Improved Diagnostic MRI around Metallic Implants

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PROJECT SUMMARY This project will develop new technology for high-resolution soft-tissue MRI immediately adjacent to orthopaedic metallic implants, an area that is “invisible” to current imaging techniques. We will leverage a novel high- performance 0.55 Tesla MRI platform and will develop new software and tools that are optimized for this platform and application. Finally, we evaluate the new metal MRI technology in two patient cohorts where it can immediately impact patient management: hip replacement and spinal fixation. Rationale: Orthopaedic metal implants are used extensively to treat late-stage osteoarthritis (total joint replacements), degenerative disc disease (spinal fixations), and fracture stabilization following trauma or bone resection. These implants fail in 10%-40% of cases, and accurate non-invasive imaging with soft-tissue contrast is essential for the evaluation of the underlying cause of hardware failure, and in surgical decision making and planning. At present, there is a major unmet need for high quality soft tissue imaging immediately adjacent to the metal surface to assess, for example, adverse local tissue response or nerve root impingement. State-of-the-art multi-spectral imaging (MSI) led to major improvements ~10 years ago, and the technology has plateaued. Innovation: We leverage a novel 0.55T MRI system that will soon be commercially available, which alone promises reduced image artifacts, because it provides much stronger imaging gradients relative to the susceptibility-induced gradients and field shifts, higher-bandwidth RF pulses, uniform RF transmission, and new opportunities for improved encoding and reconstruction. We also propose reimagined MSI pulse sequences to offer further improvements in signal-to- noise ratio, encoding time, and artifact. Approach: Our specific aims are: 1) to adapt standard metal MSI approaches for the 0.55T MRI platform to primarily assess the improvement of the 0.55T system alone due to reduced off-resonance; 2) to redesign improved metal MSI approaches that leverage the gradient-to-B0 and RF performance of the 0.55T MRI platform to compensate for lost SNR efficiency, while improving spatial resolution and artifact suppression and offering fat/water separation; and 3) to compare 0.55T MRI and 3T MRI protocols in patients with hip and spine implants, both to assess the improvement from the system alone and from redesigned MSI sequences. Broader Impact: This project aims to demonstrate improved capability to image closer to implant surfaces than what is possible at conventional 1.5T and 3T field strengths, and the impact in the context of post-surgical evaluation of hip-replacements and spinal fixations. This will broadly benefit the use of MRI in patients with metal, including orthopedic and non-orthopedic implants.