A cost-effective, scalable approach to high-resolution, sub-100 ps TOF-PET


D. Schaart, TUDelft


There remains huge untapped potential for PET in the research, diagnosis and treatment of oncological, neurological, cardiovascular, infectious, and inflammatory diseases. However, to transform PET into a cost-effective tool for personalized medicine in a wide range of clinical applications, we must reduce the radiation dose (currently 5-25 mSv), scan time (currently > 10 minutes), and costs per patient (currently > 1000 €), all by an order of magnitude, as well as improve the compatibility with other modalities to enable multi-parametric data acquisition. Technologically, this translates into a need for more than 10-fold increased sensitivity, without sacrificing other crucial system parameters such as spatial and energy resolution. In the US, the $15.5 million Explorer project aims at the world’s first total-body PET/CT scanner with a 2 m long axial length, to demonstrate the clinical value of a ~40-fold improved system sensitivity. While major scientific breakthrough are expected from this project, the system concept is intrinsically expensive as it is based on multiplication of existing detector technology. A different way to improve effective sensitivity is to push time-of-flight (TOF) resolution to less than ~100 picoseconds, ultimately to ~10 ps. Results achieved by European researchers in recent years make it likely that high-resolution TOF-PET imaging with sub-100 ps time resolution can be demonstrated within the coming years [1-3]. In particular, the so-called monolithic scintillator concept shows how timing information can be extracted optimally from the spatio-temporal distribution of the optical signal produced upon the interaction of a gamma photon inside a transparent material [4,5]. Sub-150 ps timing in combination with near-1 mm spatial resolution has already been demonstrated in a simple, scalable, and cost-effective monolithic scintillator detector based on the widely available scintillator LYSO:Ce and digital silicon photomultipliers. Experimental evidence of the clinical imaging performance of this detector as well as further steps towards sub-100 ps clinical TOF-PET imaging will be discussed at the conference. **References** [1] DR Schaart et al, LaBr3:Ce and SiPMs for time-of-flight PET: achieving 100 ps coincidence resolving time, Phys Med Biol 55 (2010) N179 [2] S Seifert et al, A Comprehensive Model to Predict the Timing Resolution of SiPM-Based Scintillation Detectors: Theory and Experimental Validation, Ieee T Nucl Sci 59 (2012) 190 [3] MV Nemallapudi, S Gundacker, P Lecoq, E Auffray, A Ferri, A Gola, C Piemonte, Sub-100 ps coincidence time resolution for positron emission tomography with LSO:Ce codoped with Ca, Phys Med Biol 60 (2015) 4635 [4] S Seifert, G van der Lei, HT van Dam, DR Schaart, First characterization of a digital SiPM based time-of-flight PET detector with 1 mm spatial resolution, Phys Med Biol 58 (2013) 3061 [5] HT van Dam, G Borghi, S Seifert, DR Schaart, Sub-200 ps CRT in monolithic scintillator PET detectors using digital SiPM arrays and maximum likelihood interaction time estimation, Phys Med Biol 58 (2013) 3243

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