Ultrasound Therapy




  • Ultrasound is an electromagnetic wave with frequencies above 20,000Hz
  • For therapy the frequency of sound waves used are between 85kHz to 3MHz and delivered at intensities between 0 and 3W/sq.cm


  • When electrical energy is applied on piezoelectric crystals they produce vibration and mechanical deformity of their molecular structure. This phenomenon is called piezoelectric effect. This principle is used for generation of ultrasound waves
  • The reverse Piezoelectric phenomenon: mechanical deformation occurs upon passage of alternating electricity to a piezoelectric material, being manifested as oscillations with cycles of contraction and expansion creating periodic cyclical pressure waves
  • Modern Ultrasound machines work on the reverse piezoelectric phenomenon
  • The piezoelectric crystals that are involved in Ultrasound production are Germanium, Quartz, Lead- Zirconium-Tartarate and are present in the transducer
  • The normal current of 110V/60 Hz is converted by the ultrasound into high frequency current (1MHz). This current is imposed on to the piezoelectric crystal and leads to the production of ultrasonic waves.
  • Types of ultrasound: Continuous (emitted continuously) and Pulsed ultrasound (emitted as pulses). Continuous US is applied to achieve thermal effects and Pulsed US is applied to achieve nonthermal effects

Mechanism of action:

  1. Enhances metabolism by acoustic streaming: Acoustic streaming is movement of fluid along the boundaries of the cell membrane resulting from mechanical pressure wave. Ultrasound enhances the metabolic process in the body like increase secretion from mast cells, increased Calcium uptake and greater growth factor production in macrophages
  2. Biological Responses: The permeability of membranes is increased by ultrasound and helps removal of pain mediated peptides and Hydrogen ion
  3. Mechanical responses:

a)      Cavitation: Ultrasound loosens molecular bonding. This is used therapeutically to breakdown adhesions, breakup calcific bonds, scar tissues

b)      Sclerolytic effect: Increases the extensibility of tendons that are shortened by inflammation.


  1. Thermal effects: produces heating of tissues and increases their extensibility and decreases joint stiffness
  2. Causes a mechanical micromassage


Dosage: 0.5 to 1W/sq.cm along with a gel-coupling medium

Maximum of 3W/ sq. cm

Transducer size: 1sq.cm to 10 sq. cm (5 sq. cm is commonly used)

Transducer size should be selected relative to the size of the treatment area

Duration of treatment: 1 to 8 minutes


Methods of application:

  • Direct contact (transducer to skin interface, moving the sound head in contact with relatively flat body surface)
  • Indirect body contact (water immersion): to be used with irregular body parts such as hand and feet. Fill a plastic container (since it reflects less acoustic energy) with water high enough to cover the treatment area. Place sound head in water keeping it half to 1 inch from the skin surface and at right angles to the body part.




ü  Recent injuries and inflammation

ü  Reduction of spasm

ü  Scar tissue lysis by increasing connective tissue extensibility

ü  Nonunion: 10 days of treatment with ultrasound has found to increase the bone blood flow. Eg., nonunion of the tibia, scaphoid, distal radius


Contra indications and Precautions:

´        Areas that have received radiotherapy

´        Cardiac pacemakers, breast implants, directly over eyes

´        Encapsulated lesions of tuberculosis shouldn’t be treated

´        Malignant and precancerous conditions

´        The vulnerable tissues are: ischaemic tissues, neural, reproductive, fluid filled cavities, atherosclerotic areas, and areas of recent venous thrombosis


Risks are minimized by continuously moving the treatment head during therapy



  • This is the movement of drugs through the skin into the subcutaneous tissues under the influence of ultrasound..
  • High frequency sonic vibration accelerates the process of drug absorption into the skin.
  • It relies on perturbation of all the tissues causing more rapid particle movement and encouraging absorption of drug
  • Lower ultrasound frequencies appear to lead to deeper drug penetration
  • Pulsed ultrasound leads to better drug penetration
  • Quantity of drug entering the skin is proportional to time and intensity of application
  • Hydrocortisone is used in treatment of skin conditions like psoriasis, scleroderma and pruritus


  1. Dr Sanjeeb kumar dash says


  2. abc says

    not an electromagnetic wave

  3. krish says

    sound waves

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