If you need an MRI but have a pacemaker or defibrillator, are claustrophobic or obese, you may not have access to this critical technology used to diagnose a large variety of diseases. What then?
Ohio State University (OSU) researchers recently collaborated with Siemens to expand essential imaging access to all patients by designing the first FDA-approved MRI machine that bypasses previous limitations.
Orlando Simonetti, research director of cardiovascular magnetic resonance at OSU, initially teamed up with Rizwan Ahmad, assistant professor of biomedical engineering, to develop new techniques to boost the signal-to-noise ratio in existing MRI machines. However, they quickly realized they were on to something bigger.
“We believed we could use this technology to create a machine with a lower magnetic field strength and still get high-quality images,” said Simonetti. “Since there is less signal to work with low-field MRI, we needed to find ways to boost that signal.”
The researchers shared their ideas and techniques with Siemens, ultimately leading to development of the new 0.55T Free.Max scanner, the first of which is currently installed at the Ohio State University Wexner Medical Center. While today’s clinical MRIs typically have magnetic field strengths of 1.5 or 3.0 Tesla, the Free.Max is much lower at 0.55 Tesla.
In addition to being able to accommodate patients with implanted devices, the lower magnetic strength actually provides better imaging than a traditional MRI in some cases, specifically when working with the heart. The new MRI machine can also be used for lung imaging without X-ray radiation, opening the door to new interventional procedures that could result in less radiation exposure.
“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,” said Simonetti. “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 Free.Max features the largest MRI opening to date—80 cm compared with the typical 60 to 70 cm. The low-field technology of the machine can also dramatically reduce both the cost of acquiring an MRI system as well as installation, further expanding their availability and use.
Ohio State researchers have partnered with Nationwide Children’s Hospital to study the used of the 0.55T with heart catherization. Children with congenital heart disease must undergo repeated heart catheterizations 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,” said Simonetti. “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 catheterizations and other procedures.”
Simonetti is also collaborating with researchers at Ohio State’s Comprehensive Weight Management, Metabolic/Bariatric Surgery Program and Richard M. Ross Heart Hospital to take advantage of the larger opening of the 0.55T to develop cardiac imaging techniques for severely obese patients.
“There’s no doubt in my mind that low-field MRI will play an important role in the future and will become more mainstream,” said Simonetti.
At Ohio State University Wexner Medical Center, the 0.55T MRI is situated next to a new 3T MRI, with both systems dedicated to cardiovascular clinical and research imaging. In the nearby Ross Heart Hospital, there is a 1.5T MRI as well, also devoted to cardiovascular imaging.
“By having three different field strengths, we’re able to pick the right machine for the right patient and provide the best patient care possible,” said Thomas Ryan, executive director of the Ross Heart Hospital and director of Ohio State’s Heart and Vascular Center.
Photo: The 0.55T Free.Max installed at the Ohio State University Wexner Medical Center. Credit: OSU