Kathryn E. Keenan¹, Michael A. Boss¹, Edward F. Jackson², Seon-joo Kown³, Dominique L. Jennings³, and Stephen Russek^1
1National Institute of Standards and Technology, Boulder, CO, United States, ²Imaging Physics, The University of Texas M.D. Anderson Cancer Center, Houston, TX, United States, ³Massachusetts General Hospital, Boston, MA, United States

An MRI system phantom was developed through collaboration between the ISMRM and NIST. We used this phantom to answer: 1) how does measured T1 compare to the known T1; and 2) is there variation in the measured T1 across multiple MRI systems? For more information on the NIST/ISMRM phantom, please visit: http://collaborate.nist.gov/mriphantoms/bin/view/MriPhantoms/MRISystemPhantom.

Ying Hao^1,2, Kai Zhang¹, Ye Wang¹, Xiaoying Wang^1,3, Jing Fang^1,4, Jue Zhang^1,4, and Brad Manor^1,2
1Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, Beijing, China, ²Gerontology Department, Beth Israel Deaconess Medical Center, Boston, MA, United States, ³Radiology Department, Peking University First Hospital, Beijing, Beijing, China, ⁴College of Engineering, Peking University, Beijing, Beijing, China

This novel foot sole stimulator elicited more simulated walking pressure stimulus to the foot sole compared to the former version, meanwhile, it remains no interfered with image quality and did not cause severe motion artifacts. This system is thus feasible for fMRI studies to explore functional brain networks involved in the perception and modulation of the real foot sole somatosensation. Combination of this new tool with functional MRI (fMRI) will afford insight into the functional brain networks underlying the afferent feedback under walking.

Sebastian Schaetz¹, Markus Untenberger¹, Aaron Niebergall¹, and Jens Frahm^2
1Biomedizinische NMR Forschungs GmbH, Max Planck Institute for Biophysical Chemistry, Göttingen, Lower Saxony, Germany, ²Biomedizinische NMR Forschungs GmbH, Max Planck Institute, Göttingen, Lower Saxony, Germany

A novel metal-free motion phantom based on a simple pneumatic rotary motor with optical rotational speed measurement is presented. The phantom facilitates the simulation of various motion speeds from 0.05 to 0.5m/s by air-pressure adjustment. It is a suitable tool for for both qualitative and quantitative evaluation of real-time MRI methods.

Gareth R. Davies¹, Kerrin J. Pine¹, and David J. Lurie^1
1Aberdeen Biomedical Imaging Centre, University of Aberdeen, Aberdeen, Scotland, United Kingdom

Fast Field-Cycling (FFC) MRI systems differ from conventional scanners by their ability to adjust rapidly the magnetic field strength B0 during the pulse sequence. This offers unique image contrast, based on the field-dependence of the spin-lattice relaxation time (T1-dispersion) giving, for example, increased sensitivity to changes in protein. We have built a whole-body FFC-MRI system with a detection field of 0.2 T. This has required novel designs of magnet, power supplies, and control hardware and software. Design issues and solutions and initial results are presented. The scanner will allow clinical applications of FFC to be explored.

Sergei Obruchkov¹ and Robin Dykstra^1
1Victoria University, Wellington, New Zealand

A 260 mm bore 1.5T MRI system was designed around a cryogen-free superconducting magnet. The system was designed for small animal imaging applications in cancer research, to be located were cryogen availability and costs are prohibitive for conventional magnet systems.

K Craig Goodrich¹, Seong-Eun Kim¹, Joshua D. Kaggie¹, J. Rock Hadley¹, William B. Handler², Blaine A. Chronik³, and Dennis L. Parker^1
1UCAIR, University of Utah, Salt Lake City, Utah, United States, ²Physics and Astronomy, Univ of Western Ontario, London, Ontario, Canada, ³Physics and Astronomy, Western University, London, Ontario, Canada

This work was done to establish PNS limits for simultaneous operation of a 3 axis head/neck gradient insert and standard gradient system (composite mode operation). PNS thresholds were measured for each gradient system as well as combined operation for each axis separately and combined. Experimental results suggest that body and insert gradient thresholds are independent of each other, allowing for increased combined gradient field strength and slew rates in composite mode until either constituent threshold is reached. These results show a definite safety advantage for composite gradient mode operation allowing larger gradients and slew rates.

