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What is an ultrasound (sonogram)?

Ultrasound imaging, also called sonography, is a diagnostic imaging technology that uses high-frequency sound waves to create still or moving images of structures inside the body. It works similarly to the echolocation used by bats, dolphins and submarines. A wand-like transducer of the ultrasound machine sends a sound wave into the body, which strikes internal structures and bounces back. A receiver in the transducer picks up and records the changes in the sound’s pitch and direction, and a computer instantaneously converts that information into images that are displayed on a monitor.

Ultrasound allows internal organs to be viewed as they function in real time, like a live TV broadcast. Single frames or video clips of these images can be captured and saved. In addition, ultrasound signals can be converted into a three-dimensional view of the organ or structure under examination, or a four-dimensional one, which is a 3D view with the addition of movement.

Ultrasound imaging is painless—the sound waves used in the technology are so gentle you won’t feel them. No radiation is used in this imaging approach.

Why it's done

Ultrasound can provide images of the body’s internal organs and other structures, and can also provide information about how the body is functioning, by showing such things as the velocity of blood flow, the softness or hardness of tissue, and other characteristics.

Ultrasound can be used to help doctors diagnose and treat a wide variety of conditions. It is often used to examine many of the body’s internal organs, including the heart and blood vessels (an ultrasound of the heart is commonly called an echocardiogram), liver, gallbladder, spleen, pancreas, kidneys, bladder, uterus, ovaries, thyroid and parathyroid glands and scrotum. It can allow a physician to determine whether a mass is a fluid-filled cyst or tumor. It can also help guide physicians in performing a variety of procedures, such as ultrasound-guided needle biopsy and fluid aspiration. Ultrasound is also the most common imaging exam used to monitor pregnancy and the development of the fetus.

Our approach

When it comes to ultrasounds (sonograms), the radiologists at Northwell Health Imaging are the power behind the exam. Every ultrasound exam is performed with state-of-the-art technology and interpreted by a fellowship-trained radiologist whose diagnostic skills have been honed by specialized training and thousands of hours of experience. If you need additional care, your radiologist will work side by side with the rest of your care team, collaborating closely to help guide your care.

Northwell Health Imaging offers the largest group of fellowship-trained and subspecialized radiologists on Long Island, as well as access to all the resources and clinical expertise of New York state’s largest health system. Whether you are here for screening, diagnostic or treatment imaging services, each of our practitioners is committed to providing a caring, comfortable environment and a positive, productive experience.

Risk factors

There are no known harmful effects of diagnostic ultrasound on humans.

Types of ultrasounds

Ultrasound can be used to help doctors diagnose and treat a wide variety of conditions. Some of the more common types of ultrasound exams include: 

  • Doppler ultrasound—Used to visualize and evaluate blood flow in vessels in the body or within the heart. Among other things, doctors can use Doppler ultrasound to assess whether plaque build-up inside the carotid arteries (the major arteries in the neck) is blocking blood flow to the brain.
  • Vascular ultrasound—Used to examine the vascular system and analyze its function. Doctors can use vascular ultrasound to detect blood clots.
  • Echocardiogram—Used to examine the heart and its valves, and to evaluate how effectively the heart is pumping.
  • Abdominal ultrasound—Used to check for abnormalities of the abdominal organs, including the kidneys, liver, pancreas and gallbladder. Abdominal ultrasound can aid in detection of gallstones and tumors, for example.
  • Renal ultrasound—Used to examine the kidneys and urinary tract.
  • Obstetrical ultrasound—Used to monitor the development of the fetus.
  • Pelvic ultrasound—Used to identify the cause of pelvic pain. It can aid doctors in diagnosing an ectopic pregnancy in women, for instance, and in detecting tumors or masses.
  • Breast ultrasound—Used to evaluate a mass in breast tissue.
  • Thyroid ultrasound—Used to visualize the thyroid and to detect any abnormalities.
  • Scrotal ultrasound—Used to investigate scrotal pain or to assess for masses in the testicles.
  • Prostate ultrasound—Used as follow-up to a physical examination, to evaluate any nodules felt during the examination and to evaluate prostate size.
  • Musculoskeletal ultrasound—Used to identify the cause of pain or other symptoms in a joint or muscle.
  • Interventional ultrasound—Used by an interventional radiologist to guide minimally invasive procedures.

What to expect

Most people find ultrasound examinations painless. If the ultrasound transducer is inserted into a body opening, such as the vagina or rectum, you may experience minimal discomfort.

For most ultrasound exams, you will lie face up on an exam table that can be tilted or moved. Occasionally, you will be asked to change positions during the examination. The sonographer (a health care professional specially trained in performing ultrasound imaging) will apply gel to the area of the body being studied to prevent air pockets that can block sound waves from passing into the body. The technician will then pass the ultrasound transducer over the area of interest, adjusting the transducer as needed to capture the images.

In some cases, the transducer must be attached to a probe and inserted into the body to obtain the images. For instance, in a transrectal ultrasound, a transducer is inserted into a man’s rectum to obtain images of the prostate. In a transvaginal ultrasound, a transducer is inserted into a woman’s vagina to view the uterus and ovaries.

After the examination is completed and the images are reviewed to confirm that they are of high quality, you can resume your normal activities.

How to prepare

For many ultrasound exams, no special preparation is needed. You should wear comfortable, loose-fitting clothing to the appointment. You may be asked to change into a hospital gown and to remove clothing and jewelry from the area to be examined.

Certain abdominal exams require you to not eat for four to six hours prior to the examination.

Certain exams require a full bladder. For these, you may be asked to drink four to six glasses of water, starting an hour to 90 minutes before the exam, and not to urinate until the exam has been completed.

Your doctor (or the person scheduling your exam) will let you know if any special preparations are required for your ultrasound exam.


Your ultrasound will be read/interpreted by a subspecialized radiologist and the results will be promptly shared with your physician. Your doctor will determine if any followup care is needed.

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