How X-Rays Work


Josh: Josh Clark

Chuck: Charles W. "Chuck" Bryant

Vo: Voiceover Speaker

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Vo: Welcome to Stuff You Should Know from HowStuffWorks.com.

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Josh: Hey, and welcome to the podcast. I'm Josh Clark, with Charles W. "Chuck" Bryant, as always, and there is Jeri over there fiddling around with stuff. So it's Stuff You Should Know, the podcast.

Chuck: Not Stuff You Should Know, the movie.

Josh: That's right.

Chuck: You know?

Josh: We were sworn to secrecy about that.

Chuck: That'd be a good movie. That'd be a bad movie.

Josh: I don't know, man. It could go either way. I always see-I imagine it like Strange Brew.

Chuck: Oh yeah?

Josh: Yes.

Chuck: They could base it on the Stuff You Should Know tell-all book I'm writing.

Josh: Oh yeah?

Chuck: That would be exciting.

Josh: That would be very exciting.

Chuck: It'd be-

Josh: I'm looking forward to that book.

Chuck: -like a Lifetime Movie of the Week.

Josh: Do you like switch people's names? Like am I "Joe"?

Chuck: Yeah. [LAUGHS] "Joe Clack."

Josh: Yeah, exactly.

Chuck: No. It's sort of like-did you see the Saved by the Bell movie on Lifetime?

Josh: Oh yeah. Didn't Screech write a book? It was based on a book by Screech, right?

Chuck: Yeah.

Josh: Wasn't it, like, all sex and drugs and stuff?

Chuck: It was, you know-it was a bunch of teenagers in Hollywood. So sure, it was some of that in there. But it was-I didn't read the book, but the movie was bad and not nearly as salacious as he wanted it to be.

Josh: Right. I remember a lot of people being disappointed. And by remember I mean I recall the, like, two weeks ago when people were talking about it when it came out.

Chuck: It stunk. Emily and I'll watch some of those just terrible, terrible biopics occasionally on TV. And it's-it can be fun. Like, we watched the-who is the one actor? Brittany Murphy-the Brittany Murphy story.

Josh: Oh really? Did she have a heck of a story? Is she alive still, or did she die?

Chuck: No. She passed away because-

Josh: That's right.

Chuck: -under kind of weird circumstances because she and her husband both passed away within weeks of each other.

Josh: Weird.

Chuck: And there were all these strange claims that her house was poisoned-that they were poisoned and-yeah. It was fun.

Josh: What's your take on it?

Chuck: Oh, I don't know.

Josh: You're just a-

Chuck: That the movie wasn't very good.

Josh: Who played Brittany Murphy, do you remember? It was Julie Bowen, wasn't it?

Chuck: It's-

Josh: She's in all of those.

Chuck: -someone who didn't look very much like Brittany Murphy.

Josh: Julie Bowen.

Chuck: Okay.

Josh: I was right.

Chuck: That Ashton Kutcher guy was pretty good, though, I got to say.

Josh: Steve Jobs played him?"

Chuck: They should've just gotten Ashton Kutcher to play himself.

Josh: Yeah. He's not doing much. He's on what, Two and a Half Men?

Chuck: I don't know.

Josh: That's got to require 15 minutes of work a week.

Chuck: He's selling cameras.

Josh: Do you remember when that whole Two and a Half Men thing was going down? We were in L.A., and for the one and only time in my entire life I see Jon Cryer, that day.

Chuck: Oh, during the Charlie Sheen meltdown?

Josh: Meltdown. Like the day of the meltdown.

Chuck: Yeah.

Josh: Like, it happened at night and within eight hours I saw Jon Cryer for the first time in person, at a McDonald's.

Chuck: Did you yell "Duckie"?

Josh: No. I left him alone; he looked stressed out.

Chuck: Well, yeah. He's probably like, "My career is going down the tubes." But little did he know.

Josh: He's a survivor.

Chuck: Yeah. His career is just fine.

Josh: Yeah. So X-rays-

Chuck: Yeah. [LAUGHS]

Josh: -is what we're talking about, right?

Chuck: Yep.

Josh: Have you ever-

Chuck: That was the lightest part of this podcast.

Josh: I like this one. This one-it's one of those things where if you can just hang on by your fingernails, it can click. And then you lose it again. But that means that it could click again, later on. That's what I like about it.

Chuck: Good. I'll leave that to you. I've got lots of other stuff about it that-

Josh: Oh, you do?

Chuck: I totally understand.

Josh: Good, good. So have you ever broken anything and needed an X-ray? Or has it all just been dental stuff?

Chuck: You know what, dude? Never broken a bone. Knock wood.

Josh: You'd better knock on wood.

Chuck: Yeah. I mean, I've had-my injuries were always stitches. I was always getting busted open.

Josh: Oh yeah?

Chuck: Rocks and sprinklers, and I was always getting cut and sewed back up. But I never broke a bone.

Josh: That's great.

Chuck: Yeah.

Josh: You should probably knock on wood one more time just to be safe.

Chuck: Yeah.

Josh: So, yeah. All of my X-rays, too, have been just going to the dentist or whatever.

