ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Power Pitch Session: MR Engineering, Safety & Interventional

Wednesday, May 11, 2016
Power Pitch Theatre, Exhibition Hall
10:00 - 12:00
Moderators: Ed Boskamp, Richard Bowtell

Click Here to view the Power Pitch introductory session

Note: The videos below are only the slides from each presentation.
They do not have audio.

    Plasma #

1 Porcine Imaging in a 10.5T Whole-Body Human MRI
Lance DelaBarre1, Russell L. Lagore1, Yigitcan Eryaman1, Gregor Adriany1, and J. Thomas Vaughan1
1Center for Magnetic Resonance Research - University of Minnesota, Minneapolis, MN, United States
Recently, our 10.5T whole-body MRI magnet achieved field strength and its installation was completed.  While waiting for IRB and IDE approval, a human-sized porcine model serves as a surrogate for later human studies, thus allowing development of techniques in vivo.  Using an 8-channel head coil on a porcine head, the first in vivo images from the 10.5T whole-body MRI were acquired.

2 The first demonstration of simultaneous transmit and receive MRI in vivo - Permission Withheld
Sung-Min Sohn1, J. Thomas Vaughan1, Michael Garwood1, and Djaudat Idiyatullin1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
This is the first demonstration of in vivo human MR imaging with simultaneous transmit and receive using continuous mode SWIFT at 4T.  Due to a large RF power difference between Tx and Rx working at the same frequency, the difficulties to obtain the high and stable Tx/Rx isolation, and the sensitivity of the Tx/Rx isolation to the loading conditions, in vivo images using the simultaneous RF pulse transmission and signal acquisition have not been reported. This work proposed the simultaneous Tx/Rx system with highly minimized effects from variation of coil loading, which allowed us to acquire the first in vivo images with continuous SWIFT at 4T.       

3 Anatomically adaptive local coils for MR Imaging - Evaluation of stretchable antennas at 1.5T - Permission Withheld
Bernhard Gruber1 and Stephan Zink2
1Medical Engineering - School of Applied Health and Social Sciences, University of Applied Sciences Upper Austria, Linz, Austria, 2R&D HW LC, Siemens Healthcare GmbH, Erlangen, Germany
This abstract is a first investigation on antenna materials and designs for anatomically adaptive local coils for MR Imaging. To overcome the SNR losses by poorly loaded and non-fitting RF coils, we proposed a stretchable antenna design. Each loop has the ability to reversible stretch up to 100% of its original size, to be anatomically adaptive to different shapes and sizes in three dimensions. Through bench measurements and MR Imaging at 1.5T we investigated different stretchable antenna materials, that fit the defined requirements. The results of stretchable loops  showed an in average SNR loss of under 10% in comparison to standard loops, but we suppose that the improved filling factor will lead to much higher SNR of the adaptive loops. Further research may consider different improvements.

4 Gradient response harvesting for continuous system characterization during MR sequences - Permission Withheld
Bertram J. Wilm1, Benjamin E. Dietrich1, Jonas Reber1, S. Johanna Vannesjo1, and Klaas P. Pruessmann1
1Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
Gradient impulse response functions were recently proposed to characterize MR gradient systems with high accuracy. However, changes of the impulse response, e.g. due to thermal drifts, can limit its accuracy and hence applicability. To overcome this problem, we present a novel method where the gradient response is continuously characterized during MR sequences from repeatedly performed field probe measurements. The benefit of this method is demonstrated by obtaining the continuous gradient output of MR sequences and first imaging results are presented.

5 A Wireless MRI system using mm-Wave Transmission
Kamal Aggarwal1, Kiran Raj Joshi1, Yashar Rajavi1,2, Mazhareddin Taghivand1,2, Ada S. Y. Poon1, John M. Pauly1, and Greig Scott1
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Qualcomm Atheros, San Jose, CA, United States
High path loss and availability of wide bandwidth make mm-waves an ideal candidate for short range, high data rate transmission for wireless MRI applications. The proposed system uses a custom designed integrated chip (IC) radio that uses mm-waves (60 GHz) as the radio frequency carrier. We report link tests up-to 500 Mb/s for distances up-to 50cm in the MRI bore.  The addition of time division multiplexing (TDM) circuitry allows multiple wireless links to be created simultaneously with minimal inter-channel interference. This leads to a highly scalable, low-power solution for wireless MRI.

6 A Broadband Spectrometer for Simultaneous Multinuclear Magnetic Resonance Imaging and Spectroscopy
Stephen Ogier1, John C Bosshard1, and Steven M Wright1
1Electrical and Computer Engineering, Texas A&M University, College Station, TX, United States
In this abstract we report progress and results towards developing a fully broadband spectrometer for multi-coil multi-nuclear MRI/MRS. This may be of interest for hyperpolarized MRI and MRS studies due to the very limited lifetime of the magnetization, as well as for quantitative MRI. A prototype spectrometer has been developed and tested by simultaneous 1H/2H imaging on a 1.0T magnet and simultaneous 1H/23Na/2H spectroscopy on a 4.7T magnet. The system is capable of acquiring data from four channel array coils for these and other nuclei.

