Virtual guide star helps focus light for medical imaging

The advance, by Lihong Wang, PhD and colleagues, is detailed today in Nature Communications.

In addition, the University team are said to have improved the speed of optical focusing deep inside tissue by two orders of magnitude, a development that represents an important step toward non-invasive optical imaging in deep tissue and photodynamic therapy.

In the new research, Wang and his team have built on a technique they developed in 2010 to improve the focusing speed of time-reversed ultrasonically encoded (TRUE) optical focusing for applications in living tissue.

To focus light, the engineers use a virtual internal guide star at the targeted location. By detecting the wavefront of light emitted from the guide star, they can determine an optimum phase pattern that allows scattered light moving along different paths to focus at the targeted location.

When light is shined into living biological tissue, breathing and blood flow changes the optical interference - or speckle pattern - which can cause previous methods to focus diffuse light inside scattering media to fail. Scientists have to act quickly to get a clear image.