete system including the developed light source and a detection unit to be able to perform clinical fluorescence measurements.


Larynx measurements
Within this project, fluorescence measurements are performed on the vocal folds in order to detect malignant lesions. The patients are given a tumour marking substance (5-aminolevulinic acid) prior to the examination. Both point monitoring and imaging are performed during the examination. The aim would be to have an additional tool to help judging site of biopsy in suspected lesions. It is also of great importance to be able to establish the exact boundary of a malignant lesion as a guiding tool during tumour resection. It is important to remove the entire lesion during the resection, but as the vocal fold is such a delicate organ, it is essential to avoid that any excess tissue is removed. Fluorescence spectroscopy/imaging is a promising tool to delineate a tumour during surgery.

 Reference list
  1. C. Eker, R. Rydell, K. Svanberg, and S. Andersson-Engels, "Multivariate analysis of laryngeal fluorescence spectra recorded in vivo," Lasers Surg. Med. 28(3), 259-266 (2001)

Brain measurements
Tools to delineate brain tumour boundaries during surgery can be important during neurosurgery.  We are developing fluorescence-based techniques for brain tumour boundary identification in close collaboration with Linköping University Hospital.