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Asked by anon-244767 on 30 Apr 2020.
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Dipendra Mistry answered on 30 Apr 2020:
Hi cBond,
Just to be clear are we talking about infrared cameras (as in a thermal imaging camera which shows hot/cold) or are you talking about a medical image of the brain like an MRI or something similar.
Kind Regards,
Dipendra
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Susan Cartwright answered on 30 Apr 2020: last edited 30 Apr 2020 10:21 am
Most images of the brain aren’t infra-red, they are produced by techniques such as magnetic resonance imaging (MRI) or positron emission tomography (PET). However, similar comments apply in all cases, so here goes…
None of these techniques actually produces colour in the true sense: that’s purely a property of visible light. The images are shown in “false colour”, where the equipment and/or the operator assigns different colours to represent (usually) different intensities of emission (in astronomical images it’s generally different wavelengths, but in medical images the key property is usually intensity). They choose the colours to make most sense to the people who will be looking at the images, and to most people (other than astronomers) red means hot and blue means cold, so generally areas of high emission are coded red and those of low emission are coded blue. So the blue regions of your image are those that aren’t emitting much, which means those that aren’t very active (activity requires cells to metabolise more intensely, so they give off more waste heat and use up more chemicals). The centre of the brain has spaces (the ventricles) that contain cerebrospinal fluid, not neurons, so they are likely to show up as blue.
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Greg Wallace answered on 1 May 2020:
Susan gave an excellent answer. I would add that , as far as I know, the role of the cerebrospinal fluid in the ventricles, that cause the blue spots you describe, is not very well understood. I’ve heard one theory that it could be the key to why we need sleep. As there is a blood-brain barrier to protect the brain from infection it’s very hard to get rid of all the waste products the brain produces. I think the idea was that when we sleep the brain literally shrinks, allowing the spinal fluid to flow in and ‘wash’ these waste products out of the brain. I’d double check that with a neuroscientist though!
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James Smallcombe answered on 1 May 2020:
I will defer to other scientists on the particulars of the brain.
One thing to bare in mind is that when you are shown a picture taken with a specialised imaging device, the colours are artificial and representative. The range of values represented might not be as extreme as our intuition of the colours might tell us they should be, it is important to ask what the scale is. We often use “heat maps”, colours going from dark blue to bright reds & yellows, but the smallest value shown in blue could still be a large value. As an example a heatmap of the sun (https://www.researchgate.net/publication/256438194_A_large-scale_solar_image_dataset_with_labeled_event_regions/figures) shows dark spots but these are still thousands of degrees, they are just the coldest point relative to those shown. -
Sophia Pells answered on 4 May 2020:
Is this the sort of image you are thinking of: theevolutionofimagingtechnology.net/pet-scan/ ?
This is a PET scan. Like others have said, the regions have been artificially coloured to be blue or red so it is easier for us to understand the difference of different regions. The colour scheme does make it look like a heat map but it’s actually showing where there is most radiation in the brain.
PET scans of the brain usually use a man-made type of glucose to see how the brain is working. The brain uses glucose for energy so areas of the brain which are working harder need more energy so they take in more of this glucose. A radioactive type of fluorine is usually attached to the glucose so we can see which parts of the brain are using more of it. The fluorine emits radiation which is detected by the PET scanner, so the regions of the brain that are working harder emit more radiation and appear brighter or hotter in the images we see. Different areas of the brain have to work harder depending on what activity we are doing, as you can see in the image in the link I sent. I’m definitely not an expert in the brain so can’t really tell you why different parts of the brain are important for different things, but I hope that answers your question about why some areas look cold in images.
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Ry Cutter answered on 8 May 2020: last edited 8 May 2020 12:32 am
So I didn’t know much about brain imaging and decided to do some reading!
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After more than a week I found some new methods physics has developed to help look into the brain! So, as others have said, the main two methods we currently use to look at the brain are MRI and PET scans. But I want to talk about three new techniques being developed and studied!
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The first is using sound waves in the brain! You’ve probably heard of sonograms, this is using sound waves to see inside an object (usually referred to seeing a baby before it’s born.) Well, when we try and do that with the brain the skull has this nasty trick of bouncing the sound waves about so the signal gets scrambled! However, physicists recently realised that this bouncing is incredibly similar to how seismic waves bounce around the Earth! This has led them to develop the first simulated deep brain image using sound waves. It’s currently being done at the Imperial College London https://www.nature.com/articles/s41746-020-0240-8.
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You may have heard of an EEG (Electroencephalography) too. These are funny hats with loads of wires coming out of them. These have been in use for a long time. They are usually used to read electrical signals in the brain, but we can also use them to send signals to the brain too! The problem is, it takes a lot of power to send a signal, a lot more than you need to feel a signal generated by the brain. This means, when we send a signal to the brain we find it very difficult to see how the brain responds. This is where particle physics comes in! The main challenge of things like the Large Hadron Collider, is to find weak signals amongst the very strongest. So a team of particle physicists teamed up which a bunch of neuro-scientists and have developed an EEG that quickly flips between generating strong signals and reading weak ones! Obviously, as true scientists, they decided to test it on themselves first 😀 https://news.stanford.edu/2019/09/28/particle-physicists-lend-hand-advance-neuroscience/
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Saving the best for last, Astronomy! In recent times, we astronomers have developed mirrors that allow us to see past the scattering caused by the atmosphere. This tech is called adaptive optics, it works by changing the shape of the mirror collecting light from the night sky. Well, living tissue has a similar effect on microscope imaging. As blood (or other fluids 😛 ) pass through the body it obscures the image. The same principals of adaptive optics has been applied to brain imaging! It has shown to give much improvement, though at the moment it can’t do deep tissue very well.
https://www.nature.com/articles/nmeth.4508
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I found this all really interesting, thanks for the wonderful question,
Ry
Comments
anon-244767 commented on :
Hi Dipendra, I was thinking about the thermal imaging camera. I don’t know much about this topic though!
anon-244767 commented on :
Thank you very much James and Greg!
anon-244767 commented on :
Thank you Ry, it’s really interesting and I didn’t realise there were so many methods! Thanks also Sophia for a brilliant answer 🙂