What are imaging tests?

Imaging tests are studies that make pictures (images) of what's going on inside your body. These tests use forms of energy (x-rays, sound waves, radioactive particles, or magnetic fields) that are passed through the body. The changes in energy patterns made by body tissues can be seen with special devices, which change them into pictures. These pictures can show normal body structure and function as well as abnormal ones caused by diseases such as cancer.

Imaging tests are different from endoscopic tests (like a colonoscopy or bronchoscopy), which use a flexible, lighted tube hooked up to a viewing lens or a video camera. Endoscopic tests allow doctors to see inside parts of the body as if they were looking with the naked eye. (For more information, see our document Endoscopy.)

What are imaging tests used for?

Imaging tests are used for cancer in many ways:

• They are sometimes used in screening -- to look for cancer in its early stages, even though a person has no symptoms. A mammogram is an example of an imaging test used for cancer screening.

• They can be used to look for a mass or lump if you have symptoms. They can also help find out if your symptoms are caused by a tumor or by some other type of disease.

• They sometimes help predict whether a tumor is likely to be cancer. This can help doctors decide if you need a biopsy (taking a tissue sample to be looked at under the microscope). A biopsy is almost always needed to know for sure that a tumor is cancer.

• They show exactly where the tumor is, even deep inside the body. This helps if a sample (biopsy) of the tumor is needed for further study.

• They help find out the stage of the cancer (figuring out how far the cancer has spread).

• They can be used to plan treatment, such as when pinpointing where the beams should be focused in radiation therapy.

• They can show if a tumor has gotten smaller, stayed the same, or grown after treatment. This can give a doctor an idea of how well treatment is working.

• They can help find out if a cancer has come back (recurred) after treatment.

Imaging tests are only part of the process of cancer diagnosis and treatment. A complete work-up for your cancer also includes a careful medical history (a series of questions about symptoms and risk factors), a physical exam, and blood or other lab tests.

Many doctors request x-rays or other images before treatment begins so they can track any changes during treatment. These are called baseline studies because they provide a basis of information that doctors can use to compare with later images to see the results of treatment over time. They can also be used later on to find out if the cancer has progressed.

Who does imaging tests and who interprets them?

A doctor, a certified technologist, or other health professional may perform an imaging test. Depending on what is involved, the test may be done in a hospital, a special clinic or imaging center, or a doctor's office. In larger medical centers, imaging tests are usually done in the radiology or nuclear medicine department (even though some types of tests do not involve high-energy radiation).

A radiologist is a doctor who specializes in imaging techniques. He or she is the person who usually reads (interprets) the image obtained through the test. The radiologist writes a report on the findings and sends the report to your doctor. A copy of the report will become part of your patient records. Your other doctors (oncologists, surgeons, etc.) may look at the images, too.

Types of imaging tests

Here are descriptions of some of the more common types of imaging tests, how they are done, and when you might need them.

Computed tomography scan

Also called CT scan, CAT scan, and spiral or helical CT.

What does it show?

CT scans show a slice, or cross-section, of the body. The image shows your organs and soft tissues more clearly than standard x-rays. Because the picture is made by a computer, it can be enlarged to make it easier to see and interpret.

Since the late 1970s, CT scans have been very useful in helping doctors find cancer. CT scans can show a tumor's shape, size, and location, and even the blood vessels that feed the tumor -- all without having to cut into the patient.

Doctors often use CT scans to help them guide a needle to remove a tissue sample (called a CT-guided biopsy). They can also be used to guide needles into tumors for some types of cancer treatments, such as radiofrequency ablation (using heat to destroy a tumor).

CT scans are quite good at finding and getting information about cancer in the liver, pancreas, adrenal glands, lungs, and bones. They are also used to collect information about cancer in the large and small intestines, swallowing tube (esophagus), stomach, brain, prostate, or other organs.

By comparing CT scans done over time, doctors can see how a tumor is responding to treatment or find out if the cancer is coming back after treatment.

How does it work?

CT scans use controlled amounts of x-rays -- beams of high-energy radiation that are passed through the body -- to create images. In a way, CT scans are like standard x-ray tests (see "Radiographic studies" section). But an x-ray test uses a broad beam of radiation aimed from only one angle. A CT scan uses a pencil-thin beam to create a series of pictures taken from different angles. Each angle produces a slightly different view of your organs and soft tissues. The information from each angle is fed into a computer, which calculates how the images overlap. The computer then creates a single black and white picture that shows a slice of a specific area of your body -- much like looking at a single slice from a loaf of bread.

The picture can be made clearer by the use of special contrast materials which can be swallowed as a liquid, injected into a vein, or put into the intestines through the rectum as an enema. Because body tissues absorb these materials differently, the CT image will show greater contrast between types of tissues. This allows abnormalities such as tumors to be seen more clearly.

In recent years, spiral CT (also known as helical CT) has become the most common type of CT used. It uses a better and faster machine that uses less radiation than the original CT scanner.

By placing CT image slices on top of each other, doctors can create a 3-dimensional (3-D) scan, which provides even more information about certain cancers. The 3-D image can be rotated on a computer screen to look at different views.

Doctors are now taking this technology one step further in a technique called virtual endoscopy. They can look at the inside surfaces of organs such as the lungs (virtual bronchoscopy) or colon (virtual colonoscopy, also called CT colonography) without actually having to put scopes into the body. They can arrange the 3-D images to create a black and white view on the computer screen, which looks something like it would if they were doing an actual endoscopy. Studies are now under way to learn if these techniques are as good at finding abnormalities as standard endoscopy. So far, the CT colonography seems just as good as colonoscopy for finding polyps and cancer. Still, a regular colonoscopy must be done if polyps or other abnormal areas are found.

How do I get ready for the test?

CT scans are most often done on an outpatient basis, so you do not need to be in the hospital to get one.

In some cases, your doctor may tell you not to eat or drink for several hours before the test. Or you may need to use a laxative or an enema to clean out the bowel and remove material that could get in the way of seeing inside the belly and intestines. Depending on the part of the body being studied, you also may need to drink contrast liquid or get a contrast enema before the test. If a contrast material is to be injected into a vein, you may have an intravenous (IV) catheter put into a vein in your arm.

You may be asked to undress, put on a robe, and remove any jewelry or other metal objects that may get in the way of the image. You may be asked remove dentures, hearing aids, hair clips, and so on, as they can affect the CT image.

What is it like having the test?

A radiological technologist does the CT scan. The scanner is a large, doughnut-shaped machine. You lie on a thin, flat table that slides back and forth inside the hole in the middle of the scanner. As the table moves into the opening, an x-ray tube rotates within the scanner, emitting thousands of tiny x-ray beams at precise angles. These beams pass through the body and are detected on the other side of the scanner. You may hear buzzing and clicking as the scanner switches on and off.

During a CT head scan, your head will be held still with a special device.

