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PHYS3008: Health Physics > Specific Values and Conversions > Flashcards

Specific Values and Conversions Flashcards

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1
Q

What is the value of the speed of light in a vacuum?

A

2.9979 x 10⁸ m/s

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2
Q

What is 1eV in J and what is the conversion factor?

A

1eV = 1.6 x 10⁻¹⁹ J

Joules to eV: ÷ 1.6 x 10⁻¹⁹
eV to Joules: x 1.6 x 10⁻¹⁹

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3
Q

What is the energy released if an electron’s rest mass is fully converted?

A

511 keV

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4
Q

What is 1 atomic mass unit (amu) in kg and what is the conversion factor?

A

1 amu = 1.6605 x 10⁻²⁷ kg

kg to amu: ÷ 1.6605 x 10⁻²⁷
amu to kg: x 1.6605 x 10⁻²⁷

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5
Q

What is the conversion energy of 1 amu (in eV)?

A

1 amu = 931 MeV

MeV to amu: ÷ 931
amu to MeV: x 931

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6
Q

What is Rydberg’s constant?

A

1.0974 x 10⁷ m⁻¹

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7
Q

What is the conversion factor between the wavelength of a photon in nm and its energy in eV?

A

1238 eV nm

(divide this value by the wavelength in nm to get the energy or by the energy in eV to get the wavelength)

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8
Q

What is 1 curie in becquerel and what is the conversion factor?

A

1 Ci = 3.7 x 10 ¹⁰ Bq

Bq to Ci: ÷ 3.7 x 10 ¹⁰
Ci to Bq: x 3.7 x 10 ¹⁰

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9
Q

What is the half-life of radium-226?

A

1600 years

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10
Q

What energy does an alpha particle have?

A

Energy in the order of 5 MeV

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11
Q

What energy does a beta particle have?

A

0.6 - 2 MeV

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12
Q

What energy does a gamma ray have?

A

0.1 - 1.5 MeV

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13
Q

What is the energy of 99-Tc?

A

140 keV

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14
Q

What is the by-product of annihilation?

A

Two 511 keV gamma rays

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15
Q

What is the average dose of FDG given to a patient?

A

200 - 400 MBq

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16
Q

What is the effective half-life of FDG?

A

110 mins

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17
Q

What is the average annual radiation dose?

A

2.3 mSv

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18
Q

What is the energy of a low energy x-ray?

A

30 - 120 keV

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19
Q

What is the energy of a high energy x-ray?

A

6 MeV

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20
Q

What is the average energy lost by a beta particle for every collision in air?

A

34eV

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21
Q

What is the fast diffusion length in water?

A

5.75 cm

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22
Q

What is the thermal diffusion length in water?

A

2.88 cm

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23
Q

What distance of water is an effective shield for neutron sources

A

~25 cm

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24
Q

How much is a human year worth to the NHS in treatment costs?

A

The NHS will pay £30,000 per QALY (this can go higher for end-of-life drugs).

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25
Q

What voltage do ionisation chambers operate at?

A

200-400 V

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26
Q

What voltage do Geiger counters operate at?

A

Above 700 V

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27
Q

What is the conversion factor between exposure units and gray in air (the conversion of exposure to absorbed dose)?

A

1 C/kg = 34 gray

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28
Q

What is the radiation weighting factor for beta?

A

1

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29
Q

What is the radiation weighting factor for alpha?

A

20

30
Q

What is the radiation weighting factor for x-rays?

A

1

31
Q

What is the radiation weighting factor for gamma rays?

A

1

32
Q

What is the risk factor per sievert of radiation in the whole body?

A

5.0%

33
Q

What is the average annual equivalent dose ?

A

2.3 mSv (in UK)

34
Q

What is the average annual equivalent dose from cosmic rays?

A

0.3 mSv

35
Q

What is the average annual equivalent dose from terrestrial gamma?

A

0.35 mSv

36
Q

What is the average annual equivalent dose from internal sources (C-14 and K-40)?

