Sources of Variability of Resting Cerebral Blood Flow in Healthy Subjects: A Study Using¹³³Xe SPECT Measurements

Abstract

Measurements of cerebral blood flow (CBF) show large variability among healthy subjects. The aim of the present study was to investigate the relative effect of established factors influencing CBF on the variability of resting CBF. We retrospectively analyzed spontaneous variability in 430 CBF measurements acquired in 152 healthy, young subjects using 133 Xe single-photon emission computed tomography. Cerebral blood flow was correlated positively with both end-tidal expiratory P CO 2 (P ET CO 2 ) and female gender and inversely with hematocrit (Hct). Between-and within-subject CO 2 reactivity was not significantly different. Including P ET CO 2 , Hct and gender in the model reduced between-subject and within-subject variance by 14% and 13.5%, respectively. Withinsubject variability was mainly influenced by P ET CO 2 and between-subject variability mostly by Hct, whereas gender appeared to be of little added value when Hct was also accounted for. The present study confirms large between-subject variability in CBF measurements and that gender, Hct, and P ET CO 2 explain only a small part of this variability. This implies that a large fraction of CBF variability may be due to unknown factors such as differences in neuron density or metabolism that could be subject for further studies.

Cerebral Perfusion in Insulin Resistance and Type 2 Diabetes

“…This phenomenon could be explained by~10% lower hemoglobin and heamatocrit levels in women, combined with the hypothesis that CBF is regulated to maintain constant oxygen delivery across different hemoglobin levels. 34,35 Our study showed a strong association between resting GM CBF and general cognitive functioning measured by multiple psychometric test scores. This association was not expected and it appears to be reported in only one other study.…”

The resting perfusion pattern associates with functional decline in type 2 diabetes

“…Given that hematocrit and gender are important predictors of CBF (Liu et al 2012; Henriksen et al 2014; Henriksen et al 2013), and hematocrit is significantly different between the two genders (p ≤ 0.001, in the current study), Pearson correlation was performed between each variable (hematocrit or gender) and CBF in order to determine which one is the most sensitive predictor of CBF. Hematocrit ( r = −0.39 , p ≤ 0.001) but not gender ( r = 0.18, p = 0.14) was negatively correlated with CBF, thus hematocrit was used as a confounder in the subsequent analysis.…”

Comparison of global cerebral blood flow measured by phase‐contrast mapping MRI with 15O‐H2O positron emission tomography

“…As spontaneous fluctuations in PaCO 2 have been shown to introduce within‐subject variability of CBF measurements, the possible influence of PaCO 2 fluctuations were investigated by including the difference in PaCO 2 (PaCO2 PCM – PaCO2 PET ) as a covariate in a multiple regression model with CBF PCM as the dependent variable and CBF PET as the independent variable.…”