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Image Compression in Optical Coherence Tomography K.E.S.Ghaleb, A.Yu.Potlov, S.N.Abdulkareem, S.A.Leonova, S.G.Proskurin Biomedical Engineering, Tambov State Technical University, Russia Abstract Conventional OCT-systems provide structural images of tissue from synthesis of a series of one-dimensional reflectivity scans (A-scans.) Application of raster averaging of adjacent A-scans increases coherence probing depth and reduces size of the image file. What wavelengths? 805 нм principles of scanning LCI (low-coherence interferometery) white light CW laser, Δλ ≈ 1 nm detector ±V pulsed laser, 30 - 50 fs SLD Δλ ≈ 30 - 50 nm light source modulation is necessary to tune the carrier off 1/f noise AOM, EO sample lateral scan OCT scanning mirror gives depth discrimination and modulation of the signal, carrier (Doppler ) frequency: fo=2V/λ carrier of OCT system Doppler spectra 2 АОМs Moscow State University, 1989 Δf=fo (Δ λ/ λo) broadening of the carrier Doppler spectra of a flow Doppler spectra 4 times wider, ΔV/V ~ 7 % 7% upper part of the Doppler spectra is Gaussian in both cases 2% raster averaging blood vessel diameter ~1 мм В-scan before В-scan after blood Quantum Electronics (2004) p.1157 А-scans before averaging after averaging 180 A-scans 900 A-scans Image of Blood OCT images of skin and blood vessel of human finger in vivo before averaging (a, d) and after averaging over three (b, e) and ten (c, f) adjacent A-scans. Arrows point at the location, where the structural image of blood is seen with contrast only after averaging. The image size is 2x2 mm. Quantum Electronics (2012) p.495 Size of the image in jpg Size of the image in bmp_zip 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 20 25 30 35 40 45 50 55 60 65 70 80 90 91 95 100 150 160 170 180 Размер (кб) Size of the image in jpg_zip jpg_zip 180 160 140 120 100 80 60 jpg_zip 40 20 0 Усреднения Conclusion The use of the remote small-angle raster scanning with subsequent averaging shows that with the number up to 60 of averaged scans, corresponding to different angles, no asymptotic saturation of the dependence of the signal-tonoise ratio on the number of averaged scans is observed. In addition it is possible to detect the photons in the intermediate regime between the back reflection and multiple diffusion scattering. Averaging over 5 – 10 A-scans allows elimination of speckles and provides maximal contrast of the image and the minimal size of the file. References Proskurin S.G., Raster scan and averaging for speckle reduction in optical coherence tomography // Quantum Electronics, Vol. 42 (6), p. 495-499, 2012. Proskurin S.G., Frolov S.V., Visualization of blood vessels by means of optical coherence tomography // Biomedical Engineering, No.3, p.9-14, 2012 Bonesi M., Proskurin S.G., Meglinski I.V., Imaging of subcutaneous blood vessels and flow velocity profiles by Optical Coherence Tomography // Laser Physics, Vol. 20, No. 4, p. 891-899, 2010.