Term
| What is the speed of sound through soft tissue? |
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Definition
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Term
Is there more or less tissue absorbtion of sound with high or low frequency transducers Greater or less depth |
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Definition
| Greater absorbtion with higher frequencies and depth |
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Term
What does B mode ultrasound mean? |
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Definition
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Term
| What are the components of duplex imaging? |
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Definition
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Term
| Is flow away from the transducer above or below the x axis? |
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Definition
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Term
Undr what circumstance would you want to increase the Pulse repetition frequency? Is a us more or less sensitive with lower PRF? |
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Definition
To sample faster flow More sensitive |
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Term
| In venous imaging what is done with the wall filter? |
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Definition
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Term
What is the accuracy of DUS in detecting thrombus in tibial veins in Symptomatic Asymptomatic patients |
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Definition
Symptomatic 80% Asymptomatic 40% |
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Term
What are two main risks for tissue damage secondary to ultrasound exposure? Define the terms |
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Definition
tissue heating and cavitation Cavitation is the formation, growth and oscillation or collapse of small, gas filled cavities within the ultrasound beam |
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Term
| When is the risk of cavitation the greatest? |
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Definition
| In the presence of air eg lung bowel |
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Term
What is SPTA and what is it used for? Explain the units involved and its abbreviation |
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Definition
Spatial peak temporal average intensity This relates to the thermal biological effects and is used to define the safe limits of US Intensity is the energy crossing a unit area(usually 1 cm2) in unit time. Ispta
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Term
Higher values of Ispta are considered safe in what applications? Are the typical valus of Ispta higher or lower for spectral and color doppler than black and white imaging? |
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Definition
Peripheral vascular Higher |
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Term
Name two other indices besides Ispta that are used to help assess US risk |
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Definition
| Mechanical index (MI) and thermal index (TI) |
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Term
| What is the mechanical index related to and what does it predict? |
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Definition
| MI is related to the amplitude and is thought to predict cavitation |
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Term
| An ultrasound exposure that does not produce a temperature rise greater than how many degrees above normal body temperature is felt not to pose a risk of producing thermal damage? |
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Definition
| A rise of no greater than 1.5 degrees C |
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Term
| Name the three models for thermal indices(TI) that have been developed for tissues being studied |
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Definition
Soft tissue TIS Tissue with bone TIB (useful in obstetrical) Cranial thermal index TIC used in trancranial doppler
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Term
| What has the potential to cause more tissue injury, increasing the gain or power of the ultrasound? |
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Definition
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