30-Second Summary
Imaging tests make pictures of areas inside the body to help doctors see whether a tumor is present.
Common imaging tests in cancer care include CT, MRI, PET, nuclear and bone scans, ultrasound, and X-rays.
Some scans use a contrast material (dye) to make certain areas easier to see.
CT, PET, nuclear scans, and X-rays use ionizing radiation; MRI uses magnets and radio waves, and ultrasound uses sound waves.
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Imaging tests create pictures of areas inside your body. These pictures help your doctor see whether a tumor is present, where it is, and sometimes whether it has spread. There are several ways to make these pictures, and each works a little differently.
No single imaging test can diagnose cancer by itself. Scans are used together with lab tests and, in most cases, a biopsy.
CT scan
A CT scan uses an X-ray machine linked to a computer to take a series of pictures of your organs from different angles. A computer combines them into detailed 3-D images. You lie still on a table that slides into a donut-shaped scanner, and the machine moves around you taking pictures. Sometimes you receive a contrast material (dye) first to make the pictures easier to read.
MRI
An MRI uses a powerful magnet and radio waves — not radiation — to take pictures of your body in slices, which are combined into detailed images that can show places where there may be tumors. During an MRI you lie still on a table that is pushed into a long chamber. The machine makes loud thumping noises and rhythmic beats. Sometimes a special contrast dye is injected into a vein to make tumors show up more brightly.
Nuclear scans, including bone scans
A nuclear scan uses a small amount of radioactive material to make pictures of the inside of the body. Before the scan, you receive an injection of a tracer that flows through your bloodstream and collects in certain bones or organs. A scanner then detects the radioactivity and creates pictures.
A bone scan is a type of nuclear scan that checks for abnormal areas or damage in the bones. It may be used to help diagnose bone cancer or to find out whether cancer has spread to the bones from elsewhere in the body. Areas where the material collects are sometimes called "hot spots." After the scan, the radioactive material loses its radioactivity over time and may leave the body through urine or stool.
PET scan
A PET scan is a type of nuclear scan that makes detailed 3-D pictures of areas inside your body where glucose (a sugar) is taken up. Because cancer cells often take up more glucose than healthy cells, these areas can show up on the scan. Before the scan you receive an injection of a tracer, and during the scan you lie on a table that moves through the scanner. PET is often combined with CT in a single PET/CT procedure.
Ultrasound
An ultrasound exam uses high-energy sound waves that people cannot hear. The sound waves echo off tissues inside your body, and a computer uses those echoes to create a picture called a sonogram. During the exam, a technologist moves a device called a transducer, covered with a warm gel, over the skin of the area being examined. Ultrasound does not use radiation.
X-rays
X-rays use low doses of radiation to create pictures of the inside of your body. A technologist positions you and directs the X-ray beam to the correct area. While the image is taken, you need to stay very still and may be asked to hold your breath for a second or two.
Putting the picture together
Results from imaging are posted in your patient portal and read alongside your other tests. It is normal to want to know right away what a scan shows, but your doctor is the best person to explain what the results mean for you — and to decide whether more tests, such as a biopsy, are needed.
Words to know
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Common questions
▸What do imaging tests do?
Imaging tests create pictures of areas inside your body that help the doctor see whether a tumor is present. These pictures can be made in several ways, such as with X-rays, magnets, sound waves, or small amounts of radioactive material.
▸What is a contrast material or dye?
For some scans, you may be given a contrast material (dye) before or during the test. It can be swallowed, given by an injection into a vein, or given by enema. Contrast material highlights certain areas inside the body, which makes the pictures easier to read.
▸Which scans use radiation?
CT scans, nuclear scans (including bone scans and PET), and X-rays use ionizing radiation. MRI uses a powerful magnet and radio waves instead of radiation, and ultrasound uses high-energy sound waves. Your doctor can explain the benefits and risks of any scan you need.
▸Can a scan tell for sure if I have cancer?
Usually not on its own. Imaging results are used together with lab tests and, in most cases, a biopsy — which is often the only way to tell for sure if you have cancer. Your doctor puts the results together to make a diagnosis.
▸What is a PET/CT scan?
A combined PET/CT scan uses two imaging methods in one procedure. The CT creates detailed pictures of the structures in your body, and the PET shows areas where cells are more active. Together they can give a more complete picture of a tumor's location and whether it has spread.
Questions for your care team
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