Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Tirple-tunable, Stacked end-ring, Birdcage coil, Uniformity

Motivation: The PET insert can be used with MRI systems of different magnetic field strengths; however, a radio frequency(RF) coil cannot be used with different tesla.

Goal(s): Our goal is to generate uniform RF transmit magnetic fields at 3T, 7T and 11.74T MRI system using single RF coil.

Approach: Based on electromagnetic(EM) simulation, we proposed a new geometry of birdcage coil, which has 6 end-rings and 4 legs for triple resonance frequencies.

Results: In EM simulation, the proposed coil showed higher than 90% uniformity in the central axial plane. In bench measurement, proposed coil clearly showed triple resonance frequencies at 123.2, 297.2 and 500MHz.

Impact: Our proposed RF coil, named triple tunable birdcage coil, can generate uniform RF transmitted magnetic fields in 3T, 7T and 11.74T MRI systems. Therefore, it can be used for frequency selection in PET/MRI systems.

Keywords: High-Field MRI, High-Field MRI, Small-Sample Imaging

Motivation: Investigate potential uses for solenoidal dipoles, such as in human finger imaging.

Goal(s): The purpose is to evaluate how well the solenoidal dipole works for imaging the finger.

Approach: Comparison to alternative coil configurations for finger imaging.
 

Results:  Evaluate the inter-element coupling, Q-factor, H-field, E-field efficiency, and SNR of the solenoidal dipole in relation to the solenoid coil and LC loop.

Impact: The proposed solenoidal dipole design, despite less efficient H-fields, holds substantial potential for ultra-high-field MRI. It reduces crosstalk, enhances SNR distribution, and improves field homogeneity, making it a promising choice for high-resolution imaging of small samples.

Keywords: New Devices, New Devices, MRI, SNR enhancement, flux-focusing elements, Lenz lens, Lenz Resonator, Signal Amplification

Motivation: Despite numerous developments since MRI’s invention, low sensitivity remains the main limitation.

Goal(s): We aimed to improve upon the Lenz lens design for passive signal amplification in MRI, ultimately improving the signal-to-noise ratio. 

Approach: We created a first-in-kind Lenz resonator, a passive frequency selective flux-focusing circuit, to isolate and enhance the signal from a desired nucleus. 

Results: Performing RF testing with a vector network analyzer there was a 60 times signal amplification for the proton resonance frequency. At 3.0T, MRI demonstrated an experimental amplification of the signal-to-noise ratio by 3.9 times using an MRI insert of two coaxial Lenz resonators.

Impact: The substantial SNR boost produced by our Lenz resonators has a paramount importance for the field of MRI. The superior increase in SNR allows quicker scans, higher resolution scans, and precise disease detection.

Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Double-resonance coil, non-proton, skeletal and simulations

Motivation: Metabolic bone disease is a prevalent health concern affecting more than 200 million individuals worldwide. MRI has the potential to noninvasively characterize bone quality. 

Goal(s): The goal was to custom-build a double-resonance RF coil capable of proton and phosphorus solid state MRI on a 1.5 T extremity scanner intended for arms, legs, and tissue specimen imaging. 

Approach: A double-resonance RF coil was constructed based on a double-tuning single solenoid configuration, employing quarter-wave transmission lines to isolate the two channels.

Results: ZTE ¹H and ³¹P MRI of bone specimens demonstrated the feasibility and effectiveness of this coil.

Impact: The constructed single-solenoid double-resonance RF coil is capable of acquiring solid state 1H and 31P MRI of bone specimens. With this coil, MR information on the organic matrix (1H) and mineral (31P) can be obtained to assess metabolic bone diseases.

Keywords: RF Arrays & Systems, RF Arrays & Systems, Balun and RF traps

Motivation: Baluns and RF traps are resonant structures and coupling among each other, as well as to receive and transmit coils must be avoided. This is a particular challenge for the efficient and compact class of wound inductor traps.

Goal(s): Wound inductor trap that is isolated from external fields, does not require metallic shielding surfaces and can be wound compactly also for cables with limited bending radius.

Approach: Employing the method of active shielding known from gradient coil design to RF trap inductors.

Results: RF traps with shielding properties comparable to metal sheath shielded versions with very low eddy current profile.

Impact: Compact and efficient RF traps can help to design better and safer RF coils. Requiring no metal sheath for shielding of the trap can help to reduce gradient-switching-induced vibrations and heating.

Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Active catheter, Interventional Devices, Flexible Coils

Motivation: ¹⁹F-MRI can be used to monitor immune cell response to myocardial infarction, yet the low signal-to-noise ratio in the myocardium must be compensated by long measurement times and low spatial resolution.

Goal(s): To enable high spatial and temporal resolution ¹⁹F-MRI using an intraventricular expanding RF coil that can be introduced via a catheter.

Approach: A superelastic, self-resonant shielded-loop-resonator was developed to fit into a guiding catheter and the SNR was measured for different coil shapes.

Results: The expandable coil does not require re-tuning even at extreme shape deformations, and it can even be used as an active marker for real time ¹H guidance.

Impact: Intraventricular MRI of 19F-labeled immune cells will enable effective monitoring at myocardial infarction after fluorine labeling. The expandable SLR coil can be inserted via guiding catheters and used as 1H tracking coil without tuning or additional adjustments.

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

Motivation: Potassium(³⁹K) imaging provides an opportunity to probe cellular processes and has recently been demonstrated in human calf muscle at 7T

Goal(s): Developing an in-house birdcage resonator for potassium imaging, enabling simultaneous imaging with proton/sodium using previously developed dipole/loop array.

Approach: A low-pass eight-rung birdcage resonator was constructed using copper strip, chosen for its high Q factor. The resonator was optimized for maximum power efficiency and phantom images were acquired at 7T.

Results: The birdcage resonator demonstrated exceptional tuning and matching on the bench, with a homogeneous phantom image acquired in around 6 minutes. The findings suggest significant potential for in-vivo potassium quantification.

Impact: A birdcage resonator was designed and constructed in-house to create a capability for enhanced potassium imaging for neurological, musculoskeletal and oncology research. Potential integration with ¹H/²³Na array would allow simultaneous acquisition with three nuclei.

Keywords: New Devices, New Devices, flexible coils, broadband matching, elastic coils, textile coils, stretchable coils

Motivation: Fixed-volume copper coils fail to accommodate volume changes and flexing of the imaging region, therefore spoil MR signal and hamper the diagnosis.

Goal(s): To design a flexible surface coil for breast MR imaging.

Approach: A 2-ch stretchable knitted textile coil and a 2-ch reference copper coil, which were compatible with three different sized phantoms were compared in terms of their sensitivity profiles and SNR results.

Results: A three-stage broadband matching network could compensate for 15MHz of frequency shift. Although the textile coil was 31-81% more lossy compared to the copper coil, it only resulted in 10-26% SNR decrease.

Impact: Despite loss of the WEAR coil, a textile-based coil can sustain a sample-loss-dominated behavior and a broadband matching network can compensate for the frequency shift without compromising on SNR.

Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Array RF Coils, Antennas & Waveguides, Novel RF coil

Motivation: Great potentials arise from multinuclear imaging modalities of ²H, ¹⁷O, ³¹P and ¹H, which could depict the complexity of tissue and physiopathology related to the disease progression from multiple dimensions.

Goal(s): To develop a triple-tuned RF coil which can operate at three resonant frequencies of interest (²H, ¹⁷O, and ¹H) or (²H, ³¹P and ¹H).

Approach: A triple-frequency tuned RF coil was developed and simultaneously tuned and match to three resonant frequencies, and evaluated using a head-size phantom at 7T.

Results: We demonstrated a novel triple-frequency tuned coil design with robust imaging results for all three imaging frequencies.

Impact: As deuterium MRS imaging (DMRSI) is gaining more attention for brain tumor imaging, this triple-frequency tuned coil design can help add another X-nuclear frequency to the current DMRSI coil design, thus creating additional contrast for the brain tumor diagnosis. 

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

Motivation: The occipital lobe is the site of a variety of brain diseases. ³¹P MRS can noninvasively detect the metabolites to monitor and diagnose related diseases timely.

Goal(s): To collect ³¹P MRS signals in the occipital lobe at 3T, the dedicated RF coil setup is designed as a double-channel transceiver integrated surface coil.

Approach: The coil was designed as a "pillow” and verified by finite element simulation, physical production, bench tests and phantom experiments.

Results: The coil showed good uniformity and strong magnetic field intensity at the imaging region. Scanning with phantom, the spectral lines had a smooth baseline, high peaks, and excellent SNR.

Impact: we propose a transceiver and transmitter integrated surface coil for 31P magnetic resonance spectroscopy in the occipital lobe, which provides an excellent signal-to-noise ratio for excitation and acquisition of 31P spectral signals at 3T.

