Physics and Instrumentation Ch 1
Density is typically measure in A Kilograms per centimeter cubed B Millimeters C Watts per square centimeter D Pascals
A
An increase in PRF would lead to: A and increase in DF B A decrease in PD C An increase in the number of cycles D A decrease in resolution
A An increase in duty factor (DF)
The prefix "centimeter-" means A thousandths B Hundredths C Millions D Hundreds
B Hundredths
Pressure is typically expressed in A Frequency B Pascals C Decibels D Kilograms per centimeter cubed
B. Pascals
SPL can be calculated by A Multiplying the number of cycles by the frequency B Dividing the period by the frequency C Multiplying the number of cycles by the wavelength D Dividing the number of cycles by the wavelength
C (cycles x wavelength)
Which of the following would be considered ultrasonic A 10 Hz B 18 kHz C .5 MHz D 200 Hz
C .5 MHz is 500,000 Hz which is ultrasonic frequency. Ultrasonic range is > 20,000 Hz
Adding damping to the transducer improves which type of resolution A Transverse resolution B Temporal resolution C Axial resolution D Elevational resolution
C Axial resolution (better when the pulse is shorter)
The inertia of the medium describes its A Attenuation and characteristics B Stiffness C Density D Elasticity
C Denisty
As imaging depth increases, the PRF must : A not change B Increase C Decrease D PRF does not relate to imaging depth
C Depth and PRF are inversely related
The percentage of time that the ultrasound system is production pulses of ultrasound describes the A PRP B PD C DF D PRF
C Duty factor
What term is defined as "the power of a wave divided by the area over which the power is distributed?" A Amplitude B Power C Intensity D Absorption
C Intensity
Which of the following is defined as the number of ultrasound pulses emitted in 1 second A PRP B DF C PRF D SPL
C Pulse repetition frequency is defined as the number of ultrasound pulses emitted in 1 second. PRF is determined by imaging depth
Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of A Tungsten acetate B Dilithium zirconium C Lead zirconate titanate B Barium sulfate
C Zirconate titanate
In clinical imaging, the wavelength typically measures between A 1 and 10 Hz B 1540 and 2000 m/s C 0 and 1 D .1 and .8 mm
D .1 and .8 mm
The maximum value or minimum value of an acoustic variable minus the equilibrium value of the variable describes the A Power B Intensity C DF D Amplitude
D Amplitude
What is the change in power if the amplitude triples A It doubles B It triples C It quadruples D It increases nine times
D Power is proportional to the amplitude squared
Which of the following is defined as only the active time A DF B PRF C Period D PD
D Pulse duration is the time is takes for a pulse to occur but only includes the "on" time
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
D Snell's Law (describes the angle of transmission at an interface based on the angle of incidence and propagation speeds of the two media)
Which of the following is described as the distance over which one cycle occurs A PD B DF C Period D Wavelength
D Wavelength
What are the units of DF? A dB B dB/cm C Hz D Unitless
Duty factor is the percentage of time that sound is being transmitted and has no units
Micro denotes A Millionth B Hundredth C Million D Billionth
A Millionth
Which of the following is an appropriate until of measurement for propagation speed A millimeters per microsecond B watts per square centimeter C Microseconds D kilohertz (kHz)
A millimeters per microsecond or meters per second
The DF for CW ultrasound is A 1.0 % B 100% C 20,000 Hz D 8 Pa
B Continuous wave ultrasound has a duty factor (on percentage time) of 100%
All of the following relate to the strength of the sound wave except A Amplitude B Wavelength C Intensity D Power
B Wavelength is a parameter for the length of the wave not the power of the wave
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
C Refraction is the change in direction of the transmitted sound beam that occurs with oblique incidence and dissimilar propagation speeds
Which of the following would have the lowest propagation speed? A Water B Soft Tissue C Bone D lung tissue
D Lung tissue (660 m/s)
Which of the following is determined by the sound source and medium? A Propagation speed B Frequency C Period D Wavelength
D Wavelength is determined by both the sound source and the medium
