Physics Exam Review 4
Which of the following actions will improve the signal - to - noise ratio ? A. increase dynamic range B. increase receiver gain C. increase output power D. increase time - gain compensation
C. Increasing output power will improve the signal - to - noise ratio . When the pulse's strength is increased , reflections arriving at the transducer are stronger as well . Strong reflections are less susceptible to the image degrading effects of noise .
What is the primary advantage of multiple focal zones along each scan line of a two dimensional image ? A. improved temporal resolution B. decreased temporal resolution C. improved lateral resolution D. improved longitudinal resolution
C. Multiple foci along a single scan line creates a composite beam that is extremely narrow . Narrow sound beams create images with superior lateral resolution at all depths . Single focus systems use a single sound beam to create each scan line , and lateral resolution is optimal at only one depth .
Of the following , which imaging modality has the poorest temporal resolution ? A. two - dimensional , real - time B. A - mode C. color flow imaging D. M - mode
C. Of the choices , color flow imaging has the lowest temporal resolution . Many pulses are required to create a single color flow image . The large number of pulses required for each image results in a low frame rate and poor temporal resolution .
appropriate answers . ( More than one answer may be correct . ) For the following 6 statements , indicate which of the transducer A. linear switched ( also called linear sequential ) array transducer B. linear phased array transducer C. mechanical transducer D. annular phased array transducer E. convex or curvilinear array transducer F. vector array transducer These transducers steer the beam with a C. motor and focus the beam with an acoustic lens or a curved PZT element .
C. Only a mechanical scanner has these characteristics
These transducers steer the beam with a motor and focus the beam with an acoustic lens or a curved PZT element.
C. Only as mechanical scanner has these characteristics
An ultrasound system with a 4.0 MHz transducer is used to image structures as deep 15 cm . Twenty images are produced each second , each requiring 100 acoustic pulses . What is the PRF of the system ? A. 1,500 Hz B. 300 Hz C. 2,000 Hz D. 4 MHz
C. Pulse repetition frequency is defined as the number of pulses produced by an ultrasound system in one second . In this example , 100 pulses are required to construct a single image , and 20 images are displayed each second . Thus , a total of 2,000 pulses are used each second to meet the imaging requirements of this system ; this is the PRF . In this question , frequency and imaging depth are unimportant .
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
A. Dynamic aperture is a technique of receive focusing that uses fewer crystals to identify echoes from superficial depths and many more crystals to monitor echoes from greater depths . Dynamic aperture is also known as variable aperture
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
A. Dynamic aperture is a technique of receive focusing that uses fewer crystals to identify echoes from superficial depths and many more crystals to monitor echoes from greater depths . Dynamic aperture is also known as variable aperture .
Which two factors determine temporal resolution ? A. speed of sound and depth of view B. pixel size and sector size C. focal zones and sector depth propagation speed and frame rate
A. Of the 4 choices , propagation speed and depth of view have the greatest effect upon frame rate and temporal resolution . Frame rate is high with shallow imaging . Frame rate is high when sound travels quickly in a medium .
All of the following are true of read zoom except : A. preprocessing function of a receiver B. same number of pixels are in the original ROI and the zoomed image C. on the screen , the pixels in the zoomed 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. Read zoom is a postprocessing function of the receiver . The data originally in the region of interest ( ROI ) , before zoom , remains intact . New information is not acquired .
What is the smallest amount of digital storage called ? A. bit B. byte C. pixel D. fractel
A. The bit is the smallest amount of digital storage or computer memory . The term bit is derived from the words " binary digit . " A combination of eight bits makes a byte . Computer memory is called random access memory , or RAM .
What happens to a digital image when the pixel density increases ? A. spatial detail improves B. temporal resolution increases C. the field of view expands D. there are more shades of gray
A. The pixel density , the number of pixels per inch , determines the detail that a digital picture can illustrate . With greater pixel density , spatial detail improves . Alternatively , the image has less detail with fewer pixels per inch .
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 .
