| Popis: |
Photoacoustic imaging is a potential medical imaging technique to reconstruct and image the inside structure of tissue. The principle of pulsed optoacoustic signal generation and the comparison between the traditional piezoelectric detectors and optical detectors are described. Through analyzing the principle of sensing film, we find that in a rigid-back sensing film the relation between pressure amplitude (P O ) and thickness amplitude (dl 0 ) is P 0 = E/2ldl 0 . In order to realize a whole field, non-touch, high precision and backward-mode photoacoustic detecting, a new kind of sensing film detector based on Fabry-Perot sensing head is proposed. For the especial configuration of dichroic mirror, the detector not only enables photoacoustic excitation laser pulses to transmite through the sensor, but also enables the laser speckle formed on the interface to reflect into the CCD. Bying using this detector we design a photoacoustic imaging system based on the outside displacement Digital Speckle Pattern Interferometry (DSPI) detecting system. To reduce the cost of system a standard CCD whose exposure time is about tens of milliseconds is adopted as light detector. By interrogating the sensor with a short laser pulse with about tens ns bandwidth, we resolve the problem of match between the CCD and acoustic field at MHz frequency. In principle, the reconstruction algorithm based on the decomposition can be applied to reconstruct a three-dimensional photoacoustic image The technique will offer a method with a whole field, backward-mode, 3D and all-optical detecting for high-resolution biomedical imaging. |
