Improved positioning methods based on MR images in the MR-guided PHIFU system

The positioning of the ultrasound system is the key problem when using the MR to guide the pHIFU(phased High Intensity Focused Ultrasound) system. This paper will discuss two methods to improve the transfer relationship between the ultrasound coordinate and the MR coordinate. First, if taking the probe as a media to guide the positioning, additional work need to reduce calculating errors including improved designs of the markers on the probe and the design of redundancy of markers. 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. In terms of experiment results, it´s proved that full use of redundant information from more than four markers can improve the accuracy of positioning obviously. And we will do further research to test the outcomes of another method.