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 stars in the sky D. the number of tires on a car
A. The weight of a person can be considered an analog number because it is continuous . and can achieve an unlimited number of values . On the other hand , the number of people in a room or the number of tires on an automobile can be represented only by discrete , whole , or integer values .
For the following 6 appropriate answers . ( More than one answer may be correct . ) statements , indicate which of the transducer types are A. linear switched ( also called linear sequential ) array transducer B. linear phased array transducer C. mechanical transducer D. annular phased array transducer E. convex or curvilinear array transducer F. vector array transducer These transducer systems typically produce an image that , throughout its entire depth , is approximately as wide as the ultrasound transducer itself .
A. The width of a linear sequential array transducer determines the width of the 2 - D image that it creates .
How are the piezoelectric crystals excited when using an ultrasound system with sequential linear array transducer A. singly and in order : the first crystal , second , then the third , etc. B. in pairs : the first two crystals , the 3rd and 4th , the 5th and 6th , etc. C. in a specific order D. in a random sequence
C. Sequential linear array transducers fire small groups of piezoelectric crystals in a specific succession or progression . The order of firing is determined by the manufacturer , and is chosen to produce the highest quality image . There is , however , no specific order that all linear arrays use . The firing pattern is best described as " in a specific order . "
At which imaging depth is the slope of the TGC curve most effective ? A. the region very close to the transducer B. the far zone C. the focal zone
C. TGC is most effective in improving image quality in the focal zone . Compensating for attenuation in the focal zone allows the ultrasound system to produce high - quality scans with detailed information
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. Dynamic receive focusing is used only with systems using array transducers . Focusing is accomplished automatically during reception and is outside the control of the sonographer .
Which of the following is a typical value for the amplification of a signal by the receiver ? A. 50 to 100 watts B. -50 to -100 dB C. 50 to 100 dB D. 5 to 25 W / cm²
C. The amplification of the weak electrical signals that first reach the receiver range from 50 to 100 decibels . This prepares the signals for further processing .
What is the smallest part of a digital picture called ? A. bit B. byte C. pixel D. fractel
C. The basic element of a digital representation of an image is the pixel . The term is derived from the words " picture element " .
Which ultrasound imaging modality has the best temporal resolution ? A. B - scanning B. duplex imaging C. color flow imaging D. M - mode
D. Temporal resolution is the ability to accurately record the position of moving reflectors . With M - mode , the ultrasound pulse tracks reflector position in only a single dimension ( depth only ) and delivers extremely fine temporal resolution . The remaining choices all operate in two dimensions and do so by compromising temporal resolution
Two imaging systems produce acoustic pulses ; one pulse is 0.4 µsec long and the other is 0.2 μsec long . Which is most likely to provide the best temporal resolution ? A. 0.4 usec system B. 0.2 µsec system C. they are the same D. cannot be determined
D. Temporal resolution is unrelated to pulse duration . Temporal resolution is determined by the number of frames , or images , that are produced each second . There is insufficient information to answer the question .
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 system 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 . Since system B has 12 bits assigned to each pixel and system A has only 4 , system B will display more gray shades and , thus , display subtle differences .
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. System B has a greater ability to display small detail in an image in comparison to system A. System B has 25,000 pixels per square inch , whereas system A only has 10,000 pixels per square inch . System B has a greater pixel density , and this determines the degree of spatial resolution .
Which transducer system is most likely to have the longest delay in its TGC curve ? A. a 5 MHz linear array B. a 2.5 MHz annular array C. a 7.5 MHz mechanical transducer D. a 5 MHz annular array
B. The 2.5 MHz transducer will have a longer delay in the TGC curve . Low frequency ultrasound waves attenuate to a lesser extent than high frequency waves . Since choice B has the lowest frequency , it will have the least amount of attenuation and will require less compensation in the near zone . The type of transducer ( e.g. , annular , linear ) does not affect the TGC .
What does the far gain of a depth gain compensation curve represent ? A. the median amplification related to compensation B. the maximum amplification related to compensation C. the minimum amplification related to compensation D. the maximum attenuation related to compensation
B. The far gain setting of a TGC curve represents the maximum amplification that a reflected wave undergoes during the compensation process .
