How Are Ultrasound & MRI Scans Used to Diagnose Breast Cancer?

Reviewed by: HU Medical Review Board | Last reviewed: December 2023

Breast ultrasound and magnetic resonance imaging (MRI) are tools used to diagnose and evaluate breast cancer. A mammogram is the most common way to screen for breast cancer. Doctors may order an ultrasound or MRI when further testing is needed or to detect certain breast changes.1-5

These types of imaging tests show pictures of the inside of the body. They may be helpful to learn more about a suspicious lump or show if cancer has spread.1-5

When is a breast ultrasound needed?

Breast ultrasound is used to examine changes in the breast, such as lumps and fluid-filled cysts. The test may be recommended for people who have dense breast tissue.2

Doctors may order a breast ultrasound to:1-3

  • Evaluate lumps that can be felt but not seen on a mammogram
  • Confirm an abnormal finding from a mammogram
  • Examine a specific area rather than the whole breast
  • Differentiate between a harmless cyst and a solid lump
  • Screen people who are younger than 25
  • Help guide a biopsy needle into the breast so that cells can be removed and tested for cancer
  • Screen people who are pregnant and cannot be exposed to X-rays from a mammogram

An ultrasound is not typically done to screen for breast cancer because it can miss some early signs of cancer.2,3

But an ultrasound can detect breast problems and see how well blood is flowing to areas of the breast. An ultrasound may also be used to look at lymph nodes under the arm, help guide a needle during a biopsy, or remove fluid from a cyst.2,3

A biopsy may be needed if a solid lump is detected. An ultrasound cannot always determine if a solid lump is cancerous or non-cancerous. A Doppler probe may be used during the ultrasound to hear the sound waves the transducer sends out. This helps determine how fast blood is flowing through a vessel or if there is a blockage.3

Some imaging centers also use automated breast ultrasound (ABUS), especially for people with dense breasts or abnormal findings. This test uses a much larger transducer to take hundreds of images that cover the whole breast.2

How to prepare for a breast ultrasound

There is not much you need to do to prepare for an ultrasound. The most important thing is to avoid putting any lotion, powder, or other substances on your breasts on the day of the ultrasound.3

You may want to wear clothing that you can easily take off. The imaging center may ask you to wear a gown that opens in the front so the sonographer or radiologist can easily reach your chest.3

What to expect during a breast ultrasound

Ultrasound imaging uses sound waves and their echoes to produce a picture of inside the breast. The test is generally quick and painless unless the lump is tender.2

Some benefits of ultrasound include:2

  • Fairly easy procedure
  • Widely available
  • Does not expose a person to radiation
  • Costs less than other testing options

An ultrasound is done using a handheld, wand-like instrument called a transducer. First, the sonographer or radiologist applies a gel on the breast. This helps the ultrasound wand glide over the skin. It also improves the conduction of the sound waves through the breast tissue.2

They may dim the lights to help see the images on the screen. The transducer sends out sound waves and captures the echoes as they bounce off deeper breast tissues under the skin.2

The technology transmits these echoes into a picture. The sonographer can then view them on a computer screen. Some people feel slight pressure as the transducer moves around, but it should not be painful.2

Breast ultrasound results and follow-up

A breast ultrasound has minimal risks or side effects. You can resume your normal activities after the procedure.2.3

Your ultrasound results should be available within a few days of the test. The doctor who ordered the breast ultrasound will discuss the results and next steps for other testing with you.2,3

When is a breast MRI needed?

A breast MRI can be used to screen, diagnose, and evaluate breast cancer and other abnormalities. MRI uses powerful magnetic fields and radio waves to produce detailed pictures of the breast. MRI does not use X-rays. It can detect cancers that may go undetected by mammograms and ultrasound.4-6

A breast MRI is often ordered to:1,4-6

  • Further evaluate abnormalities found on a mammogram
  • Screen people who are at high risk for breast cancer
  • Screen people who cannot be exposed to radiation
  • Determine the extent of a diagnosed breast cancer
  • Find out how much the disease has grown
  • Check the other breast for cancer
  • Screen people who have a history of breast cancer
  • Evaluate for silicone breast implant ruptures

MRI is sometimes used after chemotherapy or hormonal therapy treatments. This may be followed by a repeated MRI for surgical planning depending on the situation. Doctors also use MRI to monitor people after breast cancer diagnosis and treatment.1

How to prepare for a breast MRI

A breast MRI is usually not painful and takes less than an hour. The scan itself lasts about 20 minutes. A radiologist or radiology technologist usually performs the test.4-5

This test involves laying down on a movable table that slides into the machine. Some people may feel claustrophobic or anxious. Newer MRI machines are open at both ends. They have wider openings, more head space, and proper ventilation.4-5

To prepare:4

  • Remove all clothing and jewelry
  • Tell the technician about any medical devices or implants
  • Tell the technician if you are pregnant, unable to lie on your stomach, or have claustrophobia
  • Tell the technician if you wear a continuous glucose monitor, insulin pump, or any medication patches

What to expect during a breast MRI

You will need to lie face-down on a table, where your breasts will fit into a hollow depression. Some breast MRIs require the injection of a contrast dye. The dye is different from the one used during CT scans. This helps create a clear picture of the possible cancer.1,4-6

A technologist or nurse will place an IV line to inject the contrast dye during the exam. They move the table into the magnet of the MRI machine and start the test via a computer while watching from a different room.4

During the test, it is normal to hear banging and thumping noises from the machine. It is important to lie as still as possible while the machine is taking images. You can talk to the tech via intercom if needed or request earplugs before the test starts.4-5

If a contrast dye is needed, the technologist injects it after an initial series of scans. They take more images during or after the injection. Some people may have to wait while the radiologist checks the images in case they need more. When the test is complete, the technologist removes the IV line.4

Breast MRI results and follow-up

A breast MRI has minimal risks or side effects. You can resume your normal activities unless the exam was an MRI breast biopsy. Those involve some follow-up instructions at home.4

Your MRI report may look different depending on the purpose of the test and whether it was:4

  • For screening purposes
  • For diagnostic purposes
  • To evaluate cancer

Your MRI results should be available within a few days of the test. The doctor who ordered the breast MRI will discuss the results and next steps for treatment or other testing with you.4

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