Multi-element ultrasound transducer positioning method in MR-guided phased HIFU system

Phased High Intensity Focused Ultrasound (pHIFU) is an efficacious tool toward treating a variety of tumors, where procedure must be performed under Magnetic Resonance (MR) guidance. Because the MR system and the phased High Intensity Focused Ultrasound (pHIFU) system have separated coordinate systems independently, the registration of two coordinate system has to be done. To find the correct coordinate transformation matrix will affect the accuracy of the following treatment. A new method is proposed in this study to calculate the transformation matrix using specially designed markers and corresponding algorithms. Series of markers (>4) on the ultrasound probe are introduced which can be identified in the MR images. As only four markers which are not on the same plane are needed theoretically, algorithms are proposed to handle the problem of information redundancy and also further improve the accuracy of the calculation. The experiments using the proposed methods showed better results than those without using the redundant information.