A comparison of signal instability in 2D and 3D EPI resting-state fMRI.


Goerke, Ute; Möller, Harald E; Norris, David G; Schwarzbauer, Christian; (2005) A comparison of signal instability in 2D and 3D EPI resting-state fMRI. NMR in biomedicine, 18 (8). pp. 534-42. ISSN 0952-3480

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Abstract

Spatiotemporally structured noise, such as physiological noise, is a potential source of artifacts in functional magnetic resonance imaging (fMRI) and is the main limiting factor for the detection of small blood oxygen level-dependent (BOLD) signal variations. fMRI was employed to detect low-frequency BOLD signal fluctuations, which are thought to be related to spontaneous neuronal activity in the resting human brain. The sensitivity to noise, that is, signal variations of non-BOLD origin, was investigated for two- (2D) and three-dimensional (3D) imaging techniques. Incomplete relaxation between subsequent scans increases the level of temporally and spatially correlated signal variations originating from physiological and/or systemic noise. Although inflow effects are suspected to be reduced in 3D echo-planar imaging (EPI) compared with multi-slice 2D EPI, the noise level was higher in the 3D technique. The noise level in 3D fMRI experiments was significantly increased by instabilities of the transverse steady-state magnetization as the repetition time was of the order of T(2). By implementing radiofrequency spoiling, temporal signal fluctuations and erroneous inter-regional correlation in connectivity maps were diminished to a level present in data sets acquired with 2D EPI.

Item Type: Article
PubMed ID: 16206130
URI: http://researchonline.lshtm.ac.uk/id/eprint/20472

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