Development of Novel Radiofrequency coils for Hyperpolarized 13C Magnetic Resonance Imaging

Magnetic resonance imaging and spectroscopy (MRI and MRS) are routinely used to monitor cardiac structure, function and energetics, at repeated times and progressive stages of disease. MRS is ideally suited to the study of metabolism due to the extensive range of compounds it can detect, using nuclei such as carbon (13C) and phosphorus (31P). However, the application of MRS in the measurement of metabolism is limited by an intrinsically low sensitivity. In standard MRI, the high proton concentration in water (110M) compensates for this low sensitivity, but this is not the case for low concentration and limited natural abundance nuclei, such as 13C.

The use of a novel technique called hyperpolarized magnetic resonance (MR) can increase the in vivo sensitivity of MRS to detect 13C-enriched tracers by more than 10,000-fold. In this way, hyperpolarized MR enables unprecedented visualization of normal and abnormal metabolism, allowing real-time measurement of instantaneous substrate uptake and enzymatic transformation in vivo. The University of Oxford was the first academic institution in the world to develop and use hyperpolarized MR to measure in vivo metabolism in rodent models of cardiac disease. For example, alterations in the flux of hyperpolarized [1-13C]pyruvate through myocardial pyruvate dehydrogenase, assessed by the production of 13C-bicarbonate, have been shown to correlate with disease severity in an in vivo model of diabetic heart disease. This preclinical work has also been translated into clinical studies and we have recently acquired the first dynamic 13C MRS data from the human heart.

Technical developments in the field of hyperpolarized MR have expanded the technology to allow the generation of metabolic images from the measured signals, which allows the identification the spatial inhomogeneities in the metabolic processes that occur in the diseased heart. One of the greatest challenges in the acquisition of such metabolic images in the design of suitable radio-frequency (RF) coils to sensitively and homogeneously acquire the data. The aim of this project is, in collaboration with Pulseteq Ltd, to develop suitable RF coils for use in both rodent and human hyperpolarized MR imaging studies of the heart. The goal would be to develop appropriate transmit coils to ensure the homogeneous delivery of RF energy over the chest and sensitive receive coils to ensure optimal reception of signals from the rapidly beating heart.

Pulseteq Ltd are a well-established supplier of RF coils for both pre-clinical and clinical magnetic resonance applications. They have a wealth of experience in the design and manufacture of coils suitable for both MR imaging and multi-nuclear (i.e. non-proton) MR spectroscopy applications. They also have experience in the integration of such coils with MRI systems made by all the main manufacturers (e.g. Siemens, Philips, GE Healthcare, Agilent, Bruker). They are therefore well placed to provide suitable guidance and input into the design of coils to meet the unique challenges raised by the application of hyperpolarized MR imaging in the rodent and human heart. The unique requirements of imaging the heart will also provide a solid grounding in cardiac physiology (especially metabolism and perfusion) at both the pre-clinical and clinical levels.