The TT-PET Project
The Thin Time-Of-Flight Positron Emission Tomography (TT-PET) project (SNSF grant CRSII2_160808) aims at developing a pre-clinical TOF-PET scanner with very precise 3D spatial reconstruction, for ultimate use in an MRI scanner. The 3D measurement will be achieved by TOF measurement with 30ps time resolution, obtained by monolithic pixel silicon sensors in a Silicon-Germanium Bi-CMOS process. The chip we are designing with the colleagues of Rome Tor Vergata will have the world best timing performance for a monolithic silicon pixel sensor and a very low power-consumption.
The scanner (a CAD design shown in the left-figure below) will be composed of 16 towers of 250µm thickness, each containing 60 layers of photon converter, monolithic pixel silicon sensor and front-end electronics. The dense layered structures and the monolithic integration of the detector provide a photon detection granularity of 500x500x250µm3. The mechanics has been designed and is being produced by the LHEP-Bern and the DPNC. The readout system by LHEP-Bern.
The PET scanner, comprising more than 1.5 million readout channels on 1920 chips, will be synchronised with 10 ps precision with an innovative technique, purposely developed for this project.
This detector, with its very high granularity, low power consumption and the excellent 30-ps time resolution, will allow implementing new reconstruction algorithms. The TT-PET group at the DPNC and HUG-ITMI of the University of Geneva are studying the performance of these algorithms with a full-physics simulation.
The figure above (right) shows the reconstruction of a simulated Derenzo phantom. The geometry consists of an acrylic cylinder with a radius of 15 cm, placed in the center of the scanner. A 50 MBq 18F source is distributed in six sets of holes, 4 cm deep, with diameters 0.5 mm, 0.7 mm, 1 mm, 1.2 mm, 1.5 mm, 2 mm respectively. The image reconstruction has been performed by using a Filtered Back Projection algorithm combined with the time of flight information. The dimension of the pixel is 100 x 100 µm2.
In a first testbeam measurement performed at the CERN SPS with our SiGe low-noise amplifier realised with discrete components, we measured a time resolution of 106 ps for minimum-ionizing particles, dominated by the silicon sensor. The results are published in JINST 11 (2016) P03011.
A small ASIC prototype, designed by the TT-PET group at the Universities of Geneva and Rome Tor Vergata, has been produced, JINST 13 (2018) P02015 as well as a demonstrator made by a 3x10 matrix of final size pixels and full features (arXiv::1811.10246 ). The figures below show the layout and a picture of the demonstrator.
Top: Layout of the first SiGe Bi-CMOS monolithic detector prototype, designed by the DPNC and Rome groups. BOTTOM: Microscope image of the actual chip.
Few demonstrator chips were tested in lab and at the CERN SPS beam line with minimum-ionising particles. The results, reported in arxiv:1811.11114, show efficiencies above 99.98% and resolutions down to 110ps. The two figures below show the efficiency and the time resolutions of the pixels operated at the testbeam.
TT-PET Group at the DPNC and at the HUG/ITMI of the University of Geneva:
Giuseppe Iacobucci, Osman Ratib, Marzio Nessi, Lorenzo Paolozzi, Dr. Emanuele Ripiccini, Pierpaolo Valerio, Franck Cadoux, Sébastien Michal, Yannick Favre, Stephane Debieux, Daiki Hayakawa, Daniele Vitturini
- LHEP, University of Bern
- INFN of Rome Tor Vergata
- Stanford University
- IHP Microelectronics
A monolithic ASIC demonstrator for the Thin Time-of-Flight PET scanner
Valerio P. et al.
submitted to JINST (2018) [arXiv]
Characterization of the demonstrator of the fast silicon monolithic ASIC for the TT-PET project
Paolozzi L. et al.
Submitted to JINST (2018) [arXiv]
Module concept and thermal studies of the silicon-based TT-PET small-animal scanner,
Ferrere D. et al.
submitted to JINST (2018) [arXiv]
E. Ripiccini et al., “Expected performance of the TT-PET scanner,” https://arxiv.org/abs/1811.12381, 2018.
Ripiccini E. et al.
Test beam measurement of the first prototype of the fast silicon pixel monolithic detector for the TT-PET project
L. PAOLOZZI et al.
JINST 13 (P04015) (2018) [arXiv]
100 ps time resolution with thin silicon pixel detectors and a SiGe HBT amplifier
M. BENOIT et al.
JINST 11 P03011 (2016) [arXiv]