A light source can emit many colours of visible and invisible light. Part of the invisible light beyond the red colour in the light spectrum is known as ‘near infrared’ light (in the range of 650–1000 nm window).
Near infrared light has the ability to travel far into the body.
The colour of blood inside the body depends on the oxygen levels. For example, blood in the arteries is bright red because it is fully oxygenated, whereas venous blood is more reddish black in colour because there is less oxygen. A pigment in blood (haemoglobin) responds to light differently depending on the level of oxygen in blood, which helps us to measure the amount of oxygen in blood.
If we zoom into a brain cell (neuron) we can see the mitochondria, the power house of the cell. This is where oxygen and glucose are metabolised to create energy. During metabolism, there is a colour change in the mitochondrial membrane.
If we zoom further into the membrane you can see an enzyme called cytochrome-c-oxidase which changes colour when it metabolises oxygen. Using this colour change, we are able to monitor metabolism using optics.
We can now monitor the brain’s metabolism directly at the cot side, using a special ‘near infrared’ light system.
Around the time of birth, some babies unfortunately suffer from lack of blood and oxygen supply to their brain. This can cause significant brain injury leading to death and disability in the survivors. We know from previous studies that brain metabolism gets disturbed during this period.
Monitoring the brain metabolism closely will help the doctors to identify sicker infants early and provide the best possible protective strategies for their brain.