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 Magnetic Field

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 Microwave Applications
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 Microwave Diathermy
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 (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 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-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 (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 & 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(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:
Shallow depth of penetration
Reflection at tissue interfaces
Potential standing waves

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

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

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.

23. Thank you