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How do MRIs work? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, have you ever broken a bone? I have,
0:10
Speaker 1: but it's kind of embarrassing. What happened? Well, the first
0:14
Speaker 1: and last time I ever went snowboarding, the first time
0:17
Speaker 1: down the mountain broke my wrist. Really the first time?
0:20
Speaker 1: What happened? You didn't see that tree coming? No, honestly,
0:23
Speaker 1: I was trying to avoid snowboarding over my girlfriend at
0:25
Speaker 1: the time, so it was a bit chivalrous. You took
0:27
Speaker 1: a hit for the for the team. That's exactly right.
0:30
Speaker 1: And then what happened? Did they take an X ray
0:32
Speaker 1: of you? Or how did they? How did they know
0:34
Speaker 1: it is broken? Yeah, well it hurt a lot, and
0:36
Speaker 1: then it took an X ray and you can actually
0:38
Speaker 1: see inside right, You could see that little bone was
0:41
Speaker 1: snapped off and in the wrong spot. Isn't that amazing?
0:43
Speaker 1: How signs can see inside of you? Hi am RhE.
1:03
Speaker 1: I'm a cartoonist and the creator of PhD comments. Hi,
1:06
Speaker 1: I'm Daniel. I'm a particle physicist by day and a
1:10
Speaker 1: sleeper by night. How did it where you just close
1:12
Speaker 1: your eyes and it happens. You should try it sometime.
1:16
Speaker 1: It really does help because you never remember the moment
1:18
Speaker 1: you fell asleep, right it's sort of mysterious. Yeah. I
1:21
Speaker 1: remember actually trying to teach my kids how to fall asleep,
1:23
Speaker 1: and then I realized I don't really know how, you
1:26
Speaker 1: just sort of do it. To teach in to a
1:27
Speaker 1: podcast where we sleep, I know we should do a
1:30
Speaker 1: whole podcast episode about that, like why do we sleep?
1:32
Speaker 1: What happens do we when we sleep? Why do we
1:34
Speaker 1: need to sleep? What would happen if you didn't sleep?
1:37
Speaker 1: So Welcome to our podcast, Daniel and Jorge Explain the Universe,
1:41
Speaker 1: a production of I Heart Radio in which we try
1:43
Speaker 1: to take your sleeping mind and wake it up to
1:46
Speaker 1: the amazing mysteries of the universe. We zoom all around
1:49
Speaker 1: and find interesting stuff and explain it to you. Yeah,
1:52
Speaker 1: we try to permeate your dreams with thoughts of the
1:55
Speaker 1: universe and the amazing, incredible things that are happening all
2:00
Speaker 1: around you. That's right. We are spurring the great awakening
2:02
Speaker 1: in physics by making sure everybody out there who listens
2:05
Speaker 1: to this podcast really knows what's going on. Because the
2:08
Speaker 1: universe is a crazy, amazing place and we want to
2:11
Speaker 1: share it with you. Part of what we like to
2:12
Speaker 1: do is to explain how even everyday things around you
2:16
Speaker 1: that you made use on a regular basis work. That's right,
2:19
Speaker 1: because there's incredible physics and the heart of the star
2:22
Speaker 1: and in the birth of the universe and in particle collisions.
2:25
Speaker 1: But there's also really amazing physics happening all around us
2:28
Speaker 1: in technology that we take for grant and technology that
2:31
Speaker 1: we use that our lives sometimes depend on but we
2:34
Speaker 1: don't really understand. Yeah, it's technology that saves lives and
2:38
Speaker 1: can sort of tell you and help people. Right, that's right.
2:41
Speaker 1: And it seems sort of like futuristic and awesome. You know,
2:44
Speaker 1: it's incredible that you can see inside somebody without cutting
2:47
Speaker 1: them open. So today on the podcast, we'll be talking
2:49
Speaker 1: about m r ees. How do they work, Why do
2:58
Speaker 1: they work? Do they work? Why do physicists want to
3:01
Speaker 1: see inside you? Anyway? Who gave in permission to look
3:04
Speaker 1: inside of you? I think it's a real question. What
3:06
Speaker 1: are you hiding that you don't want physicists to look
3:08
Speaker 1: inside you? I mean, if you're innocent, you have nothing
3:11
Speaker 1: to hide, right, Yeah, m RIS these are its tands
3:13
Speaker 1: for magnetic resonance imaging, right, that's right. And if you've
3:18
Speaker 1: ever been to the doctor and you have an injury
3:20
Speaker 1: or a broken bone or something funny going on inside you,
3:24
Speaker 1: or you just curious, like what's going on inside of me?
3:26
Speaker 1: Let's get myself checked out. Then you know you have
3:29
Speaker 1: several options for looking inside you. You You can do an
3:31
Speaker 1: X ray, you can do a cat scan, or you
3:33
Speaker 1: can do an m r I. You can do the lobotomy,
3:35
Speaker 1: you can they can just slice you like a Deli
3:37
Speaker 1: ham and check you out. But the nice thing about
3:40
Speaker 1: some of these is that they don't need to open
3:42
Speaker 1: you up. Right, it's non invasive, and you know that
3:45
Speaker 1: there are risks every time you do surgery, and so
3:47
Speaker 1: it's a great advantage to get to figure out what's
3:49
Speaker 1: going on before they go in and cut anything. So
3:52
Speaker 1: m r s are These are the kind that you
3:55
Speaker 1: sort of go, you lie down in a little platform
3:57
Speaker 1: and then they roll you into this kind of giant
4:01
Speaker 1: donut looking thing. Right. Yeah, it's like a big physics machine. Right.
4:05
Speaker 1: It's big, it's round, it glows, it makes really loud
4:09
Speaker 1: clunking noises. It takes a while, and uh, I've bet
4:12
Speaker 1: everybody who lies in an mri I is wondering like,
4:14
Speaker 1: what is this thing doing? Like is it zapping my brain?
