A Feasibility Study on the Use of Optical Fibers for the Transfer of Scintillation Light to Silicon Photomultipliers
ABSTRACT Integrated PET/MRI units with simultaneous acquisition capability are set to play an important role in studies of human breast and prostate imaging and brain function. However, to take advantage of existing MRI units in hospitals and institutions, minimally modified combined PET MRI is highly desirable. In addition, the current MRI trend is to utilize powerful body coils to transmit radio-frequency (RF) waves and local RF coils to receive signals. The authors propose a silicon photomultiplier (SiPM) PET equipped with optical fiber bundles that transfer photons from scintillation crystal to SiPM. To investigate the feasibility of SiPM PET using optical fiber bundles, the authors studied the performances of SiPM/scintillator couplings using single optical fibers and a fiber bundle. GEANT4 Monte-Carlo simulation was used to study scintillation photon transfer from scintillation crystals to the SiPM. This simulation showed that light loss, due to the bending of an optical fiber, is not significant for a fiber with a diameter of 2.0 mm and a bending radius of greater than 25 mm. To validate the GEANT4 Monte-Carlo simulation, several simple detectors were assembled and tested. Simulation results agreed reasonably well with experimental results. Two Hamamatsu multi-pixel photon counters (MPPCs) were tested using double clad optical fibers of 1.5 mm and 2.0 mm diameter, and 25 mm and 50 mm bending radius, respectively. When two MPPCs were directly attached to 2.0 × 2.0 × 10.0 mm3 LYSO crystals, a ~14% energy and a ~1.3 ns coincidence timing resolution were obtained at full width half maximum (FWHM). With one of the MPPCs attached to an optical fiber of 1.5 mm diameter, 50 mm bending radius, and length 300 mm, energy and coincidence timing resolutions were 27% and 2.2 ns, respectively. With an optical fiber bundle made of bare fibers with 1.5 mm diameter and length 100 mm, an ~ 26% energy resolution was obtained. Even though the Monte-Carlo simulat-
ion showed light loss was not significant for a single 90° turn of bending, the mechanical integrity of the optical fiber, especially the absence of cracks which can be caused by sharp bending, seemed to be a far more important constraint on sharp bending. These initial results are encouraging with respect to the use of combined SiPM PET using optical fibers.
- Journal- Korean Physical Society 04/2007; 50:1332. · 0.51 Impact Factor
Conference Proceeding: Performance evaluation of SiPM detectors for PET imaging in the presence of magnetic fields[show abstract] [hide abstract]
ABSTRACT: The multi-pixel photon counter (MPPC) or silicon photo-multiplier (SiPM), recently introduced as a solid-state photodetector, consists of an array of Geiger-mode photodiodes (microcells). It is a promising device for PET thanks to its potential for high photon detection efficiency (PDE) and immunity to high magnetic fields. It is also very easy to use, with simple electronic read-out, high gain and small size. In this work we evaluate the performance of three 1 × 1 mm<sup>2</sup> and one 6 × 6 mm<sup>2</sup> (2 × 2 array) SiPMs offered by Hamamatsu for their use in PET. We examine the dependence of the energy resolution and the gain of these devices on the thermal and reverse bias when coupled to LYSO scintillator crystals. We find that the 400 and 1600 microcells models and the 2 × 2 array are suitable for small size crystals, like those employed in high resolution small animal scanners. The good performance of these devices up to 7 Tesla has also been confirmed.Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
Conference Proceeding: Silicon photomultiplier as an alternative for APD in PET/MRI applications[show abstract] [hide abstract]
ABSTRACT: Growing interest in the development of multi pixel photon counters (MPPC), a solid state photodetector known as the silicon photomultiplier (SiPM), prompts the researchers to characterize their performance. The MPPC is a new type of photon-counting device made up of multiple avalanche photodiode (APD) pixels operating in Geiger mode. The aim of this work was to characterize the MPPC detectors, using a laser diode pulser and next the MPPC coupled to a 3×3×20 mm<sup>3</sup> LSO pixel crystal, in positron emission tomography (PET) combined with magnetic resonance (MRI) systems applications. The light yield, number of excited pixels and pulse height resolution has been determined. In scintillation tests the measurements covered a determination of the energy resolution, non-proportionality of the light yield and the time resolution for 511 keV annihilation quanta for both types of 3×3 mm<sup>2</sup> S10362-33-025C / 050C Hamamatsu MPPC detector, with 14400 and 3600 pixels respectively.Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008