New Systems & Probes

Monday 22 April 2013

Carl Snyder¹, Lance DelaBarre¹, Aaron T. Hess², Chris Rodgers², Mattew Robson², and University of Minnesota University of Minnesota Vaughan^1
1University of Minnesota, Minneapolis, MN, United States, ²University of Oxford, Oxford, United Kingdom

Describe below is a novel 16-channel TEM transmit-Only array used with a 32-channel receive-only loop array for body imaging at 7T. Additionally, and more importantly, we describe an electromechanical method for automating the tuning and matching process for the 16 transmit elements using piezoelectric actuators. Automation of the tuning and matching procedure took, on average 50s and with an average S11 greater than 20dB. Following tuning and matching the array successfully imaged the human torso.

Hongyang Yuan¹, Qunzhi Chen², Yu Wang², Wenchao Cai³, Xiaoying Wang^2,3, Jue Zhang^1,2, and Jing Fang^1,2
1College of Engineering, Peking University, Beijing, China, ²Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China, ³Department of Radiology, Peking University First Hospital, Beijing, China

In this study, a novel flexible antenna, which is consisted of a flex cable and tuning/matching box, was developed for human foot MR imaging. Experimental results show that compared to conventional phase array coils, the FFCA have a higher SNR and better magnetic field homogeneity, and it can be easily designed for individual foot shape with higher fill factor. Meanwhile, the feasibility of FFCA has been validated by phantom and healthy human foot experiments. In the near future, it is believed that as a flexible antenna, the FFCA can be applied for hand or other unusual shape of human body.

Joseph R. Corea¹, Ana Claudia Arias¹, Anita Flynn¹, Greig C. Scott², Peter Shin³, and Michael Lustig^1
1EECS, UC Berkeley, Berkeley, California, United States, ²EE, Stanford University, Stanford, California, United States, ³EE, UC San Francisco, San Fransisco, California, United States

Taking advantage of recent advances in printed electronics, we have created a flexible 2-channel receive coil array. This array was fabricated from solution using screen-printing, a high volume manufacturing technique. The entire array is highly flexible and allows for a new level of conformity to the patient. We discuss the performance of the array and compare the printed components to traditional ceramic components under various bending conditions. We also demonstrate major steps toward clinical usability with the first phantom and in-vivo imaging results.

Nelly A. Volland^1,2, Robb Merrill¹, J. Rock Hadley^1,2, and Dennis L. Parker^1,2
1Ucair/ Radiology, University of Utah, Salt Lake City, UT, United States, ²CARMA, University of Utah, Salt Lake City, UT, United States

Purpose: An expandable catheter-mounted local RF cardiac coil was developed and evaluated. Methods: Elastic fiberglass filaments with predetermined curvature allowed the flexible inductive coil loop to fold and unfold in and out of a sheath. A microcoaxial cable electrically connected the inductive loop to the receiver circuit board through the sheath. For expansion, the support arms were pushed out of the 11 Fr catheter sheath until the loop was fully extended. Results and conclusion: The prototype of an expandable catheter-mounted local cardiac coil was successfully constructed and used to acquire MR images at 3T in a saline phantom.

Simon Auguste Lambert¹, Marie Poirier-Quinot¹, Jean-christophe Ginefri², and Luc Darrasse^1
1CRB3- INSERM U773, Univ Paris Diderot, Sorbonne Paris Cité, Clichy, France, ²CRB3- INSERM U773, Univ Paris-Sud, Clichy, France

Small high-temperature superconducting coils improve the signal-to-noise ratio (SNR) but their use is limited by the large degradation of their electrical properties due to the static magnetic field, depending both on the coil orientation relative to B0 and on the cooling temperature (THTS). In this work, by decreasing THTS from 83K to 69K, SNR improvement has been demonstrated, degree of freedom in the coil orientation has been added. Moreover THTS control has appeared to be an easy way to retune the HTS coil to the NMR frequency. Additional THTS decrease would be beneficial for imaging small animals at higher fields.

