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Laser in Dermatology
By Zeinab abdel azimMD dermatology
laserLight amplification of stimulated
emission of radiation
EMS
><
><
Highly reflective
laser
LaserMonochromatic(single color)Collimated(parallel)Coherent(synchronized phase of light waves)
LightPolychromatic
DivergentNon coherent
Application parameters of medical laser
AbsorptionWavelengthMode of emissionPowerExposure timeBeam diameter
Mode of emission
Continuous wave (CW) emit steady beam for as long as laser medium is
excited Low energy May be pulsed by mechanical shutter or by
electronic or photonic means Pulsed
emit light in individual pulses High energy Short or long Q switched :very high energy& very short pulse
Power
Power denisty(irradiance): CW laser Power/ spot area cm² Up to 300 W/cm² coagulation From 1600 W/cm² vaporization >5000 W/cm² cut tissue
Energy denisty(fluence): pulsed laser Energy/ spot area cm² Narrow limited ranges exist depending on
indication
Exposure time Thermal Relaxation Time (TRT)
Time taken for target to dissipate 50% of the energy absorbed to surrounding tissue
Or time needed for cooling of a given light absorbing site e’in skin
TRT is roughly equal to the square of the diameter of target structure
TRT in sec.= ~ d² in mm Second(S)=
10³ millisecons(ms) 106 microsecond( µs) 109 nanosecond (ns) 1012 picosecond(ps) 1015 femtosecond 1018 attosecond
TRT
targetsizeTRT
MelanosomeDermal capillary
0.5-1 µm0.1 mm
0.25-1 µs10 ms
1. Exposure time = or < TRT of target lead to selective heating of target without damaging surrounding tissue
2. Exposure time > TRT of target lead to heat diffusion to surrounding tissue
1.2.
Spot diameter
Selecting spot size depends on depth of target structure
Laser tissue interaction
1. Photothermal 2. Photochemical
3. Photomechanical
Photothermal
Laser heat 60 °c coagulation 100°c vaporization
Selective photothermolysisvaporization (ablation)
Selective photothermolysisProper wavelength which is selectively
absorbed by target tissue(chromophore)Proper fluence produces desired effectProper exposure time should be < TRT
of target tissue
Vaporization(ablation)
Laser beam absorbed by water in epidermis produces vaporization
CW laser causes slow vaporization with spreading of heat to deeper tissue
Pulsed laser causes rapid vaporization without spreading of heat to deeper tissue
Photochemical reaction
Photodynamic therapy of cancer Photosensitizing drug (porphyrin) that
retained by solid tissue,then exposure to laser (630nm) lead to release of singlet oxygen resulting in cell death
Photomechanical
Disruption of cell memb.,& organelles due to: Rapid thermal expansion Local vaporization High pressure waves
Laser hazards
Beam hazard Ignition of inflammable
material Damage to skin : scar&
dyspigmenation Damage to cornea &retina Precaution:protective eye wear
with optical density specific for laser WL
Laser hazards
Non beam hazard Inhalation of plume of tissue
destruction Contact with high voltage
electricity or fluid leakage from laser cavity
Precaution: Use of vacuum smoke plume
evacuators Wearing laser filter face masks
with 0.1 µm pore diameter
Types of laser
Lasing media ( wave length ) Solid Dye Gas
Mode of light emission Continuous wave(CW) Pulsed Q switched
TypeWave length
Mode of emission
Absorption
Argon 488514
CWHb,melanin
Copper bromide 511 PulsedMelanin
KTP(pot.titnayl phosphate)
532CW,pulsed,QS
Hb,melanin,tattoo(yellow/red)
Krypton 521568
CWCW
MelaninHb
Pulsed dye (yellow)
577585
PulsedHb
Pulsed dye(green)
504pulsedMelanin,tattoo(red)
TypeWave length
)nm(
Mode of emission
Absorption
Ruby694Pulsed,QSMelanin,tattoo(blue,black)Alexandrite755Pulsed,QSMelanin,tattoo(blue,black,
green)Diode800PulsedMelanin,HbNd:YAG1064PulsedMelanin,Hb
QSMelanin,tattoo(blue,black)Er:YAG2940Pulsed,QSWaterCO210600CW,pulsedWater
Indications
