Simultaneous imaging of hard and soft biological tissues in a low-field dental MRI scanner
J. M. Algarín, E. Díaz-Caballero, J. Borreguero, F. Galve, D. Grau-Ruiz, J. P. Rigla, R. Bosch, J. M. González, E. Pallás, M. Corberán, C. Gramage, S. Aja-Ferná… 展开作者
J. M. Algarín, E. Díaz-Caballero, J. Borreguero, F. Galve, D. Grau-Ruiz, J. P. Rigla, R. Bosch, J. M. González, E. Pallás, M. Corberán, C. Gramage, S. Aja-Fernández, A. Ríos, J. M. Benlloch, J. Alonso
Magnetic Resonance Imaging (MRI) of hard biological tissues is challenging due to the fleeting lifetime and low strength of their response to resonant stimuli, especially at low magnetic fields. Consequently, the impact of MRI on some medical applications, such as dentistry, continues to be limited. Here, we present three-dimensional reconstructions of ex-vivo human teeth, as well as a rabbit head and part of a cow femur, all obtained at a field strength of only 260 mT. These images are the first featuring soft and hard tissues simultaneously at sub-Tesla fields, and they have been acquired in a home-made, special-purpose, pre-medical MRI scanner designed with the goal of demonstrating dental imaging at low field settings. We encode spatial information with two variations of zero-echo time (ZTE) pulse sequences: Pointwise-Encoding Time reduction with Radial Acquisition (PETRA) and a new sequence we have called Double Radial Non-Stop Spin Echo (DRaNSSE), which we find to perform better than the former. For image reconstruction we employ Algebraic Reconstruction Techniques (ART) as well as standard Fourier methods. A noise analysis of the resulting images shows that ART reconstructions exhibit a higher signal to noise ratio with a more homogeneous noise distribution.
Objectives Studies that assess magnetic resonance imaging (MRI) induced radiofrequency (RF) heating of the tissue in the presence of an active electronic implant are mostly performed in horizontal, closed-bore scanners. Vertical, open-bore MRI systems have a 90° rotated magnet and generate a fundamentally different RF field distribution in the body, yet little is known about the RF heating of deep brain stimulation (DBS) systems in this class of scanners. Here, we investigated whether RF heating of DBS devices was significantly different in a vertical, open-bore MRI scanner compared to a horiz…
We propose to prototype the first CT-MRI scanner for radiation therapy and basic research, demonstrate its transformative biomedical potential, and initiate a paradigm shift in multimodality imaging. Our design consists of a double donut-shaped pair of permanent magnets to form a regionally uniform ~0.5T magnetic field and leave room for a stationary 9-source interior CT gantry at 3 tube voltages (triple-energy CT). Image reconstruction will be in a compressive sensing framework. Please discuss with Dr. Ge Wang (ge-wang@ieee.org) if you are interested in collaborative opportunities.
Prepolarized Magnetic Resonance Imaging (PMRI) is a long-established technique conceived to counteract the loss in signal-to-noise ratio (SNR) inherent to low-field MRI systems. When it comes to hard biological tissues and solid-state matter, PMRI is severely restricted by their ultra-short characteristic relaxation times. Here we demonstrate that efficient hard tissue prepolarization is within reach with a special-purpose 0.26 T scanner designed for dental MRI and equipped with suitable high-power electronics. We have characterized the performance of a 0.5 T prepolarizer module which can be s…
Objective: Accurate estimation of SAR is critical to safeguarding vulnerable patients who require an MRI procedure. The increased static field strength and RF duty cycle capabilities in modern MRI scanners mean that systems can easily exceed safe SAR levels for patients. Advisory protocols routinely used to establish quality assurance protocols are not required to advise on the testing of MRI SAR levels and is not routinely measured in annual medical physics quality assurance checks. This study aims to develop a head phantom and protocol that can independently verify global SAR for MRI clinica…
Background: Prostate cancer is one of the most common forms of cancer found in males making early diagnosis important. Magnetic resonance imaging (MRI) has been useful in visualizing and localizing tumor candidates and with the use of endorectal coils (ERC), the signal-to-noise ratio (SNR) can be improved. The coils introduce intensity inhomogeneities and the surface coil intensity correction built into MRI scanners is used to reduce these inhomogeneities. However, the correction typically performed at the MRI scanner level leads to noise amplification and noise level variations. Methods: In t…
