| dc.description.abstract | 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. | en_US |