As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of : a. attenuation b. Elevation all resolution c. Huygen's principal d. Refraction
A Attenuation
Damping of the sound beam A Reduces the SPL B Increases the SPL C Increased the PD D Has no impact on the SPL or the PD
A Damping of the sound beam decreases the spatial pulse length by decreasing the number of cycles in a pulse
Which of the following is determined by the sound source only A Frequency B Wavelength C SPL D Propagation speed
A Frequency (thickness of the element and propagation speed of the element)
All of the following are true of power except A As amplitude increases, power remains the same B Power is proportional to the amplitude squared C Intensity is proportional to power D Power is measure d in milliwatts
A Power is proportional to the amplitude squared (power decreases as amp increases)
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 PRP B PD C DF D PRF
A Pulse repetition period includes both the on and off time
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
A The attenuation coefficient (dB/cm) is the rate at which sound is attenuated per unit depth. It is equal to one half of the frequency in soft tissue
Areas of high pressure and density are referred to as: A Compressions B Rarefractions Diffractions Refractions
A compression (low pressure is rarefraction)
Density and propagation speed are A Inversely related B Directly related C Directly proportional D Unrelated
A inversely related
The typical range of frequency for diagnostic ultrasound imaging is A 20 to 20,000 Hz B 1 to 20 MHz C 2 to 15 kHz D 12 to 100 MHz
B ( 2 to 15 MHz is standard for most transducers)
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 1.5 dB
B (attenuation coefficient x path length). (F/2 x cm) = 3 dB/cm x 4 cm = 12 dB)
As imaging depth increases, PRP A Remains constant B Increases C Decreases D Doubles
B (depth and PRP are directly related)
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
B Density and propagation speed are inversely related
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
B Intensity and power are directly related so if power is decreased by half intensity is also decreased by half
What are the units for pressure A Feet, inches, centimeters or miles B Pascals, or pounds per square in C Kilograms per centimeter cubed D Hertz, kilohertz or megahertz
B Pressure is measured in pascals (Pa) or pounds per square inch
The portion of the sound beam where the molecules are farther apart describes an area of A Compression B Rarefaction C Refraction D Amplitude
B Rarefaction is an area in the sound wave where the molecules are spread wider apart
Which of the following requires an oblique interface and a propagation speed mismatch A Reflection B Refraction C Normal incidence D Damping
B Refraction
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 ms and medium 2 has a propagation speed of 1700 m/s? A 0 degrees B > 40 degrees C < 40 degrees D Cannot tell the angle of transmission
B The angle of transmission is greater than 40 because the propagation speed of medium two is greater than the propagation speed of medium 1 (angle 2 > angle 1 if C2.C1)
All of the following are true of wavelength except A It is determined by both the medium ad the sound source B It is equal to the period divided by the frequency C It is inversely related to the frequency D It is directly related to period
B Wavelength is equal to the propagation speed divided by the frequency.
The major component of attenuation is A Scatter B Absorption C Transmission D Refraction
B. absorption (creation of heat in the tissue as sound travels)
Sound is technically a A Transverse and longitudinal wave B Mechanical and transverse wave C Nonmechanical and pressure wave D Mechanical and longitudinal wave
D Sound is a mechanical (pressure waves created by mechanical action) and longitudinal wave (molecules vibrate in the direction that is parallel to the direction of wave travel)
Which of the following is considered the speed of sound in soft tissue? A 1.54 m/s B .77 m/s C 100 mW/cm2 D 1540 m/s
D The average speed of sound in all soft tissue is considered to be 1540 m/s or 1.54 mm/micro second. This number is the average of all the propagation speeds found within the human body.
Which of the following would have the highest propagation speed? A Air B Bone C Soft tissue D Water
b. bone (4080 m/s)
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
