Keywords: New Devices, Hybrid & Novel Systems Technology

Motivation: Detection of vital signs in MRI is hampered by the harsh environment of the MR-scanner and requires setup time.

Goal(s): Use integrated (i.e. no setup time) sensors that are fully MR-compatible and provide reliable cardiac and respiratory signals. 

Approach: Fiber Bragg Grating (FBG) based sensors (optical sensors) are integrated into the headrest of an MR-coil and the MR-bed for detection of heart beat and respiratory cycle. 

Results: MR-system integrated FBG sensors pick up cardiac and respiratory signals. The challenge lies in the realtime filtering of these signals to be able to use them for triggering of the scanner. 

Impact: Patient setup time can be reduced for exams requiring cardiac and/or respiratory signals by using MR-system integrated FBG sensors.

Keywords: RF Arrays & Systems, RF Arrays & Systems

Motivation: Conventional MRI breast screening is performed in the prone position with rigid RF coils. These coils are uncomfortable and imaging area limited by patient size and positioning.  

Goal(s): Our goals were to improve patient comfort, accommodate varying breast sizes, and provide faster screening through an adaptable breast coil utilizing stretchable elements.

Approach: A 20-channel breast coil was created with stretchable elements to accommodate varying bust sizes. Bench and phantom scans comparisons were made against an industry-standard flexible coil.

Results: Compared to industry-standard, highly-flexible coils, this coil demonstrated better adaptability to larger breasts, with improved sensitivity along the breast contour, and better acceleration.

Impact: Compared to the use of a traditional flexible coil of similar channel count for supine breast imaging, this coil can adapt to a wider range of breast sizes with easier setup, enhanced patient comfort, and performs better at greater acceleration.

Keywords: New Devices, New Devices

Motivation: The balun or cable trap circuits associated with the RF coil are favored to be miniaturized, light-weighting, and even flexible.

Goal(s):  We proposed a reproducible and miniaturized Bazooka balun using printed coaxial capacitors.

Approach: EM simulations were performed to guide the practical fabrication. The miniaturized Bazooka balun is made of the double-layer printed circuit board, allowing mass manufacturing ability in practice.

Results: The extremely thin layer in the printed capacitor (25 micrometers) provides a large capacitance of tens of pF per centimeter and allows the total length to be much shorter.

Impact: This reproducible and miniaturized balun is ideal for flexible and wearable RF coil designs, enhancing patient comfort and MRI image quality in diagnosis.

Keywords: New Devices, Relaxometry

Motivation: Bioreactor cell density measurements currently require removing samples from the culture. This limits how many samples can be taken in a day and precludes real-time culture monitoring.

Goal(s): We sought to take nondestructive cell density measurements every ten minutes without removing cells from the bioreactor.

Approach: We built a system that takes T₂ relaxometry measurements through the bioreactor’s silicone tubing every ten minutes and compared these to measurements taken by a commercial cytometry system.

Results: The T₂ relaxation data closely tracks the true cell density. Changes made to the culture are detected much more quickly by the relaxometer. 

Impact: Magnetic resonance relaxometry can be used to track bioreactor culture growth in real time, and makes it possible to identify and correct problems with the culture before the culture fails.

Keywords: New Devices, New Devices, Metamaterials

Motivation: High permittivity metamaterials have shown benefits in UHF MRI. However, precise dielectric constant measurement method for metamaterials is in absence, which may lead to bias in field manipulation.

Goal(s): Developing a precise measurement method to better mimicking dielectric materials’ role in field manipulation, where samples are placed at the reactive near-field region.

Approach: A microstrip line resonator was used to measure resonances of metamaterials. The resonance of dielectric materials with particular properties were chosen as the reference. Their difference in resonance frequency is required to be minimized.

Results: Metamaterials designed using our approach exhibited superior accuracy in mimicking the target dielectric pad.

Impact: The proposed method leads to better mimicking dielectric materials’ role in field manipulation at reactive near region. Metamaterials designed with this method exhibit enhanced B₁ field and lower SAR, signifying a significant advancement in UHF MRI and promising precise diagnoses.

Keywords: Phantoms, Thermometry

Motivation: To demonstrate the utility of inexpensive easy-to-use commercial MRI-readable thermometers for monitoring phantom temperatures during imaging and enable temperature corrections in an MSK relaxometry phantom developed for inter-site relaxation time (T1, T2, T1ρ) comparisons.
 

