A non-invasive infrared scanning system that will help doctors determine whether pigmented skin growths are benign moles or melanoma has been developed by US researchers.

According to Johns Hopkins researchers, the system works by looking for the tiny temperature difference between healthy tissue and a growing tumour.

Because cancer cells divide more rapidly than normal cells, they typically generate more metabolic activity and release more energy as heat. The temperature difference, however, is extremely small. To detect this, the scientists first cool a patient’s skin with a harmless one-minute burst of compressed air.

When the cooling is stopped, scientists immediately record infrared images of the target skin area for two to three minutes. Cancer cells typically reheat more quickly than the surrounding healthy tissue, and this difference can be captured by the infrared camera and viewed through sophisticated image processing.

The researchers are also hopeful that the handheld scanning system, which has begun testing on a pilot study of 50 patients at Johns Hopkins, might also be incorporated into a full-body scanning system for patients with a large number of pigmented lesions.

Johns Hopkins’ Whiting School of Engineering professor of mechanical engineering Cila Herman said that there is a lot of work to do with the system.

“We need to fine-tune the scanning system and the software and develop diagnostic criteria for cancerous lesions to find melanoma at an early stage before it spreads and becomes dangerous to the patient,” Herman said.

There were 68,720 new cases of melanoma reported in the US in 2009, and 8,65 deaths from the disease, according to the National Cancer Institute.