What is the approximate number of frames that must be presented each second for the human eye to perceive the display without flickering ? A. 2 B. 30 C. 100 D. 500
B. The frame rate required to perceive smooth , flicker - free motion is in the range of 30 frames / sec . When the frame rate is significantly below this value , the viewer experiences flicker . Flicker increases fatigue and discomfort and diminishes the perceptive ability of the observer .
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
B. The linear switched arrays ( or linear sequential arrays ) produce an image of rectangular shape . The other three transducers generate sector - shaped images that are essentially indistinguishable from each other
When looking at images produced by these transducer systems , which be distinguished from all the others one ? can A. linear phased array B. linear switched array C. annular phased array D. mechanical transducer
B. The linear switched arrays ( or linear sequential arrays ) produce an image of rectangular shape . The other three transducers generate sector - shaped images that are essentially indistinguishable from each other .
The output of an ultrasound pulser determines the of the acoustic pulse . A. imaging depth B. intensity C. duration D. pulse repetition period
B. The output of the pulser determines the strength or the intensity of the sound beam produced by the transducer . When greater electrical voltages from the pulser strike the PZT crystal of the transducer , pulses with greater intensity are created .
The process of eliminating low amplitude signals from further processing is called all of the following except_____ A. reject B. subordination C. threshold D. suppression
B. The process of removing low - level signals from further processing or display by an ultrasound system is called reject , threshold , or suppression . The term subordination does not describe this process .
What is the process of adjusting for path length related attenuation called ? A. compression B. compensation C. time - gain compensation D. reconfirmation
B. Ultrasound experiences attenuation as it travels in soft tissue . The deeper that sound travels , the weaker the reflected pulse is . Compensation is the process of adjusting for path length attenuation .
What is the primary disadvantage of multiple focal zones along each scan line . of a two - dimensional image ? A. improved temporal resolution B. decreased temporal resolution C. improved lateral resolution D. improved longitudinal resolution
B. With multiple foci along each scan line , the ultrasound system uses many pulses to create each image . This reduces the number of frames created per second . A low frame rate results in decreased temporal resolution .
What was the original purpose for the ultrasound system's analog scan converter A. to increase the dynamic range of ultrasound systems B. to make real - time imaging possible C. to increase the sensitivity of ultrasound systems D. to allow for gray scale imaging
D. The introduction of scan converter technology in ultrasound allowed for the presentation of gray scale images . That is , the images were not limited to black and white ( bistable ) , but had various shades of gray within them . Additionally , the scan converter changed the format of the system's data from penetrations to a format suitable for display .
What is the typical voltage of the signal that is the input to the receiver of an ultrasound system A. 0.1 volts B. 500 mvolts C. 250 volts D. 10 volts
D. The signal produced by the transducer upon reception and sent to the receiver of the ultrasound system is extremely small and is in the micro- to millivolt range .
All of the following are used to describe compensation except . A. swept gain B. depth gain C. time gain D. amplitude gain
D. The terms swept gain , depth gain , and time gain are used interchangeably when describing compensation . The amplitude gain is not synonymous with the other three terms .
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 and the ROI are the same C. the pixel size in the zoomed image D. in comparison to the zoomed image fewer ultrasound pulses are used to create the original ROI
B. Write zoom is a preprocessing function of the receiver where new information is acquired from the region of interest ( ROI The data originally in the scan converter , before zoom , is discarded . All the pixels in the image are now concentrated into the ROI , thereby increasing the pixel density and image quality of the zoomed portion .
With 6 bits , what is the largest number of different gray shades that can be stored ? A. 8 B. 16 C. 64 D. 256
C. A maximum number of 64 shades can be stored with the use of 6 bits . We multiply 2 by itself a total of 6 times to calculate the answer to this question : 2x2x2x2x 2 x 2 = 64 shades .
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. A two - dimensional array transducer creates a three - dimensional image .
Which receiver function creates an image of comparable brightness from top to bottom ? A. receiver gain B. output power C. swept - gain compensation
C. Compensation establishes images of uniform brightness from top to bottom . Compensation adjusts for the attenuation of sound with increasing path length .
