Abstract
A noninvasive method of assessing cerebral arterial compliance (AC) is introduced in which arterial spin labeling (ASL) is used to measure changes in arterial blood volume (aBV) occurring within the cardiac cycle. Short inversion time pulsed ASL (PASL) was performed in healthy volunteers with inversion times ranging from 250 to 850 ms. A model of the arterial input function was used to obtain the cerebral aBV. Results indicate that aBV depends on the cardiac phase of the arteries in the imaging volume. Cerebral AC, estimated from aBV and brachial blood pressure measured noninvasively in systole and diastole, was assessed in the flow territories of the basal cerebral arteries originating from the circle of Willis: right and left middle cerebral arteries (RMCA and LMCA), right and left posterior cerebral arteries (RPCA and LPCA), and the anterior cerebral artery (ACA). Group average AC values calculated for the RMCA, LMCA, ACA, RPCA, and LPCA were 0.56%±0.2%, 0.50%±0.3%, 0.4%±0.2%, 1.1%±0.5%, and 1.1%±0.3% per mm Hg, respectively. The current experiment has shown the feasibility of measuring AC of cerebral arteries with short inversion time PASL.
Highlights
The classic definition of arterial compliance (AC) by Spencer and Denison[1] is a change in arterial blood volume resulting from a given change in arterial blood pressure (BP)
It has been shown that pulsatility arising from the cardiac cycle causes modulation of pulsed ASL (PASL) signal,[23,33] to our knowledge this is the first study exploiting this modulation of PASL signal to assess cerebrovascular AC
Here we robustly show that arterial blood volume (aBV) changes in line with the cardiac cycle (Figure 4), which is as expected based on elastic properties of the cerebral arteries[34] as well as on AC measured in arteries outside the brain.[32]
Summary
The classic definition of arterial compliance (AC) by Spencer and Denison[1] is a change in arterial blood volume (aBV) resulting from a given change in arterial blood pressure (BP). The compliance of arteries ensures that they are able to accommodate the pulsatile blood flow originating from the heart and average out these pulsations into continuous blood flow in the capillary bed of human tissue.[2] When AC decreases, that is arteries become stiffer, they lose the ability to smooth the pulsatile blood flow and as a consequence downstream arterioles and capillaries are exposed to higher BP fluctuations.[3] This increase in BP in the distal arterial bed in turn causes deterioration of vessel walls, which in the brain manifests as cerebral small-vessel disease (SVD).[3] The prevalence of SVD increases with aging and has been linked to cognitive decline in patients with dementia and Alzheimer’s disease.[4] patients with diabetes mellitus[3] and hypertension[5] have an increased risk at developing SVD.
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