A detector block-pairwise dead time correction method for improved quantitation with a dedicated BrainPET scanner
Physics in Medicine and Biology, vol. 67, pp. 235004
Abstract
Abstract ‘ Objective . Dead time correction (DTC) is an important factor in ensuring accurate quantification in PET measurements. This is currently often achieved using a global DTC method, i.e., an average DTC factor is computed. For PET scanners designed to image dedicated organs, e.g., those used in brain imaging or positron emission mammography (PEM), a substantial amount of the administered radioactivity is located outside of the PET field-of-view (FOV). This activity contributes to the dead time (DT) of the scintillation detectors. Moreover, the count rates of the individual scintillation detectors are potentially very inhomogeneous due to the specific irradiation of each detector, especially for combined MR/PET systems, where radiation shields cannot be applied. Approach: We have developed a block-pairwise DTC method for our Siemens 3T MR BrainPET insert by extending a previously published method that uses the delayed random coincidence count rate to estimate the DT in the individual scans and planes (i.e., scintillation pixel rings). The method was validated in decay experiments using phantoms with a homogenous activity concentration and with and without out-of-FOV activity. Based on a three-compartment phantom, we compared the accuracy and noise properties of the block-pairwise DTC and the global DTC method. Main results . The currently used global DTC led to a substantial positive bias in regions with high activity; the block-pairwise DTC resulted in substantially less bias. The noise level for the block-pairwise DTC was comparable to the global DTC and image reconstructions without any DTC. Finally, we tested the block-pairwise DTC with a data set obtained from volunteer measurements using the mGluR5 (metabotropic glutamate receptor subtype 5) antagonist [ 11 C]ABP688. When the relative differences in activity concentrations obtained with global DTC and block-pairwise DTC for the ACC and the cerebellum GM were compared, the ratios differed by a factor of up to 1.4 at the beginning—when the first injection is administered as a bolus with high radioactivity. Significance . In this work, global DTC was shown to have the potential to introduce quantification bias, while better quantitation accuracy was achieved with the presented block-pairwise DTC method. The method can be implemented in all systems that use the delayed window technique and is particulary expected to improve the quantiation accuracy of dedicated brain PET scanners due to their geometry.’
Authors 10
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Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University
Affiliation as printed
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich,
JARA - BRAIN-Translational Medicine, Aachen,
RWTH Aachen University
Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
JARA - BRAIN-Translational Medicine, Aachen, Germany
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Jürgen J Scheins corresponding
Affiliation as printed
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich,
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
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Lutz Tellmann corresponding
Affiliation as printed
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich,
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
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Alejandro López-Montes corresponding
Universidad Complutense de Madrid
Affiliation as printed
University: Complutense University of Madrid
Nuclear Physics Group and IPARCOS, University: Complutense University of Madrid, Madrid, Spain
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Joaquín L. Herraiz corresponding
Universidad Complutense de Madrid
Affiliation as printed
University: Complutense University of Madrid
Nuclear Physics Group and IPARCOS, University: Complutense University of Madrid, Madrid, Spain
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Cláudia Régio Brambilla corresponding
Affiliation as printed
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich,
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
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Hans R Herzog corresponding
Affiliation as printed
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich,
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
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Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University
Affiliation as printed
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich,
JARA - BRAIN-Translational Medicine, Aachen,
RWTH Aachen University
Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Aachen, Germany
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
JARA - BRAIN-Translational Medicine, Aachen, Germany
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Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University
Affiliation as printed
Institute of Neuroscience and Medicine 11, INM-11, JARA, Forschungszentrum Jülich,
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich,
JARA - BRAIN-Translational Medicine, Aachen,
RWTH Aachen University
Department of Neurology, Faculty of Medicine, RWTH Aachen University, Aachen, Germany
Institute of Neuroscience and Medicine 11, INM-11, JARA, Forschungszentrum Jülich, Germany
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
JARA - BRAIN-Translational Medicine, Aachen, Germany
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Christoph W. Lerche corresponding
Affiliation as printed
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich,
Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum Jülich, Jülich, Germany
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