Chuck: You never had a bone broken?

Josh: I don't want to say because I don't even know if knocking on wood will do it.

Chuck: On laminate IKEA wood?

Josh: That would just be so horribly interesting if both of us broke a bone after this.

Chuck: Yeah. And we're at the age where, like-you should break bones when you're a kid, where you're like, "Eh, whatever. I'll get a cast." At this age it's a drag.

Josh: Yeah.

Chuck: Yeah.

Josh: I remember reading, like, a Tom Clancy novel and, like, some kid got an arm torn off or whatever and one of the surgeons was like, "If the arm is in the same room as the kid it can be healed."

Chuck: Right.

Josh: That doesn't hold true when you're Tom Clancy's age.

Chuck: [LAUGHS] No.

Josh: So you are familiar with X-rays, though? You've seen them before? You've watched ER, surely?

Chuck: Yeah. I mean, I've had X-rays for like-the dental ones like you said. And then just other various like chest X-rays for sicknesses and things like that.

Josh: Right.

Chuck: Which I think may be a little frivolous, to be honest.

Josh: Yeah, and kind of dangerous really.

Chuck: Yeah.

Josh: Conceivably.

Chuck: Sure.

Josh: Which we'll get into later. But did you-were you familiar with X-rays at all beyond that? Did you know that they were invented-or discovered-accidentally?

Chuck: Yeah. I did know that.

Josh: I did not.

Chuck: That's one of the few things I know. I saw a little, like, quickie short on some, like-it might have been actually Science Channel.

Josh: I looked all over. The most I could find was a dude on Siemens just describing it in the most flat affect one person could ever-

Chuck: I watched every single one of his videos.

Josh: Yeah. I got to five and five wouldn't load and I was like, "Forget this."

Chuck: Yeah. Five never loaded for me. I watched the other 14, though, and the whole time I was going, "Man, these are a minute long. Please join them all together into one six-minute video."

Josh: I know. It was so weird.

Chuck: Yeah. It was pretty silly.

Josh: And-

Chuck: But he was good, he was just very dry.

Josh: Yeah. And they spent zero pennies on any kind of soundtrack or anything.

Chuck: Yeah.

Josh: Like, if he grabs papers, you hear papers rustling in the classroom. It was pretty straightforward.

Chuck: Yes. But that's a very wind-about, roundabout way of getting to its discovery in 1895 by a German physicist named WilhelmRöntgen.

Josh: Nice.

Chuck: And he was testing whether cathode rays could pass through glass, and he saw that the fluorescent screen was glowing when he turned on his electron beam, which wasn't a big deal, but he was like, "Wait. This has got cardboard around it."

Josh: Right. There shouldn't be any visible light escaping.

Chuck: Which is silly to think of now.

Josh: Well, yeah, it is. But you have to put yourself in his shoes. Like, X-rays -

Chuck: 1895, sure.

Josh: -hadn't been discovered because he was literally on the verge of discovering them right then.

Chuck: That's right.

Josh: And yeah. So he was like, "This is very curious that this is fluorescing."

Chuck: Yeah, and he noticed other things were glowing and eventually he started putting other objects between the tube and the screen. They glowed-the screen did, that is. Finally, he put his hand there-

Josh: I read his wife's hand.

Chuck: Oh really?

Josh: Yeah. He's like-

Chuck: Either way.

Josh: -"Come in here for a second."

Chuck: Yeah.

Josh: "I want you to try something."

Chuck: And saw bones projected, and then I guess, probably poo-pooed his pants and said, "Man. I think I'm onto something here."

Josh: Yeah.

Chuck: It was really that quickly.

Josh: Right.

Chuck: He was, like, immediately the application was clear. It wasn't one of those things where it took 20 years.

Josh: Right.

Chuck: He was like, "Hold on. You can see bones. This could be really helpful."

Josh: Yes.

Chuck: And he won a Nobel Prize.

Josh: Very rightfully so.

Chuck: This first one ever for physics. And he named them X-rays because he didn't know what the heck it was.

Josh: No. Exactly.

Chuck: So it was like kind of signing your name if you can't write.

Josh: He probably-I think he assumed that later on future scientists would fill in the blanks. But they were like, "No. We're cool with X-rays."

Chuck: Well, he probably thought that someone would eventually call it, like, the Röntgen Ray-

Josh: Right.

Chuck: -or something.

Josh: He wasn't much of a self-promoter.

Chuck: No.

Josh: He was just like, "I'll just call them X-rays as a placeholder."

Chuck: Yeah. And he didn't patent anything, you know? He never, like, made money off of it.

Josh: No.

Chuck: And then just a few years-

Josh: And his wife has had hand cancer as a result.

Chuck: Really?

Josh: No.

Chuck: Oh. I was laughing but-

Josh: No, she didn't.

Chuck: -that would be very sad.

Josh: It was just a joke. You can proceed with the laughter.

Chuck: Okay. Plus I've never heard of hand cancer.

Josh: Right. It's got to be out there.

Chuck: And then a couple of years later they were already using it. In the Balkan War was the first time it was really put to practical use to protect-

Josh: The first Balkan War? The one around World War I?

