Ultrasound is a type of medical imaging technology which uses high frequency sound waves to generate precise images of the internal organs  and structures in the body. It is used to visualize tendons, muscles and to capture the size, structure and any pathological lesions of internal organs.

Ultrasound is a type of sound pressure which has a frequency more than the limits of human ears. Thus it cannot be heard by the humans under normal circumstances.
The sound waves are beamed into a specific part of the body by a transducer.These sound waves strike the  tissues, bones and body fluid and then bounce back very much similar to echoes. The bounced waves are then recorded and converted into pictures of the structure underneath by the compuer. Thus it helps to visualize the structures under the skin in a non-invasive manner.This technique is similar to that used by whales, dolphins and bat for hunting and also by the sonars on the boat to see the bottom of the ocean.

Ultrasound technology is being used since last 50-60 years by sonographers and radiologists for imaging of the human body structures and aid in the diagnosis of various medical problems.
As it is a non-invasive procedure and does not utilize ionizing radiation like in x-rays or CT scans, it is considered one of the safest diagnostic procedures.
The type of ultrasound that is used most often combines different still pictures to show the movement similar to the single frames which make movie. This is known as real time ultrasound.

Initially the ultrasound technology was used mainly by the obstetrician to assess the growth and development of the baby in the mother’s womb during pregnancy. But with the advancement in technologies, ultrasound is now helpful in creating the 3D(dimensional) and 4D images of the bodily structures.This has lead to its implication in a wide variety of fields like checking of the thyroid gland, diagnosing gallbladder disease, studying the heart chambers,diagnosing certain types of infection and cancer, evaluating any abnormalities in the muscles, tendon, prostate, scrotum or testis. It is also being use in guiding a needle biopsy or for the biopsy and treatment of a tumor.

A special ultrasound technique developed to evaluate the blood flow through the body’s major arteries and veins of the legs, arms, neck, abdomen etc. is called as Doppler ultrasound. This is based on the principle of Doppler effect and thus measures the frequency change of the echoes for calculating the speed with which an object is moving. It is used mostly for measuring the  blood flow rate through the major arteries and heart.  Similarly by measuring  the blood flow and  degree of blockage in the carotid arteries,it can predict the potential risk for future stroke.
Although ultrasound is a useful tool, it has certain limitations.  As the sound cannot travel well through bone or air, ultrasound is not effective in imaging parts of the body that have gas in them or that are obscured by bone. For this conditions, various other procedures are available.

However these days ultrasound is increasingly being used in various trauma and first aid cases, with emergency ultrasound being used by several EMT response teams.

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