physics ultrasound

1. US ATRFACTS
Dr. Kamal Sayed / MSc US AAU
OK
What is the principle of ultrasound?
An electric current passes through a cable to the transducer and is applied
to the crystals, causing them to deform and vibrate. This vibration produces
the ultrasound beam. The frequency of the ultrasound waves produced is
predetermined by the crystals in the transducer.

2. •
Artefacts
•
US Artifacts are any alterations in the image which
do not represent an actual image of the examined area.
•
They may be produced by technical imaging errors or result
from the complex interaction of the US with biological tissues.
Reverberation artifacts appear as a series of equally spaced
lines. One can avoid artefacts by turninig off all electric
equipment so that artefact does not hinder cardiac anatomy
exam.
•
Cauterization artifact is another example of how external
electrical equipment can cause distorted ultrasound images.

3. •
What does artifact mean in medical terms?
•
In medical imaging, artifacts are misrepresentations of tissue
structures produced by imaging techniques such as
ultrasound, X-ray, CT scan, and magnetic resonance imaging
(MRI). ... Physicians typically learn to recognize some of
these artifacts to avoid mistaking them for actual pathology.

4. •
Examples of tools causing artefacts include :
•
include stone tools, pottery vessels, metal objects such as
weapons and items of personal adornment such as buttons,
jewelry and clothing. Bones that show signs of human
modification are also examples.
•
Artifacts are items, usually found at an archaeological dig, are
any things made by or used by humans.
Some examples would be whole pottery, pot shards, stone
tools, decorative and religious artworks, bones of the animals
that the group ate, and sometimes human remains. Things
such as shelters, firepits, etc

5. •
Artifacts
•
https://radiopaedia.org/articles/blooming-artifact-
ultrasound?lang=gb
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acoustic enhancement
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acoustic shadowing
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aliasing artifact
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anisotropy
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beam width artifact
•
blooming artifact

6. •
comet tail artifact
–
colour comet tail artifact
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double aorta artifact
•
electrical interference artifact
•
hardware-related artifacts
–
transducer-related artifact
•
mirror image artifact
•
multipath artifact
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colour bruit artifact
•
colour flash artifact
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7. •
reverberation artifact
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refraction artifact
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ring down artifact
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side lobe artifact
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speckle artifact
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speed displacement artifact
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side lobe artifact
•
twinkling artifact

8. •
An image artifact is any feature which appears in
an image which is not present in the original imaged object.
An image artifact is sometime the result of improper
operation of the imager, and other times a consequence of
natural processes or properties of the human body
•
•

9. •
. Mirror image artefact is one of the beam path artefacts.
These occur when an ultrasound beam is not reflected
directly back to the transducer after hitting a reflective
surface, but rather takes an indirect return journey.
•
The primary beam reflects from such a surface
(e.g. diaphragm) but instead of directly being received by
the transducer, it encounters another structure (e.g. a nodular
lesion) in its path and is reflected back to the highly reflective
surface (e.g. diaphragm).
•
Slide (13)
•

10. •
It then again reflects back towards the transducer
•
. To avoid this artifact, change the position and angle of scanning to
change the angel of insonation of the primary
•
ultrasound beam.
In rhematology, mirrors nearly always are bone surfaces.
•
The mirror artefact is easily seen as such when the true image as
well as the mirror and mirror image are all in the image.
•
The mirror image is slightly trickier when only the mirror and mirror
image are present
•

11. •
. The ultrasound machine makes a false assumption that the
returning echo has been reflected once and hence the
delayed echoes are judged as if being returned from a deeper
structure, thus giving a mirror artifact on the other side of the
•
reflective surface
•

12. •
. It is a friendly artifact that allows the sonographer to
exclude pleural effusion by the reflection of the liver image
through the diaphragm. Examples :
•
@ reflection of a liver lesion into the thorax (the
commonest example)
•
@ reflection of abdominal ascites mimicking pleural
effusion
•
@ duplication of gestational sac (either ghost twin or
heterotopic pregnancy) 3
•
@ duplication of the uterus
•
Images slides ()

