Laser in electrotherapy for physiotherapy ppt by Dr. Mumux

1. LASER

2. WHAT DO YOU MEAN BY LASER???

3. WHAT DO YOU MEAN BY LASER???

4. BUT

7. INTRODUCTION
• The term "laser" originated as an acronym for "Light
Amplification by Stimulated Emission of Radiation".
• A laser is a device that emits light through a process of optical
amplification based on the stimulated emission of
electromagnetic radiation is used to produce very intense, highly
directional, coherent and monochromatic beam of light.
• Velocity of travel is equal in a vacuum but may vary within
different media.
• Direction of propagation is in a straight line.
• Lasers are electromagnetic wave amplifiers which can produce
pencil-like beams of electromagnetic waves with special

8. • The pencil-like beam of the laser means that the wave
energy is always concentrated on the same area: the
intensity does not decrease appreciably with distance due
to beam spreading.
• A magic rays used for physiotherapeutic purpose is known
as Low Intensity Laser Therapy used in injuries and lesions
to stimulate healing process in the tissues, pain reduction,
increase circulation and reduce swelling. The effect is
completely painless, fascinating and pleasant upon patients.

9. Apart from physiotherapeutic uses Laser is used in:
• Medicine: Bloodless surgery, laser healing, surgical
treatment, kidney stone treatment, eye treatment, dentistry
• Industry: Cutting, welding, material heat treatment,
marking parts, non-contact measurement of parts
• Cosmetic skin treatments: acne treatment, Stretch marks
reduction and hair removal.

10. • Law enforcement: used for latent fingerprint detection in the
forensic identification field
• Research: Spectroscopy, laser ablation, laser scattering, laser
interferometer etc.
• Product development/commercial: laser printers, optical discs
(e.g. CDs and the like), barcode scanners, thermometers, laser
pointers, holograms.
• Laser lighting displays: Laser light shows as an entertainment
medium

11. PROPERTIES OF LASER:
Monochromaticity
Coherence
Collimation

12. MONOCHROMATICITY
• Light from the sun, or a light bulb, is generally seen as "white",
and contains many wavelengths of light (seen as different
colors when white light is put through a prism).
• But Laser light is highly monochromatic meaning that it
contains a single specific frequency and one specific
wavelength of light.

14. • This wavelength of light can be seen as one single,
intense color (red in ruby laser at 694 nm
wavelength, blue, green, or yellow, etc., depending
on the laser) or invisible (ultraviolet or infrared).
• Lasers can, and do, produce more than one color,
but these colors are discrete individual
wavelengths of light and definite frequency, as
opposed to the broad spectrum of sunlight or
fluorescent light.

15. COHERENCE (SIMILAR)
• Laser Light is Highly Coherent.
• Wavelengths can be thought of as "organized".
• All photons have the same phase and the same
polarization that means peaks and troughs of the
electric and magnetic fields all occur at same time.
(Temporal coherence), hence they produce a very high
intensity when they superpose.

17. • Light from a light bulb, for instance, has wavelengths that
have random phases and polarization, and hence they are
relatively much weaker.
• It's the coherent, organized property of laser light that
makes it capable of delivering a high amount of energy in a
small beam. In the case of visible lasers, this makes the laser
beam very bright and intense.
• They are all travelling in the same direction (spatial
coherence). The distance at which the wavelengths stay in
phase is called the coherence length. It can be thousands in
meters in air but much less a fraction of millimeter in
biological tissues.

18. COLLIMATION
• Laser Light is Highly Directional because beams of laser light
are very small, tight, and bright. Photons in a laser beam are
traveling almost exactly parallel to each other.
• For instance, if a flashlight and a laser beam were shone on a
building across the street from your home, the flashlight beam
would appear several feet wide, while the laser beam would
be only be inches across Sharply Focused.
• Due to the laser light's parallelism, it can be focused very
efficiently compared with other types of light. Focused laser
beams can deliver very high amounts of energy over a larger
distance.

