Nuklearmedizin 2021; 60(02): 151-152
DOI: 10.1055/s-0041-1726743
WIS-Vortrag
Medizinische Physik

Methods to Improve the Timing Resolution of Positron Emission Tomography Systems

V Nadig
1   RWTH Aachen University, Physics of Molecular Imaging Systems, Aachen
,
S Gundacker
1   RWTH Aachen University, Physics of Molecular Imaging Systems, Aachen
,
M Profe
1   RWTH Aachen University, Physics of Molecular Imaging Systems, Aachen
,
H Radermacher
1   RWTH Aachen University, Physics of Molecular Imaging Systems, Aachen
,
Schug,
B Weissler
2   Department of Physics of Molecular Imaging Systems, RWTH Aachen University; Hyperion Hybrid Imaging Systems GmbH, Aachen
,
V Schulz
3   Department of Physics of Molecular Imaging Systems, RWTH Aachen University; Hyperion Hybrid Imaging Systems GmbH; Fraunhofer Institute for Digital Medicine MEVIS; Physics Institute IIIB, RWTH Aachen University, Aachen
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    Ziel/Aim Images from positron emission tomography (PET) systems require an excellent signal-to-noise ratio (SNR) allowing nuclear medicine physicians to precisely identify malignant tissue or pathogenic processes in cardiology or neurology. The SNR strongly depends on the coincidence timing resolution (CTR) of a PET system. Hence, pushing the CTR to its physically possible limit is key to improve the diagnostic value of a PET image.

    Methodik/Methods The readout electronics of a PET detector block have a large impact on the CTR. Different readout techniques are studied to quantify the limits imposed on the timing performance. The TOFPET2 ASIC (PETsys Electronics S.A.), which has been identified as a suitable candidate for system integration in prior studies, is used to provide a benchmark for the performance of a PET detector channel. Analog silicon photomultipliers (SiPMs; 4 mm x 4 mm, FBK) and doped lutetium-yttrium-oxyorthosilicate scintillator needles (LYSO:Ce,Ca; 3.5 mm and 19 mm height, Taiwan Applied Crystals) are used. To study the front-end electronics and their impact to the CTR more carefully, crystal and SiPM are connected to a separate high-frequency readout circuit.

    Ergebnisse/Results The investigated combination of SiPMs and LYSO:Ce,Ca crystals achieves CTRs down to 160 ps in coincidence experiments with a Na-22 point source, when read out by the TOFPET2 ASIC. The measured energy resolution is 10.8 %. With a 19 mm-high scintillator, CTRs of about 260 ps are measured. Employing a high-frequency readout circuit improves the CTR of the investigated configuration to about 100 ps (3.5 mm) and 200 ps (19 mm), respectively.

    Schlussfolgerungen/Conclusions High-frequency readout is a valuable tool to lower the CTR of a PET detector channel. As it is scalable, it is possible to transfer the technique applied in this study to PET system designs. To further improve the CTR, dedicated filter circuits could be used. Results on the combination of the high-frequency readout with the TOFPET2 ASIC will be presented at the conference.


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    Publication History

    Article published online:
    08 April 2021

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