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22 Cards in this Set
- Front
- Back
- 3rd side (hint)
Attenuation |
The decrease in intensity, power and amplitude of a sound wave as it travels. This is unrelated to speed. dB, decibels♥️(must be negative, since the attenuation causes intensity to decrease) |
dB can only be added or subtracted |
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Total attenuation increases with |
Higher frequency Or Longer path length |
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Soft tissue/blood interaction |
Lower frequency results in less attenuation and further penetration of low frequency sound♥️ Attenuation is unrelated to propagation♥️ |
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Components of attenuation |
Absorption (primary, sound converted into heat) Scattering Reflection |
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Attenuation in air |
Much, much more attenuation than in soft tissue. Gel is used to remove air from the path of ultrasound♥️ |
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Attenuation in lung & bone |
More then soft tissue, bone absorbs and reflects. Lung scatters♥️ |
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Attenuation in water |
Much, much less than soft tissue♥️ |
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Reflection |
Occurs when propagating sound Energy strikes a boundary between two media and some returns to the transducer♥️ |
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Reflection |
Occurs when propagating sound Energy strikes a boundary between two media and some returns to the transducer♥️ |
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Specular reflection |
Reflections from a smooth reflector(mirror) are specular and return in one direction♥️ Also occur when the Wavelength is much smaller than the irregularities in the boundary ♥️ |
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Diffuse reflection or backscatter |
When a boundary is rough, reflected sound is disorganized and random |
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Diffuse reflection or backscatter |
When a boundary is rough, reflected sound is disorganized and random |
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Scattering |
If the boundary between two media has irregularities (with a size similar to what bit smaller than the pulses Wavelength), then the wave may be chaotically redirected and all directions. |
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Rayleigh Scattering ♥️ |
A reflector is much smaller than the wavelength of sound. Is related to frequency(4) ♥️ |
The red blood cell is Rayleigh scattering♥️ |
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Attenuation and imaging depth♥️ |
Attenuation ultimately limits the maximum that from which meaningful reflections are obtained |
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Attenuation coefficient |
The amount of attenuation per centimeter. A way to report attenuation without dealing with distance dB/cm♥️ decibels per centimeter Related to frequency |
In soft tissue, attenuation coefficient (dB/cm) is approximately one half of the frequency(MHz) A mathematical expression that means half of the transducer frequency: 0.5dB/cm/MHz |
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Impedance |
A number associated with a medium. It's calculated not measured♥️ Rayls (z) |
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Example of impedance♥️ |
Two media, A & B, have the same propagation speed. Medium A's density is 10% higher than medium B's. Therefore, medium A's impedance is 10% higher than medium B's. |
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Incidence |
Normal Oblique |
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Incidence |
Normal Oblique |
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Normal incidence |
5 names Normal Perpendicular Orthogonal Right angle Ninety degrees |
PORNN |
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Oblique incidence |
Anything other than 90 ♥️not right angel Acute less than 90 Obtuse more than 90 |
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