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在光声成像中,超声信号通常需要采用接触传感器探测,这使其在很多应用中受到很大的限制,如脑功能成像。为了替代接触探测器实现非接触的光声层析成像(NCPAT),激光干涉技术被用于远程获取超声信号。本文搭建了非接触光声层析成像系统,系统采用波长为532 nm、能量17.5 m J/cm~2的激光作为光声激发源,激光外差干涉仪作为光声信号的远程探测系统,对实际生物组织模型进行了旋转几何的光声信号探测。利用激光外差干涉仪探测到的光声信号,进行反投影算法的图像重建。实验结果表明在具有组织散射特性的模型中,激光外差干涉仪在2.25 MHz带宽(峰值下15 d B强度的信号宽带)下,NCPAT成像系统可以识别500μm直径的黑色微球,并实现了在强散射介质中多层结构的光学对比成像。这将扩展光声和超声在体成像在生物医学领域的应用范围。
In photoacoustic imaging, ultrasound signals typically require contact sensor probing, which places them in great limits in many applications, such as brain imaging. To replace contact detectors for non-contact photoacoustic tomography (NCPAT), laser interferometry is used to remotely acquire ultrasound signals. In this paper, a non-contact photoacoustic tomography system is set up. The system uses a laser with a wavelength of 532 nm and an energy of 17.5 m J / cm ~ 2 as the photoacoustic excitation source. The laser heterodyne interferometer acts as a remote detection system of photoacoustic signals. The actual biological tissue model has been subjected to a rotational geometry of photoacoustic signal detection. Using the photoacoustic signal detected by the laser heterodyne interferometer, the image reconstruction of the backprojection algorithm is carried out. The experimental results show that in a model with tissue scattering properties, the NCPAT imaging system can identify 500μm diameter black microspheres at 2.25 MHz bandwidth (15 dB peak intensity under broadband), and achieved a Optical Contrast Imaging of Multilayer Structures in Strongly Scattering Media. This will expand the range of applications of photoacoustic and ultrasound in vivo imaging in the biomedical field.