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SEM VI - RAD REVIEW > **Saia Unit 4 > Flashcards

**Saia Unit 4 Flashcards

1
Q

Energy deposited into the image receptor

A

Density

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2
Q

The controlling factors of density are

A

mA
Time
mAs

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3
Q

mAs

A

The number of X-rays in polyenergetic primary beam

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4
Q

mAs has the primary control of

A

Image density

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5
Q

Density is placed in one of three categories

A

Acceptable
Underexposed (too light)
Overexposed (too dark)

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6
Q

30% rule

A

The human eye requires a change in density of at least 30% before it can be visualized

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7
Q

Fuji exposure indicator

A

S number
Range 180-220
Indirect relationship

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8
Q

Kodak exposure number

A

EI number
Range 1800-2200
Direct relationship

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9
Q

Agfa exposure indicator

A

LGM number
Range - 1.9-2.5
Direct relationship

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10
Q

A perfect exposure indicator value is

A

1mR of exposure to imaging plate/panel

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11
Q

Increasing the KVP will increase the quality or energy energy of the beam giving the beam more

A

Penetration ability

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12
Q

As KVP is increased, density…

A

Will increase

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13
Q

Energy deposited into the image receptor is

A

Density

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14
Q

15% rule

A

Used to alter KVP settings to change density and contrast
A 15% increase in KVP = a 50% decrease in mAs
A 15% decrease in KVP = a doubling in mAs

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15
Q

As KVP goes up, image contrast

A

Goes down

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16
Q

As KVP goes down, image contrast

A

Goes up

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17
Q

If SID is increased with no other change, density is

A

Decreased

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18
Q

If SID is decreased with no other change density is

A

Increased

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19
Q

SID and density have an ? relationship

A

Inverse

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20
Q

Density

A

Overall blackening of a film/image

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21
Q

Inverse square law

A

The intensity of the beam is inversely proportional to the square of the distance.

I1 (D2)2/I2 (D1)2

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22
Q

Density maintenance law

A

Formula that will compensate for changes in SID to maintain density

mAs1 (D1)2/mAs2 (D2)2

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23
Q

If you increase the OID less scatter reaches the film resulting in a decrease in

A

Density

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24
Q

Less OID will result in a greater density due to

A

More radiation reaching the film

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25
Q

OID and density have a ? relationship

A

Inverse

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26
Q

Imaging system speed

A

As speed increases the efficiency of placing energy into the IR increases, and density increases also.

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27
Q

Grids are used to

A

Absorb scatter to prevent it from reaching the film.

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28
Q

Formula to maintain density with grids

A

Mas1 GCF1 / mAs 2 GCF2

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29
Q

If collimation is increased (smaller light field) then

A

Less radiation leaves the tube
Less scatter produced
Less energy reaches IR
LESS DENSITY IS THE RESULT

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30
Q

Radiolucent tissue

A

Tissue that let’s xray energy through

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31
Q

Radiopaque

A

Tissue that will absorb ray energy

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32
Q

Disease

A

Physical and chemical changes in tissue

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33
Q

Anode heel effect

A

Variation in the beams intensity across its longitudinal axis,
More X-rays on cathode side than anode side

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34
Q

As filtration is increased,

A

More photons are absorbed resulting in fewer X-rays and less xray energy in the primary beam

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35
Q

Contrast

A

The difference in adjacent shades across the radiographic image

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36
Q

Contrasts primary function

A

To make recorded detail visible

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37
Q

Contrast is primarily controlled by

A

KVP

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38
Q

Energy deposited into the IR is

A

Density

The more energy values = more shades of density

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39
Q

High contrast

A

Few shades of gray
Increased contrast
Lower KVP
“Short scale” contrast

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40
Q

Low contrast

A

Many shades of gray
Decreased contrast
High KVP
“Long scale” contrast

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41
Q

Differential absorption

A

Differing materials absorb xray at differing degrees

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42
Q

As KVP decreases patient dose ?

A

Increases (weaker xray, more absorbed in patient)

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43
Q

As KVP increases patient dose ?

