About the Ultrasound Imaging

Ultrasound imaging, also called ultrasound scanning or sonography,  involves exposing part of the body to high-frequency sound waves to produce pictures of the inside of the body. Ultrasound exams do not use ionizing radiation (x-ray). Because ultrasound images are captured in real-time, they can show the structure and movement of the body's internal organs, as well as blood flowing through blood vessels.

Ultrasound imaging is usually a painless medical test that helps physicians diagnose and treat medical conditions. Conventional ultrasound displays the images in thin, flat sections of the body. Advancements in ultrasound technology include three-dimensional (3-D) ultrasound that formats the sound wave data into 3-D images. Four-dimensional (4-D) ultrasound is 3-D ultrasound in motion.

A Doppler ultrasound study may be part of an ultrasound examination.Doppler ultrasound is a special ultrasound technique that evaluates blood as it flows through a blood vessel, including the body's major arteries and veins in the abdomen, arms, legs and neck.

There are three types of Doppler ultrasound:

• Color Doppler uses a computer to convert Doppler measurements into an array of colors to visualize the speed and direction of blood flow through a blood vessel.
• Power Doppler is a newer technique that is more sensitive than color Doppler and capable of providing greater detail of blood flow, especially in vessels that are located inside organs. Power Doppler, however, does not help the radiologist determine the direction of flow, which may be important in some situations.
• Spectral Doppler. Instead of displaying Doppler measurements visually, Spectral Doppler displays blood flow measurements graphically, in terms of the distance traveled per unit of time.

What are some common uses of the procedure?

Ultrasound examinations can help to diagnose a variety of conditions and to assess organ damage following illness.
Ultrasound is used to help physicians diagnose symptoms such as:

1. pain
2. swelling
3. infection

Ultrasound is a useful way of examining many of the body's internal organs, including but not limited to the:

1. heart and blood vessels, including the abdominal aorta and its major branches
2. liver
3. gallbladder
4. spleen
5. pancreas
6. kidneys
7. bladder
8. uterus, ovaries, and unborn child (fetus) in pregnant patients
9. eyes
10. thyroid and parathyroid glands
11. scrotum (testicles)

Ultrasound is also used to:

1. guide procedures such as needle biopsies, in which needles are used to extract sample cells from an abnormal area for laboratory testing.
2. image the breasts and to guide biopsy of breast cancer (see the Ultrasound-Guided Breast Biopsy page).
3. diagnose a variety of heart conditions and to assess damage after a heart attack or other illness.

Doppler ultrasound images can help the physician to see and evaluate:

1. blockages to blood flow (such as clots)
2. narrowing of vessels (which may be caused by plaque)
3. tumors and congenital malformation

With knowledge about the speed and volume of blood flow gained from a Doppler ultrasound image, the physician can often determine whether a patient is a good candidate for a procedure like angioplasty.

What are the limitations of General Ultrasound Imaging?

• Ultrasound waves are reflected by air or gas; therefore ultrasound is not an ideal imaging technique for the bowel. Barium exams and CT scanning are the methods of choice for bowel-related problems.
• Ultrasound waves do not pass through air; therefore an evaluation of the stomach, small intestine and large intestine may be limited. Intestinal gas may also prevent visualization of deeper structures such as the pancreas and aorta. Patients who are obese are more difficult to image because tissue attenuates (weakens) the sound waves as they pass deeper into the body.
• Ultrasound has difficulty penetrating bone and therefore can only see the outer surface of bony structures and not what lies within. For visualizing internal structure of bones or certain joints, other imaging modalities such as MRI are typically used.

some more: The best time for Four-dimensional Color Doppler