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Module 4 - radiology > SUMMARY > Flashcards

SUMMARY Flashcards

1
Q

name the types of intra-oral x-rays

A

periapicals
bitewings
occlusal - max and man

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2
Q

name the types of extra-oral x-rays

A

DPT
Lateral cephalogram
Postero anterior mandible
Lateral oblique mandible
occipito-mental views of facial bones

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3
Q

what creates the difference in detail between intra and extra oral radiographs?

A

the distance between object and receptor

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4
Q

what is the atomic mass number?

A

number of protons + number of neutrons

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5
Q

what is an isotope?

A

same number of proton
different number of neutrons

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6
Q

what is the most favourable intra oral technique and how is it performed?

A

paralleling

uses holder which is parallel to teeth

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7
Q

what intra oral technique involves patient holding film?

A

bisected angle

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8
Q

what are the 4 types of holders and what are they used for?

A

red - bitewings
blue - anterior
yellow - posterior
green - endo

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9
Q

what are the different sizes of phosphor plates?

A

0 - periapical and bitewings
1- periapical (adult), all areas (children)
2 - posterior (adult)
4 - occlusal

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10
Q

in intra-oral radiography, what is the ideal vertical plane?

A

parallel to long axis of tooth
IF NOT
elongation of teeth

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11
Q

in intra-oral radiography, what is the ideal horizontal plane?

A

parallel to dental arch
IF NOT
overlapping teeth

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12
Q

in intra-oral radiography, what is the ideal position of the beam?

A

right angle to tooth and receptor

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13
Q

what would be the outcome if the beam was angled down, up, or poor horizontal angulation?

A

down - elongation
up - foreshortening
hor. - overlapping

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14
Q

what is at the end of the x-ray tube that helps reduce exposure?

A

collimator

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15
Q

where should the dot on the receptor be placed for periapical, and bitewings?

A

periapical - crown of tooth
bitewing - palate

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16
Q

what are the ideal magnification distance types?

A

x-ray source -> receptor - LONG
object -> receptor - SHORT

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17
Q

what is the difference in dose between vertical and horizontal bitewings?

A

vertical double exposure dose

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18
Q

what would you do if patient cant tolerate the plastic of the holder?

A

paper tab stuck to receptor

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19
Q

explain the difference between direct and indirect film and what they are used for?

A

direct film - intra oral
x-rays directly act on silver halide crystals in emulsion.

indirect film - extra oral
light from intensifying screens act on silver halide crystals in emulsion.

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20
Q

what are the types of digital receptors?

A

PSP - phosphor plate
CCD/ CMOS - solid state

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21
Q

what creates the latent image with PSP?

A

x-ray energy stored in the electrons of the phosphor crystals

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22
Q

how is an image created with the phosphor plate?

A

phosphor layer scanned by red laser
stored energy is released as blue light
blue light is collected by scanner and converted to image

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23
Q

what is the phosphor coating of PSP?

A

Barium fluoride

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24
Q

what does an ACD do?

A

converts light to digital signal

each pixel is assigned a numerical value according to intensity of light

pixel values represent shades of grey

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25
Q

how is an image on PSP erased?

A

exposed to bright light

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26
Q

what are the layers of CCD?

A

Front cover
Scintillator layer
Silicon wafer
Back cover

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27
Q

how does CCD work?

A
  • x-rays hit off sensory in the scintillator layer
  • this gives off light and hits the silicon wafer cells which make up pixels of image
  • electrons in each pixel are released and converted to a electrical signal (voltage)
  • computer converts into image
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28
Q

what differs CMOS to CCD?

A

CMOS - singular pixels (electrically isolated)
CCD - lines of pixels

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29
Q

what is the system for storing images?

A

picture archiving and communication system

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30
Q

what are the contents of a film packet?

A

barrier wrapped film
outer plastic wrapping
black paper
lead foil

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31
Q

what are the layers of a film?

A

base - plastic
blue anti-glare tint
adhesive layer
double emulsion
gelatine layer

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32
Q

what does the film emulsion consist of?

A

silver halide crystals suspended in gelatin

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33
Q

what is the function of gelatin in a film emulsion?

