<s>
Spectroscopic	B-Algorithm
optical	I-Algorithm
coherence	I-Algorithm
tomography	I-Algorithm
(	O
SOCT	O
)	O
is	O
an	O
optical	O
imaging	O
and	O
sensing	O
technique	O
,	O
which	O
provides	O
localized	O
spectroscopic	O
information	O
of	O
a	O
sample	O
based	O
on	O
the	O
principles	O
of	O
optical	B-Application
coherence	I-Application
tomography	I-Application
(	O
OCT	O
)	O
and	O
low	O
coherence	O
interferometry	O
.	O
</s>
<s>
The	O
general	O
principles	O
behind	O
SOCT	O
arise	O
from	O
the	O
large	O
optical	O
bandwidths	O
involved	O
in	O
OCT	O
,	O
where	O
information	O
on	O
the	O
spectral	O
content	O
of	O
backscattered	B-Algorithm
light	O
can	O
be	O
obtained	O
by	O
detection	O
and	O
processing	O
of	O
the	O
interferometric	O
OCT	O
signal	O
.	O
</s>
<s>
SOCT	O
signal	O
can	O
be	O
used	O
to	O
quantify	O
depth-resolved	O
spectra	O
to	O
retrieve	O
the	O
concentration	O
of	O
tissue	O
chromophores	O
(	O
e.g.	O
,	O
hemoglobin	O
and	O
bilirubin	O
)	O
,	O
characterize	O
tissue	O
light	B-Algorithm
scattering	I-Algorithm
,	O
and/or	O
used	O
as	O
a	O
functional	O
contrast	O
enhancement	O
for	O
conventional	O
OCT	O
imaging	O
.	O
</s>
<s>
Both	O
the	O
spatial	O
domain	O
and	O
spectral	O
domain	O
descriptions	O
of	O
the	O
collected	O
OCT	O
signal	O
,	O
can	O
be	O
related	O
by	O
Fourier	B-Algorithm
transformation	I-Algorithm
:	O
</s>
<s>
where	O
is	O
the	O
Fourier	B-Algorithm
transform	I-Algorithm
.	O
</s>
<s>
However	O
,	O
due	O
to	O
the	O
wavelength	O
dependence	O
with	O
depth	O
for	O
both	O
scattering	O
and	O
absorption	O
in	O
tissue	O
,	O
direct	O
Fourier	B-Algorithm
transform	I-Algorithm
cannot	O
be	O
applied	O
to	O
obtain	O
localized	O
spectroscopic	O
information	O
from	O
the	O
OCT	O
signal	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
a	O
time-frequency	B-Algorithm
analysis	I-Algorithm
method	O
must	O
be	O
applied	O
.	O
</s>
<s>
Time-frequency	B-Algorithm
analysis	I-Algorithm
allows	O
for	O
extraction	O
of	O
information	O
of	O
both	O
time	O
and	O
frequency	O
components	O
of	O
a	O
signal	O
.	O
</s>
<s>
In	O
most	O
SOCT	O
applications	O
a	O
continuous	O
short-time	B-Algorithm
Fourier	I-Algorithm
transform	I-Algorithm
(	O
STFT	B-Algorithm
)	O
method	O
is	O
used	O
,	O
</s>
<s>
As	O
a	O
result	O
,	O
there	O
exists	O
an	O
inherent	O
trade-off	O
between	O
spatial	O
and	O
frequency	O
resolution	O
using	O
the	O
STFT	B-Algorithm
method	O
.	O
</s>
<s>
A	O
wavelet	B-Algorithm
transform	I-Algorithm
(	O
WT	O
)	O
approach	O
may	O
also	O
be	O
considered	O
.	O
</s>
<s>
Unlike	O
the	O
STFT	B-Algorithm
,	O
the	O
WT	O
method	O
is	O
not	O
constrained	O
by	O
constraint	O
bandwidth	O
and	O
may	O
adapt	O
the	O
window	O
size	O
to	O
a	O
desired	O
frequency	O
.	O
</s>
<s>
For	O
SOCT	O
purposes	O
the	O
Wigner	B-Algorithm
distribution	I-Algorithm
:	O
</s>
<s>
The	O
Wigner	B-Algorithm
distribution	I-Algorithm
applies	O
a	O
Fourier	B-Algorithm
transform	I-Algorithm
to	O
the	O
autocorrelation	O
of	O
the	O
OCT	O
interferogram	O
.	O
</s>
<s>
For	O
time-frequency	B-Algorithm
analysis	I-Algorithm
,	O
the	O
WD	O
effectively	O
suppresses	O
the	O
interference	O
terms	O
and	O
as	O
a	O
result	O
compromises	O
joint	O
time-frequency	O
resolution	O
with	O
the	O
level	O
of	O
suppression	O
of	O
the	O
interference	O
terms	O
.	O
</s>
<s>
The	O
time-frequency	B-Algorithm
analysis	I-Algorithm
methods	O
described	O
above	O
,	O
result	O
in	O
a	O
wavelength	O
resolved	O
power	O
spectrum	O
as	O
a	O
function	O
of	O
depth	O
.	O
</s>
<s>
The	O
backscattering	B-Algorithm
coefficient	O
,	O
is	O
sample	O
dependent	O
and	O
is	O
discussed	O
in	O
further	O
detail	O
below	O
.	O
</s>
<s>
The	O
backscattering	B-Algorithm
coefficient	O
is	O
both	O
sample	O
and	O
source	O
dependent	O
and	O
defined	O
as	O
:	O
</s>
<s>
The	O
backscattering	B-Algorithm
coefficient	O
may	O
be	O
experimentally	O
determined	O
as	O
long	O
as	O
a	O
full	O
understanding	O
of	O
zeta	O
.	O
</s>
<s>
Commonly	O
zeta	O
is	O
measured	O
by	O
separate	O
calibration	O
with	O
a	O
sample	O
having	O
a	O
known	O
backscattering	B-Algorithm
coefficient	O
defined	O
by	O
Mie	O
theory	O
.	O
</s>
<s>
One	O
method	O
is	O
by	O
least-squares	B-Algorithm
fitting	I-Algorithm
,	O
where	O
the	O
scattering	O
dependence	O
on	O
wavelength	O
with	O
a	O
power	O
law	O
.	O
</s>
<s>
In	O
this	O
approach	O
the	O
absorption	O
spectrum	O
is	O
regarded	O
as	O
the	O
total	O
absorption	O
contribution	O
overall	O
known	O
chromophores	O
,	O
with	O
a	O
least-squares	B-Algorithm
fitting	I-Algorithm
to	O
the	O
measured	O
attenuation	O
values	O
.	O
</s>