Chuck: I guess. Was that-well, no-1897.

Josh: Oh, that Balkan War. I didn't know that existed until just now.

Chuck: Yeah. And they said, "We can see bullets and shrapnel and stuff now, which is helpful."

Josh: It is extremely helpful. So, like, this guy, Röntgen, discovers X-rays and their most practical application in one fell swoop, basically.

Chuck: Yep.

Josh: And a little further study revealed that X-rays are actually just another part of the electromagnetic spectrum, of which radio waves, microwaves, what we call visible light.

Chuck: Yeah.

Josh: What else is on there?

Chuck: Well, I've got my handy wallet electromagnetic spectrum card.

Josh: Yeah?

Chuck: And X-rays fall between gamma rays and ultraviolet rays on that spectrum.

Josh: Right.

Chuck: Which are all below-well, you say below-I don't know if it's-it's not really an above or below situation-visible light. And then infrared, microwave, and radio waves.

Josh: So it would be the higher or lower frequency. Because that's how the whole thing is divided.

Chuck: Yeah.

Josh: So like the visible spectrum of light consists of electromagnetic radiation that has a frequency, a wavelength that our eyes are sensitized to, so we can pick up visible light.

Chuck: That's right.

Josh: But there's plenty of other stuff on the spectrum of electromagnetic radiation, and all of it is delineated by the frequency, the wavelength. So at the highest end you have gamma rays that are like, "Ninini-ninini."

Chuck: Yeah, that means the squiggly line is very close together.

Josh: Exactly. And then on the furthest end you have radio waves that are like, "Wooo-wooo."

Chuck: And that means the squiggly line is far apart.

Josh: Exactly.

Chuck: And that is called Chuck Science. [LAUGHS]

Josh: That's good stuff.

Chuck: Yeah.

Josh: So-

Chuck: Put this back in my wallet.

Josh: Right next to the-what else you have in there?

Chuck: I just have my Pabst Blue Ribbon membership card.

Josh: Nice. [LAUGHS]

Chuck: Which I actually do.

Josh: Do you really?

Chuck: Yeah. But I've had it for like 20 years.

Josh: Wow. You got it when you were like seven, eight?

Chuck: Yeah. You flatter me.

Josh: So X-rays fall, I guess, where? About in the-

Chuck: Sort of below the middle-

Josh: Yeah, on the higher end. They have a higher frequency as far as the electromagnetic spectrum goes. But the point is, is that it is ultimately the same thing. It's a type of electromagnetic energy that is carried on a photon, which is a particle of what we would call light.

Chuck: Yeah. And we talked about photons aplenty in this show. And the same, like, photons produce the visible light that we can see. Photons blast out from the sun. How long does it take? Like-

Josh: It takes light a 100,000 years to get from the core to the surface, and then, like, eight minutes to get from the surface to Earth.

Chuck: That's right.

Josh: Man. I love that fact.

Chuck: So this is the only part I understand, so I'll lead with it. If you want to imagine an atom-a nucleus of an atom-and rings around that atium-atium?

Josh: That's a new word.

Chuck: An atom as orbitals, when an electron drops to a lower orbital, it releases energy in the form of a photon.

Josh: And the electron will always drop to the lower orbital.

Chuck: That's right.

Josh: So, like, if an orbital is-if an electron is kicked off of a lower orbital, an electron in the higher orbital goes, "Yeh," and drops down to that one.

Chuck: Yes. And depending on how far it drops is going to determine the energy level of that photon.

Josh: That it releases as energy when it drops, right?

Chuck: Yeah, because it doesn't have to-it can drop more than one orbital.

Josh: Right.

Chuck: It can skip down I don't even know how far. But a long way.

Josh: Yeah, it can. And like you said, the greater the distance between the two orbitals-or the greater the energy differential-the greater the energy that photon, when released, will have, right?

Chuck: That's right.

Josh: And as we said, photons are the energy carriers of the electromagnetic spectrum. And depending on that energy, or the frequency-the wavelength of that photon-that determines what kind of photon it is, right? Whether it's a radio photon or an X-ray photon, or a photon that we can see that's in the visible spectrum.

Chuck: That's right. Sometimes when these photons are flying around, they will collide with other atoms and sometimes those atoms absorb that photon's energy and then kick it up to that higher level again.

Josh: Right. But it has to be, from what I understand-and I saw that there's like-of course it's science, so there's like-atomic science-so there's little exceptions to this and that.

Chuck: Sure.

Josh: But from what I could see, Chuck, there is-the energy of that photon has to exactly match the energy differential between one orbital and another on an atom, so that it can kick it up so that it hits that one electron on the lower orbital, kicks it up to the higher orbital, and thus transfers its energy. Which means that atom just absorbed that energy that that photon was carrying, right?

Chuck: That's right.

Josh: But if it's a little less, it's not going to have the energy to kick that electron up, which makes sense to me. Right?

Chuck: Yeah.

