Is It Real or Is It an Artifact - SD

Introduction

Hi, I'm Peter Cooper Berg.
I'm a professor of radiology in the Department
of Radiology at the University
of British Columbia in Vancouver, British Columbia.
And for a long time I've been interested in artifacts in
ultrasound and is it real or is it an artifact?

Is It Real or Is It an Artifact?

Hi, we're gonna talk about is it real
or is it an artifact?
And that is things are not always like they seem.
For example, I don't know
what you thought this was, but it's not.

Now, when it comes to artifacts, every kind
of imaging modality has artifacts.
And these are things that show up on the image
that don't really appear in the patient
and can cause you to make a diagnosis
that isn't really there or miss a diagnosis that is there.
There are all sorts of artifacts,
particularly in ultrasound,
and here are some of them that we're gonna talk about.
Reverberation artifacts, mirror image, ring down,
shadowing enhancement, refractive side,
low beam width, duplication.
Then when you get into color, you get a whole lot
of new artifacts that you can see listed over
there, seascapes.

So Oct. Now, despite all the great technological advances
that have gone on in the last 30 years,
unfortunately there are still artifacts, but I'll try
and point out as we go along what some
of the advances have done
to minimize the artifacts or to prevent them.
And unfortunately, what new artifacts have come along since
we have these new physical advances.

So before we get started, many of you I'm sure already know
that some basic artifacts,
but just to start out, to show you
that there are some new ones that
you may not have seen or thought about before.

Non-Blood Flow in Cystic Structures

Here you can see a scrotal scan
and clearly there's a cystic structure
beside the right testes that you see there.
And if you turn on the color, you can get blue,
you can get a color in a cystic area,
and you might think this is the world's
largest varicose seal.
And if you turn on the power, the pulse doppler,
you can see that there actually is some movement
and in fact the movement is below the baseline.
So it's away from the transducer
accounting for the blue color.
I have a video that shows that in fact,
when you turn on the color flow doppler,
there's enough power to make some material
that is invisible on the gray scale image.
Not only become slightly visible,
but start to move away from the transducer.
There's enough power to make little dots within the image
move away from the transducer.
So in fact, it isn't an artifact, it's a real material
that is not in solution, that is in suspension
and it is moving away from the transducer.
So it's not artifactual flow, it's real flow,
it's just not real blood flow.
So that's the kind of thing that
can fool you when you're doing ultrasound in the modern day.

Basics of Ultrasound Physics and Artifact Formation

Now we all remember
that ultrasound basically detects the time of flight.
Distance equals rate times time,
and we set the rate to equal the nominal 1540 meters per
second, which by the way is about a mile per second just
to tell you how fast it's going
or one meter in a millisecond.
Now the sound goes down from the transducer,
hits an interface and bounces back up to the transducer.
But if we were to put an oblique, an angled reflector in the way where the transducer is pointing
and another interface further out,
the sound beam can go down to that oblique angled interface,
bounce off it, go over to
where there is an actual interface in the body, bounce back
to the oblique interface, back up to the transducer.
And all the transducer knows is
that the time it took from leaving the transducer from the
main bang to when the echo comes back
to the transducer is equivalent to the time it would take
for an echo to go in a pulse to go in a straight line
and hit an interface down here and come back up.
So it displays it at the appropriate distance
and in the direction that the sound beam was pointing.
So that's how you can get artifacts
and there's very little you can do
to get rid of them for the most part.
And the easiest one to understand would be a
reverberation artifact.

Reverberation Artifacts

Here the sound leaves, the transducer hits a real interface,
some of it bounces back to the transducer, is absorbed
by the transducer, puts an echo on the screen
and a blip on the screen.
Some of it however, bounces back from the transducer skin
interface into the body, comes back up again
and displays the first reverberation artifact
and then some of it can go back and forth again
and display the second reverberation artifact.

And here's an example of somebody
with a pacemaker in the right side of the chest.
The sound is going from here to there, back up to there.
Most of it comes, is absorbed so that you do get a real interface displayed.
But some of the sound goes back down, back up again is
amplified because you have a TGC set
and comes back as this,
which is completely artifactual actually there should just
be shadowing between there.
All of this is artifact coming from what's
between the transducer and the actual interface.
And that's the first reverberation
and the second reverberation.
And all of the stuff in the middle is more
and more of the sound bouncing back and forth.

Now here's an older scan,
but I think you can see the bladder here, the vagina cervix,
there's the uterus and we know
that there could be some sludge
or blood in that cystic degeneration in the fibroid.
So we know that that's real and we just ignore this.
We all know to ignore this
because clearly this is just artifactual.
But what is it? It's reverberation artifacts first rever,
first reverberation, second, third, fourth,
fifth, all the way down.
And we don't think it's floating sludge,
we just ignore it sometimes.
However, it can get in the way.

Again, this is an older slide,
but remember that anything that we see now with much, much,
much better equipment will be completely distorted If you
have a fatter patient with a lot of subcutaneous fat
and any of these things are much harder
to decide if they're real
or not, if you have an ideal situation such
as an obese patient or you're trying to get more out
of a higher frequency transducer, et cetera.

So here we see the liver.
This near zone is not being shown very well,
but we can detect that there is the deep end of a cyst
and there is enhancement through it.
So what's the story going on up here?
This is again, reverberation artifact
and it's superimposed over the rest of the cyst.
So you can't actually see it.

