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Keywords: Uterus, MR-Guided Interventions

Existing commercial body MR-guided focused ultrasound (MRgFUS) systems have limited electronic steering ranges and rely on mechanical translation/rotation to ablate large tissue volumes. Here, we describe a flat fully-populated MRgFUS phased array body system with increased electronic steering capabilities. Following extensive benchtop and pre-clinical testing, the device was evaluated in a pilot clinical trial of MRgFUS for the treatment of uterine fibroids, which demonstrated  the feasibilty and safety of the approach. The technology is extensible, stackable, and modular, allowing custom MRgFUS device development tailored to any indication.

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Karthik Lakshmanan^1,2, Ryan Brown^1,2, Giuseppe Carluccio^1,2, and Christopher M Collins^1,2
1Radiology, NYU Grossman School of Medicine, New York, NY, United States, ²Center for Advanced Imaging Innovation and Research (CAI2R), New York University, New York, NY, United States

Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Arrays & Systems

We show that novel modifications to a mock Transcranial MR-guided Focused Ultrasound (TMRgFUS) system show potential to greatly improve MR performance. By using a transfer medium with reduced electric permittivity combined with slots in the transducer array ground plane we measure a 2-3 fold increase in SNR across the middle of a head-phantom portion of a mock  TMRgFUS system. 

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Biqi Rebekah Zhao¹, Yuhan Wen¹, Alexander Chou¹, Elad Alon¹, Rikky Muller¹, Chunlei Liu¹, and Michael Lustig^1
1Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States

Keywords: New Devices, Neuroscience

We propose a new device for neuroscience studies: the MRDust, a sub-mm wireless programmable neural recording mote with on-device memory and compute. It receives power via focused ultrasound, records neural signals in burst mode, and uses a micro-coil to perturb local magnetic fields to achieve data uplink via dynamic MRI signal modulation. We demonstrate proof-of-concept experiments in which digital information is encoded in images of an SE-EPI dynamic sequence, and in which a piezoelectric harvester can harvest enough ultrasonic power to sustain device operation, and receive control signals through amplitude modulation.

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Keywords: Interventional Devices, Prostate

MR-guided focal cryoablation of prostate cancer has often been selected as a minimally-invasive treatment option. Placing multiple cryo-needles accurately to form an ablation volume that adequately covers the target volume is crucial for a better oncological/functional outcome. This work presents an MRI-compatible system combining a motorized template grid and insertion depth sensing, which allows the physician to precisely place the cryo-needles into the desired location. Our preliminary results demonstrate the advantages of adding additional degrees of freedom to the template and providing the physician with real-time feedback on the insertion depth.

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Manon Desclides^1,2, Valéry Ozenne¹, Guillaume Machinet³, Christophe Pierre³, Stéphane Chemouny², and Bruno Quesson^1
1University of Bordeaux, CNRS, CRMSB, UMR 5536, IHU Liryc, Bordeaux, France, Metropolitan, ²Certis Therapeutics, Pessac, France, ³ALPhANOV, Talence, France

Keywords: Interventional Devices, MR-Guided Interventions, Laser

Percutaneous clinical ablation devices usually create a heating pattern with an ellipsoid shape. Output power and duration of application are the only degrees of freedom, which does not allow creating conformal ablation. To overcome this limitation, we designed a Laser Interstitial Thermal Therapy (LITT) device allowing creating various heating patterns. We present here in vivo results in pig muscle monitored by real-time 2D multi-slice MR-thermometry.

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Juliane Peter^1,2,3, Sebastian Gantz^1,2, Aswin Hoffmann^1,2,4, and Jörg Pawelke^1,2
1OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, ²Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology – OncoRay, Dresden, Germany, ³Technische Universität Dresden, Dresden, Germany, ⁴Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany

Keywords: New Devices, Radiotherapy, Proton Therapy

Proton beam-induced convection in water triggered local MRI magnitude signal loss in combined imaging and irradiation experiments performed on a new research prototype in-beam low-field MRI proton radiotherapy device. In this study, the influence of convection on the MRI phase signal was tested. Both mechanical and thermal inhibition of convection in dedicated water phantoms resulted in the absence of MRI phase signatures, which were clearly visible under conditions were convection could develop. Moreover, a change in either convection velocity or Venc sequence motion sensitivity changed the observed phase contrast, confirming the convection-driven phase contrast mechanism.

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Dogangun Uzun^1,2, Dursun Korel Yildirim¹, Rajiv Ramasawmy¹, Amanda Potersnak¹, Adrienne Campbell-Washburn¹, Ozgur Kocaturk³, and Robert J. Lederman^1
1National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States, ²Institute of Biomadical Engineering, Bogazici University, Istanbul, Turkey, ³Transmural Systems, Andover, MA, United States

Keywords: Interventional Devices, Interventional Devices

In this work, an interventional device tracking method under high performance 0.55T MRI is presented using a custom designed nitinol needle. Ultra-thin miniature solenoid coil markers were designed and printed on the needle using conductive ink. A negative contrast is created around the needle by applying an alternative current to the markers and hence introducing an offset to the B1 field. A signal generator circuit is designed for supplying and controlling the AC signal and the visibility of the needle is tested under MRI with in-vitro experiments during a real time b-SSFP sequence.  

