Bent folded-end dipole head array for ultrahigh-field MRI turns "dielectric resonance" from an enemy to a friend.
RF head array
RF shimming
TE mode of a human head
folded-end dipole
ultrahigh-field MRI
whole-brain coverage
Journal
Magnetic resonance in medicine
ISSN: 1522-2594
Titre abrégé: Magn Reson Med
Pays: United States
ID NLM: 8505245
Informations de publication
Date de publication:
12 2020
12 2020
Historique:
received:
11
03
2020
revised:
16
04
2020
accepted:
03
05
2020
pubmed:
7
7
2020
medline:
15
5
2021
entrez:
7
7
2020
Statut:
ppublish
Résumé
To provide transmit whole-brain coverage at 9.4 T using an array with only eight elements and improve the specific absorption rate (SAR) performance, a novel dipole array was developed, constructed, and tested. The array consists of eight optimized bent folded-end dipole antennas circumscribing a head. Due to the asymmetrical shape of the dipoles (bending and folding) and the presence of an RF shield near the folded portion, the array simultaneously excites two modes: a circular polarized mode of the array itself, and the TE mode ("dielectric resonance") of the human head. Mode mixing can be controlled by changing the length of the folded portion. Due to this mixing, the new dipole array improves longitudinal coverage as compared with unfolded dipoles. By optimizing the length of the folded portion, we can also minimize the peak local SAR (pSAR) value and decouple adjacent dipole elements. The new array improves the SEE (< In general, we demonstrate that rather than compensating for the constructive interference effect using additional hardware, we can use the "dielectric resonance" to improve coverage, transmit field homogeneity, and SAR efficiency. Overall, this design approach not only improves the transmit performance in terms of the coverage and SAR, but substantially simplifies the common surface loop array design, making it more robust, and therefore safer.
Types de publication
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Langues
eng
Sous-ensembles de citation
IM
Pagination
3453-3467Informations de copyright
© 2020 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.
Références
Pohmann R, Speck O, Scheffler K. Signal-to-noise ratio and MR tissue parameters in human brain imaging at 3, 7, and 9.4 tesla using current receive coil arrays. Magn Reson Med. 2016;75:801-809.
Guerin B, Villena JF, Polimeridis AG, et al. The ultimate signal-to-noise ratio in realistic body models. Magn Reson Med. 2017;78:1969-1980.
Pfrommer A, Henning A. The ultimate intrinsic signal-to-noise ratio of loop- and dipole-like current patterns in a realistic human head model. Magn Reson Med. 2018;80:2122-2138.
Glover GH, Hayes CE, Pelc NJ, et al. Comparison of linear and circular polarization for magnetic resonance imaging. J Magn Reson. 1985;64:255-270.
Wen H, Jaffer FA, Denison TJ, Duewell S, Chesnick AC, Balaban RS. The evaluation of dielectric resonators H2O or D2O as RF coils for high-field MR imaging and spectroscopy. J Magn Reson B. 1996;110:117-123.
Vaughan JT, Garwood M, Collins CM, et al. 7T vs. 4T: RF power, homogeneity, and signal-to-noise comparison in head images. Magn Reson Med. 2001;46:24-30.
Collins CM, Liu W, Schreiber W, Yang QX, Smith MB. Central brightening due to constructive interference with, without, and despite dielectric resonance. J Magn Reson Imag. 2005;21:192-196.
Avdievich NI. Transceiver phased arrays for human brain studies at 7 T. Appl Magn Res. 2011;41:483-506.
Cao Z, Park J, Cho Z-H, Collins CM. Numerical evaluation of image homogeneity, signal-to-noise ratio, and specific absorption rate for human brain imaging at 1.5, 3, 7, 10.5, and 14T in an 8-channel transmit/receive array. J Magn Reson Imag. 2015;71:1432-1439.
Adriany G, de Moortele P-F, Wiesinger F, et al. Transmit and receive transmission line arrays for 7 Tesla parallel imaging. Magn Reson Med. 2005;53:434-445.
