Biomedical Engineering Reference
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showed that the Au 3 Cu 1 nanocapsules brightly lit the cardiac region
and the blood vessels of the liver and that the signal level increased
for 2 h after the injection. Au 3 Cu 1 nanocapsules enhanced the heart
chamber images immediately and increasingly enhanced the images
of the cardiac region for 2 h. In the liver region, the images of the
vessels were signiicantly enhanced as well, and the vessel branches
appeared clearly 2 h post-injection. The coronal views also showed
that Au 3 Cu 1 nanocapsules provided positive contrast images. Once
again, color maps of the T 2 -weighted images displayed the imaging
difference: the signal intensity and vessel visualization increased for
2 h in the thorax region (white arrow) and liver area (red arrow).
The in vivo experiments Au 3 Cu 1 nanocontrast agents enhanced the
contrast of blood vessels and suggested their potential use in MR
angiography as blood pool agents.
2.3.3 OpticalImaging
Optical contrast modalities involve absorption, luorescence,
scattering, and vibration (Raman and IR) spectroscopy. In contrast
to MRI and CT modalities, optical imaging for biological tracking is
versatile with color display, easy approach, and low manufacturing
cost of the imaging equipment. Optical instruments include light
sources (lasers and lamps), optical equipments (ibers and mirrors),
microscopes, and detectors, which are relatively inexpensive in
comparison to MRI and X-ray machines. Metallic nanoparticle contrast
agents for optical imaging possess greater absorption cross-section
or scattering effects and may produce enhance luminescence. 5,55,56
Noble metallic nanomaterials can generate high optical signals from
multi-photon luminescence 57,58 and SERS. 59 This ampliication is
due to resonance coupling with LSPR, particularly with anisotropic
gold and silver nanostructures.
Noble metallic nanoparticles have been greatly used as light
scattering agents for bio-labeling. 5,55,60-62 As the nanoparticle size
increases up to 80 nm, the light scattering ratio is promoted. To
collect the peak scattering intensities of nanoparticles, the dark-ield
microscopy was employed 60,61 in Ag nanomaterials 63 , Au nanocages 62 ,
and Au nanorods. 5,55 Using the antibody-modiied gold nanoagents,
the microstructures of the cell shapes were obtained by recording the
scattering images from the labeling cell membranes. 64 Similar result
was also reported for the antibody-modiied gold nanorods, where
 
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