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Oral Radiology > Lecture 5 - Radiographs > Flashcards

Lecture 5 - Radiographs Flashcards

1
Q

What crystal is chemically altered when stuck by an X-ray photon AND what does it create?

A

Silver halide

Latent image

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2
Q

The raised dot goes towards or away from tube head?

A

Towards

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3
Q

The larger the crystals of silver halide the ______ the film speed.

A

FASTER

C is slowest

D - ASA ~100

F - Fastest

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4
Q

Tell me about cassettes.

A

Contain intensifying screens

*Require less radiation to expose film

Decreased definition

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5
Q

Radiographic density is influenced by what?

A

mA

kVp

Exposure time

Focal spot to film distance

Subject density

Subject thickness

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6
Q

What is radiographic density?

A

Determined by how many photons strike the film emulsion
-This converts silver halide crystals to metallic silver
—This blocks the transmission of light thru the film

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7
Q

What do grids do?

A

Reduces scatter radiation

-Reduces scatter and fog on a radiograph

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8
Q

What is the developing process for in dark film processing?

A

Developer

Wash

Fixer

Wash

Drying

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9
Q

What do you have to do to keep darkroom hygiene?

A

Safelight

Light leakage

Chemical contamination

Infection control

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10
Q

For every 10 degrees Celsius in an increase, the rate of the rxn __________.

A

Doubles

68 F develops in 5 minutes

80 F develops in 2.5 minutes

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11
Q

What processing is the most time consuming, but produces best radiographs?

A

Manual

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12
Q

What is the most efficient film processing?

A

Auto processors

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13
Q

What are three waste products of film?

A

Chemicals

Lead

Paper

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14
Q

What are some advantages to digital radiology?

A

Lower pt exposure (usually)
-Less photons required to expose sensor
—However, temptation for more retakes
—Sensor size may need more exposures to capture all information

Faster radiographs
-No processing time

More eco friendly

  • No chemicals
  • No film
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15
Q

How much less exposure for digital compared to film?

A

E/F Speed film ~50-60%

PSP - 60-80%

Charge couple device - 80-88%

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16
Q

Other advantages of digital?

A

Easy storage

Easy sending

Easy retrieval

Easy to show pts

Enlarge and vary density

17
Q

What are some disadvantages of digital?

A

COST ($10k)

Damage

Uncomfortable

Loss of image w/o back up

Film gives a better image

18
Q

There are two types of digital systems. Name them.

A

Direct
-Sensor connects direct to a computer and provides immediate images

Indirect
-Phosphor plate is used instead of film
—Image scanned in a scanner
—Stored and read on a computer

19
Q

What 4 things should you consider when selecting a sensor?

A

Number of pixels

Placement of cord (unless cordless)

Comfort

Cost

20
Q

What part in the sensor reduces the radiation amount?

A

High sensitivity CSI scintillator

21
Q

How are medical images sent digitally?

A

Sent with DICOM
-Digital Image and Communication in Medicine

*This is the standard language for the electronic communication of digital images

22
Q

What is contrast resolution?

A

Ability to distinguish different densities in an image

Humans can only detect about 60 shades of gray ideally

23
Q

What is spatial resolution?

A

Ability to distinguish fine detail in an image.

Humans can only detect down to 6 lp/mm - technology can do much better than that.

24
Q

What is sensor latitude?

A

Ability to capture a range of exposures

-Ability to capture subtle differences in tissue density from gingiva to enamel

25
Q

What is sensor sensitivity?

A

Ability to respond to small amts of radiation

*F speed film as less sensitivity

26
Q

How does a sensor work?

A

X-ray phontons are converted to visible light as they hit the scintillator - light is channeled via the fiber optic taper to the CCD

27
Q

Overexposure of a sensor leads to what?

A

Blooming

28
Q

High res vs high contrast?

A

Average grayscale value of 4 adj pixels in a high res image is assigned to create one pixel in a high contrast image

29
Q

Digital radiography filters are a combination of 4 things.

A

Optimizing grayscale

Eliminating noise thru smoothing

Sharpening image detail

Extracting features (Information)

30
Q

A decrease in brightness means what?

A

Grayscale value of all pixels is decreased equally

31
Q

How does a grayscale work?

A

By moving the sliders away from the opposite ends of the spectrum, dark pixels are reassigned to solid black and light pixels are reassigned as pure white

32
Q

What are three ways to look at a digital radiograph?

A

Original

Inverted

Embossed

33
Q

Infection control procedures?

A

Wear gloves during all radiographic procedures

Cover all non-disposable items

Sterilize non disposable items

Disinfect surfaces

Oral Radiology (7 decks)

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