Research On Long Depth-of-field Photoacoustic Microscopy Imaging In The Tissue With Speed-of-sound Variance By Using Annular Ultrasound Array

Photoacoustic Microscopy is an embodiment of Photoacoustic imaging,which uniquely combines the advantages of optical imaging and ultrasonic imaging.It is a promising biomedical imaging technology in clinical application and has been rapidly developed in recent years.In this study,we focus on some problems to further mature this technology.1)We propose a concentric annular ultrasonic array to broaden the depth-of-field.It can improve the lateral resolution in target depth by manipulating the delay time of multi-channel signal.Ultimately,we can obtain imaging with a long depth-of-field by dynamic focusing of annular array.Furthermore,in this study,we discuss the benefits of correlation factor of multi-channel in suppressing image artifacts and side lobes.2)In most studies,variations in speed-of-sound of the subject are neglected under the assumption of acoustic homogeneity.Biological tissue with spatially heterogeneous speed-of-sound cannot be accurately reconstructed under the assumption.We have theoretically and experimentally demonstrated that speed-of-sound plays an important role in imaging.The imprecise presetting of speed-of-sound of the tissue not only decreases the image recovery,but also influences the exact positions of sound sources.In this study,the speed-of-sound image of the media is extracted according to the signal delay between each ring elements based on the annular array.The measured speed-of-sound could not only be used as a contrast,but also improve the resolution and accuracy of spatial location of photoacoustic image in inhomogeneous acoustic media.The proposed microscopy might have significances in monitoring the biological physiological.