Synopsis
Phased coil arrays have changed dramatically since their earliest inception with increasing complexity and channel density. These changes have led to the development of an innovative fully flexible coil design with highly integrated electronics, which can be placed easily within todays modern coil arrays to reduce the design complexity associated with the large number of channels. Recently, research has been done to improve the interface between RF coils and MRI systems by transferring the data over wireless or optical connections within the scanner bore. The evolution of all of these new technologies can provide a fully wireless, or lightly tethered, future for coil arrays and allow potential the realization of a patient-friendly phased array.
Target Audience
The research engineer or scientist interested in the next generation of coil arrayconstruction, coil element flexibility and novel methods of coil / system interfaces to the MRIscanner.Discussion
Since the earliest research on phased arrays1 there has been work on improving performance and clinical utility especially with the advent of parallel imaging2 and massively parallel arrays3. Additionally, research into the development of lightweight flexible coils has been reported recently by a variety of authors utilizing novel materials4,5 and flexible conductor constructions,6,7,8,9,10. Essential to the future success of flexible coil research is the development of new integrated pre-amplifier technologies, which can be placed near to the coil elements. For example, a pre-amplifier has been used to receive RF signals in a glove array used for dynamic magnetic resonance imaging of the hand11. Additionally, the miniaturization of the digital receiver footprint has recently been elegantly demonstrated with an integrated CMOS receiver design,12, 13.
Lightweight and flexible coil elements in an array have been shown to provide improved customer comfort, compliance and clinician acceptance14. To take full advantage of the light weight flexible coil design, it is desirable transfer data from the RF coil array to the MRI system via a lightly tethered with slimmer cabling or a fully wireless link that completely “cuts-the-cord” of the RF connection. To accomplish this, a number of completely new wireless coil technologies are required to be developed including wireless power transfer15, wireless data transmission16, wireless clock syncing17 and wireless decoupling18. The wireless decoupling can be enabled by using lower power voltage controlled RF MEMs19,20 and GaN HEMT21 devices, which have been created and tested with positive results inside RF coil arrays.. These devices potentially require less power for decoupling than traditional PIN diodes, which is an important consideration for the success of future wireless technologies. Lastly, an application of wireless data transfer within the bore has recently been performed to enable wireless B0-shimming with non-magnetic battery packs over a WIFI control22 data link. This technology is compatible with the flexible conductor constructions23, which will be useful in future clinical applications.
Conclusions
Flexible, lightweight coils are now a reality and current research would indicate the potentialfuture of lightly tethered or wireless interface with the MRI system.Acknowledgements
Greig Scott, Stanford University
Dean Darnell Duke University
References
1. “The NMR Phased Array”
by PB Roemer, WA Edelstein, CE Hayes, SP Souza, OM
Mueller: Magnetic
Resonance in Medicine Vol 16, 192–225, (1990).
2. “Simultaneous
acquisition of spatial harmonics (SMASH): fast imaging with
radiofrequency coil
arrays.” By DK Sodickson and WJ Manning: Magnetic Resonance
in Medicine Vol 38(4)
:591-603, (1997).
3. “128-Channel Body MRI
With a Flexible High- Density Receiver-Coil Array, by CJ Hardy,
RO Giaquinto, JE Piel, KW
Rohling, L. Marinelli, DJ Blezek, EW Fiveland, RD Darrow, TK
Foo: Journal of Magnetic
Resonance Imaging 28:1219–1225 (2008).
4. “A flexible
mercury-filled surface coil for MR imaging.” by J A Malko, E C McClees, I F
Braun, P C Davis and J C
Hoffman: American Journal of Neuroradiology March 1986,
7 (2) 246-247; \
5. “Liquid metal based
deformable transmitter for MR imaging: A feasibility study” by Q.
Duan, H. Lu, C. Cooper, X.
Zong, J.H. Duyn, M.D. Dickey and S. Wang. Abstract #3503,
ISMRM Singapore (2016).
6. “Stretchable Coil
Arrays: Application to Knee Imaging Under Varying Flexion Angles”
by JA Nordmeyer-Massner,
N. DeZanche, and K.P. Pruessmann: Magnetic Resonance
in Medicine 67:872–879
(2012).
7. “Screen-printed
flexible MRI receive coils” by J.R. Corea, A.M. Flynn, B. Lechêne, G.
Scott, GD. Reed, PJ. Shin,
M. Lustig & AC Arias: Nature Communications, Volume 7,
Article number: 10839
(2016).
8. “Development and
Clinical Implementation of Next Generation Very Light Weight and
Extremely Flexible
Receiver Arrays for Pediatric MRI” by S.S. Vasanawala, R. Stormont,
Scott Lindsay, T.