Medical lasers are Not magic -they are only tools,and one should always select the right tool for the right job
Indications
Vascular lesionsPigmented lesionsHair epilationSkin resurfacingsurgery
Vascular lesions
Laser with selective absorption by Hb Pulsed dye Nd:YAG KTP Krypton Argon
Deeper dermal penetrationPulse duration up to 40 ms
Vascular lesions
Portwine stainHemangiomaTelangectasia
Vascular lesions
Leg venules 0.5mm:PDL
(1.5-4ms,7-9 J/cm2) <3mm :alexandrite
(3ms,86J/cm2) >3mm: Nd:YAG
(up to15ms,>100J/cm2)
Vascular lesions
Venous lakesAngiofibromaAngiokeratomaPyogenic granuloma
Benign pigmented lesions & tattoo
Melanin absorbs light with WL 500-1200 nm
Q switched laser produces high energy with very short pulse which is used in melanosomes (ns) & tattoo (ps)destruction
Melanin&tattoo fragment is removed by transepidermal elimination & lymphatic
Benign pigmented lesionsType of laser Epidermal
Q switched Nd:YAG QS ruby Alex PDL (green) Er:YAG
Dermal QS Nd:YAG QS ruby QS alex
TattooMultiple WL ,short pulse laser are needed for removal of multiple tattoo ink colors
laserBlue/blackgreenRed/orange
QS rubyQS alexand.KTPPulsed dye (green)QS Nd:YAG
++--
+
++--
-
--++
-
Tattoo
No. of treatment: Traumatic: 2-4 Amateur: 4-8 Professional: 6-12
Treatment is done every 3-4 weeks
Amateur tattoo(carbon)
Professional tattooblue:cobletred:mercury
Professional tattooyellow:cadmium
bulge
laser Hair epilation
bulb
Hair growth cycle
laser Hair epilation
Bulb Diameter: 0.5-1 mm Depth: 3-7 mm +ve melanin in
matrix Bulge
Stem cells for regeneration of HF
Depth : 3mm ±ve melanin
laser Hair epilation
Laser (600-1200nm) pulsed Ruby Alex QS & long pulsed Nd:YAG Diode
laser Hair epilation
Target chromophore: melanin in hair matrix & hair shaft
Target structure: Hair bulb :
pulse= 25-50ms Temporary hair removal
Hair bulge &papillary vessels : pulse= 30-400 ms Permenant hair removal
laser Hair epilationpractical clinical aspects Ideal treatment parameters must be
individualized for each patient Dark hair & light skin have the best response Longer WL & longer pulse duration are
suitable for dark skin Red &brown hair need high fluence Blond ,gray & white hair do not respond Chin & back hair are less responsive
laser Hair epilationpractical clinical aspects Ideal immediate response is vaporization of
hair with no other apparent effect. After few minutes perifollicular edema & erythema may appear
Interval between treatment depends on duration of telogen phase Upper lip: 6 weeks Chin & cheek: 10 w Back,leg : 8-12 w Axilla,pubic area: 12 w Arm: 18 w
No. of treatment session :4-7
laser Hair epilation Post operative careIce packs to decrease pain & edemaTopical antibiotic if epidermal injury
occuredTopical mild steroid to decrease
erythema & edemaAntiviral if neededAvoid:
Trauma(picking or scratching) Sun in 1st week (use sun screen(
laser Hair epilationComplications Epidermal damage with high fluence Infections: HS,bacterial,folliculitis Scarring:with aggressive treatment or infection Dyspigmentation: in dark skin & recent tan Leukotrichia Koebnerization Livedo reticularis Pruritus, Urticaria Plume of vaporized hair leads to irritation of
respiratory tract !! Induction of hair growth in dark skin
Laser resurfacing(LRS)
AblativeNon ablative
Ablative LRS
Removal of outer layers of skin by vaporization
New skin comes from adnexal structures with new formation of collagen& elastic tissues
Ablative LRSLaser with max. absorption by water
CO2Er:YAGWLWater absorptionAblation depthDermal damageRTDHealingAnesthesia
10600 nm+
5-10 µm++Up to 120 µmDelayed++
2940 nm~ 10+
10-20 µm+10-50 µmRapid+RTD:residual tissue damage
Ablative LRS
Ablative LRS
indications Photodamage:
wrinkles, freckles, lentigines, actinic keratoses, dyschromia
Acne scars
Ablative LRS Other indications
Varicella scars Actinic cheilitis Bowen’ dis. sup.BCC Rhinophyma epidermal nevi Seb.hyperplasia Xanthelasma Benign adnexal tumours
Bowen dis.
