Using an open magnet system, we are developing methods for guiding interventional magnetic resonance imaging (IMRI) procedures including thermal ablation. Thermal ablation is minimally invasive and cost effective. Interventional MRI is different from diagnostic MRI, and in our paradigm, minimally invasive treatment of cancer tumors is performed entirely in the MR imager. MRI provides both guidance of the interventional device to the cancer tumor and monitoring the thermal treatment. This is a achieved by exploiting MRI's ability to: 1) generate contrast between tumors, normal tissues, interventional tools and thermal lesions and 2) obtain images at any angle (and dynamically adjusted, like ultrasound, via a localization device). Nonetheless, limitations exist in the current MRI techniques used for guidance, localization and treatment monitoring; unless overcome IMRI will not achieve it's vast potential in minimally invasive diagnostic and cancer treatment procedures. These limitations create a unique opportunity to develop and optimize advanced magnetic imaging pulse sequence techniques which will ultimately improve patient care through more effective IMRI capabilities. The research pursued in this project will create new imaging methods meeting the constraints of the IMRI environment by addressing four primary issues in which IMRI differs from diagnostic MRI (and these must be attained simultaneously): contrast: speed, motion insensitivity and therapy monitoring. In IMRI patient risk is related to time, and so we will create new rapid steady state free precession imaging methods with specific application for IMRI guidance. They will achieve better contrast between tissues and interventional devices than methods presently available for low field dynamic interventional applications. New radial K-space sampling methods which utilize information on the orientation of the interventional device will be designed and evaluated to improve the device tip accuracy and reduce sensitivity to motion artifacts better than 2DFT methods used commonly in IMRI. The most important anatomic locations for local control of primary and metastatic cancer are the liver, brain, kidney, pancreas, head/neck and musculoskeletal system. The research in this application will create customized IMRI methods for these anatomic locations and test them on rabbits (implanted with VX2 in the abdominal organs) and pigs. This project will provide the first systematic study in which low field IMRI techniques are designed by combining the advantages of both the MRI contrast mechanism and K-space sampling scheme together to achieve optimized IMRI methods for each anatomic location; they will offer greater performance than current 2DFT strategies used in virtually all IMRI guided procedures. Further, this project will improve emerging quantitative MR thermal mapping methods and allow attainment of accurate thermal monitoring of IMRI guided thermal cancer therapy. Based on our success to date, the second generation of IMRI guidance strategies will be created.
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