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Low-Power Lasers

Low-Power Lasers. Jennifer L. Doherty-Restrepo, MS, ATC, LAT Entry-Level Master Athletic Training Education Program PET 4995: Therapeutic Modalities. LASER. L. Light Amplification of Stimulated Emission of Radiation. A. S. E. R.

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Low-Power Lasers

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  1. Low-Power Lasers Jennifer L. Doherty-Restrepo, MS, ATC, LAT Entry-Level Master Athletic Training Education Program PET 4995: Therapeutic Modalities

  2. LASER L • Light • Amplification of • Stimulated • Emission of • Radiation A S E R

  3. Physics of the Laser • Light energy transmitted through space as waves that contain tiny "energy packets" called photons • Each photon contains a definite amount of energy depending on its wavelength (color)

  4. Physics of the Laser • If a photon collides with an electron of an atom, it causes the atom to be in an excited state • Atom stays in excited state only momentarily • Atom quickly releases an identical photon to return to its ground state • Process is called spontaneous emission

  5. Stimulated Emissions • A photon released from an excited atom will stimulate another atom to return to its ground state • For this to occur, an environment must exist with unlimited excited atoms • This is termedpopulation inversion

  6. Stimulated Emissions • Population inversion occurs when there are more atoms in an excited state than in a ground state • May be stimulated by an external power source • Photons may be contained in a chamber

  7. Stimulated Emissions • Mirrors are placed at either end of the chamber • Photons are reflected within chamber, which amplifies the light and stimulates the emission of other photons from excited atoms

  8. Stimulated Emissions • Eventually so many photons are stimulated that the chamber cannot contain the energy • Photons of a particular wavelength are ejected through the semipermeable mirror producing amplified light through stimulated emissions

  9. Types of Lasers • Classified according to the nature of material between two reflecting surfaces • Crystal lasers • Synthetic ruby (aluminum oxide and chromium) • Neodymium, Yttrium, Aluminum, Garnet • Gas lasers (under investigation in the U.S.) • Helium neon (HeNe) • Argon • Carbon dioxide (CO2)

  10. Types of Lasers • Classified according to the nature of material between two reflecting surfaces • Semiconductor or Diode lasers (under investigation in the U.S.) • Gallium-arsenide (GaAs) • Liquid lasers • Organic dyes = lasing medium • Chemical lasers • Used for military purposes

  11. Laser Classification • Laser equipment is grouped into four FDA classes with simplified and well-differentiated safety procedures for each • Low power lasers used in treating sports injuries are categorized as Class I and II laser devices

  12. Laser Classification • High power lasers = "hot" lasers • Thermal effects • Surgical cutting and coagulation, ophthalmological, dermatological, oncological, and vascular specialties • Low power lasers = “cold” lasers • Cause photo-chemical rather than thermal effects

  13. Laser Generators • Power Supply • Lasing Medium • Gas, solid or liquid • Pumping Device • Creates population inversion • Optical Resonant Cavity • Chamber where population inversion occurs • Contains reflecting surfaces

  14. Helium-Neon Lasers • Gas lasers • Deliver a red beam • Wavelength = 632.8nm • Laser delivered in a continuous wave • Direct penetration of 2 to 5 mm • Indirect penetration of 10 to 15 mm

  15. Gallium-Arsenide Lasers • Semiconductor lasers • Invisible beam • Wavelength = 904nm • Direct penetration of 1 to 2 cm • Indirect penetration to 5 cm

  16. Techniques of Application • Laser energy emitted from hand held remote applicator • Tip should be in light contact with the skin • Applicator should be directed perpendicularly to the skin

  17. Dosage • Dosage reported in Joules per square centimeter (J/cm2) • One Joule is equal to one watt per second • Dosage is dependent on • Output of the laser in mWatts • Time of exposure in seconds • Beam surface area of laser in cm2

  18. Dosage • Dosage should be accurately calculated to standardize treatments and to establish treatment guidelines for specific injuries. • Intention is to deliver a specific number of J/cm2 or mJ/cm2

  19. Pulsed vs. Continuous Laser • With pulsed laser treatment, times may be exceedingly long to deliver same energy density as compared to a continuous wave laser

  20. Depth of Penetration • Depends on type of laser energy delivered • “Direct effect” • Response that occurs from absorption of laser energy • “Indirect effect” • Lessened response that occurs deeper in the tissues

  21. Depth of Penetration • HeNe lasers • Direct effect = 2-5 mm • Indirect effect = 8-10 mm • GaAs lasers (longer wavelength) • Direct effect = 1-2 cm • Indirect effect = 5 cm • Better for treating deeper tissues

  22. Clinical Applications Wound healing Immunological responses Inflammation Scar tissue Pain Bone healing

  23. Indications for Laser • Facilitate wound healing • Pain reduction • Increasing the tensile strength of a scar • Decreasing scar tissue • Decreasing inflammation • Bone healing and fracture consolidation

  24. Contraindications for Laser • Cancerous tumors • Directly over eyes • Pregnancy

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