Doctors use imaging tests to help find and diagnose disease, recommend treatments, and monitor how well you respond to therapy. You may have more than one imaging test, because each kind gives us different information.
Some imaging tests, such as ultrasounds and magnetic resonance imaging (MRI), do not use radiation.
If you must have a test that uses radiation, such as X-rays and computed tomography (CT), our doctors use the lowest dose of radiation possible to still give us very high-quality images.
We only order a test if it will help you more than harm you from the risk of exposure to radiation. We will answer your questions and address your concerns about an imaging test. Our goal is to get the information we need to make the best decisions about your diagnosis and treatment.
Common Medical Imaging Tests Used To Diagnose Cancer
A CT scan makes 3D images of areas inside your body. The images show bone, organs, muscles, tumors, and other soft tissue. CT scans are sometimes called CAT scans.
During a CT scan, a machine uses radiation to take detailed pictures of areas in your body. It takes a series of pictures from different angles. A computer linked to the machine puts the pictures together to make a 3D image.
Some CT scans use a special material called contrast dye. The contrast dye makes differences inside your body easier to see. Whether you need a CT scan with contrast dye depends on the reason you’re having the scan. It also depends on which part of your body your care team needs to see.
Some CT scans, called low-dose CT scans, use less radiation. Low-dose CT scans are sometimes used as a screening tool for people at high risk of developing lung cancer.
Nuclear Medicine Scan
A nuclear medicine scan uses a radioactive tracer to help us find tumors. You can get the tracer in an injection (shot), or you can swallow it, or breathe it in. The type of tracer you get depends on why you’re having the scan. Different tracers work best for different types of cancer and areas of your body.
Once the tracer is in your body, we give it time to move to the scan area. Then, we’ll use a special camera or scanning machine to see how much of the tracer is the area. We’ll see the images on a computer screen.
A bone scan is an example of a nuclear medicine scan. A bone scan lets us see your bones and check for damage. Another example is a thyroid scan. A thyroid scan lets us check for cancer in your thyroid. PET scans are a third example of common nuclear medicine scans.
Positron Emission Tomography (PET)
PET scans are a type of nuclear medicine scan. They show how much glucose (sugar) is used in different areas of your body. Cells use glucose for energy. Cancer cells often use more glucose than healthy cells. A PET scan can help us find cancer cells by showing areas that are using more glucose than normal.
During a PET scan, a small amount of radioactive glucose is injected (put) into your vein. A machine then takes detailed, computerized pictures of areas where the glucose is being used.
In some cases, your doctor may recommend a PET-CT scan or a PET-MRI scan. These combine images from PET and CT or PET and MRI scans. The scans are done at the same time using the same machine. Together, the scans make a more complete picture of what’s going on in your body than they can alone.
Mammography uses low-dose X-rays to take pictures of your breast tissue. We use these images to check for signs of breast cancer.
At MSK, anyone who needs a mammogram will get tomosynthesis, also called 3D mammography. This technology helps us see breast tissue and tumors more clearly. It’s helpful for people who have dense breasts. The pictures it takes are so detailed that most people will not need to come back for more images.
MSK also offers contrast-enhanced mammography. This type of mammography uses iodinated contrast to show the blood flow in your breast. Tumors usually have more blood flow than normal tissue, so they show clearly on the images.
Contrast-enhanced mammography can show breast tumors just like a breast MRI can. They’re a good option for people who can’t have an MRI.
For a contrast-enhanced mammogram, we will place an intravenous (IV) line in your vein before your mammogram. We will put the iodinated contrast into your bloodstream through the IV. During the mammogram, we will take extra images that show where the iodinated contrast flows in your bloodstream. A computer uses these images to make a map of the blood flow in your breast.
X-rays let us see an area inside your body. They’re the oldest and most common type of medical imaging scan.
During an X-ray, an area of your body is exposed to a small dose of radiation. Some tissues and organs block radiation from passing through your body, while others let radiation through. Because of this, the X-ray machine can use the radiation to take pictures of the inside of your body.
Magnetic Resonance Imaging (MRI)
MRI makes detailed 3D images of areas inside your body. The images show bone, organs, muscles, tumors, and other soft tissue. We can use the images to see the type, size, and location of tumors.
MRI is done using radio waves, a powerful magnet, and a computer. The machine that holds the magnet and makes the radio waves is called an MRI scanner. It’s big and has a hole in the middle. During MRI, you lie on a table that slides into the scanner. The scanner takes a series of pictures that each shows a thin slice of an area of your body. The computer puts the pictures together to make a 3D image.
MRI makes better images of organs and soft tissue than other medical scans. But to get high-quality images during MRI, you need to keep perfectly still and hold your breath at certain times. Because of this, MRI may take longer than other medical scans. Some people have a hard time lying still during the imaging. This is most often true for children or people with anxiety or a fear of enclosed spaces.
Metal and electronic objects can disrupt the MRI scanner’s magnetic field. If you have medical or electronic devices or other metal objects in your body, tell the person doing your MRI. It may not be safe for you to have an MRI.
An ultrasound uses high-frequency sound waves to make still or moving pictures of areas in your body. We use ultrasound to see both structure and movement. For example, we can use it to check blood flow or see if a mass is solid or filled with liquid.
During an ultrasound, the technician places a handheld probe close to the area that needs to be imaged. The probe gives off sound waves that bounce off your tissues or organs and make echo patterns. These patterns are shown as images, called sonograms, on the ultrasound machine’s screen.