Xin Yu1 and David Hike1
1Massachusetts General Hospital and Harvard Medical School, United States
Synopsis
There
are two ongoing challenges when specifying vascular function underlying vascular
cognitive impairment in patients. One
issue is the size of vessels that altered anatomy and function can be detected in
the brain. The other issue is the location of the affected vessels to be
detected, e.g. gray matter vs. white matter, or cortical vs. subcortical cerebral
vasculature. MR
Angiography(MRA) provides the key anatomical
vasculature measurement when studying cerebrovascular diseases or impaired
cerebral blood flow related to vascular dementia. Here, we will discuss the linkage
of high-resolution MRA with single-vessel fMRI to characterize vessel-specific oxygenation(BOLD),
cerebral volume, and flow changes.
Abstract
MR angiography can be used to map the penetrating vessels in
the cortex of animals with ultra-high resolution, e.g. in-plane resolution 50x50
µm. This method has been lately applied in a
multi-gradient echo sequence with a large flip angle but shorter TR to identify
micro-vessels with 20-70um diameter. By specifying the MR contrasts at different
echoes, the arterioles and venules can be easily identified through the whole
cortex. This MRA-based arteriole-venule (A-V) map can be used to guide the high-resolution
fMRI studies in both deep layer cortex and hippocampus. One critical insight of
MRA-based single-vessel fMRI is to identify the venule-specific BOLD signal vs.
arteriole-specific CBV signals of the brain with tasks or during rest. Furthermore,
the MRA-based A-V map can be compared with a phase-contrast MR-based flow
velocity map to measure the vessel-specific velocity changes coupled with
neuronal activation, e.g. functional CBF-velocity mapping. This unique advantage of the MRA-based single-vessel
mapping scheme shows a great potential to measure altered vascular function in
diseased stages. We will go over several potential clinical applications to
apply MRA-based single-vessel functional mapping. Also, we will go over the
ongoing challenges and perspectives to applying high field MR scanners to push
the high-resolution vascular anatomical and functional mapping limits. In the
end, we will highlight the pros and cons of the high resolution MRA-coupled vascular
functional mapping methods when compared with the emerging cutting-edge method,
e.g. functional ultrasounds.Acknowledgements
This work was supported by NIH grant RF1NS113278,
R01NS120594, R01MH111438, S10MH124733, R21NS121642, U19NS123717 and NSF grant 2123971.References
No reference found.