You will be alone in the exam room during the CT scan, but the technologist will be able to see, hear, and talk to you at all times.

A CT is painless but you may find it uncomfortable to hold still in certain positions for minutes at a time. You may also be asked to hold your breath, since chest movement can affect the image. For CT colonography, air is pumped into the colon to help see the inner bowel surface. This can cause discomfort for some.

If you are to be given contrast material in a vein, you will probably have a scan first, then get the contrast dye, and then have a second scan done.

How long does it take?

This depends on how much of your body your doctors want to look at and whether contrast dye is used. A CT scan can take anywhere from 10 to 30 minutes, depending on what's being scanned. Often more time is taken getting you into position and giving the contrast dye than in taking the pictures. After the test, you may be asked to wait while the results are looked at to see if more images are needed.

What are the possible complications and side effects?

About 5% of people (1 in 20) react in some way to the contrast dye. Possible symptoms include:

• nausea
• wheezing
• shortness of breath
• a metallic or bitter taste in the mouth
• feeling flushed or warm -- this may last for a few minutes
• itching or facial swelling that can last up to an hour

These symptoms usually are not serious and they most often go away on their own, but be sure to let your radiologic technologist and your health care team know if you begin to have any of them.

Also be sure to let your health care team know if you've ever had a reaction to contrast dye, seafood, or iodine in the past. This is important because it may put you at risk for reacting to the contrast dye used in CT scans. In rare cases, people can have a severe allergic reaction that causes trouble breathing and requires treatment with medicines, such as epinephrine. If there is a risk that you might have an allergic response, you may be given a test dose of the contrast material first.

What else should I know about this test?

• Although a CT scan is sometimes described as a "slice" or a "cross-section," no cutting or incisions are involved.

• The amount of radiation you get during a CT scan is a good deal more than that with a standard x-ray.

• People who are very overweight may have trouble fitting into the CT scanner.

• Tell your doctor if you have an allergy or are sensitive to iodine, seafood, or contrast dyes.

• Tell your doctor if you could be pregnant or are breast-feeding.

• CT scans can cost up to 10 times as much as a standard x-ray.

Magnetic resonance imaging

Other names include MRI, magnetic resonance (MR), and nuclear magnetic resonance (NMR) imaging.

What does it show?

Like CT scans, MRI displays a cross-section of your body. But MRI uses strong magnets instead of radiation to create the images. An MRI scan can take cross-sectional slices (views) from several angles, as if someone were looking at a slice of your body from the front, from the side, or from above your head. MRI creates pictures of soft tissue parts of the body that are sometimes hard to see using other imaging tests.

MRI is very good at finding and pinpointing cancer in the brain, spinal cord, head, neck, and bones and muscles. An MRI done with contrast is the best way to see brain tumors. Using MRI, doctors can sometimes tell a non-cancerous (benign) tumor from a cancerous (malignant) one.

In recent years, MRI has become the main way to look carefully at the female reproductive organs, and it can help to figure out the stage of endometrial (womb) cancer before surgery. Another use for MRI is looking for signs that cancer may have metastasized (spread) to the liver from another site in the body.

MRI images can also help doctors plan treatment such as surgery or radiation therapy.

Unlike x-rays or CT scans, MRI cannot detect calcifications (tiny mineral deposits that may suggest the presence of cancer) in tissues such as the breast. But special MRI machines, now available in some hospitals, are designed just for looking inside the breast. The test is called breast MRI with dedicated breast coils. This MRI is sometimes used along with mammograms or breast ultrasound to look for breast cancer. This can be very helpful in younger women or those with very dense breast tissue. At this time MRI is not used by itself to detect breast cancer early. But we do recommend that MRI be done with a mammogram every year for women at high risk for breast cancer. If you think you may be high risk for breast cancer and want more information on breast MRI as part of breast cancer early detection, call 1-800-227-2345.

How does it work?

An MRI scanner is a cylinder or tube that holds a very strong magnet weighing several tons. As you lie on a table within the tube, the device surrounds you with a powerful magnetic field. The magnetic force causes the nuclei (centers) of hydrogen atoms in your body to line up in one direction. Once the atoms are lined up, the MRI machine gives off a burst of radiofrequency waves. These waves cause the hydrogen nuclei to change direction. When they return to their original position, they give off certain signals, which the scanner detects. Hydrogen nuclei in the body tissues change direction in different ways. A computer takes the signals from these changes and converts them into a black and white picture.

Contrast materials can be put in through a vein to improve the quality of the image. Once absorbed by the body, these agents speed up the rate at which tissue responds to the magnetic and radio waves. As a result, the signals produce stronger and clearer images.

How do I get ready for the test?

No special diet or preparation is needed before an MRI.

Some tests require use of a contrast material before imaging. If contrast is to be injected, you may have an intravenous (IV) catheter placed in a vein in your arm.

If being in an enclosed space such as the MRI scanner concerns you, you might need to take medicine to help you relax. Talking with the technologist or a patient counselor, or getting a tour of the MRI machine before the test can be helpful. You will be in the exam room alone, but you will be able to see and hear what's going on through the use of an intercom. You will also have a call button should you need to speak with the technologist. In some cases, you can arrange to have the test done with an open MRI machine that allows more space around your body (see the next section).

Before the test, you usually will be asked to undress and put on a gown or other clothes without zippers or metal. Be sure to remove objects that contain metal, like hair clips or jewelry. Before the scan, the MR technologist will ask you if you have any metal in your body, such as surgical clips or staples, pacemakers, artificial joints, metal fragments, tattoos, permanent eyeliners, and so on. Some metallic objects will not cause problems, but others can. You may need to have an x-ray to check for metal objects if there is any doubt.

What is it like having the test?

MRI scans are usually done on an outpatient basis in a hospital or clinic. You will lie down on a flat table. The technologist sometimes uses straps or pillows to help keep you from moving. The table then glides through an opening in the cylinder. The part of your body that is being looked at will be in the center of the device.

The test is painless, but you have to lie still inside the cylinder with its surface a few inches from your face. You may be asked to hold your breath during certain parts of the test. The machine may make loud, thumping and whirring noises, much like the sound of a washing machine, as the magnet switches on and off. Some facilities let you wear earplugs or headphones to block this noise out during testing.

Newer machines that are less restrictive may be easier for some people. These open MRI machines replace the cylinder with a larger ring. This design lessens the banging sound and the feeling of lying in an enclosed space. But the device does not create as strong a magnetic field. Although open MRI technology is improving, the images may not be as clear or detailed as they are with standard MRI. In some cases, this may require retesting on a standard MRI machine.

You may be given contrast material in a vein or have to swallow it. The contrast material used for an MRI exam, called gadolinium, does not contain iodine and is less likely to cause an allergic reaction than some other types. Still, let the technologist know if you have any kind of allergies.

How long does it take?

