Molecular breast imaging with directly opposing compact gamma cameras

The goal of this study was to evaluate the efficacy of operating a two-head gamma camera system in a configuration in which the two cameras are positioned on opposite sides of the compressed breast, aligned precisely with each other and with precisely anti-parallel viewing directions. The main objective of the present study was to determine if the combination of the two resulting images might allow for better sensitivity for small lesions in all regions of the breast. Two pairs of gamma cameras were evaluated; one composed of commercially available gamma cameras and the other composed of two research-based gamma cameras. For each pair, an acrylic box phantom, with two spherical lesions suspended inside, was used to evaluate contrast and SNR as a function of lesion position, first for images from the two cameras separately and then for images obtained from pixel- by-pixel multiplication or summation of the individual images. A capillary phantom was used to quantify the spatial resolution as a function of lesion depth for the cameras individually as well as for the resulting multiplied images. Lastly, gelatin phantoms were imaged, each containing a single cube-shaped lesion of ~8 mm side length positioned at varying depths within the phantom. Relative to the single camera images or the summed images, the lesion contrast and SNR of the multiplication image were superior, irrespective of lesion depth, and were much more constant with changing lesion depth. Except when the lesion was less than a centimeter from one of the cameras, the SNR of the multiplied image exceeded that of a single camera image obtained using twice the acquisition time. These findings suggest that improved lesion detectability is possible by imaging simultaneously from both sides of the breast, especially if the location of the lesion within the breast is not known a priori.