Ultrasound uses highfrequency sound waves that are converted into diagnostic information using a hand-held transducer passed over an imaged area. The resulting ultrasound is the reflection of the sound waves as they collide with the anatomy being studied.
         Because high-frequency sound waves cannot penetrate bone or air, they are especially useful in imaging soft tissues and fluid filled spaces. Ultrasound is good at noninvasively imaging a number of soft tissue organs without xrays.

These include:

• Pelvis and reproductive organs
• Kidneys, liver, pancreas, gall bladder
• thyroid
• Blood vessels
• Fetus

Color Doppler Ultrasound
Τhis test examines the blood flow in the major arteries and veins in the arms and legs with the use of ultrasound (high-frequency sound waves). The test combines Doppler ultrasonography, which uses audio measurements to "hear" and measure the blood flow and duplex ultrasonography, which provides a visual image

How the test is performed:
This test is done by a doctor who specializes in performing and interpreting imaging tests (radiologist) or by an ultrasound technologist (sonographer). It is done in an ultrasound room in a hospital or doctor's office.

You will need to remove any jewelry that might interfere with the Doppler ultrasound scan. You may need to take off all or most of your clothes, depending on which area is being examined (you may be allowed to keep on your underwear if it does not interfere with the test). You will be given a cloth or paper covering to use during the test.

· For abdominal scans, you will lie on your back.

· For chest scans, you will lie on your back with your neck slightly extended.

· For head and neck scans, your head may be turned to one side.

· For an arm or leg scan, your head is slightly raised and the exposed arm or leg is turned slightly outward. Occasionally for a leg scan, you may be asked to lie on your stomach.

Gel is applied to the skin to promote the passage of the sound waves. The transducer is placed in the gel and moved along the skin. You need to lie very still during the procedure. You may hear sounds that represent the flow of blood through the blood vessels.

The test usually takes 10 to 30 minutes.