Evaluation of Gamma Cameras for Use in Dedicated Breast Imaging

Due to the limitations of conventional gamma cameras for breast imaging, many researchers are developing dedicated imagers for use in scintimammography that can be positioned closer to the breast, thereby improving spatial resolution. The purpose of this paper was to compare the performance characteristics of several dedicated gamma cameras with two different types of position sensitive photomultiplier tubes (PSPMTs), and four different NaI crystal arrays. Quantities evaluated include intrinsic spatial resolution, spatial resolution versus source-to-crystal distance, energy resolution, intrinsic nonuniformity, and system sensitivity. In order to assess the impact of changing crystal size on lesion detectability, a contrast-detail study was also performed. Our studies demonstrate that the camera with the newer PSPMTs (Hamamatsu model H8500) shows superior performance in terms of uniformity and energy resolution. The contrast-detail performance of the camera with the highest spatial resolution (1.4-mm crystal pitch with a high resolution collimator) was poor, even with relatively high input fluence. However, the use of a high-efficiency collimator significantly improves object detectability. The camera with the largest (3.2 mm) crystal pitch performed better than the others tested, with both high resolution and high efficiency collimators. However, its performance for small lesion size was better with the high-resolution collimator. Hence, based on the results of the contrast-detail study, of the cameras evaluated here, the camera with the 3.2-mm crystal pitch and the high-resolution collimator is best suited for imaging breast tumors