Illustration: (charts) Centers for Disease Control and Prevention; (cells) National Cancer Institute
UCLA researchers have discovered a noninvasive method to measure vascular compliance, or how stiff an artery is, in the human brain, a finding that may have ramifications for preventing stroke and making the early diagnoses of Alzheimer’s disease. Using a new magnetic resonance imaging (MRI) technique, the UCLA team measured the volume of cerebral arteries twice, using a technique called arterial spin labeling, which can magnetically “label” the blood in arteries without the use of an external agent.
The team measured once at the systolic phase of the cardiac cycle, when the heart was pumping the blood into the brain, and again at the diastolic phase, when the heart was relaxing. The team found that the stiffer the arteries were, the smaller the change in the arterial blood volume between the two cardiac phases, because stiff arteries are not as able as elastic arteries to change shape or comply with the blood-pressure changes. “Vascular compliance is a useful marker for a number of cardiovascular diseases, such as hypertension and diabetes,” says Danny J.J. Wang, PhD, associate professor of neurology and researcher in the Ahmanson-Lovelace Brain Mapping Center at UCLA. “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. However, to date, few methods are available to assess that role.”
The UCLA team compared stiff ness measurements in young and elderly patients and found that arterial stiff ness is significantly increased in elderly patients. This finding is consistent with the theory that aging is associated with stiffening of the arteries. The team also found that increased arterial stiff ness is associated with reduced cerebral blood flow, suggesting stiff arteries impair the blood supply to the brain. Additionally, the researchers found artery stiff ness is correlated with the stiff ness of the largest artery of the human body, the aorta.
“We hope our technique can provide an early marker for a number of socioeconomically important diseases like Alzheimer’s,” says Lirong Yan, PhD, assistant researcher in the UCLA Department of Neurology. “A number of studies suggest that vascular dysfunctions, including arterial stiffening, are associated with the development of Alzheimer’s. The development of early bio- or imaging markers for Alzheimer’s is of great importance for slowing disease progression. Hardened arteries due to the accumulation of plaques on the vessel walls also is linked to cerebrovascular disorders such as stroke.”
“Assessing Intracranial Vascular Compliance Using Dynamic Arterial Spin Labeling,” NeuroImage, September 10, 2015