Interactive Transcript
0:01
Well, hello, everyone.
0:02
Uh, my name is Marc Gosselin.
0:04
I'm a chest radiologist, uh, 20 years,
0:08
academics, uh, mostly at OHSU, um,
0:11
currently a cardiopulmonary radiologist and
0:14
general radiologist at Vision Radiology.
0:16
So over the next, uh, uh, number of sessions here,
0:20
we're going to go through cardiopulmonary imaging.
0:23
Um, some of it you've probably been taught,
0:27
but I'm willing to bet that a lot of it you have not.
0:29
Um, the approach is somewhat different,
0:32
it's something I've worked through over my years
0:35
to effectively teach this complicated area.
0:39
And so, um, let's see what you think.
0:42
One of the quotes I usually go by is
0:44
the greatest optical discovery is not
0:45
ignorance, but the illusion of knowledge.
0:48
Okay, so this is the introductory one, and what
0:52
we're going to cover today is something really basic.
0:54
When you're the perception of
0:56
abnormalities, mostly on a radiograph.
0:58
But, you know, we'll talk about CTs and maybe even
1:01
MRs too, and we're going to review the importance
1:04
of organ density and how we visualize things.
1:07
And then I'm also going to emphasize,
1:09
and this is something that hasn't been
1:10
taught, the difference between a pathology
1:13
differential and an etiology differential.
1:16
And these are very different, but they are
1:18
almost always combined, and this leads to a
1:20
great deal of confusion regarding reports and
1:24
an understanding of cardiopulmonary imaging.
1:27
So, when you're able to separate
1:29
pathologies and etiology on your reports,
1:31
it tends to be much more clear.
1:33
Uh, the clinicians understand it
1:35
as well as you understanding these
1:36
complicated things better within yourself.
1:40
It is my hope that in these sessions,
1:41
we'll expose the old propagated myth that
1:44
chest imaging is just long differentials.
1:47
No, it isn't.
1:49
Okay, concept one.
1:51
The most important concept in all imaging.
1:54
We see structures because
1:55
of a difference in density.
1:57
That's it.
1:58
The greater the difference in density,
2:00
the better we see the organ boundaries.
2:03
Okay, pulmonary vessels in the chest are well
2:06
seen because they have blood density, and it
2:08
has surrounding lungs, so we see them sharply.
2:12
Branching throughout.
2:13
When the lung becomes abnormal and
2:15
starts to become opaque, then we
2:17
start to lose the visualization.
2:19
Airways aren't seen in the lung because they're
2:21
filled with air, and it's surrounded by air.
2:24
They're the same density, so you don't see them.
2:27
Okay?
2:28
So this is what I need you to start doing.
2:30
A lot of times we get taught to
2:32
look at heart border or diaphragm
2:34
for some sort of pulmonary disease.
2:35
That's not.
2:36
But it's a nice concept, right?
2:38
You use the pulmonary vessels.
2:40
Take a look.
2:41
When you're looking here, start with
2:43
the right pulmonary artery right here.
2:46
You see the margin is really sharp.
2:48
The left pulmonary artery, there's sharp.
2:49
You can look at the on end vessels.
2:51
They're nice and sharp.
2:52
Look at the branching ones.
2:54
And when you see this, you know that
2:56
the surrounding lung is well aerated.
2:59
There's no real disease.
3:02
As opposed to this, right?
3:03
It's widespread consolidation.
3:06
There is increasing opacification
3:08
within the parenchyma of the lung.
3:10
This approaches the same density
3:13
of the pulmonary arteries.
3:14
And when it's the same, you can't
3:15
see the pulmonary arteries anymore.
3:17
You don't see that boundary.
3:19
And what you do start to see are things like
3:21
the air bronchograms, because normally we
3:24
don't see the airways, but when the lungs
3:26
become opacified, now we see the airways.
3:29
Okay, we have a reversal.
3:31
So we see things because
3:33
of a difference in density.