MRI scans can take between 45 and 60 minutes and sometimes up to 2 hours. After the test, you may be asked to wait while the images are looked at to see if more images are needed.

What are the possible complications?

People can be hurt in MRI machines if they take metal items into the room or if other people leave metal items in the room.

Some people have mild reactions to the contrast agents. Such reactions include:

• nausea
• pain at the needle site
• headache that develops a few hours after the test is over

Be sure to let your health care team know if you have any of these symptoms.

Some people become very uneasy and even panic when lying inside the MRI scanner.

What else should I know about this test?

• People who are overweight may have trouble fitting into the MRI machine.

• Some kinds of surgical implants that contain metal, such as pacemakers, certain surgical clips or staples, or implanted pumps, may cause problems due to the strong magnetic field. Your health care team will ask you questions about these before the MRI test.

• If you have an implanted intravenous (IV) catheter or port, your doctor will need to decide whether you should have an MRI.

• If you have tattoos or permanent makeup (such as eyeliner), let the technologist know so that they can take the needed precautions and ensure the best results.

• The use of MRI during pregnancy has not been well studied. MRI is usually avoided in the first 12 weeks of pregnancy unless there is a strong medical reason to use it.

• Do not bring credit cards with you into the exam room -- the magnet could wipe out the information stored on the card.

• MRI costs more than a CT scan and may not be available in some areas.

• MRI does not expose you to radiation.

Radiographic studies (regular x-rays and contrast studies)

Other names include radiographs and roentgenograms. For names of contrast studies, see Table 1,

What do they show?

Radiographs, most often called x-rays, produce shadow-like images of certain organs or tissues. X-rays are very good at finding certain bone problems. X-rays can show some organs or soft tissues, but MRI and CT scans often give better pictures of them. Still, x-rays are often faster, easy to get, and cost less than newer scans, so they may be used to get information quickly. An x-ray of the belly may show tumors or other diseases in organs like the intestines, stomach, liver, spleen, and kidneys. A chest x-ray can help find lung diseases, including cancer. These tests, which make a single image or series of images, are sometimes called standard radiographic studies. Mammograms (breast x-rays) are another form of radiographic study (for more information, see the section "Mammography").

Special types of x-ray tests may use dyes called contrast materials. For example, a lower gastrointestinal (GI) series, often called a barium enema exam, takes x-ray pictures after the bowel is filled with barium sulfate (a contrast material). Another contrast study, intravenous pyelography (IVP), looks at the structure and function of the kidneys.

With advances in technology, many contrast studies once used for diagnosis are being replaced by other methods, such as CT or MRI scans (see sections on CT and MRI).

How do they work?

A special tube inside the x-ray machine sends out a controlled beam of radiation. Tissues in the body absorb or block the radiation to varying degrees. Dense tissues such as bones block most radiation, but soft tissues, such as fat or muscle, block less. After passing through the body, the beam falls on a piece of film, where it casts a kind of shadow. Tissues that block high amounts of radiation, such as bone, show up as white areas. Soft tissues block less radiation and show up in shades of gray, and organs that are mostly air (such as the lungs) normally look black. Tumors are usually denser than the tissue around them, so they are often seen as lighter shades of gray.

Contrast studies provide some information that standard x-ray cannot. During a contrast study, you get a dose of a contrast material that outlines, highlights, or fills in parts of the body so that they show up more clearly on an x-ray. The contrast material may be given by mouth, as an enema, as an injection (put in a vein), or through a catheter (thin tube) put into various tissues of the body. For most of these tests, the images can be captured either on x-ray film or by a computer.

Table 1: Commonly used contrast studies

How do I get ready for the test(s)?

Other than removing metal objects that might interfere with the image, no special preparation is needed before having a standard x-ray.

Preparation for a contrast study depends on the test. You may be asked not to eat anything or to prepare in other ways before the test (see next section). The radiology center where you are having the test should give you instructions. Check with them first. Your doctor also may give you instructions.

What is it like having the test(s)?

Standard x-rays: Usually x-rays are taken by an x-ray technologist. You undress to expose the part of the body that will be x-rayed, removing jewelry or other objects that may interfere with the image. You will be asked to sit, stand, or lie down, depending on what part of the body will be x-rayed. Your body is put against a flat box that contains the x-ray film. The technologist then moves the machine to aim the beam of radiation at the right area. You may have special shields put over parts of your body near the area to be x-rayed so that they are not exposed to the radiation. Usually the technologist leaves the room to operate the machine by remote control. Your exposure to the x-ray is kept to an absolute minimum -- usually less than a second. You may hear a short buzzing sound while the machine is working.

For a chest x-ray, views are taken from the front and the side. Your arms will be at your side during the front exposure and will be either above your head or in front of you during the side exposure. The technologist will tell you when to take a deep breath and hold still. During an abdominal (belly) x-ray, you lie down on a table. You may be asked to change position if more than one view is needed. Again, you will need to hold your breath and lie still while the picture is taken. After the exposure, the technologist will come back to the room to move the machine out of the way, remove any protective shields, collect the film, and help you back to the changing room where you can get dressed.

Angiography: In the past, angiography was often used to learn the stage or extent of cancers, but now CT and MRI scans are most often used to do this. Angiography is sometimes used to show surgeons the blood vessels next to a cancer so that the operation can be planned to limit blood loss. Angiography is still used to diagnose non-cancerous blood vessel diseases. These types of studies are done by a radiologist (doctor who specializes in imaging), with the help of technologists.

You will be asked to not eat before this test. Usually you will be given medicine to relax you before the test starts. As you lie still on the table, the skin over the injection site is cleaned and numbed. A catheter (thin plastic tube) is put into a blood vessel (usually the femoral artery at the top of the thigh) and slid further into the blood vessel until it reaches the area to be studied. The contrast dye is then put in (injected) quickly, and a series of x-ray images is taken. When the pictures are finished, the catheter is removed. Firm pressure may be needed on the site for a time to make sure there is no excessive bleeding from the site. You will also be asked to lie flat for up to several hours. This is also to prevent bleeding at the catheter site.

Alternatives to x-ray angiography: In recent years, advances in technology have led to the development forms of angiography that take less time and involve fewer risks than standard angiography. CT angiography takes pictures of blood vessels using a CT scanner instead of a standard x-ray machine. The contrast dye can be injected into a small vein in the arm instead of having to put a catheter into a major blood vessel. Magnetic resonance angiography (MRA) is an MRI study of the blood vessels. It may be done with or without having a contrast dye injected into an arm vein, and is also quicker and less invasive than standard angiography.

Intravenous pyelography (IVP): This test is used to study kidney function and to look for tumors in the urinary tract.

You will probably be asked not to eat or drink anything for about 12 hours before the test, and you will be given laxatives to clean out the bowel. For the test itself, you lie on a table for a series of x-rays. Contrast dye is then given through a vein in your arm. Your kidneys remove the dye from the bloodstream, and it goes into the urinary tract. Another series of x-rays is taken at intervals over the next 30 minutes or so. Pressure may be applied to the belly to help make the image clearer. Once the dye has reached the bladder, you will be asked to pass urine while another x-ray is taken.

