Single-shot dual-scale photoacoustic microscopy enables ultra-sparse sampling reconstruction of optical-resolution...

Optical-resolution photoacoustic microscopy (OR-PAM) enables label-free, subcellular-resolution microvascular imaging, but the speed-resolution trade-off remains a bottleneck. While sparse sampling accelerates acquisition, the disparity between OR-PAM's tight optical focus and enlarged scanning steps causes irreversible information loss. To mitigate the limitations of ultra-sparse sampling, a single-shot dual-scale PAM framework is proposed. An independent fiber-based optical foci-steering configuration enables synchronized OR and acoustic-resolution (AR) acquisition, which ensures scanning flexibility while harnessing AR signals to enhance reconstruction. The AR modality, governed by its broader acoustic point-spread function (PSF), acts as an intrinsic physical low-pass filter that robustly captures the target's dominant vascular architecture. Guided by the theoretical AR-PSF, a deblurring operation is performed to obtain a sharpened structural prior. Subsequently, a dual-scale super-resolution generative adversarial network fuses this prior with ultra-sparse OR measurements to reconstruct high-fidelity 2D vascular MAP images. For reconstruction evaluation, the ultra-sparse inputs were generated by retrospectively decimating densely sampled in vivo data. Experimental results demonstrate that the proposed method significantly outperforms representative leading methods. By overcoming extreme spatial information scarcity under high-ratio sparse sampling up to 16 × 16 (0.4% sampling rate), the proposed method achieves a 16.1% SSIM improvement and a 2.18 dB PSNR gain over the best-performing baseline, together with a 33.7% reduction in LPIPS.