Have you or a friend or family member ever had a CAT scan? The first time you heard that term, you might have been curious. It’s only natural to wonder why a doctor would use a cat to diagnose what’s wrong with you if you’re sick!

You may be relieved to find out that no actual cats are involved in a CAT scan. The “CAT” in CAT scan actually stands for “Computed Axial Tomography.”

Sometimes these scans are simplified to “Computed Tomography” or CT scans. Either way, it’s a mouthful to say, so you can understand why it’s easier to call them CAT or CT scans!

CAT or CT scans are advanced versions of X-rays. Whereas regular X-rays can provide doctors with a two-dimensional view of a bone or other part of the body, CAT scans give doctors a much more detailed, three-dimensional view of what’s going on inside your body.

CAT scans are used most often by doctors to help figure out what is going on inside a person’s body that is making them sick. There are other uses for CAT scans, though. Some industries use CAT scans to see inside objects without destroying them by opening them. Archeologists have also been known to use CAT scans to see inside of mummies!

A CAT scan machine looks a bit like a big donut. To scan your body, a doctor will have you lay flat on a table that then passes through the ring of the donut. This doesn’t hurt a bit, but it can be a bit nerve-wracking if you don’t know what to expect.

As your body passes through the ring of the CAT scan machine, the machine takes many pictures with X-rays from hundreds of different angles. These images are then pasted together with a powerful computer to give doctors a unique three-dimensional picture of the inside of your body.

These images can help doctors diagnose all sorts of problems, including head injuries and cancer. CAT scans are an important tool that doctors all over the world use millions of times each year.

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    • It’s OK, Nasa! We liked your guess a lot yesterday, and sometimes guessing is just a lot of FUN, whether our guesses are correct or not! Thank you for checking out today’s Wonder…YOU ROCK! :-)

  1. Hi Wonderopolis! I thought that video was cool and are CT Scan for cancer? I think tomorrow’s wonder will be about shapes.

    • Hi, Clay! Yes, cancer is one of the illnesses that doctors use the help of CT scanners to search for and diagnose. There are lots of other medical reasons to use the scanners, though! They help doctors a lot! :-)

    • Hi, Caelah! Thank you for sharing your thoughts about CT scanners. We know some Wonder Friends who have had to have a CT scan and they say it isn’t scary and that it doesn’t hurt at all. We’re glad you stopped by today’s Wonder and learned some cool new facts with us today…THANKS! :-)

    • Thanks for sharing what you think tomorrow’s Wonder might be about, Wonder Girl! We like your guess! Have a WONDERful day! :-)

  2. 5 of our classmates know someone who had a CAT scan. Someone in our class has had his own CAT scan. We think it’s neat that you can get an image of the inside of our body. We think it would be great if they made the CT scan look like a REAL giant donut. Tomorrow’s wonder might be about shapeshifting. Is there any age requirement to use the CAT scan device? Have a WONDERful day!

    • Happy Thursday, Mr. Draper’s Class! We’re not sure about the age requirements for having a CAT scan, but we know some of the folks who have had them have been REALLY, REALLY not-so-young (mummies!)! We think your idea of making CAT scans look like actual giant donuts is SUPER COOL! We bet it might make the experience of getting a scan done a little less scary for some younger Wonder Friends!

      Have a SUPER SPECTACULAR WONDER day, guys! :-)

  3. Eleven of us thought a CAT scan really involved a cat! We were surprised to find out that it is really only a special X-ray machine. We think tomorrow’s wonder might be about leaves, snowflakes, robots, or paper. There are many things that come in all shapes and sizes. We can’t wait to find out what our WONDER will be!

    Mrs. Wade’s class

    • You’re right, Mrs. Wade’s 2nd grade Class! There really are LOTS of things that can come in all shapes and sizes! We like all your great guesses, and we agree with you…we can’t wait to find out what we’ll be WONDERing about in Wonderopolis tomorrow, either! :-)

    • Hi, Adam! Thank you so much for checking up on your Wonder idea! We really value each and every suggestion our Wonder Friends give us about what they think future Wonders of the Day should be! It takes a good bit of time, research and extra WONDERing to turn a great idea from a Wonder Friend into a Wonder of the Day® that all Wonder Friends can enjoy! We appreciate your suggestion very much! :-)

    • Thanks so much for sharing your personal experience with having a CAT scan, “Wonder!” We’re so glad you stopped by today’s Wonder and let us know about it! We hope you have a GREAT day! :-)

    • That’s OK, Caelah! We’re just glad you stopped by today’s Wonder of the Day® to learn something new with us! You are a GREAT Wonder Friend! :-)

  4. One day they put me in a CAT scan when I was in the hospital. I didn’t feel anything. They told me that I had pneumonia and I made a joke. The donut ate me and spit me out. Ha Ha Ha!

