Microwave

Electromagnetic wave

Short wave diathermy

Oscillating system

• Frequency

• Damping

• Resonance

• Waves ( Continuous , Pulse )

Electromagnetic Spectrum

Type of Radiation Frequency Range (Hz) Wavelength Range Type of Transition

gamma-rays 1020-1024 <10-12 m nuclear

x-rays 1017-1020 1 nm-1 pm inner electron

ultraviolet 1015-1017 400 nm-1 nm outer electron

visible 4-7.5x1014 750 nm-400 nm outer electron

near-infrared 1x1014-4x1014 2.5 um-750 nm outer electron molecular vibrations

infrared 1013-1014 25 um-2.5 um molecular vibrations

microwaves 3x1011-1013 1 mm-25 um molecular rotations, electron spin flips*

radio waves <3x1011 >1 mm nuclear spin flips*

Electrostatic & Electromagnetic points

Diathermy

What is it?

General Information

• Another form of deep heat

• Out of favor with the PT community for the last several years.

• In general shortwave diathermy is effective for deep heating of deeper structures.

• Microwave diathermy has been used for smaller body parts such as the hands

Indications

• Any condition where it is desirable to increase the temperature mild to moderately.

• Increase the extensibility of tissues in musculoskeletal disorders

Ultrasound

• Modality which stimulates repair of soft tissue and pain relief

• Form of acoustic energy used for deep tissue heating

– Operates at inaudible frequency

– Sound scatters and is absorbed as it penetrates tissues -- losing energy = attenuation

– Impedance and penetration are determined by properties of media (densities)

• Equipment

– High frequency generator which provides electrical current through a coaxial cable to a transducer applicator

• Through piezoelectric effect electrical current is transformed into acoustic energy through contraction and expansion of piezoelectric crystals

– Frequency range between .75 and 3.0 MHz • 1 MHz ultrasound allows for deeper penetration

while 3 MHz is absorbed more superficially

– Area of transducer that produces sound is the effective radiating area • Produces a beam of acoustic energy -

collimated cylindrical beam with non-uniform distribution

• Variability in the beam (beam non-uniformity ratio - BNR) =lower BNR = more uniform energy output

• Application

– Direct skin application

• Requires a coupling medium to provide airtight contact w/ skin and a low friction surface

– Underwater application

• Used for irregularly shaped structures

• Body part is submerged in water, ultrasound head is placed 1” from surface

• Water serves as coupling medium, air bubbles should be continually swept away

• Sound head should be moved in circular or longitudinal pattern

• Should be performed in non-metal container to avoid reflection

– Bladder technique

• Used when body part can not be immersed in water

• Balloon filled w/ gel or water to allow for transmission --coated with gel to enhance contact surface

– Moving the transducer

• Leads to more even distribution of energy, reducing likelihood of hot spots

• Should be moved at a rate of 4cm/second

• Must maintain contact of transducer with surface of skin

• Circular or stroking patterns should be used

• Should not treat an area larger than 3 times the ERA

– Dosage and Time

• Varies according to depth of tissue to be treated and the state of injury

• Duration tends to last 5-10 minutes

• Intensity varies

– Low 0.1-0.3 W/cm2

– Medium 0.4 - 1.5 W/cm2

– High 1.5 - 3.0 W/cm2

– Special Considerations

• While it is a relatively safe modality, precautions still must be taken

• Be careful with anesthetized areas, reduced circulation

• Avoid high fluid regions of the body, acute injuries, and epiphyseal areas of children

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Diathermy

Shortwave and Microwave Diathermy

روش بكارگيري جريان هاي پر فركانس

Short wave diathermy

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Types of Shortwave Diathermy

• Induction field diathermy: strong magnetic forces are produced by the pt. circuit which then induces a electrical current within the body part. A single induction field coil is made of metal shaped into a coil, which is highly conductive. Deepest form of Diathermy

Types con’t

• Capacitive field: Separate pads or airspaced drums are used as the electrode. The pt. is placed between the electrodes or the plastic drums. The intensity and depths of penetration are determined by the shape and distance between the electrodes. Much is absorbed by fat. Most effective when there is little fat. Field is placed perpendicular to the area to be heated.

Capacitive field

Capacitor Electrodes

Capacitor Electrodes

• Electrical field

Capacitor Electrodes

Patient is between

electrodes

Becomes part of circuit

Tissue is between

electrodes

Capacitor Electrodes: Air Space Plates

• Sensation of heat : proportion to the distance of metal plate from the skin

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Physiological Effects

• Friction created by movement of ions produces heat

• SWD can cause heating 2-5 cm. deep and temperatures may increase 7°

• Thermal effects similar to US, but can cover a larger area and last longer

Shortwave Diathermy Unit

• A =Power switch

• B = Timer

• C = Power meter

– Monitors current from power supply, not current entering patient

• D = Output intensity (% max power to patient)

• E = Tuning control (tunes output from RFO)

Continuous Shortwave Diathermy

• Patient sensation provides basis for recommendations of continuous SWD

Pulsed Shortwave Diathermy

• Pulsed electromagnetic energy (PEME)

• Pulsed electromagnetic field (PEMF)

• Pulsed electromagnetic energy treatment (PEMET)

Pulsed Shortwave Diathermy

Shortwave Diathermy vs. Ultrasound

Pulsed SWD produces the same magnitude and depth of muscle heating as 1 MHz ultrasound (Draper, JAT 1997)

Shortwave Diathermy: Treatment Time

• Typically, 20 - 30 minutes

• Reminder:

– As skin temperature rises, resistance falls

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Induction Electrodes

• Patient placed in a magnetic field

– NOT part of a circuit

Induction Electrodes: Cable Electrode

• Two arrangements:

– Pancake coils

– Wraparound coils

Induction Electrodes

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Induction field

Capacitor Electrodes: Air Space Plates

• Two metal plates surrounded by glass or plastic guard

• Metal plates can be adjusted 3cm within guard

• Produce ________________ oscillating current

• When one metal plate is overloaded, it discharges to other plate of lower potential

Induction Electrodes: Drum Electrode

• One or more monopolar coils rigidly fixed in a housing unit

• May use more than one drum depending on treatment area

• Toweling is important

Capacitor Electrodes: Air Space Plates

• Area to be treated is placed between electrodes

• Treatment area becomes part of the external circuit

Capacitor Electrodes: Pad Electrodes

Capacitor Electrodes: Pad Electrodes

Capacitor Electrodes: Pad Electrodes

• Must have uniform contact pressure on the body

– Toweling to prevent burns

• Spacing between electrodes is equal to the pads