MICROWAVE DIATHERMY

At the end of this unit the student will be able to
 Explain the characteristics and therapeutic effects of microwave
diathermy.
 Describe and demonstrate the application techniques of
microwave diathermy.
 List the indications and contraindications microwave diathermy.
 Explain the precautions and potential harmful effects of
microwave diathermy.
 Explain the dosage of microwave diathermy.

  • The waves of 1 m (frequency 300 MHz) to 1 mm (300 GHz) in the electromagnetic spectrum.
    -
  • Radiation with a wavelength of 12.25 m and a frequency of 2450 MHz (commonly used) – UK and Australia
    .
  • Radiation with a wavelength of 69 cm and a frequency of 433.92 MHz.Also 327 mm (915 MHz)– North America.
  1. Production of Microwaves
  • Production of high frequency currents
  • Special type of valve called a magnetron is used.
  • Warm-up required.
  • HF – coaxial cable.
  • Coaxial cable- a small aerial – Emitter or director or applicator.
  1. Application

1

  • Circular or rectangular emitter with air spacing.
  • Circular emitter- rays circular in cross-section and is more dense at the periphery than in the centre.
    -
  • Rectangular emitter-beam is oval in cross-section and is of greatest density centrally.
    .
  • Rays diverge
    .
  • Spacing – commonly between 10 and 20 cm / 2-6 cm
    .
  • Small emitters- for use in contact with the tissue and for the treatment of cavities
    .
  • Concave surface emitters
  1. Physiological effects
  • Absorbed, transmitted, refracted or reflected
    .
  • Absorption of the waves results in the production of heat in the tissues by means of dipole rotation and molecular distortion
    .
  • The effects deeper than infra-red irradiation, but less than shortwave diathermy
    .
  • Microwaves are strongly absorbed by water- so tissues with good blood supply such as muscle, moist skin, blood vessels, internal organs and eyes gets appreciable heating than tissue with low fluid
    content like fat
    .
  • Physiological effects of heating is applicable
    .
  • Non-thermal effects

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5.Therapeutic effects

  • A local rise in temperature (like SWD)
    .
  • Traumatic and inflammatory lesions - increase in blood supply and relief of pain and muscle spasm are beneficial
    .
  • Bacterial infections – increase in blood supply brings more white blood cells and antibodies and reinforces the body’s normal defence mechanism
    .
  • Effective for in the superficial tissue and those of high fluid content
    .
  • Reduced joint pain and increased walking time – RA
  • Increased extensibility of collagenous tissue and reduced joint stiffness.

6.Danger of Microwave Diathermy

1.Burns -

patient sensation is the primary guide to the
intensity. Remove the metal objects.

  • Poor technique
  • Inability of tissues to dissipate heat
  • Inability of patient to detect heat (decreased thermal sensation)
  • Treatment over areas with surface or implanted metal.
  • Treatment of moist open wounds, or over wet dressings - water concentrates microwaves.
  • Treatment near the eyes, including sinuses and
    temporomandibular joint

2.Exacerbation of symptoms following treatment of:

  • Inflammatory conditions
  • Infective disorders
  • Areas of increased fluid tension such as bursitis, oedema, synovial effusion.
  • Haemorrhagic condition – menstruation is unlikely to be affected.
  • Severe cardiac disease
  1. Cardiac failure due to electric shock or interference with cardiac pacemakers
    .
  2. Spread of existing pathologies including tumours, active tuberculosis and acute infections
    .
  3. Early pregnancy (first 3 months) – heat may be teratogenic
    .
  4. Eyes – PT and patient wear protective goggles made of a wire mesh
    .
  5. Circulatory defects – ischaemic areas should not be treated. Haemorrhage, thrombosis, phlebitis and other vascular lesions should not receive MWD.
  1. Contraindications
  • Malignant growth
  • Tuberculosis infection
  • Areas recently exposed to therapeutic doses of X-rays
  • Hypersensitive skin
  • Testicles
  • Damage to equipment – reflection by metal plate can damage the Microwave machine.
  • Cardiac pacemakers
  • Hearing aids
  • PT should not remain in the direct line of the beam or within 2 m of the director.
  • Recflection -50 to 75% from the patient and nearly 100% from the metal of the apparatus.
  1. Technique of application

Preparation of apparatus:

  • The selected emitter is connect to the machine by the appropriate cable and the power switched on.
  • There will be some delay in the output.
  • Test the machine - PT hand or arm to feel the warmth by increasing the output. Then controls to zero and keep it in standby mode.

Preparation of the patient

  • Same as SWD.
  • Avoid excessive movement.
  • Full support and comfortable position.
  • Patient and PT wear a pair of wire mesh goggle to protect his eyes.
  1. Application of the emitter
  • The emitter surface should be parallel to the skin and at the appropriate distance. (the inverse square law of distance)
  • Surface marking of the structure to be treated.
  • Irregular surfaces and areas which perspire freely should, if possible, avoided.
  1. Irradiation
  • The patient is reminded of the sensation to be expected and of the need to report accurately on that experienced
    .
  • Output is increased slowly until a sensation of warmth is experiences or the selected output is reached whichever comes first
    .
  • Appropriate time
    .
  • Then output reduced and switched off
    .
  • Slight erythema may be observed and there should be no marked skin reaction.
  1. Dosage
  • The dose can be calculated from the power output from the machine, (upto 200 watts)
    .
  • In all cases the sensation experienced by the patient must be the primary guide
    .
  • Duration – 10 to 30 minutes
    .
  • Progressive increase in exposure must depend on the patient’s reaction
    .
  • Daily or on alternate days.