50 Q Flashcards
In an intra-oral X-ray set, X-ray photons are produced at the…
- aluminium filter
- cathode
- filament
- focussing cup
- tungsten target
- tungsten target
In an intra-oral X-ray set, what is the purpose of the aluminium filter?
- Absorb scattered radiation
- Help create a sharper image
- Preferentially attenuate low energy X-rays
- Prevent backscatter from fogging the image
5 . Protect the operator
- Preferentially attenuate low energy X-rays
In an intra-oral X-ray set, what is the purpose of the collimator?
- Absorb scattered radiation
- Focus the X-rays
- Protect the operator from scatter
- Remove the lower energy radiation from the beam
- Restrict X-ray beam to chosen area
- Restrict X-ray beam to chosen area
In an intra-oral X-ray set, the High Tension (Voltage) circuit…
- is in the 65-70 kVp range
- is usually about 6.5 - 7.5 mA
- is usually around 65,000 kV
- operates at around 50,000 Volts
- varies according to the exposure setting
- is in the 65-70 kVp range
Compton (inelastic) scatter…
- improves image quality
- occurs at discrete energy levels
- occurs when an electron interacts with an atomic nucleus
- produces an X-ray of energy equal to the binding energy of the k-shell
- reduces contrast in an image
- reduces contrast in an image
The mA current setting on an intra-oral X-ray set…
- controls the high tension (HT) circuit for the set
- controls the number of electrons produced at the filament
- is set higher for a bite-wing than for a periapical radiograph of an upper
molar - is the Mega Amp current
- is usually set for each exposure by means of the control box
- controls the number of electrons produced at the filament
In an intra-oral X-ray set, excess heat is …
- caused because X-ray
- production is inefficient
- conducted away by the copper block
- dissipated by convection in the oil surrounding the tube
radiated away from the outer case - All of the above
- All of the above
Rectangular collimation…
- ensures object and receptor are in the correct relationship
- helps align the tube to the film
- holds the film in the correct position
- is mandatory
- reduces the patient - dose by around 40%
- reduces the patient - dose by around 40%
The stochastic effects of ionising radiation…
- can result in radiation-induced erythema or burns
- cause no biological damage at low doses
- follow a linear-quadratic relationship
- have a safe threshold
- occur as the result of chance events
- occur as the result of chance events
. Which statement is true with regards to the paralleling intraoral technique?
- It enables the beam to be centred to the film
- It increases magnification of the image
- It is not appropriate for patients with disabilities
- It is not the technique of choice routinely
- Periodontal bone levels are poorly represented
- It enables the beam to be centred to the film
Collimation of the X-ray beam…
- is not necessary
- increases scattered radiation
- increases the volume of exposed tissue
- should be circular
- should be rectangular
- should be rectangular
The deterministic or non-stochastic effects of ionising radiation…
- are concerned with the risks of inducing cancer at low doses
- are dose-dependent
- are independent of the amount of radiation received
- have no threshold
- occur according to the laws of chance
- are dose-dependent
The X-ray beam should be…
- as close to the patient as possible
- kept on for as long as possible
- perpendicular to the tooth and image receptor to prevent distortion
- positioned perpendicular to the floor
- produced from a large focal spot
- perpendicular to the tooth and image receptor to prevent distortion
The risk of developing cancer from low doses of ionising radiation…
- clearly demonstrates a hormesis effect
- follows the linear-no-threshold model
- has a ‘dose threshold’
- is independent of the dose received
- is non-existent at very low doses
- follows the linear-no-threshold model
The Frankfort baseline is…
- a radiographic plane that bisects the first upper molar
- a radiographic plane that divides the face symmetrically from the crown
of the head to the tip of the mandible - a radiographic plane that extends from the external auditory meatus to
the infra-orbital margin - a radiographic term that describes normal anatomical appearances
viewed on an DPT - the relative position of the tube, cassette and patient during DPT
examinations
- a radiographic plane that extends from the external auditory meatus to
the infra-orbital margin
The National Diagnostic Reference Dose for intra-oral radiology is
approximately 2.0mGy.
What is this is expressed in terms of?
