ELECTROTHERAPY / THERAPEUTIC
MODALITIES – 1
DR/ AMAL MOHAMED ABD EL BAKY
L. CHANDRASEKAR MUTHUSWAMY
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First Lecture
7/1/2016
Lecture Outline
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
This lecture deals about the following:-

1. Basics of electrotherapy

2. High frequency & EM spectrum

3. Laws governing its radiations
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Lecture Objective
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At the end of this lecture / unit the students
will be able to;
Define Electrotherapy / Therapeutic Modality,
Production & physical properties of HFC.
 List some of Instruments used in Electrotherapy /
Therapeutic Modality.
 Describe EMS & Laws governing its radiations.

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Introduction - Electrotherapy / Therapeutic
Modality
• Electro – Electric Current / Electrical Energy.
• Modality – Machines/ Equipment's.
• Therapy – Treatment.
• It means various forms of THERAPEUTIC applications using
ELECTRICAL ENERGY as primary source.
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Electrotherapy - Definition:
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
Electrotherapy can be defined as the
treatment of patients by electrical
means.
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FACTS OF ELECTROTHERAPY
• All electrotherapy modalities involve the
introduction of some physical energy into a
biologic system. (Human tissue / Body)
• This energy brings about the one or more
Physiological changes, which are used for
Therapeutic benefit.
• In the Clinical environment, firstly to select the
most appropriate dose & secondly to apply the
treatment.
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General uses of Electrotherapy
1. Pain management
2. Treatment of neuromuscular dysfunction
3. Improves range of joint mobility
4. Tissue repair
5. Acute and chronic edema
6. Peripheral blood flow
7. Iontophoresis
8. Urine and fecal incontinence
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Classification of therapeutic currents according to frequency
• Current in which the
direction of electron
flow changes
periodically with a
frequency of 1-1000
Hz.
• Those current of
10,000 Hz or
more.
Low
Frequency
High
frequency
• Current in which
alternate the
direction of flow of
electrons with a
frequency between
1000-10.000 Hz .
Medium
Frequency
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First Lecture
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Instruments used in Electrotherapy
I-Low & Medium
Frequency Modalities
• TENS (transcutaneous
Electrical Nerve
Stimulation)
• High-Voltage pulsed
stimulation
• Neuromuscular Electrical
Stimulation
• Galvanic Stimulation
• Russian current
• Faradic current
• Iontophoresis
• Interferential Therapy
(I.F.T)
III-High Frequency
Modalities
Other Modalities
Shortwave Diathermy (S.W.D)
Microwave Diathermy
(M.W.D)
Ultra Sound Therapy (U.S)
Shockwave therapy
IV-Actinotherapy
Infra - red Radiations (I.R.R)
Ultraviolet Radiations (U.V.R)
Laser Therapy
Continuous Passive
Mobilizer (C.P.M)
Traction unit (Cervical &
Lumbar Traction)
Paraffin Wax Bath (P.W.D)
Hydrocollator Unit
Hydrotherapy – Whirlpool
therapy
Fluido - Therapy
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First Lecture
Ultrasound
LASER
TENS
IRR
UVR
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First Lecture
SWD
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Definition of
H.F.C
• A high frequency
current is a
current which
alternates so
rapidly that it
does not
stimulate motor
or sensory nerves.
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Oscillating Systems
• High frequency
(HF) / radio
frequencies are
between 3 and
30 MHz.
First Lecture
• Oscillation is the
repetitive
variation
• Each day we
encounter many
kinds of
oscillatory motion,
such as swinging
pendulum of a
clock, a person
bouncing on a
trampoline, a
vibrating guitar
string, and a
mass on a spring.
Oscillating system
• In an oscillating system such as the oscillation of a
simple pendulum, the oscillation does not
continue with the same amplitudes indefinitely.
• This loss in amplitude is called “damping” and
the motion is called “damped harmonic motion”.
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First Lecture
compare the motion of un-damped and
damped oscillators.
x
1
0.5
1
2
3
4
5
6
4
5
6
t
-0.5
-1
x
1.5
1
0.5
1
2
-0.5
3
t
-1
-1.5
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An Oscillating current-H.F.Current
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Production:- It is produced by discharging a
condenser through a low ohmic resistance
containing an inductance.
Physical properties of H.F.Current
1. Damping of oscillations
2. Heat Production
3. Electromagnetic waves
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7/1/2016
Radiant energy
Radiant energy is the energy in the form of waves or
rays in the ether.
Waves are set-up in the ether by movement of
electrons & are known as Electromagnetic waves.
Sunlight Is A Form Of Radiant Energy
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Electromagnetic radiation
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
They are waves and particles in motion. The energy of
the electromagnetic radiation is in the form of oscillating
electric and magnetic field perpendicular to one another
and to the direction of travel.

If currents in an AC circuit change rapidly, some energy is lost
in the form of EM waves

EM waves are radiated by any circuit carrying alternating
current
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Characteristics / Properties of electromagnetic
radiation
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
Transport energy through space & it carries energy.

