[Intl_DxMedPhys] [EXTERNAL] Radiotoxicity testing

[Timmerman,Michael]

It looks like you are in Canada but I will share the regulatory requirements here in the US, which may be helpful.

The US NRC has a regulatory guide that covers bioassay for radioiodine. In most cases, I would only recommend bioassay if there is a suspected exposure, such as an I-131 capsule breaking open. The NRC considers capsules as sealed sources for the sake of bioassay requirements and the risk to staff is minimal if the capsule is not broken. I did work with a site in the past that administered liquid radioiodine to patients who could not swallow a capsule; however, the activities used (imaging procedures only) fell well below the NRC limits requiring bioassay. We are mainly concerned with people handling unsealed airborne/volatile radioiodine, which is not common in the medical setting nowadays; I-131 capsules, for example, are formulated to be way less volatile than they used to be. This is directly from the below regulatory guide: (3) Capsules (such as gelatin capsules given to patients for diagnostic tests) may be considered to contain the iodine in sealed form, and bioassay would not be necessary unless a capsule were inadvertently opened (e.g., dropped and crushed).

https://urldefense.com/v3/__https://www.nrc.gov/docs/ML1406/ML14064A060.pdf__;!!KGKeukY!1ESpz4uV1rSR-_UfmqcnZfq1ctWqRFluRtV2TYECbRPCzUbRVfWU0PKPV0a7wLnBRJHJwHVVuZ29WXVAVeF88buDF2Q2_9_cWuYSqsejQlLU0GFUMmslZb3S$ 

The US NRC also has regulations covering when internal monitoring is required and this is based on the annual limit on intake (ALI) for the radioisotope in question. Anyone likely to exceed 10% of the ALI must be monitored for internal occupational dose. It is extremely unlikely for a nuclear medicine technologist to exceed these levels unless something goes horribly awry during an administration (or several). For example, the ALI for Tc-99m is 80 mCi by oral ingestion or 200 mCi by inhalation. For Lu-177, we are looking at 2 mCi by oral ingestion or inhalation. Radioiodine limits are a lot lower (in the uCi range for I-125 and I-131) but again, the likelihood is very low when using capsules. We see “likely to exceed” a lot in NRC regulations, which requires us to make an educated decision on what “likely” means.

https://urldefense.com/v3/__https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1502.html__;!!KGKeukY!1ESpz4uV1rSR-_UfmqcnZfq1ctWqRFluRtV2TYECbRPCzUbRVfWU0PKPV0a7wLnBRJHJwHVVuZ29WXVAVeF88buDF2Q2_9_cWuYSqsejQlLU0GFUMokebqvS$ 

I’ve never needed to perform bioassays in my previous roles as RSO. It’s not impossible but I would guess it is rather unlikely nowadays. Interested if others have any thoughts on this topic as well.

Best,

Mike
________________________________________
Mike Timmerman, MS, DABR
Diagnostic Medical Physicist
Sanford Health – Sioux Falls Region
Mobile: (541) 213-1075
[Icon  Description automatically generated with medium confidence]

From: Intl_dxmedphys_wd_osu_list <intl_dxmedphys_wd_osu_list-bounces+michael.timmerman=sanfordhealth.org at lists.osu.edu> On Behalf Of Idris Elbakri via Intl_dxmedphys_wd_osu_list
Sent: Thursday, June 5, 2025 5:36 AM
To: intl_dxmedphys_wd_osu_list at lists.osu.edu
Subject: [EXTERNAL] [Intl_DxMedPhys] Radiotoxicity testing

Dear colleagues, I received an inquiry about radiotoxicity urine testing for nuc. medicine technologists. The question is if/when should those be required, if at all. As I am not a NM expert, I am reaching out to see if someone on this list

Dear colleagues,

I received an inquiry about radiotoxicity urine testing for nuc. medicine technologists. The question is if/when should those be required, if at all.

As I am not a NM expert, I am reaching out to see if someone on this list can provide some insights. Thanks in advance for your responses.

Idris

Dr. Idris Elbakri
CANQAP LTD
https://urldefense.com/v3/__http://www.canqap.com__;!!KGKeukY!1ESpz4uV1rSR-_UfmqcnZfq1ctWqRFluRtV2TYECbRPCzUbRVfWU0PKPV0a7wLnBRJHJwHVVuZ29WXVAVeF88buDF2Q2_9_cWuYSqsejQlLU0GFUMi8d-mLw$ <https://urldefense.com/v3/__http:/www.canqap.com__;!!KGKeukY!yTQkSO5dfACjQkULfShIlpIeyU23-Zc7UdMAflCNrEt8CTkIo-5R8uPFKXyYnDNyEtM5HyuzVH7vLXWOroD172Aa0Fx4ZyeZXjy0BQ$>




-----------------------------------------------------------------------
Confidentiality Notice: This e-mail message, including any attachments,
is for the sole use of the intended recipient(s) and may contain
privileged and confidential information. Any unauthorized review, use,
disclosure or distribution is prohibited. If you are not
the intended recipient, please contact the sender by reply e-mail and destroy
all copies of the original message.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.osu.edu/mailman/private/intl_dxmedphys_wd_osu_list/attachments/20250605/0d5a8161/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 13296 bytes
Desc: image001.png
URL: <https://lists.osu.edu/mailman/private/intl_dxmedphys_wd_osu_list/attachments/20250605/0d5a8161/attachment.png>