Department of Veterinary Surgery & Radiology COVAS, Parbhani

Definition

• A laser is a device that emits light (electromagnetic radiation) through a process of optical amplification based on the stimulated emission of photons.

• The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation.

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• Intangible

• Yet able to transfer energy due to mass effect of photons

• Photon– Specific packets of electromagnetic energy that give light its

mass and therefore allow to do work.– Described by Max Planck (1905) as

•E = h f

How a photon is produced?

• Neil Bohr’ model of atom explains it.

• Electrons in specific atoms and molecules can alter their energy state to lower or higher levels without being getting destroyed.

Now stimulated emission

• Einstein (1905) proposed stimulated emission.

• Photons can be produced, amplified & induced to cascade geometrically in a continuous positive feedback mechanism.

• Accredited as Father of modern lasers.

• It was technologically possible in the mid-twentieth century to prove the utility of selected materials for energy transformation.

• Simply applying electrical energy to a material caused the repeated release of photons.

• The first actual physical model for coherent stimulated radiation emission was in sophisticated microwave equipment developed to produce radar.

• Charles Townes created MASER—microwave amplification by stimulated emission of radiation

• A.L. Schawlow (1958) provided the idea of an “optical type maser” or LASER

History • Einstein (1905) proposed stimulated emission.• Dr. Theodore Maiman (1960) under the direction of

Dr. Henry Gould demonstrated consistent laser energy with the production of a ruby crystal laser

• Hence a laser was realized in true physical form• 1964 first used in veterinary medicine shortly in a

laser assisted vocal cord nodectomy

What is special?

• Coherent- in phase in space & time

• Monochromatic- one color/wavelength

• Collimated- single direction, tight beam, parallel paths

Practically saying

Common Components of all Lasers

1. Optical resonant cavityo Tube or cylinder, more length than widtho Highly reflective mirror capo Partially transmitting but highly reflective mirror cap at opposite end

2. Lasing Medium o solid ruby or Nd:YAG, o liquid dyeso gases CO2 or Helium/Neon

3. External energy sourceo Chemical o Electrical o Optical

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Lasing Action

• Pumping

• These atoms spontaneously decay to a relatively long-lived, lower energy, metastable state.

• A population inversion is achieved when the majority of atoms have reached this metastable state.

• Lasing action occurs when an electron spontaneously returns to its ground state and produces a photon.

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• If the energy from this photon is of the precise wavelength, it will stimulate the production of another photon of the same wavelength and resulting in a cascading effect.

• The highly reflective mirror and partially reflective mirror continue the reaction by directing photons back through the medium along the long axis of the laser.

• The partially reflective mirror allows the transmission of a small amount of coherent radiation that we observe as the “beam”.

• Laser radiation will continue as long as energy is applied to the lasing medium.

Lasing Action Diagram

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En

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y

Intr

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Ground State

Excited State

Metastable State

Spontaneous Energy Emission

Stimulated Emission of Radiation

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COMMON USED LASER LIGHTS

Power of laser light• Energy-

– The capacity for doing work.– Joule (J)

• Fluence – Energy delivered per unit area– j/ cm2

• Power – Amount of energy delivered per unit of time– Ability to do work over a given period of time– watt (W)

• Power density– Radiant power striking a target per unit area of a cross section of a

laser light beam– W/cm2

LASER RegulationClassified by the FDA’s Center for Devices & Radiological

Health based on the Accessible Emission Limit (AEL).

• Class 1 < 0.5 mW Laser pointers

• Class 2 < 1.0 mW Toys

• Class 3A < 5 mW CD-players

• Class 3B < 500 mW Therapeutic lasers

• Class 4 > 500 mW Surgical lasers

LOW LEVEL LASER THERAPY

Class 3B < 500 mW Therapeutic lasers

WHAT ?

• Relatively a new biotechnology that uses the science of photobiostimulation to speed healing

• Cold laser therapy or soft laser therapy• Over 35 years• Painless• Non-invasive • Works with the body’s own healing mechanisms• No harmful side-effects.

Cont….

• Different colours are used in veterinary medicine

• Infra-red, at about 800 nm or greater

• Red, at about 610 - 800 nm

• Gives body the pure energy to use for healthy cellular regeneration

Procedure

• The laser handset is held over the skin for a few minutes in each setting, although it can be used through clothes for intimate areas. Different programmes use a range of settings with various wave-lengths and phasing to penetrate to the best level within the body and interact directly with the appropriate cells. Sessions last no more than an hour and most clients notice the benefits from the very first session.

