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A novel method for γ photons depth of interaction discrimination on monolithic LYSO crystals for brain PET/MRI

  • Roberto Pani1,
  • Marco Bettiol1Email author,
  • Enrico Preziosi2,
  • Christian Borrazzo3,
  • Rosanna Pellegrini1,
  • Antonio Gonzalez4,
  • Pablo Conde4,
  • Maria Nerina Cinti1,
  • Andrea Fabbri3,
  • Elisabetta Di Castro5 and
  • Stan Majewski6
EJNMMI Physics20152(Suppl 1):A11

Published: 18 May 2015


Computational MathematicTechnical PhysicMonte Carlo SimulationPositron AnnihilationEuropean Project

The MindView European Project pursues the development of a high efficiency and high resolution brain dedicated PET detector, simultaneously working with a Magnetic Resonance Imaging (MRI) system. Since the PET scanner is based on a small diameter ring and on thick monolithic scintillation crystals to assess high efficiency, the parallax error related to off-center positron annihilation is a critical issue. The Depth of Interaction (DoI) discrimination can reduce the blurring due to this phenomenon. In this work, we propose a novel DoI estimator, based on the ratio of the integral of scintillation light distribution to its maximum (named N/I). In a preliminary way, by means of Monte Carlo simulation, we have validated the correlation between this parameter and the DoI. Furthermore, we have experimentally tested the capability of such DoI estimator on a monolithic 20 mm-thick LYSO crystal optically coupled to a 12x12 silicon photomultipliers (SiPMs) array. Thanks to the proposed method, it is possible to select interaction events coming from different depths of the crystal. The DoI discrimination capability has been confirmed by using a collimated slanted pencil-beam: the proposed estimator allows to produce different images coming from events belonging to different depths of the crystal. From the experimental results a DoI discrimination resolution ranging from 4 mm to 6 mm has been obtained. The proposed method is expected to reduce the parallax error and, consequently, the width of lines of response coming from off- center positron annihilation of about 70% respect to the method without DoI discrimination.

Authors’ Affiliations

Department of Molecular Medicine, Sapienza University of Rome, Italy
Morphofunctional Sciences - Biophysics, Doctorate School of Biology and Molecular Medicine – Saimlal Department, Sapienza University of Rome, Italy
Post Graduate School of Medical Physics, Sapienza University of Rome, Rome, Italy
Institute for Instrumentation in Molecular Imaging, I3M-CSIC, Valencia, Spain
Department of Radiological Sciences, Oncology and Pathological, Sapienza University of Rome, Rome, Italy
West Virginia University, Morgantown, USA


© Pani et al; licensee Springer. 2015

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.