[Intl_DxMedPhys] X-ray Meter Calibration Overseas

[Robert Morrison]

When I ran RTI Inc located in NJ through 2017 and while I was there until the end of 2018, both the cal lab in Sweden and in NJ had MQSA certified calibrations.  This meant that we had to request a chamber from NIST and had to calibrate it and then send it back to NIST.  We could request the type of chamber and beam qualities that we were going to calibrate (Radcal 6M or Keithley 15cc). Then NIST upon receiving the chamber back would recalibrate the chamber and the cal factor for that chamber for that beam quality had to be within 2% and we were always a fraction of a percent different.  The same was for the factory in Gothenburg for new units coming from the factory which would be used for MQSA measurements for new units sold in the US.  We had to do that every 2 years to be compliant with MQSA for a calibration lab.  At the time Frank Cerra at NIST was the one that told us that we had to do that in order to be compliant.  I am sure Frank has long since retired.  I found the following words here off of this site, https://urldefense.com/v3/__https://www.ecfr.gov/current/title-21/chapter-I/subchapter-I/part-900/subpart-B/section-900.12__;!!KGKeukY!zhFl1Q4teqa97tj5s4JNHq8Q3Gc5IdHrVZ6_K5QTdiZwnDU4XOZBwkQhFRReg4aZE6je9mSi4wuP20Kbhe07nGcpNuiwGdI0CjS4RGj9w8gb$ 

Calibration of air kerma measuring instruments. Instruments used by medical physicists in their annual survey to measure the air kerma or air kerma rate from a mammography unit shall be calibrated at least once every 2 years and each time the instrument is repaired. The instrument calibration must be traceable to a national standard and calibrated with an accuracy of ±6 percent (95 percent confidence level) in the mammography energy range.

We actually sent all of our reference chambers to PTB in Germany for all our reference calibrations every two years.  That included all of our radiographic beam qualities as well as the mammographic beam qualities.  For our reference chambers, we used Radcal reference 6M chambers.  The benefit of sending our reference chambers to PTB was the array of calibration beam qualities that they had along with the cost.  It was much less expensive than NIST and they had beam qualities that NIST did not have and of course it is a primary lab.  I am assuming that RTI still follows this practice and I am sure if you wanted to confirm that you could contact them.

It was mandatory for any lab to be MQSA compliant and certified that they had to comply with getting a chamber from NIST as I noted.  The cost of this was $2k if my memory is correct.

Yes, all the beam qualities are traceable to each of the primary labs.  They have to do inter lab comparisons and especially if you follow ISO 17025.  As you can see from what I have written above, the beam qualities had to be compatible.  However they required for MQSA measurements we had to get the chamber from NIST.

You could also follow up with NIST to see if this is still a requirement for a lab that calibrates detectors for use in mammography to be MQSA compliant that they have to follow this routine.

Here is a link for all of PTB's beam qualities https://urldefense.com/v3/__Https://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_6/6.2/6.25/ptb_rad_qual_2015_01_07.pdf__;!!KGKeukY!zhFl1Q4teqa97tj5s4JNHq8Q3Gc5IdHrVZ6_K5QTdiZwnDU4XOZBwkQhFRReg4aZE6je9mSi4wuP20Kbhe07nGcpNuiwGdI0CjS4RBMg2ybz$ 

I hope that this info is helpful to you.

Rob Morrison

________________________________
From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+robpmorrison=gmail.com at lists.osu.edu> on behalf of Little, Kevin via Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Sent: Monday, December 8, 2025 14:28
To: Bob Kobistek <bob at rjkmedphys.com>; Michael Urgo <murgo571 at verizon.net>; intl_dxmedphys_wd_osu_list at lists.osu.edu <intl_dxmedphys_wd_osu_list at lists.osu.edu>
Subject: Re: [Intl_DxMedPhys] X-ray Meter Calibration Overseas


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!zhFl1Q4teqa97tj5s4JNHq8Q3Gc5IdHrVZ6_K5QTdiZwnDU4XOZBwkQhFRReg4aZE6je9mSi4wuP20Kbhe07nGcpNuiwGdI0CjS4RGJ6Kzm_$ <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!zhFl1Q4teqa97tj5s4JNHq8Q3Gc5IdHrVZ6_K5QTdiZwnDU4XOZBwkQhFRReg4aZE6je9mSi4wuP20Kbhe07nGcpNuiwGdI0CjS4RMmycirg$ <https://urldefense.com/v3/__https://www.bipm.org/en/cipm-mra__;!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-USJtgfA$>). According to the website for this arrangement, “The CIPM Mutual Recognition Arrangement (CIPM MRA) is the framework through which National Metrology Institutes demonstrate the international equivalence of their measurement standards and the calibration and measurement certificates they issue.” Both NIST and PTB participate in this MRA: https://urldefense.com/v3/__https://www.bipm.org/en/cipm-mra/participation__;!!KGKeukY!zhFl1Q4teqa97tj5s4JNHq8Q3Gc5IdHrVZ6_K5QTdiZwnDU4XOZBwkQhFRReg4aZE6je9mSi4wuP20Kbhe07nGcpNuiwGdI0CjS4RFdmH25b$ <https://urldefense.com/v3/__https://www.bipm.org/en/cipm-mra/participation__;!!KGKeukY!wKUIZCe4jZcxYSOFQAtTMlSiz1FK5eVwqzk15Z1adZ_cOu0kW6AFhWIWKLVpWtoOn5aC7vZZpiymekHwFyP_XPaD-gpnfmOHsAKbriu-vQ9NXf4$>, https://urldefense.com/v3/__https://www.nist.gov/calibrations/cipm-mutual-recognition-arrangement__;!!KGKeukY!zhFl1Q4teqa97tj5s4JNHq8Q3Gc5IdHrVZ6_K5QTdiZwnDU4XOZBwkQhFRReg4aZE6je9mSi4wuP20Kbhe07nGcpNuiwGdI0CjS4RB8mv_21$ <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!zhFl1Q4teqa97tj5s4JNHq8Q3Gc5IdHrVZ6_K5QTdiZwnDU4XOZBwkQhFRReg4aZE6je9mSi4wuP20Kbhe07nGcpNuiwGdI0CjS4RHXGhtwg$ <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!zhFl1Q4teqa97tj5s4JNHq8Q3Gc5IdHrVZ6_K5QTdiZwnDU4XOZBwkQhFRReg4aZE6je9mSi4wuP20Kbhe07nGcpNuiwGdI0CjS4RIBXMSZR$ <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
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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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