This document provides an overview of low power laser therapy. It discusses the physics of lasers, including stimulated emission and population inversion. The main types of lasers described are helium-neon and gallium arsenide lasers. Treatment techniques include gridding, scanning, and wanding. Important parameters for determining dosage are outlined, such as output power, time of exposure, and beam area. The effects of laser therapy include increased collagen synthesis and cell membrane permeability. Common indications are soft tissue injuries and wound healing, while contraindications include cancer and pregnancy.

1. Low Power Laser Therapy
Supervised by Capt; Myo Thein Tun
Presented by 2nd Lt; Paing Min Bwar

2. 1. Introduction
2. Physics
3. Types of laser
4. Laser generator
5. Laser treatment techniques
6. Effects of laser
7. Suggested treatment protocols
8. References
Contents

3. LASER ( Einstein – 1916)
 Light Amplification of Stimulated Emission Radiation
 Concentrates high energies into a narrow beam of
coherent, monochromatic light (Light Amplification of
the Stimulated Emission of Radiation)
 Use in industrial, military, scientific and medical
environments.
Introduction

4. • A helium/neon mixture at 632.8 nm and a variety of infra-red emissions, e.g .
865 nm and 904 nm → physiotherapy laser beams
• Helium/neon mixture → produces a red light
• Infra-red → produces no light.
• probe → may produce a single wavelength or a cluster of wavelengths.
Introduction (contd.,)

5. Physics
Visible light
400 (violet) to 700 nm (red)
Beyond red light
• Infrared
• Microwave region
Below violet light
• Ultraviolet
• X – Ray
• Gamma
• Cosmic ray region
Light
 a form of electromagnetic energy (wavelength = 100 – 10000 nm )
 Transmit through space as wave that contain tiny energy packets
called photons

6. • Top. White light contains electromagnetic energy of all
wavelengths (colors) that are superimposed on each other.
• Bottom. Laser light is monochromatic (single wavelength),
coherent (in phase), and collimated (minimal divergence)

7.  To explain principles of laser generation → Basics of the atomic theory
 Atom → smallest particle of an element that retains all the properties of that element.
 Neutrons and positively charged protons → in nucleus of the atom.
 Electrons (negatively charged) → equal in number to the protons and orbit nucleus at
distinct energy levels.
neutrons protons electrons Atom
Physics (Contd.,)

8. • Atom gains or loses an electron → become a
negatively or positively charged ion
• Difference (+ / - charged) electrons keeps electrons
orbiting nucleus at these distinct energy levels.
• Electrons neither absorb nor radiate energy as long
as they are maintained in their distinct orbit.
Physics (Contd.,)

9. • Unless electron absorbs an adequate amount of energy to move it to
one of its higher orbital levels → stay in its lowest energy level
(ground state)
• Electron changes orbit → gain or lose a distinct amount of energy; it
cannot exist between orbits.
• If a photon of adequate energy level collides with an electron of an
atom, it will cause electron to change levels. (excited state)
Physics (Contd.,)

10. • Atom stays in excited state only momentarily and releases an
identical photon (energy level) to one it absorbed and returns
to a ground state. (spontaneous emission)
• Energy is generated by collision of electrons that are
accelerated in an electrical field
Physics (Contd.,)

11. Stimulated Emissions
• When a photon interacts with an atom
already in a high energy state and
decay of the atom system occurs,
releasing two photons.
A photon released
from an excited atom
Stimulate another
similarly excited atom
De-excite itself by
releasing an identical
photon
Physics (Contd.,)

12. • Triggering photon → continue on its way unchanged
• Subsequent photon released (identical frequency, direction and phase)
• Two photons → promote release of additional identical photons as long as other
excited atoms are present
• A critical factor for this occurrence is having an environment with unlimited
excited atoms → Population inversion
Physics (Contd.,)

13.  Population inversion occurs → when there are more atoms in an excited state
than in a ground state. (applying an external power source to the lasting
medium.)
 Mirrors are placed at both side of chamber → to generate more photon.
 One mirror is totally reflective, where as the other is semipermeable.
 Photons are reflected within chamber which amplifies light and stimulate
emission of other photons from excited atom.
Physics (Contd.,)

14. • When a specific level of energy is
attained, photon of a particular
wavelengths are ejected through a
semipermeable mirror.
• Thus, amplified light through
stimulated emission (LASER) is
produced.
Physics (Contd.,)

15. • There are three properties of laser;
1. Coherence (in phase)
2. Monochromaticity (single colour or wavelength)
3. Collimation (minimal divergent)
• Coherence - Property of identical phase and time relationship.
All photons of laser light are the same wavelength.
Properties of LASER

16. • Monochromaticity - specificity of light in a single, defined wavelength; if the
specificity is in the visible light spectrum, it is only one color.
o The laser is one of the few light sources that produce a specific wavelength.
• Collimation - bending of light rays away from each other; the spreading of light.
Properties of LASER (Contd.,)