A

even distribution of crystals for readily absorption of liquid

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34
Q

explain direct action image formation

A
  • x-ray beam hits silver halide crystals in emulsion
  • silver halide becomes sensitised
  • latent image production
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35
Q

what is the main reaction in direct action image formation?

A

silver bromide crystals reduced to black metabolic silver

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36
Q

relate film speed to crystal size and detail

A

larger crystal - faster speed - less x-rays - less detail

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37
Q

what does an intensifying screen consist of?

A

base - polyester
phosphor layer
supercoat

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38
Q

explain indirect image formation?

A
  • x-ray photons hit phosphor crystals in intensifying screen and give off light
  • light hits silver halide crystals in emulsion
  • silver halide crystals sensitised
  • latent image production
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39
Q

what may pressure do to a film?

A

sensitise silver halide crystals

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40
Q

what are the stages of film handling?

A

develop
wash
fix
wash
dry

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41
Q

What does developing do?

A

makes latent image visible
- sensitised silver halide crystals are acted on by developing agent (phenidone) and hydroquinone

42
Q

what reaction is involved in developing?

A

silver bromide reduced to silver and bromide

43
Q

what does a developing solution contain?

A

developing agents - phenidone and hydroquinone
activator - calcium carbonate
restrainer - potassium bromide
preservative - sodium sulphite
solvent - water

44
Q

what does fixing do?

A

makes image permanent
unexposed silver halide crystals are made soluble and washed away

45
Q

what does fixing solution contain?

A

clearing agent - ammonium thiosulphate
acidifier - acetic acid
hardener - aluminium chloride
preservative - sodium sulphite
solvent water

46
Q

what does washing do?

A

stops development by removing unexposed silver halide crystals

47
Q

what happens if an image is under washed?

A

tacky
silver/green
deterioration

48
Q

what are deterministic effects of radiation?

A

non-stochastic biological effects of radiation that WILL occur

a. acute
b. chronic

49
Q

what are non-deterministic effects of radiation?

A

stochastic biological effects of radiation that MAY occur

50
Q

what is the mean dose for dental workers?

A

less than o.1mSv

51
Q

how far away should you stand from machines?

A

2m

52
Q

what is IRR17?

A

equipment and protection of staff and public

53
Q

what is IR(ME)R17?

A

protection of patients

54
Q

what is an RPA?

A

Radiation protection advisor
- ensures organisation has adequate radiation shielding to protect staff, operators, and patients in the radiation area.

55
Q

what is an RPS?

A

Radiation protection supervisor
- securing compliance with IRR17 in respect of work carried out in an area subject to local rules.

56
Q

what is an MPE?

A

performs radiation dose/ risk assessment for all radiation exposures.

57
Q

what is the role of the employer?

A
  • produce written procedures
  • produce protocol for taking radiographs
  • appoint an RPA/MPE and RPS
  • ensure staff read local rules
58
Q

what is the role of the refferer?

A

refer individuals for exposure

59
Q

what is the role of the dental nurse?

A

without qualification - process radiographs
with qualification - take radiographs “on prescription” of another dental registrant

60
Q

what is the role of the dental hygeinist?

A

prescribe, take, process, and interpret

61
Q

what is the role of the dental technician?

A

take and process ONLY on radiographs relating to providing removable dental appliances

62
Q

what happens if dose is greater than intended?

A

inform patient
duty of candour legislation
inform referrer

63
Q

what does the quality assurance programme asess?

A
  • image quality
  • x-ray equipment
  • processing (film and digital)
  • working procedures
  • training
  • audit
64
Q

how is image quality rated and what are the desired percentage rates?

A

1 - excellent (more than 70%)
2 - diagnostically acceptable (more than 20%)
3 - unacceptable (more than 10%)

65
Q

what happens to rate 3 films?

A

reject film analysis
- eliminate at end of each month anf categorise faults

66
Q

how is equipment checked for patient doses?

A

dosemeter for radiation output

67
Q

what information does the box of films contain?

A

film size
number of films
liability notice
best before date
storage instructions

68
Q

how is the developer checked?