EFFECTS

Main areas of application of LLLT

Physiological Effects• Stimulation of wound healing– Promotes faster wound healing/clot formation– Helps generate new & healthy cells & tissue

• Increase collagen production– Develops collagen & muscle tissue

• Increase macrophagic activity– Stimulates immune system

• Alter nerve conduction velocity– Stimulates nerve function

Physiological Effects• Biostimulation – improved metabolism, increase of

cell metabolism– Increases speed, quality & tensile strength of

tissue repair• Improved blood circulation & vasodilation• Increases ATP production• Analgesic effect– Relieves acute/chronic pain

• Anti-inflammatory & anti-edematous effects– Reduces inflammation

• Immunoregulation– stimulates IMMUNOGLOBINS and LYMPHOCYTES

Numerous disorders which respond

• Arthritis• Hip dysplasia• Post surgical pain relief

and faster healing• Numerous skin conditions• Gingivitis• Otitis - Ear

infections/inflammation

• Wound healing• Insect bites/stings• Lacerations/abrasions• Cystitis -bladder

infections/inflammation• Burns• Plus many more

Mechanism of Action

• Red light affects all cell types

o Absorbed by the mitochondria present in all cells

o Cytochromes (respiratory chain enzymes) within the mitochondria have been identified as the primary biostimulation chromophores (primary light-absorbing molecules).

o Cytochrome c oxidase (Cox) is the primary photo-acceptor

o increased oxidation of Cytochrome c and increased electron transfer

o Increased ATP production

Mechanism of Action

Mechanism of Action• The light-induced increase in ATP synthesis and increased

proton gradient leads to an increasing activity of the Na+/H+ and Ca2+/ Na+ antiporters, and of all the ATP driven carriers for ions, such as Na+ / H+ ATPase and Ca2+ pumps.

• Ca2+ regulates almost every process in the body(muscle contraction, blood coagulation, signal transfer in nerves, gene expression, etc.).

• ATP is the substrate for adenyl cyclase

• Controls the level of cAMP.

• Both Ca2+ and cAMP are very important second messengers.

Mechanism of Action

Mechanism of Action

• Redox couples• NAD/NADH,

NADP/NADPH,GSH/GSSH etc

• Change in redox state activates numerous intracellular signaling pathways

• DNA/RNA synthesis, enzyme activation and cell cycle progression.

Treatment Techniques

Gridding Technique Divide treatment areas

into grids of square centimeters

Wanding Technique A grid area is bathed

with the laser in an oscillating fashion; distance should be no farther than 1 cm from skin

Scanning TechniqueNo contact between laser tip in skin; tip is held 5-10 mm from wound

Point Application (Acupuncture point)

LASER SURGERY

Class 4 > 500 mW Surgical lasers

Introduction • Surgery using a laser to cut

tissue instead of a scalpel• Laser scalpel• Highly focused laser beam

efficiently ablate (either vaporize or chip away) the living tissue.

• At the same time, it seals (welds) capillaries, small blood vessels, lymphatics, and nerve endings, with significant benefits to both patients and surgeons.

Photovaporolysis

• Char – remnant of non-fluid cellular component

Photoplasmolysis

Canine lithotripsy by Ho:YAG laser

• As the lasers pass to the depth the energy is decreased below the vaporization threshold power density and less collateral heating of tissues but causes coagulation of vessels

• Smaller primary nociceptors are sealed and action potential is inhibited and secondary nociceptors are not stimulated

How it controls bleeding How it minimizes pain sensation

Crater

Zone of carbonization- the limit of vaporization.

Zone of coagulation and thermal necrosis- Slightly farther away from the center. This zone will eventually die.

Zone of hyperthermia- Farthest from the center.

Beyond these zones there is no effect.

Depth of the crater and the diameter of these zones are directly related to power density.

20 watt Carbon Dioxide laser with plume evacuater

• Highly absorbed by water, making it perfect for tissue cutting, vaporization and acoustical destruction.

• Thermal injury to surrounding tissue is very superficial.

• Lateral thermal injury of 0.05 mm to 0.1 mm

• Because there is such minimal lateral thermal damage, injury to surrounding tissues is limited to what you see during application of the laser energy.

General parameters for CO2 laser use

• Routine incision:– Spot Diameter: 0.4 mm– Power Setting: 6 to 10 W

• Routine ablation/vaporization– Spot Diameter: 0.8 mm– Power Setting: 10 to 20

W

• Delicate location incision:– Spot Diameter: 0.3 to 0.4

mm– Power Setting: 3 to 6 W

• Routine excision:– Spot Diameter: 0.8 mm– Power Setting: 8 to 15 W

Why use laser?• Less Pain - The laser seals nerve endings as it cuts. So the patient will have less

pain.

• Less Bleeding - The laser seals small blood vessels during surgery and speeds up surgery by minimizing bleeding.

• Less Swelling - No physical contact except the invisible laser beam. The tissue will not be crushed.

• Sterilization - The laser sterilizes the surgical site as it cuts. Bacteria and viruses are vaporized by the laser during laser surgery.

• Faster Recovery - Less bleeding and swelling will result in faster healing.

• Precision - The beam direction and power can be controlled precisely to remove thin layers of tissue and produce minimal side effects on the surrounding healthy tissue.

• Reduced hospitalization time - All of above factor will greatly reduce the procedure time.

