Breast Cancer Imaging

Imaging Techniques

Imaging studies can be an important part of a clinical work-up for breast cancer and are of most benefit when the physical examination, history and symptoms suggest that cancer has spread beyond the breast to lymph nodes or to other parts of the body. These studies can help your doctors better define the size and location of a primary tumor and the extent of disease, essential factors in determining the stage of disease.

Many different imaging techniques can be used to help stage breast cancer, and each has advantages and disadvantages in terms of value in imaging, cost and convenience. Imaging studies are painless, and there are no side effects.

X-rays

Conventional x-rays are typically the first imaging study done because they are a relatively easy, low-cost approach to ruling out metastatic disease. However, if an x-ray shows evidence of metastasis, another imaging study is usually needed to confirm the findings. X-rays are used primarily to rule out evidence of cancer in the lungs, the second most common site of breast cancer metastasis, and may also be used to determine if cancer has spread to the bone, the primary site of metastasis.

Ultrasound

Ultrasound, also known as ultrasonography, of the breast can be useful for evaluating a specific area of suspicion found on mammography and is especially useful for women with very dense breast tissue. Ultrasound of the abdomen may be done to look for cancer in the liver or other abdominal organs.

To perform ultrasound, an ultrasound technician will use a transducer (a small microphone-like instrument) to send sound waves to your body; these sound waves bounce off body tissues and echo into the transducer. The echoes are then converted into images that provide an outline of a part of the body.

Bone Scan

A bone scan is the optimal imaging study to determine whether breast cancer has spread to bone. One advantage of a bone scan compared with x-rays is that a bone scan can provide images of the all the bones in the body at the same time.

Before a bone scan is done, a small amount of a low-level radioactive substance is injected into a vein in your arm. This radioactive substance will collect in areas of metastatic disease in bone. During the scan, you will lie on a table (for about 30 minutes), and a special camera will record images of areas with an increased amount of the radioactive substance. Most of the radioactive substance will be eliminated from your body within 1 day and it will be completely gone within 2 days.

Computerized Tomography (CT)

CT is most often done to verify findings on a chest x-ray or to evaluate the abdominal organs or the brain for signs of breast cancer metastasis.

A CT scan provides three-dimensional, cross-sectional x-ray images, so it can provide more details than a conventional x-ray. A CT scanner takes many pictures of your organs as the table on which you’re laying moves slowly through the scanner. A CT takes longer than a conventional x-ray, and you will need to lie very still while the images are being made. A contrast material may be injected into a vein in your arm before the test to enhance the quality of the images. This contrast material (also referred to as dye) may cause you to feel a brief sense of warmth or flushing in your body. This feeling is normal, but some individuals can allergic to this dye.

Magnetic Resonance Imaging (MRI)

MRI of the breast may be done to look more closely at an area of concern on mammography and/or ultrasound and is especially helpful for women who have dense breast tissue. In addition, the American Cancer Society recommends that breast MRI be used to evaluate the opposite breast after a diagnosis of breast cancer in selected patients. MRI may also be done to look for metastasis in other parts of the body and is especially useful for detecting brain metastasis.

With MRI, images are produced through radiowaves and a powerful magnet linked to a computer. Although MRI is painless, an MRI machine is similar to a large tube, and you will need to lie still on a table within the tube while the MRI machine makes loud, repetitive clicking noises. If you are uncomfortable in closed-in spaces, tell your doctor, as it may be helpful for you to receive medication to decrease anxiety. As with CT scans, contrast material may be used to enhance the images.

Positron Emission Tomography (PET)

PET scans are not usually done as part of the routine work-up for breast cancer for many reasons: the test is expensive, requires special expertise to perform and to interpret the results, and is not available in every medical facility. In addition, PET has limited ability to detect small tumors. However, PET may be done to determine whether breast cancer has spread to the lymph nodes or other parts of the body and is of particular benefit when the findings of other imaging studies are inconclusive.

A PET scan involves the injection of a small amount of a radioactive sugar (or other radioactive substance) into a vein. Breast cancer cells use a high amount of energy and will therefore absorb great amounts of the radioactive sugar. The special camera in a PET scan machine will detect any increased amounts of radioactive sugar and provide an image of an area of metastasis.

A combination of a PET scan and CT scan is increasingly being used in the evaluation of breast cancer. This combination, done in the same testing session, provides a more complete perspective by enabling the radiologist to compare areas of higher radioactivity on the PET scan with the appearance of the same area on the CT scan.