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LASER HISTORY ACRONYM FOR L ight A mplification by S timulated E mission of R adiation A laser is a device that produces and amplifies light by stimulated emission. It can produce light in the ultraviolet, visible, and infrared region of the electromagnetic spectrum. 1960: Theodore Maimen develops first laser (ruby with 694 nm wavelength. 1961: Neodymium-doped ( Nd ): glass laser. 1964: Nd:YAG and argon ion ( Ar ). 1965: CO2 laser.

Ordinary light versus laser light:

Ordinary light versus laser light ORDINARY LIGHT LASER Radiation from conventional light source is emitted over a wide range of wavelengths, or spectrum The light intensity close to the source is very high. The loss of intensity is due to the divergent nature of the conventional radiation In contrast, the laser produces a beam with a very narrow divergence. Light leaves the source with a high degree of collimation. As the beam travels in space, the directionality is maintained over a long distance. As a result, high beam intensity is also maintained over a long distance.

Components of a laser:

Components of a laser A laser consists of the lasing medium, contained in an optical cavity, and a pumping system, provided by external energy. The mirrors at each end ensure that the photons bounce back parallel to the axis, so that they, in turn, collide with excited atoms and stimulate further production of photons . The device where the laser action takes place is called an optical cavity, a tube containing a suitable lasing medium which may be gas ( e.g., CO2), liquid (e.g., dyes), or crystal ( e.g., ruby).

Mechanism of production of laser light:

Mechanism of production of laser light An atom consists of a dense nucleus, around which electrons move in orbit. The orbiting electrons are free to change their orbit to a different (higher) level by absorbing energy from an external source, which may be light (photons). And acquire an excited, unstable state. The unstable electrons cannot stay in the higher unstable orbit.They tend to decay to a lower, more stable orbit.In the process, they lose the extra energy of the higher level in the form of packets of energy, or photons. This may happen spontaneously and at random .


Contd ………… A photon released from an excited atom might interact with another similarly excited atom. This results in the second atom releasing its photon, which is identical in every respect to the first photon. This phenomenon is called stimulated emission of radiation. The two photons have the same direction of travel, and are in phase.

Properties of laser light:

Properties of laser light Monochromatic : A single pure colour emitted by a single wavelength. Collimated : : A beam in which all, or almost all, the photons are travelling in the same ‘parallel direction’ Coherent : Waves produced by a laser travel through space in phase. The property of being in phase is called coherence and is responsible for the strength and intensity of the beam between different points in the field.

Different types of lasers:

Different types of lasers Four types of material are used: Solid -- Nd:YAG laser, Gas – Helium Neon ( HeNe ) laser, CO2,Argon and Krypton Gas laser. Liquid —Organic dye laser.( rhodamin 6G , disodium fluorescein ) Semiconductors – Gallium-Arsenide-Diode laser Excited dimer ( Eximer Laser) -- Argon fluoride (193 nm) and Krypton fluoride (248 nm)

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Infrared light : primarily absorbed by water. Visible and UV light are absorbed by hemoglobin and melanin As wavelength becomes shorter – scatter begins to dominate the penetration of light

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Comparison of the different types of laser CO2 Nd:YAG Argon KTP Wavelength (nm ) 10,600 1060 488-514 532 Tissue absorption high low selective – selective high in blood high in blood Tissue penetration 0.1 4 1 1 Coagulation low high medium medium Cutting effect high low low low

Laser-tissue interactions:

Laser-tissue interactions The active lasing medium in the laser tube The delivery system The beam parameters The power density on the tissue Irradiance = intensity / area = watts / cm 2 Fluence = (intensity X time) / area The absorption characteristics of the tissue The surgical skill

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Reflection Absorption Photothermal effects Photomechanical effects Photoablation Photochemical effects Conduction Coagulation

Laser crator:

Laser crator When laser radiation strikes a tissue, the temperature begins to rise. 10 C – 45 C: Conformation change of proteins. 50 C: Reduction of enzyme activity. 60 and 99°C: Coagulation begins. Vaporisation takes place when the temperature rises to 100°C. Char starts to burn at around 400-500°C.


MODES OF LASER CONTINUOUS :The laser is continuously pumped and emits light continuously PULSE : In the superpulse mode, laser energy is delivered with each peak over an extremely short period of a few nanoseconds. The peaks are interspersed with rest periods when no exposure occurs, allowing time for tissues to cool down Q-SWITCHED : Allows a high build-up of energy within the tube. This is then released over a very short duration of a few nanoseconds, reaching an enormous peak power.

