Iterative delay correction improves breath-hold cerebrovascular reactivity mapping in clinical populations

Area of Science:

• Neuroimaging
• Vascular Neurology
• Medical Physics

Background:

• Cerebrovascular reactivity (CVR) measures cerebral blood vessel response to stimuli, crucial for assessing cerebrovascular health.
• Accurate CVR estimation necessitates accounting for stimulus arrival and arteriolar response times, which vary spatially and across populations.
• Current methods for estimating these temporal offsets can significantly impact CVR results.

Purpose of the Study:

• To introduce and validate an iterative approach for automatically determining the optimal temporal search range for CVR estimation.
• To assess the impact of this iterative delay correction on CVR estimates in a cohort of stroke survivors.

Main Methods:

• Utilized breath-hold functional magnetic resonance imaging (fMRI) data from stroke survivors.
• Implemented an iterative algorithm that selectively expands the delay search range for voxels near the boundary of estimated delays.
• Applied the method to determine maximum shift for CVR calculation.

Main Results:

• The iterative approach significantly increased the number of voxels with statistically significant CVR among those initially at the boundary.
• Observed CVR polarity reversals in voxels with early estimated delays and amplified negative CVR in those with late estimated delays.
• Demonstrated the method's applicability and parameter tuning process using data from a patient with Moyamoya disease.

Conclusions:

• Iterative delay correction critically impacts CVR interpretation, especially in clinical populations like stroke survivors.
• This approach enhances CVR assessment by optimizing temporal offset calculations.
• The method shows broad applicability across different populations and acquisition protocols, with a need for careful parameter tuning.