Now with fingers crossed, we'll see if this works.
And actually it does. So you can see when the liver moves
back and forth that the reverberation artifact stays there
because the actual interfaces in the body causing the
reverberation artifact are not moving.
So the liver, the cyst and the enhancement move back
and forth, but the artifact doesn't.
So when you're moving the transducer
or the patient's moving, you can tell that
that's artifactual echoes within it.

Other things that you can do,
here's an example without tissue harmonic imaging.
Tissue harmonic imaging is a way of getting rid
of near zone reverberation artifacts.
And that happens because of looking at different frequencies.
You filter out the fundamental frequency which causes most
of the artifact and you're just left with the
harmonic frequency
and that gets rid of a lot of the artifact.
There's pulse inversion as well
and that can get rid of some of this kind of noise artifact
and clean it up so to speak.

Now here you have another technique I think most
of you can appreciate that there's a
hemangioma posteriorly in the liver.
You can actually see a mirror
image, which we'll come back to.
And can you see anything else?
Well, let's look with this other
technique called compound imaging.
Now can you see anything else?
Well, let's look over here
and magnify, in fact, there's a structure there.
And if we magnify this one here,
you can actually see the structure.
And I think here you see it with the borders outlined better
because of the so-called real-time compounding.
One of the companies calls it sono CT
and it increases the signal to noise
by aiming the beam in different directions
through the various lesions.
So sono ct, real-time compounding
can enhance the appearance of lesions.

Other things that can make lesions stand out when they
otherwise wouldn't is if you give the patient contrast enhancement, intravenous injection.
It goes to the rest of the liver
and not where there's a lesion.
So whereas there would be a lot of noise here, in this case,
you can see the lesion much better
'cause you've increased this signal to noise ratio
by giving the contrast.

Reverberation Mimicking Pathology

How about this Here we have a different kind of artifact,
but we have a patient who's got a bladder here
that you can see, maybe a slightly thickened wall,
but let's not worry about that.
And behind the bladder there's
what looks like a cystic structure.
And on the longitudinal para sagal examination
looks like a cystic structure.
And not only that, but note
that the distance from the transducer to the back
of the bladder where the rectum should be is less here
and the cyst looks smaller.
And note that over here
where the bladder is bigger, the cyst looks bigger.
So is this a left ovarian cyst?
In fact it's a
reverberation artifact causing the appearance
that looks like a cyst when it's just a reverberation from
the transducer to the rectal air
and back again, that simulates a ovarian cyst.
It's actually all an artifact.
There should be shadowing completely under there.
It's not as smooth deep surface.

Here's, you can hardly see a strong reflector at all.
And to check it out, check out those distances.
If the distance from the transducer to the interface,
the rectal air interface is the same as the distance
to the back of that cyst, you can be fairly confident.

Now sometimes you can get into a case like this
where you see an artifact, clearly an artifact,
so you assume that that isn't real.
But in fact this patient, they sent back again
and the gynecologist said, look, I feel something there.
Have another look at it. And you can tell, oh,
this is a very sound attenuating fibroid.
But nonetheless this is real.
And it was just obscured by the fact
that there's an artifact there.
So you have to be careful.
An artifact can hide real pathology
and be careful not to get stuck on that.

Mirror Image Artifacts

Now how about this to the casual observer,
this looks like an artifact.
You would like to think it's an artifact.
It hasn't got a smooth deep border.
You've got an air ring down artifact, which we'll come back
to going through the middle of it.
It should be gas and the rectum up there.
But if you look at the distance from the transducer
to the deep part of the bladder
and from the deep, the anterior wall of the rectum down
to the where the artifact shows up,
obviously this is longer than that.
And if we look at it longitudinally,
you can see what's causing it.
When the transducer is pointing in this direction,
there's a short distance through the bladder
and a long distance through the artifactual cyst when it's pointing
that in this direction, it's a longer distance through
to the back wall of the artifactual cyst.
And in fact, can I convince you
that the sound is going down here, bouncing down to the
inferior aspect of the bladder back up there
and back up here again.
So in fact, this is a mirror image of that.
So this is the same kind of artifact,
but in this case it's caused by a mirror image,
not reverberation, but a mirror image artifact.

And here we have two cases where one
of them is an artifact and one of them is real.
And I think most people when they look at it say, ah,
this must be the real one.
And then if you try to analyze the physics
and the various things that I've been talking about,
you still realize that this is real.
And this is an artifact
because the curvature that you expect from the bottom
of a cyst is present here
and the curvature you expect from the bottom
of a cyst is not present here.
It seems to go down to a point.
So this is the real one, this is the artifact one.

And what about these? Here's a patient
with a Foley catheter in a trabecular bladder
and posteriorly, you can see the mirror image
of the trabecular bladder and the Foley catheter.
So this is a mirror image of that.
On the other hand, here is a Foley catheter in the bladder,
which has collapsed in this case.
And here again, not the best scan here is a
what looks like a Foley catheter behind it.
Is this a mirror image?
In fact, that one was a patient who had an abscess
and the surgeon put a Foley catheter into the
abscess after he drained it.
So there was a Foley catheter there.
On the other hand, this one is a mirror image.

And here's another acute mirror image.
Patient has a transitional carcinoma
projecting into the bladder.
This is a complete mirror image
of the transitional carcinoma,
but it looks like it could be spread
of the transitional carcinoma
through the bladder wall into the ascites in the pelvis.
In fact, there's no ascites in the pelvis.
I don't imagine that the spread of a tumor
through the bladder wall would look identical
to the bladder tumor inside the bladder.
So this is just a mirror image,
whereas the other case was real.
Be careful not to miss real structures for artifacts.

