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radioactive_dude t1_j6z8hp0 wrote

Hello fellow Canadian! Mo-99 is NOT made from nuclear weapons waste. It is deliberately made in reactors or accelerators specifically as a medical product. Canada used to be one of the largest suppliers of Mo-99 in the world, making it in the NRU research reactor in Chalk River. That reactor shutdown in 2018. The Darlington CANDU plant is now equipped to make Mo-99, in addition to lots of carbon free power.

https://world-nuclear-news.org/Articles/Darlington-ready-to-produce-medical-radioisotope

As others have said, it's not "stocked" on a shelf like many medications. It is custom made to order and patients are scheduled.

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Gwaiian OP t1_j70ob6n wrote

Wow, thank you. Apparently my ten minute deep dive into nuclear medical isotopes didn't give me all the right info to make assumptions. And as a news junkie I do recall the Chalk River shutdown. Thanks!

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radioactive_dude t1_j71hut0 wrote

You're welcome. The Mo-99 at Darlington is specifically in Unit 2, which was just completely refurbished and can operate now for another 30 years. There is also lots of exciting work happening in Chalk River, just not with a research reactor. If medical isotopes interest you, check out the work with Ac-225 in Chalk River as a targeted alpha therapy for cancer treatment.

https://www.cnl.ca/health-science-2/actinium-225/

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EllieBelly_24 t1_j72uz09 wrote

Tom Scott has a video talking about something similar. Iirc, he visits the lab that produces radioisotopes for a hospital, mostly focusing on the tube they use to send it down the street super fast.

I don't have a link though :(

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carollois t1_j7jojd8 wrote

I believe that is at UBC. There is a lab that makes the medical isotopes and sends it to the hospital through pneumatic tubes under the ground. Very cool.

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autoantinatalist t1_j70z52d wrote

What happens if traffic is awful one day and people are an hour late? Is the scheduled injection ruined?

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radioactive_dude t1_j71haxx wrote

You can calculate decay by Nt=No(1/2)^(t/t1/2), where Nt is the number of atoms at time t, No is the original number of atoms, and t1/2 is the half-life. So 1 h later for a 6 h half-life means 89% of the dose is still there.

You would need to ask one of the pharmacists what they do if someone is late. I'm assuming there is a cutoff time.

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Tricky-Block4385 t1_j77toez wrote

There is a cutoff time. As the 99mTc decays, more and more of it becomes useless. There are several reasons it becomes useless (begins to lose its tag to whatever chemical it’s tagged to, decays and the amount of radiation left is too small to use, oxidizes, etc). There is an expiration time on each dose we receive and there are strict limits to how much and how little radiation we can give a patient depending on the type of scan we are doing. I’m a nuclear medicine tech, so I deal with this stuff all the time.

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vilhelm_s t1_j7algoz wrote

Roughly how long is the cutoff time? (E.g. if the courier is late by 1 hour?)

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Tricky-Block4385 t1_j7b2bnj wrote

An hour wouldn’t make a difference typically, but each site has their own agreed-on dose ranges. At my sites, I have usually about a 2-3 hour range before my doses would be too low.

So the pharmacy you order from prepares the doses all together and calculates how much radiation will be in each dose at a prescribed time (so if I open a dose calibrated for 2pm at 9am, the dose is WAY too high to give to someone, but if I did give it, it would still work as intended). I’m giving this example in unit doses. Some places will order bulk doses, where they can draw up their own amount of radiation at any given time.

When I order for, let’s say three patients, we will say that each of them are coming in one hour apart from each other. I’ll order 10 mCi of technetium at 9 AM, 10 AM, and 11 AM. Each of my patients come at those times . If a patient is an hour late, the dose will be lower, but it will be usable still. After a certain time you are not giving enough radiation to make good pictures. So if my 9 AM patient comes at noon and I don’t have enough radiation to give them, I would reschedule them so they get better pictures a different day.

The other reason that those does expire is because the tag breaks up on the technetium. So when I do a patient, I’ll order 10 mCi of 99m technetium sestamibi, let’s say. The sestamibi will hold its tag to the technetium for several hours. If the pharmacy makes that dose at 2 AM and ships it out to me calibrated for 9 AM, I can inject the patient with that amount of radiation from probably 8 to 10 a.m. It’s around 5 PM or so, the tag is two broken up to still go to the correct place in the human body. Straight technetium 99m goes to the stomach, the thyroid, kidneys, and other areas of the body. Technetium 99m sestamibi goes to the heart muscle, but also goes to some of those other areas of the body too. So when the sestamibi breaks off, it won’t go to the heart muscle anymore. If I’m trying to get a heart scan on a patient, it doesn’t do me any good to inject something that isn’t going to go to the target organ anymore.

Does that make sense? I feel like I might be more confusing than helpful, but there are several reasons you wouldn’t inject after a specific time, not just that the radiation is decayed.

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