Chi-Hyeon Yoo¹, Jonathan DuBois², Lu Wang³, Steven Liang⁴, David Izquierdo-Garcia¹, and Hsiao-Ying Wey^1
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States, ²Biogen, Cambridge, MA, United States, ³Department of Nuclear Medicine and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University & Institute of Molecular and Functional Imaging, Jinan University, Guangzhou, China, ⁴Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States

The goal of this study was to generate a population-based template/atlas and apply the template/atlas-based attenuation correction (AC) method for simultaneous positron-emission-tomography/magnetic-resonance-imaging (PET/MRI) neuroimaging studies on non-human primates (NHPs). Population-based template/atlas of computed tomography image and anatomical MRI, were generated from ten NHPs (rhesus macaque). By using the generated template/atlas, the linear attenuation coefficient (LAC) of objects can be reliably derived, showing good differentiation for tissues, also skull and air. Comparison of the PET images reconstructed by the template/atlas-based and simple threshold-based AC has shown that the template/atlas-based AC can increase PET signal by avoiding overcompensation of attenuation. 

Wonje Lee¹, Kanghyun Ryu¹, Fraser Robb², John Pauly³, Shreyas Vasanawala¹, and Greig Scott^3
1Radiology, Stanford University, Stanford, CA, United States, ²GE healthcare, Cleveland, OH, United States, ³Electrical Engineering, Stanford University, Stanford, CA, United States

Noncontact vital sensing applications have great potential to aid in patient care. We leverage a reconfigurable SDR to assess the feasibility of in-bore cardiopulmonary sensing using CW doppler radar that operates independently of the MRI system and data acquisition. 

Eric J Lessard¹, William B Handler¹, and Blaine A Chronik^1
1Western University, London, ON, Canada

This simulation and electromagnetic design work explored the development of an active second order spherical harmonic shim set for eddy current compensation in a shoulder cut-out head and neck imaging platform. While the small radius shoulder cut-out shims can be driven faster and stronger than the larger radius complete cylinder shims they suffer in homogeneity and eddy current compensation. This difference in compensation is minimized with the addition of two purpose designed eddy current compensation coils.

Chathura Kumaragamage¹, Peter B Brown¹, Scott McIntyre¹, Terence W Nixon¹, Henk M De Feyter¹, and Robin A de Graaf^1
1Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States

ECLIPSE, a pulsed second order gradient insert can provide robust lipid suppression over an elliptical ROI for applications in human brain MRSI. While ECLIPSE provides excellent axial slice coverage for brain shapes that closely resemble an ellipse, coverage can be compromised for other head shapes. The development of an ECLIPSE gradient coil in combination with a 54-channel multi-coil array (MC-ECLIPSE), that allows B₀ field shaping for arbitrary ROI generation is presented. Simulation results demonstrate that near-perfect (99%) axial slice coverage is achievable with MC-ECLIPSE, for a wide range of highly asymmetrical brain and head shapes.

Jason Peter Stockmann^1,2, Lucia Navarro de Lara¹, Mohammed Daneshzand¹, Qinglei Meng¹, Congyu Liao³, Hong-Hsi Lee^1,2, Lawrence L Wald^1,2, Berkin Bilgic^1,2, Susie Huang^1,2, and Aapo Nummenmaa^1,2
1A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³Lucas Center, Stanford University, Stanford, CA, United States

We show that multi-channel TMS (mTMS) probe arrays can be used to generate B-fields inside the head for spatial encoding in concurrent TMS/MRI studies.  We assess the field-synthesis capability of a 48-ch mTMS array for diffusion imaging and spatial encoding more broadly.  Proof-of-concept diffusion imaging experiments on a 3T scanner using a 3-axis TMS probe achieve spatially-varying b-values >500 s/mm² at the depth of the peripheral gray matter using only 4A of current.  We consider the potential for scaling up to 200A for studies of gray matter microstructure.  

Siyu Li¹ and Danny JJ Wang^1
1Laboratory of FMRI Technology (LOFT), Mark & Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States

B₀ field inhomogeneity can reduce the effectiveness of RF pulses, result in signal voids, blurring and image artefacts. Integrated RF-shim coil arrays^1,2,3 offer capabilities for concurrent parallel RF reception and local B0 shimming, and is superior to spherical harmonic shimming. However, its performance may still be limited due to the lack of flexibility for shimming and limited depth penetration for signal reception. We simulated the B0 shimming performance of a range of integrated RF-shim coil arrays with 3D orthogonal loop coil geometry, and compared the results with standard 2D loop coil arrays.