Avdievich NI, Hoffmann J, Shajan GA, et al. Evaluation of transmit efficiency and SAR for a tight fit transceiver human head phased array at 9.4 T. NMR Biomed. 2017;30:1-12.
Avdievich NI, Giapitzakis IA, Pfrommer A, Henning A. Decoupling of the transceiver phased array for human brain imaging at 9.4 T: loop overlapping rediscovered. Magn Reson Med. 2018;79:1200-1211.
Gilbert KM, Belliveau J-G, Curtis AT, Gati JS, Klassen LM, Menon RS. A conformal transceive array for 7 T neuroimaging. Magn Reson Med. 2012;67:1487-1496.
Shajan G, Kozlov M, Hoffmann J, et al. A 16-channel dual-row transmit array in combination with a 31-element receive array for human brain imaging at 9.4 T. Magn Reson Med. 2014;71:870-879.
Avdievich NI, Giapitzakis IA, Pfrommer A, Henning A. Decoupling of a double-row 16-element tight-fit transceiver phased array for human whole brain imaging at 9.4T. NMR BioMed. 2018;31:1-13.
Adriany A, Schillak A, Waks M, et al. A modular 16 ch. transmit/32 ch. receive array for parallel transmission and high resolution fMRI at 7 Tesla. In: Proceedings of the 23rd Annual Meeting of ISMRM, Toronto, Ontario, Canada, 2015. p 622.
Hoffmann J, Shajan G, Scheffler K, Pohmann R. Numerical and experimental evaluation of RF shimming in the human brain at 9.4 T using a dual-row transmit array. MAGMA. 2014;27:373-386.
Mao W, Smith MB, Collins CM. Exploring the limits of RF shimming for high-field MRI of the human head. Magn Reson Med. 2006;56:918-922.
Katscher U, Börnert P, Leussler C, Van den Brink JS. Transmit SENSE. Magn Reson Med. 2003;49:144-150.
Zhu Y. Parallel excitation with an array of transmit coils. Magn Reson Med. 2004;51:775-784.
Avdievich NI, Oh S-H, Hetherington HP, Collins CM. Improved homogeneity of the transmit field by simultaneous transmission with phased array and volume coil. J Magn Res Imag. 2010;32:476-481.
Wang S, Murphy-Boesch J, Merkle H, Koretsky AP, Duyn JH. B1 homogenization in MRI by multilayer coupled coils. IEEE Trans Med Imag. 2009;28:551-554.
Merkle H, Murphy-Boesch J, van Gelderen P, et al. Transmit B1-field correction at 7T using actively tuned coupled inner elements. Magn Reson Med. 2011;66:901-910.
Teeuwisse WM, Brink WM, Webb AG. Quantitative assessment of the effects of high-permittivity pads in 7 Tesla MRI of the brain. Magn Reson Med. 2012;67:1285-1293.
O’Reilly TPA, Webb AG, Brink WM. Practical improvements in the design of high permittivity pads for dielectric shimming in neuroimaging at 7 T. J Magn Reson. 2016;270:108-114.
Raaijmakers AJE, Ipek O, Klomp DWJ, et al. Design of a radiative surface coil array element at 7T: the single-side adaptive dipole antenna. Magn Reson Med. 2011;66:1488-1497.
Oezerdem C, Winter L, Graessl A, et al. 16-channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla. Magn Reson Med. 2016;75:2553-2565.
Raaijmakers AJE, Italiaander M, Voogt IJ, et al. The fractionated dipole antenna: a new antenna for body imaging at 7 Tesla. Magn Reson Med. 2016;75:1366-1374.
Chen G, Cloos M, Sodickson D, Wiggins G. A 7T 8 channel transmit-receive dipole array for head imaging: dipole element and coil evaluation. In: Proceedings of the 22nd Annual Meeting of ISMRM, Milan, Italy, 2014. p 621.
Tian J, Lagore R, Delabarre L, Vaughan JT. Dipole array design considerations for head MRI at 10.5T. In: Proceedings of 24th Annual Meeting of ISMRM, Singapore, 2016. p 3524.
