2. LASER
LASER - Light Amplification by Stimulated
Emission of Radiation.
Laser is an electro optical device that emits
organized light(rather than random pattern
light) in a very narrow intense beam by a
process of optical feedback and amplification.
It is the brightest monochromatic (same
wavelength) light known to exist.
3. HISTORY
In 1917 : Albert Einstein described the theory of stimulated
emission which is the underlying process of laser action.
In 1958 : The American physicist, Arthur Schawlow and
Charles Townes described the working principle of laser.
In 1960 : Theodore Maiman produced first laser by
stimulating solid ruby crystal.
In 1961 : Ali javan built the first helium-neon gas laser.
In 1962 : C. kumar N. patel introduced CO2 gas laser.
In 1964 : argon & Nd:YAG (Neodymium-yttrium aluminium
garnet) lasers were developed.
In 1968 : Polanyi developed the articulated arm to use CO2
laser.
In 1972 : Jako and Strong were the first to pioneer the use of
CO2 laser in otolaryngology , head and neck surgery.
4. ORDINARY LIGHT VS LASER
ORDINARY LIGHT LASER
Wide range of wavelengths. Has specific wavelengths.
Beam leaves source randomly in
all possible directions.
Beam leaves source with high
degree of collimation.
Light intensity fades as we move
away from source.
Intensity is maintained over long
distance.
Power per unit area decreases. Remains constant.
5. CHARACTERSTICS
Monochromatic- Single wavelength and single
pure colour.
Collimated- unidirectional.
Coherence- waves produced by laser light
travels in phase. This property is responsible
for strength and intensity of beam.
6. Mechanics of Laser
In an atom each proton is balanced by an
electron that orbits the nucleus in different orbits.
The smaller the orbit, lower is the energy.
When energy given- electron moves to higher
orbit – “excited”
This energy is released soon, and the electron
returns to the original orbit – Spontanuous
emission
If photons are made to strike the atoms at exited
state,the decay of atom is accelerated and both
the incident and the absorbed photon are
released- stimulated emission.
This stimulated emission is amplified with the
help of mirrors.
7.
8. COMPONENTS OF LASER
Optical resonating chamber with two mirrors - filled
with an active medium such as Argon, Nd:YAG.
An external energy source that excites the active medium.
One totally reflecting mirror
One partially reflecting mirror
9. - Gas molecules are excited by electric current
- When more than half of the atoms have reached a
particular excited state, spontaneous emission takes
place.
- Stimulated emission takes place when a photon
interacts with an excited atom which yields pair of
identical photons of equal wavelength, frequency and
phase.
- Water chamber is used for cooling the gas.
10. LASER ENERGY
Controlled by adjusting various parameters.
Power: rate at which energy is delivered,
measured in watts
Spot size : Area exposed to beam, mm2 or cm2
Exposure time : seconds
Irradiance or power density: power per unit
area
Wave length : as wave length increases, spot size
increases and power density decreases.
Fluence or Radiant exposure : power density x
duration of exposure
11. Modes of operation
A continuous wave : constant
intensity, operates for more than
0.1 second.
A pulsed laser produces a
single or train of impulses with
each individual phase less than
0.1 seconds.
Q switching : production of
very short (less than 0.1
microsecond) but high intensity
pulse of laser .
Cavity dumped- two
completely reflecting mirrors are
used.Light energy is trapped until
it reaches a maximum. Then one
mirror is removed.
14. 60 to 65 degree Celsius-protein denaturation.
100 degree Celsius-vaporization.
Fibre in contact with tissue- incision (saw like)
Fibre in near contact position- vapourisation of
tissue
Fibre not in contact- coagulation
15. Centre of wound is area of tissue
vaporization.
Immediately adjacent to this is zone of
thermal necrosis 100um wide.
Next to that area of thermal conductivity
and repair 300 to 500 um wide.
Small vessels, nerves and lymphatics are
sealed in the zone of thermal necrosis.
The minimal operative trauma combined
with vascular seal accounts for the absence
of post operative edema that is characteristic
of laser wounds.
To minimize lateral thermal damage
from thermal diffusion the tissue should
be ablated with a short laser pulse.
16. LASER TISSUE INTERRACTION
PHOTOMECHANICAL EFFECT-When the laser
energy is pulsed to disrupt tissues or stones by the
mechanism of shock waves.
Holmium YAG laser to shatter ureteric and renal
calculi.
•PHOTOABLATION- molecular bonds are divided
by laser.
