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MRT Year 1 Semester 1 > Final Review Apparatus And Image > Flashcards

Final Review Apparatus And Image Flashcards

1
Q

The slope of the characteristic curve changes?

A

More slope = more contrast

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2
Q

Pros of vertical placement of the image plate during CR reading

A
  • IP barely leaves cassette and is less likely to be damaged

- reduced occurrence of artifacts

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3
Q

What is image sampling?

A

The plate is scanned and the image location and size of signal is determined. A histogram is then generated

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4
Q

What is multiplanar reconstruction?

A

Allows you to change from an axial slice to a transverse slice, reconstructs image

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5
Q

How does window level work?

A

It increases/decreases the pixel values by the same factor to brighten or darken the image

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6
Q

Direct conversion parts, active layer material, and how it works

A

Amorphous selenium, and a TFT (thin film transistor)
Absorbs x-rays and coverts them into electrons, electrons are stored in TFT detectors
Amorphous selenium is sandwiched between two charged electrodes

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7
Q

How does density effect contrast?

A

If extremely overexposed or underexposed, the contrast will decrease

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8
Q

Synonyms for Detail

A
  • recorded detail
  • definition
  • sharpness
  • blur
  • resolution
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9
Q

How does filtration affect scatter?

A

It takes away the low energy photons and increases the penetrability of the beam
Increased filtration = decreased contrast

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10
Q

4 factors that affect radiographic image quality?

A
  • Photographic: OD and Contrast

- Geometric: detail and distortion

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11
Q

Why are imagers needed?

A
  • Backup if PACS is unavailable
  • Outside physicians
  • Legal cases
  • Teaching purposes
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12
Q

Advantages of a fixed kVp/variable mAs chart

A
  • lower dose (higher kVp settings)
  • adequate penetration of all anatomic parts
  • consistent image contrast
  • greater latitude with exposures
  • measurement of part is not critical
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13
Q

What is a histogram?

A

A graph of all of the densities that the pixels captures

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14
Q

What are imaging plate artifacts? Examples?

A
  • usually due to aging/wear
  • ex. Cracks on the plate, appear as areas of radiolucency
  • ex. Static
  • ex. Backscatter
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15
Q

Factors that control detail

A
  • Geometric unsharpness
  • Motion unsharpness
  • Image receptor unsharpness
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16
Q

Is a high SNR or low SNR better?

A

High

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17
Q

What is a review workstation?

A
  • Most interactive part of PACS
  • any computer that can be used to view a digital image
  • received image from archive or modalities for viewing
  • minor image manipulation
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18
Q

Radiographic contrast is the product of what?

A

Image receptor contrast and subject contrast

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19
Q

Why is the light filtered before it reaches the photodetector during CR reading?

A

So that none of the stimulation light swamps the emitted light signal

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20
Q

Purpose of the layers of film and what they’re made of

A

Film base: polyester or plastic, foundation of film that allows us to handle it
Emulsion: silver halide crystals suspended in gelatin, radiation and light sensitive layer
Adhesive layer: holds base and emulsion together
Supercoat/Overcoat: hard gelatin, protective layer to prevent damage to the emulsion layer beneath it

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21
Q

Is overexposure or underexposure ideal for the patient (EI numbers)

A

Underexposure

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22
Q

Radiographic contrast is a result of….?

A

Differential absorption

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23
Q

Line pairs consist of?

A

-Lead strip: line
-Air space: space
Together they are a line pair

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24
Q

How does phosphor size and thickness affect speed?

A

Greater size and thickness= higher speed

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25
Q

Network connections

A
  • Wired

- Wireless

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26
Q

2 types of magnification?

A
  • Magnifying glass function: a box placed over a section of anatomy shows a magnified version of that section
  • Zoom: enlarges the entire image, need mouse to navigate because too large for screen
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27
Q

What is causal repeat rate? Formula?

A 
Percentage of repeats from a specific cause
# of repeats from a specific cause / total # of repeats x100
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28
Q

How to decrease focal spot blur

A
  • use smallest focal spot possible
  • largest SID
  • smallest OID
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29
Q

What is health level seven (HL-7)

A
  • universal standards used for most clinical and administrative data
  • used for communication between HIS and RIS
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30
Q

2 types of spatial frequency filtering?

