Chapter 2: Waves (Ultrasound Physics)
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53 Terms
mechanical
Are sound waves mechanical or electromagnetic?
mechanical
What type of wave needs a medium in order to travel?
longitudinal
Is a sound wave transverse or longitudinal?
temperature, pressure, density, and motion
What are the acoustic variables?
frequency MHz
Number of sound cycles produced each second?
the source
What is frequency determined by?
wavelength
The measure of distance over which one sound cycles occurs?
the source and the medium
what is wavelength determined by?
propagation speed
the speed at which sound moves through a specific medium?
properties of the tissue
what is propagation speed determined by?
1.54 mm/us
what is the propagation speed of tissue?
13 us
For one centimeter of tissue, how long is the round trip?
constructive
what is it called when waves form a larger wave?
destructive
what is it called when waves are out of phase and cancel out?
Infrasound
what is the sound type below 20 Hz?
audible
What sound type is (20 Hz-20Khz)?
ultrasound
what sound type is (20 khz-20 MHz)?
diagnostic ultrasound
what sound type is (2MHz-20MHz)?
resolution
the distance between objects required to distinguish them as separate objects?
high frequency
What level frequency gives detailed resolution but poor depth penetration?re
low frequency
what level frequency penetrates well but does not have good clarity?
amplitude, power, and intensity
what are the measures of magnitude?
V or dB
what are the units for amplitude?
watts
what is the unit for power?
watts/cm²
what is the unit for intensity?
amplitude
what is the voltage applied to the crystal that determines height of wave?
power
what is the rate in which energy is transferred?
intensity
what is the power/area
attenuation
log comparison of the energy you started with versus what you actually have left after energy is lost to heat or friction?
rarefaction
what is it called when particles are in low density and decreased pressure?
compression
what is it called when there is high particle density and increased pressure?
pressure(P)=force/area
what is the formula for pressure?
lbs/in², mmHg, Pascals, ATM
what are the units for pressure?
harmonic imaging
changes in density will lead to what?
density=mass/volume
what is the formula for density?
g/cm³, kg/m³
what are the units for density?
frequency=1/period or number of cycles/number of seconds
what is the formula for frequency?
Hz, kHz, MHz
what are the units for frequency?
period=1/frequency
what is the formula for period?
s, ms, us
what are the units for period?
wavelength=propagation speed/frequency
what is the formula for wavelength?
m, mm
what are the units for wavelength?
m/s, mm/us
what are the units for propagation speed?
1.54 mm/us
what is the propagation speed of soft tissue?
distance to reflector(mm)=(1/2)propagation speed(mm/us) x round trip time(us)
what is the range equation for other tissues?
distance to reflector(cm)=round trip travel time(us)/13(us/cm)
what is the range equation for soft tissue?
intensity(W/cm²)=power(W)/area(cm²) or amplitude²/area
what is the equation for intensity?
attenuation
the longer the path over which sound travels, the greater the _____
decreases
as depth increases, attenuation increases and penetration strength ______
10log(final intensity/initial intensity)
what is the equation for decibels of attenuation for power and intensity?
20log(final amplitude/initial amplitude)
what is the equation for decibels of attenuation for amplitude?
attenuator
electronic device that absorbs energy resulting in lower intensity, power, and amplitude?
amplifier
boosts energy increasing intensity, power, and amplitude?