And here we have another mirror image artifact.
The more typical kind
that you might see sometime here is the liver,
here's the right kidney, and here is a hemangioma, not
as well seen as it could be.
And here's the mirror image of the hemangioma
above the diaphragm.
In fact, we have a mirror image of the right kidney
above the diaphragm as well.
So the sound is bouncing off the diaphragm,
actually it's the diaphragm lung air interface
and reflecting back up.
So it goes down here down to the hemangioma back up here and back to the transducer
and is displayed just like another
and the other kind of mirror image
as you can see in this diagram, mirror image artifact.

Here we have a similar one,
a mirror image artifact of a cyst.
Okay? So there are no echoes here.
So you get a mirror image where there's no echoes.
But then of course the question comes up, well
what are these echoes we're seeing there?
And what are these echoes we're seeing here?

Now here, if you're gonna have increase through transmission
to the cyst, it's gonna be over there.
There's no increased enhancement of the sound
through the cyst in this direction.
And yet here it shows you the increase through transmission,
through the artifactual cyst in this direction,
which should be that one over there.
And of course that's because the sound
that we're seeing is bouncing through there back up
and back to the transducer.
But it brings up another important point too, that all
of the echoes that you see above the diaphragm in the thorax
that look like they're coming from the lung are all mirror
image artifacts of what you see
below the diaphragm in the liver.
So the when you see noise above the diaphragm,
you think it's coming from the lung, it's not,
it's coming from the liver.

Now here's one, you could say, oh,
this one must be an example of the hemangioma
or something in the lung.
Maybe consolidate a lung with a lung tumor in there,
or a small, relatively small lung nodule.
But this is because we're only
thinking in two dimensions.
And in fact you have to think in three dimensions.
And if you move the transducer over, you can see
that there is in fact a hemangioma in the liver
and you have to manipulate the plane of section accurately
so that you can get the hemangioma, the reflector,
the diaphragm lung interface
and the artifact in the same plane of section.
So you can show the artifact
and you can show the image without showing the other,
but you have to find it to see which direction the scan is going in that plane section.
In other words here it's bouncing off the hemangioma,
which is out of the section off the diaphragm
and just showing the mirror image on that particular image.

And here's another good example longitudinally.
You can see this is the isthmus of the thyroid.
There is a mirror isthmus of the a mirror
of the isthmus of the thyroid.
Here you can see the isthmus of the thyroid.
Here you can see that mirror image.
And one of the first patients we had with this kind
of image did in fact have strider
and they were wondering if the patient had
a lesion in the trachea.
And we thought, maybe we have one.
But again, this is a mirror image.
The sound is bouncing from here up there
to show the isthmus.
Over here it shows the mirror image of the isthmus.
And interestingly, it also shows you the mirror image
of the tracheal cartilage ring.
This is the air column in the lung.
This is the air column in the lung.
These are the short axis sections of the
tracheal cartilages.
And this these are the mirror images
of the tracheal cartilages
and this is the mirror image of the isthmus.

And same thing happens with color flow.
In fact, it reverses it so that the vessel that's closer
to the transducer is red
because the flow is going towards the transducer.
And here it's blue 'cause the flow is going in the same
direction, which in the mirror image looks like it's going
away from the transducer.
So you can get mirror image artifacts of color flow.

We're gonna come back to some color flow in a minute,
but here's an example of another kind
of mirror image artifact that we're all used to,
especially if you ever comb your hair in a mirror
or look from an angle, you can see this is the surface
of water showing downtown Vancouver.
Here's something that looks a little bit like a mirror
image, it's a or a reverb.
It's a an aside
because as we were watching this, this moved away
and of course we knew what we were doing
that was a whales flipper.
And this was done quite a while ago.
But it's interesting what the media population
and reporters can get out of what you tell them.
I joke that these were the two male whales in the pool
and they wanted to know who the father was,
which of course you couldn't tell 'em.
But note that the reporter got,
he thinks he identified a fluke part
of the fetus whale's tail.
I said, if I see anything it'll be a fluke.
And of course she assumed from that,
that the fetus is fine, not an artifact.

Ring Down Artifacts

How about this one? Here's the poor image,
but of the right kidney, the right lobe of the liver.
And here are some structures, linear looking structures
that start from them in the middle of the liver and go down.
And of course this could be an ice pick
that was thrust into the patient, but it's unlikely.
In fact, these are ring down artifacts, also known
as comet tail artifacts.
In this case, patient was shot full of lead from a shotgun
and those are ring downs from the little bits of shot.
There are other things that can cause ring down artifacts
more commonly than clips or shot.
And this is some gas
that in this case is in a normal position in the duodenum
between the head of the pancreas and the gallbladder.
That's where the duodenum is
and the bubbles can cause that kind of ring down.

Here's another more recent example
where you can see gas bubbles in the duodenum
behind the gallbladder.
And again, you can identify
where the duodenum is because of that.
You can see it's not in the bowel,
which of course is over there.

And here's something that looks ring down.
Again, this is in Vancouver.
This is looking up towards gross mountain and downtown.
And you can see because of the way there's unevenness
and little wavelets in the water,
it looks like a ring down artifact in the water.

