Use of Microwave Diathermy(MWD) in Physiotherapy

What is a Microwave Therapy?

Microwave Diathermy (MWD) is a form of electromagnetic radiation lying between short waves and infrared waves.

~Microwave Diathermy does not penetrate as deep as short-wave diathermy.

~It genewrates strong electrical field and relatively little megnetic field.

~Microwave diathermy uses electromagnetic radio waves with frequencies of 915 and 2456 MHz.14 Based on the physical properties of these waves and the corresponding dimensions of the microwave antennae, microwave diathermy has two unique properties that can be used to clinical advantage.

~The first is that microwaves are selectively absorbed in tissues with high water content, such as muscle. This makes microwave diathermy ideally suited to treat pathologic processes that occur in the muscles and adjacent fat.

~The second is that microwaves are more easily focused than the short waves used in short-wave diathermy, thereby decreasing energy leakage and making heating more efficient.

Frequency and Wavelength of Microwave Diathermy:

~Microwave has a much higher frequency and shorter wavelength than SWD.

~The general frequency of microwaves is between 300MHZ  to 300GHZ with wavelength of  10 mm to 1 meter.

~the therapuetic microwave generators  used frequency of 2450 MHZ  with wavelength of 122.5 mm.

The mechanisms by which heat exerts its analgesic effect extend beyond the simple effects of heat locally on the target tissue. Locally, heat elicits the following physiologic responses:

(1) increased blood flow

(2) decreased muscle spasm

(3) increased extensibility of connective tissue

(4) decreased joint stiffness

(5) reduction of edema

(6) analgesia

Physiological Effect of Microwave Diathermy:

~ Heat Produce

~Increases Diameter of blood vessels

~ Increase Blood circulation

~ Remove Waste Products

~Increases Nutrients Supply in the affected area

~Relief Pain/Reduce Muscle Spasm

Therapeutic Effect of MWD:

~Pain – Traumatic and Rheumatic condition

~Muscle spasm

~Inflammation

~Infection

~Fibrosis

~Delayed healing.

Indication of MWD:

~Disorder Of the Musculoskeletal System

~Sprain

~Strain

~Capsular lesion

~Degenerative joint disease

~Joint stiffness

~Torticollis

~Chronic Inflammatory Condition

~Tendinitis

~Bursitis

Contraindications of MWD:

~over ischemic tissue
~ over Malignant tissue
~Severe/excessive edema
~Metallic implant
~Cardiac pacemaker0?~over growing bone
~Over wet dressing
~Acute inflammation
~Infected open wound
~Impaired thermal sensation
~Unreliable patient
~Recent radiotherapy
~Pregnancy
~Severe cardiac abnormality
~Blood pressure abnormality
~Reproductive organ (near testes)
~Brain Tuberculosis
~Bleeding tendency.

~A generator used to produce microwaves has 3 main components.

(1) a Multi cavity magnetron valve

(2)a  coaxial cable

(3)a  director

Mechanism of Microwave Diathermy (MWD):

~a magnetron produces high-frequency alternating currents which are carried by the coaxial cable to the transducer.

~the coxial cable transmittes the energy  to the director wheres  a radiating system  comrising an antenna  with in a reflector that is used to direct the microwaves to the patient.

~the alternating current in the antenna produces an electro magnetic field directed toward the tissue by curves reflecting the director surrounding the antenna.

~the presence of a director  and the short wavelength of microwave radiation  allow this type of diathermy  to be focused and applied to a  small defined areas.

~so this device can be useful during rehabilitation when only small areas of tissue are involved.

Directors used in MWD:

(1) Circular director:-the heating pattern is more intense  around the outer portion than the centre.

~there are small and large.

(2) Rectangular directors:-the heating pattern tends to be more concentrated in the center of the treated area.

Biophysics of Microwave Diathermy (MWD):

~MWD  tends to be reflected and scattered at different interphases such as air skin, skin fat, and the fat muscle which limits its penetration in the tissues.

~because of spreading of MWD , the superficial tissues tends to be heated more than deeper tissue.

~deapth of penetration depends on the  frequency of wave and medium.the effective penetration of 2450MHz  is approximately 3 cm.

~mechanism of heat production by  MWD is the same as SWD.

Precautions and Warning:

~it is recommended  to avoid   the presence of metal within the treatment field because of scattering and reflection of MWD.

~due to scattering and reflection of MWD to surrounding enviroment,it has been assosiated with high incidence of misscarriages among female therapist who regularly operate  these units than SWD.

~The eyes:-MWD may cause cataracts.

~obesity:-MWD with  2450 MHZ  , There is danger of producing  an excessive heat  in the subcutaneous fat layer.

~BURN:- there is an increasing risk of excessive heating and burning with the using of MWD due to:

1. shallow depth of penetration
2. reflection of tissue interfaces
3. potential standing waves

Dosage of MWD:

~Duration of treatment: 20 minutes is optimum.

~Intensity:-the patient should feel  mild and comfortable warmth.

~Frequency: daily or on an alternating days.

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