Goal(s): Provide convenient thermometry for temperature corrections for phantom based intersite comparisons of relaxation time and diffusion measurements.

Approach: Commercial incubator thermometers with a temperature range of 15°C to 50°C were characterized for phantom thermometry.

Results: Commercial incubator thermometers demonstrated to be MRI readable with an accuracy of ±0.2°C using standard imaging protocols, as long as the thermometer axis is perpendicular to the readout direction.

Impact: Easy to use MRI-readable thermometry is available to enable temperature corrections to minimize confounding factors in inter-site comparisons.

Keywords: RF Arrays & Systems, RF Arrays & Systems

Motivation: Wireless clock synchronization must be implemented to achieve a wireless MRI receive coil architecture.

Goal(s): Our goal was to implement atomic clock timing via global navigation satellites signals (GNSS) to the receive coil in the scanner for high precision clock correction and synchronization. 

Approach: We performed benchtop measurements to measure the precision of clock correction achievable with GNSS and precision time protocol (PTP), as well as modified an iRFW coil to receive these GNSS signal from within the scanner bore.

Results: Bench-top clock  measurements showed nanosecond precision time-synchronization using PTP-GNSS, and the iRFW-GNSS successfully acquired atomic clock time signals within the scanner bore. 

Impact: The iRFW-GNSS coil design can perform the wireless transfer MRI data and clock-syntonization regardless of scanner platform allowing for wide spread adoption of wireless MRI for new and existing scanners.   

Keywords: Hybrid & Novel Systems Technology, Hybrid & Novel Systems Technology

Motivation: The threshold to efficient use of field cameras is high and they could benefit from being less dependent on the scanner system they're being used in.

Goal(s): The aim of this work is to develop an independent field monitoring system that can synchronize itself with and make targeted measurements of MR sequences.

Approach: We employ a commercial NMR field probe system and trigger it externally using a host PC for data processing and an FPGA as a timing system.

Results: We are able to independently synchronize the monitoring system, make targeted measurements of a sequence and decompose a set of gradient waveforms.

Impact: This work is a step towards enabling scanner independent monitoring of MR sequences with NMR field probes. This could be useful in cases where the integration of a field camera is not an option. 

Keywords: Parallel Transmit & Multiband, RF Arrays & Systems, FPGA, RFPA

Motivation: Careful attention to safety is required for human research with novel parallel transmission (PTx) MRI technologies, particularly when they may cause harmful interactions with implanted devices.

Goal(s): Our goal was to add an additional layer of safety during experiments with a custom PTx research platform.

Approach: A system supervisor was created to monitor and react to a variety of amplifier faults and power conditions.

Results: Initial tests showed that it could safely disable the PTx system with acceptably short and stable response times.

Impact: A system supervisor was developed and tested for parallel transmission MRI research. The presence of such a supervisor may accelerate acceptance of PTx research systems by safety-conscious researchers and reviewers.

Keywords: New Devices, Brain, Optical position tracking

Motivation: Optical position tracking (OPT) systems have been used successfully in motion correction, however, the comparison of new and pre-existing OPT systems remains challenging due to lengthy calibration procedures.

Goal(s): Our goal was to create a testing platform capable of operating two systems concurrently for validating new OPT methods.

Approach: Two dual camera systems were set up in the magnet room with a custom calibration stage. A phantom was used to transform coordinates from the camera to the magnet coordinate frame.

Results: Camera calibration is limited to 30-minutes and outputs expected values. The pre-existing OPT system is accurate.

Impact: With this testing platform, two optical position tracking (OPT) systems can be compared simultaneously on participants in the MR environment, rather than individually on the benchtop. This allows validation of OPT methods that are highly dependent on the testing environment.

Keywords: New Devices, Hyperpolarized MR (Gas)

Motivation: In the Spin Exchange Optical Pump (SEOP) technique, the spare space between pump cell and gas manifold, called dead space, might impact polarization through dilution and dark rubidium depolarization.

Goal(s): This study aims to improve the design of the stop-flow polarizer to minimize dead gas and thus increase the polarization efficiency.

Approach: A magnetic-compatible actuator was designed for automatic control of cell stem valves opening/closing in our homemade polarizer, with good adaptability of main pumping field, Class I laser regulation and mechanical deviation. 

Results: Results show that under the same temperature, the polarization levels with actuator were always better than the control group.

