Echo Board Review
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What is sound?
the compression and rarefaction of a medium
What is the equation for velocity?
v = wavelength x frequency
What is the average velocity in soft tissue?
Does velocity vary with issue?
yes - 4080 m/sec in bone; 330 m/sec in air
What is the frequency of ultrasound?
> 20,000 hertz
What is wavelength?
the distance between peaks
What is the standard wavelength?
1540 m/sec (velocity) / 3 MHz (frequency) = 0.5 mm
What is amplitude?
Difference between maximum and minimum
What is power?
total output in watts
What is intensity?
the amount of energy delivered per unit area (watts / cm2) in u/s
On what scale is decibel?
What is the mechanical index?
the potential of a frequency to cause cavitation
- MI > 1 = destroys microbubbles
- MI < 0.1 = weak harmonics
What is thermal index?
ability of u/s to heat tissue - no important in adult echo, important in fetal echo
What would you like to do?
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