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ODDR- Dental physics > Medical Physics 2 - Radiation protection > Flashcards

Medical Physics 2 - Radiation protection Flashcards

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1
Q

What is radiation?

A

Radiation is energy. It can be transmitted in waves or as particles.

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2
Q

Name some natural sources of ionising radiation

A
  1. Cosmic Radiation

2. Food E.g. bananas

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3
Q

What is ionisation?

A

A type of incoming radiation that has enough energy to cause an electron to be ejected

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4
Q

What are the 3 different types of ionising radiation?

A
  1. Alpha
  2. Beta
  3. Gamma and x rays
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5
Q

Name some manmade sources of ionising radiation

A
  1. Medical like x rays, therapy nuclear medicine

2. Nuclear atmospheric tests

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6
Q

What is the average total radiation dose per person in the uk?

A

2.7mSv

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7
Q

Name the 4 different radiation units

A
  1. Absorbed dose
  2. Equivalent dose
  3. Dose-rate
  4. Effective dose
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8
Q

What is the absorbed dose?

A

Energy absorbed per unit mass from any type of ionising radiation

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9
Q

What is the absorbed dose measured in?

A

Gray(Gy)= J/Kg

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10
Q

What do we use the absorbed dose for?

What is the equivalent dose?

A

To specify the amount of radiation dose entering the skin surface

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11
Q

What is the equivalent dose?

A

Dose showing the damage causing capability of radiation

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12
Q

What is the equivalent dose red rived from?

A

The absorbed dose but also takes the radiation weighting facto into account for the type of radiation

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13
Q

How do we calculate the equivalent dose?

A

The absorbed dose x radiation factor

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14
Q

Why don’t we use the absorbed dose to judge the damage that radiation causes?

A

Because it does not distinguish the way in which energy is deposited in matter
Ie Alpha particles deposit energy in a very short distance whereas X-rays deposit energy over an extended path

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15
Q

What is the photon weighting factor?

A

1

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16
Q

What is the equivalent dose of X-rays and gamma rays?

A

The weighting factor & equivalent dose of x-rays & gamma rays are the same
So 1

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17
Q

What does the effective dose give us an idea of?

A

gives an idea on the effectiveness on radiation in causing damage to human tissue

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18
Q

What is the effective dose derived from?

A

Derived from the equivalent dose but takes into account the tissue weighting fact that adjust for radiosensitivity of different tissues

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19
Q

How duo we calculate the effective dose?

A

Total equivalent dose x the tissue weighting factor

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20
Q

What do the majority of people think about the dangers associated with radiographs?

A

The effect of radiation is roughly proportional to the dose received, so all radiation doses are potentially harmful

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21
Q

What is the dose rate and what do we use it for?

A

How quickly we accumulate a dose

We use it more for looking at doses in the environment or doses over time

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22
Q

Which of the 4 radiation units do we use to judge radiation risk?

A

Effective dose

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23
Q

Give some examples of how we use radiation to saves lives?

A
  1. Radiotherapy
  2. Early diagnosis
  3. Sterilisation of Blood products, Foodstuffs and Dressings
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24
Q

How can radiation cause harm?

A

It can cause:

  1. Cancer
  2. Cataracts
  3. Skin darkening / burns
  4. Hair falling out
  5. Sterility
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25
Q

What are the 3 ways x-rays interact with tissues?

A

They can be:

  1. Transmitted
  2. Scattered
  3. Absorbed
26
Q

What do transmitted x rays help us to from?

A

The image we want to see

27
Q

When are cells at risk of damage the most?

A

During the replication stage of the cell cycle

28
Q

Which type of cell active or inactive is more sensitive to radiation?

A

Active cells are more sensitive to radiation

29
Q

Who is more sensitive to radiation adults or children and why?

A

Children as they are growing so more of their cells are replicating

30
Q

What are cells lately composed of?

A

Water

31
Q

What can X-rays cause?

