Table 2.

Important optical imaging techniques that utilize absorption and scattering contrasts in biology and medicine.

Technique	Imaging depth	Imaging resolution	Mechanism	Typical imaging applications
Confocal microscopy [1]	500 μm	> 250 nm	Scattering / absorption	Tissue surfaces
Two-photon microscopy [2]	800 μm	> 250 nm	Absorption	Tissue surfaces
Optical coherence tomography [3]	2 mm	1 μm	Scattering	Surfaces/subsurfaces of tissue
Diffuse optical tomography [4]	> 20 mm	≈ 10 % depth	Scattering/absorption	Small animal;human breast and brain
Photoacoustic imaging [5]	> 20 mm	< 1 mm(detector bandwidth limited)	Absorption	Subsurface to deep imaging;small animal; human breast