MIT 231 - ERU ch1 physics principles
The prefix "centi" denotes a) Thousandths b) Hundredths c) Millions d) Hundreds
Hundredths "Centi" denotes hundredths
Which of the following would have the lowest propagation speed a) water b) Soft tissue c) Bone d) Lung tissue
Lung tissue Lung tissue, which has a propagation speed 660 m/s, has the lowest propagation speed
Pressure is typically expressed in a) Frequency b) Pascals c) Decibels d) Kilograms per centimeter cubed
Pascals Pressure is typically expressed in pascals
Which of the following is described as the ability of an object to resist compression and relates to the hardness of a medium? a) Stiffness b) Density c) Pressure d) Inertia
Stiffness Stiffness is the ability of an object to resist compression and relates to the hardness of a medium
In clinical imaging, the wavelength measures between a) 1 and 10 Hz b) 1540 and 2000 m/s c) 0 and 1 d) 0.1 to 0.8 mm
0.1 to 0.8 mm In clinical imaging, the wavelengths measure between 0.1 and 0.8 mm
Which of the following would be considered ultrasonic a) 10 Hz b) 12.5 Hz c) 1 MHz d) 200 Hz
1 MHz 1 MHz is an ultrasonic frequency
The typical range of frequency for diagnostic ultrasound imaging is a) 20 to 20,000 Hz b) 1 to 20 MHz c) 10 to 20 MHz d) 12 to 100 MHz
1 to 20 MHz The typical range of frequency for diagnostic ultrasound is 1 to 20 MHz *Note: 1-20 MHz is for medical ultrasound Diagnostic ultrasound ranges from 2-12 MHz
The duty factor for continuous wave ultrasound is a) <99% b) 100% c) >20,000 Hz d) 8 Pa
100% The duty factor for continuous wave ultrasound is 100%
What is the total amount of attenuation that occurs if a 6.0-MHz sound beam travels through 4 cm of soft tissue a) 24 dB b) 12 dB c) 6 dB d) None of the above
12 dB The total amount of attenuation that occurs if a 6.0-MHz sound beam travels through 4 cm of soft tissue is 12 dB
*Which of the following is considered the speed of sound in soft tissue a) 660 m/s b) 330 m/s c) 1480 m/s d) 1540 m/s
1540 m/s The average speed of sound in all soft tissue is considered to be 1540 m/s or 1.54 mm/µs
If the angle of incidence is 40 degrees, what is the angle of transmission at the interface if medium 1 has a propagation speed of 1320 m/s and medium 2 has a propagation speed of 1700 m/s a) <40 degrees b) >40 degrees c) 40 degrees d) Cannot tell the angle of transmission
>40 degrees The angle of transmission is greater than 40 degrees
The major component of attenuation is a) Scatter b) Absorption c) Transmission d) Refraction
Absorption Absorption is the major component of attenuation
As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of a) Attenuation b) Absorption c) Scattering d) All of the above
All of the above Attenuation is a decrease in the amplitude, power, and intensity of the sound beam as sound travels through tissue. There are three mechanisms of attenuation: absorption, reflection, and scattering.
The maximum value or minimum value of an acoustic variable minus the equilibrium value of that variable describes the a) Power b) Intensity c) Duty factor d) Amplitude
Amplitude Amplitude is the maximum or minimum deviation of an acoustic variable from the average value of that variable
An increase in pulse repetition frequency would lead to a) An increase in duty factor b) An increase in pulse duration c) An increase in the number of cycles d) A decrease in resolution
An increase in duty factor An increase in pulse repetition period would lead to an increase in duty factor
All of the following are true of power Except a) As amplitude increases, power remains the same b) Power is proportional to amplitude squared c) Intensity is proportional to power d) Power is measured in milliwatts
As amplitude increases, power remains the same Power decreases as amplitude decreases
What is defined as the ability of the ultrasound system to image structures that are positioned parallel to the sound beam as separate structures a) Transverse resolution b) Parallel resolution c) Axial resolution d) Coronal resolution
Axial resolution Axial resolution is the ability to resolve reflectors that lie parallel to the beam as distinct echoes
Which of the following would have the highest propagation speed a) Air b) Bone c) Soft tissue d) Water
Bone Bone, which has a propagation speed of 4080 m/s, has the highest propagation speed
*Areas of high pressure and density are referred to as a) Compressions b) Rarefactions c) Condensations d) Rarefractions
Compressions Areas of high pressure and density are referred to as compression
As imaging depth increases, the pulse repetition frequency must a) Not change b) Increase c) Decrease d) Pulse repetition frequency does not relate to imaging depth
Decrease As imaging depth increases, the PRF decreases
The inertia of the medium describes its a) Attenuation characteristics b) Stiffness c) Density d) Elasticity
Density The inertia of a medium describes its density
The percentage of time that the ultrasound system is producing pulses of ultrasound describes the a) Pulse repetition period b) Pulse duration c) Duty factor d) Pulse repetition frequency
Duty factor The duty factor is the percentage of time the ultrasound system is producing a sound
Which of the following is determined by the sound source only a) Frequency b) Wavelength c) Spatial pulse length d) Propagation speed
Frequency Frequency is determined by the sound source only
As imaging depth increases, pulse repetition period a) Remains constant b) Increases c) Decreases d) Doubles
Increases As imaging depth increases the pulse repetition period increases
If pulse repetition frequency increases, then the duty factor a) Remains constant b) Increases c) Decreases d) Doubles
Increases If the pulse repetition frequency increases, the duty factor increases
What is essentially equal to the power of a wave divided by the area over which the power is distributed a) Amplitude b) Power c) Intensity d) Absorption
Intensity Intensity is essentially equal to the power of a wave divided by the area over which the power is distributed
What is the change in intensity if the power decreases by half a) Intensity doubles b) Intensity is halved c) Intensity is one fourth d) Intensity does not change
Intensity is halved If power is decreased by half, intensity is decreased by half
Density and propagation speed are a) Inversely related b) Directly related c) Directly proportional d) Unrelated
