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66 Cards in this Set

  • Front
  • Back

What is an error in imaging, or something that doesn't belong, called?

Artifact
Portions of an image that are brighter than surrounding tissues, or tissues that appear brighter than normal
Hyperechoic
Portions of an image that are not as bright as surrounding tissues, or tissues that appear less bright than normal
Hypoechoic
An extreme form of hypoechoic, meaning entirely without echoes (echo-free)
Anechoic
Describes structures with equal echo brightness
Isoechoic
A portion of tissue or an image that has similar echo characteristics throughout
Homogeneous
A portion of tissue or an image that has differing echo characteristics throughout
Heterogeneous
Multiple, equally spaced echoes caused by the bouncing of the sound wave between two strong reflectors positioned parallel to the ultrasound beam
Reverberation
Name the artifact:
- appears in multiples
- appears equally spaced
- located parallel to the sound beam's main axis
- located at ever-increasing depths
Reverberations
With reverberations, which of the echoes are real, if any?
The first two
This appears as a solid, hyperechoic line directed downward, created when closely spaced reverberations merge (aka, Ring Down Artifact)
Comet Tail
Name the artifact:
- appears as a single long hyperechoic echo
- located parallel to the sound beam's main axis
Comet Tail
This appears as a hypoechoic or anechoic region extending downward from a very strong attenuating medium
Shadow
Name the artifact:
- hypo-or anechoic
- results from too much attenuation
- located beneath the structure with abnormally high attenuation
- prevents visualization of true anatomy on the scan
Shadow
Is shadowing related to the speed of sound in a medium?
No
This appears as a hypoechoic region extending along the edge of a curved reflector. The sound beam refracts at the edge resulting in an intensity drop
Edge Shadow
Shadowing by Refraction
Name the artifact:
- hypo- or anechoic
- results when the beam spreads after striking a curved reflector
- extends downward from the curved reflector's edge, parallel to the beam
- prevents visualization of true anatomy
Edge Shadow
Shadowing by Refraction
This appears as a hyperechoic region beneath tissues with abnormally low attenuation
Enhancement
Is enhancement related to the speed of sound in the medium?
No
Name the artifact:
- hyperechoic
- results from too little attenuation
- located beneath the structure with abnormally low attenuation
Enhancement
This appears when a side-to-side region of the image appears brighter than tissues as other depths
Focal Enhancement
Focal Banding
What is most often the cause of focal enhancement?
A TGC pod is set too high
Name the artifact:
- a hyperechoic side-to-side region
- results from increased intensity at the focus
Focal Enhancement
Focal Banding
This appears when sound reflects off of a strong reflector and is redirected toward a second structure, causing a replica to incorrectly appear on the image
Mirror Image
In the case of mirror images, which one is the artifact?
Deeper image is the artifact
Name the artifact:
- a second copy of a true reflector
- copy appears deeper than the true reflector
- a bright reflector, the mirror, lies on a straight line between the artifact and the transducer
- true reflector and artifact are equal distances from the mirror
Mirror Image
This appears as a mirror image artifact on a spectral doppler display
Crosstalk
This appears when a sound wave propagates through a medium at a speed other than that of soft tissue (1.54 km/s); the correct number of reflectors are displayed, but at incorrect depths
Speed Error
Range Error Artifact
Is the medium's speed of sound faster or slower than that of soft tissue?
- go-return time is too short
- system assumes reflectors are close to the transducer
- reflectors are too shallow
- distances are underestimated (too small)
Medium's speed is FASTER than that of soft tissue
Is the medium's speed of sound faster or slower than that of soft tissue?
- go-return time is too long
- system assumes reflectors are far from the transducer
- reflectors are too deep
- distances are overestimated (too large)
Medium's speed is SLOWER than that of soft tissue
Name the artifact:
- correct number of reflectors
- improper depth
- appears as a step-off
Speed Error
Range Error Artifact
This appears when sound energy is transmitted in a direction other than the sound beam's main axis, degrading lateral resolution
Lobe Artifacts
(Side Lobes - single crystal)
(Grating Lobes - arrays)
Name the artifact:
- a second copy of the true reflector
- artifact and the true reflector are located side by side at the same depth
Lobe Artifacts
(Side Lobes - single crystal)
(Grating Lobes - arrays)
What are two methods for reducing lobe artifacts?
1. Sub-dicing (dividing each crystal into small pieces)

