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RTE 1418 > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

binary # system

A

lang of 1’s & 0’s that comp’s use to process data

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2
Q

bit

A

single unit of data (binary unit)

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3
Q

byte

A

8 bits; amount of mem needed to store 1 alphanumeric character

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4
Q

RAM

A

random access memory; short-term storage for open programs (MB, GB, TB) that can be stored/accessed at random from anywhere in about equal amounts of T

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5
Q

ROM

A

read-only memory; data storage device that contain info supplied by manufacturer that cannot be written on or erased

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6
Q

teleradiology

A

transfer of imgs & pt reports to remote sites

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7
Q

LAN

A

local area network; sm area networked w a series of cables/wireless access points allowing comps to share info

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8
Q

WAN

A

wide area network; spans lg areas; connected by telephone wires, satellites, other comm cables

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9
Q

imaging plate. what does it replace? what occurs? what is it capable of doing?

A

replaces rad film; img’s formed by interaction of XRs w PSP; capable of storing latent img

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10
Q

PSP

A

photostimulable phosphor, active layer of IP

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11
Q

what chem is used as the PSP in an imaging plate?

A

Ba Fluoro Halide coated w Europium (and a dye that differentially absorbs the stimulating light)

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12
Q

prompt emission

A

when XR exposes PSP, resultant energy transfer excites e-‘s into metastable state; 50% of these e-‘s immediately return to their ground state, resulting in a prompt emission of light

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13
Q

metastable e-‘s?

A

e-‘s excited from the energy transfer when an XR exposes a PSP

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14
Q

what percentage of e-‘s is converted into normal stage soon after exposure?

A

50%

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15
Q

process of img production in CR? (4)

A
  1. expose (–> XR-induced img-forming signal)
  2. stimulate (laser interacts w PSP to stim latent img)
  3. read (light signal emitted after stimulation is detected/measured)
  4. erase (residual metastable e-‘s moved to ground state by intense light)
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16
Q

color of laser commonly used in CR to scan imaging plate?

A

infrared

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17
Q

factors affecting spatial resolution (amount of detail present in img) of CR img? (5)

A
  1. phosphor layer thickness (thinner better)
  2. pixel size (smaller better)
  3. matrix size (bigger better)
  4. # pixels (more better)
  5. diameter of laser (smaller better)
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18
Q

primary erase?

A

erases latent img

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19
Q

secondary erase?

A

erases scatter

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20
Q

explain img fading in CR and what should be done to overcome problem?

A

remaining metastable e-‘s (from stimulated laser) return to their ground state over T causing latent img to fade; process img soon after exposure

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21
Q

element used in gas laser?

A

He/Ne

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22
Q

explain how wavelength of laser beam affects detail

A

stimulating laser light is monochromatic & resultant emitted light is polychromatic; the longer the laser wavelength, the greater difference btw it’s wavelength and that of the emitted light, causing less confusion/interference when img is read

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23
Q

a ______ wavelength of laser gives better resolution

A

long

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24
Q

a _____ diameter laser produces img’s w better spatial res

A

sm

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25
Q

ADC?

A

analog to digital conversion

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26
Q

DAC

A

digital to analog converter

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27
Q

______ and _______ are the processes of analog to digital conversion (ADC)

A

sampling & quantization

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28
Q

What does an IR response of a CR system look like on a graph and what is the x & y axis?

A

straight climbing line; Optical Density on y-axis and µGy(mR) on x-axis

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29
Q

a 12 bit CR img has ______ gray levels

A

4096

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30
Q

if the bit depth is 7 what is the dynamic range of the CR img?

A

128 shades of gray

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31
Q

CCD?

A

charged-coupled device (a silicon based semi-conductor); used in indirect conversion systems

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32
Q

____________ is the ability of the CCD to respond to a wide range of light intensity, from very dim to very bright

A

dynamic range

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33
Q

explain DR indirect system and the chems used

A

XR absorbed by thin layer of cesium iodide (changes XR to light), a scintillation phosphor, which then produces a flash of light which interacts w a layer of amorphous silicon photodiode to create electric charge (2 steps - XR to light, light to signal)

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34
Q

explain DR direct system and chems used

A

XR directly interacts w a layer of amorphous selenium, which produces the electric charge (1 step - XR to signal)

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35
Q

spatial res in DR is ______ limited

A

pixel limited (limited by pixel size)

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36
Q

TFT? f(x)?

