Longitudinal alterations in brain perfusion and vascular reactivity in the zQ175DN mouse model of Huntington's disease.

Background: Huntington's disease (HD) is marked by a CAG-repeat expansion in the huntingtin gene that causes neuronal dysfunction and loss, affecting mainly the striatum and the cortex. Alterations in the neurovascular coupling system have been shown to lead to dysregulated energy supply to brain regions in several neurological diseases, including HD, which could potentially trigger the process of neurodegeneration. In particular, it has been observed in cross-sectional human HD studies that vascular alterations are associated to impaired cerebral blood flow (CBF).

Resting-state fMRI reveals longitudinal alterations in brain network connectivity in the zQ175DN mouse model of Huntington's disease.

Huntington's disease is an autosomal, dominantly inherited neurodegenerative disease caused by an expansion of the CAG repeats in exon 1 of the huntingtin gene. Neuronal degeneration and dysfunction that precedes regional atrophy result in the impairment of striatal and cortical circuits that affect the brain's large-scale network functionality. However, the evolution of these disease-driven, large-scale connectivity alterations is still poorly understood.

Composite pulses for RF phase encoded MRI: A simulation study.

Background: In B encoded MRI, a realistic non-linear phase RF encoding coil will generate an inhomogeneous B field that leads to spatially dependent flip angles. The non-linearity of the B phase gradient can be compensated for in the reconstruction, but B inhomogeneity remains a problem. The effect of B inhomogeneity on tip angles for conventional, B encoded MRI, may be minimized using composite pulses.

Least squares reconstruction of non-linear RF phase encoded MR data.

Purpose: The numerical feasibility of reconstructing MRI signals generated by RF coils that produce B1 fields with a non-linearly varying spatial phase is explored.

Theory: A global linear spatial phase variation of B1 is difficult to produce from current confined to RF coils. Here we use regularized least squares inversion, in place of the usual Fourier transform, to reconstruct signals generated in B1 fields with non-linear phase variation.