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A Silicon Photomultiplier based novel detector concept for combined PET/MR

¹ Nuclear Medicine, Klinikum rechts der Isar; ² Physics Department E18, TU München, Munich, Germany

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Objectives: Silicon Photomultipliers (SiPMs) are solid state photodetectors whose excellent gain and timing are advantageous for high resolution PET imaging. Their insensitivity to magnetic fields and their minimum noise pickup are appropriate for simultaneous PET/MR. We propose a simplified PET detector concept as insert in the FOV of an MR scanner.

Methods: SiPMs consist of an array of Geiger APDs (cells). Energy information is extracted by the sum of the output pulses of all the cells. Devices of 1 mm² area (400/1600 cells, Hamamatsu Photonics) and of 3 mm² area (3600 cells, SensL) have been evaluated. LYSO crystals of different sizes were coupled to the photodetectors and the feasibility of using PET detectors with 1 mm crystal pixel and 1-to-1 coupling to the SiPMs was investigated. Energy/timing resolution and non-linear behaviour were measured and compared to results from optical simulations. Amplifying electronics was eliminated and data were acquired by means of sampling ADCs.

Results: Energy resolution of 18-20% and 1.3 ns timing resolution (FWHM) were measured. These values did not degrade during a simultaneous MR acquisition. Planar imaging with an assembled 2x2 array was realized. The design and construction of detector arrays with individual crystal coupling is currently in progress.

Conclusions: SiPMs is a promising alternative to APDs demonstrating competitive performance especially when used for multimodality imaging. New developments in SiPM design involving a larger cell density may overcome current limitations in dynamic range and are expected to facilitate a PET detector design based on individual crystal read out with 1 mm pixel size.

Research Support: Supported in part by grants from DFG and BFS.

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Spanoudaki, V. Articles by Ziegler, S. PubMed Articles by Spanoudaki, V. Articles by Ziegler, S.