Introduction History of lasers Basics components of laser Principle and working of laser Tissue optics Applications of laser principles Cooling systems INTRODUCTION Light Amplification by the Stimulated Emission of Radiation acronym coined by ID: 909212
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Slide1
BASICS IN LASER
Slide2CONTENTS Introduction
History of lasers
Basics components of laser
Principle and working of laser Tissue optics Applications of laser principles Cooling systems
Slide3INTRODUCTION
Light Amplification by the Stimulated Emission of Radiation (acronym coined by
Gordon Gould
)
Slide4HISTORY OF LASERS
1917
Albert Einstein developed the theoretical concept of
photons & stimulated emission
1954
Charles Townes & Arthur Schawlow built the first
MASER
1960
Thomas
Maiman - the first laser using a synthetic ruby rod ( 694 nm)
Slide5history
1960s:
Dr. Leon Goldman-Father of Laser Medicine& Surgery-usage of laser in medical practice
1960: Dr. Ali Javan-first continuous laser (He-Ne)632.6
nm
red gas ion laser
1964:
Kumar
Patel - CO2 laser1964: Nd:YAG laser1969: Dye laser1975: Excimer laser (noble gas-halide)
Slide6LASER SPECTRUM
Slide7Properties of laser
Monochromatic
-
composed of a single wavelength or color.
Coherent
-
All the waves of light move together temporally and spatially.Collimated - transmission of light occurs in parallel fashion non divergent,even over long distances
Slide8Properties of laser
Slide9BASICS COMPONENTS IN LASER
Laser medium
Pumping system
Optical cavityDelivery system
Laser oscillator
Slide101. AMPLIFYING OR GAIN MEDIUM (solid, liquid or gas)Composed of atoms, molecules, ions or electrons
Energy levels are used to the power of a light wave during its
propagation.
Physical principle is called stimulated emission
Slide11TYPES OF LASER MEDIA
GAS
LIQUID
SOLID
Argon
Carbon
dioxide
Helium – Neon
KryptonXenon chlorideRhodamine dye dissolved in organic solvent-PDLCrystal AlexandriteEr-doped YAGHolmium –doped YAGNeodymium doped YAG
Potassium titanyl
phosphate
(KTP )
Ruby
semiconductor
Diode (
eg.alumnium
gallium,arsenide
)
Slide12PUMPING SYSTEM - a system to excite the amplifying medium
1.Optical (the sun, flash lamps, continuous arc lamps or tungsten-filament lamps, diode or other lasers)
2. Electrical (gas discharge tubes, electric current in semi-conductors)
3. Chemical
Slide13OPTICAL CAVITY - produce a very special radiationUses reflecting mirrors to amplify the light source by
bouncing it back and forth
within the cavity
Partially reflecting mirror allows laser light to exitLasers produces beam of light with low divergence
that are close to being
collimated
Allows beam of light to be tightly
focussed
by
converging lens Focussing is required to produce a specific spot size
Slide14BASICS COMPONENTS IN LASER
Slide15PRINCIPLE OF LASER
Atom will absorb and emit light photons at particular wavelength corresponding to the
energy differences
between orbits.
Three distinct process may occur in the medium
1. Stimulated absorption
2. Spontaneous emission
3. Stimulated emission
Slide16Two energy levels E1 and E2 (E1 < E2) whose atoms can interact with light of frequency
The group E1-E2 is called
radiative
transition if atoms can only pass from E1 to E2 (or from E2 to E1 ) by interacting with light E1 is called the lower energy level
E2 the upper energy level
Slide17ABSORPTION: An atom in a lower level absorbs a photon of frequency
hν
and moves to an upper level
Slide18SPONTANEOUS EMISSION
An atom in an upper level can decay spontaneously to lower level emit & a photon of frequency
hν
if the transition between E2 and E1 is radiative
This photon has a random direction and phase
Slide19STIMULATED EMISSION
An incident photon causes an upper level atom to decay, emitting a “
stimulated” photon
whose properties are identical to those of the incident photonAmplification arises due to the similarities between the incident and emitted photons
Slide20Slide21Basic terminology
Energy :
Fundemental
unit of work – Joules JPower
: The rate at which energy is emitted from a laser.
