Cerebrovascular Reactivity Assessment in Functional Imaging

Cerebrovascular reactivity (CVR) refers to the capacity of cerebral blood vessels to dilate or constrict in response to vasoactive stimuli, thereby maintaining stable brain perfusion. In functional imaging, CVR assessment has become central to understanding vascular health, neurovascular coupling and the interplay between haemodynamics and neural activity. Techniques to measure CVR most commonly exploit blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) during controlled hypercapnia, breath-hold tasks or end-tidal CO₂ forcing, as well as quantitative perfusion methods such as arterial spin labeling (ASL). Emerging approaches harness resting-state fluctuations in CO₂ or systemic low-frequency oscillations combined with advanced signal-processing and deep-learning algorithms to map vascular reserve without exogenous agents. Clinically, CVR mapping aids presurgical planning by identifying regions at risk of neurovascular uncoupling, informs prognosis in steno-occlusive disease and dementia, and refines interpretation of task-based and resting-state fMRI by accounting for vascular confounds. On a global scale, reliable CVR quantification underpins early detection of cerebrovascular pathology, guides therapeutic revascularisation and supports longitudinal studies of ageing and neurodegeneration.

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Cerebrovascular Reactivity Assessment in Functional Imaging publication trend

The graph below shows the total number of articles in cerebrovascular reactivity assessment in functional imaging across all publications each year (not limited to Nature Index journals).

Technical terms

Cerebrovascular Reactivity (CVR): The change in cerebral blood flow or BOLD signal in response to a vasoactive challenge, reflecting vascular reserve capacity.

Blood Oxygenation Level-Dependent (BOLD): An fMRI contrast mechanism sensitive to changes in deoxyhaemoglobin concentration, used to infer both neural and vascular activity.

Arterial Spin Labeling (ASL): A non-invasive MRI technique that labels inflowing blood magnetically to quantify cerebral blood flow.

Hypercapnia: A physiological state of elevated arterial CO₂, often induced for CVR measurement to provoke cerebrovascular dilation.

Breath-hold challenge: A simple method of increasing arterial CO₂ by voluntary breath-holding to elicit a vascular response measurable with BOLD fMRI.

Bolus Arrival Time (BAT): The interval between arterial labelling and peak perfusion in tissue, indicative of vascular transit delays.

Neurovascular coupling: The relationship between neuronal activity and the resultant vascular response that underlies functional imaging signals.

References

1. Deep-learning-enabled brain hemodynamic mapping using resting-state fMRI. npj Digital Medicine (2023).
2. A systematic review of the association between dementia risk factors and cerebrovascular reactivity. Neuroscience & Biobehavioral Reviews (2023).
3. Hemodynamic imaging parameters in brain metastases patients – Agreement between multi-delay ASL and hypercapnic BOLD. Cerebrovascular and Brain Metabolism Reviews (2023).