Radiation Protection in Practice Personal Dosimetry Flashcards
What does IRR stand for?
Ionising radiation regulations
Who is IRR used to protect?
staff, members of the public and the environment
What does IRMER 2017 stand for?
ionising radiation medical exposure regulations 2017
What is IRMER 2017 used to protect?
patients
What are the 3 basic parameters that influence the exposure that an individual receives in a radiation field?
time distance shielding
What law is associated with distance and the exposure you receive?
inverse square law
What does ALARP stand for and what are the 3 factors to consider when following this?
as low as reasonably practicable
time, shielding and distance
What are the 3 types of radiation that come out of the machine (define)?
- Primary radiation (radiation directly emitted from the radiation source through collimator opening and from radioactive source in case of brachytherapy)
- Scatter radiation (radiation produced by the scattering of primary beam from various media struck by the primary beam e.g patient or collimator)
- Leakage radiation (radiation that escapes through shielded head of X-ray tube)
What is a primary barrier?
where primary radiation beam strikes the wall, it becomes a primary barrier, including ceiling and floor
What is a secondary barrier
protection against scattered and leakage radiation
What is a controlled area?
area where specific protection measures and safety provisions are required
What is IRR regulation 32?
- Design to restrict as far as reasonably practicable exposure of persons to ionizing radiation
- Critical examination with RPA
- Must have instruction on proper use, testing and maintenance
What 3 things does a control system do as a safety measure?
- cannot start will an access door is open
- is interrupted if the access door is opened
- Does not restart solely when closing a door’
What is individual monitoring IRR regulation 9 and 19 consisting of?
- The exposure of a radiographer needs to be routinely monitored and records kept of their cumulative radiation doses
- They can be used retrospectively to determine a dose received by a worker
- Used to verify the effectiveness of radiation control measures in the workplace
- Can be used to detect changes in the workplace
- Identify working practices to minimise doses
- Provide information in the event of accidental exposure
What is a designation of classified person as mentioned in IRR regulation 21?
employer must designate as classified persons those of its employees who are likely to receive an effective dose greater than 6 mSv per year or an equivalent dose greater than 3/10ths of any relevant dose limit and must immediately inform those employees that they have been so designated
What are the 2 requirements to designated an employee as a classified person?
that employee is aged 18 years or over
- a relevant doctor has certified in the health record that that employee is fit for the work with ionising radiation which that employee is to carry out
What does PPE stand for?
personal protective equipment
What forms of PPE do radiographers use?
lead aprons and thyroid collars
By what percentage do lead aprons and thyroid collars reduce radiation?
lead aprons: 98% attenuation of scatter raediation
thyroid collar: 92% reduction
What is a personal dosimeter
detect various forms of radiation a worker may be exposed to (rays, gamma radiation, neutron and beta particles)
What unit is radiation dose measured in with a dosimeter?
milli-sieverts (mSv)
What is the most common form of dosimeter?
TLD
What does TLD stand for?
Thermo-Luminsecence Dosimeter
What is thermo-luminescence?
emission of light by heat
What does TLD respond to?
Responds accurately to beta, gamma, X-ray and neutron
How does a TLD measure radiation?
measures the amount of visible light emitted from a crystal in the detector when the crystal is heated
What are the 3 commonly used phosphors in TL?
- Lithium fluoride
- Calcium fluoride
- Lithium borate
- Calcium sulphate
What radiation dose range do TLDs have?
0.2mSv to 10Sv
What does DIS stand for?
Direct ion storage (detector)
How does a DIS work?
- Gamma and X-ray interactions with chamber wall generate secondary electrons
- Secondary electrons ionize gas in the chamber
- Ions are separated by the potential difference between electrode
and wall - Ions are stored in the memory element cell
- Stored charge controls memory element
What does the MOSFET element in a DIS dosimeter do?
MOSFETelement
* Gamma and X-ray reactions with silicon oxide
* Electrons drifting to surface states
* Channel VG STh changes
How does a DIS dosimeter work + its structure?
NonVolatileAnalog Memory Cell surrounded by a Gas Filled Ion Chamber
For photon radiation, initial interactions take place in the wall material and secondary electrons ionize the gas of the chamber
Give 3 reasons why DIS dosimeter systems are advantageous
- Immediate (or relatively immediate) feedback of dose– remote reading capabilities
- More closely monitor workers–especially those that get close to regulatory and/or site specific limits
- Can read dosimeters and get results anytime, not relegated to a specific period of time
- Stand alone networks
- Personal Computers
- Phones/iPads
Summary of DIS dosimetry systems
- Provides Immediate Feedback
- Decreases delay of important dose information to wearer
- Wearer feels like they “own” the badge since it isn’t being replaced every month/quarter (loss/damage decreases)
- Can read badges at any time
- Can still be a service model if desired
