Growing interest in optical instruments for biomedical applications has increased the use of optically calibrated phantoms. Often associated with tissue modeling, phantoms allow the characterization of optical devices for clinical purposes. Fluorescent gel phantoms have been developed, mimicking optical properties of healthy and tumorous brain tissues. Specific geometries of dedicated molds offer multiple-layer phantoms with variable thicknesses and monolayer phantoms with cylindrical inclusions at various depths and diameters. Organic chromophores are added to allow fluorescence spectroscopy. These phantoms are designed to be used with 405 nm as the excitation wavelength. This wavelength is then adapted to excite large endogenous molecules. The benefits of these phantoms in understanding fluorescence tissue analysis are then demonstrated. In particular, detectability aspects as a function of geometrical and optical parameters are presented and discussed.
During glioblastoma surgery, delineation of the brain tumour margins remains difficult especially since
infiltrated and normal tissues have the same visual appearance. This problematic constitutes our research
interest. We developed a fibre-optical fluorescence probe for spectroscopic and time domain measurements.
First measurements of endogenous tissue fluorescence were performed on fresh and fixed rat tumour brain
slices. Spectral characteristics, fluorescence redox ratios and fluorescence lifetime measurements were analysed.
Fluorescence information collected from both, lifetime and spectroscopic experiments, appeared promising for
tumour tissue discrimination. Two photon measurements were performed on the same fixed tissue. Different
wavelengths are used to acquire two-photon excitation-fluorescence of tumorous and healthy sites.
The complete resection of the brain tumour is crucial to the patient life quality and prognosis. An autofluorescence probe
aiming at helping the surgeon to improve the completeness of the removal is being developed. Autofluorescence
spectroscopy is a promising approach to define whether the tissue is cancerous or not. First ex vivo measurements have
been realised on an animal model. After tumorous cell injection in rat brain, autofluorescence intensity is revealed from
the extracted brain. These autofluorescence data are compared to results from a histological analysis of same brains. First
indicators are identified that may have the ability to differentiate tumorous and healthy tissues.
Glioblastoma are brain tumors currently incurable, however, optimized treatment gives better prognosis and quality of
life. In case of surgical treatment, there is still need to help surgeons to determine whether a tissue is tumorous or not.
Within the framework of the design of a new autofluorescence probe for this issue, optically calibrated gel phantoms
have been developed using "tumorous" inclusions in a "healthy" environment. Depending on "tumor" shape, size and
localization, the sensitivity of the probe is evaluated. The probe sensitivity for fluorescence spectroscopy will be
presented. The probe configuration is also taken into account and compared to simulated results.
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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