protection

Question 1

What are means of expressing dose?

Answer 1

Radiation energy deposited in a unit mass of tissue
Absorbed dose, Gy
1Gy=1J/kg

Absorbed dose weighted for harmfulness of different radiations
Dose equivalent, Sv

Radiation susceptibility of different tissues
Measure of risk rather than physical dose
Effective dose, Sv

Question 2

What are different weighting factors?

Answer 2

Bone marrow, breast, colon, lung, stomach, other tissues- 0.12

Bone surface, brain, salivary glands, skin- 0.10

Gonads- 0.08

Bladder, oesophagus, liver, thyroid- 0.04

Total=1= whole body effective dose

Question 3

What is the average annual UK background radiation?

Answer 3

2.7mSv

Question 4

How does radiation affect DNA?

Answer 4

Directly- breaks strand

Indirectly- electron leaves frail of ionised water molecules behind- highly reactive OH free radicals- v damaging

Question 5

What are the types of radiation health effects?

Answer 5

Deterministic- direct consequence of dose above minimum threshold, increasing severity w dose

Stochastic- effects increase in likelihood but not severity w increasing dose, no minimum threshold

Question 6

What is time distance shielding?

Answer 6

Time- minimise exposure time

Distance- inverse square law,
move away from source (2x distance= quarter dose

Shielding- use shielding to attenuate (attenuation is proportional to density)

Question 7

What are annual dose limits for staff protection?

Answer 7

20mSv to whole body
20mSv to eye lens
150mSv to skin/extremities

Question 8

What are appropriate factors to patient protection?

Answer 8

Filtration
kV- high energy more penetrating
mA- increased= bigger dose but better contrast image
focus to skin distance- closer= less scatter, higher dose, less noisy image
Collimation- defines beam size (no more than 6cm diameter), rectangular reduces dose

Question 9

What is IRR17?

Answer 9

For staff and public protection

Part I- definitions, interpretation and duties (Reg 4)

Part II- general principles and procedures
-notification, registration, consent, risk assessments, restriction of exposure, PPE, engineering controls maintenance, dose limitation, contingency plan

Part III- management of protection
-radiation protection adviser, training, cooperation

Part IV- designated areas
-controlled areas, local rules, additional requirements, monitoring of designated areas

Question 10

What does the employer do?

Answer 10

Fulfil IRR17 w regard to exposure of employees and public
May delegate tasks
Would be prosecuted if something goes wrong

Question 11

What does the radiation protection adviser?

Answer 11

Local expert to help assist w requirements for facilities and setting up QA programme