A

Decreases

Stronger xray beam, more passes through patient

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44
Q

Grid ratio

A

Height of lead strips to distance between

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45
Q

Grid frequency

A

Number of lead strips per unit distance

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46
Q

Increasing beam restriction - smaller field

A

Less tissue irradiated
Less scatter produced
- “short scale”, higher contrast

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47
Q

An increase in OID results in

A

Less scatter reaching the film - higher contrast

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48
Q

As beam filtration increases

A

Shorter scale

Higher contrast

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49
Q

Positive contrast media

A

(Iodine/barium) - temporarily make anatomy more dense than normal

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50
Q

Negative contrast media

A

Oxygen, carbon dioxide, room air

Allow more X-rays to penetrate due to the low atomic number resulting in an increase in density

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51
Q

Barium atomic number

A

56

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52
Q

Iodine atomic number

A

53

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53
Q

High contrast

A

Big difference in shades, short scale, low KVP, very black and white

Think of the top of shade triangle (small peak)

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54
Q

Low contrast

A

Little difference between shades, long scale, high KVP, many grays

Think of the bottom of shade triangle (large base)

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55
Q

Photographic factors

A

Density

Contrast

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56
Q

Density

A

Overall image blackness

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57
Q

Contrast

A

Visibility of adjacent structures

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58
Q

Geometric factors

A

Detail

Distortion

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59
Q

Detail

A

Visibility of fine anatomical structures

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60
Q

Distortion

A

Misrepresentation of an objects size/shape

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61
Q

Recorded detail aka

A

Resolution, sharpness, definition, detail

Measured in lp/mm

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62
Q

Line pair

A

A line and it’s adjacent space, as recorded in an image of the tool (resolution tool)

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63
Q

Human visual acuity is

A

5 lp/mm

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64
Q

Unsharpness

A

Degree of loss of detail of the anatomical structure by the imaging system

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65
Q

Penumbra

A

Geometric unsharpness around the periphery of the structure of the image

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66
Q

As focal spot size increases

A

Penumbra increases

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67
Q

Effective focal spot

A

focal spot projected toward the patient

Usually .5-2.0mm

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68
Q

Line focus principal

A

The effective focal spot is smaller than the true/actual focal spot

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69
Q

True/actual focal spot

A

Area where electron stream strikes the anode target

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70
Q

Small focal spot

A

Maximum image detail

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71
Q

Umbra

A

Objects true size

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72
Q

Why not always use a small focal spot

A

Small focal spot uses small filament which are mA limited, large focal sometimes needed

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73
Q

Increased SID will result in

A

Less penumbra

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74
Q

Increased OID will result in

A

More penumbra

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75
Q

Macro radiography

A

Magnification radiography

Intentionally magnifying to exaggerate small structures
Most common in mammography

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76
Q

IR speed

A

Faster speed is used to save patient dose, however resolution not good

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77
Q

Quantum mottle

A

Not enough X-rays in the primary beam to adequately form image

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78
Q

Distortion

A

Misrepresentation of an objects true size and shape

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79
Q

Size distortion is always

A

Magnification

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80
Q

Magnification

A

The misrepresentation of the actual size of an object

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81
Q

As SID increases, magnification?

A

Decreases

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82
Q

As OID increases, magnification ?

A

Increases

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83
Q

Magnification factor

A

SID/SOD (SID divided by SOD)

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84
Q

SID/SOD

A

Image width/object width = SID/SOD

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85
Q

Shape distortion

A

Misrepresentation of an anatomical part due to misalignment of source, IR, and/or part

Results in elongation or foreshortening

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86
Q

When the xray beam or IR is misaligned =

A

Elongation

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87
Q

When the body part is misaligned=

A

Foreshortening

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88
Q

Three points to perfect alignment

A

CR perpendicular to body part (most important)
CR perpendicular to IR
Body part parallel to IR

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89
Q

Magnification formula

A

Mag=SID/SOD

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90
Q

Percent magnification =

A

Image size - object size / object size X 100 = % magnification

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91
Q

Intensifying screens

A

Used to convert xray energy into visible light energy.

