Primary Standardisations and Traceability for Radioactivity supporting Nuclear Medicine John Keightley

Transcription

1 Primary Standardisations and Traceability for Radioactivity supporting Nuclear Medicine John Keightley RCTC, February 2014, NPL.

2 Introduction Primary Standards International Traceabilty Basics of the 4pb-g Coincidence Counting technique Recent standardisations Cu-64 Lu-177 Ra-223 (and Th-227) Future Standardisations

3 The Power of the Coincidence Method Snake Plissken and Clark Kent are in the back row at Anfield, and are counting the number of times Luis Suarez dives during the match. Using the fact that each of the observed dives is correlated to actual dives, they decide to combine their efforts, and also monitor the number of times they observe a blatant dive at the same time (in coincidence).

4 The Power of the Coincidence Method Snake Plissken and Clark Kent are in the back row at Anfield, and are counting the number of times Luis Suarez dives during the match. Dive! Using the fact that each of the observed dives is correlated to actual dives, they decide to combine their efforts, and also monitor the number of times they observe a blatant dive at the same time (in coincidence).

5 The Power of the Coincidence Method Snake Plissken and Clark Kent are in the back row at Anfield, and are counting the number of times luis Suarez dives during the match. Dive! Using the fact that each of the observed dives is correlated to actual dives, they decide to combine their efforts, and also monitor the number of times they observe a blatant dive at the same time (in coincidence).

6 The Power of the Coincidence Method Snake Plissken and Clark Kent are in the back row at Anfield, and are counting the number of times Luis Suarez dives during the match. Dive! Dive! Using the fact that each of the observed dives is correlated to actual dives, they decide to combine their efforts, and also monitor the number of times they observe a blatant dive at the same time (in coincidence).

7 The Power of the Coincidence Method Snake sees 12 dives in total N Snake N Clark sees 18 dives in total * NClark 12* Coincident Coincident 11 dives

8 The Power of the Coincidence Method Snake sees 12 dives in total N Snake N Clark sees 18 dives in total Coincident 11 dives * NClark 12* trueresult Coincident

9 The Power of the Coincidence Method Snake sees 12 dives in total N Snake N Clark sees 18 dives in total Coincident 11 dives * NClark 12* trueresult Coincident Efficiencies : % Snake Clark %

10 Basics of the 4pb-g coincidence method Count Rates N b = N N g = N o o b g b N c = N o b g g Efficiencies: b c/n g /N g c b Activity : N o = NN b N c g

11 Simplified Coincidence Equations b 1 b 2 for multiple beta branches : 1 N N a 1- r b 0 r br b r bcer bg r r 1 r 1 r N N a g 0 r g r r 1 r 1 1 N c N 0 ar b 1 r g - r b r c r r 1 r g 1 g 2 ce 2

12 Efficiency Extrapolation N N 1 - = N o 1 + f N b c N No as b g b c N g 1

13 Transfer of Primary Standards of Activity to NPL Secondary Standard Ionisation Chambers Primary Standard (MBq/g) Fidelis : traceable link to NPL s Primary Standards. Secondary Standard Ionisation Chamber (pa/g) Calibration Factor (pa/mbq) Factors at:

14 Cu-64 International Comparison

15 Cu-64 Equivalence Be et al ARI (70)

16 Lu-177 International Comparison Issues with Lu-177m impurity

17 Lu-177m IT 21.4% bce 100% Lu-177 Hf-177 Using available data ( T) 1.4 < b (Lu-177m) < 1.6 b- transitions (78.6%) b 78.6 % from b- Extra beta channel counts due to delayed level of half-life (1.09 s)

18 Ra-223

19 Ra-223 2p- counting Corrections to observed count rate: Background, dead-time, Divide calculated count-rate by approx 4.0: 100% (Ra-223) + 100% (Rn-219) + 100% (Po-215) + ( )% (Bi-211 and Po-211).

20 Ra-223 4p b -g counting Corrections to observed count rate: Background, dead-time, Divide calculated count-rate by approx 6.0:

21 Other nuclides : with difficulties for Coincidence Counting

22 Tc-99m

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24 I-131

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26 Traceability: Activity Measurements SIR

27 CCRI(II) KCWG John Keightley Senior Research Scientist : Radioactivity Group National Physical Laboratory, United Kingdom ICRM Life Sciences WG Meeting : PTB November 2012

28 NPL s Leading Role in Digital Coincidence Counting NPL pioneered the development of DCC, and I now chair: ICRM DCC Working Group BIPM CCRI(II) KCWG Work Package Leader: EMRP Metro-Fission WP7 DCC with up to 4 channels (TDCR) Sampling closer to detector (pre amp) Up to 1 GSPS ADC Sampling Rates

29 Mutual Recognition Arrangement The Metre Convention Diplomatic Treaty signed in 1875 Associate States and Economies of the CGPM CGPM General Conference of Weights and Measures Consists of delegates from Member States Governments of Member States CIPM International Committee of Weights and Measures Consists of 18 individuals elected by the CGPM. Supervises the BIPM and handles affairs of the Metre Convention International organisations Consultative Committees (CCs) Consists of representatives of NMIs and other experts. Act on technical matters and take important role in the CIPM MRA CIPM Mutual Recognition Arrangement (MRA) BIPM International Bureau of Weights and Measures National Metrology Institutes (NMIs) International centre for metrology, based in Paris.

30 Scheme for Key Comparisons

31 CCRI(II) KCWG REMIT Continuing support to the CCRI(II), the BIPM, and the RMOs in proposing and evaluating comparisons (including uncertainties) in radionuclide metrology, guidance in types of comparisons that may support laboratories claims on measurement capabilities, and providing advice to both the BIPM and the CCRI(II) on reports and results arising from the SIR and various other comparisons. The purpose of the KCWG(II) is to support and aid the CCRI(II) and BIPM in meeting obligations arising from the CIPM Mutual Recognition Arrangement, and to identify areas of radionuclide metrology that require further attention in the pursuit of improved standards, key comparison reference values and degrees of equivalence.

32 Activities The KCWG(II) meets at least annually, with individual members, either singly or in collaboration, taking forward the various items of the working group agenda. Correspondence by supplements these meetings. The KCWG(II) reports to the CCRI(II) on a periodic basis, including after each convened meeting of the working group and in advance of CCRI(II) meetings. The KCWG(II) maintains the master copy of the radionuclide Measurement Methods Matrix (MMM) and updates it (taking into account comparison results) with input from the WG, CCRI(II), and technical experts. Production of a Monographie on uncertainty budgets for radionuclide metrology (2013).

33 MMM

34 BIPM wishlist for Comparisons

35 10 year plan for comparisons