A handheld device that that may change the way doctors treat and diagnose melanoma is ready for clinical trials.

Researchers from Washington University in St. Louis have been able to measure the depth of tumours using a photoacoustic microscope that shines laser beams into the skin. The differing light absorption properties of healthy cells and those with a dangerously high concentration of melanin creates a pattern of high-frequency acoustic waves that can then be turned into a three-dimensional image.

The technique is thought to be potentially more accurate than ultrasound or MRI and easier and less invasive than biopsy.

The instrument, which was described in the Optical Society’s journal in August, was successfully tested on both artificial tumours made of black gelatin and on real ones in live mice.The team is now conducting further tests with human patients and the device will have to prove effective in clinical trials before it is widely available.