• Question: How does Near-Infrared Spectroscopy work?

    Asked by Jo1 to Maheen, Deborah on 14 Jun 2016. This question was also asked by 569eadf26.
    • Photo: Deborah Prunty

      Deborah Prunty answered on 14 Jun 2016:

      Spectroscopy is the study of how electromagnetic radiation interacts with things. This sounds really complicated, but it’s just waves of energy. X rays are one extreme, and radio waves are the other, with visible light sitting some where near the middle.

      Near infrared (NIR) is just beyond the red light that we can see. That’s why it’s called “near” infrared.

      When NIR is absorbed by a molecule it makes the bonds vibrate. Molecules will only absorb the wavelengths that have exactly the right energy to make their bonds vibrate. We can look at what wavelengths have been absorbed to get an idea of what types of bonds the molecule has, and from that we can try and work out what it is!

    • Photo: Maheen Siddiqui

      Maheen Siddiqui answered on 14 Jun 2016:

      The physics behind near-infrared spectroscopy is as Deborah described!

      In our lab we use it as a brain imaging technique. In that case the way it works is that there are certain substances that absorb the near infrared light. For example haemoglobin in red blood cells inside our blood.

      When a particular region of your brain is more active because you are using it, the brain cells there need more energy. So there is more blood flowing to that region of the brain so the cells can generate energy quickly and use it!

      We put two fibres on top of the head, one that gives out the light and one that detects it, a short distance away. If your brain region was more active and therefore absorbed more light, then the fibre that detects the light would see that the intensity of the light has decreased.

      We can then use this principle to understand if particular regions of the brain become more active when someone is shown particular things!

      Hope this made sense!

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