A

(thin film transistors) absorbed rad is converted into electric signals, and that electric charge is temporarily stored in TFT until readout (the pattern of electrical charges constitute the latent img)

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37
Q

spatial frequency? whats the unit?

A

of line pairs in a given length; line pairs per millimeter (lp/mm);

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38
Q

line pair?

A

a high contrast line separated by an interspace of equal width (so it’s ONE line & ONE space)

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39
Q

spatial resolution?

A

ability to img sm objects that have high subject contrast; ability of imaging system to resolve/render on the img a sm high-contrast object

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40
Q

contrast resolution?

A

ability to distinguish many shades of gray from black to white

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41
Q

pixel size is related to ______ resolution

A

spatial res

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42
Q

laser beam diameter relates to _____ resolution of CR imaging system

A

spatial res

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43
Q

dynamic range is related to _______ resolution

A

contrast res

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44
Q

bit depth is related to _____ resolution

A

contrast res

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45
Q

how is spatial frequency related to spatial resolution?

A

(direct) higher spatial frequency –> better spatial resolution

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46
Q

what is modulation transfer f(x)?

A

the ratio of img to object as a f(x) of spatial frequency; ideal img system has MTF of 1

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47
Q

what is indicated by a low MTF?

A

the img is a closer representation of the object, giving better resolution (best MTF is 1)

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48
Q

dynamic range?

A

of shades of gray that an image system can produce

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49
Q

window level?

A

controls brightness/density in post-processing

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50
Q

window width?

A

controls contrast in post-processing

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51
Q

a higher SNR indicates ____ resolution (more/less)

A

more

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52
Q

contrast resolution is limited by _______

A

noise/SNR

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53
Q

spatial resolution in screen film radiography is determined principally by _____________

A

geometric factors (primarily focal-spot size)

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54
Q

DQE?

A

(detective quantum efficiency) measure of XR absorption efficiency; measurement of % of absorbed XRs when they hit the detector

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55
Q

Which has the highest DQE? (film, CR, DR)

A

DR

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56
Q

if a system has a dynamic range of 512, what is the bit depth?

A

9 bit

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57
Q

teleradiology

A

transfer of imgs & pt reports to remote sites

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57
Q

factors affecting spatial resolution (amount of detail present in img) of CR img? (5)

A
  1. phosphor layer thickness (thinner better)
  2. pixel size (smaller better)
  3. matrix size (bigger better)
  4. # pixels (more better)
  5. diameter of laser (smaller better)
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58
Q

in CR, which IP layer stores the latent img?

A

PSP (active layer)

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59
Q

Hounsfield scale?

A

math calculation used to assign numerical value to gray

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60
Q

which laser wavelength is better and why?

A

longer wavelength bc easier to differentiate from emitted pt info light, causing less noise

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60
Q

which laser is better? why? solid state or gas?

A

solid state bc has higher/longer wavelength

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61
Q

photomultiplier?

A

amplifies light (increases intensity –> increase signal) and sends to digitizer (which assigns values to pixels)

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62
Q

In order from best to least spatial resolution, list the systems and their spatial frequency

A
  1. mammo (15 lp/mm)
  2. film (10 lp/mm)
  3. DR (5 lp/mm)
  4. CR (3 lp/mm)
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63
Q

optical filter?

A

helps differentiate laser from pt info (to reduce noise)

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64
Q

2 causes for moiré artifact

A

laser lines II to grid lines, frequency harmonics (scanning frequency matches grid frequency)

64
Q

cones v rods

A

cones for bright/photopic vision, and rods for dim/scotopic vision

65
Q

Exposure Indicator for Fuji systems?

A

S# = 200-400, (indirect relation to exposure)

65
Q

exposure indicator for Kodak/Carestream systems?

A

Ei = 2000, (direct relation to exposure)

66
Q

exposure indicator for Agfa?

A

log mean = 2.2, (direct relation to exposure)

66
Q

4 IP artifacts, and how they appear (white/black)?

A
  1. cracks (w, - density)
  2. adhesive tape (w, - density)
  3. hair (w, - density)
  4. back scatter (b, + density)
67
Q

how do you reduce the IP artifact of backscatter?

A

collimate

67
Q

Indirect conversion system?

A

XR + CsI (Cesium Iodide) –> light;

light + a-Si (amorphous silicon) –> electric signal

68
Q

Direct conversion system?

A

XR + a-Se (amorphous selenium) –> electric charge/signal

68
Q

typical grid frequency in digi?

