Custom breast phantom for an accurate tumor SNR analysis

The capability of the scintimammography to diagnose sub-centimeter sized tumors was increased by the employment of a dedicated gamma camera (SPEM). Recently the introduction of small field of view camera, based on pixellated scintillation array and position sensitive photomultiplier (PSPMT), allowed to enhance the geometric spatial resolution and contrast of the images due to reduced collimator-tumor distance. The aim of this paper is to investigate the realistic possibility of T1a tumors detection (∼5 mm size) by comparing the SNR values obtained by different imagers. To this end, we have utilized a self-designed solid breast phantom with different sized hot spots (tumors). The phantom consists of seven disks with different thickness, molded from resin epoxy activated with Co57 source. The overlapped disks represent a pendula breast with about 800 cc volume. The activity density of the breast phantom was fixed at 500 nCi/cc. One disk has holes to fit the hot spots representing the different sized lesions. The imagers utilized were: standard Anger Camera, SPEM detector, 5 inch diameter PSPMT coupled to CsI(Tl) pixellated array (2 × 2 × 3 mm3 pixel), two Small Field of View Camera (SFVC) and a Flat Panel Camera (FCP), based on flat panel PSPMT and NaI(Tl) scintillator array. The experimental results are supported by Monte Carlo simulation. All gamma cameras show close results at SNR values less than 10 and a full detectability of 8 mm tumor size. However the SNR results show the 5 mm tumor size is lower detection limit for all cameras