Nature: Optical imaging routinely uses multicoloured contrast agents ranging from traditional chemical dyes and fluorophores to specially engineered quantum dots. In magnetic resonance imaging (MRI), contrast agents have also proved extremely useful, but their effects are largely indistinguishable from one another, leading to essentially monochrome contrast based on increased or decreased signal strength. Gary Zabow Stephen Dodd, John Moreland & Alan Koretsky are bringing 'colour' to MRI. They have developed an approach to produce MRI contrast agents with characteristic spectral signals, based on the control of mechanical structures. Different versions of these probes can be used simultaneously, and are distinguishable by the geometry-dependent spectral 'colour' of their signals.

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