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