Lower GI series (barium enema): This study is used to look at the lining of the colon (large intestine) and rectum.

You may have food restrictions for few days before the test. Laxatives and/or enemas are used to clean out the colon (large intestine). For the test, you lie secured on a table, and a series of x-rays is taken. Then liquid barium is put in through a small, soft tube placed in your rectum. The liquid feels cool. More images are taken while the table tilts you into different positions. You have to lie still and hold your breath as each image is taken. After the test, you can go to the toilet to pass the barium solution out of your bowels. (It may take a few days until it is all out and your stool may be light colored during this time.)

To get clearer pictures, a "double-contrast" exam is often done. This exam uses a smaller amount of thicker barium liquid. After the barium is in, air is put into your bowel. This can cause a sense of fullness, along with an urge to empty your bowels.

Upper GI series (barium swallow): This test is used to study the lining of the esophagus (swallowing tube), stomach, and the duodenum (first part of the small intestine).

You will probably be asked to not eat or drink for 8 to 12 hours before the exam. As with the lower GI series, you lie on a tilting table while a series of x-ray images is taken. You will need to swallow a barium mixture a few times during the test. You may also be asked to swallow baking soda to create gas in your stomach. Sometimes pictures are taken a few hours later so the doctor can also see the small intestine (it takes time for the barium to move from the stomach to the small intestine). After the test you may be given a laxative to speed up getting the barium out of your body.

Lymphangiography: Although not commonly used to detect cancer, a lymphangiogram may be helpful in planning treatment or looking at the response to treatment for some types of cancer, such as lymphoma.

In some cases, you may be asked to not eat or have only liquids for some time before the test. For the test, a thin needle is used to put a blue dye between your toes to show the lymphatic vessels. After a numbing medicine is applied, a small cut is made in the foot and a very thin catheter (tube) is placed in a lymphatic vessel. A different contrast material is slowly injected (put in) through the catheter and allowed to travel through the lymph system. This may take an hour or two. Then a series of x-rays are taken. You may be asked to return on the next day or two for more x-rays, but you will not need to have more dye put in during these visits.

How long do they take?

• standard x-ray: about 5 to 10 minutes

• angiography: from 1 to 3 hours

• intravenous pyelogram: about 1 hour

• lower GI series: 30 to 45 minutes

• upper GI series: 30 minutes to 6 hours, depending on the part of the digestive system being tested

• lymphangiography: 2 to 5 hours, plus another 30 minutes each time during the next few days for repeat x-rays

What are the possible complications and side effects?

Standard x-rays: Problems are rare and very unlikely.

Angiography: You may have a warm or burning feeling as the dye is given. The contrast material may cause nausea, vomiting, flushing, itching, or a bitter or salty taste. In rare cases, people have a severe allergic reaction to the iodine in the contrast material.

There is a small risk of a blood clot forming on the end of the catheter, which could block a blood vessel. There is also a small risk of damage to the blood vessel from the catheter, which could lead to internal bleeding. A hematoma (a large collection of blood under the skin) may develop where the catheter was put in if pressure is not kept on the site long enough. (Possible complications of CT or MR angiography are like those described in the sections on CT and MRI).

Intravenous pyelogram (IVP): This test is usually safe, but it should not be given to people who are allergic to contrast material with iodine. The contrast dye causes some people to have nausea, vomiting, flushing, itching, or a bitter or salty taste. In rare cases, people have a severe reaction to the contrast material and need emergency treatment.

Lower GI series (barium enema): The test can be uncomfortable. Some patients have abdominal (belly) cramping. Many patients find the test makes them tired. The barium contrast material will make your stools a light color for a few days after the test and may cause constipation.

Upper GI series (barium swallow): The barium mixture has the thickness of a milkshake and tastes chalky. Baking soda crystals can cause gas and belching. After the test, your stools will be lighter in color for a few days, and you may be constipated.

Lymphangiography: The needle stick where the dye was put in can cause discomfort. An allergic reaction to the dye is possible, and can be serious. The dye can change the color of urine, stool, or skin for the next 1 to 2 days. Changes in the color of the skin around the toes can last for months, but will fade over time.

What else should I know about these tests?

• X-ray studies expose the body to radiation, but modern x-ray equipment uses the smallest amount of radiation possible. (See "General questions and comments on radiation risk" for more information.)

• A newer technology, called digital radiology, produces images on computer screens rather than on film. The size and contrast of the images can be adjusted to make them easier to read, and they can be sent to computers in other medical offices or hospitals.

• If you are to have a test that uses a contrast dye, tell your doctor if you have any allergy to contrast materials, iodine, or to seafood (which contains high levels of iodine).

Mammography

Other names include mammogram, and digital mammography.

What does it show?

A mammogram is an x-ray of the breast. A screening mammogram is used to look for signs of breast disease when you do not have any breast symptoms. Many breast cancers take years to develop. A mammogram can detect cancer in its early stages, even before a lump can be felt, when treatment can be most successful. Screening mammograms usually take x-ray pictures of each breast from 2 different angles.

Mammograms can also be used to look at a woman's breast if she has a breast problem or a change seen on a screening mammogram. When used in this way, they are called diagnostic mammograms. They may include extra views (images) of the breast that are not usually done on screening mammograms.

Mammograms can't prove that an abnormal area is cancer, but they can give information that shows whether more testing is needed. The 2 main types of breast changes that can be found with a mammogram are calcifications and masses.

Calcifications are tiny mineral deposits within the breast tissue, which look like small white spots on the films. They may or may not be caused by cancer. There are 2 types of calcifications:

• Macrocalcifications are coarse (larger) calcium deposits that are most likely changes in the breasts caused by aging of the breast arteries, old injuries, or inflammation. These deposits are non-cancerous (benign) and do not require a biopsy (taking a sample of tissue to look at under a microscope). Macrocalcifications are found in about half the women over 50, and in 1 of 10 women under 50.

• Microcalcifications are tiny specks of calcium in the breast. They may be alone or in clusters. Microcalcifications seen on a mammogram are of more concern, but still usually do not mean that cancer is present. The shape and layout of microcalcifications help the doctor judge how likely it is that cancer is present. If the microcalcifications look suspicious, a biopsy will be needed.

A mass, which may or may not have calcifications, is another important change seen on mammograms. Masses can be many things, including cysts (non-cancerous, fluid-filled sacs) and non-cancerous solid tumors, but they could also be cancer. Any mass that is not clearly a cyst should be biopsied.

• A cyst and a tumor can feel the same on a physical exam, and can look the same on a mammogram. To confirm that a mass is really a cyst, breast ultrasound is often done. Another option is to remove (aspirate) the fluid from the cyst with a thin, hollow needle.

