radiation protection

What is radiation

• energy that travels in the form of waves or high-speed particles

  • can span from very low energy to high energy

What is radiation syndromes

• early effects of radiation overdose to total body

• only occurs if the whole body receives a dose

What is prodromal syndrome symptoms and when do they occur

• nausea

• vomiting

• diarrhoea

  • occurs minutes after irradiation

What is the latent period symptoms and when do they occur

• symptom free

• lethal effects or recovery are starting

What is the manifest illnesses period symptoms and when do they occur

• haematologic

• gastrointestinal

• CNS

What are examples of locations where early effects of local tissue damage can occur

• skin

• reproductive system

• eye

• haemopoietic tissue

• cardiovascular system

• respiratory system

• urinary system

• gastrointestinal tract

• growing bones

• central nervous system

What is late effects → secondary malignancies

• most common is leukamia

• radiotherapy patients more likely to develop secondary malignancies

What is the absorbed dose

• quantity of ionising radiation absorbed

• SI unit → gray (Gy)

• 1Gy → 1 joule of energy absorbed per kg

What is dose equivalent

• how much biological damage expected from the absorbed dose

• SI → sievert (Sv)

• 1Sv → same biological effect as 1Gy of x-ray

How does radiation damage cells

• ionising radiation removes electrons or excites electrons

  • damage occurs when energy transfers

What is direct damage

• radiation hits certain areas on DNA chain

  • lethal damage to cell

• damage caused by ionising a molecule within DNA, RNA or protein

What is indirect damage

• radiation ionises water molecule

• ions interact with other molecules of water or oxygen

  • produce free radicals

• free radicals interact to produce poisonous hydrogen peroxide

  • causes biological damage

What are the 3 types of cellular damage

• division delay

  • mitosis rate drops then increases then back to normal

• interphase death

  • cells break down due to damage to cell membrane

• reproductive failure

  • cells don’t divide or divide into dead cells

What are stochastic effects

• random in nature

• no threshold

• probability of effect increases with dose

• dose increases → probability that cancer or genetic effect will occur increases

• incidence of effect increases with dose

What is non stochastic effects

• deterministic effects determined by dose

• definitely occur after a threshold has been crossed

• severity of effect increases with dose

Why do we need radiation protection

• ethically

  • responsibility to ensure doses are kept low

  • we have professional obligation to act in the best interests of the patient

• legally

  • registered as qualified to use ionising radiation safely

  • legislation ensures radiation poses minimal risk

What are the 3 radiation protection organisations

• ICRU

  • international commission on radiological units and measurements

• ICRP

  • International commission on radiological protection

• HPA

  • Health protection agency

What are the 2 radiation protection legislations

• IRR (2017)

  • Ionising radiation regulation

• IR(ME)R 2017

  • Ionising radiation (medical exposure) regulations

When is an exposure justified

• sufficient net benefit

• if for research purposes if females have been asked if pregnant or breastfeeding

What is ALARP

• As low as reasonably possible

  • ensures risk is reduced to a level that’s deemed to be as low as reasonably practicable

What is a clinical audit

• review of medical procedures to improve quality and outcome of patient care

• checking what’s done against agreed standard

  • to modify or apply new standards if necessary

What is the IRR99

• covers all uses of ionising radiation

  • organisational arrangement and procedures

  • dose limits and personal monitoring

  • arrangements for control of radioactive items

  • duties of employers

  • when to report an incident

  • how radioactive quantities of different substances are

How is patient shielding achieved

• good collimation

  • smallest possible field sizes

• planning

  • beam arrangment

• multi-leaf collimators

• shielding blocks

What does scatter within patient depend on

• size of field

• depth of interest

• size of block

• position of block in field

How are neutrons produced

• at high energies

  • pass through lead and steel

What factors affect barrier thickness

• maximum beam energy

• workload

• usage → frequency of irradiation

• shielding material

• distance from target to point of interest

• occupancy factor for room beyond barrier