A5047571164- Advanced MRI Techniques and Applications
- Advanced NMR Techniques and Applications
- Atomic and Subatomic Physics Research
- Neurological disorders and treatments
- Functional Brain Connectivity Studies
- Ultrasound and Hyperthermia Applications
- Ultrasound Imaging and Elastography
- Microwave Imaging and Scattering Analysis
- Electromagnetic Compatibility and Measurements
- Electron Spin Resonance Studies
- Neuroscience and Neural Engineering
- Wireless Power Transfer Systems
- Engineering Applied Research
- Energy Harvesting in Wireless Networks
- Wireless Body Area Networks
- Parkinson's Disease Mechanisms and Treatments
- Ultrasonics and Acoustic Wave Propagation
- Advanced Neuroimaging Techniques and Applications
- Neonatal and fetal brain pathology
- Structural Integrity and Reliability Analysis
- VLSI and Analog Circuit Testing
- Thermodynamic and Structural Properties of Metals and Alloys
- Cardiac Imaging and Diagnostics
- Geotechnical Engineering and Soil Mechanics
- Oil and Gas Production Techniques
Resonance Research (United States)
2019-2025
University of Minnesota
2019-2025
University of Minnesota System
2024
Bilkent University
2014-2021
TechnipFMC (Norway)
2021
Purpose The purpose of this study is to safely acquire the first human head images at 10.5T. Methods To ensure safety subjects, we validated electromagnetic simulation model our coil. We obtained quantitative agreement between simulated and experimental specific absorption rate (SAR). Using coil model, calculated radiofrequency power levels image subjects. conducted all experiments imaging sessions in a controlled lab whole‐body 10.5T scanner Center for Magnetic Resonance Research. Results...
We examined magnetic field dependent SNR gains and ability to capture them with multichannel receive arrays for human head imaging in going from 7 T, the most commonly used ultrahigh (UHF) platform at present, 10.5 which represents emerging new frontier of >10 T UHFs.
Abstract Purpose Toward pushing the boundaries of ultrahigh fields for human brain imaging, we wish to evaluate experimentally achievable SNR relative ultimate intrinsic (uiSNR) at 10.5T, develop design strategies toward approaching latter, quantify magnetic field–dependent gains, and demonstrate feasibility whole‐brain, high‐resolution imaging this uniquely high field strength. Methods A dual row 16‐channel self‐decoupled transmit (Tx) receive (Rx) array was developed 10.5T using custom...
Background Since the advent of magnetic resonance imaging (MRI) nearly four decades ago, there has been a quest for ever-higher field strengths. Strong incentives exist to do so, as increasing strength increases signal-to-noise ratio images. However, ensuring patient safety becomes more challenging at high and ultrahigh MRI (i.e., ≥3 T) compared lower fields. The problem is exacerbated patients with conductive implants, such those deep brain stimulation (DBS) devices, excessive local heating...
We present a splittable 16-channel self-decoupled (SD)1 transmit/receive (Tx/Rx) loop array combined with 64-channel receive-only (Rx) to generate 80Rx/16Tx for human head imaging at 10.5 Tesla. Compared the previously presented SD transmitter, we designed, miniaturized, and integrated MR system interface, including custom switches preamplifiers, into coil housing. also implemented our new 128 receiver system, which supported this 80 channel receive configuration. Experimental results...
Described is a 128-channel receive (Rx) array for 10.5T brain imaging, comprised of 120 small Rx loops and 8 the 16 transmitter elements used as receivers. The coil compared to another 64-Rx 7T 32- arrays. principal benefit same field strength was improved parallel imaging. Secondarily, important engineering innovations are demonstrated suppress transmit/receive interactions optimize transmit efficiency. Modest improvements peripheral SNR were achieved 128-Rx over array. A 50% improvement in...
To develop multichannel transmit and receive arrays towards capturing the ultimate-intrinsic-SNR (uiSNR) at 10.5 Tesla (T) to demonstrate feasibility potential of whole-brain, high-resolution human brain imaging this high field strength.
Ultra-high-field magnetic resonance (MR) systems (7 T and 9.4 T) offer the ability to probe human brain metabolism with enhanced precision. Here, we present preliminary findings from 3D MR spectroscopic imaging (MRSI) of conducted world's first 10.5 whole-body system. Employing a custom-built 16-channel transmit 80-channel receive coil at T, MRSI acquisitions in six healthy volunteers map metabolic compounds cerebrum vivo. Three protocols different matrix sizes scan times (4.4×4.4×4.4 mm³:...
Abstract Purpose Patients undergoing craniofacial surgery for skull reconstruction may have titanium mesh implants. The safety risks related to 7 T MRI with these patients are not well understood. This study investigates the RF heating of head implants at T. Methods A simulation model a birdcage coil was developed and validated against , 1 g‐averaged specific absorption rate (SAR), temperature measurements in presence mesh. Various sizes shapes different angular positions were simulated...
Abstract Purpose To develop and characterize a 128‐channel head array for brain imaging at 10.5 T, evaluate signal‐to‐noise ratio (SNR) relative to ultimate intrinsic SNR (uiSNR) lower field strengths, demonstrate human anatomical functional with this unique magnetic high‐channel‐count array. Methods The coil consists of 16‐channel self‐decoupled loop transmit/receive (16Tx/Rx) 112‐loop receive‐only (Rx) insert. Interactions between the 16Tx/Rx 112Rx insert were mitigated using coaxial cable...
