Shortwave and Microwave
Diathermy
Jennifer Doherty-Restrepo, MS, LAT, ATC
Entry-Level ATEP
Therapeutic Modalities
Diathermy
• Application of high-frequency
___________________ energy
• ______________ diathermy
– Used to generate ______ in body tissues
– ______ produced as a result of the __________ of
tissues to the passage of energy
• ___________ diathermy
– Used for ________________ effects
– Renewed interest due to research documenting
efficacy
Physiologic Responses To
Diathermy: Thermal Effects
•
•
•
•
•
•
•
Tissue temperature __________
Increased blood flow (vasodilation)
___________ venous and lymphatic drainage
___________ metabolism
Changes in physical properties of tissues
Muscle _________
Analgesia
Diathermy Heating
• Diathermy parameters are not precisely
controlled, thus the amount of heating
cannot be accurately measured
• Heating occurs in proportion to the square
of the current density and in direct
proportion to the resistance of the tissue
– Heating = ______ X ________
Physiologic Responses To
Diathermy: Non-Thermal Effects
• Pulsed shortwave diathermy is used to treat ________
injuries and wounds
• Mechanism of effectiveness is related to the
_____________ of damaged cells
– Loss of cell division
– Loss of proliferation
– Loss of regenerative capabilities
• ____________ occurs with treatment, thus correcting
cell dysfunction
• Not capable of producing _____________ to elicit
muscle ______
– Wavelengths too short
Shortwave Diathermy
• Shortwave diathermy unit is a radio
transmitter
• Three frequencies available:
– ______ MHz, wavelength of 11 m
– ______ MHz, wavelength of 22 m
– ______ MHz, wavelength of 7.5 m
Shortwave Diathermy Unit
• _______________: provides power to radio
frequency oscillator (RFO)
• ____: provides stable, drift-free oscillations
at given frequency
• _____________: generates power to drive
electrodes
• __________________:tunes in the athlete
as part of the circuit to allow for maximum
power transfer
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)
Shortwave Diathermy Unit
• Power output should provide energy to ______
tissue temperature to therapeutic range
– Therapeutic range = ___________
• ____________________________: represents
the rate of energy absorbed per unit area of
tissue mass
– Power range required to elicit tissue temperature
increase = ____________
Adjusting the
Shortwave Diathermy Unit
• ________________: adjusts patient circuit
– Set output intensity at ______ of maximum
– Adjust tuning control until power output meter reaches
______
– Then adjust down to ______________, which is about
50% of maximum output
– If patient is able to tolerate more than 50% of
maximum output, he/she is ___________________
• ________________: automatically sets output
intensity
– Automatically turns off if patient is _______________
Shortwave Diathermy Unit
• Generates both an _______ and a _______
field
• Ratio depends on characteristics of both the
______ and the _________
– SWD units at 13.56 MHz = stronger ________
field
– SWD units at 27.12 MHz = stronger ________
field
SWD Electrodes
• 2 types of electrodes
– _____________________
• Air space plates
• Pad electrodes
– _____________________
• Cable electrodes
• Drum electrodes
• Selection of appropriate electrodes can
influence the treatment
Capacitor Electrodes
• Create stronger ______ field than ______ field
• Ions will be attracted or repelled depending on the
charge of the ______
Capacitor Electrodes
• Electrical field
– Lines of force exerted on
charged ions that cause
_____________________
________________r
• ______ has higher current
density than __________
Capacitor Electrodes
 Patient
is between
electrodes
 Becomes
part of circuit
 Tissue
is between
electrodes
 __________
arrangement
circuit
Electrical Field
• The tissue that offers the greatest resistance
to current flow develops the __________
• Fat tissue ______ current flow
• Therefore, tissues with a ______ fat content
are heated in an electrical field
• Typical with capacitor-type electrodes
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
Capacitor Electrodes:
Air Space Plates
• Area to be treated is
placed between
electrodes
• Treatment area becomes
part of the external
circuit
Capacitor Electrodes:
Air Space Plates
• Sensation of heat in _____ proportion to the distance
of metal plate from the skin
• The closer the plate to the skin, the _____ the energy
transmission (______ reflection)
– Generates more surface heat in ____ and _____________
Capacitor Electrodes:
Pad Electrodes
• Greater ______ field than ______ field
• Patient is between electrodes
– Becomes part of external circuit
Capacitor Electrodes:
Pad Electrodes
• Must have uniform
contact pressure on the
body
– Toweling to prevent burns
• Spacing between
electrodes is equal to the
____________ ________
of pads
Capacitor Electrodes:
Pad Electrodes
• Area to be treated
should be ______
between electrodes
• Increasing the space
between electrodes
will ______ the depth
of penetration but will
_________ the current
density
– Vice versa also true
Induction Electrodes
• Creates a stronger ________ field than ________
field
• A cable or coil is wrapped circumferentially
around an extremity or coiled within an electrode
• Passing electrical current through coiled cable
creates a ________ field by inducing ________
_________
– Small circular electrical fields that generate heat
Induction Electrodes
• Patient placed in a magnetic field
– NOT part of a circuit
• Tissues in treatment area are in _________
arrangement to magnetic field
– Greatest current flow through tissue with least
resistance
– Tissue high in __________________ respond
best to a magnetic field
Induction Electrodes:
Cable Electrode
• Two arrangements:
– Pancake coils
– Wraparound coils
• Requires at least ____ of
toweling between skin
and coil
• Spacing between turns in
coil must be ______
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 important to
prevent ______
Continuous Shortwave Diathermy
• Patient sensation provides basis for
recommendations of continuous SWD
• Dose I (______): no sensation of heat
• Dose II (______): mild heating sensation
• Dose III (______): moderate or pleasant
heating sensation
• Dose IV (______): vigorous heating with pain
threshold
Pulsed Shortwave Diathermy
• Pulsed electromagnetic energy (PEME)
• Pulsed electromagnetic field (PEMF)
• Pulsed electromagnetic energy treatment
(PEMET)
Pulsed Shortwave Diathermy
Pulsed Shortwave Diathermy
• Interrupted output delivered in series of
high-frequency bursts (______)
• ______ _____selected with pulse frequency
control
• Off-time ______ than on-time
• Mean power output is ______
• Uses drum electrode
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
Microwave Diathermy
• Two frequencies available:
– 2456 MHz
– 915 MHz
• ______ frequency and ______ wavelength as
compared to shortwave diathermy
• Generates strong ______ ______ and relatively
little ________ field
• Depth of penetration is minimal in areas with
subcutaneous fat > 1 cm
Microwave Diathermy Unit
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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
Microwave Diathermy Electrodes
• Circular-shaped electrodes
– 4” or 6” in diameter
– Maximum temperature at periphery
• Rectangular-shaped electrodes
– 4.5” x 5” or 5” x 21”
– Maximum temperature at center
Microwave Diathermy:
Electrode Set-Up
• 915 MHz units
– Electrodes are placed 1 cm from skin
• 2456 MHz units
– Manuel includes manufacturer recommended
distances and power outputs (uses antenna)
• Reminder: Cosine Law
– Energy should be administered at ______ to
reduce ______
When Should Diathermy
Be Used?
If the skin or some underlying soft tissue is
tender and is unable to tolerate pressure
 When The Treatment Goal Is To Increase
Tissue Temperatures In A Large Area
 In areas where subcutaneous fat is thick and
deep heating is required