Josh: But if it's a little more-this is what doesn't make sense to me-it doesn't kick the electron up and then the photon carries on in a diminished energetic state, it just doesn't do anything. It doesn't interact with that. It has to be exact-say, like the energy differential between orbits is eight.

Chuck: Yeah.

Josh: So a photon has to have an energy of eight or else it's not going to do anything with that atom.

Chuck: That's right.

Josh: Okay.

Chuck: And so depending on the-well, let's say you have a radio wave. They don't have very much energy, so they can't move electrons between these orbitals; they just pass through things. X-rays are super powerful.

Josh: Right.

Chuck: There's lots of energy, so they can pass through things, which is key if you want to check out your bones from outside of your body.

Josh: It is. And we're going to explain exactly how right after this.

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Chuck: What's that?"

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Chuck: In that afternoon slump, buddy, you know what I do?

Josh: What?

Chuck: I chow down on some Peanut Butter Nom Noms, and that does the trick.

Josh: Yeah, well, my go-to favorite is the Salted Caramel Pretzel Pops. They're just addictive.

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Chuck: You're welcome.

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Josh: Okay. So we're back, Chuck, and you tantalized everybody by saying that this difference in absorption is what produces X-rays, right?

Chuck: Was that tantalizing?

Josh: I was tantalized.

Chuck: Okay.

Josh: And I even know what's coming.

Chuck: All right. That's how excited I am about X-rays.

Josh: Good. So consider this: like, different atoms have different atomic weights.

Chuck: Yeah.

Josh: They have different densities. They're just different. Like, different atoms are different. And atoms also have what are called differences in radiological density.

Chuck: Right.

Josh: Okay? So a really high energy, high atomic weight, very dense atom is going to be able to absorb a lot of energy. Smaller atoms that maybe are looser and have a lower atomic weight are going to get kicked around by any old photon that wants to come along.

Chuck: Yeah. And that's key, like I said, if you want to see bones, because your soft tissue-if you've ever noticed when you have an X-ray-you'll see the bones but, you know, the rest is just sort of a grayish black mess.

Josh: Exactly.

Chuck: Because your soft tissue has smaller atoms, your bones' calcium atoms are much larger. So they're going to absorb those X-ray photons.

Josh: That's exactly right.

Chuck: They do it really well.

Josh: Exactly. So imagine you have-let's say, Chuck-let's go back and hang out with Tuk-Tuk, right?

Chuck: Oh man.

Josh: Let's get back in the way-back machine.

Chuck: It's been a while.

Josh: Okay.

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Chuck: Look at him over there.

Josh: So here we are in France, in this cave. Tuk-Tuk has his hand up against the cave wall, as you'll see.

Chuck: Yeah.

Josh: And in his other hand he's got that little straw filled with pigment-red pigment-and he's blowing it on his hand, right?

Chuck: Sure.

Josh: And now that he moves his hand away, there's the outline of his hand.

Chuck: Like, it's called a stencil, right?

Josh: Exactly. He's just made an early stencil.

Chuck: Sure.

Josh: He's like Banksy, basically.

Chuck: Right. [LAUGHS]

Josh: Like a caveman Banksy. But if you look at the back of Tuk-Tuk's hand-don't get too close, but look at the back of his hand-it's covered in red pigment, right?

Chuck: Yeah.

Josh: So if you can-if you want to equate this to an X-ray, the hand absorbed all of that pigment and the stuff that passed through left the picture on the cave wall. That's kind of what happens with an X-ray, except with an X-ray photograph the X-ray photons are absorbed the denser, calcium-rich bones and they pass through the softer tissue. So the picture that we have is the outline, the silhouette, of the bones because the X-rays made it through the tissue. Didn't make it through the bones; they made it through the tissue and onto the X-ray plate, which absorbed the picture in negative.

Chuck: That's right. And I'm glad you said "picture" because that's all it is on the other side of the human being-you know, that they're shooting the X-ray at-there's a camera and you're just going to get a regular negative and they can make it a positive, but they leave it as a negative because you really don't need the positive image.

Josh: Right.

Chuck: And that's what they'll put on that little screen to show you you're cracked femur.

Josh: Exactly. And they can see the crack because some of those X-rays will make it through the gap.

Chuck: That's right.

Josh: So all you're seeing is the result of X-rays that made it through the tissue-were absorbed by the bone-so those don't make it to the plate. The ones that make it to the plate cause the chemical reaction that gives you your negative, your X-ray. And it's pretty simple really. Like, if you think about it, at least in principle, it's also extraordinarily difficult to conceive of, but if you understand, like, the principle behind it, it makes utter and complete sense.

Chuck: Yeah, and it's a pretty focused shot that they're using there. It's not like-they don't fill the entire room with X-rays, you know? They've got a thick lead shield around the whole device and it, you know, contains everything and it's got a little small window that's just going to let that narrow beam pass through, through a series of filters, and basically hit you wherever they want to hit you.

Josh: Yeah. And the reason that they use lead is because lead is an extremely dense-yeah-element, yes. Right?

Chuck: Sure.

Josh: Oh God, I hope so. With a very high atomic number, which means it can absorb tons of energy, right?

