OPTICAL CLEARING OF HUMAN SKIN FOR THE ENHANCEMENT OF OPTICAL IMAGING OF PROXIMAL INTERPHALANGEAL JOINTS Ekaterina A. Kolesnikova 1, Aleksandr S.Kolesnikov 1, Urszula Zabarylo 2, Olaf Minet 2, Elina A. Genina 1, Alexey N. Bashkatov 1, Valery V. Tuchin 1,3,4 1 Saratov State University, 2 Medizinische Physik und Optische Diagnostik, Charité – Universitätsmedizin Berlin, 3 Institute of Precision Mechanics and Control RAS, 4 Optoelectronics and Measurement Techniques Laboratory Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013

Motivation The transillumination optical imaging is a prospective technique for the diagnosis of rheumatoid arthritis in humans. But the relatively low contrast and poor spatial resolution of the result images limits the usage of the technique for the finding of differences between healthy and pathology joints. Goal of the study is to enhance the technique by reduction of skin light scattering at using of optical clearing method Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013

Materials and methods Experimental setup Fig. 1. The exterior of the experiment (left image) and the transillumination system with 3 laser diodes (right image). Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 illuminating LEDs (670, 820, and 904 nm) monochromatic digital CCD camera of an 8 bit dynamic range and variable exposure time finger The beam of the laser diodes was focused upon a spot diameter of ≤1 mm on the finger surface Using laser diodes of a fixed power, the exposure time depends on the diameter of the finger and the manifestation of rheumatoid arthritis

Materials and methods Tested specimens The experiments were carried out in vivo with human skin. Female (25 years) participated in the experiments. Proximal interphalangeal (PIP) joints of index finger (1.6 cm) and middle finger (1.8 cm) were investigated The scattered light images obtained by transillumination were taken from the PIP joints of index finger and middle finger to study the possibility of optical clearing application in optical diagnosis of rheumatoid arthritis Optical clearing agents Dehydrated glycerol and hand cream with urea (5%) were used as OCAs. Refractive indices of glycerol are: at 670 nm at 820 nm at 904 nm Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013

Materials and methods Contrast calculation Contrast was calculated in region of interest (ROI) near the middle of the finger joint (fig.2) with special software designed in LabView programming environment Fig. 2. An image of ROI for the contrast calculation (blue rectangle) Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013

Results Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Fig. 3. An image of finger joint under the action of glycerol in a transmission mode: left image – before agent application, right image – 60 min after agent application. Wavelength is 670 nm.

Results Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Fig. 4. An image of finger joint under the action of glycerol in a transmission mode: left image – before agent application, right image – 60 min after agent application. Wavelength is 820 nm.

Results Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Fig. 5. An image of finger joint under the action of glycerol in a transmission mode: left image – before agent application, right image – 60 min after agent application. Wavelength is 904 nm.

Results Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Fig. 6. An image of finger joint under the action of hand cream in a transmission mode: left image – before agent application, right image – 60 min after agent application. Wavelength is 670 nm.

Results Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Fig. 7. An image of finger joint under the action of hand cream in a transmission mode: left image – before agent application, right image – 60 min after agent application. Wavelength is 820 nm.

Results Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Fig. 8. An image of finger joint under the action of hand cream in a transmission mode: left image – before agent application, right image – 60 min after agent application. Wavelength is 904 nm.

Results Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Table 1. Contrast in a ROI near the middle of the joint for the case of glycerol topical application Time, min670 nm820 nm904 nm

Results Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Table 2. Contrast in a ROI near the middle of the joint for the case of hand cream with 5% urea application Time, min670 nm820 nm904 nm

Summary Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 Thus, our results shows that glycerol and hand cream with 5% urea allow obtaining of more distinct image of finger joint. In that way we may conclude that investigated OCAs at topical applications to skin can be effectively used as enhancer for the technique for the finding of differences between healthy and pathology joints in transillumination mode.

Acknowledgements Saratov State University Department of Optics and Biophotonics Saratov Fall Meeting 2013 This research was supported by:  Grant of President of RF NSH  FiDiPro, TEKES Program (40111/11), Finland  RF State contracts № and 14.B

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