Super-resolution acoustic-resolution photoacoustic microscopy by a novel algorithm

Abstract

Acoustic-resolution photoacoustic microscopy (AR-PAM) is a promising tool for microvascular imaging. In AR-PAM, a focused transducer is typically used. Limited by acoustic diffraction, in-focus lateral resolution is dependent on the center frequency and numerical aperture of the transducer. On the other hand, out-of-focus lateral resolution will deteriorate, which can be restored to in-focus lateral resolution by synthetic aperture focusing technique (SAFT). Previously, we demonstrated that with prior knowledge of the point-spread function of the AR-PAM imaging system, combined SAFT and Richard-Lucy deconvolution can be applied to achieve super resolution (SR) beyond acoustic diffraction limit and to enhance signal-to-noise ratio (SNR) in both focal and out-of-focus regions. However, SNR of the original AR-PAM image highly affects the performance. Moreover, discontinuities arise in the line pattern that is originally continuous. In this study, we propose a novel algorithm, which combines a novel SAFT method and a directional model-based (D-M) deconvolution method, to break the acoustic diffraction limit. By using our algorithm, FWHM of 20 ~µm for AR-PAM system over DOF of ~1.8 mm is experimentally achieved. Compared with our previous work using Richard-Lucy deconvolution, the D-M deconvolution demonstrates the advantages in high SNR, and good line continuity. Compared with the directional SAFT method, our algorithm achieves SR and higher SNR.