Physics 111 Chapter 2 Flashcards
A wave is a traveling variation in quantities called wave________________
variables
Ultrasound is sound with a frequency greater than
20,000
Ultrasound is sound with a frequency greater than
20,000 Hz
______________ is the time it takes for one cycle to occur.
Time
Wavelength is the length of _____________ over which one cycle occurs.
Space
Sound requires a ______________ through which to travel.
Medium
Stiffer media have _______________ sound speeds
Higher
Propagation speed is primarily determined by the ______________ of the medium.
Stiffness
Ultrasound pulses contain a range of frequencies called the _______________.
Bandwidth
Regions of lower pressure and density are called
rarefactions
________________ area even and odd multiples of the fundamental frequency
Harmonics
Doppler ultrasound pulses are typically _________ cycles long
5-30
The fraction of time that pulsed ultrasound is on is called
Duty Factor
The rate at which energy passes through a unity area is called
Intensity
As sound travels, the reduction of amplitude and intensity of the wave is called
attenuation
The average propagation speed in human soft tissue is ________________
1540m/s
If you switch to a lower frequency for penetration, the wavelength of the transducer ______________
Increases
1000 Hz is equal to _______________ kHz
1
If the beam power increases, intensity ___________________
Increases
If the beam area decreases, the intensity ___________
Increases
Attenuation increases with increasing ___________
Frequency
For perpendicular incidence, the incidence angle is______________
0
The ______________ _____________ is the number of pulses that occur in single second
Pulse repetition frequency
If the number of cycle in a pulse is reduced, the pulse duration _______________
is decreased
Amplitude and Intensity are indicators of the the sound wave’s _________________
strength
Duty factors for sonography are typically in the range of _____________________
0.1% - 1.0%
Impedance in equal to density multiplied by ______________
propagation speed
The unit for impedance is
rayl
If the propagation speed through the second medium is greater than through the first medium, the transmission angle is ______________
greater than the incidence angle
What does 3 dB of attenuation mean?
One half the original intensity
Lateral position errors occur on an image due to sound _______________
refraction
The proportion of intensity to amplitude is
squared
What units are used to quantify attenuation?
dB
If intensity reflection coefficient increases, intensity transmission coefficient _________________
decreases
In oblique incidence, the ___________ and _____________ angles are always equal
incidence; reflection
The liquid suspensions that have been developed can injected into the circulation intravenously to increase _______________
echogenicity
Intensity is equal to the power of a wave divided by the _______________ over which the power is spread
area
Amplitude is the maximum variation that occurs in an acoustic ________________
variable
The dominant factor contributing to attenuation of ultrasound in soft tissue is
absorption
Almost all ultrasound contrast agents contain
gas microbubbles
Ultrasound systems use propagation speed to determine
echo location of the display
_________________ determines how fast images genetated
Pulse repetition frequency
Interfaces that scatter ultrasound energy are usually considered those that ate equal to smaller than the ________________
Wavelength
Sound is a
mechanical longitudinal wave
_______________ media have higher sound speeds
Stiffer
_________________ frequencies are generated as sound travels through tissue
Harmonic
When frequency increases, period
decreases
A ______________ is one complete variation in pressure
cycle
_______________ limits imaging depth
Attenuation
The shorter the pulse, the broader the
bandwidth
With doppler techniques, the operator controls the ______________________________
pulse repetition frequency
____________pulses improve the quality of sonographic images
Shorter
For each centimeter of distance, the pulse round trip time is equal to
13 ms
From given values for propagation speed and frequency _______________ can be calculated
Wavelength
Sound travels most slowly in
Gases
Sound travels fastest in
steel
Waves can carry ____________ from one place to another
information
The time from the beginning of one pulse to the beginning of the next is
Pulse repetition period
Spatial pulse length equals the number of cycle in the pulse multiplied by________________
wavelength
Beam width can be reduced by focusing to improve
lateral resolution
