Affiliation:
1. CEA, NeuroSpin, CNRS Université Paris‐Saclay Gif‐sur‐Yvette France
2. Inria, MIND Palaiseau France
3. Siemens Healthineers Courbevoie France
Abstract
AbstractPurposeStatic and dynamic field imperfections are detrimental to functional MRI (fMRI) applications, especially at ultra‐high magnetic fields (UHF). In this work, a field camera is used to assess the benefits of retrospectively correcting field perturbations on Blood Oxygen Level Dependent (BOLD) sensitivity in non‐Cartesian three‐dimensional (3D)‐SPARKLING fMRI acquisitions.MethodsfMRI data were acquired at 1 mm and for a 2.4s‐TR while concurrently monitoring in real‐time field perturbations using a Skope Clip‐on field camera in a novel experimental setting involving a shorter TR than the required minimal TR of the field probes. Measurements of the dynamic field deviations were used along with a static map to retrospectively correct static and dynamic field imperfections, respectively. In order to evaluate the impact of such a correction on fMRI volumes, a comparative study was conducted on healthy volunteers.ResultsCorrection of deviations improved image quality and yielded between 20% and 30% increase in median temporal signal‐to‐noise ratio (tSNR).Using fMRI data collected during a retinotopic mapping experiment, we demonstrated a significant increase in sensitivity to the BOLD contrast and improved accuracy of the BOLD phase maps: 44% (resp., 159%) more activated voxels were retrieved when using a significance control level based on a p‐value of 0.001 without correcting for multiple comparisons (resp., 0.05 with a false discovery rate correction).Conclusion3D‐SPARKLING fMRI hugely benefits from static and dynamic imperfections correction. However, the proposed experimental protocol is flexible enough to be deployed on a large spectrum of encoding schemes, including arbitrary non‐Cartesian readouts.
Funder
Fondation Leducq
Horizon 2020 Framework Programme
Grand Équipement National De Calcul Intensif
Subject
Radiology, Nuclear Medicine and imaging