Chuck: Yeah. That's why you're going to wear a lead apron if you're not, you know-if you're getting your skull done, you're probably going to wear an apron on your chest, let's say.

Josh: Sure. So this lead is being bombarded with X-ray photons and electrons and it's just taking it, it's fine. And it's not being able to-it's not able to pass through because it doesn't have high enough energy. But yes, when they put that little window in the X-ray-generating machine, it passes right through there in a concentrated beam. And Chuck, let's talk about the machine, right? So-and this is basically-what we use as X-ray machines is essentially what Röntgen made-was experimenting with when he accidentally discovered them. Because if you look for X-rays, like, they propagate naturally. But I think, like, 20% of the X-rays on Earth come from humans.

Chuck: Oh really?

Josh: Yeah. Like, we generate a lot of X-rays. They don't come, like, you don't find them normally on Earth. They're coming from outer space to us.

Chuck: Okay.

Josh: Hence X-ray astronomy. But the ones here on Earth that are generated on Earth-it's not like rocks put out X-rays or something like that. We do.

Chuck: Humans. [LAUGHS]

Josh: We humans do. Humans and lead aprons put out X-rays. And they use this machine like Röntgenmade.

Chuck: Yeah. What you have in the machine, you have an electrode pair, cathode and an anode, and that's inside a good old-fashioned glass vacuum tube, which-it's amazing how vacuum tubes are still like the best way to do many of these things.

Josh: Well, it allows things to travel at the speed of light easily.

Chuck: That's right. And it allows guitar amps to sound great.

Josh: I didn't know they use vacuums in that. Oh, is that a cathode tube? Yeah.

Chuck: Yeah. Like the best amps are still made with vacuum tubes.

Josh: Nice.

Chuck: You can get solid-state amps but they're just-the sound isn't as rich. So it's kind of like this old technology that's still superior.

Josh: Right. They're all pumped out by hand by a 90-year-old man in Tennessee.

Chuck: Mr. Marshall.

Josh: Yes.

Chuck: No. So the cathode is a heated filament, just like you might see in a light bulb, and the machine is going to pass a current through that and heat that thing up. And then it's going to spit electrons off that surface and it's going to hit a disk made of tungsten, and it's going to draw those across the tube. It's basically-the tube is sort of the key piece.

Josh: Right. Because you've got the positive and the negative charge, the cathode and the anode, right?

Chuck: Yeah.

Josh: And that difference, that electrical charge, draws those electrons down to the anode.

Chuck: Yeah, with a lot of force.

Josh: Yeah, and that forced means that when those electrons hit the tungsten anode, it knocks a bunch of electrons off, creates a bunch of X-rays in the process, and you have a whole box filled with X-ray radiation.

Chuck: A box full of X-rays.

Josh: That's exactly what it is. Like, you're just-I mean, there might as well be, like, a foot crank to this thing, like an old sewing machine, for as technologically advanced as it is.

Chuck: There may be for all I know. I don't know what goes on in that other room.

Josh: Right. Yeah.

Chuck: You know?

Josh: True. There's some dude in there with like-his right leg is three times more muscular than his left leg because that's the only one he uses. So in addition, like I said, to X-rays being created, the other X-rays-other photons can go on and knock more electrons off.

Chuck: Right.

Josh: So you have what's like a process of chain reaction starting, right?

Chuck: Yeah.

Josh: It's not like one gets hit and then that's hit and a photon is created and t just hangs around until it's beamed out.

Chuck: Right.

Josh: Like, you're just generating this huge amount of X-rays and the X-rays are also continuing to propagate themselves because they're knocking more electrons free. And the more free electrons you have, the more interactions you have, right?

Chuck: Right.

Josh: So one of the ways that more electrons can be knocked off-you don't even need a direct transfer of energy where a photon is absorbed or knocks an electron from one orbit to another, or knocks it loose entirely. A photon actually has this really cool capability of just orbiting close by the nucleus of an atom, and when the nucleus basically draws it into its orbit, the photon just takes a hard left turn.

Chuck: Yeah. Just bumps it off its course.

Josh: But even, like, the Dodge Viper has to, like, slow down to take a left turn-slow a little bit, right?

Chuck: Just a little.

Josh: Just a little.

Chuck: Yeah.

Josh: But that little bit in photon world means a transfer of energy from the photon outward. And then-

Chuck: Yeah, as an X-ray.

Josh: Yeah. And then the photon, like, the photon takes that left turn and the energy is transferred to the atom.

Chuck: Yeah. And one of the byproducts-if this sounds like it's going to create a lot of heat it's because it will. And in order to combat this they rotate this anode to keep it-it would just melt down if you kept it in place.

Josh: Yeah.

Chuck: And apparently there is a cool oil bath that helps absorb heat as well, which I never have heard of that either.

Josh: It sounds oily.

Chuck: A cool oil bath.

Josh: Yeah. It doesn't sound refreshing at all; it sounds like the opposite of refreshing.

Chuck: Yeah. Cool and oil don't really go together.

Josh: No.

Chuck: Yeah.

Josh: And I misspoke. That's an electron that can be drawn into the nucleus of an atom. Appropriately enough because they orbit nuclei anyway.