A Review of Electromagnetic Elimination Methods for low-field portable MRI scanner
Harvard Medical School（哈佛医学院）；University of Michigan（密歇根大学）；Harvard University（哈佛大学）；New York University（纽约大学）；Columbia University（哥伦比亚大学）；Guangxi University（广西大学）
Image Sciences Institute, University Medical Center Utrecht（乌得勒支大学医学中心影像科学研究所）
Diffusion magnetic resonance imaging is a noninvasive imaging technique that can indirectly infer the microstructure of tissues and provide metrics which are subject to normal variability across subjects. Potentially abnormal values or features may yield essential information to support analysis of controls and patients cohorts, but subtle confounds affecting diffusion MRI, such as those due to difference in scanning protocols or hardware, can lead to systematic errors which could be mistaken for purely biologically driven variations amongst subjects. In this work, we propose a new harmonizati…
After being hyperpolarized using the technique of Metastability Exchange Optical Pumping (MEOP), 3He can be used as a contrast agent for lung magnetic resonance imaging (MRI). MEOP is usually performed at low magnetic field (~ 1 mT) and low pressure (~ 1 mbar), which results in a low magnetization production rate. A delicate polarization-preserving step of compression is also required. It was demonstrated in sealed cells that high nuclear polarization values can be obtained at higher pressures with MEOP, if performed at high magnetic field (non-standard conditions). In this work the feasibilit…
Birth of the Coil: another Milestone towards a fully reproducible low-field MRI scanner for head-imaging
Istituto Nazionale di Ricerca Metrologica (INRiM)（意大利国家计量研究所）；Institute of Biomedical Imaging, Graz University of Technology（格拉茨工业大学生物医学成像研究所）；Physikalisch-Technische Bundesanstalt (PTB) Braunschweig and Berlin（德国联邦物理技术研究院）；Universidad Comunera（科穆内拉大学）；University of Alberta（阿尔伯塔大学）；Cross Cancer Institute（交叉癌症研究所）
Towards Sustainable Magnetic Resonance Imaging: Insights from long-term, high-resolution energy recordings across an entire scanner fleet
Medical Image and Data Analysis (MIDAS.lab), Tübingen University Hospital（蒂宾根大学医院医学影像与数据分析（MIDAS实验室））；Department of Diagnostic and Interventional Radiology, Tübingen University Hospital（蒂宾根大学医院诊断与介入放射科）；Faculty of Computer Science, Eberhard Karls University of Tübingen（埃伯哈德·卡尔斯·蒂宾根大学计算机科学学院）
Multi-modality imaging hardware can be integrated in a single gantry to collect diverse datasets for complementary information and spatiotemporal correlation, with excellent examples including PET-CT and PET-MRI. However, there is no CT-MRI prototype up to today due to technical challenges and associated cost-benefit considerations. Thanks to the rapid development of medical imaging, it becomes feasible now to integrate cost-effective CT and MRI imagers together for portability, popularity, and point of care. In this paper, we present the top-level design of the first portable CT-MRI system an…
Subject grounding to reduce electromagnetic interference for MRI scanners operating in unshielded environments
Leiden University Medical Center（莱顿大学医学中心）；Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC-Universitat Politècnica de València（分子影像仪器研究所（I3M），CSIC-瓦伦西亚理工大学联合中心）
Combining the unmatched soft-tissue imaging capabilities of magnetic resonance imaging (MRI) with high precision robotics has the potential to improve the accuracy, precision, and safety of a wide range of image-guided medical procedures. However, the goal of highly functional MRI-compatible robotic systems has not yet been realized because conventional electromagnetic servomotors used by medical robots can become dangerous projectiles near the strong magnetic field of an MRI scanner. Here we report a novel electromagnetic servomotor design that is constructed from non-magnetic components and …
Magnetic resonance imaging (MRI) is the cornerstone technique for diagnostic medicine, biology, and neuroscience. This imaging method is highly innovative, noninvasive and its impact continues to grow. It can be used for measuring changes in the brain after enhanced neural activity, detecting early cancerous cells in tissue, as well as for imaging nanoscale biological structures, and controlling fluid dynamics, and it can be beneficial for cardiovascular imaging. The MRI performance is characterized by a signal-to-noise ratio, however the spatial resolution and image contrast depend strongly o…
