0:01

Hey everyone, it's Mark.

0:02

Uh, now we're going to enter the ground-glass.

0:05

I love ground-glass.

0:07

Uh, it's fun.

0:09

A lot of people don't seem to care for it.

0:11

So after you go through these

0:12

sessions, hopefully you will find

0:15

ground-glass to be less intimidating.

0:18

So we'll take a look at sort of understanding

0:20

what opacity is and that it is an accepted

0:23

terminology for both radiographs and CTs.

0:26

And I'm going to

0:27

have to subdivide ground-glass

0:29

into acute versus chronic.

0:30

Acute less than a week, chronic

0:32

usually more than two weeks, and then

0:33

in between is the subacute where you

0:35

kind of have to consider both sides.

0:38

Please understand that air-space

0:40

and interstitial are artificial

0:41

divisions and you should avoid them.

0:43

It really doesn't work for ground-glass

0:45

because ground-glass is pretty much going

0:47

to be both, just like most other things.

0:50

So let's get started.

0:52

We're here's our concept morphologic patterns.

0:54

We cover consolidation.

0:55

We're going to talk about ground-glass

0:57

again. As always, avoid the term infiltrate.

1:01

So here's what you do when you approach it

1:03

for both radiographs and CT. One, is it really

1:06

ground-glass, or is it some sort of mimic

1:08

like low lung volumes or pleural effusions?

1:11

Is it acute or is it subacute/chronic?

1:15

Is there pleural fluid if it's acute?

1:20

Is there evidence of fibrosis?

1:23

If it is chronic, is the fibrosis

1:25

mild to minimal to quite severe?

1:29

And lastly, what is the distribution

1:32

of this ground-glass process?

1:34

With these, you should be able to come

1:37

up with a pretty short or reasonable

1:39

differential on what's going on.

1:42

So let's define ground-glass.

1:44

It is an increased ill-defined opacification

1:46

or whiteness with indistinctness of the

1:49

vessel margins, but you still see the vessels.

1:52

Remember, this is a descriptive.

1:54

That's all it is.

1:55

Not air-space, not interstitial.

1:57

It's just a ground-glass process.

1:59

As opposed to consolidation, where it causes

2:01

the vessels to be completely obscured, ground

2:04

glass, it's like the vessels are in a fog.

2:07

You can see the vasculature in this patient,

2:09

nice and sharp, tells us there's nice aerated

2:12

lung because of the differences in density.

2:14

Here, the density between the vessels

2:17

and the surrounding parenchyma is less.

2:20

And so the vessels look

2:21

fuzzy, like they're in a fog.

2:25

You have a nice example here,

2:27

the patient has ground-glass opacities.

2:29

It is predominantly upper lobe.

2:31

There's sparing of the lower lobes.

2:33

You can see the vessels are sharp here.

2:35

You can kind of see them

2:36

here, but it's more difficult.

2:39

This would be an acute setting.

2:41

It'd be a blood, pus, or water upper lobe.

2:44

Well, probably going to be Pneumocystis.

2:46

If you look in the card, upper lobe,

2:48

acute ground-glass, there's Pneumocystis,

2:50

not really much of a differential.

2:51

There's a couple little things.

2:53

One of the things I want to show you on a CT,

2:56

when you're struggling to know if it's ground

2:58

glass, look for that dark bronchus sign.

3:00

The bronchi should be the same

3:02

density as the surrounding parenchyma.

3:04

When the bronchus looks dark compared to

3:07

the parenchyma, that's an indication

3:09

that there's probably ground-glass present.

3:13

Ground-glass, don't use air-space

3:15

or interstitial; both are present.

3:17

This, I mean, I'm just quoting the pathologist.

3:20

Um, this is a patient with something called

3:22

desquamative interstitial pneumonitis.

3:24

It gives you a chronic ground-glass process.

3:27

It's often related to smoking and it is,

3:30

uh, called an interstitial lung disease.

3:32

Yet, when you look at the pathology here,

3:34

it's actually predominantly filling of

3:36

the alveoli with macrophages with some

3:39

associated interstitial thickening.

3:41

Again, it's an artificial distinction

3:44

between air-space and interstitial.

3:45

It leads to vague terminology, things

3:47

like, you know, prominent interstitial

3:49

markings. What, what is that?

3:52

That's not helpful.

3:53

Um, it also leads to long differentials since

3:56

you divided the diseases into two categories.

3:59

So, again, I, I urge you to, this

4:02

is ground-glass process, this is the

4:04

distribution, this is the chronicity,

4:07

and, uh, these are the likely causes.

4:10

Now, there may, there are still radiologists

4:12

out there who say that ground-glass is, uh,

4:15

not, not supposed to be used for the radiograph.

4:19

Um,

4:22

Uh, that's wrong.

4:23

Ground-glass is an accepted

4:24

description for chest radiographs.

4:26

First of all, one, where

4:28

did ground-glass come from?

4:29

I'm a history.

4:30

I love history.

4:31

It was originally described in Fraser

4:34

and Pare, chest edition one, 1970.

4:37

There were no CTs then.

4:38

And it was one of the four major

4:40

manifestations of the generalized sort of,

4:43

um, interstitial kind of like diseases.

4:46

Again, I don't tend to call it that, but that

4:48

was the first one, and this is from their book.

4:50

It's ground glass, um, is produced when the lung

4:53

tissue has increased density, often a relatively

4:56

homogeneous clouding or haze over the lungs.

4:59

It's almost sometimes granular or stipular.

