SPI PENNY
in clinical imaging, the wavelength typically measures between:
.15 and .8 mm
the DF for CW ultrasound is:`
100%, always transmitting
which of the following is considered the speed of sound in soft tissue?
1540 m/s
the typical range of frequency for diagnostic ultrasound imaging is:
2 to 15 MHz
Sound is technically a
A mechanical longitudinal wave
which of the following may also be referred to as the far zone
Fraunhofer
what states that waves are the result of the interface of many wavelets produced at the face of the transducer?
Huygen's principle states that waves are the result of the interference of many wavelets produced at the face of the transducer
density and propagation speed are ________ related
Inversely D & S are DIFFERENT!
density is typically measured in
Kilograms per centimeter cubed
which of the following is defined as the number of ultrasound pulses emitted in 1 second?
PRF
what time 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 is the time from the start of one pulse to the start of the next pulse, and therefore, it includes the on and off time
pressure is typically expressed in:
Pascals
what does not affect temporal resolution?
SPL has no effect on temporal resolution
which of the following describes the amount of refraction that occurs at an interface?
Snell's Law
which of the following is not a true statement?
a larger aperture results in a longer near zone length. not a shorter near zone length
the major component of attenuation is:
absorption, the creation of heat in the tissue as sound travels
the maximum value or minimum value of an acoustic variable minus the equilibrium value of that variable describes the:
amplitude
all of the following relate to the strength of the sound wave except:
amplitude, intensity, and power represent the strength of the beam
what would cause a decrease in temporal resolution?
an increase in line density
which of the following is not a synonym for axial resolution?
angular resolution is a synonym for lateral resolution, not axial resolution
as a sound wave travels through the human body. the intensity of the sound wave decreases as a result of:
attenuation (absorption, reflection, scattering)
which of the following describes a range of frequencies present within a beam?
bandwidth, all PW transducers are considered broadband
which of the following would have the highest propagation speed?
bone (4080 m/s)
areas of high pressure and density are referred to as:
compressions
which type of interference results in a higher amplitude sound wave?
constructive interference occurs when in phase waves meet and amplitudes of the two waves are added in to form one large wave
which of the following electrical patterns produces electronic focusing of the ultrasound beam>
curved firing pattern indicates focusing of the beam
which of the following is not true of damping?
damping improves axial resolution by shortening the pulse length. It decreases the number of cycles in a pulse
damping material produces all of the flowing except
damping material decreases the spatial pulse length by decreasing the number of cycles in a pulse
as imaging depth increases, the PRF
decreases (inverse relationship)
Damping the sound beam: a. reduces the spatial pulse length b. increase the spatial pulse length c. Increases the pulse duration d. has no impact on spatial pulse length
decreases the spatial pulse length by decreasing the number of cycles in a pulse
what woul/d cause an increase in frame rate
decreasing the imaging depth, which is the same as increasing the PRF, would increase the frame rate
the inertia of a medium describes its:
density
which of the following is the resolution in the third dimension of the beam?
elevational resolution (slice thickness) refers to the resolution in the third dimension
which of the following is determined by the sound source only?
frequency is determined by the sound source only. specifically, it is the thickness of the element and the propagation speed of the element that determines the frequency
along with crystal diameter, the divergence in the far field is also determined by which of the following?
frequency, along with crystal diameter determines the divergence in the far field
the prefix "centi" denotes:
hundredths
what is the change in power if the amplitude triples?
if amplitude triples, power increases by 9
adding damping to the transducer improves which type of resolution?
improves axial resolution, which occurs when damping is used in a PW transducer
which of the following is true concerning the frequency and the near zone length, assuming a single element
in a single element unfocused transducer, the higher the frequency, the longer the near zone length
an increase in PRF would lead to a _______ in DF:
increase (direct relationship)
as imaging depth increases, PRP:
increases, directly related
what is the change in intensity if the power decreases by half?
