Reduction of signal fluctuation in functional MRI using navigator echoes.
Functional magnetic resonance imaging is sensitive to signal fluctuations due to physiological motion and system instability. In this paper, motion-related signal fluctuations are studied, and a method that uses navigator echoes to monitor and compensate for signal fluctuations in a gradient-echo sequence is described. The technique acquires a "navigator" signal before the application of the phase-encoding and readout gradients and corrects the phase of the subsequently acquired imaging data. This technique was implemented on a 4 Tesla whole body system and validated on normal volunteers. With this technique, temporal fluctuations in image intensity were substantially reduced and improved functional activation maps were obtained.
Department of Radiology, University of Minnesota Medical School, Minneapolis 55455.
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D016477:Artifacts; D002555:Cerebrospinal Fluid; D005583:Fourier Analysis; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009044:Motor Cortex / Q000033:anatomy & histology; D009048:Motor Skills / Q000502:physiology; D009068:Movement; D010775:Photic Stimulation; D012119:Respiration; D014793:Visual Cortex / Q000033:anatomy & histology