21-25 June 2021
Clarion Congress Hotel Prague
Europe/Prague timezone
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Large Area SiPM Pixels for SPECT: from high energy astrophysics to medical imaging

Not scheduled
3rd floor (Clarion Congress Hotel Prague)

3rd floor

Clarion Congress Hotel Prague

Freyova 945/33, 190 00 Prague 9 - Vysočany
Oral presentation 11 Current Trends in Development of Radiation Detectors


GUBERMAN, Daniel (INFN Pisa)


The gamma camera is still employed in most Single Photon Emission Computed Tomography (SPECT) clinical scanners. In particular for large cameras it provides a balance between cost, reliability and performance that is hard to obtain for instance with modern CZT cameras. A standard gamma camera for full-body SPECT features a large area 50$\times$40~cm$^2$) scintillator coupled to an array of 50-100 photomultiplier tubes (PMTs) of 4-8 cm diameter. The camera is shielded by a thick layer of lead, turning it into a heavy and bulky system that can weight a few hundred kilograms. The volume, weight and cost of a camera could be significantly reduced if the PMTs are replaced by silicon photomultipliers (SiPMs). The main obstacle to use SiPMs in full-body SPECT is their limited physical size. A few thousand channels would be needed to fill a camera if using the largest commercially-available SiPMs of of 6$\times$6~mm$^2$. We propose to reduce the number of readout channels by using Large-Area SiPM Pixels (LASiPs), built by summing individual currents of several SiPMs into a single output. Our LASiPs employ the MUSIC, an ASIC designed for high-energy astrophysics, to perform the sum of the SiPM individual currents. We built a LASiP prototype with a sensitive area 8 times larger than a 6$\times$6~mm$^2$ SiPM and evaluated its performance in a proof-of-concept detector consisting of a 40$\times$40$\times$8~mm$^3$ NaI(Tl) crystal coupled to 4 LASiPs. We were able to reconstruct simple images with an intrinsic spatial resolution of $\sim2$~mm, achieving an energy resolution of $\sim11.6$\% at 140 keV. We also performed a detailed study on the SiPM noise and its impact on the performance of a SPECT camera, focusing on the additional noise introduced by the summing stage. We simulated the proof-of-concept detector with Geant4 and validated it with experimental data. Once validated, we simulated a larger camera with more and larger pixels, which we used to study how to optimize the pixel size, geometry and trigger settings of a full-body SPECT camera equipped with LASiPs. We present the results of such optimization, which sets the basis for a first compact full-body SPECT camera based on LASiPs.

Primary authors

GUBERMAN, Daniel (INFN Pisa) PAOLETTI, Riccardo (INFN Pisa and Siena University) RUGLIANCICH, Andrea (INFN Pisa) WUNDERLICH, Carolin (INFN Pisa and Siena University) PASSERI, Alessandro (Universita degli studi di Firenze)

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