intensity and power are directly related, so it also decreases by half
what term is defined as "the power of a wave divided by the area over which the power is distributed?"
intensteiy
what would most likely increase the near zone length?
large crystal diameter and high frequency
Transducers have material within them that, when electronically stimulated, produces ultrasound waves. This is most likely some form of:
lead zirconate titanite
which of the following is not true of a linear sequenced array transducer>
linear sequenced array does not have elements arranged in a ring
imaging transducers typically have
low quality factors and wide bandwidths. low Q factor and wider bandwidths are owing to damping, which is used to shorten the SPL
which of the following would have the lowest propagation speed?
lung tissue (660 m/s)
what is not a true statement about a mechanical transducer?
mechanical transducer does have moving parts because the piezoelectric element is mounted to a motor. these obsolete transducers had fixed focus and frequency
micro denotes:
millionth
which of the following is an appropriate unit of measurement for propagation speed?
mm/usec
SPL can be calculated by:
number of cycles in the pulse multiplied by the wavelength
In an unfocused, single element transducer, the focal point of the sound beam measures how much of the total beam width?
one half of the beam width at the face of the transducer
the attenuation coefficient in soft tissue is equal to:
one half of the frequency
what are the units of DF?
percentage, DF has no units
all of the following are true of power except:
power is proportional to amplitude squared and is directly related
what are the units for pressure?
pressure is measured in pascals or pounds/sq in
if only the density of a medium is increased, then the propagation speed will:
propagation speed will decrease, they are inversely related
which of the following is defined as only the active time?
pulse duration is the time it takes for a pulse to occur, but only includes the on time
the portion of the sound beam where the molecules are farther apart describes an area of:
rarefaction is an area in the sound beam where the molecules are spread wider apart
the change in direction of the original sound wave that occurs when sound interacts with two different types that have different propagation speed is referred to as:
refraction is the change in direction of the transmitted sound beam that occurs with oblique incidence and dissimilar propagation speeds
which of the following requires an oblique interface and a propagation speed mismatch?
refraction occurs when there is an oblique angle of incidence and a propagation speed mismatch
which of the following transducers can be described as having the scan lines originate from a common point of origin/
sector array comes to a point at the top because all the scan lines come from a common point of origin
which of the following is described as the ability of an object to resist compression and relates to the hardness of a medium?
stiffness stiffness is the ability of an object to resist compression and relates to the hardness of a medium
which type of resolution is an accurate representation of moving structures?
temporal resolution is the ability to display moving structures in real time
which of the following is the part of the transducer that stops the ringing of the element?
the damping material, same as the backing material, is the part of the transducer assembly that reduces the number of cycles produced in a pulse
which of the following is true of diameter of the sound beam in the Fresnel zone?
the diameter of the beam in the near zone decreases from the face of the transducer to the focal zone
the percentage of time that the ultrasound system is producing pulses of ultrasound describes the:
the duty factor is the time that the ultrasound system is producing sound
what is considered the narrowest part of the sound beam?
the focus is the narrowest part of the ultrasound beam. the beam narrows in the near zone and diverges in the far zone
along with imaging depth, which of the following also determines frame rate
the frame rate is determined by the number of lines per frame /line density
which of the following best describes the components of the damping material?
the matching layer is composed of epoxy resin loaded with tungsten
which of the following facilitates the transmission of sound from the element into the patients skin?
the matching layer is the component of the transducer that is used to minimize the impedance mismatch between that of the element and that of the patients skin
if the depth is increased and the frame rate remains unchanged, what else must have to decrease?
the number of lines per frame
which of the following would be considered ultrasonic?
ultrasonic is considered above 20,000 Hz
which of the following is describes as the distance over which one cycle occurs?
wavelength
which of the following is determined by the sound source and the medium?
wavelength is determined by the sound source and the medium
what is not true about wavelength?
wavelength is inversely related to frequency (important concept)
