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77 Cards in this Set
- Front
- Back
A glass vacuum tube shaped like a funnel, sometimes used to display ultrasound images, is called what? |
Cathode Ray Tube (CRT)
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The narrow end of a CRT contains a/an ___ that shoots out a stream of ___ containing video information
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Electron Gun / Electrons
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The interior surface of the CRT is coated with ___ which glow when struck by electrons
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Phosphors
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The odd-numbered lines (1-525) which the electron beam writes across the CRT screen first, are called what?
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Odd Field
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The even-numbered lines (2-524) which the electron beam writes across the CRT screen last, are called what?
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Even Field
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A combination of one odd field and one even field is called what?
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Frame
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How much time is required to make a single frame? thus making CRT fame rate what?
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1/30 sec (1/60 + 1/60)
30 Hz |
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When a CRT screen is written by alternating between the odd field and the even field, what is this called?
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Interlaced
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At what Hz can human no longer detect an interlaced display?
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60 Hz
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This type of image consists of only two colors: black & white
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Bistable Images/Display
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This type of image consists of multiple levels of brightness. Different amplitudes are assigned to different shades
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Grayscale Images/Display
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What two user controls alter display characteristics?
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1) Brightness
2) Contrast |
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This user control determines the range of brilliancies within displayed images
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Contrast
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This user control determines the brilliance of the displayed image
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Brightness
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This system component converts the sound beam spoke patterns into a digital, interlaced pattern suitable for display
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Digital Scan Converter
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This type of number can have an unlimited and continuous range of values, and are found in everyday lives
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Analog Numbers
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This type of number have a limited range of discrete values, and are frequently associated with computer devices
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Digital Numbers
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For what four reasons are analog scan converters obsolete today?
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1) Image Fade
2) Image Flicker 3) Instability 4) Deterioration |
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Using computer technology to convert images into numbers is called what?
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Digitizing
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What are five advantages of digital scan converters today?
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1) Uniformity
2) Stability 3) Durability 4) Speed 5) Accuracy |
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What is the smallest building block of a digital picture?
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Pixel
(PICture ELement) |
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The number of picture elements per square inch is called what?
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Pixel Density
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The following factors define what?
- lower spatial resolution - less detailed image - larger pixels - few pixels/inch |
Low Pixel Density
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The following factors define what?
- higher spatial resolution - more detailed image - smaller pixels - many pixels/inch |
High Pixel Density
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What is the smallest amount of computer memory called?
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Bit
(BInary digiT) |
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What digits are binary numbers based on? Decimal numbers?
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Binary: 0 - 1
Decimal: 0 - 9 |
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A group of eight bits of computer memory
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Byte
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The computer memory made up of 2 bytes (or 16 bits)
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Word
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When an image displays many shades of gray, it is said to have this
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Superior Contrast Resolution
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The following factors define what?
- fewer shades of gray - degraded contrast resolution |
Fewer Bits/Pixel
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The following factors define what?
- more shades of gray - improved contrast resolution |
More Bits/Pixel
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How do we determine the number of shades of gray?
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Multiply 2 by itself, the same number of times as there are bits
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What is the number of shades that can be represented by 3 bits?
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2 x 2 x 2 = 8 shades of gray
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What is the number of shades that can be represented by 8 bits?
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256 shades of gray
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How many bits are needed to store:
- 10 shades of gray? - 11 shades of gray? - 15 shades of gray? |
4 bits
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What is the primary advantage of digital over analog?
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Digital is less susceptible to signal contamination
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The FIRST step in converting analog signals to digital, involves converting the electrical signals received by the transducer to strings of 0s and 1s. This is performed by what?
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Analog-to-Digital (A-to-D) Converter
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The SECOND step in converting analog signals to digital, involves processing of the reflected signals before storage. This is called what?
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Pre-Processing
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The THIRD step in converting analog signals to digital, involves processing after storage. This is called what?
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Post-Processing
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The FOURTH step in converting analog signals to digital, involves translating stored digital signals back to analog for display on analog CRT (televisions). This is performed by what component?
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Digital-to-Analog (D-to-A) Converter
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The FIFTH step in converting analog signals to digital, involves writing the newly converted analog signals to the CRT. This is called what?
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Video Display
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The manipulation of image data before storage in the scan converter. This manipulation cannot be reversed
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Pre-Processing
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The manipulation of image data after storage in the scan converter. This manipulation can be reversed
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Post-Processing
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The following are handled when?
- TGC - Log Compression - Write Magnification - Fill-In Interpolation |
Pre-Processing
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The following are handled when?
- any change after freeze frame - Black/White Inversion - Read Magnification - Contrast Variation |
Post-Processing
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The following are handled when?
- Persistence - Frame Averaging - Edge Enhancement - Smoothing |
Either Pre- or Post-Processing
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Zoom can also be called what?
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Magnification
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Image visualization can be improved by enlarging a portion to fill the entire screen. This is called what?
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Magnification
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This form of magnification occurs after image storage in the scan converter. It consists of 3 steps:
- anatomy scan - conversion & storage - region of interest selected and only the original data that pertains to that region is displayed (no rescan) |
Read Magnification
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Read magnification can be used on a frozen image, and thus is considered what?
