Study Of Magnetic Resonance Thermometry Based On PRONY Model

The radiotherapy and chemotherapy of tumors cause unnecessary damage to body tissues. Hyperthermia therapy based on magnetic resonance thermometry is a noninvasive, no radiation, no toxic side effect and green method. Magnetic resonance thermometry exploits temperature changes of human tissue. This change will lead to the changes of some parameters of magnetic resonance to obtain temperature information. There are many temperature sensitive magnetic resonance parameters, such as water diffusion coefficient D, pin-lattice relaxation time T1, proton density and water proton resonance frequency. Among these parameters, proton resonance frequency(PRF) method is currently the most popular method due to good temperature sensitive, good linearity and organizational independence. The phase subtraction type of the PRF method is easily affected by the static magnetic field drift, motion-induced error and fat protons. This dissertation uses the oil-water separation type of the PRF method magnetic resonance imaging to measure human temperature.Firstly, the dissertation use a fat signal is not sensitive to temperature as internal reference using. Bipolar multi-echo SE-GRE sequence completes the K space data acquisition. In order to reduce the movement effects, the compressed sensing theory exploits under sampling K spatial data and reconstructs many images of temperature measurement. In order to improve the precision of frequency estimation, a non-local sparse model for image denoising is used which improves the signal-to-noise ratio of image. A nonlinear algorithm based on Prony model estimates the chemical shifts of fat and water. Calibration experiments show results of fitting absolute temperature and the chemical shifts of fat and water. This dissertation obtains the absolute temperature information of an object.Experiments of this method on temperature measurement obtain the absolute temperature image on the vitro porcine liver and the human different bodies. That verifies the effectiveness of magnetic resonance temperature method exploited the oilwater separation type of the PRF method.