Ultrasound Therapy (UST), Principles, Physiological effects, Indication and Contraindication.

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Ultrasound Therapy (UST) was first introduced in 1992 used for therapeutic purposes which works on the principles of Ultrasonic waves. It is a mechanical vibrations which are same as sound waves but has higher frequency. Ultrasonic waves are beyond the range of human hearing power. Ultrasound therapy produces vibration in the tissues and promote tissue healing process in the body. It is also a mechanical energy which does not fall into the electrophysical agent.

Therapeutic Ultrasound used by Physical therapist which has emerged as one of the important modalities for the treatment of Muscle sprain, Rheumatoid Arthritis, Tendonitis and scar tissue adhesion. Ultrasound is a form of ultrasonic energy is used for providing deep heating in the tissues. The normal sound waves which are audible to hear ear is 16Hz to 20,000Hz, but for the treatment purpose the sound waves frequency is range from 1MHz to 3MHz which is obviously beyond the capacity of human hearing.

Ultrasound therapy is used most widely in all over the countries because it is not harmful for the tissues but induced heating effect absorbed by the biological tissues for healing purpose. For diagnostic ultrasound, temperature elevation and the potential for bio effects are kept relatively low .

Fact:- For the treatment of superficial tissues ,the frequency should be more which is 3MHz but for the treatment of deep structure of the tissues the frequency should be less which is 1MHz. So the result should be that frequency is inversely proportional to the wavelength.

{ F=1/wavelength }

Principles:-

>Ultrasound therapy uses the electric current which helps to produce ultrasound waves. There is a special type of crystal which is present in the Ultrasound device which is known as Piezoelectric crystal. This crystal vibrates within a ceramic probe because the electric current causes crystal to vibrate. When the crystal expands it compresses the material which is present in front of it and when it contracts it rarefies the material and this alternating compression .

>These are the effects which is produces when Ultrasound propagate:-

• Scattering.
• Absorption.
• Refraction.
• Reflection.
• Attenuation.
• Transmission.

The waves are eventually reflected, refracted and absorbed in the body. These changes depends upon the density of the tissues and interfaces between the tissues through the ultrasound waves transmission. When tissues are exposed to sound waves then they start to oscillate about fixed point rather than move with the wave itself.

Also Read:- shortwave Diathermy (SWD), Physiological Effects, Indications and Contraindications.

Physiological changes of Ultrasound Therapy :-

Ultrasound therapy is used for its thermal and non-thermal effects. A key element of therapeutic applications of ultrasonic energy is the capability to focus energy for few millimeters and centimeters away from the transducer plate.

• Thermal Effects- Ultrasound induced precise heat in the tissues which is the result of absorption of the ultrasound energy in biological tissues.
• Factors affecting the thermal effects:-
• Intensity.
• Time duration.
• Thermal conductivity.
• Acoustic Streaming.

Clinical uses/Indications:-

• Application of Ultrasound therapy in physiotherapy used for various musculoskeletal disorders which is beneficial for therapeutic purpose. It is precisely used for tissue healing properties.
• Pain Control:- Thermal and non-thermal effects both are beneficial for the control of pain.
• Chronic Wounds
• Tissue Repair.
• Post Burn fractures.
• Soft tissue shortening.
• Fracture healing.
• Ultrasound therapy used in the inflammatory phase causes stimulating effects on the platelets .White blood cells, macrophages and phagocytes which enhance the repairing process and facilitate healing process.
• Tennis elbow.

Contraindications of Ultrasound Therapy are as follows:-

• Reproductive organs.
• Pregnancy.
• Metal implants.
• Cancerous lesions.
• Growing epiphyseal junction.
• Eyes.
• Heart.
• Deep vein thrombosis.
• Over the Spinal Column.
• Head.

Precaution:-

• The transducer head should be kept perpendicular to the treatment area mainly over the bony prominences to prevent formation of shear process.
• The Ultrasound head should be at a optimal pressure over the treatment areas.
• The intensity of ultrasound device should be carefully calculated for the acute injuries.

Types of Method:-

• Fluid filled method.
• Immersion method.
• Stationary method.
• Moving sound head method.

Fluid-filled method- This method is used for the treatment for many irregular areas of the body. It requires water bag such as surgical gloves and coupling medium such as mineral oil or glycerin. Coupling medium is the medium between treatment area and transducer head. Transmission of ultrasound waves depend upon the acoustic impedance of the medium through which they pass. Greater the difference in acoustic impedance between two mediums, larger the reflection of the ultrasound waves.

Immersion Method- This method is used for the treatment pf peripheral distal joints such as hands and feet and the area which are too sensitive to touch or broken skin. In this are joints are exposed to the ultrasound waves in the degassed water.

Stationary Method- This method is the cyclic transmission of ultrasound waves to the tissues increases the energy gradually and produces heat but if the ultrasound head is not removed the increased heat can cause the thermal injury to the underlying tissues.

Moving sound head Method- In this method transducer head should be moved over the treatment area in a rhythmical pattern and it is important to keep the pattern in constant rhythm session. If the ultrasound head is moved slowly the tissues will receive high amount of energy, where as when the movement of transducer head is moved in a high speed then the energy in the tissues will receive less energy. The head of the transducer will be moved in small overlapping circle.

MODES:-

There are two modes of application-

• Pulse
• Continuous

Pulse Mode- Pulse mode of the ultrasound is the transmission of the acoustic energy in brief cyclical breaks in to the tissues. The breaks or brief intervals in the transmission reduces acoustic energy concentration in the tissues. The pulse mode of the therapeutic ultrasound is used for non-thermal effects in the tissues.

Continuous mode- Continuous mode of ultrasound is the transmission of the ultrasound waves continuously in to tissues till the treatment time is over. It is mainly recommended in the chronic conditions to produce significant thermal effects in the tissues .

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Also Read:- Microwave Diathermy (MWD), Physiological effects, Indications and contraindications.