Which best describes the elements in a linear sequential array transducer ? A. rectangular , 1/4 wavelength thick B. rectangular , 1/4 to 1/2 wavelength wide C. rectangular , 1 wavelength wide D. squares , 1 wavelength thick
C. Each element of a linear sequential array is rectangular . There are many elements , each with a width of one wavelength .
True or False ? A digital representation of a number can achieve only specific fixed values .
True . A digital representation of a number is limited to discrete values and cannot take on unlimited values . Because of this , digital scan converters can store only a fixed number of gray shades .
True or False ? The signal - to - noise ratio remains unchanged when a sonographer adjusts receiver gain .
True . Adjustments to receiver gain alter both the meaningful signal and the destructive noise to the same extent . Therefore , the signal - to - noise ratio is unaltered .
True or False ? Postprocessing of image data occurs after the data has been stored in the scan converter .
True . All processing that occurs after the image is stored in the scan converter is called postprocessing . Examples of postprocessing are read magnification and the various forms of gray scale assignment . Any manipulation of a frozen image is postprocessing .
True or False ? An ultrasound system with a shorter pulse repetition period ( PRP ) will have better temporal resolution than a system with a longer PRP
True . An ultrasound system with a shorter PRP has the ability to produce more pulses each second . With more pulses per second , the system creates many images per second . Increased frame rate improves temporal resolution
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 . Focusing using time delays of the electrical spikes is a form of transmit focusing
True or False ? Typically , the sonographer can adjust the compression function of a receiver .
True . Part of the compression function involves the assignment of gray scale levels on the display . This is adjusted by the operator
True or False ? With sector scanning images with greater detail ( spatial resolution ) are created when the number of acoustic pulses per degree of sector is increased .
True . Spatial resolution is improved with pulses per degree of sector . When the line density is low , gaps may exist between adjacent pulses . Reflectors within the gaps will not accurately appear on the image .
True or False ? The length of a pulse does not directly influence the temporal resolution .
True . Temporal resolution is not affected by the length of the pulses produced by the system . The factors that influence the temporal resolution are maximum imaging depth , sector angle , line density , and the number of foci per scan line .
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 .
True or False ? The sonographer can alter the pulser power
True . The output voltage of the pulser and the strength of the acoustic pulse produced by the transducer are in the sonographer's control . The output power has different names depending on the manufacturer , but the sonographer can always alter its level .
True or False ? The primary purpose of demodulation is the preparation of the electrical signal for display on a television monitor .
True . The primary purpose for demodulating a signal within an ultrasound system is to prepare it for ultimate display on a television monitor .
True or False ? For digital image information to be displayed on a conventional television screen , the data must be processed by a digital - to - analog converter .
True . The representation of an image in digital format is not suitable for display on a standard television because a TV is an analog device . After all the signal processing is completed , the image data is passed through a digital - to - analog converter It is then suitable for TV display
True or False ? The sonographer can adjust the receiver gain .
True . The sonographer is in direct control of the receiver gain . The sonographer determines the degree to which the signal returning from the transducer is amplified . It is a primary control on the ultrasound system that helps determine the ultimate quality of images .
True or False ? Typically , the sonographer can adjust the threshold level .
True . Under normal circumstances , the operator adjusts the reject ( suppression or threshold ) level that is performed during signal processing
True or False ? Annular phased array transducers focus sound beams in all planes and at all depths .
True . With annular arrays , the sound beam has the appearance of a straw . It is focused in all planes and at all depths
True or False ? Both linear and phased array technologies have the ability to variably focus an ultrasound beam to different depths .
True . With the phased delivery of electrical pulses to the crystals , the ultrasound beam may be focused at a variety of different depths .
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. A string of eight bits of computer memory is a byte . Two bytes of computer memory make a word . Since a byte is 8 bits , a word is 16 bits .
Which of these functions are performed by the receiver of an ultrasound system ? More than one answer may be correct . ) A. amplification B. threshold C. compensation D. demodulation
A , B , C , and D. All of the functions listed above are performed by the ultrasound system's receiver .
