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Updated: Jul 24, 2025
MRI Mapping of Cerebrovascular Reactivity via Gas Inhalation Challenges
Published on: December 17, 2014
Examining temporal features of BOLD-based cerebrovascular reactivity in clinical populations
Kayley-Jasmin Marchena-Romero1,2, Xiang Ji2,3, Rosa Sommer2,3,4
1Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.
Insights
This study introduces new cerebrovascular reactivity (CVR) parameters to analyze temporal features during CO2 challenges. The transition rate from hypercapnia to normocapnia predicts CVR responses, offering insights into brain health.
Area of Science:
- Neuroimaging
- Vascular Biology
- Cognitive Neuroscience
Background:
- Altered cerebrovascular reactivity (CVR) is linked to various brain diseases.
- Characterizing temporal dynamics of CVR challenges is currently uncommon.
- There is a need for CVR parameters that capture individual temporal features.
Purpose of the Study:
- To develop novel CVR parameters that characterize individual temporal features of a CVR challenge.
- To investigate signal changes in blood oxygenation level dependent (BOLD) contrast images during CVR transition periods.
- To examine regional differences in CVR responses across specific brain regions.
Main Methods:
- Collected data from 54 adults with conditions like Alzheimer's disease, vascular cognitive impairment, or sleep apnea.
- Developed a model-free, non-parametric CVR metric using simulations for BOLD signal changes.
- Analyzed BOLD signal transitions during normocapnic and hypercapnic periods and the return to normocapnia.
Main Results:
- Found a linear association between temporal features of successive CO2 challenges.
- The transition rate from hypercapnia to normocapnia significantly correlated with the second CVR response across all regions.
- The hippocampus showed the highest association (R² = 0.57, p < 0.0125).
Conclusions:
- Demonstrated feasibility of examining individual responses during BOLD-based CVR experiments.
- Individual temporal features of CVR transition periods offer insights into between-subject differences.
- This approach can enhance understanding of CVR in various neurological conditions.
Background:
Conventional cerebrovascular reactivity (CVR) estimation has demonstrated that many brain diseases and/or conditions are associated with altered CVR. Despite the clinical potential of CVR, characterization of temporal features of a CVR challenge remains uncommon. This work is motivated by the need to develop CVR parameters that characterize individual temporal features of a CVR challenge.
Methods:
Data were collected from 54 adults and recruited based on these criteria: (1) Alzheimer's disease diagnosis or subcortical Vascular Cognitive Impairment, (2) sleep apnea, and (3) subjective cognitive impairment concerns. We investigated signal changes in blood oxygenation level dependent (BOLD) contrast images with respect to hypercapnic and normocapnic CVR transition periods during a gas manipulation paradigm. We developed a model-free, non-parametric CVR metric after considering a range of responses through simulations to characterize BOLD signal changes that occur when transitioning from normocapnia to hypercapnia. The non-parametric CVR measure was used to examine regional differences across the insula, hippocampus, thalamus, and centrum semiovale. We also examined the BOLD signal transition from hypercapnia back to normocapnia.
Results:
We found a linear association between isolated temporal features of successive CO2 challenges. Our study concluded that the transition rate from hypercapnia to normocapnia was significantly associated with the second CVR response across all regions of interest (p < 0.001), and this association was highest in the hippocampus (R2 = 0.57, p < 0.0125).
Conclusion:
This study demonstrates that it is feasible to examine individual responses associated with normocapnic and hypercapnic transition periods of a BOLD-based CVR experiment. Studying these features can provide insight on between-subject differences in CVR.
