MR Guided Focused Ultrasound Surgery near Metal Implants

Stanford University, Stanford CA

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Abstract

DESCRIPTION (provided by applicant): This project aims to develop and validate magnetic resonance imaging (MRI) techniques to enable MR-guided focused ultrasound surgery (MRgFUS) treatment of subjects in the presence of implanted metal devices. Relevance: High-intensity focused ultrasound is one of the most promising new non-invasive ablation methods, and was recently clinically approved for the treatment of painful bone metastases. MRI offers excellent tissue contrast for planning treatments and for assessing the results of an ablation as well as for non- invasive real-time monitoring of the ablation using MR thermometry. Unfortunately, some patients with painful bone metastases treatments have previously had metallic implants inserted for stabilization of their bones, or have other devices such as a total hip replacement, which prohibits the use of MRI guidance due to severe image artifacts. Our group, together with others, has made substantial improvements to MRI near orthopedic implants such as spinal fusions and joint replacements. However, these 3D techniques are volumetric, slow, and inappropriate for interactive imaging applications such as MRgFUS. Approach: The proposed research seeks to overcome these limitations by developing a completely new class of rapid, interactive 2D MRI techniques with almost complete image artifact correction near metal. We will apply these specifically to MRgFUS in two specific aims: (1) to develop rapid, interactive T2 and T1 weighted scans that can be used for pre-treatment planning and for post-treatment evaluation using contrast enhancement, and (2) to develop MR thermometry techniques for real-time MRgFUS treatment monitoring in the presence of metal implants. We will validate the metal artifact correction in ex vivo animal and in vivo human studies, and verify appropriate imaging performance (contrast and SNR) in MRgFUS patients without metal who are being treated for periosteal ablations of painful bone cancers. Summary: We will develop rapid MRI approaches to image in the presence of metal with minimal artifacts, and tailor these to the interactive planning, real-time temperature monitoring, and post-treatment evaluation of MRgFUS procedures. Following our initial validation in MRgFUS subjects, this research will enable a larger clinical study to demonstrate efficacy of these methods for routine treatment of patients with metallic implants.