Research On Magnetic Resonance Ther Mometry Based On Phase Difference Compensation Model

Tumors have become one of the major causes of endangering human health,and research on the treatment of tumors has become a top priority.Hyperthermia focused ultrasound-based hyperthermia has become the most important treatment for cancer with its non-toxic and non-invasive advantages.The key to hyperthermia is to grasp the location of the lesion area and the heating temperature in real time to avoid damage to normal tissue cells and carbonized tumor cells.Magnetic resonance imaging can not only tissue structure,but also extracted from the image of the hidden temperature information to achieve green temperature measurement.Therefore,magnetic resonance guided highintensity focused ultrasound hyperthermia has become one of the hot topics in the research.In this paper,based on the analysis of the existing temperature measurement principle,this paper makes an in-depth study from the aspects of improving the temperature measurement speed and ensuring the temperature measurement effect.Aiming at the shortcomings and deficiencies of existing temperature measurement principle,a temperature measurement model of magnetic resonance based on curve fitting phase difference compensation is proposed.Based on the principle of temperature measurement based on Proton Resonance Frequency(PRF),the external factors such as hyperthermia environment,temperature measurement sequence,magnetic field drift and inhomogeneity are incorporated into the new temperature measurement model.Through the dynamic phase difference processing,the phase mutation caused by the motion is greatly reduced,and the phase difference compensation calculated and calculated by the curve fitting is deduced and programmed,and the phase difference correction amount is calculated by combining with the reference phase.Improve the temperature measurement sequence,use the bipolar multi-echo GRE sequence to further improve the time utilization of temperature measurement.The GRAPPA under-sampling reconstruction algorithm is deduced.Under the precondition of ensuring peak-to-noise ratio(PSNR)of the image,the data acquisition and reconstruction are accelerated.In-depth study of the noise characteristics of reconstructed images,using non-local average algorithm for noise reduction processing of image data implied by the phase difference.Using the phase difference correction obtained before the phase difference correction to calculate the final temperature,magnetic resonance temperature measurement.Produce the experimental body,design the test program,and verify the temperature measurement model proposed in this paper.Experimental results show that undersampling reconstruction and non-local averaging algorithm based on GRAPPA algorithm can obtain high SNR images.The temperature measurement model in this paper uses the bipolar multi-echo GRE sequence and the conventional gradient echo sequence to perform temperature measurement experiments on the flesh and ex vivo pork.The absolute maximum temperature deviations are 1.07 ? and 1.15 ? respectively,that speed up the temperature measurement of magnetic resonance guided high intensity focused ultrasound hyperthermia has important significance,under ensuring the temperature measurement results premise.