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physics spring semester 2015 > TEST 3 > Flashcards

TEST 3 Flashcards

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
heat blur artifact
caused by the image receptor being exposed to intense heat
26
what differentiates DR from CR
electronic direct readout detectors
27
types of detectors
photodiodes charge coupled devices CCD complementary metal oxide semiconductors CMOS thin film transistors TFT
28
what makes up the latent image
the pattern of electrical charges
29
2 types of flat panel detectors used
1. direct | 2. indirect
30
scintillator
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
31
why is it possible for the image to come up so fast in DR?
because more than 1 million pixels can be read and converted to a composite digital image in less than 1 second
32
direct conversion process
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
indirect conversion process
1. xray photons are converted to light | 2. light photons are converted to an electrical signal
34
advantages of CCD
sensitivity dynamic range size
35
sensitivity of CCD
the ability of the CCD to detect and respond to very low levels of visible light
36
Dynamic range of CCD
the ability of the CCD to respond to a wide range of light intensity from very dim to very bright
37
size of CCD
CCD is very small making it highly adaptable to DR
38
complementary metal oxide semiconductor CMOS
a system that uses special pixel sensors that convert xrays into light photons indirect conversion
39
CCD vs. CMOS
CMOS more susceptible to noise prettier picture with CCD CMOS cost less
40
Detective Quantum Efficiency DQE
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
T or F | systems with higher quantum efficiency can produce higher quality images at lower dose
TRUE
42
DEL size
Detector ELement size | determines resolution
43
electronic memory artifact
if exposures are taken in too rapid sequences, there may not be enough time for each previous exposure to transfer the entire signal
44
preprocessing
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
postprocessing
done by the technologist through various user functions | where exposure errors are corrected
46
image sampling
the plate is scanned and the image's location and orientation are determined
47
sampling
the intensity of light or radiation from each pixel is measured by the detectors
48
automatic rescaling
means that the images are produced with uniform density and contrast, regardless of the amount of exposure brightening the entire image
49
automatic rescaling results in:
quantum mottle underexposed | loss of contrast overexposed
50
equalization
another software in chich you are able to brighten a specific area only brightening specific areas
51
Look Up Table LUT
used as a reference to evaluate the raw information and correct the light values helps improve contrast by substituting different pixel values
52
true or false | the exposure latitude is much greater for digital than that of screen/film
TRUE
53
Modulation Transfer Function MTF
a numeric value that is used to measure spatial resolution
54
T or F | the more light spread, the less the image looks like the object and the lower the MTF
TRUE
55
MTF =
information recorded in an image/ information available in the part
56
postprocessing techniques
1. subtraction 2. contrast enhancement 3. edge enhancement 4. black/white reversal
57
subtraction
removes superimposed structures to make anatomic area of interest more visible ex: skeletal areas removed
58
contrat enhancement
alters the pixel values to display different brightness levels
59
edge enhancement
improves visibility and accentuates lines between different adjacent tissues useful for larger structures as soft tissues/organs
60
black/white reversal
reverses the gray scale from the original radiograph
61
smoothing
filtering process that suppresses image noise by averaging pixel frequency with surrounding pixel values useful for viewing smaller structures
62
Laser printers 2 ways to print image
wet - uses liquid chemicals | dry - chemicals are part of the film. image created by use of heat
63
what is the weakest link in DR
the TV monitor
64
T or F | pixel size is a major factor in level of spatial resolution in digital
True
65
window level
controls the density on the image | by adjusting it on the monitor we change the image brightness
66
as window level increases, image density
increases
67
as window level increases, the overall brightness
increases
68
window width
control that adjusts contrast
69
wide window width
lower contrast | more shades of gray
70
narrow window width
higher contrast | black and white
71
what is the primary source of noise in digital?
Quantum mottle
72
types of noise
1. statistical noise 2. dark current noise 3. amplification noise
73
statistical noise
created by lack of light photons from the scintillator or not enough xrays striking the scintillator
74
dark current noise
occurs when the CCD chip operates without radiation stimulation adds unnecessary info to the image
75
amplification noise
defects inherent in the manufacturing of the pixel elements | the more bad pixels the worse the detector efficiency
76
signal to noise ratio
1000:1 good/strong signal
77
resolution is controlled by
pixel size
78
thin film transistors TFT
a charge sensitive device that collects electrons and creates the signal

physics spring semester 2015 (5 decks)

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