Linearity assessment of the BOLD signal in response to controlled hypercapnea in healthy controls

This study addresses concerns over the degree to which the relationship between the cerebral BOLD MRI signal and a CO2 flow stimulus is non-linear. The issue was tested using a quantitative BOLD stimulus in a large population of healthy controls. The results indicate that linear modelling of the response compared to the sigmoid model underestimated the response by ≈ 10%. This would indicate that linear modelling of the BOLD is a reasonable surrogate for flow measurement in subjects undergoing cerebrovascular reactivity testing.