Normal or Negative of Scintimammography (Miraluma, Sestamibi Breast Imaging, Radionuclide Breast Imaging)
No uptake, or minimal symmetric, bilateral, uniform, diffuse uptake; equal to soft-tissue uptake.
Abnormal or Positive
Malignant lesions are noted by focal areas of increased uptake of the radioisotope. The results may be graded from 1 to 5, reflecting the progressive probability of a malignant lesion, or as equivocal, low, moderate, or high uptake of the isotope, with low, moderate, and high generally associated with malignant disease.
Usage of Scintimammography (Miraluma, Sestamibi Breast Imaging, Radionuclide Breast Imaging)
Follow-up or adjunct test to mammography in evaluating breast lesions in clients with an abnormal mammogram or palpable breast mass. Because the test depends on the molecular differences between cancer cells and normal cells and not on tissue density, it is useful in the further evaluation of breast lesions in women, especially if the woman has dense breast tissue (that is, fibrocystic disease, fatty tissue, or previous breast surgery, radiation therapy, chemotherapy, biopsy, breast implants, or silicone injections). It is not used for routine breast cancer screening, for confirming the presence or absence of breast cancer, or in place of biopsy. It helps the health care professional more accurately predict the chances of a breast lesion being cancerous. Research is being conducted to establish the effectiveness of the test in detecting axillary lymph node involvement in breast cancer and in the evaluation of breast tumor response to chemotherapy.
Description of Scintimammography (Miraluma, Sestamibi Breast Imaging, Radionuclide Breast Imaging)
A nuclear medicine planar scan in which a radioisotope, technetium-99m sestamibi (Miraluma, 99mTc-sestamibi, 99mTc-MIBI), is used to provide pictures of breast lesions. A “trace” amount of the radioisotope is injected intravenously and accumulates in areas of increased metabolic activity, such as that found in malignant cells. Images of each breast are taken by a gamma (Anger) camera to identify any areas of focal uptake of the isotope, indicating the possible presence of a cancerous lesion. A high-resolution method of this procedure has been shown to be more sensitive than a conventional camera for differentiating indeterminate breast lesions, but is still inferior to biopsy.
Professional Considerations of Scintimammography (Miraluma, Sestamibi Breast Imaging, Radionuclide Breast Imaging)
Consent form IS required.
Rare reports of severe hypersensitivity or seizures. Allergic reaction (itching, hives, rash, tight feeling in throat, shortness of breath, bronchospasm, anaphylaxis, death). Women of childbearing age should have minimal exposure because of the relatively high radiation dose to the ovaries.
Pregnant females: No studies have been done in pregnant females; the test should be administered only if clearly needed.
Nursing mothers: Components of 99mTc-sestamibi are excreted in breast milk; therefore formula feedings should be substituted for breast feedings.
Pediatric population: Safety has not been established.
Previous allergic reaction to Cardiolite or Miraluma (which are the same drug) or other radioactive dyes.
- Have emergency equipment readily available.
- Assess for hypersensitivity to radioactive dyes.
- Ask if the female client is pregnant or nursing.
- Ask the client if there are any known breast lumps or other problems with the breast, a surgery or injury to the breasts, breast implants, or injections. The test should be performed before or at least 7–10 days after fine-needle aspiration, 4–6 weeks after a breast biopsy, and at least 2–3 months after breast surgery or radiotherapy. (This decreases the risk of nonspecific uptake of 99mTc-sestamibi.)
- No fasting is necessary. The client may eat, drink, and take prescribed medications as usual before the test.
- Have client remove all clothing and jewelry above the waist and provide hospital gown.
- Establish intravenous access in the arm opposite from the breast with the suspected lesion.
- At this time there are no definite guidelines regarding the timing of the test with a specific phase of the menstrual cycle.
- Just before beginning the procedure, take a “time out” to verify the correct client, procedure, and site.
- The radioisotope (20–30 mCi of 99mTc-sestamibi) is injected intravenously in the arm opposite that of the breast in question. (This minimizes false uptake of the isotope in the ipsilateral axillary lymph nodes.) The dorsal pedal vein may be used if bilateral lesions are suspected or the client has had a mastectomy.
- The client is positioned in a prone position on an imaging table that has an overlay with “cutouts” that allow the breasts to hang free. Five minutes after the injection of isotope, the camera will be positioned to take a lateral view of each breast, beginning with the breast with the abnormality and followed by the contralateral breast. The client may be asked to lie supine or to sit up with hands clasped behind head to obtain additional images of each breast. Each view takes about 10 minutes. The total test time is about 45 minutes to 1 hour.
- Encourage the intake of fluids to aid excretion of the radioactive medium from the body.
Client and Family Teaching
- You may be asked to bring previous mammograms or other test results for the doctor to compare with scintimammograms.
- You will be asked to remove all clothing and jewelry above your waist.
- A venous access line will be necessary.
- You may experience a slight metallic taste after the injection of the isotope.
- You should remain still and breathe normally while the images are being taken by the camera.
- There is no compression of the breasts during the procedure.
- You should allow 60–90 minutes for the test.
- Most of the radioactive material will be excreted from the body through urine and feces within 48 hours and is not harmful to other persons nearby.
- The nuclear medicine physician will interpret the test and report the results to your doctor within several days.
Factors That Affect Results
- The sensitivity of scintimammography is decreased in lesions that are less than 1.0 cm at the largest dimension.
- False-positive results have been found with fibroadenomas, sclerosing adenomas, and juvenile adenomas.
- The uptake of 99mTc-sestamibi by the myocardium and the liver may mask overlying breast activity in certain client positions.
- Other radioisotopes being evaluated for use in scintimammography include 99mTc-tetrofosmin (Myoview) and 99mTc-MDP (methylene diphosphate).
- Health care professionals working in a nuclear medicine area must follow federal standards set by the Nuclear Regulatory Commission. These standards include precautions for handling the reactive material and monitoring of potential radiation exposure.