Grafendorfer, J.Y. Cheng, J.M. Pauly, G.C. Scott, J. X. Guzman, V
Taracila, D.Chirayath and
F.Robb: https://arxiv.org/abs/1705.00224 Archive
April_2017:
9. “Characterization and
evaluation of a flexible MRI receive coil array for radiation
therapy MR treatment
planning using highly decoupled RF circuits.” By K. McGee, R.
Stormont, S. Lindsay., V.
Taracila, D. Savitskij, F. Robb, R. Witte, T. Kaufmann, J. Huston
and S. Riederer: Physics
in Medicine in Biology, April (2018).
10. “The Trellis Coil: A
Morphing, Size Adaptable Array Coil” by G. Wiggins and A. Frank:
ISMRM Abstract 0493,
Singapore (2016).
11. “A High-Impedance
Detector-Array Glove For Magnetic Resonance Imaging Of The
Hand. Opens in a new tab”
by B. Zhang, D.K. Sodickson and M.A. Cloos: Nature
Biomedical Engineering.
Aug; 2(8):570-577, (2018).
12. “Integrated CMOS
receiver for wearable coil arrays in MRI applications” by B. Sporrer,
L. Bettini, C. Vogt, A.
Mehmann, J. Reber, J. Marjanovic, D.O. Brunner, T. Burger, K.
Pruessmann, G. Tröster,
and Q. Huang: Proceedings of the 2015 Design, Automation
& Test in Europe
Conference & Exhibition: Pages 1689-1694, Grenoble, France, (2015).
13. “A Fully Integrated
Dual-Channel On-Coil CMOS Receiver for Array Coils in 1.5–10.5 T
MRI” by B. Sporrer, L. Wu,
L. Bettini, C. Vogt, J. Reber, J. Marjanovic, T. Burger; D.O.
Brunner, K.P. Pruessmann,
G. Troster, Q. Huang: IEEE Transactions on Biomedical
Circuits and Systems,
11(6):1245-1255 (2017).
14. “Evaluation of a
flexible 12-channel screen-printed pediatric MRI coil” by S. Winkler, J.
Corea, B. Lechene, K.
O'Brien., J. Bonanni, A. Chaudari, M. Alley, V. Taviani., T.
Grafendorfer, F. Robb, G.
Scott, J. Pauly, M. Lustig, A. Arias, S. Vasanawala S.:
Published Online, Feb 26,
Radiology (2019).
15. “A RF Gated Wireless
Power Transfer System for Wireless MRI Receive Arrays” by K.
Byron, F. Robb, P. Stang,
S. Vasanawala, J. Pauly and G. Scott.: Concepts in Magnetic
Resonance, Vol. 47B, Issue
4, October (2017).
16. “A Millimeter-Wave
Digital Link for Wireless MRI” by K. Aggarwal, K.R. Joshi, Y. Rajavi,
M. Taghivand, J.M. Pauly,
A.S. Poon, G. Scott: IEEE Trans. Med. Imaging, 36(2), p574-
583, Feb. (2017).
17. “Software
Synchronization of Independent Receivers by Transmit Phase Tracking” by
G. Scott, F. Robb, J.
Pauly and P Stang.: ISMRM 4311, Hawaii, (2017).
18. “Wireless Q-spoiling
of Receive Coils at 1.5T MRI”, by J.Y. Lu, F. Robb, J. Pauly, and G.
Scott: ISMRM #4297, Hawaii
(2017).
19. M. Fuentes, E. Weber,
S. Wilson, B. Li, and S. Crozier, “Microelectromechanical systems
(MEMS) based RF-switches
in MRI— A performance study,” ISMRM #422, Stockholm
(2010).
20. “MEMS switch
integrated radio frequency coils and arrays for magnetic resonance
imaging” by S.B Bulumulla,
K. J. Park, E. Fiveland, J. Iannotti and F. Robb: Review of
Scientific Instruments,
Vol 88, 025003 (2017).
21. “Depletion-Mode GaN
HEMT Q-Spoil Switches for MRI Coils” by J.Y. Lu, T. Grafendorfer
T. Zhang, S. Vasanawala,
F. Robb, J. M. Pauly, and G.C. Scott, IEEE Transaction on
Medical Imaging, Vol 35,
No 12, December (2016).
22. “Integrated
radio-frequency/wireless coil design for simultaneous MR image
acquisition and wireless
communication” by D. Darnell, J. Cuthbertson, F. Robb, A.W.
Song, TK Truong: Magnetic
Resonance in Medicine, Sept (2018).
23. “The iPRES-W AIR Coil:
A Flexible RF Coil for Simultaneous MR Image Acquisition,
Wireless Communication,
and Localized B0 Shimming.” By J. Cuthbertson, D. Darnell,
J. Bresticker, R. Stormont, F. Robb, AT Song and T-K Truong.: ISMRM
Paris #16, (2018).