3:35
The same is true with CT.
3:37
When you have a good expiration here,
3:39
you can see the branching vessels.
3:40
This is my CT, by the way.
3:42
That's, that's why it's normal.
3:46
When you look at the expiration,
3:48
oh my gosh, we start to lose some air.
3:50
It becomes a little more opaque.
3:52
This is still not enough to obscure the
3:55
vessels, but it is a little bit more opaque.
3:58
And the key here is that on a normal expiration,
4:01
you should get brighter as you go back farther
4:04
where it's more dependent and there's less air.
4:06
Okay.
4:08
So that's, that's normal.
4:10
What determines density are a couple of things.
4:12
One is atomic weight of the, of the, um, organ.
4:16
So lung, which is mostly air, most of
4:19
it gets through and it comes out black.
4:21
Soft tissue like blood, some of it is stopped
4:24
and so it's more gray, and then things like
4:26
bone and metal stop most of the beams,
4:28
and it comes out white on the radiograph.
4:31
So the more dense that particular organ
4:34
is, the more photons it will stop.
4:37
Now, as opposed to the
4:38
other thing is tissue depth.
4:40
So the longer it is, or the more of the
4:44
organ it is, the more it's going to stop.
4:47
So you think of the superior vena cava,
4:49
which is filled with blood, soft tissue density.
4:52
It is vertical with fat and air on both sides.
4:55
But then over on the other side of the
4:56
mediastinum, you have the aortic arch,
4:58
and the aortic arch is horizontal blood.
5:00
It's the same density, but more
5:02
photons have to go through a farther distance,
5:05
so less get through, and as a result,
5:07
on the radiograph, it will appear whiter.
5:12
The tissue densities for
5:13
radiographs are pretty basic.
5:14
It's air, and then fat, water tissue, and metal.
5:18
So when air is next to bone, or air is next to
5:20
water or soft tissue, it will appear whiter.
5:22
They'll be sharp borders.
5:23
Air next to fat, they're a little closer
5:25
together, the borders become a little indistinct.
5:28
On CT, of course, it's much better
5:30
at picking up those differences.
5:32
So differences in density can be used
5:34
even things like for pleural effusions.
5:36
I got taught that fusions were like this veil
5:39
of opacity with hand waving from my faculty.
5:43
Well, let's look at it from
5:43
a different point of view.
5:45
You can see the vessels are nice and sharp here.
5:48
They're a little blurry over here.
5:50
And it's white.
5:51
Here it's white as well, but you
5:52
can't see any of the vessels, and
5:54
you do see little air bronchograms.
5:56
Why the difference?
5:57
Because this tells me that if you can't
6:00
see the vessels, that the surrounding
6:02
lung is abnormal, and that's obscuring the
6:05
vessels, so the problem is in the lung.
6:07
As opposed to here, it's white, but you
6:10
can still see the vessels, which tells
6:11
us there's still air around the vessels,
6:13
so it's probably outside the lung.
6:16
Like the pleura.
6:18
And what that is, is a pleural effusion on the
6:20
right side, but a consolidation on the left.
6:26
So, Imaging Concept 2, what we try to diagnose
6:30
pathology.
6:31
We always try to diagnose a pathology.
6:33
That's what's most important.
6:35
We look at the morphology of the
6:36
abnormality and its distribution.
6:38
Both are important.
6:40
Pathologic process is then suggested, and then
6:43
that is really what's important for the clinician
6:45
as far as prognosis and treatment options.
6:48
Okay.
6:49
Pathology such as this, this is a ground
6:52
glass process in the acute setting.
6:54
This is acute lung injury in a
6:56
setting of acute lung injury.
6:58
The ground glass reflects diffuse
6:59
alveolar damage pathology.
7:01
That's important because the treatment
7:03
for this is very different than say
7:05
treatment of an organizing pneumonia.
7:08
Like this.
7:09
This is a person who's got multifocal
7:11
consolidation, this coronavirus.
