One Specific Velocity Color Mapping of Flows with Complex Geometry

1. One Specific Velocity Color Mapping of Flows with Complex Geometry S.G.Proskurin, A.Yu.Potlov, K.E.S.Ghaleb Biomedical Engineering, Tambov State Technical University, Russia

2. abstract Conventional OCT-systems has a bandpass filter centered at carrier frequency, fc Application of analog and digital tunable filters in the signal processing gives new possibilities By changing bands of the filters it is possible to distinguish Doppler shift in the spectrum of the signal

3. what wavelengths? red dotted ellipses show wavelengths with minimum absorption in tissues

4. experimental set-up ODL tunable filter D1 D2 SLD – superluminescent diode, FC1 and FC2 – fiber couplers, L – collimating and focusing optics, ODL – optical delay line, D1 and D2 – balanced detectors, α – the angle between incident light and the direction of the fluid flow velocity. Scanning is performed along X-axis

5. hydrodynamic phantoms tilted capillary entry was used in the experiment capillary entry tilted capillary entry

6. Doppler spectra of interference signal from a flow with parabolic velocity profile ΔV/V ~ 7% by choosing fcand Δfc we could obtain equidvelocity images

7. processingthe signal a new algorithm of color Doppler mapping of one specific velocity (OSV) of shuttle flows is applied it is realized using the separation of the raw data to two parts corresponding to positive and negative shifts of the carrier frequency it does not have 2π-ambiguity disadvantage of color Doppler OCT images

8. panel 1 of processing interference final complexing standard structural image QuantumElectronics (2013) submitted

9. panel 2 of processing interference negative direction OSV image positive direction OSV image QuantumElectronics (2013) submitted

10. processingthe signal as a final result, the complexation of independently reconstructed structural image (green) and 2D color-coded OSV images (red and blue) is performed practical implementation of the algorithm was performed using the stream programming in the LabVIEW package

11. panel 3 of processing interference final structural image both OSV images QuantumElectronics (2013) submitted

12. image of subcutaneous human blood vessel and blood in vivo the described approach is applicable to blood flow monitoring in subcutaneous human blood vessels it gives quantitative information about the chosen value of velocity determined by the Doppler angle and shift of the carrier Proskurin S.G., QuantumElectronics (2012) p.495

13. conclusion the described algorithm does not have disadvantage of 2π-ambiguity, as in a conventional qualitative color systems, where shift of adjacent A-scans is detected determined by the registered shift of the carrier OSV mapping gives quantitative information about the chosen velocity value and direction of the flow averaging over several consecutive A-scans reduces speckles noise, increases contrast and looses information about A-scan phase, but keeps information about Doppler shift itself

14. references Proskurin S.G. Potlov A.Yu.,FrolovS.V., Doppler mapping of sign-variable flow with complex geometry using optical coherence tomography// QuantumElectronics, (2013) submitted Proskurin S.G., Raster scan and averaging for speckle reduction in optical coherence tomography// QuantumElectronics, Vol. 42 (6), p. 495-499, 2012 Proskurin S.G., FrolovS.V., Visualizationofbloodvesselsbymeansofopticalcoherencetomography // BiomedicalEngineering, No.3, p.9-14, 2012 Proskurin S.G., Meglinski I.V., Optical coherence tomography imaging depth enhancement by superficial skin optical clearing // Laser Physics Letters, Vol. 4, No. 11, p. 824-826, 2007

15. One Specific Velocity Color Mapping of Flows with Complex Geometry S.G.Proskurin, A.Yu.Potlov, K.E.S.Ghaleb Biomedical Engineering, Tambov State Technical University, Russia