Term
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Definition
-the ability of a substance or material to display different properties, depending on the angle of insonation
-if the angle is less than 85-90 degrees, the majority of the reflected waves will not be received by the transducer and tissue will appear hypoechoic
-tendons are the strongest anistrophic relectors |
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Term
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Definition
| -occur because we assume that the speed of sound is 1540 m/sec, but MSK consists largely of muscle shifting the speed of sound slightly higher to approx. 1584 m/sec. |
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Term
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Definition
-occurs because we assume the sound beam always travels ini a straight line
-Refraction occurs when the beam strikes tissue with a different density than through which it has been traveling
-positions objects slightly off axis |
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Term
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Definition
-also known as critical angle shadowing
-occurs at the edges of highly curved surfaces
-because the incident beam is both reflected by the curved surface and often refracted by the different tissue type, none of the incident sound rays striking the lateral margin return to the transducer, resulting in a lack of echoes (shadow)deep to the lateral borders of the structure |
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Term
| Partial Volume Effect or Volume Averaging |
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Definition
-the "filling-in" of cystic structures because echoes are detected outside of the central beam axis
-happens because the ultrasound system assumes that the beam produced has a finite or constant width |
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Term
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Definition
-secondary to the impedance between the transducer face and patient's skin compared to that which occurs between two strong specular reflectors
-also known as mirror image artifact
-again because it is assumed that the beam has a finite or constant width |
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Term
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Definition
-most often seen deep to the metallic or glass objects having a high propagation speed
-the artifact diminishes in intessity with increasing distance, but the spacing remains the same
-will often cross tissue boundries |
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