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BDS3 Radiology > Past paper MCQ > Flashcards

Past paper MCQ Flashcards

1
Q

The personnel involved in dental radiographic examination occur in following order?

A
  • Referrer, practitioner, operator
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2
Q

In radiographic localisation the acronym SLOB stands for?

A
  • Same lingual Opposite buccal
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3
Q

The probability of photo-electric absorption effects occuring in radiography is proportional to?

A
  • Atomic number Z3
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4
Q

What is the correct colour of film holder to use when taking PA 26?

A
  • Yellow
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5
Q

Radiograph colour for PA 11?

A
  • Blue
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6
Q

Radiograph colour for endo?

A
  • Green
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7
Q

Radiograph colour for bitewings?

A
  • Red
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8
Q

In relation to Ionising radiation regulations 2017 what is true?

A
  • Practitioner must justify every exposure
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9
Q

When positioning patient for panoramic radiograph (OPT) what anatomical reference should be horizontal ?

A
  • Frankfort plane
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10
Q

What is the most likely processing fault in a radiographic image which is too dark?

A
  • Too much time in developer
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11
Q

How often should a test film be exposed and processed in GDP for quality assurance?

A
  • Daily
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12
Q

When positioning pt for upper anterior oblique occlusal radiograph, what anatomical reference is used to assess occlusal plane?

A
  • Ala-tragus line
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13
Q

A lateral cephalometric radiograph is taken for a pt requiring what orthodontic treatment?

A
  • Functional appliance therapy
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14
Q

In dental panoramic radiography what should x-ray beam be?

A
  • Aimed upwards at approx 8degrees
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15
Q

Intra-oral charge coupled devices (CCD) digital x-ray sensors are what?

A
  • More sensitive to x-rays than F-speed film
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16
Q

What occurs in radiographic tube head?

A
  • Interacts with target to produce characteristic and continuous radiation
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17
Q

What is occuring between the electrons in the tube head?

A
  • Electrons from tungsten anode to interacting with tungsten cathode
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18
Q

What is the most important part when you send the pt down for radiographs to radiology>

A
  • Clinical justification
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19
Q

What curve affects radiographic technqiue?

A

The curve of spee affects vertical angulation

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20
Q

What is the frequency of radiographs for high risk adults?

A

6 months

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21
Q

What distance should the beam aiming device be from the skin?

A
  • 1-2cm
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22
Q

What is the best way to identify a pt arriving at radiology?

A
  • Ask for their details
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23
Q

What is the thickness of aluminium shield for 70Kv ?

A

1.5mm

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24
Q

Why are dental x-ray tubes often set for 70kV?

A
  • So that the bombarding electrons have enough energy to displace K shell electrons from the tungsten atoms
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25
Q

By what % can rectangular collimation reduce surface area irradiated by?

A
  • 50%
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26
Q

Which of the following a drawback of using rectangular collimation?

A
  • Increases risk of collimation errors
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27
Q

X-rays and visible light are both foth forms of EM radiation, compared to visible light, X-rays have lower:

A

Wave length

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28
Q

During a dental radiograph exposure, what is the primary type of interaction happening between the x-ray photons and the outer shell electrons?

A
  • The Compton Effect
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29
Q

Which of the following is measured in Grays (Gys)

A
  • Absorbed dose
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30
Q

What type of radiation effect are we most concerned about in dental radiography?

A
  • Somatic non deterministic
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31
Q

What is the most common mechinism by which x-ray photons cause carcinogenisis?

A
  • Indirect damage to DNA
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32
Q

Which of the following best decribes how an x-ray tube generates photons:

A

A tungsten cathode interacts with a tungsten anode to produce characterstic and continuous radation

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33
Q

What energy is required to displace K shell electrons from tungsten in an x-ray tube?

A
  • 69.5kv
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34
Q

Which of the following is the most important piece of information when requesting a radiograph?

A
  • The justification for taking the radiograph
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35
Q

What should focus-skin distance be for radiographs taken at 60kV or higher?

A
  • 200mm (20cm)
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36
Q

What metal is the focusing cup in an x-ray tube made of?

A
  • Molybdenum
37
Q

If a person standing 2m away from an x-ray source recieves an equivalent dose of 20uSv, how many uSv will they recieve from standing 4m away?

A
  • 5uSv
38
Q

Based on UK averages, what is the source of roughly 50% of annual ionising radiation?

A
  • Radon gas
39
Q

What are the interactions occuring in the x-ray tube?

A
  • Continuous interaction
  • Characteristic interaction
40
Q

What is continuous interaction?

A
  • Produces continuous range of x-ray photon energies
  • Bombarding e- interact with nucleus of target atom
  • Max photon energy matches peak voltage
41
Q

What is characteristic interaction?

A
  • Produces specific energies of x-ray photon , characteristic to target element
  • Bombarding e- interact with inner shell e- of target atom
  • Photon energy depend on binding energies of e- shells
42
Q

What are the two types of interaction in patient between x-ray photons and outer shell electrons?

A
  • Photoelectric effect
  • Compton effect
43
Q

What is Photoelectric effect?

A
  • Results in complete absorption of x-ray photon
  • Involves inner shell e-
  • Energy of photon must be equal to or > than binding energy of e-
  • Contributes to image contrast and pt dose
44
Q

What is the Compton effect?

A
  • Results in scatter and partial absorption of photon (absorption lead to image formation)
  • Involves outer shell e-
  • Energy of incoming photon much > than binding energy of e-
  • Contributes to pt dose
45
Q

What model can we use to estimate the risk of stochastic effects?

A
  • No threshold model
46
Q

What is somatic non-deterministic ?

