Research Of Improved Positioning Methods Based On MR Images In The MR-guided Phifu System

Magnetic Resonance(namely MR)guided Phased High Intensity Focused Ultrasound(namely pHIFU)system is a new non-invasive cancer treatment technology which combines both the advantage of p HFU and MR technology and also has accurate guidance mechanism and real-time temperature monitoring with help of MR.The paper on the basis of the pHIFU system of Biomedical Instrument Institute in school of Med X Shang Hai Jiao Tong university,introduces my research on positioning methods especially its improving based on MR images in the MR-guided pHIFU system.We always take MR images of the focus tissues as to make the final treatment plan and both pHIFU and MR system have their own coordinate system.We need to build the connecting transfer relationship between these two coordinate systems if aiming at achieving positioning of the ultrasound probe under MR.At the same time,this paper will discuss two ways to improve positioning methods about building the connecting transfer relationship between these two coordinate systems: First,if taking the probe as a media to guide the positioning,specific work will reduce calculating errors including improved design plans of the markers on the probe,diverse identification methods of markers and the redundant design of markers.As for the better design of positioning markers,we improve it from notch markers around the probe to pillar markers above the probe which can offer a more clear MR image of the focused issues;As for the picking up of positioning markers on MR image,we improve it from manual operation to auto identification;As for the redundant design for positioning information,it has been proved that effective full use of redundant information from more than four markers through some filtering algorithm can improve the accuracy of positioning obviously,compared with full use of all the redundant information directly or selecting four positioning markers randomly;Second,if taking the thermometric data from MR as a media to guide the positioning,another transfer matrix can be built between the ultrasound coordinate and the MR coordinate to calibrate outcomes of the primary location.