20. • Ordinary visible radiation is like a crowd of people all in
different clothing, walking in different directions out of
step.
• Whereas,, LASER RADIATION IS LIKE A COLUMN OF
SOLDIERS ALL MARCHING IN STEP (IN PHASE) IN THE SAME
DIRECTION (SPATIAL COHERENCE) AND WEARING A SAME
UNIFORM (MONOCHROMATIC)

21. PHYSICAL PRINCIPLES OF LASER
• It is same as electromagnetic radiation.
• Laser light can reflected, refracted, scattered and absorbed
so collimation is diminished and coherence is lost which
depends on the nature and density of matter present.
• It can pass unaffected through space and slightly altered in
air but markedly altered on entering a more dense material
like tissues. In biological tissues coherence is lost but it will
still have a precise frequency.

22. PRODUCTION OF LASER
• The Basis of production of LASER is based on..
Spontaneous emission
Spontaneous Absorption
Stimulated emission

23. • Matter is made up of atoms.
• At the centre of the atom lies the nucleus; it is constituted of
protons and neutrons. A proton carries a positive charge but a
neutron does not carry any charge. Outside the atom is a cloud of
electrons that carry negative charges; they are in motion
surrounding the nucleus.

24. • By quantum mechanics, which describes the microscopic world,
each electron stay at a certain energy level and different energy
levels correspond to different energies of the electrons.
• To simplify the picture, we could imagine the energy levels as
some orbits surrounding the nucleus; the farther away they are
from the nucleus, the higher their energy would be, as shown in
Fig.
• Moreover, the maximum number of electrons that each orbit can
accommodate differs as well. For example, the lowest orbit (the
one closest to the nucleus) has a capacity of two electrons, while
the higher orbit can hold at most eight.

25. • When energy is added to atom an outer electron may
gain sufficient energy to free itself from nucleus. The
atom then becomes a positively charged ion and electron
becomes free negative charge. When the outer electrons
are in one of the higher energy states they will tend to
return to a lower energy state, sometimes to the most
stable or ground state. Here it emits radiation in the form
of electromagnetic waves.

26. POPULATION INVERSION
• Normally, a system of atoms is in temperature equilibrium and
there are always more atoms in low energy states than in higher
ones.
• Although absorption and emission of energy is a continuous
process, the statistical distribution (population) of atoms in the
various energy states is constant.
• When this distribution is disturbed by pumping energy into the
system, a population inversion will take place in which more
atoms will exist in the higher energy states than in the lower.

27. SPONTANEOUS ABSORPTION
• An electron transit from a lower energy level to a
higher one by absorbing a photon (Fig. a) E2 - E1
＝hv

28. SPONTANEOUS EMISSION
• An electron spontaneously emits a photon to
transit from a higher energy level to a lower one.
Atom is initially in upper state E₂ drop to E₁ level
by emitting a photon of energy hv.

29. STIMULATED EMISSION
• It is a unique event which an incident photon interacts with an atom
which is already excited.
• Additionally the quantum energy of the incident photon must exactly
equal the difference in energy levels between the electron’s excited
and resting states.
• Here while returning to its original orbit the electron gives off its
excess energy as a photon of light with exactly the same properties as
the incident photon and completely in phase.
• SER are produced through the selection of an appropriate material or
substance which when electrically stimulated will produce large
number of identical photons through the rapid excitation of the
medium.

32. • In order to produce stimulated emission of the
radiation, the laser treatment devices rely upon
three essential components.
1. A Lasing medium
2. A Resonating cavity
3. A Power Source

33. LASING MEDIUM
• The gain medium is a material with properties that allow it to
amplify light by stimulated emission. Light of a specific
wavelength that passes through the gain medium is amplified
(increases in power).
• For the gain medium to amplify light, it needs to be supplied
with energy. This process is called pumping.
• The energy is typically supplied as an electrical current.
• Lasing medium may be solid crystal or semiconductor, liquid or
gas. The lasing media in low intensity laser or cold laser are
either he-Ne or operating at a wavelength of 632.8 nm or Ga-As
semiconductors producing radiation at 630-950nm.