• A simple cyst is filled with fluid. If a mass has any solid parts, you may need more imaging tests. Some masses can be watched with mammograms, while others may need a biopsy. The size, shape, and margins (edges) of the mass help the radiologist figure out whether cancer may be present.

Having your older mammograms available for the radiologist is very important. They can help to show that a mass or calcification has not changed for many years, which would mean that the mass is probably not cancer and a biopsy is not needed.

Mammograms have limitations: A mammogram cannot prove that an area of change is cancer. Still, a diagnostic mammogram may show that an area of abnormal tissue is most likely benign (not cancer). In these cases, the woman may be asked to come back sooner than usual for a re-check.

If a diagnostic mammogram and breast exam suggest cancer may be present, tissue must be removed and looked at under the microscope to tell if it is cancer. This can be done with a needle biopsy or an open surgical biopsy.

To get an accurate breast biopsy, enough cells or fluid must be removed from the area of concern for the pathologist to study. It can be hard for a doctor to put the needle right where the abnormality is, especially if the lump cannot be felt. To get the needle where it needs to be, your doctor may use different imaging studies to guide it:

• Stereotactic mammography uses mammograms taken from 2 angles (a "stereo" view). A computer calculates the precise location of the mass or calcification to help guide the biopsy needle.

• Breast ultrasound can also be used to guide biopsy needles (see the section on ultrasound).

The x-ray for a ductogram (also called a galactogram or contrast mammography) is very much like a mammogram. The difference is that the x-ray is taken after a contrast agent is put into a nipple duct with a thin tube. It is used to look at problems related to nipple discharge.

How does it work?

A mammogram uses a machine designed to look only at breast tissue. The machine takes a different form of x-ray and at lower doses than a usual x-ray. Because these x-rays do not go through tissue easily, the machine has 2 plates that compress or flatten the breast to spread the tissue apart. This gives a better picture and uses less radiation.

Digital mammography: A digital mammogram (also known as full-field digital mammography or FFDM) is like a standard mammogram in that x-rays are used to make a picture of the breast. The differences are in the way the image is made, seen by the doctor, and stored. Standard mammograms are printed on large sheets of photographic film. Digital images are recorded and saved as files in a computer. After the exam, the doctor can look at the pictures on a computer screen and adjust the size, brightness, or contrast to see certain areas more clearly. Digital images can also be sent electronically to another site for other breast specialists to see. Although many centers do not offer the digital option at this time, it is expected to become more widely available in the future.

Because digital mammograms cost more than standard mammograms, studies are now under way to determine which form of mammogram will benefit more women in the long run. Some studies have found that women who have digital mammograms have to return less often for more tests because of uncertain areas on the original mammogram. A recent large study from the National Cancer Institute found that digital mammography was more accurate in finding cancers in women younger than 50 and in women with dense breast tissue. The rates of uncertain (inconclusive) results were much the same between FFDM and film mammograms. It is important to remember that standard film mammograms are a good option for these groups of women. Women should not skip their regular mammogram if a digital mammogram is not available.

Computer-aided detection and diagnosis: Over the past 2 decades, computer-aided detection and diagnosis (CAD) has evolved to help radiologists find suspicious changes on mammograms. This is done with film mammograms and with digital mammograms.

Computers can help doctors find abnormal areas on a mammogram. For standard mammograms, the film is fed into a machine which converts the image into a digital signal that is then analyzed by the computer. This technology can also be applied to a digital mammogram. The computer shows the picture on a video screen, with markers pointing to areas the radiologist should check more closely.

It's not yet clear how useful CAD is. Some doctors find it helpful, but a recent large study found it did not really improve the accuracy of breast cancer detection. It did, however, increase the number of women who needed to have breast biopsies. Further research is needed.

Ductogram: A ductogram, also called a galactogram, is sometimes helpful in finding the cause of bloody nipple discharge. In this test a very thin plastic tube (catheter) is put into the opening of the duct at the nipple that the discharge is coming from. A small amount of contrast ("dye") is put in, which outlines the shape of the duct on an x-ray. The x-ray will show if there is a tumor inside the duct. .

How do I get ready for the test?

If you are still having periods, the best time to schedule a mammogram is one week after your period, when your breasts are likely to be less tender.

You'll need to undress from the waist up for the exam, so you might want to wear a shirt and a skirt or pants, rather than a dress, to make undressing easier. No special preparation is needed. But on the day of your mammogram, do not use deodorants, perfumes, powders, or ointments under your arms or on your breasts because these may interfere with the pictures.

A screening mammogram usually means 2 views of each breast -- one from the top and one from the side. You may need to have more images taken to include as much breast tissue as possible if you have breast implants. You also will have more images taken if the mammogram is being used for diagnosis (a diagnostic mammogram) or to guide the placement of a needle for biopsy.

What is it like having the test?

A mammogram is an outpatient test. You will be asked to undress from the waist up and to remove any jewelry around your neck. You will stand next to the mammography unit and it will be adjusted to a comfortable height. A specially qualified radiological technologist will position your breast on a special platform. The technologist will use the machine to slowly compress your breast with a paddle (often made of clear Plexiglas or other plastic). The compression will be tight and uncomfortable, but it doesn't last very long. You hold your breath while the technologist leaves the room and quickly takes the picture. Then the pressure is released right away.

For a ductogram, the nipple is first cleaned. The doctor then applies gentle pressure to look for discharge and find the opening of the duct. He or she then puts a very thin tube into the nipple duct and slowly puts in a contrast dye.

How long does it take?

The screening mammogram from start to finish takes about 15 to 30 minutes. A diagnostic mammogram, which takes images from more angles or close-up views, takes about 30 to 45 minutes. The breast is compressed for only a few seconds of that time. Ductograms may take a little longer.

What are the possible complications?

A mammogram uses low doses of radiation and is safe. The very low risk that cancer may result from exposure to radiation during a mammogram is far outweighed by the benefits of finding cancer early.

Some women find that mammograms are painful, but for most the compression causes only brief discomfort.

There have been reports of breast implant ruptures during mammography, but these are very rare. If you have breast implants, find a radiologist experienced in doing mammograms on augmented breasts and let the facility know about your situation ahead of time.

Because ductograms use a contrast material, some women may have allergic reactions. In some cases the doctor may have trouble finding the opening of the duct, which may require probing the area or even rescheduling the exam.

What else should I know about this test?

The American Cancer Society has developed guidelines for the early detection of breast cancer in women who are not having breast symptoms:

• Women 40 years of age and older should have a mammogram every year and a clinical breast exam (CBE) performed by a health care professional every year. They also have the option of performing a breast self-exam (BSE) every month. The CBE should be conducted close to and preferably before the scheduled mammogram.

• Women aged 20 to 39 should have a clinical breast exam by a health care professional every 3 years and have the option of performing breast self-exam every month.

