Interstitial detection of gold nanoparticles in deep tissues with optical radiance using porcine phantom

We have applied an optical radiance technique to map localized inclusions of gold nanoparticles in a porcine phantom. Our goal was to show that combined spectroscopic and angular snapshots of phantoms allow the obtaining of information that is relevant for prostate cancer diagnostics. A combination of the radiance spectroscopy and white light spectroscopy was used to measure angular resolved light distribution in 600-900 nm spectral range inside the porcine phantom that mimics prostate geometry. Optical radiance defines a variation in the angular density of photons impinging on a selected point in the tissue from various directions. To obtain radiance data, a specially constructed optical probe with a well-defined angular detection window must be rotated along its axis. Characteristic spectro-angular snapshots of the phantom alone and with the localized inclusion of gold nanoparticles were obtained. The inclusions were formed by immersing a capillary filled with gold nanoparticles into selected locations in the phantom. For phantoms with gold inclusions, this approach allows the isolation of the spectroscopic signatures of the inclusions from the background and identification of inclusion locations in the angular domain. Detection of ~10 10 gold nanoparticles (detector-inclusion separation 10 mm, source-detector separation 15 mm) in the porcine tissue was demonstrated. These encouraging results indicate a promising potential of radiance spectroscopy in early prostate cancer diagnostics with gold nanoparticles.