Magnetic resonance imaging (MRI) is expensive, noisy and requires bulky equipment. It can also have side effects, such as stimulating nerves in patients. These problems arise from the constant switching between positive and negative magnetic-field gradients used to manipulate the spin of hydrogen nuclei throughout the patient's body. The energized nuclei produce radiofrequency signals, which carry the information used to build up an image.

By exploiting the radiofrequency pulses used to prepare the nuclei, Jonathan Sharp at Alberta Innovates Technology Futures in Calgary, Canada, and his colleagues removed the need for switched magnetic fields. Instead, they manipulated the nuclei using pairs of resonant radiofrequency fields twisted in opposing directions and a static magnetic field. The technique could make MRI cheaper, accessible and quieter.

NMR Biomed. http://doi.org/nqf (2013)