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BYDr. B. SAMPATH REDDY

MPT ortho.

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y Ultrasound waves are produced bypiezo-electriceffect" principle. When an high frequency alternating

current is applied on this crystal, the resonantfrequency of the current is at the same naturalfrequency as that of the crystal, distortions of itsmolecular structure occur and it mechanically vibrate

by the acoustic vibration producing mechanical wavesindentical to sound waves.

y The frequency of the wave is determined by the size ofthe crystal and the frequency of the impressed current.

y Those produced waves are propogated into the tissuethrough a transducer treatment head.

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y Mode of Transmission : The treatment head ismoved to and fro to form a stream oflongitudinal

waves that forms the ultrasonic beam, which areroughtly cylindrical in shape of the same diameter asthe treatment head, and penetrated into the tissue

Peak Intensity : This is defined as the

ultrasonic fields, in which is the division theultrasonic beam is divided into "Near & FarField"

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y Near Field :. Near field is directly proportionate to thefrequency and inversly proportionate to wavelength.

y To rule out and prevent the irregularity the head is

continuously moved to and fro.

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y Far Field : where the field is less intense andprominent at the peripheral point of the head. As thiszone is always noted beyond the near field, the sonic

filed spreads out somewhat and becomes much moreregular.

y This is because the differing path lengths emitted fromdifferent points of the head become insignificant at

greater distance.

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y intensity : It is the total output of the intensity givenin a unit time. The unit of intensity when using ultrasound is watt, but this is a gross measure of the power

being emitted by the sound head. So an averageintensity is normally used (W/cm). Since ultrasoundis given in two modes the average is calculated asfollows:

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y Space Peak Average / Space Average Intensity : It is

the totalaverage intensity given over a specified area oftissue, (i.e), total output of power in watts per square

centimeter of treatment area - for eg. If 2 is total output,then space average intensity will be 2W/cm

y Time or Temporal Peak Average / Time or TemporalAverage Intensity : It is the total output calculated,when using pulsed mode, in a total given unit oftime(per second) for a specified area of tissue (i.e), if 2

W power is given with a pulse of 1:4 ratio for 5 minutes

then time average will be 2W/cm/5min

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y Factors Affecting Transmission : Since ultrasoundbehaves similarly to the rays oflight it follows all theprinciple of opticallaws. Thus the following plays a veryimportant part of the factors affecting transmission.

y Reflection : Since ultrasound cannot be transmitted in air,it is always necessary to know the acaustic or soundimpedence (Z) of each medium Physical Modalitiesresponsible for reflection.

So, if there is an acaustic impendence mismatch thereoccurs some amount of reflection and simulataneously ifthere is similar acustic impendence no reflection occurs.

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y Refraction :As light refraction ultrasound also, oninsonation, deviates. It means the insonated wavestouch the tissue at one angle continues to pass at a

different angle

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y Transmission : It is the insonated energy entering into thetissue from the sound head and gradually reducing in itsintensity before it targets the right tissue. It can be betterunderstood by knowing the term - alttenuation

y Attenuation : It is the progressive loss of insonatedenergy, which varies from tissue to tissue. This is the endresult of insonated power and two major factors contributeto this physical phenominon. They are :

y i) Absorption :After the progressive loss the resultant

energy retained in the target tissue is stated as absorbtion.It is generally accepted that absorption best occurs atmolecular level and generate heat.

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y Scattering :When the insonated energy strikes thehigher viscositylevel it reflects from its path due toformed gas bubbles or by any other such disturbances

and scatters. Thus the resultant insonated energyreaching the target tissue shows that there is reductionin internsity the deeper it passes.

y This reduction is exactly half of its surface intensity,

termed as "Half Value Distance" even this also variesfrom tissue to tissue and frequency .

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y CouplingMedium. The best way to propogateultrasound energy is through the best coupling

medium, applied in between the tissue and thevibrating source. The best medium is selected based onthe following factors :

y It should have a proper tissue matching acusticimpendence

y Increased transmission capacity

y Low grade of viscosity

y Low susceptibility in air bubbles.

y

should be non-irritative

y non corrosive to metal

y act as a lubricant

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y Degassed water

y Paraffin oil

y Low viscosity mineral oil

y Glyceroly Aqua sonic gel

y ECG gel

y Lanolin creams

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y Dosage : Effect and safety of ultrasound treatmentdepends on the availability and reliability of suitableequipment and its parameters, such as - Mode, Frequency,

Intensity, Time, Progression.y Mode :

y i) continuous - gives thermal effect; at same

y ii) pulsed - gives non thermal effect ;

intensityy Frequency : as increased frequency, increases absorption

with greatly reduced half value thickness, for all treatmentsgenerating thermal effect higher frequencies are used andfor non thermal effect lower frequencies are used. All higher

frequencies gives only superficial heating were lowerfrequencies gives deep heating.

y Intensity : it is the total output power emitted per secondfrom the circumference diameter of a sound head.

