Image production and evaluation Flashcards
1
Q
what factors provide a means for the radiographer to produce, review and evaluate radiographs
A
image quality factors
2
Q
what are the 4 image quality factor
A
contrast
density
detail
distortion
3
Q
this is the visible differences seen in adjacent anatomic structures on the radiograph
A
contrast
4
Q
what results from the amount of penetration of the x-ray beam as it passes through different parts of the body
A
contrast
5
Q
what have very few gray tones. They are mostly black and white
A
high contrast
6
Q
High contrast is also known as
A
short scale contrast
7
Q
images contain many shades of gray
A
low contrast
8
Q
low contrast is also referred to as
A
long scale contrast
9
Q
kV has an _ relationship to contrast
A
inverse
10
Q
kV ^ contrast
A
goes down
11
Q
what is the primary controlling factor for the penetrability of the x-ray beam and therefore directly controls contrast
A
kVp
12
Q
as kV increases, x-ray penetrability of scatter radiation is _ causing more scatter to reach the image receptor
A
increase
13
Q
high kV= _ contrast= _ scale contrast
A
low
long
14
Q
low kV= _ contrast= _scale contrast
A
high
short
15
Q
increase contrast by reducing the amount of scatter reaching the film
A
grids
16
Q
limits the area being irradiated and thus reduces the amount of scatter being produced
A
beam restriction
17
Q
less scatter= _ contrast
A
more
18
Q
as OID increases, contrast _
A
increases
19
Q
when OID increases contrast increases because a great deal of scatter radiation now misses the image receptor why
A
air gap technique
20
Q
this is the amount of blackness on the radiograph
A
density
21
Q
density is also known as
A
optical density
22
Q
the amount of density on a film is controlled by
A
- the # of exit rays striking the film-screen striking the film-screen combination
- the speed of the film-screen combination
- processing
23
Q
is the primary controlling factor for the quantity of x-rays being produced and therefore has a great deal of influence over the blackening of the image
A
mAs
24
Q
is the primary controlling factor for the quality of x-rays being produced
A
kVp
25
more mAs= _ density
more
26
increasing kVp, _ photons frequency and _ photon wavelength, producing _ beam
increases
decreases
more powerful, penetrating
27
what is the secondary controlling factor of density
kVp
28
kVp is also known as
potential difference and electromotive force
29
increasing kVp, _ density and why
increases
| because the more powerful beam doesn't get attenuated in the body. more x-rays reach the image receptor
30
kVp affects density according to the
15% rule
31
if kVp increases by 15%, density is
doubled
32
if kVp decreases by 15%, density is
halved
33
A _% change in kVp will create a noticeable change in density on our image
4%
34
as film-screen speed increases, density
increases
35
as film-screen speed decreases, density
decreases
36
these decrease the amount of scatter reaching the film and thereby decrease density
grids
37
this decreases density by limiting the size of the x-ray beam and reducing the amount of scatter being produced
beam restriction
38
this affects density through its variation of atomic number and tissue thickness
anatomy
39
this affects density by altering tissue integrity and thickness
pathology
40
distance is affected by distance according to the
inverse square law
41
if distance (SID) is doubled, density
decreases 4 time
42
if distance (SID) is halved, density
increases 4 times
43
detail is also called
detail
sharpness
definition
image resolution
44
increasing OID= _ magnification= _ detail
increasing
| decreasing
45
increasing SID= _ magnification= _ detail
decreasing
| increasing
46
large focal spot size = _ in detail
decrease
47
small focal spot size = _ in detail
increase
48
large silver halide crystals in film = _ film speed = _ detail
fast
| decreased
49
large phosphor crystals in intensifying screen = _ screen = _ detail
fast
| decreased
50
any motion by the patient results in
image blur
| loss of detail
51
this is the misrepresentation of an anatomic structure on an image receptor
distortion
52
there are 2 types of distortion
size
| shape distortion
53
magnification makes anatomic structures appear larger on film than in reality
size distortion
54
Size distortion is caused by
```
excessive OID ( major factor)
insufficient SID
```
55
shape distortion is divided into 2 categories
elongation
| foreshortening
56
what makes structures to appear longer than they are in reality
elongation
57
elongation is is caused by
improper tube angulation
| cassette alignment
58
what makes structures appear shorter than they are in reality
foreshortening
59
foreshortening is caused by
improper body part alignment with the cassette
60
there are 2 main types of technique charts
1. fixd kVp charts
| 2. variable kvp charts
61
what are the most commonly used type of chart. For each anatomic part, an optimum kVp is selected. The mAs is then changed in order to accommodate changes in body part thickness
fixed kVp charts
62
have a set mAs value for each anatomic part and the kVp varies according to changes in body part thickness
variable kVp charts
63
is a device that measure the amount of radiation reaching the image receptor and then automatically terminates the exposure
AEC
64
There are 2 types of AEC devices
1. Ionization chamber
| 2. photo timer
65
are the most commonly used AEC device. The gas filled chamber is located between the table top and the image receptor
Ionization chambers
66
utilize a fluorescent screen that is placed under the IR
phototimers
67
_ by the radiographer is of the utmost importance when using AEC
precise centering
68
_ have density control buttons that allow the radiographer to adjust the exposure to have more or less density
AEC devices
69
is a system in which the radiographer simply touches a picture or written description of the body part being imaged and the technique is set automatically
anatomically programmed radiography
70
_ is an important consideration when selecting film-screen combinations. The film and the intensifying screen must be sensitive to and emit the same color of light in order to work together efficiently
spectral matching
71
_ are sensitive to both blue and green light. These are used in radiography because we use rare earth intensifying screens which generally emit green light.
