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Ye Ding^1,2, Shi Su^1,2, Linfang Xiao^1,2, Yujiao Zhao^1,2, Jiahao Hu^1,2, Junhao Zhang^1,2, Vick Lau^1,2, Christopher Man^1,2, Alex T.L. Leong^1,2, and Ed X. Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, China, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, China

Keywords: Low-Field MRI, Body

Recently, there has been an impetus to develop ultra-low-field (ULF) MRI technologies, which present opportunities for low-cost and portable imaging in point-of-care scenarios. Balanced steady-state free precession (bSSFP) is a time-efficient imaging sequence yet its feasibility at ULF remains unexplored. In this study, we implemented bSSFP sequence at 0.055T, and successfully demonstrated phantom, brain and extremity imaging. 

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Sharada Balaji¹, Adam Dvorak¹, Francesco Padormo², Rui Pedro A.G Teixeira², Megan E. Poorman², Alex L. MacKay^1,3, Tobias C. Wood⁴, Steven C.R. Williams⁴, Sean C.L. Deoni⁵, Shannon H. Kolind^1,3,6, and Emil Ljungberg^4,7
1Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, ²Hyperfine Inc, Guilford, CT, United States, ³Radiology, University of British Columbia, Vancouver, BC, Canada, ⁴Neuroimaging, King's College London, London, United Kingdom, ⁵MNCH D&T, Bill and Melinda Gates Foundation, Seattle, WA, United States, ⁶Medicine, University of British Columbia, Vancouver, BC, Canada, ⁷Medical Radiation Physics, Lund University, Lund, Sweden

Keywords: Low-Field MRI, Magnetization transfer

We have demonstrated a method for introducing Magnetization Transfer (MT) weighting in a non-balanced SSFP sequence (PSIF) at 64mT by changing the total power of the on-resonance RF excitation pulse. The presence of the MT effect was validated through simulations, experiments in phantoms of water, cream, and hair conditioner, as well as in-vivo. Changes to the signal amplitude in the conditioner from the flip angle and pulse width of the RF pulse illustrated the presence of MT saturation. An example protocol with MT weighting was applied in-vivo to generate magnetisation transfer ratio maps.

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Chloé Najac¹, Florian Birk^2,3, Tom O’Reilly¹, Klaus Scheffler^2,3, Andrew Webb¹, and Rahel Heule^2,3,4
1C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, ²Department of High-Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, ³Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany, ⁴Center for MR Research, University Children's Hospital, Zurich, Switzerland

Keywords: Low-Field MRI, Data Acquisition

Point-of-care imaging with low-field MRI (<0.1T) is a potential game changer for low-income countries and the intensive care unit. The main challenge is the low SNR. Balanced steady-state free precession (bSSFP) sequences are fast and SNR-efficient. However, bSSFP is very sensitive to B₀ inhomogeneities resulting in banding artifacts. We evaluated the feasibility of using bSSFP on our 46 mT MRI scanner. By acquiring 17 bSSFP datasets with linearly increasing frequency offsets (from 0 to 1/TR), we could reconstruct banding-free maximum-intensity images as well as F₀ and F_-1 SSFP configurations, which we employed for rapid relaxation time mapping.

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Peter Hsu¹, Daniel K. Sodickson^1,2, Hersh Chandarana¹, Justin Fogarty¹, Patricia Johnson^1,2, and Jelle Veraart^1,2
1Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States, ²Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States

Keywords: Low-Field MRI, Brain, ultra-low-field MRI, point-of-care MRI

The high cost of clinical MRI has severely limited its accessibility in many regions. Ultra-low-field (ULF) MRI systems have been developed to address this issue, providing diagnostic imaging at a significantly lower cost. However, computational tools that are used for clinical scans are often not applicable to ULF images which suffer from both SNR and resolution loss. Here, we compare two approaches for improving the resolution of ULF images and two techniques for extracting volumetric information from each approach. We show that given effective post-processing, ULF images can capture expected age-related volumetric changes in the brain.

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Sai Abitha Srinivas¹, Christopher E Vaughn¹, Jonathan B Martin ¹, and William A Grissom^1
1Biomedical Engineering, Vanderbilt University, Nashville, TN, United States

Keywords: Low-Field MRI, Low-Field MRI

Traditional B₀ gradients have several drawbacks including high acoustic noise, PNS, bulkiness, and high cost. To address this, we present a coil system for Bloch-Siegert (BS) RF encoding comprising an optimized square root solenoid with a bucking coil for high efficiency encoding and a nested uniform saddle coil for the imaging Tx/Rx coil at 47.5mT (2MHz), a field strength that is especially attractive due to its low SAR and accessibility. The coil designed for in-vivo imaging was evaluated in simulation including SAR measurements and experimentally on a resolution phantom using a 3D BS phase-encoded imaging and optimized ‘U’ shaped pulses.

