MWD

INTRODUCTION,WAVELENGTH,PARAMETERS,PRODUCTION,EFFECTS,INDICATION,CONTAINDICATION

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 × 10 10 hertz to1.5 ×10 5  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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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)

12. 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 :

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

14. 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

15. Advantages Pain is relieved Healing of infections is faster Aids in relaxation

16. 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