Physics FINAL
Which of the following is the best estimate for the attenuation coefficient of sound traveling in soft tissue?
0.45 dB/cm/MHz
Which of the following would be considered ultrasonic?
1 MHz
The typical range of frequency for diagnostic ultrasound imaging is:
1 to 20 MHz
The impedance of a transducer active element is 1,900,000 rayls and for the skin is 1,400,000 rayls. What is an acceptable impedance for the matching layer?
1,726,000 rayls
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?
12 dB
The following are all ultrasound frequencies except:
15.0 kHz
Which of the following is considered the speed of sound in soft tissue?
1540 m/s
Which of the following waves is ultrasonic and least useful in diagnostic imaging?
24,000 Hz
If the power increases double the original value, how many decibels is this change?
3
If the transmitted pulse has frequencies from 3.5 MHz to 6.5 MHz, what is the bandwidth?
3.0 MHz
A sound wave, with an intensity of 40 W/cm2, strikes a boundary and is totally reflected. What is the reflected intensity?
40 W/cm2
Which of following waves has the longest period?
4Hz
The major component of attenuation is:
Absorption
A reciprocal relationship means that
All Choices are correct
The maximum value or minimum value of an acoustic variable minus the equilibrium value of that variable describes the:
Amplitude
Which of the following best describes the line identified by the letter C?
Amplitude
Terms that can be used to describe the strength of a sound beam are
Amplitude and intensity
An increase in pulse repetition frequency would lead to:
An increase in duty factor
All of the following are true of power except:
As amplitude increases, power remains the same Power is measured in milliwatts
As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of
Attenuation, Absorption, and Scattering
Which of the following shortens the length of the pulse by decreasing the number of cycles in the pulse?
Backing material
Which of the following could not be used as the coupling medium (gel)?
Barium sulfate
Which of the following would have the highest propagation speed?
Bone
How are ultrasound transducers typically sterilized?
Cold-sterilization methods
When the elasticity of a medium is high, the _________ is high.
Compressibility
Areas of high pressure and density are referred to as:
Compressions
Which of the following is the part of the transducer that stops the ringing of the element?
Damping material
Which of the following is not true of damping?
Damping worsens axial resolution
As imaging depth increases, the pulse repetition frequency must:
Decrease
As the frequency of an acoustic variable increases, the wavelength
Decreases
The percentage of time that the ultrasound system is producing pulses of ultrasound describes the:
Duty factor
Which of the following best describes the components of the damping material?
Epoxy resin loaded with tungsten
If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6 MHz, the main or center frequency of the transducer is 6 MHz.
False
The wavelength of the 2 MHz transducer is shorter than the 5 MHz transducer
False
Two piezoelectric crystals are made from the same material. The thicker crystal will make a pulsed transducer with a higher frequency.
False
Which of the following is determined by the sound source only?
Frequency
With a pulsed wave transducer, which of the following occurs if the PZT thickness is doubled?
Frequency is halved
How thick is the element if the frequency is 3 MHz?
Half the wavelength of the wave in the PZT
Which will create the slowest speed of sound?
High density, low stiffness
Damping material produces all of the follwinf except..
Increased SPL
As imaging depth increases, pulse repetition period:
Increases
What is essentially equal to the power of a wave divided by the area over which the power is distributed?
Intensity
What is the change in intensity if the Power decreases by half?
Intensity is halved
What is the change in power if the amplitude triples?
It increases nine times
All of the following are true of wavelength except:
It is equal to the period divided by the frequency
What does heat sterilization do to an ultrasound transducer?
Kills pathogens and destroys transducer
Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of:
Lead zirconate titanate
Imaging transducers have:
Low quality factors, wide bandwidths
Sound is technically a:
Mechanical and longitudinal wave
Micro denotes
Millionth
Spatial pulse length can be calculated by
Multiplying the number of cycles times the wavelength
An angle of 123 degrees is
Obtuse
The attenuation coefficient in soft tissue is equal to:
One half of the operating frequency
Which of the following is defined as the number of ultrasound pulses emitted in l second?
PRF
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?
PRP
Place the following in order of highest to lowest impedance.
PZT, matching layer, gel, skin
Pressure is typically expressed in:
Pascals
Which of the following best describes the line identified by the letter D?
Period
All of the following relate to the strength of the sound wave except:
Pressure
Which statement is true considering the propagation speed of sound through air?
Propagation speed in air is slower than in soft tissue
If only the density of a medium is increased, then the:
Propagation speed will decrease
Which of the following is defined as only the "on" time?
Pulse duration
The _______ of the transducer is the ratio of the operating frequency to the bandwidth
Q factor
The portion of the sound beam where the molecules are pulled apart describes an area of:
Rarefaction
Damping of the sound beam:
Reduces 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:
Refraction
If both propagation speed and frequency double, the wavelength will
Remain the same
Which best describes sound waves?
Series of compressions and rarefactions
Which of the following describes the amount of refraction that occurs at an interface?
Snell's law
The term bulk modulus is related to which quality?
Stiffness
Which of the following is described as the ability of an object to resist compression and relates to the hardness of a medium?
Stiffness
All of the following are true of stiffness except
Stiffness and propagation speed are indirectly associated
Which statement is correct regarding sound travel through a medium?
The molecules oscillate (vibrate) back and forth to create and transmit the sound wave
Which of the following describes the result of destructive interference?
The resulting wave is smaller than the original wave
A very LOW "Q" factor transducer is more common than high "Q" factor for diagnostic imaging.
True
To produce a transducer with a higher frequency one should:
Use a thinner piezoelectric element
Intensity is typically measured in:
Watts per centimeter squared
Which of the following is described as the distance over which one cycle occurs?
Wavelength
Which of the following is determined by the sound source and medium?
Wavelength
A decibel is
a relationship between two levels
The propagation speed in soft tissue is
an average of the speed in several types of tissue
The piezoelectric effect is best described as
deformation from voltage sent to the crystals
If intensity remains the same while the power is doubled, what happens to beam area?
doubled
If beam area is reduced by half and the power stays the same, the intensity
doubles
Which of the following would cause the PZT properties to be eliminated?
high temperatures
The prefix "centi" denotes:
hundredths
Which of the following is NOT a result of the damping layer?
increase sensitivity
In soft tissue, the attenuation is
increased with tissue thickness
Which is not an acoustic variable?
intensity
Density and propagation speed are:
inversely related
The fundamental or operating frequency
is affected by the thickness of the PZT element
If the angle of incidence is 40o, 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?
it is greater than 40 degrees
Which of the following is an appropriate unit of measurement for propagation speed?
millimeters Per microsecond (mm/µs)
What is pressure measured in?
pascals or pounds per square inch
Place the following in order of fastest to slowest propagation speed
solid, liquid, gas
All of the following are true of sound waves except:
they are transverse
Which of the following are most important in producing the frequency of the beam in soft tissue?
thickness of the PZT elements
Which of the following affect the frequency of the transmitted beam from CW ultrasound?
ultrasound system electronics
Directly related means
when one item increases or decreases, the second item responds the same direction