High-Performance, Low-Field MRI for Cardiac and Lung Imaging

National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland

A low-magnetic-field MRI system was developed that vastly improves image quality of the lungs and other internal structures of the human body. The low-field system may also be safer for patients with pacemakers or defibrillators, quieter, and easier to maintain and install.

The trend has been to develop MRI systems with higher magnetic field strengths to produce clearer images of the brain but using those systems at a modified strength might offer high-quality imaging of the heart and lungs. Metal devices such as interventional cardiology tools that were once at risk of heating with the high-field system are now safe for real-time, image-guided procedures such as heart catheterization. Lung imaging improved and oxygen itself can be observed in tissue and blood much better at a lower magnetic field, providing a unique view of the distribution of this vital molecule in the body.

A low-field MRI system equipped with contemporary imaging technology allows users to see the lungs very clearly and can use inhaled oxygen as a contrast agent. Researchers modified a commercial MRI system with a magnetic field strength of 1.5T to operate at 0.55T while maintaining the modern hardware and software needed for high-quality images. Researchers first tested the new imaging procedure using objects that mimic human tissues, then applied the procedure to healthy volunteers and patients with disease.

When compared with images obtained at 1.5T, researchers saw more clearly lung cysts and surrounding tissues in patients with lymphangioleiomyomatosis (LAM). In addition, they found that inhaled oxygen could increase the brightness of lung tissue more effectively using the lower magnetic field strength when compared to the higher field strength. Similar advantages were found using low-field MRI during heart catheterization, a procedure used to diagnose and treat some heart conditions but which has been hampered by the unavailability of suitable devices for MRI.

The new generation of low-field MRI allows increased flexibility in image acquisition. Surgeons can perform more complex procedures under MRI-guidance now that standard devices can be combined with good-quality cardiac imaging. The results also can be applied to imaging of the brain, spine, and abdomen. Imaging the upper airway with this system may also offer valuable clinical information for both sleep and speech disorders.

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