•Ruby laser can split the bonds of tattoo ink with
minimal local damage, macrophages remove the
tattoo after bonds are broken.
17. PHOTOCHEMICAL EFFECTS
Laser wavelength matches the absorption characteristics of some
chemical substance contained within the tissue.
Used for Photodynamic Therapy.
Dye laser act via this effect.
The photosensitizer is absorbed selectively by the neoplastic tissue,
it accumulates within a cell and reacts with light and oxygen to form
singlet oxygen which damages the cell and membrane.
PHOTOTHERMAL EFFECT
•The conversion of absorbed laser light into heat.
• The tissue affects can be
coagulation or vaporization depending on the laser
wavelength and device.
18. Delivery system
Articulated arm:- the beam is
transferred from a laser aperture in a
hollow metal tube known as
articulated Arm.
Micromanipulator delivery :-
consists of a system of lenses and a
mirror with a joystick attachment. It is
attached to a microscope.
HANDPIECE DELIVERY:-The beam is
focused by a system of lenses and
mirrors onto a hand piece at a fixed
point about 2 cm from its distal end.
20. Comparison of diff. types of laser
Features CO2 Nd:YAG Argon KTP
Tissue
absorption
high low Selective in
blood
Selective in
blood
Coagulation low high medium Medium
Cutting
effect
High low low low
Tissue
penetration
low high medium Medium
Wavelength
(nm)
10600 1060 488-514 532
21. CO2 LASER
1st laser used clinically in otolaryngology.
Long wave length (10,600 nm).
Infrared (invisible) range of electromagnetic spectrum
Invisible- hence Aiming beam helium-neon is necessary-provides
red color.
Absorption of radiant energy produced by CO2 laser is
independent of tissue colour, and also the thermal effect produced
by this wave length on the adjacent non target tissue is minimal-
hence it’s the most commonly used laser in otolaryngology.
Maximum absorption in water medium (extinction length is .03
mm i.e. thickness of water necessary to absorb 90 %of incident
radiation in pure water).
Reflection and scattering are negligible.
22. The maximal power is at the centre of the
beam, fades at the margin.
Used for – incision, excision and vaporization
of tissue.
Minimal edema
Vaporizes tissue , blood less field -therefore
can be used in coagulopathy and bleeding
dyscariasis.
LIMITATION- Cannot be transmitted through
flexible fibres
23. USES-
Most effective in Laryngology and
bronchoesophagology
Recurrent respiratory papillomatosis (excision ablation)
Laryngotracheal stenosis and web (radical excision and
dilatation)
B/l vocal cord immobility-laser cordotomy, medial or
total arytenoidectomy
Vocal cord nodule, polyps, cyst (microspot precision)
Laryngeal tumors- complete excision , or palliation to
reduce patient’s symptoms of airway obstruction or
hemoptysis, and in early stage carcinoma (ca insitu and
T1)
Transoral robotic surgery
Ear surgery- Stapedotomy, stapedectomy
Oral carcinoma- verrucous, superficial T1, erythroplakia,
leukoplakia
24. For many years light from Co2 laser
could not be transmitted through flexible
endoscopes as was absorbed in fibere
optic material and hence is delivered
with an articulated arm system .
More recently it has been coupled
with flexible waveguide technology to
allow passage through working channel
of an endoscope.
This advancement has coupled the
haemostatic and ablative properties of
this wavelength to apply energy to
areas that are difficult to access.
Disad.-Single non reusable fibre.
25. ADVANTAGES OF CO2 LASER
Micromanipulator coaxial delivery system
attached to microscope provides magnified and
unobstructed view
of laser.
Adequate intra operative haemostasis.
Thermal damage zone is very shallow and so
does not interfere with histological assessment.
Postoperative oedema is minimal.
Ablation on or near cartilage doesn’t cause
Perichondritis.
26. CO2 laser vs radiotherapy
Duration of treatment is shorter.
Cure rate of both laser surgery and radiotherapy is
comprable.
Less morbidity.
Greater cost effectiveness.
27. Nd-YAG LASERS
Neodymium-yttrium aluminum garnet (Nd-YAG).
Invisible(near infrared), wavelength- 1064 nm
Increased absorption in darkly pigmented tissue and charred
debris.
Can be used through a fibreoptic scope.
Produces homogenous zone of thermal coagulation and necrosis
(upto 4 mm)- can be used in control of bleeding.
DISADVANTAGE- greater damage to surrounding normal
tissue
28. USES
NOSE :- Hereditary haemorrhagic
telangiectasia (coagulation), turbinectomy.
