Assessing cerebral perfusion: transfer function analysis of the BOLD response to hypoxia-induced changes in deoxyhemoglobin

We used hypoxia-induced changes in deoxyhemoglobin concentration as a susceptibility contrast agent. Transfer function analysis of the resulting changes in the BOLD signal for each voxel provided cerebral perfusion measures that indicate the distribution of the strength of the signal response to the contrast agent (gain) and the lag of the response (phase or time). We relate the gain and lag to conventional resting hemodynamic measures cerebral blood volume and mean transit time, respectively.