Kieffer Davieau¹, Matthew Fox^1,2, Blaine Chronik^1,3, and Alexei Ouriadov^3,4
1Medical Biophysics, Western University, London, ON, Canada, ²Lawson Health Research Institute, London, ON, Canada, ³Physics and Astronomy, Western University, London, ON, Canada, ⁴School of Biomedical Engineering, Western University, London, ON, Canada

This study investigates the feasibility of changing the shield radius of an RF coil to shift the resonant frequency from ¹H to ¹⁹F for multinuclear imaging. The method proposed in this investigation was verified by changing the resonant frequency of a ¹²⁹Xe RF Coil a total of 1.18 MHz by changing the shield radius, allowing it to be used in a 2.9T Siemens MRI and a 3.0T GE MRI. It was found that altering the shield radius had similar effects on the resonant frequency as using a variable tuning capacitor, allowing for one coil to be compatible with multiple scanners.

Christopher James Sedlock¹, Aaron Purchase¹, Boguslaw Tomanek¹, and Jonathan Sharp^1
1University of Alberta, Edmonton, AB, Canada

TRASE is an MR imaging sequence that achieves k-space encoding through the use of phase gradients in the RF transmit field. The twisted solenoid is the most efficient RF transmit coil used for TRASE encoding; however, the geometry results in a long coil with a relatively short imaging volume. We introduce a new truncated design for the twisted solenoid to increase the usable imaging volume relative to the coil’s size. Simulation studies conducted indicate the truncated design can create similar imaging volumes to the untruncated version whilst significantly reducing the coils length by as much as a half.

Sri Kirthi Kandala¹, Alberto Fuentes², Gregory H Turner², and Sung-Min Sohn^1
1Arizona State University, Tempe, AZ, United States, ²Barrow-ASU Center for Preclinical Imaging, Phoenix, AZ, United States

Like most modern electronic devices, a mobile application based Radio Frequency (RF) coil monitoring system will make it easy to carry out any real-time changes to the RF coil. This work focuses on developing a mobile application based RF monitoring system, that allows the user to gather real-time RF coil characteristics and control the coil. It gives the user a chance to make changes when necessary. The opportunity to wirelessly implement such changes without physical contact with the coil, using a mobile application via Bluetooth is a step in the direction towards building next-generation RF coils for MRI.

Mariko Gardiner¹, Keith Wachowicz^2,3, and Nicola De Zanche^2,3
1University of Alberta, Edmonton, AB, Canada, ²Oncology, University of Alberta, Edmonton, AB, Canada, ³Medical Physics, Cross Cancer Institute, Edmonton, AB, Canada

Phantoms that cover large volumes are required to characterize geometrical distortion for image-guided interventions such as MR-guided radiation therapy (linac-MR). Liquid-filled phantoms of appropriate size can, however, be impractically heavy. Our phantom uses silicone rubber spheres arranged on a three-dimensional grid, resulting in a lightweight, portable structure. Displacements of each bead relative to the known grid positions are calculated in Matlab or 3D Slicer from 3D bSSFP scans. Design files and image processing code are available online.

David Rutkowski¹, Alejandro Roldán-Alzate^2,3,4, José Guerrero-González¹, Diego Hernando^1,3,5, Scott B Reeder^1,3,4,5,6,7, and Jean H Brittain^1
1Calimetrix, Madison, WI, United States, ²Mechanical Engineering, University of Wisconsin, Madison, WI, United States, ³Radiology, University of Wisconsin, Madison, WI, United States, ⁴Biomedical Engineering, University of Wisconsin, Madison, WI, United States, ⁵Medical Physics, University of Wisconsin, Madison, WI, United States, ⁶Medicine, University of Wisconsin, Madison, WI, United States, ⁷Emergency Medicine, University of Wisconsin, Madison, WI, United States

MRI proton density fat fraction (PDFF) and MR elastography (MRE) methods are frequently used to evaluate patients with known or suspected NAFLD or NASH. Reference standards (phantoms) are needed for quality assurance of these methods. Currently available phantoms mimic only a single tissue property. A phantom that simultaneously mimics PDFF and tissue stiffness would more realistically mimic NAFLD/NASH tissue and would enable robust and convenient quality assurance.  In this work, a chemical formulation and phantom configuration were developed for a multi-layer combined PDFF-MRE phantom, in which each layer simultaneously mimics different PDFF and stiffness values.

