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Logarithms and Decibels, Wavelength, Morgan's set

Terms in this set (265)

The logarithm of a numeral is defined as how many times _____ must be multiplied together to get that numeral.
10.
What is a decibel?
C. a relationship between two numbers
Decibel notation is _______ between two numbers.
D. Ratio
Which of the following reports the relative strength of an ultrasound wave?
A. decibels
The scale associated with decibel notation is _______.
C. logarithm
What is the decibel representation when an acoustic signal is amplified?
A. positive
What is the decibel notation for an acoustic signal that is attenuated?
B. negative
The intensity of a signal declines from 1.5 mW/cm^2 to 0.75 mW/cm^2. How many decibels is this change in intensity?
D. - 3 dB.
The power in a wave is increased to then times its original value. How many decibels describe this change?
C. 10.
How many decibels represent a 100-fold increase in the intensity of an acoustic pulse?
B. 20.
The intensity of an ultrasound wave is changes by -6 dB. This means that the current intensity is ________ as much as its original level.
C. one-fourth.
What units are used to describe attenuation?
D. Decibels.
What does a 3 dB change in value intensity mean?
A. the value has doubled.
The wavelength of a cycle in ultrasound wave can be reported with which units?
units of distance (feet, meter, ect)
The wavelength of an ultrasonic wave is determined by:
the sounds source
the medium through which the wave travels
What is the wavelength of 2MHz sound in soft tissue?
A. 0.77 mm.
Which of the following terms best describes the relationship between frequency and wavelength for sound traveling in soft tissue?
D. inverse
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which sound wave has a longer period?
2 MHz pulse
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which pulse has the longer wavelength?
the 2 MHz pulse
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which pulse has a lower propagation?
neither pulse
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which pulse has the lowest power?
cannot be determined
Two sound pulses travel through the same medium. One waves frequency is 2 MHz and the other is 10 MHz. Which pulse has the longer spatial pause?
cannot be determined
Lower frequency sound creates higher quality images with greater detail? T/F
False
What is the wavelength of 10 MHz sound in soft tissue?
0.15 mm
Two waves, a 5 MHz ultrasonic wave and a 5 kHz audible wave, travel through soft tissue.

True or False? Both the 5 MHz and the 5 kHz waves travel at similar speeds through the medium.
True
Two waves, a 5 MHz ultrasonic wave and a 5 kHz audible wave, travel through soft tissue.

True/False? The period pf the 5 MHz wave is less than the period of audible wave.
True
Two waves, a 5 MHz ultrasonic wave and a 5 kHz audible wave, travel through soft tissue.

True/False? The wavelength of the 5 MHz wave is greater than the wave of the 5 kHz wave.
False
Two waves, a 5 MHz ultrasonic wave and a 5 kHz audible wave, travel through soft tissue.

True/False? The ultrasound wave travels much faster than the audible wave.
False
which of the following flow patterns is associated with cardiac contraction?
pulsatile flow pattern
which of the following terms does not belong with the others?
A. phasic
B. spontaneous
C. pulsatile
D. venous
C
Which of the following is not associated with laminar flow?
A. layered
B. normal
C. aligned
D. smooth
E. chaotic
E
Which of the following is not associated with turbulent flow?
A. parabolic
B. eddy
C. vortex
D. swirling
E. spectral broadening
A
What is the primary reason blood moves from one location to another?
energy gradient
All of the following decrease the flow of energy of a fluid except:
A. frictional loss
B. viscous loss
C. inertial loss
D. velocity loss
D
Which of the following causes the greatest amount of inertial energy loss?
A. pulsatile flow
B. flow through a stenosis
C. phasic flow
D. steady flow
E. parabolic flow
B
The arterial blood pressure of a supine individual is 120 mmHg. What is the hydrostatic pressure at the subjects ankle? hips?
0 mmHg. in a supine patient, hydrostatic pressure is zero
The arterial blood pressure of a standing individual is 120 mmHg. What is the hydrostatic pressure at the subjects ankle?
100 mmHg. Hydrostatic pressure is related to the difference between heart level and the site of measurement. Since the ankle is substantially lower than heart level, the hydrostatic pressure is 100mmHg
The arterial blood pressure of a standing individual is 120 mmHg at the level of the heart. What is the measured blood pressure at the subject's ankle?
Measured blood pressure is equal to the sum of actual blood pressure at heart level and hydrostatic pressure: 120+100=220 mmHg
What happens to the diaphragm during inspiration?
it moves downward into the abdomen
what happens to venous return to the heart when an individual inhales
it increases
what happens to venous flow in the legs when an individual inhales
it decreases
what happens to the diaphragm during exhalation
the diaphragm moves upward into the chest cavity
What happens to venous return to the heart when an individual exhales
it decreases
What happens to venous flow in the legs when an individual exhales
it increases
A video display that is limited to black and white only, with no shades of gray, is called _____.
bistable
what is the approximate number of frames that must be presented each second for the human eye to perceive the display without flickering?
30
What was the original purpose for the ultrasound system's analog scan converter?
to allow for gray scale imaging
which of the following is best described as an analog number?
A. the weight of a person
B. the number of people in a room
C. the number of starts in the sky
D. the n umber of tires on a car
A. because the weight of a person is continuous and can achieve unlimited number of values. can be non-whole numbers
True or false: A digital representation of a number can achieve only specific fixed values?
true
True or false: digital scan converters do not use computer technology to process electronic data into images?
false
Two digital scan converters are undergoing evaluation. Both produce images of the same size. System A has 1,000,000 pixels, with 10 bits assigned to each. System B has 250,000 pixels, with 12 bits assigned to each. Which system is more likely to have the capability to display very small details in an image?