7:14
Um, this represents a pathology
7:17
of organizing pneumonia, which is
7:19
different than diffuse alveolar damage.
7:22
Okay, this responds to a
7:24
different form of therapy.
7:28
Now, what we can help with, and what tends to get
7:31
confusing, the etiology that injures the lung.
7:35
It is not the same as pathology.
7:38
The same etiology can cause
7:39
a variety of pathologic.
7:41
If we all took amiodarone, some would
7:44
develop nothing in the lung, others would
7:46
develop UIP, others would develop NSIP,
7:49
others would develop organized pneumonia.
7:52
And when you start to go to
7:53
lectures, or you read books.
7:56
Based on etiology, you walk out thinking
8:00
anything can look like anything.
8:02
And that's where things get confusing.
8:05
So remember people like snowflakes, we react
8:09
different to different etiologic injuries.
8:12
For example, fibrotic NSIP, that's a pathology.
8:17
Okay.
8:17
That's the injury based on the
8:19
morphology and the distribution.
8:21
We think this is fibrotic NSIP that carries
8:24
with it a prognosis and treatment option.
8:27
Now drug toxicity, that's an etiology.
8:30
So if someone says to me, hey, this person
8:32
has drug toxicity, I'm like, well, what is it?
8:36
Is it UIP?
8:37
Is it an NSIP?
8:38
Is it organized pneumonia?
8:39
Is it acute xenophobic pneumonia?
8:41
See, that's where it gets confusing
8:43
and these things get intertwined.
8:46
So there's a lot of them, but I want you to start.
8:51
To reorganize your thought process we diagnose
8:54
pathology. We look at the morphology and we
8:56
try to figure out is it one of these things?
8:59
There's a few other rare ones,
9:00
but these are the more common one.
9:02
Okay, that's what we try to diagnose.
9:07
These are etiologies and these can induce.
9:11
Most of the, of the pathologies so you try
9:14
to think well, what's the most common?
9:17
Etiology for this particular pathology and
9:19
you can list a couple. Uh, but the clinician
9:21
will have to do the workup but you know,
9:23
we can help out here now. How do you use this?
9:28
Well, you look at this. These are three
9:30
different people all with consolidation all
9:34
having an organizing pneumonia pathology.
9:37
So multifocal consolidation
9:39
consistent with organized pneumonia.
9:41
Potential etiologies would include, and this one
9:44
is graft versus host in a BMT patient, cryptogenic
9:48
organized pneumonia, which we don't know what's
9:50
inducing the organized pneumonia response.
9:52
And this one is a coronavirus patient with
9:54
acute lung injury, but with predominantly
9:57
organized pneumonia reaction, which tends to
9:59
have a better response to things like steroids.
10:04
Okay, so organize your reports,
10:07
separate pathology and etiology.
10:09
This is a patient who's got ground glass
10:11
traction bronchial excess to no honeycombing.
10:14
Um, this looks like to me
10:17
a fibrotic NSIP pathology.
10:19
And so my report would be moderately
10:21
advanced pulmonary fibrosis,
10:22
most likely fibrotic NSIP pathology.
10:25
UIP pathology is possible,
10:27
but less likely.
10:29
Consider an autoimmune disease or
10:31
drug toxicity as possible etiologies.
10:34
If tissue sampling is suggested,
10:37
you could do a VAT.
10:39
Now you see how you separate it out,
10:41
it becomes more clear in your mind
10:42
and more clear for the clinician.
10:45
So that is the introduction one.
10:48
Remember, the greater the difference in organ
10:51
border densities, the better you see them.
10:53
Pathology is what is most closely related to
10:56
prognosis and treatment options, and that's what
10:58
we try to diagnose and try to separate pathology
11:02
differential and etiology in your reports.
11:06
With that, I will say thank you for
11:08
listening and move on to introductory
11:11
session two when you're ready.
11:12
Thank you.
© 2024 MRI Online. All Rights Reserved.