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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
how is an image on PSP erased?
exposed to bright light
26
what are the layers of CCD?
Front cover Scintillator layer Silicon wafer Back cover
27
how does CCD work?
- 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
28
what differs CMOS to CCD?
CMOS - singular pixels (electrically isolated) CCD - lines of pixels
29
what is the system for storing images?
picture archiving and communication system
30
what are the contents of a film packet?
barrier wrapped film outer plastic wrapping black paper lead foil
31
what are the layers of a film?
base - plastic blue anti-glare tint adhesive layer double emulsion gelatine layer
32
what does the film emulsion consist of?
silver halide crystals suspended in gelatin
33
what is the function of gelatin in a film emulsion?
even distribution of crystals for readily absorption of liquid
34
explain direct action image formation
- x-ray beam hits silver halide crystals in emulsion - silver halide becomes sensitised - latent image production
35
what is the main reaction in direct action image formation?
silver bromide crystals reduced to black metabolic silver
36
relate film speed to crystal size and detail
larger crystal - faster speed - less x-rays - less detail
37
what does an intensifying screen consist of?
base - polyester phosphor layer supercoat
38
explain indirect image formation?
- 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
39
what may pressure do to a film?
sensitise silver halide crystals
40
what are the stages of film handling?
develop wash fix wash dry
41
What does developing do?
makes latent image visible - sensitised silver halide crystals are acted on by developing agent (phenidone) and hydroquinone
42
what reaction is involved in developing?
silver bromide reduced to silver and bromide
43
what does a developing solution contain?
developing agents - phenidone and hydroquinone activator - calcium carbonate restrainer - potassium bromide preservative - sodium sulphite solvent - water
44
what does fixing do?
makes image permanent unexposed silver halide crystals are made soluble and washed away
45
what does fixing solution contain?
clearing agent - ammonium thiosulphate acidifier - acetic acid hardener - aluminium chloride preservative - sodium sulphite solvent water
46
what does washing do?
stops development by removing unexposed silver halide crystals
47
what happens if an image is under washed?
tacky silver/green deterioration
48
what are deterministic effects of radiation?
non-stochastic biological effects of radiation that WILL occur a. acute b. chronic
49
what are non-deterministic effects of radiation?
stochastic biological effects of radiation that MAY occur
50
what is the mean dose for dental workers?
less than o.1mSv
51
how far away should you stand from machines?
2m
52
what is IRR17?
equipment and protection of staff and public
53
what is IR(ME)R17?
protection of patients
54
what is an RPA?
Radiation protection advisor - ensures organisation has adequate radiation shielding to protect staff, operators, and patients in the radiation area.
55
what is an RPS?
Radiation protection supervisor - securing compliance with IRR17 in respect of work carried out in an area subject to local rules.
56
what is an MPE?
performs radiation dose/ risk assessment for all radiation exposures.
57
what is the role of the employer?
- produce written procedures - produce protocol for taking radiographs - appoint an RPA/MPE and RPS - ensure staff read local rules
58
what is the role of the refferer?
refer individuals for exposure
59
what is the role of the dental nurse?
without qualification - process radiographs with qualification - take radiographs "on prescription" of another dental registrant
60
what is the role of the dental hygeinist?
prescribe, take, process, and interpret
61
what is the role of the dental technician?
take and process ONLY on radiographs relating to providing removable dental appliances
62
what happens if dose is greater than intended?
inform patient duty of candour legislation inform referrer
63
what does the quality assurance programme asess?
- image quality - x-ray equipment - processing (film and digital) - working procedures - training - audit
64
how is image quality rated and what are the desired percentage rates?
1 - excellent (more than 70%) 2 - diagnostically acceptable (more than 20%) 3 - unacceptable (more than 10%)
65
what happens to rate 3 films?
reject film analysis - eliminate at end of each month anf categorise faults
66
how is equipment checked for patient doses?
dosemeter for radiation output
67
what information does the box of films contain?
film size number of films liability notice best before date storage instructions
68
how is the developer checked?
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
what does an exhausted developer do to an image?
pale
70
what are the causes of fogged film?
- light entering daylight loading system/ darkroom - incorrect safelight filters
71
how do you check for fogging?
coin test - coin placed on intra oral film for 5 mins - once removed, radiograph and check for fogging
72
how are large digital sensors and EO cassettes checked?
test tool number of coloured squares - contrast and brightness number of boxes displaying line pairs - resolution
73
what are the extra-oral views?
postero-anterior mandible lateral oblique mandible DPT lateral cephalogram occipito mental views sialography
74
what are the 3 positioning landmarks?
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
what is is called when x-rays pass through tissue and some scatter?
compton scattering
76
what is an anti-scatter grid?
narrow strips of lead alternating with plastic - absorbs photons
77
what is the setup for postero-anterior mandible?
- patient faces film with nose and forehead touching - RB 90dgeree horizontal to film
78
what are the 3 positions for a lateral oblique mandible view?
isocentric vertical angulation horizontal angulation
79
how is patient set up into isocentric position for LO mandible?
- supine - machine horizontal plane - top of head tilt towards film
80
how is patient set up into vertical angulation position for LO mandible?
- patient hold cassette parallel to area - tube head beneath lower border of mandible that isnt being examined - angles slightly upwards
81
how is patient set up into horizontal angulation position for LO mandible?
- patient hold cassette parallel to area - tube head positioned along occlusal plane, just below ear
82
what machine takes a later cephalogram?
cephalogram
83
what is the positioning for a lateral cephalogram?
- mid-sagittal plane parallel to film - ear rods - x-ray aimed at EAM
84
what makes soft tissues visible in a lateral cephalogram?
aluminium filter
85
what are the 3 occipto mental views?
OM 0 OM 10 OM 30
86
what is a tomogram?
slice/ section of tissue in focus
87
explain how objects are seen in a dental panoramic depending on their location with focal trough?
further away from focal trough - blurred within focal trough - sharp
88
explain beam movement with narrow beam tomography, and its focal trough
synchronised movement of tube head and film focal trough arched shaped
89
what is the issue with arch shaped focal trough?
ectopic teeth may not be seen
90
how does a CT scan work?
- x-rays pass through body - attenuation of beam measured by detectors - computer assesses radio-opacity of each voxel - Hounsfield number for every tissue
91
what is the Hounsfield scale?
air = -1000HU water = 0HU cortical bone = 1000HU
92
what is the kV of CT tube?
120kV
93
what is a voxel?
volume of tissue
94
what makes CBCT differ from CT?
- lower dose - higher FOV - shorter exposure
95
what produces MRI?
radio waves
96
what produces SPECT?
gamma rays
97
what produces PET?
positrons
98
when would the focal trough need to be smaller?
children abnormal shaped patients better visualisation of specific anatomical areas
99
what is an orthogonal view?
90 degree to teeth
100
where is the x-ray source in relation to the focal trough?
lingual
101
explain vertical angulation?
structures further away from receptor will be projected further up on the image
102
what angle is the beam normally in panoramic?
slightly upwards by 8 degrees

Module 4 - radiology (14 decks)

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