An 8-Channel TX, 16-Channel RX Flexible Body Coil at 7 Tesla Using Both Branches of Centrally Fed Strip Lines as Individual Receive Elements
Stephan Orzada^1,2, Stefan Maderwald^1,2, Mark Oehmigen¹, Mark E. Ladd^1,2, Klaus Solbach³, Andreas K. Bitz^1,2
1Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, NRW, Germany; ²Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, NRW, Germany; ³High Frequency Engineering, University Duisburg-Essen, Duisburg, NRW, Germany

To further increase the capabilities of centrally fed strip line elements, they can be split up into two branches for reception, thereby doubling the number of elements. In this work a flexible body coil with 8 transmit and 16 receive channels built from centrally fed strip line elements with meanders is presented for imaging at 7 Tesla. The new array shows enhanced parallel imaging performance, while good decoupling and transmit penetration are maintained.

A 7-Tesla High Density Transmit with 28-Channel Receive-Only Array Knee Coil
Matthew Finnerty¹, Xiaoyu Yang¹, Tsinghua Zheng¹, Jeremiah Heilman¹, Nicholas Castrilla¹, Joseph Herczak¹, Hiroyuki Fujita^1,2, Tamer S. Ibrahim^3,4, Fernando Boada^3,4, Tiejun Zhao⁵, Franz Schmitt⁶, Bernd Stoeckel⁵, Andreas Potthast⁶, Karsten Wicklow⁶, Siegfried Trattnig⁷, Charles Mamisch⁷, Michael Recht⁸, Daniel Sodickson⁸, Graham Wiggins⁸, Yudong Zhu^8
1Quality Electrodynamics, LLC., Mayfield Village, OH, United States; ²Departments of Physics and Radiology, Case Western Reserve University, Cleveland, OH, United States; ³Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States; ⁴Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States; ⁵Siemens Medical Solutions USA, Inc., Malvern, PA, United States; ⁶Siemens Healthcare, Erlangen, Germany; ⁷Department of Radiology, Medical University of Vienna, Vienna, Austria; ⁸Department of Radiology, NYU Langone Medical Center, New York, United States

As more advanced 7T MRI technology continues to emerge, the development of a wider anatomical range of RF coils has become a greater priority.  In an effort to take advantage of the greater spatial resolution and higher SNR at 7T, a 12-rung birdcage transmitter and 28-channel receive-only array coil has been developed.  To overcome the challenges associated with the shorter wavelength within the human body at 7T, several novel design strategies have been utilized.

Age-Optimized 32-Channel Brain Arrays for 3T Pediatric Imaging
Boris Keil¹, Azma Mareyam¹, Kyoko Fujimoto¹, James N. Blau¹, Veneta Tountcheva¹, Christina Triantafyllou^1,2, Lawrence L. Wald^1,3
1A.A. Martinos Center for Biomedical Imaging, Department of Radiology, MGH, Harvard Medical School, Charlestown, MA, United States; ²A.A. Martinos Imaging Center, Mc Govern Institute for Brain Research, MIT, Cambridge, MA, United States; ³Harvard-MIT Division of Health Sciences and Technology, MIT, Cambridge, MA, United States

Compromising the size and shape of pediatric brain arrays so that “one size fits all” or using adult brain or knee arrays causes a significant degradation of SNR and parallel imaging performance compared to a coil of the appropriate size and shape for a given aged child. Unfortunately, rapid head growth in the first years of life requires either a flexible array approach or multiple sizes which span the size range with reasonable discrete increments. In this work, we developed and tested four incremental sized 32-channel receive only head coils for pediatric patients spanning an age range of 6 months to 7 years old. The constructed coils show significant SNR gains for both accelerated and unaccelerated imaging in pediatric brain imaging.

16-Channel Custom-Fitted Bilateral Breast Coil for Parallel Imaging in Two Directions
Anderson N. Nnewihe^1,2, Thomas Grafendorfer³, Bruce L. Daniel¹, Paul Calderon³, Marcus T. Alley¹, Fraser Robb³, Brian A. Hargreaves^1
1Radiology, Stanford University, Stanford, CA, United States; ²Bioengineering, Stanford University, Stanford, CA, United States; ³GE Healthcare

High spatial and temporal resolution imaging could be used to better classify breast lesions with the potential to improve breast cancer diagnosis.  In this work we compare a novel 16-channel bilateral breast coil to a standard commercially-available 8-channel coil, in terms of SNR and parallel imaging capability in two directions.  Overall we have demonstrated that a closely-fitted surface array can substantially improve both SNR and parallel imaging capability compared with standard 8-channel bilateral breast coils.

