Sources of Systematic Bias in Hypercapnia-Based CMRO2 Estimation using Functional MRI
Chiarelli P, Piechnik S, Bulte D, Jezzard P
Aerobic metabolism (CMRO2) during neural stimulation may be estimated from BOLD and CBF measurements by the hypercapnia-normalization method. We present a thorough re-examination of systematic bias in this model for CMRO2 estimation [1,2], focusing on an unexamined dependence on the value of the hypercapnia calibration constant (M), and a marked covariation between the calculated CMRO2?CBF coupling ratio and the apparent linearity of coupling. This work argues for a much more careful measurement of M to minimise this potential bias, and provides an enhanced transparency of the model itself to the MR community.