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Basics of lasers


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What is laser; Its uses in dermatology; Types of lasers; Treatment options for acne scars, melasma; hyper pigmentation; wrinkles; warts; Dark skin, facial rejuvenation; stains; rosacea; hair removal options;

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Basics of lasers

  1. 1. Basics Of Lasers:
  2. 2. Definition: “LASER” is an acronym that stands for Light Amplification by the Stimulated Emission of Radiation. Laser is an instrument that generates a beam of light of a single wavelength or color that is both highly collimated and coherent.
  3. 3. Principle of laser:
  5. 5. History: • The first functional laser (ruby, 694 nm) was developed by Maiman in 1960.
  6. 6. Characteristics of Laser Light: Monochromatic: composed of a single wavelength or color. Coherence: All the waves of light move together temporally and spatially. Collimation: where the transmission of light occurs in parallel fashion without significant divergence, even over long distances.
  7. 7. Electromagnetic Spectrum:
  8. 8. Lasers Commonly used in Dermatology: 1. Argon Laser: 488/514 nm 2. Potassium-titanyl-phosphate (KTP): 532 nm 3. Copper bromide/vapour: 510/578 nm 4. Argon-pumped tunable dye (APTD): 577/585 nm 5. Krypton: 568 nm 6. Pulsed dye laser (PDL): 585/595 nm 7. QS ruby: (694 nm) 8. QS alexandrite: (755 nm) 9. QS neodymium (Nd):yttrium-aluminum-garnet (YAG): 1064 nm 10. Erbium:YAG: 2940 nm 11.Carbon dioxide Laser: 10,600 nm V I S I B L E L I G H T I N F R A R E D
  9. 9. Terminology: Power: The rate at which energy is emitted from a laser. Watts. Joule (J): A unit of energy used to describe the rate of energy delivery. Fluence: determines the amount of laser energy per unit area and is expressed in joules/cm2. Spot Size: The mathematical measurement of the radius of the laser beam.
  10. 10. Pulse: A discontinuous burst of laser as opposed to a continuous beam. Pulse Frequency: The rate at which pulses are generated. Is expressed in pulses per second (Hz). Pulse Duration: The "on" time of a pulsed laser. Measured in terms of ms, μs, or ns.
  11. 11. Irradiance: (power density) The rate at which energy is delivered per unit area. It determines the ability of a laser to incise, vaporize, or coagulate tissue and is expressed in watts/cm2.
  12. 12. Thermal Relaxation Time(TRT): time required for the dissipation of 63% heat gained by the tissues (ms/μs) during irradiation. Thermal Damage Time(TDT): The time for the entire target including the primary chromophore and surrounding target to cool by 63%. Focus: The exact point at which the laser energy is at peak power 63%
  13. 13. Chromophores in the Skin: Are the selectively laser energy absorbing target molecules in the skin. 1. Endogenous chromophores: • Melanin: UV -1200nm • Hb: UVA, blue (400 nm), green (541 nm), Yellow (577nm) • Collagen: Visible and near infra-red spectra • Water: in the mid and far infrared regions 2. Exogenous chromophores: Such as tattoo ink.
  14. 14. Classification of Lasers: Laser are classified according to the nature of the amplifying medium: gas, liquid(dye) or solid state:
  15. 15. Modes Of Output: • Continuous wave • Quasi CW • Pulsed
  16. 16. Ablative Vs Non Ablative: ABLATIVE: outer layers of skin are (removed) through vaporization of the cells. Healing takes place by re-deposition of collagen. Egs: Er: YAG CO2 laser NON-ABLATIVE: induce dermal neocollagenesis without epidermal disruption, KTP Pulsed Dye Nd: YAG
  17. 17. FRACTIONATED LASER: Laser beam is “fractionated” into a pattern where some parts of the skin are targeted, and the other parts are left intact. A grid like pattern appears on the skin.
