MRI Machine Images: How Low-Field and Portable MRI Are Redefining Medical Imaging
A wave of smaller, less expensive and portable MRI systems promises to expand the capabilities of medicine.
Magnetic resonance imaging (MRI) has become one of the most powerful tools for visualizing internal anatomy and diagnosing disease. Unlike X-rays or CT scans, MRI machine images provide detailed views of soft tissues, including the brain, muscles, ligaments and internal organs, without exposing patients to ionizing radiation. The technique relies on the interaction between magnetic fields, radiofrequency pulses and hydrogen atoms in the body to produce high-resolution images that reflect tissue composition and physiological properties.
Conventional MRI systems use strong magnetic fields – typically 1.5 to 3 tesla – to generate these images. However, such machines are large, costly and require specialized shielding and infrastructure, restricting their use to hospitals and advanced imaging centers. To broaden accessibility and expand MRI applications, researchers and manufacturers are now developing low-field and portable MRI technologies. These next-generation systems promise to make MRI imaging more affordable, mobile and clinically versatile.
Understanding the physics of low-field MRI
Magnetic field strength and image formation
MRI images are created by aligning hydrogen nuclei within the body using a magnetic field. When these nuclei return to their original state after excitation by radio waves, they emit signals that can be reconstructed into images. The strength of the magnetic field directly influences image contrast, signal intensity and the visibility of different tissue types.
High-field MRI produces sharp, detailed images but requires superconducting magnets cooled with liquid helium – an expensive and resource-intensive process. In contrast, low-field MRI systems operate at magnetic field strengths below 0.1 tesla. These machines are lighter, consume less power and can function without cryogenic cooling.
Imaging at 64 millitesla
Researchers at the National Institute of Standards and Technology (NIST) have demonstrated that MRI machine images generated at 64 millitesla – roughly 20 times lower than standard MRI – can still provide valuable quantitative information about brain tissue. Using a portable MRI system, the team scanned the brains of ten volunteers to analyze gray matter, white matter and cerebrospinal fluid. Each tissue type responded differently to the low magnetic field, producing unique signal profiles that reflected their microstructural and biochemical characteristics.
"Magnetic resonance images of tissue differ depending on magnetic strength," explained Dr. Kalina Jordanova. "With low-field MRI systems, the contrast of the images is different, so we need to know how human tissue looks at these lower field strengths."
By characterizing how tissue properties change with magnetic field strength, NIST researchers aim to refine image reconstruction algorithms and improve diagnostic interpretation for low-field MRI scanners.
Portable MRI: Expanding access to imaging
Mobility and cost efficiency
Traditional MRI systems are confined to static clinical settings, but portable MRI offers a new level of flexibility. These systems can be deployed in intensive care units, ambulances or even remote field hospitals –bringing imaging capabilities directly to patients who may not have access to large-scale facilities.
Because low-field magnets are smaller and require less shielding, portable MRI units can be built for a fraction of the cost of standard machines. This affordability could help extend diagnostic imaging services to underserved regions and developing countries, reducing global disparities in healthcare access.
Applications in emergency and point-of-care medicine
Portable MRI systems could transform emergency medicine by enabling real-time brain imaging during stroke triage or head trauma assessment. Imaging in ambulances or rural clinics could accelerate diagnosis and treatment decisions, particularly when immediate access to full-scale MRI is impossible. While it has been publicized that the lower field strengths make MRI safer for patients with implants, research has also suggested that low-field MRI is not always safer.
Advancing image quality with novel MRI contrast agents
MRI contrast agents enhance the ability to:
- Improve signal differentiation between tissues
- Increase overall tissue contrast
- Identify anatomical abnormalities and pathological changes
MRI contrast agents improve the visibility of anatomical structures and pathologies by altering the magnetic relaxation properties of nearby hydrogen nuclei. Traditionally, these agents are gadolinium-based compounds that shorten the relaxation time (T1 or T2) of tissues, thereby increasing image contrast.
However, at low magnetic field strengths, the behavior of these agents changes. Understanding these differences is crucial for developing materials optimized for low-field imaging.
NIST researchers evaluated several contrast materials to determine their performance in low-field MRI. They found that iron oxide nanoparticles provided superior contrast at 64 millitesla compared with gadolinium-based agents. These nanoparticles achieved effective contrast at concentrations roughly one-ninth that of gadolinium agents.
Iron oxide nanoparticles offer an additional advantage: they are biodegradable and can be metabolized by the body. In contrast, some research has shown that small amounts of gadolinium may accumulate in tissues, posing potential risks and complicating subsequent MRI scans.
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The team’s findings demonstrate that iron oxide nanoparticles could be a promising alternative for low-field imaging.
Table 1. A summary of key differences between iron oxide and gadolinium-based MRI contrast agents.
| Property | Iron Oxide Nanoparticles | Gadolinium-Based Agents |
| Magnetic Type | Superparamagnetic | Paramagnetic |
| Optimal Field Strength | Low-field (~64 mT) | High-field (1.5–3 T) |
| Effective Concentration | ~1/9 of gadolinium | Standard clinical dose |
| Biocompatibility | Biodegradable, metabolized | May accumulate in tissue |
| Image Contrast | Strong T1 enhancement at low fields | Reliable at high fields |
Implications for future MRI development
The progress in low-field and portable MRI technology demonstrates that imaging precision no longer depends solely on magnetic strength. Through improved understanding of tissue relaxation at lower fields, better contrast agent chemistry and portable hardware innovation, MRI is poised to become more accessible and adaptive across clinical environments.
For laboratory professionals, these advancements highlight the growing intersection of magnetic materials research, biomedical engineering and instrument design. Continued standardization will be essential for validating low-field MRI measurements, ensuring reproducibility and integrating these systems into medical workflows.
As low-field MRI continues to mature, it could redefine how and where diagnostic imaging occurs, making high-quality MRI machine images available from centralized hospitals to remote healthcare sites worldwide.
This article is a rework of a press release issued by NIST. Material has been edited for length and the content has been updated to provide additional context and details of related developments since the original press release was published on our website. This content includes text that has been created with the assistance of generative AI and has undergone editorial review before publishing. Technology Networks' AI policy can be found here.