7 MR Probe Design with On-Coil Digital Receiver - Permission Withheld
David Otto Brunner1, Benjamin Sporrer2, Christian Vogt3, Jonas Reber1, Josip Marjanovic1, Luca Bettini2, Lianbo Wu2, Thomas Burger2, Gerhard Troester3, Qiuting Huang2, and Klaas P Pruessmann1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Integrated Systems Laboratory, ETH Zurich, Zurich, Switzerland, 3Electronics Laboratory and Wearable Computing Group, ETH Zurich, Zurich, Switzerland
RF receivers placed directly on coil in conjunction with fibre-optical data transmission can provide various advantages for the design of array coils in terms of avoidance of dangerous sheath currents, common-mode noise and unwanted coil to coil interactions, as well as reduction of cable weight and routing problems. This helps to further increase channel counts but also usability or even wear-ability of RF receive arrays. Here we present first results from coil designs employing fully integrated (in 130 nm CMOS technology) digital receivers with a form factor and power requirements to be placed directly on the coil footpoint.

8 Ultra-fast MRI based transfer function determination for the assessment of implant safety.
Janot Tokaya1, A.J.E. Raaijmakers1, J.F. Bakker2, P.R. Luijten1, and C.A.T. van den Berg1
1Imaging Division, UMC Utrecht, Utrecht, Netherlands, 2Medtronic, Eindhoven, Netherlands
Tissue heating induced by sharply peaked scattered electric fields at the tip of elongated implants is a severe safety hazard refraining patients with active implants from undergoing MRI examinations. Transfer functions (TFs) are widely used in modern safety standards to assess implant safety. Currently, dedicated setups are required to determine TFs in challenging and time consuming experiments. We introduce a new experimental technique based on the principle of reciprocity and exploiting the ability to map induced currents with MRI. The proposed method can accurately determine TFs with high spatial resolution in a single, quick and relatively simple measurement. It furthermore has the potential to be applied in heterogeneous media allowing safety assessment in more realistic scenarios where the conventional methods become inapplicable.

9 Improving Peak Local SAR Prediction in Parallel Transmit Using In-situ S-matrix Measurements
Matthew Restivo1, Alexander Raaijmakers1, Cornelis A.T. van den Berg1, Pedro Crespo-Valero2, Peter Luijten1, and Hans Hoogduin1
1Center for Imaging Sciences, University Medical Center Utrecht, Utrecht, Netherlands, 2Zurich Med Tech, Zurich, Switzerland
We propose a technique where we measure the real S-matrix of the array/subject setup in-situ and then closely match it in simulation using circuit co-simulation with a modified cost function. We show that by accurately simulating coupling, the B1+ and thus the SAR can be better predicted using FDTD simulations. Better pTx SAR predictions will ensure RF safety while reducing the overly conservative pTx SAR predictions that are used currently.

10 Percentage of change in the calculated SAR values in human head during 3T MRI of patients with deep brain stimulation implants: A computational study of realistic vs. simplified lead trajectories
Laleh Golestanirad1, Maria Ida Iacono2, Leonardo M Angelone2, and Giorgio Bonmassar1
1Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, MD, United States
Each year approximately 300,000 patients with medical implants including deep brain stimulation (DBS) devices are denied magnetic resonance imaging (MRI) examination due to safety concerns. One of the major contraindications of MRI for DBS patient population is due to the potential for permanent injuries from excessive tissue heating. One open question when evaluating RF-induced heating with DBS is the effect of the lead path and the need for patient-specific information. Using finite element method, we report results of calculated SAR maps for patient-specific lead paths based on CT images, and compare them to simplified path trajectories.

11 Accurate MR Thermometry by Hyperpolarized 129Xe
Le Zhang1,2, Alex Burant2,3, Andrew McCallister2,3, Karl Koshlap4, Simone Degan5, Michael Antonacci2,3, and Rosa Tamara Branca2,3
1Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 2Biomedical Research Imaging Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 3Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 4Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 5Center for Molecular and Biomolecular Imaging, Duke University, Durham, NC, United States
A new thermometry method based on the temperature dependence of lipid-dissolved 129Xe was proposed, while its accuracy was assessed by direct comparison with Proton Resonance Frequency (PRF) based MR thermometry methods. The temperature dependences of chemical shifts of lipid-dissolved 129Xe, water and methylene spins were first measured in vitro with high accuracy on various fat-rich tissues. The results were then used to obtain relative temperature maps in vivo in mice acclimated at different temperatures. Lipid-dissolved 129Xe based MR thermometry demonstrated superior accuracy in both in vivo and in vitro results when compared to PRF based MR thermometry in fatty tissues.

