Chapter 21 Artificats Flashcards
When creating an ultrasound image, all of the following assumptions are made except?
A: Sound travels in a straight line
b: Sound travels att 1.54 km/s
C: The sound beam is extremely thin
D: All structure create reflectors of equal magnitude
D- All structure create reflectors of equal magnitude
Which statement regarding axial resolution is incorrect?
A: Axial resolution artifact is related to beam diameter
B: Higher quality images are associated with similar 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: Axial resolution is not related to beam diameter.
An ultrasound pulse has a width of 4mm, a length of 2 mm, and is produced by a transducer 3,000 times per second. What is the best estimate of the systems axial resolution?
A: 4mm
B: 2mm
C: 1mm
D: 1,500 Hz
C: 1 mm
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: It can be improved by focusing
All of the following artificats result in the placement of too many echoes on the image except;
A: shadowing
B: reverberation
C: mirror image
D: grating lobes
A: Shadowing
Which of the following determines the spatial resolution of a display?
A: number of pixels
B: number of lines on the display
C: number of bits per pixel
D: spatial pulse length
B: number of lines on thee display
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: pixel density
Which artifact produces an image with an incorrect number of reflectors ?
A: propagation speed error
B: multipath
C: enhancement
D: side lobes
D: side lobes. (Artifacts places a second echo on an image from a single structure)
True or false. 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: Refraction
True or false. It is common to visualize artifacts when the dimension of the sound beam is larger than the reflector’s dimension.
True.
Propagation artifacts occur when
Bending (refraction), redirection (reflection0 or reverberation of the sound wave
Two distinct reflections are observed on an image, but they actually arise from a single anatomical structure. The artifact is positioned deeper than the correct reflection. What is the most likel cause of this artifact.
A: grating lobe
B: side lobe
C: refraction
D: mirror image
D: mirror image
Which one of these artifacts does not result from multiple reflections?
A: comet tail
B: reverberations
C: ring down
D: enhancement
D: enhancement
What is an artifact ?
An error in imaging
Causes of Artifacts
Violation of assumptions
Equipment malfunction or poor design
The physics of ultrasound
Operator error
Six assumptions of Imaging systems
Sound travels in a straight line
Sound travels directly to a reflector and back
Sound travels in soft tissue at exactly 1,540 nm/s
Reflections arise only from structures positioned in the beams main axis
Imaging plane is very thin
Strength of a reflection is related to the characteristics of the tissue creating the reflection
Artifacts are seen in what two planes?
Transverse and Sagittal
Reverberation appear on the display as?
Multiple, equally, spaced echoes
When is reverberation are created when?
Sound wave. Bounces back and forth between
Characteristics of reverberation
Appear in multiples
Appear equally spaced
Are located parallel to the sound beam main axis
Located at ever- increasing depths
Reverberations resemble ?
Ladder or Venetian blind
Comet tail is also known as ?
Reverberation and can be ring down artifact
Comet tail appears as
Solid hyper echo if line directed downward.
