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XR220 Image Production and Evaluation II > Digital, PACS, Artifacts. > Flashcards

Digital, PACS, Artifacts. Flashcards

1
Q

DR utilizes an array of electronic x-ray detectors that take the remnant beam &

A

convert it to electronic signals to make available to the computer

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2
Q

In DR detectors, the materials used for detecting the x-ray signal and the sensors are

A

permanently enclosed inside a rigid protective housing

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3
Q

The permanent location of the detectors of a DR system is usually:

A

usually just below the radiographic tabletop, where the Bucky tray is

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4
Q

The image receptor can vary in:

A

size. 14 x 14, 14 x 17, or 17 x 17 inches

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5
Q

Electronic direct readout detectors are what differentiate

A

DR from CR.

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6
Q

Examples of types of collection elements:

A

Photodiodes
Charge-coupled devices (CCD)
Complementary Metal Oxide Semiconductors (CMOS) or
Thin-film transistors (TFT)

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7
Q

The CCD and photodiode are light sensitive devices that

A

collect light photons.

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8
Q

The photoconductor utilizes

A

specialized pixels that convert x-rays into light

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9
Q

The TFT is a charge-sensitive device that

A

collects electrons and creates the signal.

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10
Q

The DR flat panel image receptor consists of

A

an array of detectors and thin film transistors (TFT)

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11
Q

Exit radiation interacts with the detector and an electrical charge is created
This charge is stored temporarily in the

A

transistor (TFT) until ready to be read out.

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12
Q

The pattern of electrical charges is what makes up the

A

latent image.

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13
Q

There are two types of flat panel detectors utilized:

A

Direct and Indirect. They differ in how the x-ray exposure is converted to an electric charge

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14
Q

Thin-film transistor (TFT) detector arrays may be used in

A

both direct and indirect-conversion detectors

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15
Q

X-ray photons are absorbed by a scintillator, which is

A

a radiation-conversion material

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16
Q

In direct conversion, a scintillator absorbs x-rays and converts them to:

A

electrons which are stored in the TFT detectors

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17
Q

The TFT absorbs the electrons and does what with them?

A

generates electrical charges

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18
Q

The scintillator used in direct conversion is:

A

amorphous selenium

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19
Q

The thin film transistor is an array of:

A

small pixels which absorb electrons and generates electrical charges.

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20
Q

The thin film transistor reacts like ______ to send the electrical charges to the image processor

A

a switch

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21
Q

How many pixels can be read and converted to a composite digital image in less than 1 second?

A

Over 1 million.

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22
Q

Indirect also uses TFT technology

The difference is:

A

that indirect has a two-step process:

1) x-ray photons are converted to light
2) light photons are converted to an electrical signal

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23
Q

The scintillator in indirect conversion converts X-rays into:

A

visible light.

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24
Q

The scintillator in indirect conversion is made up of:

A 
Cesium iodide (CsI)
Gadolinium -  Rare-earth element used in intensifying screens
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25
Q

After the indirect conversion scintillator converts X-rays into light, the light is then converted into an electric charge by

A

photodetectors such as:
Amorphous silicon photodiode
Charge-coupled devices (CCDs)

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26
Q

Cesium Iodide Crystals are crystalline needles that act as:

A

light directing tubes (much like fiber optics).

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27
Q

What is the benefit of using cesium iodide crystals as a scintillator?

A

This process allows greater detection of x-rays because there is almost no light spread therefore creating better resolution

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28
Q

CsI has a high capture rate because of

A

its high atomic number

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29
Q

Since x-ray interaction with CsI is high it results in

A

low patient dose

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30
Q

CsI needles absorb the x-ray photons, convert their energy into light & channels it to the

A

amorphous silicon photodiode array.

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31
Q

Indirect conversion by CsI crystalline needles process X-ray photons with _______ and very _____.

A

low noise, quickly. Approximately 30 million pixels/sec)

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32
Q

What is is the oldest indirect-conversion DR system?

