Optimization of dedicated scintimammography procedure using detector prototypes and compressible phantoms

Jefferson Lab., Hampton University, and University of Virginia are collaborating on optimization of dedicated scintimammography mini gamma cameras. Several prototype imagers with a FOV of 4"×4" and 8"×6" were tested for an application in a dual modality mode as an adjunct technique to digital mammography imagers, or as stand-alone instruments in a dedicated breast SPECT mode. The goal of this study was to obtain experimental data allowing for selection of the best imaging geometry to detect small lesions labeled with Tc-99m. The design of the small scintimammography gamma camera prototypes used in these studies, with an active FOV from 10 cm×10 cm and 15 cm×20 cm, is based on an array of Hamamatsu R7600-00-C8 position sensitive photomultiplier tubes (PSPMTs). Optically coupled to the PSPMT array via specially designed efficient multi-element light guide is a matrix of NaI(Tl) scintillator pixels (made by Bicron Corporation) with each element 3 mm×3 mm×6 mm in size and separated by 0.4 mm thick septa. Several designs of this basic structure were used in prototypes used to detect small lesions inserted in gelatin breast phantoms under compression and in a non-compressed SPECT mode. Anthropomorphic torso phantoms were also employed to simulate realistic scatter radiation fields. Two data acquisition systems were used to collect and analyze the data: one based on a Macintosh G3 workstation with FERA ADCs and one based on a PC computer running Windows NT/KmaxNT software which makes use of two sixteen channel ADC PCl cards. The present results show that the preferred imaging geometry is planar imaging with two opposing detector heads and breast under compression, however, further study of the dedicated breast SPECT is warranted