Trachea :- Most imp in Obstructing malignant
lesion (debulking, coagulation).
Photocoagulation of vascular lesions of head
and neck and lymphatic malformations.
Coagulation of hemorrhagic lesions ( GI
varices)
29. Argon Laser
Produce Blue-green light
Short wavelength of 488 and 514 nm in visible spectrum.
High absorption by hemoglobin and pigmented tissue.
Fibre optic delivery.
USES-
Primary used in ophthalmic procedures as easily transmitted through
clear fluids like lens, cornea and vitrous.
When the beam of argon laser is focussed on a small spot its power
density increases sufficiently to vaporize the target tissue,therefore can be
used in stapedotomy ( a drop of blood has to be placed in the stapes)
Ear :- lysis of middle ear adhesions (optical fibre delivery haemoglobin
absorption).
Photocoagulate pigmented lesions-hemangioma, telangiectasis
30. ARGON TUNEBLE DYE LASER
It works on the same principle as argon laser.
It makes a high density beam that is focussed on
dye, that circulates in a second laser optically
coupled with argon laser.
By varying the type of dye different wavelengths
can be produced.
photodynamic therapy for cancer.
absorbed by(630 nm) hematoporphyrin(remains
long in cancer tissue).
Long term control has been achieved by using
photodynamic therapy for recurrent nasopharyngeal
cancer.
31. DIODE LASER
810nm wavelength infra red invisible( Gallium
arsenide semiconductor laser ).
Fibreoptic delivery system.
Tissue-cutting effect comparable to CO2 laser.
Coagulation effect comparable argon laser.
Higher degree of absorption by tissue than
Nd:YAG laser.
Large (up to 10 mm) penetration depth in
biologic tissue.
Ideal for photocoagulation.
Used for DCR.
32. KTP laser
Potassium titanyl phosphate.
Wavelength- 532nm (visible spectrum).
Visible green light.
Transmitted through optical fibre, handheld
probes.
Comparable with argon laser but more strongly
absorbed by hb.
33. Uses
NOSE :-polyps, chonca bullosa (debulking),
epistaxis
Larynx :-obstructing squamous cell carcinoma
(debulking airway), MLS-laryngocele, glottic ca
2 nd choice in vocal cord surgeries.
Oropharynx :-sleep apnea
(uvulopalatopharyngoplasty).
Palatine tonsil :-tonsillectomy.
Recently pulsed KTP laser is used for selective
vascular effect on laryngeal lessions like
papilloma, dysplastic lesions.
34. Lasers in rhinology
KTP is used because-
Fibre transmissible
High affinity for pigmented tissues (Sinus
blood vessels)
Adequate power of ablation of bones of MMC
CO2 laser is not preferred because-
Lack of fibre transmissibility
Increased risk of synechiae formation
Poor coagulation and hemostasis
36. For Endonasal dcr
Ho:YAG, KTP, Diode laser may be used.
Laser cause bloodless vaporisation of mucosa
and ablation of bone.
Side effect -collateral thermal damage.
37. LASERS IN LARYNX
Chronic inflammatory conditions- nodule, polyp,
mucus retension cyst, reinke’s edema
Neuromuscular disorders- B/L vocal cord
immobility
Functional dysphonia : excision of both
ventricular cords
Chronic trauma : hematoma, granuloma
Neonates- laryngomalacia, congenital mucous
cyst
Benigh laryngeal tumours
Webs
Reccurent respiratory papillomatosis
Excission of malignancy (early stage- ca in
situ, T1, and for palliation)
39. Uvulopalatopharyngoplasty
UPPP is a procedure that removes
excess tissue in the throat to make the
airway wider.
Helps in reducing the severity of
obstructive sleep apnoea (OSA).
The tissues that are removed may
include:
uvula
Part of soft palate
Excess throat tissue, tonsils.
If an enlarged tongue is a factor in
sleep apnea, the surgeon may remove a
small part of the tongue. This is called an
uvulopalatopharyngoglossoplasty.
40. LASER IN OTOLOGY
Advantages
Reduces mechanical trauma
Increases surgical precision
Improves hearing results
Reduces post op disequilibrium
USES-
To vapourize small amount of vascular tissue like
granulation tissue, small glomus, fragments of
acoustic neuroma
EAC stenosis
Stapedotomy
41. LASER STAPEDOTOMY
The stapes bone removed and
replaced with a microprosthesis – a
stapedectomy
Creating a small hole in the fixed
stapes footplate and inserting a tiny,
piston-like prosthesis – a
stapedotomy.
