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

Abstract

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 ∼2 mm, SAFT+Deconv ARPAM improves the −6 dB lateral resolutions from 65–700 μm to 20–29 μm, and the −6 dB axial resolutions from 35–42 μm to 12–19 μm. 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.