Subpixel and On-Line Motion Correction for Photoacoustic Dermoscopy

Photoacoustic dermoscopy (PAD) has been proven to visualize the microvascular network within the dermis noninvasively, and has great application potential and advantages. In practice, some subjects are children or unwell and may have difficulty in controlling their breathing or trembling. The artifacts caused by the uncontrollable trembling will degrade the image quality, resulting in deviation of the pathophysiological features. This work introduces a subpixel and on-line motion correction method for clinical application of PAD. The high-accuracy motion correction was realized by the subpixel motion estimation, which was achieved by five-fold upsampling the cross-correlation matrix between A-lines or B-scan images. Since the motion correction algorithm only takes the acquired data as a priori, it can be processed immediately when a B-scan is input, so it can be embedded in the acquisition program, leading to the motion correction during the data acquisition. Moreover, the algorithm was verified by the experimental data of human skin. The results demonstrated that the images after sub-pixel motion correction are obviously improved visually, and the structural similarity index measurement (SSIM) and peak signal-to-noise ratio (PSNR) between adjacent B-scan images after correction are increased by 31.6% and 47.7% compared to the uncorrected images. To conclude, the proposed algorithm can make it robust in terms of accuracy and reliability and will help PAD fulfill its clinical promise.