Microwave Diathermy Mohammed Taher Ahmed Ph.D PT, Rehabilitation Health Science College of Applied Medical Science

Outline Define microwave current Review the physics of the current Effects of application Indications, Contra-indications Procedure of application 2

What dose Diathermy Means ? Diathermy is a Greek word “ through heating”, in which a high frequency (>10.000Hz) electromagnetic current applied to induce deep heating within body tissue, to induce physiological effects for therapeutic purpose. Shortwave Diathermy (SWD) Microwave Diathermy(MWD) Pulsed Electromagnetic (PEM)

Microwave Diathermy Microwave Diathermy (MWD) is a high frequency electromagnetic radiation lies between infrared and shortwave. Their frequency ranges between 300-3000MHz, with corresponding wavelengths of 1m-10mm. Frequency MHz Wavelength Cm 2450 12.33 915 32.7 433.9 69

Microwave Diathermy Generator Power supply Magnetron Timing circuit Applicators (emitter, a director)

Magnetron The high frequencies of micro-thermy are obtained from the magnetron, which is perforated with tiny holes, through which the electrons flow into the treatment heads. The special design of the treatment heads shapes focuses the field directly at the target area. The whole device is used to direct the waves onto the tissues.

Emitter = Applicators Applicator must be very flat to avoid reflection of energy . Circular shape Rectangular shaped Diameter 4-6inches 4.5X5/ 5X21 inches Temperature Maximum at periphery of each radiation area Maximum at central of radiation area

Principle Related To Use Of MWD Deep heating modality Emits strong electrical field/ little magnetic field. Depth of penetration is frequency dependent. Produces much more localized & concentrated heating effect than SWD. Providing a more shallow tissue heating effect, depends on the type of tissue involved. Reflection Refraction Absorption,

Principle Related To Use Of MWD The effective depth of MWD penetration (half-value depth) is about 4.5 cm, so the depth of heating is intermediate between that of infrared radiation (2cm) and short wave diathermy (>5cm). MWD are strongly absorbed by tissues with high fluid content are heated most, while penetrated by tissues with low fluid content (e.g. fat or bones). Tissues with low water content (fat) are penetrated to a greater depth (half value thickness=3.5cm). Tissue with high water content (muscle, blood) are penetrated to superficial depth (=0.7cm).

Principle Related to Use of MWD The patients does not form apart of the circuit in MWD, so no tuning is necessary as in SWD. Transmits as free space radiation, so needs only one emitter (applicator). No Metal should be within 4 feet of MWD, since it will interfere with the signal. Spacing is required between the skin and the applicators with MWD, where the applicator on a short wave unit my be placed in contact with treatment area.

Physiological and Therapeutic Effects of MWD When the electromagnetic radiation of MWD enters the body causes Ionic movement (vibration). Rotation of dipoled. Distortion of non-polar molecule Physiological effects Therapeutic effects Effects on metabolism Effects on blood supply Effects on nervous tissue Effects on muscular tissue Effects on sweat glands Relief of pain and muscle spasm Promote healing Infection Increase the extensibility

INDICATIONS Soft tissue injury Mobilization Pain relief

Contradictions of MWD Eyes: Irradiation to the eyes may develop opacities/ cataract. Malignancy: should not be applied to regions of malignant growth or tuberculosis. Cardiac pacemakers. Genital area (sterility). Pregnancy (miscarriage , hemorrhage) Unreliable patients, Metallic implants, Hypersensitivity to heat, Impaired sensation Circulatory defects: Such as hemorrhage, thrombosis, phlebitis and other vascular lesions. 13

Dangerous of MWD Burn Poor techniques Inability of tissue to dissipate heat (circulatory defect) Inability to detect heat (impaired sensation) Implanted metal Moist skin Treatment near the eye Pregnancy (miscarriage , hemorrhage) Damage to the eye Damage to the equipment 14

Microwave Diathermy Advantages Disadvantages Operation of the machine is simple Comfortable for the patient Localized heat to small surfaces No overheating if precautions are followed Disadvantages Not for deep structures Heats only one aspect of the joint Risk of burn

Treatment Parameter of MWD The MWD requires warm-up period of 4 minutes, to allowed the magnetron to develop enough energy Spacing of Applicators For small treatment area is 2-6cm For large treatment area is 10-15cm Intensity of Treatment Sensation of warmth Feel no more than a mild comfortable warmth. Trim of Treatment: 20 -30minutes Frequency of Treatment; daily or alternating days depending on Response to treatment Patients condition/availability

General Guideline & Safety When Using Diathermy Question patients (contraindications and previous treatment). Position patient ( comfort, support, relaxed). Inspect part to be treated (check for skin rashes, infection, or open wound). If indicated, drape area with toweling. Place electrodes on treated area then switch on the machine. Set pulse duration, pulse frequency, treatment time, and adjust intensity. Periodically ask patient if heating is too vigorous. When timer shuts off, terminating the treatment and turn all dials to zero. Assess treatment efficiency ( inspect area, feedback from patients ). Record treatment parameters

Self test questions Compare and contrast between SWD and MWD MWD SWD Frequency &wavelength Therapeutic frequency and wavelength Circuit used Field used Factors affecting heat penetration/ absorption Depth of penetration Treatment time /intensity Advantages