The Research Of Photoacoustic And Thermoacoustic Tomography On Biological Tissues

Photoacoustic tomography(PAT) and thermoacoustic tomography(TAT) are two non-invasive and non-ionizing medical imaging modality and have developed rapidly in recent years.When the periodic short pulse of electromagnetic wave, usually a laser or microwave, is delivered into biological tissues, the thermal expansion caused by rapid absorption of electromagnetic energy generate ultrasonic wave in the air, it carries the electromagnetic absorption characteristics of biological tissues, an ultrasonic transducer is used to scan around the tissues to detect the ultrasonic signals.With the signals detected, the electromagnetic absorption distribution in biological tissues can be reconstructed using corresponding reconstruction algorithms. PAT and TAT are generated based on such a progress.PAT or TAT combined the pure optical or microwave imaging with pure ultrasonic imaging has the advantages of high spatial resolution and high contrast. PAT and TAT are based on the different biological composition.The result of PAT is mainly determined by the optical absorption properties of biological tissues,however, the result of TAT is mainly related to the conductivity and permittivity of biological tissues. In the future, combined the two imaging methods, more biological information can be obtained, which can be more useful for the structural and functional imaging of biological tissues and the related disease detection.This article mainly focuses on the early research on biological tissue of bone and joint with the photoacoustic imaging and thermoacoustic imaging, it mainly covers:Firstly, we introduce the research and development background of PAT and TAT. In this section, at first, we introduce several biomedical imaging methods we commonly used and discuss the development history and characteristics of PAT and TAT. Then, the PAT and TAT research status in biological tissue imaging are described, and we give specially description of the research status of bones and joints tissues.Secondly, we introduce the basic theory of PAT and TAT and discusse in five aspects, that is the generation mechanism of PAT and TAT signals,the acoustic properties of biological tissues including attenuation, absorption, scattering,the detect methods of signals and the basic reconstructed theory of PAT and TAT images, the image reconstruction algorithm of PAT and TAT,such as back-projection algorithm, delay-and-sum algorithm and so on.Thirdly, we introduce the research of the PAT of bone and joint.We firstly describe the experimental PAT system.Subsequently, we conduct experiments used the PAT system on bone and joint in vitro and in vivo and make a frequency spectrum analysis for some photoacoustic singals obatained at specific position. Finally, the results of image reconstruction are analyzed.Fourthly, we introduce the research of the TAT of bone and joint. At first, we make a simply description of the TAT system.Subsequently, we conduct experiments used the TAT system on bone and joint in vitro and in vivo and make a frequency spectrum analysis for thermoacoustic singals,also, make an analysis for the reconstructed image.In addition,we make a comparative analysis of the photoacoustic image and thermoacoustic image and conclude the main difference between PAT and TAT in biomedical imaging.