34. Resonating chamber
• It is the chamber that consists of a structure that contains the
lasing medium which is surrounded by an optical cavity—a pair
of mirrors on either end of the gain medium.
• Within chamber photons of light produced by the medium are
reflected back and forth between the mirrors and As one of the
reflecting surface does not reflect 100% of the light striking its
surface but some of the radiation allowed to pass through as the
output of the device.
• Depending on the design of the cavity (whether the mirrors are
flat or curved), the light coming out of the laser may spread out
or form a narrow beam. This type of device is sometimes called a
laser oscillator.

36. POWER SOURCE
• Power source to pump the lasing media to
produce stimulated emission. In most cases,
therapeutic devices tend to be mains supplied
and incorporate a base unit to contain the
transformer and control unit.
• Alternatively, some devices incorporate
rechargeable & battery powered units to enhance
their portability.

38. TYPES OF LASER
• DEPENDING ON MEDIUM USED:
• Ruby laser,
• He-Ne laser,
• Gallium- Arsenide laser,
• Aluminum laser,
• Carbon laser

39. RUBY LASER
• This consists of a small synthetic ruby rod made of aluminum
oxide.
• A helical electric discharge tube (Flash tube) is wound around the
ruby rod.
• Both the ends are made reflecting by silvering the flat surfaces
with one end as 100% reflective and other partially transparent
to emit radiation.
• The xenon tube is used to give intense flash of white light which
excites the ruby molecules and raises the electrons return to
ground state by releasing a photon. This is known as

41. • The rate of supply of energy exceeds to a greater extent which
leads to a large number of atoms at higher energy levels. This is
known as population inversions.
• Atoms in their excited state are encountered by the photons and
this leads to further stimulated emissions.
• The excited electron falls to its resting state and gives off a
photon of exactly the same energy as that of photon which
collided with it. Hence a beam of red laser with a wavelength
694.3 nm is emitted.
• Thus all the energy stored in the ruby molecules is released in a
very brief time as a pulse of red light of identical photons and so
of a single wavelength of coherent radiation.

42. HELIUM-NEON LASER
• Gas laser consists of a mixture of primarily helium and neon in a
long low pressure tube.
• In most He-Ne lasers the gas, a mixture of 5 parts helium to 1
part neon, is contained in a sealed glass tube. This low pressure
tube is surrounded by a flashgun which excites the atom to a
higher energy level.
• Thus photons released by the spontaneous emission and have a
wavelength of 632.8 nm. These photons reflect to and fro along
the tube and collide with the atoms of higher energy levels.
• This leads to stimulated emission with the release of similar
photons. Intense beam of light emerges as a narrow beam of
about 1mm diameter from the partially transparent end.

44. • He – Ne laser gives red visible radiation in color at a
wavelength of 632.8 nm and has a frequency higher than
that of IR laser.
• Energy can penetrate up to 8 to 15 mm deep and output is
about 14 to 29 mJ.

45. DIODE LASER OR SEMICONDUCTOR LASER OR IR
LASER
• The special property of diode laser is that when current
flows through the diode, the electrical energy is
converted into laser radiation energy.
• Gallium and aluminum arsenide are used as a diode or
semiconductor to produce an infrared -invisible laser with
a wavelength of 830 nm.
• In these with an external electric potential, positively
charged holes are thrown from the p- type gallium-
aluminum- arsenide layer into the active layer and thus

46. • The photons are reflected to and fro and emitted as a laser beam from
one partially transparent end.
• By varying the ratio of gallium to aluminum desired specific wavelengths
are obtained.
• The advantage of semiconductor laser diode is that these can either
emit a continuous or pulsed output.
• Due to their small size, semiconductor laser can be applied directly to
the tissues in a hand held applicator.
• For larger area several diode lasers are assorted to form emitter known
as cluster probes.
• A suitable electronic circuit is provided to generate appropriate currents
to power the diodes.

