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1. Diathermy is a Greek word “ through
heating”, in which a high frequency
(>10.000Hz) electromagnetic current
applied to induce deep heating within
body tissue, to induce physiological
effects for therapeutic purpose.
1. Shortwave Diathermy (SWD)
2. Microwave Diathermy(MWD)
3. Pulsed Electromagnetic (PEM)

2.  Microwave Diathermy (MWD) is a high frequency
electromagnetic radiation lies between infrared
and shortwave. Their frequency ranges
between 300-3000MHz, with corresponding
wavelengths of 1m-10mm.
Frequency MHz Wavelength Cm
2450 12.33
915 32.7
433.9 69

3.  Power supply
 Magnetron
 Timing circuit
 Applicators (emitter, a director)

4.  The high frequencies of
micro-thermy are obtained
from the magnetron,
which is perforated with
tiny holes, through which
the electrons flow into the
treatment heads.
 The special design of the
treatment heads shapes
focuses the field directly at
the target area.
 The whole device is used to
direct the waves onto the
tissues.

5. Applicator must be very flat to avoid reflection of
energy .
Circular shape Rectangular shaped
Diameter 4-6inches 4.5X5/ 5X21 inches
Temperature Maximum at periphery of
each radiation area
Maximum at central of
radiation area

6.  Deep heating modality
 Emits strong electrical field/ little magnetic field.
 Depth of penetration is frequency dependent.
 Produces much more localized & concentrated
heating effect than SWD.
 Providing a more shallow tissue heating effect,
depends on the type of tissue involved.
 Reflection Refraction Absorption,

7.  MWD are strongly absorbed by tissues with high fluid
content are heated most, while penetrated by tissues with low
fluid content (e.g. fat or bones).
 Tissues with low water content (fat) are penetrated to a
greater depth (half value thickness=3.5cm).
 Tissue with high water content (muscle, blood) are
penetrated to superficial depth (=0.7cm).
The effective depth of MWD penetration (half-value depth)
is about 4.5 cm, so the depth of heating is intermediate
between that of infrared radiation (2cm) and short wave
diathermy (>5cm).

8. Principle Related to Use of MWD
 The patients does not form apart of the circuit in MWD, so no
tuning is necessary as in SWD.
 Transmits as free space radiation, so needs only one emitter
(applicator).
 No Metal should be within 4 feet of MWD, since it will
interfere with the signal.
 Spacing is required between the skin and the applicators with
MWD, where the applicator on a short wave unit my be
placed in contact with treatment area.

9. When the electromagnetic radiation of MWD enters the body
causes
 Ionic movement (vibration).
 Rotation of dipoled.
 Distortion of non-polar molecule
Physiological effects Therapeutic effects
Effects on metabolism
Effects on blood supply
Effects on nervous tissue
Effects on muscular tissue
Effects on sweat glands
Relief of pain and muscle spasm
Promote healing
Infection
Increase the extensibility

10. Soft tissue injury
Mobilization
Pain relief

11. Eyes: Irradiation to the eyes may develop
opacities/ cataract.
Malignancy: should not be applied to regions
of malignant growth or tuberculosis.
Cardiac pacemakers.
Genital area (sterility).
Pregnancy (miscarriage , hemorrhage)
Unreliable patients,
Metallic implants,
Hypersensitivity to heat,
Impaired sensation
Circulatory defects: Such as hemorrhage,
thrombosis, phlebitis and other vascular lesions.
11
Contradictions of MWD

12. Burn
1. Poor techniques
2. Inability of tissue to dissipate heat (circulatory defect)
3. Inability to detect heat (impaired sensation)
4. Implanted metal
5. Moist skin
6. Treatment near the eye
Pregnancy (miscarriage , hemorrhage)
Damage to the eye
Damage to the equipment
12
Dangerous of MWD

13. Advantages
 Operation of the machine is
simple
 Comfortable for the patient
 Localized heat to small surfaces
 No overheating if precautions are
followed
Disadvantages
 Not for deep structures
 Heats only one aspect
of the joint
 Risk of burn

14. Spacing of Applicators
 For small treatment area is 2-6cm
 For large treatment area is 10-15cm
The MWD requires warm-up period of 4 minutes, to allowed the
magnetron to develop enough energy
Intensity of Treatment
 Sensation of warmth
 Feel no more than a mild comfortable warmth.
Trim of Treatment: 20 -30minutes
Frequency of Treatment; daily or alternating days depending
on
 Response to treatment
 Patients condition/availability

15. 1. Question patients (contraindications and previous treatment).
2. Position patient ( comfort, support, relaxed).
3. Inspect part to be treated (check for skin rashes, infection, or open wound).
4. If indicated, drape area with toweling.
5. Place electrodes on treated area then switch on the machine.
6. Set pulse duration, pulse frequency, treatment time, and adjust intensity.
7. Periodically ask patient if heating is too vigorous.
8. When timer shuts off, terminating the treatment and turn all dials to zero.
9. Assess treatment efficiency ( inspect area, feedback from patients ).
10. Record treatment parameters