Lena Nohava^1,2, Michael Obermann¹, Roberta Frass-Kriegl¹, Karyna Isaieva², Claire Dessale³, Jacques Felblinger^2,3, and Elmar Laistler^1
1High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²IADI, Inserm, Université de Lorraine, Nancy, France, ³CHRU-Nancy, Inserm, Université de Lorraine, CIC, Innovation Technologique, Nancy, France

A dedicated radio frequency coil design for MR mammography needs to optimize sensitivity, reduce scan time, and improve patient comfort to ultimately facilitate diagnosis. We investigate signal-to-noise ratio and parallel imaging performance differences between widely used commercial 16-/18-channel receive coils for breast MRI at 3 T in prone and supine position and an in-house developed 28-channel wearable coil array (“BraCoil”). An SNR gain of up to a factor of 6 with BraCoil was found in this phantom study.

Jessica Ann McKay-Nault¹, Catherine J Moran¹, Jeremiah Hess², Jana Vincent³, Fraser Robb³, Bruce L Daniel¹, and Brian A Hargreaves^1
1Department of Radiology, Stanford University, Stanford, CA, United States, ²Department of Bioengineering, Stanford University, Stanford, CA, United States, ³GE Healthcare, Aurora, OH, United States

Recent work has developed supine breast imaging for improved correlation with surgery and comfort but will likely require breast-specific coils to maximize the SNR. Comparing prone and supine SNR can be difficult due to substantial deformation between the positions and heterogeneity of the patient population. We measured SNR in a constant-tissue model to reduce dependence on tissue heterogeneity and provide an overall SNR across the volume of interest. We compared SNR of a novel 60-channel supine coil and a standard prone coil. In the cosntant-tissue images, the supine 60-channel coil increased SNR by 33%, 78% and 80% across 3 volunteers.

Konstantinos Papoutsis¹, Jérémie Clément¹, Stephen E Ogier¹, Joseph V Hajnal^1,2, Vicky Goh³, Gary J R Cook³, and Özlem Ipek^1
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, ²Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, ³Department of Cancer Imaging, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom

We present the first continuous 30-channel loop receive coil array combined with the 10-channel dipole parallel-transmit array for 7 Tesla body imaging. Array comprises a flexible anterior part with 6 dipoles and 18 loops, with 35cm longitudinal coverage along with a hard plastic posterior part containing 4 dipoles and 12 loops. Special features were added to help patient comfort and overcome cabling limitations. Simulations with computational human model show adequate B₁⁺ coverage in areas of interest such as the prostate. Phantom images were taken showing promising results. Further development will follow, and human imaging is planned in the near future.

Manvitha Sreereddy¹, Michael Bock¹, and Ali Caglar Özen^1
1Dept. Radiology, Medical Physics, Medical Center - University of Freiburg, Freiburg, Germany

Light-weight and flexible RF coil arrays are needed to obtain high SNR which is translated into shorter scan times and to increase patient compliance. Trans­mission line resonators or shielded loop resonators (SLR) are insensitive to the changes in geometry and form, since the tuning is determined by the length of the transmission line. In this study, we propose two parameters and a test setup to evaluate coaxial cables and relate this to the SLR performance. Modularity is demonstrated on facial coil that can be attached to the face masks. 

Aimé Labbé¹ and Marie Poirier-Quinot^1
1Université Paris-Saclay, CEA, CNRS, Inserm, Laboratoire d'Imagerie Biomédicale Multimodale Paris Saclay, Orsay, France

We introduce pycoilib, a python library developed for the computation of self and mutual inductance of coils. The library allows the user to design coils by dividing their three-dimensional geometry into collections of lines, arcs and circles, and by specifying the geometry of the cross-section of the coil wire.  In a case study, the self-inductance of a deformable coil is computed as a function of its configuration. Pycoilib has the potential to become a valuable tool for prototyping, as well as teaching.

Stephen E. Ogier¹, Shaihan J. Malik¹, and Joseph V. Hajnal^1,2
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, ²Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom

A typical parallel transmit system has an equal number of RF power amplifiers individually connected to an equal number of coil elements. When performing B₁⁺ shimming, the maximum B₁⁺ available is limited by single channel amplifier performance. RF networks which allow for power to be shared between transmit channels have been proposed as a way to overcome this limitation, but fixed networks only offer performance gains over limited ranges of relative phases between channels. Adding a high-power phase shifter between a power-sharing network and coil element can combat this, even with only a few bits of resolution.