Modular Multi-Channel Parallel-Imaging Microfluidics Platform with Exchangeable Capillary Diameters
Dario Mager¹, Andreas Peter¹, Elmar Fischer², Patrick James Smith¹, Jürgen Hennig², Jan Gerrit Korvink^1,3
1Dept. of Microsystems Engineering – IMTEK, University of Freiburg, Freiburg, Germany; ²Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; ³Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany

Solenoidal receiver coils have been directly patterned onto glass capillaries using inkjet printing; in an extension of work that has successfully been used to produce planar receiver coils. Each patterned capillary is housed in a PCB/PMMA holder, which acts as a parallel imaging system for microfluidic analysis.

Travelling Wave Parallel Imaging
David Otto Brunner¹, Jan Paska², Ingmar Graesslin³, Jürg Froehlich², Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; ²Electromagnetic Fields and Microwave Laboratory, ETH Zurich, Zurich, Switzerland; ³Philips Research Europe, Hamburg, Germany

Since the sample becomes considerably larger than the wavelength in human ultra high field MRI, the electrodynamic degrees of freedom within the loaded bore increases. Using a mode selectively fed waveguide section coupling into the loaded bore it is demonstrated that parallel imaging techniques in transmission and reception such as RF shimming and SENSE can be applied in a travelling wave approach in the absence of a RF array coil close by the object. A direct dependence between the parallel imaging performance of this 8 channel system and the number of modes in the waveguide could be shown.

A Modular Automatic Matching Network System
Matteo Pavan¹, Klaas Paul Pruessmann^1
1ETH Zurich, Zurich, Switzerland

In MR measurement, coils are detecting proton signal; they are usually connected through a matching network to very low noise amplifier. The Noise Figure of the amplifier depends on the impedance that its input port sees. To optimize SNR, is important to match this impedance to the one that is reducing at the minimum the noise figure. A new approach for automatic impedance measurement is here presented. This new approach is easy and modular in such a way that it can be scaled to any number of reception channels.

Accurate Noise Level and Noise Covariance Matrix Assessment in Phased Array Coil Without a Noise Scan
Yu Ding¹, Yiu-Cho Chung², Orlando P. Simonetti^1
1The Ohio State University, Columbus, OH, United States; ²Siemens Medical Solutions, Columbus, OH, United States

In this study, we propose an novel method to assess noise level and noise covariance matrix in the k-space data when both signal and noise are present. Experimental results show that the noise level as well as the noise covariance matrix can be accurately derived from multi-frame k-space data without deploying a separate noise scan.

A Magnetic-Field-Tolerant Low-Noise SiGe Pre-Amplifier and T/R Switch
David Ian Hoult¹, Glen Kolansky^1
1Institute for Biodiagnostics, National Research Council Canada, Winnipeg, Manitoba, Canada

The noise figure and gain of GaAs field effect transistors degrade in magnetic fields. A SiGe bipolar transistor is advocated as a replacement giving at 123 MHz a noise figure of 0.6 dB with ~ 20 dB current blocking. Our SiGe pre-amplifier has a noise figure < 1dB from 90 to 200 MHz, a gain of 30 dB, a bandwidth of 73 to 163 MHz and a group delay of 5.4 ns. The accompanying 300 W quarter-wave PIN diode transmit/receive switch has 0.1 dB noise figure, an insertion loss of 1 dB and isolation of ~ 65 dB.

Frequency Selective Negative Feedback to Avoid Preamplifier Oscillation in Multi-Channel Arrays
Thomas Grafendorfer^1,2, Greig Scott², Paul Calderon³, Fraser Robb⁴, Shreyas Vasanawala^5
1RX & ATD Coils, GE Healthcare, Stanford, CA, United States; ²Electrical Engineering, Stanford University, Stanford, CA, United States; ³MR Hardware Engineering, GE Healthcare, Fremont, CA, United States; ⁴Advanced Technology, GEHC Coils, Aurora, OH, United States; ⁵Radiology, Stanford University, Stanford, CA, United States

Placing the preamplifiers close to the coil elements in multi-channel arrays increases preamplifier-decoupling performance, which leads to better SNR and better acceleration performance. Unfortunately it also opens a new feedback path that can easily lead to oscillation. We developed a new strategy by applying frequency selective negative feedback that suppresses the gain at the so-called match split peaks outside the frequency band relevant for MRI. This greatly reduces the possibility for oscillation, and the gain within the signal band stays more or less unaffected.