A

Ionisation

32
Q

What can the ionisation of cellular water

A

can lead to molecular changes and the formation of chemicals that can damage chromosomes
This leads to changes in the structure and function of the cell

33
Q

What can ionising radiation lead to in cells?

A
  1. Death
  2. Recovery
  3. Dysfunctional
34
Q

What is the effect ionisation radiation has on the body dependent on?

A
  1. Dose and doserate
  2. Area irradiated
  3. Sensitivity of organs/individual irradiated
35
Q

What are the 2 types of radiation effects?

A
  1. Deterministic (acute effects)

2. Stochastic (chronic, potential long term effects)

36
Q

When does a deterministic radiation effect occur?

A

If someone is exposed to high doses over a short period of time
Only occurs above a certain threshold dose

37
Q

What can increase the severity of a deterministic radiation effect?

A

Severity increases with dose &dose-rate

38
Q

What are some symptoms of a deterministic radiation effect?

A 
Effects include “radiation sickness”,
erythema
epilation
loss of fertility, 
death
Skin reddening 
Temporary hair loss
Ulceration
39
Q

When does a Stochastic radiation effect occur?

A

Occur at high and low doses

Occur randomly, but probability of effect depends on dose received

40
Q

Which of the 2 types of radiation effect may occur in dental radiology?

A

Stochastic radiation effect

41
Q

Name the different models we can use to estimate the risk

A
  1. Linear threshold
  2. Quadratic
  3. Wasted dose
  4. Hormesis
  5. LINEAR NO THRESHOLD
42
Q

What can Stochastic radiation effect cause?

A
  1. Cancer

2. Can cause harm to future generations

43
Q

When is a risk ‘acceptable’ to a patient?

A

Risk acceptable if the individual understands the risk and enjoys some commensurate benefit

44
Q

What is the ‘acceptable’ risk of death statistic in most communities?

A

risks of 1 in 100,000 per year or less

45
Q

What risk does 1mSv of radiation pose?

A

1 in 20,000 risk of developing fatal cancer

46
Q

What 3 things are taken into consideration tomato sure x rays are administrated safely?

A
  1. Limitation: Doses must not exceed the ICRP recommended limits
  2. Justification: Benefit must outweigh risk
  3. Optimisation: Doses must Beas low as reasonably practicable
47
Q

What is the annual ICRP effective dose limit for employees?

A

20 mSv

48
Q

What is the annual ICRP effective dose limit for trainees under 18?

A

6 mSv

49
Q

What is the annual ICRP effective dose limit for members of the public?

A

1 mSv

50
Q

What is the risk to an adult dental patients of developing cancer when having an intra oral exam?

A

less than 1 in 6 million

51
Q

What is the risk to an adult dental patients of developing cancer when having an OPT exam?

A

Less than 1 in 4 million

52
Q

What is the risk to a child dental patients of developing cancer when having an intra oral exam?

A

Less than 1 in 20 million

53
Q

What is the risk to a child dental patients of developing cancer when having an OPT exam?

A

Less than 1 in 4 million

54
Q

What do dose limits aim to do?

A
  1. Avoid deterministic effects completely

2. Reduce the risks of stochastic effects to an “acceptable” level

55
Q

What is the annual ICRP dose limit to the lens of the eye for employees?

A

20 mSv

56
Q

What is the annual ICRP dose limit to the lens of the eye for trainees under 18?

A

15 mSv

57
Q

What is the annual ICRP dose limit to the lens of the eye for members of the public?

A

15 mSv

58
Q

What is the annual ICRP dose limit to the skin for employees?

A

500 mSv

59
Q

What is the annual ICRP dose limit to the skin for trainees under 18?

A

150 mSv

60
Q

What is the annual ICRP dose limit to the skin for members of the public?

A

50 mSv

61
Q

What is the ICRP dose rate for pregnant women?

A

o Employer must ensure under 1 mSv will be exceeded during declared time

62
Q

What is the dose limit for medical and dental patients ?

A

No dose limit for patients but justification for the dose is requires

ODDR- Dental physics (3 decks)

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