A
  • High pass filtering: when frequencies are amplified, increases contrast and edge enhancement
  • Low pass filtering: when frequencies are suppressed, smoothing, decrease contrast
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31
Q

Repeat rate maximums for different departments

A

General x-ray: less than 4-6%

Mammography: less than 5%

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32
Q

3 types of x-ray tube charts

A
  • Radiographic rating chart
  • Anode cooling chart
  • Housing cooling chart
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33
Q

What is a CCD (charged couple device)

A

Is a photodetector and electronics embedded into a silicon chip
Converts light to an electric charge and stores it
Charge is released to the ADC (analog to digital converter)

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34
Q

Advantages to digital imaging

A
  • wider range of exposure
  • linear response
  • greater density range
  • easily manipulated with computer
  • post processing
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35
Q

What is bit depth and what does it mean?

A

-the number of bits in a pixel
-the number of greys a pixel can produce
Ex. 8 bit = 2^8 = 256 greys

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36
Q

Configurations of RAID

A
  • DAS: direct attached storage, couples to system with cable connections
  • NAS: network attached storage, stand alone RAID arrays attached to network
  • SAN: storage area network, high speed, special purpose network that link data storage devices with data servers
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37
Q

Exposure indicators represent?

A

The average gray shade values of the image

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38
Q

DQE

A
  • Detective quantum efficiency

- % of x-rays absorbed by the screen

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39
Q

What has the greatest effect on geometric unsharpness?

A

OID

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40
Q

Formula to calculate magnification factor

A

MF = SID/SOD

MF= image size/object size

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41
Q

3 components of film

A
  • Cassette
  • Intensifying screen
  • Film
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42
Q

Purpose of Anode Cooling Chart?

A

Shows maximum heat capacity for anode and how long it will take to completely cool

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43
Q

How direct conversion works

A
  • Charge is applied from top surface of amorphous selenium layer
  • Ionization from radiation causes selenium to release electrons
  • Free electrons are collected at the bottom of the selenium layer
  • Charged collected by a storage capacitor and read out line by line by the TFT to the computer
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44
Q

Define low subject contrast

A

Anatomy with similar tissue types (types that absorb the photons similarly)

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45
Q

Layers of film

A
  • Film Base/base layer
  • Emulsion
  • Adhesive Layer
  • Supercoat/Overcoat
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46
Q

Factors that limit detail

A
  • phosphor size
  • layer thickness
  • concentration
  • scanning of the screen and processing
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47
Q

2 types of luminescence

A
  • Fluorescence: light it emitted only while being stimulated

- Phosphorescence: light is emitted even after stimulation

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48
Q

2 types of scintillator material and what does a scintillator do?

A

-Cesium Iodide (CsI)
-Gadolinium Oxysulfide (Gd2O2S)
Converts x-rays to light

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49
Q

Slope of the line is drawn between the point corresponding to OD 0.25-2 above the base and fog densities.

A

Add 0.25 and then add 2 to that and in between is your slope

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50
Q

How does fill factor affect resolution?

A

Higher fill factor (area of detector that is light sensitive) = higher resolution

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51
Q

How does magnification affect blur?

A

More magnification = more blur

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52
Q

If you have a technique chart do you still need to assess the patient and adjust technical factors accordingly?

A

Yes

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53
Q

Network classifications

A
  • LAN: local area network, linked computers that are close together
  • WAN: wide area network, computers that are far apart, connected by telephone lines, cables, or radio waves, internet
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54
Q

Layers of the intensifying screen

A
  • Protective layer
  • Phosphor layer
  • Reflecting layer
  • Base
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55
Q

Layers of intensifying screen

A
  • Protective Coating
  • Phosphor Layer
  • Reflective Layer
  • Base
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56
Q

What do array processors do?

A

Allow us to see the image instantaneously, puts all the info together into an image

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57
Q

What is an intensifying screen?

A

Device found in cassettes containing phosphors to convert x-rays into light which then exposes the film

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58
Q

Why are digitizers needed?

A
  • teleradiology
  • comparison
  • duplication
  • computer aided diagnosis
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59
Q

4 main types of artifacts

A
  • Image plate artifacts
  • Plate reader artifacts
  • Image processing artifacts
  • Printer artifacts
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60
Q

What is image stitching?

