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2nd Year > Radiography > Flashcards

Radiography Flashcards

1
Q

what is a radiograph?

A

an image produced by xrays passing throuh an object and interacting with photogenic emulsion on a film

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2
Q

what is the job of a collimator?

A

restricts shape and size of formation

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3
Q

how is an xray produced?

A

electric current in filament passes through step down transformer
excitation of electrons gives off heat and outer electrons lost
= electron cloud
potential difference at cathode and anode
step up transformer
focusing cup points electrons to anode
attraction of positive and negative pulls electrons across
energy conversion = 99% heat and 1% xrays
copper absorbs heat and puts it into oil
xrays travel in all directions, some absorbed by lead - xrays pass through unleaded window
= beam of radiation

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4
Q

what are the types of xray spectra?

A
  • continuous spectrum - brehstrahlung or breaking radiation, wide photon energy range
  • characteristic spectrum - depends on anode material, emitted by loss of K and L shells
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5
Q

what are some xray properties?

A 
travel in straight lines in free space
form a divergent beam
travel through a vacuum
penetrate matter
scatter
absorb
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6
Q

uses of a peri apical?

A 
detect apical inflammation
assess perio problems
trauma and fractures
pre extraction
position and presence of unerupted teeth
endodontics
implant evaluation
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7
Q

what is paralleling technique?

A

holder used to facilitate positioning
film parallel to tooth
accurate and reproducible image

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8
Q

what is bisected angle technique?

A

without a holder
operator dependent
not reproducible

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9
Q

what are the components of a holder?

A

bite block
indicator arm
aiming ring

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10
Q

how should the vertical plane of the film be positioned?

A

against the long axis of the tooth

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11
Q

what happens when the collimator down and pointing up?

A

elongation

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12
Q

what happens when the collimator is up and pointing down?

A

foreshortened

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13
Q

what affects the image size?

A

xray source to film distance

object to film distance

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14
Q

what does a long source to film distance cause?

what does a short source to film distance cause?

A

reduced magnification

increased magnification

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15
Q

where should the dot be placed in a periapical?

where should the dot be placed in a bitewing?

A

crown

palate

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16
Q

what should the distance of the controlled area be?

A

1.5 to 2m

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17
Q

what are the use of BW’s?

A

detect caries
monitor caries progression
asses perio status
asses existing restorations

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18
Q

what are features of horizontal bitewings?

what are features of vertical bitewings?

A 
4 distal to 8 mesial
crown and a third of roots
2 on each side
pre molars and molars
more of roots
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19
Q

why might horizontal overlap happen?
when is it acceptable?
what might it obstruct views of?

A

if tooth not parallel
crowding and tilting of teeth

ok if less than half the enamel is superimposed

miss early carious lesions

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20
Q

child of > 10 years use what holder size?

child under 10 years what holder size?

A

size 2

size 0/1

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21
Q

what does rectangular collimation reduce the dose by?

A

reduces dose by 50%

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22
Q

what is bisected angle used for?

A

changing position or shape of tooth
pt cant tolerate a holder
access is difficult

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23
Q

how is bisected angle technique done?

A
  • place film as close to the tooth as possible
  • observe angle of film to tooth
  • operator bisects angle between tooth and film and angles x ray tube so beam is 90 to the bisector
  • align collimator to the film
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24
Q

why might you use a bisected angle holder?

A

avoids irradiating finger
aids visualising angulation
reduces bending in film
stabilises film

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25
Q

what is an occlusal radiograph used for?

A

shows larger area than PA. Unerrupted teeth, cysts, SN’s.

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26
Q

what are types of film radiography?

what are types of digital radiography?

A
  • direct and indirect action

- solid state sensor and PSP

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27
Q

what is direct film?

A

dental intraoral

xrays act on silver halide crystals in emulsion of film

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28
Q

what is indirect film?

A

extra oral

light from intensifying screens act on silver halide crystals in emulsion

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29
Q

what is DR?

A

solid state CCD or CMOS sensor

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30
Q

what is CR?

A

PSP
latent image produced by interaction of xrays and phosphor layer of plate
scanned by laser to produce an image

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31
Q

how does a PSP plate work?

A

phosphor layer traps xrays in electrons
plate in scanner and scanned by red laser = light released
light converted to electrical signal and image produced
bright light removes residual energy = re usable

32
Q

how does solid state CCD work?

A

xrays hit sensor and light emitted
light hits photosensitive cells and image pixels produced
electrons released and electrical signal converted to image

33
Q

what is the difference with CMOS compared to CCD?

A

photosensitive cells are isolated

34
Q

what are advantages of digital imaging?

A 
no chemicals
easy to archive
easy image transfer 
image manipulation 
dose limitation
35
Q

what are disadvantages of digital imaging?