Standard coils can cause inhomogeneities due to the standing wave patterns at ultra high field MRI. This B1 inhomogeneity can be overcome using the travelling-wave MRI (twMRI) approach. The ma- jority of twMRI research has been done with clinical MRI scanners at 7T or above. More recently, this concept has been also used with animal MRI systems, using circular-cross section waveguides and dielectric materials for both type of scanners. We have demonstrated that twMRI can be used at 3 T with clinical systems and a parallel-plate waveguide. Here, we investigated the use of a parallel- plate wave…
We demonstrate an experimental method for direct 2D and 3D imaging of magnetic radio-frequency (rf) field distribution in metal-dielectric structures based on traveling wave (TW) magnetic resonance imaging (MRI) at ultra-high field (> 7T). The typical apparatus would include an ultra-high field whole body or small bore MRI scanner, waveguide elements filled with MRI active dielectrics with predefined electric and magnetic properties, and TW rf transmit-receive probes. We validated the technique by obtaining TW magnetic-resonance (MR) images of the magnetic field distribution of the rf modes of…
In-vivo imaging with a low-cost MRI scanner and cloud data processing in low-resource settings
MRILab, Institute for Molecular Imaging and Instrumentation (i3M), Consejo Superior de Investigaciones Científicas (CSIC) & Universitat Politècnica de València (UPV)（分子成像与仪器研究所 (i3M)，西班牙高等科学研究理事会 (CSIC) 与巴伦西亚理工大学 (UPV)）；Mbarara University of Science and Technology (MUST)（姆巴拉拉科技大学 (MUST)）；McGill University（麦吉尔大学）；Leiden University Medical Center (LUMC)（莱顿大学医学中心 (LUMC)）；Microsoft Research, Health Futures（微软研究院，健康未来部门）；Facultad de Ciencias Aplicadas, Universidad Comunera（应用科学学院，科穆内拉大学）；Yale University（耶鲁大学）
University College London（伦敦大学学院）；University of Ibadan（伊巴丹大学）；Great Ormond Street Hospital for Children（大奥蒙德街儿童医院）；UCL Great Ormond Street Institute of Child Health（伦敦大学学院大奥蒙德街儿童健康研究所）；King’s College London（伦敦国王学院）；Microsoft Research Cambridge（微软剑桥研究院）；Department of Radiology, College of Medicine, University of Ibadan, Nigeria（伊巴丹大学医学院放射科）；Department of Paediatrics, College of Medicine, University of Ibadan, Nigeria（伊巴丹大学医学院儿科）；Centre for Medical Image Computing and Department of Computer Science, University College London, UK（伦敦大学学院医学影像计算中心和计算机科学系）；Department of Biomedical Engineering, King’s College London, UK（伦敦国王学院生物医学工程系）；Machine Intelligence and Perception Group, Microsoft Research Cambridge, UK（微软剑桥研究院机器智能与感知组）
1.5T or 3T scanners are the current standard for clinical MRI, but low-field (<1T) scanners are still common in many lower- and middle-income countries for reasons of cost and robustness to power failures. Compared to modern high-field scanners, low-field scanners provide images with lower signal-to-noise ratio at equivalent resolution, leaving practitioners to compensate by using large slice thickness and incomplete spatial coverage. Furthermore, the contrast between different types of brain tissue may be substantially reduced even at equal signal-to-noise ratio, which limits diagnostic value…
Background: Parallel transmit (pTx) has introduced many benefits to MRI with regard to decreased specific absorption rates and improved transmit field homogeneity, of particular importance in applications at higher magnetic field strengths. PTx has also been proposed as a solution to mitigating dangerous RF induced heating of elongated conductive devices such as those used in cardiac interventions. In this work we present a system that can augment a conventional scanner with pTx, in particular for use in interventional MRI for guidewire safety. Methods: The pTx system was designed to work in-l…
Quantitative mapping from conventional MRI using self-supervised physics-guided deep learning: applications to a large-scale, clinically heterogeneous dataset
Qualitative and quantitative hard-tissue MRI with portable Halbach scanners
MRILab, Institute for Molecular Imaging and Instrumentation (i3M), Spanish National Research Council (CSIC) and Universitat Politècnica de València (UPV)（分子成像与仪器研究所 (i3M)，西班牙国家研究理事会 (CSIC) 和瓦伦西亚理工大学 (UPV)）；Full Body Insight S.L.；PhysioMRI Tech S.L.