  • 90-99% of film exposure is due to visible light
  • 1-10% of film exposure is due to direct xray
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92
Q

Xray film is much more sensitive to

A

Visible light energy than it is to xray energy

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93
Q

Spectral emission

A

The color of visible light emitted by a phosphor crystal when stimulated

94
Q

Intensifying screen construction:

A

Base layer
Reflective layer
Phosphor layer (phosphor crystals)
Protective layer

95
Q

Function of radiographic film

A

To record and store a permanent anatomical image

96
Q

Radiographic film construction

A 
Protective layer
Emulsion layer (silver halide crystals)
Adhesive layer
Base layer
Adhesive layer
Emulsion layer (silver halide crystals)
Protective layer
97
Q

Density

A

Energy deposited into an image receptor

98
Q

Emulsion layer

A

Silver halide crystals - gelatin whose function is to absorb and then release the processing chemistry and water

99
Q

Colloid

A

A material that can absorb and release water without itself being dissolved in the process.

Like a sponge.

100
Q

Function of the silver halide crystals

A

Respond when stimulated by xray or light energy

101
Q

Latent image

A

Formed in the films emulsion as a shadow representation of anatomy. Due to chemical changes in AgBr crystals. Invisible to human eye.

102
Q

Manifest

A

Visible

103
Q

Latent

A

Hidden

104
Q

Manifest image

A

Formed in films emulsion due to chemical changes in AgBr crystals, made visible to the human eye by processor.

105
Q

Gurney Mott theory

A

Photon breaks ionic bond releasing shared electrons which drift to and are captured by speck. Electrons attaching to the development center. Silver ion attracted to the development center. Sensitivity speck is now neutral and able to attract an electron.

More energy absorbed = more debris = bigger sensitivity speck

106
Q

Grid conversion

A

No Grid = 1

5: 1 = 2
6: 1 = 3
8: 1 = 4
12: 1 = 5
16: 1 = 6

107
Q

Filtration

A

Minimum of 2.5mm Al/Eq

108
Q

Purpose of filtration

A

Remove weaker X-rays from primary beam

109
Q

Half value layer

A

Amount of filtration required to lower xray intensity to half of its original volume

110
Q

Collimator illuminance

A

Brightness of collimator bulb and field

- at least 15 foot candles (160 lux) at 40”

111
Q

Xray to light field

A

Collimator to xray beam alignment

- +/-2% semiannual

112
Q

Nine penny test

A

Test done for xray to light field (diameter of penny is .8 inches)

113
Q

Positive beam limitation

A

Auto collimation of light field to IR size, can be smaller - never larger!
- +/-2% semiannual

114
Q

Focal spot size is tested by

A

Pinhole camera, star pattern or slit camera

- +/-50% annual

115
Q

KVP accuracy is measured with

A

Voltmeter and radiation meter

- +/-10% annual

116
Q

Exposure timer accuracy

A

+/-5% greater than 10ms

+/- 20% less than 10ms

117
Q

Exposure linearity

A

Using the same mAs but different combinations of mA and S

i.e. 100mA @1/2S or 200mA @1/4S

118
Q

AEC backup timer is set to self terminate if

A

If 600 mAs is reached

119
Q

If AEC backup timer is manually set, it should be set to

A

150% of expected mAs

120
Q

AEC optical density versus change

A

+/-.3 OD

121
Q

Film illuminator standard is

A

15W daylight bulb

122
Q

Fluoro exposure rate ESE shall not exceed

A

10R/min

123
Q

Interventional exposure rate ESE shall not exceed

A

20R/min

124
Q

Repeat analysis goal

A

To minimize patient exposure

125
Q

Wire mesh test is used to evaluate

A

Contact between intensifying screen and film

- annually

126
Q

Speed uniformity is tested to assure that all like speed intensifying screens

A

Respond to the same xray stimulation by releasing the same amount of visible light
- +/-10% annual

127
Q

Darkroom fog density can be no greater than

A

.08 (xray) or .05 (mammo)

