Current mobile MRI machines have smaller magnets and nonuniform magnetic fields which limit them to low-resolution work. The new machine overcomes this limitation by sending a series of RF pulses precisely varied in energy, duration, and timing through the sample being imaged. This lets scientists derive high-resolution images even with nonhomogeneous magnetic fields.

The prototype machine features two concentric U-shaped, rare-earth magnets arranged to create a "sweet spot" 7 mm above the magnet. A rectangular coil generates RF pulses that use the U-shaped magnets to optimize interactions between the static magnetic field and the one generated by the RF pulses. In tests, this gives the MRI image enough resolution to reveal chemical shifts of 8 ppm within 3 min. Researchers believe the new imager can be used in applications outside security, including medical diagnosis, archeological analysis, exploring objects in space, and other instances in which samples can't be brought to the lab.