17. • Lasers are classified according to the nature of the material placed between two
reflecting surfaces.
• Lasing mediums used to create lasers include the following categories:
1. crystal and glass (solid-state),
2. gas and excimer,
3. semiconductor,
4. liquid dye, and
5. chemical.
Types of Lasers

18. Crystal
lasers
garnet lasers
aluminum
yttrium
neodymium
synthetic ruby (aluminum
oxide and chromium)
Gas lasers carbon dioxide
(CO2)
helium neon
(HeNe)
argon
gallium arsenide
(GaAs)
Types of Lasers (Contd.,)

19. • Liquid lasers → known as dye lasers because they use organic dyes
as the lasing medium.
o By varying the mixture of the dyes → wavelengths of the laser can
be varied.
• Chemical lasers → extremely high powered and frequently used for
military purposes.
Types of Lasers (Contd.,)

20. depending on intensity of energy
high
power
low
power
• Known as "hot" lasers
• thermal responses
• use in surgical cutting and coagulation,
ophthalmologic, dermatologic, oncologic,
and vascular specialties.
• known as "cold" or "soft" lasers
• for wound healing and pain
management
• No tissue warming occurs.
Types of Lasers (Contd.,)

21. Common use of
laser types
Gallium Arsenide
Lasers (GaAs)
(semiconductor
laser).
Helium Neon
Lasers (HeNe)
(gas laser)
Low- power laser
Types of Lasers (Contd.,)

22. Helium Neon Lasers
• uses a gas mixture of primarily helium with neon in a pressurized tube
• creates a laser in red portion of electromagnetic spectrum (wavelength 632.8 nm)
• Power output → vary from 1.0 to 10.0 mW (depending on the gas density used)
• Higher-power outputs → need larger tubes
• In Canada → up to 6mW (fewer US)
Types of Lasers (Contd.,)

23. • Laser output can decrease, depending on
1. care of equipment,
2. number of operating hours
3. whether fiber-optics is used.
• fiber-optics → causes a divergence of the beam from 18° to 21°
• fiber-optics → can decrease output delivery (50% or more)
• Fiber-optics is used to make delivery more convenient because the
size of the gas tube would make direct application difficult.
Types of Lasers (Contd.,)

24. Gallium Arsenide Lasers
• use a diode to produce an infrared (invisible) laser
(wavelength of 904 nm)
• Diode lasers → a solid-state semiconductor silicone
materials that are precisely cut and layered and used as a
lasing medium
• Electrical source → applied to each and lasing action is
produced at the junction of two material.
Types of Lasers (Contd.,)

25. • produce a beam (elliptical shape) →10° to 35° divergence, no fiber-optics
• Pulsed mode → 904 nm, Peak power → 2 W (US)
• In Canada (for clinical use)
o 780nm wavelength with a 5mW output, continuous mode delivery
o 810nm wavelength with a 20mW output, continuous mode delivery
o 830nm wavelength with a 30mW output, continuous mode delivery
• ES → spontaneous pain relief, Laser → more latent tissue reaponses
• Divergence → HeNe > GaAs
Types of Lasers (Contd.,)

26. Laser Generators
Laser
Generators
Optical
resonant
cavity
Pumping
Lasing
medium
Power
supply
lasers use an electrical power
supply that can potentially
deliver up to 10,000 V and
hundreds of amps
material that generates laser light.
type → gas, solid, or liquid.
used to describe process of
elevating an orbiting electron to a
higher, “excited” energy level
Contain lasing medium.
Once population inversion →
directs the beam propagation.

27. • should measure exact energy density emitted from applicator before treatments.
• Dosage is the most important and difficult to determine.
• Laser energy → is emitted from a handle remote applicator
• HeNe → semiconductor in the tip of applicator
• GaAs → componentry inside the unit and deliver laser light to target area through
a fiber-optic tube
LASER Treatment Techniques

28. LASER Treatment Techniques (Contd.,)
LASER
Techniques
Gridding
techniques
Scanning
techniques
Wanding
techniques
Tip → light contact with skin and directed perpendicular to target tissue

29. Gridding techniques
• a treatment area is divided into a grid of square centimeters,
with each square centimeter stimulated for the specific time.
• most frequently utilized method of application
• Lines and points should not be drawn on the patient’s skin,
because this may absorb some of the light energy
• If open areas are treated, a sterilized clear plastic sheet can
be placed over the wound to allow surface contact.
LASER Treatment Techniques (Contd.,)

