Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

PURPOSE: To estimate dynamic off-resonance due to vigorous body motion in accelerated fMRI of awake behaving nonhuman primates (NHPs) using the echo-planar imaging reference navigator, in order to attenuate the effects of time-varying off-resonance on the reconstruction. METHODS: In NHP fMRI, the animal's head is usually head-posted, and the dynamic off-resonance is mainly caused by motion in body parts that are distant from the brain and have low spatial frequency. Hence, off-resonance at each frame can be approximated as a spatially linear perturbation of the off-resonance at a reference frame, and is manifested as a relative linear shift in k-space. Using GRAPPA operators, we estimated these shifts by comparing the navigator at each time frame with that at the reference frame. Estimated shifts were then used to correct the data at each frame. The proposed method was evaluated in phantom scans, simulations, and in vivo data. RESULTS: The proposed method is shown to successfully estimate spatially low-order dynamic off-resonance perturbations, including induced linear off-resonance perturbations in phantoms, and is able to correct retrospectively corrupted data in simulations. Finally, it is shown to reduce ghosting artifacts and geometric distortions by up to 20% in simultaneous multislice in vivo acquisitions in awake-behaving NHPs. CONCLUSION: A method is proposed that does not need sequence modification or extra acquisitions and makes accelerated awake behaving NHP imaging more robust and reliable, reducing the gap between what is possible with NHP protocols and state-of-the-art human imaging.

Original publication




Journal article


Magn Reson Med

Publication Date





2922 - 2932


EPI, dynamic off-resonance, fMRI, nonhuman primates, simultaneous multislice, Algorithms, Animals, Artifacts, Brain, Echo-Planar Imaging, Image Processing, Computer-Assisted, Magnetic Resonance Imaging, Phantoms, Imaging, Primates, Retrospective Studies, Wakefulness