Guidelines For Limiting Radiofrequency Exposure - Short Wave Diathermy - Safety Code 25

5. Safe Use Guidelines - Control of Operator Exposure

The recommendations provided here address only those aspects of safe use that are specific to radiofrequency (RF) exposure from short-wave diathermy devices, and do not deal with electrical safety rules. The recommendations are aimed at keeping the operator exposure to RF within the limits recommended in Canada.

5.1 Care of Equipment

1. Short-wave diathermy devices should be thoroughly examined at least yearly to ensure that all the parts are in good working order. Particular care should be taken to ensure that cables and electrodes are not cracked or burned, and the hinges of the applicator (electrode) support are working properly.
2. The operation of electrodes should only be tested when they are placed over a tissue phantom such as a plastic container with physiological solution. Power must not be switched to the electrodes unless they are properly applied to a patient or the tissue phantom.
3. Manufacturer's instructions on equipment care should be followed, and whenever there are any doubts whether the device operates properly, a qualified person should be called in to test the device.

Figure 3 - The diathermy treatment configuration producing high intensity stray fields.

5.2 Use of Equipment

Operators of short-wave diathermy devices should minimize potential exposure to RF radiation. To maintain exposures within the recommendations of the Federal government:

1. Short-wave diathermy devices should be used only for treatments prescribed by a physician.
2. The electrodes should be carefully placed over the treatment area. Minimizing the gaps between the electrodes and patient or towels helps to limit stray RF radiation.
3. The RF power should be turned on only after the electrodes are in place.
4. The operator should remain at least 1 m from the electrodes and 0.5 m from the cables during the treatment. Short duration excursions closer to the electrodes or cables are permitted, but only when necessary.
5. No metal beds or chairs should be used during short-wave diathermy treatments. Other large metal objects should be kept at least 3 m from the electrodes and cables, when the short-wave device is in operation.

Care must be taken to ensure that the patient does not receive any unnecessary exposure to tissues other than those prescribed for treatment. To minimize such exposure:

1. The applicator should be carefully placed to conform to the treated area as closely as possible.
2. The cables leading to the applicator should not be placed in the vicinity of the patient's nonprescribed tissue.
3. A patient-operated safety switch should always be operational, so that the patient can terminate the treatment.
4. The patient should remove all metal objects.

If the patient has metal or other implants which may interact with RF energy, the physician must be aware of this before prescribing the treatment. Unless specifically recommended by the patient's physician after risk benefit considerations, the patient with implants must not be treated by short-wave diathermy.

e.  Patients with cardiac pacemakers should only be treated if recommended by their physician. The diathermy operator should remain in the treatment room or be able to observe the patient during the whole treatment duration.

f.  No pregnant patient should receive short-wave diathermy treatment in any area of the body which is likely to result in exposure of the fetus.

To avoid fire hazard, cables and electrodes should be kept away from flammable materials, as stray RF fields can heat such synthetic materials as nylon, polyvinyl chloride (PVC), polyethyl-ene terephthalate (PET) and combinations of cotton with synthetics. Further information concerning thermal hazards associated with short-wave diathermy devices can be obtained from the Bureau of Medical Devices, Environmental Health Directorate, Health Protection Branch, Ottawa, Ontario K1A 0L2.

Short-wave diathermy devices should only be operated by a qualified nurse, medical practitioner or physiotherapist who has taken a course in the use of such devices.