Behind The Research​​: Low-Field MRI

More than 1.8 million people in India suffer from a stroke every year. Teams at IIT Guwahati are part of an international open source community creating devices that can bring life-saving emergency MRI diagnostics closer to patients - increasing access, affordability, and portability. 

Published 15 May 2026 | Category Research and Development | Office SHST and EEE

What is an MRI? 

Magnetic Resonance Imaging (MRI) is one of medicine's most powerful diagnostic tools. It uses the magnetic properties of hydrogen atoms in the body to emit a signal that a computer translates into detailed images of soft tissue — the brain, the spinal cord, ligaments, or organs.  

The hospital MRI most people have encountered operates at 1.5 Tesla — a magnetic field roughly 30,000 times stronger than the Earth's. That field strength produces crisp, high-resolution images that can guide complex surgery or detect early-stage tumours. But that is also what makes the machine so large, so expensive, and so immovable. 

What is a Low Field MRI?

“We have only this universal machine,” says Erwin Fuhrer, Assistant Professor at the Jyoti and Bhupat Mehta School of Health Sciences, IIT Guwahati. “It is optimised for performance and imaging, but it's not optimised for specific diagnostics and portability.” 

A Low Field (LF) MRI, on the other hand, operates at roughly 50 to 64 millitesla. That is about 500 to 600 times weaker than a standard clinical scanner. This machine can be engineered, in principle, to be portable, affordable, and serviceable without specialist infrastructure.  

"Our task is to get information about the patient's status to the doctor," says Fuhrer. "That is the equivalent of trying to go from A to B." The question is simply: what is the right vehicle for that journey? 

A conventional high-field MRI is, in Fuhrer's words, "a car that is also a truck and a motorbike at the same time."  

It is a remarkable, multipurpose machine capable of full-body imaging, measuring diffusion, flow, and producing images of extraordinary resolution.  This universality is one of its greatest strengths but it comes at a price. Conventional MRIs can support a wide range of diagnostic needs but the machines are complex and expensive – and thus limiting access where rapid diagnostic information is needed.   

"You don't need that for the school run," says Fuhrer. "But you pay like several crores for it." 

A low-field MRI is like a specific vehicle optimised for the journey and task that actually needs to be made. A tailor-made device for a specific purpose. 

What is the potential impact of an LF MRI?  

India records more than 1.8 million strokes every year — a number that has risen by 50% over the past 30 years. 

When a stroke occurs, the clinical situation is urgent but full of uncertainty. Inside the brain, two entirely different crises can unfold, and they require opposite responses. 

An ischaemic stroke occurs when a blood vessel is blocked, and consequently the brain does not receive enough blood, oxygen and nutrients. The treatment is to restore blood flow — typically with a clot-dissolving drug that clears the obstruction. A haemorrhagic stroke, on the other hand, occurs when a blood vessel ruptures and bleeding starts in and around the brain. In this case, a clot-dissolving drug is not just ineffective — it is dangerous, potentially fatal. The treatment here involves stopping the bleed. 

The two conditions look identical from the outside. Without imaging, clinicians often cannot confidently distinguish between them. And without that diagnosis, treatment cannot begin. 

So the key question that an emergency MRI must answer is this: ischaemic or haemorrhagic. An LF MRI can answer that one question, fast, at the point of care. And open the treatment window. 

The cost of delay is not abstract. Research by Menon et al., tracked the probability of a good functional outcome — whether a stroke patient retains the ability to live independently — against the total time from symptom onset to treatment. A patient treated at 100 minutes has roughly a 70% probability of a good outcome. By 750 minutes, that probability has fallen below 30%.  

In most of India, the bottleneck is imaging. Getting a patient to an advanced imaging facility within the treatment window is, for a large proportion of the population, simply not feasible. A portable LF MRI addresses this bottleneck at the point where it matters most.

What are the challenges in building an LF MRI? 

"Shifting to LF MRI changes a lot of things,” says Fuhrer. “The constraints imposed by the physics change. For example, image acquisition settings have to be adapted, hardware requirements change and contrast agents, if they are used, need to be designed differently. 

The machine’s purpose brings in additional constraints. An LF MRI must be affordable. This means replacing expensive, high-end components with cost-effective alternatives without compromising diagnostic reliability.  

An LF MRI must also be portable, which imposes strict limits on size, weight, and power consumption. And it must be maintained by local technicians, without specialist equipment or imported parts. 