Orthochromatic films
72
for Orthochromatic films, prior to 1970, calcium tungstate screens were used and they emitted a
blue/violet light
73
Radiographic film has 2 main parts
the base
| the emulsion
74
most x-ray film has the emulsion on both sides of the base and is therefore called
double emulsion film
75
double emulsion filme is used to
increase film speed
76
The base of the film is made of _ and it is used to support the
polyester
| emulsion
77
the base is _ and has a _ tint
lucent
| blue tint
78
the emulsion consists of 2 main ingredients
1. gelatin
| 2. silver halide crystals
79
The gelatin is a clear substance that is used to hold the layer of _ in place
silver halide crystals
80
the silver halide crystals are made of both
silver iodide and
| silver bromide
81
The size and concentration of the silver halide crystals determines the
speed of the film
82
bigger crystals = _ film speed
faster
83
films can also be designed to display different levels of contrast. The lower the contrast of a film, the _ the exposure latitude
wider
84
this is the range of exposure techniques that can be used to produce an acceptable image
exposure latitude
85
sensitometric curves, characteristic curves, and D-log E curves
H and D Curves
| Hurter and Driffield
86
H & D, this is a graphic representation of the relationship between
density and exposure
87
In radiography, the useful range of optical density is between
0.25 to 2.5
88
the closer the curve to the y axis, the faster the film
speed
89
the steeper the curve, the _ the contrast
| the more shallow the curve, the _ the contrast
higher
| lower
90
the steeper the curve, the _ the latitude.
| the more shallow the curve, the _ the latitude
more narrow
| the wider
91
Less than _% of the radiographic image is created by x-rays striking the film
1
92
Over _% of the image is made by light from the intensifying screens striking the film
99
93
The main purpose of intensifying screens is to reduce pt dose by converting
x-rays into a great deal of visible light
94
4 layers of film
1. protective
2. emulsion-silver halide, black metallic (active layer
3. adhesive
4. base
95
4 layers of screen
1. protective
2. phosphor
3. reflective
4. base
96
a screen that can produce a great deal of light is said to be a _ speed intensifying screen
high
97
screen speed is detrained by
phosphor crystal size
| thickness of phosphor layer
98
bigger crystals= _ speed
faster
99
thicker phosphor layer= _ speed
faster
100
while bigger crystals and thicker phosphor layers _ patient dose, _ screen speed, _ image detail
reduce
increase
decreasing
101
a rating of 100 is considered a
par speed screen
102
anything rated below 100 is considered a
detail or extremity screen
103
anything above 100 is a
high speed screen
104
Before the invention of the automatic film processor, it took _ to completely develop a film
60 min
105
The standard time to develop a film with an automatic processor is
90 sec
106
the automatic processor has 3 separate tanks
1. developer tank
2. fixer tank
3. wash tank
107
the job of the _ is to change the exposed silver halide crystals into metallic silver. This creates the black and gray areas of the film
developer
108
what stops the development process and makes sure that the image on the film doesn't fade. It also clears all of the unexposed silver halide crystals from the film
fixer
109
developer and fixer temperature is set at
95 degrees F
110
what removes the chemicals that remain on the film
wash
111
wash temperature is set at
90 degrees
112
once the film has traveled through the 3 tanks, it is
blown dry in the dryer
113
Dryer temperature is
120 degrees
114
moves film through processor
transport
115
replaces chemicals after film travel
replenishment
116
regulates temperature
temperature regulation
117
keeps chemicals from settling at bottom of processor
recirculation
118
dries
dryer
119
6 steps for the start up procedure
1. close wash tank valve
2. turn on water
3. turn on processor
4. put lid in place
5. run several old 14 x 17 films
6. wait for proper chemical temperatures
120
4 steps for the shut down procedures
1. turn off water
2. turn off processor
3. open wash tank valve
4. leave lid open
121
what is the measurement of the responses of film to exposure and processing.
