We present fast functional photoacoustic microscopy (PAM), which is capable of three-dimensional high-resolution high-speed imaging of the mouse brain, complementary to other imaging modalities. A single-wavelength pulse-width-based method was implemented to image blood oxygenation with capillary-level resolution and a one-dimensional imaging rate of 100 kHz. We applied PAM to image the vascular morphology, blood oxygenation, blood flow, and oxygen metabolism in the brain in both resting and stimulated states.

A photoacoustic microscope system provides label-free multilayered histology-like imaging of unprocessed human breast specimens.

Three-dimensional (3D) optical imaging of whole biological organs with microscopic resolution has remained a challenge. Most versions of such imaging techniques require special preparation of the tissue specimen. Here we demonstrate microtomy-assisted photoacoustic microscopy (mPAM) of mouse brains and other organs, which automatically acquires serial distortion-free and registration-free images with endogenous absorption contrasts. Without tissue staining or clearing, mPAM generates micrometer-resolution 3D images of paraffin- or agarose-embedded whole organs with high fidelity, achieved by label-free simultaneous sensing of DNA/RNA, hemoglobins, and lipids. mPAM provides histology-like imaging of cell nuclei, blood vessels, axons, and other anatomical structures, enabling the application of histopathological interpretation at the organelle level to analyze a whole organ. Its deep tissue imaging capability leads to less sectioning, resulting in negligible sectioning artifact. mPAM offers a new way to better understand complex biological organs.