Imaging performance of PEM-1: a high resolution system for positron emission mammography

Positron emission tomography with ¹⁸F-fluoro-deoxyglucose (FDG) is known to detect the increased metabolism of breast tumours. The authors have built a positron emission mammography system which produces metabolic breast images co-registered with conventional mammography. Two position sensitive photomultipliers are coupled to four BGO blocks which are partially cut into 2×2 mm elements from both faces. This provides 72×72 BGO crystals in coincidence yielding over 26 million lines of response. A real time display is formed by performing a weighted back-projection onto seven image planes through the breast. The prototype instrument is currently being tested on phantoms. The spatial resolution in the central region has been measured at 2.05 mm FWHM, less than half that of a conventional PET scanner. The coincidence resolving time is 12 nsec. This device should be able to identify breast tumours <5 mm in diameter and provide 3-D localization registered with conventional mammography