A

When 2 or more images or combined to create one image

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61
Q

Why do we need technique charts?

A

To provide a level of consistency among images and radiographers

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62
Q

Characteristics of a digital image

A
  • spatial resolution
  • contrast resolution
  • noise
  • dose efficiency (of the IR)
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63
Q

2 methods of image compression

A
  • Lossy: reduced storage by eliminating information

- Lossless: exact replica of original

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64
Q

What is the fast scan mechanism?

A

When a laser is deflected across the image plate during reading

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65
Q

Advantages of digital

A
  • Wide exposure latitude: detect a lot of greys
  • Reduction in repeats
  • Can compensate for over/under exposure
  • Environmentally friendly
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66
Q

Film base plus fog

A

Base: colour added to the film base
Fog: any exposure during storage, contamination, storage

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67
Q

What is dynamic range?

A

The ability to respond to varying levels of exposure (how many greys the system can detect)

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68
Q

List and describe the role of the two types of contrast media

A
  • Positive contrast agent: high atomic number, absorbs more photons, appears white
  • Negative contrast agent: low atomic number, transmits more photons, appears black
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69
Q

When critiquing an image, techs must…

A

Magnify the image to check for noise or overexposure (burnout/saturation)

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70
Q

With an LCD monitor, what is response rate?

A

The amount of time for crystal to go from off state to on and vice versa

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71
Q

Why are beam shaping optics required during CR reading

A

To correct/even out the shape/intensity of the laser across the image plate

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72
Q

Why do we need LUTs?

A

Without it the images would look very low contrast because too many greys are able to be recorded.

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73
Q

Exposure indicators are affected by?

A
  • technical factors
  • histogram analysis errors
  • patient positioning
  • image processing algorithms
  • SID
  • collimation
  • beam centering
  • artifacts
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74
Q

What is offset correction?

A

Corrects image lag, determines the amount of signal inherent in the detector, creates a mask of residual signal

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75
Q

What is a matrix?

A

A display of the shades of grey of each pixel as numerical values

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76
Q

Advantages of repeat analysis

A
  • improved department efficiency
  • lower costs
  • lower patient dose
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77
Q

Image receptor speeds affect what?

A
  • Radiation sensitivity
  • Density
  • Dose
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78
Q

What does automatic rescaling do?

A

Produces an image with uniform density and contrast regardless of exposure-fixes under/over exposure to look good

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79
Q

In CRT monitors, what is the refresh rate?

A

How fast the monitor rewrites the screen “flicker” sometimes seen

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80
Q

What is fill factor?

A

% of the pixel face that is sensitive to x-rays

-Approx. 80% meaning 20% of the x-ray beam doesn’t contribute to the image

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81
Q

PACS fundamentals

A
  • Image acquisition
  • Display workstations
  • Archiving
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82
Q

S numbers

A

Sensitivity numbers

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83
Q

How does electron beam scanning work in a CRT monitor?

A

Starts in upper left corner and scans across the glass from side to side, top to bottom

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84
Q

Purpose of layers of intensifying screens

A
  • Protective Coating: protect active layer
  • Phosphor: converts x rays into light
  • Reflective Layer: reflects light toward film to enhance efficiency
  • Base: mechanical support for active layer
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85
Q

Intensification Factor

A

Exposure without screen/ exposure with screen

Gives information about patient dose

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86
Q

Cons of intensifying screens

A

Recorded detail is reduced because of increased blur

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87
Q

How to minimize shape distortion

A

Proper alignment of:

  • x-ray tube
  • part
  • IR
  • Entry/exit point of CR
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88
Q

How does screen speed affect dose?

A

Higher speed= lower dose

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89
Q

Types of Networks

A
  • Peer-to-peer: every computer is considered equal
  • Client-Server based: server-facilitates communication between and delivers info to clients, clients-request information
90
Q

CD/DVD burners

A
  • less costly than printing films

- have DICOM viewer and minor enhancements are possible

91
Q

We can minimize distortion with careful attention to?

A
  • distances
  • central ray
  • patient position
  • IR position
92
Q

2 reasons image processing artifacts occur

A
  • incorrect part position

- incorrect sampling

93
Q

HU are calculated by

A

Heat Units = kVp x mA x time x modification factor

94
Q

Common functions of workstations

A
  • navigation
  • image manipulation/enhancement
  • image management
  • advanced
95
Q

What is image orientation?

