Arterial Spin Labelling: MRI reveals brain artery stiffness

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  • Published: Oct 1, 2015
  • Author: David Bradley
  • Channels: MRI Spectroscopy
thumbnail image: Arterial Spin Labelling: MRI reveals brain artery stiffness

Systolic to diastolic

Assessing intracranial vascular compliance using dynamic arterial spin labeling

The stiffness of arteries in the brain, vascular compliance, is important to the risk of cerebral stroke and dementia. Now, a team at the University of California Los Angeles have extended the functional MRI technique of Arterial Spin Labelling to give medicine a non-invasive method for assessing vascular compliance, which could have implications for predicting and even preventing those debilitating and potentially lethal conditions.

ASL can magnetically label without addition of a putatively toxic agent the blood carried in brain arteries and with two sets of measurements taken during the systolic phase of the cardiac cycle, when the heart is pumping blood into the brain and again in the diastolic phase, when the heart relaxes back down. Senior author of the study published in the journal NeuroImage, Danny Wang explains that the team found that stiffer, less compliant arteries, display the smaller changes in the volume of the arterial blood between systolic and diastolic phases.

"Vascular compliance is a useful marker for a number of cardiovascular diseases, such as hypertension and diabetes," Wang explains. He adds that, "Growing evidence suggests intracranial vascular pathology also may be associated with the origin and progression of cerebrovascular disorders and neurodegenerative diseases, such as Alzheimer’s disease. This novel technique now gives us a relatively straightforward way to assess vascular compliance without surgery.

Vascular compliance

The UCLA researchers compared vascular compliance in young and elderly patients, and found that, perhaps obviously, that brain arteries are much stiffer in older patients than the young. Hardening of the arteries is considered an almost inevitable consequence of the aging process. Moreover, stiffening of the arteries, is associated with reduced blood flow to the brain. The team was also able to confirm that a lack of vascular compliance in brain arteries correlated with the degree of stiffness in the largest artery of the human body, the aorta. This finding perhaps suggests that measuring aortal compliance would provide a proxy result for cerebral arterial stiffness. However, Yan told us that, "We want to stress that stiffening of the aorta and cerebral arteries may be caused by different mechanisms, so it is important to directly measure the arterial stiffness inside the brain."

Mark my words

"We hope our technique can provide an early marker for a number of socioeconomically important diseases like Alzheimer’s, adds first author of the study Lirong Yan, an assistant researcher in Neurology. "A number of studies suggest that vascular dysfunctions, including arterial stiffening, are associated with the development of Alzheimer's," she adds. The development of early biomarkers or imaging markers for Alzheimer's is of great importance for early diagnosis and putatively slowing or even halting disease progression. Hardening of the arteries due to the accumulation of fatty plaques on the interior of the blood vessel wall also is linked to cerebrovascular disorders such as stroke. "We hope our technique may provide an early marker for the prevention of stroke," Yan adds. The research was funded by the US National Institutes of Health and the California Department of Public Health.

"Our next step is to further improve our technique and evaluate its clinical utility," Yan told SpectroscopyNOW. "Our final goal is to evaluate intracranial vascular compliance as a useful marker in cerebrovascular diseases using our proposed non-invasive VC technique."

Related Links

Neuroimage 2016, 124A, 433-441: "Assessing intracranial vascular compliance using dynamic arterial spin labeling"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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