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21 Cards in this Set
- Front
- Back
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artifacts |
error in imaging |
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reverberation artifact |
(looks like a latter) -multiple vibration within 2 strong reflectors |
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comet tail artifact (ring down) |
(single, long hyperechoic line) -closely spaced reverberations that merge -seen with air and mediums with high propagation speeds *rays of sunshine |
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shadow artifact |
-absence of echoes distal to an object -highly attenuating objects like bone -appears hypoechoic or anechoic *can be helpful in diagnosing |
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edge shadow (shadowing by refraction) |
-created as sound beam refracts and diverges along the edge of a curved structure -sound attenuates more at edge due to thicker wall |
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enhancement artifact |
-hyperechoic region posterior to tissues with low attenuation rate (fluid filled structures) -useful for diagnosing |
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focal enhancement artifact (focal banding) |
-side to side region appears brighter -adjust with TGCs |
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mirror image artifact |
-sound reflects off a strong reflector and is redirected towards a second structure -copy artifact will always be deeper than real structure -may occur on (gray scale imaging, color doppler, spectral doppler) |
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crosstalk |
mirror image artifact seen on spectral doppler |
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speed error artifact(range error artifact) |
-occurs when sound propagates through a medium at a speed other than soft tissue -correct reflectors occur but at deeper depths |
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lobe artifacts |
-originate from sound energy outside the main beam axis -reflector may appear in beam axis if strong enough to pass the threshold |
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refraction artifact |
-sound pulse changes direction during transmission -occurs when sound beam strikes boundary obliquely with two structures with different propagation speeds -copy is placed side by side to true reflector |
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slice thickness artifact (section thickness artifact or partial volume artifact) |
-occurs b/c sound beam produced by a rectangular PZT |
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lateral resolution artifact (point spread artifact) |
-two structures will appear as one -occurs when two structures located side by side, perpendicular to main axis are closer together than the beams diameter |
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axial resolution artifact |
-two structures will appear as one -occurs when a long pulse strikes two closely spaced structures (one in front of the other) -reduced by using XDR's with short pulses |
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multipath artifact |
-sound pulses glance off a second structure -may not be visible on image |
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curved or oblique reflectors |
-appears different from other similar reflecting boundaries -when sound strikes a curved / oblique reflector |
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temporal resolution artifact |
0low fram rates resul in drag |
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spatial resolution artifact |
-determined by line density, axial and lateral resolutions |
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range ambiguity artifact |
-occurs when imaging deep in body -reflection from deep structures return too late after the next pulse has already fired -will place reflection too shallow on the image when it should be deeper in body |
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noise and speckel |
noise- small amplitude echoes speckle: a form of noise |