Impact: The application of actuator in stop-flow polarizer shows the feasibility of improving polarization through minimizing dead space. It can be quite useful when acquiring small amount of HP gas but with higher requirement on polarization.

Keywords: RF Arrays & Systems, New Devices

Motivation: Float cable trap has gained widespread adoption in RF coil owing to its unique advantages. However, conventional float trap requires considerable dimensions to achieve an excellent performance.

Goal(s): This study is aiming to propose a novel float balun that can achieves high performance but with a compact size.

Approach: It was inspired by the well-established solenoid trap. The solenoid structure leverages strong inductive coupling between the cable shield and float resonator, ensuring high efficiency and enabling a compact design.

Results: With a compact size of 1.5x3cm², solenoid float balun shows a measured CMRR of -31 dB (vs. -5 dB using conventional float trap). 

Impact: The novel, compact and float balun offers significant advantages in the field of MRI RF coil and RF safety. It reduces the overall bulkiness of the RF coil, enables the incorporation of a greater number of elements in receive arrays.

Keywords: RF Arrays & Systems, RF Arrays & Systems

Motivation: Wireless MRI signal transfer reduces the need for physical cabling that can complicate patient table design and impede local coil preparation. Proposed techniques to eliminate cabling can involve complex subsystems for clock synchronization, high-fidelity ADC, low EMI, and high-speed data transfer. 

Goal(s): Our goal was to implement a short distance contact-free signal and power transfer system without complex circuitry. 

Approach: We designed a system to eliminate coil-to-scanner connections by transferring coil signals and preamplifier power over short distances using inductively coupled loops. 

Results: SNR in images acquired with the contact-free and traditional (wired) systems were within 3-5%. 

Impact: The proposed contact-free signal and power transfer system eliminated the physical connection between the coil and scanner while maintaining SNR, which opens the door to wireless coils and more robust and low-cost, detachable patient tables.

Keywords: New Devices, New Devices, In-bore electronics

Motivation: Due the noise emission of switch mode power supplies, linear regulators are often present in electronics in and around the MR bore, with the related thermal challenges. 

Goal(s): In this work we present a switched capacitor converter witch is capable of providing high output currents without emitting noise in the MR RF band. 

Approach: The goal was achieved by controlling the slew rate of the gate source voltage of the switching GaN FETs. 

Results: High efficiency, low output ripple and no unexpected transient behavior could be measured on the bench.

Impact: The presented 10A switched capacitor converter can provide efficiently power to electronics without emitting RF noise around the MR RF band. Enlarging the integration possibilities of high density electronics in and around the MR bore.

Keywords: New Devices, New Devices, Force Measurement

Motivation: Conventional load cells are not MRI-compatible, and MRI-compatible fiber optic force sensors are expensive and require specialized data collection systems.

Goal(s): Our goal was to develop and test a low-cost, MRI-compatible device for continuous force measurement.

Approach: We developed a hydraulic-based system for measuring continuous compressive forces within the magnet bore during scans.

Results: Pre-cycling increased the measurement repeatability of the device. The device was completely MRI-compatible and measured continuous compressive forces while simultaneous MRI data was acquired.

Impact: Our newly developed device is an inexpensive option for measuring continuous compressive forces during simultaneous MRI scans and is particularly useful for researchers who want to use a conventional electronic data acquisition system.

Keywords: Signal Representations, Signal Representations

Motivation: Point-of-Care Low Field MRI scanners are predominantly stifled by generic time-varying EMI, engendered by adjoined scanner electronics, environmental interference & radiation close to the lamor frequency and extraneous , creating decreased signal-to-noise ratio and artifacts on images.

Goal(s): Passive Faraday Shielding & Effectiveness Testing, EMI Detection, Cancellation using a single RF coil.

Approach: Passive Faraday Shielding using Aluminium and Copper sheets, Shielding Effectiveness testing using calibrated transmitters and receivers, EMI detection & cancellation using a single RF coil.

Results: Faraday Passive Shielding done and upto 74dB EMI attenuation effective. Active EMI detection & cancellation showed  EMI reduction up to approximately 53% in signal strength and 46%  image quality.

Impact: Broadband and Structured EMI elimination using passive faraday shielding with additional suppression techniques like system grounding, detection and elimination using a single coil will significantly improve signal strength by curbing signal loss and consequently better image quality.