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y Time : it is the total maximum duration of insonation andmeasured in minutes in relation to the area treated.Timing is always based on the mode and stage of thecondition.

y Mode :y Continuous : 5 min. - 10 min. maximumy Pulsed : 8 min. - 15 min. maximumy Average : minimum.5 min. to maximum. 8 min. is must

y Stage :y Acute : Non thermal - minimum time (5 min.)y Sub-acute : thermal and micromassage - short time (8

min.)y Chronic : thermal - maximum. time (10 min.)

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y Application Techniques :

y a) In Contact or Direct method

y b) Acquatic or Water Bath method

y c) Sub-Acquatic or Water Bag method.

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y Thermal Effect : This effect is more destructive in nature and requiresat least 5 min. to raise the temperature to 40 to 45C

y Increases circulation more locallyy Increases metabolismy Mild raise in temperature 3 to 8Cy Relaxes the musclesy Facilitates calcium penetrationy Helps in release of enzymes like hystamine and such other chemicalsy Accelerates healing processy Increase collagen extensibility of connective tissues

y Helps in scar tissue mobilisationy Increase membran permiabilityallowing for increased ionic exchange

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y Non-Thermal Effect : This effect is very soothing,does not give any sensation changes at the site of

interface. The effects produced are based on thephysiological changes taking place in the tissue.y Cavitations : it is an important feature of high intensity and

care must be taken to avoid producing this. This is producedduring the period of relaxation. The nature of production isblood naturally contains dissolved gas and when these are

insonated with sound waves during relaxation periodmolecules move more freely followed by immediatecompression. During this period, free moving molecules catchup air bubbles filled with already dissolved gas. These bubblescan be Stable or Unstable. Stable cavities are notdangerous, as it increases cell permeability or otherwise calledMicro Streaming. While unstable cavities are moredangerous, can get dislodged in any path of the artery andblock the flow or get collapsed and create high concentrationof energy (temperature raise)

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MicroMassage : It is created due to alternate compression andrelaxation of tissue by sounds pressure and mechanicalreactions of tissues to sound.

y Standing Waves : Isonated energy reflected back to soundhead and gets superimposed to incident wave leading to heatconcentration. It is best avoided by moving the sound headcontinuously.

y Ultrasound non-therma

leffects have an usefu

leffect in a

ll3 stages of repair

y Inflammation,

y Proliferation

y R

emodelling

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y Indications :

y Pain and muscle spasm - localized

y

Acute and sub acute injuriesy Chronic arthritic conditions

y Scar and adhesive tissue stretching

y Localized low back pain spot due to disc prolapse

y Wound healing

y All types of immediate and late soft tissue sports injuries

y Occupational injuries

y Chronic indurated oedema

y Plantar fasciitis, retro calcaneal bursitis, calcaneal spur, etc..

y Traumatic neuralgia and neuromas

y Calcified tendinitis

y Recent healing fractures

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y Contraindications :

y Brain and spinal cord

y

Eyesy Reproductive and abdominal organs

y Pregnant uterus

y Acute infection and sepsis

y

Malignant tumorsy Recent x-ray therapy

y Phlebitis and thromboplebitis

y Hemophilia

y Tuberculosis

y Anesthetic areas

y Metal in treatment part

y Air filled sinuses

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y Advantages :

y Easy to carry & apply

y A verylocal treatment with few generalized responses

producedy Application time is usually short

y Capable of producing significant temperature changesdeep within the tissue

y Can apply to immediate injuries though it is an heatmodality.

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y Disadvantages :

y Verylittle sensation is associated with treatment,making dosage difficult to monitor

y Pressure is exerted on the treatment part, aggravatingany tenderness present

y Regular damage to crystal occurs

y A very costly equipment due to the presence of delicate

crystaly

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y Dangers :

y Burns

y Shocky Cavitations

y Overdose

y Standingwaves

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y Precaution :

y Keep the sound head moving

y Do not expose the sound head to air

y Maintain even contact

y Use only suitable and appropriate copulant

y

Remove air bubblesy Avoid bony prominences

y Avoid using high intensities and prevent cavitation

y Take care of aneasthetic skin and malignancy

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