13. Scrotum (upper image) /Liver lesion (lower image)

14. •
Acoustic enhancement
•
Acoustic enhancement also called posterior
enhancement or enhanced through transmission, refers to
the increased echoes deep to structures that transmit sound
exceptionally well.
•
This is characteristic of fluid-filled structures such as cysts,
the urinary bladder and the gallbladder.
•
The fluid only attenuates the sound less than the surrounding
tissue.
•
Slide (15)

15. Acoustic enhancement: upper (hep cyst + GB)/ lower (epidermal inclusion cyst)

16. •
The time gain compensation (TGC) overcompensates through
the fluid-filled structure causing deeper tissues to be brighter.
•
Simply it is seen as increased echogenicity (whiteness)
posterior to the cystic area.
•
The presence of acoustic enhancement aids in the
identification of cystic masses but some solid masses,
especially lymphoma, may also show acoustic enhancement
posteriorly.

17. •
Acoustic shadowing (posterior acoustic shadowing)
•
is characterised by a signal void (dark or black area) behind
structures that strongly absorb or reflect ultrasonic waves.
•
it is a form of imaging artifact.
•
This happens most frequently with solid structures, as sound
conducts most rapidly in areas where molecules are closely packed,
such as in bone or stones.
•
Slide (18)
•
•
•

18. LT image (cholelithiasis)/ MID image (renal calculus)/
RT image (gas in colon diverticulum)

19. •
Beam width artifact
•
Occurs when a reflective object located beyond the widened
ultrasound beam, after the focal zone, creates false
detectable echoes that are displayed as overlapping the
structure of interest.
•
it occurs when scanning an anechoic structure and some
peripheral echoes are identified, i.e. gas bubbles in the
duodenum simulating small gallstones and peripheric echoes
in the bladder.

20. •
It is possible to avoid this beam width artifact by 1- adjusting
the focal zone to the depth level of interest
•
2- and by placing the transducer at the centre of the object
being studied.

21. •
Mirror image artifact is seen when there is a highly reflective
•
surface (e.g. diaphragm) in the path of the primary beam.
•
The primary beam reflects from such a surface
(e.g. diaphragm) but instead of directly being received by
the transducer, it encounters another structure (e.g. a nodular
lesion) in its path and is reflected back to the highly reflective
surface (e.g. diaphragm). It then again reflects back towards
the transducer
•
. To avoid this artifact, change the position and angle of
scanning to change the angel of insonation of the primary
ultrasound beam.
•

22. In rheumatology, mirrors are nearly always bone surfaces.
•
The mirror artefact is easily seen as such when the true image
as well as the mirror and mirror image are all in the image.
•
The mirror image is slightly trickier when only the mirror and
mirror image are present
•
. The ultrasound machine makes a false assumption that the
returning echo has been reflected once and hence the
delayed echoes are judged as if being returned from a deeper
structure, thus giving a mirror artifact on the other side of the
reflective surface.
•

23. •
It is a friendly artifact that allows the sonographer to exclude
pleural effusion by the reflection of the liver image through
the diaphragm.
•
Examples:
•
@ reflection of a liver lesion into the thorax (the commonest
example)
•
@ reflection of abdominal ascites mimicking pleural effusion
•
@ duplication of gestational sac (either ghost twin or
heterotopic pregnancy) 3
•
@ duplication of the uterus
•
Images slides (24)

24. Liver lesion (upper image) Scrotum / scrotum (lower image)

25. •
reverberation artifact
•
Reverberation artifact occurs when an ultrasound beam
encounters two strong parallel reflectors.
•
When the ultrasound beam reflects back and forth between
the reflectors ("reverberates"), the ultrasound transducer
interprets the sound waves returning as deeper structures
since it took longer for the wave to return to the transducer.
•
when the ultrasound beam reflects back and forth between
the reflectors ("reverberates"),
•
Slides (29/30)

26. •
the ultrasound transducer interprets the sound waves
returning as deeper structures since it took longer for the
wave to return to the transducer.
•
Reverberation artifacts can be improved by changing the
angle of insonation so that reverberation between strong
parallel reflectors cannot occur.

