Ultrasound uses high-frequency sound waves to create real-time images or videos of internal organs and other soft tissues. Ultrasounds are a non-invasive way to “see” details of these tissues inside your body without any incisions. While most people relate ultrasound with pregnancy, there are many other ways healthcare providers use ultrasound to view, evaluate the function, and treat various areas inside of your body.
Diagnostic, Functional, and Therapeutic Ultrasound Uses
Healthcare providers use ultrasound in three main ways:
If something is wrong or not working correctly, diagnostic ultrasounds view internal parts of your body. They can help your doctor learn more about what’s causing an abnormal blood test or various symptoms such as unexplained pain. Ultrasound images are displayed in either 2D, 3D, or 4D (which is 3D in motion)
One of the most common uses of ultrasound is to monitor the growth and development of the fetus during pregnancy. Diagnostic ultrasound can be used in imaging the following:
- Blood vessels
- Uterus and ovaries
Functional ultrasound applications include Doppler and color Doppler ultrasound and elastography to measure blood flow and speed in vessels within the body or in the heart. It can also measure the speed of the blood flow and direction of movement. This is done using color-coded maps called color Doppler imaging. Doppler ultrasound is commonly used to determine whether plaque build-up inside the carotid arteries is blocking blood flow to the brain.
Doppler ultrasound is a unique technique that evaluates the movement of materials in the body. Doctors commonly use it to see and evaluate blood flow through arteries and veins in the body. Doppler ultrasound helps the doctor to see and evaluate:
- Obstructions in blood flow (such as clots)
- Narrowing of vessels
- Tumors and congenital blood vessel abnormalities
- Reduced or absent blood flow to various organs
- Signs of infection such as inflammation or increased blood flow
- Heart conditions, including:
- Valve problems
- Congestive heart failure
- Assess damage after a heart attack
There are three types of Doppler ultrasound:
- Color Doppler is where different colors help define each direction of blood flow.
- Power Doppler is an ultrasound technique used to obtain images that are difficult or impossible to obtain using standard color Doppler. It gathers greater detail of blood flow, especially in vessels located inside organs. While more sensitive to the detection and demonstration of blood flow, it provides no information about flow direction.
- Spectral Doppler displays the blood flow measurements graphically, showing recorded flow velocities over time. Doppler signals are also converted to audio signals, which enable your provider to “hear” the blood flow during the exam. Higher velocities are heard as high-pitched sounds, while lower velocities play as low-pitched sounds.
Elastography is a method for measuring and displaying the relative stiffness of tissues, which can be used to differentiate tumors from healthy tissue. This information can be displayed as either color-coded maps of the relative stiffness, black-and-white maps that display high-contrast images of tumors compared with anatomical images, or color-coded maps overlayed on the anatomical image. Elastography can be used to test for liver fibrosis, a condition in which excessive scar tissue builds up in the liver due to inflammation.
Ultrasound is also an essential method for therapeutic imaging in the body. For example, during an ultrasound-guided needle biopsy, the physician can see the position of a needle while guiding it to a selected target. Providers utilize the same method to deliver medications to specific body areas or to guide a catheter along a blood vessel’s length.
Therapeutic ultrasound also uses highly-targeted sound waves called high-intensity focused ultrasound (HIFU) to modify or destroy diseased or abnormal tissues such as tumors in the body.
Among the modifications possible are:
- Moving or pushing tissue
- Heating tissue
- Dissolving blood clots
HIFU is currently FDA approved for the treatment of:
- Uterine fibroids
- Alleviate pain from bone metastases
- Ablation of prostate tissue
In most cases, ultrasound therapies are non-invasive, meaning no incisions or cuts are made to the skin, and ultimately, no wounds or scars.
Preparing for Your Ultrasound
Preparation for the procedure will depend on the type of exam. Your doctor will give you instructions on whether you need to refrain from eating or drinking before the procedure. Some procedures require you not to eat or drink for up to 12 hours before your exam. Some scans need you to have a full bladder to get the best view. In these cases, your doctor may tell you to drink up to six glasses of water two hours before your exam and to avoid urinating.
