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Radiology > Sensors and Digital Imaging > Flashcards

Sensors and Digital Imaging Flashcards

1
Q

Which type of imaging is faster?

A

digital

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2
Q

Which type of imaging uses less radiation?

A

digital

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3
Q

What does the lead foil in the film do?

A

limit secondary scattering of radiation

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4
Q

What does the black paper do in the film?

A

sturdiness

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5
Q

What is a piece of film composed of?

A
  1. supercoat - thin layer of hard plastic
  2. emulsion - gel and Ag halide crystal
  3. adhesive
  4. base - plastic
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6
Q

During film processing chemicals are used to…

A

form elemental Ag from silver halide salt

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7
Q

Chemical changes in film processing are dependent on what?

A

time, temperature and concentration

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8
Q

What is a digital image?

A

Digital image can be conceived as a table with columns and rows, with each cell (aka pixel) being assigned a number value which is then assigned a gray intensity

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9
Q

How is a visual image constructed from pixels?

A

The composite collection of pixel values are used by a computer’s software processing ability to construct an image for visual display

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10
Q

What is a pixel (px)?

A

A px (pixel) is the smallest portion of a sensor, image or display that is capable of being recorded and then printed or displayed

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11
Q

What are the general steps in digital image formation?

A
  1. x-ray shadow
  2. shadow image detected by digital sensor
  3. numerical pixel values sent to the computer
  4. digital image on the computer screen
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12
Q

What are the specific steps in digital image formation?

A
  • Pixels are electrified
  • Each pixel has a pre-exposure electrical charge
  • X-ray photons that make it to the sensor change the electric charge in those pixels
  • The thicker/denser the body part adjacent the sensor, the less the x-photons can affect the electrical charge
  • The net effect is that there is a shadow of electric charges on the sensor reflective of the thickness/density of the body part.
  • Electric charge value of each pixel is read by computer chip and the electrical voltage is converted to a numerical value
  • Pixel values sent to the computer for processing
  • The computer assigns the gray value of each number to the location on the X:Y grid axis of the sensor
  • The gray values are displayed in a visual format on a display monitor
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13
Q

What are the types of historic (indirect) dental digital radiography?

A

Flatbed scanner
Slide scanner
Digital cameras

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14
Q

What are the types of indirect (semidirect) dental digital radiography?

A

Phosphor Storage Plate (PSP)

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15
Q

What are the types of direct dental digital radiography?

A
  • Charge-Coupled Device (CCD)
  • Complementary Metal Oxide Semiconductor (CMOS)
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16
Q

What is the issue with indirect digital radiography?

A

Loss or alteration of information due to partial volume averaging

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17
Q

The first film-like sensor was introduced in ____

A

1994

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18
Q

What are the components of semidirect digital system?

A
  • laser scanner
  • PSP plate
  • x-ray source
  • screen monitor
  • CPU, Server, or PACS
  • Printer EPR PACs
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19
Q

What are the steps of the PSP detector?

A

→ X-ray
→ PSP plate coated with crystalline halide emulsion made up of BaFBrEu2+ producing a latent image of ionized phosphors
→ scanned with red laser beam
→ emits fluorescent light from excitation of valence electrons in ionized fluorophophors
→ intensified by a photomultiplier tube
→ light intensity is converted to digital data
→ expose to strong light to erase residual images by neutralizing charges in ionized fluorophophors
→ reuse

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20
Q

How sensitive to light are PSP plates?

A

less sensitive than film but more than solid state

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21
Q

What are the components of direct digital system?

A
  • x-ray source
  • CCD/CMOS
  • digital interface cord
  • Analog-to-digital converter (CCD only)
  • screen monior
  • CPU, server, or PACS
  • printer, ERP, PACs
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22
Q

What is the size comparison between direct digital sensors and film/PSP?

A

similar in size

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23
Q

How wide is the direct digital sensor?

A

4-5 mm wide

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24
Q

What are the components of the digital sensor?

A
  • plastic housing
  • CSI scintillator
  • Fiber Optic Face Plate (FOP)
  • CMOS imaging chip
  • electronic substrate
  • cable
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25
Q

What is the CSI scintillator in the sensor?

A
  • takes the photons and multiplies it (increases strength of signal)
  • optimized for resolution and low noise
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26
Q

What is the CMOS imaging chip?

A
  • has the pixels
  • patented techology with cut corners
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27
Q

What are some drawbacks of CCD/CMOS?

A
  • uncomfortable (don’t bend like film)
  • internal active area (portion of the sensor that produces the image) is smaller
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28
Q

What are the types of digital sensors?

A

CCD (charge coupling device)
CMOS (Complementary Metal-Oxide-Semiconductor)

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29
Q

What are most types of digital sensors?

A

CMOS

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30
Q

What is the simplified sensor concept?

A
  • each pixel is like a tiny battery with its charge equal to the number of electons trapped inside
  • the computer records the charge in each pixel and converts it into a gray value
31
Q

What is the sensor thickness sweet spot?

A

4-6 mm

32
Q

What type of sensor is preferred?

A

open source

33
Q

What is the pixel size/image quality for most sensors?

A

~ 15 µM (10-6 M)
~ 15 microns (10-6 M)
~ 15 10-3 mm

34
Q

How sharp is the image quality of most sensors?

A

Actual – visible
- >20 lp/mm

Theoretical – calculated
- >26 lp/mm

35
Q

What is the line pair resolution?

A

how sharp an image is or the image quality

36
Q

What are the characteristics of a CCD?

