Techniques used to image tumours and infections improve when the carbon nanotube 'contrast agents' are gold plated, researchers in the US have discovered. The gold plating reduces the nanotubes' potential toxicity while boosting their effect as contract agents, thereby allowing far fewer of them to be used for the same effect.Doctors use both photoacoustic and photothermal imaging to examine diseased tissue. The techniques involve shining a laser onto the tissue and measuring either the emitted heat - that is, the infrared radiation - or ultrasound. By adding contrast agents, such as pigmented biomolecules, the tissue responds better to the laser and...