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Different types of laser

CO2 Laser:

CO2 Laser 10,600 nm wavelength Water is target chromophore Aiming helium-neon ( HeNe ) beam Highest power continuous-wave laser Cutting or ablating tool Focus to <500 m m Seals blood vessels less than 0.5 mm Pulsed to accommodate thermal relaxation time, less pain and less edema Used in majority of procedures except those requiring coagulation of larger vessels No current optical fiber to carry beam

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The thermal damage zone is shallow: less than 500 μm . Therefore, it is a comparatively poor haemostat , not being effective in controlling bleeding from vessels greater than 0.5 mm in diameter. It is not fibre -transmissible through the common silica optical fibre , although flexible guides are available with limited flexibility for delivery. Its use on the cords has the advantage of producing minimal scarring,with the preservation of vocal function. It causes a minimal inflammatory reaction, and glottic competency is rarely jeopardised , even after extensive application.

Nd:YAG Laser:

Nd:YAG Laser 1064 nm wavelength (neodymium-doped yttrium aluminum garnet ) Aiming helium-neon ( HeNe ) beam Wavelength is between minimal absorption of water and a small amount of scatter Solid state laser Fiberoptic carrier Application Deeper penetration (up to 4 mm) for ablative therapy and hemostasis Preferentially absorbed by pigmented tissues Vascular malformations amenable to treatment Limitations Greater scatter than CO2 Deep thermal injury Risk for transmural injury It is an ideal laser with a deep thermal effect for coagulation and haemostasis , for example, in the management of haemorrhagic lesions in pulmonary surgery and gastroenterology .

KTP Laser:

KTP Laser 532 nm wavelength (potassium- titanyl -phosphate) Frequency doubling Nd : YAG laser passes through a KTP crystal – emission is ½ its wavelength Oxyhemoglobin is primary chromophore Fiber optic carrier Continuous wave (CW) mode to cut tissue Pulsed mode for vascular lesions Q-Switched mode for red/orange tattoo pigment Delivery CW/pulsed mode: insulated fiber, fiber handpiece , scanner, or microscope Q-Switched mode: articulating arm


HELIUM –NEON LASER Helium-Neon (He-Ne) laser: The He-Ne laser emits at 633 nm in the visible spectrum. It is a low power laser. Its main use is to act as an aiming beam for invisible lasers. The He-Ne laser is superimposed on the path of invisible lasers, such as the CO2 or Ho:YAG , and used as an aiming beam. The low power HeNe beam has also been used in wound healing and in the treatment of pain.

Argon Laser:

Argon Laser 488 - 514 nm wavelength (ion laser) (BLUE GREEN SPECTRUM) Oxyhemoglobin is target chromophore Small spot size (0.1 – 1 mm) – variable in size and intensity Flexible delivery system mainly used in the ophthalmological procedures Limitations Also absorbed by epidermal and dermal tissues due to melanin Continuous mode of operation Higher prevalence of postoperative pigmentary alteration and fibrosis


DIODE LASER The most common diode laser is the gallium arsenide diode laser, with a central emission of 840 nm, and is fibre transmissible.

The delivery system:

The delivery system Articulated arm The emerging beam is transferred from the laser aperture in a hollow metal tube, usually known as an articulated arm


LASER DELIVERY SYSTEM Micromanipulator delivery The micromanipulator is a device consisting of a system of lenses and a mirror with a joystick attachment.It is attached to the microscope Handpiece delivery The beam is focused by the system of lenses and mirrors onto the handpiece at a fixed point some 2 cm from its emergence at the distal end. A guide probe extends from the end of the handpiece

Theatre protocol:

Theatre protocol Illuminated warning signs All entrance/exit doors should be marked with a warning sign, indicating that a laser is in use and that entry is only permitted to authorised persons wearing protective eye wear Smoke evacuators Laser surgery results in considerable pollution of the operating theatre with smoke and vapour . The operating theatre must be well ventilated and equipped with dedicated smoke evacuators


Contd ………. Fire extinguishers for electrical fires A fire extinguisher containing CO2 gas or dry powder, together with a fire blanket, is positioned in close proximity to the main entrance door of the operating theatre Protective eye wear Wavelength-specific eye wear is provided for all staff working in the theatre

Anaesthesia for laser airway surgery:

Anaesthesia for laser airway surgery The challenge of anaesthesia for laser airway surgery revolves around three major considerations: combustion, the airway, and anaesthetic risk. Combustion The risk is greatest with a collimated beam such as a CO2 laser. Risk of combustion is also less in lasers that operate in a pulsed mode, as heat can dissipate between bursts. Commonly used tubes such as red rubber, latex,and plastics such as PVC, are easily ignited in a typical anaesthetic gas mixture, burning with a blowtorch-like flame.