Bernhard Gruber^1,2, Michael Obermann¹, Lena Nohava¹, Maxim Zaitsev¹, Lawrence L. Wald³, Jason P. Stockmann³, and Elmar Laistler^1
1High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ²A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA, United States, ³A.A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States

Integrated B₀ shimming capability with RF coil arrays has already shown advantages in dense configurations. For highly flexible arrays this approach is a challenge due to the bulky RF chokes required to bypass the segmenting capacitors of classical loop coils. In this work we present a flexible 4-channel coaxial coil array module with integrated B₀ shimming requiring only two RF chokes per shim channel and thereby demonstrate the feasibility of integrating B₀ shim capability into flexible arrays.

Wenjun Wang¹, Vitaliy Zhurbenko¹, Juan Diego Sánchez Heredia², and Jan Henrik Ardenkjær Larsen^2
1Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark, ²Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark

Si diodes can require elevated forward bias voltage to achieve sufficient forward bias current when they are placed in a strong static magnetic field B₀ at cryogenic temperatures. This may disrupt active decoupling circuit operation in cryogenic MRI coils. Diodes may still operate if aligned in a certain way with the B₀ field, which is studied in this work.

Vitaliy Zhurbenko¹, Juan Diego Sanchez Heredia¹, Wenjun Wang¹, and Jan Henrik Ardenkjær-Larsen^1
1Techical University of Denmark, Kgs. Lyngby, Denmark

Self-resonant coils are well suitable for flexible array design. The size of such coils is dictated by the RF signal wavelength, which makes the design challenging at low frequencies.  In this work, 13C tuning is achieved by combining distributed and lumped capacitance with the self-inductance of an RG-178 coaxial cable. A ¹H trap is moved from the coil to the board of the preamplifier for better coil flexibility. The active ¹³C decoupling circuit is compact and broadband. The approach is used to develop a flexible 8-channel receive array of parallel-resonance coils for ¹³C-imaging. The array elements exhibit low noise correlation.

Wenjun Wang¹, Vitaliy Zhurbenko¹, Juan Diego Sánchez Heredia², and Jan Henrik Ardenkjær Larsen^2
1Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark, ²Department of Health Technology, Technical University of Denmark, Kongens Lyngby, Denmark

The SNR performances of a three- and a four-element matching circuit topologies are compared for the case of 3 T ¹³C imaging. The benefit to SNR of cryogenic cooling is also compared against the choice of matching networks. Results show that while cryogenic cooling can improve the output SNR by 2–3 dB, a less lossy matching network design can improve the SNR performance by 7–8 dB. The importance of matching network design ought not to be dismissed.

Camila Pereira Sousa^1,2, Jean-Lynce Gnanago¹, Valernst Gilmus¹, Tony Gerges¹, Philippe Lombard¹, Michel Cabrera¹, Hugo Dorez², and Simon August Lambert^1
1Université de Lyon, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, CNRS, Ampère UMR5005, Villeurbanne, France, ²Hawkcell, Marcy l'Etoile, France

In the last few years, there has been an increasing interest from the scientific community in the fabrication of flexible coils. Several methods can be used for the manufacture of flexible coil, mainly screen-printed coils on flexible substrates. In this work, three different screen printing coils with different layers of silver ink were manufactured and their quality factors were measured on bench. A MR-coil combining screen-printed process with electrodeposition step was also built. The additional manufacture step allowed improving drastically Q factor of our screen-printed coil with more than one order of magnitude while maintaining good flexibility of the substrate.

Edith Valle¹, Travis Carrell², Peter P. Nghiem³, Steven M. Wright^1,2, and Mary P. McDougall^1,2
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States, ²Biomedical Engineering, Texas A&M University, College Station, TX, United States, ³Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, United States

Duchenne muscular dystrophy (DMD) is a debilitating genetic muscle disorder. To study and characterize this disease efficiently, our group has developed a set of custom single-tuned and multi-tuned coils. We have acquired ¹H, ²³Na and ³¹P data from 20 healthy and diseased samples. Some of the studied biomarkers have shown clear distinctions between healthy and diseased samples.