Accurate 3D Positron Range Correction Method for Heterogeneous Material Densities in PET

medRxiv

Abstract

Abstract Objective The positron range is a fundamental, detector-independent physical limitation to special resolution in positron emission tomography (PET) as it causes a significant blurring of the reconstructed PET images. A major challenge for positron range correction methods is to provide accurate range kernels that inherently incorporate the generally inhomogeneous stopping power, especially at tissue boundaries. In this work, we propose a novel approach to generate accurate three-dimensional (3-D) blurring kernels both in homogenous and heterogeneous media to improve PET spatial resolution. Approach In the proposed approach, positron energy deposition was approximately tracked along straight paths, depending on the positron stopping power of the underlying material. The positron stopping power was derived from the attenuation coefficient of 511keV gamma photons according to the available PET attenuation maps. Thus, the history of energy deposition is taken into account within the range of kernels. Special emphasis was placed on facilitating the very fast computation of the positron annihilation probability in each voxel. Results Positron path distributions of 18 F in low-density polyurethane were in high agreement with Geant4 simulation at an annihilation probability larger than 10 −2 ∼10 −3 of the maximum annihilation probability. The Geant4 simulation was further validated with measured 18 F depth profiles in these polyurethane phantoms. The tissue boundary of water with cortical bone and lung was correctly modeled. Residual artifacts from the numerical computations were in the range of 1%. The calculated annihilation probability in voxels shows an overall difference of less than 20% compared to the Geant4 simulation. Significance The proposed method significantly improves spatial resolution for non-standard isotopes by providing accurate range kernels, even in the case of significant tissue inhomogeneities.

Authors 7

1. Chong Li corresponding

   Forschungszentrum Jülich · Chinese Academy of Sciences · Institute of High Energy Physics

   Affiliation as printed

   Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China

   Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany

2. Jürgen J Scheins

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany

3. Lutz Tellmann

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany

4. Ahlam Said Mohamad Issa Aachen Department of Neurology JARA–BRAIN–Translational Medicine

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Department of Neurology, RWTH Aachen University, Aachen, Germany

   Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany

   JARA—BRAIN—Translational Medicine, RWTH Aachen University, Aachen, Germany

5. Long Wei

   Chinese Academy of Sciences · Institute of High Energy Physics

   Affiliation as printed

   Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China

6. Nadim Jon Shah Aachen Department of Neurology JARA–BRAIN–Translational Medicine

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Department of Neurology, RWTH Aachen University, Aachen, Germany

   Institute of Neuroscience and Medicine, INM-11, Forschungszentrum GmbH, Jülich, Germany

   Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany

   JARA—BRAIN—Translational Medicine, RWTH Aachen University, Aachen, Germany

7. Christoph W. Lerche

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany