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radiology > digital radiography: best practices > Flashcards

digital radiography: best practices Flashcards

1
Q

when were Digital radiographs first invented

A

in the late 80’

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2
Q

Characteristics of the first radiographs

A

V. large
TV not computer
no storage or manipulation of image
cost

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3
Q

when did Digital x-rays become like today

A

In the 90s

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4
Q

what is a digital image

A

A representaion of a 2d image as a finite set of digital values called pixels

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5
Q

what do pixels represent

A

represent gray levels, colors, heights….

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6
Q

is a digital scene actually the real image

A

No an approximation of a real scene

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7
Q

Benifit of Digital X-ray to standard to patient

A

reduction compared to F-sped between 0-50 percent (lower dose)
Increase in number of radiographs made
INcrease in ease of remakes

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8
Q

why do digital

A

Efficient work flow
Image enhancement
Better case acceptance
Co-diagnosis

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9
Q

Digital Imaging chain

A

Image acquisition
Image processing
Image display

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10
Q

retake rate of digital vs. Film

A

digital: 20%
FILM: 9%

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11
Q

what is involved in image Acuisition

A

X-ray tube
Sensor
sensory placement and exposure

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12
Q

How should the X-ray tube act for digital X-rays

A

timer capable of making reproducible short exposures if image quality is suoptimal (may need to upgrade)

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13
Q

systems for making digital X-rays

A

CCD
CMOS
Phosphors

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14
Q

what type of digital x-rays are indirect

A

Phosphors (scanning)

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15
Q

How does CCD digital X ray work

A
  • X-ray hits sensor and produces electrons at the same rate of the x-ray hitting
  • One well transfers the electrons to the next
  • edge of the CCD provides Electrical signal
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16
Q

How does a CMOS work

A

each pixel has its own transistor and this is read directly

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17
Q

what happens if too many electrons in a well

A

spill over and muddy image (over exposure)

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18
Q

which type of sensor has more noise

A

The CMOS due to the extra transistors

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19
Q

what is a Wireless sensor mades of (PSP)

A

plastic plate coated with phosphor material sensitive to X-rays

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20
Q

what is a PSP

A

the plate of a wireless sensor (photostimulable phosphor plate)

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21
Q

how does a PSP work

A
  • Sensor exposed to an x-ray which creates a latent image stored on the plate
  • then image digitalized with scanner
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22
Q

what must be done to a PSP after an image is taken

A

cleared by light exposure for several minutes before next use

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23
Q

steps of a PSP

A

Exposure
Stimulate with laser
reading due to light emision
Ease with light

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24
Q

what is the weakest part of the sensor

A

the junction to the computer

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25
Q

what are extraoral digital radigraphs

A

PAnoramic

Cephalometric

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26
Q

do most current X-ray detectors work well

A

GEnerally yes, interms of spatial and contrast resoltuions and in terms of exposure latitude
- indepent of modality applied`

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27
Q

Characteristics of digital detector characteristics

A

Contrast REsolution
Spatial rsolution
Detector Latitude
Detector sensitivity

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28
Q

what is contrast resolution

A

Dynamic range (ability to distriguish different densities in the image

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29
Q

what affefcts contrast resolution

A

Attenuation of radiation by tissues
Capacity of receptor
computer display
ability of observer

30
Q

what does bit mean

A

it is the power 2 is raised to to determine the amount of gray levels are capable of being made

31
Q

what is spatial resolution

A

the capacity to distinuish fine detal

32
Q

smallest picel size

A

20 microns (24 lp/mm)

33
Q

HUman eye can differentiate how many lp/mm without maginification

A

6-8 (less than the smallest pixel)

34
Q

what is detector latitude

A

Ability of receptor to capture a range of exposure

35
Q

what is detector sensitivity

A

Ability to respond to small amouts of radiation

36
Q

standard for detector sensitivity

A

No classification yet

37
Q

what is Detector quantum effeciency

A

Is the measure of noise and contrast expressed as a function of object detail

38
Q

what does a DQE of 100% mean

A

A perfect detector, meaning all info that reaches detector is trasferred out of detector

39
Q

what are qualities of sensors

A

Spatial resolution
Bit depth
Active area

40
Q

what should the bit depth be at least for a senosr

A

at least 12

41
Q

important things to think about when it comes to sensory

A 
Sensory reliablility (life span)
Software integration with practice management software
42
Q

Roll of image processing

A

To restore, enhance, or analyze image

43
Q

aspects of image enhancement

A

Brightness and contrast
Sharpening and smoothing
color
Digital subtraction

44
Q

what does a histogram do

A

Shows certain spectrums of color

45
Q

what are kinds of analysis tools

A

Zoom
Measurement
Digital subtraction

46
Q

what is digital subtraction

A
  • when 2 radiographs are taken with the same exposure geometry over a time interval
  • images superimposed
  • computer compares and removes whatever is exactly the same giving a clear image of anything that is different
47
Q

how do changes look in digital subtraction

A

displayed as a resultant image against a neurtral gray background

48
Q

how much bone mass can digital subtraction notice

A

A change as little as 5%

49
Q

how many practicing dentist have experience problems with digital radiography

A

about 65%

50
Q

what is one of the weaker links in the technical chain of digital radiograph

A

Monitor

51
Q

room lighting affect on analysis of radiographs

A

Affects the diagnosistic outcome of low contrast patterns (low light good)

52
Q

affect of high luminance

A

results in better image quality, making subtle lesions easier to detect

53
Q

Luminance of different things

A 
Viewboxes (1000-2000 Cd/ Msequared
reg monitors (250-300
medical monitors (1000)
54
Q

What is luminence

A

MAx and Min amount of light emitted from display monitor (contrast ratio)

55
Q

what kind of devices have small picture elemets

A

High quality photographic and medical display devices

56
Q

how much does contrast ratio drop at a vewing angle of 85 degrees

A

10:1

57
Q

shades of gray in a medical display

A

4096(12 bit)

- consumer display is 8 bit

58
Q

important things for image storange

A

Prevention of permanent deletion or modification

Backup considerations

59
Q

Size of aradiograph

A

200 kb to 6MB

60
Q

what is the standard for for didigtal communcation

A

Digital imaging and Communication in mediicine stand (DICOM)

61
Q

benifit of Following DICOM

A

makes sharing images simpler between providers

62
Q

where should you test new X-ray machines and why

A

In your own office so images can be standaradizes and not preselected
also know how to integrate and environement

63
Q

how long do X-ray ray equipment work

A

5-7 years

64
Q

cost of CCD and CMOS

A

5-8k

65
Q

cost of PSP plates

A

30-50

66
Q

how much ram should you have

A

4 gigabytes

67
Q

CPU speed

A

2 gigahertz

68
Q

Storage in server

A

Terabyte

dedicated server need a hardrive of 500GB

69
Q

USB?

A

Always good

70
Q

should you go wireless or nah

A

Sinve large files, wired is faster and secure

radiology (10 decks)

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