Microwave Diathermy
Microwave diathermy is a deep heating modality, similar to short
wave diathermy but differs in its physics and mechanical properties.
Physics:
The clinical microthermy frequency is limited to 2.450 Mc range
(10-12 cm wavelength), which is shorter than short wave diathermy. The
high frequencies of microthermy are obtained from a unique device called
the magnetron, which is perforated with tiny holes, through which the
electrons flow into the treatment heads. The special design of the
treatment heads shapes and focuses the field directly at the target area.
The whole device is used to direct the waves onto the tissues. This device
is sometimes termed *the emitter, *the director or *the applicator. 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.
The heat produced by microthermal radiation is known to be more
concentrated than that produced by short wave diathermy. Although
penetration is theoretically increased with higher frequencies, absorption
still depends on the target density and the intervening tissues. According
to the differences in absorbability of tissues, the clinical effect of
microwave radiation depends on the type of tissue involved.
Physiological effects:
Absorption of the waves results in production of heat in the tissues,
but differs from other heat treatment methods in the distribution of heat.
Microwave penetrates more deeply than infrared rays but not deeply as
short wave diathermy, so microwave is not suitable for deeply placed
structures. The effective depth of microwave penetration is about 3 cm,
1
so the depth of heating is intermediate between that of infrared radiation
and short wave diathermy. As the microwaves are strongly absorbed by
water, tissues with high fluid content are heated most, while less heat is
produced for tissues with low fluid content as fat. Moreover, there is an
appreciable heating of tissues having good blood supply such as muscles.
Indications:
The clinical indications for microthermy are, more or less, similar
to those for short wave diathermy. Microthermy may be preferable to
short wave when more concentrated or localize heating is needed.
- Traumatic and inflammatory lesions, in which increase of blood supply
and relief of pain and muscle spasm are required.
- Lesions in the superficial regions and those of high fluid content.
- Traumatic and rheumatic conditions affecting soft tissues and small
superficial joints.
- Superficial infections such as septic fingers, carbuncles and other
superficial abscesses.
Contraindications and precautions:
- Burns: As water is heated rapidly by microwaves, burning of wet skin
may occur.
- Eyes: Irradiation to the eyes may develop opacities.
- Circulatory defects: Such as hemorrhage, thrombosis, phlebitis and
other vascular lesions.
- Malignancy: Microwave diathermy should not be applied to regions of
malignant growth or tubercular infections.
- Cardiac pacemakers.
- Genital area.
2
Treatment procedures:
1. Selection of the treatment head (Director):
Generally, two designs of directors are found:
- Circular: In which heat is denser at the periphery more than at the
center. Two sizes of circular directors are available:
Small: for small areas.
Large: for large areas.
- Rectangular: for elongated areas.
So, director selection depends on the shape and the anatomical
configuration of the treated area. The actual distance from the director to
the skin will determine the extent of the treatment zone, which can be
detected by passing an ordinary fluorescent lamp between the treatment
head and the patient’s skin.
2. Preparation of the patient:
- The target area should be bare skin.
- Clean the skin thoroughly.
- Choose the comfortable position for the patient.
- No towel is needed.
3. Monitoring the treatment:
The target distance will determine the power levels, as the closer
the director to the skin, the lower the power levels and vice-versa. A
warm-up period must be allowed to permit the magnetron to develop
enough efficiency. The desired sensation of the patient is gentle warmth.
Thus, reports of hot spots should be attended immediately either by
reducing the power or increasing the distance.
3
4. Duration of treatment:
Treatment by microthermy requires between 10 and 20 minutes.
Generally, smaller target areas need less time, while larger ones need
more. Treatment may be applied daily or every other day.
4