МОНИТОРИНГ СООТНОШЕНИЯ СИГНАЛ

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Transcript МОНИТОРИНГ СООТНОШЕНИЯ СИГНАЛ

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
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
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
hydrodynamic phantoms
tilted capillary entry was used in the experiment
capillary entry
tilted capillary entry
Doppler spectra of interference signal from a flow
with 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
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.,
Quantum Electronics (2012) p.495
conclusion
the described algorithm does not have disadvantage of 2πambiguity, 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 Ascan phase, but keeps information about Doppler shift itself
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
S.G.Proskurin,
A.Yu.Potlov, K.E.S.Ghaleb
Biomedical Engineering,
Tambov State Technical University,
Russia