Technology to Realize the Full Potential of UHF MRI (Supplement)

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ABSTRACT The pathophysiology of Alzheimer’s disease involves a plethora of structural and functional abnormalities of multiple brain structures and related circuits, including neurodegeneration of the hippocampus, a critical hub responsible for memory and executive function. While progress has been made in documenting the hallmarks of the disease’s pathophysiology, the sequence of events that lead to hippocampus atrophy, loss of memory, and loss of executive function with disease progression remain insufficiently characterized due to the lack of in- vivo markers sensitive to the process of neurodegeneration. To address this unmet need our goal is to establish rotating frame MRI relaxation mapping based on Frequency Swept (FS) pulses, adiabatic T1ρ and RAFFn, as novel, non-invasive biomarkers of neurodegeneration and demyelination. This goal is supported by the fact that the rotation frame relaxation parameters that will be investigated, allow us to probe slow motional components of the spectral density function unlike standard free-precession MRI metrics. This slow motional regime is most relevant to characterize multiple biological processes at the molecular and cellular levels in tissue as we and others have demonstrated in other pathologies. As such, our overarching hypothesis is that adiabatic T1ρ will serve as an early marker of neural degeneration of the hippocampus, while RAFFn will be able to detect demyelination, and both markers will correlate with neural network dysfunction at different stages of Alzheimer’s disease, as detected by resting state functional MRI. Three specific aims will be pursued to investigate this hypothesis: 1) optimization of parameters for obtaining high-resolution mapping of rotating frame MRI metrics from hippocampal subregions and layers, 2) identify rotating frame MRI markers of brain tissue abnormalities in a rat model of Alzheimer’s disease as compared to age-matched wile-type rats and 3) uncover the Alzheimer’s disease pathophysiological substrates that best correlate with the novel rotating frame MRI biomarkers, as revealed by resting-state fMRI, histology and spatial genomics. Accomplishing these aims will establish the potential of rotating frame MRI markers as novel biomarkers of neurodegeneration in Alzheimer’s disease by extending technical developments proposed in the parent grant. Spatial genomic analysis will allow us to identify the molecular basis of the MRI outcomes, thus providing an invaluable validation needed for optimizing therapies, monitoring treatment response and supporting subsequent applications in humans.