Utility of Real-Time Field Control in T-2*-Weighted Head MRI at 7T

作者：Duerst Yolanda; Wilm Bertram J; Wyss Michael; Dietrich Benjamin E; Gross Simon; Schmid Thomas; Brunner David O; Pruessmann Klaas P^*

来源：Magnetic Resonance in Medicine, 2016, 76(2): 430-439.

DOI：10.1002/mrm.25838

• NMR field probes
• field control
• field camera
• T-2*-weighted imaging
• 7 Tesla
• dynamic shimming

Purpose: Real-time field control can serve to reduce respiratory field perturbations during T-2* imaging at high fields. This work investigates the effectiveness of this approach in relation to key variables such as patient physique, breathing patterns, slice location, and the choice of sequence.
Methods: To cover variation in physical constitution and breathing behavior, volunteers with a wide range of body-mass-indices were asked to breathe either normally or deeply during T-2*-weighted image acquisition at 7T. Ensuing field fluctuation was countered by real-time field control or merely recorded in reference experiments. The impact of the control system on image quality was assessed by classifying and grading artifacts related to field fluctuation.
Results: The amplitude of respiratory field changes and related artifacts were generally stronger for subjects with higher body-mass-index and for lower slices. Field control was found effective at mitigating all five types of artifacts that were studied. Overall image quality was systematically improved. Residual artifacts in low slices are attributed to insufficient spatial order of the control system.
Conclusion: Real-time field control was found to be a robust means of countering respiratory field perturbations in variable conditions encountered in high-field brain imaging. Reducing net fluctuation, it generally expands the feasibility of high-field T-2* imaging toward challenging patients and brain regions.

• 出版日期2016-8