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Oral Radiology > Sensors and Digital Imaging > Flashcards

Sensors and Digital Imaging Flashcards

(43 cards)

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1
Q

in 2016 and 2017 survey of practicing dental assistants in the US estimate that up to ____% of dental offices use digital radiology

A

90%

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2
Q

what are the contents of film packets

A
  • outer cover
  • lead foil
  • black, light proof paper wrapper
  • film
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3
Q

what are the sizes of film and what are they each for

A

size 0- pediatric
size 1- PA, pediatric
size 2- standard
size 4 - occlusal

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4
Q

what is the film composition

A
  • supercoat- thin layer of hard plastic
  • emulsion - gel and Ag- halide crystal
  • adhesive
  • base - plastic
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5
Q

what is Ag formed from

A

silver halide salt

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6
Q

chemical changes are ____,_____,_____ dependent

A

time, temperature, and concentration

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7
Q

how is a digital image made

A

a digital image is a table with columns and row which each cell (pixel) is assigned a number value which is then assigned a gray intensity. the composite collection of pixel values are used by a computers software processing ability to construct an image for visual display

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8
Q

what is the word pixel derived from

A

PEL- picture element

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9
Q

what is a pixel

A

the smallest portion of a sensor, image or display that is capable of being recorded and then printed or displayed

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10
Q

what are the general steps in digital image formation

A
  • X ray shadow
  • electric shadow signal is detected by digital sensor
  • numerical pixel values sent to the computer
  • digital image on the computer screen
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11
Q

how is the electric shadow signal detected by digital sensor

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
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12
Q

what are the types of historic/indirect digital radiography

A
  • flatbed scanner
  • slide scanner
  • digital scanner
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13
Q

what are the types of indirect/ semidirect digital radiography

A

phosphor storage plate (PSP)
- aka photostimulable phosphor storage plate (PPSP)

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14
Q

what are the types of direct digital radiography

A
  • charge coupled device (CCD)
  • complementary metal oxide semiconductor (CMOS)
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15
Q

why is indirect digital radiography not preferred

A

loss or alteration of information due to partial volume averaging

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16
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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17
Q

what are the principles of PSP detector

A
  • X ray
  • PSP plate coated with crystalline halide emulsion made up on BaFBrEu2+ producing a latent image of ionized phosphors
  • scanned with red laser beam
  • emits fluorescent light from excitation of valence electrons in ionized fluorophosphors
  • intensified by a photomulitplier tube
  • light intensity converted to digital data
  • expose to strong light to erase residual images by neutralizing charges in ionized fluorophophors
  • resuse
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18
Q

what are the componenets of direct digital system

Study These Flashcards
A
  • screen monitor
  • CPU, server or PACS
  • printer EPR PACs
  • analog to digital converter to CCD
  • digital interface cord
  • CCD/CMOS
  • X ray source
19
Q

how big are XDR size 1 sensors

20
Q

how big are XDR size 2 sensors

21
Q

what are the components of sensors

Study These Flashcards
A
  • electronic substrate
  • CMOS imaging chip
  • fiber optic face plate (FOP)
  • CSI scintillator
22
Q

what are the portions of the CCD/CMOS area

Study These Flashcards
A
  • external size
  • internal active area- the portion of the sensor producing the image
23
Q

in a sensor, each pixel is like a tiny battery with its charge equal to the number of ______

Study These Flashcards
A

electrons trapped inside

24
Q

what is the thickness of sensors

25
what are the shapes of sensors
square, rounded or cut
26
what are the types of sensors
CMOS and CCD
27
what is the principle of the CCD detector
- Xray -> scintillating material -> light photos -> silicon -> electrons deposited in electron wells -> transferred in a sequential manner (charge-coupling) -> read out amplifier -> images on monitor
28
describe CMOS compared to CCD
- CMOS is newer technology - require less power - superior image quality
29
what is bit depth
the number of colors that a pixel is able to show
30
what are the benefits to digital imaging
- less radiation - better image - lower costs - reduced patient chair time - no cost for film and chemicals - no darkroom needed - environmentally friendly- less toxic chemicals disposed in sewage
31
why SHOULD digital imaging be appealing
- electronic communication improves efficiency - rapid acquisition - image portability
32
how do CCD/CMOS sensors work
- cesium iodide scintillator converts x rays into visible light - photosensitive pixels convert scintillator's light into electrical signals. on chip circuitry turns electrical signals into digital output - digital data is sent to a computer
33
describe digitization in CCD,CMOS types
X ray photons cause ionization of pixel silicone; ejected electrons are trapped in the pixel similar to the charge in a battery. the computer records the charge in each pixel and converts it to a gray value
34
what is the size of pixels in sensors
15 microns or 15 x 10^-3 mm
35
describe CCD sensors compared to CMOS
- older technology - require an additional power via an adjunct box - need additional power to convert the photon energy to an electrical digital signal
36
when was the first CCD system created and by who
- 1988 - Dr. Francis Mouyen
37
describe the prinicple of CMOS detector
- 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
38
what is the power consumption, sensitivity to XR, cost to manufacture, readout, pixel signal, chip output of CMOS
- 40 mW - low - medium - simple - voltage - bit/digital
39
what is the system complexity and sensory complexity of CCD and CMOS
- CCD: high and low - CMOS: low and high
40
what types of extraoral digital radiography have been applied in panormaic and plain skull images
CCD and PSP plates
41
describe extraoral digital radiography
- similar spatial resolution as film based format 4Ip/mm - inferior contrast resolution possibly compensated by manipulation functions
42
what is the actual and line pair resolution of sensor image wuality
- actual: visible >20 Ip/mm - theoretical- calculated >26 Ip/mm
43
what are the brand of CMOS sensors
- AFP imaging - Planmeca - XDR

Oral Radiology (26 decks)

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