Project description

Project LIDER, NCBiR

The thematic area of the project is Fourier domain Optical Coherence Tomography (FdOCT) imaging of neural tissue functioning. The research focuses on development of methods and devices for activity detection in model neurons and in the retina. The study is a contribution to functional OCT which uses Optical Coherence Tomography techniques for detection of biological tissue functioning.

The project is carried at the Medical Physics Group, Department of Biophysics and Medical Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, in collaboration with the Department of Biophysics, Faculty of Biology and Earth Sciences, Nicolaus Copernicus University, Poland.

The funds for project realization were obtained from the National Centre for Research and Developmnet, LIDER Programme.

The project consists of two research aims:
1) development of low coherence interferometry methods for detection of activity in model neurons,
2) development of FdOCT reflectometry techniques and instrumentation for detection of neural activity in the retina.

Aim 1. Development of low coherence interferometry methods for detection of activity in model neurons

The main hypothesis of the research is that changes in optical and mechanical properties of neurons induced by their activation can be detected by Fourier domain OCT technology. These changes include scattering properties, birefringence, absorption and volume changes (shortening, shrinkage, swelling). Although OCT has been successfully used for detection of functioning of different neural tissues little has been done for understanding possibilities and limitations of OCT methods for detection of neural activity. The purpose of this study is to investigate how neuronal activity influences different parameters of the OCT signal and to identify possible detection techniques and methods for further development of functional OCT. Changes in the OCT signal may be related to intensity variations and polarization changes of the scanning beam of light, to the phase shifts of the interference signal, or to the spectral changes of light propagating inside the object. This suggests four OCT detection techniques which perhaps could be applied for imaging of activity of neurons: OCT reflectometry, polarization sensitive OCT, phase sensitive OCT and spectroscopic OCT.
This project focuses on development of reflectometry and phase sensitive methods. Neurons partially or completely isolated from the nervous system of American cockroach will serve as a model.

Aim 2. Development of FdOCT reflectometry techniques and instrumentation for detection of neural activity in the retina

The main assumption of this research subject is that the neural activity may change optical properties of retinal tissue which can be detected by high speed, high resolution OCT with Fourier domain detection. Visual processes (conversion of light into electrical signals during phototransduction) and propagation of electrical pulses in neural cells can cause changes in reflectivity of different retinal layers. These functional changes can be estimated by a very sensitive analysis of the intensity variations of the OCT signal.
This project focuses on development of methods for reflectivity changes detection in the photoreceptor layer. The function of the photoreceptor layer can be impaired by degenerative retinal diseases like age related macular degeneration (AMD). Study on reflectivity changes in the nerve fiber layer and in the optic nerve head will be also undertaken. Pathology development in these structures can be a result of eye diseases (e.g. glaucoma) or central nervous system diseases (e.g. multiple sclerosis).
There are several motivations to undertake studies on functional OCT in the retina. Eye diseases are a growing problem in industrialized countries with increased life expectancy. Diseases like age related macular degeneration (AMD) or glaucoma are leading causes of legal blindness. However, their pathogenesis and causes of progression remain unknown in most cases. More interestingly, retinal health is dependent on condition of other vital systems of the human organism, e.g. the central nervous system of which the retina is a part, or cardiovascular system. Retinal disease may be a symptom of development of pathology in these systems. Two important examples are diabetes mellitus causing diabetic retinopathy and multiple sclerosis causing optic neuritis.
Development of sight threatening diseases whether connected to the eye only or being a result of other pathology, influences retinal morphology and physiology. The methods of detection of changes in both of them would constitute a powerful tool for elucidating disease pathogenesis and for early diagnosis and monitoring disease progression as well as effectiveness of medical procedures.

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