Utility of real-time field control in T2-Weighted head MRI at 7T

• Published in: Magnetic resonance in medicine Vol. 76; no. 2; pp. 430 - 439
• Main Authors: Duerst, Yolanda, Wilm, Bertram J., Wyss, Michael, Dietrich, Benjamin E., Gross, Simon, Schmid, Thomas, Brunner, David O., Pruessmann, Klaas P.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.08.2016; Wiley Subscription Services, Inc
• Subjects: 7 Tesla; Algorithms; Brain - anatomy & histology; Computer Systems; Diffusion Magnetic Resonance Imaging - methods; dynamic shimming; Electromagnetic Fields; Female; field camera; field control; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Male; NMR field probes; Radiometry - methods; Reproducibility of Results; Respiratory Mechanics; Respiratory-Gated Imaging Techniques - methods; Sensitivity and Specificity; T2-weighted imaging; NMR field probes; dynamic shimming; T2-weighted imaging; field control; 7 Tesla; field camera
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.25838

Purpose Real‐time field control can serve to reduce respiratory field perturbations during T2* 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 T2*‐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 T2* imaging toward challenging patients and brain regions. Magn Reson Med 76:430–439, 2016. © 2015 Wiley Periodicals, Inc.