Term
| Name the 6 artifact catagories. |
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Definition
- Not real
- Missing
- Improperly located
- Improper brightness
- Improper shape
- Improper size
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Term
What are the 6 assumptions of artifacts?
(In any order) |
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Definition
- Sound travels in a straight line.
- Sound travels directly to the reflector and back.
- The amplitude of the returning echoes is directly related to the reflecting properties of the medium.
- Sound travels at exactly 1540 m/s in the body.
- The imaging plane is very thin.
- Reflections arise only from structures along the beams main axis.
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Term
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Definition
An error in imaging.
A misrepresentation of data on the display. |
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Term
| List 5 causes of artifacts. |
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Definition
- Violation of assumptions.
- Equipment malfunction or poor design.
- The physics of ultrasound.
- Operator error.
- Patient movement.
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Term
| Slice thickness artifact is also called: |
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Definition
- Beam width artifact
- Elevational resolution artifact
- Section thickness artifact
- Partial volume artifact
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Term
| What causes elevational resolution artifact? |
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Definition
The beam is too tall.
(Echoes are received that originate, not only from the center of the beam (axial & lateral resolution), but also from the 3rd dimension - the height of the beam.) |
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Term
| What does a beam width artifact look like? |
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Definition
Echoes in anechoic structures. Improper placement of structures in elevational plane.
(The true reflector lies either above or below the assumed imaging plane, but is displayed within the image.)
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Term
| Where would you see a partial volume artifact? |
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Definition
| In fluid filled structures. |
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Term
| How can you reduce or eliminate slice thickness artifacts? |
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Definition
- Reduce overall gain.
- Move the TGC's to the left.
- Subdicing.
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Term
| What assumption does a section thickness artifact violate? |
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Definition
| The imaging plane is very thin. |
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Term
| What causes an Acoustic Speckle artifact? |
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Definition
| Constructive & destructive interference of small sound wavelets. |
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Term
| What does acoustic speckle look like? |
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Definition
| Bright & dark grainy spots on the display. |
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Term
| Where would you see acoustic speckle? |
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Definition
| In soft tissue like the liver. |
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Term
| How can you reduce or eliminate acoustic speckle? |
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Definition
| You really can't, but the book suggests spatial compounding. |
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Term
| What assumption does acoustic speckle violate? |
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Definition
| The strength of a reflection is related to the characteristics of the tissue creating the reflection. |
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Term
| What causes noise artifact? |
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Definition
| Electrical interference, pulsing vessels, internal movement. |
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Term
| What does noise artifact look like? |
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Definition
| Ghosting (color bleed) or small bands of strong echoes. |
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Term
| Where would you see noise artifact? |
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Definition
| On the Doppler spectrum (clutter) and/or on the Color spectrum (ghosting). |
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Term
| How can you reduce or eliminate noise artifact? |
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Definition
| Increase the wall filter to reduce clutter. Harmonics are preprogrammed in the system to improve quality at deeper locations. |
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Term
| What assumption does noise artifact violate? |
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Definition
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Term
| What causes a Crosstalk artifact? |
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Definition
| A poor Doppler angle (like 80o) and overdriven gain. |
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Term
| How can you correct a crosstalk artifact? |
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Definition
| Shift your transducer angle and avoid 90o angles. |
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Term
| What causes a spectral mirror artifact? |
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Definition
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Term
| How can you fix spectral mirror artifact? |
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Definition
| Turn down the PW Doppler gain. |
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Term
| What causes an aliasing artifact? |
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Definition
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Term
| What does an aliasing artifact look like? |
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Definition
| The Doppler signal wraps around the baseline scale.. |
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Term
| How can you eliminate an aliasing artifact? |
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Definition
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Term
| What causes a Reverberation Artifact? |
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Definition
2 strong reflectors that are very close together and parallel to the beam.
Small gas bubbles can cause Ringdown reverberation.
Foreign objects in the body (metal, IUD) can cause Comet Tail reverberation. |
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Term
| What does reverberation artifact look like? |
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Definition
Equally spaced, parallel line. Ladder like.
Comet Tail reverberation fans out more at the bottom.
Ringdown reverberation is more solid. |
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Term
| Where would you see reverberation? |
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Definition
| From gas bubbles or foreign objects like metal in the body. |
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Term
| How can you reduce or eliminate reverberation? |
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Definition
| Change your view or angle of the transducer. |
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Term
| What assumption does reverberation violate? |
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Definition
| Sound travels directly to the reflector and back. |
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Term
| What causes a Mirror-Image artifact? |
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Definition
| A strong reflector that redirects the sound beam. |
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Term
| What does a mirror-image artifact look like? |
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Definition
2 reflections are seen on the display, but only 1 is real.
The artifact is always DEEPER. |
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Term
| Where would you see a mirror-image artifact? |
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Definition
| Common around the lung/diaphragm/liver interface. |
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Term
| How can you eliminate a mirror-image artifact? |
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Definition
| Change the angle of your scan. |
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Term
| What assumption does a mirror-image artifact violate? |
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Definition
Sound travels in a straight line.