How anaethesist manage!:

How anaethesist manage ! Intubation anaesthesia Water is fire retardant as well as being a heat sink, so all swabs and fabric should be wet. Protection of standard tracheal tubes -Protection with wet swabs///Reflective wrapping of tracheal tubes////Protection of the tracheal tube cuff///Factory-wrapped tracheal tubes///Silicone rubber tubes with metallic protection////Metal cuffed tubes/// Jet ventilation anaesthesia Intermittent apnoeic technique Tubeless anaesthesia


INDICATIONS FOR LASER IN LARYNX Functional dysphonia plicae ventricularis - CO2 laser-assisted excision of both ventricular cords. Chronic inflammatory conditions- Exudative lesions in Reinke’s space– nodules polyps Reinke’s oedema Intracordal mucous retention cysts Intracordal epidermoid cysts Sulcus vocalis and sulcus vergeture Mucosal bridge Anterior microwebs Chorditis vocalis Chronic trauma- Haematoma


Contd …….. Ulceration and granuloma Scarring Subluxation of the arytenoid cartilage Neuromuscular disorders- Bilateral vocal cord immobility CO2 laser-assisted total arytenoidectomy Subtotal arytenoidectomy Recurrent respiratory papillomatosis Neonatal laryngopathy - Laryngomalacia Subglottic haemangioma Congenital mucous cysts Benign laryngeal tumours - Cysts( Intracordal epidermoid mucous retention cysts) Laryngocoeles


Contd ……. Webs and synechiae - Laryngo -tracheal synechiae Congenital anterior webs Anterior synechiae and fibrous bands Chonic hyperplastic laryngitis - leucoplakia white hyperplastic laryngitis red hyperplastic laryngitis erythroplakia , speckled erythroplakia Excisions for malignancy Carcinoma in situ (CIS) Micro-invasive carcinoma Verrucous carcinoma management of TIS, T1 and some early T2 glottic , supraglottic carcinoma

Why lasers for nasal surgery? :

Why lasers for nasal surgery? Lasers offer certain unique advantages in endonasal surgery of the middle meatus complex (MMC). The relatively bloodless field in the MMC offered by lasers means that the surgical procedure is under better visual control. The CO2 laser is not commonly used in endonasal laser surgery for a number of reasons . Lack of fibre transmissibility Increased risk of synechiae formation Poor coagulation Poor haemostasis


Contd … The KTP/532 wavelength (KTP) is fibre transmissible. It has a high affinity of absorption for pigmented tissue, such as haemoglobin . The energy conducted into the tissue is well absorbed by the sinusoidal blood vessels of the turbinate and results in a coagulation zone with very little intraoperative bleeding. The KTP laser has adequate power for ablation of the bony framework of the MMC.

Benefits to the patient from laser technology in Nose:

Benefits to the patient from laser technology in Nose Minimally invasive surgery Minimal bleeding Minimal postoperative oedema and crusting Revision surgery Ambulatory surgery Cost benefit


INDICATIONS Reduction of turbinates Nasal polypi Residual peritubal adenoid tissue, stenosis , and cysts Dacryocystorhinostomy Laser-assisted septoplasty Indications for laser functional endoscopic sinus Surgery Removal of polypi as a preliminary procedure to FESS Manipulation of middle turbinate Solitary sphenoid or frontal sinus disease Intraoperative haemostasis Revision endoscopic sinus surgery


Contd …. Excision of the uncinate process,removal of bulla ethmoidales , and creation of middle meatal antrostomy Any suspicion of orbital, facial, or intracranial extension of the disease process is a contraindication for laser use . Miscellaneous— Rhinophyma Recurrent idiopathic nasal bleeding. Telangiectatic , cavernous or pyogenic septal granuloma Hereditary haemorrhagic telangiectasia (HHT) Choanal atresia or stenosis , nasopharyngeal stenosis , polyps, adenoid hypertrophy, juvenile angiofibroma and nasopharyngeal cancer. Laser cartilaginous eustachian tuboplasty

Laser selection in otology:

Laser selection in otology CO2, KTP and argon lasers have all been used in ear surgery. In vascular lesions of ear -The Nd:YAG laser, with its deep scatter,appears to be the laser of choice. For debulking of tissue,stenosis CO2 laser are used. The visible KTP laser light is well suited for undertaking temporal bone surgery. Fibre transmissibility of the KTP beam gives an added dimension to laser usage in ear surgery. Because of the optical property of “total internal reflection”such fibres can guide the light around corners.

