Ultrasound-modulated optical tomography with dark-field illumination and functional photoacoustic imaging.

摘要

Imaging optical properties in the visible and near-infrared regions in biological tissues has become increasingly important because the optical properties are directly related to the functional and morphological parameters of tissues. However, owing to strong light scattering in tissue, keeping high spatial resolution in relatively deep tissue (beyond one transport mean free path) is still a challenge in pure optical imaging techniques such as diffuse optical tomography (DOT). Ultrasound-aided optical imaging techniques such as photoacoustic (PA) imaging and ultrasound-modulated optical tomography (UOT) overcome the drawback of pure optical imaging by taking advantage of optical contrast and ultrasonic spatial resolution. The image resolutions of both techniques, as well as the maximum imaging depths, are scalable with ultrasonic frequency within the reach of diffuse photons. In biological tissues, the imaging depth can be up to a few centimeters deep.;The first part of this study is focused on the development of high-SNR UOT with intense acoustic bursts, the feasibility study of functional UOT using multi-optical wavelengths in phantoms, the development of dark-field illumination UOT systems in both transmission and reflection modes, and its application for sentinel lymph node (SLN) detection ex vivo.;The second part of this study is focused on non-invasive SLNs and lymphatic vessels mapping in vivo using FDA-approved indocyanine green (ICG) in rats with volumetric spectroscopic PA imaging and planar fluorescence imaging. In addition, the optical absorption cross sections of Au-Ag nanocages and Au nanorods are measured using PA imaging.