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Mwd lecture

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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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    5

    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


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