Laser in otology:

Laser in otology External auditory canal Vascular lesions – haemangiomas , telangiectasias Aural polyps and granulations Stenosis of the external auditory canal Debulking of large, inoperable EAC carcinoma Laser reshaping of cartilage Tympanic membrane lesions Epidermoid cysts of the tympanic membrane. Middle ear cleft Laser-assisted myringoplasty Perforations of the tympanic membrane

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Graft-welding of tympanic membrane defects Medialisation of the malleus Laser-assisted ossicular surgery Removal of inflammatory disease Vascular lesions of the middle ear Laser-assisted, totally implantable electronic hearing aids Cholesteatoma surgery Laser applications in the inner ear Cochleostomy Laser labyrinthectomy

Orofacial Surgery:laser preference:

Orofacial Surgery:laser preference For vaporisation and cutting in soft tissue, a wavelength such as the carbon dioxide (CO2) modality at 10.6 μm is indicated For coagulation in soft tissue, a wavelength which is poorly absorbed by water but is maximally penetrative, is required. The near infrared modality of the Nd:YAG at 1.06 μm is most suited for this purpose. For hard tissue such as bone, dentine or enamel, hydroxyapatite is the chromophore of importance so that a wavelength such as the erbium:YAG at 2.9 μm is indicated.


Indications High intensity laser treatment(HILT) Oral mucosal premalignant leucoplakia Mucosal haemangiomatous lesions of the mouth Temporomandibular joint : Division of adhesions, coagulation of redundant capsule in recurrent dislocation, and shrinkage of retrodiscal tissue, as an aid to retrieval of an anteriorly displaced meniscus. Laser hemiglossectomy Temporomandibular joint disorder pain Low intensity laser therapy (LILT) Post-herpetic neuralgia Idiopathic neuralgia Intractable ulcerations :Of Pemphigus vulgaris , Crohn’s disease, and AIDS

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Surgery for snoring and obstructive sleep apnoea : Uvulopalatoplasty Laser midline glossectomy and lingualplasty Laser palatine tonsillectomy Laser lingual tonsillectomy Cryptolysis for halitosis

Laser selection in lower airways:

Laser selection in lower airways The most common lasers used for the lower airways are the CO2 and the Nd:YAG . The CO2 laser beam is directed towards the lesion through articulated arm, limiting its use to rigid bronchoscopy It is presently used more for lesions involving the larynx and proximal trachea. The Nd:YAG laser beam can be passed through a flexible endoscope It affords deeper penetration, allows better coagulation, and produces better haemostasis Its main disadvantage is the unpredictable interaction of the laser beam with the tissue, making it difficult to determine the depth of penetration

Lower airway indications:

Lower airway indications Laser photoresection of obstructive airway lesions Malignant -------- bronchogenic carcinoma, metastatic neoplasm, carcinoid tumour Benign ---------- subglottic and tracheal stenosis , granulation tissues, broncholith,foreign body, benign tumours,congenital tracheo-oesophageal fistula Photodynamic therapy- ----- curative therapy for carcinoma in situ, juvenile laryngotracheobronchial papillomatosis , unresectable early stage lung cancer palliative treatment for advanced obstructive lung cancer Autofluorescence bronchoscopy - ----- localisation of carcinoma in situ and superficial bronchogenic cancer

Hazards of laser:

Hazards of laser Damage caused unintentionally by laser strikes on biological but non-target tissue, such as corneal or retinal eye injuries, skin and mucosal burns. • Hazards caused by laser strikes on non-biological material such as the anaesthetic tube and draping material. Side-effects due to laser by-products such as laser-generated smoke. Laser malfunction such as electric shock


………. THANK YOU ! !

Slide 49:

A laser produces a beam, like a sunbeam, but with four fundamental characteristics: intensity (tremendous energy in a very focused, narrow beam), coherence (in phase spatially and temporally), high collimation (light waves are parallel with minimal divergence and thus minimal dissipation of energy), and monochromacity (uniform wavelength).

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Monochromatic Coherent Collimated A chromophore may be defined in the broad sense as a group of atoms capable of colouring a substance. How Does It Work? A laser is an optical oscillator, which is made out of a solid, liquid or gas with mirrors at both ends. To make the laser work, the material is excited or "pumped," with light or electricity. The pumping excites the electrons in the atoms, causing them to jump to higher orbits, creating a "population inversion." A few of the electrons drop back to lower energy levels spontaneously, releasing a photon (quantum of light). The photons stimulate other excited electrons to emit more photons with the same energy and thus the same wavelength as the original. The light waves build in strength as they pass through the laser medium, and the mirrors at both ends keep reflecting the light back and forth creating a chain reaction and causing the laser to " lase ."