47. • DEPENDING UPON THE ORIGIN
• Solid LASER
• Liquid LASER
• Gas LASER (Excimer Laser and Semiconductor
Laser)

48. • Solid state lasers have lasing material distributed in a solid
matrix, e.g., the ruby lasers.
• Liquid lasers are those which uses liquid as a active
medium. Dye laser is a liquid laser. Dye lasers use complex
organic dyes like rhodamine 6G in liquid solutions or
suspension as lasing media. They are tunable over a broad
range of wavelengths.
• Gas lasers have added the gases and gives a primary output
of a visible red light. E.g. helium-neon, Argon laser, krypton
laser, xenon laser etc. ( He-Ne, are the most common gas
laser)

49. • Excimer lasers (the name is derived from the terms excited
and dimers) use reactive gases such as chlorine and
fluorine mixed with inert gases such as argon, krypton, or
xenon. When electrically stimulated, a pseudomolecule or
dimer is produced and when lased, produces light in the
ultraviolet range.
• Semiconductor lasers, sometimes called diode lasers, in
which the active laser medium is formed by a p-n
junction of a semiconductor diode. These electronic
devices are generally very small and use low power.

50. BASED ON INTENSITY
• Cold LASER
• Hot LASER

51. COLD LASER
• LILT average power is less than 60mw which is
below the power which causes tissue heating.
• Normally it does not cause tissue destruction.
Wavelength ranges from 1nm to 1mm. includes
UV, visible and IR light. Wavelength or frequency
determines the color of laser light.

52. HOT LASER
• High intensity surgical laser, average power is more than
60 mw which causes thermal changes in the tissues
causing the tissues to be destroyed, evaporated, and
dehydrated or protein coagulation occur.

53. • Depending upon Eye damage
• Lasers are classified depending on the potential for the beam
to cause harm.
• The hazard and hence the classification depends on the
wavelength, power, energy and pulse characteristics.
• This classification of the laser can be used to help decide what
safety control measures are required when using the laser.
• The Accessible Emission Limit (AEL) is the maximum level of
laser radiation which a laser can emit (and be accessible) at
any time after its manufacture. The AEL depends on the
wavelength, exposure duration and the viewing conditions and
specifies the maximum output within each laser class.

54. Class Power effect Usage
1 Low – less than 0.5 mV None on eye/skin
Laser Pointer
Barcode reader
2 Low – up to 1 mV
Safe on skin & eyes but
is hazardous for
extended intra beam
viewing
Therapeutic Laser
Laser Pointer
3A
Low to medium – 1 mV
to 5 mV
Viewing with optical
aids may be hazardous
but safe for skin
Therapeutic Laser
Laser Pointer
3B Medium – up to 500 mV
Viewing may be
hazardous
Therapeutic Laser
4 & 5
High – more than 500
mV
Hazardous to both skin
and eye
Destructive - surgical

55. PHYSIOLOGICAL EFFECTS OF LASER
• Laser may be reflected from the surface of the
body, may penetrate into the deeper structures
depending upon its wavelength, nature of the
tissues surface and the angle of incidence of the
beam. When beam enters the tissue it is
attenuated due to absorption, scattering,
reflection and refraction.

56. BIO-CHEMICAL EFFECTS
Bio-Chemical
effects
Short term
effects
Long term
effects

57. SHORT TERM EFFECTS
• Production and release of beta-endorphins
• Cortisol production is increased

58. LONG TERM EFFECTS
• ATP production is increased Improved metabolism
• DNA production increases
• Neurotransmitter facilitates
• Mitochondrial activity is stimulated
• Modulation of macrophages, fibroblast & other cells
• Angiogenesis
• Regulates cell membrane potentials

59. OTHER EFFECTS
• The immune response is stimulated
• Lymphatic drainage is improve
• The histamine response is improve
• Production of growth hormone is increased
• Stimulation of healing processes.

60. BIO SIMULATIVE EFFECT: (PHOTOCHEMICAL
EFFECT)
• Visible radiations absorbed in the Hb whereas IR light is
strongly absorbed by water. Human body consists of 70% of
water and 30% of organic material.
• Organic material (Hb and Melanin) which absorbs visible
light contains Chromophores which are enzymes or
membrane molecules. They are photo acceptors which
absorb different lights like laser and get excited, exert bio
simulative effect.

