Journal ArticleDOI
Design of a radiative surface coil array element at 7 T: the single-side adapted dipole antenna.
Alexander J.E. Raaijmakers,Özlem Ipek,Dennis W. J. Klomp,Cecilia Possanzini,Paul R. Harvey,J J W Lagendijk,C.A.T. Van den Berg +6 more
TLDR
This work presents a novel design approach, regarding coil array elements as antennas, which is characterized by comparison with three other, more conventional designs using finite difference time domain (FDTD) simulations and B +1 measurements on a phantom.Abstract:
Ultra high field MR imaging (≥7 T) of deeply located targets in the body is facing some radiofrequency-field related challenges: interference patterns, reduced penetration depth, and higher Specific Absorbtion Ratio (SAR) levels. These can be alleviated by redesigning the elements of the transmit or transceive array. This is because at these high excitation field (B1) frequencies, conventional array element designs may have become suboptimal. In this work, an alternative design approach is presented, regarding coil array elements as antennas. Following this approach, the Poynting vector of the element should be oriented towards the imaging target region. The single-side adapted dipole antenna is a novel design that fulfills this requirement. The performance of this design as a transmit coil array element has been characterized by comparison with three other, more conventional designs using finite difference time domain (FDTD) simulations and B measurements on a phantom. Results show that the B level at the deeper regions is higher while maintaining relatively low SAR levels. Also, the B field distribution is more symmetrical and more uniform, promising better image homogeneity. Eight radiative antennas have been combined into a belt-like surface array for prostate imaging. T1-weighted (T1W) and T2-weighted (T2W) volunteer images are presented along with B measurements to demonstrate the improved efficiency. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.read more
Citations
More filters
Journal ArticleDOI
Pros and cons of ultra-high-field MRI/MRS for human application.
Mark E. Ladd,Peter Bachert,Peter Bachert,Martin Meyerspeer,Ewald Moser,Armin M. Nagel,Armin M. Nagel,David G. Norris,David G. Norris,Sebastian Schmitter,Sebastian Schmitter,Oliver Speck,Sina Straub,Moritz Zaiss +13 more
TL;DR: An overview of some of the latest methodological developments in human ultra-high field MRI/MRS as well as associated clinical and scientific applications is presented, with emphasis on techniques that particularly benefit from the changing physical characteristics at high magnetic fields.
Journal ArticleDOI
The fractionated dipole antenna: A new antenna for body imaging at 7 Tesla.
Alexander J.E. Raaijmakers,Michel Italiaander,Ingmar J. Voogt,Peter R. Luijten,Johannes M. Hoogduin,Dennis W. J. Klomp,Cornelis A. T. van den Berg +6 more
TL;DR: A fractionated dipole antenna is presented: a dipole where the legs are split into segments that are interconnected by capacitors or inductors.
Journal ArticleDOI
Magnetic resonance thermometry: Methodology, pitfalls and practical solutions
Lukas Winter,Eva Oberacker,Katharina Paul,Yiyi Ji,Celal Oezerdem,Pirus Ghadjar,Alexander Thieme,Volker Budach,Peter Wust,Thoralf Niendorf +9 more
TL;DR: This review summarises and discusses advances in MR thermometry, providing practical considerations, pitfalls and technical obstacles constraining temperature measurement accuracy, spatial and temporal resolution in vivo.
Journal ArticleDOI
Parallel transmission for ultrahigh‐field imaging
TL;DR: This review discusses the many ways in which parallel transmission provides previously unavailable degrees of freedom that allow full spatial and temporal control of the radiofrequency (RF) fields, ranging from making more uniform transmit fields to the design of subject‐tailored RF pulses for both uniform excitation and spatial selection.
Journal ArticleDOI
A 16-channel combined loop-dipole transceiver array for 7 Tesla body MRI
TL;DR: To develop a 16‐channel transceive body imaging array at 7.0 T with improved transmit, receive, and specific absorption rate (SAR) performance by combining both loop and dipole elements and using their respective and complementary near and far field characteristics.
References
More filters
Journal ArticleDOI
High-field MRI of brain cortical substructure based on signal phase
Jeff H. Duyn,Peter van Gelderen,Tie-Qiang Li,Jacco A. de Zwart,Alan P. Koretsky,Masaki Fukunaga +5 more
TL;DR: In MRI of the human brain, large improvements in contrast to noise in high-resolution images are possible by exploiting the MRI signal phase at high magnetic field strength, an almost 10-fold improvement over conventional MRI techniques that do not use image phase.
Journal ArticleDOI
High-field fMRI unveils orientation columns in humans.
TL;DR: It is demonstrated, by using high-field (7-T) fMRI, the existence and spatial features of orientation- selective columns in humans, and striking similarities were found with the knownatial features of these columns in monkeys.
Journal ArticleDOI
Sensitivity and power deposition in a high-field imaging experiment.
TL;DR: Image signal‐to‐noise ratio and power dissipation are investigated theoretically up to 400 MHz; the free induction decay is sometimes found to be annulled and the traditional, low‐frequency formulation is compared.
Journal ArticleDOI
Transmit and receive transmission line arrays for 7 Tesla parallel imaging
Gregor Adriany,Pierre-Francois Van de Moortele,Florian Wiesinger,Steen Moeller,John P. Strupp,Peter Andersen,Carl Snyder,Xiaoliang Zhang,Wei Chen,Klaas P. Pruessmann,Peter Boesiger,Tommy Vaughan,K. Ugurbil +12 more
TL;DR: With both the four‐ and the eight‐channel arrays, parallel imaging with sensitivity encoding with high reduction numbers was feasible at 7 T in the human head.
Journal ArticleDOI
Local B1+ shimming for prostate imaging with transceiver arrays at 7T based on subject-dependent transmit phase measurements.
Gregory J. Metzger,Carl Snyder,Can Akgun,Tommy Vaughan,Kamil Ugurbil,Kamil Ugurbil,Pierre-Francois Van de Moortele +6 more
TL;DR: This study demonstrates the tremendous impact of fast local B1+ phase shimming on ultrahigh magnetic field body imaging with high‐quality prostate images obtained with transceiver arrays at 7T.
Related Papers (5)
The Virtual Family—development of surface-based anatomical models of two adults and two children for dosimetric simulations
Andreas Christ,Wolfgang Kainz,Eckhart G. Hahn,Katharina Honegger,Marcel Zefferer,Esra Neufeld,Esra Neufeld,Wolfgang Rascher,Rolf Janka,Werner Bautz,Ji Chen,Berthold Kiefer,Peter Schmitt,Hans Peter Hollenbach,Jianxiang Shen,M. Oberle,Dominik Szczerba,Anthony Kam,Joshua Guag,Niels Kuster,Niels Kuster +20 more