Now what causes that for a long time we were trying
to figure out why would you get ring down
sometimes and not other times.
And one of our residents was interested
and he worked in the evenings
and he developed this plastic cap that he held down
and he injected bubbles into it.
And you don't get this ring down
or comet tail artifact
until you've injected one bubble into the second layer.
You fill up the top layer.
When you inject one bubble into the second layer, you get
what he called a bubble tetrahedron, four bubbles together.
And the fluid that the bubbles were surrounding,
he called a fluid bugle.
And if a tiny pulse of sound goes into
that fluid bugle like blowing into the back of a bugle
or a trombone or another instrument,
the sound coming out of it lasts longer.
And if the sound lasts longer, it'll ring in the transducer
and give you a longer looking sound as you can see here.
So something you probably never wanted to know,
but if you ever see these ring down artifacts,
you can tell the others this is caused
by a bubble tetrahedron containing a fluid bugle.

Now you can differentiate the air
in structures as you see here.
This is the bile duct
and you can see some air now sometimes you get the air here
and you can see some air there.
And this one doesn't have a
fluid bugle I guess in a bubble tetrahedron.
So there's no ring down here.
There is some ring down here,
there is ring down intermittently,
but notice how different the air in the bile duct looks from
a stone in the bile duct
because the air reflects the sound back
and there's a much higher reflection
of sound whereas the stone absorbs the sound.
So you get a shadow deep to it.
You never get ring downs from stones,
but you do from air bubbles.
So that's air in the bile ducts with ring down.

This is a pneumobilia and a common duct stone.
Here you can see another example
and you get a little off axis artifacts.
So it looks like a little cap on where the bubble is in
that ring down and you can see some other
non bubble tetrahedrons.
So that again is pneumobilia. And how about this one?

This is actually a very important clinical diagnosis
that you might be able to use the artifact to identify.
And you can see a little ring down up here.
It's not in the liver, it's outside the liver.
So this is a case of pneumoperitoneum.
In fact, the patient had a perforated duodenal ulcer causing
the pneumoperitoneum
and our sonographer was able to make that diagnosis
by seeing the ring down.

Other things that can cause V-shaped artifacts
or comet tail artifacts
or ring down artifacts are cholesterol crystals which are
flat and if you hit them on the edge,
they'll ring just like a metal clip or a shot BB
or gun shotgun pellet.
Here you can see stones here,
you can see these little tiny echoes in the wall
of the gallbladder with ring down deep to them
and they sometimes but not always indicate adenomyosis,
which we don't have to get into here.

Beam Width and Shadowing Artifacts

Now what about the width of the beam?
There is a definite width to the beam
and I'm sure you remember,
or at least you vaguely remember,
that there's a near zone called the Fresnel zone
and a distal zone called the Fraunhofer zone.
And the sound is relatively parallel in the Fresnel zone
and then starts to splay apart like a flashlight
splaying apart in the Fraunhofer zone.
And they're related to the diameter
and the frequency and things like that.
You can curve the transducer.
Originally they used to make different transducers
with different radius of curvature,
which would focus the sound beam in the near or Fresnel zone,
but then it got worse out in that Fraunhofer or distal zone.
And now of course we can do it all electronically
and we can change the relative curvature
by putting in the delay lines
between the outsides and the inside.
And I won't get into that.
But nonetheless, the narrowness
of the zone is very important.

And one of the things that's very important
for is showing a shadow.
You know that shadows can help us make a diagnosis
of a stone or edge shadows for other reasons,
but you have to block out the entire sound beam in order
to be able to show a shadow.
If you have the structure that is not allowing sound to
traverse in the focal zone
but too small, you won't get a shadow.
So you'll get an echo coming back from it,
but the sound will zip around beside it to interface with
interfaces deep to it and echoes will come back.
So you won't notice that there's a shadow if the structure
is too small and if the structure's big enough
but not in the focal zone, electronic
or mechanical, then you also won't get the shadow.
So you have to have the beam narrow enough to be able
to be blocked out completely by that stone
so that you can see it.

And here's a good example.
This is in an OB case,
but look at the ribs that you can see there.
And this is when we could pick a focal zone.
This is a an array.
So you can pick a focal zone that does show the ribs
to best advantage and also shows the shadow
'cause the rib is completely blocking out the sound and
therefore you get that shadow deep to it.

What if we move that focal zone down as we see here?
Now you can see the ribs way up here
and they're a little bit broader.
They're not as finely focused as you can see up there.
What happened to the shadows?
We can see them here a little bit
and here we don't see them at all.
So this is terrific if you don't want the effect
of the shadow from structures in front of it.
On the other hand, it's not as good if it was a gallstone
you're looking for and you want to see the shadow.

And here's something really interesting just
to show you a little bit about how
multiple focal zones work in the original ultrasound machines, the
you could pick a couple of focal zones.
Now you can pick a whole focal area,
but you could pick a couple of focal zones
and this one would give you the information up here.
And this one would give you the information down here.
So as the rest of the image, the deeper part
of the image from this focal zone would've shown you the
artifactual shadows, the shadows,
it doesn't if you have this part of the image produced
by the transducer when the focal zone was down here.
So this is just two focal zones
and the integration between the two focal zones didn't used
to be as good as it is now.
So you could see a clear cut interface.
So this is the focal zone right through the ribs.
You see the ribs well in the shadows.
Well this is the focal zone through the deeper part of the
fetal body.
And you can see that information better
and you don't see the interfering shadows from the ribs.