- Absorbed dose
- Committed dose
- Dose-width product
- Effective dose
- Equivalent dose
- Absorbed dose
An X-ray of a female patient of child-bearing age…
- can only be undertaken if she is given a lead apron to wear over her abdomen
- can only be undertaken within 10 days of the last menstrual period
- is prohibited under the Ionising Radiations(Medical Exposure ) Regulations unless a check is made if she is pregnant
- must be undertaken in accordance with local written procedures
- must not be undertaken if she is pregnant
- must be undertaken in accordance with local written procedures
Under IRMER Optimisation ensure that the…
- dose is as low as achievable and image quality is acceptable
- image quality is high
- patient dose is less than the Diagnostic Reference Level
- patient dose is low
- patient receives a dose at the diagnostic reference leve
- dose is as low as achievable and image quality is acceptable
Under IRMER…
- operators do not require theoretical training
- students under supervision must be trained before carrying out exposures
- the Operator must have practical training
- the Practitioner does not require theoretical training
- the Referrer must be appropriately trained
- the Operator must have practical training
Regarding Justification…
- Does not apply to asymptomatic exposures
- Examinations on children under 5 are not justified
- Examinations on pregnant patients are not justified
- Justification is not required for routine x-rays
- Justification must be carried out for every exposure
- Justification must be carried out for every exposure
Regarding Justification the…
- exposure is approved by the Practitioner and justified by the Operator
- exposure is justified by the Referrer and authorised by the Practitioner
- Operator is responsible for justifying the exposure
- Practitioner is responsible for justifying the exposure
- Referrer is responsible for justifying the exposure
- Practitioner is responsible for justifying the exposure
The Ionising Radiation (Medical Exposure) Regulations 2017…
- are an Approved Code of Practice
- are intended to protect patients
- place a limit on the number of x-rays a patient can receive
- protect members of the Dental Team
- protect members of the public
- are intended to protect patients
What do the Ionising Radiations Regulations 2017 require?
- All exposures to be restricted as far as reasonably practicable
- All exposures to patient to be within diagnostic reference levels
- All staff to be monitored for radiation exposure
- Doses to patients to be recorded
- Exposures of patients to be within Dose Limits
- All exposures to be restricted as far as reasonably practicable
Members of staff should…
- inform her employer in writing if they believe they are pregnant
- not work with X-ray equipment
- tell their colleagues if they are more than six months pregnant
- tell their employer if they are in the first trimester of pregnancy
- wear a lead protective apron
- inform her employer in writing if they believe they are pregnant
Concerning Controlled Areas…
- Access is permitted for employees only
- Are monitored by the Radiation Protection Adviser
- Are subject to written arrangements to control access
- Non-classified workers are not permitted to enter Controlled Areas
- Pregnant patients are not permitted to enter Controlled Areas
- Are subject to written arrangements to control access
The Radiation Protection Supervisor (RPS)…
- is usually either the Practice Administrator or Senior Dental Nurse
- isn’t usually required in a hospital/dental school
- must be a dentist
- must be identified in the practice information leaflet
- must have received appropriate training
- must have received appropriate training
The role of the Radiation Protection Supervisor is to…
- ensure Radiation Badges are changed monthly
- ensure that Local Rules are being followed and enforced
- ensure the Register of Training is kept updated
- ensure X-ray equipment has been regularly serviced
- write Local Rules for the Practice
- ensure that Local Rules are being followed and enforced
The absorbed dose at the cone for a mandibular molar radiograph is
approximately…
- 0.1 Sv
- 2 mGy
- 3.2 mSv
- 10 cGy
- 25 mGy
- 2 mGy
Bremsstrahlung or ‘braking radiation’ is…
- emitted at a particular (discrete) wavelength
- only produced at tube voltages above 50 kV
- produced when an X-ray photon strikes a Calcium atom
- the major source of photons in X-ray
- the primary cause of image noise
- the major source of photons in X-ray
The useful interaction of photons with matter when taking intra-oral xrays is…
- characteristic radiation
- compton or inelastic scatter
- elastic recoil
- pair production
- photo-electric absorption
- photo-electric absorption
What is a Diagnostic Reference Level (DRL)?
- It applies to any patient having an X-ray
- It defines the risk to the patient
- Is the radiation dose which should not be normally exceeded for a standard exposure
- The optimum dose from a procedure
- The prescribed radiation dose to the patient
- Is the radiation dose which should not be normally exceeded for a standard exposure
Beam collimators should provide a minimum focus to skin distance
(FSD) of…
- 50mm
- 100mm
- 150mm
- 200mm
- 250mm
- 200mm
Intra-oral radiography equipment should operate within which tube
potential range?
- 50 - 60 kV
- 60 - 70 kV
- 70 - 80 kV
- 80 - 90 kV
- 90 - 100 kV
- 60 - 70 kV
X-ray production in a diagnostic X-ray tube is approximately how
efficient?
- 1%
- 5%
- 52%
- 95%
- 99%
- 1%
How far away from the dental X-ray tube does the controlled area
extend?