Watts
Fluence
:
Determines the amount of laser energy per unit
area and is expressed in joules/cm2.Irradiance : determines the ability of laser to incise, vaporize,or coagulate a tissue W/ cm2
Slide22Spot Size: The mathematical measurement of the radius of the laser beam.
Pulse:
A discontinuous burst of laser as opposed to a
continuous beam.Pulse Frequency: The rate at which pulses are generated. Expressed in pulses per second (Hz).
Pulse Duration
: The
"on"
time of a pulsed laser.
Measured in terms of ms,
μs, or ns.
Slide23Modes of outputContinuous wave
Pulsed-long ,short
Q -Switched
Slide24CONTINUOUS WAVE : continuous uninterrupted beam of light eg
. Argon & Co2 laser
QUASI CW
:
CW mechanically shuttered to deliver pulses of light as short as 20 ms
eg
. KTP
Slide25Pulsed lasers Long pulsed 0.5 -400 ms - hair removal / vascular
Short pulsed -reduce the amount of
thermal damage -
safer skin resufacing measured in micro seconds
Eg
. Co2 laser
Q switched laser
–creating a ultra short pulse
(5-100ns ) with extremely high power
measured nanoseconds / picosecondsEg. Nd-YAG, Ruby ,Alexandrite
Slide26Tissue optics
Reflection
.
4–6% of light is reflected. increases with increase in angle of incidence Lowest when the beam is perpendicular.
Slide27ABSORPTION
Specific absorption at a wavelength
After absorption photon surrenders its energy to chromophore
and gets excited
ENDOGENOUS CHROMOPHORES:
Melanin: UV -1200nm, visible light
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 EXOGENOUS CHROMOPHORES: eg. Tattoo ink.
Slide28Chromphore and wavelength
Slide29Lasers and its wavelengthSlide30SCATTERING-
Is the deviation of light by non-uniformities in the medium through which it passes .
Eg
. CollagenIt reduces the energy available for the target
chromophores,thereby
decreasing
the clinical effect
TRANSMISSION-
Light that is not Reflected, absorbed or scattered passes to deeper tissue.Longer the wavelength( 600-1200nm) penetrate more deeply because they are scattered lessShorter wavelength (300-400 nm) being scattered and penetration is less than 0-1mm .
Slide31Penetration of lasers
280 -1300 nm- penetration
increases
with wavelength>1300nm penetration decreases due to absorption by water.Dermal collagen scatter the laser light
Slide32Slide33Ablative Outer layers of skin are removed through vaporization
Healing takes place by re-deposition of collagen.
Er
: YAG ,CO2 laser
Non-ablative
Induce dermal
neocollagenesis
without
epidermal distruption KTP ,Pulsed Dye,Nd: YAGFractionated laser Works on both epidermal and dermal layers of skin Some parts of the skin are targeted & other parts are intact.
Slide34Laser tissue interaction
Photostimulation
Photochemicalphotothermal
PHOTOSTIMULATION
Low energy lasers expedite wound healing.