4:17
Speaker 1: How does this thing actually work? Yeah, and it's because
4:20
Speaker 1: it doesn't really touch you, right, You just lie on
4:22
Speaker 1: this little platform and somehow it takes pictures inside of
4:27
Speaker 1: your body. Yeah, exactly. It can show you what's going on,
4:31
Speaker 1: and that's pretty powerful. If you're wondering if you have cancer,
4:34
Speaker 1: or if you have a tumor, or if there's you know,
4:36
Speaker 1: if your body is filled with bananas or something, m
4:38
Speaker 1: rs can answer that question, right. And what's amazing about
4:41
Speaker 1: m R I s I think is that they don't
4:43
Speaker 1: just take sort of like a picture, you know, like
4:45
Speaker 1: a like an impression, like a like a whole body picture.
4:49
Speaker 1: They really just kind of capture a slice of your body,
4:53
Speaker 1: and so you can get a really detailed model or
4:57
Speaker 1: reconstruction of your your entire all your all the tissues
4:59
Speaker 1: and a body. Right. Yeah, it's really pretty incredible. We
5:02
Speaker 1: had an m R I done of our daughter once
5:04
Speaker 1: and you can sort of turn the knob and see
5:06
Speaker 1: how like all the bits of the brain and the
5:08
Speaker 1: ear and stuff are all connected. It's it's amazing. It's
5:11
Speaker 1: like taking somebody and slicing them like a Deli hym
5:13
Speaker 1: without actually slicing them. Thank goodness for physics. Have you
5:18
Speaker 1: ever seen that Body Works exhibit where they actually take
5:21
Speaker 1: corpses and slice them super thin. I have, yeah, a
5:24
Speaker 1: few times. It's pretty shocking. It's pretty shocking, but that's
5:27
Speaker 1: basically what an m r I does. Also, right, gives
5:29
Speaker 1: you all these little slices that lets you look back
5:31
Speaker 1: and forth and see how things are connected and what's
5:33
Speaker 1: going on inside you. It's an incredible machine the body. Yeah,
5:36
Speaker 1: I guess what I mean is, you know, like when
5:37
Speaker 1: you I think a lot of people are familiar with
5:39
Speaker 1: X rays, you know, like if you go to the
5:40
Speaker 1: dentist or you broke a bone, will take an X
5:43
Speaker 1: ray of you. But an X rays is really just
5:46
Speaker 1: like they shoot you with rays, they go through your
5:48
Speaker 1: body and then they capture them on the other side, right,
5:52
Speaker 1: and so you're you're getting everything. You're getting like everything
5:55
Speaker 1: inside of your body's mushed into one image. That's right. Yeah,
5:59
Speaker 1: it's like integrated along the line of the X ray. Yeah,
6:01
Speaker 1: you're learning about the whole body that way. X rays
6:04
Speaker 1: can't do slices, yeah, and so the image is very
6:06
Speaker 1: like fuzzy, and it's hard to tell what's bone and
6:09
Speaker 1: what's an organ. But with an m r I you
6:11
Speaker 1: really get like a detailed, step by step slice of
6:14
Speaker 1: the entire the volume of your body. Yeah, and the
6:18
Speaker 1: benefit is you don't get cancer causing radiation. You get
6:22
Speaker 1: other kinds of cancer possibly, So I mean, you do
6:26
Speaker 1: get other kinds of radiation. But you know X rays
6:28
Speaker 1: are dangerous. They are ionizing radiation, and they deposit energy,
6:32
Speaker 1: and they can break up your DNA, And there's reasons
6:34
Speaker 1: why you should be careful when you make the decisions
6:37
Speaker 1: about having an X ray. You know X rays are great,
6:39
Speaker 1: but you know you wouldn't want an X ray every
6:41
Speaker 1: five minutes, um, you wouldn't want an X rays on
6:44
Speaker 1: tiny babies. An anti X rayer, I'm a judicious X
6:47
Speaker 1: rayer that you should start any movement there with MC
6:54
Speaker 1: say no to X rays every other time. No X
6:56
Speaker 1: rays or are wonderful, but you shouldn't just do them
6:58
Speaker 1: without thinking about it, because there really is the health cost.
7:00
Speaker 1: But with m R S it's different. You don't have
7:02
Speaker 1: that ionizing radiation and so you're not increasing your cancer risk.
7:06
Speaker 1: Even though it does sound crazy and feel weird to
7:08
Speaker 1: lie inside this two for an hour, have you ever
7:10
Speaker 1: taken an m R I of yourself like I've had
7:12
Speaker 1: my m R I taken. Have you ever done it
7:15
Speaker 1: and done it on yourself? I have had an m
7:17
Speaker 1: R I done once of my leg because I tore
7:20
Speaker 1: a muscle. I had the m R of my brain
7:21
Speaker 1: and my head done and they gave me the data.
7:24
Speaker 1: Whoa and what question were they looking to answer? There?
7:27
Speaker 1: How does this guy survive with no sleep? It's just
7:29
Speaker 1: a bunch of monkeys and bananis inside there? Where did
7:31
Speaker 1: all those amazing funny ideas and creative genius come from?
7:35
Speaker 1: That's what they wanted to know, surely for posterity, But no,
7:40
Speaker 1: it's weird. It's weird first of all because you you
7:42
Speaker 1: kind of get you get a sense of what your
7:45
Speaker 1: head looks like without hair. I mean no offense to
7:49
Speaker 1: bald people out there, but it's kind of shocking if
7:51
Speaker 1: you've always had hair to suddenly see kind of like
7:53
Speaker 1: the outline of what your head looks like. It's kind
7:55
Speaker 1: of that's bizarre, think number one. But then it's really
8:00
Speaker 1: weird to see all the you know, your eyeballs and
8:03
Speaker 1: the passages of your nose and and your tongue, and
8:07
Speaker 1: to think that like that's also you see all the
8:10
Speaker 1: fillings in your teeth, which is you know, a little embarrassing. Yeah.
