光纤光声显微成像的噪声特性分析与信噪比提升研究  

Noise Analysis and Signal-to-Noise Ratio Enhancement of Fiber-Based Photoacoustic Microscopy

作　　者：黄杰 梁贻智 仲晓轩 金龙 关柏鸥 Huang Jie;Liang Yizhi;Zhong Xiaoxuan;Jin Long;Guan Baiou(Guangdong Provincial Key Laboratory on Optical Fiber Sensing and Comm unications,Institute of Photon ics Technology,Jinan University,Guangzhou 510632,Guangdong,China)

机构地区：[1]暨南大学光子技术研究院广东省光纤传感与通信技术重点实验室,广东广州510632

出　　处：《中国激光》2022年第15期93-100,共8页Chinese Journal of Lasers

基　　金：国家自然科学基金(61860206002,61775083,61805102);广东珠江团队项目(2019BT02X105);广东省科技计划项目(2020A0505100044,2020A0505140005);广州市科技计划项目(201904020032)。

摘　　要：光纤光声成像技术利用光纤传感器来探测由激光脉冲在生物体内激发出的超声波,从而实现对目标组织成分的高对比度成像。光纤超声传感系统的噪声特性是成像信噪比的决定性因素之一,本研究团队详细分析了超声敏感元件——正交双频光纤激光器与光放大器、光电探测器及数据采集模块等各环节对噪声的贡献,同时分析了系统噪声、拍频信号功率和频率噪声与光功率(或者光电流)之间的关系。研究结果表明,通过光放大器提升注入光探测器的光功率能够显著提升光纤传感系统的信噪比,当注入光探测器的光功率达到10 mW以上时,拍频信号频率抖动的均方值可由74 kHz降低到44 kHz,在50 MHz带宽内提供的噪声等效声压由32.9 Pa降低到19.5 Pa,信噪比提升4.5 dB。进一步,本研究团队基于光纤超声传感器构造了光纤光声显微镜,并采用该显微镜对小鼠耳部血管进行活体成像,结果发现提升信号光功率能够显著增强图像的信噪比。Objective Photoacoustic imaging(PAI)has been a fast-growing biomedical imaging modality in recent years.Absorbers a re imaged in biological tissue by detecting laser-induced ultrasound waves via PAI.This provides hemodynamic information for the diagnosis of tumors,strokes,and other critical diseases.A typical photoacoustic microscope uses piezoelectric ultrasonic transducers to detect the photoacoustic signals.However,owing to the tradeoff between sensitivity and sensor size,building a miniaturized photoacoustic microscope with superior imaging capability is highly challenging.Therefore,the applications of PAI in wearable and endoscopic applications are limited.Our research group has developed a new optical ultrasonic sensor using a self-heterodyne fiber laser as the acoustically sensitive element.However,the laser,optical amplifier,photodetector,and signal demodulator may all cause noise and limit the detection capability.This study analyzes the noise characteristics and constructs a high-performance fiber-based photoacoustic microscope.This imaging probe can be used as a gastrointestinal endoscope for tumor screening or as a head-mounted microscope for brain imaging in a free-moving state.Methods We exploited a compact fiber laser as the ultrasound sensor.Ultrasound waves can deform the sensor and i nduce a change in the lasing frequency.To measure the acoustic response,we used both x-and y-polarized light and beat them at the photodetector to generate a radio-frequency.The variation in lasing frequency was then measured at radio frequency using modern electronics with high resolution.Here,we theoretically analyzed the noise of the fiber sensor,optical amplifier,photodetector,and signal demodulation acquisition module in the ultrasonic detection system.By measuring the noise n0,beat signal power P,and frequency noiseΔfwith different input optical powers,we e xamined the dependence of the noise on the input power.Further,we implemented a photoacoustic microscope using an optical sensor for ultrasound detection

关 键 词：医用光学 光声显微成像 光纤超声传感器 噪声特性 

分 类 号：R319[医药卫生—基础医学] TH744[机械工程—光学工程]