Transcript MWD

MICROWAVE DIATHERMY
M.W.D
Dr. Amal, & Mr. Chandrasekar.L
PHT 221 – 1st SEM – 1435-1436H
LECTURE OUTLINE
2

This lecture deals about the topic MWD in following
sub-categories;
1. Basics principles & production of MWD
2. Indications & Contraindications of MWD
3. Physiological & Therapeutic effects of MWD
4. Methods of application / Treatment procedure – An
overview of clinical application
PHT 221 - MWD
8/4/2016 12:12 AM
LECTURE OBJECTIVE
3

At the end of the lecture the student should be able to

Understand physics and properties of MWD

Know different directors of MWD

Identify therapeutic effects, indications, contraindications of
MWD

Recognize dangers and precautions with MWD

Know the difference between SWD and MWD

Analyze and discuss different cases
PHT 221 - MWD
8/4/2016 12:12 AM
Properties of Microwaves
4




Microwave diathermy (MWD), is a form of electromagnetic
radiations lying between shortwave and infrared waves.
Microwave diathermy does not penetrate as deep as
shortwave diathermy.
The energy is first absorbed at the surface of the body (skin)
and a part of it penetrate and absorbed in deep tissues.
It generates Strong Electrical Field and relatively Little
Magnetic Field
PHT 221 - MWD
8/4/2016 12:12 AM
Microwave Diathermy - Definition
5

Microwave Diathermy (MWD) is a high frequency
electromagnetic radiation lies between infrared and shortwave.
PHT 221 - MWD
8/4/2016 12:12 AM
Frequency and wavelength
6

Microwave has a much higher frequency and a shorter
wavelength than shortwave diathermy.

The general frequency of microwave is between 300 MHz to
300 GHz with wave length of 10 mm to 1 meter.

The therapeutic microwave generators uses the frequency of
2450MHz with wave length of 122.5mm.
PHT 221 - MWD
8/4/2016 12:12 AM
Microwave Diathermy Generator – Panel diagram
7
PHT 221 - MWD
8/4/2016 12:12 AM
Microwave Production
8
The generator used to produce microwaves has three main
components:
1- A multi-cavity magnetron valve
2- A coaxial cable
3- A director.
PHT 221 - MWD
8/4/2016 12:12 AM
Mechanism of MW production
9
The high frequencies of microwave diathermy are
obtained from the magnetron, which is perforated
with tiny holes, through which the electrons flow
into the treatment heads via coaxial cable
PHT 221 - MWD
8/4/2016 12:12 AM
Magnetron
10
It is a special type of
thermionic valve characterized
by centrally placed cathode,
which is surrounded by a
circular metal anode.
Primary function of the
magnetron is to generate
oscillating currents directly
from high velocity electron
motion.
PHT 221 - MWD
8/4/2016 12:12 AM
Mechanism of MW production
11

The coaxial cable transmits the energy to the director, whereas a
radiating system comprising an antenna within a reflector that is used
to direct/focus the microwave to the patient.
•
The antenna is a piece of wire that is mounted in front of a
metal reflector which emits the waves in one direction.

Therefore these devices can be useful during rehabilitation when only
small areas of tissue are involved. (small, defined areas.)
PHT 221 - MWD
8/4/2016 12:12 AM
Directors Used in Microwave Applications
12

Circular directors
- The heating pattern is more
intense around the outer portion than
the centre.
- There are small and large

Rectangular directors
The heating pattern tends to be more
concentrated in the center of the
treated area.
PHT 221 - MWD
8/4/2016 12:12 AM
Emitter =Applicators
13
Applicator must be very flat to avoid reflection of energy
.
Circular shape
Rectangular shaped
Diameter
Temperature
4-6inches
4.5X5/ 5X21 inches
Maximum at periphery of
Maximum at central of radiation
area
each radiation area
PHT 221 - MWD
8/4/2016 12:12 AM
Biophysical properties of MWD
14
1.
REFLECTION
2.
REFRACTION
3.
ABSORPTION
4.
PENETRATION
5.
TRANSMISSION
PHT 221 - MWD
8/4/2016 12:12 AM
Principle Related To Use Of MWD
15

Deep heating modality

Emits strong electrical field/ little magnetic field.

Depth of penetration is frequency dependent.

Produces much more localized & concentrated heating
effect than SWD.

Providing a more shallow tissue heating effect, depends
on the type of tissue involved.
PHT 221 - MWD
8/4/2016 12:12 AM
Principle Related To Use Of MWD
16
The effective depth of MWD penetration (half-value depth) is
about 4.5 cm, so the depth of heating is intermediate between that
of infrared radiation and short wave diathermy
 MWD are strongly absorbed by tissues with high fluid content are
heated most, while penetrated by tissues with low fluid content
(e.g. fat or bones).
 Tissues with low water content (fat) are penetrated to a greater
depth (half value thickness=3.5cm).
 Tissue with high water content (muscle, blood) are penetrated to
PHT 221 - MWD 8/4/2016 12:12 AM
superficial depth (=0.7cm).
Principle Related to Use of MWD
17

The patients does not form apart of the circuit in MWD, so no
tuning is necessary as in SWD.

Transmits as free space radiation, so needs only one emitter
(applicator).

No Metal should be within 4 feet of MWD, since it will interfere
with the signal.

Spacing is required between the skin and the applicators with
MWD, where the applicator on a short wave unit my be placed in
contact with treatment area.
PHT 221 - MWD
8/4/2016 12:12 AM
Microwave diathermy: Physiological
effects
18
When the electromagnetic radiation of MWD enters the body causes
 Ionic
movement (vibration).
 Rotation of dipole.
 Distortion of non-polar molecule
Physiological effects
Effects on metabolism
Effects on blood supply
Effects on nervous tissue
Effects on muscular tissue
PHT 221 - MWD
Effects on sweat glands
8/4/2016 12:12 AM
Therapeutic Effects of Microwave Diathermy
19



Pain: MWD is useful in the treatment of traumatic and
rheumatic conditions affecting superficial muscles,
ligaments and small superficial joints.
Muscle spasm: which may be reduced directly by
MWD or may be reduced by relieving of pain.
Inflammation: MWD reduces inflammation by increase
blood supply that will increase venous return from the
inflamed area and aids the reabsorption of edema
exudates.
PHT 221 - MWD
8/4/2016 12:12 AM
Therapeutic Effects (cont.)
20



Delayed healing: MWD promotes healing of open skin
by increase cutaneous circulation.
Infection: MWD can control the chronic infection by
increasing the circulation.
Fibrosis: The heating effect of MWD increase the
extensibility of fibrous tissues such as tendons, joint
capsules and scars.
PHT 221 - MWD
8/4/2016 12:12 AM
Indications of MWD
21
- The clinical indications for MWD are, more or less, similar to those for SWD.
- MWD may be preferable to SWD when more concentrated or localize
heating is needed.


Musculoskeletal disorders:
- Sprain
- Muscle & tendon tear
- Strain
- Degenerative joint disease
- Joint stiffness in superficial joints
- Capsular lesions.
Superficial inflammatory or infective conditions :
- Tenosynovitis
- Bursitis
- Synovitis
- Abscess
- Infected surgical incisions
PHT 221 - MWD
8/4/2016 12:12 AM
Contra-indications
22

Over malignant tissues.

Over ischemic tissues.

Over wet dressings and adhesive tapes.

Metal implants.

Pacemaker.

Over growing bone.

Male gonads: repeated irradiation can cause sterility.

Hemorrhage.

Impaired thermal sensation.
PHT 221 - MWD
8/4/2016 12:12 AM
Contra-indications (cont.)
23

Recent radiotherapy.

Hypersensitivity to heat.

Acute infection or inflammation.

Venous thrombosis or phlebitis.

Pregnancy: heat applied to pelvis or hip in pregnancy may cause
hemorrhage or miscarriage.

Acute dermatological conditions.

Severe cardiac conditions.
PHT 221 - MWD
8/4/2016 12:12 AM
Microwave Diathermy
24
Advantages

Operation of the machine
is simple


Disadvantages

structures
Comfortable for the patient
Localized heat to small

No overheating if
precautions are followed
Heats only one
aspect of the joint
surfaces

Not for deep

Risk of burn
PHT 221 - MWD
8/4/2016 12:12 AM
Precautions & Dangers
25

The same as SWD, but it is recommended to avoid the
presence of metal within the treatment field (4 feet)
because of scattering and reflection of MWD

Due to scattering and reflection of MWD to the surrounding
environment, it has been associated with high incidence of
miscarriages among female therapists who regularly
operate these units than SWD.