30. Scanning techniques
• not contact between laser tip and skin (5 to 10 mm from the wound)
• beam divergence → decrease in the amount of energy as the distance
from the target increases.
• not recommended to treat at distances greater than 1 cm.
• a laser tip of 1 mm (30° of divergence), the red laser beam of the HeNe
should fill an area the size of 1 cm2 .
• infrared laser (invisible) → same consideration
• laser tip contact with an open wound → tip should be cleaned
thoroughly with a small amount of bleach or other antiseptic agents to
prevent cross-contamination.
LASER Treatment Techniques (Contd.,)

31. Wanding techniques
• different from the scanning technique, in which a grid area is birthed
with the laser in an oscillating fashion for the designated.
• As in the scanning techniques, the dosimetry is difficult to calculate if a
distance of less than 1 cm cannot be maintained.
• The wanding techniques is not recommended because of irregularities
in the dosages.
LASER Treatment Techniques (Contd.,)

32. Dosage
Parameters of Low-Output Laser
HeNe GaAs
Laser Type Gas Semiconductor
Wavelength 623.8 nm 904 nm
Pulse Rate Continuous wave 1-1000 Hz
Pulse width Continuous wave 200 nsec
Peak Power 3 mW 2W
Average Power 1.0 mW 0.04 – 0.4 mW
Beam area 0.01 cm 0.07 cm
FDA class Class II laser Class I laser
Copied with permission from Physio Technology

33. • The pulsed mode drastically reduce the amount of energy emitted from the laser.
E.g., a 2-W laser is pulsed at 100Hz:
• Average Power = pulse rate x peak power x pulse width
= 100Hz x 2W x (2x10-7 sec)
= 0.04 mW
• Pulse rate = 1000 Hz → Average power = 0.4 mW
• Adjustment of pulse rate → alter average power (Significantly affect treatment
time if specific amount of energy is required)
Dosage (Contd.,)

34. • Total number of Joules is more important (recent evidence)
• Dosage or energy density of laser = J/cm2 or m J/cm2
• One Joule = 1 W/sec
Dosage (Contd.,)
dosage is dependent on;
Output of laser in mW
Time of exposure in sec
Beam surface area of laser in cm2

35. • After setting pulse rate (determine average power of laser), treatment time per
cm2 needs to be calculated
Dosage (Contd.,)
TA = (E/Pav) X A
• TA = Treatment time for given area
• E = mJ of energy per cm2
• Pav = Average laser in mW
• A = Beam area in cm2

36. • E.g., To deliver 1 J/cm2 (E ) with a 0.4 mW (Pav ) average power GaAs laser
with a 0.07 cm2 ( A ) beam area:
• TA = (E/Pav) X A
• TA = (1 J/cm2 / 0.0004 W ) X 0.07 cm2
= 175 sec or 2:55 min
• GaAs → can only pulse 1000 Hz, resulting in average energy of 0.4 mW
• Treatment time may be exceedingly long to deliver same energy density with a
continuous wave laser
Dosage (Contd.,)

37. • Any energy applied to body can be absorbed, reflected, transmitted and refracted.
• Absorption of energy → result biological effect
• Laser light’s penetration → depends on type of laser energy delivered
Depth of Penetration
Absorption
of HeNe
indirected effect (deeper tissue)
directed effect (superficial structure) 2 to 5 mm of soft tissue
Normal metabolic process in deeper tissue are catalyzed
from energy absorption in superficial structure
8 to 10 mm of soft tissue

38. • GaAs → better potential for treatment of deeper soft tissue injuries (e.g., strains,
sprain, contusion)
Depth of Penetration (Contd.,)
Absorption
of GaAs
indirected effect
directed effect 1 to 2 cm
up to 5 cm

39. 1. Increases collagen synthesis – useful for tissue repair.
2. Increases permeability of cell membranes with increase efficiency of
sodium pump.
3. Increase number of fibroblasts and promotes granulation tissue – useful for
wound healing.
4. Increase in cellular ATP, which is useful for pain relief.
5. The effects spread from one cell to another, and therefore to surrounding
tissues.
6. Decrease microorganisms
Effect of LASER

40. 1. Open wounds – ulcers, postoperative wounds.
2. Skin conditions – psoriasis, burns.
3. Soft-tissue injuries – tendons, ligaments and muscles.
4. Scar tissues
5. Degenerative and inflammatory arthropathies.
6. Pain relief over trigger or acupuncture points. The main beam is useful for
localized lesions, e.g. soft-tissue injuries and trigger points.
Indications

41. • The potential applications for low-power lasers include treatment of
o tendon and ligament injury,
o arthritis,
o edema reduction,
o soft-tissue injury,
o ulcer and burn care,
o scar tissue inhibition, and
o acutherapy.
Indications (Contd.,)

42. 1. Carcinoma → cancerous growth
2. Skin irritation.
3. First Trimester of pregnancy
4. Chest treatment in cardiac patients should be avoided, together with those who
have a pacemaker.
5. Directly over eyes → retinal burns
Contraindications

44. • Therapeutic modalities, Second edition
References