MRI offers outstanding soft tissue contrast that may reduce uncertainties in target and organ-at-risk delineation and enable online adaptive image-guided treatment. Spatial distortions resulting from non-linearities in the gradient fields and non-uniformity in the main magnetic field must be accounted for across the imaging field-of-view to prevent systematic errors during treatment delivery. This work presents a modular phantom and software application to characterize geometric distortion (GD) within the large field-of-view MRI images required for radiation therapy simulation. The modular pha…
Portable low-cost MRI systems have the potential to enable point-of-care and timely MRI diagnosis, and to make this imaging modality available to routine scans and to underdeveloped areas. With simplicity, no maintenance, no power consumption, and low cost, permanent magnets or arrays are attractive to use as a source of magnetic field to realize portability and low cost for a scanners. However, when taking the Fourier imaging approach and using linear gradient fields, homogeneous fields are required, thus either a bulky magnet is needed, or the imaging volume is too small to image an organ if…
Real-time, inline quantitative MRI enabled by scanner-integrated machine learning: a proof of principle with NODDI
Hawkes Institute, Department of Computer Science, UCL（伦敦大学学院霍克斯研究所计算机科学系）；NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Queen Square Institute of Neurology, Faculty of Brain Sciences, UCL（伦敦大学学院脑科学学院神经炎症系女王广场多发性硬化中心核磁共振研究单元）；Research and Collaborations GBI, Siemens Healthcare Ltd（西门子医疗有限公司研究与协作GBI部门）；Lysholm Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, University College London Hospitals NHS Foundation Trust（伦敦大学学院医院NHS基金会信托国家神经病学和神经外科医院Lysholm神经放射科）；Neuroradiological Academic Unit, Dept of Translational Neuroscience and Stroke, UCL Queen Square Institute of Neurology, UCL（伦敦大学学院女王广场神经学研究所转化神经科学与卒中系神经放射学学术单元）；Centre for Cardiovascular Imaging, Institute of Cardiovascular Science, UCL（伦敦大学学院心血管科学研究所心血管成像中心）；Department of Brain & Behavioural Sciences, University of Pavia（帕维亚大学脑与行为科学系）；Digital Neuroscience Centre, IRCCS Mondino Foundation（IRCCS蒙迪诺基金会数字神经科学中心）
BART Online Open-Source Sequence Toolbox for Computational MRI
Graz University of Technology（格拉茨工业大学）；Harvard Medical School（哈佛医学院）；German Centre for Cardiovascular Research (DZHK)（德国心血管研究中心）；BioTechMed-Graz（BioTechMed格拉茨）
High-spatial resolution, high-quality white matter tractography using DTI with dynamic slice-by-slice B0 shimming in a head-only high-gradient performance 3T MRI scanner
Karolinska Institutet（卡罗林斯卡医学院）；Karolinska University Hospital（卡罗林斯卡大学医院）；Stavanger University Hospital（斯塔万格大学医院）；University of Stavanger（斯塔万格大学）；University of Brescia（布雷西亚大学）；Masaryk University（马萨里克大学）；St. Anne’s Hospital（圣安妮医院）；University G d’Annunzio of Chieti-Pescara（基耶蒂-佩斯卡拉加布里埃莱·邓南遮大学）
Deep learning (DL) methods have in recent years yielded impressive results in medical imaging, with the potential to function as clinical aid to radiologists. However, DL models in medical imaging are often trained on public research cohorts with images acquired with a single scanner or with strict protocol harmonization, which is not representative of a clinical setting. The aim of this study was to investigate how well a DL model performs in unseen clinical data sets---collected with different scanners, protocols and disease populations---and whether more heterogeneous training data improves…
Contrast agents with a strong $R_1$ dispersion have been shown to be effective in generating target-specific contrast in MRI. The utilization of this $R_1$ field dependence requires the adaptation of a MRI scanner for fast field-cycling (FFC). Here, we present the first implementation and validation of FFC-MRI at a clinical field strength of 3 T. A field-cycling range of $\pm$100 mT around the nominal $B_0$ field was realized by inserting an additional insert coil into an otherwise conventional MRI system. System validation was successfully performed with selected iron oxide magnetic nanoparti…
Quantitative Magnetic Resonance Imaging (MRI) is based on a two-steps approach: estimation of the magnetic moments distribution inside the body, followed by a voxel-by-voxel quantification of the human tissue properties. This splitting simplifies the computations but poses several constraints on the measurement process, limiting its efficiency. Here, we perform quantitative MRI as a one step process; signal localization and parameter quantification are simultaneously obtained by the solution of a large scale nonlinear inversion problem based on first-principles. As a consequence, the constrain…