A

Charge Coupled Device

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33
Q

Within charged couple devices, the light from the phosphor is linked by _______ to the CCD array

A

fiber optic bundles

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34
Q

After the image is transferred to the charge coupled device it

A

converts the light into an electrical charge

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35
Q

Where is the charge created within a charge coupled device sent to?

A

an analog-digital converter

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36
Q

Even though these CCD-based detectors require special equipment they are:

A

widely available and relatively low cost

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37
Q

The advantages of CCD are:

A

Sensitivity
Dynamic Range
Size

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38
Q

Sensitivity of a charge coupled device:

A

the ability of the CCD to detect and respond to very low levels of visible light

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39
Q

Dynamic range of a charge coupled device:

A

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

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40
Q

Size of a charge coupled device:

A

CCD is very small making it highly adaptable to DR (1-2cm)

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41
Q

Complementary Metal Oxide Semiconductor (CMOS) Indirect conversion

A

A system that utilizes special pixel sensors that convert x-rays into light photons

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42
Q

Each sensor in CMOS has an amplifier which:

A

converts the light photons into electrical charges.
This charge is converted by an analog-to-digital converter.
Takes up less space/highly efficient.

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43
Q

CCD vs. CMOS

A
  • CMOS more susceptible to noise
  • Light sensitivity, resolution and quality slightly less than CCD
  • Uses very little power compared to CCD
  • CMOS costs less
  • Less pixel fill factor with CMOS
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44
Q

Regardless of type of digital imaging system the varying electrical signals are sent to

A

the ADC for conversion into digital data

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45
Q

Digitized x-ray intensities or pixels are patterned in computer to form

A

the image matrix

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46
Q

Image matrix is

A

digital composite of varying x-ray intensities exiting the pt

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47
Q

DQE is

A

a measurement of x-rays that are absorbed when they hit the detector

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48
Q

DQE shows

A

how efficiently a system converts the x-ray input signal into a useful output image

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49
Q

Systems with higher quantum efficiency can produce

A

higher quality images at lower dose

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50
Q

Both indirect & direct DR has increased DQE over CR

In addition to this, direct conversion has:

A

increased DQE because there is no light conversion step, no light spread and therefore no light to blur the recorded signal output

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51
Q

Detector size is critical

They must be

A

large enough to cover the entire area to be imaged and small enough to be practical

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52
Q

In DR the ________ size determines resolution

A

Detector ELement (DEL)

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53
Q

The major cause of noise in the digital system is

A

electronic noise. This is the main factor limiting quality.

If not enough time is allowed for signal conversion the image will suffer.

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54
Q

electronic memory artifact

A

If exposures are taken in too rapid sequences, there may not be enough time for each previous exposure to transfer the entire signal

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55
Q

Preprocessing

A

takes place in the computer where the algorithms determine the image histogram

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56
Q

Postprocessing

A

is done by the technologist through various user functions. This is when exposure errors are corrected

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57
Q

Postprocessing Image Enhancement

A

Once the image is converted into digital (numerical) data the computer can perform post processing image enhancement.

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58
Q

The data within the collimated area produce a graphic representation of the optimal densities called

A

a histogram

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59
Q

image sampling

A

the plate is scanned and the image’s location and orientation are determined.
Size of signal is determined and a value is placed on each pixel.
A histogram is generated from the image data.

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60
Q

sampling:

A

the intensity of light or radiation from each pixel is measured by the detectors

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61
Q

Each histogram varies for:

A

each body part (anatomy specific)

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62
Q

What are the values of the x axis and y axis on a histogram?

