Low-field MRI expands access to more patients

Novel MRI technology, developed by Siemens in collaboration with researchers at The Ohio State University, is set to expand imaging access to patients with implanted medical devices, severe obesity or claustrophobia.

The technology uses a lower magnetic field to open up new possibilities for imaging the lungs and for patients with implanted devices, and will potentially support new interventional procedures that could result in less radiation exposure. The Ohio State University Wexner Medical Center is said to be the first in the United States to install the FDA-approved, full-body MRI for patient care.

MRI uses a powerful magnetic field and radio waves to produce detailed images of a patient’s body to help diagnose conditions, plan treatments and determine the effectiveness of previous treatments. MRI is used predominantly to image the brain, spine and joints, but can also be used to image the heart and blood vessels.

Professor Orlando Simonetti, Research Director of Cardiovascular Magnetic Resonance at Ohio State, noted, “Many of our patients have pacemakers or defibrillators, and while many of those devices are now safe for MR scanning, the metal in them can distort the magnetic field and corrupt the image quality. We were looking for ways to improve the quality of images in these patients, and lower magnetic field strength could offer an advantage. The problem with low-field MRI is that there is less signal to work with, and we needed to find ways to boost that signal.”

Prof Simonetti teamed up with Assistant Professor Rizwan Ahmad to develop techniques that could suppress noise (interference) in the images, and produce clearer images at lower field strength. They shared their ideas and techniques with Siemens, leading to the development of the MAGENTOM Free.Max scanner.

The Free.Max is claimed to feature the largest MRI opening to date — 80 cm, compared to the typical 60–70 cm — and a lower magnetic field strength that offers the potential for it to be used for lung imaging without X-ray radiation. Whereas today’s clinical MRIs usually have magnetic field strengths of 1.5 or 3.0 Tesla, the Free.Max is much lower at 0.55 Tesla.

“There’s no doubt in my mind that low-field MRI will play an important role in the future and will become more mainstream,” Prof Simonetti said. “Going to lower field can reduce the cost of MRI systems and installation considerably, and with modern techniques for scanning and image processing we can overcome the inherent loss of signal.”

Ohio State researchers have partnered with the Nationwide Children’s Hospital to study use of the 0.55T with heart catherisation. Children with congenital heart disease must undergo repeated heart catheterisations throughout their lives, and they are exposed to radiation every time they have an X-ray to guide the tube through a blood vessel to the heart.

“The doses of radiation accumulate over time and can be harmful, especially to children who are still growing,” Prof Simonetti said. “It may be possible to perform MRI-guided cardiology procedures safely at low field using standard catheters and guidewires; this will be safer for anyone who has to have repeated heart catheterisations and other procedures.”

In addition, Prof Simonetti is working with Dr Sabrena Noria, Surgical Director of Ohio State’s Comprehensive Weight Management, Metabolic/Bariatric Surgery Program, and heart failure specialists at the Richard M. Ross Heart Hospital to take advantage of the larger opening of the low-field scanner to develop cardiac imaging techniques for severely obese patients. He is also optimistic that the new MRI technology can be used to image the lungs, which typically is done with nuclear imaging or X-ray CT scans.

“This is an important advancement for patients with cystic fibrosis, pulmonary hypertension, heart failure, COVID-19 and any other disease where we’re trying to understand the source of shortness of breath and evaluate both the heart and lungs,” Prof Simonetti said. “The air in the lungs cancels out the MRI signal at higher field strength; however, at lower field, there’s potential to see lung tissue more clearly with the MRI.”

The 0.55T MRI is part of Ohio State’s cardiovascular imaging program and located in the Wright Center of Innovation in Biomedical Imaging, next to a new 3T MRI. In addition, there is a 1.5T MRI located in the Ross Heart Hospital, also devoted to cardiovascular imaging.

“We’re proud to be the first hospital to install this new technology and to play a part in its development,” said Dr Thomas Ryan, Executive Director of the Ross Heart Hospital. “What’s really unique is that we have a comprehensive imaging program that’s dedicated to patients with cardiovascular disease. By having three different field strengths, we’re able to pick the right machine for the right patient and to provide the best patient care possible.”

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