Mariko Gardiner¹, Anthony G. Tessier², Keith Wachowicz^2,3, and Nicola De Zanche^2,3
1University of Alberta, Edmonton, AB, Canada, ²Medical Physics, Cross Cancer Institute, Edmonton, AB, Canada, ³Oncology, University of Alberta, Edmonton, AB, Canada

Phantoms for pre-clinical systems have not been standardized, and none in the literature permit the wide variety of measurements possible with the ACR phantoms. We present a low-cost, open-source, modular phantom made of 3D-printed and off-the-shelf parts that mimics the functionality of the ACR phantoms on an appropriate scale. Standard, inexpensive manufacturing techniques are sufficient to create the fine features required at this scale. Configuration of the phantom can be customized to suit each site’s needs. Possible measurements include image uniformity, distortion and SNR; slice location, thickness, and angle; radial, linear, and low-contrast resolution.

Kisoo Kim¹, Peter Jones², Chris J Diederich², and Eugene Ozhinsky^1
1Radiology & Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Radiation Oncology, University of California, San Francisco, San Francisco, CA, United States

We developed a low-cost and simple MR-compatible respiratory motion simulator to support proof-of-concept studies of MR monitoring approaches with respiration-induced organ motion. The motion system integrates pneumatic control via an actuator subsystem outside the MRI and coupled via plastic tubing to a compressible bag for distention and retraction within the MRI motion subsystem and phantom within the MRI scanner. The proposed respiratory motion simulator provided consistent periodic respiratory motion with displacement in the range 3.7-9.0 mm. The respiratory simulator could be easily assembled with off-the shelf and 3D-printed parts, based on open-source design models.

An T Vu^1,2, Alexander JS Beckett^3,4, Salvatore T Torrisi^3,4, Sinyeob Ahn⁵, Michael Koehler⁶, Peter Dietz⁶, and David A Feinberg^3,4
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²Radiology, San Francisco Veteran Affairs Health Care System, San Francisco, CA, United States, ³Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States, ⁴Advanced MRI Technologies, Sebastopol, CA, United States, ⁵Siemens Medical Solutions USA, Inc., Melvern, PA, United States, ⁶Siemens Healthcare, Erlangen, Germany

The newly developed head gradient (200 mT/m Gmax, 900 T/m/s SR) on the new NexGen 7T system provides many potential benefits for high-resolution diffusion imaging. Faster, stronger gradients can significantly reduce diffusion encoding times and TE for up to a 3-fold improvement SNR while also reducing TR and total scan time. We demonstrate these benefits in high resolution diffusion imaging applications with b-values of up to 10,000 s/mm² at 7T.

Sihao Chen¹, Tyler J. Fraum¹, Cihat Eldeniz¹, Joyce Mhlanga¹, Weijie Gan¹, Thomas Vahle², Uday B. Krishnamurthy³, David Faul⁴, H. Michael Gach¹, Michael M. Binkley¹, Ulugbek S. Kamilov¹, Richard Laforest¹, and Hongyu An^1
1Washington University in St. Louis, Saint Louis, MO, United States, ²Siemens Healthcare GmbH, Erlangen, Germany, ³Siemens Medical Solutions USA, Saint Louis, MO, United States, ⁴Siemens Medical Solutions USA, Malvern, PA, United States

Respiratory motion causes signal blurring and image artifacts. Simultaneous PET/MRI allows for MR-assisted motion correction (MoCo) in PET imaging, leading to improved PET images for detection and evaluation of lesions. In this study, we proposed and examined a PET MoCo approach using motion vector fields (MVFs) from a deep-learning reconstructed MRI scan. MRI-based MVFs were derived from either 2000 spokes (MoCo₂₀₀₀, 5-6 minutes acquisition time) using a Fourier transform reconstruction or 200 spokes (MoCo_P2P200, 30-40 seconds acquisition time) using a deep-learning Phase2Phase (P2P) reconstruction and then incorporated into PET MoCo reconstruction.