Diathermy is a Greek word for “ through heating”, in which
a high frequency (>10.000Hz)
An electromagnetic current is applied to induce deep
heating within body tissue, to induce physiological effects
for therapeutic purposes.
1. Shortwave Diathermy (SWD)
2. Microwave Diathermy(MWD)
3. Pulsed Electromagnetic (PEM)
3. Microwave Diathermy
Microwave Diathermy (MWD) is a high-frequency
electromagnetic radiation that lies between infrared and
Their frequency ranges between 300-3000MHz, with
corresponding wavelengths of 1m-10mm.
5. Principles Of MWD
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, and Absorption
6. Principle Of MWD
MWD are strongly absorbed by tissues with high fluid
content and 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) is
penetrated to a 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
7. Principle 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
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.
8. Physiological and Therapeutic Effects of MWD
When the electromagnetic radiation of MWD enters the
◦ Ionic movement (vibration).
◦ Rotation of dipoles.
◦ Distortion of the 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
Increase the extensibility
9. Soft tissue injury
Eyes: Irradiation to the eyes may develop
Malignancy: should not be applied to regions of malignant
growth or tuberculosis.
Genital area (sterility)
Pregnancy (miscarriage, hemorrhage)
Hypersensitivity to heat,
Circulatory defects: Such as hemorrhage, thrombosis,
phlebitis, and other vascular lesions.
Contradictions of MWD
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
Dangerous of MWD
11. Microwave Diathermy
Operation of the machine is simple
Comfortable for the patient
Localized heat to small surfaces
No overheating if precautions are followed
Not for deep structures
Heats only one aspect of the joint
Risk of burn
12. General Guideline &
Question patients (contraindications and previous treatment).
Position of the patient ( comfort, support, relaxed).
Inspect the part to be treated (check for skin rashes, infection, or
If indicated, drape the area with toweling.
Place electrodes on the treated area then switch on the machine.
Set pulse duration, pulse frequency, and treatment time, and adjust
Periodically ask the patient if the heating is too vigorous.
When the timer shuts off, terminate the treatment and turn all dials
Assess treatment efficiency ( inspect area, feedback from patients ).
Record treatment parameters