Breast-Dedicated Radionuclide Imaging Systems

Abstract

Breast-dedicated radionuclide imaging systems show promise for increasing clinical sensitivity for breast cancer while minimizing patient dose and cost. We present several breast-dedicated coincidencephoton and single-photon camera designs that have been described in the literature and examine their intrinsic performance, clinical relevance, and impact. Recent tracer development is mentioned, results from recent clinical tests are summarized, and potential areas for improvement are highlighted. Br east cancer is the most common cancer in women worldwide, with 1.3 million cases diagnosed per year. The current standard of care in breast cancer management has challenges. Physical examinations often find palpable tumors that are already invasive and node-positive. Mammograms are well known for having low specificity and often being inconclusive for patients with dense breasts, leading to unnecessary surgical procedures and patient trauma. The use of noninvasive molecular imaging provides sensitive and specific cellular biologic information to aid in the diagnosis, staging, and treatment evaluation of breast cancer. PET and single-photon emission imaging have shown great diagnostic power in detection of malignant lesions in the body. The conventional systems sitting in the nuclear medicine clinic, however, are generalpurpose and have neither the photon sensitivity nor the spatial resolution required to affect earlier stages of breast cancer management. Technologic advances have enabled the creation of high-performance breast-dedicated (BD) radionuclide cameras that show promise for more sensitive cancer detection than standard clinical cameras while also providing better specificity than traditional anatomic imaging modalities such as x-ray mammography. This paper presents novel instrumentation from several different BD system designs that have been studied and evaluates the performance of different BD systems in the clinic. BD POSITRON EMISSION MAMMOGRAPHY (PEM) AND PET CAMERA DESIGNSSystem Configuration BD PET requires a field of view (FOV) large enough to be clinically relevant for breasts of all sizes, ranging from an average of 11.1-13.7 cm in diameter and 5.7-9.7 cm in length for bra cup sizes A-D (1). Detectors are typically arranged in a ring around the breast (annular systems), or in panels on 2 sides (dual-panel systems) or 4 sides (rectangular systems) of the breast. Translatable (2,3) and rotatable (4-7) detector heads can be used to extend the imaging FOV beyond the detector volume, but to date have had lower sensitivities than stationary systems with equivalent FOVs, and require longer scan times and more complex mechanical designs. For example, the sensitivity of the Shimadzu O-ring system is a factor of 5 higher than that of the Oncovision MAMMI system, which has a similar imaging FOV but uses translating heads (Table 1). Higher photon sensitivity generally allows for shorter scan times to achieve equivalent image quality, as seen with imaging protocols used for stationary (8) and translating systems ...

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