    • Humor is a WONDERful way to make yourself and others feel better about situations that might be a little scary (like getting a CAT scan), Veronica! We’re proud of you for having such a SUPER positive attitude! Thanks for sharing your story with us today! :-)

  5. Great to learn about cat scans today. Three of us here have had cat scans for different reasons. Our guesses for tomorrow are: matter, boxes, water, band aids, or bugs.

    • We think your guesses for tomorrow’s Wonder are SUPERB, Mrs. Schrader’s Switch Class…way to go! We’re glad you guys learned some new things about CAT scans today by exploring this Wonder together! In fact, we think that ROCKS! :-)

    • We can see how some of our Wonder Friends might have thought a CAT scan is for cats, Muskaan! That’s creative thinking! Thank you for hanging out in Wonderopolis with us today…we appreciate your comment! :-)

    • That’s an AWESOME question, Mrs. Foster’s Class! Before CAT scanners and other imaging devices, doctors often had to perform surgery to “see” inside a person’s body and look for what might be causing pain or other symptoms. Even though surgery might still be the only way to do that in certain instances, imaging devices like CAT scanners can really help doctors diagnose health issues without causing the patient any undo stress or recovery time!

      Thanks for WONDERing more about 3-D imaging and CAT scanners today! :-)

  6. Hey guys. I knew it was a CT scan. At first, I thought no way, then I thought for a while and then I guessed and I was right. But I’m begging you please tell me where you live please, please, please. And every Wednesday (Wonder Wednesday) my teacher (Ms.T) calls it we come on the web. It’s so fun. I love Wednesdays. Again please tell me where you live :( Tell me and this will happen :) See you next Wednesday or sooner.

    • We’re so glad that Wonderopolis is part of your classroom’s Wonder Wednesdays, Dominic! That is AWESOME! We appreciate you asking again where we live, but we REALLY DO live in Wonderopolis! It’s a FUN place full of learning, sharing and growing! It’s a GREAT place to be yourself and have a blast with all your Wonder Friends! :-)

  7. I have been in a CAT scan. Also I always look for the wonder of the day on my ipod using the Wonderopolis app. I even downloaded it myself. (Evan)

    My brother fell off of the hot tub and got a CAT scan. (Myleigh)

    • Way to go about downloading the Wonderopolis app by yourself and checking out the Wonder of the Day® that way, Evan! That ROCKS! We’re sorry you had to get a CAT scan, though. We hope you are all better now!

      Thanks for sharing about your brother, Myleigh! We hope he is OK!

      We really appreciate all the WONDERful comments our KF Dragons friends share with us…they’re GREAT! :-)

  8. I learned something new about the cat scan. They can scan all different parts of your body. Thanks Wonderopolis for the great wonder!

    • Thanks for letting us know something new you learned by exploring today’s Wonder about CAT scans, Kyle! We think it is GREAT that you stopped by Wonderopolis today! :-)

    • We like the creative way your Wonder brain thinks, Maddie! We WONDER that about cats and CAT scans now, too! :-)

  9. Think. We think a Cat scan is a machine that looks inside of you because we think if you broke a bone or had an injury you might have to go in a Cat scan.


    Two ways to say cat scan CT Scan or cat scan

    A cat scan looks a bit like a big donut

    Cat scan means computer Axial tomography

    A cat scan is a verson of X – rays

    Cat scans give doctors much more detail of three dimensional a view what’s going inside your body

    Allison Matthew and Ashley

    • That’s some REALLY awesome WONDERing about CAT scans, Allison, Matthew and Ashley! Way to go, guys! Thanks for sharing your THINK and LEARN with everyone in Wonderopolis today! :-)

    • That’s a really great question, Kate! We’re not sure about the answer, but now we WONDER about that, too! Thanks for visiting this Wonder of the Day®! :-)

  10. I have always Wondered what a cat scan is like, thanks for letting me know and I hope I never need one.

    I think tomorrow’s wonder will be about…hmmmm
    I dont really know, guess I need to wait.
    :D :D :D :D

