State-of-the-Art Ultra-High-Field MRI for Crossing Scales in Basic Neuroscience

Magnetic resonance imaging (MRI) is a well-known medical imaging technology that allows safe scanning of the human body. For this reason it is well used by hospitals to help diagnose disease. It is also a valuable technology for studying the healthy human, to better understand normal anatomy and function of the body's organs. For the best image resolution and quality it is helpful to use a magnetic field strength that is as high as possible. Over recent years, research MRI scanners have been produced that are between two and five times stronger than the scanners used in hospitals. The University of Oxford installed one of these 'high-field' scanners in 2011 and has used it to study the healthy human brain. Exquisite spatial detail and functional information can be obtained, but there are parts of the brain that cannot be imaged well, due to distortions in the way the images are acquired. In this grant we seek to add newly developed technologies to our high-field scanner that substantially resolve these distortions so that information from all parts of the brain can be obtained.

In particular, with the proposed upgrade, we will be able to obtain good imaging data from the temporal lobes of the brain (involved in functions like memory, visual and sound processing, and language), the brain stem (involved in basic functions such as breathing, heart rate and the perception of pain), and the cerebellum (involved in movement, posture and balance). We can also examine the chemistry of the brain using magnetic resonance spectroscopy, that allow measurements to be made of the principal chemicals involved in brain processes and internal communication.

The University of Oxford acquired a 7 tesla MRI large-bore scanner in 2011 and has been using it substantially for basic neuroscience research, alongside a small component of clinical neuroscience research and some basic and clinical cardiac physiology research. The technology supplied with the original scanner is now obsolete and has been superseded by improved technology that allows more of the potential of 7T to be realized. In particular, there have been significant advances since the purchase of the scanner in radio-frequency transmit-chain technology (using transmit arrays to improve the homogeneity of the MRI excitation field, giving improved signal and more uniform image contrast) and fast imaging acquisition and reconstruction techniques (enabling a huge improvement in acquisition and image reconstruction speed). We therefore seek to upgrade the scanner to modern capabilities that include a fully-implemented parallel transmit capability, high-performance image reconstruction hardware and software, fully-integrated 3rd-order static field compensation capability, and a new operating system to run these new technologies.

This will allow high-quality imaging of parts of the brain from which we have hitherto been unable to obtain good data. In particular, the temporal and frontal lobes, brain stem and cerebellum will benefit significantly. We will also use the improved excitation and static field homogeneity to deploy spectroscopic imaging, to allow neuro-metabolite and neurotransmitter levels to be measured.

Examples of new questions that can be addressed include dissociation of hippocampal subfields via their functional and cytoarchitectural features, visual, auditory and language processing, cognitive decision making, the neuronal bases of pain perception and respiratory control in the brainstem, and the role of gamma-aminobutyric acid (GABA) in learning, memory and perception using magnetic resonance spectroscopic imaging.