Dr. Amal, & Mr. Chandrasekar.L
PHT 221 – 1st SEM – 1435-1436H
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Laser devices
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This lecture deals about the topic laser in following
sub-categories;
Overview, definition, Basic principles & production
of laser
1.
2. Indications & Contraindications of laser
3. Physiological & Therapeutic effects of laser
4. Methods of application / Treatment procedure – An
overview of clinical application
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At the end of the lecture the student should be able
to

Recall physics, definition, properties & production
of laser.

Describe types of laser, classification of laser,
therapeutic effects, indications, contra-indications,
dangers and precautions of laser

Technique of laser application
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Overview
Definition: -

Laser is an Acronym for the Light amplification

by the Stimulated emission of Radiation.
Therapeutic laser is also known as Soft laser,

Cold laser, Low intensity laser, class III A B,
optic laser
Laser is a beam of light which is used for
various purposes.
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
Low intensity or low level laser is the
therapeutic application of relatively low
output (500 mw) laser and monochromatic
super luminous diode for the treatment of
disease and injury at dosages (usually 35
J/cm2)

Laser photo modulation: is the biological
mechanism involved to get the beneficial
effects of laser
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1. Penetrate the skin with no heating effect,
no damage to the skin & no side effects.
2. It directs bio-stimulative light energy to
body cells which convert into chemical energy
& promote natural healing & pain relief.
3. Optimize the immune response, & ha anti
inflammatory effects.
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

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Mono chromaticity
Collimation
Coherence
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Mono chromaticity:

The light produced by a laser is of a single color.

The radiation emitted being of a single wavelength.
e.g. ruby laser give a red light at694.3 nm
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Collimation

The rays of light or photons produced by the laser
are practically parallel with almost no divergence
occurring.

This lead to optical power to be bundle in small
area
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Coherence

The light emitted is in phase, which means that the troughs
and peaks of the emitted waves match perfectly in time
(temporal coherence) and space( spatial coherence).

The coherence length : is the distance over which the wave
length is stay in phase. It varies from less than a millimeter
to hundred of meters.
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PRODUCTION
1.Principle of production
2.Functional Parts
3.Working



4.Parameters

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1.Lasing medium
2.Energy Source
3.Mechanical Structure
PODUCTION
Energy
Components of a typical
laser:
1. Gain medium
2. Laser pumping energy
3. High reflector
4. Output coupler
5. Laser beam
Lasing Medium
LASER
Mechanical Structure
A helium–neon laser demonstration
A commercial laser diode
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
In a laser when electrons are stimulated at a rate resultant
photons are aligned in a reflecting chamber or resonant
cavity, composed of mirrors.

Photons hit a semi-permeable silver resonating mirror and are
reflected back to a reflecting mirror.

This back and forth reflection of photons intensifies the light
until the chamber can’t contain energy level. The photons are
then ejected through the semi-permeable mirror and out
through the diode in the applicator head.
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
Diode based unit

Multisource cluster array , made from a
number of diodes (up to 180) used for large
area

Flexible multisource array devices, allow
efficient delivery of light to tissue.
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Class II
Class I
Low power out
-
-
-
Power out put
Placed in the
-
visible region of
invisible EMS
EMS
and eyes
for momentary
Used for black
board pointer
-
Limited clinical
application
High power out
put  500 mW
Placed in the
-
visible and
invisible EMS
-
Unsafe for skin
and eyes
Safe for skin but
-
viewing only
-
-
mW
Safe for skin and
-
Class IV
put 1mW-500
Placed in the
visible and
Danger to skin
Mild power out
-
one mW
put (5mw)
-
Class III
not for eyes
-Surgical application
protective
goggles is needed
-
Used for Pt
treatment
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Types of Laser
1.Helium Neon Laser : 632.8nm
2.Ruby Laser: 694.3nm

3.Gallium Laser : 750nm

4.Aluminum Laser : 780nm
5.Arsenide : 810nm



6.Diodes Laser :820nm

7.Carbon Dioxide : 10000nm

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INFRARED LASER

Emit infrared radiation at a wavelength of 830 nm either
from Ga-As, or Ga-Al-As semi-conductors diodes

The depth of penetration is deeper than He- Ne laser

This device is small and relatively cheap

It give both continuous and pulsed out put

The continuous wave diode laser are usually of low power,
while the pulse mode the pulse frequency can be varied.
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SUPER LIMINOUS DIODES

It is fully monochromatic, collimated but not
coherent

They are widely used in therapy
RUBY LASER:

Produce red light at a wavelength 694.3nm
He- Ne LASER:

Produce red light at a wavelength 633nm and
frequency which is higher than that of IR laser
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
Laser wavelength