Used in treatment of otosclerosis
Using CO2 laser, a tiny opening is
created in the stapes in which the
prosthesis is secured. The CO2 laser
allows the surgeon to create very
small hole, precisely the size of
prosthesis without increasing the
temperature of the inner ear fluid by
more than one degree, making this an
extremely safe surgical solution.
42. Revision Laser Stapedectomy
It depends on the depth of oval window, any
residual stapes footplate, and the relationship
of the prosthesis with the vestibule.
After elevating the tympanotomy flap, the
above parameters are assessed, and the size
of the stapedotomy and the prosthesis
required are determined accordingly
43. CO2 laser is preferred as argon and KTP laser
can penetrate perilymph and cause damage to
inner ear.
CO2 Laser produces round symmetrical
stapedotomy as compared to mechanical
stapedotomy techniques, or visible laser which
produces irregular scalloped stapedotomy.
Prosthesis migration is minimal with CO2
laser stapedotomy and hence long term hearing
results are improved.
45. SAFETY
The surgeon should attend a hands on training course
in laser surgery including laser physics, tissue
interactions, safety precautions and supervised hands on
training.
Hospitals should appoint a laser safety officer and set
up a laser safety committee.
An in service workshop for O.T. staff and nurses is also
recommended.
A warning sign plus locked doors can prevent
unprotected and unprepared individuals from walking
into operating room.
The key to switch on the laser should be held by a
senior member of the operating room .
EDUCATION
46. Eye protection
Lasers with visible or near infrared range (400-1400 nm)-
damage RETINA
Laser <400 nm and >1400 nm_ damage CORNEA and
LENS.
Precautions:- Sign board should be there outside OT.
Glasses with side protectors , wave length specific.
Plain glasses -for CO2 laser
Blue Green glasses – for Nd YAG
Amber glasses : for Argon
Doors of operating room should remain close during LASER
use
47. Double layer of saline moistened eye pads are
placed over patient’s eye.
When undergoing photocoagulation of
vascular lesions of face, the patient should wear
protective metal eye shields.
In CO2 laser surgery, only assistant surgeon
needs to wear glasses. Eyes of the operating
surgeon are already protected by optics of the
operating microscope.
48. Skin protection
Double layer of saline
saturated surgical towels and
surgical sponges.
Care must be exercised to keep
the wet draping from drying out
and should occasionally be
moistened during the procedure.
Teeth protection : saline-
saturated Telfa, surgical sponges,
specially constructed metal dental
impression trays can be used.
49. SMOKE EVACUATION
Lase smoke Can be
mutagenic
Two separate suction
setups should be available
for all laser.
One for suctioning
adequate smoke and steam
evacuation, and other for
blood and mucus.
50. Anesthetic considerations
Any noninflammable general anesthetic is suitable
(halothane and enflurane most often used. Nitrous
oxide being oxidizing agent is not used).
Mixture of helium, nitrogen or air plus oxygen are
commonly used to maintain FiO2 less than 40
percent.
Flash ignition of 100 percent oxygen can occur.
Polyvinyl ET tubes should not be used because it
offers least resistance to penetration by lasers of all
ET tubes.
Nowadays wavelength specific ET tubes are also
available .
51. Methylene blue colored
saline should be used to
inflate the cuff.
Saline saturated cotton are
placed above the cuff in
subglottic region to further
protect the cuff.
A 60 ml bulb syringe and
basin of saline are kept beside
the surgeon.
52. Approaches to reduce airway fire
Reducing flammability of ET tube-
Laser resistant special tube
Wrapping of standard tubes (with aluminium or
copper foil, merocele laser guard)
Cuff to be inflated with methylene blue
Using different mode of ventilation-
Intermittent extubation
Jet ventilation
Total IV anaesthesia
53. Special tubes-
Mallinkrodt Laser flex endotracheal tube
Paediatric uncuffed tube
Adult cuffed tube with 2 cuffs- distal cuff
remains intact even if proximal cuff is
damaged by fire
54. Xomed laser shield
II cuffed
endotracheal tube
Wrapped with
copper foil inside
and tefflon outside
55. In event of tube ignition -
Ventilation must be stopped immediately
ET tube is withdrawn simultaneously as
saline is flushed down the ET tube
Airway must be re-established
IV steroids
Bronchoscopy should be done later to see
the extent of damage
