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PHYS853: Radiation Protection in Medicine > Non-Ionising Radiation: UV and Microwave Safety > Flashcards

Non-Ionising Radiation: UV and Microwave Safety Flashcards

(71 cards)

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1
Q

What is ultraviolet radiation?

A

The portion of the electromagnetic spectrum extending from the violet end of the visible wavelength range to ~ 100 nm.

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2
Q

What is the wavelength range of UV radiation?

A

400 nm - 100 nm

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3
Q

What are the 3 wavelength bands of UV radiation?

A

UVA
UVB
UVC

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4
Q

What is the wavelength range of UVA?

A

400 nm - 315 nm

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5
Q

UVA is the _____ energetic type of UV radiation.

A

Least

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6
Q

How penetrating is UVA?

A

It penetrates deeper layers of skin.

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7
Q

What is the wavelength range of UVB?

A

315 nm - 280 nm

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8
Q

Which wavelength band of UV radiation is responsible for sun tan/burn effects?

A

UVB

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9
Q

Which wavelength band of UV radiation can affect the immune system?

A

UVB

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10
Q

What is the wavelength range of UVC?

A

280 nm - 100 nm

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11
Q

UVC photons in the range 100-200 nm are absorbed in ___ and other UVC wavelengths are absorbed by keratin in the ________ and can cause ___ ______.

A

Air
Epidermis
DNA damage

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12
Q

How penetrating is UVC?

A

It does not penetrate the dermis.

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13
Q

What is the natural source of UV radiation?

A

Sunlight

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14
Q

What are the artificial sources of UV radiation?

A
  • Medical applications (germicidal lamps for sterilisation, dermatological treatments, lasers)
  • Industrial uses (electric welding arcs, arc lamps, curing lamps)
  • Sunbeds
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15
Q

Which wavelength bands of solar UV radiation reach Earth?

A

UVA (the highest component reaching Earth) and UVB. UVC is filtered out/absorbed in the atmosphere before reaching Earth.

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16
Q

Where is the eye is UV radiation absorbed?

A

< 300 nm UV is absorbed by the cornea and conjunctiva
> 300 nm UV is absorbed by the lens

The depth of penetration increases as the wavelength approaches the visible range.

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17
Q

What are the effects of UV radiation on the eye (cornea, conjunctiva, and lens)?

A

Cornea: photokeratitis (inflammation)
Conjunctiva: photoconjunctivitis
Lens: cataract formation (thresholds exist for permanent and transient cataracts)

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18
Q

What is minimal erythemal dose (MED)?

A

The lowest dose of UV radiation that will produce a barely detectable erythema. This dose is dependent on skin type.

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19
Q

What determines whether UV effects on the skin are chronic or acute?

A
  • UV level
  • Duration and frequency of exposures
  • Individual sensitivity
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20
Q

What natural protection methods does the body have against UV radiation?

A

Skin darkening: increasing the amount of pigment
Skin thickening: increasing cell proliferation

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21
Q

What are the acute effects of UV on the skin?

A

Erythema

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22
Q

What is erythema?

A

A skin response to UV radiation overexposure, categorised by increased blood flow to the dermis which causes reddening of the skin. The skin also blisters and peels.

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23
Q

Which type of UV radiation causes the most acute effects?

A

UVB

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24
Q

What are chronic effects of UV on the skin?

