Certification Exam - Student Questions

Okay here's one... regulations are not my strong point but since we have a Corporate Radiation Safety Office (CRSO), who gets on everyone's case, they generally have a good grasp on the regulations.

Q1.

1)  Can you clarify what exactly is the difference between thyroid monitoring, thyroid screening and thyroid bioassay for nuclear medicine workers handling radioactive iodine?  I thought they were all pretty much the same thing but it seems like the CNSC considers them three different things. 

2)  There are a few different documents that have some conflicting information on them about how much radioactive iodine a nuc med worker can be exposed to before they must participate in thyroid screening program.  I think that some of these documents are older and that the rules have changed...I just wanted to make sure I am learning the most up to date regulations for the exam:  According to document RD-52, you must participate in a thyroid screening program if you are exposed to 2MBq (benchtop), 200MBq (fumehood) or 20,000MBq (glove box) of volatile I-131 or I-125 and your screening must take place within 1 to 5 days....is this correct?  According to another document INFO-0546 it said you must participate in thyroid bioassay if you manipulate greater than 5MBq (benchtop), 50MBq (capsule form), 50MBq (fumehood) or 500MBq (glove box) of volatile I-131 or I-125 in a time period of 3 months and your bioassay must take place within 1 week.  Is INFO-0546 still relevant?  

A1.  The response from CRSO:

1)   Your best reference is CNSC RD-58 “thyroid screening for radioiodine”.  To sum it up: The term thyroid monitoring isn’t really used anymore.  Your two main terms are thyroid screening and thyroid bioassay.  The term “screening” refers to a routine program that can detect the presence of iodine in the thyroid above or below certain threshold levels.  Essentially what you all do in Nuc Med on a routine basis.  Thyroid bioassay is done to quantify not just the presence but the resulting committed effective dose, if one of the screening levels were exceeded.  That calculation can only be performed by somebody certified by the CNSC.

2)   RD-58 has the current requirements and they are the 2, 200, 20000 MBq and they were implemented this year.  The 5, 50, 500 MBq are now old numbers.

Click on the link CNSC RD-58 for documentation.

There you have it!!!!!