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- Application of High-Frequency Electromagnetic Energy
- Used To Generate Heat In Body Tissues
- Heat Produced By Resistance of Tissues
- Also Used For Non-Thermal Effects
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- Not Capable of Producing Depolarization and Contraction of Muscles
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- Physiologic Effects Are Those of Heat In General
- Tissue Temperature Increase
- Increased Blood Flow (Vasodilation)
- Increased Venous and Lymphatic Flow
- Increased Metabolism
- Changes In Physical Properties of Tissues
- Muscle Relaxation
- Analgesia
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- Doses Are Not Precisely Controlled Thus The Amount of Heating Cannot Be
Accurately Measured
- Heating= Current2 X Resistance
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- Pulsed SWD Used To Treat Soft Tissue Injuries and Wounds
- Related To Depolarization of Damaged Cells
- Loss of Cell Division
- Loss of Proliferation
- Loss of Regenerative capabilities
- Repolarization Corrects Cell Dysfunction
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- Radio Transmitter With FCC Assigned Frequencies
- 27.12 MHz at 11 M
- 13.56 MHz at 22 M
- 40.68 MHz at 7.5 M
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- Power Supply Powers Radio Frequency Oscillator (RFO)
- RFO Provides Stable Drift-Free Oscillations at Given Frequency
- Power Amplifier Generate Power To Drive Electrodes
- Output Resonant Tank Tunes In The Patient for Maximum Power Transfer
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- A=Power Switch
- B=Timer
- C=Power Meter(monitors current from power supply not current entering
patient-volume control)
- D=Output Intensity(%max power to patient)
- E=Tuning Control(tunes output from RFO)
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- Power Output Should Provide Energy To Raise Tissue Temp To Therapeutic
Range (40-45 deg C) (80-120 watts)
- Should Exceed SAR-Specific Absorption Rate (rate of energy absorbed
/unit area of tissue mass)
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- Manual vs Automatic Tuning
- Manual Tuning (adjusts patient circuit)
- Set Output Intensity at 30-40%
- Adjust Tuning Control Until Power Output Meter Reaches Max
- Then Adjust Down to Patient Tolerance Which Is About 50%
- If More Than 50% Patient Is Out of Resonance
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- Generates Both an Electrical and a Magnetic Field
- Ratio Depends on Characteristics of Both The Generator and the
Electrodes
- SWD Units at 13.56 MHz= Stronger Magnetic Field
- SWD Units at27.12 MHz = Stronger Electrical Field
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- Capacitor Electrodes
- Inductor Electrodes
- Selection of Appropriate Electrodes Can Influence The Treatment
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- Create Stronger Electrical Field Than Magnetic Field
- Ions Will Be Attracted Or Repelled Depending on the Charge of the Pole
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- Electrical Field Is The Lines of Force Exerted on Charged Ions That
Cause Movement From One Pole To Another
- Center Has Higher Current Density Than Periphery
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- The Tissue That Offers The Greatest Resistance To Current Flow Develops
The Most Heat
- Fat Tissue Resists Current Flow
- Thus Fat Is Heated In An Electrical Field
- Typical With Capacitor Electrodes
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18
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- Two Metal Plates Surrounded By Plastic Guard
- Can Be Moved 3cm Within Guard
- Produce High-Frequency Oscillating Current
- When Overheated Discharges To Plate Of Lower Potential
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- Area To Be Treated Is Placed Between Electrodes Becoming Part of Circuit
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- Sensation Of Heat In Direct Proportion To Distance Of Electrode From
Skin
- Closer Plate Generates More Surface Heat
- Parts Of Body Low In Subcutaneous Fat Best Treated
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21
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- Greater Electrical Field
- Patient Part of Circuit
- Must Have Uniform Contact (toweling)
- Spacing Equal To Cross-sectional Diameter of Pads
- Part To Be Treated Should Be Centered
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- Increasing The Spacing Will Increase The Depth Of Penetration But Will
Decrease The Current Density
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- Creates A Stronger Magnetic Field Than Electrical Field
- A Cable Or Coil Is Wrapped Circumferentially Around An Extremity Or
Coiled Within n Electrode
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- Passing Current Through A Coiled Cable Creates A Magnetic Field By
Inducing Eddy Currents (small circular electrical fields) That Generate
Heat
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- Patient In A Magnetic Field Not Part Of A Circuit
- Tissues In A Parallel Arrangement
- Greatest Current Flow Through Tissue With Least Resistance
- Tissue High In Electrolytic Content Respond Best To A Magnetic Field
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- Two Arrangements:
- Pancake Coils
- Wraparound Coils
- Toweling Is Essential
- Pancake Coil Must Have 6” in Center Then 5-10cm Spacing Between Turns
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- One Or More Monopolar Coils Rigidly Fixed In A Housing Unit
- May Use More Than One Drum Depending On Area Treated
- Toweling Important
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- Patient Sensation Provides Basis For Recommendations Of Continuous
SWD Dose I (Lowest) - No Sensation of Heat Dose II(Low) - Mild Heating
Sensation Dose III(Medium)- Moderate
or Pleasant Heating Sensation Dose IV(Heavy)-Vigorous Heating
Within Pain Threshold
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- Referred To By Different Names
- Pulsed Electromagnetic Energy (PEME)
- Pulsed Electromagnetic Field (PEMF)
- Pulsed Electromagnetic Energy Treatment (PEMET)
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31
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- Interrupted Output Delivered In Series Of High-Frequency Bursts
(20-400usec)
- Pulse Rate Selected With Pulse Frequency Control
- Off-Time Longer Than On-Time
- Low Mean Power Output
- Uses Drum Electrode
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- Pulsed SWD Produces The Same Magnitude And Depth Of Muscle Heating as
1MHz Ultrasound (Draper, JAT 1997)
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- Most Typically SWD Treatments Last For 20-30 Minutes
- Remember As Skin Temperature Rises Resistance Falls
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- Two FCC Assigned Frequencies-2456 MHz and 915 MHz
- MWD Has Higher Frequency and Shorter Wavelength Than SWD
- Generates Strong Electrical Field and Relatively Little Magnetic Field
- Depth Of Penetration Is Minimal In Areas With Subcutaneous Fat > 1 cm
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- A= Power Switch
- B=Timer
- C=Output Meter (indicates relative output in watts
- D= Power Output Level Knob
- E= Amber Light-Warming up / Red Light- Ready
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36
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- Circular Shaped Applicators
- 4” or 6”
- Maximum Temperature At Periphery
- Rectangular Shaped Applicators
- 4.5 x 5” or 5 x 21”
- Maximum Temperature At Center
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- Microwave Applicator Beams Energy To Patient
- Must Pay Attention To Cosine Law
- In 915 MHz Units Applicators Placed 1 cm From Skin
- 2456 MHz Units Have Manufacturer Recommended Distances and Power Outputs
(Uses Antenna)
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40
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