8:13
Speaker 1: For me, it really highlights how much our bodies really
8:16
Speaker 1: are a machine. You know. I like to think of
8:18
Speaker 1: myself as a person and the mechanics of what supports
8:21
Speaker 1: that are, like to sort of abstract that away and
8:22
Speaker 1: think of myself with my identity, my personality, my thoughts.
8:26
Speaker 1: But when you look inside yourself, you see your this
8:28
Speaker 1: basically this meat machine, right, and this this organic robot,
8:33
Speaker 1: and it all has to work and pump and move
8:34
Speaker 1: and squish all the time, and it's incredible that it
8:36
Speaker 1: actually works. Ever, not to mention like mostly working for
8:40
Speaker 1: like seventy years at a time. No, I think that's
8:42
Speaker 1: the name of a heavy metal band meat machine machine.
8:46
Speaker 1: But anyway, so we were wondering how many people out
8:48
Speaker 1: there know how m R machine works. You know, a
8:51
Speaker 1: lot of people get them for various reasons and they
8:54
Speaker 1: can help save lives. But we were wondering if people
8:58
Speaker 1: out there new how this is amazing to achnology works. Yeah,
9:01
Speaker 1: So I walked around campus does I usually do, and
9:03
Speaker 1: I ask people if they knew what is an m
9:05
Speaker 1: R I and how does it work? Would you know
9:07
Speaker 1: how to respond if somebody asked you how an m
9:10
Speaker 1: R I works. Here's what people had to say. I
9:13
Speaker 1: have to do with strong magnetic fields. Okay, so how
9:17
Speaker 1: does that let you take a picture of the inside
9:18
Speaker 1: of your body? I'm not really sure. I'm probably there.
9:23
Speaker 1: The magnetic field will go through a certain part of
9:26
Speaker 1: your body, and depending on I guess how dense or
9:29
Speaker 1: how that the properties of the body part, it shows
9:32
Speaker 1: up differently with an image. It's a machine which scans
9:36
Speaker 1: you for abnormalities within the body. Do you know how
9:40
Speaker 1: it works? How does it see inside you? My guess
9:42
Speaker 1: would be radiation of some sort and punny, I think
9:46
Speaker 1: you drink something and they're able to see it. Um,
9:49
Speaker 1: I guess something's wrong with you. You know, you would
9:51
Speaker 1: get an MRI to pretty much figure out. It's more
9:53
Speaker 1: kind of like an extra scan. I think it's extra
9:55
Speaker 1: or something an MRI is or yeah, it's scan your
10:03
Speaker 1: your brain? Right. How does it work? How does it
10:05
Speaker 1: scan the brain? I would assume like similar to what
10:08
Speaker 1: they used like for X rays. So like maybe like
10:13
Speaker 1: some sort of laser. I don't know, laser. I don't know,
10:16
Speaker 1: no m R I actually I think it it's scans
10:19
Speaker 1: your brain or your organs and like it gives your
10:22
Speaker 1: the estimation of where is the tomorrow whatever it is.
10:26
Speaker 1: I m hmm, I don't know. I have no idea.
10:34
Speaker 1: So what do you think of those answers? Impressed or not? Well,
10:36
Speaker 1: it's interesting. Most people, um sort of knew what it was,
10:39
Speaker 1: so they know that it's kind of a scan of
10:41
Speaker 1: your body for medical reasons, and they kind of related
10:46
Speaker 1: it to X rays. Yeah, that's right. Everybody seemed to
10:48
Speaker 1: have an understanding of what it's for why you might
10:50
Speaker 1: do it, but almost nobody actually knew how it worked.
10:54
Speaker 1: And you're right, people thought about the same way they
10:56
Speaker 1: sort of think about like X rays or lasers or something.
10:59
Speaker 1: Everybody thought it was shooting something into you. Yeah, but
11:02
Speaker 1: and they're not too far off, right, Like, it does
11:04
Speaker 1: involve electromagnetic radiation, right, and pulses and things that go
11:11
Speaker 1: through you. Yeah, And of course it has to. If
11:13
Speaker 1: you want to see inside something, then you have to
11:16
Speaker 1: probe it somehow, right, You have to somehow gather information
11:19
Speaker 1: about what's beyond the skin or through the wall or
11:22
Speaker 1: whatever it is you're trying to look past. And the
11:24
Speaker 1: only way we really to do that is to send
11:26
Speaker 1: some kind of radiation in. But remember radiation is a
11:28
Speaker 1: broad term. We had a whole episode about that. Radiation
11:31
Speaker 1: can just mean sound, you know, like when you get
11:33
Speaker 1: an ultrasound done, you're sending sonic radiation into your body
11:37
Speaker 1: and you're seeing how it bounces around and comes back.
11:40
Speaker 1: And that's basically the the idea behind all medical imaging
11:43
Speaker 1: is shoot some radiation in there, see how it bounces around,
11:47
Speaker 1: because you know, if it's this kind of goop, it's
11:49
Speaker 1: going to bounce around differently than if it's that kind
11:50
Speaker 1: of group, you know, fat versus bone versus brain, and
11:54
Speaker 1: then you can reconstruct the picture. Yeah, so it's very
11:56
Speaker 1: different than X rays. But let's maybe for those of
11:59
Speaker 1: us who aren't not at all i'm there with medical imaging,
12:02
Speaker 1: maybe it steps us through. First of all, it's started
12:04
Speaker 1: with X rays. How do how do X rays work? Right?
12:06
Speaker 1: So X rays are also electromagnetic radiation. Remember X rays
12:10
Speaker 1: are just light, right, a very very high frequency, and
12:14
Speaker 1: so they shoot them into your body and X rays
12:17
Speaker 1: are very powerful. They can penetrate like most light, like
12:20
Speaker 1: photons that come from the sun that you can see,
12:22
Speaker 1: don't go through your body. That's why your body is
12:24
Speaker 1: not transparent. Right, your opaque, but X rays are much
12:27
Speaker 1: more powerful. They can go all the way through your body. Um.
