Transcript МОНИТОРИНГ СООТНОШЕНИЯ СИГНАЛ

Image Compression
in Optical Coherence Tomography
K.E.S.Ghaleb, A.Yu.Potlov,
S.N.Abdulkareem, S.A.Leonova,
S.G.Proskurin
Biomedical Engineering,
Tambov State Technical University,
Russia
Abstract
Conventional OCT-systems provide structural images of
tissue from synthesis of a series of one-dimensional
reflectivity scans (A-scans.)
Application of raster averaging of adjacent A-scans increases
coherence probing depth and reduces size of the image file.
What wavelengths?
805 нм
principles of scanning LCI
(low-coherence interferometery)
white light
CW laser, Δλ ≈ 1 nm
detector
±V
pulsed laser, 30 - 50 fs
SLD Δλ ≈ 30 - 50 nm
light source
modulation is
necessary to
tune the carrier
off 1/f noise
AOM, EO
sample
lateral scan
OCT
scanning mirror gives
depth discrimination and
modulation of the signal,
carrier (Doppler )
frequency: fo=2V/λ
carrier of OCT system
Doppler spectra
2 АОМs
Moscow State University, 1989
Δf=fo (Δ λ/ λo)
broadening of the carrier
Doppler spectra of a flow
Doppler spectra 4 times wider, ΔV/V ~ 7 %
7%
upper part of the Doppler spectra is Gaussian in both cases
2%
raster averaging
blood vessel diameter ~1 мм
В-scan before
В-scan after
blood
Quantum Electronics (2004) p.1157
А-scans
before averaging
after averaging
180 A-scans
900 A-scans
Image of Blood
OCT images of skin and blood
vessel of human finger in vivo
before averaging (a, d) and
after averaging over three (b,
e) and ten
(c, f) adjacent A-scans.
Arrows point at the location,
where the structural image of
blood is seen with contrast
only after averaging.
The image size is 2x2 mm.
Quantum Electronics (2012) p.495
Size of the image in jpg
Size of the image in bmp_zip
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Усреднения
Conclusion
The use of the remote small-angle raster scanning with
subsequent averaging shows that with the number up to 60 of
averaged scans, corresponding to different angles, no
asymptotic saturation of the dependence of the signal-tonoise ratio on the number of averaged scans is observed.
In addition it is possible to detect the photons in the
intermediate regime between the back reflection and multiple
diffusion scattering.
Averaging over 5 – 10 A-scans allows elimination of speckles
and provides maximal contrast of the image and the minimal
size of the file.
References
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
Bonesi M., Proskurin S.G., Meglinski I.V., Imaging of subcutaneous blood
vessels and flow velocity profiles by Optical Coherence Tomography // Laser
Physics, Vol. 20, No. 4, p. 891-899, 2010.