Video Transcript
In this video, we will be
discussing X-rays and just how useful they can be in the field of medicine. We’ll be looking at one diagnostic
use of X-rays and one use in the treatment of certain illnesses. But let’s begin by recalling what
X-rays are in the first place. X-ray radiation, sometimes known as
Röntgen radiation after the scientist who discovered, is a form of electromagnetic
radiation. X-rays fall in the electromagnetic
spectrum between ultraviolet or UV rays, which carry less energy and have a longer
wavelength than X-rays and gamma rays, which carry more energy and have a shorter
wavelength than X-rays.
Now let’s take a look at one way in
which X-rays can be used in the field of medicine. We may already be familiar with
X-ray images, which depict the inside of the human body and are most commonly taken
when the patient is suspected to have broken a bone. These X-ray images, commonly just
called X-rays in everyday language, allow us to quickly and easily see what’s
happening inside the human body without actually having to operate on the
patient. But exactly how are these image is
formed and what do X-rays have to do with them? Well, informing these familiar
black and white images, X-ray radiation is fired at our patient, who in this
particular case is patiently standing there in the way of these X-rays. And there’s also a screen placed on
the other side of the patient.
Now, these X-rays being fired at
our patient will penetrate the patient’s skin and pass into their body, at which
point they will encounter different body parts. For example, inside the patient’s
hand, there are bones, and the rest of the hand we can imagine to be made up off
soft tissue. Well, any X-rays interacting with
the bone of the patient will be absorbed by the bone. This is because bone contains a lot
of calcium, and calcium is a good absorber of X-rays. And this means that X-rays passing
through the patient will not be able to get through to the other side if they
interact with bone. However, other X-rays which do not
interact with bone, i.e., they only pass through soft tissue, will actually be able
to penetrate through the patient’s entire body.
In other words, they’ll be able to
pass out the other side because soft tissue is not a good absorber of X-rays. And so what we’re saying is that
some of the X-rays will be absorbed by the patient’s body. And these will be the ones trying
to pass through something like bone or teeth because these are both good absorbers
of X-rays. Other X-rays only passing through
soft tissue and organs will be able to pass through the patient’s body. And this is where the screen comes
in. The screen, originally light in
color, changes color whenever X-rays interact with them. In other words, the X-rays that are
allowed to pass through the patient’s body will hit the screen behind the
patient. And this causes the screen to go
darker in color.
Therefore, all of the regions where
the X-rays have passed through the patient and interacted with the screen will go
darker in color and all of the regions where the X-rays were absorbed, such as, for
example, by the bones inside the patient, will remain lighter in color because no
X-rays have passed through to those regions. And this is how X-ray images are
produced. They’re often useful in helping us
see if any cracks or fractures exist in the patient’s bone. And it’s this contrast between
parts of the body that do absorb X-rays, such as bones and teeth, and parts of the
body that don’t, such a soft tissue organs and flesh, that allows us to produce
X-ray images. And this is one very common use of
X rays in the field of medicine.
So now that we’ve looked at a way
in which X-rays are used to image the inside of the human body, let’s look at how
X-rays can be used to treat certain kinds of illnesses. To understand this, though, let’s
first recall that X-rays are form of very high energy electromagnetic radiation. In fact, only gamma rays carry more
energy than X-rays do. But we should also realize that the
electromagnetic spectrum is a continuum. In other words, the energy
continuously increases as we go from left to right the way that we’ve drawn it
here. This means that even within the
part of the electromagnetic spectrum that we’ve called X-rays, there is a range of
energies present. This means that there are X-rays
with slightly lower energy down this end and X-rays with slightly higher energy down
this end. Importantly though, all X-rays are
form of ionizing radiation.
Let’s recall that ionizing
radiation is radiation that has enough energy to remove electrons from atoms,
turning those atoms into ions. This means that as X-rays enter the
human body, it is possible that they will interact with some of the atoms forming
the human body and ionize these atoms or turn them into ions. This ionization process can end up
damaging or destroying the cells that these atoms are making up. And when we’re just imaging the
inside of the human body, like we did when we were forming X-ray images, we do not
want this ionization to happen. We do not want to damage the human
body cells. In that situation, all we’re trying
to do is to see what’s happening inside the human body without damaging it in
anyway. And so to minimize the risk of any
damage occurring to the human body, when we’re imaging, we use low-energy
X-rays.
And we can recall that the lower
the energy of an electromagnetic wave, the longer the wavelength because on the
diagram that we’ve drawn here as we move from left to right, the energy
increases. But the wavelength increases in the
opposite direction from right to left. So we use low-energy X-rays for
imaging purposes to minimize the risk of any damage occurring to the human body. However, in some cases, we actually
want to harness the ionizing power of X-rays. And we will, therefore, end up
using high-energy X-rays. One such use is an X-ray
therapy. This is where high energy X-rays
are sent into the human body, usually in very specific locations, to damage the
cells that form a cancerous tumor. We want these X-rays to ionize the
cells forming this cancerous tumor so that those cancerous cells get destroyed.
