Intervoxel heterogeneity of event-related functional magnetic resonance imaging responses as a function of T1 weighting

Research output: Contribution to journalArticle

Abstract

Inflow effects on activation-related BOLD signal changes in event-related fMRI experiments were assessed by varying the repetition time (TR) and flip angle (FA) values for gradient-echo echo-planar imaging (GE-EPI). Surprisingly, both increases and decreases were detected in these signal changes with increased T1 weighting (reduced TR, increased FA). The well-known "positive" effect is attributed to in-flow of fresh spins in the slice, leading to an apparent reduction in T1. The "negative" effect is attributed to voxels containing pure parenchyma, where large-vessel inflow effects are very small and the BOLD effect is dominated by microvascular blood volume and oxygenation changes. Because blood T1 is greater than tissue T1 (at 1.5 T, the fractional BOLD effect decreases with increased T1 weighting. To aid in the interpretation of these experimental results, numerical simulations were performed based on a physiological multi-compartment model, including pure tissue, large vessels (arteries, veins), microvessels (arterioles, capillaries, venules), and cerebrospinal fluid.

Original languageEnglish (US)
Pages (from-to)943-955
Number of pages13
JournalNeuroImage
Volume17
Issue number2
DOIs
StatePublished - Jan 1 2002

Keywords

  • Blood oxygen level-dependent
  • Blood volume
  • Event-related
  • Functional magnetic resonance imaging
  • Gradient echo
  • Inflow

ASJC Scopus subject areas

  • Neurology
  • Cognitive Neuroscience

Fingerprint Dive into the research topics of 'Intervoxel heterogeneity of event-related functional magnetic resonance imaging responses as a function of T<sub>1</sub> weighting'. Together they form a unique fingerprint.

  • Cite this