The results of a recently described
streamlined quantitative BOLD (qBOLD) technique suggest that this method may
overestimate the deoxygenated blood volume (DBV), leading to an underestimate
of the oxygen extraction fraction (OEF). We hypothesise that this is due to the
effect of diffusion, which is assumed to be zero in the analytical qBOLD model.
In this study we performed Monte Carlo simulations to investigate this
hypothesis and found that DBV and OEF measurements were vessel size dependent.
However, the R2’ measurements which underlie qBOLD were found to be a
reliable measure of deoxyhaemoglobin content above a vessel radius of 10μm.