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Driving Theory > Radiology > Flashcards

Radiology Flashcards

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1
Q

What does the black paper in direct action film do?

A

Protects from light

Stiffens/supports

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2
Q

What does the foil in direct action film do?

A

Composed of lead and aluminium to absorb x-rays and prevent back scatter
Pattern so if film placed wrong way round will know

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3
Q

Describe the layers of the film in direct action film

A

Plastic base
Adhesive layer
Emulsion
Supercoat- Protective layer of gelatine

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4
Q

What does the plastic base of direct action film do?

A

Supports emulsion

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5
Q

What does the adhesive in direct action film do?

A

Fixes the emulsion to base

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6
Q

What does the emulsion in direct action films contain?

A

Silver halide crystals embedded in gelatin matrix

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7
Q

What reaction occurs in the emulsion layer?

A

The x-ray photons sensitise the silver halide crystals which are then later reduced to black metallic silver during the development process

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8
Q

What does the protective layer of gelatine in direct action film do?

A

Shields the emulsion

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9
Q

What side should the dot be placed, towards or away from the x-ray beam?

A

Towards the x-ray beam

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10
Q

Indirect action film is used in conjunction with what?

A

Intensifying screens in a cassette

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11
Q

Name the layers of indirect action film

A 
Cassette front
Sponge rubber
Front intensifying screen
Emulsion
Back intensifying screen
Sponge rubber 
Cassette back
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12
Q

What could cause extreme blackening of an image?

A

Light

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13
Q

How is ALARP achieved?

A 
IRR 1999 (appropriate equipment well maintained)
IRR 200 (only take radiograph if clinically necessary)
Rectangular collimation
Use fast film to reduce dose
Lead protection (thyroid collars)
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14
Q

What kind of patient is more sensitive to X-rays?

A

Young patient

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15
Q

Where is the radiographic base line from?

A

Outer canthus of eye to EAM

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16
Q

Where is the frankfort plane from?

A

Inferior orbital border to upper border of EAM

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17
Q

Where is the maxillary occlusal plane from?

A

Ala of nose to triages of ear

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18
Q

What are the layers of phosphor plates?

A

Protective layer
Phosphor layer
Reflective layer
Backing layer

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19
Q

What are the layers of CCD?

A

Back cover
Silicon wafer
Scintillator layer
Front cover

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20
Q

What are the layers of phosphor plates?

A

Protective layer
Phosphor layer
Reflective layer
Backing layer

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21
Q

What are the differences between phosphor plate and CCD?

A

Phosphor plates have a phosphor coating on plates which absorb x-rays and are scanned to release energy as light whereas solid state is similar to image capture in a digital camera

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22
Q

What are the advantages of phosphor plate?

A

Can be used with existing film holders

Tolerated well by patients

23
Q

What are the disadvantages of phosphor plate?

A

Plates easily damaged
Relatively expensive
Sensitive to background radiation

24
Q

What are the disadvantages of CCD?

A

Can only be used with its own holders
Not tolerated well by patients- can be bulky
Sensors very expensive
Easily damaged

25
Q

What does the practitioner do?

A

Justifies the exposure

26
Q

How does characteristic radiation work?

A

Incoming electron collides with an inner shell electron and either displaces it into a more peripheral shell (excitation) or removes it completely (ionisation)

27
Q

How does continuous radiation work?

A

Incoming electron passes close to target nucleus, causing it to be rapidly slowed down and deflected and produces bremsstrahlung x-ray photons

28
Q

How would you do an occipito mental radiograph?

A

Radiographic base line of 45 degrees to film, angle beam 10 or 30 degrees to feet, aim centre of beam through midline of patient and through base on nose

29
Q

What are the contents of a film packet?

A

The outer wrapper
The film
The sheet of lead foil
The protective black paper

30
Q

What does the high voltage between the cathode and the anode do?

A

Accelerates

31
Q

What does the high voltage between the cathode and the anode do?

A

Accelerates the e- from the negative filament to the positive target. Sometimes referred as a kilovoltage peak

32
Q

What is the measure for the quantity of e- being accelerated?

A

Current

33
Q

What does the surrounding oil do?

A

Facilitates removal of heat

34
Q

Describe the production of x-rays

A

Filament is electrically heated. Cloud of e- produced. A high voltage across the tube accelerates the e- to the anode at high speed. Focusing device aims the e- stream at the focal spot on the target. E- bombarded target and are brought to sudden rest. Energy lost converted to heat (99%) or X-rays (1%). Heat produced is removed and dissipated by the copper block and surrounding oil. X-rays are emitted from all directions from the target. Those emitted from the small lead free window make up the beam used for diagnostic purposes

35
Q

Name the law that gives us the safe distance from a source of x-rays

A

Inverse square law

36
Q

What is the inverse square law?

A

Intensity= 1/d^2

37
Q

What does doubling the distance from an x-ray source do?

A

Reduces the intensity to 1/4

38
Q

Do shorter wavelength x-rays have a greater or less energy than longer wavelength x-rays?

A

Greater energy

39
Q

What does the photoelectric effect relate to?

A

Interaction with mater, not production of x-rays, this is what happens when an x-ray photon hits an object

40
Q

What happens when an x-ray photon hits an object?

A

Compton scattering

Photoelectric effect

41
Q

List 4 advantages of the photoelectric effect

A
  • easy to learn
  • accurate geometry of image
  • rectangular collimator
  • no dose to patient fingers, reduces repeats
42
Q

What radiographs would you request for identification of an unerupted maxillary canine?

A

Horizontal parallax

Vertical parallax

43
Q

What is parallax?

A

You need two views distinctly different in angulation to each other to localise it e.g if vertical go from a DPT to an occlusal, or a PP to occlusal

44
Q

What are the indications for a lateral oblique of mandible?

A

Fracture of mandible
Pathology
Look at 8’s

45
Q

What are the three different technique for lateral oblique of mandible?

A

Isocentric positioning
Vertical angle
Horizontal angle

46
Q

What angle is the x-ray beam for isocentric positioning?

A

25 degrees

47
Q

Who discovered x-rays and when?

A

Wilhelm Conrad Roentgen 1895

48
Q

Each packet of x-rays is what?

A

A photon

49
Q

What does one photon equal?

A

One quantum of energy

50
Q

What is compton effect?

A

Scattering and partial absorption interaction with outer shell electrons, predominating with higher energy photons

51
Q

What is the photoelectric effect?

A

Complete absorption interaction with inner shell electrons, predominating with lower energy photons

52
Q

What are the similarities between the cathode and the anode?

A

Both made of tungsten

Both electrodes

53
Q

Why is there a vacuum?

A

To allow e- to fly across

Driving Theory (3 decks)

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