How CT Scanners Work and A TechStuff Update

How does CT (computed tomography) scanners work? What's going on with TechStuff? In this episode, you are invited into Jonathan's brain to find out.

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Episode Transcript

Speaker 1 (00:04):
Welcome to Tech Stuff, a production from iHeartRadio. Heydarreon Welcome
to Tech Stuff, I'm your host, Jonathan Strickland. I'm an
executive producer with iHeart Podcasts and How the Tech Are You? So?
Over the holiday weekend on December thirtieth, twenty twenty three,

(00:27):
I had the occasion to get my very first CT scan.
This was because I was experiencing a medical emergency. More
on that later, because it's actually going to impact this
show a bit, and I'm still struggling under a a
few nasty effects today, so it's a little bit of

(00:47):
a chore to do this and stay coherent. But this
is first and foremost a tech podcast, not a Jonathan's
All Messed Up podcast, and by golly, I owe you
episode about something technical. So I thought, Hey, I've never
had a CT scan before. How about I do an
episode on CT scanners. Now. I have talked a bit

(01:10):
about related medical technologies on the show, like X ray
machines and MRI machines, and I've talked about tomography with
regard to three D printing. That's what the T in
CT stands for, stands for tomography. The C in case
you're curious, stands for computed so CT is computed tomography.

(01:30):
But unless you work with that kind of technology, knowing
that probably doesn't help you out very much. To understand
CT scans, we need to have a quick reminder about
X rays. Now. I've talked a decent amount about X
rays not that long ago, because I did an episode
about how in the early twentieth century shoe shops used

(01:50):
cabinets containing X ray lamps essentially, and then some viewfinders
that would let customers see their own feet while their
feet are still inside their shoesies. Well, there are plenty
of reasons to suspect this was perhaps an unwise marketing campaign.
After all, it did have the potential to seriously harm
customers and more likely shoe store staff. The trend actually

(02:13):
stuck around for an alarmingly long time. Anyway, there's a
whole episode about this from November. It is titled AI
and Radioactive Shoes Salesman if you want to learn more
about that. Also, I don't think I did this on purpose,
but the episode that published about those shoe salesmen went

(02:34):
out on November eighth, twenty twenty three, and we traced
the discovery of X rays back to November eighth, eighteen
ninety five. So I recorded a podcast about X rays
one hundred and twenty eight years to the day after
their discovery. I don't remember doing that on purpose, so
I'm pretty sure it was just pure luck. We have
a nineteenth century smarty pants named Wilhelm Conrad Rintgen to

(03:00):
thank for X rays. Well, not exactly, because X rays
are a type of electromagnetic radiation and they exist whether
or not. Rentgen figured it out, and surely someone else
would have susted out if he hadn't. There were other
people who were kind of looking around the area at
the time. But the point is Rentgen did it, and so,
gosh darn it, he deserves the credit for it. So

(03:21):
Rentgin was experimenting with what was called a Crook's tube,
a glass bulb inside which there were a pair of
electrodes that could be run at high voltage, essentially a
cathode ray tube, and it also was filled with more
or less a vacuum. So he had covered up this
tube with some heavy black cardboard. But then he saw

(03:42):
that there was a sheet of platino barium in his
lab that was several feet away, like nine feet away,
and it was glowing while the tube was active, but
there was no visible light passing from the tube because
the cardboard was covering it up. So this got into wondering,
how could this tube illuminate something if the light was

(04:02):
being blocked by cardboard. Clearly, some form of energy was
passing directly through the cardboard as if it weren't there,
just as visible light can pass through a pane of glass.
It wasn't long before he found out that this energy
could pass through human tissue as well. In fact, it
was the very same day his wife famously held her

(04:22):
hand up and he was able to take a photograph,
an X ray photograph of her hand. So if you
were to hold up your hand between the tube and
the sheet of platino barium, then you would cast a
shadow that would show the skeletal structure of your hand,
and you would have sort of a hazy area that

(04:43):
would be other tissue in your hand. It didn't take
long at all before various doctors, engineers, and scientists purposefully
began to build devices to take X ray images projected
again onto special film, not necessarily a sheet of platino barium,
and this would let them get a little and see
stuff like bones and other kinds of tissue that normally

(05:06):
you know are on the inside of a person. As
it turns out, X rays have much shorter wavelengths and
much higher frequencies than visible light. So if you're looking
at the electromagnetic spectrum and you go from the types
of radiation that have the smallest wavelengths and you work
your way up, it starts at gamma radiation, then X ray,