Why use laser?

- The laser seals nerve endings as it cuts. So the patient will have less pain.

•Less Pain

- The laser seals small blood vessels during surgery and speeds up surgery by minimizing bleeding.

•Less Bleeding

- No physical contact except the invisible laser beam. The tissue will not be crushed.

•Less Swelling

- The laser sterilizes the surgical site as it cuts. Bacteria and viruses are vaporized by the laser during laser surgery.

•Sterilization•Faster Recovery

Less bleeding and swelling will result in faster healing•Precision

- The beam direction and power can be controlled precisely to remove thin layers of tissue and produce minimal side effects on the surrounding healthy tissue.

•Reduced hospitalization time All of above factor will greatly reduce the procedure time.

Laser surgery benefits for surgeons

• Unique surgical capabilities: Laser surgery improves many surgical procedures by making them simpler and reducing risk. This enables surgeries that are not practical with conventional methods.

• Enhanced visibility of the surgical field: The laser light seals capillaries and small blood vessels as it cuts, thereby dramatically reducing bleeding. This results in a much clearer and drier surgical site.

• Increased precision and control: The focal spot size of the beam may be adjusted down to a small fraction of a millimeter or expanded for a much wider coverage. The laser power may be set for rapid removal of relatively large tissue amounts, or adjusted to remove only one cell layer at a time.

• Reduction of surgery time: The hemostatic effect of the laser beam and the improved visibility of the surgical field often reduce the duration of the surgery

Laser surgery improves many surgical procedures by making them simpler and reducing risk. This enables surgeries that are not practical with conventional methods.

•Unique surgical capabilities

The laser light seals capillaries and small blood vessels as it cuts, thereby dramatically reducing bleeding. This results in a much clearer and drier surgical site.

•Enhanced visibility of the surgical field

The focal spot size of the beam may be adjusted down to a small fraction of a millimeter or expanded for a much wider coverage. The laser power may be set for rapid removal of relatively large tissue amounts, or adjusted to remove only one cell layer at a time.

•Increased precision and control

The hemostatic effect of the laser beam and the improved visibility of the surgical field often reduce the duration of the surgery

•Reduction of surgery time

Laser surgery benefits for surgeons

Operations

Scalpel blade or a nail trimmer is the traditional way of declaws, that was painful and time consuming. Laser surgery to declaw will make cats have little pain

One of the CO2 laser features, selectively and gently going through layers of tissue, makes the CO2 laser excellent for ear hematoma due to the small opening needed to drain the fluid. Laser can completely ablate the small tumors lesion and make pets have less discomfort during the recovering time.

• Declaws

• Ear Hematoma

• Skin Tumor

• Dog NeuterCO2 laser can also treat dog neuters due to the advantages of minimal bleeding and less pain.

• AmputationThe laser is particularly good at amputations. Minimal bleeding during the laser surgery allows the surgery to perform much faster.

Canine Skin Incision

Canine Skin Incision

Canine Dewclaw Amputation

Canine Dewclaw Amputation

Feline Ovariohysterectomy

Feline Ovariohysterectomy

Canine Aural Hematoma

Canine Aural Hematoma

Canine Aural Hematoma

Uncomplicated Acral Lick Granuloma

Uncomplicated Acral Lick Granuloma

Canine Cystotomy

Conclusion • Lasers have a wide range of utility in veterinary

practice• The LLLT technique is very versatile for numerous

medical applications.• LLLT is non invasive, painless with no side effects• LLLT provides a unique way of healing in sync with

the natural healing processes of the body • More research has to be done to understand the

interaction of Laser light with cells and tissues.

Conclusion

• Laser surgery is a specialized technique of performing surgery.

• The great advantage of laser surgery in large animals is that it allows your surgeon to reach obscure areas and perform surgery through a minimally invasive approach.

• Laser surgery provides a better alternative for a blood less and pain less surgery.

• It makes possible otherwise the difficult procedures• It helps in faster recovery of patients

References • Veterinary Laser Surgery A Practical Guide By Noel Berger, Peter H. Eeg• Veterinary Cold Laser Therapy By Wm. L. Inman BS, DVM, CVCP• What is Cold-Laser Therapy? By Craig Amrine L.Ac.• Laser Surgery in Small Animal Practice—A Personal Perspective John C Godbold Jr,

DVM• Low Level Laser Therapy By Laurence J. Walsh. The University of Queensland,

Brisbane, Australia.• Mechanisms of Low Level Light Therapy By Michael R. Hamblin• Veterinary Cold Laser Therapy By Wm. L. Inman BS, DVM, CVCP• Please visit:

– www.mgh.harvard.edu/wellman/people/mhamblin.asp– www.Wikipedia.org– http://www.acvs.org– http://low-level-laser-therapy.org

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Laser will not make a practitioner abetter surgeon; it will, however, allow a good surgeon to dosurgery in a way that helps their patients and owners.