Chuck: Right.

Josh: But it doesn't have to hook up with that atom. When it takes that hard left it emits the photon, like you said.

Chuck: That's right. And like I said earlier, there's a camera on the other side of the patient and it's going to record that pattern of light when it passes through the body, and it's not so different from a regular camera. And then the end you're just going to get a picture like I said, a negative image.

Josh: Yeah, and if you hook it up with a computer that allows you to take X-rays basically in slices, you can come up with computerized tomography.

Chuck: Yeah, AKA CT.

Josh: Right.

Chuck: A CT scan.

Josh: Exactly. If you use-if you get a breast exam or you're using a type of X-ray called mammography.

Chuck: Yep.

Josh: And then there's a fluoroscopy, which the man in the extraordinarily dry presentation from Siemens said was basically like moving picture video.

Chuck: It's like a movie.

Josh: Exactly. And then he showed us-

Chuck: A flipbook. [LAUGHS]

Josh: -what a movie is with a flipbook, right?

Chuck: That old flipbook trick.

Josh: And if you listen to this podcast, I'm sorry-I just want to apologize for both of us, Siemens guy.

Chuck: Oh yeah.

Josh: Like, hat's off to you for doing that at all.

Chuck: Yeah. Because he's probably saying, "Well, at least I was correct in everything I said." [LAUGHS]

Josh: Exactly. [LAUGHS] That's a good point, sir. But with fluoroscopy it's basically like a movie of-an X-ray movie-and you would do this to make sure, like, a heart is beating correctly because you wanted to see it. But you have to have an additional instrument, because as we've said, X-rays will pass through tissue like heart tissue and muscle tissue and all-and blood vessels, and all the stuff you want to get pictures of using an X-ray. So you have to use something called a contrast media for it.

Chuck: Yeah. A contrast agent is basically more dense than the soft tissue. So if you want to, let's say swallow-it's usually like a barium compound-and if you want to examine, like, your blood vessels or your circulatory system, sometimes they can inject that, or you might drink it, to see if you are doing like a gastrointestinal-like a GI tract-you're going to swallow that stuff.

Josh: Yeah.

Chuck: Which I've never had to do. I think my dad had to do that.

Josh: Yeah.

Chuck: I don't think it's super pleasant.

Josh: I get the impression not too.

Chuck: But-

Josh: I think my dad did it, as well.

Chuck: Yeah. It's an old guy thing.

Josh: Yeah.

Chuck: So I should be getting one soon.

Josh: Yeah.

Chuck: And then it allows you, you know, to see a moving image. Basically, how that liquid is, if there is any blockage. There's all sorts of applications for it.

Josh: Yeah, because your-that liquid has a high radiological density, which means that the X-rays don't just pass right through the tissue that it's being suspended in, like your blood vessels. It absorbs it for it. So you get a picture of your blood vessels, your circulatory system, which is pretty cool; it's pretty clever. It's also extraordinarily elementary in principle, my dear Watson.

Chuck: That's right. In that single picture I think, you know, we mentioned CT and mammography and all that, and fluoroscopy, but the single picture is just called standard radiography, and that's when you're taking a photo of your skull or your lungs, or your bones or your teeth.

Josh: And so speaking of the lead apron thing, man, it's always made me kind of nervous. Like, if the rest of my body has to wear a lead apron, but you're shooting an X-ray into my head, am I going to be okay?

Chuck: Well, we'll answer that right after this message.

Josh: Okay.

[MUSIC]

Josh: Chuck?

Chuck: Yo.

Josh: Security is huge these days, right?

Chuck: Oh yeah, man.

Josh: Everybody wants their email secure, their phone calls secure, their chats secure. Like, everything that you do in life you want secure, because there's a lot of people listening and watching and that would love to get their hands on that info-whatever it is your have to say, right?

Chuck: Yeah, I mean, it seems like every day in the news we're hearing about some new security leak.

Josh: Exactly. But the goofy thing is all of us are just holding our web conferences like they just exist outside of this whole security idea.

Chuck: Yeah. They're just leaving this so unprotected, and that is not a good idea.

Josh: No.

Chuck: That's why it's super important to consider the security of your web conferencing by using OmniJoin web conferencing from Brother. They make security priority number one.

Josh: Yep. OmniJoin web conferencing from Brother, and its military-grade encryption, is used today to provide services to industries in the healthcare, government, education, and other sectors. Why wouldn't you use it yourself?

Chuck: Yeah, because if you think about it, it's even creepier for a web conference to be spied in upon, you know?

Josh: Yeah. And it doesn't matter how you hold your web conferences, there's public and private cloud options. So there's a solution that fits everybody's security needs.

Chuck: That's right, buddy. And right now we have a great deal for our listeners if you www.OmniJoin.com/stuff for a 14-day risk-free trial, and you can see for yourself how easy it is to use. That's www.OmniJoin.com/stuff, and you can take web conferencing security seriously finally, and meet smarter with OmniJoin.

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Chuck: All right. X-rays, are they bad for you?" The answer is yes. Pretty unequivocally. But like all things, it's in moderation is the key.