Slide35PHOTOCHEMICAL : forms the basis of photodynamic change
Uses
topical or systemic photosensitizers. Subsequent irradiation elicits a
photooxidative
reaction and an immediate
cytotoxic
effect
PHOTOTHERMAL
Heat generated by interaction of light with chromophore results in thermal distruption of chromophore
Slide36Laser light is delivered to the
tissue
via a probe in contact mode with surface of skin
Light enters cell’s mitochondria absorbed by
chromophores
,
cytochrome
c
oxidase & increases the activityThree molecules are affectedATP,Reactive oxygen species,Nitric oxide
Mechanism of laser
Slide37ATP
Increase cell ability to fight infection,
Accelerates healing process
REACTIVE OXYGEN SPECIES Activate transcription factors Cellular repair and healing
NITRIC OXIDE
Increases circulation
Decreases inflammation
Enhance the
transport of oxygen
and immune cells throughout the tissue
Slide38Selective photothermolysis
A concept used to target
chromophore
based:WavelengthEnergy fluence
Pulse duration ≤ Thermal relaxation time
Slide39THERMAL RELAXATION TIMEIt is the time taken for the target to
dissipate 63%
of incident thermal energy
TRT is related to the size of target chromophore & pulse duration
Slide40Pulse duration and targets of selective photothermolysis
Chromophore
Target
size
TRT
Pulse
duration
Tattoo
ink particle0.1 micron10 ns 10 nsMelanosome 0.5 micron250 ns
10-100 nsPort
wine stain vessels
30-100 microns
1-10 ns
0.4
-20ns
Terminal hair follicle
300 microns
100ms
3-100 ms
Leg vein
1mm
1s
0.1 s
Slide411.VASCULAR LESIONS
Chromophore
-hemoglobin
LASERS Port wine stains
PDL
( 595 nm)
KTP (532 nm)
Alexandrite (755nm)
Q switched
Nd: YAG (1064 )Infantile hemangiomasPDL ( 595 nm)Nd: YAG (1064 nm)
Telangiectases,angiomas
,
venous lakes
KTP (532 nm)
Nd
:
YAG (1064 nm)
PDL
( 595 nm)
Slide42USES OF LASER
LASERS
2. HAIR REDUCTION
Chromophore
- melanin
Long pulsed
Nd
: YAG ( 1064 nm)
Diode ( 800 nm)Alexandrite laser (755 nm )Ruby (692 nm)IPL3.HYPERPIGMENTATION Chromophore - melaninEpidermal type Freckles,lentigens
,café-au-
lait
-spots
Q switched
KTP ( 532nm)
Q switched
Nd
: YAG ( 1064 nm)
Q switched Ruby (694nm)
Q switched Alexandrite( 755 nm)
Dermal type
Nevus
of Ota
Ita
,
Drug induced
Mongolion
blue spot
Q switched Ruby (694nm)
Q switched
Nd
: YAG
( 1064 nm)
Q switched Alexandrite( 755 nm)
Mixed type
melasma
Q switched
Nd
: YAG
( 1064 nm)
Slide434.FACIAL REJUVENATION
Chromophore
–water
LASERS
Abalative
Co2 laser (10600 nm)
Erb:YAG
laser (2940 nm)
Non
abalative PDL Q switched Nd: YAG ( 1064 nm)5.Hypertrophic scars, warts, neoplasm PDL6.HEMOSTASIS
Co2 laser (10600 nm)
7. LASER LIPOLYSIS
Nd
: YAG
( 1064 nm)
Slide44TATTOOS
Chromophore
: Tattoo Ink LASERS
Blue / black
Q switched
Nd
: YAG
( 1064 nm)
Q switched Alexandrite( 755 nm)Q switched ruby (694nm)Green Q switched Alexandrite( 755 nm)Q switched ruby (694nm)Red/orange/purple/ yellow Q switched Nd
: YAG ( 532 nm)
Slide45Cooling system
CONTACT SKIN COOLING
ACTIVE-
Copper, or sapphire tips:For delivering longer pulse durations(>10 ms)
PASSIVE-
Ice cubes:
Reduces inflammation post procedure.
Aqueous gels:
Cannot provide prolonged cooling.
Slide46NON CONTACT COOLING:
1)
Cryogen spray (liquid nitrogen):
Not recommended now causescryonecrosis.
2)
Pulsed cryogen spray (dynamic cooling device):
Provides uniform cooling at -30 degree C
Method of choice
3)
Forced refrigerated air: Delivers chilled air pre, parallel andpost procedure. By convection cooling.