A

Induction of skin cancer

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25
What are the 3 types of skin cancer?
- Basal cell carcinoma (most common, easily treatable) - Squamous cell carcinoma (treatable if caught early) - Malignant melanoma (least common, most aggressive)
26
What impact can UV radiation have on skin?
- Ageing - Loss of elasticity - Dryness - Blemishes - Freckles - Moles
27
State 3 beneficial systemic effects of UV radiation
- Production of Vitamin D - Treatment of seasonal affective disorder - Medical treatment/therapy
28
State the negative systemic effect of UV radiation
Compromised immune system (UV radiation is an immuno-suppressor)
29
What is the UV dose limit to the eyes and skin (180-400nm)?
Exposure limits are averaged over an 8 hour day
30
Who defines the UV exposure standards?
ICNIRP (UV Guidelines 2004)
31
Give the equation for UV irradiance
32
What is maximum permissible exposure time?
The maximum time that someone can be exposed to a given UV irradiance before they surpass the UV dose limit.
33
Give the equation for maximum permissible exposure time
t_max = maximum permissible exposure time E_eff = biological effective irradiance
34
What is the UVA dose limit to eyes and skin (315-400nm)?
For exposure times < 1000s: total irradiance < 10W/m² For exposure times > 1000s: total exposure < 10000J/m² Exposure limits are averaged over an 8 hour day
35
What measures are required to keep patients safe around UV?
- Provision of glasses or goggles - Adequate protection against electrical hazards - Protection against bare lamps - Doors openable from within UV cabinets - Non-skid flooring within UV cabinets
36
How is UV equipment managed to keep patients safe?
- Suitable design features - Maintenance - Signage and labels
37
What working practices are followed to protect patients from UV?
- Limit access to UV areas - Staff training - Quality assurance
38
What should UV local rules contain?
- A description of potential UV hazards - Safe operating procedures - Contact details of duty holders - Use of PPE - Contingency plans in the event of an untowards occurence
39
How are the principles of radiation protection followed when working with UV radiation?
Time: - Reduced time of exposure (reduced dose) Distance: - Remote control of equipment Shielding: - Clothing - Drapes - Adequately labelled visors and goggles matching the spectral output of the source
40
How is UV eye protection labelled?
It should be marked with a scale number that displays its Optical Density (OD)
41
What PPE should be worn to protect the skin from UV?
Hands and wrists: tight woven cotton gloves (low exposure) or more substantial gloves (high exposure) Lower arms: heavy duty, dark coloured, opaque clothing and gloves should overlap to cover whole arm Face: UV protection factor (UPF) of 40+ should be worn
42
What glove type best protects against UVA?
Nitrile
43
What glove type best protects against UVB?
Latex
44
What glove type best protects against UVC?
Nitrile
45
What is the frequency range of microwave radiation?
300 MHz - 300 GHz
46
What is the frequency range of RF radiation?
3 KHz - 300 GHz
47
Why are the biological effects of microwaves and RF not fully understood?
As their effects depend on multiple variables, including: frequency, bandwidth, directionality, pulse rate, duty cycle, modulation, exposure level, exposure times, proximity, age, weight, height, sex, population size, and longitudinal data.
48
What are the main medical applications of microwaves and RF?
- Diathermy (RF or microwave) - Physiotherapy (RF or microwave) - Microwave ablation
49
What is diathermy?
A technique used in surgery that uses high frequency currents to cut and seal blood vessels. It uses a frequency range of 0.4-3 MHz and a power level of 50-300 W.
50
What are the potential hazards of diathermy?
- Accidental burns from paddles - EM interference with other equipment (particularly cardiac devices) - Fire
51
What rules must be followed to ensure safety when using diathermy?
- Only those involved in the treatment should be close to cables, electrodes, and applicators - The patient ground plate should be in good contact - Jewellery/metallic objects must be removed on staff and patients - Minimise exposure to patient's eyes - Keep other electrical equipment at leave 1m away
52
How are microwaves/RF used in physiotherapy?
They are used to heat tissue for pain relief and healing. EM energy is passed through the tissue (either pulsed or continuous wave).
53
What is the frequency of RF diathermy used in physiotherapy?
10-100 MHz
54
What is the frequency of microwave diathermy used in physiotherapy?
2.4 GHz
55
What are the potential hazards of using RF/microwaves for physiotherapy?
Patient burns
56
What is microwave ablation?
A technique used to remove tumours by inserting a microwave antenna into the tissue, allowing localised heating around the antenna tip.
57
What is the frequency and power of microwave ablation?
2.4 GHz and 50 W
58
What is SAR?
Specific absorption rate. It is the rate at which energy is absorbed by the body from RF sources.
59
Give the equation for specific absorption rate
60
The rate of tissue heating is a function of ___.
SAR
61
What is the time averaged exposure limit on SAR for < 300GHz?
0.8 W/kg
62
How are SAR and tissue heating related?
A SAR of 4 W/kg of raises the body temperature by 1ºC.
63
What is the SAR occupational exposure limit for < 300GHz?
SAR must never exceed 0.4 W/kg over an 8 hour period.
64
Who defines the SAR exposure standards?
ICNIRP
65
What studies have been done on the biological effects of non-ionising radiations < 300GHz?
- Epidemiology - In vitro - In vivo - In silicon
66
Define electromagnetic compatability
The ability of electronic devices of different types to operate in their environment without loss of intended function
67
Define electromagnetic immunity
The sensitivity of a device to the entry of an EM field
68
State 5 internal sources of electromagnetic fields in hospitals
- Electrosurgery - Physiotherapy - Imaging equipment - Mobile radio transmitters - WiFi
69
State 3 external sources of electromagnetic fields
- TV/radio masts - Base stations - Emergency service vehicle transmissions
70
State 5 medical devices that can be affected by electromagnetic fields
- Electrically powered wheelchairs - Cardiac pacemakers - Defibrillators - ECG monitors - Syringe drivers - Infusion pumps
71
What is the maximum permissible exposure (MPE) for a 270nm UV lamp?
30 J/m²

PHYS853: Radiation Protection in Medicine (19 decks)

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