Keywords: RF Arrays & Systems, RF Arrays & Systems

Motivation: Diffusion MRI utilizing ultra-high performance gradients for high b-value in vivo brain images still suffers from low SNR and increased eddy currents artifacts.

Goal(s): To construct a high-density coil array with an integrated field monitoring system. To enhance SNR and parallel image encoding, while capturing 3^rd-order field dynamics.

Approach: Utilizing simulations, 3D printing technology, and radiofrequency electronics to construct a 72-channel head coil and incorporate a field monitoring system. Optimization of the combined system to operate jointly in a space-constraint MRI gradient coil environment.

Results: High-resolution, high b-value diffusion in vivo imaging with greatly minimized image artefacts.

Impact: The constructed 72-channel head coil along with the new Connectome 2.0 scanner will enable the investigation of new microstructure features and connectivity in the living human brain.

Keywords: RF Arrays & Systems, RF Arrays & Systems

Motivation: Our newly operational 11.7 T machine provides an improved signal-to-noise ratio (SNR) in the human brain. This gain in SNR can be even enhanced by designing region-focused receive arrays.

Goal(s): Our main goal was to maximize the SNR in the temporal lobes and provide high-acceleration capabilities for fMRI studies.

Approach: We developed a modular 32-channel receive array made of non-overlapped hexagonal loops placed on a flexible cap, using high-impedance coils (HIC). We compared our coil to a 32-channel whole-brain receive array at 11.7 T.

Results: The cap receive array provides a significant SNR boost in the targeted region.

Impact: Our cap receive array should ease sub-millimeter resolution fMRI with high SNR in the temporal lobes. Moreover, the detachable hexagonal modules could easily be re-arranged to target any other brain region, with no need for retuning.

Keywords: Parallel Transmit & Multiband, High-Field MRI

Motivation: Dipole RF elements with electronically switchable B₁ field patterns have been shown to improve receive performance. The question whether they are beneficial for transmission is still open.

Goal(s): Improve flip angle homogeneity by modulating the Tx sensitivity of a dipole during excitation.

Approach: An RF coil built from eight dipoles with electronically switchable sensitivities was constructed. Achievable flip angle homogeneity with 2-kT-points pulses was evaluated in simulations and in experiments.

Results: Flip angle homogeneity could be increased by electronically switching the Tx sensitivity during the course of the RF pulse.

Impact: RF elements with switchable transmit sensitivities offer a novel degree of freedom for excitation that promises improved flip angle homogeneity. This addresses one of the most pressing problems in ultra-high field MRI.

Keywords: RF Arrays & Systems, RF Arrays & Systems

Motivation: In addition to peripheral SNR gain, the promise of a quadratic increase of SNR at the center of a human head with field strength draws significant attention to many ultrahigh field head MRI applications.  

Goal(s): Assess the performance of state-of-the-art RF receive array coils in capturing the theoretical upper limit of central head SNR across different field strengths. 

Approach: We experimentally investigated the impact of combining transceiver elements with highly-dense conventional loop arrays to capture the ultimate intrinsic SNR in head applications.

Results: We demonstrated that achieving central SNR gains at UHF requires an increased number of receive elements and larger transceiver elements.

Impact: Capability of conventional loop technology to capture the SNR's upper-limit in human head is investigated across different field strengths, which can pave the way for the RF technology developments focused on capturing the SNR gain in ultrahigh field head applications.

Keywords: RF Arrays & Systems, RF Arrays & Systems

Motivation: Since RF power requirements increase with operating frequency, SAR levels at UHF represent practical limitations. Here we evaluate possible improvements in overall transmit efficiency and SNR of array coils for the human head at 10.5T through the utilization of high permittivity materials.

Goal(s): Our goal was to evaluate the impact of high permittivity materials (HPM) on the transmit efficiency and SNR for various transceiver array designs.

Approach: We experimentally evaluated four multichannel transceiver arrays of different architectures with and without a formfitting HPM former.

Results: The HPM coil former achieved improvements in transmit efficiency and SNR compared to a typical polycarbonate coil former.

Impact: Incorporating high permittivity dielectric materials into the design and fabrication of pTx-capable transceiver array coils demonstrated improved transmit efficiency and SNR. This technology has the potential to improve imaging and spectroscopic applications in the human head at 10.5T and beyond.

Keywords: RF Arrays & Systems, RF Arrays & Systems

Motivation: Conventional MRI coils offer suboptimal parallel imaging performance for young children. 

Goal(s): Our goal was to enhance imaging acceleration by dedicated flexible high-density coil design for pediatric patients at 3T.

Approach: We design, construct, and evaluate a highly flexible small element dense array constituted by dual turn loops with minimum inter-component interference layout design.

Results: Both phantom and in-vivo studies demonstrated superior parallel imaging performance using the proposed coil.

Impact: A dedicated high-channel count coil that allows highly localized coil sensitivities by minimum interference layout design may benefit small pediatric patients.

Keywords: RF Arrays & Systems, Brain

Motivation: Previous studies have reported central SNR improvements at 7T with dipole transceivers, but not with loops-based arrays.

Goal(s): Assess the performance of an 8TxRx56Rx loop-based transceiver array against three conventional 8Tx32/64Rx arrays.

Approach: SNR and g-factor maps were acquired from phantom and healthy volunteers for four head coils (1Tx32Rx, 8Tx32Rx, 8Tx64Rx, 8TxRx56Rx) at 7T

Results: The modified 8TxRx56Rx coil showed a 12.6% increase in central SNR for in vivo scans. The peripheral SNR and g-factor maps remain comparable to their 8Tx64Rx counterpart, and both 64Rx coils performed significantly better than 32Rx coils at high acceleration factors.

Impact: A 56-channel receive 8-channel loop-based transceiver array can improve central image SNR at 7T without compromising g-factor compared to a conventional 64-channel receive 8-channel transmit coil.

Keywords: RF Arrays & Systems, RF Arrays & Systems, MSK

Motivation: Many musculoskeletal disorders cannot be detected in static MRI, making surgical intervention necessary.

Goal(s): Our Goal was to enable motion controlled dynamic MRI to potentially add diagnostic findings and reduce surgical interventions.

Approach: We advanced our apparatus for controlled passive movement of the foot (Robotic Motion Device) and implemented an adapted 16-channel Ankle Coil for accelerated imaging.

Results: Combining the Robotic Motion Device and the 16-channel Ankle Coil allowed us to perform controlled passive foot movement and acquire high SNR images.

Impact: The combination of a Robotic Motion Device and an adapted 16-channel Ankle Coil enables dynamic image acquisition with controlled passive movement of the ankle joint, potentially adding and improving diagnostic findings and reducing surgical interventions.