Cerebral circulation time derived from fMRI signals in large blood vessels

Abstract

Background: The systemic low-frequency oscillation (sLFO) functional (f)MRI signals extracted from the internal carotid artery (ICA) and the superior sagittal sinus (SSS) are found to have valuable physiological information.

Purpose: 1) To further develop and validate a method utilizing these signals to measure the delay times from the ICAs and the SSS. 2) To establish the delay time as an effective perfusion biomarker that associates with cerebral circulation time (CCT). 3) To explore within subject variations, and the effects of gender and age on the delay times.

Study type: Prospective.

Subjects: In all, 100 healthy adults (Human Connectome Project [HCP], age range 22-36 years, 54 females and 46 males), 56 healthy children (Adolescent Brain Cognitive Development project) were included.

Field strength/sequence: Echo planar imaging (EPI) sequence at 3T.

Assessment: The sLFO fMRI signals from the ICAs and the SSSs were extracted from the resting state fMRI data. The maximum cross-correlation coefficients and their corresponding delay times were calculated. The gender and age differences of delay times were assessed statistically.

Statistical tests: T-tests were conducted to measure the gender differences. The Kruskal-Wallis test was used to detect age differences.

Results: Consistent and robust results were found from 80% of the 400 HCP scans included. Negative correlations (-0.67) between the ICA and the SSS signals were found with the ICA signal leading the SSS signal by ∼5 sec. Within subject variation was 2.23 sec at the 5% significance level. The delay times were not significantly different between genders (P = 0.9846, P = 0.2288 for the left and right ICA, respectively). Significantly shorter delay times (4.3 sec) were found in the children than in the adults (P < 0.01).

Data conclusion: We have shown that meaningful perfusion information (ie, CCT) can be derived from the sLFO fMRI signals of the large blood vessels.

Level of evidence: 1 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019;50:1504-1513.

Keywords: BOLD signal; cerebral circulation time; fMRI signal; internal carotid artery; low-frequency oscillations; superior sagittal sinus.