A. System A
B System B
C. both are the same
D. cannot be determined
A. the scan converter with the greatest number of pixels assigned to an image of fixed size will provide the viewer with the greatest spatial detail. In this case, system A has a higher pixel density, and therefore has the ability to display greater detail.
What happens to a digital image when the pixel density increases?
spatial detail improves. pixel density, the number of pixels per inch, determines the detail that a digital picture can illustrate. With greater pixel density, spatial detail improves.
Two digital scan converters are undergoing evaluation. System A has 1,000,000 pixels and the picture size is 100 square inches. System B has an image size of 10 square inches composed of 250,000 pixels. Which image is more likely to display very small details?
A. System A
B System B
C. both are the same
D. cannot be determined
B.
What is the smallest part of a digital picture called?
pixel
True or false: the greater the number of bits assigned to each pixel of a digital image, the greater the number of shades of gray the image has?
True. the number of gray shades in an image increases when the number of bits assigned to each pixel increases
What is the smallest amount of digital storage called?
A bit
Which of these is a binary number?
A. 12211221
B. 1000000
C. 98765432
D. 01010102
B. A binary number is a string of zeroes and ones only.
Two digital scan converters are undergoing evaluation. System A has 1,000,000 pixels, with 4 bits assigned to each. System B has 250,000 pixels, with 12 bits assigned to each. Which image is more likely to display images with very subtle differences in grayscale.
A. System A
B System B
C. both are the same
D. cannot be determined
B. gray scale levels are determined by the number of bits assigned to each pixel in an image.
A byte is composed of _____ bits. A word is composed of _____ bytes.
A. 2, 2
B. 8, 2
C. 16, 16
D. 8, 16
B.
True or false: the greater the number of bits assigned to each pixel of a digital image, the greater the spatial resolution of the image is
False
What happens to an image when the number of bits allocated to each pixel increases?
more shades of gray
What is the maximum number of shades of gray that are represented by 4 bits
16. to calculate this multiply 2 by itself the same number of times that there are bits.
With 6 bits, what is the largest number of different gray shades that can be stored?
64. to calculate this we multiply 2 by itself 6 times
How many bits are required to display 10 different shades of gray? 14 shades? 15 shades?
four bits
What is the number of binary digits required to store 29 levels of gray
5.
True or false: for digital image information to be displayed on a conventional television screen, the data must be processed by a digitial-to-analog converter?
True
True or false: preprocessing of image data occurs after the data has been stored in the scan converter?
False
True or false: postprocessing of image data occurs after the data has been stored in the scan converter?
True
All of the following are true of read zoom except:
A. preprocessing function of receiver
B. same number of pixels are in the original ROI and the zoomed image
C. on the screen, the pixels in the zoom image are larger than those in the ROI
D. the same number of ultrasound pulses are used to create the original ROI and the zoomed image.
A
All of the following are true of write zoom except:
A. preprocessing function of the receiver
B. the same number of pixels are in the original ROI and the zoomed image
C. the pixel size in the zoomed image and the ROI are the same
D. in comparison to the zoomed image, fewer ultrasound pulses are used to create the original ROI
B
True or false: the assignment of different shades of gray to the digital numbers stored in the scan converter acts to improve diagnostic value of an ultrasound exam?
True
The relationship between the largest and the smallest signal amplitudes processed by a component of an ultrasound system is called the ... and has units of...
dynamic range, dB
Which of these components typically has the greatest dynamic range?
A. display
B. pulser
C. amplifier
D. demodulator
C
Which of the following components typically has the lowest dynamic range?
A. display
B. pulser
C. amplifier
D. demodulator
A
Why is it necessary for the receiver to perform compression on the electrical signals that it processes?
the dynamic range of the system's electronics is less than the dynamic range of the received sound reflection
A signal with a 120 dB dynamic range is compressed by 40 dB. What is the dynamic range of the compressed signal?
A. 40 dB
B. 120 dB
C. 3 dB
D. 80 dB
D
A signal with a 120 dB dynamic range was previously compressed by 40 dB. What is the dynamic range of the original uncompressed signal?
160 dB
Which display is limited to a single pair of brightness or display levels?
A. CRT
B. binary
C. bistable
D. grayscale
bistable
All of the following are consistent with an image containing black and white only with no shades of gray except:
A. bistable
B. high contrast
C. wide dynamic range.
C
Which of the following terms is not associated with a wide dynamic range image?
A. low contrast
B. many shades of gray
C. bistable
C.
With these transducers, the ultrasound beam is steered by a motor, a rotating reflecting mirror, or a similar device.
mechanical and annular phased array transducers
These transducers focus the ultrasound beam electronically
linear switched array, linear phased array, annular phased array, convex/curvilinear
with these transducers the ultrasound beam is focused with an acoustic lens, a mirror, or by milling the piezoelectric crystal in a curved shape.
linear switched array transducers, mechanical, convex/curvilinear
With regard to mechanical transducers, TRUE OR FALSE.

*The ultrasound beam is not focused electronically
true
with regard to mechanical transducers, TRUE or FALSE
the ultrasound beam is directed in many different directions to create an imaging plane
True
With regard to mechanical transducers, TRUE OR FALSE.

*There is communication between the pulser of the ultrasound system and the PZT crystal of the transducer
true
With regard to mechanical transducers, TRUE OR FALSE.

