Studies On Photoacoustic Imaging Based On Deconvolution Method Of Master Thesis

Photoacoustic imaging is a new biomedical imaging method based on the photoacoustic effect. It uses the short laser pulse as the excitation, and the ultrasonic wave is used as the information carrier to reconstruct the structure characteristics.Compared with the traditional medical imaging methods such as CT, ultrasonic imaging,optical coherence tomography, magnetic resonance imaging, photoacoustic imaging has many advantages, such as safe, noninvasive, high contrast, high resolution, simple equipment and so on. Therefore, photoacoustic imaging has been paid more and more attention by researchers and has become a hot spot in the field of biomedical imaging.However, the photoacoustic image can not achieve the desired effect in the aspect of image signal to noise ratio and contrast. This is the degradation of the image. The reason for the degradation of the photoacoustic image can be attributed to two points.First, the presence of noise leads to the deterioration of the signal noise ratio, which affects the quality of the reconstructed image. Second, the signal used to reconstruct the image is obtained by convolving the system's impulse response and ultrasound signal.So the signal contains useless information, which is the root cause of image degradation.Therefore, it is necessary to eliminate the influence of noise and system impulse response and improve the quality of the photoacoustic image.In this paper, the photoacoustic imaging system and photoacoustic image restoration are studied. The main contents include as follows.1. The mechanism of photoacoustic imaging is studied theoretically. The generation principle of photoacoustic signal and the characteristics of ultrasound were analyzed. The interaction between ultrasound and biological tissues was described in detail. The development history and research status of photoacoustic imaging technology are introduced from the aspects of photoacoustic imaging system and algorithm.2. The work flow and principle of photoacoustic imaging system were analyzed.From the aspects of hardware and software, the function of each functional module was analyzed. A series of experiments were designed to verify the reliability of the photoacoustic imaging system, and the reason of degradation of photoacoustic image during the experiment was analyzed.3. According to the influence of noise on image degradation, the de-noising algorithm based on wavelet analysis was used to de-noise the observed signal and improve the signal to noise ratio. Aiming at the influence of the system impulse response on the reconstructed image, the system identification algorithm based on the higher order spectrum was studied to estimate the impulse response of the system. The reconstructed image method by the deconvolution method was studied. A series of experiments were designed to verify the feasibility of the whole algorithm.