Now here you have a transverse section
of a gallbladder here there's a gallstone
and clearly the sound is being absorbed by the gallstone.
It's bigger than the sound beam.
So there is a clear cut shadow.
But notice on the other hand you also see some shadows here
where there aren't any gallstones.
And these are called edge shadows or refractive shadows.
And a refractive shadow is caused
by the beam being defocused at the edge of a
water solid interface at the edge of the cyst.
The sound beam is being defocused, not reflected defocused
because of refraction and
therefore you can get shadows at the edge of structures,
which sometimes can help you
but sometimes can cause trouble
as here you can see an oblique interface.
The sound beam is being defocused here so
that it looks like could be fluid between the placenta
and the bladder could be fluid outside the uterus
between the uterus
and the bladder, both of which are extremely unlikely.
And the way to take care of it is just move the transducer
down towards the symphysis and aim up
or if necessary fill up the bladder
and then you can see that.

So this is a refractive shadow
that you can completely get rid of
and show it clearly by filling up the bladder.
Of course then it looks a little bit like there's a placenta
previa, but I'm sure you can differentiate that,
change the angle and you'll be able to see that.

Now other things that can happen
with refractive shadows aside from the edges
is the beam may be diffracted to show you the diaphragm
where it's actually deeper than it should be.
So it looks like there's a discontinuity
or a ruptured diaphragm here it looks like there's a
discontinuity in the kidney.
So that edge shadow by bending the beam to where the
kidney is actually further away makes it look like
there's a disruption of the kidney.
And hopefully that won't cause you any trouble.

Enhancement and Refractive Artifacts

Now you know that there's enhancement of the sound deep
to a cyst and
therefore you get the echoes brighter deep to the cyst.
And that's because we have a TGC
and we're amplifying the echoes in the deeper part
of the liver more than we're amplifying the echoes in the
near part of the liver because the machine,
the equipment is expecting that the
sound is gonna be attenuated all the way
down in a uniform fashion.
And if you interject a cyst
that is not attenuating the sound, then
the echoes are displayed from the deeper part of the cyst
with increased intensity.
So that's the usual reason for seeing enhancement deep
to a cyst because
of lack of attenuation.

But look at this one, this is
one interesting case that we had.
Here's a small cyst behind the big cyst
and I turned the gain down so that this
echogenicity isn't as bright as you see it over there,
but you can see from the small cyst there's additional
enhancement deep to that small cyst relative
to the enhancement deep to this large cyst.
And how could that occur? Is that caused by the lack
of attenuation in the cyst?
Well in fact in addition to the lack
of attenuation in this cyst, there is refocusing
of the sound deep to that
and refocusing causes enhancement of the
echoes deep to it.
So we talked about defocusing shadows
and refractive refocusing that makes it look even brighter.
So the cyst can be due to several, the enhancement deep
to cyst can be due to several causes.

Now how about this, this is on the left side
as you can see the left kidney, the should be the spleen.
And then what about what's going on up here?
Is this some sort of refractive defocusing
that's giving us a relatively echo poor area?
It looks like there's some vessels in
that relatively echo poor area.
And we actually did unfortunately cause trouble in some
of the early days thinking this could have been an abscess a
patient was operated on.
We didn't see it as clearly as that.
Another patient we thought had a hematoma, she was
did a lot of fitness and was a fitness instructor
and she had a pain in her left side
and we thought this could be a subcapsular
hematoma of the spleen.
But in fact when you watch it you can see
that this moves separately from that.
And here's one of the early uses of MRI to help ultrasound
and we can see that the liver comes all around
to the left side and is interposed between the spleen
and the left side of the abdominal wall
and it's just the liver.
So this is in fact not an artifact, it's not any kind
of shadowing or refractive artifact, it's just the liver
that happens to be there in left
individuals, almost always women.
So that's the liver over the spleen, not an artifact.

And here you can see a similar thing except instead
of being echo poor it's echogenic.
Although we usually think that the liver is
echogenic relative to the spleen.
I've just shown you that it's usually echo poor when it's on
the left when you see it in the left side.
And this patient, in fact in the rest
of the liver had fatty infiltration steatosis of the liver.
So that's why in this case the liver interjected is brighter
than on the than the spleen.
And this is looks the same, looks like the
liver over the spleen but in fact this is the liver.

So do you think the spleen could get large enough
to come over to the right side
and interpose itself between the diaphragm
and the rest of the liver?
In fact not, is this an artifact? In fact not.
This is geographic fatty infiltration,
this is fatty infiltration.
There's less or no fatty infiltration in there.
So it is not an artifact that looks like an artifact And
you can find all sorts of interesting things.

This is a patient who has ascites
and this looks like either a metastasis
or fat somehow superimposed
or sitting on top of the liver in the ascites.
And in fact if you're able to move the transducer down,
you would see that this is just liver tissue,
normal liver tissue,
but there's enhancement deep to the fluid
and there's a refractive shadow heightening the appearance
that maybe this is not normal liver
and should be something different.
On the other hand that's just ascites.
On the other hand this is a metastasis in the ascites
sitting on the liver
and clearly you would have a hard time explaining a convex
indentation shape
and bending into the liver as caused by an artifact.
So that is a metastasis.

Here are two other cases of structures in the liver
that looks like a hemangioma in this case except instead
of the enhancement deep to it,
we're seeing shadowing deep to it.
We're seeing that the sound is going slower through it
because it's displacing the diaphragm backwards.
And this would be characteristics of fat.
So this is turns out to be a lipoma
or a low grade liposarcoma in the liver on the other hand
looks like there's something wrong down here.
In fact there's something wrong is up here
and it's relatively poor.
This is an atypical hemangioma with
through transmission through it.
So this is normal liver, this is the abnormality
and it's just an atypical that you can tell
because there's through transmission through it.
So that is a hemangioma that you can diagnose
because of the artifact here on the other hand is a lot of
through transmission through the endometrium in an
endovaginal scan of the uterus.
This in fact is the endometrium.
Be careful if you're measuring endometrium endometrial
thickness not to measure this
'cause that's just enhancement through it.
This should be the outline of the endometrium right there.
That's enhancement. How about this?

