Resting State Brain Function Analysis Using Concurrent BOLD in ASL Perfusion fMRI

Abstract

The past decade has seen astounding discoveries about resting-state brain activity patterns in normal brain as well as their alterations in brain diseases. While the vast majority of resting-state studies are based on the blood-oxygen-level-dependent (BOLD) functional MRI (fMRI), arterial spin labeling (ASL) perfusion fMRI can simultaneously capture BOLD and cerebral blood flow (CBF) signals, providing a unique opportunity for assessing resting brain functions with concurrent BOLD (ccBOLD) and CBF signals. Before taking that benefit, it is necessary to validate the utility of ccBOLD signal for resting-state analysis using conventional BOLD (cvBOLD) signal acquired without ASL modulations. To address this technical issue, resting cvBOLD and ASL perfusion MRI were acquired from a large cohort (n = 89) of healthy subjects. Four widely used resting-state brain function analyses were conducted and compared between the two types of BOLD signal, including the posterior cingulate cortex (PCC) seed-based functional connectivity (FC) analysis, independent component analysis (ICA), analysis of amplitude of low frequency fluctuation (ALFF), and analysis of regional homogeneity (ReHo). Consistent default mode network (DMN) as well as other resting-state networks (RSNs) were observed from cvBOLD and ccBOLD using PCC-FC analysis and ICA. ALFF from both modalities were the same for most of brain regions but were different in peripheral regions suffering from the susceptibility gradients induced signal drop. ReHo showed difference in many brain regions, likely reflecting the SNR and resolution differences between the two BOLD modalities. The DMN and auditory networks showed highest CBF values among all RSNs. These results demonstrated the feasibility of ASL perfusion MRI for assessing resting brain functions using its concurrent BOLD in addition to CBF signal, which provides a potentially useful way to maximize the utility of ASL perfusion MRI.

Neuronal and Physiological Correlation to Hemodynamic Resting-State Fluctuations in Health and Disease

“…These findings are in line with resting-state MRI measurements of blood flow and blood volume (Miao et al, 2014;Zhu et al, 2013;Zou et al, 2009), whereby typical low-frequency and connectivity patterns were observed. The findings obtained in this work indicate greater value in blood-oxygenation-based fcMRI compared with CBF-or CBV-sensitive fcMRI for reporting neuronal connectivity.…”

Characterizing Resting-State Brain Function Using Arterial Spin Labeling

“…While BOLD rs-fMRI is the dominant technique used in studies of resting brain networks (RBNs), the possibility of using ASL perfusion MRI for assessing RBNs has been attracting increasing interest (Chuang et al, 2008;Zou et al, 2009), due to the closer coupling (relative to BOLD) between CBF and neuronal activity (Lauritzen, 2001;Wong et al, 1997). Resting-state functional connectivity (FC) based on CBF fluctuations was first demonstrated by Biswal et al This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction.…”

“…For instance, due to the relatively low temporal resolution of ASL scans, perfusion time series from multiple subjects are often concatenated, for instance, in a group ICA (Jann et al, 2015a;Jann et al, 2013). In addition, as CBF and BOLD provide complementary information, it is appealing to combine ASL and BOLD for characterizing spatiotemporal and quantitative properties of specific brain networks, as proposed by a few recent studies (Jann et al, 2013;Zhu et al, 2013). Furthermore, joint CBF-and BOLD-based FC analyses offer mutual validation of findings using each modality, thereby improving confidence for statistical inferences.…”

Functional Magnetic Resonance Imaging with Arterial Spin Labeling: Techniques and Potential Clinical and Research Applications

“…As BOLD is affected by macrovascular effects, CBF can reflect activity better in tissue capillary bed. Therefore, ASL CBF might be a more precise approach to measure differences in resting brain activity (5,10). In our study, ASL perfusion data were obtained by using 2D pCASL and concurrent BOLD contrast was used for rs-fMRI study instead of CBF time series.…”

“…Owning to recent development of high magnetic field equipment and advanced imaging technology, ASL has been used as an imaging tool to understand the pathophysiology of various brain disorders (3,4). Recently, with improved signal to noise ratio (SNR) and spatial resolution such as pseudo-continuous technique, ASL can also be applied to functional magnetic resonance imaging (fMRI) study (5). Up to date, blood oxygenation level-dependent (BOLD) technique has been established as a standard method for fMRI study.…”