*Foci exist at multiple depths as an ultrasound beam propagates through the body
false
which two of the following terms are associated with phased array transducers?
A. lens
B. multi-focus
C. mirror
D. adjustable
E. external
B. D.
the minimum number of active elements in a mechanical transducer is
1
Which best describes the elements in a linear phased array transducer?
rectangular, 1/2 to 1.4 wavelength wide.
True or false: all phased array transducer systems direct ultrasound pulses in many directions to create a 2-D image
True
How are the piezoelectric crystals of a linear phased array transducer fired?
A. in a single specific pattern
B. in order, from top to bottom
C. at exactly the same time
D. at almost exactly the same time
D.
The pattern of electrical signals exciting the piezoelectric crystals of a linear phased array transducer _______.
A. typically changes from one acoustic pulse to the next
B. changes every fourth or fifth acoustic pulse
C. changes only when the maximum imaging depth changes
D. none of the above
A.
True or False: the curved pattern of delays in the electrical spikes used in a linear phase array transducer focuses the beam during transmission
True
True or False: the curved pattern of delays in the electrical spikes used in a linear phase array transducer focuses the beam during reception
False.
True or False: both linear and phased array technologies have the ability to variably focus an ultrasound beam to different depths.
True
Which of the following forms of focusing is different from the others?
A. lens
B. mirror
C. phased
D. dynamic receive
D
all of the following describe dynamic receive focusing except:
A. delay pattern changes continuously throughout reception
B. may be used by single crystal transducers
C. focusing occurs at many depths
D. automatically performed by system
B
What is the shape of the elements in an annular phased array transducer?
circles, arranged as a collection of concentric rings
True or false: annular phased array transducers focus sound beams in all planes and at all depths
True
What is true of the electrical pulses that excite the active elements of an annular phased array transducer?
they arrive at each PZT crystal at different times, microseconds apart.
How are the piezoelectric crystals excited when using an ultrasound system with a sequential linear array transducer?
A. singly and in order: the first crystal, the second crystal, etc
B. in pairs: the first 2 crystals, the 3rd and 4th, etc
C. in a specific order
D. in a random sequence
C
which best describes the elements in a linear sequential array transducer?
rectangular, 1 wavelength wide
What image is created with a two-dimensional array transducer?
A. two-dimensional static image
B. two-dimensional real-time image
C. three-dimensional real-time image
D. B-mode
C.
These transducers steer the beam with a motor and focus the beam with an acoustic lens or a curved PZT element.
mechanical transducer
These transducer systems typically produce an image that, throughout its entire depth, is approximately as wide as the ultrasound transducer itself.
linear switched/linear sequential array
ultrasound systems using these transducers do not actually steer the ultrasound beams to create 2-D image.
linear switched, convex/curvilinear array
A special sector shape is produced when this transducer is used. It looks like a wedge or a slice of pie, but it doesn't originate at a point. The sector has a blunted, curved shape at the top. The arc at the top of the image may be a few centimeters wide.
convex/curvilinear array transducer
With these transducers, a sector (wedge-shaped or "slice of pie") image is produced. At the top, the sector is very narrow and tapers to a point.
linear phased array, mechanical transducer, annular phased array
With these transducers, a trapezoidal image shape is produced. The image is flat at the top and becomes progressively wider at increasing depths.
vector array transducer
When looking at images produced by these transducer systems, which one can be distinguished from all the others?
A. linear phased array
B. linear switched array
C. annular phased array
D. mechanical transducer
linear switched array
What is the advantage of using a 1.5 dimensional array transducer?
improved elevational resolution
which transducer possesses the best slice thickness resolution?
1.5 dimensional arrays
What is the use of a greater number of channels to receive echoes from ever increasing depths called?
A. dynamic aperture
B. apodization
C. dynamic frequency tuning
D. subdicing
dynamic aperture
The excitation of array elements with dissimilar voltages is called ... and is used to...
apodization, reduce lobe artifact
The focus of an ultrasound beam is the location where the ____.
A. beam is the broadest
B. optimum transverse resolution is
C. frequency is the highest
D. finest depth resolution is obtained
B. the focus of an ultrasound beam is the location where the beam is most narrow. The narrowest portion of the beam provides the optimal transverse or lateral resolution.
Lateral resolution is determined by
Width of the sound beam (narrower beams have better resolution)
Two ultrasound systems produce acoustic pulses. One pulse is 0.4 microseconds in duration and the other is 0.2 microseconds. Which pulse will most likely provide the best lateral resolution?
A) 0.4 microsecond pulse
B) 0.2 microsecond pulse
C) they are the same
D) cannot be determined
D. the duration of a pulse is unrelated to the lateral resolution. pulse duration affects axial resolution
True or false: the pulse duration does not profoundly influence the lateral resolution.
True. Generally the primary determinant of lateral resolution is the sound beam's diameter. The pulse length, or duration, does not dramatically alter the lateral resolution
Two ultrasound systems have near zone lengths of 8 cm. At the focus, System G's lateral resolution is 3.0 mm, whereas System P's is 5.0 mm. Which system will produce higher quality pictures at their foci?
System G will produce higher quality images at that depth since it has a narrower beam than System P at the end of the near field.
True or false: when using standard ultrasonic imaging instrumentation, the lateral resolution has a higher numerical value than the axial resolution.
True. Most systems have better axial resolution than lateral resolution
Two ultrasound systems have near zone lengths of 8cm. At their foci, System Q's lateral resolution is 3.0 mm and System H's is 5.0 mm. Which system will correctly display two small structures at a depth of 8 cm? The objects are side by side and are .4 cm apart.
