| Ultrasound / Ultrasonography |
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What is Ultrasound Imaging? |
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Ultrasound imaging, also called ultrasound scanning or sonography, is a method of obtaining images from inside the human body through the use of high-frequency sound waves. The reflected sound wave echoes are recorded and displayed as a real-time visual image. No ionizing radiation (x-ray) is involved in ultrasound imaging. Obstetric ultrasound refers to the specialized use of sound waves to visualize and thus determine the condition of a pregnant woman and her embryo or fetus so called obstetric ultrasound.
Ultrasound is a useful way of examining many of the body's internal organs, including but not limited to the heart, liver, gallbladder, spleen, pancreas, kidneys and bladder. Because ultrasound images are captured in real time, they can show movement of internal tissues and organs and enable physicians to see blood flow and heart valve functions. This can help to diagnose a variety of heart conditions and to assess damage after a heart attack or other illness. |
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What are some common uses of the procedure? |
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Millions of expectant parents have seen the first "picture" of their unborn child with pelvic ultrasound examinations of the uterus and fetus. Ultrasound imaging is used extensively for evaluating the eyes, pelvic and abdominal organs, heart and blood vessels, and can help a physician determine the source of pain, swelling or infection in many parts of the body. Because ultrasound provides real-time images it can also be used to guide procedures such as needle biopsies, in which needles are used to sample cells from organs for laboratory testing. Ultrasound is now being used to image the breasts and to guide biopsy of breast cancer. Ultrasound is also used to evaluate superficial structures such as the thyroid gland and scrotum (testicles).
Doppler ultrasound is a special technique used to examine blood flow. Doppler images can help the physician to see and evaluate:
- Blockages to blood flow (such as clots).
- Narrowing of vessels (which may be caused by plaque).
- Tumors and congenital malformation.
Obstetric ultrasound should be performed only when clinically indicated. Some indications may be:
- To estimate the age of the pregnancy.
- To diagnose congenital abnormalities.
- To evaluate the position of the fetus.
- To evaluate the position of the placenta.
- To determine if there are multiple pregnancies.
- To determine the amount of amniotic fluid around the fetus.
- To check for opening or shortening of the cervix or mouth of the womb.
| Gallbladder |
Liver |
Liver |
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| Sludge within the gallbladder |
Color and spectral Doppler flow within the upper abdomen from |
Gray scale image of sag liver with hemangioma |
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How should I prepare for the procedure? |
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You should wear comfortable, loose-fitting clothing for your ultrasound exam. Other preparation depends on the type of examination you will have. For some scans your doctor may instruct you not to eat or drink for as many as 12 hours or overnight fasting before your appointment. For others you may be asked to drink few glasses of water one hour prior to your exam and avoid urinating so that your bladder is full when the scan begins.
For OBSTETRIC: Only the lower abdominal area needs to be exposed during this procedure; consequently, a two-piece outfit will prevent you from having to readjust or remove all of your clothing. If an ultrasound is referred by your clinician early in your pregnancy, you may be instructed to have a full bladder for the procedure. Air interferes with sound waves, so if your bladder is distended, the air-filled bowel is pushed out of the way and an image of the uterus and embryo or fetus is obtained. About an hour before the procedure you should empty your bladder. You may be instructed to drink up to six glasses of water and avoid urinating until the procedure is completed. A full bladder is not necessary in most cases, especially after the first two to three months of pregnancy. The radiologist or sonographer may elect to examine an early pregnancy by means of transvaginal ultrasound. This requires an empty urinary bladder. You should ask for instructions when you make your appointment. |
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What does the equipment look like? |
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Ultrasound scanners consist of a console containing a computer and electronics, a video display screen and a transducer that is used to scan the body. The transducer is a small hand-held device about the size of a bar of soap, attached to the scanner by a cord. The physician or technologist spreads a lubricating gel on the patient's abdomen in the area being examined and then presses the transducer firmly against the skin to obtain images. The ultrasound image is immediately visible on a nearby screen that looks much like a computer or television monitor. The physician or technologist watches this screen during an examination and captures representative images for storage. Often, the patient is able to see it as well.
An example of the ultrasound equipment at Focus Imaging is shown at the of this page. |
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How does the procedure work? |
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Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships at sea and anglers with fish detectors. As the sound passes through the body, echoes are produced that can be used to identify how far away an object is, how large it is, its shape and its consistency (fluid, solid or mixed).
The ultrasound transducer functions as both a generator of sound (like a speaker) and a detector (like a microphone). When the transducer is pressed against the skin it directs inaudible, high-frequency sound waves into the body. As the sound echoes from the body’s fluids and tissues the transducer records the strength and character of the reflected waves. With Doppler ultrasound the microphone captures and records tiny changes in the sound wave's pitch and direction of the sound. These echoes are instantly measured and displayed by a computer, which in turn creates a real-time picture on the monitor. The "live" images of the examination are usually recorded on videotape but one or more frames of the moving picture may be "frozen" to capture a still image.
For Obstetric: Conventional ultrasound displays the images as thin sections (like looking at single slices of bread in a loaf). 3-D ultrasound is the result of modern computer technology that can reformat data into three-dimensional images (like looking at the entire loaf of bread from various projections). 4-D ultrasound is 3-D ultrasound in motion.
