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Alexander Vavilov Optical topography principles and example of an application. Bachelor Thesis Work

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Contents: Hitachi ETG-4000 Device Description Fields of use The Principle of Technology Visual Stimulus experiment overview Conclusion

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Hitachi ETG-4000 Device Description The ETG-4000 is a device that measures relative changes in tissue concentration of oxy-hemoglobin and deoxy-hemoglobin and total hemoglobin (it is proportional to the level of blood) in the cerebral cortex by beaming near-infrared light, that can penetrate the body efficiently, and is absorbed by the hemoglobin in the blood. The ETG-4000 displays the changes of overall Hemoglobin concentration in time- course graphs, 2D topography images and 3D topography images based on the data from multiple point measurements.

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Infant Hospital, Trieste, Italy Biomedical Research Center, La Corua, Spain Brain Computer Interface research, Graz, AustriaDepartment of Experimental Psychology University of Tartu, Estonia Field of use

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> < 1 mm bundle type fiber element wire 30.. 50 m from laser 4 mW to diode 1 pW adult Optical Topography principle Operation Principle ETG-4000 The principle of technology

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The light is transmitted at one end of the tissue and collected at the back end. Light propagated through tissue (Io) and transmitted at the output (I) traversing a distance L allows for chromophore concentration [C] calculations using Beer Lamberts Law. The principle of technology A -Absorption spectrum Io - Light propagated through tissue I Light transmitted at the output Extintion coefitient [C] - Chromophore concentration L - distance

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In case of head model we need to measure the light on the same side of tissue. The principle of technology OD - the change in the optical density Extintion coefitient [C] - Chromophore concentration L - distance

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Absorption Spectra of Hemoglobin Wavelength (nm) Molar absorption coefficient (mM -1 mm -1 ) Oxy Hb Deoxy Hb 830695 The principle of technology

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Example: Visual Stimulation Visual Stimulus experiment overview

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Monitor Display Visual Stimulus experiment overview

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Oxy-hemoglobin Deoxy-hemoglobin

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Topo MRI image combined Visual Stimulus experiment overview

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Hitachi ETG-4000 optical topography system, which is used in medicine as well as in chemistry, is a good example of successful cooperation in the fields of electronics, physics and chemistry. Conclusion It has made it possible to get such a glimpse of the working brain, which has not been possible to get ever before.