At a depth of 8 cm, System Q will produce a more accurate picture of two structures that are .4 cm apart. A system's lateral resolution is approximated by the beam diameter at that depth. System Q's beam diameter is 3.0 mm at its focus and will display this pair of reflectors accurately. System H's beam with a diameter of 5mm is too wide to display this pair of reflectors as distinct and separate.
The lateral resolution of an ultrasound system is 4mm. Two structures are separated by 3mm and lie side by side in relation to the sound beam's main axis. What will most likely appear on the system's display.
one echo. When two structures are closer together than the resolution of an ultrasound system, the images of the structures will blur together. Since these structures are 3mm apart and the lateral resolution is 4mm, only a single echo representing both reflectors will appear on the image.
True or false: when using an instrument typical of today's imaging devices, a higher frequency transducer is likely to mildly improve the system's lateral resolution
True
True or false: When using an instrument typical of today's diagnostic imaging devices, a higher frequency transducer is likely to improve the axial resolution.
True
What will lower the value of an ultrasound system's lateral resolution?
A. decrease the # of cycles in the pulse
B. increase the effective damping material
C. increase the PRP
D. use an acoustic lens
D.
which of the following focusing techniques is different from the others?
A. lens
B. curved crystal
C. fixed
D. phased
D
which of the following techniques is internal focusing?
A. lens
B. curved crystal
C. electronic
B
which of the following techniques is external focusing?
A. lens
B. curved crystal
C. electronic
A
which of these terms means adjustable focusing or multi-focusing?
A. dynamic aperture
B. harmonics
C. frequency agility
D. phased array
D.
Which of these techniques is consistent with variable or multi-focusing?
A. lens
B. curved crystal
C. electronic
C
All of the following occur with focusing except:
A. lower intensity at the focus
B. shorter near zone length
C. more compact focal zone
D. smaller diameter beam diameter at the end of the near zone
A.
In which region of a sound beam is focusing most effective?
the end of the near zone
True or false: in comparison to other locations along the length of an ultrasound beam, focusing is generally ineffective in the far zone
True
Two ultrasound system have near zone lengths of 8 cm. At the focus, System S's lateral resolution is 3.0 mm, whereas System C's is 5.0 mm. Which system is most likely to appropriately display two small body structures that lie, one in front of the other, at depths of 8.6 and 9.0 mm?
cannot be determined
The diameter of a disc-shaped, unfocused piezoelectric crystal is 1 cm. What is the best estimate for the minimum lateral resolution?
A. 1 mm
B. 5 mm
C. 1 cm
D. 5 cm
B
The diameter of a disc-shaped, unfocused piezoelectric crystal is 1.2 cm. The near zone length is 8 cm. What is the best estimate for the lateral resolution at a depth of 16 cm.
1.2
which component of an ultrasound system is made of lead zirconate titanate (PZT)?
transducer's active element
How thick is the active element of a 3 MHz pulsed wave transducer?
A. 1.54 mm
B. 0.51 mm
C. half of the wavelength of the sound wave in the PZT
D. one quarter the wavelength of sound in the matching layer
C.
True or false: the purpose of the backing material of an ultrasound transducer is to shorten the pulses, thereby creating images with better image quality
true
The main purposes of a transducer's case are:
A. protect the patient from shock
B. protect the patient from heat
C. protect the internal components of the transducer
D. protect the patient from radiation
A and C
Which component of an ultrasound transducer is made from a slab of epoxy embedded with tungsten particles?
the damping material aka backing material
True or false: the characteristic impedance of acoustic gel is greater than the matching layer's impedance but less than the piezoelectric element's impedance
False.
The impedance of a transducer's matching layer is 2.6 MRayls and the impedance of the piezoelectric crystal is 3.4 MRayls. If this is assumed to be a good imaging system, what is the best estimate for the impedance of the skin?
A. 1.5 MRayls
B. 3.8 MRayls
C. 3.4 MRayls
D. 2.8 MRayls
A.
True or false: the piezoelectric crystal of a transducer typically has an impedance higher than the impedance of skin
true
which of the following lists orders the impedance from highest to lowest?
PZT, matching layer, gel, skin
what is the thickness of the matching layer of a 2MHz pulsed wave transducer?
matching layer is 1/4 the wavelength of sound in the matching layer
True or false: The acoustic impedance of the skin is greater than the acoustic impedances of both the matching layer and the piezoelectric element
false
True or false: the damping material helps to decrease the PRP achieved at a given imaging depth
false
true or false: the backing material helps to decrease the duty cycle at a particular PRF
true
true or false: the pulse duration is increased as a result of the presence of backing material
false
true or false: the backing material decreases the quality factor
true
true or false: the spatial pulse length is decreased with the application of backing material
true
Assume the frequency of sound with the greatest power emitted by a transducer is 5 MHz. However, pulse contains acoustic energy with frequencies as low as 3.5 MHz and as high as 6.5 MHz. What is the bandwidth of the transducer?
A. 6.5MHz
B. 5.0MHz
C. 3.5MHz
D. 3.0 MHz
D. 3.0MHz. to calculate bandwidth subtract the lowest frequency from the highest frequency
True or false: in general, ultrasound imaging transducers have a lower quality factor and wider bandwidth than therapeutic ultrasound transducers
true
damping material is secured to the piezoelectric material during fabrication of an ultrasonic imaging transducer. Which of the following is not a consequence of this attachment
A. bandwidth increases
B. quality factor decreases
C. sensitivity increases
D. transducer case is longer
C.
which of the following actions would cause a PZT crystal to lose its special properties?
exposing it to high temperatures. It will depolarize and lose its piezoelectric properties. This temperature is the Curie point
all of the following are true about transducers except:
A. it is necessary to sterilize transducers before use
B. most transducers simply require disinfection as they no not penetrate mucous membranes
C. sterilization could depolarize PZT
D. they are unlikely to transmit infection
A.
