Feature Of The Week 10/06/13: Vanderbilt University Investigates Gold Nanorod Contrast Agents for Photothermal OCT
Photothermal OCT (PTOCT) is a functional extension of OCT that images oscillations in optical path length due to heat release from an absorber. These oscillations are induced by an amplitude-modulated photothermal laser that is incident on the sample. After photon absorption, heat is released into the microenvironment, which alters the local geometric path length and index of refraction. Phase-sensitive PTOCT is then used to map these index of refraction oscillations. We demonstrate that PTOCT is especially sensitive to near infrared absorbing gold nanorods, a promising contrast agent and drug carrier. The PTOCT signal is also characterized with respect to imaging speed, photothermal laser power, OCT magnitude signal, and gold nanorod concentration, and directly compared to photothermal heating models. Finally, we demonstrate the first documented in vivo PTOCT images, by injecting gold nanorods directly into the mouse ear.
PTOCT has the potential to enable molecular imaging with an impressive combination of spatial resolution and imaging depth. The signal is well characterized and sensitive, and can identify the presence of molecules independent of background tissue scattering. In the future, PTOCT could be used as a molecular imaging tool to monitor drug or contrast agent pharmacokinetics.
For more information see recent Article. Courtesy of Melissa Skala from Vanderbilt University.