12:30
Speaker 1: But it turns out that X rays are absorbed differently
12:32
Speaker 1: by different kinds of stuff in your body. So, for example,
12:34
Speaker 1: bone is really good at absorbing X rays. So shoot
12:38
Speaker 1: a bunch of X rays through somebody and then try
12:40
Speaker 1: to capture them those X rays on the other side.
12:43
Speaker 1: What you'll see is that where there was bone, for example,
12:46
Speaker 1: very few of the X rays passed through, whereas whereas
12:48
Speaker 1: mostly like gas from your lungs, then a lot of
12:51
Speaker 1: the X rays do pass through. So what you'll see
12:53
Speaker 1: is like the shadow of the bones. It's like doing
12:56
Speaker 1: shadow puppets. Right. You hold up a light bulb and
13:00
Speaker 1: your hand and you can make a shadow on the wall,
13:02
Speaker 1: so you can see where your hand was, right X
13:04
Speaker 1: raysor like that, except that your body is mostly transparent
13:07
Speaker 1: to X rays except for some of the stuff inside,
13:09
Speaker 1: like bones. So you're really sort of getting the difference
13:13
Speaker 1: in transparency between the different kinds of things inside of you.
13:17
Speaker 1: That's right, and different kinds of light. UM, find different
13:20
Speaker 1: things transparent like visible light can pass through air, no problem, right,
13:23
Speaker 1: But it can't pass through a rock or your hand.
13:26
Speaker 1: X rays are a different kind of light, so they
13:28
Speaker 1: have a different set of stuff that they can go
13:30
Speaker 1: through or not. So, yeah, you're right, you're seeing the
13:32
Speaker 1: difference in transparency between bone and fat or tumors and
13:37
Speaker 1: gas and all the kind of stuff that makes up
13:39
Speaker 1: your body. Yeah, and you sort of get the shadow
13:41
Speaker 1: of them, the impression of them on the other side
13:44
Speaker 1: on the on like a sensor or a film. Yeah, exactly.
13:48
Speaker 1: And you know it used to be filmed. They used
13:49
Speaker 1: to like take a picture and have to develop it.
13:51
Speaker 1: These days they use a digital camera, which is why
13:53
Speaker 1: it's so fast. And the thing X rays are good
13:56
Speaker 1: at is telling like bone from other tissue. X ray
13:59
Speaker 1: is not that good telling the difference between like water
14:02
Speaker 1: or fat or that kind of stuff. It all comed
14:04
Speaker 1: out about the same and X rays. And the other
14:06
Speaker 1: thing is you mentioned is that the X rays passed
14:09
Speaker 1: all the way through you, so you're just seeing sort
14:10
Speaker 1: of like the overall shadow. You can't see slices. And
14:14
Speaker 1: that's why when you take an X ray sometimes ask
14:16
Speaker 1: you to turn so they can take it from the
14:17
Speaker 1: front and they can take it from the side or
14:19
Speaker 1: from a different angle so they can get a sense
14:21
Speaker 1: for what's going on inside from shooting X rays through
14:24
Speaker 1: you at different at different angles. With that, let's take
14:27
Speaker 1: a break. We'll be back in just a short minute.
14:42
Speaker 1: So that's one way to look inside of you. But
14:45
Speaker 1: m r I is sort of smarter, right, Like, it
14:47
Speaker 1: doesn't shoot radiation through you. It it just sort of
14:50
Speaker 1: like kind of it does something a lot cleverer. Right, Well,
14:54
Speaker 1: it actually does shoot radiation through you, right, I mean,
14:57
Speaker 1: it does send electromagnetic pulses, but they're safer, right, It's
15:02
Speaker 1: not really high energy. In fact, they're very very low energy.
15:05
Speaker 1: They're radio waves, which means a very long frequencies, So
15:09
Speaker 1: they're not the kind of radiation that cannet deposit energy
15:11
Speaker 1: and break up your DNA and cause cancer. And that's
15:14
Speaker 1: the problem with X rays. And that's why when you
15:15
Speaker 1: take an X ray sometimes they give me like a
15:17
Speaker 1: lead skirt or a lead helmet or something, you know,
15:20
Speaker 1: or a lead jock strap or whatever to protect your
15:22
Speaker 1: all of your important bits that you don't want to
15:24
Speaker 1: send radiation into. But an m r I you can
15:27
Speaker 1: use much lower energy radiation uses the same radiation as
15:31
Speaker 1: like what you listen on the radio that's pumped out
15:33
Speaker 1: by radio antennants exactly the same kind of radiation. You
15:37
Speaker 1: don't usually think of that as light because you can't
15:39
Speaker 1: see it, but it's all part of the electromagnetic radiation spectrum.
15:42
Speaker 1: You know. It starts out really low frequency with radio waves,
15:45
Speaker 1: comes up to visible light, and then you can UV
15:48
Speaker 1: lighted higher frequencies, and then gamm or X rays and
15:51
Speaker 1: gamma rays at very high frequencies. It's also part of
15:54
Speaker 1: the same family, but you know, just like in families
15:57
Speaker 1: were all different, and so radio waves feel very front
16:00
Speaker 1: of the body than X rays because they don't deposit
16:02
Speaker 1: very much energy, so they can't really do much damage.
16:05
Speaker 1: All right, So step us through Daniel. How does an
16:07
Speaker 1: m r I work? So, and let's start maybe with
16:10
Speaker 1: the ideita is that in an m r I you
16:12
Speaker 1: are sending radiation into your body, but you're sort of
16:15
Speaker 1: doing it proton by proton, right like yours. You're trying
16:19
Speaker 1: to poke one proton inside of your body. And so
16:21
Speaker 1: how does that work? Like if you if there's a
16:24
Speaker 1: proton inside of your body, how do you get it
16:25
Speaker 1: to light up or to see it? Yeah? Exactly, Well,
16:28
Speaker 1: remember the protons can absorb energy sometimes, so you're sending
16:32
Speaker 1: these radio waves in, and the radio waves have energy,
16:35
Speaker 1: and the idea is that you want to poke those
16:37
Speaker 1: protons and give them that energy, so they get like excited,
16:41
Speaker 1: and then they relax and they send the energy back.