(05:27):
then ultraviolet, then visible light, then infrared, then microwave, than
radio from smallest to longest wavelengths, and X rays are
a type of ionizing radiation, along with some other forms
of radiation, like gamma radiation is also ionizing. Alpha and
beta particles are ionizing. There are a few others. So
ionizing radiation is radiation that has the energy required to

(05:51):
strip electrons away from atoms right that can ionize an
atom by removing electrons. This also can potential damage living cells.
So most X ray radiation passes through a human body,
but some of it can end up getting absorbed and
potentially it can cause harm, potentially serious harm, and this

(06:14):
potential increases with increased exposure. This is why radiologists set
up a machine to take X rays and then they
leave the room before they start snapping photos of your inerts.
By the way, we can contrast this with non ionizing radiation.
That is radiation that lacks the energy needed to strip
electrons away from atoms. So your plain old radio waves,

(06:36):
you know, the stuff that we use to communicate on
cell phones and Wi Fi routers and radio and television
broadcast TV, that's non ionizing radiation. Those big transmitter towers
might look intimidating, but they do not have the same
effect as ionizing radiation sources do. So when you hear

(06:57):
people talk about the potential dangers for things like cell
phone signals, you do need to know that the energy
of those signals is orders of magnitude lower than what
you would find with ionizing radiation like X ray and
gamma rays. That's not to say that it's a guarantee
that it's perfectly safe, just that based on that one

(07:18):
particular vector, you are not seeing an effect. Right. It's
not like if you sit too close to the TV
you get cancer or something, at least not directly from
sitting close to the television. All right, So we have
the basics with the X ray. You've got a tube
similar to a cathode ray tube, and it emits X

(07:38):
rays when you pass a high voltage current through the
filament inside the tube. It's kind of like a light bulb,
but instead of giving off visible light or say ultraviolet
light with a UV light, it gives off X rays.
So the cathode focuses these X rays so that you
can actually direct them properly. And then with an X
ray machine on the opposite side from where the X

(08:00):
ray tube is, you have a detector. Now, once upon
a time, the detector was a sheet of film, right
like it was contained within something else, and you would
just take a photo and the X rays would go
through the person and hit the film behind them, and
then you develop that film and you've got your image
of the X ray. But now a lot of X

(08:22):
ray machines have digital detectors. They have a sensor on
the other side that picks up those X rays, so
you're not actually capturing stuff to film, you're capturing it digitally.
And then once that's gone through, once the X rays
have passed through and they've hit either the film or
the sensor, then you have a radiologist and doctors who

(08:42):
can look at and interpret the results. They can look
at the image and determine what's going on inside. Now,
the reason that I'm talking about X rays instead of
CT scanners is that a CT scan is a specialized
kind of X ray. A CT scanner is an X
ray machine. Now you've likely seen one of these, either

(09:03):
in person or in media. Typically it looks like you
have like a little kind of white wall, like it's
a machine where part of the machine is a vertical
barrier kind of like a wall, and the center of
it is a large hole large enough for a person
to be passed through the middle of that hole, and

(09:24):
extending out from it is a motorized bed if you're
feeling generous. I thought of it just as like a
table or platform, because there was nothing bed like about it.
When I was on it. I laid down on this
platform in my case, and a technician positioned me so
that my head was at the right spot at the

(09:44):
beginning of the hole in the center of this vertical barrier.
So it's like I was slowly being fed into a
doughnut hole as the process was going on. But this
hole is a housing for an X ray tube and detector,
and the reason for its shape. The reason why you
have this round hole that you're being passed through is
that the ct scan is taking a series of X
ray images in a circle around you. It snaps a shot,

(10:08):
and then the mechanism rotates inside the vertical barrier. It
snaps another shot, and it does this very very very fast.
If you could see through the machine, like the machine
can see through you, you'd see that an X ray
tube might start at a location such as directly overhead. Right,
you're looking straight up, you can see the X ray tube,
and then after it takes a picture, it moves slightly.

(10:29):
Let's say it moves clockwise from your perspective, and so
it's moving down the perimeter of the hole. From your perspective.
You're keeping your eyes straight up, and eventually you would
see the detector directly above you as it rotated one
hundred and eighty degrees. So it does this a bunch
of times until it has essentially gone around you, and
then what results is a series of X ray images

(10:51):
of part of your body. So in my case, it
was monogan, and you get it from various angles. The
CT scan generates a series of two dimensional quote unquote
slices of whatever it's imaging, and these slices can range
between one to ten millimeters thick. The actual thickness depends
upon the specific machine in use. More than that, after

(11:13):
gathering a full slice image, the machine can move the
motorized platform forward a bit, a little further into the
machine and the process can repeat. And this way the
engineers can collect the number of slices needed for whatever
is going on, Like if they're trying to image an
entire organ, then they will keep doing this until they've
hit all the slices that make up that organ. Now

(11:34):
the images are pretty darn cool. You can look at
each slice individually. That's useful if you suspect there could
be something concerning in there, like a mass that shouldn't
be there, for example, or you can stack them together
and then collectively, with these stacked slices, you can create
a three D image of whatever it was you were scanning.