Ablative LRS
Contraindications Smoking VC complications during
healing Predisposition to keloid Koebnerizing diseases Severe systemic dis. Isotretinoin therapy (6m prior to LRS)
scar
Ablative LRS Perioperative considerations
Topical tretinoin: all pt.for 3-6 ws Topical hydroquinone: skin type 3 & 4 for 3-6 ws Acyclovir or other antiviral(800mg/d. one d. before
&10 d. after LRS) Antibiotic Antiseptic(non alcoholic): irgrasan Topical antibiotic after LRS Dressing:hydrogel,hydrocolloid After repithelization:topical vit.c &tretinoin Topical steroid to speed erythema resolution
Ablative LRS
Anesthesia Injectable anesthesia:cosmotic units Systemic:full face peel
IM or IV sedation+ nerve block+local anesthesia Inhalation anesthesia IV anesthesia
Post operative pain: decrease 2 d. after LRS Narcotic for post operative night Acetaminophen or NSAI drugs
Ablative LRSMethod
1st pass: (pass is one contagious pulse or scan of laser) Rough whitish yellow surface due to vaporization
of cell water. Removal of this material with wet gause reveals
pink color 2nd pass:
Progressive yellowing & visible tissue contraction 3rd pass:
Fine papillations due to exposure of piloseb.units & acrosyringium
Ablative LRSMethod
Acne scars Ablate edges of scars before treating whole
face Deeper injury to obtain good result In fair skin you can treat scar without
treating entire cosmotic unit In other skin type it is better to treat entire
face to avoid demarcation line between treated & untreated areas
Ablative LRSSide effects Erythema: 1-8 m Hyperpigmentation
25-100% Start one month after LRS & last 3.8m Pretreatment with bleaching agent does not prevent it
Hypopigmentation 6-20% After 6-12m or more True: melanocytes Pseudo:return to natural color prior to sun damage
Ablative LRSSide effects Acne /milia
10-86% After 3-6 w Last 4-8 w Due to
Petroleum based oint Disruption of seb.glands sebum
Treatment: Antibiotic Topical retinoid Manual extraction
Ablative LRSSide effects
Scarring:results from Overlapping pulses Isotritinoin Bacterial infection Extensive electrolysis
Ablative LRSSide effects Pruritus
91% Last 3-21 d Due to
Physiological sensation with epithelization Dryness Irritant dermatitis Infection
Treatment:after exclusion of infection&dermatitis Antihistamines Cool soaks Topical steroid
Ablative LRSSide effects Contact dermatitis
5-10% Due to
Topical antibiotic Vehicle Preservative
Telangectasia after mild trauma Petechiae
after healing Clear after several weeks without treatment
Ectropion
Ablative LRSSide effectsInfections
LRS 2nd degree burn Fertile environment for pathogens Bacterial:
Staph.:toxic shock syndrome,scarring Pseudomonas: scarring Others:E.coli,proteus Treatment: antibiotic from night of LRS for 10 d
Candida: healing time treament: fluconazole from night of LRS for 5 d
Ablative LRSSide effectsInfections
Viral: HS:valacyclovir 500mg twice /d/10d Warts: spontaneous resolution
Mycobacterium fortuitum:non tender nodules
Demarcation lines
Non ablative LRS (laser toning,subsurface resurfacing) Non invasive treatment of photodamaged
skin & scars Done by laser inducing mild erythema lasting
for a few hours Dermal temp.of 55-65ºc is required for
collagen denaturation. Stimulate new collagen synthesis
(trauma&inflam.induced by laser increase organized horizontally arrayed bundles of normal collagen in papillary dermis)
3-6 sessions or more are needed every 3-4 w.
Non ablative LRS
Patient selection Young 35-55y Minimal sagging of face Minimize treatment discomfort & down time Dark skin (mid infrared laser(
Non ablative LRSlaser selection
Wrinkles & scarsPulsed dye
Red colorKTP,pulsed dye,pulsed Nd:YAG,IPL
Brown colorKTP,Nd:YAG,QS lasers,IPL
Texture & color(red,brown)Many laser ,IPL
Thank you
