First application of dynamic oxygen-17 magnetic resonance imaging at 7 Tesla in a patient with early subacute stroke.

Dynamic oxygen-17 (17O) magnetic resonance imaging (MRI) is an imaging method that enables a direct and non-invasive assessment of cerebral oxygen metabolism and thus potentially the distinction between viable and non-viable tissue employing a three-phase inhalation experiment. The purpose of this investigation was the first application of dynamic 17O MRI at 7 Tesla (T) in a patient with stroke. In this proof-of-concept experiment, dynamic 17O MRI was applied during 17O inhalation in a patient with early subacute stroke. The analysis of the relative 17O water (H217O) signal for the affected stroke region compared to the healthy contralateral side revealed no significant difference. However, the technical feasibility of 17O MRI has been demonstrated paving the way for future investigations in neurovascular diseases

Electrodynamics and radiofrequency antenna concepts for human magnetic resonance at 23.5 T (1 GHz) and beyond

Objective: This work investigates electrodynamic constraints, explores RF antenna concepts and examines the transmission fields (B 1 + ) and RF power deposition of dipole antenna arrays for 1H magnetic resonance of the human brain at 1 GHz (23.5 T). Materials and methods: Electromagnetic field (EMF) simulations are performed in phantoms with average tissue simulants for dipole antennae using discrete frequencies [300 MHz (7.0 T) to 3 GHz (70.0 T)]. To advance to a human setup EMF simulations are conducted in anatomical human voxel models of the human head using a 20-element dipole array operating at 1 GHz. Results: Our results demonstrate that transmission fields suitable for 1H MR of the human brain can be achieved at 1 GHz. An increase in transmit channel density around the human head helps to enhance B 1 + in the center of the brain. The calculated relative increase in specific absorption rate at 23.5 versus 7.0 T was below 1.4 (in-phase phase setting) and 2.7 (circular polarized phase setting) for the dipole antennae array. Conclusion: The benefits of multi-channel dipole antennae at higher frequencies render MR at 23.5 T feasible from an electrodynamic standpoint. This very preliminary finding opens the door on further explorations that might be catalyzed into a 20-T class human MR system

In vivo X-Nuclear MRS Imaging Methods for Quantitative Assessment of Neuroenergetic Biomarkers in Studying Brain Function and Aging

Brain relies on glucose and oxygen metabolisms to generate biochemical energy in the form of adenosine triphosphate (ATP) for supporting electrophysiological activities and neural signaling under resting or working state. Aging is associated with declined mitochondrial functionality and decreased cerebral energy metabolism, and thus, is a major risk factor in developing neurodegenerative diseases including Alzheimer’s disease (AD). However, there is an unmet need in the development of novel neuroimaging tools and sensitive biomarkers for detecting abnormal energy metabolism and impaired mitochondrial function, especially in an early stage of the neurodegenerative diseases. Recent advancements in developing multimodal high-field in vivo X-nuclear (e.g., 2H, 17O and 31P) MRS imaging techniques have shown promise for quantitative and noninvasive measurement of fundamental cerebral metabolic rates of glucose and oxygen consumption, ATP production as well as nicotinamide adenine dinucleotide (NAD) redox state in preclinical animal and human brains. These metabolic neuroimaging measurements could provide new insights and quantitative bioenergetic markers associated with aging processing and neurodegeneration and can therefore be employed to monitor disease progression and/or determine effectiveness of therapeutic intervention

A 16-Channel Receive Array Insert for Magnetic Resonance Imaging of the Breast at 7T

Breast cancer is the second leading cause of cancer death among females in the United States. Magnetic resonance imaging (MRI) has emerged as a powerful tool for detecting and evaluating the disease, with notable advantages over other modalities, and the advent of ultra-high field strength scanners promises even more potential. In comparison to standard clinical MRI field strengths (1.5, 3.0 tesla), breast MRI at 7T provides increased signal-to-noise ratio (SNR) and spectral resolution. These benefits, however, are accompanied by significant challenges in hardware design, limiting the availability of commercial radiofrequency coils for 7T. The primary objective of this work is to enable the study of breast cancer at 7T with the development of a 16-channel receive array coil. The use of array coils to receive is standard in clinical MRI, as it provides higher SNR over a field of view than a single coil. In this case, when combined with the increased sensitivity provided by the high field strength, this will enable the ability to acquire images with higher resolution than could be achieved at 3T or 1.5T in clinically standard scan times. This has the potential to improve the morphological characterization of tumors and their involvement in the surrounding tissues. This thesis discusses the design and construction of a 16-channel receive array insert, characterization of its performance as an array, and comparison of the achievable SNR to a transmit-receive quadrature volume coil. With the 16-channel receive array insert, the results demonstrate a 6.5 times improvement in mean SNR and the ability to accelerate up to a reduction factor of 9 with a mean g-factor of 1.3. Finally, we present initial in vivo images acquired with the array, demonstrating the utility of the array coil through higher resolution imaging than the current protocols at lower field strengths