University of Otago physicist Dr Jevon Longdell examines a transparent silicate crystal containing atoms of the rare metal praseodymium which are excited by a laser beam and used to store light. Photo by Peter McIntosh.
University of Otago physicists have achieved a technical
breakthrough which could eventually lead to improved body
scanners, using a combination of ultrasound and lasers.
Such a combined scanning approach - called
''ultrasound-modulated optical tomography'' (UOT) - was first
proposed as a method for early cancer detection in soft
tissue in 1993 but persistently difficult technical problems
have since severely limited its development.
Research leader Dr Jevon Longdell was previously part of an
Australian-led team whose work featured prominently in the
prestigious journal Nature in 2010, for developing the
world's most efficient quantum memory for light.
The ANU-led scientists had pioneered a technique to stop and
control light from a laser, manipulating electrons in a
crystal cooled to about -270degC, about 3deg above absolute
The Otago research team, which included Dr David McAuslan -
now at the University of Queensland - and Dr Luke Taylor,
recently used some of the earlier techniques, initially used
in a bid to develop a highly-powerful quantum computer. And
the researchers applied the methods, successfully, to the UOT
''It's exciting that we currently have world-beating
performance and that this research might be applied in the
near future,'' Dr Longdell said.
''The promise of such an imaging system is that it will one
day give doctors more information about the characteristics
of pieces of tissue, and, for example, better distinguish
between dangerous and harmless growths.''
The Otago group had combined ''quantum memory techniques with
the optical detection of ultrasound'', and achieved ''record
Both light and ultrasound were used extensively for medical
imaging, each with benefits and drawbacks.
Optical imaging techniques, using lasers, were ''very
sensitive'', but the light scattered in biological tissue,
limiting penetration depth.
Ultrasound imaging was less sensitive but could ''image deep
into tissue without significant scattering''.
It was hoped to ''combine the best aspects of both''.
The researchers should be able to use their crystal-related
filter to make ''high quality 3D images of tissues'' and
further development work was under way. A scientific paper by
the researchers at Otago's Jack Dodd Centre for Photonics and
Ultra-Cold Atoms was published in the international journal
Applied Physics Letters late last year, and recently
highlighted by Nature Photonics.
Human tissues vibrated in the presence of ultrasound and
there were very slight changes in the frequency of light
waves when they encountered the vibrations.
Otago researchers had used ''more sophisticated filters'' to
detect the changes.