Activity measurement of (68)Ge-(68)Ga by use of 4π(β(+)+γ) integral counting method

T Yamada; H Ishizu; Y Kawada; A Yunoki; S Yano

doi:10.1016/j.apradiso.2015.12.006

Activity measurement of (68)Ge-(68)Ga by use of 4π(β(+)+γ) integral counting method

Appl Radiat Isot. 2016 Mar:109:325-329. doi: 10.1016/j.apradiso.2015.12.006. Epub 2015 Dec 5.

Authors

T Yamada¹, H Ishizu², Y Kawada³, A Yunoki³, S Yano⁴

Affiliations

¹ Japan Radioisotope Association, 2-28-45, Hon-komagome, Bunkyo, Tokyo 113-8941, Japan. Electronic address: tyamada@jrias.or.jp.
² Japan Radioisotope Association, 2-28-45, Hon-komagome, Bunkyo, Tokyo 113-8941, Japan.
³ National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 2, 1-1-1 Umezono, Ttsukuba, Ibaraki 305-8568, Japan.
⁴ Japan Radioisotope Association, 2-28-45, Hon-komagome, Bunkyo, Tokyo 113-8941, Japan; RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.

PMID: 26701660
DOI: 10.1016/j.apradiso.2015.12.006

Abstract

A 4π(β(+)+γ) integral counting method using 4πβ-4πγ detector configuration composed of a large well type NaI(Tl) scintillation detector and stacked plastic scintillators positioned in the center of the well and coupled with a slender PMT was adopted for activity measurement of (68)Ge-(68)Ga. Several source preparation schemes were studied to reduce the activity loss due to volatility. The possible contribution of EC events were rejected with pulse-height discrimination. Owing to the high counting efficiencies in both channels and the multiplicity of photons and β-particles emitted, the 4π(β(+)+γ) integral counting system gives a count rate very nearly equal to the positron emission rate. The activity can be determined simply from this value divided by the positron emission branching ratio. The remaining overall inefficiency was evaluated by the EGS5 code.

Keywords: Absolute measurement; High efficiency detector; Plastic scintillator; Positron; Radioactivity; Standardization; Well-type detector.