Nature of tissue surface

Angle of incidence

The penetration depth of 1-2 mm for red light of
He-Ne laser and 2-4 mm for IR laser of 800900nm
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Cellular effects
Effect on nerve
conduction and
regeneration
Effect on
vasodilatation
• Increase ATP
synthesis
• Increase rate of nerve
conduction
• Reduce cellular pH
• Increase frequency of
action potential
• Initiate reaction of
cell membrane
• Increase
macrophage,
fibroblast, and
lymphocyte activity
• Increase
microcirculation that
help in acceleration
of wound healing
• Decrease sensory
latency
• Accelerate nerve
regeneration
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THERAPEUTIC EFFEECTS OF
LASER
PAIN RELIEF ◦
G.C.T. ◦
 Serotonin ◦
Endorphin secretion ◦
Acute & Chronic pain ◦
Pain site, trigger points, ◦
Acupuncture points ◦
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THERAPEUTIC EFFEECTS OF
LASER
Tissue healing

Phagocytosis, Collagen Synthesis, Contracture
CUMMING’S EXPERIMENT


BIOSTIMULATION THEORY (Biochemical,

Physiological, Proliferative  Proliferation of
fibroblasts, reepithelisation & remodeling)
PHOTOCHEMICAL THEORY

Chromophores  Bio stimulation

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BEFORE & AFTER LASER
BEFORE & AFTER LASER
1.Incisions
2.Osteoarthritis
3.Rheumatoid arthritis
4.Ankle sprain
5.Chronic Low back pain
6.Tennis Elbow
7.Bicipital tendinitis
8.Trigger Finger
9.Chronic ulcers
10.Wounds
11.Tenosynovitis
12.Carpal Tunnel Syndrome
13.Periarthritis
14.Sports injuries
Active or suspected carcinoma
With in 4-6 months following radiotherapy
Hemorrhage
Local endocrine gland
Pregnant uterus
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Epilepsy
Disoriented
patients
Sympathetic
ganglia
Vagus nerve
Fever
Decrease
sensation
Epiphyseal
line in
children
Infected
tissue
Cardiac region
with heart
disease patient
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1.
Preparation of patient
2.
Preparation of the device
3.
Application of the treatment
4.
Termination of treatment
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Parameters
1.Security switch
2.Timer
3.Mode
4.Sensor
5.Fiber optic cable
6.Probe
7.Probe switch
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Wavelength :

Visible red laser used for superficial

Infrared laser used for deeper musculoskeletal system
Power out put :

It is measured with mW or thousand of watt.

Higher out put devices 30-200 mw that should be applied for
short time.

Popular devices out put are 1-10 mw
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Irradiance (power density):

It is measured with mW/cm2

In contact application the irradiance is calculated dividing the
power output by the spot size of the treatment head the typical
value of head is 0.1 -0.125 cm2
Energy:

This is given in joules (J) for point irradiated or sometimes for
the total area where a number of points are treated
Energy density = Power (W)  Time (sec) 
Treatment Area ( cm²)
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Energy density:

Measured by J/cm2

It is ranged from 0.5- 32 J/cm2

1-10J/cm2 is the most common
Pulse repetition rate:

It is either continuous or pulsed

For acute cases low pulse frequency and long pulse duration

For chronic cases, high pulse frequency and short pulse duration
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Area of the treatment:

Large area , the part is divided into centimeter
square like a grid and each area is separately
stimulated or scanning technique is used.
Progression of the treatment:

Five to six treatment are sufficient
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Select the most appropriate treatment
method:

Large area : use scanning technique.

Pain for small area: use infrared laser unit.
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
The treatment head should be held firmly
and perpendicular to the target tissue.

The amount of the pressure is depend on
the depth and the site of the target tissue.

In open wound disposable film can be used
over the end of the treatment head
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
Minimal reflection so more light energy is delivered
to the target tissue.

Depression between the treatment head and the
target tissue helps to minimize attenuation of the
beam.
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
spot method: isolated point are treated.

Lineal method: irradiate along the neural
route related to the painful area.

Combined method.
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
It used mainly for the treatment of broke
skin or open wounds.
Types:

Scanning methods

Gridding method
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
It is classified into two stages:
a. First stage: marginal application:

Contact technique is used to treat a
series of points around the wound
margin approximately about 1 cm from
the end of the margin.

The initial dosage is 0.5-1 J/ point or 4-8 J/cm2.
The primary aims in this stage are:

Accelerate the migration of cells.
Increase blood flow to the wound area

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b. Second stage: wound bed application:

Using the non-contact technique for wound
bed

Scanning devices and multisource cluster
treatment units are used.
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Scanning devices:

It is used for treatment of a large area. The
scanner technique provide a uniform dosage
across the whole area.

He-Ne systems have been used on a movable
arm which manipulated by the therapist.
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Multisource cluster device:

It is used for non-contact technique represent a
good means of irradiating a sizable area of wound
simultaneously.
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
The area to be treated is visualized as being
covered with grid work of squares measuring 1cm
x1 cm.

Treatment is applied systematically to each square
using a single diode or fibreoptic applicator from
a distance of no more than 0.5-1 cm.
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
An energy density of 1.5-2.5 J/cm2 in each
irradiated gird square is recommended as a
minimum
for
the
early
stages
of
wound
management.

A 30 mW unit for such treatment , the treatment
probe would be used to irradiated each square
for a total of 50 sec to deliver 1.5 J/cm2 in non
contact mode.
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