[Intl_DxMedPhys] X-ray Meter Calibration Overseas

[Little, Kevin]

Raysafe has this explanation of how their German/European PTB traceability is equivalent to NIST:
https://urldefense.com/v3/__https://www.raysafe.com/sites/default/files/22885_452_PTB_NIST_Flyer.pdf__;!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-ywZfdOM$ 

Raysafe’s general conclusion is that both NIST and PTB have signed the International Committee for Weights and Measures (CIPM) Mutual Recognition Arrangement (https://urldefense.com/v3/__https://www.bipm.org/en/cipm-mra__;!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-USJtgfA$ ). According to the website for this arrangement, “The CIPM Mutual Recognition Arrangement (CIPM MRA) is the framework through which National Metrology Institutes demonstrate the international equivalence of their measurement standards and the calibration and measurement certificates they issue.” Both NIST and PTB participate in this MRA: https://urldefense.com/v3/__https://www.bipm.org/en/cipm-mra/participation__;!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-vQ9NXf4$ , https://urldefense.com/v3/__https://www.nist.gov/calibrations/cipm-mutual-recognition-arrangement__;!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-VLvlU44$ . Both have been approved within the CIPM MRA for air kerma<https://urldefense.com/v3/__https://www.bipm.org/kcdb/cmc/search?domain=RADIATION&areaId=9&keywords=x-ray&specificPart.branch=32&specificPart.quantity=6&specificPart.medium=-1&specificPart.source=-1&specificPart.nuclide=&_countries=1&countries=21&countries=77&publicDateFrom=&publicDateTo=&unit=-1&minValue=&maxValue=&minUncertainty=&maxUncertainty=__;!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-DZDT4cM$ >. NIST and PTB also published a direct comparison for mammography in 2009: https://urldefense.com/v3/__https://pmc.ncbi.nlm.nih.gov/articles/PMC4646528/__;!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-25YDAQ4$ .

NIST says traceability to another National Metrology Institute (NMI) doesn’t automatically mean something is NIST-traceable (https://urldefense.com/v3/__https://www.nist.gov/metrology/metrological-traceability*:*:text=5.5.2__;I34!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-C0BH4Uo$ ), but “users of measurement results, who may be either commercial or regulatory entities, may well decide that sufficient evidence exists under the MRA to provide mutually acceptable traceability of these results to the standards and measurements of two or more participating NMIs.”

So, I agree that it might be nice to get an “official” recognition of Raysafe’s logic from the MQSA hotline.

Kevin Little
Ohio State University



From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces at lists.osu.edu> On Behalf Of Bob Kobistek via Intl_dxmedphys_wd_osu_list
Sent: Monday, December 8, 2025 11:44 AM
To: Michael Urgo <murgo571 at verizon.net>; intl_dxmedphys_wd_osu_list at lists.osu.edu
Subject: Re: [Intl_DxMedPhys] X-ray Meter Calibration Overseas

You might want to contact the MQSA hotline and inquire about this. Doing so could motivate the FDA to create an alternative standard. There’s no practical reason why traceability to a European standard agency would not be acceptable. Robert
You might want to contact the MQSA hotline and inquire about this. Doing so could motivate the FDA to create an alternative standard. There’s no practical reason why traceability to a European standard agency would not be acceptable.


Robert J. Kobistek, MS, FACR, DABR, MRSE(MRSC™)
Medical Physicist
RJK Medical Physics, Inc.
440-463-7879

From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+bob=rjkmedphys.com at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list-bounces+bob=rjkmedphys.com at lists.osu.edu>> On Behalf Of Michael Urgo via Intl_dxmedphys_wd_osu_list
Sent: Friday, December 5, 2025 7:24 AM
To: intl_dxmedphys_wd_osu_list at lists.osu.edu<mailto:intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: [Intl_DxMedPhys] X-ray Meter Calibration Overseas

Happy Friday. I was thinking about this in reference to overseas calibration. I checked the MQSA (CFR 21 part 900) regs again, and they are very specific about a NIST traceable calibration lab. See attached screenshots for national standard
Happy Friday.  I was thinking about this in reference to overseas calibration.  I checked the MQSA (CFR 21 part 900) regs again, and they are very specific about a NIST traceable calibration lab.  See attached screenshots for national standard calibration and definition.  Does anyone know if any overseas labs participates with NIST?  Of course the calibration certificate lists their national standard.  Thanks for any info you can provide.   Donna Davis-Urgo
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