Tatiana Savelieva, Nina Kalyagina, Maxim Loschenov
GPI RAS, Russia
Many tissue pathologies, including a majority of cancers, exhibit significant metabolic and architectural changes at the cellular and subcellular level. Spectral measurements of elastically scattered and emission light from tissue are sensitive to tissue structure and biochemistry and may be used to detect and diagnose tissue pathologies.
We developed three simultaneously usable techniques for obtaining and analysis of spectroscopic measurements in one point of tissue surface and parallel-serial analysis of multispectral images. Three types of spectroscopic signal are subjected to analysis and decomposition to determine optical properties of biological tissue – diffuse reflectance of light in wide spectral range containing hemoglobin and oxidized hemoglobin absorption peaks, backscattered laser light and fluorescence of porphyrins. Thus we can estimate the total haemoglobin concentration, level of haemoglobin oxygen saturation, alterations of cell and tissue structure and concentration of porphyrins accumulating as a rule in tumorous cells due to haem metabolic disturbance.
A complex analysis of the fluorescent and scattered light signals was made in order to determine the malignization level of the perifocal areas of brain glial tumours. The in vivo measurements of the diffuse-reflected fluorescent and laser light were compared with mathematical simulations, performed in a Monte Carlo program using the calculated scattering and absorption parameters of the cellular organelles for different grades of the tumours. The method allows to analyze the photosensitizer concentration and to detect the structural changes of the brain tissue. A good compliance of the results of the mathematical modelling with the clinical studies was revealed.
The one-point techniques were successfully used in clinical studies during ALA-mediated spectral navigation in neurosurgery. The developed multispectral techniques were used in ophthalmology for closed-angle glaucoma and subretinal neovascular membrane diagnosis. The clinical data, obtained from the spectroscopic studies, allows to carry out cluster analysis of neural tissue optical properties to differentiate several types of neural tissue.
Ms. Tatiana Alexandrovna Savelieva
GPI RAS, jr. researcher
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