Laser goes skin deep for 3D picture

Dr Jevon Longdell is leading the imaging project. Photo / Peter McIntosh

Cosmetics companies interested in procedure which combines light and ultrasound to give tissue information.

Imagine being able to peer deep below your own skin in 3D - and without even having to break the surface.

New Zealand scientists are investigating how lasers could combine with ultrasound technology in a jump likened to moving from black and white television to full-HD colour.

And ultrasound-modulated optical tomography, or UMOT, could advance research in areas spanning cosmetics to medicine.

The concept, being explored by researchers at the Otago University-based Dodd-Walls Centre for Photonic and Quantum Technologies, builds on the normal ultrasound scanning process, where the imaging is done by sending out an ultrasound pulse and then listening for the reflected echoes.

The reflections are produced when the ultrasound reaches a boundary in the moving parts of an object.

"This means that with normal ultrasound you only get information about the mechanical properties of the tissue," said Dr Jevon Longdell, who has been leading the project.

"With our technique, you get lots of rich information about optical properties of the tissue."

While it's not difficult to push light through your body - just put a torch against your hand - trying to build a clear picture out of the thick fog that is our biological tissue isn't so easy.

Imaging using purely optical techniques becomes highly scattered beyond a few millimetres - yet ultrasound can travel through tissue with minimal scatter.

During their research, Dr Longdell and his colleagues bathed a tissue sample in light from a laser with a "very, very, precisely" controlled wavelength.

"We then send a short, well localised pulse of ultrasound through the sample," he said. "As it travels through the sample ultrasound produces wavelength-shifted, or ultra-sonically tagged photons."

By detecting these photons as the ultrasound pulse passes through, a 3D image can be produced.

"The trouble is that the wavelength shift that the ultrasonically tagged photons get is very small, so you need a very special filter to separate them out - however, what we have is the world's best such filter."

Internationally, UMOT has been touted as a potential new way to detect cancer. Cosmetic companies, keen to see what happened beneath the skin when their products were applied, had also shown strong interest in the technology.

Dr Longdell said the filters used by the centre for acousto-optic imaging were the world's best.

Nobel winner to visit NZ

One of the world's most renowned physicists and the former Energy Secretary of the United States is to visit New Zealand next month.

Professor Steven Chu, who received a shared Nobel Prize in 1997 for his work on methods to cool and trap atoms using lasers, will speak at a graduation ceremony and give a public lecture at the University of Otago.

He will also visit the university-based Dodd-Walls Centre for Photonic and Quantum Technologies, recently established as a Centre of Research Excellence.

The centre's director, Associate Professor David Hutchinson, said it was a coup to host Professor Chu, who served as Energy Secretary between 2009 and 2013.

Under the skin - how it works

• Tissue is bathed in light from a laser with a precisely controlled wavelength.
• A short, sharp pulse of ultrasound is then sent through the tissue, producing a scatter of photons that are ultrasonically tagged.
• Researchers use a sophisticated filter to separate out each photon.
• From this, they can construct a three-dimensional picture of our biological tissue, centimetres below the skin.
• This approach has been touted for use in cancer detection and gauging the effectiveness of cosmetic creams.