Regional and interindividual relationships between cerebral perfusion and oxygen metabolism

Abstract

Quantitative measurements of resting cerebral blood flow (CBF) and metabolic rate of oxygen (CMRO2) show large between-subject and regional variability, but the relationships between CBF and CMRO2 measurements regionally and globally are not fully established. Here, we investigated the between-subject and regional associations between CBF and CMRO2 measures with independent and quantitative PET techniques. We included resting CBF and CMRO2 measurements from 50 healthy volunteers (aged 22-81 years), and calculated the regional and global values of oxygen delivery (DO2) and oxygen extraction fraction (OEF). Linear mixed model analysis showed that CBF and CMRO2 measurements were closely associated regionally, but no significant between-subject association could be demonstrated, even when adjusting for arterial PCO2 and hemoglobin concentration. The analysis also showed regional differences of OEF, reflecting variable relationship between DO2 and CMRO2, resulting in lower estimates of OEF in thalami, brainstem, and mesial temporal cortices, and higher estimates of OEF in occipital cortex. In the present study, we demonstrated no between-subject association of quantitative measurements of CBF and CMRO2 in healthy subjects. Thus, quantitative measurements of CBF did not reflect the underlying between-subject variability of oxygen metabolism measures, mainly because of large interindividual OEF variability not accounted for by PCO2 and hemoglobin concentration.

Test-retest reliability of 3D velocity-selective arterial spin labeling for detecting normal variations of cerebral blood flow

“…In contrast, the higher between-region CoV of relative GM CBF averaged across subjects (11.4%) over within-region CoV (2–4%) yielded excellent ICC values of VSASL for detecting normal variations of regional CBF ( Table 3 ). The higher relative CBF values in the occipital lobe (1.05), cerebellum (1.07), and posterior cingulate cortex (1.15) were consistent with the regional patterns derived from 15 O-water PET measurements ( Henriksen et al, 2021 ; Kilroy et al, 2014 ; Xu et al, 2010 ; Zhang et al, 2014 ). Furthermore, as a core node of the default mode network which high metabolic demand needed to maintain arousal ( Raichle et al, 2001 ), the posterior cingulate cortex has been shown to be one of the brain regions with the highest relative CBF ( Pfefferbaum et al, 2011 ).…”

MRI assessment of cerebral oxygen extraction fraction in the medial temporal lobe

“…For example, in fourteen healthy elderly subjects, Ishii et al found that MTL-OEF was ~7 units (%) lower than OEF in other cortical regions ( Ishii et al, 1996 ). Another three 15 O-PET studies reported that MTL-OEF was significantly lower than OEF in other cortical regions by 4–7 units ( Hatazawa et al, 1995 ; Henriksen et al, 2021 ; Yamaguchi et al, 1986 ). Ibaraki et al also showed lower MTL-OEF than OEF in other cortical regions in two 15 O-PET studies, although the authors did not perform statistical comparisons ( Ibaraki et al, 2008 ; Ibaraki et al, 2009 ).…”

Toward vendor‐independent measurement of cerebral venous oxygenation: Comparison of TRUST MRI across three major MRI manufacturers and association with end‐tidal CO2

“…30,49,50 If CMRO 2 is relatively stable, then it is apparent that a higher EtCO 2 would lead to a reduced OEF (because OEF is related to the ratio of CMRO 2 to CBF), which, in turn, would result in elevated Y v (Y v ≈ 1 À OEF). The crosssubject correlation between EtCO 2 and Y v can be similarly explained, as reports have shown a positive correlation between EtCO 2 and CBF across individuals, 51,52 while CMRO 2 values are relatively similar (or exhibits less variability compared with OEF or CBF) among subjects. 24 In this study, although we did not find any significant differences in Y v , intrasession CoV or intersession CoV values across the three scanners, we did observe that the GE TRUST had significantly higher ΔR 2 values than those of the other two scanners.…”

“…If CMRO 2 is relatively stable, then it is apparent that a higher EtCO 2 would lead to a reduced OEF (because OEF is related to the ratio of CMRO 2 to CBF), which, in turn, would result in elevated Y v ( Y v ≈ 1 − OEF). The cross‐subject correlation between EtCO 2 and Y v can be similarly explained, as reports have shown a positive correlation between EtCO 2 and CBF across individuals, 51,52 while CMRO 2 values are relatively similar (or exhibits less variability compared with OEF or CBF) among subjects 24 …”