Biomedical Engineering Reference
In-Depth Information
60
SDPM
50
WFDI
40
30
20
10
0
0
0.001
0.0025
Glutaraldehyde (%)
0.005
0.025
2.5
Figure 13.9
Membrane displacement values of 10 RBCs from single-point phase OCM (SDPM) and wide-field
phase interferometry (WFDI) for different glutaraldehyde conditions. Each shape represents
a single cell membrane displacement standard deviation (STD) over a 30-s time period.
The horizontal line is the average value of the displacement in each concentrations.
Source: Taken with permission from Ref.
[22]
Copyright of SPIE.
also to monitor disease progression. Gold nanoshells consist of an inner silica core
surrounded by a thin gold shell. They can be engineered with different dimensions of the
core and shell. The optical resonance frequency of the particles can vary from ultraviolet to
near infrared wavelengths according to their dimensions. This allows customized tailoring
of the optical scattering and absorption properties of the particles to suit the needs of the
specific application. Gold nanoshells are highly biocompatible, water-soluble, and
commercially available.
The detection of a gold nanoparticle contrast agent is demonstrated using a photothermal
modulation technique and phase-sensitive OCM
[23]
.
An active contrast agent detection technique was demonstrated for high-speed OCM
imaging based on photothermal modulation. The technique uses gold nanoshells designed to
have high absorption at 808 nm whereas tissue absorption at this wavelength is inherently
low. A multimode laser diode operating at 808 nm is used to heat up the gold particles,
causing small-scale, localized temperature gradients, in places where the gold particles are
present. These temperature variations cause a local change in the OPD of sample. These
changes were detected using an SS-/FD-OCM phase microscopy system built using a
double-buffered FD mode-locked laser operating at 1315 nm and a sweep rate of 240,000
sweeps/s (240 kHz). By modulating the 808 nm laser diode at a known frequency and
observing variations in the OPD that occur only at the frequency, the contrast agent
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