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Radiation Protection > Lasers > Flashcards

Lasers Flashcards

(51 cards)

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1
Q

What is a class 1 laser?

A

40 microW Blue
400 microW Red

Considered safe

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2
Q

What is a class 1M laser?

A

40 microW Blue
400 microW Red

Safe without optics

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3
Q

What is a class 2 laser?

A

1 mW Visible only

Protection provided by eye response

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4
Q

What is a class 2M laser?

A

1 mW Visible only

Safe without optics

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5
Q

What is a class 3R laser?

A

5 mW

May be hazardous

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6
Q

What is a class 3B laser?

A

500 mW

Will be hazardous

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7
Q

What is a class 4 laser?

A

Not limited

Hazardous plus risks to skin and of fires

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8
Q

What is optical radiation?

A

IR, Visible and UV

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9
Q

What is a laser?

A

Light
Amplification by
Stimulated
Emission of
Radiation

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10
Q

How is laser light generated?

A

Inside a resonator cavity
High reflector, lasing medium, output coupler, with an excitation mechanism powered by a power supply

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11
Q

What are the key properties of laser light?

A
  1. Monochromatic
  2. Directional
  3. Coherent
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12
Q

What does a monochromatic laser mean?

A

Narrow spectral range

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13
Q

What does a directional laser mean?

A

Well collimated/parallel and travels long distances without spread

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14
Q

What does a coherent laser mean?

A

All the individual photons of light move together in-phase through time and space

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15
Q

What is the unit of power?

A

Watt (J/s)

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16
Q

What are the types of laser emissions?

A

Continuous wave (CW)
Pulsed

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17
Q

What is a pulsed emission laser?

A

Short pulse duration with pause between each pulse

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18
Q

What are the types of pulsed emssion lasers?

A

Free running
Triggered (high peak power)

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19
Q

How is laser radiation quantified?

A

Power

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20
Q

What is the definition of power in the context of a laser?

A

The rate of energy flow (energy flow per unit time)

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21
Q

What is irradiance?

Study These Flashcards
A

Power/Area
Power density
measured in Watts per square metre (Wm-2)

22
Q

What is the relationship between power and energy?

Study These Flashcards
A

Total energy (J) is the area under a Power(W) vs time(s) graph

23
Q

What is radiant exposure?

Study These Flashcards
A

Energy/area
Energy density
measured in Joules per square metre (Jm-2)

24
Q

How is a laser focused and what happens the the power density where it is focused vs where it is more spread out?

Study These Flashcards
A

With a lens
Power density high at focus point (area is small)
Power density low where it is spread (area high)

25
What are some types of lasers?
CO2 KTP Diode
26
What is a CO2 laser?
CO2:He:N2 mix in a glass tube with RF/electrical excitation Wavelength 10.6 microm (invisible - mid IR) - well matched to water absorption (tissue) Pulsed mode via fast electrical switching giving rapid vaporisatoin
27
What is a KTP laser?
1064 nm Nd:YAG passes through a non-linear crystal, wavelength halves to 532 nm ~30% efficiency Green light aborbed by haemoglobin and melanin Used to cut tissue (CW) or for vasculate lesions and vessels (pulsed) Delivered through fibre
28
What is a diode laser?
Emit near-IR (800-900 nm) Operate with electrical circuit across semi-conductor material which causes charges to combine and release light energy Very reliable, compact and low maintenance ~50 W Very deep penetration - tissue heating
29
What is a chromophore?
A substance that absorbs light
30
What chromophores exist in the body?
Haemoglobin (blood) Melanin (pigment) Water
31
What hazards are associated with laser exposure?
Eye Skin Reflection Non-beam hazards
32
What is the difference in light emission between a lamp and a laser?
laser is very directional which is focused by the eye lens to a spot on the retina, whereas a lamp has multiple emission directions and not focused to one spot
33
What natural mechanism is there for eye protection from a laser?
Blink reflex aversion response - ~0.25s response but some patients may be delayed - basis of class 2 laser definition
34
What are the UV laser hazards for the eye?
Photokeratitis Cataract
35
What is the visible laser eye hazard?
Retinal lesion
36
What are the IR laser eye hazards?
Corneal burn Cataract
37
What are the laser skin hazards?
Erythema Accelerated akin aging Increased pigmentation Photosensitive reactions Skin burn
38
What are non-beam laser hazards?
Laser plume of infectious tissue (class 4) Fire/explosion (class 4) - highly focused high power density beams can ignite flammable materials Laser dyes - carcinogen Hazardous substances (e.g. toxic excimer)
39
What legislation is there for laser use?
Control of Artificial Optical Radiation at Work Regulations 2010 Health and Safety at Work Act 1974 Management of Health and Safety at Work Regulations 1999 Provision and Use of Work Equipment Regulations 1998
39
What is AEL?
Accessible Emission Limit Maximum allowable emission for each class of laser (W or J)
39
What guidance exists for using lasers in healthcare?
MHRA 2015: Lasers, intense light source systems and LEDs - guidance for safe use in medical, surgical, dental and aesthetic practices BS EN 60825 - 1: Laser safety
40
What is MPE (in terms of lasers)?
Maximum Permitted Exposure Maximum exposure level at which adverse effects could occur. Rated values for the eye and skin (Wm-2 or Jm-2)
41
What is NOHD?
Nominal Ocular Hazard Distance Distance at which beam irradiance equals the corneal MPE (m)
42
What do MPE values for the eye depend on?
Wavelength Duration and others
43
How are controlled areas for lasers defined?
Set closer than the NOHD - accidental exposure may be hazardous Access is controlled by signs, lights, door interlocks Local rules must be written and followed when working within the controlled area, including emergency procedures
44
What is an LPS?
Laser Protection Supervisor / Laser Safety Officer Ensures compliance with local rules, supervises laser environment safety Should be closely involved with treatments
45
What is an LPA?
Required for laser classes 3B and 4 Must have knowledge of laser hazards Advises on laser control Hazard analysis and risk assessment Produces/advises on local rules Certified by RPA2000
46
What should laser local rules contain?
Appointments Hazards Controlled and safe use Authorised user responsibilities Safety checks Normal operating procedures PPE Prevention of unauthorised use Adverse incident procedure List of authorised users
47
What is required of an authorised laser user?
Approved by clinical laser expert Suitable training and evidence
48
What is the laser risk assessment process?
1. Evaluate all risks 2. Assess risks 3. Establish safety control procedures 4. Re-assess risk 5. Use laser
49
How are eyes protected when using lasers?
Safety goggles

Radiation Protection (20 decks)

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