12 MR Guided Focused Ultrasound Thalamotomy for Essential Tremor - Maryland Experience
Rao P Gullapalli1, Jiachen Zhuo1, Dheeraj Gandhi1, Charlene Aldrich2, Erma Owens1, John Hebel1, Paul Fishman3, Howard Eisenberg2, and Elias Melhem1
1Diagnostic Radiology & Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States, 2Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, United States, 3Neurology, University of Maryland School of Medicine, Baltimore, MD, United States
In the context of the remarkable reduction in tremors and improvement in quality of life at one year following MRgFUS thalamotomy procedure to treat Essential Tremors in a recently concluded multi-center trial, we examined pre- and post-imaging data including an assessment of the accuracy of MRgFUS targeting of the VIM nuclei and lesion evolution over 12 months.  Lesions generated by this procedure were accurately placed, and matched well with the known location of VIM nucleus based on anatomical atlases. The lesions appear to regress in size over a 12 month period but the therapeutic effect is maintained.

13 Magnetic Resonance-Guided Focused Ultrasound Treatment of Extra-Abdominal Desmoid Tumors: A Retrospective Multicenter Study
Pejman Ghanouni1, Andrew Dobrotwir2, Alberto Bazzocchi3, Matthew Bucknor4, Rachelle Bitton1, Jarrett Rosenberg1, Kristen Telischak5, Maurizio Busacca3, Stefano Ferrari6, Ugo Albisinni3, Shannon Walters1, Kristen Ganjoo7, Alessandro Napoli8, Kim Butts Pauly1, and Raffi Avedian9
1Radiology, Stanford University, Stanford, CA, United States, 2Radiology, The Royal Women's Hospital, Parkview, Australia, 3Diagnostic and Interventional Radiology, The Rizzoli Orthopaedic Institute, Bologna, Italy, 4Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, 5Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA, United States, 6Oncology, The Rizzoli Orthopaedic Institute, Bologna, Italy, 7Medicine, Stanford University, Stanford, CA, United States, 8Radiology, Sapienza University, Rome, Italy,9Orthopaedic Surgery, Stanford University, Stanford, CA, United States
Desmoid tumors are benign, but can result in pain and dysfunction. Surgery, radiation and chemotherapy are only only partially effective and can cause significant morbidity. MR guided focused ultrasound (MRgFUS) was used to treat patients with desmoid tumors, sometimes in lieu of surgery, radiation or chemotherapy. This retrospective multicenter feasibility study of 15 patients demonstrates that MRgFUS is safe and that this technique may be used to control the growth of symptomatic desmoid tumors.

14 White-Matter-Nulled MP-RAGE Predicts Clinical Outcome of Focused Ultrasound Thalamic Ablation for Essential Tremor
Jason Su1, Christian Federau2, Thomas Tourdias3, Manojkumar Saranathan4, Casey Halpern5, Jaimie Henderson5, Veronica Santini6, Kim Butts-Pauly2, Pejman Ghanouni2, and Brian Rutt2
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Radiology, Stanford University, Stanford, CA, United States, 3Neuroradiology, Bordeaux University Hospital, Bordeaux, France,4Radiology, University of Arizona, Tucson, AZ, United States, 5Neurosurgery, Stanford University, Stanford, CA, United States, 6Neurology, Stanford University, Stanford, CA, United States
This retrospective analysis of MR-guided focused ultrasound ablation for essential tremor (ET) treatment is centered on clinical outcome (CRST A+B) and segmentation of ablation lesions using the white-matter-nulled MP-RAGE contrast. There is no significant correlation between the volume of ablation and clinical outcome at 1 month. We identify a new potential target region based on the best-responding patient and compute the percent coverage of that region by each subject’s ablation via nonlinear registration. This measure correlates with the outcome after 1 month in 8 subjects with r2=0.8 and p=0.003, a remarkable association that may aid future targeting strategies in ET.

15 Evaluation of thermal ablation with a 230 kHz transcranial MRI-guided focused ultrasound system in a large animal model
Nathan McDannold1, Jonathan Sutton1, Natalia Vykhodtseva1, and Margaret Livingstone2
1Radiology, Brigham and Women's Hospital, Boston, MA, United States, 2Neurobiology, Harvard Medical School, Boston, MA, United States
This work evaluated the feasibility of thermal ablation in the brain in nonhuman primates using a 230 kHz transcranial MRI-guided focused ultrasound system. We aimed to determine whether using this low frequency can expand the treatment envelope where focused ultrasound can be used in the brain without overheating the skull. We found that focal heating was increased and skull heating decreased compared to prior work in macaques that tested a higher frequency version of this system, suggesting that it can indeed increase this envelope. Furthermore, closed-loop feedback maintained a low level of cavitation activity.

16 MR safety screening -  Is it really worth the time investment?
Derek K Jones1, John Evans1, and Richard G Wise1
1CUBRIC, Cardiff University, Cardiff, United Kingdom
Safety screening is considered essential to any MR lab's working practice. However, it is time-consuming and reduces participant throughput. Here, we capitalise on the rare opportunity to experiment with a 3T system prior to it being decommissioned.  We test the hypothesis that large ferrous-containing objects, if released into the magnet with a participant inside, do indeed inflict pain and injury. A selection of house-hold objects was used and a subjective pain rating employed to quantify the response.  Our results are highly consistent with the main hypothesis, lending support to continued safety screening. However, we discuss alternative options to improve workflow

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