Frequency Domain Based Virtual Detector for Heterogeneous Media in Photoacoustic Imaging

There has been a growing attention to using acoustic-resolution photoacoustic microscopy (ARPAM) for medical applications in the recent decade. To eliminate the distortion induced by acoustic diffraction in ARPAM, synthetic aperture focusing technique (SAFT) methods that incorporate the virtual detector (VD) concept are used to reconstruct the images. However, most of these algorithms assume homogeneous media and therefore perform poorly in heterogeneous media cases. On this note, we propose an ARPAM reconstruction technique that can be adapted to cases where layered heterogeneous media are present. This method rebuilds a VD-based receiving system by using virtual scan plane theory. It then extrapolates wave fields with the proposed phase-shift factors of different multi-layered media. Afterwards, it adopts a non-uniform fast Fourier transform to reconstruct images. The wave extrapolation eliminates the artifacts induced by refraction, simplifying the computation for layered media. According to the simulations, our proposed method is capable to reconstruct high-quality images for layered heterogeneous media.