Which properties of the piezoelectric crystal of a continuous wave transducer result in the highest emitted acoustic wave frequency?
A. thin, high propagation speed
B. thick, slow propagation speed
C. thin, slow propagation speed
D. none of the above
D. the frequency of sound emitted by a continuous wave transducer is determined only by the frequency of the electrical signal that excited the PZT crystal. The crystal's thickness and propagation speed do not affect the frequency of sound from a CW transducer
What helps to determine the frequency of the sound produced by the transducer of a continuous wave ultrasound system?
ultrasound system electronics
With pulsed wave ultrasonic imaging, what helps to establish the primary frequency of the acoustic energy discharged by the transducer?
A. piezoelectric crystal diameter
B. piezoelectric crystal thickness
C. damping material density
D. ultrasound system electronics
B.
An ultrasonic pulse is traveling in soft tissue. Which of the following is most important in the determination of the frequency of the sound?
A. The propagation speed of the ultrasound transducer's matching layer
B. the thickness of the transducer's backing material
C. the impedance of the transducer's matching layer
D. the propagation speed of the transducer's active element
D.
what is the best estimate of the propagation speed of the ferroelectric element of a transducer used in a typical diagnostic imaging laboratory?
the range is approximately 4 to 8 km/sec
which properties of the piezoelectric crystal of an imaging transducer result in the highest emitted acoustic wave frequency?
A. thin, high propagation speed
B. thick, slow propagation speed
C. thin, slow propagation speed
D. none of the above
A. thin, high propagation speed
you are asked to fabricate a pulsed ultrasound transducer with the highest possible frequency. Which piezoelectric crystal would you select?
2 mm thick, 6 cm diameter, 6.0 mm/us propagation speed
The frequency is greater when the crystal is thin and its propagation speed is high. The diameter of the active element does not affect the frequency of the pulse
you are asked to fabricate a pulsed ultrasound transducer with the lowest possible frequency. Which piezoelectric crystal would you select?
8 mm thick, 2 cm diameter, 2.0 mm/us propagation speed
The frequency is lowest when the crystal is thick and the propagation speed is low
axial resolution describes the accuracy related to visualizing two structures that are... to a sound beam's main axis
parallel
you are purchasing a diagnostic ultrasound system. System X has axial resolution of .7 mm whereas System D's is .4mm. Based on this information which system will produce the better quality picture?
System D. Higher image quality is achieved by systems with lower numerical values for resolution
the axial resolution of an imaging system is reported to be .85 mm at the beam's focus. What is the closest estimate of the system's radial resolution at a location that is 5 cm deeper than the focus?
equal to .85mm. Radial resolution is determined by the SPL or the pulse duration. These variables remain constant regardless of the depth of the pulse. The radial resolution is the same at all imaging depths.
Two systems are undergoing evaluation. System A has 1,000,000 pixels, each with 4 bits. System B has 750,000 pixels, each with 12 bits. Which system has the best longitudinal resolution?
A. system A
B. system B
C. both are the same
D. cannot be determined
cannot be determined. Since no information is provided on the length of the pulse, it is impossible to determine which of the systems will have superior longitudinal resolution
True or false: the lower the numerical value of the longitudinal resolution, the worse the picture
False
True or false: one way that a sonographer can alter the axial resolution achieved during an exam is to adjust the maximum imaging depth.
false. depth of view and axial resolution are unrelated
True or false: with a specific ultrasound system and transducer, the system's axial resolution is invariant, and the sonographer can do nothing to improve it
true.
true or false: the shorter the pulse duration, the better the picture
true
An ultrasonic pulse has a PRP of 1.2 msec, a SPL of 2.0 mm, and a wavelength of 0.4 mm. What is the axial resolution of the system?
1.0. axial resolution equals 1/2 SPL
True or false: the more cycles there are in a pulse, the greater the detail that will be visualized in the ultrasound scan.
false. a pulse with many cycles is long. Systems with long pulses cannot produce images with final detail. When many cycles are in a pulse, less detail is presented on the scans. Transducers with pulses composed of more cycles can be described as "more ringing"
Two ultrasound systems produce acoustic pulses. A pulse from System 1 has a wavelength of .5mm, 4 cycles per pulse and a pulse repetition period of 1.2 msec. The pulses from system 2 have a wavelength of 1.0 mm, 2 cycles per pulse, and a pulse repetition period of 1.8 msec. Which ultrasound system will have a lower numerical value of axial resolution?
both are the same. range resolution is equal to 1/2 SPL. SPL equals the number of cycles in the pulse multiplied by the wavelength.
Which transducer has the best axial resolution?
A) 2 cycles/pulse, 4 MHz
B) 4 cycles/pulse, 4 MHz
C) 4 cycles/pulse, 2 MHz
D) 2 cycles/pulse, 2 MHz
A. pulses with the fewest cycles and the highest frequency have the best axial resolution
Which transducer has the worst axial resolution?
A) 2 cycles/pulse, 4 MHz
B) 4 cycles/pulse, 4 MHz
C) 4 cycles/pulse, 2 MHz
D) 2 cycles/pulse, 2 MHz
C. pulses with the most cycles and the lowest frequency have the worst axial resolution
Two ultrasound systems produce acoustic pulses. One pulse is 0.4 microseconds in duration and the other is 0.2 microseconds. Which pulse is most likely to provide the best radial resolution?
