Brain injury is a common cause of disability in prematurely born infants who survive intensive care. Currently, there are no reliable methods for assessing the degree of injury or the effectiveness of procedures that can be safely used on such infants. This has led researchers to investigate methods based on the transmission of visible and near infrared light.

Hebden and co-workers’ new technique – an improvement on an existing technique known as “optical tomography” - allows them to acquire images of the entire three-dimensional volume of the brain. Optical tomography uses a finite set of measurements of transmitted light between pairs of points on the surface of an object to construct either a transverse slice or a 3D image of the whole object.

The method needs to be sensitive to deep tissues which means that the transmitted light must be integrated over periods of several seconds - or longer - to obtain an adequate signal. Although this can prevent effective imaging of some fast phenomena, it is useful for monitoring long-term changes throughout the entire brain over several hours or even days.

The UCL imaging system measures the arrival time of photons from lasers at wavelengths of 780 nm and 815 nm at 32 different points on the baby’s head. The helmet, used as the interface between the infant and the instrumentation, contains a fibre source coupled with a single detector fibre bundle.

Work still needs to be done on the development of the complex head models. “These models must be able to represent all the possible geometries and optical properties of the infant head in order to get accurate images,” Hebden told PhysicsWeb. “We are steadily introducing more complexities into our models as this work progresses.”

The researchers hope that their method will one day become a routine technique for the monitoring of premature infants in intensive care.