Research On Photoacoustic Imaging Techniques For Microstructure Characterization

As a burgeoning biomedical imaging technology,photoacoustic imaging has attracted more and more attention in the past decades.In photoacoustic imaging,biological tissues are illuminated by pulse laser or modulated laser and finally emits ultrasound waves,i.e.,photoacoustic signals.After measuring and analyzing the ultrasound waves,photoacoustic imaging achieves anatomical and functional images,or physiological information of tissues.In comparison to optical imaging methods,ultrasonography,magnetic resonance imaging and computed tomography,photoacoustic imaging has the advantages of high imaging depth,high resolution,high contrast,multiple contrasts,safety and low cost.Photoacoustic imaging has already been applied in detecting anatomical and functional images in vivo,including three dimensional vascular networks,blood flow,tissue elasticity and tumors.Tissue microstructure decides functions of the tissue,reflecting the health conditions.Benefiting from the capabilities of photoacoustic imaging in measuring physiological and pathological information,this thesis proposes several new photoacoustic detection methods for microstructure characterization.Firstly,this thesis introduces the medical significances of tissue microstructure characterization and the existing detection techniques.To compensate for some drawbacks of these methods,photoacoustic imaging technology is developed.The chapter 1 shows the potential applications of photoacoustic imaging technology in tissue microstructure characterization after explaining the mechanism and the multi-parameter detection capability of photoacoustic imaging.The chapters 2-6 are the main parts of this thesis.They introduce the photoacoustic spectrum analysis method,photoacoustic signal envelope Nakagami statistical analysis,photoacoustic eigen-spectrum analysis and a self-developed dual-modality photoacoustic and ultrasound imaging system,respectively.These methods can measure different properties of microstructures,including size,number density,elasticity and fatigue.The chapter 7 concludes this thesis,and gives an outlook of the future investigations.This thesis proposes new photoacoustic detection methods for noncontact and noninvasive measurement of different properties of microstructures.Since many diseases are closely related to the microstructure change,this thesis may potentially contribute to the diagnosis of these diseases.