chap 20 physics

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an error in imaging?: artifact
artifact include reflection?: 1. not real
2. not seen on the image
3. not of correct shape or size
4. not in correct position
5. not of correct brightness
violation of assumptions and equipment malfunciton or poor design cause___?: artifacts
the physics of ultrasound and operator error cause____?: artifacts
ultrasound image are discribed by_______?: 1. hyperechoic
2. hypoechoic
3. anechoic
4. isoechoic
5. homogeneous
6. heterogeneous
brighter image than sounding tissues?: hyperechoic
not brighter image than surroundin tissues?: hypoechoic
equal echo brightness?: isoechoic
tissue or image that has similar echo characteristics?: homogeneous
tissue or image that has differing echo characteristics?: heterogeneous
six assumptions of imaging system?: 1. sound travel in a straight line
2. sound travels directly to a reflector and back
3. sound travel at 1,540m/s
4. reflection arises from beam's main axis
5. the image plane is very thin
6. the strength of reflection is related to characteristics of the tissue creating the reflection
artifact_____and disappear in some views?: appear
actual anatomy always remains___?: visible
reverberation appears on the display when _____?: multiple, equally spaced echoes
bouncing of the sound wave betweeen two strong reflectors positioned parellel to the ultrasound beam cause_____?: multiple, equally spaced echoes
sound travels directly to a reflector and back, is invalid that causes_____?(assumption 2): reverberation
characteristics of reverberation?: 1. appears in multiples
2. appears as equally spaced
3. located parallel to the sound beam's main axis
4. increasing depths
reverberation artifact places____?: many reflections on the image
the first and second reflection, closest to the transducer, are____?: real
reverberations resemble a____?: ladder or Venetian blind
comet tail artifact described as____?: reverberation with the spaces squeezed out
comet tail artifact appears as___?: solid hyperechoic line directed downward
comet tail artifact also known as____?: ring down artifact
closely spaced reverberations emerge causes_____?: comet tail artifact
if the reflecting surfaces in a medium with a very high propagation speed, then____?: comet tail artifact appears
comet tail artifact also arises from____?: resonance, vibration, of small structure like gas bubbles
sound travels directly to a reflector and back, is invalid that causes___? (assumption 2): comet tail artifact
characteristics of comet tail artifact?: 1. appears as a single long hyperechoic echo
2. located parallel to the sound beam's main axis
shadowing appear as a_____?: hypoechoic or anechoic downward from strong attenuating medium
shadow has the same color as____?: image background
shadowing prevents the display of____?: true anatomic structure
if the attenuation is higher in the tissue above the shadow than in the surrounding tissue, then____?: shadows appear
(assumption 6), the intensity of a reflection is related to the tissue creating the reflection, is invalid that cause___?: shadow
characteristics of shadowing?: 1. hypo or anechoic (background color)
2. too much attenuation
3. abnormally high attenuation
4. prevents visualization of true anatomy on the scan
shadow provides____?: diagnostic information
shadowing is unrelated to___?: the speed of sound in a medium
edge shadow artifact appears as____?: hypoechoic region extending along the edge of a curved reflector
hypoechoic region are the same color as___?: image background
edge shadow artifact prevents the display of____?: true anatomic structures within hypoechoic region
the decrease in intensity causes_____?: edge shadowing
edge shadowing also called___?: shadowing by refraction
(assumption 6), the intensity of a reflection is related to the characteristics of tissue creating the reflection, is invalid that causes____?: edge shadow
characteristics of edge shadow?: 1. hypo-or anechoic background color
2. results when the beam spread after striking a curve reflector
3. extend downward from the curved reflector's edge, parallel to the beam
4. prevents visualization of true anatomy on the scan
enhancement artifact appears___as a?: hyperechoic with abnormally low attenuation
hyperechoic regions are the same color as___?: the foreground or echoe of the image

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