The use of improvised explosive devices (IEDs, or roadside bombs) has led to an increase in the numbers of troops sustaining traumatic brain injury during military service in Afghanistan and Iraq. Such injuries are caused by the high pressure shock waves generated by the explosions, which cause rapid head movements, such that the brain is sheared and torn as it comes into contact with the inside of the skull.
Whereas conventional traumatic brain injuries caused by penetrative head wounds are easily diagnosed, those who sustain this kind of closed head injury often exhibit no external wounds. As a result, this type of TBI is often difficult to detect, and so may go undiagnosed for long periods of time. The incidence of TBI among U.S. troops is believed to be much higher than official figures would suggest, and it is now estimated that up to 15% of troops returning from the theater of war have been affected by it.
Although the brain damage caused by the shockwaves from IEDs cannot be picked up by conventional magnetic resonance imaging, recent research shows that it can be identified using a relatively new neuroimaging technique called diffusion tensor imaging. However, even in those troops suspected of sustaining a closed head injury, it may be some time before a brain scan can be performed.
Researchers from the University of Pennsylvania have now developed a device which may be used to aid in the diagnosis of TBI. Developed by Shu Yang and her colleagues, the device was presented at the 26th Annual National Neurotrama Symposium in Orlando, Florida, last month. It consists of a sticker containing 6 micrometre-thick layers of a crystalline material which can be worn by troops on their uniforms or helmets.
The photonic crystals in the sticker have a specific three-dimensional structure which refracts light to produce colour of a given wavelength. Shockwaves from the blasts generated by IEDs alter the structure of the crystals, causing a visible change in their colour. Because blasts of different intensities produce different changes in the structure of the crystals, the stickers can reveal the force of a blast.
Such a device therefore help doctors to make a decision about whether or not treatment for a brain injury might be required. However, the exact relationship between colour change and blast intensity has yet to be determined, so the sticker still cannot be used to quantify the extent of brain damage sustained in a blast. It may therefore take years for such a device to be put into practical use on the battlefield.