11 - Laser

Question 1

Light amplification by stimulated emission of radiation (LASER)

Answer 1

• visible light wavelengths = 400 – 700 nm
• higher frequency = higher energy (x-ray, gamma ray, UV)
• light travels as photons

Question 2

Principles of laser generation

Answer 2

• adding energy to electrons causes them to move to higher orbit (excited state)
• if the electron gives of energy, it moves to a lower orbit
• giving of electrons = “spontaneous emission”

Question 3

stimulated emissions

Answer 3

occurs when an excited atom releases a photon

• if that photon interacts with another Adam, it will release another photon
• both photons have identical frequencies, direction, and phase
• both photons continue to cause the release of other identical photons, as long as the excited atoms are present

Question 4

Population inversion

Answer 4

the # of excited atoms outweighs the # of ground state

Question 5

Pumping

Answer 5

the application of an external source of power to the lasing medium which –> population inversion

Question 6

Mechanism of laser production

Answer 6

1. pumping of active medium
2. population inversaion
3. spontaneous emission
4. stimulated emission
5. amplification

Question 7

Coherence

Answer 7

same wavelength an all in phase

Question 8

Monochromatic

Answer 8

single color (same wavelength)

Question 9

Collimation

Answer 9

photons move in a parallel fashion

Question 10

Wavelength

Answer 10

longer wavelength (lower frequency) = deeper penetration

Question 11

Types of Lasers

Answer 11

• gas
• solid
• semiconductor = MC
• liquid

Question 12

Therapeutic window

Answer 12

630 – 900 nm

• visible red = 600 – 700nm
• near infrared = 700 – 900 nm

Question 13

Depth of penetration

Answer 13

As [melanin and hemoglobin] increase, light’s depth of penetration decreases

• wavelength determines overall depth of penetration

Question 14

Types of Lasers

Answer 14

• Helium-Neon
  
  • 630 nm
• Indium-Gallium-Aluminum-Phosphide (inGaAIP)
  
  • 630 – 700 nm
  • Semiconductors
• Gallium-Aluminum-Arsenide (GaAIA)
  
  • 800 – 830 nm
  • Semiconductor laser
• Gallium-Arsenide (GaAs)
  
  • 904 nm
  • Semiconductor
  • More likely to have therapeutic effect, but less likely to be absorbed by other tissues

Question 15

Laser application

Answer 15

• Should lightly contact skin
• 90^o to Tx area
• Alternate method = “scanning technique”
  
  • Hold laser 5 – 10 mm from skin
  • Energy level decreases with distance
  • Alter intensity to take

Question 16

4 Law of Laser Tx

Answer 16

• Arndt-Schultz law
• Grotthuss-Draper law
• Inverse Square law
• Lambert’s cosine law

Question 17

Photobiomodulation

Answer 17

photochemical effects

• Effect is not from heating tissues but from the absorption of photons of light by cells
• Types
  
  • Photobiostimulaiton
  • Photobioinhibition

Question 18

Photobiostimulation

Answer 18

a chain of chemical rxn is triggered by light

• Stimulates respiratory ETC
  
  • Light changes REDOX status
  • Actives Na/K pump
• Cell is provided more energy
• Thus cell is stimulated to start natural healing

Question 19

Photobioinhibition

Answer 19

higher dose of laser

• High = Inhibition

Question 20

Protobiositmulation primary effect

Answer 20

due to interaction of photos with cytochrome

• occurs in the cell

Question 21

Protobiostimulation secondary effect

Answer 21

occur in the same cell in which photos produce the primary effect

• They are induced by primary effect
• Include: cell proliferation, protein synthesis, the regulation, growth factor secretion, myofibroblast contraction, neurotransmitter modification
• occurs in the cell

Question 22

Protobiostimulation tertiary effects

Answer 22

the indirect responses of distance cells to changes in other cells that have interacted directly with photons

• least predictable
• dependent on environmental factors, and intracellular interactions
• occurs in area around cell

Question 23

Chromophores

Answer 23

molecules which accept energy from photons

• Example = cytochrome

Question 24

Cellular Mechanism of laser

Answer 24

1. Changes Na/K channel
2. Increase intracellular Ca
3. Ca2+ influx affects levels of cyclic nucleotides

Question 25

Laser indications

Answer 25

1. Wound healing
2. TMD
3. Myofasical pain
4. osteoarthritis
5. rheumatoid arthritis
6. Tendinopathy
7. trigger points
8. epicondylitis
9. neck and lower back pain

Question 26

Laser safety

Answer 26

glasses should what specifically will

• class IM = non eye protection necessary
• class II = hazard this laser directed continuously into eyes
• Class III = requires eye protection
  
  • Class IIIB = MC therapeutic laser
• Class IV = research labs, surgery, Photothermal

Question 27

Laser contraindications

Answer 27

• cancer
• pregnancy
• direct exposure to eyes
• over hemorrhage
• over thyroid
• directly over open wounds
• epileptic patients

Question 28

Laser dosage

Answer 28

measured in J/cm²

• takes into account to cycle and:
• output of laser(mWatts)
• number of diodes
• time of exposure (seconds)
• being surface area of laser (cm²)

Question 29

Super pulsed laser

Answer 29

Pulses (or bursts) of energy with higher peak power and less thermal effects

• low thermal influence with high energy density
• more direct energy to target tissue
• greater safety and enhance clinical outcome

Question 30

Stimulatory frequencies

Answer 30

• low-frequency (smaller energy dose)
  
  • repair and regeneration of tissue
  • immune response
  • anti-inflammatory response
• lower ranges of frequencies (0.25 – 500 Hz)