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MWD

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Introduction

MWD is irradiation of tissue with radiation in the

shorter wireless part of electromagnetic spect.

Wavelength between infrared and SWD radiation.

like other electromagnetic radiation, i.e., they are

reflected, and refracted at interfaces depending

on the nature of the materials.

They are also used in telecommunications and intracking ships, aircrafts, rockets, and satellites as

radar.

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Thus, microwaves can be directed to, and

will penetrate, the tissues while being

strongly absorbed by water. This makes it an

effective method of tissue heating, especially

muscles.

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Microwave Diathermy

Two Assigned Frequencies-2456 MHz and 915MHz

MWD Has Higher Frequency and Shorter

Wavelength Than SWD Generates Strong Electrical Field and Relatively

Little Magnetic Field

Advantage: better focus wave on body, therebymore local heating affects

Disadvantage: Depth Of Penetration Is Minimal In

Areas With Subcutaneous Fat > 1 cm

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Characteristics

1cm-100cm wavelength.

Decimeter wave.

Commonly :1) 12.25cm wavelength and 2450 MHz

2) 69cm wavelength and 433.92 MHz

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Penetrate more deeper than IR and lessdeeper than SWD.

The effective depth of penetration is about

3cm. Microwaves are strongly absorbed by water so

there is appreciable heating of tissues with

good blood supply such as muscle but lessheat is produced in structures with low fluidcontent.

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Production

High-frequency oscillating currents will produce

electromagnetic radiations of radio frequencies,

which can be radiated from suitable antennae

as radio and television transmissions.

For the higher frequencies of microwave at

relatively high power a device called a magnetron

is used which generates oscillating currentsdirectly from high-velocity electron motion.

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These currents are collected and fed along acoaxial cable to the antenna or emitter, whichradiates microwaves.

The antenna, which is simply a suitable, sized andshaped piece of wire, is mounted in front of ametal reflector so that a beam of microwaves isemitted in one direction.

delay switch may be fitted to allow time for the

magnetron to reach its proper workingtemperature.

A standby switch for successive Rx.

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Microwave Diathermy Unit

A= Power Switch

B=Timer

C=Output Meter (indicates relative output in watts

D= Power Output Level Knob

E= Amber Light-Warming up / Red Light- Ready

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MWD Applicators (Electrodes)

Circular Shaped Applicators

4 or 6

Maximum Temperature At Periphery Rectangular Shaped Applicators

4.5 x 5 or 5 x 21

Maximum Temperature At Center

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Microwave Applicator Set-Up

Microwave Applicator Beams Energy To

Patient

Must Pay Attention To Cosine Law In 915 MHz Units Applicators Placed 1 cm

From Skin

2456 MHz Units Have ManufacturerRecommended Distances and Power Outputs

(Uses Antenna)

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Physiologic effects of MWD

Physiologic effects are those of heat in generalby ionic movt, rotation of dipoles and electronorbit distortion.

Tissue Temperature Increase

Increased Blood Flow (Vasodilatation) Increased Metabolism

Changes In Physical Properties of Tissues

Muscle Relaxation

Analgesia

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Therapeutic effect

Superficial tissue heating such as muscle and

articular structures close to the surface such

as Wrist or Ant. aspect of Knee.

Rheumatic condition.

Heating muscle tissues to achieve an increase

in intramuscular blood flow.

Localized than widespread condition.

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Techniques of application

Preparation of apparatus.

Preparation of patient.

Setting up of emitter. Instruction and warnings.

Application.

Termination.

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Dosage

Output can be increased Up to 200 watts.

Sensation of Comfortable warmth.

10-30 minutes.

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Best Treated areas for Microwave

Tendons of foot, hand and wrist

AC and SC joints

Patellar tendon Distal tendons of hamstrings

Achilles tendon

Other areas of low subcutaneous fat

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Dangers

Effects of Metal:

Effects of Surface Moisture:

Cardiac Pacemakers: Eyes:

Testes:

Pregnancy: Circulatory Defects:

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Contraindication

Diminished thermal sensation

Defective arterial circulation

Acute inflammation

Recent hemorrhage

Metal in the area under treatment

Malignancy

Implanted cardiac pacemakers

Intrauterine devices when using a vaginal electrode

Eyes and testes, due to poor heat dissipation

Pregnant uterus

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Thank You