COLOR MAPPING OF ONE SPECIFIC VELOCITY OF A FLOW WITH COMPLEX GEOMETRY USING OPTICAL COHERENCE TOMOGRAPHY Potlov A.Yu, Frolov S.V., Proskurin S.G. Biomedical Engineering, TSTU http://bmt.tstu.ru/ http://spros.tamb.ru/ spros@tamb.ru Saratov Fall Meeting 2017

OBJECTIVES The aim of our research is to implement the sign sensitive colour mapping of one specific velocity (OSV) in the flow with complex geometry on the basis of an OCT system with the source of continuous low-coherence IR radiation.   The key features of the presented method are: the raw data are separated into three parts, corresponding to the unmoving biological tissue, the positively and negatively directed biological fluid flows; the further independent signal processing procedure yields the structure image and two images of the chosen velocity, which are then normalised, encoded and joined. 2

The tilted capillary entry is used as the object of study EXPERIMENTAL SETUP The experimental setup is based on the scanning Michelson interferometer using single-mode optical waveguides. The tilted capillary entry is used as the object of study 3 Quantum Electronics (2014), p. 54

RAPID-SCANNING OPTICAL DELAY LINE 4 Useful Model Patent RU 147266U1

ACQUISITION RAW DATA & BACKGROUND PROCESSING The SLD radiation (l = 1300 nm, Dl = 60 nm) passing through the fibre coupler is directed into the reference arm – the optical delay line (ODL) – and the object arm, i.e., to the object of study. On the way back the radiation from both arms of the interferometer is focused on the detectors, incorporated in the balance scheme. The electric signal is read from the balance detectors, passes through the amplifier and the band-pass filter and is digitised in the time domain by means of a 12-bit ADC. 5

OSV COLOR MAPPING ALGORITHM The frequency shift by 1 kHz corresponds to the velocity 2.1 mm/s 6 Journal of Biomedical Optics (2015), p. 051034

DOPPLER SPECTRA OF INTERFERENCE SIGNAL FROM A LAMINARY FLOW by choosing fc and Δfc we could obtain equivelocity images 7

STRUCTURAL & OSV IMAGES OF CHOSEN VELOCITIES IN A LAMINARY FLOW Dimensions of the images are 0.7 mm × 0.7 mm. 8 Quantum Electronics (2014), p. 54 Dimensions of the images are 0.7 mm × 0.7 mm.

STRUCTURAL & OSV IMAGES OF CHOSEN VELOCITIES IN A TURBULENT FLOW Dimensions of the images are 0.7 mm × 0.7 mm. 9 Journal of Biomedical Optics (2015), p. 051034

FURTHER DEVELOPMENT Future work will be concentrated on simulating an interference signal and constructing a STRUCTURAL AND OSV IMAGES OF A REAL BIOLOGICAL OBJECT using optical coherent tomography. Modelled medium structure obtained by transforming an experimental image and (b, c) the result of modelling the structural image of the subcutaneous blood vessel when the speckle-structure was (b) neglected or (c) taken into account. 10 Quantum Electronics (2017), p. 347

CONCLUSIONS The method of sign-sensitive mapping of the given range of velocities in a flow with complex geometry based on the principles of optical coherence tomography is described. Bidirectional rapid scanning optical delay of optical coherence tomography system is applied in the reference arm. The 1 % aqueous intralipid solution and the tilted capillary entry with the contraction coefficient 4 : 1 are used to produce an alternating-sign flow. The mapping is controlled using two parameters, the value of OSV for mapping and the accuracy of its determination. The structural image and two OSV images (for positive and negative direction of motion) are obtained as a result of selecting and processing the relevant parts of the signal spectrum. The final image is a result of summing these three images and can be used as a Doppler equivelocity contour map. 11