Lasers provide non-invasive cancer screening

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Chemists at Duke University in the USA have made the first step towards screening malignant skin cancers without cutting the skin, by using a laser-based system to provide a detailed picture of the processes going on beneath the surface.

‘This is the first approach that can target molecules like haemoglobin and melanin and get microscopic resolution images the equivalent of what a doctor would see if he or she were able to slice down to that particular point,’ said Professor Warren Warren , director of Duke University’s new Centre for Molecular and Biomedical Imaging.

The distributions of haemoglobin, a component of red blood cells, and melanin, the skin pigment, are important because they provide the early warning signs for cancer growth. Previously, they were both too dark and inaccessible to see using laser methods. However, Warren’s group has developed a way of making the molecules emit light by exciting them with laser pulses.

The innovation uses a delicate interplay between two laser beams, each emitting a different colour of light. To keep the skin from overheating in the process, the lasers must also be able to pulse on for only femtoseconds - a thousand trillionths of a second - at a time.

The glow of the haemoglobin and melanin-bearing structures can be magnified by a microscope outside the skin and manipulated by computers to create cellular-scale images. The technique could enable doctors to see as much as a millimetre below the skin's surface - more than enough for diagnosis.