- semiannual

128
Q

Sensitometry

A

Measuring the response of film to exposure and processing

- daily

129
Q

Developer is sensitive to changes in

A

Temperature, oxidation, concentration, contamination

130
Q

Sensitometer

A

Device that emits varying intensities of light in a star pattern on a film

131
Q

Pemetrometer

A

Aluminum step wedge that is exposed on to radiographic film and developed

132
Q

21 step sensitometer is

A 
Most common (41% difference between steps)
Also a 11 step (100% difference between steps)
133
Q

Densitometer

A

Reads/measures image density, measures how much light is emitted to film and how much is transmitted

134
Q

Optical density

A

Incident light striking the film to the intensity of light transmitters thru film

135
Q

The higher the optical density, the less light transmitted

A

Therefore the greater the density

136
Q

Density difference or contrast indicator

A

Found by subtracting Dmin from Dmax

+/- .15OD

137
Q

Hyporetention (fixer = hypo)

A

Must be less that .05Gr/m2 - emulsion turns brown in storage due to inadequate washing of film in processor
- quarterly

138
Q

+/-2%

A

Collimator dial accuracy (2% of SID)
SID accuracy (2% of SID)
Xray to light field
Positive beam limitation

139
Q

+/-5%

A

Exposure reproducibility

AEC reproducibility

140
Q

+/-10%

A 
KVP accuracy
mR/mAs (from installation)
Exposure linearity
AEC density steps
Film illuminators
Speed uniformity
141
Q

+/-50%

A

Focal spot size

142
Q

Daily

A

Sensitometry

143
Q

Quarterly

A

Hyporetention

144
Q

Semiannual

A

Collimator dial accuracy
Xray to light field
Positive beam limitation
Darkroom fog

145
Q

Annual

A 
Filtration
Half value layer
Collimator illuminance 
SID accuracy
Focal spot size
KVP accuracy
mR/mAs 
Exposure timer accuracy
Exposure linearity
Exposure reproducibility
Protective apparel 
Film illuminators 
Film screen contact
Speed uniformity
146
Q

developer solution

A

electron soup - lots of electrons, when silver added = black metallic silver

147
Q

the automatic processors four sections

A

developer
fixer
washer
dryer

148
Q

function of developer

A

convert exposed silver halide crystals into black metallic silver.
latent to manifest.
95 degrees

149
Q

function of fixer

A

remove unreduced silver halide crystals.

permanently “fix” image into emulsion

150
Q

function of washer

A

to wash residual fixer from emulsion to improve archival quality

151
Q

hyporetention

A

retention of fixer by films emulsion resulting in degrading of the stored image over time

152
Q

dryer section

A

like a hair dryer, heated air blows across film to evaporate water from emulsion; emulsion is hardened and ready for handling.
130-135 degrees.

153
Q

the basic theme to ALL digital imaging systems

A

to convert X-ray energy into electrons

154
Q

analog

A

a device or system that represents info as continuously variable physical quantities, like a mechanical watch. X-ray film is analog.

155
Q

digital

A

a device or system that represents info as continuously variable numeric values, like a digital watch. CR/DR are digital.

156
Q

CR - Computerized Radiography

A

Projection Radiography which uses a PSP (photostimulable phosphor plate - IR/IP). No film.

157
Q

A PSP is composed of

A

Europium Barium Fluorohalide

158
Q

Phosphor plate function

A

latent image is formed by remnant radiation striking the plate. Xray is absorbed within the PSP crystal.

159
Q

fading

A

the loss of latent image information over time

160
Q

CR scanner

A

IR casette is read by a CR scanner which is placed in the scanner and opened up internally to remove the phosphor plate.

161
Q

readout

A

CR scanner scans the IR plate with a Helium Neon light and reads the latent image fro the phosphor

162
Q

raster pattern

A

side to side pattern by the laser to obtain image

163
Q

f centers

A

electrons elevated out of their normal orbital rings and into higher orbitals, containing potential energy, latent image is held in this chemical code of rearranged electrons

164
Q

“F” in F Center is for

A

Fabre - the German word for color

165
Q

Latent to Manifest Image

A

As laser beam travels over the plate, the latent image is released as visible light, the electrons elevated to a higher orbital are “slapped” back to their normal orbit by laser. The transfer of electron energy results in the release of visible light energy.