Daiki Tamada^1,2, Takashi Nakamura^1,2, and Katsumi Kose^1,2
1Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan, ²RIKEN, Wako, Saitama, Japan

A high critical temperature (Tc) superconducting bulk magnet is a promising magnet for magnetic resonance (MR) microimaging since it produces a strong (up to 17 T) and very stable (0.018 ƒÊT/hour) magnetic field with a small installation space. However, the major application for the bulk magnet is now limited to MR microimaging of small objects because the room temperature bore diameter is limited. In such case, a long signal averaging time is required to achieve sufficient signal-to-noise ratio due to the small voxel volume.In this study, we demonstrated usefulness of compressed sensing in MR microimaging using the high Tc bulk magnet.

Clarissa Zimmerman Cooley^1,2, Jason P. Stockmann^2,3, Brandon Dean Armstrong^2,3, Matthew S. Rosen^2,3, and Lawrence L. Wald^2
1Electrical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States, ²Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ³Department of Physics, Harvard University, Cambridge, MA, United States

A lightweight brain scanner based on a rotating permanent-magnet Halbach array is constructed and tested in phantom imaging. As the magnet is rotated around the object, the multipolar static field inhomogeneity creates generalized projections. The image is reconstructed using an iterative algebraic reconstruction technique based on knowledge of the field map. We show 2D phantom images containing aliasing artifacts similar to radial PatLoc images, which share the multipolar encoding field. These artifacts are greatly reduced through parallel imaging methods, which further reduce streaking and other residual artifacts while improving resolution.

Jesse Bellec¹, Scott B. King^1,2, Chen-Yi Liu¹, and Christopher P. Bidinosti^3
1Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada, ²National Research Council of Canada, Winnipeg, Manitoba, Canada, ³Physics, University of Winnipeg, Winnipeg, Manitoba, Canada

Transmit array spatial encoding (TRASE) is novel gradient-free imaging technique relying on Tx RF phase gradients to spatially encode the transverse magnetization. Ideal phase gradients have uniform magnitudes and linear phase gradients. To perform a 3D TRASE MRI experiment, 2 distinct phase gradients are required for each dimension. A target field approach was used to design a five coil Tx array that can be driven to produce a set six RF phase gradients necessary for 3D TRASE MRI at 3T.

Michael Twieg¹, Matthew J. Riffe², Natalia Gudino², and Mark A. Griswold^1,3
1Dept. of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, OH, United States, ²Dept. of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ³Dept. of Radiology, Case Western Reserve University, Cleveland, OH, United States

We present an improved mobile and low-cost NMR hardware platform aimed for use in simple NMR relaxometry experiments. The platform includes all necessary hardware, with the exception of the NMR probe itself, in a single enclosure. The platform is versatile, allowing for operation across a wide frequency range and with various NMR probes. The flexible system firmware allows for many relaxometry experiments, including measurement of T₁, T₂, ρ₀, and self diffusion coefficient (D). The total cost of the system, neglecting the host computer, is less than $750. Documentation on the platform is open source and available online.

Emine U. Saritas¹, Patrick W. Goodwill¹, Justin J. Konkle¹, Laura R. Croft¹, Kuan Lu¹, Bo Zheng¹, and Steven M. Conolly^1,2
1Department of Bioengineering, University of California, Berkeley, Berkeley, CA, United States, ²Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States

Magnetic Particle Imaging (MPI) is a new imaging modality that re-uses FDA-approved superparamagnetic iron oxide (SPIO) nanoparticle contrast agents in a new imaging scanner (i.e., not an MRI scanner) [1-3]. The MPI method has ideal SNR, penetration, linearity and contrast, and is completely non-invasive. Moreover, compared to iodine and gadolinium, the SPIO contrast agents are much safer for patients with Chronic Kidney Disease (CKD). This work describes our state-of-the-art MPI scanners and MPI’s potential for applications such as angiography and quantitative cell tracking.