Flashcards in DMS 120 - PHYSICS MIDTERM Deck (64):
Interfaces that scatter ultrasound energy are usually considered to be...
those that are equal to or smaller than the wavelength.
Regions of lower pressure and density are called...
If you switch to a lower frequency for penetration, the wavelength of the transducer will...
The attenuation of a 5.0-MHz transducer at a depth of 4 cm is ____ dB.
The higher the transducer frequency, the higher the...
The following are all ultrasound frequencies except:
The duty factor will increase with all of the following :
- pulse repetition frequency.
- pulse duration.
The attenuation of a 5-MHz transducer in soft tissue would be...
5.0 dB at 2 cm of depth
What is the period of a 5.0-MHz transducer in soft tissue?
Impedance is equal to density multiplied by:
Continuous wave Doppler has a duty factor of ____ %.
For perpendicular incidence, the incidence angle is ___ degrees.
Attenuation decreases with an increase in:
The average propagation speed in human soft tissue is ____.
Frequency is _____ proportional to wavelength.
The distance to a reflector in soft tissue is 15 cm. What is the round-trip time to this depth?
Period is the ____ it takes for one ____ to occur.
In oblique incidence the sound is refracted at a boundary between ____ where propagation speeds are different.
The propagation speed in soft tissue is not:
____ Law relates the transmitted beam direction to the incident beam direction and the speeds of sound in the two materials forming the interface.
The pulse repetition frequency is the number of pulses that occur in a ____.
When frequency increases, the period...
Amplitude is the maximum variation that occurs in an acoustic ____.
3 dB of attenuation means?
One half the original intensity.
If beam power increases, intensity will...
Propagation speed is the speed at which a wave:
travels through a medium.
Sound is a ____ longitudinal wave.
The wavelength of 3-MHz ultrasound in soft tissue is ____
CW sound is NOT described by:
____ is the number of complete cycles per second.
As sound travels, the reduction in amplitude and intensity of the wave is called:
Propagation speed is higher or lower in bone than soft tissue?
Sound requires a ___ through which to travel.
Ultrasound pulses contain a range of frequencies called the ____.
Duty factor is:
The spatial pulse length will not increase with:
The propagation speed for a round-trip time of 39 µs is ____ mm/µs.
NONE OF THE ABOVE
Cycle, period, and frequency are examples of acoustic ____
The fraction of time that pulsed ultrasound is on is called ____.
Pulse repetition frequency is the ____ of pulses occurring in 1 second.
Attenuation is higher OR lower in bone than in soft tissue?
Compression is not an _____.
The best way to describe the role of ultrasound scattering in diagnostic imaging is:
that it allows us to see the tissue interfaces .
The distance to the reflector in soft tissue with a round-trip time of 39 µs is:
30 mm or 3 cm.
If the beam area decreases, the intensity will____.
The four intensity values from the greatest to the least are:
SPTP, SATP, SPTA, SATA.
Heat production depends most directly on the ____ intensities.
Pulsed wave ultrasound is not described by the terms such as:
frequency, wavelength, and propagation speed
The rate at which energy passes through a unit area is called _____.
If the density of medium 2 is 10% greater than that of medium 1 and the propagation speeds are equal, the impedance of medium 2 is ____ for medium 1.
Propagation speed is primarily determined by the ____ of the medium.
The unit for impedance is:
In oblique incidence the incidence and reflection angles are always:
If frequency increases, period will _____.
Stiffer media have higher or lower sound speeds?
Intensity is equal to the power of:
a wave divided by the area over which the power is spread.
20 kHz is equal to...
500 Hz is equal to...
TRUE OR FALSE
Stiffer media have higher sound speeds.
TRUE OR FALSE
The impedances of the media determine how much of the incident sound wave is reflected and transmitted into the second medium.
TRUE OR FALSE
Spatial pulse length is determined by the length of the pulse and the propagation speed.
Impedance increases when ____ increases.
Density and propagation speed