光聲成像系統同時擁有光學影像和超音波影像的優點，其能夠及時成像及高對比度、高解析度和非侵入式等優點，光聲效應利用物體對光波長的選擇性吸收，及利用超音波的高穿透性來接收訊號，超音波成像雖然有高穿透的特性，其利用聲音在遇到不同介質時的反射波來判斷物體的結構，但遇到人體上較多軟組織時，超音波探測器將會難以接收到反射聲波，導致對比度下降影像無法分辨物體，且超音波成像的解析度與聲波波長有關，波長太長也會造成相鄰物質無法分辨，影響影像解析度及真實性，而光聲成像利用物體選擇性吸收的高差異性來製作影像，造成影像的高對比性，且擁有光學影像的高解析度及超音波影像的低散射性。 本研究的光聲成像系統使用波長為1064 nm的Q-switch雷射激發物體，能夠讓吸收體在短時間內吸收高能量，以利偵測光聲訊號，及使用Galvo system控制雷射光路掃描物體得到到影像，另外本研究還將雷射光導入光學顯微鏡，整合光學顯微鏡同時得到光學影像及光聲影像，且顯微物鏡也提供給本光聲成像系統高解析度。 Photoacoustic imaging systems have the advantages of both optical imaging and ultrasonic imaging. It is capable of doing real-time imaging noninvasive, while at the same time providing both high contrast and high resolution images. Photoacoustic effect uses the high transmittances of ultrasonic waves and the fact that materials absorb different wavelengths of light to obtain the signal. The basic principle of ultrasonic imaging is when a wave goes from one medium to another, part of the wave will be reflected, and can be used to restructure the shape of the object. Ultrasonic waves can go really deep inside the human body, but the contrast inside soft tissues aren’t really good and would be difficult to distinguish the difference of it. The resolution of ultrasonic imaging is also related to the wavelength of the ultrasonic wave, wavelengths that are too long will result in a lower resolution image, and would be difficult to distinguish objects close to each other. However, photoacoustic imaging uses the highly different light absorption of materials to obtain high contrast images, and has the high resolution characteristic of optical imaging and the low scattering property of ultrasonic imaging The photoacoustic imaging system used in our system contains basically a Q-switch laser with central wavelength of 1064 nm, a galvo system and an optical microscope. Using the Q-switch laser will allow the sample to absorb lots of energy in a short period of time, and will thereby enhance the photoacoustic signal we detect when the sample is excited. The galvo system allows us to control the laser light path, so that we can scan the sample and get photoacoustic image. Finally, by guiding the laser into the optical microscope, both the optical image and the photoacoustic image can be obtained at the same time. Moreover, the objective lens inside the microscope will also provide high resolution to the photoacoustic system.