A

The way the anatomy is oriented on the CR or detector

96
Q

Types of distortion

A

Size: magnification
Shape: elongation, foreshortening

97
Q

What is volume rendering technique?

A

Similar to MIP, but can assign colours to the different densities

98
Q

Technologist workstation

A
  • for reviewing images after acquisition
  • Q/C station
  • can make minor adjustments before sending
99
Q

Total repeat rate formula

A

of repeats / total # of views x100

100
Q

How does the data recognition program work?

A

Finds the collimation edges and eliminates scatter outside of the collimation

101
Q

What is directly related to magnification?

A

OID

102
Q

What is edge enhancement?

A

When fewer pixels are used for the averaging, the fewer pixels used, the greater the enhancement

103
Q

Limitations of film

A
  • Limited dynamic range
  • Cost
  • Time
  • Film processors
  • Permanent
  • Can’t be stored electronically
104
Q

What is the purpose of the intensifying screen?

A

Reduces patient dose because it converts x-rays to light (image will consist of not just x-rays but light)
Decreases resolution

105
Q

Speed

A

Ability of an image receptor to respond to an x-ray exposure

Measure of sensitivity

106
Q

On a characteristic curve, the slope is the contrast

A

.

107
Q

What is photostimuable luminescence?

A

When the metastable electrons are stimulated by a laser and release visible light

108
Q

Cesium Iodide vs. Gadolinium Oxysulfide

A

CsI: manufactured in thin crystal columns that direct light down to the TFT, higher spatial resolution due to less light spread
Gd2O2S: random, unstructured (turbid) crystal layer, light can escape through air pockets before reaching TFT, lower spatial resolution, good for rugged applications

109
Q

SNR

A

Signal to noise ratio
Signal: meaningful pattern of information
Noise: chaotic pattern, no info- quantum noise, electronic noise

110
Q

How does phosphor size affect detail?

A

Larger phosphor = less recorded detail

111
Q

RAID

A

Redundant array of independent discs: several magnetic discs that are linked as an array

112
Q

Purpose of europium in CR

A

To capture energy during interaction process-no latent image without it
Keep electrons in excited state as latent image

113
Q

What is a network?

A

A group of 2 or more computers linked together

114
Q

How does screen speed affect detail?

A

High speed= less detail

115
Q

How does an LCD monitor work? What does it consist of?

A
  • 2 pieces of polarized glass with a liquid crystal layer between the 2
  • images are produces by shining/reflecting light through the crystal layer and a series of colour filters
116
Q

Human errors that cause artifacts

A
  • Collimation: can result in improper histogram
  • Cassette use: cassette upside down
  • Technical factors: over/under exposure
117
Q

What does the TFT (thin film transisitor) do?

A

Light hits pixels and is converted to an electrical signal

TFT reacts like a switch to send electrical charge to image processor

118
Q

How are values outside the set window width seen?

A

As either black or white. Anything inside the window width is grey

119
Q

Screen speeds

A

Described efficiency of x-ray conversions to light

Calcium tungstate is used as a basis of comparison (100)

120
Q

Different types of long term storage

A
  • RAID
  • Optical disc: MOD, DVD, ultra density optical
  • Tape
  • Magnetic disc
121
Q

Changing speeds formula

A

RS1/ RS2 = mAs2/ mAs1

122
Q

What is shuttering/masking?

A

Automatic shuttering is used to black out the white collimation borders eliminating veil glare

123
Q

Purpose of cassette

A

The container for intensifying screen and film

124
Q

Phosphor factors that affect the image (4)

A
  • Material Composition: calcium tungstate vs rare earth
  • Thickness of the layer: thicker layer increases DQE
  • Concentration: more concentrated = higher screen speed
  • Size of phosphor: larger = more light produced per x-ray interaction
125
Q

What does image management consist of?

A
  • Modification of demographic info
  • query/retrieve function
  • CD burning
  • Printing
126
Q

Network topologies

A
  • Star: most common, devices connected to a central hub/switch
  • Bus: all devices physically attached to and listen for communication on a single wire
  • Ring: devices connected in a circle, info only travels one way
  • Mesh: multiple pathways connect devices and network
127
Q

What is gain calibration?