A

● Older technology
● Require an additional power via an adjunct box
● Need additional power to convert the photon energy to an electronic digital signal

37
Q

What type of digital sensor needs to go through an analog-to-digital converter box?

A

CCD

38
Q

What are the steps of a CCD detector?

A

X-ray → scintillating material → light photos → silicon → electrons deposited in electron wells → transferred in a sequential manner (charge-coupling) → read-out amplifier → images on monitor

39
Q

What is charge-coupling?

A
  • pixel signals in row are transferred in sequential manner to be digitized
  • CCD
40
Q

What makes digital CCD detectors “slow”?

A

charge-coupling

41
Q

What was the first type of digital sensor?

A

CCD

42
Q

What are the steps of the CMOS detector?

A

X-ray → scintillating material → light photos → silicon → electrons deposited in electron wells and converted to voltage in each pixel→ smoother signal digitization → software processing → images on monitor

43
Q

Which digital sensor is cheaper: CCD or CMOS?

A

CMOS

44
Q

Which is more sensitive to X-rays: CCD or CMOS?

A

CCD

45
Q

Which has a higher system complexity but lower sensor complexity: CCD or CMOS?

A

CCD

46
Q

Which has a lower system complexity but higher sensor complexity: CCD or CMOS?

A

CMOS

47
Q

What are the characteristics of CMOS?

A

● Newer technology
● Require less power
● Superior image quality

48
Q

Which can you use less radiation because it is more sensitive: CCD or CMOS?

A

CCD

49
Q

What is the usual bit depth for a sensor?

A

8-12 bit

  • 8 bit (2^8) = 256 shades of grey
50
Q

What is bit depth?

A

the number of colors (or grey shades) that a pixel is able to show

51
Q

Which of these has the highest bit depth and which has the highest contrast?

A

A - highest bit depth
D - highest contrast

52
Q

Which is better for an image: high or low contrast?

A

high and low contrast are good depending on what you are trying to see

53
Q

What gives you more information about an object: high or low contrast?

A

low contrast

54
Q

What type of sensors have been applied in panoramic and plain skull images?

A

CCD and PSP plates

55
Q

Why is digital imaging appealing?

A

 Significantly less radiation
 Better image (?)
 Lower costs — more net income
- reduced patient chair time
- no variable costs
- elimination of dark room
 Environmentally friendly - less toxic chemicals are disposed into the sewage systems
 Electronic communication improves efficiency
 Rapid acquisition and storage
 Image portability

56
Q

What has a lesser effective dose for common exam radiographs?

FMX PSPP
FMX CCD
FMX D-speed

A

FMX D-speed - 388
FMX PSPP - 171
FMX CCD - 85

CCD has the smallest effective dose

57
Q

What are the mathematical manipulations of image data?

A
  • Compression
  • Imaging manipulations (qualitative)
  • Automated image analysis (quantitative)
  • Image reconstruction
58
Q

What is image processing?

A

Mathematical manipulation of image data

59
Q

What are qualitative digital image modifications?

A

● Uses mathematical operations called matrix transformations
● Magnify, adjust contrast, brightness, gray scale, colors, swap black and white

60
Q

What are quantitative/analytical digital image modifications?

A

● Measure lengths (# of pixels for length, area, circumference, etc.)
● Measure pixel values (bone, enamel, dentin, pulp, soft tissue densities)

61
Q

What is compression of a digital image?

A

– affects image file size in memory storage
- useful for storage issues eg. “zipping” files
- actual file size is larger that stored file size
- compression is an algorithm that can shrink the file size for storage and recreate the data when retrieving the data

62
Q

The file memory size of a digital image can become large due to…

A

– size of grid (sensor size)
- number of images
- bit depth

63
Q

What are the different types of qualitative image manipulations?

A

➢ Edge Enhancement – sharpening filter
➢ Noise Reduction – softening filter
➢ Optimization of density/contrast
➢ Inversion of gray scale
➢ Magnification
➢ Emboss function
➢ Pseudocolor enhancement

64
Q

What is image manipulation?

A
  • are post-display mathematical algorithms that manipulate the digital signal
  • the computer will change density values to predetermined numbers which then changes the image’s presentation i.e., lighter darker, etc
65
Q

Does manipulating an image increase the diagnostic accuracy?

A

NO

66
Q

What does image manipulating do?

A

 Depend on viewer preference
 Make the images subjectively more appealing
 DO NOT increase the diagnostic
accuracy

67
Q

What is good about altering the brightness/contrast?

A

The brightness and contrast adjustments are done together to subjectively find the “best” combination of brightness and contrast to highlight the clarity of the structures in the image

68
Q

What can “softening” or noise reduction do to an image?

A

May degrade or remove important diagnostic informatio

69
Q

What does sharpening or edge enhancement do to an image?

A

 Remove low-frequency noise; increases image contrast
 Exaggerate the contrast difference between adjacent pixels; to increase contrast, all pixel values are stretched; the dark shades become darker and the light shades become lighter
 Enhances local contrast and makes edges sharper to diagnose caries, restoration fit, and fractures
-can simulate disease

70
Q

What is magnification of an image?

A

Enlarge a specific area till the biggest detail

71
Q

What is the emboss function (inactive)?

A
  • Applies a three dimensional effect to the image
  • Could be useful in presentation situations
72
Q

What are the different types of analytical/quantitative automated image analysis?

A
  • Length
  • Angles
  • Bone Density
  • Area
  • Circumference
  • Etc…
73
Q

What is image reconstruction?

A

Data is utilized by other software programs and produces different image presentations

Radiology (35 decks)

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