基于激光诱导超声机制的光声成像技术结合了光学成像的高对比度和超声成像的深穿透性，能无标记、非侵入反映生命体内源性吸收物质的分布，适合啮齿类动物模型全脑的即时成像。为了证明光声技术在脑科学研究和脑疾病监测中的应用，搭建了光声显微成像系统，其空间分辨率可达几十微米，有效成像深度可达1 mm以上，并以APP/PS1转基因阿尔茨海默症（Alzheimer’s disease, AD）模型小鼠和野生型WT小鼠为研究对象，从脑组织切片、离体全脑和活体全脑三个层面探究了光声成像在表征AD鼠和WT鼠脑结构变化和血管网络的能力，证明了光声技术在研究脑疾病发展过程中监控脑结构变化和脑血管网络特征的巨大潜力，可以为诸多脑科学研究和神经退行性疾病发展机制提供更深入的见解。

We proposed a nonlinear photoacoustic (PA) technique as a new imaging contrast mechanism for tissue thermal-nonlinearity characterization. When a sine-modulated Gaussian temperature field is introduced by a laser beam, in view of the temperature dependence of the thermal diffusivity, the nonlinear PA effect occurs, which leads to the production of second-harmonic PA (SHPA) signals. By extracting the fundamental frequency PA and SHPA signal amplitudes of samples through the lock-in technique, a parameter that only reflects nonlinear thermal-diffusivity characteristics of the sample then can be obtained. The feasibility of the technique for thermal-nonlinearity characterization has been studied on phantom samples. In vitro biological tissues have been studied by this method to demonstrate its medical imaging capability, prefiguring great potential of this new method in medical imaging applications.