Lecture 15

Question 1

How much radiation should workers be receiving?

Answer 1

ALARA. As little as reasonably achievable

Question 2

What are the main biological effects of radiation that will be observed?

Answer 2

1. Cell damage - stops a cell reproducing and leads to mutation
2. Somatic/genetic effects seen - somatic = exposed person, genetic = hereditary (passed onto the offspring/descendants)

Question 3

What is meant by a stochastic effect?

Answer 3

Means there is no threshold. The probability of occurrence and not the severity is dose related.

Question 4

What are some examples of stochastic conditions?

Answer 4

1. Malignencies - leukaemia, tissue damage, eyes
2. Mutagenic effects
3. Delayed response

Question 5

What is an example of a deterministic condition (non-stochastic)?

Answer 5

May have a threshold, the severity is dose related. cataracts, radio-dermatitis, infertility,

Question 6

What are some examples of deterministic (non stochastic)?

Answer 6

1. These are often tissue specific - e.g. cataracts, infertility, radio-dermatititis
2. Acute temporary or permanent

Question 7

What is the absorbed dose of radiation and what is the unit for it?

Answer 7

Absorbed radiation dose in tissues is the energy that is absorbed by the tissue. Unit for absorbed dose = Gray (Gy)

Question 8

What is the formula for radiation dose equivalent?

Answer 8

The dose equivalent is the absorbed dose multiplied by the radiation weighting factor for type and energy of the radiation.

Question 9

What is the unit for measuring radiation dose equivalent and what is the weighting factor for X-rays?

Answer 9

• The unit used = Sv
• Old unit = rem
• Weighting factor for X-rays = 1

Question 10

What is the formula for effective radiation dose?

Answer 10

Effective dose: is the radiation dose equivalent multiplied by the tissue weighting factor

Question 11

What is the unit for measuring effective radiation dose?

Answer 11

The sievert (Sv)

Question 12

What does the acronym ADL stand for?

Answer 12

Annual dose limits

Question 13

What is the regulation for whole body dose limits?

Answer 13

• limit = 20msv/year, averaged over 5 consecutive calendar years
• No more than 50 msv in any one year

Question 14

What is the regulation for pregnant radiation workers and for the general public?

Answer 14

Pregnant radiation measures = not exceeding 0.5 mSv

General public = 1 msv/year.

Question 15

Where should radiation badges be worn?

Answer 15

The badges should be worn under the apron at chest or at waist height

Question 16

What are the three principles of radiation safety?

Answer 16

1. Time
2. Distance
3. Shielding

Question 17

What is the inverse square law?

Answer 17

Electron radiation = 1/(D x D)

Question 18

What is thickness of lead required for less than 100kV?

Answer 18

0.25mm of lead

Question 19

What thickness of lead is required for more than 100kV?

Answer 19

0.5mm lead

Question 20

Rank the three different types of badge detectors in order of sensitivity:

Answer 20

1. Film badges
2. Thermoluminescent dosimetry
3. Luxel badges/OSL (optically stimulated luminescence)

Question 21

What are the lead requirements for a table?

Answer 21

0.5mm lead on sides and 1mm of lead beneath

Question 22

What workload is it necessary to use protective screens?

Answer 22

Workloads of greater than 2000 mAs/wk

Question 23

What two groups of people should never be allowed in the X-ray room?

Answer 23

1. Pregnant women

2. Children under the age of 16