Illustration: Viktor Koen
By Zeeya Merali
It seemed too good to be true, says Allard Mosk. It was 2007, and he was working with Ivo Vellekoop, a student in his group at the University of Twente in Enschede, the Netherlands, to shine a beam of visible light through a ‘solid wall’ — a glass slide covered with white paint — and then focus it on the other side. They did not have a particular application in mind. “I really just wanted to try this because it had never been done before,” Mosk says. And in truth, the two researchers did not expect to pick up much more than a faint blur.
But as it turned out, their very first attempt1 produced a sharp pinprick of light a hundred times brighter than they had hoped for. “This just doesn’t happen on the first day of your experiment,” exclaims Mosk. “We thought we’d made a mistake and there must be a hole in our slide letting the light through!”
But there was no hole. Instead, their experiment became the first of two independent studies1, 2that were carried out that year pioneering ways to see through opaque barriers. So far it is still a laboratory exercise. But progress has been rapid. Researchers have now managed to obtain good-quality images through thin tissues such as mouse ears3, and are working on ways to go deeper. And if they can meet the still-daunting challenges, such as dealing with tissues that move or stretch, potential applications abound. Visible-light images obtained from deep within the body might eliminate the need for intrusive biopsies, for example. Or laser light could be focused to treat aneurysms in the brain or target inoperable tumours without the need for surgery.
“Just ten years ago, we couldn’t imagine high-resolution imaging down to even 1 centimetre in the body with optical light, but now that has now become a reality,” says Lihong Wang, a biomedical engineer at Washington University in St. Louis, Missouri. “Call me crazy, but I believe that we will eventually be doing whole-body imaging with optical light.”
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