Real-Time Prospective Slice-by-Slice Motion Correction for fMRI in Freely Moving Subjects

INTRODUCTION Functional Magnetic Resonance Imaging (fMRI) is being used extensively in neuroscientific studies and is entering the clinical field. Due to its low inherent effect to noise ratio even at high field strength the results are often compromised by adverse events during the acquisition. The most frequent cause of signal fluctuations that degrade the detection of paradigm induced neuronal activation is subject motion. A number of methods have been proposed to cope with motion. Most of the established methods correct motion based on the acquired imaging volumes either retrospectively [1] or prospectively [2]. They don’t require changes in the acquisition but can only correct for motion between successive volume acquisitions. Navigator based motion correction has been demonstrated [3]. However, it introduces additional disturbance of the spin system and requires extra scan time. We have developed and introduced a prospective motion correction method based on optical tracking of the object motion with unprecedented spatial and temporal accuracy [4]. The method adapts the position of each slice to follow the motion of the subject in real time. The goal of this study was to apply this method to fMRI measurements and compare it to image based retrospective and prospective motion correction methods.