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Issa ASM, Scheins J, Tellmann L, Brambilla CR, Lohmann P, Rota-Kops E, Herzog H, Neuner I, Shah NJ, Lerche C. Impact of improved dead time correction on the quantification accuracy of a dedicated BrainPET scanner. PLoS One 2024; 19:e0296357. [PMID: 38578749 PMCID: PMC10997125 DOI: 10.1371/journal.pone.0296357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 12/11/2023] [Indexed: 04/07/2024] Open
Abstract
OBJECTIVE Quantitative values derived from PET brain images are of high interest for neuroscientific applications. Insufficient DT correction (DTC) can lead to a systematic bias of the output parameters obtained by a detailed analysis of the time activity curves (TACs). The DTC method currently used for the Siemens 3T MR BrainPET insert is global, i.e., differences in DT losses between detector blocks are not considered, leading to inaccurate DTC and, consequently, to inaccurate measurements masked by a bias. However, following careful evaluation with phantom measurements, a new block-pairwise DTC method has demonstrated a higher degree of accuracy compared to the global DTC method. APPROACH Differences between the global and the block-pairwise DTC method were studied in this work by applying several radioactive tracers. We evaluated the impact on [11C]ABP688, O-(2-[18F]fluoroethyl)-L-tyrosine (FET), and [15O]H2O TACs. RESULTS For [11C]ABP688, a relevant bias of between -0.0034 and -0.0053 ml/ (cm3 • min) was found in all studied brain regions for the volume of distribution (VT) when using the current global DTC method. For [18F]FET-PET, differences of up to 10% were observed in the tumor-to-brain ratio (TBRmax), these differences depend on the radial distance of the maximum from the PET isocenter. For [15O]H2O, differences between +4% and -7% were observed in the GM region. Average biases of -4.58%, -3.2%, and -1.2% for the regional cerebral blood flow (CBF (K1)), the rate constant k2, and the volume of distribution VT were observed, respectively. Conversely, in the white matter region, average biases of -4.9%, -7.0%, and 3.8% were observed for CBF (K1), k2, and VT, respectively. CONCLUSION The bias introduced by the global DTC method leads to an overestimation in the studied quantitative parameters for all applications compared to the block-pairwise method. SIGNIFICANCE The observed differences between the two DTC methods are particularly relevant for research applications in neuroscientific studies as they affect the accuracy of quantitative Brain PET images.
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Affiliation(s)
- Ahlam Said Mohamad Issa
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
- JARA, BRAIN, Translational Medicine, Aachen, Germany
- Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany
| | - Jürgen Scheins
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
| | - Lutz Tellmann
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
| | | | - Philipp Lohmann
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
| | - Elena Rota-Kops
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
| | - Hans Herzog
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
| | - Irene Neuner
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
- JARA, BRAIN, Translational Medicine, Aachen, Germany
- Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Aachen, Germany
| | - N. Jon Shah
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
- JARA, BRAIN, Translational Medicine, Aachen, Germany
- Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany
- Institute of Neuroscience and Medicine 11, INM-11, JARA, Forschungszentrum Jülich, Jülich, Germany
| | - Christoph Lerche
- Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
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Li C, Scheins J, Tellmann L, Issa A, Wei L, Shah NJ, Lerche C. Fast 3D kernel computation method for positron range correction in PET. Phys Med Biol 2023; 68. [PMID: 36595256 DOI: 10.1088/1361-6560/acaa84] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 12/09/2022] [Indexed: 12/13/2022]
Abstract
Objective. The positron range is a fundamental, detector-independent physical limitation to spatial resolution in positron emission tomography (PET) as it causes a significant blurring of underlying activity distribution in the reconstructed 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 (3D) 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 511 keV 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 of18F in low-density polyurethane were in high agreement with Geant4 simulation at an annihilation probability larger than 10-2∼ 10-3of the maximum annihilation probability. The Geant4 simulation was further validated with measured18F 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 is expected to significantly improve spatial resolution for non-standard isotopes by providing sufficiently accurate range kernels, even in the case of significant tissue inhomogeneities.
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Affiliation(s)
- Chong Li
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany.,Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Jürgen Scheins
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany
| | - Lutz Tellmann
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany
| | - Ahlam Issa
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany.,Department of Neurology, RWTH Aachen University, Aachen, Germany.,JARA-BRAIN-Translational Medicine, RWTH Aachen University, Aachen, Germany
| | - Long Wei
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - N Jon Shah
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany.,Institute of Neuroscience and Medicine, INM-11, Forschungszentrum GmbH, Jülich, Germany.,Department of Neurology, RWTH Aachen University, Aachen, Germany.,JARA-BRAIN-Translational Medicine, RWTH Aachen University, Aachen, Germany
| | - Christoph Lerche
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum GmbH, Jülich, Germany
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