Low-cost Magnetic Resonance Imaging Research Articles

Feasibility and success of a non-sedated brain MRI training protocol in 7-year-old children from rural and semi-rural Colombia.

Brain magnetic resonance imaging (MRI) is a crucial tool for clinical evaluation of the brain and neuroscience research. Obtaining successful non-sedated MRI in children who live in resource-limited settings may be an additional challenge. To present a feasibility study of a novel, low-cost MRI training protocol used in a clinical research study in a rural/semi-rural region of Colombia and to examine neurodevelopmental factors associated with successful scans. Fifty-seven typically developing Colombian children underwent a training protocol and non-sedated brain MRI at age 7. Group training utilized a customized booklet, an MRI toy set, and a simple mock scanner. Children attended MRI visits in small groups of two to three. Resting-state functional and structural images were acquired on a 1.5-Tesla scanner with a protocol duration of 30-40minutes. MRI success was defined as the completion of all sequences and no more than mild motion artifact. Associations between the Wechsler Preschool and Primary Scale of Intelligence (WPPSI), Movement Assessment Battery for Children (MABC), Behavioral Rating Inventory of Executive Function (BRIEF), Child Behavior Checklist (CBCL), and Adaptive Behavior Assessment System (ABAS) scores and MRI success were analyzed. Mean (SD) age at first MRI attempt was 7.2 (0.2) years (median 7.2 years, interquartile range 7.1-7.3 years). Twenty-six (45.6%) participants were male. Fifty-one (89.5%) children were successful across two attempts; 44 (77.2%) were successful on their first attempt. Six (10.5%) were unsuccessful due to refusal or excessive motion. Age, sex, and scores across all neurodevelopmental assessments (MABC, TVIP, ABAS, BRIEF, CBCL, NIH Toolbox Flanker, NIH Toolbox Pattern Comparison, WPPSI) were not associated with likelihood of MRI success (P=0.18, 0.19, 0.38, 0.92, 0.84, 0.80, 1.00, 0.16, 0.75, 0.86, respectively). This cohort of children from a rural/semi-rural region of Colombia demonstrated comparable MRI success rates to other published cohorts after completing a low-cost MRI familiarization training protocol suitable for low-resource settings. Achieving non-sedated MRI success in children in low-resource and international settings is important for the continuing diversification of pediatric research studies.

Low-field MRI at high magnetic field instability and inhomogeneity conditions

Understanding the effects of the magnetic field time instabilities in magnetic resonance imaging (MRI) is fundamental for the success of portable and low-cost MRI hardware based on electromagnets. In this work we propose a magnetic field model that considers the field instability in addition to the inhomogeneity. We have successfully validated the model on signals acquired with a commercial NMR instrument. It was used to simulate the image defects due to different types of instability for both the spin-echo and the gradient-echo sequences. We have considered both random field fluctuations, and an instability having a dominant harmonic component. Strategies are suggested to minimize the artifacts generated by these instabilities. Images were acquired using a home-made MRI relaxometer to show the consistency of the analysis.

New challenges and opportunities for low-field MRI

In this manuscript we deal with recent advances in low-field Magnetic Resonance Imaging (MRI). The development of low-cost MRI solutions allowing portability and trustable diagnosis is a hot topic worldwide by these days. We analyze basic technical issues of recent examples of fixed-field instruments operating at low-field. Then we discuss pros and cons of the pre-polarized approach, from both physical and technical perspectives. Permanent magnet and electromagnet technology are confronted. Finally, magnetic field-cycling is introduced as an alternative MRI technique, where field-dependent experiments can be exploded for the development of new contrast mechanisms that are not feasible for fixed-field MRI instruments. As field cycled machines usually deals with switched currents in electromagnets, magnetic field instability and inhomogeneity are the main limiting factors affecting image quality. We finalize this manuscript discussing how it turns possible to overcome these limitations, thus opening new possibilities for the development of cost effective MRI technology.

An Ultrasound-Guided Hemispherical Phased Array for Microbubble-Mediated Ultrasound Therapy.