Sound travels directly to a reflector & back. |
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Term
| What causes a Multipath artifact? |
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Definition
| When the reflection glances off of another strong reflector on its way back to the transducer and its path changes. |
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Term
| What does a multipath artifact look like? |
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Definition
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Term
| Where would you see a multipath artifact? |
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Definition
| The structure will show DEEPER on the display than it really is. |
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Term
| How can you correct a multipath artifact? |
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Definition
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Term
| What assumption does a multipath artifact violate? |
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Definition
| A pulse travels directly to the reflector and back. |
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Term
| What causes Refraction artifact? |
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Definition
| Oblique incidence and different propagation speeds cause the beam to change directions during transmission. |
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Term
| What does a refraction artifact look like? |
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Definition
| A 2nd copy of the reflector that is side-by-side or at the same depth as the true reflector. |
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Term
| Where would you see a refraction artifact? |
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Definition
| At any interface with 2 different propagation speeds. Like a mass. |
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Term
| How can you remove or eliminate a refraction artifact? |
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Definition
| Change the scanning angle. Multiple views. |
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Term
| What assumption does a refraction artifact violate? |
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Definition
| Sound travels in a straight line. |
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Term
What causes Side/Grating Lobes?
(Lateral artifact) |
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Definition
| When sound energy is transmitted in a direction other than along the beam's main axis from a strong reflector. |
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Term
| What do side/grating lobes look like? |
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Definition
Side lobes: Reflections produced & received from "off axis positions" will be placed at proper distances, but wrong locations. They produce low-level echoes.
Grating lobes: If they encounter a strong reflector, the echoes will usually appear lateral (side-by-side) to the real ones.
*Echoes produced by lobes are weaker than the main beam and do not normally make echoes that are imaged. |
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Term
| Where would you see side/grating lobe artifacts? |
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Definition
| Usually close to the surface & with fluid filled structures. |
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Term
| How can you reduce or eliminate side/grating lobe artifacts? |
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Definition
| Apodization or use a gel pad. |
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Term
| What assumption does side/grating lobe artifact violate? |
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Definition
| Reflections arise from structures located along the beam's main axis. |
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Term
| What causes Propagation speed/Range error artifacts? |
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Definition
| When a sound wave propagates through a medium at a speed other than that of soft tissue. |
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Term
| What does propagation speed/range error artifact look like? |
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Definition
If "C" is greater than 1540m/s, the echoes will arrive sooner and the display will put the reflector too close to the transducer.
If "C" is less than 1540m/s, then the reflector will be displayed too far from the transducer because the echoes arrive later.
(Correct # of reflectors, wrong depths, appears as a step-off) |
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Term
Where would you see a propagation speed/range error artifact? |
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Definition
| Tissues with different propagation speeds. |
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Term
How can you reduce or eliminate a propagation speed/range error artifact? |
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Definition
| May not want to because it can be useful for diagnosing. |
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Term
What assumption does propagation speed/range error artifact violate? |
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Definition
| Sound travels at a speed of exactly 1540m/s. |
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Term
| What causes a Range Ambiguity artifact? |
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Definition
| When the reflection from the 1st pulse is not received by the transducer before the 2nd pulse is sent. Caused by deep structures. |
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Term
| What does a range ambiguity artifact look like? |
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Definition
| The reflector is placed at a SHALLOW location on the image. |
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Term
| Where would you see a range ambiguity artifact? |
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Definition
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Term
| How can you remove or eliminate a range ambiguity artifact? |
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Definition
| By increasing the PRP. The PRP/PRF is linked to the Depth button on the machine. |
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Term
| What assumption does a range ambiguity artifact violate? |
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Definition
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Term
| What causes a Shadowing artifact? |
|
Definition
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Term
| What does a shadowing artifact look like? |
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Definition
| A dark path beneath/behind a high attenuating structure. |
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Term
| Where would you see a shadowing artifact? |
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Definition
| Gallstones, fecal impactions, bones (ribs), etc. |
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Term
| How can you remove or eliminate a shadowing artifact? |
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Definition
| You shouldn't. It can provide valuable diagnostic information. |
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Term
| What assumption does a shadowing artifact violate? |
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Definition
| The intensity of a reflection is related to the tissue creating the reflection. |
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Term
| What causes an Enhancement artifact? |
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Definition
| Weak attenuators. It is the opposite of shadowing. |
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Term
| What does an enhancement artifact look like? |
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Definition
| Hyperechoic below the structure. |
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Term
| Where would you see an enhancement artifact? |
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Definition
| With any weak attenuators or fluid filled structures. |
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Term
| How can you reduce or eliminate an enhancement artifact? |
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Definition
| You don't want to. It can be clinically useful. |
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Term
| What assumption does an enhancement artifact violate? |
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Definition
| The intensity of a reflection is related to the characteristics of the tissue. |
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Term
| What causes a Focal Banding/Enhancement artifact? |
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Definition
| Increased intensity at the focus. Using multiple foci. |
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Term
What does a Focal Banding/Enhancement artifact look like? |
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Definition
| A bright band of echoes from one side of the image to the other. |
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Term
Where would you see a Focal Banding/Enhancement artifact? |
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Definition
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Term
How can you reduce or eliminate a Focal Banding/Enhancement artifact? |
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Definition
| Reduce your focus or remove some of the focal zones. |
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Term
| What assumption does a Focal Banding/Enhancement artifact violate? |
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Definition
| The intensity of a reflection is related to th characteristics of the tissue. |
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