The process of demodulation incorporates which of the following tasks ? ( More than one answer may be correct . ) A. smoothing B. amplification C. rectification D. decompression
A and C. Demodulation is a two - step process . These steps are rectification and smoothing .
For the following 6 appropriate answers . ( More than one answer may be correct . ) statements , indicate which of the transducer types are A. linear switched ( also called linear sequential ) array transducer B. linear phased array transducer C. mechanical transducer D. annular phased array transducer E. convex or curvilinear array transducer F. vector array transducer Ultrasound systems using these transducers do not actually steer the ultrasound beams to create a two dimensional image .
A and E. Linear and convex switched ( or sequential arrays ) do not steer sound beams . Rather , a small group of elements produce a pulse that travels straight ahead .
What is the advantage of using a 1½ dimensional array transducer ? A. improved elevational resolution B. improved lateral resolution C. improved axial resolution D. improved temporal resolution
A. A 1½ dimensional array transducer creates a thinner imaging plane . Thin imaging planes have superior elevational , or slice thickness , resolution .
What is the advantage of using a 1½ dimensional array transducer ? A. improved elevational resolution B. improved lateral resolution C. improved axial resolution D. improved temporal resolution .
A. A 1½ dimensional array transducer creates a thinner imaging plane . Thin imaging planes have superior elevational , or slice thickness , resolution .
Which one of the following does not A. belong in the group below ? A. receiver gain B. energy output C. pulser power D. acoustic power E. transmitter output F. output gain
A. All of the terms listed as answers , except for choice A , refer to the strength of the signal produced by the transducer and transmitted into the body . Receiver gain is not synonymous with the other five choices .
Which of these is a binary number ? A. 12211221 B. 10000000 C. 98765432 D. 01010102
B. A binary number is a string of zeroes and ones only . Binary numbers are based on two choices . Digital numbers are based on ten choices .
What is the number of binary digits required to store 29 levels of gray ? A. 4 B. 5 C. 6 D. 29
B. A minimum of 5 bits are required to display 29 shades of gray . Actually , 5 bits can display a maximum of 32 shades of gray . Because only 16 shades of gray can be represented by 4 bits , a fifth bit must be added to achieve adequate memory to display more than 16 shades .
Which choice will result in increased frame rate and temporal resolution ? A. decreased propagation speed B. decreased sector size C. decreased lateral resolution D. decreased pulse repetition frequency
B. A narrower sector diminishes the number of pulses required to produce each image Frame rate and temporal resolution improves when fewer pulses make each image .
Which of the following sector imaging systems will have the best image detail if all other parameters are identical ? A. a 90 ° sector with 100 pulses / image B. an 80 ° sector with 40 pulses / image C. a 70 ° sector with 84 pulses / image D. a 60 ° sector with 60 pulses / image
C. The best image detail is provided by the system with the highest line density . Line density is defined as the number of acoustic lines per degree of sector angle . The more lines per sector degree , the closer together the scan lines are , and the greater the anatomic detail displayed . Choice C has 1.2 acoustic pulses per degree ( 84/70 ) , choice A has a line density of 1.11 ( 100/90 ) lines / degree , choice B has 0.5 ( 40/80 ) lines / degree , and choice D has 1 ( 60/60 ) line / degree . Choice C has the highest line density and the best spatial resolution .
Which transducer possesses the best slice thickness resolution ? A. linear phased arrays B. 2 - D arrays C. 1½ dimensional arrays D. linear sequential arrays
C. The greatest advantage of 1½ dimensional arrays is that they create very thin ultrasound slices .
Which transducer possesses the best slice thickness resolution ? A. linear phased arrays B. 2 - D arrays C. 1½ dimensional arrays D. linear sequential arrays
C. The greatest advantage of 1⁄2 dimensional arrays is that they create very thin ultrasound slices .
A sonographer reduced the sector size from 90 degrees to 30 degrees . Frame rate , however , did not change . What else happened ? A. imaging depth decreased B. pulse duration increased C. multi - focus was turned on D. PRF was increased
C. The question states that sector size was decreased . By itself , this would increase frame rate . Thus , the correct answer to this question is something that would decrease frame rate . The only selection that decreases frame rate is the use of multiple focal points , choice C.