A

sensitometry
- daily
- compare with fresh film

step wedge test
- different thicknesses of metal
- shows steps of blackening when radiographed

readily exposed test film
- unwrap in darkroom conditions
green - good
amber - OK
red - exhausted

69
Q

what does an exhausted developer do to an image?

A

pale

70
Q

what are the causes of fogged film?

A
  • light entering daylight loading system/ darkroom
  • incorrect safelight filters
71
Q

how do you check for fogging?

A

coin test
- coin placed on intra oral film for 5 mins
- once removed, radiograph and check for fogging

72
Q

how are large digital sensors and EO cassettes checked?

A

test tool

number of coloured squares - contrast and brightness
number of boxes displaying line pairs - resolution

73
Q

what are the extra-oral views?

A

postero-anterior mandible
lateral oblique mandible
DPT

lateral cephalogram
occipito mental views
sialography

74
Q

what are the 3 positioning landmarks?

A

radiographic baseline - outer canthus of eye to EAM
frankfort plane - inferior orbital border to EAM
maxillary occlusal plane - ala of nose to tragus of ear

75
Q

what is is called when x-rays pass through tissue and some scatter?

A

compton scattering

76
Q

what is an anti-scatter grid?

A

narrow strips of lead alternating with plastic - absorbs photons

77
Q

what is the setup for postero-anterior mandible?

A
  • patient faces film with nose and forehead touching
  • RB 90dgeree horizontal to film
78
Q

what are the 3 positions for a lateral oblique mandible view?

A

isocentric
vertical angulation
horizontal angulation

79
Q

how is patient set up into isocentric position for LO mandible?

A
  • supine
  • machine horizontal plane
  • top of head tilt towards film
80
Q

how is patient set up into vertical angulation position for LO mandible?

A
  • patient hold cassette parallel to area
  • tube head beneath lower border of mandible that isnt being examined
  • angles slightly upwards
81
Q

how is patient set up into horizontal angulation position for LO mandible?

A
  • patient hold cassette parallel to area
  • tube head positioned along occlusal plane, just below ear
82
Q

what machine takes a later cephalogram?

A

cephalogram

83
Q

what is the positioning for a lateral cephalogram?

A
  • mid-sagittal plane parallel to film
  • ear rods
  • x-ray aimed at EAM
84
Q

what makes soft tissues visible in a lateral cephalogram?

A

aluminium filter

85
Q

what are the 3 occipto mental views?

A

OM 0
OM 10
OM 30

86
Q

what is a tomogram?

A

slice/ section of tissue in focus

87
Q

explain how objects are seen in a dental panoramic depending on their location with focal trough?

A

further away from focal trough - blurred
within focal trough - sharp

88
Q

explain beam movement with narrow beam tomography, and its focal trough

A

synchronised movement of tube head and film
focal trough arched shaped

89
Q

what is the issue with arch shaped focal trough?

A

ectopic teeth may not be seen

90
Q

how does a CT scan work?

A
  • x-rays pass through body
  • attenuation of beam measured by detectors
  • computer assesses radio-opacity of each voxel
  • Hounsfield number for every tissue
91
Q

what is the Hounsfield scale?

A

air = -1000HU
water = 0HU
cortical bone = 1000HU

92
Q

what is the kV of CT tube?

A

120kV

93
Q

what is a voxel?

A

volume of tissue

94
Q

what makes CBCT differ from CT?

A
  • lower dose
  • higher FOV
  • shorter exposure
95
Q

what produces MRI?

A

radio waves

96
Q

what produces SPECT?

A

gamma rays

97
Q

what produces PET?

A

positrons

98
Q

when would the focal trough need to be smaller?

A

children
abnormal shaped patients
better visualisation of specific anatomical areas

99
Q

what is an orthogonal view?

A

90 degree to teeth

100
Q

where is the x-ray source in relation to the focal trough?

A

lingual

101
Q

explain vertical angulation?

A

structures further away from receptor will be projected further up on the image

102
Q

what angle is the beam normally in panoramic?

A

slightly upwards by 8 degrees

Module 4 - radiology (14 decks)

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