Purpose In this study, we investigate a strategy to reduce the local specific absorption rate (SAR) while keeping constant inside region of interest (ROI) at ultra‐high field (B 0 ≥ 7T) MRI. Methods Locally raising resonance structure under discontinuity (i.e., creating bump) increases distance between accumulated charges and tissue. As result, it reduces electric SAR generated by these The point that is sufficiently far from coil, however, not affected modification. three different resonant...
Higher signal-to-noise ratio (SNR) is the primary maxim for increasing magnetic field strength of MRI scanners. However, RF coils comprised loops do not capture highest achievable SNR that theoretically available at ultrahigh (defined as ≥7T) MRI. In this study, we investigate hypothesis central head 10.5T by combining loop and dipole receiver elements. For purpose, manufactured a 32-channel hybrid coil 25 receive-only 7 transceiver NODES dipoles. This 32ch achieved ~80% higher compared to array.
Purpose The purpose of this study is to introduce a new antenna element with improved transmit performance, named the nonuniform dielectric substrate (NODES) antenna, for building arrays at ultrahigh‐field. Methods We optimized dipole 10.5 Tesla by maximizing ‐SAR efficiency in phantom human spine target. optimization parameters included permittivity variation substrate, thickness, length, and conductor geometry. conducted electromagnetic simulations as well experiments compare...
Abstract The purpose of this work is to propose a tier‐based formalism for safety assessment custom‐built radio‐frequency (RF) coils that balances validation effort with the put in determinating factor. has three tier levels. Higher tiers require increased when validating electromagnetic simulation results but allow less conservative factors. In addition, we new method calculate modeling uncertainty between simulations and measurements propagate uncertainties into factor minimizes risk...
Abstract Purpose The purpose of this study is to present a strategy calculate the implant‐friendly (IF) excitation modes—which mitigate RF heating at contacts deep brain stimulation (DBS) electrodes—of multichannel coils 7 T. Methods An induced current on an implantable electrode generates scattered magnetic field whose left‐handed circularly polarizing component () approximated using ‐mapping technique and subsequently used as gauge for electrode's current. Using approach, relative currents...
Purpose The purpose of this study is to present a workflow for predicting the radiofrequency (RF) heating around contacts deep brain stimulation (DBS) lead during an MRI scan. Methods induced RF current on DBS accumulates electric charge metallic contacts, which may cause high local specific absorption rate (SAR), and therefore, heating. accumulated was modeled by imposing voltage boundary condition in quasi‐static electromagnetic (EM) simulation allowing thermal simulations be performed...
Purpose To obtain efficient operation modes of transmit array (TxArray) coils using a general design technique based on the eigenmode analysis scattering matrix. Methods We introduce concept modal reflected power and excitation eigenmodes, which are calculated as eigenvalues eigenvectors S H , where superscript denotes Hermitian transpose. formulate normalized power, is ratio total to incident TxArray for given signal weighted sum power. By minimizing coils, we increase space with low...
ABSTRACT Purpose To develop and characterize the performance of a 128-channel head array for brain imaging at 10.5 tesla evaluate potential this unique, >10 magnetic field. Methods The coil is composed 16-channel self-decoupled loop transmit/receive with 112-loop receive-only (Rx) insert. Interactions between outer transmitter inner 112Rx insert were mitigated using coaxial cable traps placed every 1/16 wavelength on each feed cable, locating most preamplifier boards outside field...
ABSTRACT One of the most important new frontiers in effort to improve spatial resolution and accuracy imaging human brain activity is recent development greater than 10 Tesla magnetic fields. Here we present initial results for 10.5 Blood Oxygenation Level Dependent (BOLD) based functional (fMRI) acquired with previously unavailable or difficult attain resolutions contrast. We data obtained nominal isotropic ranging from 0.65 0.35 mm partial coverage stimulus evoked responses, 0.75 whole...
Purpose Multi‐slice radiofrequency (RF) pulses have higher specific absorption rates, more peak RF power, and longer pulse durations than single‐slice pulses. Gradient field design techniques using a z‐gradient array are investigated for exciting multiple slices with single‐band pulse. Theory Methods Two different methods formulated to solve the required current values of gradient elements given slice locations. The method requirements specified, optimization problems minimum norm an...
Abstract Background Heating around deep brain stimulation (DBS) in magnetic resonance imaging (MRI) occurs when the time‐varying electromagnetic (EM) fields induce currents electrodes which can generate heat and potentially cause tissue damage. Predicting heating electrode contacts is important to ensure safety of patients with DBS implants undergoing an MRI scan. We previously proposed a workflow predict introduced parameter, equivalent transimpedance, that independent trajectories,...
We present a general framework for detecting the shape and electrical properties of unknown objects by using Newton minimization approach solving inverse-scattering problems. This procedure is performed evolving an initial-guess object iteratively until cost function decreases to desired value. Rapid convergence this method demonstrated some numerical results.
Multichannel transmit (Tx) arrays are essential for ultra-high fields. In the absence of commercial options, such must be built in-house. Prior to human imaging, however, safe operations limits specific absorption rate (SAR) established. This is done using EM simulations, accuracy which has verified by comparing measured and simulated data. Unfortunately, simulations may not fully represent experimental conditions, especially complex transmitter designs. this work, we propose a numerical...
Susceptibility-weighted imaging (SWI) and quantitative susceptibility mapping (QSM) have been shown to provide unique contrasts that can be used study pathophysiologic changes of tissue magnetic in various brain diseases. As effects increase with the main field strength, there has a rapidly growing interest performing SWI QSM at ultrahigh (UHF) (7 Tesla above). The aim this was demonstrate how use UHF 10.5 may promote human brain.