Fast-channel LSO detectors and fiber-optic encoding for excellent dual photon transmission measurements in PET

Improved attenuation correction remains critical to PET. Currently with dual photon rotating rod sources, benefits of windowing are limited by counting losses of detectors nearest the rods, the near detectors. With single photon sources, improved statistics are offset by a greater need for collimation and more complex emission background correction. Now, a dual photon point source array with fast-channel, near detectors improves on these earlier techniques-here, adding transmission measurement to dual-head rotating PET. Arrays of collimated point sources (/sup 68/Ge/Ga-3 to 21 per head) are aligned axially and orbit the FOV. With each source is a dedicated near detector (LSO crystal). Crystals couple to photomultipliers (PMTs). As the crystals are not "block" encoded, pulse-processing time is reduced (to 120 ns). Reduced processing time lowers dead time and permits hotter sources. For improved axial sampling, larger arrays (21 sources/head) may be configured. To reduce cost, crystals couple fiber-optically into unique PMT pairs-decreasing the total number of near-detector PMTs by 71%.