[Paper Review] Portable magnetic resonance imaging of patients indoors, outdoors and at home

Teresa Guallart‐Naval, José Miguel Algarín+16 more|arXiv (Cornell University)|Mar 7, 2022

Advanced MRI Techniques and ApplicationsMedicine56 references61 citations

TL;DR

This study presents a low-cost, portable 70 mT extremity MRI scanner built around a permanent Halbach magnet, enabling in vivo imaging of human knees in diverse environments—laboratory, office, outdoors, and at home—without compromising diagnostic image quality. Despite varying electromagnetic interference and power sources, all scans achieved clinically viable signal-to-noise ratios (SNR ≈11–19) and clearly visualized anatomical structures and metallic implants, demonstrating the feasibility of accessible, point-of-care MRI beyond traditional clinical settings.

ABSTRACT

Mobile medical imaging devices are invaluable for clinical diagnostic purposes both in and outside healthcare institutions. Among the various imaging modalities, only a few are readily portable. Magnetic resonance imaging (MRI), the gold standard for numerous healthcare conditions, does not traditionally belong to this group. Recently, low-field MRI start-up companies have demonstrated the first decisive steps towards portability within medical facilities, but these are so far incompatible with more demanding use cases such as in remote and developing regions, sports facilities and events, medical and military camps, or home healthcare. Here we present in vivo images taken with a light, home-made, low-field extremity MRI scanner outside the controlled environment provided by medical facilities. To demonstrate the true portability of the system and benchmark its performance in various relevant scenarios, we have acquired images of a volunteer's knee in: i) an MRI physics laboratory; ii) an office room; iii) outside a campus building, connected to a nearby power outlet; iv) in open air, powered from a small fuel-based generator; and v) at the volunteer's home. All images have been acquired within clinically viable times, and signal-to-noise ratios (SNR) and tissue contrast suffice for 2D and 3D reconstructions with diagnostic value, with comparable overall image quality across all five situations. Furthermore, the volunteer carries a fixation metallic implant screwed to the femur, which leads to strong artifacts in standard clinical systems but appears sharp in our low-field acquisitions. Altogether, this work opens a path towards highly accessible MRI under circumstances previously unrealistic.

Motivation & Objective

• To develop a low-cost, portable MRI system capable of functioning outside controlled clinical environments.
• To evaluate the diagnostic image quality of a low-field extremity MRI scanner across diverse real-world settings, including indoor offices, outdoor locations, and home environments.
• To demonstrate that metallic implants, which cause severe artifacts in high-field MRI, remain clearly visualized in low-field acquisitions.
• To assess the system’s performance under varying electromagnetic interference (EMI) and power supply conditions, including battery and generator operation.
• To enable point-of-care and home healthcare MRI by overcoming the limitations of traditional high-field systems.

Proposed method

• The system uses a custom-built 70 mT permanent magnet in a Halbach configuration to generate a homogeneous field over a 20 cm spherical volume.
• A single RF transmit/receive coil tuned to ~3.07 MHz (proton Larmor frequency at 70 mT) is used for signal excitation and reception.
• Control electronics are based on the open-source MaRCoS platform, enabling flexible sequence control and real-time data acquisition.
• The scanner is mounted on a wheeled, transportable structure (total weight ≈250 kg) for mobility across varied terrains and settings.
• All images were acquired using a 3D turbo spin echo (3D-TSE) sequence with consistent parameters across all environments.
• Image reconstruction and post-processing were performed using standard MRI techniques, with no advanced denoising or super-resolution applied.

Experimental results

Research questions

• RQ1 Can a low-field, portable MRI scanner produce diagnostically useful images in uncontrolled, non-clinical environments such as homes and outdoors?
• RQ2 How does electromagnetic interference (EMI) from diverse power sources and ambient environments affect image quality in portable low-field MRI?
• RQ3 Can metallic implants, which cause severe artifacts in high-field MRI, be clearly visualized in low-field acquisitions?
• RQ4 Does the image quality and signal-to-noise ratio (SNR) remain clinically acceptable across multiple deployment scenarios with varying EMI and power sources?
• RQ5 To what extent can a low-cost, portable MRI system support point-of-care and home healthcare applications?

Key findings

• The portable 70 mT extremity MRI scanner successfully acquired 3D-TSE images of a volunteer’s knee in five distinct environments: MRI physics lab, office, outdoors with a generator, outdoors with a power outlet, and at home.
• All scans were completed within approximately 12 minutes, meeting clinically viable scan times.
• Signal-to-noise ratios (SNR) ranged from ≈11 in the noisiest outdoor setting (generator-powered) to ≈19 in the home environment, both sufficient for diagnostic evaluation.
• Despite varying EMI spectra, all images preserved key anatomical structures, tissue contrast, and sharp visualization of a metallic femoral implant.
• The metallic implant, which causes severe susceptibility artifacts in standard high-field MRI, appeared sharply defined in all low-field acquisitions.
• The system demonstrated robustness to environmental variability, including transport over tiled sidewalks and reconnection of loose connectors, with minimal setup required post-transport.