Which term best describes the region of minimum amplification on a standard TGC curve ? A. far field B. focus only C. area close to the transducer D. focal zone
C. The region of minimum amplification on a TGC curve , often called the " delay , " is always associated with the area close to the transducer .
What is a typical pulser output voltage that excites a piezoelectric crystal ? A. 0.1 volts B. 500 millivolts C. 40 volts D. 10 microvolts
C. The signal typically produced by the pulser of an ultrasound system , used to excite the transducers's piezoelectric crystals , may be in the range of tens of volts .
Which of the following will improve a system's temporal resolution ? A. increased sector angle B. increased line density C. increased PRF D. increased frequency
C. To improve temporal resolution , increase the number of images produced each second . If the number of pulses emitted per second is increased ( choice C ) then the system can increase the frame rate . Increased PRF is obtained by decreasing the maximum imaging depth . A , B , and D all decrease frame rate and decrease temporal resolution .
What is the maximum number of shades of gray that are represented with 4 bits ? A. 4 B. 8 C. 12 D. 16
D. A maximum of 16 shades of gray can be represented with 4 bits . To calculate this , multiply 2 by itself the same number of times that there are bits . In this example , multiply 2 by itself a total of 4 times ( there are 4 bits ) : 2 x2x2x2 = 16 shades .
Which of the following is not considered a component of an ultrasound system ? A. master synchronizer B. pulser C. receiver D. image intensifier
D. An ultrasound system is considered to have six components : transducer , pulser , receiver image processor , display , and master synchronizer . An image intensifier is part of an x - ray imaging system .
What is true of the electrical pulses that excite the active elements of an annular phased array transducer ? A. they arrive at each piezoelectric crystal at exactly the same time hey vary in amplitude based on the direction of the steering and focusing C. they excite the crystals at different times , nanoseconds apart D. they arrive at each PZT crystal at different times , microseconds apart
D. Annular array technology fires the piezoelectric crystals in a particular sequence to produce a focused ultrasound beam . The electrical pulses that excite the ringed elements of the array arrive at slightly different times , separated by only very small fractions of a second .
What is the shape of the elements in an annular phased array transducer ? A. rectangles . B. squares C. wedges D. circles
D. Annular array transducers have piezoelectric crystals that are donut or ring shaped . They are arranged as a collection of concentric rings .
The excitation of array elements with dissimilar voltages is called and is used to A. dynamic aperture , reduce refraction B. subdicing , eliminate lobes C. apodization , remove flash artifact D. apodization , reduce lobe artifact
D. Apodization describes the excitation of a number of PZT elements with different . strength of off - axis sound beams and voltages . This acts to decrease the reduce lobe artifact .
Which of the following tasks is not performed by the receiver of an ultrasound system ? ( More than one answer may be correct . ) A. rectification B. smoothing C. compression D. degaussing
D. Degaussing is the only task listed above that is not performed by the system's receiver .
Which of the following best describes the demodulation process ? A. changing the gray scale of an image B. changing the frequency of a signal C. changing the form of a sound pulse D. changing an electrical signal's form
D. Demodulation alters the form or shape of electrical signals within the receiver .
Which two controls determine a system's temporal resolution ? A. frame rate and sector size B. focal zones and sector depth C. propagation speed and frame rate D. depth of view and pulses per image
D. Depth of view and number of pulses per image determine the frame rate ( and temporal resolution ) of an ultrasound system . The sonographer can alter both of these factors .
Which of the following forms of focusing is different from the others ? A. lens . B. mirror C. phased D. dynamic receive
D. Dynamic receive focusing is accomplished during reception of reflected sound . The other three techniques are forms of focusing during transmission .
