Comparison of air kerma-length product measurements between the PTB and the IAEA for x-radiation qualities used in computed tomography (EURAMET.RI(I)-S12, EURAMET project #1327)

Abstract

A comparison of air kerma-length product determinations for standard radiation qualities defined for use in computed tomography (CT) was performed between the PTB and the IAEA as EURAMET project #1327, registered in the KCDB as the EURAMET.RI(I)-S12 comparison. A pencil type reference-class ionization chamber of the IAEA and the three RQT beam qualities established according to the IEC standard 61627:2005 were selected for the comparison. The calibration coefficients for the transfer chamber in terms of Gycm/C at the PTB and the IAEA using the partial irradiation method recommended in the IAEA TRS 457 were determined. The results show the calibration coefficients of both laboratories were in a very good agreement of about 0.2 % well within the estimated relative standard uncertainty of the comparison of about 0.8 %. Residual correction due to the additional aperture required for partial irradiation of pencil chambers and feasibility of the full irradiation method were also studied.

Comparison of air kerma area product and air kerma meter calibrations for X-ray radiation qualities used in diagnostic radiology

“…It is expressed as the difference of the companion result and the respective CRV. When a number of radiation qualities and instruments are used in a comparison, the results are deduced for each quality and instrument, separately [2,3,4,17,20], as described in the previous sections.…”

“…A limitation of the weighted mean method is that there should be no correlations between laboratories. In this comparison, although such correlations existed, there were restricted to the physical constants being used by the PSDL and has limited influence to the calculation of the CRV and its uncertainties [17]. In order to further reduce such limitations, the methodologies proposed and applied by the CCRI(II) key comparison [14] and other statistical checks described in other parts of this repost, have been considered in this project .…”

“…BIPM.RI(I)-K2 and BIPM.RI(I)-K3, between MKEH and BIPM at low and medium CCRI therapy radiation qualities [18,19,20,21]. According to the BIPM and EURAMET database, only the EURAMET RI(I)-S10 has been reported, which is a bilateral supplementarysupporting comparison between IAEA and PTB [17,22], as well as the EURAMET 536 project which concerned mammography radiation qualities [2].  The transfer KAP meters used in this comparison were commercial instruments that read directly the P KA and they could not measure electric current; so any correlation of the measurement components between participating laboratories and PSDL or BIPM were not feasible.…”