Introduction to laser dermatology 2

Laser in Dermatology

By Zeinab abdel azimMD dermatology

laserLight amplification of stimulated

emission of radiation

EMS

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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

Varicella scars

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