Doppler ultrasonography is the application of diagnostic ultrasound to detect moving blood cells and measure their direction and speed of movement. The Doppler effect is used to evaluate blood flow by measuring changes in the frequency of the echoes reflected from blood cells.
The movement of the embryo or fetus and the heart beat can be seen as an ongoing ultrasound "movie." The Ultrasound machine have an audio component that processes the echoes produced by blood flowing through the fetal heart, blood vessels and umbilical cord. This sound can be made audible to human ears and has been described by patients as a "whooshing" noise. |
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How is the procedure performed? |
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The patient is usually positioned on an examination table. A clear gel is applied to the patient's body in the area to be examined to help the transducer make secure contact with the skin. The sound waves produced by the transducer cannot penetrate air so the gel helps eliminate air pockets between the transducer and the skin. The technologist or radiologist presses the transducer firmly against the skin and sweeps it back and forth to image the area of interest.
When the examination is complete the patient may be asked to dress and wait while the ultrasound images are reviewed either on film or on a TV monitor. Often though, the technologist or radiologist is able to review the ultrasound images in real time as they are acquired and the patient can be released immediately.
For Obstetric: The transducer also detects the echoes that bounce off anatomic structures as reflections. Sometimes the radiologist determines that a transvaginal scan will need to be performed. Instead of a transducer being moved over your abdomen, the high-frequency waves will be emitted by a transducer placed in the vagina. This technique often provides improved, more detailed images of the uterus and ovaries. It is especially useful in early pregnancy. With this approach the urinary bladder needs to be empty. Shown is an example of a transvaginal transducer. Only two to three inches of the transducer are inserted into the vagina. The rest of the transducer is a handle for use by the operator. |
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What will I experience during the procedure? |
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Most ultrasound examinations are painless, fast and easy. You will lie on your back on an examining table. The technologist or doctor will spread some warm gel on your skin and then press the transducer firmly against your body, moving it until the desired images are captured. There may be varying degrees of discomfort from pressure as the technologist guides the transducer over your abdomen, especially if you are required to have a full bladder. The examination usually takes less than 30 minutes. Also, you may dislike the feeling of the water-soluble gel applied to your abdomen. With transvaginal scanning, there may be minimal discomfort as the transducer is moved in the vagina, especially when the bladder begins to refill. |
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Who interprets the results and how do I get them? |
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Your ultrasound examination is interpreted by a panel of highly qualified and experienced radiologists (see our doctors). After your visit for a diagnostic imaging procedure, the images from your exam are transferred to one of our radiologists who specializes in analyzing images of the specific area of the body you had examined. Next, the radiologist prepares a diagnostic report to share with the doctor that sent you to us. We retains exam films and reports electronically for a set length of time. Please contact our reception counter after your diagnostic imaging procedure if you have questions regarding the timings (Usually available within few hours unless emergency case) and procedure for collecting the reports or next steps or follow-up appointments. New technology also allows us for distribution of diagnostic reports and referral images over the Internet at many facilities. Our radiologists have established themselves as valued consultants and colleagues with our referring physicians. They pride themselves on being accessible and responsive. |
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What are the benefits vs risks? |
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Benefits
- Ultrasound scanning is noninvasive (no needles or injections in most cases) and is usually painless.
- Ultrasound is widely available and easy to use.
- Ultrasound uses no ionizing radiation and is the preferred image modality for diagnosis and monitoring of pregnant women and their unborn infants.
- Ultrasound provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies.
- Ultrasound images can visualize structure, movement and live function in the body's organs and blood vessels.
Risks
- For standard diagnostic ultrasound there are no known harmful effects on humans.
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What are the limitations of General Ultrasound Imaging? |
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Ultrasound has difficulty penetrating bone and therefore can only see the outer surface of bony structures and not what lies within. For visualization of bone, other imaging modalities such as Magnetic Resonance Imaging (MRI) may be selected.
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 suffering from obesity are more difficult to image—this is because tissue attenuates (weakens) the sound waves as they pass deeper into the body.
Obstetric ultrasound cannot identify all fetal abnormalities. Consequently, when there are clinical or laboratory suspicions for a possible abnormality, a pregnant woman may have to undergo nonradiologic, invasive testing such as amniocentesis (the evaluation of fluid taken from the sac surrounding the fetus) or chorionic villus sampling (evaluation of placental tissue) to determine the health of the fetus, or she may be referred by her primary care provider to a perinatologist (an obstetrician specializing in high-risk pregnancies). |
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Why do I need to have a full bladder for a pelvic ultrasound? |
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Sound waves travel more easily through liquids than through surrounding tissues and air. Consequently, a full bladder facilitates passage of sound waves through it, making the uterus and ovaries behind the bladder easier to see. |
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Why can’t I eat or drink anything before my abdomen ultrasound? |
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When you eat, drink or even chew gum, you introduce air into the stomach and bowel. Sound waves do not penetrate air, making it harder to see target organs. |
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If there are ulcers in my stomach, can you see them? |
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No. Due to the intestinal gas (air) in the stomach and intestines, it’s hard to see these areas with ultrasound. |
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Can ultrasound be harmful to my baby? |
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To date, no proven ill effects have been seen doing regular ultrasound exams on pregnant women. |
