Advanced 7 Tesla imaging of the knee for root cause of Osteoarthritis

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ABSTRACT: The recent FDA approval of 7T for clinical imaging of the knee, opens the possibility that this ultrahigh field MRI platform will become a more prominent tool in biomedical research and patient management. Musculoskeletal (MSK) research and diagnostic imaging have been traditionally performed at magnetic fields of 1.5 and 3T. While there is increasing availability of ultrahigh field (UHF) 7T instruments and FDA approval of 7T clinical use in the head and knee, only a fraction of the system’s true capability is being exploited. First, approval has only been given for operation in a single transmit mode configuration. As such, clinicians cannot take advantage of the available parallel transmit (pTx) functionality to integrate state-of-the-art solutions for tackling B1+ homogeneity and local SAR management. Even if available, the RF coils and optimization routines to use the pTx functionality do not exist. Second, traditional diagnostic imaging methods for evaluating the knee do not fully exploit the array of morphologic, compositional, and functional data available when performing MRI at UHF. Both the traditional and novel imaging approaches alike benefit from the increased signal-to-noise ratio at 7T. The increased sensitivity can be exploited to provide higher resolution images that are known to have a real and significant impact on diagnostic accuracy in the knee. Furthermore, certain methods are simply too compromised at lower field strengths to be obtained as part of routine imaging at 3T and below including techniques like quantitative sodium imaging and perfusion as measured through arterial spin labeling. In this proposal we focus on the engineering, methodological and protocol developments to realize the full potential of 7T knee imaging and provide a critical translational study focusing on the utility of the methods to impact clinical care. This work will be accomplished by completing four specific aims. Aim 1 will focus on the development, integration, and optimization of a pTx RF coil coil using ultrahigh dielectric constant (uHDC) material and RF management strategies to provide high-resolution morphological knee imaging methods including zero echo time imaging. Aim 2 will implement and optimizequantitative compositional and functional methods for evaluating the knee joint at 7T including T1rho andarterial spin labeling (ASL) perfusion methods. Aim 3 will involve the development and optimization of a sodium (23Na) knee coil using uHDC material and strategies for accurate quantification of 23Na concentration in the articular cartilage of the knee. Finally, the translational Aim 4, will involve a pilot study to explore the ability of the developed technologies and methods to impact patientcare. The technical developments in this proposal will advance knee imaging at 7T and likely accelerate its clinical adoption. The results of the pilot study are expected to have an immediate and important impact,by forming the basis of future longitudinal prospective studies evaluating the effects of medical treatmentson clinical outcome.