What are the 3 factors of attenuation?
absorption, scattering, reflection
Aas the sound beam travels through the body, what happens to amplitude and intensity?
Heat energy is produced when this happens to the sound.
This occurs at the tissue interfaces.
reflection and scatter
The amount of heat produced by it is too small to cause a measurable temperature change.
Sound energy that cannot be recovered is caused by what?
If a woman is less than 5 weeks pregnant none of this should be used to scan the embryo.
color or Doppler
Attenuation in tissue is hightly dependent on what?
The higher the frequency, the higher the ________ and ________.
attenuation and absorption
The higher the frequency the lower the _________.
What units are used to quantify attenuation?
Decibles are units of what?
POWER and % of acoustic output
If frequency is increased by 1, then what happens to attenuation and absorption?
increased by 1
What is the maximum of acoustic output?
What does blood disapate?
Other than attenuation, decibles can also be used to measure what?
instrument output, dynamic range, gain
A logarithmic way of comparing ratio of 2 intensities that include attenuation and amplification is to measure in what?
The amount of attenuation/per cm/per MHz which equals db/cm is the what?
At 1.54 mm/μs the lung has what type of attenuation?
At 1.54 mm/μs bone has what type of attenuation?
low (it's a reflector)
The range of the attenuation coefficient of soft tissue is what?
0.5 - 1db/cm/MHz
When power is increased by 3db, what happens to intensity?
When power is decreased by 3db, what happens to intensity?
What is the intensity of power increased by?
As frequency and attenuation increase, this will also increase...
As penetration decreases, these will increase...
attenuation and resolution
The distance that a sound must travel to reduce the intensity of sound to 1/2 of its original value is what?(decease by 3db)
half value layer thickness
The shorter the spatial pulse length, the ______ the penetration will be, but the ______ the resolution will be.
For superficial structures, you need to have a shorter what?
spatial pulse length
For abdominal imaging you need what?
The time that the pulse is on (measured in μsec) is what?
The length of the pulse (measured in mm) is what?
If there are many cycles in a pulse it has a longer ________.
A pulse that creates more penetration is a what?
The shorter the wavelength the fewer the _______ in the pulse.
A short pulse will create what?
What does pulse travel time equal? (time it takes for one pulse to travel round trip)
The maximum displacement of any particles measured from an undistured postion is what?
Amplitude of a wave decreases as it what?
How can amplitude be increased?
If amplitude is doubled than intensity is...
If amplitude is halved than intensity is...
What is the energy in a sound wave?
Although intensity can be adjusted with the POWER/OUTPUT, it originally is determined by what?
sound source (transducer)
mW/cm² is a measurement for what?
100 mW/cm² is the maximum power used in what?
What happens to the power in a wave as it travels through a tissue?
What is amplitude² equal to?