Microwaves are electromagnetic waves with a frequency between 300 MHz and 300 GHz that can be used for diathermy therapy. Microwaves are produced using a power supply, magnetron, and emitter/antenna. They are absorbed more by tissues with high water content like muscle and heat the surface more than deeper tissues. Microwaves can be used to treat pain, inflammation and other conditions by increasing blood flow and metabolism through localized heating, but risks include burns if moisture is present or the eyes/testes are exposed directly to the beams. Proper positioning and monitoring of the patient is needed during treatment.

1. MICROWAVE
DIATHERMY By Charishma .N
M.P.T. 1st year

2. MICROWAVES

3. MICROWAVES
• The micro waves has high frequency and low wavelength when compared to
SWD.
• Frequency ranges from 300MHz to 300GHz
• Wave length is of 1cm to 1m
• Commonly used frequency and wave length in therapy are
Frequency (MHz) Wave length(cm)
2450 12.2
915
434
32.8
69.1

4. MICROWAVES
• These microwave are also used in microwave ovens (frequency 2450MHz),
telecommunications, radar for tracking ships, aircrafts, rockets and satellites.
• Microwaves also reflect and refract at interfaces and absorption varies on the
degree ,on the nature of material and frequency.
• Microwaves are particularly useful in therapy as they are more rapidly absorbed
in tissue with a high water and ion content, such as in a muscle and less rapidly
absorbed in fatty tissue and bone .

5. PRODUCTION OF MICROWAVES

6. PRODUCTION
• It consists of
1. Power supply
2. Magnetron
3. Emitter
• Antenna
• Reflector

7. MAGNETRON
• It is a special type of thermionic value
• It produce high frequency current required for the production of microwaves
• Centrally placed cathode and surround circular metal anode

9. EMITTER
• It has two parts
• Antenna – it is a metal reflector which radiates the miCrowaves from the high
frequency currents
• Reflector – it is a metal plate which directs the microwaves in only one direction
• The out put of the microwave energy is controlled by varying the power supply
to the magnetron.

10. • The machine have a intensity control and output is indicated on a meter
• Frequency of microwaves depends on the construction of magnetron.
• Delay switch – allows the time for the magnetron to reach its proper working
Temperature
• Standby switch – Successive treatment may be given or adjustment of emitter
made without having switch off the magnetron and wait for it to warm up again
• A means of switching the mains power on and off and suitable indication lights
• Emitter gives a out a beam of microwave which diverges somewhat it is
technically difficult to produce a uniform beam
• Effect of divergence is to decrease the intensity of radiation considerably with
distance
Intensity is inversely proportional to distance square

12. EFFECT OF EMITTER SHAPE
• Emitters are of various sizes and shapes
• Basically emitters are either circular or rectangular In shape
• Circular emitter produce microwaves which are circular in cross sectional and
denser in periphery
• Rectangular emitter produces waves which are oval in cross section and sensor
at centre than at the periphery

14. EFFECT OF DISTANCE BETWEEN THE TISSUE AND
EMITTER
• These are two types
• Distance emitter – distance must be about 10-20 cm.However it can be varied
according to size of the emitter, part to be treated and condition.
• Contact emitter- these are smaller in size (1.5 or 3.5 cm in diameter ) will radiate
microwaves directly into tissues.
• small emitters Can be placed in body cavities such as rectum, vagina and external
auditory meatus - emit radially to heat the walls of the cavity
• Microwaves transmission is better with contact emitter as power input is limited to
low level (25W)

16. MORPHOLOGICAL EFFECT
• Basing on the shape of the tissue to the microwave beam is being applied will have
significant effect due to both reflection and refraction.
• Reflection of microwave radiation from skin which is greater when it is not being applied
perpendicularly to the surface
• Refraction occurs while passing through the tissue, as wave velocity decreases from air
to skin, fat and muscle the beam bents to normal. Hence converging and produce
relatively greater heating at depth.
• Both are greater in small radius curvature tissues like forearm and leg
• This shows that the heating in the tissues depends not only on microwave absorption but
also in the rate of heat transfer within and between the tissues .