A

x-axis is the amount of exposure read
y-axis is the number of pixels for each exposure
(how often pixels occurred and how many pixels were recorded)

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63
Q

Automatic rescaling:

A

means that the images are produced with uniform density and contrast, regardless of the amount of exposure

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64
Q

Automatic rescaling can result in:

A 
Quantum mottle (too little exposure)
Loss of contrast and loss of distinct edges (too much exposure)
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65
Q

Equalization

A

another software in which you are able to brighten a specific area

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66
Q

The LUT (Look Up Table) is used as

A

a reference to evaluate the raw information and correct the light values

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67
Q

LUT are data stored in the computer that is used to

A

substitute new values for each pixel during the processing

68
Q

There is a LUT for every anatomic part

The appropriate LUT is automatically selected to give desired contrast characteristics to

A

match the type procedure

69
Q

The LUT can be graphed by plotting the

A

original values on the horizontal axis and the new values on the vertical axis

70
Q

Using the Look Up Table, Contrast can be increased or decreased by

A

changing the slope of this graph.

Brightness (density) can be increased or decreased by moving the line up or down the y-axis

71
Q

Latitude refers to

A

the amount of error that can be made and still result in the capture of a quality image

72
Q

The exposure latitude is much ______ for digital than that of screen/film

A

greater

73
Q

If exposure is more than 50% below the ideal exposure then

A

quantum mottle results

74
Q

If the exposure is more than 200% above the ideal exposure then __________ results

A

contrast loss

75
Q

The biggest difference between digital and film/screen radiography lies in the ability to

A

manipulate the digitized pixel values that leads to greater exposure latitude

76
Q

there is less _______ latitude with digital as compared to film/screen.

A

positioning

77
Q

When positioning in DR, Beam, part and receptor alignment must be

A

right on in order to get a properly exposed image

78
Q

In digital detectors where x-ray photon energy stimulates a phosphor there is always a spreading of light. The more light spread:

A

the less the image looks like the object and the lower the Modulation Transfer Function (MTF)

79
Q

Modulation transfer function is

A

a numeric value that is used to measure spatial resolution. It is obtained from a graph utilizing numbers from 0 to 1 (0% to 100%)

80
Q

MTF (Modulation transfer function) is a ratio of the image to the object so if a system is perfect it would have an MTF of

A

100% or if measured on a scale of 0 to 1 the MTF would be 1

81
Q

“Formula” for MTF (Modulation transfer function):

A

MTF= information recorded in an image

information available in the part

82
Q

When any component of the system is compromised the overall quality of the system is affected
MTF is showing us

A

if each system is “doing its part “ to contribute to the efficiency of the entire system

83
Q

Types of Postprocessing Techniques:

A

Subtraction
Contrast Enhancement
Edge Enhancement
Black/white reversal

84
Q

Subtraction

A

Removes superimposed structures to make anatomic area of interest more visible

85
Q

Contrast Enhancement

A

Alters the pixel values to display different brightness levels

86
Q

Edge Enhancement

A

Improves visibility & accentuates lines between difference adjacent tissues.
Should be viewed with & without edge enhancement so as not to miss any details that may be obscured by enhancement process.

87
Q

Black/white reversal

A

Reverses the gray scale from the original radiograph

88
Q

Smoothing

A

Filtering process that suppresses image noise by averaging pixel frequency with surrounding pixel values

89
Q

Disadvantages to smoothing:

A

Reduction in noise comes with a reduction in contrast

Some spatial resolution is sacrificed

90
Q

Edge Enhancement is useful for:

A

larger structures such as organs & soft tissues

91
Q

Smoothing is useful for:

A

viewing smaller structures

92
Q

Digital images can be altered while being viewed on a CRT and then printed onto film by

A

a laser camera.

93
Q

Laser printers - describe wet & dry

A

Wet – use liquid chemicals (developer & fixer)

Dry – chemicals are part of the film (image created by use of heat)

94
Q

Digital vs. film-screen – computer has the ability to adjust density to

A

compensate for technique errors

95
Q

Transformation from analog to digital results in

A

loss of info

96
Q

Flat panel direct capture detectors improved spatial resolution compared to

A

CR

97
Q

Pixel size – major factor in level of

A

spatial resolution

98
Q

High resolution monitors (1000 lines) have

A

improved image display.

