Types of Medical Imaging

You’ve probably had to undergo some type of medical imaging at some point in your life. Maybe it was something routine, like a simple X-ray at the dentist. Or maybe something more uncommon, like “contrasted magnetic resonance angiography of the brain.” Have you ever gotten confused on what test you’re getting done or what the difference between a CAT scan and an MRI is? Well, here’s a list of some the most common types of medical imaging that your doctor might order and what makes them unique. 

X-ray

X-rays are essentially really tiny beams of light (so small we can’t see them) that are good at passing through things to light up whats on the other side. Imagine shining a flashlight through a window at night. Some of the light goes through the window (if they’re clean) and let’s you see what’s in your yard. Now, put a piece of paper in front of the flashlight. Much less helpful, right? Well, we can use these same principles with X-rays in order to see things in our bodies. Bones are like the paper in front of the flashlight. Your clothes, skin, and internal organs are like the window. That’s why X-rays are really good at seeing your bones; they don’t let the light (X-rays) pass through them.

There’s a specific type of X-ray test called a “mammogram.” This is an X-ray with adjusted settings in order to specifically look at someone’s breasts for signs of anything concerning (usually cancer).

• Pros:
  • Very common and available.
  • Cheap (compared to other types of medical imaging).
  • Quick and easy.

• Cons:
  • Radiation* exposure (although only a little bit).
  • Good at seeing bones, but very limited ability to see anything else in the body.
  • May need to sit/stand in awkward positions in order to get the best picture. (Shout out to mammograms 👍) 

CAT scan (CT scan)

These scans use specially trained house cats that shoot lasers out of their eyes to light up your insides. 

Just Kitten…🙃

CAT scans, also called “CT scans,” are like an X-ray that called all his buddies over to hang out and they all want a turn to play Fortnite (or whatever you’re into). Instead of a single angle like a traditional X-ray, CAT scans shoot a lot of X-ray light beams at you from multiple angles. These pictures are then combined with computer magic to give us much higher detail of what’s going on inside you. If a traditional X-ray is a grainy picture from the mid 1800s, a CAT scan is a new high-megapixel digital camera from the 2000s. 

• Pros
  • Fast (good for emergencies).
  • Quiet, comfortable, and not claustrophobic. (You just lay on a table that quickly passes through a ring unlike the tight tube of an MRI). 
  • No problem with anything metal in your body (see “cons” for MRI below). 
  • Highly detailed pictures of bones, like traditional X-rays.
• Cons
  • Large amount of radiation* exposure (Imagine getting 100-200 X-rays). 
  • Not very detailed at seeing things that are not bones, although much more detailed than traditional X-ray. 
  • Expensive.

Ultrasound (Sonogram)

Ultrasound is exactly what it says, ultra high pitched sound waves. So high pitched we can’t hear them. Imagine we are talking on the phone while I am walking around my house. You’d probably be able to tell exactly when I walk into my bathroom due to how the sound of my voice changes. Bathrooms have a lot of hard surfaces that sound waves bounce off of (echo). My voice on the phone would change again if I walked into a room with a lot of carpet. That’s what ultrasound does. The high pitched sound waves echo differently depending on what the ultrasound probe is being aimed at in the body. We can then take this info and turn it into a image on a screen using more computer magic to see what’s happening under your skin. 

There’s a very specific type of ultrasound called an “echocardiogram,” or just “echo” for short. This is a special type of ultrasound (and specially trained ultrasound technologist) that is specific to looking and examining your heart in detail. 

• Pros
  • Relatively cheap.
  • No radiation exposure.
  • Usually very comfortable to have done.
• Cons
  • Limited detail (Imagine an old grainy black and white TV compared to today’s HD TVs).
  • Have you ever seen those signs in line at a water ride that says, “You WILL get wet, you MAY get soaked?” Well, be prepared to get lathered in some ultrasound gel, which is moisturizing. So maybe this is a pro?

MRI

MRI stands for “magnetic resonance imaging.”

An MRI is a giant super powerful magnet that you lay inside of. Imagine a set of blinds on a window. When they’re closed you can’t see what’s on the other side. But when they’re open you can see through them pretty well. There are even in-between stages (partially open blinds) that allow you see through, but only at a very specific angle. This is how an MRI works. It uses a giant magnet that, when turned on, lines up the molecules in your body in such a way it can see through them. The magnet rotates around your body so it can take a peak at you through all those little in-between stages of opening the blinds. All those in-between stages are then combined into a single image using more computer magic. 

• Pro
  • Very detailed (the 4k ultra-HD TV of the medical imaging world).
  • No radiation exposure!
• Con
  • Not friendly with metal. Being a giant super magnet, ANYTHING metal inside of you will try to become outside of you. Also any metal in the room will become a lethal projectile as it shoots toward the magnet.
  • Loud (you will need to wear ear protection).
  • It’s pretty tight inside the magnet (Not good for people who don’t do small spaces).
  • Time consuming (not good for emergencies).
  • Expensive (even more so than a CAT/CT scan).

*Radiation, what is that?

As you may have noticed, some of the studies above expose you to radiation. Radiation is a type of energy wave that causes damage to our bodies at a sub-atomic level (much smaller than microscopic). You are exposed to radiation everyday (e.g. the sun, cell phones, airplanes) and small amounts are generally considered ok. However larger amounts can be dangerous and carry a risk of developing cancer later in life. Although, some of the studies above involve significant levels of radiation, none would be considered extreme by themselves. The concern is with repeated exposure to radiation, as it adds up over time. Having one CAT scan is ok, but having 10 over the years is concerning. But as with everything in medicine, it’s all about the risk/benefit ratio. 

Contrast

Some of these studies may or may not use something called “contrast.” Contrast is basically a fluid you swallow, have injected, or given as an enema that acts like a highlighter in the body to highlight something we want to see. Or for you tech-savvy readers, contrast is like using “control/command + F” in the body.

A few notes on contrast:

• Contrast is generally safe, but some people are allergic to it. 
• There is more than one type of contrast. Being allergic to one type does not mean you’re allergic to the other types. 
• Contrasting agents are NOT a source of radiation. 

Additional Imaging Studies

I should also let you know that there various different types of each of the above imaging studies. I’ve mentioned some of the most common ones, but there are more (e.g. CT-myelogram, CT-angiogram, MR-angiogram, MR-venogram, carotid doppler, etc). Just know that if it has a “CT” in the front, it’s a type of CT (CAT) scan. Likewise, “MR” means a type of MRI and “doppler” or “echo” mean it’s a type of ultrasound.

There are also many more types of medical imaging not mentioned here. I wanted to focus on the most common types in this post. Perhaps there will be a “Part 2” in the future with an overview of some other types of imaging such as DEXA scan, PET scan, colonoscopy/endoscopy, VQ scan, etc. If there’s any specific type of medical imaging you want to hear about, just let me know!

Learn more, stay humble.