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High-resolution volumetric optical imaging modalities, as confocal microscopy, two-photon microscopy, and coherence tomography, have become increasingly in the biomedical imaging field. However, due to light scattering, the penetration depths of these modalities are limited to the optical transport mean path in biological tissues, for example, ∼1 mm in the. Photoacoustic tomography (PAT), an emerging hybrid modality that can provide strong endogenous and optical absorption contrasts with high ultrasonic resolution using the photoacoustic (PA) effect, has the fundamental depth limitation. The image is scalable with the ultrasonic frequency. The depth is limited to the reach of photons and up to few centimeters deep in biological tissues. This Review focus on the following aspects of PAT described in published from 2003 to 2009: (1) multiscale PAT, (2) morphological and functional PAT using contrasts (hemoglobin or melanin), and (3) functional molecular PAT using exogenous contrast agents (organic dyes, nanoparticles, reporter genes, or fluorescence).
Kim et al. (Mon,) studied this question.