Study guide Ch 21,22,23:test 4 Flashcards
What describes portions of an image that are brighter than surrounding tissues or tissues that appear brighter than normal?
hyperechoic
What describes images that are not as bright as surrounding tissues or appear less bright than normal?
hypoechoic
What describes a structure without echoes?
anechoic
What describes a tissue or structure that has a similar echo throughout?
isoechoic
What describes a tissue displaying a variety of different echogenic characteristics?
heterogeneous
What are considered errors in imaging?
reverbation, comet tail, shadow & edge shadow, enhancement & focal enhancement, mirror image & cross talk, curved & oblique reflectors, temporal resolution, spatial resolution, speed error, lobes: side & grating lobes, refraction, slice thickness, lateral resolution, axial resolution, multipath, range ambiguity, noise: speckle & clutter
Equipment malfunction and design, the physics of ultrasound, and operator error: what are these called?
causes of artifacts
Multiple, equally spaced, parallel lines: what does this describe?
characteristics of reverberation
Which artifact is unrelated to the dimensions of an ultrasound pulse?
refraction
Which artifact produces an image with an incorrect number of reflectors side by side?
side lobes
What does not result in the placement of too many echoes on the image?
shadowing
What does not result from multiple reflections?
enhancement
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 of this artifact?
mirror image
Two reflections, side by side, only one is real. What is most likely the cause of this artifact?
refraction
Which artifacts create one reflection on an image from two closely spaced reflectors?
axial resolution
When the beam dimention is greater than the reflector size, what type of artifact can occur?
What are lobes created by array transducers called?
grating lobes
What methods can be used to eliminate lobe artifacts?
subdicing and apodization
A single, solid, hyperechoic line parallel to the sound beam with no spaces in the echogenic line is what artifact?
comet tail
What artifact occurs when the beam is unable to pass through a structure?
shadowing
Refraction at the end of a circular structure can cause what artifact?
edge shadow (shadowing by refraction)
What artifact occurs when there is too much gain in the focal zone?
focal enhancement
What artifact occurs when the medium to which the sound travels has a lower attenuation rate than soft tissue?
speed error
Which artifact occurs when you see reflectors at incorrect depths?
speed error
When propagation speed is greater than 1,540 m/s, the reflector will be placed to what on the display?
reflectors are too shallow on the image
Grading lobes are caused by which type of transducer?
array transducers
What artifact can be cured by lowering the PRF?
range ambiguity
Which artifact is only found with doppler?
cross talk
A grainy appearance not directly from tissues created by interference is called what?
speckle
If the media in which the ultrasound travels doesn’t propagate at 1,540 m/s, then the assumed relationship between time and distance is invalid. What artifact occurs?
speed error (range error artifact)
Propagation speed errors appear as a what?
a step off
What are errors in imaging?
not real
not seen on the image
incorrect shape or size
incorrect position
incorrect brightness
What are causes of artifacts?
violation of assumptions
equipment malfunction or poor design
the physics of ultrasound
operator error
What are the two causes for crosstalk?
Doppler gain is set too high
incident angle is near 90° between the sound beam and the flow direction, when flow is at the beam’s focus
What is color flash also referred to as?
What are wall filters used to reject?
If the path to a reflector is of a different length than the returning path, the reflector will be in an incorrect position, it results in general image degradation. What artifact is it?
speed error
What produces shadowing?
attenuation is higher in the tissues above the shadow
Where does enhancement appear on an image?
beneath tissues with abnormally low attenuation
Which transducer may have poor elevational resolution?
What term is defined by avoidance of unnecessary risk, harm or needless injury?
nonmaleficence
What provides the basis for an informed consent?
autonomy
When can a patient revoke consent?
at any time
What is the first action when a sonographer enters a patient’s room?
intorduce themselves to the patient
What is the study between a worker and their environment called?
ergonomics
What standard is best used in a quality assurance program?
objective
All of the following are characteristics of a tissue equilavent phantom except:
density similar to that of soft tissue
What form of resolution is evaluated by measuring the width of reflections arising from small, point targets?
lateral resolution
What form of resolution is evaluated by visualizing closely spaced pins that are parallel to the sound beam’s main axis?
axial resolution
At what interval should quality assurance evaluations be performed?
routinely