18. PHYSIOLOGICAL EFFECTS
• When microwaves radiation is absorbed in tissues it provokes ionic movement,
rotation of dipoles and electron orbit distortion.
• Similar to SWD
• The amount of heating is directly proportional to the amount of absorbed radiation.
• As the microwave strongly absorbed by muscle as it is high water and ion content,
less in fatty tissue and bone which have a lower water and ion content.
• In each tissue heating would be greatest at the surface and diminish exponentially
with depth.

19. PHYSIOLOGICAL EFFECTS
• Effect on metabolism
• Effect on blood supply
• Effect on nervous tissue
• Effect on muscular tissue
• Effect on sweat glands

20. THERAPEUTIC EFFECTS
• Microwaves are suitable for deep heating tissue, both muscle and soft tissue
with high water and ion content.
• Articular structures close to the surface, such as the wrist joint or anterior aspect
of the knee, might also heated effectively, but it is not likely to affect deeply
placed structures covered with muscle tissue like hip joint.
• It should be emphasized that heating patterns are highly irregular and probably
vary considerably along with the individual’s distribution of fat and muscle

21. THERAPEUTIC EFFECTS
• The depth of pentration of microwaves in tissue is less and is ranges between
3mm and 3 cm but SWD pentrate as deep as 6cm
• Other effects are same as SWD in decreasing pain , muscle spasm ,
inflammation, Infection , fibrosis and delay the healing
• It can be used in traumatic and inflammatory conditions, degenerative
arthropathies, enthesopathies, arthritis of joints etc.
• It is useful in treatment of soft tissues and superifical joints because it is generally
possible to irradiate only one aspect of the body at a time.

22. METHODS OF APPLICATION
STAGES
1. PATIENT
Explanation :
• Describe the nature of the treatment to the patient,
• Only small temperature rice will occur, Unlike the situation of a microwave oven in
which the temperature can be made to raise to cooking level,because the heat and
reflected microwave can’t escape.
Examination :
• Test the thermal sensitivity of the skin to which the microwave are to be applied.
• Inspect the skin for evidence of any inflammatory skin conditions as they should be
avoided.
Protection
• Give the patient a pair of microwave goggles as if radiation could enter the eye.

23. 2.Apparatus
• The choice of the emitter is dictated by the size of tissue area to be
treated.
• The power should be switched on and the machine given time to
up, if necessary.
3.Preparation of part
• Position the patient so the part to be treated is comfortably supported
and sufficiently exposed.
• Microwave should not be applied through clothing or where there is
metal in the field.
• Use wooden furniture and take care that the emmiter does not
any large metal surfaces.

24. 4.Setting up
• Position the emitter so that the radiation strikes the surface at right angels,bearing in
mind that the distant emmiters have diverging beams,only the axial radiation will be
striked at right angels,while the peripheral radiation will strike incident angels.
• While this may not make much difference when the writer is ‘square on’,slight angling of
the emitter increase the already considerable reflection from the skin surface,making the
treatment ineffective.
4.Instructions and warnings
• Explain the degree of heating required to the patient.
• The intensity and site of heating in the tissue is based on their sensation.
• As the indicator givens only machines output.patient should be aware of cutanious
thermal sensation.
• They must be warned to call the therapist immediately if the heat becomes more than
comfortable warmth
• If any discomforts or pain and to remain still throughout the application

25. 6.Application
• Switch the microwave output on for the predetermined length of time.
7.Termination
• After switching off and removing the apparatus, the treated area is examined and the
surface temperature and presence of any erythema are noted and recorded.
DOSAGE
• In acute conditions :5-10min
• In chronic condition :15-30min.
• it depends on the condition and type of applicatior used.
• The patient should feel comfortable warmth.
• Power output can be around 200watts so as to raise the body temperature in the
therapeutic range of 40°-45°C.
• Treatment may be given daily or on the alternate days.

26. Potential dangers
1. Burns:
• It can cause burn on the superficial tissues
• Skin must be kept dry to avoid burns.
• Water is heated more rapidly by microwave because of high degree of absorptive power of
theses waves.
• Patient perception of heat is the only guide of the treatment.
2.Effect of metal
• It is strongly reflected from metal surfaces.
• Any metal between the target tissue and the microwave emitter will shield the underlying
tissues from the radiation.
• Metals may also distort and concentrate a microwave field and causes llocal
overheating.which can be dangerous.
Eg:metals embedded in the tissue, either surgicaly or by accident .
• As there are no heat receptors in the deep tissues the patient will Only be aware of deeper
damage if pain occures subsequently, after the damage has occurred.

