Mohammed Taher AhmedMohammed Taher Ahmed Ph.D PT,Ph.D PT,

Rehabilitation Health Rehabilitation Health ScienceScience

College of Applied Medical College of Applied Medical ScienceScience

1. Define microwave current2. Review the physics of the

current3. Effects of application4. Indications, Contra-

indications5. Procedure of application

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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)

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 MHzWavelength Cm

245012.33

91532.7

433.969

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

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.

Applicator must be very flat to avoid reflection of energy .

Circular shape Rectangular shaped

Diameter 4-6inches4.5X5/ 5X21 inches

Temperature Maximum at periphery of each radiation

area

Maximum at central of radiation area

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,

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).

Principle Related to Use of Principle Related to Use of MWDMWD

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.

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 InfectionIncrease the extensibility

Soft tissue injury Mobilization Pain relief

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.

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Contradictions of MWD

Burn 1. Poor techniques2. Inability of tissue to dissipate heat (circulatory defect)3. Inability to detect heat (impaired sensation)4. Implanted metal5. Moist skin6. Treatment near the eyePregnancy (miscarriage , hemorrhage)Damage to the eye Damage to the equipment

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Dangerous of MWD

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

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

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

Compare and contrast between SWD and MWD

MWDSWD

Frequency &wavelength

Therapeutic frequency and wavelength

Circuit used

Field used

Factors affecting heat penetration/ absorption

Depth of penetration

Treatment time /intensity

Advantages