This work presents an open-source, optimized solenoid head coil tailored for the 50 mT open-source scanner (OSII ONE v2.1), set the basis for a fully reliable and reproducible component for the open-source OSII ONE MRI scanner.
Abstract
Low-field magnetic resonance imaging (MRI) provides an accessible, portable, and low-cost alternative to high-field scanners, expanding diagnostic imaging to point-of-care settings. However, widespread adoption is fundamentally hindered by a severely reduced signal-to-noise ratio (SNR). At low frequencies, radiofrequency (RF) coil conductor losses - rather than tissue sample losses - predominantly govern the system's total noise, making meticulous RF coil optimization critical to recovering image quality. This work presents an open-source, optimized solenoid head coil tailored for the 50 mT open-source scanner (OSII ONE v2.1). The paper validates production reproducibility across three independent international institutions and introduce an open-source connector with integrated digital circuitry for coil identification and DC or logic signals. Comprehensive benchtop measurements, Electromagnetic Interference (EMI) coupling analysis, Specific Absorption Rate (SAR) safety simulations, and phantom and human volunteer imaging confirm the design's efficacy, safety, and reproducibility. The results of the paper, when combined with the material provided in the open-source dedicated repositories, set the basis for a fully reliable and reproducible component for the open-source OSII ONE MRI scanner. In addition, the same optimization strategy and design material can be exploited for designing other RF coils for imaging of other body parts.
Magnetic Resonance Imaging (MRI) is indispensable in clinical diagnosis and biomedical research due to its advantages such as non-ionizing radiation and high soft tissue resolution. As a core component of the MRI system, the performance of radiofrequency (RF) coils directly affects imaging quality. Wired RF coils are the standard configuration in clinical practice, but they have several limitations including cable constraints and high costs. Active wireless coils face technical challenges such as high system complexity, difficult clock signal synchronization and data throughput limitation. As a passive wireless signal transmission solution, the inductively coupled wireless coil (ICWC), serving as a complementary RF component, achieves signal and energy transmission through near-field magnetic coupling with the wired coil. They possess numerous advantages including localized reception unique advantages of non-ionizing radiation, high soft-tissue resolution, multi-parametric analysis, and metabolic information monitoring. Since the 1970s [1, 2], MRI has not only revolutionized the traditional medical understanding of human anatomy and pathological changes but also achieved groundbreaking advancements in numerous specialized subfields, such as neuroscience [3-5] and oncology [6-8]. sensitivity enhancement, cross-tissue/species transplantability, adaptability to different main magnetic fields, reduction of the g-factor, B1 + field shaping, cable-free advantages in special scenarios, design scalability, and cross-manufacturer compatibility. This review elaborates on the inductive coupling mechanism of ICWCs, the derivation of the SNR formula, potential causes of g-factor reduction, and recommendations for fabrication methods. Additionally, it systematically summarizes the application progress in scenarios such as invasive imaging, multi-site human imaging, animal imaging, and applications in special scenarios. Finally, it discusses the development prospects ICWCs in fields including neuroimaging, ultra-high/ultra-low field MRI, and X-nucleus MRI/MRS, as well as ICWCs' advantages and limitations, providing a reference for the innovation of MRI RF coil technology and the clinical translation of ICWCs.
An open-source reference system for portable low-field MRI designed to support replication, reproducibility, benchmarking, and quantitative comparison is presented, aiming to support cross-site comparability, reproducible research, and collaborative development of future portable low-field MRI technologies.
D. Schote, H. Herthum, Umberto Zanovello et al.· 0 citations
The recent developments in ultra-low-field brain MRI are reviewed, which enable imaging in open environments and demonstrate initial clinical applicability in point-of-care settings, and future developments are envisioned to address the current limitations of image quality and contrast in ultra-low-field brain MRI systems.
Ed X. Wu, Yujiao Zhao, Yilong Liu et al.· Stroke· 1 citation
OBJECTIVE
The objective of this work is to develop an electromagnetic induction coil (EMIC)-based motion tracking system with low footprint and in-place calibration, enabling high-temporal-resolution prospective motion correction (PMC) for short-TR MRI sequences.
METHOD
We designed an MR-visible EMIC that supports in-place calibration and flexible distribution of the coils. To demonstrate the benefits of improved temporal resolution with EMIC, EMIC and fat navigator (FatNav)-based PMC were performed for 2D phase contrast MRI (PC-MRI) under similar motion conditions.
RESULTS
EMIC increased the temporal resolution of motion tracking by 10 times compared to FatNav and demonstrated high sensitivity to small motions, with random errors in the range of 0.06-0.12 mm for translation and 0.075-$0.078^{\circ }$ for rotation. EMIC-based PMC significantly improved image quality for PC-MRI compared with both no PMC and FatNav-based PMC.
CONCLUSION
By providing higher temporal resolution motion tracking than FatNav, EMIC achieved superior PMC performance in 2D PC-MRI and significantly improved image quality.
SIGNIFICANCE
The developed MR-visible EMIC eliminated the need for sensor calibration in advance and improved patient comfort and RF coil compatibility, enabling more effective PMC with improved image quality.
Zhanbin Dong, Tuo Yu, Bingbing Zhao et al.· IEEE transactions on bio-med...· 0 citations
Magnetic resonance imaging (MRI) scanning remains largely restricted to specific modalities, typically involving low radiofrequency (RF) power levels and stringent protocols for patients with deep brain stimulation (DBS) implants, due to safety concerns related to RF-induced heating of the implants. A 6-channel dual-role head coil array capable of modulating the electric-field (E-field) distribution was designed and evaluated using electromagnetic (EM) simulations. By optimizing the resonant frequency of each coil element during RF transmission, the transmit field was reshaped, leading to a significant reduction in RF-induced heating near the DBS lead tip. The proposed method was validated across two scenarios of increasing complexity: 1) a simple straight conductive wire for concept validation and 2) four realistic DBS leads representing complex real-world scenarios. The coil settings can be optimized either to suppress the E-field at a specific location, such as the DBS lead tip, or to suppress the peak specific absorption rate (SAR) across the entire human head. For location-specific E-field suppression, the simplified predefined-state control scheme and the fine-tuning genetic algorithm (GA)-based framework were implemented, achieving E-field reductions of 45.9% and 68.3%, respectively. For whole-head peak SAR suppression, the annealed Log-Sum-Exp (LSE)–Adaptive Moment Estimation (Adam) framework (LSE–Adam) was implemented, achieving an average 1 g SAR reduction of 72.09% across four realistic DBS lead models. The dual-role coil demonstrated a high degree of flexibility in controlling the transmit field and reducing RF-induced heating at DBS implants, offering a novel approach to mitigate RF-induced heating of the implants in MRI.
Zhonghao Zhang, Ming Lu, Zhengyi Lu et al.· IEEE Access· 0 citations