The eyes: MWD may cause cataract.
PHT 221 - MWD
8/4/2016 12:12 AM
Precautions & Dangers(cont.)
26

Obesity: MWD with 2450MHz, there is danger of producing
an excessive heat in the subcutaneous fat layer

Burn: There is an increasing of risk of excessive heating and
burning with the using of MWD due to:
1.
Shallow depth of penetration
2.
Reflection at tissue interfaces
3.
Potential standing waves
PHT 221 - MWD
8/4/2016 12:12 AM
General Guideline & Safety When Using Diathermy
27
1.
Question patients (contraindications and previous treatment).
2.
Position patient ( comfort, support, relaxed).
3.
Inspect part to be treated (check for skin rashes, infection, or open wound).
4.
If indicated, drape area with toweling.
5.
Place electrodes on treated area then switch on the machine.
6.
Set pulse duration, pulse frequency, treatment time, and adjust intensity.
7.
Periodically ask patient if heating is too vigorous.
8.
When timer shuts off, terminating the treatment and turn all dials to zero.
9.
Assess treatment efficiency ( inspect area, feedback from patients ).
10.
Record treatment parameters
PHT 221 - MWD
8/4/2016 12:12 AM
Treatment Parameter of MWD
28
The MWD requires warm-up period of 4 minutes, to allowed the magnetron
to develop enough energy
Spacing of Applicators


For small treatment area is 2-6cm
For large treatment area is 10-15cm
Intensity of Treatment


Sensation of warmth
Feel no more than a mild comfortable warmth.
Duration of Treatment: 20 -30minutes
Frequency of Treatment; daily or alternating days depending on


Response to treatment
Patients condition/availability
PHT 221 - MWD
8/4/2016 12:12 AM
Microwave diathermy: Application
29

The patient should be positioned in well comfortable manner with adequately
exposing the part to be treated.

Explain the procedure to the patient.

Check for contraindications.

Localize the site to be treated.

Test the skin for hot and cold sensation.

Pair of microwave goggles should be given to the patient.

Select the type of director and fix it to the machine.

Check all the connections.
PHT 221 - MWD
8/4/2016 12:12 AM
Microwave diathermy: Application
30

Emitter should be position to get a beam of radiation which
strikes the skin at right angles. Emitter- skin distance is about 2
cm.

Test the machine by placing the therapists hand under the
director.

Switch on the machine after setting the timer

Instruct the patient to not to look at the applicator and warn him
regarding the burns.
PHT 221 - MWD
8/4/2016 12:12 AM
Microwave Device
31
PHT 221 - MWD
8/4/2016 12:12 AM
32
PHT 221 - MWD
8/4/2016 12:12 AM
33
PHT 221 - MWD
8/4/2016 12:12 AM
Pulsed Microwave Therapy
34
• The effect of pulsed MWD are the same as
those of non pulsed MW with the exception of
the production of rise in temperature in the
tissues.
• Many conditions that contraindicated to MW
can be treated via pulsed MW.
• It also treated one aspect of the part at time
and the depth of penetration is superficial.
PHT 221 - MWD
8/4/2016 12:12 AM
Comparison of different types of diathermy
35
Type
Thermal SWD
Thermal
MWD
Frequency 27,12MHZ
Applicator
Inductive coil
2450MHZ
Capacitive Magnetron
plate
Incident field Electromagnetic Electric
Tissues most Deep and
superficial
affected
Electromagnetic
Superficial
Small areas
PHT 221 - MWD
Non
thermal
SWD
27,12MHZ
Inductive coil
drum
Electromagnetic
Deep and
superficial
8/4/2016 12:12
AM
Comparison of heat distribution by different
diathermy applicators and ultrasound
36
Type
Fat
Muscle
Bone
Inductive coil
Minimum
Maximum
None
Capacitive
plate
Maximum
Moderate
Low
Magnetron
MWD
Maximum
Maximum
None
Ultrasound
Slight
Maximum
None
PHT 221 - MWD
8/4/2016 12:12 AM
Case study
37
Case 1
MS is a 50-year-old female. She has been diagnosed with
adhesive capsulitis of the right shoulder and has been referred
to physical therapy. She complains of shoulders stiffness. The
objective exam reveals restricted right shoulder active and
passive range of motion.
Case 2
AB is a 24-year-old male, football player who suffered from left
ankle inversion sprain approximately 48 hours ago. He
complains of moderate pain and swelling at the lateral ankle.
PHT 221 - MWD
8/4/2016 12:12 AM
When Should Diathermy
Be Used?

If The Skin Or Some Underlying Soft Tissue Is
Tender And Will Not Tolerate Pressure

In Areas Where Subcutaneous Fat Is Thick And
Deep Heating Is Required

When The Treatment Goal Is To Increase Tissue
Temperatures In A Large Area
38
PHT 221 - MWD
8/4/2016 12:12 AM
Self test questions
39

Compare and contrast between SWD and MWD
MWD
SWD
Frequency &wavelength
Therapeutic frequency and
wavelength
Circuit used
Field used
Factors affecting heat
penetration/ absorption
Depth of penetration
Treatment time /intensity
Advantages
PHT 221 - MWD
8/4/2016 12:12 AM
40
PHT 221 - MWD
8/4/2016 12:12 AM