To develop a low-cost magnetic resonance imaging (MRI)-free transcranial focused ultrasound (FUS) system for microbubble-mediated therapy. A 128-element 11 MHz array for skull localization was integrated within a 256-module multi-frequency (306/612/1224 kHz) dual-mode phased array. The system's transcranial transmit and receive performance was evaluated with ex-vivo human skullcaps using phase aberration corrections calculated from computed tomography (CT)-based simulations via ultrasound-based (USCT) and landmark-based (LMCT) registrations, and a gold-standard fixed source emitter (FSE)-based method. Displacement and rotation registration errors of 1.4 ± 0.4 mm and 2.1 ± 0.2 ° were obtained using USCT, resulting in sub-millimeter transmit targeting errors driven at 306 kHz (0.9 ± 0.2 mm) and 612 kHz (0.9 ± 0.3 mm), and source localization errors of 1.0 ± 0.3 mm and 0.6 ± 0.2 mm at receive frequencies of 306 kHz and 612 kHz, respectively (mean ± SD). Similar errors were obtained using LMCT and no significant differences between these two approaches were found on either transmit (p = 0.64/0.99) or receive (p = 0.45/0.36) at 306 kHz/612kHz. During volumetric multi-point exposures, approximately 70% and 60% of the transmit frames in which microbubble activity was detected via FSE were recovered using USCT when imaging at the second-harmonic and half-harmonic, respectively, compared to 60% and 69% using LMCT. This low-cost ultrasound-guided transcranial FUS system affords USCT skull registration with accuracy comparable to LMCT methods. Such systems have great potential to advance the adoption of microbubble-mediated FUS brain therapy by improving access to the technology.

A Compact High Field Magnet System for Medical Applications

High magnetic field gradients can be used for various medical applications including magnetically targeted drug delivery, magnetic cell separation and controlled local heating for the ablation of tumours. These processes involve the use of biocompatible magnetic nanoparticles directed to the area of interest by the use of a field gradient. The force on the nanoparticle is proportional to the field gradient product, so high fields are required for effective delivery. Bulk superconductors are an attractive solution for both drug delivery and the next generation of low cost magnetic resonance imaging magnets. In particular, MgB2 is seen as an attractive material due to its low cost, simple processing and relatively high transition temperature (~39 K).This paper describes the development of a breadboard compact delivery system suitable for medical applications. This incorporates a cryogenic stage which utilises long life space-proven technology and state of the art ex-situ processed MgB2 pellets.

Characterization and cellular studies of molecular nanoparticle of iron (III)-tannic complexes; toward a low cost magnetic resonance imaging agent.

Herein, a new magnetic resonance imaging (MRI) agent based on molecular nanoparticles of iron(III)-tannic complexes (Fe-TA NPs) is reported. The paramagnetic and molecularlike Fe-TA NPs were successfully synthesized at room temperature within a few minutes without the use of any toxic agents or expensive equipment. The coordination states of the Fe-TA NPs were pH-dependent. The r1 relaxivity values of the bis-dominated and tris-dominated structures of the Fe-TA NPs were determined to be 6.31 and 5.24 mM-1 s-1, respectively, by using a Philips Achieva 1.5T MRI scanner. The Fe-TA NPs were 177 ± 12 nm in diameter (hydrodynamic size) with a zeta potential value of -28 ± 0.9 mV, dispersing very well in aqueous solution and were highly stable in phosphate buffered saline buffer (pH 7.4) containing competitive ligands and metals. From in vitro studies, it was evident that the Fe-TA NPs exhibited good biocompatibility, with high cellular uptake in HepG2 cells. Clearly, the Fe-TA NPs were found to induce signal enhancement in the T1-weighted image of the HepG2 cells. As a result, it can be stated that the Fe-TA NPs may have the potential for being developed as low-cost and clinically translatable magnetic resonance imaging agents in the near future.

