basic knowledge about laser dermatology. quoted from learning course.

2. Laser in Dermatology
By
Zeinab abdel azim
MD dermatology

3. laser
Light amplification of stimulated
emission of radiation

4. EMS
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6. Highly reflective

8. laser
Laser
Monochromatic(single
color)
Collimated(parallel)
Coherent(synchronized
phase of light waves)
Light
Polychromatic
Divergent
Non coherent

9. Application parameters of medical laser
Absorption
Wavelength
Mode of emission
Power
Exposure time
Beam diameter

11. 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

12. 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

13. 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

14. TRT
target size TRT
Melanosome
Dermal
capillary
0.5-1 µm
0.1 mm
0.25-1 µs
10 ms

15. 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.

16. Spot diameter
 Selecting spot size depends on depth of
target structure

17. Laser tissue interaction
1. Photothermal
2. Photochemical
3. Photomechanical

18. Photothermal
Laser heat
 60 °c coagulation
 100°c vaporization
Selective photothermolysis
vaporization (ablation)

19. Selective photothermolysis
Proper wavelength which is selectively
absorbed by target tissue(chromophore)
Proper fluence produces desired effect
Proper exposure time should be < TRT
of target tissue

20. 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

21. 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

22. Photomechanical
Disruption of cell memb.,& organelles
due to:
 Rapid thermal expansion
 Local vaporization
 High pressure waves

23. 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

24. 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

25. Types of laser
Lasing media ( wave length )
 Solid
 Dye
 Gas
Mode of light emission
 Continuous wave(CW)
 Pulsed
 Q switched

26. Type Wave
length
Mode of
emission
Absorption
Argon 488
514
CW Hb,melanin
Copper bromide 511 Pulsed Melanin
KTP(pot.titnayl
phosphate)
532 CW,pulsed,
QS
Hb,melanin,tattoo
(yellow/red)
Krypton 521
568
CW
CW
Melanin
Hb
Pulsed dye
(yellow)
577
585
Pulsed Hb
Pulsed dye
(green)
504 pulsed Melanin,tattoo(red)

27. Type Wave
length
(nm)
Mode of
emission
Absorption
Ruby 694 Pulsed,QS Melanin,tattoo(blue,black)
Alexandrite 755 Pulsed,QS Melanin,tattoo(blue,black,
green)
Diode 800 Pulsed Melanin,Hb
Nd:YAG 1064 Pulsed Melanin,Hb
QS Melanin,tattoo(blue,black)
Er:YAG 2940 Pulsed,QS Water
CO2 10600 CW,pulsed Water

28. Indications
Medical lasers are Not magic
-they are only tools,and one
should always select the right
tool for the right job

29. Indications
Vascular lesions
Pigmented lesions
Hair epilation
Skin resurfacing
surgery

30. Vascular lesions
Laser with selective absorption by Hb
 Pulsed dye
 Nd:YAG
 KTP
 Krypton
 Argon
Deeper dermal penetration
Pulse duration up to 40 ms

32. Vascular lesions
Portwine stain
Hemangioma
Telangectasia

38. 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)

40. Vascular lesions
Venous lakes
Angiofibroma
Angiokeratoma
Pyogenic granuloma

44. 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

45. Benign pigmented lesions
Type of laser
 Epidermal
 Q switched Nd:YAG
 QS ruby
 Alex
 PDL (green)
 Er:YAG
 Dermal
 QS Nd:YAG
 QS ruby
 QS alex

46. Tattoo
Multiple WL ,short pulse laser are needed
for removal of multiple tattoo ink colors
laser Blue/black green Red/orange
QS ruby
QS alexand.
KTP
Pulsed dye
(green)
QS Nd:YAG
+
+
-
-
+
+
+
-
-
-
-
-
+
+
-

47. Tattoo
No. of treatment:
 Traumatic: 2-4
 Amateur: 4-8
 Professional: 6-12
Treatment is done every 3-4 weeks

48. Amateur tattoo(carbon(

49. Professional tattoo
blue:coblet
red:mercury

50. Professional tattoo
yellow:cadmium

52. bulge
laserHair epilation
bulb

53. Hair growth cycle

54. 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

55. laser Hair epilation
Laser (600-1200nm)
 pulsed Ruby
 Alex
 QS & long pulsed Nd:YAG
 Diode

57. 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

58. laser Hair epilation
practical 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

59. laser Hair epilation
practical 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

62. laser Hair epilation
Post operative care
Ice packs to decrease pain & edema
Topical antibiotic if epidermal injury
occured
Topical mild steroid to decrease
erythema & edema
Antiviral if needed
Avoid:
 Trauma(picking or scratching)
 Sun in 1st
week (use sun screen(

63. laser Hair epilation
Complications
 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

65. Laser resurfacing(LRS)
Ablative
Non ablative

66. Ablative LRS
Removal of outer layers of skin by
vaporization
New skin comes from adnexal
structures with new formation of
collagen& elastic tissues

67. Ablative LRS
Laser with max. absorption by water
CO2 Er:YAG
WL
Water
absorption
Ablation depth
Dermal damage
RTD
Healing
Anesthesia
10600 nm
+
5-10 µm
++
Up to 120 µm
Delayed
++
2940 nm
~ 10+
10-20 µm
+
10-50 µm
Rapid
+
RTD:residual tissue damage

68. Ablative LRS

69. Ablative LRS
 indications
 Photodamage:
wrinkles,
freckles,
lentigines,
actinic
keratoses,
dyschromia
 Acne scars

70. Ablative LRS
 Other indications
 Varicella scars
 Actinic cheilitis
 Bowen’ dis.
 sup.BCC
 Rhinophyma
 epidermal nevi
 Seb.hyperplasia
 Xanthelasma
 Benign adnexal tumours

71. Varicella scars

72. Bowen dis.

73. Ablative LRS
Contraindications
 Smoking VC complications during
healing
 Predisposition to keloid
 Koebnerizing diseases
 Severe systemic dis.
 Isotretinoin therapy (6m prior to LRS)
scar

74. 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

75. 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

76. Ablative LRS
Method
 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

77. Ablative LRS
Method
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

78. Ablative LRS
Side 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

79. Ablative LRS
Side 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

80. Ablative LRS
Side effects
 Scarring:results from
 Overlapping pulses
 Isotritinoin
 Bacterial infection
 Extensive electrolysis

81. Ablative LRS
Side 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

82. Ablative LRS
Side 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

83. Ablative LRS
Side effects
Infections
 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

84. Ablative LRS
Side effects
Infections
 Viral:
 HS:valacyclovir 500mg twice /d/10d
 Warts: spontaneous resolution
 Mycobacterium fortuitum:non tender
nodules
Demarcation lines

86. 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.

87. Non ablative LRS
Patient selection
 Young 35-55y
 Minimal sagging of face
 Minimize treatment discomfort & down time
 Dark skin (mid infrared laser(

88. Non ablative LRS
laser selection
Wrinkles & scars Pulsed dye
Red color KTP,pulsed dye,pulsed
Nd:YAG,IPL
Brown color KTP,Nd:YAG,QS
lasers,IPL
Texture & color(red,brown) Many laser ,IPL

89. Thank you