Sasna.p.s

Laser & Its

Applications in

Biology

What is a Laser ?

A laser is an amplifier which emits electromagnetic energy in the form of a concentrated light beam.

LASER –Light Amplification by Stimulated Emission Of Radiation

Based on the principle of stimulated radiation by Einstein in 1917.

A laser differs from other sources of light because it emits light coherently.

Spatial coherence allows a laser to be focused to a tight spot.

Charles H. Townes (left), winner of the 1964 Nobel Prize for Physics, and associate James P. Gordon in 1955 with the first maser ( Microwave amplification by stimulated emission of Radiation)

Laser principle If a few photons of energy E(excited state energy) – Eo (ground state energy ) are introduced these immediately stimulate the emission of a number of photons of the same kind.There is a increase in number of photons and theses again stimulate the emission of more photons .In this way a chain reaction is formed and as a result all the atoms present give up their photons rapidly .

This process is called laser action or light amplification by stimulated emission of radiation as the original pulse of photons has been amplified in to a more powerful pulse of light .

Nature of laser light

Monochromatic light ( all Photons have same energy above the ground level, same frequency ,single wave length )

Coherent light (all photons or waves in phase )

Unidirectional light (emitted waves are parallel )

High intensity

Ruby laser beam First successful development of laser (1960) Ruby crystal ( aluminium oxide with a chromium

impurity) Laser beam is produced by exciting the molecules of

ruby crystal . Molecules of ruby crystal then emit a characteristic red

light and excite neighbouring molecules and process continues like a chain reaction.

Both ends are silvered which keeps on reflecting and thus amplifying intensity of light (one end is partially silvered )

Sides are kept free to allow light from pumping lamp Powerful beam of red light emerges through a section

at one end of ruby crystal which is only partially silvered .

Types of Lasers(medical use)

Argon

Argon/Krypton

Tunable Dye

Yttrium-Aluminium –Garnet (YAG )

Mechanism of lasers

Photocoagulation (thermal lasers)

Photo Disruption(cutting effect on Tissues)

Photo Evaporation(carbon dioxide laser) -long wavelength IR heat beam

Photo decompostion-Excimer laser (breaks chemical bonds of biological materials, very short wavelength)

Application of laser beam

Diagnostic

Therapeutic

Surgical

Diagnosis Ultrasensitive analytical methods To detect even a single

atom or molecule (metabolic study & Toxicology)

To localize early lung cancer

Laser beam exhibits Fluorescence pattern difference b/n normal and atherosclerotic vessels ( Vascular surgery)

Fiber optic endoscopy( can be focused to internal organs

Holography (3 dimensional photography)

Measurement of capillary blood flow

Surgeries such as laser-assisted in situ keratomileusis (LASIK) are aimed at reshaping the tissues ofthe eye to correct vision problems in people with particular eye disorders, including myopia and astigmatism.

Therapeutics Phototherapy of neonatal jaundice ,cancer & various

skin diseases

Cancer photo chemotherapy( laser beam can be focused to internal organs which helps for single administration of therapeutic dose In the organ)

In the standard form of phototherapy, baby lies in a bassinet or enclosed plastic crib (incubator) and is exposed to a type of fluorescent light that is absorbed by baby's skin.

During this process, the bilirubin in the baby's body is changed into another form that can be more easily excreted in the stool and urine.

Phototherapy doesn't damage a baby's skin.

PHOTOTHERAPY

Photodynamic therapy (PDT) fiber optic surgery photosensitive drug absorbed by cancer cells can be activated by a laser beam guided through optical fibers to selectively destroy a tumour.

Surgery Proliferative Diabetic Retinopathy (Photocoagulation)

Treatment of Glucoma( to open up Blocked canals-Microsurgery )

Microsurgical Technique for alteration of structure at sub cellular level.

Microsurgical technique For genetic study

DIABETIC RETINOPATHY

Other uses in Medicine Surgical removal of tumours in selected cases Endoscopic diagnosis for early malignancy Laser knife for reduction in blood loss & pain Cosmetic surgery(facial wrinkles & deep scars) Holmium cold laser (alternative to bypass surgery and

angioplasty ) Copper vapour laser (vascular disorders ) Holmium laser (orthopedic surgery ) Nd:YAG laser (for approaching difficult recesses of the

mouth remaining painless & no local anaesthesia) Uv excimer Lasers (Treatment of rootcanal ) Eye therapy

ROOT CANAL TREATMENT

Glucoma Treatment

The laser beam (a high energy light beam) is focused upon the eye's drain. The laser does not bum a hole through the eye. Instead, the eye's drainage system is changed in very subtle ways so that aqueous fluid is able to pass more easily out of the drain, thus lowering IOP (intraocular pressure)

Advantages The unique Properties of laser light allow the beam to

be focused down to extremely small spots resulting in very high energy densities that are the basis of the tissue altering effects.

Patient compliance increases because of Reduced hospital stay.

A safer & quicker alternative to surgery.

Serious ocular diseases can be treated.

Effective therapeutic modality is offered by experienced surgeon.