16:43
Speaker 1: And the interesting thing, the reason that you can see
16:46
Speaker 1: inside the body with an m R I you can
16:47
Speaker 1: see the different kinds of tissue, is that different kinds
16:50
Speaker 1: of tissue take different amounts of time to absorb that
16:53
Speaker 1: energy and then send it back. So like fat or
16:57
Speaker 1: bone or water or whatever, you poke the proton in
17:00
Speaker 1: those different kinds of tissue, some of them will hold
17:02
Speaker 1: that energy for a while and then send it back,
17:04
Speaker 1: and some of them will send it right away. So
17:06
Speaker 1: you can tell what different kind of tissues there are
17:10
Speaker 1: by telling by seeing how long it takes for that
17:12
Speaker 1: energy that you're deposited to to get sent back to you.
17:15
Speaker 1: So it's not like you're sending X rays through and
17:18
Speaker 1: then whatever makes it out to the other end you
17:20
Speaker 1: see it. This is more like you're you're sending rata
17:24
Speaker 1: waves in and then that lights up the protons inside
17:28
Speaker 1: of you in different ways, And depending on how they
17:31
Speaker 1: light up and how long they take to stop lighting up,
17:34
Speaker 1: then you can tell what kind of tissue it is,
17:36
Speaker 1: or what kind of whether it's bone or fat or
17:39
Speaker 1: bananas exactly. And it's it's just like you know when
17:42
Speaker 1: you walk along a wall and you're looking for a stud, right,
17:44
Speaker 1: what do you do? You knock on the wall, and
17:46
Speaker 1: you're sending a wave in and you're waiting for that
17:48
Speaker 1: wave to come back, right, And if the wave sounds
17:51
Speaker 1: this way or sounds that way, it takes a long
17:53
Speaker 1: time or a short time to come back. That tells
17:55
Speaker 1: you about what's behind the wall. It's the same basic idea.
17:59
Speaker 1: It's also the way we kind of like an echo,
18:00
Speaker 1: more like an echo, but with electromagnetic radiation and pantum mechanics. Yes, exactly,
18:07
Speaker 1: it's like an echo and the radio wave goes in
18:10
Speaker 1: and gets and tickles those protons and makes them excited,
18:13
Speaker 1: and then it sends a radio wave back. So you
18:14
Speaker 1: have to have a radio emitter and a receiver, so
18:17
Speaker 1: it like it talks to the protons and then it
18:20
Speaker 1: waits for the protons to talk back, and based on
18:23
Speaker 1: how long it took for them to talk back, it says, Oh,
18:25
Speaker 1: this one's probably fat, this one's probably bone, this one's
18:29
Speaker 1: probably brained, this one's probably water. This is probably brilliant
18:32
Speaker 1: in the brain exactly. Okay, cool, all right, So it's
18:39
Speaker 1: it's kind of like you're sending a signal in your
18:42
Speaker 1: how it gets reflected back. Then you you recorded how
18:45
Speaker 1: when it bounces back, and then that tells you that
18:48
Speaker 1: sort of gives you the image of what's inside of
18:50
Speaker 1: your body exactly. And then there's some really cool quantum
18:53
Speaker 1: mechanics about how you get those protons to absorb that
18:56
Speaker 1: radio information and why they send it back, and that's
18:59
Speaker 1: where the magnets come in. And the way understand it,
19:01
Speaker 1: it's sort of like a spinning top, right, Like you
19:03
Speaker 1: need to think of a proton as a spinning top,
19:07
Speaker 1: and so you when you put it inside of this
19:09
Speaker 1: giant magnet, it makes all the tops sort of a
19:12
Speaker 1: ligne in a particular way or in one direction. Right,
19:15
Speaker 1: that's right, because remember we talked on our quantum Spin
19:17
Speaker 1: episode about how all these little particles they're not really spinning,
19:21
Speaker 1: but they have this thing about them called spin, which
19:23
Speaker 1: gives them a little magnetic field. To think of, every
19:26
Speaker 1: little particle is having a little magnet in it, and
19:28
Speaker 1: so if you put a really big magnet on the
19:31
Speaker 1: outside of the body, then all the protons in your
19:33
Speaker 1: body are going to line up with that magnet. But
19:36
Speaker 1: some of them line up with the magnet and some
19:37
Speaker 1: of them line up against the magnet, but you know,
19:39
Speaker 1: they all go along that line, and then that primes
19:42
Speaker 1: them for you to poke them right, for you to
19:44
Speaker 1: send in the radio wave, and then depending on how
19:47
Speaker 1: they react to that, that's the signal you get back exactly.
