Filtered Back-projection Photoacoustic Denoising Reconstruction Based on Empirical Mode Decomposition

摘要

Filtered back-projection (FBP) is a classic imaging method in photoacoustic tomography in both frequency and time domain. However, the FBP algorithm itself will produce large artifacts, especially under extremely low signal-to-noise ratio which makes the acquisition, analysis and processing of photoacoustic signals (PASs) more difficult. Traditional filtering methods may cause modal aliasing of the filtered signal, loss of effective information, and the introduction of new interference in the process of using de-noising algorithms, which increases the difficulty of signal extraction, so select the appropriate filtering method has become an important part of this imaging mode. In addition, many algorithms tend to ignore the phase delay caused by filtering, which has a great impact on the accuracy of cross-correlation processing and distance inversion. According to the physical and mathematical principles of each step of the algorithm, this paper introduces the Empirical Mode Decomposition (EMD) algorithm to decompose the collected PASs, and puts forward the non-phase delay sifting proposal without introducing additional phase delay. A new strategy aimed at linear frequency modulation light sources under the framework of FBP algorithm. By keeping the center frequency of the ultrasonic transducer and the modulation signal unchanged, the validity of the algorithm is verified through experiments, which improved the reconstruction quality of the image. The new EMD strategy can effectively extract low signal-to-noise ratio of PASs and complete the photoacoustic tomographic reconstruction in FBP mode with higher quality.