Radiation protection in NM Flashcards
What sort of radiation hazards are there in clinical areas in a NM department?
- Injections.
- Patient.
- Contamination.
- Sealed sources (e.g. for QC and calibration).
Delacroix estimates the dose to operator fingers from a Tc-99m injection as 3.54 x 10^-1 microSv/hr/kBq. For a typical bone scan injection (600 MBq in 3 ml), what finger dose would this correspond to? How would this change with a syringe shield in place?
- 600 x 3.54 x 10^-1 = 212 microSv/hr.
- A syringe shield would reduce this by a factor of ~100 (= 2.12 microSv/hr).
Delacroix estimates the dose to operator skin from a 0.05 ml Tc-99m droplet as 8.77 x 10^-3 mSv/hr/kBq. What would the typical dose to an operator skin be for a 10 MBq droplet? How can gloves help in this situation?
- 10 MBq = 10 000 kBq => 10 000 x 8.77 x 10^-3 = 88 mSv/hr = 1.5 mSv/min.
- Gloves would not protect from the radiation but could be removed to minimise the exposure.
What are some ways that operator exposure from NM patients can be minimised?
- Maximise distance from patients, where possible.
- Split the workload between multiple operators.
What are some causes of contamination within a NM department? How can we minimise spread of contamination in these cases?
- Spills from injections. Reduce spread by bagging waste and PPE and monitoring for residual activity after decontamination/at the end of the day.
- Incontinent patients. Can reduce spread by using incontinence pads.
How are staff protected from exposure to sealed sources used in a NM department?
- Time, distance and shielding concepts when using.
- Sealed source safe for smaller sources and bespoke individual shielding for larger sources.
What additional risks are apparent in a NM radiopharmacy when compared to clinical areas?
- Higher dose rates.
- Higher risk of contamination.
What is the classification level for extremity dose?
150 mSv.
What considerations are required for the extremity dose measured with ring dosimetry? How can this be accounted for?
- The ring is worn at the base of the finger and so will underestimate the dose to the tip of the finger.
- Multiplication factors from literature can be applied.
- They can also be measured directly using real time dose rate monitors at the base and tip of the fingers.
What two sources of exposure need to be considered when designing SPECT-CT facility shielding?
- Dose rates from the patient.
- Dose rates from the CT scanner.
What radiation safety implications are there for radionuclide therapies?
- Beta and 364 keV gamma ray emitter.
- Contamination (e.g. through urine, sweat, saliva etc.).
- External (e.g. gamma rays).
What are some general design considerations for a radionuclide therapy facility?
- Controlled area with restricted access (e.g. through systems of work to minimise/prevent patient contact, warning signage and training).
- Large room to minimise exposures outside of the room and to remove the need for the patient to leave the room (e.g. includes kitchen, other required equipment etc.).
- Shielded walls and perhaps ceilings, floors and windows.
How is contamination from radionuclide excretion minimised for therapy patients?
- Patients encouraged to drink plenty of water and use the toilet.
- Patients asked to shower twice a day.
What are some general points for minimising contamination/spread where radioactive materials are used?
- Sinks close to exits of rooms to decontaminate hands. Soap, paper towels and bins included.
- Designated sinks for disposal of radioactivity.
- Contamination monitors at exits.
- Smooth, non-absorbent surfaces for easy decontamination.
- Tidy working areas for easy decontamination.
- Labelled drainage pipes for radioactive waste pipes.
- Floor/benches strong enough to withstand weight of lead shielding.
What are the advantages/disadvantages of using a cyclotron for PET tracer production?
Advantages:
- Many different kinds of positron emitters can be generated which provide easier radiochemistry when compared to F-18.
Disadvantages:
- Large space required.
- Lots of shielding required due to high activity and resultant annihilation of products produced.
- Radioactive gases are produced which must be monitored in the exhaust stack.
- Neutron activation of the target and subsequently of other parts of the facility.
