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Cancer surgeons may be able to find sites in the body where tumour cells have spread to by using a new kind of portable camera that detects gamma radiation as well as visible light.

At the moment, gamma imaging is generally done using machines the size of a small room, which cannot be moved into an operating theatre.

When cancer cells escape from a primary tumour, they often take up residence in the nearest lymph nodes; these are a network of several hundred glands distributed around the body, each about the size of a baked bean.

When people have surgery to remove cancer, doctors often need to also remove the nearest lymph nodes to see if they contain tumour cells. If they are free of such cells, the person may be able to avoid further surgery or aggressive cancer treatment.

But lymph nodes can be hard to find, so doctors often inject a slightly radioactive dye that releases gamma radiation near the site of the cancer. The dye drains from the tissue into the nearest lymph nodes.

During the operation, the way surgeons currently locate the lymph nodes giving off gamma radiation is to use a wand-like probe that gives a visual or sound readout like a metal detector 鈥� but that cannot form images.

That makes it hard to locate the right lymph nodes in a complex area like the neck that is packed with crucial nerves and blood vessels, says Sarah Bugby at Loughborough University in the UK. 鈥淚t could be be beeping and you take out one lymph node but it could be another lymph node behind it that was giving the signal.鈥�

Bugby鈥檚 team has developed a handheld device containing two gamma detectors that work like pinhole cameras slightly offset from each other, to create a three-dimensional image of the radiation source. This is overlayed on an ordinary optical image to help surgeons pinpoint the radiation source within the body. It is being commercialised by UK firm .

Bugby鈥檚 group is also working with the former UK nuclear power site at Sellafield to explore if the camera could be used in nuclear decommissioning.