5:01

So the original description of

5:03

ground glass was for the radiograph.

5:06

Later, it was applied to thin section

5:08

CT, and then from there it was just

5:11

Oh, you can only use it for CT.

5:13

No, keep going.

5:15

Well, if you don't want to use ground glass for

5:17

the radiograph, what do you want to call it?

5:18

Interstitial alveolar pattern?

5:20

That's so not accurate.

5:21

Nonspecific opacity?

5:23

Man, earn your paycheck.

5:25

Not acceptable.

5:27

Do you want to call it increased ill-defined

5:28

opacity that partially obscures the vasculature?

5:30

Sure, but that's actually the

5:32

definition of ground glass.

5:34

So, The key thing with ground glass is

5:36

that it's much more difficult to appreciate

5:38

in the radiograph, but everything is.

5:40

I mean, you see a nodule in the lung,

5:42

you do a CT, there's 20 nodules.

5:44

Oh, well, you know, you can't say nodule on a

5:46

radiograph then because you see it better on CT.

5:49

No, that, that, that doesn't hold.

5:52

Lastly, the Fleischner Society, and from 2008,

5:55

this is what they define as ground glass.

5:57

It is an appropriate term that

5:59

is used for radiographs and CT.

6:01

On chest radiographs, ground

6:02

glass opacity appears as an area

6:04

of hazy, increased lung opacity.

6:06

Alright, so, let's just put an end to that.

6:09

If someone tells you they can't use it

6:11

for radiographs, just, um, walk away.

6:14

Alright, this is what it looks like

6:16

on the radiograph, um, CT, um, CT.

6:18

We use the same terminology here, increased

6:21

ill-defined opacity, still see the vessels.

6:24

It's a ground glass process.

6:26

Now this radiograph looks relatively good.

6:29

I, you know, maybe there's ground glass.

6:31

I don't know.

6:31

Probably.

6:32

I don't know.

6:33

But in CT, yeah, it's ground glass.

6:35

There's the dark bronchus sign.

6:37

So yeah, there's going to be a number

6:38

of instances where you're not going

6:41

to be able to appreciate it in the

6:42

radiograph and you'll find it on CT.

6:45

Doesn't mean you don't use it, just

6:47

if you see it on the radiograph,

6:48

you use it, if you don't, you don't.

6:51

Okay, if you can't explain it

6:53

simply, you simply don't understand

6:55

it well enough, Albert Einstein.

6:58

So, here's how we're gonna do ground glass.

7:01

Acute symptoms, rule of thumb less than a week.

7:04

Again, just like consolidation,

7:05

it's blood, pus, or water.

7:08

And the distribution and the presence or

7:09

absence of pleural fluid is really helpful.

7:12

If there's a small amount of pleural fluid with

7:14

acute ground glass, think edema, um, capillary

7:18

leak edema, or congestive heart failure.

7:20

It's a leaky system.

7:23

Then think of the dry disease, okay?

7:25

That's ground glass with absolutely no

7:27

pleural fluid, and that's when you start

7:28

thinking of pneumocystis, pulmonary

7:30

hemorrhage syndrome, acute lung injury.

7:33

All right.

7:34

Um, this, by the way, comes from a, just

7:37

a phenomenal radiologist I get to work

7:38

with, Greg Johnson, and this was his

7:40

observation, and over the about 15 years,

7:44

um, yeah, this has held up amazingly well.

7:49

So acute ground glass, uh, diffused.

7:52

This is, uh, very extensive

7:54

ground glass, no effusion.

7:56

This is ground glass with a small effusion.

7:59

This was congestive heart failure.

8:00

This is acute lung injury.

8:02

Um, this is an acute lung

8:03

injury from a systemic cause.

8:05

Because, right?

8:07

When it's diffuse, that usually

8:08

means the injury comes from outside.

8:10

The patient also has a pneumomediastinum

8:12

because it was so acute in onset.

8:16

Now, ground glass with chronic symptoms

8:18

rule of thumb greater than two weeks.

8:19

The most important thing you want

8:21

to know here, how much fibrosis

8:23

is present and the distribution.

8:25

So if you have no or minimal fibrosis, these

8:27

are your players and we'll talk about them.

8:30

If they have a lot of fibrosis,

8:32

These are your players.

8:33

Notice the list isn't too bad.

8:36

So, this is a patient with a lot of ground

8:39

glass, centrilobular nodularity, has chronic

8:42

dyspnea, no imaging evidence of fibrosis.

8:45

You go back here and say, well, it is

8:47

airway related, so probably extrinsic

8:50

allergic alveolitis, hypersensitivity

8:52

pneumonitis, or if they're a smoker, RB-ILD.

8:55

This turned out to be RB-ILD.

8:57

The patient was indeed a smoker.

8:59

So, this is a chronic ground glass

9:01

with extensive amounts of fibrosis, in

9:04

this case, very characteristic for UIP.

9:07

Again, it's how we organize this ground glass

9:10

process, and it allows you to come up with

9:13

a very short differential or a diagnosis.

9:17

So, ground glass, this is

9:19

what we'll be covering.

9:20

The acute, chronic, and, uh, degree of fibrosis.

9:24

That's how we organize it.

9:26

So, the intro is basically ground glass.

9:29

It's an accepted term for both radiographs

9:31

and CTs, acute versus chronic symptoms.

9:35

Try to avoid the words

9:36

airspace and interstitial.

9:37

They're artificial divisions.

9:39

Both are almost always present, and

9:40

as always, avoid the term infiltrate.

9:43

Thank you very much.