Optical-resolution photoacoustic microscopy for in vivo imaging of single capillaries.

Capillaries, the smallest blood vessels, are the distal end of the vasculature where oxygen and nutrients are exchanged between blood and tissue. Hence, noninvasive imaging of capillaries and function in vivo has long been desired as a window to studying fundamental physiology, such as neurovascular coupling. Existing imaging modalities cannot provide the required sensitivity and spatial resolution. We present in vivo imaging of the microvasculature including single capillaries in mice using optical-resolution photoacoustic microscopy (OR-PAM) developed in our laboratory. OR-PAM provides a lateral resolution of 5 microm and an imaging depth >0.7 mm.