Although nanodiamonds have long being considered as a potential tool for biomedical research, the practical in vivo application of nanodiamonds remains relatively unexplored. In this paper, we present the first application of in vivo MRI contrast enhancement using only iron embedded magnetic nanodiamonds. MR image enhancement was clearly demonstrated in the rendering of T2-weighted images of mice obtained using an unmodified commercial MRI scanner. The excellent contrast obtained using these nanodiamonds opens the door to the non-invasive in vivo tracking of NDs and image enhancement. In the f…
Identification of lymph nodes (LN) in T2 Magnetic Resonance Imaging (MRI) is an important step performed by radiologists during the assessment of lymphoproliferative diseases. The size of the nodes play a crucial role in their staging, and radiologists sometimes use an additional contrast sequence such as diffusion weighted imaging (DWI) for confirmation. However, lymph nodes have diverse appearances in T2 MRI scans, making it tough to stage for metastasis. Furthermore, radiologists often miss smaller metastatic lymph nodes over the course of a busy day. To deal with these issues, we propose t…
In this paper we design and construct gradient coils for a Halbach permanent magnet array magnetic resonance (MR) scanner. The target field method, which is widely applied for the case of axial static magnetic fields, has been developed for a transverse static magnetic field as produced by a Halbach permanent magnet array. Using this method, current densities for three gradient directions are obtained and subsequently verified using a commercial magneto-static solver. Stream functions are used to turn the surface current densities into wire patterns for constructing the gradient coils. The mea…
The introduction of neuroendoscopy, microneurosurgery, neuronavigation, and intraoperative imaging for surgical operations has made significant improvements over other traditionally invasive surgical techniques. The integration of magnetic resonance imaging (MRI)-driven surgical devices with intraoperative imaging and endoscopy can enable further advancements in surgical treatments and outcomes. This work proposes the design and development of an MRI-driven endoscope leveraging the high (3-7 T), external magnetic field of an MR scanner for heat-mitigated steering within the ventricular system …
Developments in metamaterials and related structures such as metasurfaces have opened up new possibilities in designing materials and devices with unique properties. The main progress related to electromagnetic waves applications was done in optical and microwave spectra. Here we report about a new hybrid metasurface structure, comprising a two-dimensional metamaterial surface and a very high permittivity dielectric substrate that was designed to enhance the performance of an ultra-high field MRI scanner. This new flexible and compact resonant structure is the first one which can be integrated…
Light-field imaging facilitates the miniaturization of 3D cameras while it requires the extension of the depth-of-field (DoF) for practical applications such as endoscopy and intraoral scanning. Here we report a light-field camera (LFC) using solid immersion microlens arrays (siMLAs) for 3D biomedical imaging. The experimental results show that the focal length of MLAs is increased by 2.7 times and the transmittance is enhanced up to 6.9% by immersion in PDMS film. In particular, the f-number of siMLAs exceeds the limit of conventional MLAs fabricated by thermal reflow, resulting in a larger D…
Direct imaging of impressed dc currents inside the head can provide valuable conductivity information, possibly improving electro-magnetic neuroimaging. Ultra-low field magnetic resonance imaging (ULF MRI) at $μ$T Larmor fields can be utilized for current density imaging (CDI). Here, a measurable impact of the magnetic field $B_{J}$, generated by the impressed current density $J$, on the MR signal is probed using specialized sequences. In contrast to high-field MRI, the full tensor of $B_{J}$ can be derived without rotation of the subject in the scanner, due to a larger flexibility in the sequ…
In this article, we present an up-to-date overview of the potential biomedical applications of sodium MRI in vivo. Sodium MRI is a subject of increasing interest in translational research as it can give some direct and quantitative biochemical information on the tissue viability, cell integrity and function, and therefore not only help the diagnosis but also the prognosis of diseases and treatment outcomes. It has already been applied in vivo in most of human tissues, such as brain for stroke or tumor detection and therapeutic response, in breast cancer, in articular cartilage, in muscle and i…
