Microwave Diathermy

BETWEEN RADIOWAVES AND INFRARED WAVE LENGTHS BETWEEN 1m & 1cm FREQUENCY BETWEEN 300MHz to Frequency Wavelength 30GHz (MHz) (cm) 2450

12.245

915 433.9

32.79 69.14

Reflector

Fan and cathode Heater control circuits

Power supply from mains

Main s

Magnetron

Intensit y

Antenn a

Coaxial cable

Emitter

Production of MW 

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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

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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 

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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

Tissue composition and Microwave Absorption 

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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.

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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

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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

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

Principles of Application    

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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 

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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