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Oral Radiology > Midterm > Flashcards

Midterm Flashcards

1
Q

What helps to cool the tube head?

A

oil

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2
Q

What produces maximum energy Bremsstrahlung x-rays?

A

When an incident electron collides with the nucleus of a tungsten atom

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3
Q

The more an incident electron curves around an atom’s nucleus, the [more/less] energy is produced.

A

More energy is given off when an electron curves more around the nucleus. Caused by the electron passing close to the nucleus.

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4
Q

What accounts for the bulk of x-ray photons produced?

A

Bremsstrahlung radiation

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5
Q

What is characteristic radiation?

A

When an incident electron collides with an orbiting inner ring electron in the tungsten atom - electrons from outer rings fill the void

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6
Q

What accounts for only a small fraction of x-ray photons?

A

characteristic radiation

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7
Q

What is the cathode in the x-ray tube?

A

Tungsten filament and molybdenum focusing cup (cathode = negative lead)

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8
Q

What is the anode in the x-ray tube?

A

The tungsten target and copper stem (anode = positive lead)

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9
Q

What is the most common thing to go bad in an x-ray tube?

A

The tungsten filament on the cathode

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10
Q

What is the molybdenum focusing cup for?

A

Narrowing beam of electrons, and directing them toward the tungsten target

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11
Q

What does the low voltage tube current do?

A

heats the tube filament

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12
Q

What does the high tube voltage do?

A

accelerate the electron stream

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13
Q

What is the kVp dial on the control panel for?

A

controlling the auto transformer, which adjusts the step-up transformer

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14
Q

As tube current is _________ more electrons are released to collide with the target.

A

increased

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15
Q

Filtration absorbs ___ ______ _______ that would not reach the image receptor.

A

low energy photons

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16
Q

What reduces the size of the x-ray beam?

A

Collimator

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17
Q

What occurs when low energy photons are deflected by outer ring electrons, and contributes to film fog?

A

Coherent scattering

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18
Q

_________ ________ is the process when incident photons are absorbed by an atom by interacting with inner shell electrons.

A

Photoelectric absorption

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19
Q

_________ ________ occurs when a photon interacts with an outer orbital electron, and account for 49% of dental x-ray degradation.

A

Compton scattering

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20
Q

What photon interactions make it possible to produce radiographs?

A

Photoelectric absorption

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21
Q

A black “X” through a tooth charts what?

A

congenitally missing teeth

22
Q

Gold is charted with?

A

cross hatches

23
Q

Composite resin is charted as?

A

outlined in blue if previously done, or red it future tx

24
Q

amalgam is charted as?

A

A solid color

25
Q

Name 3 ways you can maximize sharpness and resolution of a radiograph.

A
  1. Use small effective focal spot (tungsten plate)
  2. Increase distance from focal spot to object with aiming cylinder
  3. Minimize distance from object to image receptor
26
Q

What four ways can you prevent distortion?

A
  1. increase distance from focal spot to image receptor
  2. decrease distance from object to image receptor
  3. position film parallel to long axis of tooth
  4. orient tube head perpendicular to object/film
27
Q

How does foreshortening happen?

A

Happens when x-ray beam is perpendicular to film, but tooth is not

28
Q

How does elongation occur?

A

Happens when x-ray beam is perpendicular to the object, but not to the film

29
Q

What technique reduces foreshortening and elongation?

A

bisecting angle technique

30
Q

What is the SLOB rule?

A

Used to determine if an object is lingual or buccal to a tooth based on two radiographs from different angles. Same Lingual - Opposite Buccal

31
Q

If you positioned a tube head mesially of a tooth and an object moves mesially, is the object lingual or buccal?

A

Lingual. (remember SLOB)

32
Q

What images are included in an FMX?

A

Includes 14 periapical images and 4 bitewings

33
Q

________ radiographs are vertical, and _________ radiographs are horizontal.

A

Anterior, posterior

34
Q

The transmission of energy through space and matter is ________.

A

Radiation

35
Q

X-rays are a (higher/lower) frequency than ultraviolet light.

A

higher

36
Q

What is our biggest source of natural radiation?

A

radon (contributes 37% of total radiation exposure)

37
Q

What is our biggest source of man-made radiation?

A

CT scans (24% of total exposure, twice as much as x-rays)

38
Q

X-rays are what type of ionizing radiation?

A

Electromagnetic radiation (photons)

39
Q

______ _____ is the energy absorbed by any type of matter.

A

Absorbed dose (unit: Gray)

40
Q

_______ ____ is used to compare the biologic effect on a tissue from different types of radiation.

A

Equivalent dose (unit: Sievert)

41
Q

_______ ____ is used to measure the estimated risk to humans.

A

Effective dose (unit: Sievert)

42
Q

Which tissues are at high risk for cancer after exposure to radiation?

A

bone marrow, lymphoid organs, testes, breasts, ovaries, etc

43
Q

The reason we may cover the reproductive organs of a patient is best described by the concept of…

A

Effective dose

44
Q

What is direct effect in radiation chemistry?

A

When a photon (or secondary electron) ionizes biologic macromolecules. Accounts for ⅓ of biologic damage from x-rays.

45
Q

When free radicals and toxins produced by water radiolysis interact with biologic macromolecules to cause damage is called what?

A

Indirect effect

46
Q

The greater the dose, the greater the severity of injury describes which concept?

A

Deterministic effect – exposure must reach a threshold to be clinically observable

47
Q

Radiation injury based on the probability of occurrence describes what concept?

A

Stochastic effect – no threshold because there is always risk regardless of level of exposure

48
Q

What are 3 guiding principles to follow in order to reduce patient’s exposure to radiation?

A
  1. justification for image
  2. ALARA
  3. dose limitation
49
Q

Do not perform regular radiographs on pregnant patients.

A

Duh.

50
Q

What can you use to reduce the area of exposure 60% over circular collimators?

A

rectangular collimator

51
Q

How far away should you stand to avoid radiation exposure?

A

at least 2 meters away at 90-135* from x-ray beam

Oral Radiology (1 decks)

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