A) 0.4 microsecond pulse
B) 0.2 microsecond pulse
C) they are the same
D) cannot be determined
B. radial resolution is determined by the pulse duration or the SPL. The shorter the time span that a pulse exists the better the radial resolution. The device producing the shorter pulse, .2 microseconds has the best radial resolution
A sonographer is performing a study on a patient and desires superior depth resolution Which of the following changes would create such a system?
A. higher frequency
B. shorter wavelength
C. fewer cycles per pulse
D. less ringing
E. all of the above
E.
True or false: the higher the frequency of the cycles within a pulse, the lower the numerical value of the axial resolution
true
True or false: the shorter the pulse length, the better the picture
true
if the... of two media are different and sound strikes a border between the media at 90 degrees incidence, then reflection will occur.
a. conductances
b. densities
c. impedances
d. propagation speeds
C. impedances. under conditions of normal incidence, reflection depends on differences in acoustic impedances of the media on either side of the boundary. With normal incidence, as long as the impedances are dissimilar, reflection always occurs
True or false: the proportion of the incident intensity that is reflected at a border between two media will increase as the impedances of the media become increasingly dissimilar?
true. as sound waves strike the border between two media, reflection occurs if their impedances are different. Greater differences between the two impedances create stronger reflections. If the impedances are only slightly different than a weak reflection will be produced
A sound pulse strikes a boundary between two media with normal incidence. The speed of sound in the two media are very different; however, the impedances of the media are identical. What will happen?
there will be no echo at all. When a sound wave is normally incident at a boundary, reflection will occur only when the media have dissimilar impedances. 100% of the sound will be transmitted
Two acoustic waves strike a boundary between two media. The waves are traveling in a direction 90 degrees to the boundary. Reflection of these waves depends on differences in the ___.
impedances of the two media
An ultrasound wave approaches an interface between two media at a 90 degree angle. The propagation speeds and the densities of the two media are different. Which is correct?
a. reflection will definitely occur
b. reflection will definitely not occur
c. refraction may occur
d. none of the above
D. The information provided is insufficient to determine whether reflection will take place.
An ultrasound wave strikes an interface between two media at a 90 degree angle. the propagation speeds of the media are different. However the densities of the media are different. Which is true?
a. reflection will definitely occur
b. reflection will definitely not occur
c. refraction may occur
d. none of the above
A. reflection will definitely occur.
An acoustic wave is traveling from medium X to medium Z. Medium X has a propagation speed of 1,457 m/sec and an impedance of 1.44 MRayls. Medium Z's propagation speed is 1,644 m/s and its impedance is 1.26 MRayls. The angle of incidence is 32 degrees. What is true of the angle of reflection?
A. it is greater than 32 degrees
B. it is equal to 32 degrees
C. it is less than 32 degrees
D. cannot be determined
B. in cases of oblique incidence the angle of reflection is always equal to the angle of incidence
True or false: when reflection occurs with oblique incidence, the angle of reflection equals the angle of incidence. This is known as Snell's law
False. This is not known as Snell's law.
What event does Snell's law govern
refraction
which of the following best describes the process described by Snell's Law?
a. reflection with normal incidence
b. reflection with oblique incidence
c. transmission with normal incidence
d. transmission with oblique incidence
D. Snell's law defines the physics of refraction. Refraction describes the behavior of sound beams that transmit after striking a boundary obliquely. Refraction is transmission with a bend
True or false: refraction occurs at the border between two media if and only if there is oblique incidence of the wave at the boundary
true. refraction cannot occur if a wave is normally incident to the boundary between two media. it can occur only if the incident wave is oblique to the boundary
What conditions are necessary for refraction to occur at a boundary between two media?
dissimilar propagation speeds and oblique incidence at the boundary
True or false: refraction always occurs at the interface between two media when the propagation speeds of the media are unequal
false
An acoustic wave is traveling from medium X to medium Z. Medium X has a propagation speed of 1,457 m/sec and an impedance of 1.44 MRayls. Medium Z's propagation speed is 1,644 m/s and its impedance is 1.26 MRayls. The angle of incidence is 32 degrees. What is true of the angle of the transmitted wave
A. it is greater than 32 degrees
B. it is equal to 32 degrees
C. it is less than 32 degrees
D. cannot be determined
A. it is greater than 32 degrees
An acoustic wave in medium B is traveling toward medium A. The sound beam strikes the boundary at a 45 degree angle. The propagation speed is 1547 m/s for medium A and 1745 m/s for medium B. What is true of the angle of transmission?
it is less than 45 degrees. With refraction, when the medium that the sound is in has greater propagation speed than the propagation speed of the medium that the wave is entering, the angle of transmission is less than the angle of incidence
True or false: the period of a sound wave determines whether refraction will occur
false. refraction does not depend upon the characteristics of wave. refraction only depends upon the incidence of the sound beam and the speeds of the media
A wave of acoustic energy is leaving soft tissue and transmitting into fat with an 86 degree incident angle. what is true of the angle of transmission?
it is less than 86 degrees. Fat's propagation speed is less than that of soft tissue. The angle of transmission is less than the angle of incidence when a wave travels into a second medium that reduces the wave's propagation speed
An acoustic wave is in medium A and traveling toward medium B. The sound beam's angle of transmission into medium B with relation to the boundary is 79 degrees. Sound's propagation speed is 1547 m/s in medium A and 1745 m/s in medium B. If reflection and transmission both occur at the boundary, what can be said of the reflection angle?
