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

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

3. 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.

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

5. > < 1 mm bundle type fiber element wire 30.. 50 µm from laser 4 mW to diode 1 pW adult Optical Topography principle Operation Principle ETG-4000 The principle of technology

6. 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 ε – Extintion coefitient [C] - Chromophore concentration L - distance

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

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

9. Example: Visual Stimulation Visual Stimulus experiment overview

10. Monitor Display Visual Stimulus experiment overview

12. Oxy-hemoglobin Deoxy-hemoglobin

13. Topo MRI image combined Visual Stimulus experiment overview

14. 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.