review Flashcards
Wavelength is a measure of_________________?
distance
In order for us to see an image on the monitor what MUST occur?
Reflection
Reflection is essential for ultrasound imaging, as it allows the system to detect echoes.
The power of a system is at 100% and this is 0 dB. What is the dB change when the system’s power is 50%?
-3 dB
A decrease in power corresponds to a negative dB value, with -3 dB representing a halving of power.
As frequency increases, the period will
Decrease
The period is inversely related to frequency; as frequency increases, period decreases.
When frequency increases, penetration decreases.
True
Higher frequencies result in less penetration into tissues due to increased absorption.
A wave with a frequency of 15,000MHz is ultrasonic.
True
Frequencies above 20 kHz are considered ultrasonic.
Sound requires a ___________ in order to travel.
Medium
Sound waves need a medium (solid, liquid, or gas) to propagate.
How many milliliters are contained in a jar filled with 5 liters of fluid?
5,000
1 liter is equivalent to 1,000 milliliters.
The ultrasound system is operating at 100% power and the power setting is at 0 dB. What would the power setting be when the system is operating at 10% power?
-10 dB
A reduction to 10% power results in a decrease of 10 dB.
If frequency of sound is doubled, what happens to wavelength? It is _____________
halved
Wavelength is inversely proportional to frequency.
Which of the following terms describes the amount of time it takes for one cycle to occur?
Period
The period is the duration of one complete cycle of a wave.
Sound travels in a straight line.
True
Sound can bend and change direction when it passes through different media.
How many Hertz is 3Mhz?
3,000,000
1 MHz equals 1,000,000 Hz.
Which of the following is important in discussing bioeffects and safety of ultrasound imaging?
Intensity
Intensity is a crucial factor in assessing the safety and bioeffects of ultrasound.
The Piezoelectric Principal is a property of certain materials to create a ______when they are mechanically deformed?
Voltage
The piezoelectric effect allows materials to generate voltage in response to mechanical stress.
Sound is a ______________ that travels in the form of a wave.
Vibration
Sound is a mechanical wave that results from vibrations of particles in a medium.
Which of the following terms describes the number of complete variations an acoustic variable goes through in one second?
Frequency
Frequency is measured in Hertz (Hz) and indicates how many cycles occur per second.
Compressions are areas of increased pressure and density.
True
Compressions occur in longitudinal waves where particles are closer together.
As a rule we should always use the _______ frequency probe we deem reasonable when beginning an exam.
highest
Which of the following determines the propagation speed of a sound wave through a medium?
Medium
The properties of the medium (density and stiffness) primarily affect sound speed.
Sound is a propagating variation in quantities called acoustic variables. Which of the following is NOT an acoustic variable?
Mass
Acoustic variables include pressure, particle motion, and density, but not mass.
What are the units for power?
Watts
Power in ultrasound is measured in Watts.
Ultrasound travels best through a vacuum.
False
Sound requires a medium to travel and cannot propagate in a vacuum.
A signal’s power increases from 1 watt to 100 watts, How is this expressed in decibels?
20 dB
The formula for dB change is 10 log10(P2/P1), resulting in 20 dB for a 100-fold increase.
Longitudinal waves are always characterized by particle motion being_________ to wave motion?
Parallel
In longitudinal waves, particle motion occurs in the same direction as wave propagation.
The initial amplitude of the ultrasound beam is determined by sound source (machine) and does not change as it propagates through the body.
False
The amplitude can change due to attenuation as sound travels through different tissues.
Which of the following has the greatest impact on propagation speed?
Stiffness of media
Stiffness is the most significant factor affecting sound speed in a medium.
Which of the following terms relates to the ‘strength’ of sound?
Amplitude
Amplitude reflects the strength or intensity of the sound wave.
In B-Mode scanning, the brightness of the dot is proportional to the echo signal _____________.
Amplitude
The brightness in B-Mode is related to the strength of the returning echoes.
Ultrasound frames that are rapidly being replaced creating a ‘motion picture’ effect are called ‘Rapid-Time scanning’.
False
Rapid-Time scanning is not a standard term in ultrasound imaging.