• Women at high risk (greater than 20% lifetime risk) should get an MRI and a mammogram every year. Women at moderately increased risk (15% to 20% lifetime risk) should talk with their doctors about the benefits and limitations of adding MRI screening to their yearly mammogram. Get Breast Cancer: Early Detection from your American Cancer Society (1-800-227-2345) for more information on breast cancer risk.

Mammography alone cannot find all breast cancers. For this reason, mammograms should be used in addition to a clinical breast exam by a health care professional. Knowing how your breasts normally look and feel, and reporting any changes to a doctor, is also very important.

A negative mammogram (no sign of calcifications or masses) does not always mean that cancer is not present or that cancer will not develop later.

The need for a biopsy does not mean that you have cancer. About 70% to 80% of biopsies turn out to be benign (not cancer).

Mammography facilities must be certified by the FDA and accredited by an official organization to make sure they meet standards for personnel, equipment, and quality control. You can get information on qualified facilities from us, or on the FDA Web site (www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMQSA/mqsa.cfm).

For more information on specific tests related to breast cancer, see our document Mammograms and Other Breast Imaging Procedures.

Nuclear scans

Other names include nuclear imaging, radionuclide imaging, and nuclear medicine scans.

What do they show?

Nuclear scans make pictures based on the body's chemistry rather than on physical shapes and forms (as is the case with other imaging tests). They use substances called radionuclides (also known as tracers or radiopharmaceuticals) that release low levels of radiation. The amount of radioactivity used is very small and not known to cause harm.

Body tissues affected by certain diseases, such as cancer, may absorb more or less of the tracer than normal tissues. Special cameras pick up the pattern of radioactivity to create images that show where the material travels and where it collects. The scans show certain disorders of internal organs and tissues better than standard x-ray images.

If cancer is present, the tumor may show up on the image as a "hot spot" -- an area of increased tracer uptake. Depending on the type of scan performed, the tumor may instead be a "cold spot" -- a site of decreased uptake.

Nuclear scans are used to find tumors, especially in the bones and thyroid gland. They are also used to study a cancer's stage (extent of its spread) and to decide if treatment is working.

Nuclear scans may not find very small tumors, and cannot always tell the difference between benign (not cancer) and malignant (cancer) tumors. They are often used along with other imaging tests to give a more complete picture of what is going on. For example, bone scans that show "hot spots" on the skeleton are usually followed by x-rays of the affected bones, which are better at showing details of the bone structure.

Nuclear scans have different names, depending on the organ involved. Some of the more commonly used nuclear scans (described in more detail below) include:

• bone scans
• gallium scans
• PET scans

How do they work?

The type of scan done depends on what organ or tissue the doctor wishes to study. In most cases you are given a dose of a substance that sends out small doses of radiation. Some are swallowed while others are given into a vein or inhaled as a gas.

Radionuclide scans: Because they look at more than just the shape of a tumor, radionuclide scans are used for more than just creating pictures. Here are some of the more common radionuclides now in use:

• Gallium-67 is used to look for cancer in the lungs, in lymph nodes, or in the bone marrow (such as Hodgkin disease or non-Hodgkin lymphoma). Gallium can also be used for a whole body scan (also called a gallium scan).

• Technetium-99 is used in whole body scans, especially in bone scans that look for metastasis (spread) to bones from breast, lung, prostate, or other cancers. Technetium sestamibi (Miraluma^®) scans are being studied for their usefulness in finding breast cancer, as well as in looking at whether some tumors are resistant to chemotherapy.

• Thallium-201 scans, more often used in cardiology (the study of heart disease), are sometimes used to look at how well treatment is working for brain or lung tumors and may be useful for finding lymphomas, as well as thyroid and breast cancers.

• Radioactive iodine (iodine-123 or iodine-131) can be used to find and treat thyroid cancers.

Radionuclides send out gamma rays which are picked up by a special camera (known as a gamma camera, rectilinear scanner, or scintiscan). The signals are processed by a computer, which turns them into 2- or 3-dimensional (3-D) images, sometimes with color added for extra clarity. A radiologist or a doctor who specializes in nuclear medicine interprets the image and sends a report to your doctor.

Positron emission tomography scans: Positron emission tomography (PET) is a scan that uses a form of radioactive sugar. Body cells take in different amounts of the radioactive sugar, depending on how fast they are growing. Cancer cells, which grow quickly, are more likely to take up larger amounts of the sugar than normal cells. The radioactive sugar gives off tiny atomic particles called positrons, which run into electrons in the body, giving off gamma rays. A special camera picks up these rays as they leave the body and turns them into pictures.

PET scans are most often used to find cancer. The chemical changes they show can also help doctors look at the effects of cancer treatment. Because PET scans look at body function, they may show changes that suggest disease before the changes can be seen on other imaging tests.

PET scans are especially useful for studying the brain. They are also widely used to look at cancers of the head and neck, thyroid, esophagus (swallowing tube), breast, colon, rectum, ovary, and lung, as well as melanomas and lymphomas.

PET/CT scans: A newer imaging machine combines PET scans with CT scans. PET/CT scanners give more detailed information on the location of any increased cell activity, helping doctors to pinpoint tumors. They are now commonly being used.

Use of monoclonal antibodies in nuclear scans: A special type of antibody produced in the lab, called a monoclonal antibody, can be designed to stick to substances found only on the surface of cancer cells. A radioactive substance can be attached to a monoclonal antibody, which is then given into a vein. It travels in the bloodstream until it reaches the tumor. The antibody, still carrying its radioactive cargo, attaches to the surface of the tumor. This causes the tumor to "light up" when seen through a special scanner. Monoclonal antibody scanning is sometimes used to look at cancers of the prostate (ProstaScint^® scan), colon (OncoScint^®, CEA-Scan^®), ovaries (OncoScint^®), breast, skin (melanoma), and other organs.

How do I get ready for the test?

The steps to take in preparing for a nuclear scan depend on the type of test and the tissue that will be studied. Gallbladder, liver, or thyroid scans require that you don't eat or drink for 2 to 12 hours before the test. In other cases, you may be asked to take a laxative or use an enema. Be sure your doctor or nurse knows everything you take, even over-the-counter drugs, vitamins, and herbs. You may need to avoid some medicines (prescription and over-the-counter) before the test. Your health care team will give you instructions.

The radioactive material is given by mouth, injection into a vein (IV), or inhaled as a gas anywhere from a few minutes to many hours before the test. For example, in a bone scan, the tracer is put into a vein in your arm about 2 hours before the test begins. For gallium scans, however, the tracer is given a few days before imaging.

What is it like having the test?

A nuclear scan can be done on an outpatient basis. Because of the special materials and equipment needed, the scans are usually done in the radiology or nuclear medicine department of a hospital.

The scanner has a hole in the middle and looks like a large doughnut. You lie on a padded table which fits through the hole and the scanner moves back and forth. The technician may ask you to change positions to allow different views to be taken. The test is not painful. But you may get uncomfortable after lying on the table for a while.