(11:55):
So that means there's a hospital here in Atlanta that
has a three D scan of my brain. And no,
I didn't think to ask if I could have a copy.
In fact, I don't. I don't know if I actually
want to see it. That might freak me out to
see my own brain. All right. Anyway, now you have
a basic idea of how a CT scanner works. We're
gonna take a quick break. When we come back, I'm

(12:16):
gonna answer a few other questions relating to CT scanners,
some interesting facts and trivia. But before we do that,
let's take a quick break to thank our sponsor. Okay,
so we talked a bit about computed tomography, But what

(12:40):
the heck does tomography mean? So tomography is using some
form of penetrating energy or wave to section a three
dimensional object, which is pretty much what we talked about
with the imaging process just now. But there are different
types of tomography. It's not all X rays. Uh. For example,
I once recorded an episode about how using a particular

(13:02):
kind of photosensitive resin and a machine that used tomography,
you could three D print objects. So in this case,
it's not about taking photos of a three dimensional object. Rather,
it's about directing light at precise angles and positions so
that this photosensitive resin solidifies when the light hits it,

(13:23):
and you can get a very precise three D printed
object from this. So a computer controlled light source zapp's
the resin over and over again, and then you end
up with a three D printed object. It's pretty darn cool,
is not like your desktop three D printer type thing.
There are lots of other applications for tomography as well,
but I think most folks who have heard the term

(13:44):
think of the medical device. So who the heck came
up with this? Well, that credit goes to an engineer
named Godfrey Houndsfield, and he actually didn't work in medical
tech at all. Rather, he was employed by Electric and
Musical Industries aka EMI. You know the record label, the

(14:06):
same company that produced records for the Beatles, because of
course that's who did it. But I'm not giving Housefield
enough credit. It sounds like he was sitting there working
on like turntables and cassette players. That was not the case.
Before he worked for EMI. Houndsfield had worked on radar
technology for the Royal Air Force, and while at EMI,
he wasn't trying to make sure I want to hold

(14:28):
your hand played at just the right speed on a turntable.
He was developing guided weapons systems for EMI. That, my friend,
is what you call a diversified portfolio. So the story
goes that back in the nineteen sixties, Houndsfield was on
vacation when he got into a conversation with the doctor,
and the doctor explained that it was really hard to

(14:50):
get a good X ray image of the human brain.
Images were limited to two dimensions, and often the quality
was pretty low and grainy. So Houndsfield goes on his
merry way, but he keeps thinking back to this issue.
Could there be a way to create a device that
could produce better X ray images of structures like the brain?
He essentially identified all the elements that would be needed

(15:12):
in order to accomplish that goal. There would need to
be some way to either rotate the patient, which frankly
didn't seem very practical, or rotate the X ray apparatus,
which seemed more achievable. There would also have to be
a computer system programmed to assemble individual images together to
create a three D image. These were non trivial challenges

(15:34):
and it took him a long time, working with lots
of other very smart people to make it happen, but
he partnered with various neuroexperts. In nineteen seventy one, he
and his team were able to build and test a
CT scanner and produce the first CT scans of a
human brain. Houndsfield actually received a Nobel Prize in Medicine

(15:54):
for his contributions, and countless people have benefited from the
technology since its first introduction. A CT scan can help
doctors identify potential health threats like blood clots and tumors
if you're scanning the brain. Obviously other stuff too. Anyway,
that's just a quick overview of how CT scans work.
And I apologize that this is a short episode, but

(16:15):
I am a bit limited when it comes to researching, writing,
and recording at the moment. And that brings me to
why I had to have a CT scan on December thirtieth,
twenty twenty three. So I've had migraine headaches on and
off for a few years, but usually I just get
a couple each year, like maybe like three or four,
maybe five or six on a really bad year. But

(16:36):
late last year I started getting them more frequently and
I was generally feeling pretty bad. And on December thirtieth,
I was feeling really bad. And normally I would just
kind of try and sit things out because I'm not
good about going to the doctor, but something felt so
wrong that I've changed my mind, so my partner and
I actually headed off to the urgent care center, so

(16:59):
they're the urgent care center. They took my blood pressure
and it was off the charts, not literally, I mean
literally it was in the neighborhood of two sixty five
over one thirty. But if you're familiar with blood pressure,
you know that is crazy high. They urged me that
I should go to an emergency room. They explained I
could be at risk of a stroke. So off we

