BETWEEN RADIOWAVES AND INFRARED WAVE LENGTHS BETWEEN 1m & 1cm FREQUENCY BETWEEN 300MHz to 30GHz

Frequency (MHz)

Wavelength (cm)

2450 12.245

915 32.79

433.9 69.14

Fan and cathodeHeater control

circuits

Powersupplyfrom

mains

Magnetron

Mains

Intensity control

Reflector

Emitter

Antenna

Coaxial cable

Production of MW Wireless waves are caused by high

frequency currents Special valve called magnetron is

used Standby switch to provide to use

the machine betw patients without disconnect current to the valve intensity

Current from the valve is carried by a coaxial cable which contain a central wire with outer metal sheath separated with a an insulating material

Wire and sheath run parallel Coaxial cable carry current to the aerial from

which the microwave is emitted The aerial is mounted in a reflector which is

packed with some material which transmits the waves into the tissue

Its called the emitter, director ,applicators. Pt does not form a part of the circuit

The physiological effects of Microwaves on the tissues When electromagnetic energy of

Microwave radiation is absorbed in the tissues it provokes ionic movement, rotation of dipoles and electron orbit distortion which leads to heating

The propagation characteristics of microwaves are first determined by the wavelength and frequency of energy

Tissue composition and Microwave Absorption Microwave energy has a tendency to penetrate tissue with low

electrical conductivity and be absorbed in tissues with high conductivity

High electrical conductivity equates with high fluid content (typically blood vessels, muscle, moist skin, internal organs and eyes)

There is greater rise in muscle temperature (muscle tissue) when microwave diathermy is used

Therapeutic microwave radiation is largely absorbed in the first few centimeters of tissue traversed.

The approximate half value depth of penetration is 3cm. The shape and size of the emitter influences the energy

distribution into the tissues Good transmission to the skin can be achieved with contact

emitters. The frequency of the microwaves produced depends on the

structure of the magnetron.

Therapeutic Effect The different effects of heating are

the consequence of such factors as The volume of tissue absorbing the energy The composition of the absorbing tissue The capacity of the tissue to dissipate

heat-largely a factor of blood supply The temperature to tissue is raised. The rate of rise of temperature

Microwave irradiation increases skin and tissue temperature and blood flow

Enhances rate of tissue heating and infection control by increasing the metabolic activity of the phagocytic and reparative cells.

Improves joint range of movement by decreasing stiffness and improving extensibility of contracted soft tissues.

Subacute stage of arthritis- improves circulation and resists the resolution of oedema and hemorrhage

Pain relieving effects Muscle guarding Degenerative joint disease Bursitis Sacroiliac strains Ankylosing spondylitis Increased extensibility of collagen

tissues

Principles of Application

Preparation of patient Preparation of apparatus Preparation of part to be treated Setting up- emitter should be positioned

so that radiations strike the surface at right angles

Instruction and warning Application Termination

Dosage

20 min for vascular adjustment If significant heating required 30

min would be reasonable

Hazards of Microwave

All electrotherapy equipment should be handled with care and be regularly maintained and serviced

Frayed leads and improperly functioning safety leads are not used

Microwave units should be regularly tested by the physiotherapist

The presence and distribution of the microwave field can be tested by using an appropriate fluorescent tube

Contraindications

Diminished thermal sensation Defective arterial circulation Acute inflammation Recent hemorrhage Metal in area under treatment Malignancy Implanted cardiac pacemaker Intrauterine devices Eyes and testes Pregnant uterus

EFFECTS OF METAL EFFECTS OF SURFACE MOISTURE CARDIAC PACEMAKERS EYES TESTES PREGNANCY GENERAL SAFETY WITH MICROWAVE