Research Of Thermal Analysis,treatment Strategy And Thermometry Based On MRpHIFU Fast Scanning Method

MRpHIFU system combines MR Thermometry and HIFU noninvasive treatment,which has special advantages in the clinical treatment.The purpose of this paper is to investigate the fast scan method and MR Thermometry.This article introduces three methods of MR Thermometry and their principles,advantages,disadvantages and the applicable environment as well.The method based on chemical shift of the proton resonance frequency and phase map subtraction is the most suitable for MRpHIFU system.In this paper,the relationship between temperature and thickness both in the coronal and sagittal plane is studied,and we analyze and make a reasonable explanation on the experimental results.According to the clinical requirements,we believe 3mm is the appropriate thickness value.To solve the problem that the fast scanning method cannot form a similar ablation shape for irregular areas or areas with details,we propose an unequal sonication duration method.To be more detailed,the sonication duration of the focus represent the detailed point is different from the focus represent the non-detailed point.We design two plans,one is applied the method,the other is not.Two plans are compared by heating the same target and thermal dose is set to control the treatment process.The ablation results are evaluated by the total treating time,the target tissue ablation ratio,nontarget tissue ablation ratio and the match of ablation shape with the target shape.The simulation results show that this method is effective.We also analyze the effect of the scan path,the time scale,the single sonication duration and focus ultrasonic intensity on the ablation result.We simulate the application of this method in the target with different details and give a reasonable explanation how the method works.To implement the ex-vivo experiments,we develop the control software of HIFU device.Key features include parameters setting,treatment process control,display of treatment information and software error information track.We use this software to implement ex-vivo experiments.The experimental results show that our method is effective.