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Dahmane Boudries¹, Philippe Massot¹, Elodie Parzy¹, Seda Seren¹, Philippe Mellet², Jean-Michel Franconi¹, Sylvain Marque³, Florian Fidler⁴, Stefan Wintzheimer⁵, Markus Mützel⁵, and Eric Thiaudiere^1
1CNRS, Bordeaux, France, ²INSERM, Bordeaux, France, ³CNRS, Marseille, France, ⁴Fraunhofer, Würzburg, Germany, ⁵Pure devices, Rimpar, Germany

Keywords: Low-Field MRI, Molecular Imaging, Ultra low field, OMRI, DNP, Magnetic prepolarization

A new MRI system at Ultra-low field (206 µT) was designed for Overhauser-enhanced MRI. It allows both conventional MRI with pre-polarization at 20 mT and Dynamic Nuclear Polarization in the 70MHz range in living rats. Anatomical images in 3D allowed a correct visualization of the rat body shape. OMRI with injected or instilled stable and non-toxic nitroxides permitted to detect the free radicals in the lungs, the kidneys and the bladder. The work opens the way of molecular imaging of abnormal proteolysis in the context of a variety of diseases in large animals.

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Shi Su^1,2, Ye Ding^1,2, Jiahao Hu^1,2, Vick Lau^1,2, Yujiao Zhao^1,2, Junhao Zhang^1,2, Christopher Man^1,2, Alex T.L. Leong^1,2, and Ed X. Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, the University of Hong Kong, Hong Kong, China, ²Department of Electrical and Electronic Engineering, the University of Hong Kong, Hong Kong, China

Keywords: Low-Field MRI, Elastography

Recent development of ultra-low-field (ULF) MRI presents opportunities for low-cost and portable imaging in point-of-care scenarios or/and low- and mid-income countries. Magnetic resonance elastography (MRE) is an essential part of MR abdominal imaging especially for chronic liver diseases. In this study, we explore the MRE at 0.055 Tesla. We demonstrate the feasibility of MRE based on phantom experiments at 0.055 Tesla.

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Teresa Guallart-Naval^1,2, José Miguel Algarín^2,3, Rubén Bosch¹, Francisco Juan-Lloris⁴, Eduardo Pallás^2,3, Juan Pablo Rigla¹, Pablo Martínez⁴, José Borreguero¹, José María Benlloch^2,3, Fernando Galve^2,3, and Joseba Alonso^2,3
1Tesoro Imaging SL, Valencia, Spain, ²Institute for Instrumentation in Molecular Imaging (i3M), Universitat Politècnica de València, Valencia, Spain, ³Institute for Instrumentation in Molecular Imaging (i3M), CSIC, Valencia, Spain, ⁴Physio MRI SL, Valencia, Spain

Keywords: Low-Field MRI, Low-Field MRI, Portable MRI, Sport event MRI

Here we study the potential MR value of a low-field portable system for use in major sporting events, specifically in the Motorcycle Grand Prix held in Valencia (Spain) between November 3rd and 6th, 2022. The system was transported in a small truck, installed in the main surgery room of the circuit medical facilities, and operational around 30 minutes after arrival. Overall, 15 subjects were scanned in four days, with a total of 21 extremity acquisitions. This work demonstrates that portable MRI machines can aid the diagnostic capabilities of medical staff in sporting events and competitions.

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Arthur de Lange¹, Lejla Alić¹, Bennie ten Haken¹, and Frank F.J. Simonis^1
1TechMed Centre, University of Twente, Enschede, Netherlands

Keywords: Low-Field MRI, New Devices

After sentinel lymph nodes are detected using SPIONs and excised, their characterization is important to detect possible metastases. In this research a low-field (0.5T) tabletop MRI scanner was tested for this purpose using 4x accelerated high resolution 3D acquisition. Both simulations and experiments on excised pig lymph nodes showed promising results, with the accelerated scans showing similar image quality with respect to fully sampled datasets. This protocol shows lymph nodes can be imaged at 0.25 mm isotropic resolution within reasonable scan times. Clinical usage should be proven by scanning true metastatic lymph nodes.

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Iman Khodarahmi¹, Mary Bruno¹, Ryan Brown¹, Jan Fritz¹, and Mahesh B Keerthivasan^2
1NYU Langone School of Medicine, New York, NY, United States, ²Siemens Medical Solutions USA Inc., Malvern, PA, United States

Keywords: Joints, MSK

Modern 0.55 T MRI promises to increase worldwide healthcare access through lower costs. Knowledge of the tissue relaxation parameters is essential to achieve the desired image contrast. Here for the first time, we quantify the T1 and T2 relaxation times of the musculoskeletal tissues through a Bloch model-based fitting approach. Our results show that the T1 relaxation time of non-fluid tissues is about 47% of those at 1.5 T. T2 relaxation times are about 70% of that of 1.5 T for synovial fluid, bone marrow and subcutaneous fat, and approximately similar to that of 1.5 T for cartilage and muscle.