You may need to change into a gown and remove all clothing and jewelry before the procedure. Make sure to wear comfortable, loose-fitting clothing and leave any jewelry at home.
How Does Ultrasound Work?
Ultrasound machines consist of a computer console, monitor, and transducer. The transducer is a small hand-held device that emits ultrasound waves and detects the ultrasound echoes reflected. During an ultrasound exam, the technician will apply a gel to the skin while passing the transducer over the specified area. The gel helps prevent air pockets, which can block the sound waves that create the images. The transducer sends small pulses of inaudible, high-frequency sound waves into the body. The sound waves bounce off the structures inside your body, and it records tiny changes in the sound’s pitch and direction and converts them into electrical signals. The computer creates the image based on the loudness, pitch, and how long it takes for the ultrasound signal to return to the transducer. The type of body structure and tissue the sound is traveling through are also considerations. The signals are then displayed in real-time pictures on a monitor. The sonographer typically captures multiple frames of the moving pictures as still images and may also save short video loops of the images.
What Will I Experience During My Exam?
You’ll lie face up on the examination table while a gel is applied to your skin in the area being examined. A trained technician (sonographer) will then press a hand-held device (transducer) against the exam area and move it to capture the images. You may also be asked to move to a different side to obtain a better image. As the transducer sends sound waves into your body, those that bounce back get sent a computer, which then produces the images.
Parents with young children requiring an ultrasound should receive instructions from their doctor before the procedure regarding whether sedation will be needed. Sedation is sometimes necessary for very young patients to remain still during imaging procedures. Your provider will make you aware of any food and drink restrictions that sedation requires.
Sometimes, ultrasounds are done from inside your body to optimize the image quality. In these cases, the transducer is attached to a probe with a protective sheath that’s inserted into a natural opening in your body. Examples include:
- Transesophageal echocardiogram is a procedure where a probe is inserted into the esophagus to get images of the heart.
- Transrectal ultrasound is when a probe is inserted into a man’s rectum to view the prostate.
- Transvaginal ultrasound is when a probe is inserted into a woman’s vagina to view the uterus and ovaries.
After gathering all the images they need, the sonographer will wipe off the ultrasound gel from your skin.
Are There Any Special Precautions Needed After the Procedure?
While most ultrasound exams take about 30 minutes, more extensive exams can last up to an hour. Once the technologist completes the exam, they may ask you to change back into your clothes and wait while your doctor reviews the images. Or they may ask that you set a follow-up with your doctor to review. You should be able to return to your normal activity level immediately after the exam.
How Do I Get My Results?
Ultrasound exam results vary and depend on what type you get. In some cases, your provider may examine the images and discuss the results during the test, like during a prenatal ultrasound exam.
In other cases, a radiologist will analyze the images and then send the findings in a report to the provider who requested the exam. A radiologist is a healthcare provider trained to supervise and interpret radiology exams. Your provider will then share the results with you in a follow-up appointment. The radiologist report may also be available before your provider reviews the results in your electronic medical record (if applicable and you have an account set up).
What Are the Benefits and Risks of Ultrasound?
- Most ultrasound scanning is non-invasive (no needles or injections). Some exams may cause temporary discomfort, but they should not be painful.
- Ultrasound is a widely available, easy-to-use imaging method. It’s also less expensive than most other imaging methods.
- Ultrasound scanning gives clear, real-time images of soft tissues that can be a tool for guiding minimally invasive procedures and capturing what an x-ray does not.
- Ultrasound is the preferred imaging approach for diagnosing and monitoring pregnant women and their unborn babies.
- Standard diagnostic ultrasound does not produce ionizing radiation and is considered generally safe.
Ultrasound Imaging Limitations
Ultrasound waves are disrupted by air or gas and cannot penetrate bone. However, it may be used to detect fluid around or within the lungs, view bone fractures, or for infection surrounding a bone. Additionally, it may be difficult for an ultrasound to see objects located very deep in the human body. Your health care provider may order other forms of imaging such as CT and MRI scans or X-rays to view these areas.