- 1.5 metres
- 2 metres
- 2.5 metres
- As defined in the Local Rules
- At the extent of the exposure cable
- As defined in the Local Rules
Regarding the Photoelectric effect…
- May result in scattered radiation
- The effect is independent of atomic number
- The incident photon interacts with a free electron
- The incident photon is completely absorbed
- The probability of photoelectric absorption does not depend on photon
energy
- The incident photon is completely absorbed
Regarding effective dose, it…
- expresses a cancer mortality risk to an individual
- expresses the probability of cancer incidence in a population
- expresses the radiation dose from an individual exposure
- is a measure of the chance a patient will die from cancer
- should be calculated for each examination undertaken
- expresses the probability of cancer incidence in a population
Regarding absorbed dose…
- Absorbed dose is a measure of the energy deposited in tissue per unit mass
- Absorbed dose is a measure of the risk of exposure to ionising
radiation - Absorbed dose is defined only at the surface of the tissue we are interested in
- For the same amount of X-rays falling on tissue, the absorbed dose will
be the same irrespective of tissue type - The correct unit for absorbed dose is the Sievert
- Absorbed dose is a measure of the energy deposited in tissue per unit mass
- Regarding the Bremsstrahlung (braking radiation) process…
- An incident electron interacts with the nucleus releasing an x-ray photon
- It describes how electrons move within atomic shells
- It is dependent on the binding energy of the atomic electrons
- It results in the ejection of an atomic electron
- The incident electron collides with a K-shell atomic electron
- An incident electron interacts with the nucleus releasing an x-ray photon
Image unsharpness is not affected by…
- focal spot size
- geometric magnification
- grain size in film emulsion
- increase in kVp
- patient movement
- increase in kVp
Patient dose is not affected by…
- decreasing exposure time
- increasing the Focus to Skin Distance
- increasing the tube filtration
- increasing tube potential (kVp)
- using a rotating anode target
- using a rotating anode target
Dose optimisation is the process by which…
- a diagnostically relevant image is obtained at the lowest dose
- equipment is maintained
- maintenance engineers assess the quality of the equipment
- the best possible image quality is ensured
- the smallest dose to the patient is ensured
- a diagnostically relevant image is obtained at the lowest dose
The minimum legal filtration for a dental X-ray set (up to 70kVp) is…
- 2.5mm Al
- 1.5mm Al
- 0.1mm Pb
- 2.0mm Cu
- 1.0mm Pb
- 1.5mm Al
Deterministic effects of ionising radiation…
- are a necessary side effect of ionising radiation in dental practice
- are normally seen in routine dental exposures
- cannot be predicted before the exposure has happened
- have a threshold dose below which they do not occur
- include hereditary effects in future generations
- have a threshold dose below which they do not occur
Stochastic radiation effects…
- are assumed to follow a linear no threshold relationship to dose
- are not present in dental radiography
- can be seen in patients a few weeks after exposure
- from a DPT are likely to be similar in magnitude to those resulting from
average annual background radiation. - have a threshold
- are assumed to follow a linear no threshold relationship to dose
Compton or inelastic scattering…
- discriminates between hard and soft tissues
- helps build image contrast
- improves the quality of the captured image
- is the most likely source of radiation exposure to an operator
- predominates at low X-ray energies
- is the most likely source of radiation exposure to an operator
The X-ray beam should be collimated to…
- ensure X-rays reach the target
- limit extraneous radiation that does not play a part in the imaging process.
- maximise Compton over photoelectric interactions
- minimise the photoelectric effect in tissue
- stop film fogging
- limit extraneous radiation that does not play a part in the imaging process.
Equivalent dose is the…
- absorbed dose to an organ or tissue weighted for age and sex
- absorbed dose to an organ or tissue weighted for type of radiation
- absorbed dose to an organ or tissue weighted for type of radiation and
tissue - absorbed dose to an organ or tissue weighted for type of tissue
- same as absorbed dose
- absorbed dose to an organ or tissue weighted for type of radiation
The Health and Safety Executive…
- can prosecute a practice under the Ionising Radiations Regulations
2017 - can serve enforcement notices including those which could stop work
with X-rays - have statutory powers which allow inspectors to visit a practice unannounced
- must have issued a registration before work with an x-ray device
commences - All of the above
- All of the above
. Which of the following is not required in the local rules?
- A dose investigation level
- An exposure chart containing both local and national diagnostic
reference levels - Name of the Radiation Protection Supervisor
- Systems of work for entry into and work within the controlled area
- The identification and description of each controlled area
- An exposure chart containing both local and national diagnostic