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• LASER


  Light Amplification by Stimulated Emission of Radiation
• Laser properties

  • Coherence: relation between amplitude and phase of the wave at different points in time and space
  • Monochromaticity: all radiation emitted at discrete narrow band wavelengths
  • Collimation: highly collimated beam with very little divergence
  • Brightness
  • High energy

  
• In 1917, Einstein postulated that incident photons of energies equal to the energy that an excited atom must eject if it falls to its lower energy state will stimulate the excited atom to fall to the lower state and the photon ejected will be in phase with the incident photon
• Components of a typical LASER

  • Gain medium
  • Pumping mechanism
  • Optical cavity
  • Output coupler

  
• Types of LASER in medical field


  • CO2 lasers
  • Diode lasers
  • Dye lasers
  • Excimer lasers
  • Fiber lasers
  • Gas lasers
  • Free electron lasers
  • Semiconductor diode lasers

  
• CO2 lasers


  • One of the first gas lasers created, still a powerful laser
  • Highest-power continuous wave lasers available, quite efficient
  • Produce infrared beam with wavelengths around 9.6 and 10.6 μm
  • Useful in surgical operations due to water's ability to absorb this light frequency
• Diode lasers


  • Semiconductor devices like light-emitting diodes, pumped directly with electrical current
  • Can transform electrical energy into light
  • Smaller and cheaper, more user-friendly for doctors
  • Wavelengths from 810 to 1,100 nm, weakly absorbed by soft tissue
  • Soft tissue is not sliced by the beam but cut by touching a hot charred glass point

  
• Dye lasers


  • Use an organic dye solution as the lasing medium, typically as a liquid
  • Lasing medium allows use of a broader range of wavelengths, covering 50 to 100 nanometers or more
  • Broad bandwidth is excellent for tunable lasers and pulsed lasers
  • Can produce wavelengths from near-infrared to near-ultraviolet

  
• LASER interaction with biological tissue

  • Absorption: Photons absorbed by chromophores, light energy transformed into other forms of energy
  • Reflection: Laser beam bounces off surface without penetration or contact
  • Transmission: Laser energy penetrates through superficial tissues to interact with deeper regions
  • Scattering: Laser energy scatters in various ways, generally ineffective but can be beneficial for biostimulative characteristics

  
• LASER effects on biological tissue

  • Thermal effects: Conversion of light to heat, transfer of heat, and tissue reaction related to temperature and heating time
  • Leads to denaturation or destruction of tissue

  
• Thermal effects of lasers on biological tissue


  • Homeostasis: Any procedure that stops bleeding
  • Photocoagulation: Heating a blood vessel to coagulate and block the vessel
  • Photo Vaporization: Making incisions and vaporizing tissue
  • Sonic: Membrane disruption
• Medical applications of LASER


  • Ophthalmology: Photocoagulation of the retina
  • Dermatology: Skin tumor therapy, tattoo removal
  • Dentistry: Repairing teeth decays, treating gum bleeding and ulcers
  • Surgery: Sealing of vessels, internal treatment through fiber optics
• Advantages of LASER Surgery


  • No-touch technique
  • Dry surgical field
  • Reduced blood loss
  • Reduced edema
  • Limited fibrosis and stenosis
  • Precision
  • Reduced post-operative pain
  • Effective, fast, safe
  • Painless, especially in eye and dental treatment
  • Anesthesia not indicated in some treatments