66 research outputs found
Deep-Tissue Anatomical Imaging of Mice Using Carbon Nanotube Fluorophores in the Second Near Infrared Window
Fluorescent imaging in the second near infrared window (NIR II, 1-1.4 {\mu}m)
holds much promise due to minimal autofluorescence and tissue scattering. Here,
using well functionalized biocompatible single-walled carbon nanotubes (SWNTs)
as NIR II fluorescent imaging agents, we performed high frame rate video
imaging of mice during intravenous injection of SWNTs and investigated the path
of SWNTs through the mouse anatomy. We observed in real-time SWNT circulation
through the lungs and kidneys several seconds post-injection, and spleen and
liver at slightly later time points. Dynamic contrast enhanced imaging through
principal component analysis (PCA) was performed and found to greatly increase
the anatomical resolution of organs as a function of time post-injection.
Importantly, PCA was able to discriminate organs such as the pancreas which
could not be resolved from real-time raw images. Tissue phantom studies were
performed to compare imaging in the NIR II region to the traditional NIR I
biological transparency window (700- 900 nm). Examination of the feature sizes
of a common NIR I dye (indocyanine green, ICG) showed a more rapid loss of
feature contrast and integrity with increasing feature depth as compared to
SWNTs in the NIR II region. The effects of increased scattering in the NIR I
versus NIR II region were confirmed by Monte Carlo simulation. In vivo
fluorescence imaging in the NIR II region combined with PCA analysis may
represent a powerful approach to high resolution optical imaging through deep
tissues, useful for a wide range of applications from biomedical research to
disease diagnostics.Comment: Proceedings of the National Academy of Sciences (PNAS), 201
Real-time imaging using a 4.3-THz quantum cascade laser and a 320×240 microbolometer focal-plane array
Abstract: We report on the development of a compact, easy-to-use terahertz radiation source, which combines a quantum-cascade laser (QCL) operating at 3.1 THz with a compact, low-input-power Stirling cooler. The QCL, which is based on a two-miniband design, has been developed for high output and low electrical pump power. The amount of generated heat complies with the nominal cooling capacity of the Stirling cooler of 7 W at 65 K with 240 W of electrical input power. Special care has been taken to achieve a good thermal coupling between the QCL and the cold finger of the cooler. The whole system weighs less than 15 kg including the cooler and power supplies. The maximum output power is 8 mW at 3.1 THz. With an appropriate optical beam shaping, the emission profile of the laser is fundamental Gaussian. The applicability of the system is demonstrated by imaging and molecular-spectroscopy experiments. Hübers, "Sub-megahertz frequency stabilization of a terahertz quantum cascade laser to a molecular absorption line," Appl. Phys. Lett. 96(7), 071112 (2010). ©2010 Optical Society of Americ
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