Monte Carlo study and experimental measurements of breast tumor detectability with the YAP-PEM prototype

A prototype for positron emission mammography is under development within a collaboration of the Italian Universities of Pisa, Ferrara, Bologna and Roma. The device is composed of two stationary detection heads, each with an active area of 6 cm × 6 cm, made of 30×30 YAP:Ce finger crystals of 2 mm × 2 mm × 30 mm. The EGSnrc Monte Carlo code has been used to perform a complete simulation of this camera. We have used a fast three-dimensional iterative algorithm (30 s per iteration on a PC-Pentium III 800 MHz processor) for image reconstruction. The performed study indicates that tumors of 5 mm diameter, i.e., 0.065 cm³ volume, with 37 kBq/cm³ (1 μCi/cm³) specific activity embedded in a breast active phantom, are detectable in 10 minutes for a 10:1 tumor/background ratio with an 8.7 Signal-to-Noise Ratio value. Experimental measurements with the small animal tomograph YAP-PET have validated the Monte Carlo predictions.