Microwave diathermy (MWD) uses electromagnetic radiation in the microwave frequency range to generate heat in tissue. MWD uses a magnetron to produce microwaves with frequencies commonly between 300 MHz to 300 GHz. These short wavelength microwaves generate strong electrical fields that cause heating through ionic movements and molecular distortion within tissues. MWD provides superficial heating that is more localized than shortwave diathermy and penetrates deeper than infrared radiation. Key uses of MWD include reducing pain, swelling and muscle spasm in inflammatory conditions like tendinitis as well as accelerating healing for injuries and infections.

1. MICROWAVE DIATHERMY
Dr. Paras Bhura PT
MPT (Musculoskeletal-Ortho.),MIAP, CMT, DNHE, YTTC.

2. INTRODUCTION
 Microwave Diathermy(MWD) is irradiation of tissue
with radiation in shorter wireless part of
electromagnetic spectrum.
 Its wavelength between infra-red rays and short
wave diathermic waves (hertzian rays).
 hertzian rays: An electromagnetic wave with a
frequency : 3 × 1010 hertz to1.5 ×105 hertz
 Also k/a Decimeter waves, as their wavelength lies
between 1-100cm.

3. PARAMETERS
 Frequency ranges from 300 MHz to 300 GHz.
 Wavelength ranges from 1 mm to 1 m.
 The commonly used for treatment
 Frequency : 2450 MHz, Wave length – 12.25 cm
 Frequency : 915 MHz, Wave length –32.8 cm
 Frequency : 434 MHz, Wave length – 69.1 cm

4. DIAGRAM MWD

5. PRODUCTION OF WAVES
 Its is not possible to produce microwaves by
mechanical means.
 Hence microwaves are obtained from a unique
special type of thermionic valve called the
Magnetron,
 which is perforated with tiny holes, through which
the electrons flow into the treatment heads.
 Magnetron is thermionic valve characterized by
centrally placed cathode and a surrounding circular
metal anode.

7. PRODUCTION CONT…
 Coaxial cable carries these high frequency currents
from magnetron and passes it to the antenna of
emitter.
 The applicators consist of an antenna element
backed by a reflector and endorsed within a plastic
case, one face of which is transparent to microwave
energy.
 The special design of the treatment heads shapes
and focuses the field directly at the target area.
 In this kind of treatment, the patient does not form a
part of the circuit, so no tuning is necessary as in
short wave application.

9. LAWS OF MICROWAVE RADIATIONS
 Microwave has a much higher frequency and a
shorter wavelength than shortwave diathermy.
 Generates Strong Electrical Field and Relatively
Little Magnetic Field
 Obey the laws of radiation, absorption, reflection,
refraction, inverse square.

10. PHYSIOLOGICAL EFFECT (P/E)
 Ionic movements
 Rotation of dipoles
 Distortion of molecules
 The amount of heating will be proportional to the
amount of absorbed radiation and the water content
of the tissue.
 Heating is More in muscle tissues and tissue with
more water and iron content and less in fat and
bone.

11. P/E CONT…
 Produces more superficial heating compared to
SWD and deeper compared to IRR.
 Heat production decreases as the depth increases.
 This could be because of microwaves are reflected
at various interfaces s/a
 skin-air,
 skin-fat,
 fat-muscle,
 muscle-bone interfaces.

12. P/E CONT… DEPTH OF PENETRATION
 Higher DOP with lower frequency
 DOP: 4.3 cm. with half value depth (HVD) 3 cm.
 For Muscle :HVD is 0.7 cm at frequency 2450
MHz.
 For fat, bone HWD is 3.5 cm at frequency of 2450
MHz.
 So, heating of the subcutaneous fat can be avoided
by MWD.

13. P/E CONT… DEPTH OF PENETRATION
 Higher Depth of penetration with lower frequency.
 So, frequency 915 MHz is more suitable for
therapeutic heating than 2450 MHz.
 As the wavelength increases penetration and
absorption increases in the deeper tissues.
 So, the wavelength of 32.8 cm (915 MHz) produces
more deeper heating than the wavelength 12.2
cm.(2450 MHz)

14. THERAPEUTIC USES:
 Inflammatory conditions:
 Increases blood supply and relieve muscle spasm
 Pulse mode can be used 72 hrs following trauma.
 Jumpers knee, tennis elbow, sprain, strain, etc.
 Traumatic conditions:
 For the remediation of early trauma.
 Resolve inflammation and pain.
 Enhance the extensibility of collagen fibers.
 Sports injuries, surgical lengthening of tight muscle.
 Arthritic conditions:
 Reduces pain, swelling, inflammation, increases
extensibility of collagen fibers.
 Pain relief :

15. INDICATIONS
 Pain and muscle spasm
 Tennis elbow, jumpers knee
 Sprain and strain
 Sports injuries
 Rheumatoid arthritis, O.A, A.S.
 Bacterial infection.

16. CONTRA INDICATIONS
 Diminished thermal sensation
 Defective arterial circulation
 Recent hemorrhage
 Metal implantation
 Cardiac pacemaker
 Malignancy,Cancer
 Tuberculosis of Bone, acute infection.
 Recent exposure to X-rays
 Pregnant uterus

17. ADVANTAGES
 Pain is relieved
 Healing of infections is faster
 Aids in relaxation

18. CONTRAST MWD/SWD
 Frequency is high
 Wave length is low
 Special valve-
magnetron
 Require emitter only
 Does not require tuning
 Lesser than MWD
 Wave length is high
 Oscillator circuit
 Require two electrodes
 Require tuning
MWD SWD