Jennifer M Watchmaker¹, Ding Xia², Idoia Corcuera-Solano¹, Etan Dayan¹, Justin Ngeow¹, Fang Liu³, Zahi Fayad², Mingqian Huang¹, and Li Feng^2
1Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ³Athinoula A. Martinos Center for Biomedical Imaging, Harvard Medical School, Boston, MA, United States

Keywords: Tendon/Ligament, Low-Field MRI, knee, hardware

At last year’s ISMRM, a pioneering work was presented to demonstrate the initial feasibility and performance of point-of-care knee MRI at 0.064T using a Hyperfine Swoop portable MRI scanner. This work extended that study for further evaluation in an expanded cohort of healthy subjects and subjects with knee pathology, and compare low-field imaging with clinical 3 Tesla imaging in a subset of volunteers.

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Abhijit J Chaudhari¹, Robert D Boutin², Yongwan Lim³, Sophia Cui⁴, Robert M Szabo⁵, and Krishna S Nayak^3
1Radiology, University of California Davis, Sacramento, CA, United States, ²Radiology, Stanford University, Palo Alto, CA, United States, ³University of Southern California, Los Angeles, CA, United States, ⁴Siemens Medical Solutions, Malvern, PA, United States, ⁵Orthopaedic Surgery, University of California Davis, Sacramento, CA, United States

Keywords: Joints, Skeletal, Real-time imaging; Wrist Kinematics; Dynamic imaging.

We acquired real-time MRI of the actively moving wrist in humans utilizing a high-performance 0.55T system. Resulting images and associated static wrist scans were assessed by two expert readers blinded to acquisition parameters. Our results show that images acquired at a high temporal resolution of 12.6 ms per frame demonstrate minimal image degradation compared to images acquired at temporal resolution of 100 ms or higher, and enable improved characterization of wrist motion. These benefits support further studies to assess high-performance 0.55T systems for the evaluation of dynamic dysfunction of the wrist.

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Mauro Spreiter¹, Reina Ayde^1,2, Necati Ozcakal¹, Tobias Senft¹, Najat Salameh^1,2, and Mathieu Sarracanie^1,2
1Center for Adaptable MRI Technology (AMT Center), Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland, ²AMT Center, Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Aberdeen, United Kingdom

Keywords: Low-Field MRI, Low-Field MRI

Electromagnetic interference cancellation method EDITER is implemented in an unshielded low-field MRI scanner at 100mT by addition of only two EMI detection coils to the acquisition chain. The method’s effectiveness is illustrated in high resolution MSK images of healthy volunteer’s hands. Full 3D images with sub-millimeter in-plane or isotropic millimeter voxel dimensions can be obtained in clinically acceptable acquisition times. This approach, in combination with acceleration strategies, opens perspectives in MSK imaging in the field with portable scanners and/or in low resource environments.

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Sola Adeleke¹, Sanjana Murali², Hao Ding², Fope Adedeji³, Cathy Qin⁴, Johnes Obungoloch⁵, Tamir Sirkis⁶, Iris Asllani⁷, Ntobeko Ntusi⁸, Regina Mammen⁹, Udunna Anazodo¹⁰, and Thoralf Niendorf^11
1School of Biomedical engineering and imaging sciences, King's College London, London, United Kingdom, ²School of Medicine, Imperial College London, London, United Kingdom, ³School of Medicine, University College London, London, United Kingdom, ⁴Department of Radiology, Imperial College Healthcare Trust, London, United Kingdom, ⁵Department of Biomedical Engineering, Mbara University of Science and Technology, Mbara, Uganda, ⁶Royal Berkshire NHS Foundation Trust, Reading, United Kingdom, ⁷Department of Biomedical Engineering, Rochester Institute of Technology, New York, NY, United States, ⁸Department of Medicine, University of Cape Town and Groote Schuur Hospital, Cape Town, South Africa, ⁹Department of Cardiology, Essex Cardiothoracic Centre, Chelmsford, United Kingdom, ¹⁰Montreal Neurological Institute, McGill University, Montreal, QC, Canada, ¹¹Berlin Ultrahigh Field Facility, Berlin, Germany

Keywords: Low-Field MRI, MR Value, Accessible MRI; Affordable MRI; Sustainable MRI

While innovations in MRI technology continue to advance healthcare in the global north, there is a persistent disparity in MRI access and research opportunities in low- and middle-income countries (LMICs). Reasons for this longstanding disparity include technological, economic, geopolitical, and social factors. As awareness of the situation expands, concerted efforts are underway to address it by developing sustainable approaches designed with and for local communities. Here, we provide a framework of such approaches by tackling different aspects of MRI development and access in LMICs. 