Inversely related Density and propagation speed are inversely related
What is the change in power if the amplitude triples a) It doubles b) It triples c) It quadruples d) It increases nine times
It increases nine times If amplitude triples, then power increases by nine times
All of the following are true of wavelength Except a) It is determined by both the medium and the sound source b) It is equal to the period divided by the frequency c) It is inversely related to frequency d) It is directly related to period
It is equal to the period divided by the frequency Wavelength is equal to the propagation speed divided by the frequency
Density is typically measured in a) Kilograms per centimeter cubed b) Millimeters c) Watts per centimeter squared d) Pascals
Kilograms per centimeter cubed Density is typically measured in kilograms per centimeter cubed
Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of a) Copperhirm titonize b) Zinconian sulfate c) Lead zirconate titanate d) Barium
Lead zirconate titanate Transducers have material within them that, when electronically stimulated, produces ultrasound waves. These materials most likely consist of some form of lead zirconate titanate
*Sound is technically a a) Transverse and longitudinal wave b) Mechanical and transverse wave c) Non-mechanical and pressure wave d) Mechanical and longitudinal wave
Mechanical and longitudinal wave Sound is technically a mechanical and longitudinal wave
Which of the following is an appropriate unit of measurement for propagation speed a) Millimeters per microsecond (mm/us) b) Watts per centimeter squared (W/cm²) c) Microseconds (µs) d) Kilohertz (kHz)
Millimeters per microsecond (mm/µs) Propagation speed can be measured in millimeters per microsecond
Micro denotes a) Millionth b) Hundredth c) Million d) Billionth
Millionth Micro denotes millionth
Spatial pulse length can be calculated by a) Multiplying the number of cycles times the frequency b) Dividing the period by the frequency c) Multiplying the number of cycles times the wavelength d) Dividing the number of cycles by the wavelength
Multiplying the number of cycles times the wavelength Spatial pulse length equals the number of cycles in the pulse multiplied by the wavelength
The attenuation coefficient in soft tissue is equal to a) One half of the operating frequency b) Double the operating frequency c) Frequency times path length d) The total decibels
One half of the operating frequency The attenuation coefficient (in dB/cm) is the rate at which sound is attenuated per unit depth. It is equal to one half of the frequency (f/2) in soft tissue
What is pressure measured in a) Feet, inches, centimeters, or miles b) Pascals or pounds per square inch c) Kilograms per centimeter cubed d) Hertz, kilohertz, or megahertz
Pascals or pounds per square inch Pressure is measured in pascals or pounds per square inch
If only the density of a medium is increased, then the a) Propagation speed will increase b) Propagation speed will decrease c) Propagation speed will stay the same d) None of the above
Propagation speed will decrease If only the density of the medium is increased, then the propagation speed will decrease
Which of the following is defined as only the active time a) Duty factor b) Pulse repetition frequency c) Period d) Pulse duration
Pulse duration Pulse duration is only the active time or "on" time
Which of the following is defined as the number of ultrasound pulses emitted in 1 second a) Pulse repetition period b) Duty factor c) Pulse repetition frequency d) Spatial pulse length
Pulse repetition frequency Pulse repetition frequency is defined as the number of ultrasound pulses emitted in 1 second
What is defined as the beginning of one pulse to the beginning of the next pulse, and therefore includes both the "on" and "off" time a) Pulse repetition period b) Pulse duration c) Duty factor d) Pulse repetition frequency
Pulse repetition period The pulse repetition period is the time from the start of one pulse to the start of the next pulse, and therefore, it includes the "on" (or transmit) and "off" (or listening) times
*The portion of the sound beam where the molecules are pulled apart describes an area of a) Compression b) Rarefaction c) Refraction d) Amplitude
Rarefaction Rarefaction is an area in the sound wave where the molecules are spread wider apart
Damping of the sound beam a) Reduces the spatial pulse length b) Increases the spatial pulse length c) Increases the pulse duration d) Has no impact on spatial pulse length or pulse duration
Reduces the spatial pulse length Damping of the sound beam decreases the spatial pulse length
The change in the direction of the original sound wave that occurs when sound interacts with two different tissue types that have a different propagation speed is referred to as a) Wavelength b) Scattering c) Refraction d) Absorption
Refraction Refraction is the change in direction of the transmitted sound beam that occurs with oblique incidence and dissimilar propagation speeds
Which of the following describes the amount of refraction that occurs at an interface a) Bernoulli's law b) Poiseuille's law c) Law of reflection d) Snell's law
Snell's law Refraction is a redirection of the transmitted sound beam. Snell's law describes the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media
All of the following are true of stiffness Except a) It is defined as the ability of an object to resist compression b) Stiffness and propagation speed are indirectly associated c) Increasing stiffness increases propagation speed d) Stiffness may also be referred to as elasticity
Stiffness and propagation speed are indirectly associated Stiffness and propagation speed are directly related: the stiffer the medium, the faster the propagation speed
All of the following relate to the strength of the sound except a) Amplitude b) Wavelength c) Intensity d) Power
Wavelength Wavelength does not relate to the strength of the sound wave
Which of the following is determined by the sound source and medium a) Propagation speed b) Frequency c) Period d) Wavelength
Wavelength Wavelength is determined by both the sound source and the medium
Which of the following is described as the distance over which one cycle occurs a) Pulse duration b) Duty factor c) Period d) Wavelength
Wavelength Wavelength is distance over which one cycle occurs, or the distance from the beginning of one cycle to the end of the same cycle
