Term
| The impedance of a medium is |
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Definition
| equal to density x propagation speed |
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Term
Which of the following produces the least resistance to the transmission of the beam?
a. blood
b. bone
c. fat
d. muscle |
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Definition
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Term
| For a specular reflector__ |
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Definition
| the angle of reflection is equal and opposite the angle of incidence |
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Term
| Specular reflection occurs when__ |
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Definition
| the reflecting surface is smooth |
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Term
| The amount of reflection at an interface of two different media is determined by__ |
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Definition
| the differences in impedances |
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Term
| What is the result of adding the IRC and ITC together? |
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Definition
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Term
| What units are used for intensity reflection coefficient (IRC)? |
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Definition
| NONE it is a unitless percentage |
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Term
| A sound wave, with an intensity of 50W/cm2, strikes a boundary and is totally reflected. What is the intensity reflection coefficient? |
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Definition
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Term
| The intensity transmission coefficient of sound is 99.9%. What percent of sound is reflected back to the transducer? |
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Definition
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Term
| The change of beam direction from medium 1 into medium 2 is called__ |
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Definition
|
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Term
| (True or False) No refraction can occur at an interface of medium 1 and medium 2 if the impedances are the same. |
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Definition
| False. Refraction is caused by differences in propagation speeds. |
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Term
| What part of beam response does Snell's Law explain? |
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Definition
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Term
| If the beam passes from soft tissue into fat at an oblique angle, what happens to the angle of transmission? |
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Definition
| The angle decreases. ( the propagation speed of fat is less than soft tissue) |
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Term
| (True or False) Refraction can occur with both normal and oblique incidence? |
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Definition
| False. (Only with oblique incidence) |
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Term
| Sound wave strikes a boundary at normal incidence. The impedances of the two media are identical. What percentage of the sound wave is refracted? |
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Definition
| 0% (refraction requires oblique incidence) |
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Term
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Definition
| the gradual weakening of the beam as it transmits through the medium |
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Term
| Absorption in a medium is from__ |
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Definition
|
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Term
| Attenuation is determined by__ |
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Definition
| path length and frequency of the beam |
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Term
| The attenuation coefficient usually varies__ |
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Definition
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Term
Which of the following does NOT contribute to attenuation?
a. reflection
b. focusing
c. absorption
d. redirection in multiple directions |
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Definition
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Term
| The usual value of attenuation in soft tissue is__ |
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Definition
|
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Term
| An irregular boundary between two media creates which type of reflection? |
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Definition
| Backscatter (also called diffuse) |
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Term
| When the beam is reflected in multiple directions from very small particles, the reflection is probably__ |
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Definition
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Term
| When attenuation is reported as an amount per cm of path length it is called__ |
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Definition
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Term
| Attenuation through lung tissue is _____ through soft tissue. |
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Definition
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Term
| A 10 dB increase in intensity is equivalent to a difference of__ |
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Definition
|
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Term
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Definition
| a ratio between the two levels |
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Term
| Amplitude is measured in__ |
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Definition
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Term
| Decibel notation uses which scale? |
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Definition
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Term
| If the intensity decreases from 1.5W/cm2 to 0.75W/cm2, how many decibels is this change? |
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Definition
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Term
Which of these media has the greatest attenuation and the fastest speed?
a. bone
b. tendon
c. lung
d. fat
e. air |
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Definition
|
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Term
| Which describes the physics of refraction mathematically? |
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Definition
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Term
| At an interface of 0.25 Rayls and 0.75 Rayls, what percentage of intensity is reflected? |
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Definition
| 25% (uses the reflection coefficient formula to calculate Rayls) |
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Term
| The range equation refers to__ |
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Definition
|
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Term
| What is the result when the transmitted intensity is divided by the incident intensity? |
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Definition
| ITC (Intensity Transmitted Coefficient) |
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Term
| (True or False). When the angle of reflection is equal and opposite the angle of incidence, this refers to Snell's Law. |
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Definition
| False. (Snell's Law refers to refraction, not reflection) |
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Term
| Which apply to diffuse reflections? |
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Definition
| the echoes return in many directions |
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Term
| If the attenuation coefficient is 3 dB/cm and the path length is 9cm, what is the total attenuation? |
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Definition
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Term
| A 3 MHz sound beam travels 10 cm, 6 cm in medium A and 4 cm in medium B. The total attenuation is 14 dB. If the sound beam attenuated 4 dB in medium A, then how much attenuation occured in medium B? |
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Definition
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Term
| Which of the following is the best estimate for the attenuation coefficient of sound traveling in soft tissue? |
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Definition
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Term
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Definition
| a relationship between two levels |
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Term
| An example of a non-specular reflector is___ |
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Definition
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Term
| The ratio of particle pressure to particle velocity within the imaging field is__ |
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Definition
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Term
| What is refers to an angle of 45 degrees? |
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Definition
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Term
| An angle of 123 degrees is___ |
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Definition
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Term
| What is required for reflection to occur? |
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Definition
| a difference in impedance |
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Term
| What is the Maximum value possible for either ITC or IRC? |
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Definition
|
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Term
| Refraction at an interface when there are differences in___ |
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Definition
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