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physics spring semester 2015 > TEST 3 > Flashcards

TEST 3 Flashcards

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1
Q

PACS

A

Picture Archival and Communication System

a networked group of computers, servers, and archives that can be used to manage digital images

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2
Q

what does DICOM stand for

A

Digital Imaging and COmmunications in Medicine

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3
Q

what is DICOM

A

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

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4
Q

RIS

A

Radiology Information System

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5
Q

HIS

A

Hospital Information System

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6
Q

EMR

A

Electronic Medical Record

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7
Q

teleradiology

A

the process of remote transmission and viewing of images

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8
Q

archive servers

A

the file room for PACS

where records are preserved

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9
Q

Archives are chosen for:

A

system need
system cost
system compatibility

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10
Q

Archives

A

PACS archive controls the receipt, storage and distribution of new and historic images

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11
Q

image manipulation and enhancement

A

any tool used to change the appearance of the image

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12
Q

image manipulation and enhancement tools

A 
window/level
annotation 
flipped image
pan, zoom, magnify
measurements
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13
Q

multiplanar reconstruction

A

one of the most commonly used 3-D rendering techniques

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14
Q

volume rendering technique

A

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

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15
Q

backscatter

A

can cause dark line artifacts

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16
Q

plate reader artifacts

A

intermittent appearance of extraneous line patterns caused by problems in the plate readers electronics

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17
Q

multiple exposure

A

results in what looks like a double exposure in film/screen

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18
Q

moire

A

happens when grid lines are parallel to the plate

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19
Q

incorrect erasure setting

A

results in a residual image left in the IP before the next exposure

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20
Q

flatfielding

A

software correction that equalizes the response of each pixel to create a uniform xray beam
evening of the overall brightness across entire image

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21
Q

rough handling

A

can cause kinks and bends in image

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22
Q

insufficient collimation

A

results in unattenuated radiation striking the IP scatter will degrade the image

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23
Q

exposure field recognition error

A

exposure field is not properly collimated, sized, and positioned

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24
Q

upside down cassette

A

results in an image with white grid type pattern and white areas that correspond to the hinges

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25
Q

heat blur artifact

A

caused by the image receptor being exposed to intense heat

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26
Q

what differentiates DR from CR

A

electronic direct readout detectors

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27
Q

types of detectors

A

photodiodes
charge coupled devices CCD
complementary metal oxide semiconductors CMOS
thin film transistors TFT

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28
Q

what makes up the latent image

A

the pattern of electrical charges

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29
Q

2 types of flat panel detectors used

A
  1. direct

2. indirect

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30
Q

scintillator

A

a radiation conversion material that absorbs xrays and converts them to electrons which are stored in the TFT detectors
the material is amorphous selenium a-Se

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31
Q

why is it possible for the image to come up so fast in DR?

A

because more than 1 million pixels can be read and converted to a composite digital image in less than 1 second

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32
Q

direct conversion process

A

the a-Se absorbs xrays and converts them to electrons
the electrons are stored in the TFT detectors
the pixels in the TFT absorbs the electrons and generates electrical charges and sends the charges to the image processor

33
Q

indirect conversion process

A
  1. xray photons are converted to light

2. light photons are converted to an electrical signal

34
Q

advantages of CCD

A

sensitivity
dynamic range
size

35
Q

sensitivity of CCD

A

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

36
Q

Dynamic range of CCD

A

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

37
Q

size of CCD

A

CCD is very small making it highly adaptable to DR

38
Q

complementary metal oxide semiconductor CMOS

A

a system that uses special pixel sensors that convert xrays into light photons
indirect conversion

39
Q

CCD vs. CMOS

A

CMOS more susceptible to noise
prettier picture with CCD
CMOS cost less

40
Q

Detective Quantum Efficiency DQE

A

a measurement of xrays that are absorbed when they hit the detector
shows how efficiently a system converts the xray input signal into a useful output image

41
Q

T or F

systems with higher quantum efficiency can produce higher quality images at lower dose

A

TRUE

42
Q

DEL size

A

Detector ELement size

determines resolution

43
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

44
Q

preprocessing

A

takes place in in the computer where the algorithms determine the image histogram
corrections made to the raw digital image due to flaws in the image acquisition

45
Q

postprocessing

A

done by the technologist through various user functions

where exposure errors are corrected

46
Q

image sampling

A

the plate is scanned and the image’s location and orientation are determined

47
Q

sampling

A

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

48
Q

automatic rescaling

A

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

49
Q

automatic rescaling results in:

A

quantum mottle underexposed

loss of contrast overexposed

50
Q

equalization

A

another software in chich you are able to brighten a specific area
only brightening specific areas

51
Q

Look Up Table LUT

A

used as a reference to evaluate the raw information and correct the light values
helps improve contrast by substituting different pixel values

52
Q

true or false

the exposure latitude is much greater for digital than that of screen/film

A

TRUE

53
Q

Modulation Transfer Function MTF

A

a numeric value that is used to measure spatial resolution

54
Q

T or F

the more light spread, the less the image looks like the object and the lower the MTF

A

TRUE

55
Q

MTF =

A

information recorded in an image/ information available in the part

56
Q

postprocessing techniques

A
  1. subtraction
  2. contrast enhancement
  3. edge enhancement
  4. black/white reversal
57
Q

subtraction

A

removes superimposed structures to make anatomic area of interest more visible
ex: skeletal areas removed

58
Q

contrat enhancement

A

alters the pixel values to display different brightness levels

59
Q

edge enhancement

A

improves visibility and accentuates lines between different adjacent tissues
useful for larger structures as soft tissues/organs

60
Q

black/white reversal

A

reverses the gray scale from the original radiograph

61
Q

smoothing

A

filtering process that suppresses image noise by averaging pixel frequency with surrounding pixel values
useful for viewing smaller structures

62
Q

Laser printers 2 ways to print image

A

wet - uses liquid chemicals

dry - chemicals are part of the film. image created by use of heat

63
Q

what is the weakest link in DR

A

the TV monitor

64
Q

T or F

pixel size is a major factor in level of spatial resolution in digital

A

True

65
Q

window level

A

controls the density on the image

by adjusting it on the monitor we change the image brightness

66
Q

as window level increases, image density

A

increases

67
Q

as window level increases, the overall brightness

A

increases

68
Q

window width

A

control that adjusts contrast

69
Q

wide window width

A

lower contrast

more shades of gray

70
Q

narrow window width

A

higher contrast

black and white

71
Q

what is the primary source of noise in digital?

A

Quantum mottle

72
Q

types of noise

A
  1. statistical noise
  2. dark current noise
  3. amplification noise
73
Q

statistical noise

A

created by lack of light photons from the scintillator or not enough xrays striking the scintillator

74
Q

dark current noise

A

occurs when the CCD chip operates without radiation stimulation
adds unnecessary info to the image

75
Q

amplification noise

A

defects inherent in the manufacturing of the pixel elements

the more bad pixels the worse the detector efficiency

76
Q

signal to noise ratio

A

1000:1 good/strong signal

77
Q

resolution is controlled by

A

pixel size

78
Q

thin film transistors TFT

A

a charge sensitive device that collects electrons and creates the signal

physics spring semester 2015 (5 decks)

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