Gamma Emission Breast Tomosynthesis

In x-ray mammography, sensitivity is significantly reduced among the 40–600f women with radiodense breasts. Molecular breast imaging (MBI) is a relatively new functional imaging modality that has entered clinical practice. It uses dedicated gamma cameras to track the distribution of radiopharmaceuticals such as 99m Tc-sestamibi, whose higher energy (140 keV) radiation is not affected by variations in radiodensity within the breast. However, as a planar imaging technique, MBI suffers from tracer superposition, photontissue attenuation and depth-dependent detector blurring. These effects lead to suboptimal lesion contrast and signal to noise ratio (SNR). The amount of injected tracer activity needed to produce images of sufficient quality for diagnosis results in a much higher effective whole body radiation dose compared to that of screening mammography. A novel imaging tool called gamma emission breast tomosynthesis (GEBT) has been developed. The new tool uses a dedicated gamma camera as in MBI and acquires multiple 2-D images over a limited angular range. An algorithm was designed, optimized and implemented for 3-D image reconstruction from those 2-D projection views and for correction of image-degrading effects during the acquisition process. The results of simulations and phantom experiments have demonstrated that the algorithm can greatly reduce the background artifacts due to photon-tissue attenuation and angular undersampling inherent in tomosynthesis. It also significantly improves quantification of lesion tracer concentration by applying corrections for depth-dependent blurring and attenuation. The overall lesion detection sensitivity of GEBT has been shown to be far superior to and much less location-dependent than that of MBI. A further dose study has ii shown that when using one-fourth of the injected tracer radioactivity as in MBI, GEBT has superior contrast and comparable SNR for all lesion sizes and depths that are practically observed in clinic. These results suggest that, compared to the current clinical practice, GEBT could permit a large reduction in the amount of injected radiotracer while maintaining image quality.

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