Travel through a vacuum or a material substance at a constant speed
of 300 million meters\sec
Energy carried by EM waves is shared equally by the electric and

magnetic fields
It is categorized according to its wavelength and frequency which are

inversely proportion to each other.

Long wavelength-lowest frequency

Short wavelength highest frequency

The higher the frequency the higher the energy.
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
Wavelength: it is the horizontal distance from one
wave beak to the next.

Frequency: it is the number of cycle that occurs in
second.(cycle / second) and expressed in hertz.

Amplitude: The magnitude of the maximum
displacement from equilibrium is called the amplitude
of the motion.
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General Physiological effects of
electromagnetic radiation
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


Electromagnetic radiation can affect biological system
via thermal and or the non-thermal mechanisms.
Infrared radiation and both continuous
diathermy(shortwave and microwave) can increase
tissue temperature, as they primarily affect tissue by
thermal mechanism.
Ultraviolet radiation, therapeutic laser, and pulsed
diathermy don't increase tissue temperature and
though to affect tissues by non-thermal mechanisms.
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
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Electromagnetic Spectrum—name for the range of
electromagnetic waves when placed in order of
increasing frequency
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

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The electromagnetic spectrum is the entire range of
electromagnetic waves arranged according to their
frequencies or wavelengths.
Electromagnetic waves all have different properties. But
they all travel the same speed – what we call “The speed
of light”
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Regions of electromagnetic spectrum
Ionizing range :

It includes X-ray and gamma rays.

It can break molecular bonds to form ions.

It can easily penetrate the tissue and deposit its
energy within the cell. If the energy is sufficient high
the cell division is inhibited and the cell will be
killed.

This energy can be used in diagnosis and
therapeutically in radiation treatment for some
forms of cancer.
•Non ionizing rang:
It includes lower frequency range as light spectrum,
diathermy, electric currents
it can't break molecular bonds or produce ions.
It can be used for therapeutic medical applications.
The light spectrum:
This portion of the spectrum includes ultraviolet, visible light, laser
and infrared.
Diathermy:
It is electromagnetic radiation of longer wavelength. It has an
intensity sufficient to increase tissue temperature. As shortwave and
microwave . These electromagnetic energies create a magnetic field
that changed into heat.
Electrical currents:
It lies in range above shortwave. It is used for therapeutic purposes
to stimulate muscles and nerves.
Physical laws governing the application of electromagnetic
radiation
Reflection
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Refraction
Absorption
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Inverse square law:
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LAW OF REFLECTION
When a ray strikes a new medium which will not
transmit it causes the ray to turned back.
The incident ray, the reflected ray, and the
normal to the surface all lie in the same plane.
The angle of reflection θr equals the angle of
incidence θi:
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LAW OF REFRACTION
When a beam of light passes from one medium to
other the rays are BENT.
This causes the rays to be deflected from its original
course by an amount depending on the medium
involved & the angle of incidence.
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REFRACTION
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LAW OF ABSORPTION
When rays strike the surface of a new medium
some may be ABSORBED by the new medium.
The proportion of the rays absorbed depends on
the nature of the medium, wavelength of the rays
& the angle of incidence.
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LAW OF ABSORPTION
When the angle of incidence is 90˚ then NO RAYS
will be absorbed as they will be travelling parallel
to the surface.
If the angle of incidence is 0˚ then the rays are
striking the surface so as to make a right angle with
it & the maximum rays will be absorbed.
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LAW OF ABSORPTION
When applying I.R.R & U.V.R. to the patient greater
efforts should be made to ensure that the maximum
number of rays strike the surface perpendicularly.
The angle of incidence is ZERO DEGREES for most
effective treatment.
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Inverse square law
The relationship between the distance from the source
& intensity of radiation is expressed in the inverse
square law. All radiations is subject to the inverse
square law.
It states that “ The intensity of the radiation from a
point source is inversely proportional to the square of
the distance from the source
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Source
d
Full strength
2d
One quarter strength
d3
One ninth strength
Target
The inverse square law. At twice the distance (2d) the intensity is
only one quarter of that at the source (d) and at three times the
distance (3d), the intensity is one ninth of that at (d)
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
I = 1/ D²

According to this formula;
I = Intensity of radiation
 D = Distance travelled by the radiation.


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This has greater practical importance.
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Cosine law:
When the angle of incidence is 90˚ then NO RAYS will be absorbed as •
they will be travelling parallel to the surface.
If the angle of incidence is 0˚ then the rays are striking the surface so
as to make a right angle with it & the maximum rays will be absorbed.
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Maximum penetration angle
of incidence=0 Cos0=1
70% of maximum penetration
angle of incidence= 45 , Cos
45= 0.707
Zero penetration angle of
incidence= 90, Cos 90=0
surface
The cosine law
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The Arndt-Schulz law:
-According to this law, a certain minimum intensity of
electromagnetic radiation is needed to initiate a biological
process.
-Beyond a certain level stronger intensity will have a progressively
less positive effect and become inhibitory. They would explain the
non-thermal effect of electromagnetic radiation.
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