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Junzhou Chen^1,2, Ye Tian³, Namgyun Lee³, Mingsong Cao⁴, Wensha Yang⁵, Sophia Cui⁶, Krishna Nayak³, Debiao Li^2,7, Anthony Christodoulou^2,7, and Zhaoyang Fan^1,5
1Radiology, University of Southern California, Los Angeles, CA, United States, ²Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States, ³Electrical Engineering, University of Southern California, Los Angeles, CA, United States, ⁴University of California, Los Angeles, Los Angeles, CA, United States, ⁵Radiation Oncology, University of Southern California, Los Angeles, CA, United States, ⁶Siemens Medical Solutions, Los Angeles, CA, United States, ⁷Cedars-Sinai Medical Center, Los Angeles, CA, United States

Keywords: Low-Field MRI, Radiotherapy

MR applications in radiation therapy has shown great promise for highly conformal treatment. However, MRgRT in the abdomen remains challenging due to motion and the sheer number of organs. In this work, we have demonstrated at 0.55T an integrated multi-task MR platform for adaptive radiation planning and treatment monitoring in the abdomen. We propose using a hybrid GRE-TSE sequence, from a single "pre-beam" scan we are able to generate a volumetric, multi-contrast and motion resolved images for adaptive treatment planning as well as enabling multi-contrast 3D real-time display during treatment.

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Ecrin Yagiz¹, Parveen Garg², Krishna S. Nayak¹, and Ye Tian^1
1Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, ²Division of Cardiology, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States

Keywords: Low-Field MRI, Low-Field MRI

A standard cine MRI exam typically collects a stack of short-axis slices to cover all left ventricular myocardium and uses electrocardiogram gating and breath-holds. Real-time imaging methods are often used to resolve issues with insufficient gating signal or breath-hold failure. In this work, we demonstrate that real-time SMS cardiac imaging at 0.55T provides sufficient blood-myocardium contrast and regional wall motion evaluation with three-fold acceleration compared to real-time single-band and Cartesian breath-hold ECG-gated cine. We also show an alternative reconstruction approach, clustered locally low rank that can improve image quality.

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Ulrich Katscher¹ and Peter Vernickel^1
1Philips Research Europe, Hamburg, Germany

Keywords: Low-Field MRI, Electromagnetic Tissue Properties

Electric conductivity depends on the frequency of the probing electric field. The impact of the frequency differs between human tissue types, e.g., it is lower for body fluids than for cellular tissue types. The upcoming mid-field systems suggest to investigate this frequency dependence with MRI. This study investigated two phantoms, with and without cellular structure, to explore the frequency dependence of conductivity using “Electrical Properties Tomography”. The conductivity results obtained at three different Larmor frequencies were used to estimate the conductivity at lower frequencies in the range of kHz as required for, e.g., EEG source localization.

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Gabriel Zihlmann^1,2, Mathieu Sarracanie^1,2, and Najat Salameh^1,2
1Center for Adaptable MRI Technology (AMT center), Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland, ²AMT center, Institute of Medical Sciences, school of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Aberdeen, United Kingdom

Keywords: Low-Field MRI, MR Fingerprinting

Magnetic susceptibility changes at interfaces induce artefacts, and hence compromises MRI diagnostic value. Low-Field (LF) MRI is inherently less sensitive to susceptibility artifacts making it suitable for imaging near metallic implants. In addition, the dispersion in T₁-contrast is enhanced at LF. To evaluate the potential for new contrast mechanisms, quantitative imaging would be key if acquisition times are compatible with clinical constraints. In that context, model-based multi-parametric OPTIMUM was performed in a healthy volunteer’s forearm carrying a titanium plate from plate-osteosynthesis surgery. Performance of two signal models, one oblivious to intravoxel dephasing and the other accounting for it was compared.

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Muller De Matos Gomes¹, Sourajit Mustafi¹, Meredith Sadinski¹, Kartiga Selvaganesan², and Aleksandar Nacev^1
1Promaxo, Oakland, CA, United States, ²Yale School of Engineering & Applied Science, Yale, New Haven, CT, United States

Keywords: RF Pulse Design & Fields, Low-Field MRI

A method for saturating the outer volume in a single sided low field MRI scanner has been developed. By saturating the outer volume using this method, magnetization from regions where the gradient fields are highly nonlinear may be removed from the image, resulting in less image artifacts.