A Detector Block-Pairwise Dead Time Correction Method for Improved Quantitation with a Dedicated BrainPET Scanner

medRxiv

Abstract

Abstract 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. 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. While 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 mGlu5R (metabotropic glutamate receptor subtype 5) antagonist [ 11 C]-ABP688, when comparing the time-activity curves (TACs) obtained with the global DTC with the block-pairwise DTC, relative differences in the anterior cingulate cortex (ACC) and the cerebellum of up to 25% were observed during the first 30 minutes of these measurements.

Authors 10

1. Ahlam Said Mohamad Issa corresponding Aachen Department of Neurology

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   Department of Neurology, RWTH Aachen University, Aachen, Germany

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

   JARA - BRAIN - Translational Medicine, Aachen, Germany

2. Jürgen J Scheins

   Forschungszentrum Jülich

   Affiliation as printed

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

3. Lutz Tellmann

   Forschungszentrum Jülich

   Affiliation as printed

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

4. Alejandro López-Montes

   Universidad Complutense de Madrid

   Affiliation as printed

   Nuclear Physics Group and IPARCOS, University: Complutense University of Madrid, Madrid, Spain

5. Joaquín L. Herraiz

   Universidad Complutense de Madrid

   Affiliation as printed

   Nuclear Physics Group and IPARCOS, University: Complutense University of Madrid, Madrid, Spain

6. Cláudia Régio Brambilla

   Forschungszentrum Jülich

   Affiliation as printed

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

7. Hans R Herzog

   Forschungszentrum Jülich

   Affiliation as printed

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

8. Irene Neuner Aachen Department of Psychiatry, Psychotherapy and Psychosomatics

   Forschungszentrum Jülich · RWTH Aachen University

   Affiliation as printed

   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

9. Nadim Jon Shah Aachen Department of Neurology

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   Department of Neurology, 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

10. Christoph W. Lerche

    Forschungszentrum Jülich

    Affiliation as printed

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