If you are having a brain scan, many sets of pictures may be needed. The first scans are taken as the radioactive material moves through the arteries into the brain. The second set, taken a few hours later, shows the material in the brain itself. You will be asked to move your head into different positions. Likewise, a thyroid scan may require 2 sets of scans using doses of radioactive iodine that you swallow.

How long does it take?

A nuclear scan takes about 30 to 60 minutes, plus the waiting time after the radioactive material is given. For bone scans, the material takes 2 to 3 hours to be absorbed, and the scan itself takes another hour or so. Gallium scans take several days between the injection and the actual scan. Results of nuclear scans are usually available within a few days.

What are the possible complications?

For the most part, nuclear scans are safe tests. The doses of radiation are very small, and the radionuclides have a low risk of being toxic or causing an allergic reaction. Some people may have pain or swelling at the site where the material is injected. Rarely, some people will develop a fever or allergic reaction when given a monoclonal antibody.

What else should I know about this test?

• The amount of radiation exposure from a nuclear scan is about the same as that from standard x-rays. The scanner itself does not put out radiation. The body gets rid of the radionuclide used for the test within a few hours or a few days. Talk to your health care team about having sex, or being close to children or pregnant women during this time.

• You will be asked to drink a lot of water to flush out any of the radioactive material that is not absorbed.

• To reduce the risk of exposure to radioactive material in your urine after a scan, you should flush the toilet as soon as you use it.

• Nuclear scans are rarely recommended for pregnant women, so let your doctor know if you are or might be pregnant.

• If you are breast-feeding, be sure to tell the doctor ahead of time. You may need to pump breast milk and discard it until the radionuclide is gone from your system.

Ultrasound

Other names include ultrasonography, sonography, or sonogram.

What does it 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 your organs and tissues, they create echoes.

Ultrasound is very good at giving pictures of some diseases of soft tissues that do not show up well on x-rays. Ultrasound is also a good way to tell fluid-filled cysts from solid tumors because they make very different echo patterns. In looking at breast lumps, for example, ultrasound can help tell cysts from solid tumors. Ultrasound can also be used to find out how far a tumor of the esophagus (swallowing tube), rectum, or uterus (womb) has gone through the wall of the organ.

Still, ultrasound images are not as detailed as those from CT or MRI scans. Ultrasound cannot tell a benign (not cancer) tumor from one that is cancer. Its use is also limited in some parts of the body because the sound waves cannot go through air (such as in the lungs) or through bone.

Doctors often use ultrasound to find out where to put a needle to do a biopsy (taking out fluid or small tissue samples to be looked at under a microscope. The doctor looks at the ultrasound screen while moving the needle and actually sees the needle moving toward and into the tumor.

For some types of ultrasound exams, the transducer (the wand that produces the sound waves and detects echoes) is placed on the skin surface. The sound waves pass through the skin and reach the organs underneath. In other cases, to get the best images, the doctor must use a transducer that is put into a body opening, such as the esophagus, rectum, or vagina.

Special ultrasound machines, known as Doppler flow machines, are able to show how blood is flowing through the vessels. This is helpful because blood flow is different in tumors than it is in normal tissue. Some of these machines make color pictures. Unlike other forms of blood vessel imaging, color Doppler studies do not use contrast agents. 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 it work?

An ultrasound machine has 3 key parts: a control panel, a display screen, and a transducer, which looks like a microphone or a computer mouse. The transducer sends out sound waves and picks up the echoes. The doctor or ultrasound technologist moves the transducer over the part of the body being studied. The computer inside the main part of the machine analyzes the signals and puts an image on a 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, which makes them look black on the display screen. (Doctors sometimes call this pattern hypoechoic.) But the waves will bounce off a solid tumor, creating a pattern of echoes that the computer will show as a lighter-colored image.

How do I get ready for the test?

As a rule, no preparation is needed, but it depends on what is being studied. Your doctor or nurse will give you instructions about any steps to take before your test. Depending on the organ being studied, you may need to not eat, take a laxative, or use an enema. If you are having an abdominal (belly) ultrasound, you may need to drink a lot of water just before the study to fill your bladder. This will create a better picture because sound waves travel better through fluid.

What is it like having the test?

Ultrasound can be done in a doctor's office, clinic, or hospital. You will lie down on a table. The technologist will put a gel on the skin over which the transducer will pass. The gel both lubricates the skin and improves the transmission of the sound waves. The gel feels cool and slippery. If a probe is used, it will be covered with gel and put into the body opening. This can cause pressure or discomfort.

During the test the technologist or the doctor moves the transducer. You may be asked to hold your breath during the scan. The operator may adjust knobs or dials to increase the depth to which the sound waves are sent. You may feel slight pressure from the transducer, but you will not hear the high-frequency sounds.

How long does it take?

An ultrasound usually takes 20 to 30 minutes. 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 complications?

Ultrasound is a very safe procedure with a low risk of complications. Good images are harder to get in people who are obese.

What else should I know about this test?

• Ultrasound does not use radiation.

• Ultrasound costs much less than CT or MRI.

• The quality of the results depends to a large extent on the skill of the technologist or doctor operating the transducer, which is not the case with CT or MRI.

• Newer forms of ultrasound can provide 3-D images.

• Contrast agents that may be used to enhance the quality of the picture are being studied.

Categories of some common imaging tests

Angiogram: see "Radiographic studies"

Arteriogram: see "Radiographic studies -- Angiogram"

Barium enema: see "Radiographic studies -- Lower GI series"

Barium swallow: see "Radiographic studies -- Upper GI series"

Bone scan: see "Nuclear scans"

Gastrointestinal series: see "Radiographic studies -- upper and lower GI series"

Positron emission tomography (PET): see "Nuclear scans"

Pyelography, intravenous (IVP): see "Radiographic studies"

X-ray: see "Radiographic studies"

General questions and comments on radiation risk

In large doses, radiation can cause serious tissue damage and increase a person's risk of later developing cancer. The low doses of radiation used for imaging tests can increase a person's cancer risk slightly, but it is important to put this risk into perspective. In this section we will answer some of the more common questions people have about radiation risk linked to imaging tests.

How much does an imaging test increase a person's radiation exposure?

Background and non-medical radiation

We are constantly exposed to radiation from a number of sources, including radioactive materials in our environment and cosmic rays from outer space. This is called background radiation.

The average person is exposed to about 3 mSv (millisieverts) of radiation from natural sources over the course of a year. (A millisievert is a measure of radiation exposure.) Much of this exposure is from radon, a natural gas with levels that vary across the country. Because the earth's atmosphere blocks some cosmic rays, living at a higher altitude increases a person's exposure. For example, residents in Denver, Colorado, have an annual exposure level of about 5 mSv. And a 5-hour airline flight increases exposure by about 0.03 mSv. Smoking a pack of cigarettes a day exposes the smoker to an extra 53 mSv per year.