Josh: Sure.

Chuck: In the 1930s and '40s and into the '50s, they had X-ray machines at shoe stores-

Josh: Oh yeah, I knew that.

Chuck: -so they could X-ray your feet to get a better fit. And they didn't realize at the time that they were X-raying people way, way too much.

Josh: You had talkative kids in class, they'd just shoot 'em with an X-ray and-

Chuck: Would they?

Josh: No.

Chuck: Oh. They probably did.

Josh: Man, I've got you like twice today.

Chuck: Well, no, I'd believe that. Like, "Hey, let's look at his brain. There may be a mouse running around inside of it."

Josh: Yeah. People in the '30s were dumb.

Chuck: Well, it's basically radiation sickness. It's a form of ionization, or ionizing radiation.

Josh: Right.

Chuck: So what can happen, like, if just normal light hits an atom it's no big deal. But when an X-ray hits an atom, it knocks electrons off of it, creates an ion, which is an electrically charged atom, and basically anything from cellular death to mutation can happen at that point.

Josh: Yeah.

Chuck: And mutation can spread and it can cause cancer.

Josh: Right. Because stable atoms are neutral, right? Because they have an equal number of protons and electrons. You lose an electron, all of a sudden you have a positively charged ion and that negatively charged electron running around and it just causes trouble. And you said, light-visible light-can be absorbed and it's no big deal because visible light is-exists on a wavelength that's about in tune with the soft tissues of our body, right? So we know how to absorb it and it makes us tan, and that's cool, right? But with these ionized atoms-these positively charged atoms, like, going around in your body-it can cause a lot of problems, like mutations like cancer, right?

Chuck: Yeah. I mean, if you break that DNA chain, that's not good for your cells.

Josh: No, it isn't. And one of the results is the DNA can basically lose its ability to regulate itself and it-the cell replicates more frequently than it should. And all of a sudden you have a tumor on your hands, and that can spread. It can also be a problem if that DNA break occurs in utero because then that can lead to birth defects, which is why pregnant women shouldn't get X-rays.

Chuck: Yeah.

Josh: And it can also just lead to plain old cellular death.

Chuck: Yeah.

Josh: If you have cellular death in the tissues that are made up by those cells break down and you have a problem on your hands with that, as well.

Chuck: So here's the deal: we get exposed to radiation every day, just walking around on the planet.

Josh: Yeah.

Chuck: It depends on where you live, but every year the average person is going to be exposed to anywhere from one to four-it's measured in millisieverts per year-like I said, depending on where you are. I think in higher elevations it's less than at sea level. So if you live in Denver, Colorado, you're going to be exposed to less.

Josh: Well, yeah, because-

Chuck: Than at like Death Valley.

Josh: -you're higher up in the atmosphere and that makes a difference.

Chuck: Exactly.

Josh: You have less protection, right?

Chuck: Yeah. So you know, what they want to do, medically speaking, they want to use-or they're supposed to use-the minimum amount to achieve the pictures you need. It's not like the old days where they're just like, "Let's do 20 X-rays."

Josh: Just blast you with the-

Chuck: Like, let's do the minimum amount we need to get the information that we need. A CT scan can get your-you know, you lay down in the tube and it rotates around you and your whole body can be photographed in less than five seconds these days.

Josh: Nice.

Chuck: But you know, there are concerns if you get too many X-rays, still. Like, a dental panorama, I think, what did I say? One to four millisieverts per year. A dental-

Josh: And it's cumulative, too, you should say.

Chuck: Yeah.

Josh: Like, it's not like you get one and then, you know, eight months later you get another one and that first one went away.

Chuck: Sure.

Josh: Like, it accumulates over the course of a year.

Chuck: Yeah. So here's just a few examples of how much radiation you're being exposed to with X-rays. A dental panorama is going to be 0.01 millisieverts-so not very much. Like, two chest X-rays might be 0.1, a mammogram is around 0.4, your pelvis 0.6, your back-upper back-may be 1.0.

Josh: I wonder why? Because there's so much-

Chuck: I don't know.

Josh: -bone there?

Chuck: Maybe. Yeah, maybe it has to do with exposure to-yeah, that makes sense.

Josh: I got a ton of bone in my upper back.

Chuck: [LAUGHS] A full CT scan, it depends on what you are-it depends on what you're X-raying, but a CT scan is obviously more. Like an abdominal or pelvic CT scan can be as many as 10 millisieverts.

Josh: Yeah.

Chuck: So that's like up to two or three years' worth of radiation in a single CT scan.

Josh: Yeah.

Chuck: Which can be problematic, which is why they don't say "Get in the CT machine" like every other week.

Josh: Right.

Chuck: But, you know, some of the reasons you might: if you had a traumatic injury, they're going to X-ray you; a lot of times for disease confirmation they'll use an X-ray machine; during surgery as a visual guide-like if you do endoscopic surgery, the surgeon actually needs to look at something, so sometimes there's X-rays for that. Or to monitor your healing process. You know, when you break a bone, it's not just that first X-ray.

Josh: Right.

