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2nd Year > Radiography > Flashcards

Radiography Flashcards

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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
what is an occlusal radiograph used for?
shows larger area than PA. Unerrupted teeth, cysts, SN's.
26
what are types of film radiography? | what are types of digital radiography?
- direct and indirect action | - solid state sensor and PSP
27
what is direct film?
dental intraoral | xrays act on silver halide crystals in emulsion of film
28
what is indirect film?
extra oral | light from intensifying screens act on silver halide crystals in emulsion
29
what is DR?
solid state CCD or CMOS sensor
30
what is CR?
PSP latent image produced by interaction of xrays and phosphor layer of plate scanned by laser to produce an image
31
how does a PSP plate work?
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
how does solid state CCD work?
xrays hit sensor and light emitted light hits photosensitive cells and image pixels produced electrons released and electrical signal converted to image
33
what is the difference with CMOS compared to CCD?
photosensitive cells are isolated
34
what are advantages of digital imaging?
``` no chemicals easy to archive easy image transfer image manipulation dose limitation ```
35
what are disadvantages of digital imaging?
expensive reduced isolation back up security
36
what is the job of the films outer plastic?
dry and protects film from light
37
what is the job of the films paper?
protects from light and supports
38
what is the job of the films lead foil?
absorbs xrays, prevents back scatter
39
what is the make up of radiographic film?
silver halide crystals - bromide and iodine in gelatin
40
how does direct film work?
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
what is film speed?
sensitivity of film to xrays dependent of crystal size increased crystal size = faster film = reduced detail = reduced dose
42
how does indirect film work?
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
what are the stages of film processing?
``` develop - latent image made visible wash - stop development fix - image made permanent wash - stop fixer dry - easier to handle ```
44
what is used as a developer? develop for too long? too short? developer too hot? too cold? developer to strong? to weak?
phenidone, hyroquinone dark light dark light dark light
45
what is the job of the fixer? what happens to over fixed image? under fixed?
change unexposed crystals to soluble to wash away image removed if over fixed green tinge
46
what types of processor exist?
automatic manual instant processing
47
what is the abosrbed dose?
amount of energy deposited into a medium
48
what s the equivalent dose?
accounts for the radio biological effectiveness of different radiations
49
what is the effective dose?
allows doses from different areas of the body to be compared
50
what are types of somatic effects?
deterministic | non deterministic
51
what are types of effects on the genetic offspring of those irradiated?
non determinsitic stochastic
52
what are deterministic effects of radiation and when do they occur?do they occur in dentistry?
will occur above a threshold hair loss skin erythema cataract GI upset erythropoiesis suppressed does not occur in dentistry
53
what are non determinsitic effects of radiation?
random development do no occur at any threshold increased probability with increased dose leaukaemias and solid tumours occurs in dentistry
54
what is the intra oral cancer risk? | what is the DPT cancer risk?
0. 06-0.7 in 1000000 | 0. 29-1.9 in 100000
55
how is dose contained?
justification - exposure must be justified optimisation - ALARP dose limitation
56
when is lead protection used in dental radiography?
thyroid in the main beam
57
when can caries be radiographically detected?
30-40% demineralisation has to have occured
58
what can be mistaken for caries?
cervical burnout shadows radiolucent restorations
59
what are xrays used for in perio disease?
to show the remaining bone in relation to the root
60
why is there more scatter min skull radiography?
increased field of beam
61
what is an antiscatter grid?
stop photons scattered in pt reaching the film | lead and plastic
62
what are PA of the mandibles used for?
fractures | cysts and malignancies
63
what are reverse townes used for?
trauma and pathology | head and neck of condyles
64
what lateral obliques of the jaw used for?
dental assessment in special needs pts and kids. Assess wisdom teeth. Fractures. Pathology.
65
what are ceph radiographs used for?
ortho assessment. Pre orthagnathic surgery
66
what are Occipito mental radiographs used for?
facial bone fractures
67
what legislations are in place for dental radiography?
ionising radiations regulations 1999 | ionising radiation medical exposure reg 2000
68
what is the job of IRR 99?
protects public and those working with radiation. Equipment
69
what is the job of IRMER 2000?
protects those being irradiated
70
for general loss of attachment of 4-5mm take what type of bw's? for loa of >6mm?
horizontal bws | vertical bws
71
what problems does a DPT present?
anterior region - spine superimposition overlap at premoalr region/molar region can obscure bone lack of fine detail and burnout
72
what topics undergo quality assurance?
``` image quality xray equipment processing working procedures training audit ```
73
what percent of graded films should be 1,2,3?
1 >70% of films 2< 20 % of films 3<10% fims
74
what does initial acute inflammation look like on an xray?
nil or widening of the PDL
75
what does initial inflammation spread look like on an xray?
loss of lamina dura at the apex | which can lead to periapical bone loss
76
what does initial chronic inflammation look like?
dense sclerotic bone

2nd Year (4 decks)

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