Keywords: Low-Field MRI, Low-Field MRI, X-nuclei

Motivation: Our project aims to refine MRI technology for a specific clinical purpose, focusing on a double-resonant coil design. This innovation bridges knowledge gaps and enhances diagnostic precision.

Goal(s): Our goal during the current semester is to create a double-resonant coil for MRI experiments on fluorine and protons. Achieving this involves circuit design and hardware construction.

Approach: Our approach includes capacitor and inductor integration, two separate output channels, and the development of essential hardware for signal acquisition using a didactic low field MR system.

Results: The design allows us to measure T₁ and T₂ relaxation times and enables us to perform imaging as well. 

Impact: With the coil we performed proof-of-principle fluorine and proton measurements in a didactic low MR-system. It can be used to investigate samples with 1H and 19F without moving the sample. The non-proton channel can be tuned to other x-nuclei frequencies.

Keywords: Analysis/Processing, Brain, Optical position tracking

Motivation: Deep learning methods are popular for head pose tracking in many applications; however, most models focus on large motions that are not applicable to the sub-millimeter accuracy required for motion correction in magnetic resonance imaging.

Goal(s): We aim to create a deep neural network capable of “markerlessly” tracking incremental changes in head pose in 6 degrees of freedom (DOF) with sub-millimeter/degree accuracy. 

Approach: We pre-trained a network on simulated images of a face in our expected environment as preparation for real-world data collection and training.

Results: Initial test results show a low average mean squared error of 0.0588 mm/degrees across the 6DOF. 

Impact: A deep neural network for sub-millimeter head pose tracking for motion correction was successfully pre-trained on simulated face data, with a test mean MSE of 0.0588 mm/degrees. This method shows potential towards motion correction applications in MRI.

Keywords: RF Arrays & Systems, RF Arrays & Systems, preamplifiers, preamplifier decoupling, power matching, noise matching, matching networks

Motivation: While preamplifier decoupling is a widely accepted technique, based on impedance mismatching, it appears counter-intuitive and still introduces confusion in the MRI community and scientists, who are not electrical engineers by training.

Goal(s): This work aims to develop a simulation setup, which clearly illustrates the signal-to-noise ratio (SNR) in preamplifier decoupled and power matched receive coils.

Approach: Circuit simulations are used to compare SNR at the output of power matched and preamplifier decoupled coils in 3T MRI systems.

Results: The networks yield similar SNR, despite having significantly different input reflection coefficients; demonstrating that preamplifier decoupling and power matching approaches lead to equivalent SNR.

Impact: The developed demonstrator is useful in understanding properties of preamplifier decoupling and breaking down a range of associated misconceptions. This can facilitate mastering a proper use of this decoupling method.

Keywords: Non-Array RF Coils, Antennas & Waveguides, RF Arrays & Systems, signal-to-noise ratio, high-resolution, cryogenic, RF coils.

Motivation: The signal-to-noise ratio of high-field RF surface coils decays with distance, and we propose cryogenic coils to compensate for the SNR of MR Imaging.

Goal(s): The cryogenic coil in our work aims to significantly improve the SNR of the images at long distances while guaranteeing a large imaging FOV.

Approach: We design a large size RF coil and cool it down for rat imaging.

Results: The experimental results show that the cryogenic coil obtained a SNR of 1.8-fold higher than a room-temperature coil and 1.1-fold higher than that of a commercial multi-channel rat coil.

Impact: The designed coil can help to improve the quality of MR imaging in some scenarios where the object to be measured is far away from the RF receive coil.

Keywords: RF Arrays & Systems, RF Arrays & Systems, matching networks, baluns, common-modes, noise matching, preamplifier decoupling

Motivation: Lattice baluns are traditionally used in receive arrays to achieve common mode rejection and preamplifier decoupling. They, however, are limited to real impedance transformations only.

Goal(s): New matching networks are sought that achieve noise matching and preamplifier decoupling, as well as common-mode rejection.

Approach: In this abstract, new network topologies are introduced and their bandwidths are studied.

Results: In addition to being more compact, the new networks offer a wider bandwidth as well as higher common-mode rejection. Thus, it is expected that the new networks are more resilient to component tolerances and loading effects, and they may enable multinuclear imaging.

Impact: New topologies of preamplifier decoupling networks with integrated balun functionality are introduced. They offer wider bandwidth and higher common-mode rejection compared to traditional networks.