CRYOTHERAPY: ’kryos ’=cold That branch of therapeutics which relies upon its value on local tissue changes,produced by rapidly achieved ,profoundly low temperature . Procedure based on JOULE THOMPSON EFFECT -R apid expansion of compressed gas through a small hole produces cooling. The

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Cryosurgery was carried out for the first time by James Arnott in 1845 in an operation on a patient with cancer. Dehydration

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The fundamental properties utilized in the applications of lasers are that the laser is a beam of light that is collimated and monochromatic. Thus a laser beam can travel over large distances without dispersing (beams of ordinary light spread out and hence lose intensity). A laser beam can also be focused down into a spot of light smaller than an atom. This allows enormous amounts of heat to be generated at a very precise spot

Different types of spray techniques :

Different types of spray techniques

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Cryosurgery Procedure. As the temperature falls to less than 0°C, water crystallizes. This results in more significant damage than with mere prolonged cooling. Effective “cellular dehydration” occurs predominantly between 0°C and −20°C. Given enough time in this dehydrated state, the increased intracellular electrolyte concentration is often sufficient to destroy the cells.

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Cryosurgery Procedure. As cooling is continued intracellular ice crystal formation starts. It is more efficient at rapid cooling rates; slower rates of cooling will result in cellular dehydration. Rapid cooling does not allow time for water to leave the cells. During thawing, ice crystals fuse to form larger crystals, a process called recrystallization , which occurs at temperatures warmer than -40°C. Therefore, upon thawing of the ice, more free water will exist outside the cells. This will enter the damaged cells, and the subsequent increase in cell volume might lead to cell membrane rupture.

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The initial CO2 laser microwave was a continuous wave. At a given power, it provided continuous output. The continuous exposure resulted in much heating of collateral, nontarget tissue by conduction. To minimize the thermal effect; a pulsed mode was developed for the CO2 laser ( Sharpulse ).

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Common indications for laser in ENT 1 Oral leucoplakia : Leucoplakia is strikingly responsive to the CO 2 laser. Recurrence of new patches of leucoplakia after laser treatment is also less likely. The operating microscope enables one to see much more of the targeted field. The reduced ground tissue reaction adds to the advantage of laser. 2 Oral Verrucous carcinoma: Lesions, which are 2 cms or less, are amenable to laser treatment. The results of treating small-circumscribed oral verrucous carcinomas are excellent, especially if adjacent epithelial dysplasia is limited. 3 Oral carcinomas: Removal of intra-oral carcinomas by CO 2 laser is much preferred these days due to the more rapid and less painful process. Some surgeons do advocate leaving the wound open to facilitate better healing and reduced pain. Other conditions where laser has been advocated in diseases of the Oral cavity are • Oral and Oropharyngeal haemangiomas . • Pleomorphic adenomas. • Tonsillectomy • Uvulo-palato-pharyngoplasty . KKR ENT Hospital introduced CO 2 LASER in the year 1998 and since then have completed a series of head and neck surgeries using this technology. The results are outstanding when compared to conventional technique. Nasal indications: Listed are some of the commonly encountered indications in the nose which can be dealt very effectively with laser. Nasopharyngeal Angiofibromas : These are extremely aggressive and vascular tumours of the nose and paranasal sinuses. The CO 2 laser attains markedly reduced blood loss and precise incision. Familial haemorrhagic telangiectasia : This disease has lesions which cause bleeding in the nose due to capillary dilatations. Ablation of the mucosa by laser is extremely useful to control the bleeding. However, there have been some cases of recurrence after laser. Choanal atresia : The major advantage of the CO 2 laser in these conditions in infants is the minimal tissue trauma and the bleeding. The laser beam is directed along the axis close to the floor of the nose using the inferior turbinate as a landmark. The bleeding is usually minimal and an indwelling elastic or polyvinylchloride tube can be used to prevent contraction of the new orifice. The surgery may need to be repeated at times. Nasal polyposis : Polyps in the nose are usually a vascular and have a restricted area of the disease. Ethmoidal polyps have a high recurrence rate and laser surgery is very useful to reduce it.

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Lasers can be used to ablate a given tissue by vaporising it, layer by layer. Thus, vaporisation is the prime, and most important effect in the clinical application of lasers. Excision Lasers can also be used to ‘excise’ a tissue, by vaporising a narrow band of tissue in the line of the incision, in order to develop a flap, deep enough to hold