A

0.38 mSv

37
Q

What is the average annual equivalent dose from inhalation (radon Rn-222 and decay sources)?

A

0.97 mSv

38
Q

What is the average annual equivalent dose from nuclear weapons, Chernobyl, leaks, etc.?

A

0.03 mSv

39
Q

What is the average annual equivalent dose from medical exposure?

A

0.25 mSv

40
Q

Describe the pie chart for the distribution of annual equivalent dose

A
41
Q

What is the dose of a CT scan?

A

~10 mSv (> ~10 mGy)

42
Q

What is the lifetime risk of fatal cancer from a CT scan?

A

1:2000

43
Q

What is the normal risk of fatal cancer?

A

~1:5

44
Q

What is the total tissue weighting factor for the whole body?

A

1.00

45
Q

What is the dose of a paediatric CT scan?

A

5 mSv - 60 mSv

46
Q

What is the range of sensitivities for a film badge?

A

0.1 - 10 mSv

47
Q

What is the typical photon wavelength used for scintillation crystals?

A

410 nm

48
Q

What are the effects of 3-5 Gy of radiation (and what effect does that have on the time to death)?

A

Hematopoietic syndrome in bone marrow: the production of red blood cells is stopped.

Time to death: 30-60 days

49
Q

What are the effects of 5-15 Gy of radiation (and what effect does that have on the time to death)?

A

The gastrointestinal tract and lung epithelia are impacted.

Time to death: 10-20 days

50
Q

What are the effects of >15 Gy of radiation (and what effect does that have on the time to death)?

A

The central nervous system is impacted.

Time to death: 1-5 days

51
Q

What is the radiation dose that causes permanent sterility in males and females?

A

Males: 3.5-3.6 Gy
Females: 2.5-2.6 Gy

52
Q

What is the radiation dose that causes temporary sterility in males and females?

A

Males: 0.15 Gy
Females: 0.6 Gy

53
Q

What is the allowed radiation dose for the general public annually?

A

1 mSv (5 mSv if a medical procedure is required)

54
Q

What is the allowed radiation dose for a radiologist annually?

A

20 mSv

55
Q

What is the maximum permissible exposure (MPE) for ocular exposure to visible light?

A

For a 400 - 700 nm wavelength, the continuous (1hr) limit is 1 mW/cm².

56
Q

What is the maximum permissible exposure (MPE) for ocular and skin exposure to HeNe (632 nm)?

A
  • Occular: 2.5 mW/cm² for a 0.25s blink reflex
  • Skin: 200 mW/cm² for 1hr
57
Q

What is the wavelength of UVA?

A

320 - 400 nm

58
Q

What is the wavelength of UVB?

A

280 - 320 nm

59
Q

what is the wavelength of UVC?

A

100 - 280 nm

60
Q

What are the wavelengths of fluorescent light?

A

253.7 nm to 185 nm

61
Q

What % of non-melanoma skin cancer comes from UV radiation?

A

~90%

62
Q

What is the total flux from the Sun?

A

1000 W/m²

63
Q

How long does it take for sunburn to occur?

A

15 mins

64
Q

What is the energy of UVA at 400nm (in eV)?

A

3.1 eV

65
Q

What is the energy of UVB at 320 nm (in eV)?

A

3.9 eV

66
Q

What is the energy of UVC at 280 nm (in eV)?

A

4.4 eV

67
Q

What are the safe and maximum allowed degrees of heating of tissue?

A

Safe: 0.1ºC
Maximum: 1ºC

68
Q

What is the SAR limit in the EU?

A

2 W/kg averaged over 10g of tissue

69
Q

What is the SAR limit in the US?

A

1.6 W/kg averaged over 1g of tissue

70
Q

What current through the heart can kill you?

A

A few µA

71
Q

What is the electric field required for nerve stimulation?

A

6 V/m

PHYS3008: Health Physics (19 decks)

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