Investigating performance of limited angle dedicated breast TOF PET

Abstract

The development of dedicated breast PET imaging has great potential for improving the diagnosis and staging of breast cancer. A number of positron emission mammography (PEM) systems have been developed for imaging of the compressed breast in conjunction with mammography. Another class of breast PET systems is being investigated for imaging of the uncompressed breast in the prone position (referred to as BPET). In this study, a computer simulation is used to evaluate the effect of TOF PET on various BPET geometries using an average size, cylindrical breast phantom model (14 cm diameter, 11 cm axial length) and a BPET system with 25 cm diameter. The Geant4-based GATE Monte Carlo package was used to model a dedicated full ring breast PET scanner consisting of 96 rings with 12 modules and 32×96 2×2×20 mm LYSO crystals in each module. The diameter of the rings was 250 mm and the axial length in field of view (FOV) was about 200 mm. PET geometries consisting of 5/6 ring and 2/3 ring were also studied. To investigate performance of time-of-flight (TOF) PET, different coincidence time resolutions (FWHM) of 280 ps, 425 ps, and 850 ps were modeled. It was observed that TOF using full-ring breast PET provided SNR improvement for 3 mm spheres of 8%, 35%, and 42% for 850 ps, 425 ps, and 280 ps timing resolution. Using TOF reconstruction with an incomplete ring geometry caused reconstructed spheres to be slightly geometrically distorted, and in general using TOF did not fully compensate for the loss of SNR due to the incomplete ring geometry.