sensitometry
122
some of the tools used for sensitometry are
penetrometer
sensitometer
densitometer
123
this may also be called a step wedge. Its used to produce a series of densities on a film by exposing it to x-rays. This is a method for monitoring both x-ray equipment and film-screen combinations
penetrometer
124
this is designed to expose a reproducible, uniform, optical step wedge onto a film. It contains its own light source and is used for processor quality control
sensitometer
125
this device provides a readout of the amount of blackening (density) on a film
densitometer
126
each image is created in a square frame called a
matrix
127
THe matrix is made up of small boxes that contain a numeric value. These boxes are called
pixels
128
the numeric value of each pixel is converted into a certain amount of density that is then displayed on the monitor. The higher the numeric value of the pixel, the appears on the
screen
129
the number of shades of gray that a digital system can display is called is
dynamic range
130
the smaller the size of the pixels, the more of them that can be placed in the
matrix
131
as more pixels are placed in the matrix,
image resolution increases
132
the minimum acceptable resolution in digital imaging is a matrix size of
2048 x 2048
133
each pixel represents a 3 dimensional volume of tissue that is called a
voxel
134
the # of photons striking the detector
signal
135
background information which is placed in the image but does not contribute to image quality
noise
136
noise has the same appearance on the image as
quantum mottle
137
is the comparison of these 2 characteristics on the image.
signal to noise ratio
138
a signal to noise ratio is what and why
desirable
| indicates little noise in the image
139
what allows both the technologist and the radiologist to alter the image that has been produced in many different ways
post processing
140
digital imaging has what vs conventional film
wider exposure latitude
141
this adjusts both the contrast and the brightness of the image
windowing
142
controls the contrast
window width
143
when window level is increased, density
increased
144
parts of the image can be magnified
magnification
145
brightness can be increased along edges of structures
edge enhancement
146
the removal of background anatomy to visualize contrast filled vessels
subtraction
147
dark and light pixels are reversed
image reversal
148
adding text to an image
annotation
149
the numeric value that is representative of the amount of exposure the image receptor received. The number must be within a specific range in order for the image to be acceptable
exposure index
150
the 2 types of digital imaging are
```
Computed radiography (CR)
digital radiography
```
151
uses a photostimulable storage phosphor imaging plate (PSP or IP) inside a cassette. This captures the latent image. The IP is then placed in an Image reader device (IRD)
computed radiography
152
uses a laser beam to convert the image into an electronic signal that is then sent to the television monitor
image reader device (IRD)
153
Layers of an imaging plate
```
protective layer
phosphor layer
conductor layer
support layer
light shield layer
```
154
insulates IP from trauma
protective layer
155
active component of IP/ made of barium flourohalide bromides with europium activators
phosphor layer
156
grounds the plate
conductor layer
157
support base
support layer
158
prevents light from erasing data
light shield layer
159
what is much more sensitive to scatter than conventional film, so correct kVp and grid use is important
IP
160
the latent image will lose _% of its energy in 8 hrs, so the image must be processed shortly after exposure
25%
161
Does not use a cassette
directly converts the x-ray photons into an electrical signal.
the photons strike a flat panel detector that creates the conversion
digital radiography
162
There are 2 types of digital radiography. They are separated by the type of flat panel detector they use
direct digital radiography
| indirect digital radiography
163
has an amorphous selenium flat panel detector. This releases electrons when struck by the x-ray photons
direct digital radiography
164
has amorphous silicon flat panel detector. this detector requires a phosphor to create light when struck by x-ray photons. The light then causes the silicon to release electrons
indirect digital radiography
165
Direct digital radiography advantage over indirect digital radiography ; direct digital radiography has the advantage of
creating a more accurate image because no divergent light beam (phosphor screen) is being used
166
Indirect digital radiography has the advantage over direct digital radiography by
reducing patient dose because its phosphors work in the same way an intensifying screen
167
both systems contain _ which collect the electrical charges and send the signal to the television monitor
Thin Film Transistors
168
a disadvantage of both CR and DR when compared to conventional film
is a loss of resolution
169
PACS stand for
picture archiving and communication systems
170
incorporate the acquisition, storage, transmission and display of digital images into one computer network
PACS
171
if an imaging center does not have digital imaging, actual films can be sent to a _ by using a film digitizer
PACS system
172
the 2 types of film digitizers are
laser digitizers
| charged coupled devices
173
which is the least expensive and therefore the most commonly used film digitizer
CCD
174
What does DICOM stand for
Digital Imaging and Communications in medicine
175
what is a universal standard for the storage of medical images. This allows images to be passed back and forth on a PACS system, no matter who manufactures the imaging equipment
DICOM