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Andreas Reichert¹, Ali Caglar Özen¹, Simon Reiss¹, Samantha Hickey¹, Thomas Lottner¹, Niklas Verloh², Srdjan Milosavljevic³, Michael Vogele³, and Michael Bock^1
1Division of Medical Physics, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, ²Division of Interventional Radiology, Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, ³Interventional Systems GmbH, Kitzbuehel, Austria

Keywords: Interventional Devices, Interventional Devices

We present a small and flexible piezo-driven assistance system, which can be steered from outside the magnet bore via a control unit. The assistance system is combined with a tracking sequence, which is able to follow in-bore manipulations of a dedicated end effector in real-time. For an initial evaluation, the assistance systems is equipped with a biopsy needle and targeting experiments are performed in a phantom setting.

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Johannes Petzold¹, Berk Silemek¹, Lukas Winter¹, Bernd Ittermann¹, and Frank Seifert^1
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany

Keywords: Safety, Data Acquisition

Embedded sensors in implants that communicate with an MRI system can improve patient safety substantially, in particular when parallel transmission is applied to mitigate the RF-heating risk. Calibration procedures and virtual models are presented in this work to support a rigorous safety assessment of this novel approach to implant safety. Experiments show a good correlation (r>0.96) between sensor signal (voltage at the tip) and field-probe measurements (E-field and temperature) for a custom-built reference implant. These results are further supported by simulations that can be extended to investigate more complex implant heating scenarios in human voxel models.

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Keywords: New Devices, Body

A wireless, battery-powered, MR-compatible ultrasound device consisting of an integrated RF/wireless coil, an organ-configuration motion sensor and its associated electronics was used to acquire OCM sensor signals on a healthy volunteer. Signals were obtained that characterized internal motion, which were wirelessly transmitted to the console room. Validation was performed against a real-time MR acquisition.

Wonje Lee¹, John Pauly¹, Shreyas Vasanawala¹, and Greig Scott^1
1Stanford University, Palo alto, CA, United States

Keywords: Hybrid & Novel Systems Technology, RF Arrays & Systems, motion sensing

This study investigates complex baseband doppler radar signal integrity with linear and phase demodulations to confirm feasibility for in-bore MRI vital sensing applications.  

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Keywords: Multimodal, fMRI (task based), EEG, EEG recording, MRI compatible EEG

A cost-effective, 8-channel, MRI-compatible optical EEG prototype was implemented and tested. The protoype has the potential to be especially suited for low-field MRI applications. The system uses Photrode^TM technology, a high impedance device that can pick up signals without the need for "wet" contact with the skin. The minimum resolvable voltage of the modulator was ~ 12.5 uV, sufficient for most EEG waves.

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Suma Anand¹ and Michael Lustig^1
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States

Keywords: Hybrid & Novel Systems Technology, Cardiovascular, RF Arrays and Systems, Motion Correction

We previously proposed the Beat Pilot Tone (BPT), a motion sensing method that uses microwave frequencies and preamplifier intermodulation to obtain increased motion sensitivity compared to Pilot Tone (PT). Here, we show that cardiac signals acquired with BPT correlate strongly with displacement ballistocardiograms (dBCG). We compare the BPT signals to dBCG acquired with an accelerometer. Additionally, we show that BPT has greater signal modulation compared to PT in sensing cardiac motion. BPT could be a novel, non-contact, and wireless method for acquiring dBCG signals, offering robustness in setup for patients and rich physiological information complementary to the MRI exam.

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Oskar Bjoerkqvist¹ and Klaas P. Pruessmann^2
1ETH Zürich, Zurich, Switzerland, ²ETH Zürich, Zürich, Switzerland

Keywords: New Devices, New Devices, RF Harvesting; Wireless energy;

In this abstract we present a solution for harvesting RF excitation pulses in MRI while suppressing interference caused by the harvesting system, which is otherwise known to be an issue. This approach to RF harvesting offers an alternative for powering circuitry that needs to be within the field of view free from cables and without dedicated energy transmission. 

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Petra Albertova^1,2, Maximilian Gram^1,2, Verena Schirmer², Martin Blaimer³, Martin J. Herrmann⁴, Matthias Gamer⁵, Peter Nordbeck^1,6, and Peter Michael Jakob^2
1Department of Internal Medicine I, University Hospital Würzburg, Würzburg, Germany, ²Experimental Physics 5, University of Würzburg, Würzburg, Germany, ³Fraunhofer Institute for Integrated Circuits IIS, Würzburg, Germany, ⁴Department of Psychiatry, Psychosomatics, and Psychotherapy, University Hospital Würzburg, Würzburg, Germany, ⁵Department of Psychology, University of Würzburg, Würzburg, Germany, ⁶Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg, Würzburg, Germany

Keywords: Bioeffects & Magnetic Fields, Quantitative Imaging, spin-lock

Rotary excitation based MRI, which enables spatially resolved, non-invasive, direct detection of biomagnetic fields, complements the measurement range accessible via MEG since detection is independent of the distance to the body surface. We present an extension of the REX method towards quantitative imaging. A calibration function can be composed from REX data of two measurements of adjustable fields projected onto the tissue by the scanner’s gradient system. In subsequent measurements, the field strength can be inferred from the calibration model. First in vivo proof-of-concept measurements show that the calibration successfully eliminates influences of tissue properties and accurately quantifies oscillatory nT-fields.