Ultrasound Artifact

1. ULTRASOUND
ARTIFACT
By:Muhammad Amer Sohail
Roll no: 19
DVM 6th morning
Session : 2012-2017

2. DEFINITION
 An ultrasound artifact is a structure in an
image which does not directly similar with
actual tissue being scanned.
 Artifact assumes different forms including :
• Structures in the image that are not
actually present
• Objects that should be represented but
are missing from the image.
• Structures which are misregistered on the
image.

3. COMMON ARTIFACTS
1. REVERBERATION
2. ACOUSTIC SHADOWING
3. ACOUSTIC ENHANCEMENT
4. EDGE SHADOWING
5. BEAM WIDTH ARTIFACT
6. SLICE THICKNESS ARTIFACT
7. SIDE LOBE ARTIFACT
8. MIROR IMAGE
9. DOUBLE IMAGE
10. EQUIPMENT-GENERATED ARTIFACT
11. REFRACTION ARTIFACT

4. REVERBERATION
• This is the production of false echoes due to repeated
reflections between two interfaces with a high acoustic
impedance mismatch.
• The echo from the interface is received by the transducer
and displayed on the image.
• Some of the energy in the returned echo is reflected at the
transducer face, and return to the reflecting interface as if it
was a weak transmitted pulse, returning as a second echo.
• As the time taken for the second echo to arrive is twice that
taken by the depth.

5. • This sequence of reflection and transmission can occur
many times, with the third echo taking three times as
long to return to the transducer and being displayed at
three times the depth, and so on.
• The reverberation echoes will be equally spaced
because the time for each additional echo is multiple of
the time of return of the first echo.
• These reverberation echoes will be strong because of
the high acoustic mismatch.

6. This artifact will be seen at the skin-transducer interface
and behind bowel gas.
Rectification:
• Increase the amount of gel used.
• Use a stand-off pad.
• Reduce the gain.
• Move the position of the transducer.

8. ACOUSTIC SHADOWING
• This appears as an area of low amplitude echoes
behind an area of strongly attenuating tissue.
• It is caused by severe attenuation of the beam at an
interface, resulting in very little sound being transmitted
beyond.
• The attenuation can be due to either absorption or
reflection of the sound waves, or a combination of the
two.
• Acoustic shadowing will occur at interfaces with large
acoustic mismatch such as:
Soft tissue and gas
Soft tissue and bone or calculus

11. ACOUSTIC ENHANCEMENT
• This artifact appears as a localized area of increased
echo amplitude behind an area of low attenuation.
• On a scan it will appears as an area of increased
brightness, and can commonly be seen distal to fluid-
filled structures such as the urinary bladder, GB or a
cyst.
• The artifact arises due to the application of the time-gain
compensation(TGC) to areas of low attenuating
structures such as fluid.
• It is caused by the low level of attenuation of the beam
as it passes through fluid relative to the greater
attenuation of the beam in the adjacent more solid
tissue.

12. • This artifact can often be an useful diagnostic aid,
particularly when scanning a soft-tissue mass or cyst
containing low level echoes.
• These echoes may often cause the structure to
disappear in the image as it blend into the surrounding
echo pattern.

13. EDGE SHADOWING
• A combination of refraction and reflection occurring at
the edges of rounded structures will result in edge
shadowing artifact.
• It arises due to refraction of the beam caused by both
the curvature of the rounded edges and difference in
speed of two materials.
• When the ultrasound beam reaches the rounded edge
of a structure, reflection will occur, with an angle of
incidence equal to the angle of reflection.
• The outer part of the beam will be totally reflected, but
the reminder of the beam passes through the rounded
structure and is refracted.

14. • This combination of reflection and refraction of the
beam at the edges of a rounded structure results in a
thin strip of tissue behind the edge not being
insonated and causes a shadow.

15. BEAM WIDTH ARTIFACT
• This artifact can be demonstrated by scanning a point
reflector in a phantom, where the display will clearly
portray this as a line.
• During routine scanning, the artifact can be seen
when spurious echoes are displayed in an echo-free
area.
• Correct positioning of the focal zone will help to
reduce this artifact.
• The focal zone is controlled by electronically
narrowing the beam

17. SLICE THICKNESS ARTIFACT
• These occurs due to the thickness of the beam, and
are similar to beam width artifacts.
• These artifacts will typically be seen in transverse
views of the urinary bladder when structures adjacent
to the slice through the bladder being scanned will be
incorporated into the image.
• These echoes are then displayed as if they were
arising from within the bladder.
• Although the appearance of this artifact is similar to the
beam width artifact, the differentiating factors is that the
reflector causing the slice thickness artifact will not be
seen on the display.

18.  This artifact is a result of inherent characteristics of the
transducer, and apart from trying a different transducer,
cannot be eliminated

19. SIDE LOBE ARTIFACT
• The energy within the ultrasound beam exists as
several side lobes radiating at a number of angles
from a central lobe.
• Echoes are generated by these side lobes in addition
to the main lobe, but all the returning echoes are
assumed by the transducer to have arisen from the
central axis of the main lobe.
• Side lobe echoes will therefore be misregistered in the
display.
• This artifact can often be seen in area such as the
urinary bladder and may also arise within a cyst.

21. MIRROR IMAGE ARTIFACT
• These artifacts results in a mirror image of a structure
occurring in an ultrasound display.
• They arise due to specular reflection of the beam at a
large smooth interface.
• An area close to a specular reflector will be imaged
twice, once by the original ultrasound beam and once
by the beam after it has reflected off the specular
reflector.
• Mirror image artifacts are most commonly seen where
there is a large acoustic mismatch, such as a fluid-air
interface.

22. • Typically this artifact can occur during the scanning
of a full bladder, when air in the rectum behind the
bladder act as specular reflector and mirror image of
the bladder is displayed posteriorly.
• It will then have the appearance of a large cyst
behind the bladder.
• It can also be seen when scanning the liver, and the
diaphragm act as a specular reflector.

24. DOUBLE IMAGE ARTIFACT
• This image is caused by refraction of the beam and
may occur in areas such as the rectus abdominis
muscle on the anterior abdominal wall.
• In the transverse plane the edges of the muscle act as
a lens and the ultrasound beam to be refracted and
this causes the single structure to be interrogated by
two separate refracted beams.
• Two sets of echoes will therefore be returned and
these will cause display of two structures in the image.

25. This results in, for example, two images of the transverse
aorta side by side in the abdomen.

26. EQUIPMENT-GENERATED ARTIFACT
• Incorrect use of the equipment controls can lead to
artifact appearing.
• Misuse of controls such as the gain or TGC can result
in echoes being recorded as too bright or too dark.
• Care must be taken when setting these controls, to
ensure an even brightness throughout the image.
• If the dynamic range control is incorrectly set, this can
lead to an image which has too much contrast, and
result in the loss of subtle echo information.

27. • Gain must be in medium level.
• Blurring of a moving image can occur if the frame rate
is too low or if the persistence is too high.
• It is important to ensure that the frame rate is capable
of recording a moving structure at the speed.
• Use of multiple focal zones can give rise to a
prominent banding effect within the image.

29. REFRACTION ARTIFCT
• The refraction is the change of the sound direction
on passing from one medium to another.
• In ultrasound, refraction is due to sound velocity
mismatches combines with oblique angles of
incidence, most commonly with convex scanheads.
• When the ultrasound wave crosses at an oblique
angle the interface of two materials, through which
the waves propagate at different velocities,
refraction occurs, caused by bending of the wave
beam.
• Refraction artifact cause spatial distortion and loss
of resolution in the image.