But critically, an LF MRI needs to be designed for a robust operation in an electromagnetically  noisy environment.  

A standard high-field MRI operates inside a Faraday cage — a heavily shielded metal enclosure that blocks out all external electromagnetic interference. An LF MRI cannot carry a Faraday cage with it. It must operate in the full electromagnetic noise of mobile phones, power lines, fluorescent lights, and medical equipment, all of which generate interference. 

Building a system that can extract a diagnostically useful image from a faint signal in a noisy, uncontrolled environment is an engineering challenge that sits at the intersection of physics, electronics, materials science, and signal processing. 

The task is to navigate these trade-offs without losing what makes the machine clinically useful. The design philosophy is optimisation for a specific mission.

How are researchers addressing the signal-to-noise problem? 

The weakest point in any LF MRI system is signal strength. This is not a solvable problem in the conventional sense — it is a physical consequence of operating at lower field strengths, and no amount of optimisation fully compensates for it. What is needed is a way to amplify the signal itself, before it even reaches the detection system. 

This is where metamaterials enter the picture. 

Metamaterials are engineered structures whose electromagnetic properties are determined not by their chemical composition but by their geometry. By designing the structure carefully, researchers can create materials that interact with magnetic fields in ways that no naturally occurring material does.  

In the context of MRI, metamaterials can be designed to concentrate and amplify the signal in a specific region. 

Debabrata Sikdar is an Associate Professor in Electrical and Electronic Engineering at IIT Guwahati. His group has been developing metamaterials for MRIs. In high-field MRI, metamaterials function as accessories — a wrap or a cuff that can be placed around the region being imaged.  

“You can get a higher resolution image with a metamaterial,” says Sikdar. On the other hand, it can also cut down the scan time. 

In LF MRI the static magnetic field is weak compared to a conventional MRI. Metamaterials can boost the signal to noise ratio by amplifying the raw signal.  

In addition, an indigenously built LF MRI system presents some unique opportunities. Fuhrer and Sikdar’s teams can co-design the metamaterial and the coil together. The metamaterial will not remain an accessory bolted onto an existing machine. It will be an integral component of a system designed, from the ground up, to get the most out of a weak signal in a difficult environment. 

The freedom to experiment at the level of the machine's core components — to redesign, to iterate, to integrate — is the freedom that indigenisation provides.  

Where does the research stand today — and what comes next? 

The IIT Guwahati prototype is at Technology Readiness Level 4. All subsystems have been individually tested. The team is on the verge of extracting the first NMR signal.  

It is not yet ready for clinical deployment. 

The work will progress by extracting and validating the NMR signal, acquiring the first images, testing in a relevant clinical environment, and eventually moving toward a deployable system that can be manufactured, maintained, and improved in India.  

Alongside that hardware development, the metamaterial work will continue with the goal of integrating signal-boosting technology directly into the machine. 

However, as LF MRI machines get deployed in hospitals, in research institutions, in teaching settings, the possibilities are likely to grow in directions that are genuinely difficult to predict today.   

Researchers who currently have no access to MRI will be able to ask questions they cannot currently ask. Medical students and radiology trainees in smaller cities will have hands-on access to imaging technology for the first time. Clinicians working in resource-limited settings will be able to make diagnostic decisions that currently require a referral and a journey.  

The researchers themselves are cautious about speculating too far ahead — the science is still developing, and the machine is not yet deployed. But the trajectory is suggestive. As the hardware becomes more flexible and the engineering more mature, purpose-built machines for specific tasks become imaginable: a dedicated neonatal scanner, a compact limb-imaging unit, eventually systems designed for specific research questions that no current MRI is built to address.

References

[1] B. K. Menon et al., “Analysis of workflow and time to treatment on thrombectomy outcome in the Endovascular Treatment for Small Core and Proximal Occlusion Ischemic Stroke (ESCAPE) randomized, controlled trial,” Circulation, vol. 133, no. 23, pp. 2279–2286, 2016.

---

The research is being done by the students and staff at the laboratories headed by Erwin Fuhrer and Debabrata Sikdar. The work is in close collaboration with Assam Advanced Healthcare Innovation Institute (AAHII).  The OSI2 magnet built with collaborators and industrial partners in AAHII has put India on the map of the open source community working on LF MRI