So chest radiographs are one of the most commonly encountered
imaging exams that you'll see regardless of what specialty you go into.
So let's begin our chest radiography section
with just some basic information on the different types of projections
and techniques that can be used to perform a chest x-ray.
So this is an overview of the different types of projections that we can use.
Each one has its pros and cons and each one can be used in a different situation.
So the most commonly used is the PA and the lateral.
So when you have a normal chest x-ray that consists of these two views.
So as you can see up here, we have a standard PA
and then we have a standard lateral and this just tells you how the patients
stands in relation to the x-ray beam when these images obtained
and we'll talk about these in a little bit more detail as well.
This is an example of an AP or an anteroposterior view
which is occasionally obtained, particularly in patients
that aren't able to stand upright.
This is an example of a lordotic or semi-upright position
and we'll talk a little bit more about that as well.
So the standard PA and lateral,
again this is the view that's most commonly encountered when the patient
has a normal chest x-ray.
This here tells you what a PA film looks like when the patient is obtaining it.
So we have the x-ray machine here, we have the patient standing,
facing the detector which is right here and then we have the x-ray beam
coming and penetrating the patient from posterior to anterior.
So when you take a look at the terminology when it says posteroanterior,
that tells you the direction of the x-ray beam.
It means that it's entering the patient posteriorly and exiting anteriorly.
And it means that the detector is located anteriorly.
This is an example of what a normal PA film would look like.
An anteroposterior film means that the x-ray is entering anteriorly
and exiting posteriorly and that the detector is located posterior to the patient.
So again this is usually performed in patients that aren't able to stand upright,
so patients that are supine or possibly semi-upright
are the ones that undergoes an anteroposterior film.
So this is an example of lordotic or semi-upright positioning.
Lordotic views are performed usually when a patient is unable
to fully set up straight or stand up, so you can imagine that this patient here
is lying on their back, this would be the detector and this is the x-ray beam
coming in and this patient is either sitting slightly upright
or the beam is slightly angled when they're going into the patient.
So this would be performed in an anteroposterior projection
with the beam coming in anteriorly and exiting posteriorly.
And you can see here that this square, green square
is actually a structure located anteriorly within the patient
and the blue circle is the structure located posteriorly within the patient.
But when you perform an exam in the lordotic or semi-upright position,
anterior structures are going to appear superior to posterior structures.
So anatomically, the circle is higher up than the square
but when the beam penetrates the patient,
the square is going to appear as if it's higher up than the circle.
So it's important to keep in mind that lordotic and semi-upright positioning
results in this kind of image so that when you see the image
you can recognize it as a normal artifact of the positioning.
This is just another example of a similar situation
with the patient being in the semi-upright position
and again resulting in the same kind of artifact
with the square being located superior to the circle
just because it's anterior in position.
This is what a normal AP upright would look like,
so you would have the beam going in perpendicular to the patient,
exiting posteriorly and because it's straight perpendicular
you have normal positioning of the square inferior to the circle
which is how it's represented anatomically.
This is an x-ray view of a lordotic position,
you can see here that the clavicles appear very superior
because they are the most anterior structure,
they're located way up here rather than their normal anatomic position
which would be normally down here.
The heart also appears enlarged and somewhat distorted in appearance,
again because of this position.
So another type of position that we can use is called the decubitus position
and that can be performed in the left or the right.
So left decubitus means that the patient is lying on their left side down
and right decubitus means that the patient is lying on their right side down.
This is a very helpful projection and patients who can't undergo a lateral film,
again the standard PA and lateral are both performed in the upright view.
So if a patient can't sit or stand we then substitute the lateral for a decubitus.
So let's take a look at the difference between a PA view and an AP view.
The standard is always performed in the PA and why is that?
Why isn't an AP view used as the standard?
So if you take a look at the AP view here,
the structures that are further from the cassette appeared magnified.
The heart which is the furthest from the cassette or the detector
appears larger on the AP view than it does on a PA view.
So the PA is actually gives us a better anatomical representation
and that's why that's the one that's used the most.
You can also see it on the AP view, everything up here is slightly hazy
while on the PA view, the structures are more clearly defined.