Conventional mammography is a screening procedure constrained by low specificity in the detection of breast cancer. Approximately 40% of women undergoing mammography screening have dense breast tissue, and conventional mammographic imaging has a sensitivity range of only 50%-85% for malignant lesions. Magnetic resonance imaging (MRI) is now recommended for breast cancer screening in high-risk patients. However, approximately 15% of patients cannot tolerate MRI. These are the clinical situations in which positron emission mammography (PEM) and breast-specific gamma (BSG) camera systems fulfill a need for primary breast cancer imaging. Because breast cancer is the most common malignancy and the second most common cause of cancer death among women, many nuclear medicine imaging techniques are essential in the evaluation and therapy of patients with this disease. Nuclear medicine surgical techniques consist of sentinel lymph node localization and the use of radiolabeled seeds for intraoperative localization of nonpalpable breast cancers. The Food and Drug Administration (FDA) has approved the PEM Flex Solo II scanner, which has the capability for stereotactic biopsy, with an array of pixelated lutetium yttrium orthosilicate (LYSO) crystals, position-sensitive photomultiplier tubes (PS-PMT), and a spatial resolution of 2.4 mm. Clear PEM is a scanner in development with cerium-doped LYSO (LYSO:Ce) crystals, multipixel avalanche photodiodes, depth of interaction measurement with a resolution of 1.3 mm. The Dilon 6800 Gamma Camera is a BSG device approved by the FDA with stereotactic biopsy guidance capability, a pixelated array of sodium iodide crystals, PS-PMTs, and an extrinsic spatial resolution of 6 mm at 3 cm from the camera. GE has just received clearance from the FDA for a molecular breast imaging camera, the Discovery NM 750 b, with pixelated cadmium zinc telluride crystals, semiconductor photoelements and an extrinsic resolution of 3.5 mm at 3 cm. The Society of Nuclear Medicine has issued guidelines for BSG camera image interpretation recommendations and clinical indications. Different crystals and camera architectures are under investigation to further improve resolution for both PEM and BSG imaging.
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