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Impact of hematocrit on measurements of the intrinsic brain.

ABSTRACT: Blood oxygenation level dependent (BOLD)-based functional MRI (fMRI) is a widely utilized neuroimaging technique for mapping brain function. Hematocrit (HCT), a global hematologic marker of the amount of hemoglobin in blood, is known to impact task-evoked BOLD activation. Yet, its impact on resting-state fMRI (R-fMRI) measures has not been characterized. We address this gap by testing for associations between HCT level and inter-individual variation in commonly employed R-fMRI indices of intrinsic brain function from 45 healthy adults. Given known sex differences in HCT, we also examined potential sex differences. Variation in baseline HCT among individuals were associated with regional differences in four of the six intrinsic brain indices examined. Portions of the default (anterior cingulate cortex/medial prefrontal cortex: ACC/MPFC), dorsal attention (intraparietal sulcus), and salience (insular and opercular cortex) network showed relationships with HCT for two measures. The relationships within MPFC, as well as visual and cerebellar networks, were modulated by sex. These results suggest that inter-individual variations in HCT can serve as a source of variations in R-fMRI derivatives at a regional level. Future work is needed to delineate whether this association is attributable to neural or non-neuronal source of variations and whether these effects are related to acute or chronic differences in HCT level.

SUBMITTER: Yang Z

PROVIDER: S-EPMC4299407 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Impact of hematocrit on measurements of the intrinsic brain.

Yang Zhen Z Craddock R Cameron RC Milham Michael P MP

Frontiers in neuroscience 20150120

Blood oxygenation level dependent (BOLD)-based functional MRI (fMRI) is a widely utilized neuroimaging technique for mapping brain function. Hematocrit (HCT), a global hematologic marker of the amount of hemoglobin in blood, is known to impact task-evoked BOLD activation. Yet, its impact on resting-state fMRI (R-fMRI) measures has not been characterized. We address this gap by testing for associations between HCT level and inter-individual variation in commonly employed R-fMRI indices of intrins ...[more]

PMID: 25653582

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Project description:BackgroundThe extracellular volume (ECV), derived from cardiovascular magnetic resonance (CMR) T1 mapping, is a biomarker of the extracellular space in the myocardium. The hematocrit (HCT), measured from venipuncture, is required for ECV measurement. We test the clinic values of synthetic ECV, which is derived from the longitudinal relaxation of blood-based (T1blood) synthetic hematocrit in 3 T CMR.MethodsA total of 226 subjects with CMR T1 mapping and HCT measurement taken on the same day as the CMR were retrospectively enrolled and randomly split into derivation (n?=?121) and validation (n?=?105) groups, comprising healthy subjects (n?=?45), type 2 diabetes mellitus (T2DM) patients (n?=?60), hypertrophic cardiomyopathy (HCM) patients (n?=?93), and 28 other patients. Correlation of T1blood with the measured HCT (HCTm) was established in the derivation group and used in both the derivation and the validation groups. The relationships between the ECV values derived from both the synthetic HCT (HCTsyn) and HCTm were explored. In addition, the differences in the ECV values among the HC, T2DMs, and HCMs were compared.ResultsRegression between the HCTm and 1/T1blood was linear (R2?=?0.19, p?<?0.001), and the regression equation was: HCTsyn?=?[561.6*(1/T1blood)] +?0.098 in the derivation group. The measured ECV (ECVm) was strongly correlated with the synthetic ECV (ECVsyn) (R2?=?0.87, p?<?0.001) and mildly correlated with the difference between the ECVsyn and ECVm (R2?=?0.10, p?<?0.001) in the derivation group. Also in this group, the ECVm was larger in T2DMs than that in healthy cohort (29.1?±?3.1% vs. 26.4?±?2.4%, p?=?0.002), whereas, the ECVsyn did not differ between T2DMs and healthy cohort (28.3?±?2.9% vs. 26.9?±?2.2%, p?=?0.064). Compared with the healthy cohort, the HCMs were associated with higher ECVsyn and ECVm of the mid-ventricle in both the derivation and the validation groups. Using our center's normal cut-off of 31.8%, the use of ECVsyn would lead to a 6-25% incorrect categorization of patients in the derivation and validation groups.ConclusionsECVsyn derived from HCTsyn may lead to clinical errors in 3 T CMR, especially for patients who have only a subtle elevation in ECV.

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Impact of hematocrit on measurements of the intrinsic brain.

Publications

Impact of hematocrit on measurements of the intrinsic brain.

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