A

Corrects flaws in the detector, fills in white spots (dead pixels) with grey

128
Q

EI_s

A

Exposure index sensitivity

129
Q

Types of workstations

A
  • Review workstations
  • Radiologist workstation
  • Technologist workstation
  • Image management workstation
130
Q

2 Primary factors that affect the resolution of all types of digital imaging systems?

A
  • Geometric properties of the IR

- image processing system

131
Q

PSP phosphor layer arrangements and what they are activated by

A

Turbid: random distribution of phosphor crystals
Structured: columnar phosphor crystals

Activated by barium flurorohalide or europium

132
Q

Another name for high contrast is?

A

Short scale

133
Q

What is maximal and minimal intensity projection?

A

Used for visualizing vessels and air filled structure, makes the, 3-D

134
Q

Two types of technique charts

A
  • Variable kVp/Fixed mAs: +2 kVp for every additional cm of part thickness, accurate measuring is critical, only effective for peds and small extremities
  • Fixed kVp/ Variable mAs: selects optimal kVp and adjusts mAs for variations in part thickness, mAs x2 for every 4-5cm in part thickness
135
Q

How does decreasing OID decrease blur?

A

Less room for diverging rays between patient and IR

136
Q

On a histogram, values at the left are more black or white?

A

Left: black
Right: white

137
Q

What is aspect ratio?

A

Ratio of the width of the monitor to the height of the monitor

138
Q

What allows additional information to be added to the image?

A

Image annotation

139
Q

What is recorded detail?

A

-degree of sharpness of structural lines on a radiograph

140
Q

Refers to the amount of exposure received by the IR

A

Exposure indicators

141
Q

Resolution is the combination of?

A
  • Spatial resolution: ability to image small objects

- Contrast resolution: ability to distinguish between two objects with similar subject contrast

142
Q

Factors that affect geometric unsharpness

A
  • Focal spot size: ranges from 0.1-3.0mm

- Distance: SID and OID

143
Q

What is repeat analysis and why is it useful?

A

Where rejected images are catalogued and classified with reasons for repeat
Provides info regarding equipment, performance, department procedures, and staff skill levels

144
Q

Radiologist workstation

A
  • has highest quality software and the best monitor
  • requires little downtime
  • has access to nearby RIS, connected to PACS
145
Q

Digital radiography consists of what 2 things?

A

DR: direct radiography
CR: computed radiography

146
Q

Primary parts of the CR system

A
  • Cassette
  • PSP plate (inside cassette)
  • Cassette/CR Reader
  • Computer work station
147
Q

What does PACS do?

A

Allows the integration of many systems

148
Q

Purpose of radiographic rating chart?

A

Provides info about which radiographic techniques are safe for the x-ray tube.
Different charts for focal spot, speed of anode rotation, target angle, and voltage rectification

149
Q

What part is the basic picture element on a display?

A

Pixels

150
Q

2 main types of imagers (printers)

A
  • Wet imager: uses chemicals to process film, needs darkroom

- Dry laser imager: uses heat to process film, exposed with laser, quality slightly lower, takes up less space

151
Q

What is the controlling factor of radiographic contrast?

A

kVp

152
Q

What is DICOM

A

Set of standards for medical image interchange, allows images to be viewed and processed by many different types/brands of devices

153
Q

Uncontrolled speed factors

A
  • Phosphor composition
  • Phosphor thickness
  • Reflective layer (has or doesn’t have)
  • Dye in phosphor layer
  • Crystal size
  • Crystal concentration
154
Q

Distortion is directly related to?

A

Positioning

155
Q

With a Q/C program in place, most repeats are due to?

A

Positioning errors

156
Q

Is there more or less distortion with a thick object? With an irregular shaped object?

A

More distortion with both

157
Q

How does window width affect contrast?

A

Wider window width = less contrast because more shades of grey

158
Q

What are Look Up Tables?

A

Manipulates the histogram values to change density/contrast on an image based on an ideal image of that body part

159
Q

Define radiographic contrast

A

The difference in OD between adjacent structures

160
Q

How an image in acquired- CR

A
  • PSP plate is exposed to x-rays, phosphor atoms are ionized
  • electrons are excited into metastable state and form the latent image
  • laser beam of light is directed at PSP
  • metastable electrons return to ground state and emit visible light
  • light is detected and measured by photodetector
  • phosphor is flooded with intense light to erase any leftover latent image
161
Q

What is shade surface display?

