The effect of attenuation map,scatter energy window width,and volume of interest on the calibration factor calculation in quantitative 177Lu SPECT imaging: Simulation and phantom study |
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| Institution: | 1. Institute of Radiation Protection, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany;2. Nuklearmedizinische Klinik und Poliklinik, Klinikum Rechts der Isar, Technische Universität München, 81675 Munich, Germany;3. Department of Electrical and Computer Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD 21218, United States;4. The Russell H Morgan Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, Baltimore, MD 21287, United States;5. Computer Faculty, Computer Aided Medical Procedures, Technische Universität München, Boltzmannstr. 3, 85748 Garching, Germany;6. Department of Nuclear Medicine, University Hospital of LMU Munich, Marchioninistr. 15, 81377 Munich, Germany;1. Medical Radiation Physics, Department of Physics, Stockholm University, Stockholm, Sweden;2. RaySearch Laboratories AB, Stockholm, Sweden;1. Exploratory Oncology Research and Clinical Trial Center, National Cancer Center, 277-8577 Chiba, Japan;2. Radiation Safety and Quality Assurance Division, Hospital East, National Cancer Center, 277-8577 Chiba, Japan;3. Department of Radiology, Saiseikai Yokohamashi Tobu Hospital, 230-8765 Kanagawa, Japan;4. Department of Radiological Technology, Kobe City Medical Center General Hospital, 650-0047 Hyogo, Japan;5. Department of Radiology, Itabashi Chuo Medical Center, 174-0051 Tokyo, Japan;6. Department of Radiation Oncology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, 113-8677 Tokyo, Japan;7. Department of Medical Technology, Japanese Red Cross Medical Center, 150-8935 Tokyo, Japan;8. Department of Radiology, Kitasato University Hospital, 252-0375 Kanagawa, Japan;9. Department of Radiation Oncology, Saitama Cancer Center, 362-0806 Saitama, Japan;10. Department of Radiology, Nagoya City University Hospital, 467-8602 Aichi, Japan;11. Department of Radiation Oncology, Shonan Kamakura General Hospital, 247-8533 Kanagawa, Japan;12. Department of Radiation Oncology, The National Cancer Center, 104-0045 Tokyo, Japan;13. Division of Medical Physics, Department of Information Technology and Medical Engineering, Human Health Sciences, Graduate School of Medicine, Kyoto University, 606-8507 Kyoto, Japan;14. Department of Radiology, Ogaki Tokushukai Hospital, 503-0015 Gifu, Japan;15. School of Health Sciences, Fujita Health University, 470-1192 Aichi, Japan;p. Department of Radiation Oncology, The Cancer Institute Hospital of Japanese Foundation of Cancer Research, 135-8550 Tokyo, Japan;q. Division of Radiation Oncology, Kanagawa Cancer Center, 241-0815 Kanagawa, Japan;r. Department of Radiation Oncology, Funabashi Municipal Medical Center, 273-8588 Chiba, Japan;1. Radiopharmaceutical Research and Development Lab (RRDL), Nuclear Science and Technology, Research Institute (NSTRI), P.O. Box 14395-836 Tehran, Iran;2. Research Institute for Nuclear Medicine, Tehran University of Medical Sciences, Tehran, Iran;1. Department of Oncology, Unit of Radiotherapy, Tampere University Hospital, POB-2000, 33521 Tampere, Finland;2. Department of Medical Physics, Medical Imaging Center, Tampere University Hospital, POB-2000, 33521 Tampere, Finland;3. Micropos Medical AB, Gothenburg, Sweden |
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| Abstract: | PurposeThe objective of this study was to evaluate the image degrading factors in quantitative 177Lu SPECT imaging when using both main gamma photopeak energies.MethodsPhantom measurements with two different vials containing various calibrated activities in air or water were performed to derive a mean calibration factor (CF) for large and small volumes of interest (VOIs). In addition, Monte Carlo simulations were utilized to investigate the effect of scatter energy window width, scatter correction method, such as effective scatter source estimation (ESSE) and triple energy window (TEW), and attenuation map on the quantification of 177Lu. Results: The measured mean CF using large and small VOIs in water was 4.50 ± 0.80 and 4.80 ± 0.72 cps MBq−1, respectively. Simulations showed a reference CF of 3.3 cps MBq−1 for the water-filled phantom considering all photons excluding scattered events. By using the attenuation map generated for 190 keV photons, the calculated CFs for 113 keV and 208 keV are 10% lower than by using the weighted mean energy of 175 keV for 177Lu. The calculated CF using the TEW correction was 17% higher than using the ESSE method for a water-filled phantom. However, our findings showed that an appropriate scatter window combination can reduce this difference between TEW and ESSE methods.ConclusionsThe present work implies that choosing a suitable width of scatter energy windows can reduce uncertainties in radioactivity quantification. It is suggested to generate the attenuation map at 113 keV and 208 keV, separately. Furthermore, using small VOIs is suggested in CF calculation. |
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| Keywords: | SPECT/CT Scatter window Scatter fraction Attenuation map Calibration factor |
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