19:50
Speaker 1: And that's the that's the magnetic part. And so you
19:52
Speaker 1: send in the radio wave and then some of the
19:54
Speaker 1: ones that were not aligned flip and become aligned because
19:57
Speaker 1: that takes more energy, and so that's how they absorb
20:00
Speaker 1: the energy of the radio waves. Some of the ones
20:02
Speaker 1: that were unaligned to become aligned with the magnet. So
20:04
Speaker 1: it's just like switching directions, right. They absorb that energy,
20:08
Speaker 1: but they don't they don't hold onto it for very long,
20:10
Speaker 1: and then eventually they flip back and they send the
20:12
Speaker 1: radio wave back. So that's the magnetic part. That's how
20:15
Speaker 1: you get the protons to absorb this energy. That you
20:17
Speaker 1: put them in this magnetic field that allows them to
20:19
Speaker 1: align or unaligned, and that gives them an opportunity to
20:22
Speaker 1: absorb this kind of energy. It's kind of like the
20:24
Speaker 1: spinning top. You flip it and then but then it
20:26
Speaker 1: wants to flip back, and when it's flipping back, it
20:29
Speaker 1: releases some energy back. Right, that's right, and that's the
20:32
Speaker 1: resonance part. Remember um m RI is magnetic resonance imaging,
20:36
Speaker 1: and the magnet comes from putting things people in a
20:38
Speaker 1: big magnet. And the resonance part is the part about
20:41
Speaker 1: absorbing the radio frequency. Right, normally you send radio wave
20:45
Speaker 1: through your body, they won't get absorbed, rather just pass
20:47
Speaker 1: right through because they're not at the right energy to
20:50
Speaker 1: be absorbed. Remember we talked about in quantum mechanics, how
20:53
Speaker 1: like atoms have different energy levels. Right, they can't just
20:55
Speaker 1: absorb a photon of a random energy. The energy that
20:59
Speaker 1: comes in us to be the right size because for example,
21:02
Speaker 1: electrons have levels and they want to go up one
21:05
Speaker 1: level or up two levels the right they're like along
21:07
Speaker 1: this ladder. So you can't just absorb any random amount
21:10
Speaker 1: of energy. You have to absorb the right size of energy. Now,
21:13
Speaker 1: normally radio waves are not the right sized energy for
21:16
Speaker 1: your body to absorb. They pass right through you. But
21:18
Speaker 1: when you put these protons in the magnetic field, then
21:22
Speaker 1: they have this new way to absorb energy. And that's
21:24
Speaker 1: this resonance part. The energy is the resonant energy is
21:27
Speaker 1: the right energy to push these things to make them
21:30
Speaker 1: spin one way instead of the other way. And now
21:32
Speaker 1: is it all all the protons in your body or
21:35
Speaker 1: only certain protons? It's all the protons that I want, man,
21:38
Speaker 1: I have total control over it, like in all all
21:42
Speaker 1: the atoms in your body react to this signal or
21:45
Speaker 1: only like water? Or how does that work? Now? All
21:47
Speaker 1: the protons in your body can react to this, right
21:50
Speaker 1: because your body is made of protons, rights, protons and
21:52
Speaker 1: neutrons and electrons, but mostly it's water, right, Like most
21:56
Speaker 1: of your body is water. But all the protons and
21:58
Speaker 1: the nuclei can respond onto this kind of thing. Um.
22:02
Speaker 1: And there's also a really cool trick they do to
22:05
Speaker 1: allow themselves to see slices. You're talking earlier about how
22:08
Speaker 1: you could see like you know, just to slice through
22:10
Speaker 1: your body your shoulders, or slice through your body at
22:12
Speaker 1: your stomach or your feet or whatever. They do a
22:15
Speaker 1: really cool trick by tuning the magnet strength to make
22:18
Speaker 1: sure that only protons and one slice are able to
22:21
Speaker 1: absorb that energy at a time. That's where the giant
22:23
Speaker 1: magnet comes in, right, yeah, exactly. You know, like when
22:27
Speaker 1: you're in that platform and you roll in, you go
22:28
Speaker 1: into the giant donut. That donut is basically like a
22:32
Speaker 1: giant it's really just a magnet, right, like like like
22:36
Speaker 1: a it's just a giant coil of wire that creates
22:39
Speaker 1: a magnet. That's right. It creates a magnet. And the
22:42
Speaker 1: magnet is stronger on one side than on the other,
22:44
Speaker 1: Like it's really stronger your head and it's a little
22:47
Speaker 1: weaker at your feet. And what that means is that
22:50
Speaker 1: the radio waves that they send in are better absorbed
22:53
Speaker 1: by just one slice of your body. The slice of
22:55
Speaker 1: your body has just the right magnetic strength to absorb
22:58
Speaker 1: those radio waves. That's the resonance part. That's how they
23:01
Speaker 1: can take a slice of you, right, because it the
23:04
Speaker 1: magnetic field changes along your body and so and and
23:09
Speaker 1: those protons react differently depending on the slice. That's right.
23:13
Speaker 1: Only the protons that are in the magnetic field that's
23:16
Speaker 1: the right strength are primed to absorb that radio wave
23:20
Speaker 1: and then you know, send it back. And so basically
23:22
Speaker 1: your whole body is just totally transparent to the radio
23:25
Speaker 1: waves except for this one slice where the protons will
23:28
Speaker 1: grab the radio energy and then send it back, and
23:31
Speaker 1: so it's like, yeah, it's like you can only see
23:34
Speaker 1: one slice at a time. And then you're lying there
23:36
Speaker 1: and you're hearing like clank, boom, bang booming. It's like
23:40
Speaker 1: sort of disconcerting all the weird noises that happened. Yeah,
23:43
Speaker 1: what is that noise? Anyways? When you you know, when
23:45
Speaker 1: you're in there, you just hear like a chunk, chunk, chunk.
23:48
Speaker 1: What is And you see it on TV two when
23:50
Speaker 1: people are getting their MR ees you hear them, you
23:52
Speaker 1: just hear this noise going good, chunk chunk. What is
23:54
Speaker 1: that noise? That's just a physically sounding noise they added
23:57
Speaker 1: to make people feel like it's worth all the money.
24:00
Speaker 1: Did some sound editor putting in the special effects later?
24:03
Speaker 1: Are people going to pay more if it sounds? If
24:05
Speaker 1: it sounds, you know, like some physics is happening. Now,
24:07
Speaker 1: there really is something happening there. That's them adjusting the
24:10
Speaker 1: magnetic field so they can see different slices of your body. Remember,
24:14
Speaker 1: those radio waves only can talk to protons that are
24:17
Speaker 1: in a magnetic field that has the right strength. So
24:19
Speaker 1: what they're doing is they're adjusting the magnetic field. They
24:21
Speaker 1: can either slide you back and forth, but that's a
24:24
Speaker 1: little more uncomfortable, or they can leave you sitting there
24:27
Speaker 1: and they can adjust the magnetic field, and so you're
24:29
Speaker 1: hearing all the coils move and whatever. So the magnetic
24:32
Speaker 1: field is now good for protons at your feet, or
24:35
Speaker 1: good for protons at your head or whatever. They're moving
24:38
Speaker 1: which slice of your body they can talk to by
24:40
Speaker 1: changing where the magnetic field has just the right strength.