  18. 18. How Fractionated Lasers Work:
  19. 19. Tissue optics:
  20. 20. Tissue optics: 1. Reflection. • 4–6% of light is reflected. • Lowest when the beam is perpendicular. 2. Absorption. Depends on the properties of the substance through which the light passes. Target molecules are called chromophores: (1) Melanin (2) Hemoglobin (3) Water (4) Collagen
  21. 21. 3. Scattering. Is the deviation of light by non-uniformities in the medium Eg: collagen in the dermis. It reduces the energy available for the target chromophores. 4. Transmission. Light that is not Reflected, absorbed or scattered passes to deeper tissue.
  22. 22. Light–tissue interaction: 1)Photostimulation: Low energy lasers expedite wound healing.
  23. 23. 2. Photodynamic change: uses topical or systemic photosensitizers. Subsequent irradiation elicits a photo- oxidative reaction and an immediate cytotoxic effect.
  24. 24. 3)Photo-thermolytic and Photo-mechanical Effect: works on the principal of Selective photothermolysis: A concept used to target chromophore based: • on its absorption characteristics, • the wavelength of light used, • amount of energy delivered. • the duration of the pulse,
  25. 25. 4. Photo Acoustic Effect:
  26. 26. Uses of Laser: Lasers 1. Hair Reduction: Long pulsed Nd:Yag (1064nm) Alexandrite laser (755nm) 2. Hyperpigmentation: (a) Epidermal Type Q switched, Nd:Yag (532nm) PDL Uses of Lasers: (b) Dermal Type: Q switched Nd:Yag (1064nm) (c) Mixed Type: Q-switched Ruby (694nm) Chromophore: Melanin Chromophore: Melanin
  27. 27. (c) Large Vessel Telengiectasia Krypton Laser (568nm) Copper vapour Laser 3. Vascular Lesions: (a) Port wine stain PDL Alexandrite laser (755nm) Q switched Nd:Yag (1064nm) (b)Small calibre Telengiectasia PDL Chromophore: Hemoglobin
  28. 28. (4) Facial Rejuvenation: (a) Ablative: CO2 laser(10,600nm) Erb:Yag laser (2940nm) (b) Non-Ablative: PDL Q-switch Nd:Yag (1064,532) (5) Hypertrophic scars, warts, benign neoplasm PDL (7) Acne PDL(6) Hemostasis CO2 Laser (10600nm) (7) Laser Lipolysis: Nd: Yag Laser (1064nm) Chromophore: Water
  29. 29. (8) Tattoos: (a) Blue/ Black Q-switched ruby, Q-switched alexandrite Q-switched 1064-nm Nd:YAG (b)Green Q-switched ruby, Q-switched alexandrite (c) Red/ Orange/ Purple Q-switched Nd:YAG 532-nm Chromophore: Tattoo Ink
  30. 30. Cooling Systems:
  31. 31. Cooling Systems: Contact skin cooling • Active Copper, or sapphire tips: For delivering longer pulse durations(>10 ms) Provide pre, parallel and post laser cooling. • Passive Ice cubes: Reduces inflammation post procedure. Easy method. Disadvantages: a waiting period Melting water on the skin Aqueous gels: Not advised nowadays. Cannot provide prolonged cooling.
  32. 32. Non Contact Cooling: 1) Cryogen spray (liquid nitrogen): (a) Not recommended now causes cryonecrosis. 2) Pulsed cryogen spray (dynamic cooling device): (a) Provides uniform cooling at -30C (b) Method of choice 3) Forced refrigerated air: (a) Delivers chilled air pre, parallel and post procedure. (b) By convection cooling.
  33. 33. Preparing A Patient for Laser session:
  34. 34. Patient selection: 1. Take History to find out: • Immunocompromised status, esp diabetes • Isotretinoin use. • Active local or systemic infections especially recurring HS infection. (Aciclovir or valaciclovir given 1 day prior to & 5–14 days post treatment) • Tendency to keloid scarring. • Personal or family history vitiligo. 2. Prophylactic antibiotics and antivirals for ablative procedure 3. To minimize post laser hyperpigmentation: 2 weeks before and 8 weeks after laser: 0.2% Retinoid preparation 2% Hydrocortisone 4% Hyroxyquinone Anesthesia: Topical anesthetic ointment under occlusion for 1 hr. For ablative procedures, nerve blocks, tumescent anesthesia.