A

Used a range of pixel intensity values and everything below is removed, everything above with be assigned a colour and shown as a 3-D object

162
Q

What is image lag?

A

Image taken before the detector has released all of the signal from the previous image, looks like a double exposure
-caused by images taken too quickly back to back, overexposure, area with little beam attenutation

163
Q

Less blur on the anode side

A

.

164
Q

Gradient on a characteristic curve

A

Slope of the tangent at any point on the curve
Toe gradient: more important than average because many clinical ODs appear in this region
Shoulder Gradient: more important in mammography

165
Q

2 main types of film digitizers

A
  • Laser film digitizer: “gold standard”, expensive, Q/C and maintenance critical
  • CCD film digitizer: less expensive, slower
166
Q

Parts of an indirect conversion detector

A
  • Scintillator

- TFT or CCD (charged coupled device)

167
Q

How to intensifying screens affect patient dose

A

Decrease because less mAs is required to obtain exposure (using light as well as x-rays)

168
Q

Factors that affect scatter and how they affect contrast

A
  • Grids: absorb scatter before it hits IR. Less scatter = increase contrast
  • Collimation: more matter more scatter, less matter less scatter
  • OID: increase OID means that more scatter will miss the IR = increase contrast
169
Q

CE

A
  • Conversion efficiency

- amount of light emitted for each x-ray absorbed

170
Q

Controllable speed factors

A
  • Radiation quality: high kVP = high IF
  • Processing
  • Temperature: higher IF @ lower temp
171
Q

Levels of RAID

A

-expands to level 11
-most common: 0, 1, 3, 5
Most PACS use RAID 5

172
Q

What is contrast media used to image?

A

Anatomy with low subject contrast

173
Q

Quantum Mottle

A

Not enough radiation hits the IR
Appears splotchy, mottles, grainy
Decreases image detail
Need to increase mAs to correct it

174
Q

Modification factors of types of generators

A

Single phase: 1.0
3 phase: 1.4
High frequency: 1.4

175
Q

What is Moiré artifact?

A
  • a plate reader artifact

- when grid lines run parallel with laser scan direction lines are seen on the image

176
Q

How does increasing SID reduce blur?

A

Straighter rays hitting the anatomy

blur on the sides misses the IR

177
Q

Most important factor for spatial resolution

A

Focal spot blur

High contrast objects that are smaller than the focal spot blue can’t be imaged

178
Q

What is resolution?

A

-the ability of an imaging system to distinguish between two adjacent structures
Expressed in line pairs per millimeter (lp/mm)

179
Q

What contains the pixels?

A

Photodetector

Amorphous silicon

180
Q

Spectral Matching

A

Film sensitivity must be properly matched to the spectrum of light emitted by the screen (green to green, red to red)

181
Q

Only direct transmission photons hitting the IR would result in high or low contrast?

A

Extremely high contrast because no scatter

182
Q

What is the slow scan mechanism?

A

The image plate of the cassette is moved at a constant rate along the horizontal axis during reading

183
Q

Only indirect transmission hitting the IR would result in what?

A

No image, only grey because of so much scatter

184
Q

How does image receptor speed affect unsharpness on the image?

A

Faster IR = more unsharpness

185
Q

What is window width sometimes called?

A

Grey scale expansion or compression

186
Q

What does a CRT monitor consist of and how does it work?

A
  • Cathode and anode in a vacuum tube

- works like an x-ray tube

187
Q

3 types of computers found on a network

A
  • Server: manages resources for other computers, data storage etc.
  • Thick client: computer that can work independently from the network, can process and manage its own files
  • Thin client: requires a server to complete its tasks, requests services and resources from server
188
Q

2 types of detectors

A
  • Direct conversion: immediate conversion into electrical signal
  • Indirect conversion: x-rays converted to light and then light converted to electrical signal
189
Q

What is dot pitch?