166
Q

Helium Neon laser

A

red in color

167
Q

photomultiplier TUbe

A

a device that converts light energy to electrical energy

168
Q

digitizing

A

the process of converting colors, shades, and shapes held as analog information into numbers

169
Q

erasing the PSP plate for re-use

A

exposure to high intensity fluorescent light

170
Q

3 inherent factors responsible for image resolution capability

A

image plate size
laser beam size
monitor matrix size

171
Q

current resolution for CR digital imaging is

A

2-5 line pairs per millimeter, conventional radiography can demonstrate 6 lp/mm

172
Q

spatial resolution

A

ability to see small objects

measured as lp/mm

173
Q

Image resolution is synonymous with

A

image detail or image quality

174
Q

Contrast resolution is

A

the number one advantage of digital imaging versus film/screen imaging

175
Q

Quantum Detection Efficiency (QDE)

A

measures the efficiency of a CR system to convert remnant radiation into useful image signals

176
Q

High QDE systems

A

reduce patient dose due to requiring less radiation to produce an acceptable digital signal

177
Q

Fuji Systems

A 
"s" number
Inverse relationship (
178
Q

Kodak (carestream)

A 
"EI" value
Direct relationship (>2050=overexposed)
Expected range - 1950-2050 (2000 ideal)
179
Q

Agfa

A 
"LGM" number
Direct Relationship (>2.5=overexposed)
Expected range - 1.9-2.5 (2.2 ideal)
180
Q

Direct Radiography

A

the use of detectors that convert X-ray energy into electrical energy that is then delivered to a computer where the anatomical image is digitally processed and displayed

181
Q

DR is a direct readout image acquisition technology.

A

the detector is in the flat panel and directly sends the image to a computer upon exposure. No need for processor, ADC, digitizer.

182
Q

Steps in indirect digital image formation with Amorphous Silicon

A

Remnant xray beam enters Amorphous Silicon
X-ray energy converted to visible light
Photoconductive material receives light (converts light to electron energy)
Electron energy captured by TFT device (information converted to digital signal)

183
Q

Steps in Direct DR Formation with Amorphous Selenium

A

Remnant xray beam enters Amorphous Selenium and ionizes - electrons released
Electrons collected by storage capacitor and transferred to TFT
(information converted to digital signal)

184
Q

Direct DR

A

Amorphous Selenium

xray to electron to digital

185
Q

Indirect DR

A

Amorphous Silicon

xray to light to electron to digital

186
Q

No visible light in the image formation process with ?

A

Direct DR

187
Q

Thin Film Transistors

A

Used with both Direct and Indirect DR
Collect electric charges, positioned in a matrix, detect charges on a pixel by pixel basis.
Capable of very high spatial resolution (greater than 20p/mm)

188
Q

DELS

A

Detector elements of a thin film transistor

189
Q

Receiving the DR signal

A

Each Pixel (DEL) from the detector array (TFT) collects electrons in a capacitor, the number collected is directly proportional to the strength of the X-ray received.

190
Q

Algorithms

A

A finite sequence of instructions often used for calculation and data processing. The computers mathematical recipe for processing the digital signal from the pixels.

191
Q

Window Width

A

image contrast

192
Q

Window level

A

image brightness/density

193
Q

Histograms

A

Anatomy specific.

a graphical representation of the distribution of numerical data.

194
Q

with a histogram the raw data is collected, then…

A

then interpreted and presented to the human eye

195
Q

Look up table

A

a table of predetermined luminance values, a mapping function in which every pixel is changed to a new shade of gray simultaneously resulting in an image with appropriate brightness and contrast.

