Appearance time of blood in the brain as a possible indicator of oxygen extraction fraction: a feasibility study

Imaging examination of cerebral blood flow (CBF), oxygen extraction fraction (OEF), and metabolic rate of oxygen is crucial for understanding the normal functioning and pathophysiology of the brain. A recently developed method estimates the appearance time of cerebral blood (ATB) pixel-wise from the imaging examination of CBF alone. In this study, we aimed to test the potential of ATB as an indicator of OEF.

We retrospectively reviewed patients (n = 62) with suspected cerebrovascular disorders including steno-occlusive disease who underwent positron emission tomography (PET) with ¹⁵O-labelled tracers. Regarding the generated OEF and ATB images, a visual assessment was performed to test the consistency of the elevated OEF and delayed ATB. The OEF and ATB values and the absolute differences between their ipsilateral and contralateral sides were extracted and obtained for the entire hemisphere and the middle, anterior, and posterior cerebral arterial regions. Consistency was observed in 52 PET scans (83.9%) in visual assessment. The OEF and ATB values were moderately correlated (r = 0.553, p < 0.001), and the differences between their ipsilateral and contralateral sides were weakly correlated (r = 0.276, p < 0.001).

Our results indicate the potential of ATB as an indicator of OEF.