27. •
Comet-tail artifact is a specific type of reverberation artifact.
This results a short train of reverberations from an echogenic
focus which has strong parallel reflectors within it (e.g.
cholesterol crystals in adenomyomatosis).
•
It is advisable always to let the colour box go to the top of the
image to be aware of possible reverberation sources
•
Slide (31).
•

28. •
With comet tail artifact, the space between the two strong
parallel reflectors may be less than 1/2 the space pulse
length, causing the echoes to be displayed as triangular lines
(the later echoes get attenuated and have a decreased
amplitude, manifesting on the display as decreased width).

32. •
Anisotropy artefact is an angle-generated artifact.
•
It is produced in tissue that contains multiple, parallel linear
sound interfaces (e.g., tendons, ligaments) that lead to the
preferential reflection of the beam in one direction
•
. When the ultrasound beam is incident on a fibrillar structure
as a tendon or a ligament, the organised fibrils may reflect a
majority of the insonating sound beam in a direction away
from the transducer. When this occurs, the transducer does
not receive the returning echo and assumes that the
insonated area should be hypoechoic.

33. •
This anisotropic effect is dependant on the angle of the
insonating beam. The maximum return echo occurs when the
ultrasound beam is perpendicular to the tendon.
•
Decreasing the insonating angle on a normal tendon will
cause it to change from brightly hyperechoic (the actual echo
from tightly bound tendon fibres) to darkly hypoechoic. If the
angle is then increased, the tendon will again appear
hyperechoic
•
Slide (35).
•

34. •
If the artefact causes a normal tendon to appear hypoechoic,
it may falsely lead to a diagnosis of tendinosis or tear
•
. In some situations, anisotropy may be useful in diagnosis. If a
tendon is surrounded by other brightly hyperechoic structures
(e.g. fat), then altering the angle of the transducer will cause
the tendon to become hypoechoic, differentiating it from the
other structures.
•

35. Anistropy : upper: TXR NOT perp. To volar (palmar) wrist
lower : TXR perpendicular to volar wrist

36. Grating lobes Artefacts are the maxima of the main beam.
Side lobes and grating lobes are both unwanted parts of
the US beam emitted off axis that produce image artifacts due
to error in positioning the returning echo.

37. •
POINT SPREAD ARTEFACT
•
This artifact occurs when two reflectors are perpendicular to
the beam's main axis create one reflection on the image.
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It is also called point spread artifact.
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Lateral resolution is determined by beam width.
•
Point spread artifact is another term of describing suboptimal
lateral resolution.

38. •
Speed displacement artifact, also known as propagation
velocity artifact,
•
is a gray scale ultrasound finding that can be identified as an
area of focal discontinuity and displacement of an echo
deeper than that its actual position in an imaged structure.
Depth determination by an US machine is based on the
principle that the average propagation velocity of sound in
human tissue is 1540 m/s, and as such the {go return} time
between transmission and detecting the returned sound wave
to the transducer is multiplied by this number and halved to
determine distance, regardless of tissue type

39. •
As a result, if the true propagation velocity of a tissue falls
significantly below or above 1540 m/s, such as fat or bone,
then the distance calculated by the machine will be false,
displaying an inaccurate depth measurement.
•
By this same principle, if there is differential variation in tissue
composition of the tissues under the same ultrasound beam,
then different return times to the transducer will be
processed as different depths of tissue as opposed to
differences in propagation velocity between the tissues.

40. •
This may result in discontinuity in the displayed ultrasound
image, and as such is referred to as a propagation velocity
misrepresentation.
•
A commonly encountered scenario is speed displacement
artifact due to slowing of the US beam by focal fat, such as in
focal fatty sparing in case of hepatic steatosis.
•