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Oral Radiology > Sensors and Digital Imaging > Flashcards

Sensors and Digital Imaging Flashcards

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

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

A

3.5mm x 2 mm

20
Q

how big are XDR size 2 sensors

A

4mm x 2.5mm

21
Q

what are the components of sensors

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

what are the portions of the CCD/CMOS area

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 ______

A

electrons trapped inside

24
Q

what is the thickness of sensors

A

4-6mm

25
Q

what are the shapes of sensors

A

square, rounded or cut

26
Q

what are the types of sensors

A

CMOS and CCD

27
Q

what is the principle of the CCD detector

A
  • 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
Q

describe CMOS compared to CCD

A
  • CMOS is newer technology
  • require less power
  • superior image quality
29
Q

what is bit depth

A

the number of colors that a pixel is able to show

30
Q

what are the benefits to digital imaging

A
  • 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
Q

why SHOULD digital imaging be appealing

A
  • electronic communication improves efficiency
  • rapid acquisition
  • image portability
32
Q

how do CCD/CMOS sensors work

A
  • 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
Q

describe digitization in CCD,CMOS types

A

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
Q

what is the size of pixels in sensors

A

15 microns or 15 x 10^-3 mm

35
Q

describe CCD sensors compared to CMOS

A
  • older technology
  • require an additional power via an adjunct box
  • need additional power to convert the photon energy to an electrical digital signal
36
Q

when was the first CCD system created and by who

A
  • 1988
  • Dr. Francis Mouyen
37
Q

describe the prinicple of 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
38
Q

what is the power consumption, sensitivity to XR, cost to manufacture, readout, pixel signal, chip output of CMOS

A
  • 40 mW
  • low
  • medium
  • simple
  • voltage
  • bit/digital
39
Q

what is the system complexity and sensory complexity of CCD and CMOS

A
  • CCD: high and low
  • CMOS: low and high
40
Q

what types of extraoral digital radiography have been applied in panormaic and plain skull images

A

CCD and PSP plates

41
Q

describe extraoral digital radiography

A
  • similar spatial resolution as film based format 4Ip/mm
  • inferior contrast resolution possibly compensated by manipulation functions
42
Q

what is the actual and line pair resolution of sensor image wuality

A
  • actual: visible >20 Ip/mm
  • theoretical- calculated >26 Ip/mm
43
Q

what are the brand of CMOS sensors

A
  • AFP imaging
  • Planmeca
  • XDR

Oral Radiology (26 decks)

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