Ultrasound (US) (Sonogram)

Principle

• The use of high-frequency sound waves to produce real-time images provides a simple and painless way to examine structures.
• An ultrasound machine sends out high-frequency sound waves which reflect off body structures. 
• A computer receives these reflected waves and uses them to create a picture. 

How it is done

• A clear, water-based conducting gel is applied to the skin over the area being examined to help with the transmission of the sound waves. 
• A hand held transducer is then moved over the area being examined. 
• Transducer sends high frequency sound waves into the body.
• The waves are reflected back by various tissues they go through.
• The reflected waves, with a help of a computer, form an image on the screen.
• Color coding of the various reflected echoes provides color images which can tell you the direction of flow.

Doppler

• Doppler examination is done using US waves aimed at a moving object - arteries or veins or cardiac valves. 
• The reflected waves, with computer aid, give us the velocity of blood in various vessels.

Example Indications

• Pregnancy evaluation
• Ectopic pregnancy
• Torsion testis
• Echocardiography
• Localization of loculated pleural effusion for tap and biopsy of organs (kidney) or masses close to the chest or abdominal wall.

Advantages

• Non-invasive test.
• Requires no preparation.
• Involves no pain
• Provides accurate anatomic information, including dimensions.
• No radiation risk. Useful to study reproductive organs and evaluation of pregnancy.
• Avoids the potential allergic and toxic complications of contrast media.
• Can be used on individuals with poor kidney function, in whom contrast cannot be given.
• No complications. 
• Can be done at bedside.
• Relatively economical exam.
• No IV needed.

Limitation

• Operator dependant.
• Gas in the GI tract and lungs prevent the sound waves from passing; thus not useful in portions of abdomen and lungs.

Cost: $