  35. 35. Contraindications: Absolute: • Active bacterial,viral or fungal infections • Unrealistic expectations • Uncooperative pts • Malignancy Relative: • Immunocompromised: Diabetes, HIV, Hepatitis B,C • Oral isotretinoin • Fitzpatrick skin 5-6 phototypes • History of keloids. • Patients taking gold salts are at the risk of chrysiasis (gold- related skin discoloration).
  36. 36. Precautions:
  37. 37. Precautions: The operating room: • Laser room should be properly labeled. • Hang eye goggles on the door. • Unauthorized people should not be allowed. • The room should not contain volatile substances such as ether, alcohol . • Plume evacuator: for larger lesions and warts.
  38. 38. Safety measures for the patient: • Special glasses should be used. • Patient Consent General measures: • The surgeon should use the special glasses for the particular laser. • NEVER look directly into the laser source. • NEVER point the hand probe in any direction, except towards the area to be treated.
  39. 39. SKIN CARE INSTUCTIONS AFTER LASER SURGERY: • Do not rub, scratch or put pressure on the treated area • Do not apply make-up in case of severe reaction. • Avoid sunlight; Sun blocks can be advised. • Ice bags to alleviate erythema and edema. • Emollients to keep skin moist. • Avoid irritants to the resurfaced areas • Erythema and edema settle with topical corticosteroids
  41. 41. Side Effects of Lasers: (1) Immediate: • Pain, burning sensation, edema (2) Early: • Oozing, crusting • Secondary infection • Reactivation of HS infection
  42. 42. (3) Late: • Dyspigmentation (hypo/hyper) • Change in skin texture • Demarcation lines (in facial rejuvenation) • Keloids and hypertrophic scars • Scarring • Milia • Persistent erythema • Dilated follicular ostia
  43. 43. Nd: Yag Laser: Nd:YAG (neodymium-doped yttrium aluminum garnet) is used as a laser medium. • Wavelengths: 532nm and 1064 nm, • Penetrates 2-3mm into dermis QSNd:YL 1064-nm: Has the least absorption by melanin Deepest penetration. Effective for both epidermal and dermal pigmented lesions. QSNd:YL 532-nm: Is well absorbed by both melanin and hemoglobin. Has superficial penetration, Limited to treating epidermal pigmented lesions.
  44. 44. Vascular lesions Spider and thread veins Varicose veins Telangiectasia Haemangioma Pigmented lesions Solar lentigines Freckles Nevus of Ota and Ito Mongolian spot Café-au-lait-macules.
  45. 45. Hair removal: Tattoos:
  46. 46. Pulsed Dye Laser: • Contains a rhodamine dye • Wavelength: 585–600 nm. • Pulse duration:0.45 ms (short-pulse) 1.5–40 ms (long-pulse PDL) • Penetrates the dermis to a depth of 1.2 mm & photocoagulates vessels of up to 100 μm in diameter. • Primary chromophore: hemoglobin.
  47. 47. USES: Cutaneous vascular lesions: • Port wine stains • Superficial hemangioma • Telangiectasia Non-vascular skin conditions • Plane warts • Pyogenic granuloma. • Melasma • Hypertrophic scars • Nail psoriasis/plaque psoriasis
  48. 48. Carbon Dioxide Lasers: Active laser medium: 10–20% carbon dioxide, Exists as Ablative nonfractinated laser Ablative fractinated laser Wavelength: 10,600 nm Primary chromophore: Water
  49. 49. • Depth: 20-30 µm of skin (epidermis and superficial papillary dermis) • In the healing period: re-epithelialization
  50. 50. The following skin disorders can be treated with carbon dioxide laser beams: • Rhytides • Acne scars • Varicella and smallpox scars • Verruca vulgaris/plana • Junctional & compound Nevi • Small syringomas