Radiation Protection Flashcards
What is absorbed dose measured in?
Gray
What is dose equivalent?
Absorbed dose weight for harmfulness at different radiations
Measured in Sv
What is direct affect of radiation?
Secondary electron breaks DNA strand
What is indirect affect of radiation?
E- levels trail of ionised water - highly reactive OH* free radical
what are chance of DNA damage?
Can be high or low risk depending where radiation hits depends on risk of permanent cell damage
What happens following DNA damage?
Mutation repaired = viable cells
Cell die = unviable cell
Cell survives but mutated = cancer
What is deterministic effect?
Direct consequence of dose above minimum threshold - increase in severity w/ dose
What is stochastic effect?
NO threshold - but probability of effect increase w/ dose
But severity is independent of dose
Occur in the individual as result of exposure to dose of radiation
What is genetic effect?
Effect arise in offspring of individual exposed to dose of radiation
Which dental radiographs most harmful?
CT > panoramic > intraoral
What are 3 key things in protection?
Time
Distance
Shielding
Why is time important in protection?
Longer spend near source of radiation - higher the dose
Why is distance important in protection?
As move away from source dose rate decreases rapidly
Inverse square law - twice distance = quarter dose
How is shielding important in protection?
Shielding attenuates radiation reducing the dose
Examples - barium blaster/ lead pannels
RPA decided
What radiation protection is considered for staff?
Dose limits - 6 mSv PPE Controlled area Training Risk assessment Local rules Dose badge
How are patients protected?
No legal dose limits but must justify risk - dose mustn’t be greater than intended
How does increase current affect radiograph?
Increased no. of photons - increase dose but improved image contrast
How does filtration protect pt?
Gets rid of low energy x-ray
How does altering kV protect pt?
Maximum energy photons released - more pentration
How does altering mA protect pt?
Increase no. photons increases dose - but improve image
How does focus protect pt?
Closer focus to pt less x-ray scatter - higher dose but less noisy
How does collimation protect pt?
Defined beam size - no larger 6 cm
Rectangular collar reduce dose
