Receive Arrays & Technology
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Wednesday 9 May 2012
Room 202  13:30 - 15:30 Moderators: Lawrence L. Wald, Graham C. Wiggins

13:30 0428.   
Detunable Transmit Array and Flexible Receive Array for 7T Shoulder Imaging
Ryan Brown1, Bei Zhang1, Cem M Deniz1,2, Gene Young Cho1,2, Cornel Stefanescu1, Shumin Wang3, Daniel K Sodickson1, and Graham C Wiggins1
1Radiology, New York University School of Medicine, New York, NY, United States, 2Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States, 3MRI Research Center, Auburn University, Auburn University, AL, United States

Musculoskeletal imaging is becoming a fruitful application at 7T, particularly for the knee and other extremities. Design of a 7T coil for shoulder imaging is more challenging due to the inability to surround the shoulder with a birdcage and the challenges of RF inhomogeneity. A 7T shoulder coil was constructed with a flexible detunable 8 element loop array for transmit and a 10 element flexible domed receive array. Applying birdcage-like phase to the transmit elements produced a serviceable transmit excitation, and SNR gains in deep cartilage of better than 2-fold were obtained compared to 3T.

13:42 0429.   An Open Faced 4 ch. Loop Transmit / 16 ch. Receive Array Coil for HiRes fMRI at 7 Tesla
Gregor Adriany1, Matt Waks2, Brandon Tramm2, Scott Schillak2, Essa Yacoub1, Federico de Martino1,3, Pierre-Francois Van de Moortele1, Thomas Naselaris1, Cheryl Olman1, Tommy Vaughan1, and Kamil Ugurbil1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, 2Virtumed LLC, Minneapolis, MN, United States,3Maastricht University, Netherlands

Utilizing rapid prototyping for an open-faced holder design a 4 channel loop transmit /16 channel receive array coil was built. The coil operates inside a spatially constrictive head gradient insert but still supports full visual field task presentation. The design is particularly suitable for visual, occipital and auditory cortex neuroscience applications. The coil did not require subject dependent tuning or matching, saving valuable setup time. Significant improvements in transmit efficiency and SNR over comparable whole head arrays were observed.

13:54 0430.   
A 16-channel micro strip Tx/Rx array for bilateral breast imaging at 7 Tesla
Stephan Orzada1,2, Stefan Maderwald1, Linda Kopp1, Mark E. Ladd1,2, Kai Nassenstein2, and Andreas K. Bitz1,2
1Erwin L. Hahn Institute for MRI, Essen, NRW, Germany, 2Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, NRW, Germany

Breast imaging at 7 Tesla is promising due to the higher SNR in comparison to 1.5 and 3 Tesla, but at the same time it is challenging due to the short wavelength and the lack of a body coil for transmission. In this work we present a 16-channel transmit/receive array for bilateral breast MRI at 7 Tesla consisting of two U-shaped arrays of 8 micro strip lines each.

14:06 0431.   
19-channel Rx array coil and 4-channel Tx loop array for cervical spinal cord imaging at 7T MRI
Wei Zhao1, Julien Cohen-Adad1, Jonathan R Polimeni1, Bastien Guerin1, Boris Keil1, Peter Serano1, Azma Mareyam1, Philipp Hoecht2, and Lawrence L Wald1
1Athinoula A. Martinos Center for Biomedical Imaging, Dept. of Radiology Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, United States, 2Siemens Medical Solutions USA Inc., Charlestown, Massachusetts, United States

In this work, we developed a 19-channel receive array and a 4-channel parallel transmit loop array for imaging the cervical spinal cord at 7T. We addressed the challenge of obtaining uniform B1+ excitation by mounting a 4-channel degenerate-loop transmit array in the plane posterior to the subject similar to previous work. The 4-channel transmit loop array had the sufficient decoupling <-16dB between each element and produced a relatively uniform excitation when driven with a single amplifier with a 45 degree phase increment in each element. The receive array loops closely contoured to the body and yielded high SNR performance as well as the ability to accelerated EPI imaging with R=3 in the C-spine.