Duplication Artifacts

I am also have been interested in the
how nicely you could see vessels in ultrasound.
Of course that's been superseded by CTA and MRA.
But here's the left lobe of the liver,
there's the pancreas, there's the splenic vein.
And look at this. Have you ever seen two
SMA two superior mesenteric arteries?
Well it looks like we have them here
But if we move the transducer over a note,
here's the linear echo.
There's fat behind the rectus muscles,
here are the rectus muscles there,
the rectus muscles are here and there's the fat behind it.
And note now we haven't got this in the center
of the beam here, it's in the center of the beam
and the sound is being refracted back when it's in
the center of the beam to where the SMA is in the middle
and it's displaying it as though there are two.

And here you can see color flow.
So it even does it the color flow.
So it's a duplication artifact caused by refraction.

And here's the diagram, the sound is refracted back to the middle where there is an SMA
and displayed to the side
and the sound going through this side is refracted back
to the middle and displays it on the side
making it look like that.
And you can see that quite a bit.

This looks like a Foley catheter might look like
after you might look like if you had
too much to drink the night before.
But again it's that duplication
artifact caused by refraction.

And here you can see what looks like early twins.
And here you can see the reason we call this artifact
sometimes the Copper 7 artifact from two Copper 7s.
So in fact you have to be careful,
you don't hear the ups as he goes over this.
But there are snow stakes
and there are ultrasound artifacts that can cause trouble.

Artifacts in Reporting

Now this is a really interesting one
'cause we used to scan in our reports,
now they're coming at all electronic
but we used to scan them in so they'd be part
of our PACS system.
And here you notice that we didn't mention a fibroid
anywhere, but you see we have a picture
that looks like a fibroid in the anterior myometrium
extending anteriorly from the anterior myometrium
but not mentioned anywhere else
and not even displayed on the transverse.
And if you look carefully you can see
that these letters are also sort
of elongated at about the same level
that the fibroid appears.
And in fact what happened was as you scan in the piece
of paper it can get stuck and get elongated.
So in fact this is an artifact just in the
report not in the patient.
So artifacts can occur for all sorts of reasons.
There really wasn't a fibroid
and there really wasn't one on the image
but there was on the scanned in image of the report
as you can see there again, see how it makes the bottom line
of the L and the S and the E look thicker.

Side Lobe Artifacts

Okay, moving on to some other real artifacts
that can cause real trouble.
What about side lobe artifacts?
Some of the sound comes out on the side like a flashlight.
In fact, if you ever see a pointer you can try it yourself
with a laser pointer as finely focused as the beam is.
You'll if you shine the beam over your head,
you'll still be able to see some red light coming
out of your laser pointer.
You can try it. And so that means that some
of the light is going around the main focus beam
and that happens in ultrasound too.
In fact it happens even more.
And you can get enhanced areas called side lobes
and the side lobes are fairly strong sound
and if there happens to be a parabolic reflector outside,
especially if it's a parabolic reflector,
that sound could be reflected back to the transducer
and it can show up as a blip on the screen
where there isn't a real interface in the body.

Here's something similar called sun dogs given
to me by Lee Rogers.
And you can see the sun in the middle and two sister
or brother suns on either side that's caused
by ice crystals in the air.

This is a very old ad for a company that no longer exists.
And here's a picture of the liver
and you can see the individual lines of information.
And these crystals over here are firing not only in this
direction but some of the sound is going way off in
that direction to where there's some lung.
So the crystals that are firing here are detecting
that there's an interface way out there across the other
side of the image and displaying it over here so
that you get, and certainly when the crystals are firing
here, still picking up something from there
and displaying it here so you get not another diaphragm.
But this is a an image that they thought was
so good they used it in their ad in one of the journals
and yet look at that off axis artifact
or side lobe artifact that it's showing.

You can see the diagram again, okay,
and this is a relatively recent one
but you can see the
the uterus projecting into the bladder at least the hump
of the posterior wall of the bladder in a very full bladder.
And you can see off axis artifacts
or side lobe artifacts projecting off on either side
and none of you would say that's a septation in the bladder,
but nonetheless you can see those and it's not real.

And here's another one showing this kind of artifact.
It's a parabolic reflector
and you can see way over in this side some
of the sound when the beam is pointing in
that direction is being picked up, is being sent
and picked up from here
and displayed way on the other side of the image.
So this can happen, it can happen here again
and you know it's an artifact, it's going from
outside the endometrial cavity into the gestation from a
tightly curved array.

And here you can see it when you take a linear array
and you make it into a larger sector view,
you can get all these fuzzy artifacts on either side there
so you can get them.

Here's another interesting one
that I actually had very recently on
most up to date of equipment.
This is a breast prosthesis where there is fluid.
This is a breast cyst where there is fluid.
This is the back of the chest wall up against the lung
and you can see a mirror image artifact back here,
but this looks like a lymph node.
Now how can we explain that the cyst is causing an artifact,
which in this case would be a mirror image artifact
by the way a reverberation artifact goes from the transducer
to the real interface
and back to the transducer again,
a mirror image artifact is similar
but it goes from the transducer
to the real interface back up to the structure in the body
and then back down again.
In any case, there's a lot
of off axis artifact just like side lobe artifact
that we don't see in the original image,
but we can see in the mirror image.
So sometimes the mirror image doesn't look exactly like the
the original structure that's causing the trouble.
Maybe there's even enhancement there
because there is really a cyst.

