LASER AND CRYOSURGERY AND ITS APPLICATION

Prepared by:Ganga Prasad Yadav

INTRODUCTION

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

The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation”.

Laser produce electromagnetic radiation, requires no medium for its transmission because it can travel through the vacuum of space. It can also travel through matter in the form of gases, liquids or solids. The speed and direction of the propagation of radiation will be changed upon the transition from one medium to another in the form of heat. Red (660 & 635 nm), green (532 & 520 nm) and

blue-violet (445 & 405 nm) lasers

PRODUCTION OF LASER

Functional laser Production requires 3 things, optical resonant cavity that contains the lasing medium and external energy source.

Electron is pumped to a higher energy level by supplying energy

The electron in the meta stable state jumps to a lower level releasing a photon

The photon interacts with another electron in the meta stable state. This interaction produces another photon at the same wavelength and same phase.

These photons are reflected by mirror and the laser beam comes through the partially transparent mirror.

PROPERTIES OF LASER

MONOCHROMATIC : Single color/ wavelength.

COLLIMATED : Non-divergent (single direction), tight beam and parallel paths

COHERENT : Parallel waves of laser light moves in a phase, reinforcing each other as they travel through space

CLASSIFICATION OF LASER

Broadly classified into 2 groups High power lasers or surgical lasers: indicated for surgery (cutting,

coagulation, cauterization) and ablation effects (cavity preparations, prevention).

Low power lasers or therapeutic lasers: widely used for therapeutic and bio-stimulating purposes, which mainly act as accelerators of healing processes.

PURPOSE OF LASER SURGERY

Cut or destroy tissue that is abnormal or diseased without harming healthy or normal tissue.

Shrink or destroy tumors & lesions. Close off nerve endings to reduce

postoperative pain. Cauterize blood vessels to reduce blood

loss. Seal lymph vessels to minimize swelling

& decrease spread of tumor cells.

BENEFITS OF LASER SURGERY FOR PATIENTS

Less Bleeding

Less Pain

Less Swelling

Reduced risk of infection

Quicker recovery time

BENEFITS OF LASER SURGERY FOR SURGEON

Unique surgical capabilities.

Enhanced visibility of the surgical field.

Increased precision & control.

Reduction of surgery time.

INTERACTION OF LASER WITH TISSUE

A highly focused laser beam can efficiently ablate the living tissue. At the same time, it seals capillaries, small blood vessels, lymphatic & nerve endings

Depends upon target tissue composition and laser wavelength and time of its use.

Four different basic interactions of laser light at the surface it strikes i.e., reflection, scatter or transmission and absorption.

PHOTOBIOLOGY

Photobiologic effect consists of 1. Photochemical 2. Photothermal 3. Photomechanical

Photochemical effect Laser light is absorbed and converted into chemical energy, resulting in

tissue destruction. Directly breaks the complex organic biochemical bonds, resulting in tissue

destruction or alteration.

PHOTOTHERMAL EFFECT

Laser light is absorbed & converted to heat within the tissues . Water, hemoglobin, melanin & some proteins – Absorb varying wavelengths

of laser light. At 40-60 degree Celsius – Hyperthermia occurs causing contract, constrict or

destroy blood vessels resulting in tissue hypoxia and cell death. At 60-100 degree Celsius – Coagulation occurs, collagen contracts and

proteins are denatured. Vaporization occurs as tissues are superheated (> 100 degree Celsius) and

solid tissue becomes gaseous vapor. Used for endoscopic control of bleeding. Examples : Bleeding ulcers

PHOTOMECHANICAL EEFECT

Pulsed laser light can be converted into acoustical energy upon impact create a shock wave that disrupts the target tissue.

Short, high power laser energy pulses are directed at tissue through a small core optical fibre.

Maximum vaporization efficiency & minimum energy deposition into the tissue .

Reduces tissue carbonization & thermal necrosis at the edge of incision.

Example : Lithotripsy & Ophthalmic surgery.

SELECTION OF LASER Depends on:

Tissue characteristics. Whether procedure requires cutting, ablation or coagulation.

Carbon dioxide laser & Erbium: YAG laser Good cutters but poor coagulators.

Wavelengths greater than 2,500nm. Extinction depth – less than 1mm.

Diode laser & Nd : YAG laser. Good coagulators but poor cutters. Wavelength between 600nm to 1,400nm. Area affected – 5mm to 10mm. Thermal damage.

DIFFERENT TYPES OF LASER

Carbon dioxide laser (10,600 nm ) : highly absorbed by water and rapidly absorbed within the first 0.1 to 0.3 mm of tissue. Good ‘cutter’ but poor cauterizer.

Argon laser (524 nm) : Penetrates 2-3mm . Highly absorbed by haemoglobin.

Tunable dye laser (400 -1000 nm) Nd : YAG laser (1064 nm ) - Penetrates 4-5 mm of tissue.

Highly absorbed by water & haemoglobin. Good cauterization.

Potassium titanyl phosphate laser (KTP : 532 nm ) Diode lasers (635-675nm): used for photodynamic therapy

POWER DENSITY

Intensity of laser beam. Directly proportional to the power that a laser can deliver. Inversely proportional to the surface area that the beam

strikes. Units: W/cm2 For optimal ablation & incision of tissue : High power density and Small focal spot size. For coagulation : Low power density and Large focal spot

size.

EQUIPMENTS AND PREPARATION

Specially trained veterinarians. Laser hazards & safety. Laser delivery system

Flexible fiber. Eg., Nd:YAG laser, Argon laser Articulated arm. Eg., CO2 laser

Smoke evacuation system. Protective goggles and face mask. Hand piece – Straight & angled. Focusing tips – To focus laser beam emerging

from the fiber. 1.4mm , 0.8mm, 0.4mm & 0.3mm.