2. Apodization (differential excitation; inner elements receive higher voltages while outer elements receive lower voltages)
This appears when a sound pulse changes direction during transmission, degrading lateral resolution
Refraction
Name the artifact:
- a second copy of the reflector
- the copy is side by side or at the same depth as the true reflector
Refraction
This appears when reflections from structures above or below the assumed imaging plane appear in the image, or hollow structures appear filled in
Slice Thickness Artifact
Elevational Resolution
How can slice thickness artifact/elevational resolution problems be reduced?
1 1/2 dimensional array transducers (matrix) which create thinner imaging planes
This appears when a beam is wider than the distance between two reflectors that are located side-by-side. In this case, the two objects appear as one reflection
Lateral Resolution Artifact
This appears when a long pulse strikes two closely spaced structures, where one is in front of the other. Only one reflection will appear if the structures are closer together than 1/5 the SPL
Axial Resolution Artifact
What type of transducers reduce axial resolution artifacts?
Higher Frequency
These appear when sound pulses glance off a second structure on the way to or from the primary reflector, resulting in a transmit path length different from the receive path length and subtle, non-specific errors
Multipath Artifacts
This appears when a sound beam strikes a curved or oblique reflector, causing some of the reflected sound to be directed away from the transducer
Curved/Oblique Reflectors
Name the artifact:
- reflections are absent OR
- reflections appear too weak OR
- reflections appear different than other similar reflecting boundaries
Curved/Oblique Reflectors
This appears as a result of low frame rates and causes less accurate positioning of reflectors in motion
Temporal Resolution Artifact
This appears as a result of low line density causing less detail in the image
Spatial Resolution Artifact
When the image is in analog format for display on a CRT, how is spatial resolution determined?
Number of scan lines per frame (more the better)
When the image is in digital format, how is spatial resolution determined?
Pixel Density (more the better)
Small amplitude echoes resulting from many sources including electrical interference, signal processing and spurious reflections. Most likely affects low-level hypoechoic regions
Noise
A form of noise arising from small amplitude sound waves interfering with each other; most likely to appear close to the transducer
Speckle
A form of noise associated with Doppler
Clutter
A high-tech solution for reducing an image's noise content; selectively distinguish meaningful reflections from noise, thereby improving signal-to-noise ratio
Harmonics
When creating an ultrasound image, all of the following assumptions are made except:
A. sound travels in a straight line
B. sound travels at 1.54 km/s
C. reflections arise only from structures in the pulse's main beam
D. The sound beam is extremely thin
E. all structures create reflections of equal magnitude
E
Which statement regarding axial resolution is correct?
A. axial resolution artifact is related to beam diameter
B. higher quality images are associated with smaller numbers
C. axial resolution may be reported in units of meters
D. numerically, axial resolution equals one-half the pulse length
E. too few reflectors appear on the image
A
An ultrasound pulse has a width of 4 mm, a length of 2 mm, and is produced by a transducer 3000 times per second. What is the best estimate of the system's axial resolution?
A. 4 mm
B. 2 mm
C. 1 mm
D. 1500 Hz
C
Which of the following statements is true about lateral resolution?
A. it is also called angular, transverse, and depth resolution
B. it is reported in units of time
C. it is the same at all depths
D. it can be improved by focusing
D
All of the following artifacts result in the placement of too many echoes on the image except:
A. shadowing
B. reverberation
C. mirror image
D. grating lobes
A
Which of the following determines the spatial resolution of an analog display?
A. number of pixels
B. number of lines on the display
C. number of bits per pixel
D. spatial pulse length
B
Which of the following determines the spatial resolution of a digital display?
A. pixel density
B. number of lines on the display
C. number of bits per pixel
D. spatial pulse length
A
Which artifact produces an image with an incorrect number of reflectors?
A. propagation speed error
B. multipath
C. enhancement
D. side lobes
D
T/F: Mirror image artifacts always appear deeper than the true anatomy
True
Which artifact is unrelated to the dimensions of an ultrasound pulse?
A. lateral resolution
B. depth resolution
C. slice thickness
D. refraction
D
T/F: It is common to visualize artifacts when the dimension of the sound beam is larger than the reflector's dimension
True
Two reflections, one true and one artifact, are displayed on an ultrasound image. In the body, only one anatomic structure is present. The correct reflection and the artifact are found side by side. What is the most likely cause?
A. mirror image
B. grating lobe
C. enhancement
D. multipath
B
Two distinct reflections are observed on an image, but they actually arise from a single anatomic structure. The artifact is positioned deeper than the correct reflection. What is the most likely cause?
A. grating lobe
B. side lobe
C. refraction
D. mirror image
D
Which one of these artifacts does not result from multiple reflections?
A. comet tail
B. reverberations
C. ring down
D. enhancement
D