14:18 0432.   An Investigation of RF Frontend Scalability
Yudong Zhu1, Xing Yang1, Bei Zhang1, and Leeor Alon1
1NYU School of Medicine, New York, New York, United States

Most workhorse receive coils are each optimized for a certain body region, parallel acceleration, and frequency. To improve workflow a significant recent development strives to consolidate a scanner’s suite of coils with a multi-element coil ensemble that encloses a subject in a fixed way but allows application-dependent multi-port signal combination. The task of creating a “one-structure-fits-all” coil to replace dedicated coils is very challenging. We explore the perspective of optimizing RF frontend scalability, the ability for a same RF coil structure to adapt to most tasks by leveraging flexible and advantageous signal combination afforded by a large number of channels.

14:30 0433.   
Noise contributions in receive coil arrays
Matteo Pavan1, Roger Lüchinger1, and Klaas Paul Pruessmann1
1ETH and University Zurich, Zurich, ZH, Switzerland

Receive coil arrays are used in MR to maximize the Signal to Noise Ration (SNR) of measured signal. Engineer’s goal is to build such arrays with high filling factor using electrical components with minimal losses, and decoupled coil elements such that elements noise and noise correlation is reduced. In this work we experimentally show that the design a proper matching network is critical because the matching network is the first component in the receive chain. Simple one channel and two channels experiments were performed with the use of an Automatic Matching Network (AMN) system.

14:42 0434.   
Bespoke Coils: Screen-Printed, Tailored Flexible MRI Receiver Coils
Joseph Corea1, Anita Flynn1, Greig Scott2, Ana Claudia Arias1, and Michael Lustig1
1EECS, UC Berkeley, Berkeley, California, United States, 2Electrical Engineering, Stanford, Stanford, California, United States

Our aim is to fabricate custom-made (e.g. bespoke) tailored flexible coils that can fit to a wide variety of patients and anatomy, thus improving sensitivity and signal-to-noise. Utilizing advances in printed electronics, we present a new technique for designing and fabricating flexible MRI receiver coils. These coils are printed on cloth-like mesh substrates using a screen printing technique. All components are processed from solution and printed onto several plastic mesh substrates.

14:54 0435.   
An investigation on the channel spacing limits in SSB-based wireless MRI receiver arrays
Matthew J Riffe1, Natalia Gudino1, Michael D Twieg2, Jeremy A Heilman3, and Mark A Griswold1,4
1Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 2Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, Ohio, United States, 3Quality Electrodynamics (QED), Mayfield Village, Ohio, United States, 4Radiology, Case Western Reserve University, Cleveland, Ohio, United States

Ideally in SSB-based wireless MRI, the frequency spacing between encoded signals is limited by the bandwidth of the MR acquisition. This would allow for a very dense wireless transmission spectrum, which is necessary when transmitting all the signals present in highly parallel detector arrays. Unfortunately, this dense spacing only works if the noise outside the MRI signal bandwidth does not impact the other multiplexed signals. In this work, we show that this interference can have a substantial impact and must be considered during design. We demonstrate this by constructing an eight channel wireless head array for 1.5T.

15:06 0436.   Superconducting Receive-only 7 Tesla Coil for High Resolution Rat Brain DTI permission withheld
Jarek Wosik1,2, Kurt H Bockhorst3, Tan I-Chih4, and Ponnada A Narayana3
1Electrical and Computer Engineering, University of Houston, Houston, Texas, United States, 2Texas Center for Superconductivity, 3Department of Radiology, University of Texas Health Science Center, Houston, Texas, United States, 4The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center, Houston, Texas 77030, United States

We report on the recent development and improvements of a 300-MHz cryogenic (both copper and superconducting) coil for high resolution MRI. The coil comprises of two split rings rotated 180 deg. versus each other and has built-in gold contacts for attaching coupling/matching and detuning circuitry. The coil was fabricated by patterning double-sided thin film on 0.33 mm sapphire substrate (ε=10.4). SNR gains of 77K copper and YBCO coils were measured and compared with theoretical predictions and calculations. SNR/resolution limits of the HTS coil are currently tested for DTI of rat brain and also for 3 D imaging of sciatic mouse nerve.

15:18 0437.   A 12-element Receive Coil Array for the Rat Brain at 11.7T
Stephen Dodd1, Joseph Murphy-Boesch1, Hellmut Merkle1, Afonso Silva1, and Alan Koretsky1
1Laboratory of Functional and Molecular Imaging, NINDS, National Insitutes of Health, Bethesda, MD, United States

A design for 12-element receive array optimized for the geometry of the rat brain is presented. The sensitivity of the array compares favorably with a large surface coil for the whole rat brain. Representative images showing the acceleration capabilities and coverage are shown.