Oh C-H, Lee C, Kumar S, et al. Top-hat dipole RF coil with large field of view for 7 T brain MR imaging. In: Proceedings of 25th Annual Meeting of ISMRM, Honolulu, Hawai, 2017. p 767.
Connell IRO, Mennon RS. Shape optimization of an electric dipole array for 7 Tesla neuroimaging. IEEE Trans Med Imag. 2019;38:2177-2187.
Clément JD, Gruetter R, Ipek Ö. A human cerebral and cerebellar 8-channel transceive RF dipole coil array at 7T. Magn Reson Med. 2019;81:1447-1458.
Roemer PB, Edelstein WA, Hayes CE, Souza SP, Mueller OM. The NMR phased array. Magn Reson Med. 1990;16:192-225.
Jevtic J. Ladder networks for capacitive decoupling in phased-array coils. In: Proceedings of the 9th Annual Meeting of ISMRM, Glasgow, Scotland, 2001. p 17.
Avdievich NI, Solomakha G, Ruhm L, Scheffler K, Henning A. Evaluation of short folded dipole antennas as receive elements of ultra-high field human head array. Magn Reson Med. 2019;82:811-824.
Beck BL, Jenkins KA, Rocca JR, Fitzsimmons JR. Tissue-equivalent phantoms for high frequencies. Concepts Magn Reson B. 2004;20:30-33.
Christ A, Kainz W, Hahn EG, et al. The virtual family-development of surface based anatomical models of two adults and two children for dosimetric simulations. Phys Med Biol. 2010;55:N23-N38.
Avdievich NI, Solomakha G, Ruhm L, Henning A, Scheffler K. Decoupling of folded dipole antenna elements of a human head array at 9.4T. In: Proceedings of the 29th Annual Meeting of ISMRM, Sydney, Australia, 2020. p 2436.
Alecci M, Collins CM, James Wilson J, Liu W, Smith MB, Jezzard P. Theoretical and experimental evaluation of detached endcaps for 3 T birdcage coils. Magn Reson Med. 2003;49:363-370.
Hoffmann J, Henning A, Giapitzakis IA, et al. Safety testing and operational procedures for self-developed radiofrequency coils. NMR Biomed. 2016;29:1131-1144.
Yarnykh VL. Actual flip-angle imaging in the pulsed steady state: a method for rapid three-dimensional mapping of the transmitted radiofrequency field. Magn Reson Med. 2007;57:192-200.
Pruessmann KP, Weiger M, Scheidegger MB, Boesiger P. SENSE: sensitivity encoding for fast MRI. Magn Reson Med. 1999;42:952-962.
Marques JP, Kober T, Krueger G, van der Zwaag W, Van de Moortele PF, Gruetter R. MP2RAGE, a self bias-field corrected sequence for improved segmentation and T1-mapping at high field. NeuroImage. 2010;49:1271-1281.
Hurley AC, Al-Radaideh A, Bai L, et al. Tailored RF pulse for magnetization inversion at ultrahigh field. Magn Reson Med. 2010;63:51-58.
Nabetani A, McKinnon G, Nakada T. In: Proceedings of the 14th Annual Meeting of ISMRM, Seattle, Washington, 2006. p 2608.
Avdievich NI, Pan JW, Hetherington HP. Improved longitudinal coverage for human brain at 7T: a 16 element transceiver array. In: Proceedings of the 19th Annual Meeting of ISMRM, Montreal, Canada, 2011. p 328.
Lattanzi R, Wiggins GC, Zhang B, Duan Q, Brown R, Sodickson DK. Approaching ultimate intrinsic signal-to-noise ratio with loop and dipole antennas. Magn Reson Med. 2018;79:1789-1803.
Avdievich NI, Giapitzakis IA, Bause J, Shajan G, Scheffler K, Henning A. Double-row 18-loop transceive/32-loop receive tight-fit array provides for whole-brain coverage, high transmit performance, and SNR improvement near the brain center at 9.4T. Magn Reson Med. 2019;81:3392-3405.