In Vivo Photoacoustic Tomography of Chemicals: High-Resolution Functional and Molecular Optical Imaging at New Depths

摘要

High-resolution volumetric optical imaging modalities,udsuch as confocal microscopy, two-photon microscopy, andudoptical coherence tomography, have become increasinglyudimportant in the biomedical imaging field. However, due toudstrong light scattering, the penetration depths of theseudimaging modalities are limited to the optical transport meanudfree path in biological tissues, for example, ∼1 mm in theudskin. Photoacoustic tomography (PAT), an emerging hybridudimaging modality that can provide strong endogenous andudexogenous optical absorption contrasts with high ultrasonicudspatial resolution using the photoacoustic (PA) effect, hasudovercome the fundamental depth limitation. The imageudresolution is scalable with the ultrasonic frequency. Theudimaging depth is limited to the reach of photons and up touda few centimeters deep in biological tissues. This Reviewudwill focus on the following aspects of PAT described inudworks published from 2003 to 2009: (1) multiscale PATudsystems, (2) morphological and functional PAT usingudintrinsic contrasts (hemoglobin or melanin), and (3) functionaludand molecular PAT using exogenous contrast agentsud(organic dyes, nanoparticles, reporter genes, or fluorescenceudproteins).