MaxPET: a dedicated mammary and axillary region positron emission tomography imaging system for breast cancer

The authors have built a dedicated PET system for breast cancer patient imaging. The modular detector is composed of a 9×9 array of 3×3×20 mm LSO scintillator crystals coupled to an optical fiber taper, which in turn is coupled to a Hamamatsu R5900-C8 position-sensitive photomultiplier tube. Two modules have been characterized with the following results: average intrinsic spatial resolution=2.26 mm, average energy resolution=19.5% at 511 keV, coincidence time resolution=2.4 ns, and detector efficiency=53% using a 350 keV energy threshold. To create the maxPET system, the authors have tiled 50 of these modular detectors into 5×5 arrays forming two parallel detector plates measuring 15 cm×15 cm. Using a multiplexed sector readout scheme the authors have obtained singles flood histograms allowing identification of >90% of the 2025 crystals in each plate without any optimization. The authors are in the process of improving the crystal look-up tables and will fully characterize the complete imaging system. The data is acquired in projection mode or by rotating the plates to obtain tomographic datasets. The promising results from the individual detector modules support the feasibility of developing a high resolution, high sensitivity dedicated PET system for breast cancer applications