Nuklearmedizin 2020; 59(02): 129
DOI: 10.1055/s-0040-1708247
Wissenschaftliche Vorträge
Medizinische Physik
© Georg Thieme Verlag KG Stuttgart · New York

Towards the Development of a PET Detector based on TriMethyl Bismuth. Measurements of Free Ion Yield and Drift Charges in TetraMethyl Silane

B Gerke
1   University of Münster, European Institute for Molecular Imaging, Münster
,
SN Peters
2   Westfälische Wilhelms-Universität Münster, Institut für Kernphysik, Münster
,
K Bolwin
1   University of Münster, European Institute for Molecular Imaging, Münster
,
V Hannen
2   Westfälische Wilhelms-Universität Münster, Institut für Kernphysik, Münster
,
C Weinheimer
2   Westfälische Wilhelms-Universität Münster, Institut für Kernphysik, Münster
,
KP Schäfers
1   University of Münster, European Institute for Molecular Imaging, Münster
› Author Affiliations
Further Information

Publication History

Publication Date:
08 April 2020 (online)

Also available at
 
 

    Ziel/Aim Bold-PET is a drift detector using a heavy organometallic liquid - TriMethyl Bismuth (TMBi). TMBi is a transparent dielectric liquid. Because of the high atomic number (Z = 83) TMBi effectively converts 511 keV photons by the photo-electric effect (47 % photo fraction). These properties allow to build PET detectors with high spatial resolution.

    Methodik/Methods We built a plate ionization chamber manufactured from electropolished ultra-high-vacuum compatible components, consisting of two opposite plates.

    Prior to handle larger amounts of TMBi, first tests have been performed with the well-known liquid TMS. To determine the number of drift electrons following gamma interaction, current measurements were performed under the presence of a Cs-137.

    In order to enable spatial resolution inside the detector, pulses, i.e. the electrons caused by a photoelectric effect, must be measured individually.

    Ergebnisse/Results The experimental measurement using TMS showed an induced current in a range of 100~fA up to 200~fA after irradiation with the Cs-137 source with activity of A = 1.03MBq.

    The charges induced by the electrons by drift in the electric field are measured with a charge-sensitive preamplifier. The amplitude of charge induced depends on the number, velocity and distance travelled by the electrons in the electric field.

    Schlussfolgerungen/Conclusions In the current study, we have performed charge measurements in TMS induced by gamma radiation. The results demonstrate that smallest currents of the drifting charges in the range of a few femto amperes can be detected. Pulses generated by those drifting charges could be quantified, indicating the capability to perform energy measurements. Since TMBi has a higher photo fraction compared to TMS at 511 keV gamma energy, more electrons are expected from ionization which should results in even better detector performance.


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