it is less than 79 degrees
Sound propagates from one medium with a density of 1.16 kg/m3 to a second medium with a density of 1.02 kg/m3. If the angle of transmission is 49 degrees, what can be correctly stated about the angle of incidence?
it cannot be determined. Since the propagation speeds of the media are unknown, we cannot make any conclusions about incident angle
A sonographer is using a 3 MHz transducer & increases the output power in order to visualize structures that are positioned deeper in the patient. No other controls are adjusted. What will happen to each of the following parameters? (Increase, decrease, unchanged)
period
Frequency
wavelength
speed
Power
Intensity
Pulse duration
PRF
duty factor
SPL
PRP
a. remains the same
b. remains the same
c. remains the same
d. remains the same
e. increases
f. increases
g. remains the same
h. remains the same
i. remains the same
j. remains the same
k. remains the same
What are the units of pulse duration?
Units of time. Pulse duration is the actual time that a transducer is creating a pulse. The typical range in diagnostic imaging equiment is 0.3 to 2 usec. But it is valid to report pulse duration in any unit of time
What determines pulse duration?
The pulse duration is the actual time that a transducer is creating one sound pulse and is determined by the ultrasound system. Pulse duration does not include listening time.
True or False: The pulse duration of an ultrasound and transducer system does not change significantly as long as the system components remain unchanged?
True. The pulse duration is the timespan that a pulse exists. It is determined by the ultrasound system and the transducer. Generally, it remains constant for a particular transducer.
The pulse duration is expressed in the same units as the
the pulse duration and the period are measured in units of time, such as seconds, minutes, or hours. PRF has units of Hertz. Wavelength has units of distance. Density has units of mass per volume.
True or false: a sonographer can adjust the duration of an acoustic pulse since it depends upon the pulse's propagation speed
False. a sonographer cannot change the pulse duration. It is a fixed feature of the transducer and ultrasound system. It does not depend upon propagation speed.
True or false: a sonographer can adjust the duration of an acoustic pulse since it depends upon the maximum imaging depth
False. a sonographer cannot change the pulse duration. It has a constant value and is not dependent on imaging depth
True or false: the sonogapher cannot change the duration of a sound pulse unless the transducers are switched
True. the pulse duration depends upon the interaction of the pulser electronics of the machine and the transducer. The pulse duration may change when the sonographer changes transducers.
True or false: the pulse duration cannot be changed under any circumstances or by any action of the sonographer
false: a sonographer can alter the pulse duration by using a different imaging transducer or ultrasound system
What is pulse duration equal to?
The pulse duration is the total time that the transducer is producing a pulse. It is equal to the period multiplied by the number of cycles in the pulse
What happens to pulse duration when a sonographer decreases the maximum imaging depth in an ultrasound scan?
The time that a transducer is pulsing does not change with alterations in depth of view
The spatial pulse length describes certain characteristics of an ultrasound pulse. What are its units?
Spatial pulse length is the distance that a pulse occupies in space. Its length is measured from the beginning to the end of the pulse. It can be reported in any unit of distance
In diagnostic imaging, what determines the spatial pulse length?
the spatial pulse length is the distance or length of a pulse. It depends in part upon the wavelength of each cycle in the pulse. Wavelength depends upon both the source of the sound and the medium through which the sound travels. The length of the entire pulse also depends upon both the source and the medium
Which of the following best describes the spatial pulse length?
wavelength multiplied by the number of cycles in the pulse
Two transducers send ultrasound pulses into soft tissue. One transducer emits sound with a 4 MHz frequency, and the other produces sound at a 6 MHz frequency. Each pulse contains 4 cycles. Which has a greater spatial pulse length?
the 4MHz pulse. Waves with lower frequencies have longer wavelengths and therefore longer spatial pulse lengths
Using a specific transducer, what happens to the spatial pulse length as the sonographer increases the maximum imaging depth?
It remains the same. The spatial pulse length is determined by the number of cycles in the pulse and the wavelength of each cycle.
True or false: while imaging soft tissue, the spatial pulse length does not change as long as the components of the ultrasound system are the same?
True. The overall length of a pulse is equal to the wavelength multiplied by the number of cycles in the pulse. Using a particular ultrasound system and transducer the pulse length cannot change.
On what does the pulse repetition period depend?
the source of the sound wave
What is the pulse repetition period?
The time from the start of one pulse to the start of the next and includes the pulse duration and the receiving time. When the sonographer adjusts the depth of view, the PRP is altered. The listening time is lengthened with deeper imaging and shortened with shallower imaging
A sonographer adjusts the maximum imaging depth of an ultrasound system. Which of the following also changes?
As imaging depth is altered the PRF and the PRP change.
What happens to the pulse repetition period if the sonographer decreases the maximum imaging depth achieved in an ultrasound scan?
it decreases. PRP and depth of view are directly related
Two ultrasound systems one producing sound with a frequency of 3MHz and the other at 6MHz are used to image a patient. The maximum imaging depth of both exams is 8cm. True or false: the period of the 3MHz sound is greater than the period of the 6MHz sound.
True. Period and frequency are reciprocals.
Two ultrasound systems one producing sound with a frequency of 3MHz and the other at 6MHz are used to image a patient. The maximum imaging depth of both exams is 8cm. True or false: The wavelength of the 3MHz ultrasound is greater than the 6MHz sound.
