A LASER imaging device could soon help doctors to identify newborn babies who
were starved of oxygen during delivery. By passing laser light through the head,
the machine produces images revealing oxygen levels in the brain.
Jeremy Hebden, a physicist at University College London, told the BA meeting
that his device should provide near-instantaneous images, allowing doctors
to identify and treat newborns who are at risk. In Britain alone, about 300
babies a year suffer lasting brain damage as a result of asphyxiation during
Imaging the body’s internal organs using light is notoriously difficult.
Anyone who has ever shone a torch through their hand knows that light scatters
when it passes through soft tissue, making it almost impossible to get a sharp
image. The same is true of infrared and ultraviolet radiation. But Hebden has
managed to turn this scattering to his advantage.
Instead of imaging the brain directly, his machine measures the flight times
of light pulses passing through the brain, which vary according to how much the
light has been scattered. Scientists know from experiments on samples of brain
tissue how it absorbs and scatters light, and how this varies with the tissue’s
level of oxygenation. Using this information, a computer creates a series of
simulations of the distribution of oxygen in the baby’s brain until it finds one
that matches the flight-time data. It then displays an image derived from this
Babies whose brains are being imaged don’t suffer any stress, says Hebden.
They are fitted with a headband containing optical fibres that shine light from
a 0.5-watt, near-infrared laser into their skulls, and 32 light sensors to
detect the light as it emerges. A 1-picosecond pulse is emitted from each
optical fibre in turn. “Even though we’re using a fairly powerful laser, there
is no chance of damaging the brain because we keep it moving all the time,”
Simon Bignall, a specialist in neonatal medicine at St Mary’s Hospital in
London, says it can be difficult to identify babies who need to be given oxygen
or other treatment. “It would be very useful if we could actually look at the
levels of oxygenation in the brain,” he says. Hebden expects to begin clinical
trials within a year.