Deep heat: shortwave and microwave diathermy

1. How does shortwave diathermy work? What is the most common frequency and to what depth is heating provided?
2. What is the difference between the induction and conduction method of shortwave diathermy? What are indications for each?
3. What are indications and contraindications for shortwave diathermy?
4. What is microwave diathermy?
5. What are indications and contraindications for microwave diathermy?

Answers:
1. SWD produces deep heating through conversion of electromagnetic energy to thermal energy. The most common frequency is 27.12 MHz and it heats to a deapth of 4-5cm.
2. Induction method produces high temperatures in water-rich tissues via a coiled magnetic field and is indicated when heat to more superficial muscles or joints is desired. Conduction method produces high temperatures in water-poor tissues with low conductiveity via rapid oscillation in an electric field, and is more effective for deeper joints. Precise dosing is difficult and is monitored via patient's pain perception.
3. Indications for SWD include chronic prostatitis, refractory PID, myalgia, back spasms. Contraindications include general heat precautions, metal, contact lenses, gravid or menstruating uterus, or skeletal immaturity.
4. Microwave disthermy is conversion of microwaves to thermal energy. It does not penetrate as deeply as US or SWD and is better for muscle heating.
5. Indications include heating superficial muscles and joints, to speed hematoma resolution, and for local hyperthermia in cancer patients. Contraindications include general heat precautions, skeletal immaturity. It should be avoided in edematous tissue, moist skin, eyes, blisters, and fluid-filled cavities due to selective heating of fluid-filled cavities. Eye protection should be worn due to cataract risk.