Michael S. Poole¹, Nadim Jon Shah^1,2, and Rob Hawkes^3
1INM-4, Forschungszentrum Juelich, Juelich, Nordrhein-Westfalen, Germany, ²Neurologische Klinik, Universitaetsklinikum Aachen, Aachen, Nordrhein-Westfalen, Germany, ³Wolfson Brain Imaging Centre, Addenbrookes Hospital, Cambridge, Cambridgeshire, United Kingdom

The redesign of split gradient coils for a hybrid MR-PET system is considered. Numerous changes in the coil design are assessed for their performance with the aim of making the coil more robust. New design strategies and a slackening of design constraints are also assessed for their ability to mitigate any performance loss from making the coils more robust. A linking annulus was found to be essential, but we enforce radial connections for simplifying the construction. A complex relationship exists between the design constraints and the coil performance, which needs to be considered carefully before a final design is constructed.

Hector Sanchez Lopez¹, Fabio Freschi², Adnan Trakic¹, Elliot Smith¹, Jeremy Herbert¹, Miguel Fuentes¹, Stephen Wilson¹, Limei Liu¹, Maurizio Repetto², and Stuart Crozier^1
1ITEE, The University of Queensland, Brisbane, QLD, Australia, ²Department of Energy, Politecnico di Torino, Torino, Torino, Italy

We present a new accurate and efficient eddy current simulation method capable of calculating induced currents in finite thickness conducting volumes of arbitrary geometry induced by arbitrary arrangements of gradient coils. The method has been experimentally validated using a z-gradient coil and its performance tested against COMSOL and the Fourier Network method. We present an example to demonstrate the capabilities of the method in terms of predicting the induced currents, power losses and pre-emphasis simulations using the excited eigenvalue corresponding to the surrounding structure. The method is accurate and fast enough to be performed in a laptop Intel corei7 CPU.

Peter T. While¹ and Jan G. Korvink^1,2
1Department of Microsystems Engineering (IMTEK), Laboratory for Simulation, University of Freiburg, Freiburg im Breisgau, Baden-Württemberg, Germany, ²Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg im Breisgau, Baden-Württemberg, Germany

Conventional shim systems are comprised of a set of dedicated coils for inducing low-order spherical harmonic fields. In contrast, shim arrays consist of multiple simple coil structures, such as circular loops, arranged on a uniform grid. These elements generate an alternative set of non-orthogonal basis fields that offer the potential for high-order shimming. In this study, a design concept is presented for generating shim arrays with irregular element geometry that afford field accuracy and efficiency advantages over the use of regular circular loops for inducing low-order fields.

Limei Liu¹, Hector Sanchez-Lopez¹, Feng Liu¹, and Stuart Crozier^1
1The University of Queensland, Brisbane, Queensland, Australia

Combined Linear accelerator (LINAC) - MRI systems can provide image-guided radiotherapy treatment. These systems require splitting of the MRI scanner to provide a central gap large enough to ensure dual access for the accelerator and the patient. This raises technical difficulties for maintaining high gradient coil performance. In this research, a dedicated split transverse gradient coil was designed with a flange connected to the central coil end and compared to existing coil designs. It was found that a flanged-edge coil design produced manageable coil performance and eddy currents.

Quentin Herreros¹, Hadrien A. Dyvorne², Paolo Campiglio¹, Amala Demonti¹, Guenaelle Jasmin-Lebras¹, Myriam Pannetier-Lecoeur¹, and Claude Fermon^1
1CEA, Gif-sur-Yvette, France, ²Mount Sinai School of Medicine, New York, NY, United States

Avoiding numbers of high field drawbacks, very low field MRI requires sensitive detection devices .We have developed a novel magnetic sensor based on a combination of spin electronics and superconductors, labelled mixed sensor, and reaching sensitivities in the fT range at low frequencies down to 1kHz. This mixed sensor was inserted in a small scale prototype system and in vivo images were successfully acquired at 7mT, showing high performance and versatility of the sensor for very low field MRI.

Saikat Saha¹ and Washington De Lima^2
1GE, Waukesha, WI, United States, ²GE, Florence, SC, United States

During high field MR scans, patients become uncomfortable due to the high acoustic noise and vibration produced inside the patient bore. This noise can be as high as ~125dBA depending on the field strength of the scanner and PSD being used. The main source of noise inside the scanner is due to the gradient coil (when pulsed) vibrating in a static magnetic field generated by the magnet. This noise is transmitted through the RF body coil to the patient ears. Another major source of noise is vibration of the RF body coil itself. RF body coil vibrates due to the eddy current generated by the gradient coil pulsing on the copper sections of the RF coil. Some of the previous work, which addresses the issue of acoustic noise and vibration have been documented in [1-2]. The design described here addresses the issue of acoustic noise by significantly reducing the vibration which in turn reduces the noise by upto 9 dBA in a conventional Birdcage RF coil without compromising the RF performance.