    • We think waiting to see what the next Wonder is going to be is SUPER FUN, Jocelyn! We’re glad you learned some new, interesting facts about CAT scans by exploring this Wonder…we did, too! YOU ROCK! :-)

  11. Hi wonderopolis. I think today’s wonder was AWESOME:) I loved it. You guys post TERRIFIC wonders on wonderopolis. :) I really loved today’s wonder of the day, but it is night right now. Well, bye. :)


    • Thanks for leaving us such a WONDERful comment, Nikki! You are an AWESOME Wonder Friend and we really appreciate your enthusiasm for learning in Wonderopolis! :-)

    • Thanks so much for sharing what you think the next Wonder will be about, Nikki! We sure do appreciate you visiting Wonderopolis and leaving us comments today! :-)

  12. When I think of cat scans,I think of my two cats, Smokey and Minou. The machine looks like
    a doughnut. PS: This wonder rocks :D

  13. I actually just had a CAT scan a few days ago! I had to have surgery because they found something wrong with my appendix. At first, going into the CAT scanning room, I was scared because I did not know what to expect! After the kind doctor explained briefly what was going to happen to me, it was so easy and I felt nothing! After reading this wonder, I now know more about what happen to me during the CAT scan!

    • We are SUPER happy that you learned about what goes on while a patient has a CAT scan, Gracie, and are especially happy that you are okay! We think you are a SUPER brave Wonder Friend– thank you for sharing your CAT scan experience with us! You ROCK! :)

  14. It’s a scanning system for cats, duh. Why else is it called a cat scan? If it was for us, it would be people scan.
    HA HA. I love making jokes.

    • You’ve got us chuckling, Tyler! We know that a people scan would make sense, but we learned all about the real meaning behind the CAT scan, and what the acronym stands for! We hope you’ll check out the Wonder to learn all about it, Tyler! :)

  15. We never knew that CAT scans can see if you’re sick.The doctor can take pictures of inside your body. This is cool and interesting because the CAT scan won’t hurt you even though it’s taking pictures of inside your body. It’s also a little scary because you have to stay still.

    We learned something new today!

    From Cool Girls

    • We’re so glad you learned some new facts with us about CAT scans, Cool Girls! We hope you each have an awesome day!! :)

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Have you ever wondered…

  • What is a CAT scan?
  • What does CAT stand for?
  • How are CAT scans different than traditional X-rays?

Wonder Gallery

CAT scan_shutterstock_74356504CATscan-3CATscan-2CATscan-1Vimeo Video

Try It Out

Ready to learn even more about what a powerful tool the CAT scan is? Find a friend or family member to help you explore one or more of the following activities:

  • Have you ever had a CAT scan? If you become a medical professional one day, you may need to use CAT scans to diagnose patients. If you’re WONDERing what CAT scan images look like, just check out this online CT Image Gallery for some examples of actual CAT scan images. Don’t worry if you can’t make sense of them. Doctors are trained to know what to look for in CAT scan images.
  • Are you interested in becoming a doctor one day? Learn more about what doctors do during a typical day by taking a field trip to a hospital. Talk to an administrator to see if you can make an appointment to return at a time when a doctor can talk with you and show you examples of some of the technology that’s used in modern medicine. Even if you don’t want to go into medicine one day, maybe you’ll find that you foresee a future in building new technology for doctors to use down the road. Have fun learning about the other amazing life-saving machines used in hospitals today.
  • OK, so now you know that a CAT scan doesn’t actually involve cats. But what if it did? Imagine that you live in a world where cats are doctors. You haven’t been feeling well lately, so you make an appointment with a furry, feline doctor. You’re told a CAT scan may be involved. What is your trip to the doctor like? How does the cat scan you? What does he or she discover? What medicine are you given? Alternatively, you could imagine a world in which regular human doctors actually use real cats to scan people. How do they use them? What are they able to tell from the cat’s reaction to you? Have fun and write down your thoughts about these wacky scenarios. If you want, share them with your Wonder Friends by posting them on Facebook. We can’t wait to read about your feline adventures!

Still Wondering

CAT scans help doctors see what can’t be seen from the outside. Did you realize your body is made up of all sorts of tiny particles that can’t be seen with the naked eye? Nuclear science begins with the atom. Learn more about this building block from Science NetLinks’ The Atom and Nuclear Science lesson.


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