A

expensive
reduced isolation
back up
security

36
Q

what is the job of the films outer plastic?

A

dry and protects film from light

37
Q

what is the job of the films paper?

A

protects from light and supports

38
Q

what is the job of the films lead foil?

A

absorbs xrays, prevents back scatter

39
Q

what is the make up of radiographic film?

A

silver halide crystals - bromide and iodine in gelatin

40
Q

how does direct film work?

A

photons hit silver halide crystals = sensitized = latent image
latent image produced by sensitizing silver halide crystals - not visibile
image made visible by reduction of silver bromide to black metallic silver

41
Q

what is film speed?

A

sensitivity of film to xrays
dependent of crystal size
increased crystal size = faster film = reduced detail = reduced dose

42
Q

how does indirect film work?

A

sensitive to light
light produced by phosphor crystals in direct proportion to xrays hitting the screen
reduced exposure needed for image = dose reduced = reduced detail image

43
Q

what are the stages of film processing?

A 
develop - latent image made visible
wash - stop development 
fix - image made permanent 
wash - stop fixer
dry - easier to handle
44
Q

what is used as a developer?
develop for too long? too short?
developer too hot? too cold?
developer to strong? to weak?

A

phenidone, hyroquinone
dark light
dark light
dark light

45
Q

what is the job of the fixer?
what happens to over fixed image?
under fixed?

A

change unexposed crystals to soluble to wash away
image removed if over fixed
green tinge

46
Q

what types of processor exist?

A

automatic
manual
instant processing

47
Q

what is the abosrbed dose?

A

amount of energy deposited into a medium

48
Q

what s the equivalent dose?

A

accounts for the radio biological effectiveness of different radiations

49
Q

what is the effective dose?

A

allows doses from different areas of the body to be compared

50
Q

what are types of somatic effects?

A

deterministic

non deterministic

51
Q

what are types of effects on the genetic offspring of those irradiated?

A

non determinsitic stochastic

52
Q

what are deterministic effects of radiation and when do they occur?do they occur in dentistry?

A

will occur above a threshold
hair loss skin erythema cataract GI upset erythropoiesis suppressed
does not occur in dentistry

53
Q

what are non determinsitic effects of radiation?

A

random development do no occur at any threshold
increased probability with increased dose
leaukaemias and solid tumours
occurs in dentistry

54
Q

what is the intra oral cancer risk?

what is the DPT cancer risk?

A
  1. 06-0.7 in 1000000

0. 29-1.9 in 100000

55
Q

how is dose contained?

A

justification - exposure must be justified
optimisation - ALARP
dose limitation

56
Q

when is lead protection used in dental radiography?

A

thyroid in the main beam

57
Q

when can caries be radiographically detected?

A

30-40% demineralisation has to have occured

58
Q

what can be mistaken for caries?

A

cervical burnout
shadows
radiolucent restorations

59
Q

what are xrays used for in perio disease?

A

to show the remaining bone in relation to the root

60
Q

why is there more scatter min skull radiography?

A

increased field of beam

61
Q

what is an antiscatter grid?

A

stop photons scattered in pt reaching the film

lead and plastic

62
Q

what are PA of the mandibles used for?

A

fractures

cysts and malignancies

63
Q

what are reverse townes used for?

A

trauma and pathology

head and neck of condyles

64
Q

what lateral obliques of the jaw used for?

A

dental assessment in special needs pts and kids. Assess wisdom teeth. Fractures. Pathology.

65
Q

what are ceph radiographs used for?

A

ortho assessment. Pre orthagnathic surgery

66
Q

what are Occipito mental radiographs used for?

A

facial bone fractures

67
Q

what legislations are in place for dental radiography?

A

ionising radiations regulations 1999

ionising radiation medical exposure reg 2000

68
Q

what is the job of IRR 99?

A

protects public and those working with radiation. Equipment

69
Q

what is the job of IRMER 2000?

A

protects those being irradiated

70
Q

for general loss of attachment of 4-5mm take what type of bw’s?
for loa of >6mm?

A

horizontal bws

vertical bws

71
Q

what problems does a DPT present?

A

anterior region - spine superimposition
overlap at premoalr region/molar region can obscure bone
lack of fine detail and burnout

72
Q

what topics undergo quality assurance?

A 
image quality
xray equipment
processing
working procedures
training
audit
73
Q

what percent of graded films should be 1,2,3?

A

1 >70% of films
2< 20 % of films
3<10% fims

74
Q

what does initial acute inflammation look like on an xray?

A

nil or widening of the PDL

75
Q

what does initial inflammation spread look like on an xray?

A

loss of lamina dura at the apex

which can lead to periapical bone loss

76
Q

what does initial chronic inflammation look like?

A

dense sclerotic bone

2nd Year (4 decks)

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