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Lower magnetic field broadens MRI applications

The study may lead to new clinical uses for MRI. Mark Kostich / E+ via Getty Images

MRI is a non-invasive imaging technology that produces 3D images of structures in the body. It can help with disease detection and diagnosis��as well as treatment monitoring.

MRI uses strong magnets and radio waves to generate signals from tissues within the body. The MRI machine detects these signals, and software uses the��information to create 3D pictures.

The trend in recent years has been to develop MRI systems with higher magnetic field strengths to boost the signal intensity. However, higher magnetic fields introduce image distortions and additional costs. They also limit what the machines can be used for. For example, certain metal devices, such as tools used during heart procedures, can’t be used with high-magnetic-field systems because they heat up.

A team of researchers led by Drs. Adrienne Campbell-Washburn and Robert S. Balaban at NIH’s National Heart, Lung, and Blood Institute (NHLBI) modified a commercial MRI system with a magnetic field strength of 1.5 tesla (T) to operate at 0.55 T. They maintained all the modern hardware and software needed for high quality images. The study was published in the November��2019 issue of��Radiology.

Lung cysts and surrounding tissues in a patient with lymphangioleiomyomatosis are seen more clearly using high-performance low field MRI (bottom) compared to standard MRI (top). Campbell-Washburn A E, Ramasawmy R, Restivo M C, et al., Radiology

The researchers first heat tested 16 commercial guidewires and catheter devices used for cardiovascular interventions that are considered unsafe for 1.5 T scanners. Nine of these devices, and a pacemaker, did not heat up to unsafe temperatures in the 0.55 T system. The team then successfully used these devices during MRI-guided heart catherization in seven study participants. They found no adverse events.

The team also compared lung images taken in patients with lymphangioleiomyomatosis, a rare disease that creates cysts in the lung. Images of the cysts and the surrounding tissue taken with the lower magnetic field were clearer than those taken at 1.5 T. The system not only improved lung imaging, but also was more sensitive to changes in image contrast caused by oxygen, providing a unique view of the distribution of this vital molecule in the body.

Because MRI systems with lower magnetic field can be more cost-effective, the team also tested routine imaging of brain, abdomen, spine, and heart in healthy volunteers and patients with disease. The image quality was in line with current standards. Future studies will be needed to fully assess the system’s diagnostic abilities.

“We can start thinking about doing more complex procedures under MRI guidance now that we can combine standard devices with good quality cardiac imaging,” says Campbell-Washburn.

“We continue to explore how MRI can be optimized for diagnostic and therapeutic applications,” Balaban adds.

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