Intravascular photoacoustic (IVPA) imaging that aims to detect atherosclerotic plaques with differential
composition is studied computationally and experimentally. IVPA images are usually reconstructed by simply aligning
photoacoustic signals with scan conversion, which results in images with severe blurring and increases the difficulty in
signal detection. The scanning aperture in IVPA, in contrast to other photoacoustic tomography applications, is enclosed
within the imaged object. Consequently, quantitative image reconstruction becomes infeasible, as the data sufficiency
condition for stable image reconstruction is not satisfied in such a limited-view scanning. However, useful information
regarding certain plaque boundaries can still be reconstructed, which can facilitate plaque detection. In this study,
strategies for limited-view reconstruction will be investigated for the IVPA scanning geometry. Computer simulations are
carried out to validate the developed method.
The combination of intravascular ultrasound and intravascular photoacoustic imaging has been proposed. In
this study, we propose a scan head design that is sufficiently small to fit in the tip of the catheter. In
addition, the design is also suitable for ultra high frame rate imaging. The scan head consists of a single
element, ring-shaped transducer for sideward ultrasound transmission. The transducer has a diameter of
3mm. On acoustic detection, we propose the use of a polymer microring array. For demonstration purposes,
a single micro-ring is used with mechanical scanning in this study. For optical illumination, a multimode
fiber with a cone-shaped mirror is used. Note that only a single ultrasound/laser pulse is required to acquire
an ultrasound/photoacoustic image frame. Phantom imaging results are demonstrated.
Alpha-fetoprotein (AFP) detection by using a localized surface plasmon coupled fluorescence (LSPCF) fiber-optic biosensor is setup and experimentally demonstrated. It is based on gold nanoparticle (GNP) and coupled with localized surface plasmon wave on the surface of GNP. In this experiment, the fluorophores are labeled on anti-AFP which are bound to protein A conjugated GNP. Thus, LSPCF is excited with high efficiency in the near field of localized surface plasmon wave. Therefore, not only the sensitivity of LSPCF biosensor is enhanced but also the specific selectivity of AFP is improved. Experimentally, the ability of real time measurement in the range of AFP concentration from 0.1ng/ml to 100ng/ml was detected. To compare with conventional methods such as enzyme-linked immunosorbent assay (ELISA) or radioimmunoassay (RIA), the LSPCF fiber-optic biosensor performs higher or comparable detection sensitivity, respectively.
Previous work with amplitude-sensitive paired surface plasma waves biosensor (PSPWB) demonstrated that the
detection sensitivity of PSPWB is able to experimentally detect 0.001% sucrose-water solution and biomolecular
interaction of 10pg/ml mouse IgG interacting with immobilized anti-mouse IgG successfully.
Further development of the detection sensitivity of PSPWB has been conducted by using 20nm in diameter colloid gold
nanoparticles conjugated with target molecules that can result in a higher mass coverage and a larger resonant angle
change of plasmon resonance, thereby its detection sensitivity is further enhanced significantly. Bare gold nanoparticles,
which is randomly suspended in solution, is adopted to differentiate biospecific binding induced further signal
enhancement. Experimentally, the sensitivity at 330fg/ml of Au-nanoparticle conjugated protein A (PA-Au) interacting
with mouse IgG which is immobilized on a CM5 sensor chip was detected successfully. By this arrangement, 6-fold
signal amplification is demonstrated compared with the same concentration of PA without conjugated gold nanoparticles.
We proposed and developed a novel fiber-optic biosensor based on localized surface plasmon coupled emission (LSPCE)
which consists of sandwich format of immuno-complex. It is immobilized on the
surface of optical fiber where is a fluorescence probe produced by mixing Cy5 labeled antibody
and protein A conjugated gold nanoparticles (Au-PA). The fluorophores are excited by localized surface plasmon (LSP)
on gold nanoparticle (GNP) surface where the evanescent field is applied near the core surface of unclad optical fiber.
Meanwhile, the fluorescence signal is detected by a photomultiplier tube being set beside the unclad optical fiber with
high collection efficiency. In the experiment, this novel LSPCE biosensor demonstrates the minimum detectable
concentration of mouse immunoglobulin G (IgG) at 1pg/ml (7fM) in the biomolecular interaction with anti-mouse IgG.
From the experimental result, it verifies that LSPCE biosensor is a very high sensitive biosensor which is capable of
measuring biomolecular interaction at very low concentration.
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