24:43
Speaker 1: All right. So it's sort of like, can I call
24:45
Speaker 1: it quantum echo, like a quantum echo effect, Oh, that
24:48
Speaker 1: would be awesome, Yeah, quantum echo imaging. We should have
24:53
Speaker 1: name to that. That's a new product name, all right.
24:55
Speaker 1: So then that gives you an image of your body.
24:58
Speaker 1: Because each proton, depends on what kind of stuff it
25:01
Speaker 1: is in your body, will kind of reflect that energy
25:04
Speaker 1: back differently, and so you can sort of tell what's fat,
25:07
Speaker 1: what's bone, what's water. Yeah, exactly. They all reflect the
25:10
Speaker 1: energy back, but they take different amounts of time. So
25:12
Speaker 1: like fat takes a different amount of time to send
25:14
Speaker 1: the energy back than water does or bone does, and
25:17
Speaker 1: that's how they can tell the difference. And that's a
25:19
Speaker 1: really cool thing about m r I. Unlike X ray,
25:21
Speaker 1: they can tell the difference between these different kinds of tissue,
25:24
Speaker 1: so it's so valuable. But you can see like, oh,
25:26
Speaker 1: there's a tumor there next to this other organ or
25:29
Speaker 1: you know, you can see the differences there, which which
25:31
Speaker 1: makes it really valuable from a medical point of view.
25:33
Speaker 1: And now a quick word from our sponsor. I think
25:48
Speaker 1: my question is how did they figure this out? How
25:50
Speaker 1: did they ever think to use this? How did they
25:53
Speaker 1: how did they come up with the idea to use
25:55
Speaker 1: it to look inside your body? Yeah, well, it came
25:57
Speaker 1: out of people doing basic research with atoms. You know.
26:00
Speaker 1: They were, you know, like, let's take a bunch of
26:01
Speaker 1: atoms and put in a magnetic field and poke them,
26:04
Speaker 1: and you know, let's see if quantum mechanics works, and
26:06
Speaker 1: can we understand why they absorb frequencies that you know
26:09
Speaker 1: here and there. And then they discovered, I think quite accidentally,
26:13
Speaker 1: that the relaxation time, this time it takes the energy
26:16
Speaker 1: to come back is different for different kinds of materials.
26:19
Speaker 1: And then you know, somebody had this bright idea. They're like, oh, wait,
26:22
Speaker 1: maybe we can use this for imaging. And I think
26:24
Speaker 1: there's a huge field of people working on imaging and
26:27
Speaker 1: imaging techniques and new ways to see inside the body
26:30
Speaker 1: because you know, m RIS they work pretty well, but
26:33
Speaker 1: they're also they take a long time, and they're really expensive, right,
26:36
Speaker 1: so there are cons to an m r I. So
26:38
Speaker 1: there's a huge field of researchers working to develop better, faster,
26:43
Speaker 1: cheaper scanning technology. My guess is that it was some
26:46
Speaker 1: physicists in a lab, you know, poking doing quantum physics,
26:50
Speaker 1: and somebody left their sandwich in the middle, and then
26:52
Speaker 1: they got this image of the inside of the sandwich.
26:55
Speaker 1: They're like, oh my god, I think of what we
26:57
Speaker 1: can do. You know, there are easier ways to tell
26:59
Speaker 1: what's in your image then accidentally inventing an MRI machine.
27:03
Speaker 1: You could just open it up. But if it's a burrito,
27:05
Speaker 1: let's go with burrito, that's a little harder with this inside.
27:08
Speaker 1: That's true, there's no noninvasive way to see what's inside
27:11
Speaker 1: of burrito. Yeah, I guess you can eat it, yeah exactly. Um,
27:15
Speaker 1: that's that's definitely a destructive way of seeing it, all right.
27:18
Speaker 1: So that's kind of the general picture of out m
27:20
Speaker 1: RIS work. That's pretty cool. Yeah, And you know, every
27:22
Speaker 1: time you're getting an m R I. It means that
27:24
Speaker 1: they're sending these these pulses into you, and there's a
27:27
Speaker 1: very strong magnetic field that's applied to your body, and
27:30
Speaker 1: as far as we know, there's no adverse health effects
27:32
Speaker 1: to having a strong magnetic field. You might be thinking,
27:35
Speaker 1: oh my gosh, they're sending this magnetic field in me
27:38
Speaker 1: and all my protons are getting pointed in one direction,
27:40
Speaker 1: and that sounds really destructive, but as far as we know,
27:43
Speaker 1: you know, getting your protons to align with the magnetic
27:45
Speaker 1: field doesn't hurt you. Unless you're a robot, then that
27:48
Speaker 1: might be bro or actually, this is serious, unless you're
27:51
Speaker 1: partially a robot, Like if you have metal screws or
27:55
Speaker 1: something inside of you, then m RIS could be dangerous
27:57
Speaker 1: because magnetic fields could like pull them out out or
28:00
Speaker 1: you know, rip out parts of you. That would be
28:02
Speaker 1: pretty bad. Yeah. Yeah, I've heard of stories in MRI
28:05
Speaker 1: labs where people accidentally bring their keys in and then
28:08
Speaker 1: they get you know, they fly through the room, across
28:12
Speaker 1: the room and get stuck on the magnet and they
28:14
Speaker 1: really have to like they can't pull them out because
28:17
Speaker 1: there's it's so strong. You can't just pull the keys away.
