Open AccessAccounting for the role of hematocrit in between‐subject variations of MRI‐derived baseline cerebral hemodynamic parameters and functional BOLD responses
Author(s) -
Xu Feng,
Li Wenbo,
Liu Peiying,
Hua Jun,
Strouse John J.,
Pekar James J.,
Lu Hanzhang,
van Zijl Peter C.M.,
Qin Qin
Publication year - 2018
Publication title -
human brain mapping
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.005
H-Index - 191
eISSN - 1097-0193
pISSN - 1065-9471
DOI - 10.1002/hbm.23846
Subject(s) - cerebral blood flow , hematocrit , hemodynamics , functional magnetic resonance imaging , correlation , population , cardiology , magnetic resonance imaging , medicine , psychology , nuclear medicine , anesthesia , neuroscience , radiology , mathematics , geometry , environmental health
Abstract Baseline hematocrit fraction (Hct) is a determinant for baseline cerebral blood flow (CBF) and between‐subject variation of Hct thus causes variation in task‐based BOLD fMRI signal changes. We first verified in healthy volunteers ( n = 12) that Hct values can be derived reliably from venous blood T 1 values by comparison with the conventional lab test. Together with CBF measured using phase‐contrast MRI, this noninvasive estimation of Hct, instead of using a population‐averaged Hct value, enabled more individual determination of oxygen delivery (DO 2 ), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO 2 ). The inverse correlation of CBF and Hct explained about 80% of between‐subject variation of CBF in this relatively uniform cohort of subjects, as expected based on the regulation of DO 2 to maintain constant CMRO 2 . Furthermore, we compared the relationships of visual task‐evoked BOLD response with Hct and CBF. We showed that Hct and CBF contributed 22%–33% of variance in BOLD signal and removing the positive correlation with Hct and negative correlation with CBF allowed normalization of BOLD signal with 16%–22% lower variability. The results of this study suggest that adjustment for Hct effects is useful for studies of MRI perfusion and BOLD fMRI. Hum Brain Mapp 39:344–353, 2018 . © 2017 Wiley Periodicals, Inc.