WorksheetsImages characteristics artifacts ch 18
Total questions: 42
Worksheet time: 37mins
Hyperechoic
Portion of an image that are brighter than surrounding tissues, or tissues that appear brighter than normal
Portion of an image that are not as bright as surrounding tissue, or tissues that appear less bright than normal
A portion of tissue or a structure that has similar echo characteristics throughout
Display a variety of different echo characteristic within the tissue
Hypoechoic
Portion of an image that are brighter than surrounding tissues, or tissues that appear brighter than normal
Portion of an image that are not as bright as surrounding tissue, or tissues that appear less bright than normal
A portion of tissue or a structure that has similar echo characteristics throughout
Display a variety of different echo characteristic within the tissue
Homogeneous
Portion of an image that are brighter than surrounding tissues, or tissues that appear brighter than normal
Portion of an image that are not as bright as surrounding tissue, or tissues that appear less bright than normal
A portion of tissue or a structure that has similar echo characteristics throughout
Display a variety of different echo characteristic within the tissue
heterogeneous
Portion of an image that are brighter than surrounding tissues, or tissues that appear brighter than normal
Portion of an image that are not as bright as surrounding tissue, or tissues that appear less bright than normal
A portion of tissue or a structure that has similar echo characteristics throughout
Display a variety of different echo characteristic within the tissue
without echoes; echo- free
(a)
Describes structures with equal echo brightness
(a)
Multiple echoes appearing on the display as a result of US "ping ponging" between two reflectors. Looks like ladder or a venetian blind.
(a)
Reverberation
Multiple
Equally spaced
Parallel to the sound beam
Deeper and along a straight line
Appears as a solid line directed downward, merged reverberation
(a)
Comet Tail or Ring Down
Single, solid hyperechoic line
Long echo
Parallel to sound beam
A reverb with the " space " squeezed out
Small metal objects create ?
(a)
There are occasions when the US beam is unable to pass through a structure because the structure has higher than usual attenuation. When this occurs, any structures that lie deeper than initial structure are not imaged or displayed. Thus, a hypoechoic region appears distal to a hyperchoic structure. This is a shadow- anechoic or hypoechoic
(a)
Refraction at the edge of a circular structure can also create an artifact
(a)
Hyperechoic occurs the medium through which the sound travels has a lower attenuation rate than soft tissue. Since the attenuation is less, echoes returning from deeper areas appear brighter on the display- Hyperechoic
The correct # of anatomic reflectors appear on the image
(a)
Sound may bounce off of a strong reflector, called a mirror, in its path and be redirected. US system assume that sound travels directly to a reflector and back to the transducer
(a)
A duplicate of real anatomy appearing on a scan (a) be an artifact
If the media through which the US travels doesn't propagate at 1.54 km/s, then the assumed relationship between time and distance is invalid
(a)
Propagation speed Errors syn
(a)
Propagation Speed Errors
Correct number of reflections on scan
Improper depths Speed errors as a step- off, split or cut
Faster than soft tissue when the propagation speed is greater than 1,54-m/s. The reflector will be placed too shallow on the display
Slower than soft tissue when the speed is less that soft tissue's the reflector will be placed too deep on the display
Sound changes direction, striking a boundary
Obliquely
When the media have different propagation speeds
(a)
(a) degrades lateral resolution. Cannot identify refraction artfact from true anatomy with a single static image
Extra acoustic energy may be transmitted in directions other than the beam's main axis
(a)
Side lobes
Mechancal or single crystal transducers create slide lobes
Arrays create grating lobe
Grating lobe artifact can be reduced or cured by dividing each element into even smaller, miniature pieces.
Grating lobe are further reduced by exciting the subdiced elements with different voltages. Subelements closer to the center of the sound beam are excited with higher voltages, while the outermost sublements, further away from the center of the beam, are excited with lower voltages
Grating lobes
Mechancal or single crystal transducers create slide lobes
Arrays create
Grating lobe artifact can be reduced or cured by dividing each element into even smaller, miniature pieces.
Grating lobe are further reduced by exciting the subdiced elements with different voltages. Subelements closer to the center of the sound beam are excited with higher voltages, while the outermost sublements, further away from the center of the beam, are excited with lower voltages
Subdicing
Mechancal or single crystal transducers create slide lobes
Arrays create
Grating lobe artifact can be reduced or cured by dividing each element into even smaller, miniature pieces.
Grating lobe are further reduced by exciting the subdiced elements with different voltages. Subelements closer to the center of the sound beam are excited with higher voltages, while the outermost sublements, further away from the center of the beam, are excited with lower voltages
Apodization
Mechancal or single crystal transducers create slide lobes
Arrays create
Grating lobe artifact can be reduced or cured by dividing each element into even smaller, miniature pieces.
Grating lobe are further reduced by exciting the subdiced elements with different voltages. Subelements closer to the center of the sound beam are excited with higher voltages, while the outermost sublements, further away from the center of the beam, are excited with lower voltages which reduces lobes
Lobe artifact degrade lateral resolution
(a)
Slice Thickness
Artifact occurs when beam has a greater width than the reflector
Elevational resolution
US beams have measurable thickness However, we assume that the imaging plane is razor thin.
none
The reflection produced by structures above or below the ideal imaging plane appear in the image. This may act to fill in follow structures such as cysts Fill-in of an anechoic structure
(a)
This artifact is cured with the (a) transducer, since they make thin slices.
Generally, linear array transducer have poor
(a)
Speckle
Grainy appearance not directly from reflections from tissues in the shallow part of the image
Created by interference effects of scattered sound, both constructive & destructive, from the many tissue reflectors
Look for these words, you will not be asked to identify
none above
Range Ambiguity Artifact
caused when very deep reflections from a previous pulse arrive at transducer after the next pulse was created
System thinks reflection came from most recent pulse
places late-arriving reflection (artifact) too shallow on the image
Cured by lowering the PRF (imagining deeper) because the PRF is too high, or by using coded excitation
lobes make a sound beam wider, create artifact and degrade
(a)
Long pulses create artifacts and degrade
(a)
Wide pulses create artifacts and degrade
(a)
Thick pulses create artifact and degrade
(a)
Artifact are created when the sound beam is larger than the reflector
(a)
The wall filter determines whether low velocity flows are displayed the wall filter is also called
(a)
Cross Talk
found in Doppler only
Speacial form of mirror image where the Doppler spectrum appears above and below the baseline. Called Doppler mirror on the vascular technology
true unidirectional flow appears bidirectional, flow that should appear only on one side of the baseline, incorrectly appears on both sides
none above
Cross talk two causes
Doppler gain set too high (electronic cross-talk
incident angle near 90 when flow is at focues
Six basic Assumptions of Imaging systems
1.Sound travels in a straight line
2.Sound travels directly to a reflector and back
3.sound travels exactly 1,540 meters/second
4Reflections arise from structures positioned along the beam's main axis
5.Intensity of the reflections is related to the scattering characteristics of the tissue
6.The imaging plane is extremely thin