27. 3.Effect of changed blood flow
• Heating any collection of fluid.,such as an acute haematoma, a tense haemarthrosis,
or joint effusion,may cause considerable pain.
• Applying heat to an area with an acute inflammation increases the risk of causing local
tissue damage.
• Extent of any damage will depend on the extent of inflammation.
4.Effect of surface moisture
• If moisture appears on the surface from any source,
Eg:open wounds of wet dressings,it will absorb radiation.
• So treatment should be stopped and the moisture is removed.

28. 5.Implanted electronic equipment
• Hearing aids or cardiac pacemaker
• Avoided as the equipment might malfunction.
6.Eye
• Avoid exposing the eyes directly to microwave radiation.
• They are reflected from the curved,bony orbit and focused in the eye.
• There may be concentration of heat in the intraocular fluid.
Eg: when treating the anterior aspect of the shoulder goggles should be given which are
impervious to microwaves

29. 7.Testes
• Small temperature rises can interfere with spermatogenesis in mammals because the
testes are located outside the abdominal cavity
• Heating of 100mW-2 could possibly produce testicular damage in humans.
• Direct irradiation of the testes should be avoided and care should be taken to prevent
large amount of radiation.

30. 8.Pregnancy
• In early pregnancy,the risk is possibly considerably lower than with shortwave given the
depth in the pelvic of the uterus and the Specific absorption rate of microwave,
with a frequency of 2450MHz.
• Diathermy should not be applied to the abdomen or pelvis during pregnancy.
9.Tumors
• The treatment could accelerate the growth of the tumor.
• Due to increased circulation metastasis occurs(spreading of tumor).

31. 10.Deep X-ray or cobalt therapy
• Due to this the devitalizatio of tissue occurs
• It leads to further damage due to the application of microwave Diathermy
Other local ppapathologies.
Heat treatments are not advisable for 2reasons
1. The reduced capacity of skin to manage an increased local temperature.
2. A possible effect of local heating on any remaining malignant cells.

32. • Local heating is also not advisable for areas of local infection.
Contraindications and risks
• Defective arterial circulation
• Acute inflammation of area under tension such as
bursitis
Tense haemarthrosis .
Acute haematoma
• Surface moisture increases the extent of skin heating
• Metal in the area under treatment
• Indwelling electronic equipment
Eg:cardiac pacemakers.

33. • Malignancyand skin treated in the past 6 Months with radiotherapy
• Eyes and testes,due to energy concentration and poor heat dissipation.
• Pregnant uterus
• Circulatory defects like hemorrhage, vascular disease, thrombosis
• Children
• Mentally retarded patients
• Uncooperative patients
• Epileptic
• As they can not appreciate the heat required and can’t report overheat.

34. Long wave Diathermy
• LWD is the use of high frequency electromagnetic waves of the frequency 1mhz and
wavelength 300m.
• These devices produce local heating through the application of a pair of metal
electrodes to the skin by using mediater
• Heating occurs throughout the intervening tissues, but is greater close to the elelectres.
• If unequal size electrodes are used, greater heating occurs under the smaller electrodes

35. Advantage
• LWD has less frequency 1MHz than SWD so there is minimal loss of energy
• Power output is 25-75watts only where as in SWD it is 250-1000watts
• LWD does not produce any interference with other equipments
• It can be used even with patients having metal implants
• Portability and affordability of equipment is good in LWD.

36. Pulsed Short wave Diathermy
• Pswd is refered to as pulsed electromagnetic energy or field, dipulse etc.
• Pswd is created simply by interrupting the output of continuous SWD at regular
• Pswd was invented in 1930s but became popular only after 1950s.
• The frequency of Pswd is same as SWD ie.27.12MHZ but interpulse Interval or off-time is
added to it.
• Pulse frequency is between 25 and 600pps.

37. • Pulse width is between 20 and 40ms(65 is most commonly used).
• By adding rest period to the treatment the average power is considerably reduced.
• The heat developed in the tissue is dispersed by the circulation and treatment is thus
referred to as nonthermal treatment.
• Pswd increases the cellular activity.
• It also increases the reabsorption of haematoma.
• It reduces swelling and increases the repair process.
• Treatment duration varies from 15-60min.

38. Thank you....