Research On Multi-Mode Medical Imaging System(Algorithm And Software)

Ultrasound imaging system is widely utilized in modern medical diagnosis.Due to its properties of easy to use and accuracy in imaging,the system is playing an important role in medical imaging diagnostic field.Recently,photoacousitic imaging is proposed as a new imaging method.With a short pulse of laser delivered into biological tissues,some of the energy will be absorbed,leading to transient thermoelastic expansion and thus wideband ultrasound emission.The generated ultrasound waves are detected by ultrasound transducers and then processed to generate the optical absorption image,which is closely related to the biological structures.Two methods are proposed in this paper to produce images from received ultrasound waves.As the most traditional and simplest algorithm,Delay and Sum(DAS)is introduced with some effective methods such as dynamic focusing,apodization and dynamic aperture.With DAS,satisfactory image quality is achieved in photoacoustic imaging,while DAS is not so suitable for ultrasound imaging.In order to improve the ultrasound imaging quality,a kind of synthetic aperture(SA)imaging method is proposed in this paper.The transducer array is divided into several emitting and receiving units.Each unit transmits ultrasound one by one and then the echo signals are received by the receiving units to construct the corresponding region.Compared with DAS,higher resolution and image contrast is achieved.However,SA imaging is much more complex in computation,which is 6 times more complex than DAS in this paper.Focused on the computation complexity,a real-time imaging system,based on the FPGA,is proposed in this paper.The system consists of Xilinx Kintex7 series FPGA,and is backward compatible with Artix7 series.With analysis of DAS and SA,the whole reconstruction procedure can be divided into one simple reconstruction procedure on small region,which then repeats several times to make up the full image.The simple procedure is replanted into FPGA as a hardware module to accelerate the whole one.Meanwhile,an embedded system based on Microblaze is implemented in FPGA,taking the accelerating module as a peripheral and control it through the data bus.The whole rebuilding procedure is controlled by Microblaze according to the given algorithm.Finally,ultrasound and photoacoustic imaging reconstruction is verified on the real-time imaging system with several groups of simulating and real data.The rebuilding result is compared with theoretical result from Matlab to confirm the accuracy of the real-time system.The average elapsed time of image reconstruction is also given as proof of the real-time property of the system.