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Difference between Short wave diathermy Microwave diathermy Ultrasonic diathermy

This page compares Short wave diathermy vs Microwave diathermy vs Ultrasonic diathermy and mentions difference between Short wave diathermy, Microwave diathermy and Ultrasonic diathermy types.

Introduction : The meaning of diathermy is electrically induced heat. It is used in medical field for two purposes viz. physiotherapy and surgery. High frequency current (~100 KHz) is utilized to generate heat to treat body tissues and muscles. There is no major risk to human body by diathermy method.

Diathermy in physiotherapy is carried out using different waves such as short wave, microwave and ultrasonic waves. The main function of diathermy in physiotherapy is to heat tissues without unduly raising skin temperature. Diathermy in surgery is valuable in neurosurgery and surgery of eye.

Short wave diathermy

Short wave diathermy

The figure-1 depicts short wave diathermy treatment method. This diathermy type uses either capacitor plates (i.e. pads) or inductor coil to generate short waves for heating the tissues.

In capacitor method, two pads or electrodes are mounted on either side of the area under treatment. Here body portain acts as dielectric and forms capacitor circuit. When short waves are applied, capacitor produces heat due to dielectric losses in the tissues. In inductor method, body portion to be treated is placed in the coil. The current of short waves is applied to the coil which heats up the tissues.

It is used to relieve pain and to heal deep seated sports related injuries. It does not produce any discomfort to the patients during and after treatment.
Refer advantages and disadvantages of Short wave diathermy >> type.

Microwave diathermy

Microwave diathermy

The figure-2 depicts microwave diathermy treatment method. Microwave frequencies in the range 300 to 30000 MHz are used in this method. The most commonly used frequency is 2450 MHz.

It uses magnetron device with antenna to generate microwave frequency waves. These waves are transmitted towards body area under treatment. The technique is very simple and does not require any pads or electrodes or coils as in short wave diathermy type. Microwave frequency waves are absorbed to heat up tissues as per desired depth.
Refer advantages and disadvantages of Microwave diathermy >> type.

Ultrasonic diathermy

Ultrasonic diathermy

The figure-3 depicts Ultrasonic diathermy treatment method. In this method, heating is produced by absorption of ultrasonic energy by certain tissues. Due to absorpion, high speed mechanical vibrations are produced in the cells of absorptive tissues. This provides micro level massage to the tissues.

Piezoelectric crystal is used to generate ultrasonic energy when oscillator output is applied to it. In this method, depth of penetration can also be controlled which helps in treatment of desired tissues.
Refer advantages and disadvantages of Ultrasonic diathermy >> type.

Difference between Short wave, Microwave and Ultrasonic diathermy

Following table mentions difference between Short wave diathermy, Microwave diathermy and Ultrasonic diathermy types with respect to various parameters.

Comparison Parameters Short wave diathermy Microwave diathermy Ultrasonic diathermy
Wave type Electrostatic field (in capacitive method) and Electromagnetic field (in inductor method) Electromagnetic (EM) waves Ultrasound waves
Frequency and Wavelength Frequency of 10 to 100 MHz at wavelength of 3 to 30 meters Frequency of 300 to 30000 MHz at wavelength of 1 m to 1 mm Frequency of 1 to 3 MHz range
Working principle In capacitor based diathermy, pads or electrodes are placed such that body part to be treated is sandwiched between them and act as dielectric. Short waves are applied to produce heat due to dielectric losses in the tissues. In inductor coil method, body part to be treated is placed in inductive coil. The current flowing within the coil produces rotating field which generates eddy currents in the tisssues. The eddy currents cause friction and heat is produced. Magnetron is used to generate microwave frequencies/wavelengths at specific values to focus on target area for treatment. 2450 MHz with 12.33 cm, 915 MHz with 32.7 cm and 433.9 MHz with 69 cm are used by microwave diathermy devices. High frequency sound waves (at 1 MHz and 3 MHz) are used to treat deep tissues.
Circuit components As shown in the figure-1, it uses inductor coil or capacitor based circuits. As shown in the figure-2, it uses magnetron, transducer, timer circuit etc. As shown in the figure-3, it uses piezo-electric transducer, timer and intensity/frequency control circuit etc.
Depth of penetration deep upto 50 mm or 7 cm More superficial than short wave type, upto 3 to 4.5 cm (depends on tissues with high or low fluid content) 1 MHz for deep penetration upto 5 cm, 3 MHz for superficial penetration upto 2 cm
Test duration 5 to 20 minutes depending on indications and dosage 20 to 30 minutes

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