196
Q

The look up table controls

A

automatic rescaling

197
Q

automatic rescaling

A

computers ability to display an image with a diagnostically correct gray scale (within limits)
Overexposed pixels are “turned down”
Underexposed pixels are “turned up”

198
Q

digital image quality factors

A 
pixel/matrix size
spatial resolution
contrast resolution
automatic rescaling
histogram
windowing
phosphor material
exposure indicator
technical factors
199
Q

contrast manipulation

A

A post processing tool used to manipulate the contrast of an image to achieve a desired image.

200
Q

dynamic range

A

The range if grays that can be assigned to a pixel.

The higher the range, the more grays available to display the image.

201
Q

image stitching

A

process of combining multiple images with overlapping fields of view to produce a high-resolution image

202
Q

sampling

A

Process used to digitize the spatial information in an image, typically achieved by dividing an image into a square or rectangular array of sampling points.

203
Q

shutter

A

The process of removing border from image as a post processing tool. Not to be used to compensate for poor collimation.

204
Q

modulation transfer function

A

the ability of a system to record spatial frequencies (lp/mm) and maintain adequate contrast between adjacent line pairs

205
Q

Nyquist Theorem

A

when sampling a signal, the sampling frequency must be greater than twice the bandwidth of the input signal so that image reconstruction will be nearly perfect.

206
Q

Aliasing

A

When an image contains frequencies above its lp, they are under-sampled upon digitisation and appear as lower frequency information in the digital image

207
Q

aliasing in DR occurs when

A

spatial frequency is greater than the Nyquist frequency

sampling occurs less than twice per cycle

208
Q

aliasing in CR occurs when

A

grid errors, grid frequency must be at least 178 lpi

209
Q

edge enhancement

A

computer looks for areas of common pixel signal strength across the matrix, which are then averaged and amplified to the area of interest and other tissues suppressed resulting in decreased contrast, potential for loss of detail/quantum mottle

210
Q

smoothing

A

computer looks for areas of common pixel signal strength across the matrix, which are then averaged resulting in increased contrast and reduction of unwanted noise.

211
Q

edge enhancement aka

A

high pass filtering

useful for viewing large anatomical structures such as organs

212
Q

smoothing aka

A

low pass filtering

useful for viewing smaller anatomical structures such as trabecula

213
Q

Signal to noise ratio (SNR)

A

wanted (useful) anatomical information (signal) versus the unwanted electrical interference (noise)

214
Q

noise

A

detected information that adds nothing to the anatomy - quantum mottle is an example

215
Q

spatial resolution

A

the ability to see small objects (lp/mm)

controlled by crystal size in CR, detector element size in DR and pixel size on a digital monitor

216
Q

contrast resolution

A

Ability to differentiate between shades of gray, controlled by Bit depth, Bit range, Pixel depth

217
Q

spatial resolution is measured in

A

lp/mm

218
Q

maximum spatial resolution is the result of

A

a large matrix and small pixels

219
Q

small pixels =

A

Better spatial resolution

220
Q

Image matrix

A

contributes to spatial resolution, the layout of cells in rows and columns; the larger the matrix, the better the spatial resolution
pixels, voxels, hounsfield units (CT)

221
Q

pixel density

A

the number of pixels per given area

222
Q

The human eye is capable of seeing ? shades of grey

A

30-32

223
Q

the higher the contrast resolution, the more distinct adjacent structures are

A

with similar densities

224
Q

digital imaging systems have significantly higher

A

contrast resolution than film screen

225
Q

contrast resolution aka

A

pixel depth
bit range
dynamic range

226
Q

contrast resolution is rated in

A

bit depth

227
Q

latitude

A

margin for technique error

228
Q

thousands of shades of gray

A

low contrast

229
Q

Bit range

A 
1 bit = 2 shades
2 bit = 4 shades
3 bit = 8 shades
4 bit = 16 shades
5 bit = 32 shades
6 bit = 64 shades
7 bit = 128 shades
etc...
230
Q

Window width

A

selecting which of the available grays are to represented to the eye upon the monitor
controls digital image contrast

231
Q

window level

A

the exact center of the window selected

controls digital image brightness (density)

SEM VI - RAD REVIEW (8 decks)

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