基于声透镜的三维光声成像技术

基于声透镜的光声成像系统中, 由样品的光声压分布等效样品的吸收分布, 进行光声像重建, 但之前的这种等效是一种近似, 理论上并不准确. 本文阐述了声透镜三维光声成像的基本原理, 揭示了声透镜像面上光声压信号的时间分布与样品轴向吸收分布之间的关系; 提出用积分法和希尔伯特变换提取光声信号瞬时值法, 解调样品吸收系数分布并重建光声像; 实验上, 对不同样品分别用积分法和希尔伯特变换法获取样品的吸收系数, 重建光声像的横向和轴向分辨率均约为1 mm, 实现了真正的三维快速光声成像.

Three-dimensional photoacoustic imaging technique based on acoustic lens

Reconstruction of a sample photoacoutic (PA) image is the research focus in PA imaging system that is based on acoustic lens. Among all existing reconstruction methods, the reconstructing PA image is usually obtained by the projection of the absorption distribution which is regarded as PA signal of a sample. However, this equivalent relationship is just approximate and not accurate in theory. In this paper, the accurate relationship between the absorption coefficients of the sample placed on the object plane and its PA pressure signals focused on the image plane is successfully demonstrated. Both the integral and the extraction envelope methods are firstly proposed to reconstruct the axial PA image of an absorbent sample. The resolution of the reconstructed PA image obtained by Hilbert transform is theoretically higher than that by integral method, and the reason is explained. Different samples are chosen to experiment on the acoustic lens PA imaging system. A three-dimensional fast PA imaging of the absorbent sample is realized by combining its axial imaging capability with its lateral imaging capability of acoustic lens. The reconstruction result shows that both the lateral and the axial resolutions of the reconstruction image are both about 1 mm. The quality of a sample PA image obtained by Hilbert transform is better than that by integral method.