How many bits are required to display 10 different shades of gray ? 14 shades ? 15 shades ? A. 4 bits , 5 bits , 6 bits B. 10 bits , 14 bits , 15 bits C. 4 bits , 4 bits , 2 bits . D. 4 bits , 4 bits , 4 bits
D. Four bits of memory are required to display 10 , 14 , or 15 shades of gray . Three bits can display a maximum of 8 gray shades ( 2 x 2 x 2 = 8 ) . Adding a single bit to the collection increases the number of gray shades to 16 ( 2x2x2x2 = 16 ) .
What happens to an image when the number of bits allocated to each pixel increases ? A. spatial detail improves B. frame rate increases C. field of view expands D. more shades of gray
D. In a digital representation of an image , as the number of bits assigned to each pixel increases , the number of different shades of gray in the image increases .
All of the following reduce temporal resolution by increasing the number of pulses per image except A. increasing the number of foci B. increasing line density C. increasing field of view D. increasing depth of view
D. Increasing the depth of view does not alter the number of pulses per image . Increasing depth of view decreases temporal resolution by changing the pulse repetition period while leaving the number of pulses in each image unchanged .
A. linear switched ( also called linear sequential ) array transducer B. linear phased array transducer C. mechanical transducer D. annular phased array transducer E. convex or curvilinear array transducer F. vector array transducer 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 crystals blunted , curved shape at the top . The arc the at the top of the image may be a few centimeters wide .
E. Curved array transducers create a special form sector that starts at an initial width and gets progressively larger . If the PZT crystals are arranged in an arc of 2 to 4 cm , the image will be 2 to 4 cm wide at its top . From that dimension , the image becomes progressively wider .
With these transducers , a trapezoidal image shape is produced . The image is flat at the top and becomes progressively wider at increasing depths .
F. Vector arrays create this image shape . The vector transducer is a combination of linear phased and linear switched array technologies .
True or False ? The pulser of a mechanical transducer is typically more complex than . the pulser of a phased array transducer .
False . A single electrical signal excites the PZT crystal of a mechanical transducer . With phased array technology , many crystals are excited nearly simultaneously to produce an acoustic pulse . Phased array systems use this technique to steer and focus sound beams . Thus , phased array systems have more complex pulsers .
True or False ? Digital scan converters do not use computer technology to process electronic data into images .
False . Digital scan converters use computer technology to process data .
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 . Focusing using time delays of the electrical spikes is a form of transmit , not receive , focusing .
True or False ? The sonographer can make an image of uniform brightness by adjusting both output power and receiver gain
False . Neither output power nor receiver gain can create images of uniform brightness because they do not correct for attenuation . The function that corrects for attenuation is called time - gain compensation , or TGC .
True or False ? Preprocessing of image data occurs after the data has been stored in the scan converter .
False . Preprocessing of image data is achieved before image storage in the scan converter . TGC and write magnification are examples of preprocessing .
True or False ? An ultrasound system with a longer pulse duration will generally have better temporal resolution
False . Temporal resolution of a system is unaffected by the pulse duration
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 . The number of bits assigned to each pixel of a digital image does not directly affect the spatial resolution of the image
True or False ? The lower the frequency of the ultrasound beam , the shallower is the delay of the TGC curve .
False . With lower sound frequencies , the delay of the TGC curve is deeper . There is less attenuation with low frequency sound , and this allows for a deeper TGC delay .
True or False ? Typically , the sonographer can control the demodulation process performed by a receiver
False . With the majority of ultrasound systems , the process of demodulation is not under the sonographer's control . The parameters of demodulation are set within the ultrasound system and cannot be adjusted .
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 .
Mechanical transducer and annular phased array transducer
A video display that is limited to black and white only , with no shades of gray , is called . A. binary B. bistable C. monochrome D. inchworm
ability to show B. A video display with the black and white only , without any intermediate shades of gray , is called bistable .
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
each acoustic pulse . Each sound wave is determine the direction and focusing of to the next . The electrical patterns array transducer changes from one pulse excite the PZT crystals of a linear phased A. The pattern of the electrical signals that directed in a slightly different direction to create a two - dimensional imaging plane Thus , the electrical signals vary for each the varying patterns is called the beam acoustic pulse . The electronics that creates former .