A Large Field of View Coincidence Imaging System Based on One-Dimensional Sharing Block Detectors

For such as breast cancer imaging, dedicated coincidence imaging detector will be promising for new instrumentation of nuclear medicine. For this purpose, a large field of view (FOV) coincidence imaging system was developed and tested. The imaging system consists of four sets of one-dimensional sharing block detectors and a single gamma probe and measures coincidence between these two detectors. The one-dimensional sharing detector uses 5 GSO blocks optically coupled to 6 dual photomultiplier tubes (PMT). The size of a single GSO is 2.9 mm times 2.9 mm times 15 mm. The signals from four one-dimensional sharing detectors are fed to weighted summing circuits. They are digitized by 100 MHz free running analog to digital (A-D) converters and are used to calculate the position of gamma interaction. Coincidence was measured between this gamma imaging detector (panel detector) and a hand-held single gamma probe. Acquired data was transferred to a personal computer and displayed. Most spots corresponding to GSO crystals were resolved in the position histogram. Spatial resolution was around 4 to 6 mm FWHM when the detector is greater than 25 mm. The sensitivity was 0.1-0.2% when the single probe was 25 mm away from the imager surface. Images of phantoms were successfully obtained. We conclude developed coincidence imaging system has large FOV and easy to handle, reasonable spatial resolution and may have potential to be a new instrument for nuclear medicine.