Week 9

Question 1

LASER acronym

Answer 1

Light
Amplification by
Stimulated
Emission of
Radiation

Question 2

Quantum Physics

Answer 2

In 1917, Einstein proposed the possibility of stimulated emission, the physical process that makes the maser and the laser

Question 3

Review components of the first ruby laser

Answer 3

Pg. 6

Question 4

Low intensity laser therapy (LILT)

Answer 4

synonyms
-therapeutic laser
-low level laser therapy
-low power laser therapy
low level laser
low power laser 
low energy laser
soft laser
low reactive level laser
low intensity-level laser
photobiostimulation laser
photobiomodulation laser
mid laser
medical laser
biostimulating laser
bioregulating laser

Question 5

Class of lasers

Answer 5

Class I : low power lasers
Class II: power out put up to 1mW (400-700nm wavelength)
Class IIIa: power out put up to 5mW
Class IIIb: power output up to 5-500mW
Class IV: Power output up to 500-700mW

Question 6

Lasing medium

Answer 6

a substance of being ‘pumped’ with energy
gaseous mixture
-helium neon (He-Ne) red light 632nm
Gallium - arsenide (Ga-As) red light 632nm
*Gallium - aluminium-arsebude (GAAIAs) semiconductors visible red to near infra red 630-950nm

*cheaper, higher power, less dangerous to eyes

Question 7

Resonating cavity

Answer 7

chamber to contain lasing medium
contains a pair of parallel reflecting surfaces / mirrors
Photons are reflected back and forth to produce an intense photon resonance
one reflecting surface (output coupler) is not a perfect ‘mirror’ and allows output of the light

Question 8

Power source

Answer 8

a power source is required to ‘pump’ the lasing medium to produce stimulated emission
Usually mains supplied power but can be battery operated e.g. rechargeable NiMH x20AA

Question 9

Characteristics of laser radiation

Answer 9

monochromaticity
collimation
coherence

Question 10

Monochromaticity characteristics

Answer 10

single coloured
clustered around a single wavelength
wavelength is a critical factor for determining biological effect

Question 11

Collimation characteristics

Answer 11

rays of light / photons are all parallel
almost no divergence over distance
optical power is ‘bundled ‘ on to a small area
but increases danger to the eye

Question 12

Coherence characteristics

Answer 12

light emitted is in phase
troughs and peaks perfectly matched
-in time (temperal coherence)
-in space (spatial coherence(

And crawling on the planet’s face some insects called the human race lost in time, and lost in space and meaning

Question 13

Laser tissue interaction LILT

Answer 13

Scattering of incident light
- change in direction of light as it passes through tissue with varying refractive indices relative to water content = loss of coherence

absorption of incident lightr

• chromophores are biomolecules that absorb photons and include melanin and haemoglobin
• therefore penetration is limited to several millimetres but is wavelength dependant

Question 14

Laser tissue interaction LILT

Answer 14

of these two modes, absorption is the most important in terms of the photobiological basis of laser therapy

Question 15

photobiological effects of laser

Answer 15

Multiple possible effects
complex interactions
irradiation parameters based
poorly understood

Question 16

Arndt-Schultz law/rule

Answer 16

weak stimuli increases physiologic activity, moderate stimuli inhibits activity, and very strong stimuli abolish activity

Question 17

Biological and physiological

Answer 17

cellular research
animal studies
human studies

Question 18

cellular research

Answer 18

fibroblasts
macrophages
collagen production

generally positive results but come equivocal

Question 19

Animal studies

Answer 19

photobiostimulatory effects of wound healing 
-bone defects
burns
soft tissue injury
nerves

antinociceptive

• hypoalgesic effect noted
• naloxone reversible in some studies

Question 20

Human studies

Answer 20

experimentally induced pain 
-variable findings
nerve conduction
-clinical relevance
clinical trials 
-limited due to poor design
Wound healing 
-ulcerated lesions (variable findings)

Question 21

Human studies cont

Answer 21

`arthritic conditions
-mixed conclusions
RA relief of ain and stiffness short term

Msk conditions

• most studies and applied area
• confusion over parameters confounds research
• tennis elbow equivocal
• tendon disorders - mostly positive

Question 22

Principles of clinical application

Answer 22

indications
-wound management
soft tissue injuries 
arthritis 
pain relief

Question 23

Dosage and irradiation parameters

Answer 23

Power output 
-expressed in milliwatts (mW)
-more powerful machine (30-200mW) now common as deliver energy quicker 
Irradiance (power density)
-mW/cm2
-usually kept high 
Energy
-joules (j)
-power output in W x secs application 
e.g. 30mW device for 60 sec = 1.8J

Question 24

Dosage and irradiation parameters

Answer 24

pulse rate

• Hz
• Variable Hz to kHz

Treatment 
-keep treatment head in contact with tissue 
-reduces accidental intrabeam viewing 
-decreases inverse square law 
Useful for trigger/acu-points

Question 25

Open wound ulcers

Answer 25

two stage technique - contact around wound margins - non contact over wound bed

Question 26

Indications of laser therapy

Answer 26

increasing local blood circulation relieving minor muscle and joint aches, pains and stiffness relaxing muscles relieving muscle spasms relieving minor pain and stiffness associated with arthritis promoting nerve regeneration, bone growth, and ligament repair healing wounds

Question 27

Contra-indications of laser therapy

Answer 27

for direct aim into eyes of humans or animals over areas injected with steroids in the past 2-3 weeks over areas that are suspicious or contain potentially cancerous tissue over areas of active haemorrhage over a pregnant uterus over the neck (thyroid or carotid sinus region) or chest (vagus nerve or cardiac region of the thorax) directly over areas with open wounds unless covered with a clear. protective barrier treatment over sympathetic ganglia for symptomatic local pain relief unless etiology is established or unless a pain syndrome has been diagnosed infections, diseases over bony growth centres thoracic area with pacemaker eye vascular diseases