Light amplification by stimulated emission of radiation (LASER)
- visible light wavelengths = 400 – 700 nm
- higher frequency = higher energy (x-ray, gamma ray, UV)
- light travels as photons
Principles of laser generation
- 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”
stimulated emissions
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
Population inversion
the # of excited atoms outweighs the # of ground state
Pumping
the application of an external source of power to the lasing medium which –> population inversion
Mechanism of laser production
- pumping of active medium
- population inversaion
- spontaneous emission
- stimulated emission
- amplification
Coherence
same wavelength an all in phase
Monochromatic
single color (same wavelength)
Collimation
photons move in a parallel fashion
Wavelength
longer wavelength (lower frequency) = deeper penetration
Types of Lasers
- gas
- solid
- semiconductor = MC
- liquid
Therapeutic window
630 – 900 nm
- visible red = 600 – 700nm
- near infrared = 700 – 900 nm
Depth of penetration
As [melanin and hemoglobin] increase, light’s depth of penetration decreases
- wavelength determines overall depth of penetration
Types of Lasers
- 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
Laser application
- Should lightly contact skin
- 90o to Tx area
- Alternate method = “scanning technique”
- Hold laser 5 – 10 mm from skin
- Energy level decreases with distance
- Alter intensity to take
4 Law of Laser Tx
- Arndt-Schultz law
- Grotthuss-Draper law
- Inverse Square law
- Lambert’s cosine law
Photobiomodulation
photochemical effects
- Effect is not from heating tissues but from the absorption of photons of light by cells
- Types
- Photobiostimulaiton
- Photobioinhibition
Photobiostimulation
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
Photobioinhibition
higher dose of laser
- High = Inhibition
Protobiositmulation primary effect
due to interaction of photos with cytochrome
- occurs in the cell
Protobiostimulation secondary effect
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
Protobiostimulation tertiary effects
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
Chromophores
molecules which accept energy from photons
- Example = cytochrome
Cellular Mechanism of laser
- Changes Na/K channel
- Increase intracellular Ca
- Ca2+ influx affects levels of cyclic nucleotides
