Understanding CT scans

CAT or CT scans are used to achieve high resolution images inside the body. But how do they work?
Watch the video to find out
See more Medical imaging techniques here -
• Medical Physics
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[@sifatullahanwary343]

Thanks so much very nice explanation

[@myzzetyzia3063]

thanks!

[@trayanc1496]

best explanation i found, thank u

[@PhysicsHigh]

Glad it was helpful!

[@conorgoldsmith9348]

Awesome explanation, thank you!

[@reikokirkland1939]

THANK YOU SO MUCH! please continue uploading Radiology related videos like these :)

[@rodevans602]

@Ardeth Bey A very bad scene! The patient is instantaneously uploaded to the nearest wormhole and downloaded to the nearest parallel universe. All that remains in the CAT machine is a very small puff of malodorous blue smoke....

[@rodevans602]

@Ardeth Bey Much safer option!

[@aidacarmengubalane]

😊😊

[@chaitanyamahajan7872]

thank you

[@earnestthompson5136]

Thank you!

[@PhysicsHigh]

You’re welcome

[@finishtime916]

ty

[@rahalhettiarachchi8967]

Thank you very much! Please do a video on MRI scanner if you can

[@PhysicsHigh]

You need to check out my modern physics playlist. I have 5 videos on MRI.

[@sarahmccoy1941]

Radiation? Danger Will Robinson! Danger!

[@micah7685]

Can cause radiation poisoning and sickness by causing massive cell death. Huge amounts of ionizing radiation and often are not worth the risks

[@zeitgeist909]

I am not sure why at 0deg we don't just see a solid black block? Surely, the densest part of the block is at the 'top (left)' (ie the first things the x-rays hit) so the less dense layers underneath are shaded out? When we see an image of say a hand in Xrays the bones are dark and the flesh and skin is light? So it's a top-down 2-d image with the (dark) bones inside the (lighter) fleshy hands. I just can't seem to understand why we see a white rectangle with black either side? How is it not just a solid black rectangle?

[@866152]

X ray film is clear by default, exposure to x rays will cause it to turn black. The denser the object in the path of the x ray the lighter it remains on the image. In an x ray of a hand the bones are white and the soft tissues are darker. To add to my previous point when the x ray source is at 0 deg the image is just white because the x ray beam will be blocked by the layer on top which is the most dense.

[@intexclouds9607]

I wonder how it pictures the brain...since the brain is completely surrounded by dense cranium, should we not see only a white ring around a dark region ?....and how does it estimate the thickness of the skull (as the x-rays only impinge on the skull from the surface and the back of a given section is always obscured by the front of a diametrically opposite section of the cranium)?

[@kaymarie321]

The skull is not impenetrable, therefore xrays can still pass through and be measured by the detectors

[@intexclouds9607]

@@kaymarie321 if the skull can let pass the x-rays, then is it not true that we should not see the skull? I was thinking, it's because x-rays can pass through the flesh that we don't see the flesh in an x-ray film and the bones don't let them pass and the film that is placed directly below/behind does not get developed.... sorry for my poor English.

[@kaymarie321]

Intex Cloud S9 you’re kind of on the right track! So the reason that bones show up on xrays is because they are more dense than soft tissues. Which means they will attenuate or absorb the xrays more so than soft tissue. The absorbed xrays will not reach the film which allows us to see the bone. But that doesn’t mean that NO xrays make it through the bone. Same goes for soft tissues. While soft tissues do not absorb as many xrays as bone, they still absorb some which just gives them a different shade of gray on the image. This is why we choose certain “techniques” or certain amount of kV to determine the energy of the X-ray photons. The higher the energy, the more they will penetrate.

[@intexclouds9607]

@@kaymarie321 makes sense...thank you sir/ma'am.

[@chafikjaaouan7347]

@@intexclouds9607 brother, i was thinking the exact same thing.

[@marcojouve8448]

Which one is better CT Scan or MRI or less danger Please ?

[@PhysicsHigh]

MRI is less dangerous for sure. CT uses xrays. MRI uses radio and magnetic field. MRI much more costly. Each have their benefits over the other.

[@micah7685]

Ct scans use harmful ionizing radiation that causes cell death and damage that is irreversible. Mri or ultrasound to protect your health

[@ravindranathhospital1362]

Why do substances with more density are going to be white in color?

[@PhysicsHigh]

The CT scan simulated a negative X-ray so the blacker the images the greater the exposure to X-ray. Since bone is dense and absorbs X-rays less get through to the sensor, hence whiter.

[@HowRadiologyWorks]

Thanks for the great video Paul. Since a general audience is watching these videos please be very careful with your word choices. CT scans are low radiation dose and low risk of cancer induction although it is higher than x-ray it is not common to refer to it as a high level of radiation. Thanks again

[@sarahmccoy1941]

No amount of ionized radiation is deemed safe for human beings. Using the term low-dose radiation makes it seem harmless. It is not harmless.

[@TheNettforce]

@@sarahmccoy1941 thanks for the response. Yes words are important here and I did not say harmless. I agree It is important for the general public to know about the potential damage from radiation. However, we also don’t want people opting out of valuable medical diagnostic information which could outweigh the risk of potential cancer induction. Thanks again for weighing in.

[@SleepingCat129]

And now that pic is in my head :(

[@BeautyBehindTheScience]

Can you please tell me for how long is the head exposed to these rays? What are the dangers ?

[@PhysicsHigh]

Not long at all. Each slice maybe a second or two. So overall a head scan make take a 10 min or so but each part of your head only receives a small exposure. Yes you do get more X-rays than a single traditional X-ray and like any scan such as this can potentially slightly increase risk of damage, but if you are having only one scan, there’s really no issue. For X-rays to be more hazardous it’s many many scans that have a cumulative effect. And the benefits of a CT scan in diagnosing conditions accurately is a benefit that far outweighs the risks.

[@BeautyBehindTheScience]

High School Physics Explained thank you for your explanation! I wanted to make sure each slice minimizes exposure. How about two scans in three years to investigate head aches ? Is that too much ?

[@PhysicsHigh]

Not at all. Thats not many. Straight from Harvard medical "The more scans you have, the higher your lifetime exposure and therefore the higher your risk. The American College of Radiology recommends limiting lifetime diagnostic radiation exposure to 100 mSv. That is equal to 10,000 chest x-rays, or up to 25 chest CTs."

[@BeautyBehindTheScience]

High School Physics Explained thank you. So that means that ultimately the X-rays are distributed among the slices and the exposure time is limited for each fragment of the head ?

[@PhysicsHigh]

Yes

[@Fatima-fo4bv]

So it's just a click bait and you aren't scanning a cat