A

150+ lines/in

69
Q

underexposure in digi causes what?

A

quantum mottle (grainy)

69
Q

overexposure in digi causes what?

A

an affect on contrast

70
Q

all DR systems use what to temporarily store the latent img?

A

TFT

71
Q

Which network is faster?

A

LAN (PACs rooms)

72
Q

dynamic range is IDed by?

A

bit capacity of ea pixel

73
Q

principle descriptor of contrast res?

A

dynamic range

74
Q

the greater area of TFT, the greater the _____, which means ____ rad required to make img

A

DQE; less

75
Q

A bigger Hounsfield scale means what?

A

better contrast res

76
Q

what is found in the reader that helps to improve the SNR, which increases spatial resolution?

A

optical filter

77
Q

pixel pitch?

A

space btw pixels

77
Q

how do you determine pixel size?

A

FOV/matrix size (make sure they are in the same units)

77
Q

how many bytes usually constitute a word?

A

2 bytes

77
Q

+ pixel pitch –> ?

A
  • spatial res
77
Q

what do you increase to increase SNR?

A

+ mAs

77
Q

what makes up dynamic range?

A

Hounsfield scale

118
Q

shuttering?

A

(post-processing) black bg is added to original coll. edges

120
Q

dynamic range is IDed by?

A

bit capacity of ea pixel

121
Q

principle descriptor of contrast res?

A

dynamic range

122
Q

what do you increase to increase SNR?

A

+ mAs

123
Q

the greater area of TFT, the greater the _____, which means ____ rad required to make img

A

DQE; less

125
Q

A bigger Hounsfield scale means what?

A

better contrast res

126
Q

what is found in the reader that helps to improve the SNR, which increases spatial resolution?

A

optical filter

127
Q

histogram?

A

data w/in coll. area produce a graphic representation of the optimal densities (can be changed using window level/width or LUT - lookup table)

132
Q

reflective layer of IP sends light in a ______ direction and is ______ to reduce light spread

A

forward; black

133
Q

phosphor center?

A

stimulated e-‘s (from XR interaction w BFH crystals in PSP) enters conductive layer where they get trapped in a “phosphor center”

134
Q

Raster pattern

A

laser scanning beam sweeps horizontally from L to R

135
Q

photomultiplier?

A

detects (blue) light emitted from IP –> amplifies light –> sends to digitizer

136
Q

digitizer?

A

(ADC) divides analog img into matrix & assigns ea pixel a value based on brightness

137
Q

which system has the most exposure latitude?

A

digital

138
Q

how do you reduce quantum mottle?

A

+ mAs

139
Q

Europium is the _______ of PSP

A

activator

140
Q

PSP screen is handled in ________?

A

reader

141
Q

With CR, contrast is ______ regardless of exposure

A

constant

142
Q

principle source of noise in CR is?

A

scatter rad

143
Q

output signal from PSP is converted (ADC) by ________

A

photodetector

144
Q

ghosting is prevented by?

A

erasing w white light

145
Q

CR produces __________ gray levels

A

10,000

146
Q

In DR, the latent img is formed on the ____________

A

rad detector

147
Q

brightness of region is determined by what 2 things?

A

Z & mass density

148
Q

increasing FOV does what?

A

reduces spatial res (makes pixel size bigger)

149
Q

dynamic range determines contrast res and _________

A

motion blur

150
Q

what has the best spatial resolution? why?

A

mammography; highest spatial frequency (most lp/mm)

151
Q

speed determined by?

A

PSL (photostimulable luminescence); more PSL –> more speed (and less dose)

152
Q

extremities and mammo IR’s have…?

A

highest resolution

153
Q

salt and pepper effect?

A

grainy quantum mottle; salt/white - XR doesn’t reach IR; pepper/black - XR reaches IR

154
Q

what is the typical grid frequency in digi?

A

150+ lines/in

156
Q

4 IP artifacts and whether they represent pos/neg densities?

A
  1. cracks - neg (white)
  2. adhesive tape - neg
  3. hair - neg
  4. backscatter - pos (black)
157
Q

plate reader artifacts?

A

intermittent appearance of extraneous line patterns

158
Q

horizontal white lines may be caused by _____ on ____________ in plate reader

A

dirt; light guide

159
Q

loading multiple IP’s in 1 cassette can cause what?

A

ghosting

160
Q

what specific problem can cause a moire pattern plate reader artifact?

