Research On Excitation Driver For Magnetic Resonance Elastography Of Liver

Elasticity of human tissues vary over a wide range, and may change drastically in the presence of disease, such as liver fibrosis and tumors. Palpation is an important way to assess tissue elastic properties of various organs in clinical practice. Assessing tissue elasticity in an non-invasive and quantitative way will be very valuable in the early diagnosis of diseases like cancer. Magnetic resonance elastography has been proposed for this purpose, but the patant barriers together with the limited support from MRI equipment manufacturers make the application of this technology inaccessible in China. In light of these issues, we proposes to build an MRE system platform that comprises of three parts:the MRE driver with its design clear of infringing the existing patents.The excitation driver is the key to magnetic resonance elastography (MRE) which requires an excitation driver with high-intensity synchronized shearwave and good magnetic compatibility. In this thesis, we design a pneumatic driver with audio speaker as its excitation source. By using photoelectric conversion module to extract trigger signals from the MRI sequence, the pneumatic driver will provide high-precision shear wave synchronized with the MRE sequence for the following experiments. In view of the driver transmits the vibration by air whose compressibility can lead to the delay of the vibration, this paper will apply the ultrasonic method to conduct a study on the feasibility of the pneumatic driver. Experiments show that the audio speaker can meet the design requirements of pneumatic driver.Based on the MRE principle, this thesis basically completed the study of several key technologies in the MRE, including a) designing and realizing a pneumatic driver for liver examination, thus setting up a MRE platform synchronized with its sequence; b) exploring the links between acquisition parameters and image quality and optimizing acquisition parameters, based on Siemens 3.0 T MRI system and the improved MRE sequence from GRE; c) designing a simple program for elasticity reconstruction by applying Matlab GUI, which, after a brief processing of phase image, will conduct elastic algorithm reconstruction whose results prove that the pneumatic driver can carry out MRE effectively, laying the foundation for the study of sequence and elastic algorithm in the future.