DMS Physics Exam 1
Which of the following is the resolution in the third dimension of the beam?
Elevational resolution
Which of he following would be considered the narrowest part of a sound beam?
Focus
The portion of the transducer that comes in contact with the patient is the:
Footprint
Which of the following is not a component of spatial resolution?
Frame resolution
Which of the following may also be referred to as the far zone?
Fraunhaufer Zone
What states that waves are the result of the interference of many wavelets produced at the face of the transducer?
Huygens Principle
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. Intensity = Power Intensity = Amplitude2 Power = Amplitude2
Density is typically measured in:
Kilograms per centimeter cubed (Kg/Cm^3)
Which of the following transducers is also referred to as a sector or vector transducer?
Linear Sequential Array
Which of the following would have the lowest propagation speed?
Lung: Remember the lungs are filled with air
Which of the following facilitates the transmission of sound from the element into the patient's skin?
Matching Layer
Spatial pulse length can be calculated by:
Multiplying the number of cycles times the wavelength
Which of the following is defined as the number of ultrasound pulses emitted in 1 second?
PRF
Pressure is typically expressed in:
Pascals
What is pressure measured in?
Pascals (Pa)
Which of the following produces a pie-shaped image?
Phased Array
Which of the following is defined as changing the timing of the shocking of the elements in order to shape and steer the beam?
Phasing
If only the density of a medium is increased, then the:
Propagation speed will decrease
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?
Pulse Repetition Period (PRP)
Which of the following is defined as only the active time?
Pulse duration
Damping of the sound beam:
Reduces the spatial pulse length
Which of the following describes the amount of refraction that occurs at an interface?
Snell's Law
All of the following are true of stiffness except:
Stiffness and propagation speed are indirectly associated
Which of the following is represented as time, or the ability to display structures in real time?
Temporal Resolution
Which type of resolution is an accurate representation of moving structures?
Temporal Resolution
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 13 20 m/s and medium 2 has a propagation speed of 1700 m/s?
The angle of transmission is greater than >40 deg If the propagation speed of medium 2 is less than the propagation speed of medium 1, then the angle of transmission will be less than the angle of incidence.
Which of the following is not true of the linear sequenced array transducer?
The elements are arranged in a ring
Which of the following is true concerning the frequency and the near zone length?
The higher the frequency, the longer the near zone length
Along with image depth, which of the following also determines the frame rate?
The number of lines per frame
Which of the following describes the result of destructive interference?
The resulting wave is smaller than the original wave
Which of the following is not a true statement about a mechanical transducer?
There are no moving parts
What is the total amount of attenuation that occurs if a 6.0-MHz sound beam travels through 4 cm of soft tissue?
Total attenuation = atten. coefficient x distance. Atten. Coefficient = frequency/2 So, 3dB/cm x 4cm = 12
To produce a transducer with a higher frequency on should:
Use a thinner PZT element
Which of the following is determined by the sound source and medium?
Wavelength
All of the following relate to the strength of the sound wave except:
Wavelength Think: Sound parameters are API: amplitude, power, intensity
Which of the following is not a true statement?
a larger aperture results in a shorter near zone length
The major component of attenuation is:
absorption
An increase in pulse repetition frequency would lead to:
an increase in duty factor
Which of the following is not a synonym for axial resolution?
angular
Which of the following is the type of transducer that utilizes elements arranged in a concentric pattern?
annular array
Which type of transducers are no longer used?
annular array transducer
Which of the following is not a characteristic of an unfocued single-element transducer?
at the face of the transducer, the beam is twice the size of the element
As a sound wave travels through the human body, the intensity of the sound wave decreases as a result of:
attenuation, absorption, and scattering (all of the above)
Which resolution is best in clinical imaging?
axial
What is defined as the ability of the ultrasound system to image structures that are positioned parallel to the sound beam as separate structures?
axial resolution
In clinical imaging, the wavelength measures between:
between 0.1 and 0.8 mm
Which of the following would have the highest propagation speed?
bone
Which type of interference results in a larger sound wave?
constructive interference
Which of the following transducers is not used for imaging?
continuous wave
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
Which of the following would cause an increase in frame rate?
decreased imaging depth
As imaging depth increases, the pulse repetition frequency must:
decreases As you increase depth, you have to send the signal deeper, therefore less US pulses are emitted because it must wait for the echoes to get back to the transducer.
The inertia of the medium describes its:
density
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
Along with crystal diameter, the divergence in the far field is also determined by which of the following?
frequency
Which of the following is determined by the sound source only?
frequency
The attenuation coefficient in soft tissue is equal to:
frequency/2
The prefix "centi" denotes:
hundredths
Which of the following would cause a decrease in temporal resolution?
increased line density
As imaging depth increases, pulse repetition period:
increases
What is the change in power if the amplitude triples?
increases by 9 times power = amplitude^2
If pulse repetition frequency increases, then the duty factor:
increases. Since duty factor is the fraction of time that the system transmits sound/"on time", Increasing the PRF will cause the Duty Factor to be on longer/increase
Density and propagation speed are:
inversely related
Which of the following is true of the diameter of the sound beam in the Fresnel zone?
it decreases
Which of the following will decrease beam divergence in the far field?
large crystal diameter, high frequency
Which of the following will increase the near zone length?
large crystal diameter, high frequency
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
Which of the following transducers uses a motor for steering the beam?
mechanical
Micro denotes:
millionth
Which of the following is an appropriate unit of measurement for propagation speed?
mm/Us (microseconds)
Which of the following is defined as the minimum distance two reflectors can be, parallel to the beam, and still appear on the screen as two dots?
range resolution
The portion of the sound beam where the molecules are pulled apart describes an area of:
rarefaction
The change in the directions 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
Which of the following is described as the ability of an object to resist compression and related to the hardness of a medium?
stiffness
All of the following are true of wavelength except:
the formula for Wavelength is NOT period/frequency
Which of the following best describes the frame rate?
the frame rate is equal to the PRF divided by the lines per frame.
Which of the following is described as the distance over which one cycle occurs?
wavelength
Which of the following would be considered an advantage of a curved linear array over a phased array transducer?
wider near field
Which of the following would be considered ultrasound?
1 MHz
The typical range of frequency for diagnostic ultrasound imaging is:
1-20 MHz
In an unfocused, single-element transducer, the focal point of the sound beam measures how much of the total beam width?
1/2
The duty factor for continuous wave ultrasound is:
100%
Which of the following is considered the speed of sound in soft tissue?
1540 m/s
Sound is technically a:
A mechanical longitudinal wave
The maximum value or minimum value of an acoustic variable minus the equilibrium value of that variable describes the:
Amplitude
Which of the following would be best utilized for imaging of deep structures in the abdomen?
Annulary Array Transducer
All of the following are true of power except:
As amplitude increases, power remains the same power and amplitude are directly related
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 is the range of frequencies present within the beam?
Bandwidth
How are ultrasound transducers typically sterilized?
Chemical Sterilization
Areas of high pressure and density are referred to as:
Compressions
Which of the following electrical patterns produces electronic fousing of the ultrasound beam?
Curve
Damping material produces all of the following except:
Decreased sensitivity
What does heat sterilization do to an ultrasound transducer?
Depolarizes