Monte-Carlo simulations with mathematical phantoms to investigate the effectiveness of a whole-body counter for thyroid measurement. (July 2020)

• Record Type: Journal Article
• Authors: Tani, Kotaro; Igarashi, Yu; Kim, Eunjoo; Iimoto, Takeshi; Kurihara, Osamu
• Is Part Of: Radiation measurements. Volume 135(2020:Apr.)
• Publication Date: 2020-07
• Subjects: Internal contamination -- 131I -- Thyroid measurement -- Whole-body counter; Nuclear emulsions -- Periodicals; Particle tracks (Nuclear physics) -- Periodicals; Thermoluminescence -- Periodicals; Cosmic rays -- Periodicals; Radiation -- Measurement -- Periodicals; Radiometry -- Periodicals; Radiation Monitoring -- Periodicals; Émulsions nucléaires -- Périodiques; Particules (Physique nucléaire) -- Traces -- Périodiques; Thermoluminescence -- Périodiques; Rayonnement cosmique -- Périodiques; Radiométrie -- Périodiques; 539.77
• DOI: 10.1016/j.radmeas.2020.106335
• Languages: English
• ISSNs: 1350-4487

Abstract

Abstract: FASTSCAN (Canberra, Meriden, CT, USA), a standing-type whole-body counter with upper and lower NaI(Tl) detectors, has been mostly used to determine local residents' level of internal contamination with 134/137 Cs following the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster in 2011. In the present study, we performed Monte-Carlo simulations with age-specific mathematical human phantoms to investigate the counting efficiencies of the FASTSCAN counter for 131 I thyroid measurements. As a result, although the lower detector had low sensitivity for 131 I in the thyroids of the adult and 15 y phantoms as well as the 10 y phantom standing on a 30-cm-high stool, the response of this detector may be used as an indicator of surface contamination overlooked on a subject. The total counting efficiency investigated in this study was 0.017–0.018 (cps/Bq) among all age groups. Based on this sensitivity, the determination level for thyroid activity could be calculated to be ~300 Bq under the slightly elevated background radiation level observed after the FDNPP disaster. Highlights: The present study investigated the counting efficiencies of the whole-body counter called FASTSCAN for 131 I thyroid measurements. The lower detector could provide a good indication of the presence of surface contamination for adult, 15 y and 10 y phantoms. It is necessary to assume that surface contamination can be overlooked occasionally in the elevated background radiation level in challenging emergency situations.