Physics of Medical Scans
Image Source: Southwest Diagnostic Center for Medical Imaging
What’s a CT scan?
CT scans let doctors see inside your body without even needing to be in the same room as you! The pictures from CT scanning can be very useful in helping to diagnose what's going on inside you. The scanner has multiple parts to it including a table that you can lie down on, and a big doughnut-shaped hole that you can move into.
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What's it like to have a CT scan?
The first thing that happens is that you get into loose comfortable clothes so that you don't have anything on your clothes that might confuse the scanner. Nursing staff might also tell you not to eat or drink anything a few hours before, depending on where on your body you’re getting scanned. They might also give you what’s called a contrast dye that helps the doctor see your scan better. Sometimes, this can be given to you orally, like in a juice which you would drink normally, or through an injection which only takes a second [1].
Once you’re in the room with the scanner, the doctor in charge, called the radiographer, will ask you to lie on the table. When you’re strapped in and ready to go, the table will move you into the doughnut-shaped part of the machine which acts like the machine’s ‘camera’. While you’re in there, you’ll still be able to talk to the doctor through the room’s intercoms so they can give you more instructions if necessary. The entire scan may last from several minutes to half an hour.
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How does it work?
CT scanners use a type of light called X-rays (just like the ones used to see your bones!) to look inside your body. This is possible because unlike the light our eyes can see such as red, blue, and green, X-rays can go through solid objects; even walls! CT scanners shoot these X-rays into your body and some come right out the other side. Depending on how many X-rays go through you, a computer can make an image from this information to see what's going on inside your body.
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What's the point of CT?
Sometimes there are things in your body that doctors want to look at. Instead of doing X-rays which let doctors see your bones, CT lets them see the soft, squishier stuff inside you like your heart or even your brain!
Hold still and say cheese...
Exactly like when you’re posing for a photo with a smartphone, it’s better to hold still in a CT scan so that the images it takes of you aren’t blurry.
How do I look?
This is what a CT scan of a brain looks like! I bet your smartphone can’t do that.
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Image Source: CDEM Curriculum
CT - Standard
