1. SAFIR: a fast PET insert for pre-clinical MRI with high temporal resolution Becker Robert 1, Jean-Pierre Cachemiche 2, Casella Chiara 1, Dissertori Günther 1, Fischer Jannis 1, Howard Alexander 1, Jeitler Astrik 3,1, Lustermann Werner 1, Christian Morel, Josep Oliver 4, Röser Ulf 1, Wang Qiulin 5,1, Weber Bruno 6 1 ETH Zurich, Institute of Particle Physics - Zurich, Switzerland 2 Aix Marseille Université, CNRS/IN2P3, CPPM UMR - Marseille, France 3 HTWG Konstanz, Computer Sciences - Konstanz, Germany 4 CSIC, Instituto de Física Corpuscular - Valencia, Spain 5 Tsinghua University, Institute of Medical Physics - Beijing, China 6 University of Zurich, Institute of Pharmacology and Toxicology - Zurich, Switzerland SAFIR - Small Animal Fast Insert for mRi - http://safir.ethz.ch Coincidence time resolution Introduction Construction Simulations ObjectiveDevelopment of a high rate PET insert for pre-clinical 7T MRI system (Bruker 70/30) with unprecedented temporal resolution MotivationQuantitative dynamic PET imaging truly simultaneous with MRI using (among others) short lived isotopes 15 O Highlights- Temporal resolution of ~5s - Very fast data acquisition – large number of counts 10 kHz / mm 2 of detector area Requirements- High injected activity: up to 500 MBq – compensate partially the low number of counts for short time intervals - Small coincidence time window (CTW): < 1ns – limiting random coincidences - Excellent coincidence time resolution (CTR): ~300ps FWHM - High sensitivity: ~6% - Good spatial resolution ~1.5 mm FWHM CrystalCTR SIPAT LYSO:Ce190 ps SIPAT LYSO:Ce:Ca(0.5)139 ps Crystals1.5x1.5x12 mm 3 Setup 22 Na + 2 LYSO crystals in coincidences SensorsDigital SiPM (PDPC,Philips) InterfaceAir coupling (no grease) WrappingNone ToFPET: 411 ps FWHM 2) CTR using ToFPET and STiC ASICs, single crystals STiC: 388 ps FWHM 1) CTR LYSO standard vs Ca co-doped (fig. 1) Coincidence setup, crystals are ‘air-coupled’ to Hamamastu MPPCs  Improved results expected using optical glue and crystal wrapping 3) CTR using ToFPET and MPPC + crystal matrices 1) Geant4 detector model Geometry200 mm length 120 mm diameter Crystals2x2x12 mm 3 NECR T 2 / (T + f*R+ S) (fig. 2) Point source5M decays / activity point dE20% FWHM dT (crystal)180 ps sigma CTR600 ps FWHM Energy window(350-650) keV Fig. 2: NECR simulated data, f=1 Laboratory tests with 22 Na, ~2MBq  CTR = 482 ps FWHM Setup: 2 matrices of 4x4 crystals - ESR foil Crystal size: 2.1x2.1x12mm 3 Hamamatsu MPPC array 4x4, TSV Pixel size 50x50 µm 2, LC no trenches Sensor size 2x2 mm 2, pitch 2.2 mm System tests at Univ. of Zurich Hospital with FDG (see fig. 8)  measured CTR activity dependent CTR 672 ps FWHM at 0 MBq CTR 890 ps FWHM at 400 MBq Fig. 1: Newly installed Bruker 70/30 MR scanner at the Animal Imaging Center of ETH and University of Zurich at ETH-Hönggerberg campus. PET insert development: 3 steps Phase 1 (~1y) close to completion Components evaluation, i.e. crystals, crystal matrices, photo- sensors, front-end readout ASICs System design optimization using MC simulations (GEANT4) and Image Reconstruction (STIR) Phase 2 (~1y)-Construction of first ring system SRS1 -performance evaluation in real life application -Development of dedicated 4-D reconstruction software Phase 3 (~1y)- Construction of optimized full scanner based on SRS1 results Detector concept CrystalsLYSO, 8x8 arrays crystal orientationRadial coupling to photo sensorsone-to-one Sensors8x8 SiPM arrays, TSV Sensor gain stabilityActive control CoolingActive (Air, Freon) 1.0 mm 1.2 mm 4.0 mm 3.2 mm 2.4 mm 1.6 mm 3) Derenzo phantom (fig. 3) Activity500 MBq Duration1s BackgroundZERO ReconstructionOSMAPOSL (STIR) Fig. 3: Reconstructed Derenzo phantom Spheres down to 1.6 mm can be reconstructed Fig. 2: Artistic of the detector tube, half equipped, with components of realisitic dimensions. Serivces, are not drawn. Fig. 3: Agile LYSO 8x8 (left), Hamamatsu MPPC 4x4 (right) Readout electronics Amplification and Digitization on the detector ASIC developed for ToF applications STiC or ToFPET (64ch, CTR ~350 ps, low power, LVDS signal outputs (160/320) bit/s TransmissionOptical links (5-10) Gbit/s DAQuTCA based 2) Spatial resolution -Following NEMA -FORE re-binning -2DFBP Radial: ~1.5 mm Tangential: ~1.5mm Axial: ~(1-3) mm depending on ring difference Fig. 8: CRT vs activity Fig. 1: LYSO – LYSO:Ca, CTR comparison Fig. 2: CTR resolution, TOFPET ASICFig. 2: CTR resolution, STIC ASIC Fig. 3: MC simulation: spatial resolution