Chuck: You're going to keep getting them to see how you're healing up. Or-

Josh: This is right out of the Siemens video, huh?

Chuck: No.

Josh: It isn't?

Chuck: Uh-uh.

Josh: Oh, okay.

Chuck: I don't think so. I mean, I looked at so much stuff; it all runs together.

Josh: Yeah, I mean.

Chuck: I call it cumulative research.

Josh: So I did a BrainStuff on sieverts and how many we can take.

Chuck: Yeah?

Josh: And yeah, it's kind of like-it's a little alarming-

Chuck: Sure.

Josh: -how much radiation we're exposed to. People who fly a lot, too, are exposed to tons of radiation. Because you're, again, higher up in the atmosphere so you're less protected by the atmosphere.

Chuck: Speaking of flying, of course baggage that is X-rayed, the food industry uses X-rays a lot. Archeologists use it if they don't want to, like, destroy an object and they want to see what's inside. Or scientists will use X-rays for rocks to see what kind of mineral composition. So there's all sorts of applications; it's not just medical. Space. X-ray telescopes out on satellites. Apparently you can see a lot. You can see things you can't detect from an Earthbound telescope because X-rays are absorbed by our atmosphere so you can't, like, shoot it into space like that.

Josh: So this article makes a pretty good point, if you ask me. It says, like, yes X-rays are bad for you and you should use them with care and caution. And one good point is to always ask if there is an alternative to an X-ray, just to basically say, "Hey, Doc"-or dentist-"Slow your roll."

Chuck: Yeah.

Josh: "Let's-is there another way we can get this information without an X-ray? I know it's the easiest, but what are the alternatives?" But then the article makes the point, like, it's still safer than the ultimate alternative-the thing that X-rays replaced-which was exploratory surgery. You know?

Chuck: Yeah. Back in the day if they thought you had cancer, they would cut you open and see. And this is definitely better than that.

Josh: Yeah, or broken bone. Imagine getting that arm cut open just to see how it's doing.

Chuck: Yeah. They're like, "No. It's not broken."

Josh: Right. And we haven't invented anesthetic yet, so joke is on you.

Chuck: Good luck with your dentist, by the way, because I always get the feeling that the dentists are like, "No. Your insurance allows us to bill for so many per year."

Josh: Right. Exactly.

Chuck: "So that's how many you're going to get."

Josh: "These X-rays are putting my kid through college."

Chuck: Yeah.

Josh: You got anything else on X-rays?

Chuck: No.

Josh: That was a fine amount of stuff. I'm feeling good about it. You feel good about this one?

Chuck: Sure.

Josh: I do too.

Chuck: Yeah.

Josh: If you want to know more about X-rays, you can check out this really informative article on HowStuffWorks.com. It's got some great diagrams that explain a lot of the stuff we were saying visually. And you can type "X-ray" into the search bar at How Stuff Works and it'll bring that up. Since I said search bar, it's time for listener mail.

[CHIMES]

Chuck: This is from my buddy Poppi in Vancouver, Stuff You Should Know listener that I met while I was there. And Poppi has this to say. He's got a pretty cool job. He listened to the PTSD show and wanted to write in about another option that he works with. He's a registered acupuncturist in Vancouver with special training in trauma and addictions. He has a program called Neurotrophic Stimulation Therapy, NTST, and a large part of the program uses ear acupuncture and electroacupuncture to promote neuroplasticity in the brain. He says, "You can't necessarily directly fix the brain, but you can stimulate the ear nerves and it will help the brain re-regulate certain functionality so it can heal itself." He's been treating trauma and PTSD patients for several years and the evidence for its efficacy is high. It can be done with acupuncture needles alone or in combination with a mild electrical stimulation. Remember we talked about-

Josh: Transcranial electromagnetic stimulation?

Chuck: Yeah. Transdermal cranial stimulation. He says that's one of the things that he's also using to treat PTSD, which is pretty cool.

Josh: Wow.

Chuck: And he said, "It makes cognitive behavioral therapies so much easier to introduce because it promotes neuroplasticity and the results help a PTSD sufferer to be more open to and able to receive positive social programming." So he has a program we want to promote. If you want to see all the components in action in his program, you can visit Last Door Recovery Society at LastDoor.org/ntst, or you can donate funds to help purchase a brain scanner so that they can scientifically measure the results of the program, which would really help show the validity of the therapies. And if you're interested in helping out Poppi's cause there-because he's really big on treating veterans in Canada and the U.S. I shortened his little URL to Bitly. Bit.ly/11YNLOQ. And that is from Poppi and he says, "Namaste."

Josh: Thanks a lot, Poppi. Is it Poppi with an O?

Chuck: P-O-P-P-I.

Josh: Nice. If you want to get in touch with us, you can tweet to us @SYSKPodcast, you can join us on Facebook.com/StuffYouShouldKnow, you can send us an email to StuffPodcast@HowStuffWorks.com. That's right. And as always, join us at our home on the web: StuffYouShouldKnow.com.

[MUSIC]

Vo: For more on this and thousands of other topics, visit HowStuffWorks.com.

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