Skin deep

    Dermatologists are good at spotting unusual bits of skin that might or might not be cancers. Testing whether they actually are, though, is quite literally a bloody pain. For a piece of skin to be identified as malignant or benign, it must be cut out and sent to a laboratory for examination under a microscope. But a team of researchers led by Rainer Leitgeb, a physicist at the Medical University of Vienna, hope to change that. As they describe in Biomedical Optics Express, Dr Leitgeb and his colleagues are exploring a technique called optical coherence tomography (OCT), which they think will allow skin cancer to be diagnosed in situ.
    OCT works by sending infra-red light into tissues and analysing what bounces back. The behaviour of the reflected rays provides information on the structures that they collided with. That, Dr Leitgeb hoped, could be used to generate a map of features just beneath the surface of the skin. Dr Leitgeb and his colleagues set up an experiment that let them test the system on a range of skin conditions, including a healthy human palm, allergy-induced eczema on the forearm, inflammation of the forehead, and two previously diagnosed cases of basal-cell carcinoma. They expected to see normal blood vessels in the healthy palm, increased perfusion caused by dilated and altered vessels in the eczema and the inflammation, and a chaotic jumble of vessels feeding the cancers.
    And that is exactly what they saw. Moreover, the images of the vessels supplying blood to the tumours were good enough to allow them to calculate blood-flow rates. That could also help treatment by allowing doctors to identify the times during their development when tumours are most vulnerable to starvation by having their blood supply cut off.

Internet: <www.economist.com> (adapted).

Based on the text above, judge the items from 16 to 20.