Slide47SIDE EFFECTS
Immediate:
Pain, burning sensation, edema
Early:• Oozing, crusting• Secondary infection
Slide48Late: Dyspigmentation
(hypo/hyper)
Change in skin texture
Demarcation lines(in facial rejuvenation) Keloids and hypertrophic scars Milia
Persistent
erythema
Slide49BASICS COMPONENTS IN LASER
Slide50Slide51LASER CHARACTERISTICS
CHARACTERISTICS
SYMBOL
UNIT OF MEASUREMENT
Wave length
ƛ
–
labda
nm
Spot sized ( diameter)s ( square)cmPulse durationp (power)energy delivered per unit time
Watt ( w) = joules × sec(j/sec)
Fluence
ɸ
Energy delivered per unit area
joule/cm2
Irradiance
Power delivered per unit area
w/cm2
Slide52Laser
Wavelength
(nm)
Mode Target
chromophore
Excimer
308mn
Pulsed DNA/ RNA proteinsArgon 488/514nmCWHemoglobin ,melaninCopper vapour
511,578Quasi-CW
Hemoglobin
,melanin
KTP
532
Quasi-CW
Hemoglobin
,melanin
Q switched
Double
frequencyNd
-YAG
532
Pulsed
(ns)
Melanin
,red tattoos
Pulsed
dye
585-600
Pulsed
Hemoglobins
Ruby
694
Pulsed
melanin
Q switched
Ruby
694
Pulsed (ns)
Melanin ,black and green tattoos
Alexandrite
755
Pulsed
Melanin
deoxyhemoglobin
Q
switched alexandrite
755
Pulsed
Melanin ,black and green tattoos
Diode
800
CW/Pulsed
Melanin,hemoglobins
Slide53Laser
Wavelength
(nm)
Mode Target
chromophore
Nd
-YAG
1064
CWHemoglobin Q –switched Nd-YAG1064Pulsed (ns)
Black tattoos
Long
pulsed
Nd
-YAG
1064
Pulsed
Hemoglobin
,melanin
Pico second
Nd
-YAG
1064
Pulsed
Melanin,black
and red tattoos
Long
pulsed
Nd
-YAG
1320
Pulsed
water
Diode
1450
Pulsed
water
Erbium : glass
1540
Pulsed
water
Holmium : YAG
2000
Pulsed
water
Erbium : YAG
2940
Pulsed
water
Carbon dioxide
(co2)
10600
CW/pulsed
water
Slide54Thank you
Slide55Slide56Laser Hazards
56
Slide57precautions The operating laser room:
Should be properly labeled.
Hang eye goggles on the door.
The room should not contain volatile substances such as ether, alcohol . Plume evacuator: for larger lesions and warts.
Slide58Safety 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.
Slide59SKIN CARE INSTRUCTIONS AFTER LASER SURGERY
Do not rub, scratch or put pressure on the treated area
Do not apply any cosmetic creams 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
Slide60Slide61Laser
Wavelength
(nm)
Mode Target
chromophore
Excimer
308mn
Pulsed DNA/ RNA proteinsArgon 488/514nmCWHemoglobin ,melaninCopper vapour
511,578Quasi-CW
Hemoglobin
,melanin
KTP
532
Quasi-CW
Hemoglobin
,melanin
Q switched
Double
frequencyNd
-YAG
532
Pulsed
(ns)
Melanin
,red tattoos
Pulsed
dye
585-600
Pulsed
Hemoglobins
Ruby
694
Pulsed
melanin
Q switched
Ruby
694
Pulsed (ns)
Melanin ,black and green tattoos
Alexandrite
755
Pulsed
Melanin
deoxyhemoglobin
Q
switched alexandrite
755
Pulsed
Melanin ,black and green tattoos
Diode
800
CW/Pulsed
Melanin,hemoglobins
Slide62Laser
Wavelength
(nm)
Mode Target
chromophore
Nd
-YAG
1064
CWHemoglobin Q –switched Nd-YAG1064Pulsed (ns)
Black tattoos
Long
pulsed
Nd
-YAG
1064
Pulsed
Hemoglobin
,melanin
Pico second
Nd
-YAG
1064
Pulsed
Melanin,black
and red tattoos
Long
pulsed
Nd
-YAG
1320
Pulsed
water
Diode
1450
Pulsed
water
Erbium : glass
1540
Pulsed
water
Holmium : YAG
2000
Pulsed
water
Erbium : YAG
2940
Pulsed
water
Carbon dioxide
(co2)
10600
CW/pulsed
water