electro 11 (microwave)

Electrotherapy O h Lecture: Microwave Diathermy

  • Instructor: Dr. Ghada Abd Elmoniem

  • Course Code: PT206

Microwave Diathermy (MWD) Overview

Objectives

  • Define microwave diathermy.

  • Identify the physics and production of MWD.

  • Recognize the physiological effects of MWD.

  • Identify the indications and contraindications of MWD.

  • Recognize pulsed microwave diathermy.

  • Describe the practical application of MWD.

Definition and Physics

  • Microwaves:

    • Form of electromagnetic radiation between short waves and infrared waves.

    • Frequencies: 300-30,000 MHz (commonly 2450 MHz, 915 MHz, 433.9 MHz).

    • Wavelengths commonly used: 12.25 cm, 33 cm, 69 cm.

    • Principal function: Produce local rise in temperature where absorbed.

Production of Microwave Radiation

  • Components:

    • Multicavity magnetron valve: Generates high-frequency electrical current.

    • Coaxial cable: Transmits high-frequency energy to an antenna.

    • Antenna: Transmits energy to the patient (free space radiation).

Important Notes

  • Microwaves do not require a medium for transmission.

  • Patients are not part of the circuit; requires only one emitter (applicator).

  • Microwaves interact with materials through reflection, refraction, interference, absorption.

  • Absorption is highest in high fluid content tissues (e.g., blood, muscles).

  • In patients with >1 cm subcutaneous fat, heating may occur in the fat before deeper tissues are affected.

Directors of MWD

  • Circular Director:

    • Produces circular cross-section beam, denser at periphery.

  • Rectangular Director:

    • Produces oval cross-section beam, greater density centrally.

Physiological Effects of MWD

  • Absorption results in heat production in tissues.

  • MWD penetrates deeper than Infrared Radiation (IRR) but less than Shortwave Diathermy (SWD).

  • Effective penetration depth is approximately 3 cm, varying with water content in tissues.

Comparison of Heat Production

  • Microwave vs. Shortwave Diathermy:

    • MWD heats subcutaneous fatty layer more, less therapeutic value than muscle penetration.

Therapeutic Effects

  • Similar to SWD but effective mainly for superficial structures and those with high fluid content.

  • Suitable for treating traumatic and rheumatic conditions in soft tissues and small joints.

  • More effective for localized than widespread lesions; usually only one body aspect can be treated at a time.

Indications for MWD

  • Pain Relief: Effective for treating superficial muscle pain from trauma and rheumatism.

  • Muscle Spasm: Reduced via direct heat or pain relief.

  • Chronic Inflammation: Accelerates resolution by increasing blood supply.

  • Delayed Healing: Enhances skin circulation, aiding in healing.

  • Infection: May control chronic infections by boosting circulation and immune response.

Contraindications of MWD

  • Poor skin sensation or thermal sensation impairment.

  • Presence of metal in tissues.

  • Conditions such as malignancy, pregnancy, acute inflammation/infection, circulatory deficits.

  • Dermatological conditions, especially acute, can worsen with heat.

Additional Contraindications

  • Specific areas like eyes and testicles should be avoided due to temperature concerns.

  • Patients with cardiac pacemakers, obesity, active tuberculosis, or recent deep x-ray therapy should not undergo treatment.

Dosage Guidelines

  1. Duration: 10-30 minutes, preferably 20 minutes for stable tissue temperature.

  2. Intensity: Patient should feel mild warmth; excessive heat can cause burns.

  3. Frequency: Treatments may be daily or alternate days, depending on the patient’s response and condition.

Pulsed Microwave Therapy

  • Effects are similar to non-pulsed MWD but do not produce the same temperature rise in tissues.

Practical Application of MWD

  • Similar to SWD, using a director instead of an electrode.

  • Position director 2-3 inches from treated area, aiming beam perpendicular to the skin.

Guidelines for Safety in MWD Application

  • Patient Questionnaire: Assess contraindications and prior treatments.

  • Patient Positioning: Ensure comfort and support.

  • Inspection: Check the treatment area for rashes or infections.

  • Drape: Use towels as needed.

  • Treatment Setup: Record parameters before starting.