Metabolic and haemodynamic resting-state connectivity of the human brain: a high-temporal resolution simultaneous BOLD-fMRI and FDG-fPET multimodality study

Abstract

Simultaneous FDG-PET/fMRI ([18F]-fluorodeoxyglucose positron emission tomography functional magnetic resonance imaging) provides the capacity to image two sources of energetic dynamics in the brain -glucose metabolism and haemodynamic response. Functional fMRI connectivity has been enormously useful for characterising interactions between distributed brain networks in humans. Metabolic connectivity based on static FDG-PET has been proposed as a biomarker for neurological disease; but static FDG-PET cannot be used to estimate subject-level measures of connectivity, only across-subject covariance. Here, we applied high-temporal resolution constant infusion functional PET (fPET) to measure subject-level metabolic connectivity simultaneously with fMRI connectivity. fPET metabolic connectivity was characterised by fronto-parietal connectivity within and between hemispheres. fPET metabolic connectivity showed moderate similarity with fMRI primarily in superior cortex and frontoparietal regions. fPET metabolic connectivity showed little similarity with static FDG-PET metabolic covariance, indicating that metabolic connectivity is a nonergodic process that cannot be used to infer individual-level connectivity from across-subject covariance. In sum, our results highlight the complementary strengths of fPET and fMRI in measuring the intrinsic connectivity of the brain, and opens up the opportunity for new multivariate metabolic neuroimaging biomarkers for neurological disease.

Simultaneous BOLD-fMRI and constant infusion FDG-PET data of the resting human brain

“…(g) Subject-level matrices for sPET, fPET and fMRI were then group averaged. Matrices are indicative of potential connectivity matrices, and are those that are reported in Jamadar et al 20 . 2020 sex of the participant as reported by the participant "M": "male", "F": "female" handedness handedness of the participant as reported by the participant "L": "left", "R": "right" Self-report education_years years of education calculated as formal education of 6 months or more.…”

“…Spatial variability of fMRI and fPET images. fMRI and fPET connectomes showed a low region degree (i.e., little correlation with other brain regions) in subcortical regions 20 . These observations contrast with the known high degree of inter-connectedness of the subcortical areas with the rest of the brain: the cortico-basal ganglia-cerebellar (Middleton and Strick 40 ; Bostan and Strick) 41 and cortico-thalamic circuits 42 .…”

“…We found highly consistent metabolic connectivity across a range of standard deviations. We have previously reported resting-state fPET connectivity with one voxel spatial gaussian and two frames temporal gaussian 20 . This set of parameters provided the least amount of smoothing whilst preserving the fidelity of the observed connectivity.…”

“…Participants underwent a 95-minute simultaneous MR-PET scan in a Siemens (Erlangen) 3 Tesla Biograph molecular MR (mMR) scanner (Syngo VB20 P). Quality control is performed daily on the scanner using a 68-Ge www.nature.com/scientificdata www.nature.com/scientificdata/ 27 and panels e-g indicate the workflow for the results presented under Technical Validation, and in Jamadar et al 20 . (a) Participants completed a demographics, safety screening and cognitive assessment an hour prior to MR-PET scanning.…”

Monash DaCRA fPET-fMRI: A DAtaset for Comparison of Radiotracer Administration for high temporal resolution functional FDG-PET

“…Using fPET data acquired simultaneously with (non-functional) MRI (i.e., MRI/fPET), Villien et al was able to estimate a general linear model response for blocked stimuli presented 5-10mins apart. Subsequent studies have extended these findings, and achieved fPET temporal resolutions of 1-minute [6,7,[9][10][11] or less (12sec [5]; 16sec [12][13][14]; 30sec [15]).…”