Dynamic characteristics of oxygenation-sensitive MRI signal in different temporal protocols for imaging human brain activity

S. S. Kollias, X. Golay, P. Boesiger, A. Valavanis

Research output: Contribution to journalArticlepeer-review

Abstract

The temporal characteristics of cerebral blood oxygenation during human brain activation were monitored with dynamic echo-planar imaging (EPI) using the blood oxygenation level dependent (BOLD) fMRI. We investigated oxygenation-sensitive signal changes: 1. during repetitive block stimuli, to determine the latency of the activation-induced signal change in the primary visual cortex; 2. on shortening the rest periods between constant stimulated phases, to investigate the limitations that this latency poses in temporal resolution of the technique; and 3. on sustained steady-state stimulation, to characterise oxygenation changes during prolonged brain activation using different stimuli. Delayed intrinsic haemodynamic response and a finite signal-to-noise ratio limit the temporal resolution achieved with BOLD fMRI. Separate activation periods were resolved when the delay between consecutive stimulations was at least 2 s. In this study oxygenation remained elevated throughout sustained activation, suggesting a constant rate of oxygen consumption by the primary cortical neurones during activation. Characterisation of fMRI signal dynamics in dynamic temporal protocols is significant both in terms of optimising stimulation protocols and the potential to gain insight into the physiological mechanisms underlying neuronal activation which could increase the clinical applicability of the technique.

Original languageEnglish (US)
Pages (from-to)591-601
Number of pages11
JournalNeuroradiology
Volume42
Issue number8
DOIs
StatePublished - 2000

Keywords

  • Functional
  • Magnetic resonance imaging

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Clinical Neurology
  • Cardiology and Cardiovascular Medicine

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