61. • Penetration depth of red visible and short IR
radiation is about few millimeters, 1-2 mm for red
light of He-Ne laser and 2-4 mm for IR of 800-
900nm in soft tissues.
• The energy that are absorbed by the tissues leads
to greater kinetic energy at the molecular and
cellular levels. Limited depth of penetration and
athermal nature of the modality indicate that the
physiological effects are produced by the
photochemical means.

62. CELLULAR EFFECTS
• Activation of electron transport chain,
• Increased ATP synthesis
• Reduction of cellular PH with the application of LILT
• Also LILT can initiate reaction at cell membrane level via
photo physical effect on the calcium channels. These
changes are believed to cause the increase in macrophage,
fibroblast and lymphocyte activity.

63. EFFECTS ON NERVE CONDUCTION AND
REGENERATION
• Increase rate of nerve conduction,
• Increased frequency of action potential,
• Decreased distal sensory latencies,
• Accelerate regeneration

64. EFFECT ON VASODILATATION
• Increase in microcirculation, due to laser, can help in
acceleration of wound healing.

66. THERAPEUTIC USES
• Tissue healing
• Arthritic conditions
• Musculoskeletal disorders
• Pain

67. TISSUE HEALING
• Wounds and ulcers are treated due to increase
phagocytosis. Facilitation of collagen synthesis, increase
wound closure and increases wound strength.
• Laser stimulates biological functions including biochemical,
physiological and proliferation of fibroblasts, re-
epithelization and remodeling.
• It stimulates intracellular components such as
mitochondria, DNA, RNA and other substance which are
vital for growth and repair.

68. ARTHRITIC CONDITIONS
• In RA, LASER helps in short term relief of pain and
morning stiffness
• It is proposed that, improvements in arthritic
conditions are the results of reduced inflammation due
to changes in inflammatory mediators, or the result of
reduced pain due to changes in nerve conduction or
activation.

69. MUSCULOSKELETAL CONDITIONS
• A number of groups of researches have assessed the
efficacy of low intensity laser in the management of
musculoskeletal disorders, and the results obtained
was both positive and negative.
• The negative results obtained in some cases could be
due to the inappropriately low dose.

70. PAIN
• It was broadly assumed that the effect of laser therapy
with regards to pain relief was primarily a secondary
effect of dealing with the inflammatory state.
• Also there is growing evidence that laser therapy can
have a more direct effect of nerve conduction
characteristics and hence may result in reduced pain as a
more direct effect of the therapy.

71. INDICATIONS
• Soft tissue injuries:
• Tendinopathies
• Back and neck pain
• Carpal tunnel syndrome
• Myofascial trigger point
• Sprains
• Strains
• RSI
• Chondromalacia Patellae
• Planter fasciitis

72. • Degenerative joint condition
• RA
• OA
• Neurogenic Pain
• CRPS
• Post traumatic injury
• Trigeminal neuralgia
• Fibromyalgia
• Diabetic neuropathy

73. • Chronic Non-healing wounds
• Venous ulcers
• Amputee stumps
• Diabetic foot ulcers
• Burns

74. CONTRAINDICATIONS
• Carcinoma as it can accelerate carcinogenesis
• Within 4-6 months following radiotherapy - because
radiotherapy increases tissue susceptibility to malignancy and
burns
• Pacemaker
• Pregnancy as there is chances of foetal damage
• Locally to endocrine glands – such treatment may alter the
function of endocrine glands.
• Application to Retina
• DVT / thrombophlebitis (local)
• Tuberculosis (local)
• Haemorrhage area due to the possibility of laser induced
vasodilatation, which would exacerbate the condition

75. PRECAUTIONS
• Infected tissues
• Over sympathetic ganglia, vagus nerve and cardiac
region in patients with cardiac disease
• Cognitive difficulties or unreliable patient
• Over photosensitive areas
• Epilepsy
• Altered skin sensation
• Fever
• Epiphyseal lines in children

76. THANK YOU..