Ultrasound (US) imaging, US scanning, ultrasonography, or sonography
Ultrasound scans are high frequency sound waves too high for humans to hear. After the Titanic hit an iceberg and sank in 1912, scientists researched ways to find underwater icebergs. During this time, SONAR (sound navigation and ranging), which uses ultrasound, was developed.
Ultrasound waves sent to the part of the body being examined are reflected, refracted, or absorbed at the interfaces inside the body. Echoes that return in this way carry information about the size, distance, and uniformity of internal organs. This is displayed on a monitor to create an ultrasound image.
During ultrasonography, a hand-held device called a "transducer" is placed on the area being examined and moved around. This transducer generates ultrasound and sends it through the body. It also detects the returning echoes and transmits them as electrical signals. Because one transducer continuously generates many ultrasound waves while detecting echoes, a real time image can be produced on a viewing monitor. These images can be recorded on videotape, or images can be frozen and recorded on to film.
During ultrasound, lubricating gel is applied to the skin so that the transducer can be moved around to produce real time images. Ultrasound is similar to audible sound in that it can pass through water and human organs easily, but it can't pass through air or bone. So gel is applied between the transducer and the skin to bridge the gap, and effectively send the ultrasound waves.
Because US images are real time images, blood flow, blood vessels, bowel movement, and the movement of internal organs from breathing can be seen.
Types of ultrasound:
Doppler ultrasound of extremities
- Abdominal ultrasound
- Obstetric ultrasound (pregnancy ultrasound)
- Pelvic ultrasound
- Transvaginal ultrasound
- Musculoskeletal ultrasound
Safe, painless, easy, fast, and widely available
Real time imaging -- ultrasonography can be used to guide invasive procedures such as biopsy, and to visualize bowel movement and blood flow.
In case of an emergency, bedside sonography can be done without particular patient preparations.
During pregnancy -- to evaluate fetus, uterus
To determine the causes of pain, swelling, bleeding, or infection -- stones, tumor, cyst, inflammations, injury, congenital anomalies
To examine blood flow and discover blockages -- atherosclerotic plaque, blood clots in the arteries and veins of extremities, abdomen, pelvis, and neck
To guide invasive procedures -- needle biopsy (i.e., breast cancer), sampling or withdrawal of fluid (i.e., amniocentesis, amoebic liver abscess), insertion of tubes, catheters, stents, wires
Abdominal ultrasound: gallstones, kidney stones, appendicitis, enlarged organs (liver, spleen, kidneys, lymph nodes, etc.)
Obstetric (pregnancy) ultrasound: abnormalities in the unborn child (fetus), uterus, and placenta (such as placenta previa), monitoring fetal development
Pelvic ultrasound: cysts, fibroid (uterine myoma), ovarian cancers, uterine cancers, uterine anomalies, abscesses, ectopic pregnancy, abortion, prostate cancer/hyperplasia, bladder tumor
Transvaginal ultrasound: ectopic pregnancy, fetal death, hydatidiform mole, cysts, tumor of uterus/ovaries
Hysterosonography (especially in patients with abnormal uterine bleeding): polyps, fibroids, cancer, congenital anomaly, endometrial scars, evaluating the patency of fallopian tubes
Musculoskeletal ultrasound: tendon tears (i.e., tears of Achilles tendon), tears of muscles, masses or tumors, bleeding or other fluid collections within the muscles, bursae, and joints
Thyroid ultrasound: cysts, goiter (enlarged thyroid), tumor/cancer
Testicle ultrasound: cysts, tumor, fluid collection, torsion, inflammation (epididymitis, tuberculosis, etc.)
Vascular ultrasound: blood clots, atherosclerotic plaque, injury, congenital malformation, monitoring of vascular graft or bypass blood vessels
Doppler ultrasound of the extremities: venous occlusion, deep vein thrombosis, arterial occlusion, arteriosclerosis, trauma to the arteries/veins, monitoring vascular graft/stent/other reconstruction, vascular masses (such as, aneurysm, pseudoaneurysm), measurement of blood flow
Carotid duplex: carotid stenosis (narrowing), occlusion, thrombosis
Breast ultrasound: breast cancer, cyst, benign tumor (such as fibroadenoma), fibrocystic breast condition
Neurosonography: prenatal hypoxic brain damage, congenital anomaly
Transrectal ultrasound: prostate cancer, benign prostatic hyperplasia
Others: pleural effusion, superficial mass
You will be asked to remove clothing and jewelry, and put on a hospital gown.
You will be positioned on an examination table; Depending on what's needed you might lie down, sit, lie down on your side, put your hands above your head, or leave them in a comfortable position.
A lubricating gel is applied to the patient's body area to be examined.
An apparatus known as a transducer is placed on the examination area and moved around to get real time images. Sometimes you will have to breathe in and hold your breath according to the technologist, sonologist, or physician's instructions.
After the examination, the gel is cleaned off and you can change clothes.
Examinations usually take 10-30 minutes.
Wear comfortable, loose-fitting clothing.
Take off your clothes in the examination area and put on a hospital gown.
For an abdominal ultrasound, you shouldn't eat or drink for as many as 12 hours before your examination.
For pelvic ultrasounds, you may need to drink six glasses of water one to two hours prior to your examination and avoid urinating.
For transvaginal ultrasound, you need to urinate before your examination.
For thyroid and breast sonography, you will be asked to remove all jewelry.
No special preparation is needed in other ultrasound exams.
In an emergency, exams can be done without special preparations.
Tell the sonographer, sonologist, or physician sonologist conducting the examination about pain, bleeding, discharge, fever or any other symptoms you might have. Also, telling the examiner about past ultrasounds and surgeries is helpful, and sometimes it is crucial information.
The image recorded on film or videotape is interpreted and analyzed by a radiologist (a physician specialist experienced in ultrasound and other radiology exams). The official report is sent to the practitioner who requested the examination.
The personal doctor's office informs the patient when the results are in and the outcome, and uses them as a reference in evaluating and treating the patient.
There is no known risk to humans from diagnostic ultrasound.
Unlike X-ray examinations, ultrasound does not use radiation. Pregnant women and fetuses can be safely examined.
Ultrasound does not penetrate air or bone. So if an abnormality is behind bowel gas, ribs, or calcified rib cartilage, it may not be discovered.
Because ultrasound is absorbed and reflected inside the body, only some of the waves reach deep places farthest from the transducer. There's a limitation to ultrasound's ability to look deep into the body. Of two tumors of equal size, the tumor closest to the transducer will be discovered more readily than the more distant one. Examinations, consequently, are not as productive for obese, tall patients as they are for thin or petite ones.
Ultrasonography is an operator-dependent, subjective test. The more experience the operator has, the better the patient listens to his instructions (hold your breath, do not eat, repress the urge to urinate), the better the results. Further, the more the operator knows about the patient's past medical history, current medical history, and the results of other radiological and laboratory tests, the better the examination. For best results, before taking ultrasonography, ask if the practice where the scan is being performed is accredited either by the American Institute of Ultrasound in Medicine or the American College of Radiology.
Ultrasonography can't discover all abnormalities. If there's an ulcer, small polyps, or diverticuli, or infection/inflammation in the stomach, intestine, or colon, ultrasound will not be effective in finding them. In such cases, endoscopy, barium enema, or an upper GI series must be done. Ultrasound is an incomplete examination, and a CAT scan or MRI will have to be done for more accurate diagnosis.