Construction And Applications Of Array-based Photoacoustic Tomography System Based On PVDF Material

The development of multiple imaging technologies has greatly increased the successful rate of clinical screening and diagnosis of diseases.However,the low temporal resolution has limited the applications of many imaging techniques.Thus,improvement of temporal resolution has become a challenge and urgent need for various biomedical imaging technologies.Recently,photoacoustic imaging(PAI),combining rich optical contrast and high acoustic resolution in a single modality,has been evolving rapidly and applied for fundamental and clinical studies of various diseases.The appearance of array-based photoacoustic tomography technologies has significantly improved the temporal resolution.Polyvinylidene fluoride(PVDF),which is widely used in the field of acoustic detection,has been utilized in array-based photoacoustic imaging systems because of its good flexibility and broad detection spectrum.In order to develop a photoacoustic tomographic system with a good imaging quality and a high imaging speed,we fabricated an ultrasound transducer array using PVDF and designed an array-based photoacoustic tomographic system.Single-element ultrasonic transducer was fabricated using PVDF material with a size of 30 mm×2.8 mm and a curvature radius of 82 mm.A total number of 60 single-element ultrasonic transducers with the same size were assembled in a ring-shaped resin holder as the imaging interface.Then we completed the design and construction of the entire hardware platform,including animal holder,amplifier-array and multi-channel data acquisition system.Furthermore,we developed the data acquisition program using LabView,and image reconstruction code as well as functional parameter algorithm using Matlab.To test the system performance,in vivo and ex vivo experiments including phantoms,animals and human fingers were performed.The test results show that the transducers have an average center frequency of 6.3MHz,and a mean bandwidth of 95%.The lateral and axial resolutions of the entire system are 110?m and 800?m,respectively,and the diameter of active imaging region is larger than 50 mm.We applied the system to monitor cerebral hemorrhage inside the mouse brain and in vivo functional imaging of human finger joints.We successfully captured the bleeding spots induced by cerebral hemorrhage and obtained the bleeding information in different depths,which shows the potential of this technique in the study of clinical cerebral hemorrhage.Through human finger joint imaging,we successfully recovered both morphology and oxygen saturation of the blood vessels in the human finger joints,which shows a great potential for early diagnosis of arthritis using multiwavelength based photoacoustic tomographic system.Based on current studies,the development of this array-based photoacoustic tomographic system provides a new solution for various diseases in clinic.