And here you can see some photographic kind of
off axis artifacts.
Here's another one very pretty in this days,
in these days when there was a shutter with 11,
I think it's 11 there or nine leaves, you can see
that now we'll move on quickly to some color flow artifacts

Color Flow Artifacts

and with color flow,
what color flow is really good at is detecting the presence
of flow, detecting the direction of flow
and detecting the velocity of flow.
And with all of those you can get artifacts
that will fool you into thinking there is flow when there
isn't, there isn't flow when there is thinking
that the flow is going away, when it's going towards
and telling you that the flow is going faster
or slower than it actually is.
I'm not gonna talk about any pulse doppler
but we're just go quickly over some
of these color flow artifacts.

As I've mentioned now no color where there is flow, you have
to make sure you've adjusted everything properly.
The transducer, you have to use the right transducer,
the right transducer frequency if you can change it,
the power and the gain controls you have
to make sure the wall filter isn't set too high.
Color echo priority.
The machine can only display
where there's a white echo coming back or color.
It can't display both in the same pixel.
So that's a very important part that variable
that you can change on some machines whereas it's changed
automatically for you and others.
The scale is very important.
If you change the scale too high, you will not show color
where there actually is flow.
And it is said that you can only be confident if you show
flow in an adjacent structure where you know there's flow
and you know there's no flow.
Of course if there's a different velocity of flow, you have
to make sure that you've set all these properly.
In other words, if you look at a vein
and you don't show flow
and you do show flow in an artery,
that doesn't mean there's no flow in the vein.

And here you can see a simple-minded thing.
Obviously if there's a transverse process you'll get a
shadow and no echoes through the transverse process,
but obviously you won't be able
to see the vertebral artery either if there's a shadowing structure between it and the transducer.

And how about this, you can clearly see the hepatic veins
but you don't see the IVC
'cause it's perpendicular, so you're missing it
because you've got the wrong angle.

How about this? There's an old scan of a carotid bifurcation
and it looks like there's no flow here.
Is that because there's thrombus or is that
because there's a reverse eddy?
The reverse eddy should show up as blue,
but it may be just slow enough
that you don't show any color at all.
If you have low power versus high power, you can show color.
In fact you get the opposite.
You can show color where there isn't any flow.
We'll get back to that. How about the echo,
color priority?
That's the two dots that you see down here when it's low.
So you don't show color, you emphasize the echoes here,
you're emphasizing the colors,
so you're making the vessels look even bigger than they are
because those two little dots are up much higher.

And here you can show the difference
between diastole and systole.
In diastole there's very little flow
or relatively little flow in the arteries compared to here.
You're even seeing tiny arteries I guess
as they're moving out towards the surface of the kidney,
the renal transplant.
And yet the venous flow is going continuously in
in systole as well as the diastole.
So it looks about the same.

How about color where there's no flow?
As I just alluded to, intrinsic movement as we saw in
that first slide of the patient with the epididymal cyst
and arterial venous fistula can have what looks like flow
between the fistula and the skin.
All these other things. If you move the transducer while
you're trying to hold it still,
if you change the power gain the wall filter the
color priority.
And as I showed you,
mirror image artifact will make it look like
there's flow where there isn't anything.

Now this looks like a an aneurysm of a vessel in the liver.
There's enhancement deep to it, which you don't expect
to see with a vessel vessels.
Even aneurysms tend not to have enhancement deep to it.
And yet clearly there's color there.
What's that caused by that's caused,
especially if it's under the diaphragm,
if it's under the diaphragm by motion adjacent to the heart.
So you can show what looks like an aneurysm when it's just a
cyst, especially if there's any particulate matter whatsoever
in the cyst here, the color echo priority,
you don't see the vessel at all, you don't see the lumen.
But when you turn on the color
where you didn't even see a lumen,
now you're getting a lot of color flow.
So it's obviously much bigger than the actual vessels were.

And here's an interesting one.
You can see the portal vein and the hepatic artery.
So clearly this must be a dilated bile duct.
At least that's what you'd assume. This is the portal triad.
If you have three structures there
and two of them are big, one
of them is the normal sized portal vein.
The other one must be the dilated bile duct,
common hepatic duct.
And that's of course you'd expect
the patient to be jaundiced.
What if the patient wasn't jaundiced And one
of our sonographers loved to push that color flow button
and pushing the color flow button, she showed hmm,
there is flow in what looks like a dilated bile duct.
So in fact that isn't an artifact that's real.
And this turned out to be cavernous transformation
of the portal vein, which we confirmed in our other studies.
So you can have a cavernous transformation, a vein
that looks like a duct and you can make a mistake
because of that since it looks like an artifact.

Twinkle Artifact

Now frequently when we're looking for a cause
of hydronephrosis
or flank pain, especially if we think there might be a stone
there, we turn on the color flow
to see if there's a jet as you can see here.
And the jet may show you something else or not.
The jet, the color flow may show you something else
that you hadn't appreciated before
and that's called a twinkle artifact.
And here you can see all these colors all mixed up together
and when you turn off the color flow you can say, hey,
there was a stone in the distal urethral vesical junction.
There's a distal urethral calculus
that's causing the patient's clinical problems
that you hadn't seen before you turned the color flow on.