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Post-Processing
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This form of magnification occurs during data acquisition, before storage in the scan converter. It consists of 4 steps:
- anatomy scan - conversion & storage - region of interest selected - rescans only the region of interest |
Write Magnification
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If the number of pixels or scan lines in the region of interest is greater than in the original image (improved spatial resolution), name the form of magnification used
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Write Magnification
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If the number of pixels or scan lines in the region of interest is the same as the original image (same spatial resolution), name the form of magnification used
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Read Magnification
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Write nagnification cannot be used on a frozen image and thus is considered what?
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Pre-Processing
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The following describes what kind of magnificaiton?
- uses old data - post-processing - larger pixel size - same # pixels as original ROI - unchanged spatial resolution - unchanged temporal resolution |
Read Magnification
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The following describes what kind of magnificaiton?
- acquires new data - pre-processing - identical pixel size - more pixels than original ROI - improved spatial resolution - possible improved temporal resolution |
Write Magnification
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Name the storage media:
ADVANTAGES: portability, requires no device to read DISADVANTAGE: bulky, hard to store, difficult to copy, cannot display dynamic images |
Paper Media
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Name the storage media:
ADVANTAGES: can store large amounts of info efficiently, can store and play dynamic images, can record color DISADVANTAGE: Can be erased by strong magnetic fields |
Magnetic Media
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Name the storage media:
ADVANTAGES: High resolution, accepted in the medical community, can produce color images DISADVANTAGE: bulky, difficult to store and retrieve, requires chemical processing, artifacts can arise from dirt or chemical contamination |
Chemically Mediated Photographs
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Name the storage media:
ADVANTAGES: can store huge amounts of data, inexpensive, not erased by exposure to magnetic fields DISADVANTAGE: Requires a display system, no standardized format for image display and storage |
Optical Media
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This describes the digital ultrasound lab in which images and reports are digitized and stored on a large computer network
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PACS - Picture Archiving and Communications System
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What are three advantages of PACS?
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1) Instant access to archived studies
2) No degradation of data 3) Electronically transmit images and reports to remote sites |
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This describes a form of storage based on a combination of magnetic and optical technology, which is often used by PACS
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Magneto-Optical (MO) Storage
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What are two advantages of magneto-optical storage?
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1) can store large amounts of data on a single disc
2) high degree of security (cannot be erased by strong magnetic fields) |
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All of the following are true of ordinary CRTs, except:
A. It contains large vacuum tubes with a phosphor-coated screen B. Electrons are emitted by a gun and swept across the screen by varying magnetic fields C. There are 600 horizontal scan lines from top to bottom, painted in order from 1 to 600 D. There are 60 fields generated each second that combine into 30 fames per second |
C (525 lines, interlaced format)
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Which of the following correctly describes a typical television display?
A. interlaced B. progressive scan C. bistable D. non-interlaced |
A
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Which electronic component is required for grayscale imaging?
A. VCR B. non-interlaced display C. computer memory C. scan converter |
D
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All of the following are disadvantages of analog scan converters except:
A. image fade B. low-resolution image C. image flicker D. deterioration |
B
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Which of the following scan converters will provide the best spatial resolution?
A. digital with 256x256 pixels B. digital with 512x512 pixels C. digital with 128x128 pixels D. analog with 1000x1000 array |
D
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Which of these statements regarding a bit of computer memory is false?
A. it is the smallest element of an image B. it is bistable C. eight bits combine to make a byte D. it is a component of a digital scan converter |
A
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How many gray shades can be represented by a group of 4 bits? 2 bits?
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16 shades
4 shades (multiply 2 by itself as many times as there are bits) |
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Which of the following statements regarding a pixel is false?
A. smallest part of a digitized image B. a collection of bits, assigned to each pixel, stores the shad of gray C. it displays up to 3 gray shades simultaneously D. image quality is improved when the number of pixels is high |
C
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Are the following procedures usually pre- or post-processing?
A. modifyng a frozen image B. read zoom C. write zoom D. adjusting the brightness of the CRT E. increasing the receiver gain |
A. post-processing
B. post-processing C. pre-processing D. post-processing E. pre-processing |
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Are the following forms of information usually digital or analog?
A. signal from the transducer to the receiver B. input signal to the digital-to-analog converter C. output signal from the analog-to-digital converter D. input signal to the analog-to-digital converter E. output signal from the digital-to-analog converter F. typical video signal |
A. analog
B. digital C. digital D. analog E. analog F. analog |
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All of the following are characteristics of write magnification except:
A. pre-processing function B. more pixels in the ROI C. identical regions stored in the scan converter before and after zooming D. it is the preferred method of image magnification |
C
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What is the primary disadvantage of video tape and computer disc storage?
A. cost B. vulnerable to erasure by strong magnetic fields C. only low resolution images are stored D. only black and white images are stored |
B
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All of the following are advantages of PACS systems except:
A. data will not deteriorate over time B. images can be delivered to distant locations C. studies can be reviewed easily D. images have a higher resolution that what appears on the display |
D
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