Ultrasound for Cancer

An ultrasound can be used to find cancer or plan further cancer treatment. You might also hear it called ultrasonography, sonography, or sonogram.

What is an ultrasound?

An ultrasound is an imaging test that uses sound waves to make pictures of the inside of your body.

This type of test helps doctors monitor a baby during pregnancy, but it also helps them monitor other conditions and diseases, including tumors. Ultrasound can help doctors see tumors in parts of the body that don’t show up well on x-rays.

This test can be done quickly and safely. It does not expose you to radiation.

What does ultrasound show?

An ultrasound machine creates images called sonograms by giving off high-frequency sound waves that go through your body. As the sound waves bounce off organs and tissues, they create echoes. The machine turns these echoes into real-time pictures on a computer screen. Some types of ultrasounds also create 3-D images.

An ultrasound can show:

• Organ structure and movement
• The flow of blood through blood vessels
• Some soft tissue diseases that can’t be seen clearly on x-rays

It can also help doctors:

• Tell a fluid-filled cyst from a solid tumor
• Guide a needle for a biopsy, called an ultrasound-guided biopsy
• Guide a needle for an ablation

Ultrasound images are not as detailed as images made from CT or MRI scans. An ultrasound might not be able to tell whether a tumor is cancer. It isn’t as useful in some parts of the body because the sound waves can’t go through air, such as in the lungs, or through bone.

Special ultrasounds, known as Doppler ultrasounds, can show how fast and in which direction blood flows through vessels. This is helpful because blood flows differently in tumors than it does in normal tissue.

Some of these machines create color pictures. Color Doppler has made it easier for doctors to find out if cancer has spread into blood vessels, especially in the liver and pancreas.

How does ultrasound work?

An ultrasound machine has 3 main parts:

• Control panel
• Display screen
• Transducer

Producing sound waves

The transducer is a wand that sends out sound waves and picks up echoes. It usually looks a lot like a microphone or a computer mouse. The doctor or ultrasound technologist (tech) moves the transducer over the part of the body being checked. Gel is used to help the sound waves travel back and forth.

For some types of ultrasound exams, the transducer is pushed against and moved over the skin surface. The sound waves pass through the skin and reach the organs underneath. Sometimes, the doctor or tech must put a transducer into a body opening such as the esophagus, rectum, or vagina. This helps get the best images in some cases.  

Displaying the images

The computer inside the main part of the machine analyzes the signals and puts an image on the display screen.

The shape and intensity of the echoes depend on how dense the tissue is. For example, most of the sound waves pass right through a fluid-filled cyst and send back very few or faint echoes. This makes them look black on the display screen. But the waves will bounce off a solid tumor, creating a pattern of echoes that the computer shows as a lighter-colored image.

How do I get ready for an ultrasound?

You don’t need to do anything to prepare for most ultrasounds, but this will depend on what’s being studied. Your health care team will tell you if you need to take any steps to prepare before your test.

Depending on what organ doctors are looking at, you may be told to take a laxative, use an enema, or stop eating and drinking before the test.

If you are having an abdominal (belly) ultrasound, you might need to drink a lot of water to fill your bladder just before the test. This creates a better picture because sound waves travel well through fluid.

What is it like having an ultrasound?

An ultrasound can be done in a doctor’s office, clinic, or hospital. Wear comfortable clothes. You might need to change into a hospital gown, depending on the body part being looked at.

Most often, you will lie down on a table. The tech will put a water-based gel on your skin and move the transducer over the area being checked. The gel feels cool and slippery. After the test, the gel is wiped off your skin. It doesn’t stain your skin or your clothing. You may feel slight pressure from the transducer.

If the transducer is put into an opening in your body, it can cause pressure or discomfort. Before it is placed, it will first be covered with gel, followed by a single-use sterile plastic cover, then another sterile gel.

During the test, the tech or doctor presses the transducer firmly to your skin and moves it around. You might be asked to hold your breath. The operator may adjust knobs or dials to increase the depth to which the sound waves are sent.

How long does an ultrasound take?

An ultrasound usually takes 20 to 30 minutes, but it can take longer. The length of time depends on the type of exam and how hard it is to find any changes in the organs being studied.

What are the possible risks and side effects of an ultrasound?

An ultrasound is a very safe procedure with a low risk of issues.

What else should I know about ultrasound?

• Ultrasound does not use radiation.
• Ultrasound usually costs much less than other imaging tests.
• The quality of the results can depend on the person getting the test and on the skill of the tech or doctor operating the transducer.
• Imaging deeper structures is harder in people with excess body weight.
• Newer forms of ultrasound can provide 3-D images.

Learn more

• Imaging Tests for Cancer