One Specific Velocity Color Mapping of Flows with Complex Geometry
Biomedical Engineering, Tambov State Technical University,
Russia
S.G.Proskurin, A.Yu.Potlov, K.E.S.Ghaleb
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
what wavelengths?
red dotted ellipses show wavelengths with minimum absorption in tissues
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
experimental set-up
ODL
D1
D2
tunable filter
capillary entry
hydrodynamic phantomstilted capillary entry was used in the experiment
tilted capillary entry
Doppler spectra of interference signal from a flow Doppler spectra of interference signal from a flow with parabolic velocity profilewith parabolic velocity profile
ΔV/V ~ 7%
by choosing fc and Δfc we could
obtain equidvelocity images
processing the 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
panel 1 of processing interference
standard structural image
final complexing
Quantum Electronics (2013) submitted
panel 2 of processing interference
positive direction OSV image
negative direction OSV image
Quantum Electronics (2013) submitted
processing the 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
panel 3 of processing interference
final structural image
both OSV images
Quantum Electronics (2013) submitted
image of subcutaneous human blood vessel and blood in vivo
Proskurin S.G., Quantum Electronics (2012) p.495
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
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
conclusion
references
Proskurin S.G. Potlov A.Yu., Frolov S.V., Doppler mapping of sign-variable flow with complex geometry using optical coherence tomography // Quantum Electronics, (2013) submitted
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
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
One Specific Velocity Color Mapping of Flows with Complex Geometry
Biomedical Engineering, Tambov State Technical University,
Russia
S.G.Proskurin, A.Yu.Potlov, K.E.S.Ghaleb