Studies And Application Of Photoacoustic Imaging System Based On Fiber Bragg Grating

Photoacoustic imaging, as a new noninvasive imaging technology, has drew extensive attention of the society from all walks of life. Due to the high contrast and resolution of the image, its very important to get the accurate receiving ultrasonic signal in the whole working process. At present, in the field of medical imaging, ultrasonic signal is received by commercial ultrasonic transducer, but it is bulky, and subject to electromagnetic interference, can not working at high temperature. In this condition,optical fiber Bragg grating can be used as a new type of ultrasonic probe to replace the existing ultrasonic transducer.Based on the above situation, we have studied the optical fiber Bragg grating sensing and demodulation characteristic, studied the working principle of the reflection and transmission type, and designed a set of system to detect the bandwidth of the fiber Bragg grating, the results show that ultrasonic signal between 100 KHz to 10 MHz can be received. In addition, we also set up a set of photoacoustic imaging system based on fiber Bragg grating, using a pencil lead、hair and other things as the object to verify the feasibility and stability of the system, and do the experiment on the approximate equilateral triangle which composed of three pencil lead, according to the results we can see the center of the image is clearer, but the edge position is fuzzy, there are two reasons, firstly, the edge position of the image is composed of high frequency ultrasound signal, and the ability of the optical fiber Bragg grating receiving the high frequency signal is weak; Secondly, as we use delay superimposed image reconstruction algorithm, the ultrasonic signal reflected from the edge of phantom and the ultrasonic signals emitted by objects mix together, this also make the edge of the image blur.During the experiment, noise and temperature can affect the fiber Bragg grating receiving ultrasonic signals, so we take measures to encapsulate the fiber Bragg grating,after analysis we chose epoxy resin adhesive as the encapsulation material, the reason is that the young’s modulus and poisson’s are both low, encapsulating method for the polymer with metal case isolation, the reason is that in this way can gain more multiple.Analysis of the spectrum of fiber Bragg grating before and after the packaging, the results showed that encapsulation completed of the fiber Bragg grating move to the low-frequency resonance frequency.Using encapsulated before and after of the fiber Bragg grating for the same imaging simulation respectively, compared the imaging results, found that after the encapsulation, the effect of the image is good, the reason is that polymer on the fiber Bragg grating had isolation the affect of external factors.Fiber Bragg grating has many advantages, like small size, strong ability to resist electromagnetic interference, can work at under high temperature. Besides, it has own unique advantages in medical endoscope, can also be combined with magnetic resonance imaging(MRI) technology, is worth further research.