7T RESEARCH APPLICATIONS
What We Do
MRI performs very well in measuring anatomical detail due to excellent image contrast between individual soft tissue types (e.g. water vs. fat, normal vs. cancerous). A voxel size of 0.1x0.1x0.5 mm in a living subject is easily achievable through careful experimental design and moderately long acquisition times, while a 50 micron isotropic resolution is possible with ex vivo specimens and longer acquisition times.
Detection of microstructural information
Beyond standard morphological scans, MRI also has the ability to measure the overall effect of structures much smaller than the resolution of the image. For example, diffusion tensor imaging (DTI) measures the amplitude of the diffusion of water, which allow us to infer the nature of microstructure that impedes the diffusion (e.g. neuronal axons).
Imaging of Biological function
Magnetic resonance spectroscopy (MRS) can be used to study metabolic processes through measurement of in vivo metabolite concentrations: it is possible to detect high-energy phosphates and hydrogen-based metabolites in brain, heart, muscle and tumour. Vascular parameters such as blood flow, vessel permeability and tissue perfusion can also be investigated, most commonly through rapid monitoring of signal enhancement while an endogenous or exogenous contrast agent passes through the organ of interest. Functional MRI (fMRI) is also possible, where MRI signal changes in the nervous system reflect increases in local blood flow, which relate to local neurological activity.
Image of rat brain implanted with retinal epithelial cells: labeled (red arrows) and unlabeled (blue arrows)
Molecular imaging, aims to noninvasively detect events on the cellular and subcellular level. This approach typically involves attaching a payload of MRI-visible contrast agent to a cell or nanoparticle that would otherwise be undetectable under MRI. In this way, therapeutic agents such as drugs, lentiviral vectors, and stem cells can be labeled in order to monitor the distribution and pharmacokinetics of the agent. MRI provides the advantage of acquiring images that elucidate both the molecular events and the anatomy simultaneously with the same instrument.
H spectrum acquired in rat hippocampus
Dynamic contrast-enhanced MRI of orthotopic mouse model of pancreatic cancer.
50 micron isotropic resolution of fixed mouse brain specimen
Quantitative density maps of water-based tissue (left) and fat (right) in a living mouse
Diffusion anisotropy map of ex vivo rat spinal cord (left) compared to myelin basic protein histology (right)