(17:20):
rushed to the closest hospital and I check in and
before long I'm brought into the CT scanner room and
that's where I got my brain's pictured. I also was
given an EKG for the first time, and if I
ever were to consider shaving my chest, it would be
because I'd be told I'd need to do another EKG,
because y'all you could call me patches. Now, let's put

(17:42):
it that way. It is not kind to the chest here. Anyway,
the doctors looked after me. They told me that the
EKG and the CT scans looked pretty good. There was
nothing there to be of immediate concern. I was not
having a stroke, but my high blood pressure is absolutely
a problem. And they gave me a mic grain cocktail, which,
despite the name, did not make me feel like I
was in The Great Gatsby or anything like that, and

(18:05):
they gave me some meds to bring my blood pressure
down a bit. Now I'm currently on a blood pressure
medication while I wait to see my doctor, which I'm
gonna do in literally a couple of days. My hope
is that my doctor and I can find a medication
and a dosage that will help bring my blood pressure
down to normal levels, because right now, the medication they
have me on it's still having me deal with abnormal

(18:27):
levels of blood pressure, and I'm still having really bad
migrain headaches. I can't even lie down because if I
put any pressure on my head, if my head hits
a pillow or anything like that, the pain becomes intolerable.
It just it adds to the pressure. So I haven't
really slept much for the last few days. Anyway, this

(18:48):
isn't a poor Me episode. I'm telling you all this
for a few reasons. One is that one of the
many things I need to do in order to deal
with my blood pressure is I have to adjust my
stress levels, and to that end, I have arranged to
reduce my publication schedule for tech stuff a little bit,
so I had been publishing five times a week seven

(19:08):
times a week toward the end of twenty twenty three,
but I'm going to switch back to three times a week,
which longtime listeners will know that's what I used to do,
but I'm going back to that. And my thought is
that if I can get things in a good rhythm,
I want to do two standard Tech Stuff episodes and
then on Fridays maybe do a news round up episode.
I also still have a ton of classic episode intros

(19:30):
and outros recorded and ready to go, so my hope
is to actually reserve those for days when either my
health isn't cooperating and I simply cannot record, or if
maybe I'm on vacation or something. So I hope you
all understand for at least a month or two, we're
going to have a lighter schedule than normal. And the
other reason I'm telling you all all this is because
I'm one of those folks who very reluctantly goes to

(19:52):
the doctor. I have no good reason for this. I
got a lot of really bad reasons, but none of
them are good. They range from en Zo to being
used to a time when my partner and I could
not easily make our way to the doctor. So we
did without. But the point is, I have these resources
available to me now, and it's dumb for me not
to take advantage of them. And I realized lots of

(20:14):
people aren't fortunate to be in a position where they
can easily seek medical care, and it's insulting that I
took it for granted when I did so. Had I
been going to a doctor regularly, I might have caught
the blood pressure problem ages ago. I could already be
treating it. Maybe I would have prevented the trip to
the er, as well as the terrible migraines that I'm
fighting now. So this is really just me urging all

(20:36):
of y'all out there. I love you guys. Okay, if
you have access to doctors but you're not really taking
advantage of it, please consider getting out of that rut.
I know it's hard because I've been there. I was
in that same rut for years and it was actually
a matter of great shame to me. It was hard
to even think about. I knew rationally that I needed

(20:58):
to be going to a doctor, and yet I wasn't
doing it. And so I'm paying for that now. And
I realize that not everyone has that kind of access,
and that stinks. I'm fully in support of making healthcare
accessible and affordable to everyone. It's not just the right
thing to do for the individual person, it also ends

(21:18):
up being right for society. Because healthy people are more productive,
then they place less of a demand on society's resources.
So healthcare is an investment that actually does pay off
for everybody, not just the patient. But enough of my soapboxing,
so there may be some inconsistency with publication in the
near future. My plan is to publish on Mondays, Wednesdays,

(21:39):
and Fridays, but there may be days where I slip earlier. Today,
for example, I couldn't even imagine sitting at my desk
and writing or recording this episode. I was in way
too much pain. But my hope is that once my
doctor and I dial in the meds I need, and
I start making some lifestyle changes that help support those meds,
I'll be back to normal, or as close to normal

(22:01):
as I get anyway. In the meantime, thank you all
so much for listening. I hope you have an amazing
new year, and I promise that I'll talk to you
again really soon. Tech stuff is an iHeartRadio production. For
more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,

(22:26):
or wherever you listen to your favorite shows.