Abstract
A micro-electromechanical system (MEMS) scanning mirror accelerates the raster scanning of optical-resolution photoacoustic microscopy (OR-PAM). However, the nonlinear tilt angular-voltage characteristic of a MEMS mirror introduces distortion into the maximum back-projection image. Moreover, the size of the airy disk, ultrasonic sensor properties, and thermal effects decrease the resolution. Thus, in this study, we proposed a spatial weight matrix (SWM) with a dimensionality reduction for image reconstruction. The three-layer SWM contains the invariable information of the system, which includes a spatial dependent distortion correction and 3D deconvolution. We employed an ordinal-valued Markov random field and the Harris Stephen algorithm, as well as a modified delay-and-sum method during a time reversal. The results from the experiments and a quantitative analysis demonstrate that images can be effectively reconstructed using an SWM; this is also true for severely distorted images. The index of the mutual information between the reference images and registered images was 70.33 times higher than the initial index, on average. Moreover, the peak signal-to-noise ratio was increased by 17.08% after 3D deconvolution. This accomplishment offers a practical approach to image reconstruction and a promising method to achieve a real-time distortion correction for MEMS-based OR-PAM.
Highlights
Photoacoustic microscopy (PAM) is a hybrid imaging technique, which benefits from the effect of laser-induced ultrasound in the designed optical absorbers [1,2,3]
It is suitable for a variety of optical-resolution photoacoustic microscopy (OR-PAM) instruments in rapid microscopic imaging [8], including a highspeed dual-view photoacoustic imaging pen [9], a microelectromechanical system (MEMS) scanning mirror enhanced photoacoustic laparoscope with an adaptive resampling method [10], and a combination of a MEMS scanning mirror and multimode fibers [11]
MEMS-based OR-PAM The imaging system used in this study was the same as that used in previous studies, as shown in Figs. 1a and b [10]
Summary
Photoacoustic microscopy (PAM) is a hybrid imaging technique, which benefits from the effect of laser-induced ultrasound in the designed optical absorbers [1,2,3]. One of the methods to address this challenge is to simplify the acquisition system and construct a straightforward linear backprojection algorithm. A MEMS mirror has the advantages of high-speed scanning, minimum power consumption, a comparatively small size, and light weight. It is suitable for a variety of OR-PAM instruments in rapid microscopic imaging [8], including a highspeed dual-view photoacoustic imaging pen [9], a MEMS scanning mirror enhanced photoacoustic laparoscope with an adaptive resampling method [10], and a combination of a MEMS scanning mirror and multimode fibers [11].
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