Radiation from imaging tests

A single chest x-ray exposes the patient to about 0.1 mSv, which is about the radiation dose people are exposed to naturally over the course of 10 days. A mammogram exposes a woman to 0.7 mSv, or about the amount of exposure a person would expect to get in just under 3 months.

Some other imaging tests have higher exposures. A lower GI series using standard x-rays exposes a person to about 4 mSv, while a CT scan of the abdomen (belly) exposes a person to about 10 mSv. A total body CT scan exposes a person to about 10 mSv. A CT colonography can be as little as 5 to 8 mSv exposure if newer techniques are used. (MRI and ultrasound exams do not expose a person to radiation.)

How much does the extra radiation increase a person's cancer risk?

This is a hard question to answer. Most studies on radiation and cancer risk have looked at people exposed to very high doses of radiation, such as uranium miners and atomic bomb survivors. The risk from low-level radiation exposure is not easy to calculate from these studies. Researchers have estimated that radiation exposure from the average diagnostic x-ray may increase cancer risk very slightly (likely on the order of hundredths to thousandths of one percent). Of course, this can be affected by the type of test done, the area of the body exposed, and other factors. And for the most part, children are more sensitive to radiation and should be protected from it as much as possible.

Because of this very small but real effect, and the fact that radiation exposure from all sources can add up over one's lifetime, imaging tests that use radiation should only be done for a valid medical reason. In many cases, other imaging tests such as ultrasound or MRI may be used. But if there is a reason to believe that an x-ray or CT scan is the best way to look for cancer or other diseases, the patient will most likely be helped more than the small dose of radiation can hurt.

How imaging tests are used in certain types of cancer

Many different scans are used to get images of what is happening inside the body, including x-rays, ultrasound, MRI, nuclear medicine scans, and so on. The tests your health care team recommends may depend on a number of factors, such as:

• where the tumor is and what type it is; some imaging studies work better for certain organs or tissues

• whether or not a biopsy (tissue sample) is needed

• the balance between any risks or side effects and the expected benefits

• the costs

Table 2 lists the imaging tests that may be used for various types of cancers. Other types of tests, such as endoscopy (looking at body organs or cavities using a thin flexible tube that holds a camera), may be used along with or in place of those listed. Tests are chosen based on the extent and type of cancer. If you have questions about a test that your health care team wants you to have, ask them to explain the purpose of the test.

Table 2: Common cancer-related uses of imaging tests

Screening tests refer to procedures used to find a disease, such as cancer, in people who do not have symptoms of that disease.

Detection refers to diagnostic tests used if your doctor has special reason to think that you may have a disease such as cancer. These reasons could include symptoms, abnormal physical exam results, or changes seen on screening tests. Imaging tests for detection can help find a mass or other abnormal tissue and can often predict whether it is likely to be a cancer or some other type of disease. Still, in almost all cases, a tissue sample (biopsy) must be taken and looked at under the microscope to be sure cancer is present.

Image-guided biopsy refers to the use of imaging tests to help guide a biopsy needle into the area of concern. An image-guided biopsy can often provide tissue for study that might otherwise require surgery to reach.

Staging is the process of finding out how far a cancer has grown and spread. Imaging tests are often used to estimate the size of a cancer; to find out how far it has spread in the organ in which it started; and to see whether it has spread to nearby tissues and organs, nearby lymph nodes, or distant organs. Most of the tests listed in this section are used to look for metastases (spread) to distant organs or tissues. For instance, men with prostate cancer often have bone scans to see if the cancer has spread to bones.

Selection of imaging tests for staging will depend on the doctor's impression of how far the cancer is likely to have spread, based on symptoms and other factors. These tests may not be done in people who have small tumors that do not seem to have spread. People with larger cancers or cancers that have already spread to lymph nodes may need tests such as nuclear scans, CT scans, or MRI to look for distant spread. People with bone pain, nerve-related symptoms (such as numbness, paralysis, or problems with balance or coordination), or other symptoms suggesting distant spread will need more careful evaluation by imaging tests.

Additional resources

More information from your American Cancer Society

The following information may also be helpful to you. These materials may be viewed on our Web site, www.cancer.org, or ordered from our toll-free number, 1-800-227-2345.

• Endoscopy

• Mammograms and Other Breast Imaging Procedures

• A Message of Hope: Coping with Cancer in Everyday Life (also available in Spanish)

• After Diagnosis: A Guide for Patients and Families (also available in Spanish)

• Helping Children With Cancer in the Family: Dealing With Diagnosis

• Choosing a Doctor and a Hospital

• Health Professionals Associated With Cancer Care

• Testing Biopsy and Cytology Specimens for Cancer

No matter who you are, we can help. Contact us anytime, day or night, for information and support. Call us at 1-800-227-2345 or visit www.cancer.org.

References

American College of Radiology/Radiological Society of North America. RadiologyInfo. Accessed at: www.radiologyinfo.org on September 3, 2009.

Fenton JJ, Taplin SH, Carney PA, et al. Influence of computer-aided detection on performance of screening mammography. N Engl J Med. 2007;356:1399–1409.

Hricak H, Akin O, Bradbury MS, et al. Advanced imaging methods: Functional and metabolic imaging. In: DeVita VT, Hellman S, Rosenberg SA, eds. Cancer: Principles & Practice of Oncology. 7th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2005:589–720.

Kleinerman RA. Cancer risks following diagnostic and therapeutic radiation exposure in children. Pediatr Radiol. 2006;36 Suppl 2:121–125.

Levin B, Lieberman DA, McFarland B, et al. Screening and Surveillance for the Early Detection of Colorectal Cancer and Adenomatous Polyps, 2008: A Joint Guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. CA Cancer J Clin. 2008;58:130–160.

Little JB. Ionizing radiation. In: Kufe DW, Pollock RE, Weichselbaum RR, Bast RC, Gansler TS, Holland JF, Frei E, eds. Cancer Medicine. 6th ed. Hamilton, Ontario: BC Decker; 2003:289–301.

Pisano E, Gatsonis C, Hendrick E, et al. Diagnostic Performance of Digital Versus Film Mammography for Breast Cancer Screening - The Results of the American College of Radiology Imaging Network (ACRIN) Digital Mammographic Imaging Screening Trial (DMIST). N Engl J Med. 2005;353(17):1773–1783.

U.S. Department of Energy. Radiation in Perspective. Accessed at: www.hss.energy.gov/HealthSafety/WSHP/radiation/Radiation-final-6-20.pdf on September 3, 2009.

U.S. Food and Drug Administration. Reducing Radiation from Medical X-rays. Accessed at: www.fda.gov/downloads/ForConsumers/ConsumerUpdates/ucm095824.pdf on September 3, 2009.

Last Medical Review: 10/08/2009
Last Revised: 10/08/2009