Reflection-mode Bessel-beam photoacoustic microscopy for in vivo imaging of cerebral capillaries.

A reflection-mode Bessel-beam photoacoustic microscope (BB-PAM) is developed for the in vivo imaging of cerebral capillaries with extended depth of field (DoF). The non-diffraction characteristic of Bessel beams means that a larger DoF can be expected in the PAM compared to that using a Gaussian beam (GB). In our system, we generate the Bessel beam using an axicon and an annular mask. The lateral resolution of the system is estimated to be 1.6 μm. The DoF is measured to be 483 μm, and this is verified by imaging a carbon fiber network. The DoF of BB-PAM is about 7 times that of a GB-PAM. The cerebral vasculature of an open-skull mouse is imaged using the developed BB-PAM to demonstrate its in vivo imaging capability and advantages over GB-PAM.