Toward imaging the body at 10.5 tesla

• Published in: Magnetic resonance in medicine Vol. 77; no. 1; pp. 434 - 443
• Main Authors: Ertürk, M. Arcan, Wu, Xiaoping, Eryaman, Yiğitcan, Moortele, Pierre‐François, Auerbach, Edward J., Lagore, Russell L., DelaBarre, Lance, Vaughan, J. Thomas, Uğurbil, Kâmil, Adriany, Gregor, Metzger, Gregory J.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-01-2017
• Subjects: 10.5 Tesla; Adult; Animals; Antenna arrays; body imaging; body imaging at ultra‐high field; Computer Simulation; dipole antenna; Dipole antennas; Equipment Design; Female; Heart; Humans; Image Processing, Computer-Assisted - methods; Imaging; Kidneys; Livestock; Magnetic resonance; Magnetic Resonance Imaging - instrumentation; Magnetic Resonance Imaging - methods; Male; Mathematical models; Models, Anatomic; Nonuniformity; Numerical methods; Organs; parallel transmission; Phantoms, Imaging; Prostate; Radio frequency; Robustness (mathematics); Spokes; Swine; Whole Body Imaging - methods; body imaging at ultra-high field; 10.5 Tesla; body imaging; parallel transmission; dipole antenna
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.26487

Purpose
To explore the potential of performing body imaging at 10.5 Tesla (T) compared with 7.0T through evaluating the transmit/receive performance of similarly configured dipole antenna arrays.
Methods
Fractionated dipole antenna elements for 10.5T body imaging were designed and evaluated using numerical simulations. Transmit performance of antenna arrays inside the prostate, kidneys and heart were investigated and compared with those at 7.0T using both phase‐only radiofrequency (RF) shimming and multi‐spoke pulses. Signal‐to‐noise ratio (SNR) comparisons were also performed. A 10‐channel antenna array was constructed to image the abdomen of a swine at 10.5T. Numerical methods were validated with phantom studies at both field strengths.
Results
Similar power efficiencies were observed inside target organs with phase‐only shimming, but RF nonuniformity was significantly higher at 10.5T. Spokes RF pulses allowed similar transmit performance with accompanying local specific absorption rate increases of 25–90% compared with 7.0T. Relative SNR gains inside the target anatomies were calculated to be >two‐fold higher at 10.5T, and 2.2‐fold SNR gain was measured in a phantom. Gradient echo and fast spin echo imaging demonstrated the feasibility of body imaging at 10.5T with the designed array.
Conclusion
While comparable power efficiencies can be achieved using dipole antenna arrays with static shimming at 10.5T; increasing RF nonuniformities underscore the need for efficient, robust, and safe parallel transmission methods. Magn Reson Med 77:434–443, 2017. © 2016 International Society for Magnetic Resonance in Medicine.