The document discusses microwave diathermy (MWD), including its properties, production, therapeutic effects, indications, contraindications, and precautions. MWD uses electromagnetic waves between 300 MHz to 300 GHz to generate heat in superficial tissues up to 3 cm deep. It can be used to treat pain, muscle spasms, inflammation and other conditions affecting small, superficial areas like joints, muscles, and tendons. Proper application and monitoring are needed to avoid risks such as burns.

1. Microwave Diathermy
By
Prof.Dr. Gehan Mosaad

2. At the end of the lecture the student
should be able to
 Understand physics and properties of MWD
 Know different directors of MWD
 Identify therapeutic effects, indications,
contraindications of MWD
 Recognize dangers and precautions with MWD
 Know the difference between SWD and MWD
 Analyze and discuss different cases

3. Properties of Microwaves
 Microwave diathermy (MWD), is a form of
electromagnetic radiations lying between shortwave and
infrared waves.
 Microwave diathermy does not penetrate as deep as
shortwave diathermy.
 The energy is first absorbed at the surface of the body
(skin) and a part of it penetrate and absorbed in deep
tissues.
 It generates Strong Electrical Field and relatively Little

4. Frequency and wavelength
 Microwave has a much higher frequency and a shorter
wavelength than shortwave diathermy.
 The general frequency of microwave is between 300 MHz
to 300 GHz with wave length of 10 mm to 1 meter.
 The therapeutic microwave generators used frequency of
2450MHz with wave length of 122.5mm.

5. Microwave Production and Device
The generator used to produce microwaves has three
main components:
1- A multi-cavity magnetron valve
2- A coaxial cable
3- A director.
Mechanism of MW production
 The magnetron produces a high frequency alternating
current which is carried by coaxial cable to the
transducer (director).
 The coaxial cable transmits the energy to the director
whereas a radiating system comprising an antenna
within a reflector that is used to direct the microwave
to the patient.

6. Microwave Production and Device
 The alternating current in the antenna produces an
electromagnetic field that is directed toward the
tissue by a curved reflecting 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 small, defined areas.
 Therefore these devices can be useful during
rehabilitation when only small areas of tissue are
involved.

7. Production of microwave

8. Directors Used in MicrowaveDirectors Used in Microwave
ApplicationsApplications
 Circular directors
- The heating pattern is more
intense around the outer
portion than the centre.
- There are small and large
 Rectangular directors
The heating pattern tends to
be more concentrated in the
center of the treated area.

9. Biophysics of MWD
 MWD tend to be reflected and scattered at different
interfaces as air-skin, skin-fat, and the fat-muscle which
limit its penetration into the tissues.
 Because of the spreading of MW, the superficial tissues
tend to be heated more than deeper tissues.
 Depth of penetration depends on the frequency of the
wave and the medium. The effective penetration of
2450MHz is approximately 3 cm.
 Mechanism of heat production by MWD is the same as
SWD

10. Therapeutic Effects of MicrowaveTherapeutic Effects of Microwave
DiathermyDiathermy
 Pain: MWD is useful in the treatment of traumatic
and rheumatic conditions affecting superficial
muscles, ligaments and small superficial joints.
 Muscle spasm: which may be reduced directly by
MWD or may be reduced by relieving of pain.
 Inflammation: MWD reduces inflammation by
increase blood supply that will increase venous
return from the inflamed area and aids the
reabsorption of edema exudates.

11. Therapeutic Effects (contTherapeutic Effects (cont.(.(
 Delayed healing: MWD promotes healing of
open skin by increase cutaneous circulation.
 Infection: MWD can control the chronic infection
by increasing the circulation.
 Fibrosis: The heating effect of MWD increase the
extensibility of fibrous tissues such as tendons, joint
capsules and scars.

12. Indications of MWDIndications of MWD
- The clinical indications for MWD are, more or less, similar to
those for SWD.
- MWD may be preferable to SWD when more concentrated or
localize heating is needed.
 Musculoskeletal disorders:
- Sprain - Muscle & tendon tear
- Strain - Degenerative joint disease
- Joint stiffness in superficial joints
- Capsular lesions.
 Superficial inflammatory or infective conditions :
- Tenosynovitis - Bursitis
- Synovitis - Abscess
- Infected surgical incisions

13. Contra-indicationsContra-indications
 Over malignant tissues.
 Over ischemic tissues.
 Over wet dressings and adhesive tapes.
 Metal implants.
 Pacemaker.
 Over growing bone.
 Male gonads: repeated irradiation can cause
sterility.
 Hemorrhage.
 Impaired thermal sensation.

14. Contra-indications (contContra-indications (cont.(.(
 Recent radiotherapy.
 Hypersensitivity to heat.
 Acute infection or inflammation.
 Venous thrombosis or phlebitis.
 Pregnancy: heat applied to pelvis or hip in
pregnancy may cause hemorrhage or
miscarriage.
 Acute dermatological conditions.
 Severe cardiac conditions.

15. Precautions & DangersPrecautions & Dangers
 The same as SWD, but it is recommended to
avoid the presence of metal within the
treatment field (4 feet) because of scattering
and reflection of MWD
 Due to scattering and reflection of MWD to
the surrounding environment, it has been
associated with high incidence of
miscarriages among female therapists who
regularly operate these units than SWD.
 The eyes: MWD may cause cataract.

16. Precautions & Dangers(contPrecautions & Dangers(cont.(.(
 Obesity: MWD with 2450MHz, there is danger
of producing an excessive heat in the
subcutaneous fat layer
 Burn: There is an increasing of risk of excessive
heating and burning with the using of MWD due
to:
1. Shallow depth of penetration
2. Reflection at tissue interfaces
3. Potential standing waves

17. Dosage of MWDDosage of MWD
 Duration of treatment: 20 minutes is the
optimum.
 Intensity: the patient should feel mild and
comfortable warmth.
 Frequency: daily or on alternating day.

18. Microwave Device

20. Comparison of different types of
diathermy
Type Thermal SWD Thermal
MWD
Non thermal
SWD
Frequency 27,12MHZ 2450MHZ 27,12MHZ
Applicator Inductive coil Capacitive
plate
Magnetron Inductive coil
drum
Incident field Electromagnetic Electric Electromagnetic Electromagnetic
Tissues most
affected
Deep and
superficial
Superficial Small areas Deep and
superficial

21. Comparison of heat distribution by
different diathermy applicators and
ultrasound
Type Fat Muscle Bone
Inductive coil Minimum Maximum None
Capacitive
plate
Maximum Moderate Low
Magnetron
MWD
Maximum Maximum None
Ultrasound Slight Maximum None

22. Case study
Case 1
MS is a 50-year-old female. She has been diagnosed with
adhesive capsulitis of the right shoulder and has been
referred to physical therapy. She complains of shoulders
stiffness. The objective exam reveals restricted right
shoulder active and passive range of motion.
Case 2
AB is a 24-year-old male, football player who suffered from
left ankle inversion sprain approximately 48 hours ago.
He complains of moderate pain and swelling at the
lateral ankle.