# Dmi 100 Review image evaluation

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1. what is density?
amount of blackness on a given area of a radiograph
2. how do you calculate density?
3. what is light incident?
light striking the radiograph from the back, coming from the view box
4. what is light transmitted?
light that is seen coming through the radiograph whilte it is being viewed by either the human eye or a densitometer
5. how is optical density made visible?
when the crystals in the film's emulsion are converted to black metallic silver in the developer solution
6. what is the reciprocity law?
any combination of mA and time that produce the same mAs value will result in the same density on the radiography
7. what relationship does mAs have with density?
direct proportional
8. how does kVp affect density?
directly affects it, although not in a directly proportional relationship
9. what is the 15% rule?
an increase in kVp of 15% will double the density
10. what is inverse square law?
the intensity of the x-ray beam is inversely proportional to the square of the distance between the source of x-rays and the image receptor

11. what is the density maintenance formula?
12. what type of relationship does film-screen combination have with density?
• direct proportion
• as speed (sensitivity) increases, density increases
13. What do grids accomplish?
• decrease the amount of scatter radiation striking the image receptor
• decreases density unless is increased to compensate
14. what do beam restriction devices do to density?
decrease density by limiting the size of the x-ray beam unleass mAs is increased to compensate
15. what does filtration do to the density?
• negligible effect on density
• reduces soft, long wavelength rays
16. what is contrast?
17. how do grids affect contrast?
less scatter = fewer gray tones = higher contrast
18. how does beam restriction affect contrast?
less radiation = less scatter = fewer gray tones = higher contrast
19. how does filtration affect contrast?
decreases small wavelength x-rays = stronger beam = increase scatter = more gray tones = decrease contrast
20. what is subject contrast?
patient's body controlling contrast
21. what are the three controlling factors for subject contrast?
• atomic number
• tissue density
• tissue thickness
22. what are the factors that affect recorded detail?
• OID
• SID
• Focal spot size
• Film-Screen combo
• Motion
23. what are the two type of shape distortion?
• size
• shape
24. what are the different parts of film?
• protective coat
• emulsion (active layer)
• base
25. what is the base of the film made out of?
polyester
26. what is the anatomy of a double emulsion film?
• super coat
• emulsion
• base
• emulsion
• super coat
27. what does the emulsion of a film contain?
silver halide crystals suspended in gelatin
28. what are the sensitive specks on silver halide crystals for?
serve as centers for making the latent image visible
29. what is the latent image?
image contained in the silver halide crystals after exposure but beforew development
30. what determines the speed of a film?
• size of silver halide crystals
• number of silver halide crystals
• thickness of emulsion
• (the larger the crystals and the thicker the emulsion, the faster the film)
31. how does the speed of the film affect contrast?
the faster the film the higher the contrast
32. what determines the latitude of a film?
• depends of the inherent contrast
• the lower the inherent contrast the wider the latitude
33. what are the other names for H&D curves?
• sensitometric curves
• characteristic curves
• D log E curves
34. what is plotted on a H & D curve?
• x-axis: exposure
• y-axis: density
35. what does the toe portion of the H & D curve represent?
• low exposure
• low density
36. what does the toe portion of the H&D curve also called
base plus fog
37. what does the body portion of the H&D curve also called
• straight line portion
• gamma
• slope
38. what does the body portion of the H & D curve represent?
• measures usable densities
• indicates overall gray scale of the film
39. what does the shoulder portion of the H & D curve represent?
• maximum density
• blackest portion
40. how do you determine the speed of a film by looking at the H&D curve?
the closer the curve to the y-axis the faster the speed
41. how do you determine the conrast of a film by looking at the H&D curve?
• the steeper the slope of the curve the higher the contrast
• the shallower the slope the lower the contrast
42. how do you determine the recorded detail of a film by looking at the H&D curve?
• based on the speed of the film
• the faster the speed, the poorer the recorded detail
43. what is the safe temperature for storing film?
no greater than 68 to 78 degrees
44. how much humidity is safe to store film?
40 to 60%
45. what causes the crinkle or half-moon marks on film?
bending film over fingernail during handling
46. what are the different parts of an intensifying screen?
• protective layer
• phosphor layer
• reflective layer
• base
47. what determines the speed of an intensifying screen?
• phosphor used
• phosphor size (larger = faster)
• active layer thickness (thicker = faster)
• efficiency of reflective layer (higher = faster)
• kvp used (higher = faster)
• prescene of yellow dye in active layer (dye absorbs light)
• conversion effciency of  phosphors
48. what controls what in a film-screen combination?
• speed controlled by screen
• contrast controlled by film
49. how many intensifying screens are used with a single emulsion film? how many for double emulsion film?
• single = one intensifying screen
• double = two intensifying screens
50. what is the intensification factor?
• ratio of exposure in mAs needed to produce image without screens compared with exposure in mAs needed to produce image with screens
51. how is film-screen contact tested?
52. what does a grid accomplish?
reduces amount of scatter radiation reaching the image receptor
53. when is a grid used?
• when part thickness is 10 cm or greater
• 70 kvp or higher
54. how is a grid constructed?
lead strips separated by aluminum interspacers
55. what is grid ratio?