A

grid orientation (if grid lines II to plate reader’s scan lines –> grid lines SHOULD be perpendicular to plate reader’s scan lines)

161
Q

electric charge is briefly stored in ______ until readout (in both systems)

A

TFT

162
Q

DR systems use ____________________ to absorb rad & converts the energy into electrical signals which are temp. stored in TFT (constituting the latent img)

A

flat panel direct capture detector

163
Q

line spread f(x) is largest for ___________ and least for __________

A

screen-film mammo; a-Se digi mammo

164
Q

what eliminates distracting white/clear areas?

A

shuttering

165
Q

what is the data recognition program?

A

searches for the anatomy on the IR by finding the collimated edges and eliminates the scatter outside the coll.

166
Q

what happens if the data recognition program fails to find the coll. edges?

A

incorrect data collection –> img will be too bright/dark

167
Q

what is generated from the img data collected from CR sampling?

A

histogram

168
Q

what ID’s all densities on an IP in form of a graph?

A

histogram?

169
Q

what is on the x- and y-axis of a histogram?

A

x: amount of exposure read
y: # of pixels for ea. exposure

170
Q

the shape of a histogram is _________? and ______________ per part exposed

A

anatomy specific; stays fairly constant

171
Q

Nyquist theorem?

A

when sampling a signal (ADC), sampling frequency must be greater than twice the bandwidth of the input signal (so img reconstruction nearly perfect)

172
Q

3 conversions that cause loss of detail (or - res) in CR

A
  1. e- –> light
  2. light –> digi info
  3. DAC
173
Q

when _________ is greater than Nyquist frequency and ______ occurs less than 2x’s/cycle –> info is lost and a fluctuating signal is produced (called?)

A

spatial frequency; sampling

wrap around image

174
Q

wrap around img is? causing what kind of artifact?

A

2 superimposed img’s slightly out of alignment (from spatial freq.>Nyquist freq.; samplings/cycle); causes moire artifact

175
Q

what states that at least 2x’s the # of pixels needed to form the img must be sampled to combat the loss of resolution?

A

Nyquist theorem

176
Q

CT/MRI have a dynamic range of what?

A

12 bit dynamic range

177
Q

Digi Mammo has what dynamic range?

A

16 bit

178
Q

img noise limits ______ resolution

A

contrast

179
Q

spatial res. (img detail) is determined by?

A

MTF (sm better)

180
Q

contrast res. is determined by?

A

noise and SNR (bigger SNR better)

181
Q

Dose creep?

A

digi is capable of - pt dose by 20-50% but bc tech’s tend not to use optimal exposures, pt’s dose actually + w digi

182
Q

higher DQE means what?

A

less rad required to make img

183
Q

Out of DR, CR and film, which has highest and lowest DQE?

A

highest DQE - DR

lowest DQE - film

184
Q

the _____ has higher sensitivity for rad & much wider dynamic range than screen-film IRs

A

CCD

185
Q

2 types of indirect conversion systems?

A

CsI/CCD and CsI/a-Si

186
Q

_______(contrast/spatial) resolution is more important for soft tissue radiography

A

contrast

187
Q

imaging system spatial resolution is spatial frequency at ________

A

10% MTF

188
Q

with increasing spatial frequency, img ____ worsens in radiography

A

blur

189
Q

output hardware?

A

devices that translate comp info into a form ppl understand (i.e. display screens, printers)

190
Q

input hardware?

A

devices that convert data into a form comps can use (i.e. keyboards, mice, fax, scanners, etc)

191
Q

_______ allows visualization of all shades of gray

A

postprocessing

192
Q

spatial res. in screen-film radiography is determined principally by?

A

focal-spot size

193
Q

_________ is preserved in digital imaging, regardless of dose

A

contrast res.

194
Q

___________ should replace dose creep.

A

technique creep

195
Q

pt dose in DR should be _____ bc of high _____

A

low; DQE

196
Q

the ____ XR beam has lower energy than the _______ XR beam

A

scatter; primary

197
Q

7 factors that affect contrast resolution?

A
  1. IR size (sm better)
  2. coll. (+ better)
  3. overexposure ( - contrast)
  4. dynamic range/Hounsfield units (+ better)
  5. bit depth (+ better)
  6. SNR (+ better)
  7. Acquisition Error - incomplete charge transfer (electronic noise/memory artifact)

RTE 1418 (3 decks)

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