TIME-OF-FLIGHT PET

Time-of-Flight (TOF) positron emission tomographs (PET) were developed during the 1980s and early 1990s. Initial investigations into the pot ential improvements in signal-to-noise ratios if TOF information was u tilized were published in 1980. By 1982. two groups (Washington Univer sity and Commissariat a I'Energie Atomique-Laboratorie d'Electronique et de L'Informatique [CEA-LETI]) were designing and building the first TOF tomographs. A third group at the University of Texas also designe d and built a TOF system. These systems were optimized for high count- rate imaging of short-lived radiotracers for applications such as card iac blood flow, The first system put into operation for patient scans was the Super PETT I built at Washington University by Michel Ter-Pogo ssian and his colleagues. The Washington University group went on to d esign two additional versions of TOF systems and the CEA-LETI group de veloped two basic tomograph designs, As Bismuth Germanate (BGO)based s canners were refined, it became clear that the TOF systems could not p rovide the same high spatial resolution as offered by the newer system s. The use of the fast scintillators required for TOF systems also res ulted in lower intrinsic sensitivity that was only partially compensat ed for by the effective gain in sensitivity offered by TOF image recon struction techniques. Further development of TOF systems was suspended in the early 1990s. With the development of new scintillators that pr ovide more light output and are denser than those available in the 198 0s and considerably faster than EGO. there is new interest in the appl ication of TOF techniques for future tomograph designs. Copyright (C) 1998 by W.B. Saunders Company.