Molecular Breast Imaging: A New Technique Using Technetium Tc-99 Scintimammography to Detect Small Tumors of the Breast

Abstract

ABSTRACT

Although scintimammography using technetium Tc-99m is a helpful adjunct to conventional mammography, this method has never been fully optimized for breast imaging and it performs poorly in detecting small lesions. The major reason is that a lack of breast compression, and the inability to place the detector close to the breast, degrades image quality. This study evaluated molecular breast imaging (MBI), a form of scintimammography specifically designed to image the breast that uses a cadmium-zinc-telluride semiconductor detector in place of the conventional sodium iodide detector. The unit is mounted on a modified mammographic gantry. It has a field of view of 20 × 20 cm and an energy resolution of 6.5%, compared with approximately 10% for a conventional gamma camera. Patients receive 20 mCi of 99mTc sestamibi by injection and were imaged 10 minutes later. Using light compression, craniocaudal and mediolateral oblique views were obtained from each breast.

The study group consisted of 40 women with a mammographic lesion smaller than 2 cm that was considered to be highly suggestive of malignancy. Twenty-six of them had a total of 36 malignant lesions confirmed at surgery. All but 3 lesions were detected by MBI, for an overall sensitivity of 92%. Nineteen of 22 malignancies 1 cm or less in diameter were detected (sensitivity, 86%), as were all 14 larger lesions. Two patients had false-negative MBI studies. In 4 cases, MBI detected additional lesions not seen on conventional mammography; 3 of them were in the breast not initially found to be affected. All of these lesions were later confirmed by magnetic resonance imaging and at surgery. Five of 14 patients with no evidence of cancer had false-positive MBI scans. The examination was well tolerated by all the women.

The MBI technique, using a prototype gamma camera system designed specifically for mammography, detects breast malignancies measuring 1 cm or less in diameter with a high degree of reliability. MBI may prove most useful for women having dense breast tissue and those with a family history of breast cancer.