So this new kind of artifact
that's relatively recently described can
help you make a diagnosis
that you otherwise might have missed.
The twinkle artifact, let's see if you can see
that's what it actually looks like.
So it's really hard to miss when it's moving like that,
The twinkle artifact.

And here you can see one where you can see both the jet
and the twinkle artifact.
Here you can see another one
where it looks like the twinkle artifact is coming
from all around the stone.
And you can see the jet
and sometimes you can see these twinkling artifacts from
other structures like the wall of the gallbladder.
And these were actually moving but it doesn't really matter.
And these can I guess come from
from cholesterol crystals in the wall.
'cause this looks just like those kind of cases
that you can see when there's adenomyosis
or sometimes when there isn't adenomyosis.

And here's an example of little bits
of air within the liver
and sometimes those can show you twinkling artifacts.

Here's a really nice one,
I hope I can show it to you in the movie.
There you can see it, there's a twinkle artifact
that comes from a calcified plaque,
but usually you don't see this in carotid plaques
and it's most commonly seen when there are actual
calcification in structures like a urethral stone.

The cause of these is not clearly understood, frankly,
I think it's that we're getting echoes back in different frequencies relative to the
transducer main frequency.
And some of them are higher
and some of them are lower so
that they're showing up in color.
But others believe that it's related to
how far away the structures are from the
transducer if they're close to it.

Direction and Aliasing in Color Flow

Now what about the wrong color shade?
The wrong direction of flow?
Certainly you can push that button to invert it
and then it'll look different.
The angle of flow laminar flow aliasing,
we'll just quickly go through these.

Clearly that's aliasing
and that's beyond the scope of this lecture.
In the middle, it's aliasing the blood flow
is going in the right direction.
On the other hand, in that in the carotid bulb, I told you,
you can get reversal flow so that
that is actually true flow going in the other direction.

And here's an example of a very tortuous carotid.
So this is the direction it's going.
It changes to blue
because it's still going in the same direction now away from
the transducer now back towards the transducer.
And so here the aliasing is in the same direction
or at least apparently the same direction
as the blood was going over here,
whereas it's actually faster in that direction, et cetera.
And we won't go into a detail,
but it does show you which direction the flow is going.

So in the splenic vein, it's going from the it's going
away from the transducer or towards the spleen.
And this is a reversal flow.
It should be going in the same direction
as the renal vein, which is here.
So you should see it in this direction.
I won't go into that.

Here's an interesting one again from quite a while ago.
But you can see in the cord
that the blood flow is going in this direction in the
arteries and in this direction in the veins.
Although it'd be nice to think that it's oxygenated
blood, but that's not true.
When you look at it in short axis though,
you can see the red in this case is
'cause the venous blood is going
away from the transducer.
But note in the two arteries, one's red and one's blue.
And that's 'cause one is going slightly towards the
transducer and the other slightly away.

And here you can see that clearly the blood, not the blood,
but the flow in the nostril is going towards the transducer
on this side and away on that side.
So you can even see flow in the nostrils

power versus color flow doppler.
When power doppler came out, people thought it was
so sensitive that you could even show flow in a hemangioma.
And it turns out that whereas with color flow,
if there are no echoes, there's a tendency
to put in a color flow echo.
If there was a choice. Where there are echoes is a tendency
to make it brighter with power doppler.
So that's been corrected for the most part.
But you notice that here we can see in the yolk sack it
looks like there's color flow.
It could actually just be a strong reflector
because there clearly wasn't any flow in the wall
of this Foley catheter and yet it looks like it.
So that's an artifact making it look like there's flow.

I don't know if any of you are doing a seascape or sono or
extended field of view, real time ultrasound,
but sometimes if there's a shadow you can have the direction
get all skewed and it'll go up into the air.
And whereas the patient's lying supine,
it looks like their legs and their whole lower
body is up in the air.

Artifacts in Extended Imaging

Now sometimes you can see something on an image like here it
looks like there's a lesion and if the sonographer produces
all these images and one of them shows something
that you didn't see, if ever you should go into the room, is
to make sure that something that shows up on an image
that the sonographer didn't see
during the examination is really there.
People should obviously go into the scanning room
and touch the transducer, sonologist,
I mean people interpreting the examination should go in much
more often than they do, but definitely go in if instead
of making a diagnosis from the image that wasn't seen
during the scan.

So this is not a metastasis, this wasn't really there.
It's related to that. These ring down artifacts.
And I don't know why the edge looked like that,
but this is obviously the same area.
There's nothing there. Sometimes things
can look a little differently.

Recognizing and Managing Artifacts

This one you can see looks like a duck.
There's a beak, there's a head,
there's a body, there's a tail.
And so it looks like a duck.
And when this the patient said, what are you seeing there?
What's so interesting?
And I said, it looks like a duck.
The patient was all upset and she said, oh, I wanted a boy.
Here you can see a bird
there you can see another kind of bird.
So again, you have to look at images carefully.
You have to see what's really going on.

And if you look at your images carefully,
you'll see there are all sorts of artifacts.
They just look like messy images
and many of these are cleaned up these days.
But basically you can have reverberations off axis
or side lobe artifacts.
You can have mirror image artifacts.
This is just a lot of noise
and bright echoes, ring down artifacts.
There are all sorts of artifacts in these images and none,
and despite that, we can still make
good diagnosis with ultrasound.
You just have to be able to recognize them
and if you know what causes them,
you have a better chance of recognizing them.

So thank you. For me, that's all.