Light allows us to see the world around us, in all the colours of the rainbow.
It might sound strange, but there are also colours of light that we can’t see. Just beyond the red end of the rainbow is a colour known as ‘near infrared’, which has a longer wavelength than visible red light.
This near infrared light can travel far into the body – even through bone – while other colours with shorter wavelengths are absorbed and don’t pass through.
Light can reveal changing oxygen levels in the blood pumping through our arteries and veins. When oxygen binds to haemoglobin inside blood cells, it changes colour and becomes more red. So oxygen-packed blood in the arteries is bright red, while blood in the veins is bluer because the oxygen has been used up.
Let’s zoom inside a brain cell (neuron). All cells use oxygen and sugar (glucose) to make energy inside tiny ‘power stations’ called mitochondria. This process is known as metabolism.
During metabolism, lots of protein molecules work together to generate energy by shuttling chemicals around. One of them is called cytochrome c oxidase, which changes colour as energy is made.
We can use near infrared light to monitor this colour change, giving us information about how cells are using oxygen and generating energy. This tells us how healthy they are, and whether they are working normally.
We’ve developed a way of safely and non-invasively shining near infrared light into the brain and detecting it with sensitive digital cameras. This information is converted into a detailed readout of the oxygen and metabolism levels inside the brain, revealing how well the cells are working.
Unfortunately some babies suffer a lack of oxygen to the brain during birth. This affects metabolism and causes damage to the brain cells. Quick treatment, including rapid cooling or other therapies, can help to limit or reverse the harm. Measuring what’s going on inside these babies’ brains is vital in the first few hours of life so that doctors can work out how best to treat them to avoid long term damage, disability or even death.