Research On The Different Excitation Source Based Acoustic Tomography Technology

Recently,acoustic tomography technology based on different excitation sources?laser,microwave,X-ray?has attracted wide attention in biomedical field.As a promising hybrid imaging modality,it combines the advantages of both excitation and ultrasound imaging,and provides the possibility of high resolution and high contrast for biological tissue imaging.This kind of technology has a broad development prospect in cancer imaging and dose monitoring during radiotherapy due to the close relationship between the imaging target and the excitation signal absorption by biological tissues.Based on this,this paper discusses the research topics according to the different excitation sources,and mainly introduces three works related to the above technologies embarked from the basic theory.The main contents are as follows:1.The feasibility of electric pulse based electroacoustic tomography?EAT?was investigated for in situ monitoring electric field distribution in soft tissue.In our computer simulations,the electric field distribution in soft tissue was generated by solving general partial differential equations using finite element analysis.The electric field distributions were converted into initial pressure distributions,and the propagation of the induced acoustic waves was simulated using k-Wave simulation.A circular array of 128 ultrasound transducers was placed around the target to detect the acoustic waves,and a time reversal reconstruction algorithm was used to reconstruct the EAT image.Different number of the electrodes,set at different distance with different voltage inputs on the electrodes were performed to simulate different electric field distributions during electroporation.We also have investigated the sensitivity of the EAT imaging with different voltage inputs.The results of this study demonstrated that EAT is a feasible technique for monitoring electric field distribution and guiding the electrotherapy in future clinical practice.2.The feasibility of using a transperineal ultrasound transducer array for X-ray-induced acoustic computed tomography?XACT?imaging to guide the prostate radiotherapy was investigated.A customized two-dimensional?2D?matrix ultrasound transducer array with 10000?100×100 elements?ultrasonic sensors with a central frequency of 1MHz was designed on a5cm×5cm plane to optimize three-dimensional?3D?volumetric imaging.The CT scan and dose treatment plan for a prostate patient undergoing intensity modulated radiation therapy were obtained.Inhouse simulation was developed to model the time varying X-ray induced acoustic signals detected by the transperineal ultrasound array.A 3D filtered back projection algorithm has been used for 3D XACT image reconstruction.This work will greatly enhance the potential of XACT imaging for real time in vivo dosimetry during radiotherapy.3.Pulsed fiber laser has great potential as an excitation source of photoacoustic tomography?PAT?due to its unique advantages.In order to further optimize the performance of PAT technique,the successfully prepared zirconium diselenide?ZrSe₂?-polyvinyl alcohol film was employed as a saturable absorber?SA?to demonstrate the pulse fiber laser for the first time.In this work,we also investigated the characteristics of the nonlinear saturable absorption of SA.The saturation intensity of the SA is 12.72MW/cm²,while its modulation depth is 2.3%.The stable soliton state with a maximum output power of 11.37mW and a narrowest single pulse duration of 12.5ps at a repetition frequency of 21.22MHz was detected.The experimental results conclusively proved that ZrSe₂,with its excellent nonlinear absorption properties,should have extensive potential applications within the field of ultra-fast pulse lasers.