The Influence And Enhancement Methods Of Acoustic Heterogeneity On Image Quality In Photoacoustic Imaging

Photoacoustic imaging is a novel biomedical imaging modality that has wide applications in the field of biomedical imaging due to its high resolution,non-radiation,non-invasiveness,and non-ionization advantages.Image reconstruction is a key step in photoacoustic imaging,and the accuracy of the reconstruction algorithm directly determines the image quality of photoacoustic imaging.Currently,the main photoacoustic image reconstruction algorithms are based on the assumption that the acoustic properties within the imaging area are uniform,that is,the imaging area has a constant density and a uniform sound speed distribution.However,in practical imaging processes,this assumption is not valid.Different components in biological tissues have acoustic heterogeneity,and the coupling medium used for imaging cannot be completely consistent with biological tissues in terms of acoustic properties.If the sound speed distribution is still assumed to be uniform during image reconstruction,it will lead to a decrease in image reconstruction quality and may cause artifacts in the image.This paper mainly studies the acoustic heterogeneity in photoacoustic imaging and proposes an improved image reconstruction method.The specific research contents are as follows:In order to solve the problem of image degradation caused by acoustic heterogeneity in image reconstruction,a semi-time image reconstruction method is introduced.This method utilizes the symmetry of the ultrasound transducer array and can reconstruct the complete image using the signal from the first half of the time domain,which is less affected by acoustic heterogeneity,effectively improving the quality of image reconstruction.A dual sound speed image reconstruction model is established,which divides the imaging area into two different regions,biological soft tissue and coupling medium,through image segmentation and assigns different sound speeds for image reconstruction.Numerical simulation and in vivo experimental results show that both methods can improve the quality of image reconstruction and alleviate the influence of acoustic heterogeneity on image reconstruction.In addition,this paper proposes an adaptive photoacoustic image reconstruction method based on ultrasound prior from the perspective of photoacoustic signal processing.This method first collects ultrasound signals in the imaging area and reconstructs the ultrasound image in the imaging area using delay-and-sum algorithm.Then,an active contour segmentation algorithm is used to segment the region with nonuniform sound speed in the ultrasound image and use it as a prior to adaptively truncate the artifact signal in the photoacoustic signal.Finally,the processed photoacoustic signal is used to reconstruct a photoacoustic image without artifacts.Numerical simulation and in vivo experimental results demonstrate that the proposed method can improve the quality of image reconstruction.In summary,this paper mainly analyzes the influence of acoustic heterogeneity on image reconstruction quality in photoacoustic imaging and proposes methods to enhance image quality.The research work of this paper effectively improves the image reconstruction quality of photoacoustic imaging and provides theoretical and practical basis for the research and clinical application of photoacoustic imaging.