Experimental activation assessment of open-type yoke in a PET cyclotron by non-destructive/destructive γ-ray measurement approaches.

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Τίτλος:	Experimental activation assessment of open-type yoke in a PET cyclotron by non-destructive/destructive γ-ray measurement approaches.
Συγγραφείς:	Yoshida G; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan., Matsumura H; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan., Toyoda A; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan., Nakamura H; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan., Masumoto K; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan., Miura T; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan., Watanabe E; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan., Tsugane K; High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan., Saito K; Sumitomo Heavy Industries, Ltd., Tokyo, Shinagawa-ku, Japan., Koumura I; Sumitomo Heavy Industries, Ltd., Tokyo, Shinagawa-ku, Japan., Uno H; Sumitomo Heavy Industries, Ltd., Tokyo, Shinagawa-ku, Japan., Kozaki M; SHI-ATEX Co., Ltd., Saijo, Ehime, Japan., Yamamoto A; SHI-ATEX Co., Ltd., Saijo, Ehime, Japan., Toyohara J; Tokyo Metropolitan Institute for Geriatrics and Gerontology, Tokyo, Itabashi-ku, Japan., Wagatsuma K; Tokyo Metropolitan Institute for Geriatrics and Gerontology, Tokyo, Itabashi-ku, Japan.; Hokkaido University, Sapporo, Hokkaido, Japan.
Πηγή:	Medical physics [Med Phys] 2026 Sep; Vol. 53 (9), pp. e70649.
Τύπος έκδοσης:	Journal Article
Γλώσσα:	English
Στοιχεία περιοδικού:	Publisher: John Wiley and Sons, Inc Country of Publication: United States NLM ID: 0425746 Publication Model: Print Cited Medium: Internet ISSN: 2473-4209 (Electronic) Linking ISSN: 00942405 NLM ISO Abbreviation: Med Phys Subsets: MEDLINE
Imprint Name(s):	Publication: 2017- : Hoboken, NJ : John Wiley and Sons, Inc. Original Publication: Lancaster, Pa., Published for the American Assn. of Physicists in Medicine by the American Institute of Physics.
Ιατρικοί όροι (MeSH):	Positron-Emission Tomography/instrumentation , Cyclotrons , Gamma Rays*, Cobalt Radioisotopes
Περίληψη:	Background: During decommissioning of positron emission tomography (PET) cyclotron facilities, metallic components-including the iron yoke-are typically classified as radioactive waste, incurring substantial disposal costs. In contrast to concrete, standardized decommissioning procedures for metallic components have not yet been established. Purpose: This study aimed to experimentally assess activation in a PET cyclotron and provide fundamental data for establishing decommissioning guidelines for metallic components. The investigation focused on residual activity in the yoke and center pole, which are among the heaviest structural parts. Methods: A PET cyclotron that operated for 23 years at the Tokyo Metropolitan Institute for Geriatrics and Gerontology was examined 6 years after the cyclotron's complete shutdown using two complementary approaches: non-destructive γ-ray measurements and destructive core-boring analysis. Results: ⁶⁰Co was the predominant residual radionuclide. On the outer surfaces, ⁶⁰Co specific activity typically ranged from 0.02 to 0.10 Bq/g, with many locations below the 0.1 Bq/g clearance level. Cross-sectional mapping showed exponential attenuation behavior from the interior outward. Higher activation in the center pole (up to ∼1.0 Bq/g) was observed. ⁵⁴Mn was one to two orders of magnitude lower than ⁶⁰Co at 6 years post-shutdown. Non-destructive and destructive results were in close agreement, validating the quantitative use of γ-detectors for near-surface activity. A hypothetical time-dependent decay estimation, based on the non-destructive/destructive findings, was performed to project a required cooling period to meet clearance. Conclusions: Activation levels in PET cyclotron components can be effectively assessed using combined non-destructive and destructive approaches. The complex distribution of residual activity was observed in the yoke and center poles. Decay projections indicated that approximately half of the yoke would fall below the clearance level within 15 years and nearly all components within 23 years after shutdown. These findings provide essential benchmarks for improving simulation-based activation modeling and can be broadly applied to similar PET cyclotron systems. (© 2026 The Author(s). Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)
References:	Ann ICRP. 2008;38(3):7-96. (PMID: 19285593) Med Phys. 2019 May;46(5):2457-2467. (PMID: 30870578) Appl Radiat Isot. 2021 Feb;168:109446. (PMID: 33358068) Ann ICRP. 1996;26(3-4):1-205. (PMID: 9105539)
Grant Information:	Sumitomo Heavy Industries, Ltd; JPJ007057 Radiation Safety Research Promotion Fund
Contributed Indexing:	Keywords: activation; cyclotron; non‐destructive measurement; positron emission tomography; radioactive waste
Substance Nomenclature:	0 (Cobalt Radioisotopes)
Entry Date(s):	Date Created: 20260825 Date Completed: 20260825 Latest Revision: 20260827
Update Code:	20260827
PubMed Central ID:	PMC13504305
DOI:	10.1002/mp.70649
PMID:	42638460
Βάση Δεδομένων:	MEDLINE

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Περιγραφή
ISSN:	2473-4209
DOI:	10.1002/mp.70649