Combined synthetic aperture focusing technique and three-dimensional deconvolution for resolution enhancement in photoacoustic microscopy

Acoustic-resolution photoacoustic microscopy (ARPAM) is a promising tool for deep imaging of biological tissues. Synthetic aperture focusing technique (SAFT) can improve the degraded lateral resolution in the out-of-focus region of ARPAM when using a high numerical aperture acoustic transducer. We previously reported a three-dimensional (3D) deconvolution technique to improve both lateral and axial resolutions in the focus region of ARPAM. In this work, we extended resolution enhancement of ARPAM to the out-of-focus region based on two dimensional SAFT combined with the 3D deconvolution (SAFT+Deconv). In both the focus and out-of-focus regions, depth-independent lateral and axial resolution after SAFT ensures a depth-independent point spread function for 3D deconvolution algorithm. In an extended depth of focus (DOF) of similar to 2 mm, SAFT+Deconv ARPAM improves the -6 dB lateral resolutions from 65-700 mu m to 20-29 mu m, and the -6 dB axial resolutions from 35-42 mu m to 12-19 mu m. The signal-to-noise ratio is also increased by 6-30 dB. The enhanced resolution in extended DOF by SAFT+Deconv ARPAM may enable important applications in biomedical photoacoustic imaging.