Cerebrovascular Reactivity Assessment with Breath-Hold Functional MRI in Patients with Moyamoya Angiopathy: Which...

Background/Objectives: Quantifying cerebrovascular reactivity (CVR) is essential for stroke risk assessment in patients with Moyamoya Angiopathy (MMA). Breath-hold functional MRI (bh-fMRI) is an easily implementable method to assess CVR. Determining the optimal time period of the BOLD signal for analyzing the best bh-fMRI data quality remains an open question. Methods: A retrospective analysis of 46 bh-fMRI data sets of MMA patients was conducted. The percentage BOLD signal changes were evaluated at different time periods (time point of the maximum cerebellar signal peak (TP_{cereb. max}) ± 0 s, TP_{cereb. max} ± 1 s, TP_{cereb. max} ± 2 s, TP_{cereb. max} ± 3 s, TP_{cereb. max} ± 4 s, TP_{cereb. max} ± 5 s). The agreement between the bh-fMRI maps and [¹⁵O]water PET maps was independently and consensually rated on a 4-point Likert scale (1 = poor, 2 = moderate, 3 = good, 4 = excellent) and compared with the Friedman test. The inter-rater agreement was calculated separately for each time period using quadratic weighted Cohen's kappa κ_w. Results: The selected time period had a significant impact on the agreement between bh-fMRI and [¹⁵O]water PET (χ²(5) = 79.448, p < 0.001, W = 0.345). Short time periods of TP_cereb.max ± 0 s or TP_cereb.max ±1 s demonstrated the highest level of concordance between bh-fMRI and [¹⁵O]water PET (median = 3.5 for TP_cereb.max ± 0 s; median = 3 for TP_cereb.max ± 1 s, modus = 4 in both cases). The agreement between bh-fMRI and [¹⁵O]water PET was significantly higher when evaluating time periods of TP_cereb.max ± 0 s than when evaluating all time periods ≥ TP_{cereb. max} ± 2 s. The inter-rater agreement was almost perfect for all time periods except one (TP_{cereb. max} ± 1 s). Conclusions: Short time periods should be selected when evaluating CVR with bh-fMRI, as this study suggests a high level of validity in comparison to [¹⁵O]water PET.