Autofluorescence spectroscopy from brain tissue may help to discriminate cancerous from healthy tissue. The
characteristics of our probe are studied on phantoms and confronted to Monte Carlo simulations. Geometrical origins of
fluorescence light are evaluated.
Fluorescence spectroscopy of endogenous emission of brain tumors, in particular glioblastoma multiforme, will be used
for intraoperative localization of brain tumor margins. Our future surgeon's probe aims to discriminate tumor from
normal brain tissues using beta and autofluorescence detection at the same time.
Within this study we have implemented C6 glioma cells into rat brains to analyze the endogenous fluorescence of tumor
and normal rat brain tissue. Systematic differences have been observed when comparing the autofluorescence spectra
obtained from white and grey matters: both the fluorescence intensity and the shape of the spectra differ. These results
were obtained by means of a 2-fiber probe, one used to guide the laser to the tissue, the other for fluorescence light
collection. Excitation light was delivered by a 405 nm picosecond laser and fluorescence detection was realized by a
CCD-camera. In parallel we have developed brain phantoms allowing systematic analysis of fiber - sample geometries.
Based on gelatin gels, they include silica particles with 235 and 329 nm diameters to simulate the diffusion
characteristics of the tissue, ink for the absorption characteristics of the tissue and organic dyes like Rhodamin B to
replace biofluorophores.
The present work aims a new medical probe for surgeons devoted to brain cancers, in particular
glioblastoma multiforme. Within the last years, our group has started the development of a new intra-operative
beta imaging probe. More recently, we took an alternative approach for the same application: a
fluorescence probe. In both cases the purpose is to differentiate normal from tumor brain tissue.
In a first step, we developed set-ups capable to measure autofluorescence. They are based on a
dedicated epi-fluorescence design and on specific fiber optic probes. Relative signal amplitude, spectral
shape and fluorescence lifetime measurements are foreseen to distinguish normal and cancer tissue by
analyzing fluorophores like NADH, lipopigments and porphyrines. The autofluorescence spectra are
recorded in the 460-640 nm range with a low resolution spectrometer. For lifetime measurements a fast
detector (APD) is used together with a TCSPC-carte. Intrinsic wavelength- and time-resolutions are a few
nm and 200 ps, respectively. Different samples have been analyzed to validate our new detection system
and to allow a first configuration of our medical fluorescence probe. First results from the tissue
measurements are shown.
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