T2: Radiation Safety Flashcards
Radiation Incident
- Abnormal event where the source of ionising radiation is uncontrolled temporarily
- person exposed to more than twice effective does then what they should receive
Radiation Accident
- More severe abnormal events due to the source of ionising radiation being out of control
- continues to remain out of control
- dispersal of radioactive material takes place
- person exposed to over twice effective does in expected situation
Radiation Exposure (Internal and External)
- External: Radioactive materials handled and beams direct from source equipment
- Internal:
- Ingested
- Inhaled
- Absorbed
ALARA
As Low as Reasonably Achievable
Medical radiation exposure MAIN risks
High-Intensity Exposures:
- Skin burns, lesions and possible damage to eye tissue
Long Term Chronic Exposures:
- Possible chromosomal damage and long-term risk of cancer
Rationale behind ALARA
- Radiation may be harmful
- Radiation in diagnostic and therapeutic medicine
- Receive benefits of radiation, the public must accept the possibility of harmful effects from radiation
- Protect the public and employees, potential and amount of exposure should be reduced
- Reduction should be as low as economically feasible
Implementing ALARA
- minimising the Activity that you handle
- minimising the Time spent in a radiation field
- maximising the Distance from the source
- using appropriate Shielding
Minimising Time
- less time spent near source, less radiation received
Radiation is directly related to duration of exposure
- If time is doubled, radiation dose doubles
Exposure = Exposure rate x time
Maximising Distance
- Further from the source, the less radiation will receive
Maximising Shielding
More shielding, less radiation dose recieved
- Tenth Value layer of shielding material (thickness that reduces radiation intensity to 10% of initial value)
ALARA: shielding should be cost-effective (concrete is better metal) and should be reduce rate beyond the shield to insufficient levels)
- Radiology department: lead is most common, having reinforced concrete are used
The effectiveness of Shielding material depends on:
- Atomic number, Density Thickness
Minimise Internal Exposure
Protection Methods
1. Prevent Inhalation: Use ventilation, air cleaners, and respiratory PPE with the correct filter
2. Prevent Ingestion: wear protective clothing when handling raw materials
3. Prevent exposure through skin or wounds: Avoid direct contact with raw materials PPE
Plan your work: handling, storage/disposal, detection, decontamination of equipment
Practice procedures before handling radioactive materials
Whenever possible use tools (forceps or tongs) to handle radioactive samples and potentially contaminated items
Record Of Occupational Exposure
To monitor dose and limits, all personnel need to wear a personal radiation monitoring device.
Badge Dosimeters: absorbed dose is calculated every three months, only detect radiation at location where worn, do not alarm for acute exposure
Electronic Dosimeters: semiconductor personal monitors measure exposure during a procedure
Desgin of RT bunkers
Signage
Shielding: bunker wall is important in controlling primary, scattered and leakage radiation
- contain entrance (maze/neutron door), a primary and a secondary barrier
- Rooms that adjoin the linac bunker should be minimal use
Ventilation: cycling air in the room at least 6 times per hour to prevent build-up of radioactive gases from photodisintegration and neutron interactions
Control room: outside of the bunker with a CCTV system and intercom devices for monitoring patients
Emergency shut off lianc, couch, bunker walls, bunker entry and in control room
Radiography Examination Room
Protective barrier between examination room and operating console must have a window for viewing patient
Room designed so posible to reach perating console without having to enter “radiation area”
Protective x-ray tube housing preventing leakage radiation (reduces patient dose)
Filtration: at least 2.5mm of aluminium
Protective curtains/panels/barrier for operating console or between fluoroscopy and patient
Bucky slot cover
Protective barriers (sheets of lead) in walls of examination rooms (and ceiling or floor, depending on the location of the exam room in the building)
Shieling directly behind a chest board (primary radiation so primary protective barrier)
Protective Techniques
Minimising patient exposure
High-kVp techique reduce patient does
- increasing kVp means more x-ray penetrating patient to reach the detector, therefore less tube current/lower scan time is required to achieve image quality
Patient positioning
- when upper body parts, have patient seated, ensuring the beam is lateral and having some form of shielding to prevent beam interception with gonands
How to avoid repeating imaging?
- Effective communication with patients
- Proper patient preparation
- Good radiographic skills and knowledge
- Minimising motion unsharpness (shorter exposure time, patient immobilisation)
- reduce the number of views, consider the necessity of procedures, standard exposure factors to prevent exposure creep, avoid exposing pregnant women
Gonad Shielding
- female and male area
- specific area
Always use gonad shield
- when the reproductive organs are 5cm of the collimated beam
- without compromising the value of the exam
Females receive 3 more doses than males in the pelvic exam without shielding
- Female: 50% reduction
- Male 90-95% reduction
Specific Area Shielding
- sensitive organs like eyes and breasts
Shielding for foetus
- pregnant worker
The dose limit for the abdomen is 2mSv
- excluded from any employment activity with higher doses
- brachytherapy, fluoroscopy and radiopharmaceuticals
The second badge for the abdomen needs to be checked every 3 months
- lead abdomen shielding is available
Shielding for foetus
- pregnant patient
Imaging and radiotherapy can be done
- foetal does and minimises where possible
- Use customised shielding when appropriate (5VL)
- Stimulation of treatment with custom phantom of estimate foetal does and judge the efficacy of shielding
- Modification of treatment/shielding as pregnancy progresses
- total dose of foetus has to be documented
