Development Of Low-noise Preamplifiers In MRI And Non-uniform Field Correction Algorithms For Magnetic Resonance Images

Magnetic Resonance Imaging(MRI)has gradually become an important tool in the field of medical image detection,and has also been fully applied in other fields.The good or bad of the MRI will cause a great impact in medical diagnosis,object characteristics analysis,and many other applications,committed to obtain good magnetic resonance imaging has been the focus of MRI detection research field.Low noise preamplifier as an important part of the magnetic resonance receiver system directly affects the quality of magnetic resonance images.First of all,this paper describes the relevant design theory of low noise preamplifier in the low-field MR system in detail,and then complete the simulation and design of low noise preamplifier in low-field MR system using Keysight's ADS simulation and design software,At the same time according to the simulation design results to complete the production of the low noise preamplifier actual objects and debugging work,at last the use of Keysight's VNA E5061B and NFA N8974A to complete the measurement of amplifier performance parameters and compared with the preamplifier in the same commercial MR system,measurement result shows that the gain of 30dB,and the noise figure of about 0.5dB in fact,the low noise preamplifier designed in this paper achieves a level comparable with the preamplifier performance of commercial MR systems and even better than that of some commercial products.Finally,the completed object will be used in the MRI system to complete the imaging experiment of water model,the imaging results are good,it is further verified that the performance of the low noise preamplifier designed in this paper is stable and reliable.In addition,aim to the intensity inhomogeneities caused by multichannel receiving coils,the inhomogeneities field correction algorithm in MRI is also studied in this paper.Firstly,two traditional correction algorithms based on filtering and nonparametric are introduced,then,an improved energy minimization method based on homomorphic filtering is used to correct the inhomogeneities of MRI,and the qualitative and quantitative analysis of the corrected image,compared with the results based on filtering and nonparametric calibration.The results show that the algorithm used in this paper can effectively correct the intensity inhomogeneities of the magnetic resonance image,with a higher homogeneity in the target area,significantly reduce background interference,with a higher degree of recognition,and the result is better than the other two algorithms.