2000-line resolution have been recommended

99
Q

Because the range of stored densities in the computer is so much wider than what we can see, the digital image is only a small part of total data obtained by the computer
Therefore each image is only a ______ on the total range of data

A

“window”

100
Q

As window level increases image density

A

increases.

101
Q

As window level increases the overall brightness ______ and when window level decreases the overall brightness _______.

A

increases, decreases

102
Q

By adjusting the window level on monitor we change

A

the image brightness

103
Q

Window width

A

control that adjusts contrast

104
Q

Wide window width =

A

lower contrast (more shades of gray)

105
Q

Noise contributes

A

no useful information and detracts from quality of the image

106
Q

What is primary source of noise in digital?

A

Quantum mottle.

107
Q

Noise related to CCD technology

A

Statistical noise

Dark current noise

Amplification noise

108
Q

Statistical Noise

A

Created by lack of light photons from the scintillator or not enough x-rays striking the scintillator
This causes the output signal to be noisy resulting in Quantum Mottle

109
Q

Dark Current Noise

A
  • Occurs when the CCD chip operates without radiation stimulation
  • As a result of temperature rising
  • Adds unnecessary info to the image
  • Some manufacturers add thermostat cooling device
110
Q

Amplification Noise

A
  • Defects inherent in the manufacturing of the pixel elements
  • Some pixels may not work at all
  • The more bad pixels, the worse the detector efficiency
  • The lower the cost of the CCD, the higher the number of defects
111
Q

Noise is measured as

A

a signal-to-noise ratio (S/N)

112
Q

The Signal (in signal to noise ratio) is:

A

the information required from the image

113
Q

The Noise (in signal to noise ratio) is:

A

the unwanted information on an image

114
Q

A high S/N indicates

A

little noise in the image 1000:1

115
Q

The noisiest component of most digital systems is

A

the television camera (fluoro)

116
Q

Image Stitching

A

Algorithms rely on overlapping exposures to verify registration marks & image contrast edges to align multiple exposures

117
Q

Depending on system, annotation may not

A

transfer to PACS

118
Q

PACS

A

Picture Archival and Communication System is a networked group of computers, servers, and archives that can be used to manage digital images

119
Q

PACS can accept any image that is in _________________ format

A

Digital Imaging and COmmunications in Medicine (DICOM)

120
Q

DICOM is

A

a network that allows imaging of modalities and PACS to communicate in the same “language”

121
Q

DICOM is a universally accepted standard for:

A

exchanging medical images among the modality, viewing stations, and the archive

122
Q

PACS serves as a

A

file room, reading room, duplicator and courier

123
Q

PACS is custom designed for

A

each facility

124
Q

facilities pushed to have RIS, HIS and EMR interfaced with PACS. What is RIS, HIS, and EMR?

A

RIS – Radiology Information system
HIS – Hospital Information System
EMR – Electronic Medical Record

125
Q

Parts of PACS

A 
Reading stations
Physician review stations
Web-access
Technologist quality control stations
Administrative stations
Archive systems
Interfaces to various hospital & radiology systems
126
Q

Fundamental Parts of PACS

A

Image Acquisition
Display Workstations
Network
Archive Servers

127
Q

Display Workstations

A

any computer that health care worker uses to view images
Workstations inside & outside of Radiology
Software enables user to manipulate image
`

128
Q

File Room/Image Management

A
  • May be used to look up exams for a physician or to print copies for pt
  • More popular is burning CDs
  • File room also used for correcting pt demographics
129
Q

Network

A

The manner in which many computers can be connected to interact with one another

130
Q

Various types of devices that allow storage, retrieval and viewing of images

A

PACS workstations
Remote PACS workstations
Departmental mainframe
Hospital mainframe

131
Q

Teleradiology is

A

the process of remote transmission and viewing of images

132
Q

Who produced DICOM?