Magnetic resonance force detection using a membrane resonator

The availability of compact, low-cost magnetic resonance imaging instruments would further broaden the substantial impact of this technology. We report highly sensitive detection of magnetic resonance using low-stress silicon nitride (SiNx) membranes. We use these membranes as low-loss, high-frequency mechanical oscillators and find they are able to mechanically detect spin-dependent forces with high sensitivity enabling ultrasensitive magnetic resonance detection. The high force detection sensitivity stems from their high mechanical quality factor Q∼106[1,2] combined with the low mass of the resonator. We use this excellent mechanical force sensitivity to detect the electron spin magnetic resonance using a SiNx membrane as a force detector. The demonstrated force sensitivity at 300K is 4fN/Hz, indicating a potential low temperature (4K) sensitivity of 25aN/Hz. Given their sensitivity, robust construction, large surface area and low cost, SiNx membranes can potentially serve as the central component of a compact room-temperature ESR and NMR instrument having spatial resolution superior to conventional approaches.

A utilization of internal/external quasi-static magnetic field gradients: transport phenomenon and magnetic resonance imaging of solid polymers

Two topics concerning the utilization of internal and external magnetic field gradients are discussed. The first topic concerns the transport of conformons in the quasi-ordered phase of a regioregular, π-conjugated polymer, poly(4-methylthiazole-2,5-diyl), using a combination of longitudinal and transverse relaxation dispersion measurements. The effects of conformon diffusion on the relaxation exponent were successfully estimated via a numerical approach that used the Fourier spectrum solution of the one-dimensional Bloch-Torrey equation. The second topic demonstrates a low-cost magnetic resonance imaging method using a magnetic field gradient from a neodymium ferromagnet. Spin echo experiments are shown for three-layered thin films of PDMS/PTFE/PDMS under a large magnetic field.

A Small 1.5 T Persistent Current Operating Test Magnet Using ${\rm MgB}_{2}$ Wire With High $j_{\rm c}$ Joints

Persistent current (PC) operating magnet with bore diameter of about 32 mm was design and developed based on multi- and mono-filament MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wires. The magnet was in a multi-solenoid structure. One pilot coil was wound and joints were fabricated at both ends, connecting it to a superconducting switch for PC operation tests. The magnet was to demonstrate the high field and high temperature performance at different temperatures. Numerical and experimental results demonstrated a promising future of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wires in low cost magnetic resonance imaging (MRI) systems and high field scientific magnets.

Low-field dedicated and desktop magnetic resonance imaging systems for agricultural and food applications

Dedicated low-field (0.1 T) resistive magnets equipped with solenoid coils were devised for high-resolution and rapid magnetic resonance imaging (MRI) in agricultural and food science. The maximum pixel resolution is 0.1×0.1 mm with a 0.8 mm slice thickness, and 3D T1, T2 and T2* weighted images are obtained in 3 s–6 min depending on the contrast and number of slices. In place of resistive magnets two desktop permanent magnet designs are also described and their field characteristics and possible usefulness for small-sized low-cost MRI scanners, are discussed. © 1997 John Wiley & Sons, Ltd.

A low-cost magnetic resonance imaging system

The design, construction and performance of a low-cost magnetic resonance imaging (MRI) system is described. The system uses a unique, PC-based, task-oriented multiprocessor design, resulting in a high-performance MRI system able to run most pulse sequences. This type of design could lead to a new generation of low-cost MRI systems with applications in research and teaching.

Low-Cost Magnetic Resonance Imaging

AbstractOf the established medical imaging teclmiques magnetic resonance imaging (MRI) is the most sophisticated and one of the most expensive. The high capital cost of MRJ systems is due in part to the requirement of a large magnet and also the supporting computer system. For the last three years Exeter has been developing a low-cost MRI system to image wrists and hands for the study of arthritis. The Exeter system utilizes the latest generation of specialist microprocessors to undertake image reconstruction at a fraction of the cost of a commercial system. This paper describes a practical realization of a low-cost microprocessor based MRI image reconstruction system that demonstrates the elegance of this imaging modality and its potential for medical research and diagnosis.