True. frequency and wavelength are inversely proportional
Two ultrasound systems one producing sound with a frequency of 3MHz and the other at 6MHz are used to image a patient. The maximum imaging depth of both exams is 8cm. True or false: the pulses produced by both systems travel at the same speed in the patient
true. all sound waves travel in the same medium at identical speed. frequency and speed are unrelated
Two ultrasound systems one producing sound with a frequency of 3MHz and the other at 6MHz are used to image a patient. The maximum imaging depth of both exams is 8cm. True or false: The PRF of the 6MHz transducer is greater than the PRF of the 3MHz transducer
false. PRF is derived from the maximum imaging depth as established by the sonographer. The PRF changes only when the imaging depth changes. Since depth of view for both systems is the same, PRF is the same
The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. True or false: the pulse repetition period is increased
False. PRP is determined by the depth of view
The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. True or false: the pulse repetition frequency is increased?
false. PRF and PRP are reciprocals. If PRP remains unchanged, PRF also remains unchanged
The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. True or false: The duty factor is increased
true. The duty cycle is calculated by dividing pulse duration by PRP
The maximum imaging depth during an exam is unchanged. A new transducer with a longer pulse duration is used. True or false: the frequency is increased
false. nothing can be concluded about frequency
What are the units of pulse repetition frequency?
1/seconds. PRF has the same units as frequency
The pulse repetition frequency of ultrasound produced by a transducer typical of diagnostic imaging systems
can be changed by the sonographer. PRF is inversely related to maximum imaging depth.
In diagnostic imaging what establishes the pulse repetition frequency?
the source of the sound
When a sonographer increases the maximum imaging depth during an exam, what happens to the the PRF
it decreases. as imaging depth increases the PRF decreases. imaging depth and PRF are inversely related
True or false: the PRF and the frequency are unrelated
true. PRF is determined only by the depth of view
The pulse repetition frequency is the
reciprocal of pulse repetition period
What is a typical value for duty factor of pulsed sound waves used in diagnostic imaging?
.001
What is the value of the duty cycle for continuous wave ultrasound?
100%. The transducer is producing an acoustic signal at all times
In the case of pulsed ultrasound what is the maximum value of the duty factor?
less than 100%
While using a particular imaging system, what happens to the duty factor when the depth of view increases?
decreases. duty factor is inversely related to depth of view
What is duty factor?
the percentage or fraction of time that the system transmits a pulse
true or false: the sonographer alters the duty cycle when adjusting the maximum imaging depth of a scan
true. DF is inversely related to depth of view
true or false: the duty factor is a characteristic of an ultrasound and transducer system and does not change as long as the system components remain unchanged
false. the duty cycle changes when the maximum imaging depth is adjusted
While using the same ultrasound machine and transducer, which of the following can a sonographer alter?
PRP, PRF, duty cycle
which of the following terms does not belong with the others?
a. increased depth of view
b. increased duty factor
c. increased PRP
d. decreased PRF
B. increased duty factors are related to shallower imaging
which of the following terms does not belong with the others?
a. increased depth of view
b. decreased duty factor
c. increased PRP
d. decreased SPL
D. spatial pulse length if unrelated to alterations in depth of view
What is the importance of describing sound beam intensities in a variety of ways with regard to space and time?
it's important when studying bioeffects
which is most closely correlated to tissue heating?
SPTA
Which of these four values for pulse repetition frequency would have the longest pulse repetition period?
A. 2 kHz
B. 4,000 Hz
C. 6 Hz
D. 1 kHz
C. PRP is the reciprocal of PRF
Four pulses have pulse repetition periods as listed below. Which of the following four waves has the highest pulse repetition frequency?
A. 8 s
B. 80 ms
C. 5 ms
D. 400 ks
C. the pulse with the shortest pulse duration will have the highest PRF
which of these four pulses with PRFs listed below has the shortest pulse repetition period
a. 12 kHz
b. 6000 Hz
c. 20 kHz
d. 1 kHz
C.
Four waves have pulse repetition periods as listed below. Which of the following four waves has the lowest PRF?
a) 8 s
b) 80 us
c) 8000 ns
d) 800 ms
A.
True or false: two waves can have identical PRFs even if their PRPs are different
False
True or false: two waves can have identical PRFs even if their frequencies are different
True
True or false: two waves can have identical PRFs even if their periods are different
True
True or false: PRF and PRP are determined only by the imaging depth
true
If all other factors remain unchanged, what happens to the duty factor (increases, decreases, remains the same) when imaging depth increases?
decreases
If all other factors remain unchanged, what happens to the duty factor (increases, decreases, remains the same) when PRF increases
increases
If all other factors remain unchanged, what happens to the duty factor (increases, decreases, remains the same) when PRP increases
decreases
If all other factors remain unchanged, what happens to the duty factor (increases, decreases, remains the same) when the sonographer uses a new transducer with a longer pulse duration
increases
What is the duty factor if the pulse duration is 1 microsecond, and the pulse repetition period is 1 ms?
.001
By changing the imaging depth, which of the following does the operator also change ?
PRF, duty factor, PRP
the speed of a 5MHz continuous wave is 1.8km/sec. The wave is then pulsed with a duty factor of 0.5. What is the new propagation speed?
1.8 km/sec
A sonographer is using a 3 MHz transducer & changes to a 6 MHz transducer. The imaging depth remains the same. What will happen to each of the following parameters? (Increase, decrease, unchanged)
Period
Frequency
Wavelength
Speed
intensity
PRF
PRP
a. decreases
b. increases
c. decreases
d. remains the same
e. remains the same
f. remains the same
g. remains the same
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