In other words then, these
high-energy X-rays are used to treat cancer. The reason for this is that cancer
cells have a form of genetic mutation that allows them to multiply rapidly. In other words, the tumor will grow
in size. And cancer cells don’t even die
quickly. So the tumor grows and grows, which
is why we use these high-energy X-rays to kill the cancer cells. But when we do so, it’s important
to ensure that not damaging any of the patient’s other healthy cells. In other words, we wanna try and
make sure that these X-rays are very specifically targeted at the tumor and nowhere
else. There are very clever techniques
that allow very narrow beams to be targeted at a cancerous tumor whilst minimizing
the damage felt by other healthy cells.
For example, if we have lots of
narrow beams of relatively weak intensity, all pointed at the tumor, then all of the
bits of the body that each beam passes through is not going to be massively affected
because, as we said already, the intensity of each beam is weak. However, because all of these beams
converge at the tumor, the tumor itself is going to feel the full brunt of all of
these X-rays. And because all of these X-rays are
high energy X-rays, they’re highly likely to damage the cells in the cancerous
tumor, therefore, killing the tumor without damaging too many of the healthy
cells. So that’s the second use of X-rays
in medicine that we’ll be looking at in this lesson. Once again, it’s known as X-ray
therapy. So now that we’ve looked at both
X-ray imaging and X-ray therapy, let’s take a look at an example question.
Do the X-rays used in X-ray therapy
have a higher frequency, a lower frequency, or the same frequency as those used in
X-ray imaging?
Okay, so in this question, we’re
comparing the frequencies of X-rays used in X-ray therapy and X-ray imaging. So let’s first recall that, in
X-ray imaging, X-rays are sent into a patient’s body because some parts of the body,
such as bones and teeth, will absorb X-rays, whereas other parts, such as flesh and
soft tissue, will not absorb X-rays. Therefore, some of the X-rays pass
out the other side of the human body and then hit a screen placed behind the
patient. This then results in an image of
the inside of the patient forming on the screen because the regions of the screen
that remain white are the regions where no X-rays have interacted with the screen
because those X-rays were absorbed by the bone in the patient’s body. Whereas the regions that go dark
are regions where X-rays have interacted with the screen because they’ve been able
to pass through the patient’s body due to interacting with regions that as soft
tissue, which don’t absorb X-rays very well.
And so the end result of this is an
image that shows the contrast between regions that do absorb X-rays and regions that
don’t absorb X-rays, resulting in an image of the inside of the patient’s body. Now in X-ray imaging, all we’re
trying to do is to take an image of the patient’s body as we’ve mentioned
already. We do not want to damage the
patient’s body using the X-rays that we’re sending into the patient because,
remember, X-rays are a form of ionizing radiation, which we can recall is radiation
that has enough energy to ionize atoms. Now, if these X-rays that we’re
sending into our patient were to ionize lots of the cells in this patient’s body,
then this could seriously damage the cells that these atoms were making up,
therefore greatly harming the patient. This is exactly what we do not want
to happen. We want to minimize the risk of any
ionization occurring when we pass X-rays into a patient. And so to minimize this risk, we
use low-energy X-rays.
Now, let’s contrast this with X-ray
therapy. Let’s say we’ve now got a patient
who’s got a cancerous tumor in their body. In this case, what we can do is to
use high-energy X-rays and target them towards the tumor specifically so that these
high-energy X-rays will have a high chance of ionizing the atoms forming cells in
the tumor. This ends up killing the cells in
the tumor and therefore shrinking the tumor. In other words, we’re using
high-energy X-rays to treat cancer. And so what we’ve realized is that
X-ray imaging uses low-energy X-rays, whereas X-ray therapy uses high-energy
X-rays.
However, in this question, we’ve
been asked to compare the frequencies of the X-rays used in X-ray therapy and X-ray
imaging. Well, at this point, we can recall
a property of electromagnetic waves, the fact that the energy of an electromagnetic
wave is directly proportional to the frequency. In other words, an electromagnetic
wave with high energy is also going to have a higher frequency. And from this we can deduce that,
in X-ray imaging, we use low-frequency X-rays, whereas in X-ray therapy, we use
high-frequency X-rays, which means that the X-rays used in X-ray therapy have a
higher frequency than the X-rays used in X-ray imaging. And that is the answer to our
question.
So now that we’ve taken a look at
an example question, let’s summarize what we’ve talked about in this lesson. Firstly, we saw that X-rays are
form of electromagnetic radiation. They are found in the
electromagnetic spectrum between ultraviolet or UV light and gamma rays. Secondly, we saw that X-rays with
comparatively low energies are used in X-ray imaging to visualize the inside of a
patient’s body. Some parts of the body, for
example, bones and teeth, absorb X-rays better than other parts. And we use this difference in
absorption to form X-ray images. Lastly, we saw that X-rays with
comparatively high energies are used in X-ray therapy. These X-rays are targeted at
cancerous tumors, thus ionizing the atoms forming the cells in the tumor and killing
these cells.