A

How close the dots are in the pixel, smaller dot pitch = higher resolution

190
Q

PSP plate layers

A
  • Protective layer
  • Phosphor layer
  • reflective layer
  • conductive layer
  • support layer
191
Q

List some subject factors that affect radiographic contrast

A
  • Anatomy
  • Thickness
  • Composition
192
Q

Image management workstation

A

-used to look up exams or print copies

193
Q

What do window level and width do?

A

Window level: adjusts brightness

Window width: adjusts contrast

194
Q

What will happen to radiographic contrast if the kVp is increase?

A

Contrast will decrease because less absorption and more scatter

195
Q

Nyquist Theorum: if too few pixels are sampled what happens?

A

There will be a loss of resolution on the image

196
Q

Smallest element on a digital image?

A

Pixel

197
Q

What does the Nyquist Theorum state?

A

When sampling a signal, the sampling frequency must be greater than twice the frequency of the input signal so you’ll have accurate reconstruction of the original image

198
Q

What is the primary purpose of radiographic imaging?

A

To transfer the information from the x-ray beam to the eye

199
Q

Factors that affect recorded detail for film/screen systems?

A
  • phosphor size
  • phosphor layer thickness
  • phosphor concentration
  • film screen contact
200
Q

What is image acquisition with regards to PACS?

A

Images are acquired in a digital format and can be transferred by a computer network

201
Q

What are artifacts?

A

Any undesirable density on the processed image

202
Q

Latitude in Digital Imaging

A

The amount of error that can be made and still maintain and quality image
200% above ideal exposure
50% below ideal exposure

203
Q

Latitude

A
  • range of exposures that the image receptor can display
  • wider latitude: lower contrast
  • narrow latitude: higher contrast
204
Q

How does pixel size affect detail?

A

Smaller pixel = greater detail

205
Q

Two types of monitors

A
  • CRT: cathode ray tube

- LCD: liquid crystal display

206
Q

What is Aliasing?

A

An image produced that looks like two superimposed images just slightly misaligned

207
Q

What is repeat rate affected by?

A
  • Quality of equipment
  • Staff skill level
  • Patient type
  • Data collection method
  • Shift
  • Radiologist
208
Q

A computer consists of?

A
  • input devices
  • output devices
  • processing devices
209
Q

Shape distortion can occur from?

A
  • inaccurate central ray alignment of the tube
  • inaccurate alignment of the part- (foreshortening)
  • Inaccurate alignment of the IR- (elongating)
210
Q

2 categories of PACS archiving

A
  • Image manager: contains master database of everything in archive, receipt, retrieval, and distribution of the images stored
  • Image storage or archive server: physical storage of archive system, short/medium/long term
211
Q

2 types of patient motion?

A
  • Involuntary

- Voluntary

212
Q

What is reject film?

A
  • Scrap film

- anything that did not require a repeat on a patient (test images, Q/C etc)

213
Q

Purpose of layers of a PSP plate

A
  • Protective Layer: protect phosphor layer
  • Phosphor layer: active layer traps electrons during exposure
  • Reflective layer: reflects light released during reading phase
  • Conductive layer: reduces/conducts away static electricity
  • Support layer: sturdy material to give structure to plate
214
Q

How do line pairs affect resolution?

A

More line pairs= high resolution=higher recorded detail

215
Q

What is quantum mottle?

A

The image is formed mostly by light and not by x-rays. Not enough x-rays hit the IR and it looks grainy. Quantum noise is what we see

216
Q

What are HIS, RIS, and EMR?

A

HIS: hospital info system, holds patient’s full medical info
RIS: radiology info system, holds all radiology specific info
EMR: electronic medical record, contains all of the patients records

217
Q

The most detrimental effect on recorded detail?

A

Motion unsharpness: motion of anatomy, tube, or IR

218
Q

Flat panel artifacts

A
  • dead pixels

- incorrect gain calibration

219
Q

Plate reader artifacts

A
  • line patterns that appear randomly on the image (issue with electronics
  • if multiple IPs are loaded into a cassette
  • insufficient erasure
220
Q

Types of film

A
  • Direct exposure: non-screen film, single emulsion, requires more exposure
  • Specialty film: for copies, already exposed to max OD
  • Screen film: most widely used, single/double emulsion
221
Q

Purpose of the housing cooling chart?

A

Max heat capacity for the housing and how long it will take to cool

MRT Year 1 Semester 1 (9 decks)

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