Cerenkov PET detector based on silicon photomultipliers

Consuegra Rodríguez, Dania (author), Korpar, Samo (mentor)

The use of Cherenkov light in positron emission tomography (PET) has the potential to improve the time-of-fight (TOF) resolution and reduce the cost of detectors. Lead fuoride (PbF2) has emerged as a highly performing radiator material suitable for TOF-PET application due to its excellent gamma stopping power and optical properties. Previous studies using coincidences between a small number of crystals have shown good performance in terms of coincidence time resolution (CTR). In this work, the feasibility of Cherenkov TOF-PET is studied in detail, extending the number of channels and optimizing the detectors for better performance. Simulations were used to study different detector geometries and PbF2 crystal optical surface treatments, up to a whole-body PbF2 TOF-PET scanner. The simulation data showed that the quality of reconstructed images obtained when using different Cherenkov TOF-PET scanner geometries is comparable to current state-of-theart scintillator scanners. Experiments with different detector confgurations were carried out to measure CTR and e ciency. The HRFlexTOT electronics enabled measurements of coincidences between two Cherenkov TOF-PET modules placed in a back-to-back confguration with up to 16 channels per module. Of particular interest is a multi-layer detector geometry, which improves the TOF resolution and reduces the parallax error without compromising the detection e ciency. With a multi-layer detector geometry, the CTR of the simulated whole-body PbF2 TOFPET scanner was 143 ps, out of which the fundamental limitation due to light production and transportation was only 22 ps. Experimentally, such CTR value could not yet be achieved due to the limited performance of silicon photomultiplier photodetectors currently available. With further development of the photodetectors and the readout electronics, Cherenkov TOF-PET could become a competitive reality in PET.

• Language: English
• Keywords: PET, Cherenkov, PbF2, TOF, CTR, SiPM.
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FMF - Faculty of Mathematics and Physics
• Year: 2022
• PID: 20.500.12556/RUL-142139
• COBISS.SI-ID: 128062723
• Publication date in RUL: 21.10.2022

Secondary language

• Language: Slovenian
• Title: Uporaba silicijevih fotopomnoževalk za zaznavanje fotonov Čerenkova pri pozitronski tomografji

Abstract

Uporaba svetlobe Čerenkova v pozitronski tomografiji (PET) omogoča izboljšanje ločljivosti meritve časa preleta (TOF) in znižanje cene detektorjev. Svinčev fuorid (PbF2) se je izkazal kot visoko zmogljiv sevalec Čerenkove svetlobe za uporabo v TOF-PET, zahvaljujoč njegovim odličnim optičnim lastnostim in moči ustavljanja žarkov gama. Pretekle študije z manjšim številom kristalov so potrdile, da je mogoče doseči odlično ločljivost meritve časa med koincidencami (CTR). V tem delu je podrobno preučena praktičnost Čerenkove pozitronske tomografije z meritvijo časa preleta (Čerenkova TOF-PET), s študijami, ki vključujejo večje število kanalov detektorja, in z optimizacijo detektorjev za boljšo zmogljivost. S pomočjo simulacij so bile raziskane različne geometrije detektorjev in površinske obdelave kristalov PbF2, vse do celotne naprave za Čerenkovo TOF-PET. Rezultati simulacij kažejo, da je kvaliteta slik, rekonstruiranih z različnimi geometrijami Čerenkov TOF-PET skenerjev, primerljiva s kvaliteto ki jo omogočajo trenutno najboljše scintilatorske naprave za TOF-PET. V eksperimentih z različnimi konfiguracijami detektorja sta bili izmerjeni CTR in učinkovitost zaznavanja. Posebej zanimiva je večplastna geometrija detektorja, ki omogoča izboljšanje časovne ločljivosti in zmanjšanje napake zaradi paralakse brez zmanjšanja učinkovitosti zaznavanja. Z večplastnim detektorjem je bila CTR simuliranega Čerenkov TOF-PET skenerja 143 ps, pri čemer je fundamentalna omejitev zaradi nastajanja fotonov in njihovega potovanja skozi kristal le 22 ps. Eksperimentalno tako dobre ločljivosti še ni mogoče doseči, zaradi omejene zmogljivosti uporabljenih fotodetektorjev, silicijevih fotopomnoževalk. Elektronika HRFlexTOT je omogočila meritve koincidenc med dvema moduloma za Čerenkovo TOF-PET, s 16 kanali na modul. Z nadaljnjim razvojem fotodetektorjev in elektronike bi Čerenkova TOF-PET lahko postala konkurenčna metoda za PET.

• Keywords: PET, Čerenkov, PbF2, TOF, CTR, SiPM.