28:20
Speaker 1: And so they have to shut down the whole thing
28:22
Speaker 1: just to get that person's keys. That's right, I gotta
28:24
Speaker 1: go home. My keys are stuck to the m R
28:27
Speaker 1: look good with this that aspect, but also while it's
28:29
Speaker 1: flying through the air, the thing is like a bullet,
28:31
Speaker 1: you know, that could really hurt somebody. We have the
28:33
Speaker 1: same problem in particle physics because we have really really
28:36
Speaker 1: strong magnets around the collision point and we use that
28:40
Speaker 1: because we want to bend the particles. We see how
28:42
Speaker 1: fast they were going. And anytime you turn on the
28:44
Speaker 1: magnet there's like a loose screw driver. That's a bullet
28:47
Speaker 1: that could kill somebody. So so it's pretty cool technology,
28:52
Speaker 1: and so there are some pros and cons. So the
28:54
Speaker 1: pro is that there's no radiation that can kill you
28:57
Speaker 1: like X rays, right, yeah, X rays and cat scans
29:00
Speaker 1: all those come with significant doses of radiation and mean
29:02
Speaker 1: more cat scans and X rays X rays. These days,
29:04
Speaker 1: they've they figured out how to do it with a
29:06
Speaker 1: sort of minimum amount of radiation. So you know, I
29:09
Speaker 1: don't want to scare anybody. You should get X rays
29:11
Speaker 1: that your dentists because they're the benefits of seeing inside
29:14
Speaker 1: your body. Outweigh the radiation, but shouldn't just look at
29:17
Speaker 1: like an X ray camera at home and happily take
29:19
Speaker 1: pictures of your body just for fun. And actually, you know,
29:25
Speaker 1: they used to have really really high intensity on X rays,
29:28
Speaker 1: dental X rays and medical X rays. They used to
29:30
Speaker 1: really crank it up because they didn't understand the dangers
29:33
Speaker 1: um And then recently, more recently, they realize they can
29:36
Speaker 1: get the same images with much less radiation UM and
29:39
Speaker 1: so they've been tuning them down for a long time.
29:41
Speaker 1: But yeah, X rays have ionizing radiation, which is dangerous,
29:45
Speaker 1: but mrs don't. And so that's a big advantage, especially
29:48
Speaker 1: if you're dealing with like an infant or something. Right,
29:50
Speaker 1: you don't want to you don't want to pile a
29:51
Speaker 1: huge amount of radiation into the brain of an infant,
29:53
Speaker 1: let to give them superpowers. Then that maybe that is
29:57
Speaker 1: a tough parenting choice, right, Do I give my kid
30:00
Speaker 1: cancer or maybe superpowers? Yeah, I don't know, think about that.
30:04
Speaker 1: But then the problem is that it kind of takes
30:06
Speaker 1: a long time, it's loud, and you have to sit
30:09
Speaker 1: in a tube for a long time. Yeah, exactly, And
30:11
Speaker 1: so there are some downsides and it costs lots. You
30:13
Speaker 1: need your insurance whatever to approve it, but you know
30:15
Speaker 1: it's irreplaceable. There's kinds of pictures that m RI I
30:19
Speaker 1: s can take that nothing else can do. Right, there's
30:21
Speaker 1: no better technology for doing that, right, That's right, exactly,
30:24
Speaker 1: all right. Well, it's uh, that explains it. So if
30:26
Speaker 1: you need an m r I and you want to
30:28
Speaker 1: take a picture of your body, you should be thinking
30:30
Speaker 1: quantum physicists for developing this technology to tickle your protons
30:34
Speaker 1: and and have them talk back. I'm a little piece
30:37
Speaker 1: of fat, I'm a little piece of bone. Hey over here,
30:39
Speaker 1: I'm a cancer or I'm a cancer tumor. That's right.
30:41
Speaker 1: And m RI is just a giant tickling machine quantum tickling.
30:45
Speaker 1: There you go. Yeah, But it's just amazing that technology
30:49
Speaker 1: and science have work together to create these incredible machines
30:52
Speaker 1: that can literally see inside your body. That's right, all right.
30:56
Speaker 1: We hope you enjoyed that and found that useful. Thank
30:58
Speaker 1: you for listening. And next time you get an m
31:00
Speaker 1: r I they will see inside your brain. An understanding
31:03
Speaker 1: of the m R I that you got from this podcast.
31:06
Speaker 1: Oh my god, that's right. Our voices are leaving an
31:09
Speaker 1: imprint in all those people's neurons. And that's that might
31:12
Speaker 1: show up on the m R I And that's right. Yeah,
31:14
Speaker 1: and the mr I you see a little picture of
31:16
Speaker 1: jorhand Daniel going and thumbs up. What And that's when
31:22
Speaker 1: the doctor goes, this is interesting. Yeah, we coded into
31:25
Speaker 1: this podcast. Is really a specific frequency that will leave
31:29
Speaker 1: an image in your brain of us. This sounds like
31:33
Speaker 1: an awesome sci fi episode. I love this idea. Viruses
31:37
Speaker 1: embedded in podcasts that right themselves into people's brains. Right,
31:40
Speaker 1: we are tickling your protons people, the quantum tickling virus.
31:45
Speaker 1: That sounds like a Michael Bay movie. Yeah, sign up
31:47
Speaker 1: canaries for that movie. Everything he does turns to gold.
31:54
Speaker 1: All right, see you next time. Thanks for tuning in,
31:56
Speaker 1: and thanks for asking questions. If you'd like something in
31:58
Speaker 1: your world explained, to send it to us at Questions
32:00
Speaker 1: at Daniel and Jorge dot com. If you still have
32:11
Speaker 1: a question after listening to all these explanations, please drop
32:14
Speaker 1: us a line. We'd love to hear from you. You
32:17
Speaker 1: can find us at Facebook, Twitter, and Instagram at Daniel
32:20
Speaker 1: and Jorge that's one word, or email us at Feedback
32:24
Speaker 1: at Daniel and Jorge dot com. Thanks for listening, and
32:27
Speaker 1: remember that Daniel and Jorge Explain the Universe is a
32:30
Speaker 1: production of I heart Radio. For more podcast from my
32:33
Speaker 1: heart Radio, visit the i heart Radio app, Apple Podcasts,
32:37
Speaker 1: or wherever you listen to your favorite shows.