What Is a Breast Specific Gamma Imaging Test?
Breast cancer is considered one of the leading cancers worldwide. The incidence is progressively increasing in women, resulting in increased mortality rates. Enhanced awareness and early screening measures have benefitted many patients. Early diagnosis and expeditious treatment have resulted in better survival rates and improved quality of life in these patients.
Sonography and mammography, along with physical examination, are widely used screening tools to evaluate breast lumps or any abnormalities in the breast tissue. However, due to the lack of specificity and certain limitations with mammography, there was a need for the development of adjunct diagnostic modalities. Breast-specific gamma imaging is a novel diagnostic procedure in breast cancer detection. This is a molecular test that uses radioactive material and a specialized gamma camera to evaluate breast tissues. This test is also known as scintimammography.
What Is the Principle of This Procedure?
In this procedure, a radioactive material, namely technetium-99 m (Tc-99m) sestamibi, is injected into the vein. This material emits energy in the form of gamma rays which are captured with the help of a specialized gamma camera. The radioactive material tends to accumulate in varying body tissues depending on the molecular activity and metabolic rates of the tissues. Areas with increased activity, such as tumor cells (as they divide rapidly and their growth rate is exponential), tend to have increased concentration of the radioactive material and are hence known as hot spots. Areas with less activity, such as normal breast parenchyma, will have reduced concentration of the radioisotope, thus appearing as cold spots. This difference in concentration will enable the identification of abnormal (tumor) cells.
What Are the Uses of Breast-Specific Gamma Imaging Procedures?
Breast-specific gamma imaging is indicated in the following situation:
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When mammograms are inconclusive in detecting breast cancer.
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As an adjunct diagnostic tool along with mammography to diagnose breast cancer.
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Used in patients with breast implants as the breasts need not be flattened much as in mammography.
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Women with scar tissue in breasts.
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Women with dense breast tissues.
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To identify the presence of additional multiple breast tumors in patients with diagnosed breast cancer.
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To check for tumor cells in the armpit lymph nodes.
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Used as a screening tool in patients in whom MRI is contraindicated.
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To follow up post-surgically or post-chemotherapy.
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In hormone replacement therapy patients.
What Is the Preparation Done Before the Procedure?
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Female patients should inform the doctor if they are pregnant or could be pregnant.
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Lactating mothers should also inform the doctor and may be advised to stop breastfeeding for 24 hours after the procedure.
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Patients will be asked to remove all the jewelry or accessories before the procedure.
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Patients should notify the doctor of any history of allergy.
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Patients are required to give a detailed medical history before the procedure, including the prescription medicines, supplements, and over-the-counter medicines taken.
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Patients will be asked to carry their recent mammography and ultrasonography reports with them on the day of the procedure.
How Is the Procedure Done?
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A physical examination of the breast along with the associated lymph nodes needs to be performed initially.
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Also, a note of the patient’s menstrual history should be made.
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The patient will have to change into a hospital gown.
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Scintimammography is done on an outpatient basis in a hospital. The entire procedure would take 45-60 minutes.
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An Intravenous (I. V) line would be secured in the arm of the patient through which radioactive material technetium-99 m (Tc-99m) sestamibi would be injected into the vein.
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Usually, a contralateral vein is chosen for the breast with the abnormality. If both breasts are involved, then the leg vein is used.
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The patient may experience a metallic taste as the material is injected.
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The patient will be made to wait for 5 to 10 min after injecting the radioactive material.
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The patient would then be seated in an imaging room where one breast is placed at a time adjacent to the gamma camera and compressed firmly with a flat plate, just like in a mammogram. The compression ensures the breast doesn’t move while the images are being captured. Patients are also required to sit still while the images are being taken.
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Two images are usually captured of each breast, and each image takes roughly about 10 minutes.
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Dense breast tissue may require more images.
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The gamma camera captures the gamma irradiation emitted by the radioisotope in the breast.
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The computer then processes the amount of radiation absorbed and creates an image.
What Are the Instructions to Be Followed After the Procedure?
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Patients can continue their normal activities.
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They would be advised to drink enough water to remove the radioactive material from the body. It is usually expelled via urine or feces.
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Patients may be advised to flush the toilet twice after using it to remove the radioactive material completely.
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Patients need not avoid other people as the material loses its radioactivity rapidly.
What Are the Benefits of the Procedure?
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Noninvasive and painless.
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Extremely useful in patients with dense breasts and breast implants where mammography may not prove helpful.
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Increased sensitivity and high predictive values in diagnosing breast cancer.
What Are the Risks and Complications of This Procedure?
Nuclear radioactive materials are generally considered safe with negligible radiation risk. However, certain risks may be associated with the procedure as mentioned below:
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Rare allergic reactions to the radioactive material.
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The site of injection may develop an infection resulting in redness and pain.
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Extravasation of the radioactive material results in abnormal distribution of the material in the axillary region.
Where Is This Procedure Contraindicated?
Breast-specific gamma imaging is contraindicated in the following conditions:
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Pregnant women and lactating mothers. Lactating mothers may be advised to stop breastfeeding for 24 hours after the procedure.
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Not valuable to detect very small tumors (smaller than 1 cm in diameter).
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Patients who have had a surgical intervention such as fine-needle aspiration biopsy, core biopsy, breast surgery, excisional biopsy, or radiation therapy. These candidates may need to wait for two to six weeks depending on the procedure done for a scintimammography because the healing tissues also tend to accumulate radioactive material resulting in inappropriate results.
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Not recommended in menstruating women though further studies are warranted.
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Patients with a known allergic reaction to the radioactive material.
Conclusion:
A cancer diagnosis can prove challenging to the patient as well as their family. The incidence of cancer is on the rise, and breast cancer contributes to the highest cancer death rate amongst female patients. Increased awareness, early screening, and routine physical examinations have helped the timely identification of malignancies, thereby ensuring prompt treatment and superior outcomes. Though breast-specific gamma imaging cannot replace conventional mammography, they prove to be a valuable adjunct in diagnosing breast cancer. The high sensitivity, specificity, and remarkable predictive value make scintimammography a valuable imaging tool.