A

The ACR in conjunction with National Electrical Manufacturers Assoc. (NEMA)

133
Q

Archive Servers

A

– the file room of PACS. The central hub that receives all images before being released to radiologists

134
Q

Archives are chosen for:

A

System need
System cost
System compatibility

135
Q

Images are stored in archives on:

A

on magnetic tape or optical disc

136
Q

PACS archive controls

A

the receipt, storage and distribution of new and historic images

137
Q

Workflow is

A

the amount of work or exams completed over a period of time

138
Q

Workflow Manager in Radiology is

A

how the examination is completed from order entry to transcribed report

139
Q

Navigation functions are used to

A

move through images, series studies and patients

140
Q

The work list is used to

A

navigate through patients.

Access orders through work list

141
Q

Image Manipulation & Enhancement Function

A

Any tool used to change the appearance of the image

142
Q

Image Manipulation & Enhancement tools include:

A 
Window/level
Annotation
Flipped image
Pan, zoom and magnify
Measurements
143
Q

Pan, zoom, and magnify

A

used primarily by the radiologist to increase the size of an area on the image

144
Q

Measurements

A

most commonly used is the distance measurement

145
Q

Query/retrieve Function

A

used to retrieve studies from the archive
CD burning option
Print films for outside use

146
Q

Advanced Workstation Function

A

Usually placed on specialty workstations for the radiologist or tech QC station to further enhance images

147
Q

Reading station advanced functions:

A

Multiplanar reconstruction (MPR)
Maximum intensity projection & minimum intensity projection (MIP and MinIp)
Volume rendering technique (VRT)
Shaded surface display (SSD)

148
Q

Multiplanar Reconstruction (MPR)

A

One of the most commonly used 3-D rendering techniques

149
Q

Maximum intensity projection (MIP)Minimum intensity projection (MinIp)

A

Used to visualize vessels and air-filled structures. Performed after injection of contrast on CT & MRI.

150
Q

Volume rendering technique (VRT)

A

Allows user to assign colors based on intensity of tissue so that bone, contrast agent, and organs can be seen in different colors

151
Q

Shaded surface display

A

Uses a threshold of pixel intensity values: everything below is removed, everything above is assigned a color and shown as
3-D

152
Q

Application Service Provider (ASP)

A

A company that provides outsourcing of archiving and management functions for a pay-per-use –per-month charge. Used by hospitals that do not have the capital funds or the personnel to implement and operate the complex archive needed for a PACS

153
Q

ASPs give smaller institutions access to

A

the level of hardware and software they could not otherwise afford

154
Q

ASP also used as

A

a disaster recovery mechanism

155
Q

Disaster Recovery

A

Involves making copies of each tape or disk and sending to another building or off-site location

156
Q

What is the most integral part of a PACS?

A

Archive.

157
Q

Artifacts are

A

any undesirable densities on the processed image other than those caused by scatter radiation or fog.

158
Q

The four types of artifacts seen in digital are:

A

Imaging plate artifacts

Plate reader artifacts

Image processing artifacts

Printer artifacts

159
Q

Imaging Plate Artifacts

A

As plate ages becomes prone to cracks from action of removing and replacing plate within reader

160
Q

What does an imaging plate artifact appear as?

A

Cracks appear as areas of lucency on the image. Cracks usually first become visible on the IP edges. As deterioration progresses cracks appear closer to the clinically used areas of the IP

161
Q

Adhesive tape used to secure markers can

A

leave residue on the IR

162
Q

When humidity is low static can cause hair to

A

cling to IP creating artifact

163
Q

Backscatter can cause

A

dark line artifacts. Areas of the lead coating on the cassette that are worn or cracked allow scatter to image these weak areas

164
Q

Plate Reader Artifacts

A

Intermittent appearance of extraneous line patterns can be caused by problems in the plate reader’s electronics
Reader electronics may have to be replaced to remedy this problem

165
Q

Horizontal white lines caused by dirt on the light guide in the plate reader are examples of what type of artifact?

A

plate reader artifact.

166
Q

In the event where a plate reader artifact is discovered:

A

Service personnel will need to clean the light guide

XR220 Image Production and Evaluation II (8 decks)

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