Ultrasound | Thermal effects, Uses, Contraindications

Ultrasound Definition:

Ultrasound, also called sonography or diagnostic medical sonography, is an imaging method that uses high-frequency sound waves to produce images of structures within your body. The images can provide valuable information for diagnosing and treating a variety of diseases and conditions.

Ultrasound frequency:

Therapeutic frequencies lie in the region of 1 MHz or 3 MHz.

  • 1MHz used for deep penetration.
  • 3MHz used for superficial penetration.

Reflection of Ultrasound:

Air will not transmit ultrasonic waves, air reflects back ultrasonic waves and therefore crystal may damage, so in ultrasonic treatment great care is taken to avoid reflection.

Attenuation of Ultrasound:

Attenuation is the term used to describe the gradual reduction in intensity of the ultrasonic beam once it has left the treatment head.

Thermal Effects of Ultrasonic Waves:

The local rise in temperature could be used to accelerate healing. The extensibility of collagen is increased by a rise in temperature, and so stretching of scars or adhesions (eg. in frozen shoulder) is easier following ultrasound.


Ultrasonic therapy is used in following conditions:

  • Recent injuries and inflammation
  • Scar Tissue
  • Chronic Indurated Oedema
  • Accelerates healing
  • Adhesions

Recent injuries and inflammation: Sonography is often of use after soft-tissue injuries, as the mechanical effect helps to remove traumatic exudate and reduces the danger of adhesion formation. Inflammatory conditions treated with appropriate doses of ultrasound respond in the same way.

Scar Tissue: Scar tissue is made more pliable by the applications of ultrasound, which allows for more effective stretching of contracted scars.

Chronic Indurated Oedema: The mechanical effects of ultrasound has an effect on chronic oedema and helps in its treatment.


Ultrasonic therapy is contraindicated in following conditions:

  • Vascular Conditions
  • Acute Sepsis
  • Radiotherapy
  • Tumours
  • Pregnancy
  • Cardiac Disease

Vascular Conditions: Conditions such as thrombophlebitis, where insonation may cause emboli to broken off, are not treated with ultrasound.

Acute Sepsis: An area which presents acute sepsis should be treated cautiously with ultrasound because of the danger of spreading the infection, or in some instances breaking off septic emboli.

Radiotherapy: Radiotherapy has a devitalizing effect on the tissues, therefore ultrasound is not applied to a radiated area for at least six months after irradiation.

Tumours: Tumours are not insonated because they may be stimulated into growth or throw off metastases.

Pregnancy: A pregnant uterus is not treated as the insonation might produce fetal damage. Ultrasonic scanning as a diagnostic aid in pregnancy is different from that used for therapeutic purposes.

Cardiac Disease: Patients who have had cardiac disease are treated with low intensities in order to avoid sudden pain, and areas such as the cervical ganglion and the vagus nerve are avoided because of the risk of cardiac stimulation.

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