• height of lead strips divided by the distance between them
• grid ratio = H/D
56. what is grid frequency?
• number of lead strips per inch or cm
• lines per inch or lines per cm
57. what happens to the lead strip thickness when grid frequency increases?
• decreases
• becomes less visible
58. what are the different types of grids?
• linear
• focused
• crossed
59. what is a linear grid?
• lead strips are parallel to one another
• x-ray tube may be angled along the length of the grid w/o cutoff
• used primarily with large SID or small field
60. what is a focused grid?
• lead strips are angled to conincide with divergence of beam
• used with specific ranges of SID
• distance at which focused grid may be used
• also called focal distance or focal range
62. what is a crossed grid?
• consist of two linear grids placed perpendicular to each other
• superior scatter cleanup
• allow no angulation of x-ray beam
• require perfect positioning and centering
• primary use is biplane cerebral angiography
63. what is contrast improvement factor?
• measure of a grid's ability to increase contrast
• ratio of the contrast with a grid to the contrast without a grid
64. what is grid selectivity?
ratio of primary radiation transmitted through the grid to secondary radiation transmitted through the grid
65. what happens to selectivity when the grid frequency and grid ratio are high?
more selectivity
66. what does high selectivity mean?
indicates high efficiency of scatter cleanup
67. what is grid conversion factor?
amount of exposure increase necessary to compensate for the absorption of image forming rays and scatter in the cleanup process
68. what are the grid conversion factors?
• 5:1 - 3
• 8:1 - 4
• 12:1 - 5
• 16:1 - 6
69. upside down focused grids will produce what type of grid error?
normal density in the middle with decreased density on the sides
70. off level focused grids will produce what type of grid error?
decreased density over the entire image
71. lateral decentering of focused grids will produce what type of grid error?
cutoff visible to one side of the image
72. focused grid decentering will produce what type of grid error?
normal density in the middle with cutoff visible on the sides
73. air gap technique is similar to what grid ratio?
10:1
74. what does a grid do to contrast?
increases contrast because it absorbs scatter radiation which decreases the amount of gray tones
75. each step on the density control for AEC represents how much change in density?
25%
76. what does the developer do during processing of film?
• converts exposed silver halide (bromide) crystals to black metallic silver
• or convert latent image to manifest image
77. what are the different types of agents in the developer?
• reducing agents
• activator
• hardener
• restrainer
• preservative
• solvent
78. what are the reducing agents and what do they accomplish?
• phenidone- quickly build gray tones
• hydroquinone- slowly fill in black tones
79. what does an activator do during processing?
soften and swells film emulsion
80. what does a hardener do?
controls swelling of film emulsion to allow safe transport through the processor
81. what does a restrainer do?
prevents reducing agents from producing fog, which is created when unexposed silver bromide crystals develop
82. what does a preservative do?
slows oxidation of reducing agents by room air
83. what is the solvent in the processor?
water which is the medium in which chemicals are dissolved
84. what does the fixer accomplish?
clears and removes unexposed silver bromide crystals
85. what does the transport system do?
• moves film through processor
• agitates chemistry
86. what do deep racks do?
• move film into and through solutions in developer, fixer, and wash tanks and between drying tubes in dryer section
• has turnaround assembly at the bottom
87. what does a crossover accomplish?
moves film from the developer tank into the fixer tank and from the fixer tank to the wash tank
88. when does replenishment of chemicals occur inside the processor?
• for each film fed into the processor
• activated by micro switch at end of entrance roller
89. replenishment rates in a typical workday are based  on what size of film?
14x17
90. what is the temperature maintained in inside the developer?
90 to 95 degrees F
91. what is the temperature in the dryer?
120 degrees F
92. Maintenance of processor: what is recommended daily?
• wash crossover racks twice daily
• drain wash tank
93. Maintenance of processor: what is recommended weekly?
clean deep racks
94. Maintenance of processor: what is recommended monthly?
• drain and clean by hand all tanks and dryer
• put in fresh developer and fixer
• add starter solution to developer chemicals
• change developer filter
• change water wilters
95. When is sensitometric testing done for automatic processors?
daily
96. what does sensitometric testing check?
• speed
• contrast
• base plus fog
97. what does a densitometer measure?
• speed step
• contrast step
98. what are pi line artifacts?
• small marks 3.14 inches apart
• caused by raised nick on roller scratching film
• also by chemical stain or dirt
99. increased developer temperature does what to a film?
• chemical fog
• increased density
100. what type of malfunction to the processor causes light films?
developer too low
101. what type of malfunction to the processor causes film to appear milky?
poor fixer replenishment
102. what type of malfunction to the processor causes dark flakes to appear?
algae from wash water
103. what type of malfunction to the processor causes dark films?
• developer temp too high
• developer overreplenishment
• fixer contamination of developer
• white light leak
• crack in safelight
104. what type of malfunction to the processor causes film fog?
• developer contamination
• developer overreplenishment
• crack in safelight
• developer temp too high
• outdated film
 Author: swtjo3joe ID: 184822 Card Set: Dmi 100 Review image evaluation Updated: 2012-11-24 17:43:27 Tags: density grids filters SID OID mAs kVp intensifying screen film developer curve AEC artifacts Folders: Description: image evaluation Show Answers: