Vocabulary of CT, MRI & PET Imaging

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  • 0:01 X-Rays
  • 0:48 Computed Tomography
  • 2:03 Magnetic Resonance Imaging
  • 3:39 Positron Emission Tomography
  • 5:02 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

In this lesson, you'll learn the definitions as well as general advantages and disadvantages of magnetic resonance imaging, computed tomography, and positron emission tomography.


The very first x-ray machine was developed a long time ago. X-rays are a really great, simple, and quick way for a doctor to take a look inside the body.

The problem with x-rays is there is a limit to how sensitive they are. Meaning, they are only able to pick up on any abnormal changes within the body only once those changes become large enough.

It's like your vision. You can only see so much and so far. You have limitations, and so do, quite frankly, x-rays. They can't spot everything.

So, people developed more powerful and more sensitive technology to spot a problem sooner than later. These technologies are called CT, MRI, and PET. Their vocabulary is defined as you take a leading role as a doctor in this lesson!

Computed Tomography

Let's say that you're working at a hospital as a doctor who can do just about anything equally well! All of a sudden, a patient is wheeled in. All you really know is they have what looks like a broken nose, maybe a broken jaw, and other head trauma after a car accident.

Again, you could take an x-ray to see if something is broken, but you want more detail. So you turn to CT, or computed tomography. 'Tom/o' means to 'section' or 'slice,' and '-graphy' refers to the process of recording a picture.

On that note, a CT scanner takes many x-ray slices from different angles of a section of a person's body in order to render a more detailed and even 3D image of the body part being examined.

Just look at the image of an x-ray of the head versus a CT scan of the head on screen. You can clearly tell the CT scan reveals a lot more detail than a regular old x-ray, can't you? And that will help you make a better and more conclusive diagnosis for your patient!


In general, a CT or CAT scan (it's the same thing), is preferred in instances when compact bone, like that of the head in our case, needs to be visualized.

Magnetic Resonance Imaging

But if you want better delineation between internal soft tissue structures, a CT scan may not be your first choice. Although a CT scan is used in such instances some of the time, MRI is considered to be better at imaging soft tissue structures than CT.

MRI is magnetic resonance imaging, and unlike a CT scanner that uses potentially harmful radiation to render an image, MRI uses basically harmless radio waves and a magnetic field to create a detailed image of internal body structures. However, because of this magnetic field, patients with metal implants may not be allowed to have an MRI scan performed.

So, let's say that a person without any sort of implants in their body comes in, and you suspect that they have something like lung cancer. You can conduct an MRI scan since both the lungs and cancer are soft tissue structures. Remember, an MRI scan is better than CT at delineating between soft tissue structures, and that's what you need in this case!

And so, look at the image on screen of an x-ray of a person's chest versus an MRI scan of the same area. Can you appreciate how there's far more detail in the MRI scan?

Actually, you can even conduct a real time MRI of an area like the chest nowadays, something you cannot do with a simple x-ray. Isn't that video amazing?

We can even conduct something known as MRA, magnetic resonance angiography, to image blood vessels for abnormalities.

Positron Emission Tomography

And for your last case of the day, dear doctor, you get a patient who has a confirmed case of cancer. But you want to find out if it has spread anywhere. What can you turn to?

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