Sterile surgical pack – Additional hand piece, instruments, gauze, sterile saline.

Moistened gauze – barrier to absorb any stray beams of laser energy.

Octylated cyanoacrylate – clear tissue adhesive, most useful in feline declaw procedures, routine spay and neuter procedures.

EQUIPMENTS AND PREPARATION

SURGICAL TECHNIQUE

Laser surgery done either by contact or non-contact mode.

Tension is applied across the planned incision site using digital manipulation .

The hand piece is held perpendicular to the target, and the incision is made with hand speed appropriate for tissue separation under tension.

Using a pulsed pattern allows the tissue to cool between laser energy bursts, thus minimizing char.

Once completed, the edges are wiped free of excessive char using sterile, saline-soaked gauze.

APPLICATIONS OF LASER SURGERY

GENERAL SURGERY PROCEDURES: Traumatic wound debridement, Everted saccule resection, Hepatic lobectomy, Thyroidectomy, Cystotomy, Mast cell tumors, fibrosarcoma, Enterotomy, Perianal tumors, Urethral prolapse removal, Granulation tissue shaving, Tail amputation etc.

OPHTHALMOLOGY SURGERY PROCEDURES: Cherry eye , Entropian , Distichia , Eyelid tumor removal, Ectopic cilia etc.

APPLICATIONS OF LASER SURGERY

ENT AND ORAL SURGERY PROCEDURES: Oral mass excision, Ear cropping, Aural hematoma, Ear canal polyps, Stenotic nares repair, Gingival hyperplasia, Ranulas, Salivary gland removal etc.

DERMATOLOGY SURGERY PROCEDURES: Cutaneous masses ,Hyperkeratosis of digital pads, Papillomas, Acral lick granuloma ablation etc.

ELECTIVE PROCEDURES: Castration, Ovariohysterectomy etc.

LASER SAFETY A sign indicating a laser is in use should be kept at the entryway of the laser treatment

area Aseptic technique should be maintained . Eye shields/goggles, protective face mask must be worn at all times by all personnel. Safety shields on the patient’s eyes must be used. Safety orientation for laser use should be required of all surgeons, anesthesia personnel

and operating room staff. If cloth drapes are required, it is recommended that heavily moistened sterile towels be

used in the immediate area of the surgical field; the towels become flammable if they are dry.

Paper drapes should not be used because they can be easily burned; laser resistant drapes are available.

If general anesthesia is used, it is recommended that oxygen supplementation be minimized during laser surgery.

Avoid use of alcohol or any flammable material in the surgical field preparation. Use a smoke evacuation system while the laser is at work.

CRYOSURGERY

Cryosurgery (cryotherapy) is the use of extreme cold in surgery to destroy abnormal or diseased tissue.

Used to treat a number of diseases and disorders, especially a variety of benign and malignant skin conditions.

Cryosurgery works by taking advantage of the destructive force of freezing temperatures on cells. When their temperature sinks beyond a certain level ice crystals begin forming inside the cells and, because of their lower density, eventually tear apart those cells. Further harm to malignant growth will result once the blood vessels supplying the affected tissue begin to freeze.

DIFFERENT METHODS OF CRYOSURGERY

Liquid nitrogen Cryogun used to spray liquid nitrogen

A common method of freezing lesions is using liquid nitrogen as the cooling solution. This −196 °C (−321 °F) cold liquid may be sprayed on the diseased tissue, circulated through a tube called a cryoprobe, or simply dabbed on with a cotton or foam swab.

Carbon dioxide Carbon dioxide is also available as a spray and is used to treat a variety of benign spots. Less

frequently, doctors use carbon dioxide "snow" formed into a cylinder or mixed with acetone to form a slush that is applied directly to the treated tissue.

Argon Recent advances in technology have allowed for the use of argon gas to drive ice formation.

This gives excellent control of the ice, and minimizing complications using ultra-thin 17 gauge cryoneedles.

Dimethyl ether – propane A mixture of dimethyl ether and propane is used. The mixture is stored in an aerosol spray type

container at room temperature and drops to −41 °C (−42 °F) when dispensed. The mixture is often dispensed into a straw with a cotton-tipped swab.

TYPES OF CRYOSURGERY DEVICES

1. Cryoprobe: Accurate Pinpoint Precision Penetration of lesion is faster and deeper

with minimal surface truma Freezing Power and Pressure with the touch

of your Fingertip Freezing rate of cryoprobe is 1mm per 5

seconds Depth of treatment: the cryoprobe freezes

up to a maximum 5 mm cell structure2. Cryo spray by using straight spray aperture

having different aperture sizes.Used for lesion on outside of the body.3. Cryo swab: less preferred

BENEFITS OF CYROSURGERY IN VETERINARY MEDICINE

PainlessNo PreparationNo post operative careNo open wounds – No BleedingNo suturingNo general anthesia – safe for older animalsRapid treatment timeCost EffectivePressure to treat lesionPinpoint Accuracy

USED TO TREAT

• Perianal Adenomas• Epulis• Pappilomas• Lick Granulomas• Warts• Small Sarcoids• Eye Lid Tumors

Skin Tumor before treatment

REFERENCES

Veterinary Laser Surgery A Practical Guide by Noel Berger and Peter H. Eeg

http://support.cpdpro.org.uk/article/171-photobiology-and-safety https://en.wikipedia.org/wiki/Cryosurgery

Thank you