A
  • Biological effects of radiation that are probabilistic (non-deterministic) and occur in exposed individuals body tissues (somatic)
47
Q

What is the risk of death in panoramic radiograph?

A
  • 1 in 1 million risk of death
48
Q

What is the risk of death in PA radiograph?

A
  • 1 in 10 million risk of death
49
Q

What is the film processing common steps ?

A

Developing = Converts crystals to black metallic silver particles
Washing = Removes residual developer solution
Fixing = Removes non-sensitised crystals and hardens emulsion
Washing = Removes residual fixer sol
Drying = Remove water so film ready to be handled

50
Q

What does under exposure of film lead to?

A
  • Lighter image
51
Q

What occurs if developer in film is too warm or too concentrated ?

A
  • Darker image
52
Q

What occurs if the developer solution is too old i.e past expiration date?

A
  • Lighter image
53
Q

What occurs if there is inadequate fixation of film?

A
  • Contrast of image reduced
54
Q

What occurs if film is exposed to visible light before processing?

A
  • Darker image
55
Q

What occurs if film appears greenish (and browns over time)

A
  • Inadequate fixation
56
Q

What is the main factor that affects digital radiographs?

A
  • Exposure issues
57
Q

What is a suitable method of viewing film images?

A
  • On a light box
58
Q

What are some indications of taking lateral cephalogram?

A
  • Assess skeletal pattern
  • Assess angulation of anterior teeth
  • Monitor changes to above during growth/txt
  • Assess antero-posterior position of unerupted teeth in anterior sextants
59
Q

Why is collimation used in lateral cephalogram?

A
  • Reduces radiation dose to head
60
Q

How is the x-ray beam positioned in lateral cephalogram?

A
  • Perpendicular to receptor and pt mid-sagittal plane
61
Q

What is the distance between x-ray source and receptor on conventional cephalogram units?

A
  • 1.5m+ (150cm+)
62
Q

Why is there a large distance between x-ray sources and receptor on conventional cephalogram units?

A
  • To reduce asymmetrical magnification of anatomy
63
Q

During a lateral cephalogram what does the pt wear for protection and what does it protect?

A
  • Wear lead protection
  • Protects thyroid gland
64
Q

What is the cephalostat?

A
  • Head positioning apparatus
65
Q

Why is the cephalostat important?

A
  • Accuracy of image created
  • Consistency (produces standardized images - useful for comparison)
  • Safety to minimise amount of radiation dose to pt by using collimator to focus x-ray beam only on area of interest
  • Keeps pt head still
66
Q

What is parallax shift?

A
  • Apparent movement of object when viewed from diff positions
  • More shift occurs if objects further apart
67
Q

What are the fundamental for parallax shift technique?

A
  • 2 or more radiographs of object of interest
  • Radiographs need ot be taken from diff angles/positions
  • Shared reference point on all radiographs
  • No physical movement of object and reference point between exposures
68
Q

What pair of radiographs can’t be used reliably for parallex shift technique?

A
  • Paralleling PA and panoramic
69
Q

What is a diagnostically acceptable image?

A
  • No errors or minimal errors
  • Sufficient image quality to answer clinical question
70
Q

What is the target for digital and film imaging for diagnostically acceptable?

A

Digital = not < 95%
Film = not <90%

71
Q

Positive of panoramic over PA radiograph?

A
  • Capture entire dentition in one image
  • Able to image non-dental areas
  • Lack of I/O holder easier for gaggers, trauma, young children
72
Q

Negatives of panoramic over PA radiograph?

A
  • Lower spatial resolution
  • More superimposition
  • More artefacts
  • Longer exposure time
  • Higher radiation dose per image
73
Q

What are double shadows?

A
  • Created by structures located near centre of rotation so captured twice
  • e.g soft palate and hyoid bone and cervical spine
74
Q

What are ghost structures?

A
  • Created by structures between x-ray source and centre of rotation
75
Q

What are features of a ghost image?

A
  • Appear magnified
  • Blurry
  • Higher due to beam inclination
  • Transposed on opposite side of true anatomical position
76
Q

What are the basic principles of ICRP system for radiation exposures?

A
  • Justified
  • Optimised (ALARP)
  • Limited
77
Q

What does IRR17 deal with?

A
  • Occupational exposures and exposure of general public
78
Q

What does IRMER17 deal with?

A
  • Medical exposure of pt
79
Q

What is the controlled area of intra-oral x-ray units?

A
  • 1.5m from x-ray tube and within primary beam
80
Q

What is the controlled area for cone beam CT?

A
  • Usually entire room
  • No one enter
81
Q

What are some benefits of I/O radiographs?

A
  • High spatial resolution
  • Minimal superimposition of other anatomy
  • Fast exposure
  • Low radiation dose per image
82
Q

What are some negatives of I/O radiographs?

A
  • Limited to imaging a small area
  • Invasive for pt
  • Relatively difficult technique
83
Q

What size receptor is used for anterior PA?

A
  • Size 0
84
Q

What size receptor is used for bitewings and posterior PA?

A
  • Size 2
85
Q

What size of receptor is used for occlusals?

A
  • Size 4
86
Q

Why is the focal trough important?

A
  • 3D zone where structures are well-defined and sharp AKA plane of focus
  • Curved area where x-ray beam focused to produce clear, well defined images
  • Teeth must be positioned within focal trough so parallel to x-ray beam and film/sensor
87
Q

In a panoramic what causes the incisors to be horixontally magnified?

A
  • Pt too far back
88
Q

In a panoramic what causes the posterior teeth to be horizontally magnified ?

A
  • Pt rotated in machine

BDS3 Radiology (11 decks)

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