Characteristics of acoustic noise in echo-planar imaging

Effect of fMRI acoustic noise on sensorimotor activation examined using optical topography

Functional magnetic resonance imaging (fMRI) is an important tool for noninvasively imaging the hemodynamic responses accompanying brain activity, but fMRI measurements are accompanied by loud acoustic noises resulting from Lorentz forces that cannot be completely excluded when the present technology is used. We used recorded fMRI acoustic noise and examined its effect on sensorimotor activation in optical topography measurement when subjects were instructed to tap the fingers of the right hand under a 23-dB non-noise condition and 46-, 56-, and 65-dB noise conditions. The results showed that the amplitude of the activation signal (relative change in concentration) for oxygenated hemoglobin in the sensorimotor cortex decreased with increasing noise. The activation signal for deoxygenated hemoglobin did not depend significantly on the noise level but did tend to decrease with increasing noise. These results suggest that fMRI acoustic noise affects the hemodynamics of cortical areas associated with the processing of information other than auditory information.

Acoustic noise concerns in functional magnetic resonance imaging

Magnetic resonance (MR) acoustic scanner noise may negatively affect the performance of functional magnetic resonance imaging (fMRI), a problem that worsens at the higher field strengths proposed to enhance fMRI. We present an overview of the current knowledge on the effects of confounding acoustic MR noise in fMRI experiments. The principles and effectiveness of various methods to reduce acoustic noise in fMRI are discussed, practical considerations are addressed and recommendations are made.