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major background/contamination in Lu channel

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mcohen

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Posts: 1

Joined: Thu Mar 09, 2017 4:29 pm

Post Mon Apr 10, 2017 12:50 pm

major background/contamination in Lu channel

HI all,

Has anyone experienced background/contamination signal in the Lutetium (Lu) channel?

While running my sample (from human whole blood) on the Helios I noticed massive signals in the Lu channel. I did not take a screen shot, but I was essentially seeing a solid black line on the rain plot. This resulted in an error message on the software due to the excessive event count. Signals in this channel were normal when running the EQ beads alone, and the instrument was tuned properly.

Not sure where this contamination came from and was hoping someone might have a suggestion.

Thanks,

- Mike
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Verhoeff

Participant

Posts: 19

Joined: Wed Mar 02, 2016 10:25 am

Post Thu Apr 13, 2017 7:52 am

Re: major background/contamination in Lu channel

Hi Mike,

Is the 175Lu the highest channel you have open at the time of measurements? If the contaminating particles are larger than the proper signal range I can imagine that they show up on the end of your TOF-spectrum. I haven't come across any contamination specifically involved with Lutetium, but had some experiments where I suspect my cones were very dirty. I then had a lot of contamination in the highest channel I had open, which was 208Pb.

Maybe someone with more knowledge of the TOF behaviour can shed some light on this?

Jan
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mleipold

Guru

Posts: 5796

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Thu Apr 13, 2017 3:08 pm

Re: major background/contamination in Lu channel

Hi Mike,

Could you give us more detail about your samples? Such as:
1. Was the whole-blood stained *as* complete whole-blood (ie, before RBC lysis)? RBC lysed whole blood? Fixed WB (Fix-lyse, or Smart-tube)?
2. What marker did you have on the 175 channel? Did you have anything on 174 or 176?
3. How was the background in your other channels? Were they all completely clear, or did they also have background? How was your Ir staining?


Mike
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lcmenard

Participant

Posts: 2

Joined: Thu Dec 15, 2016 8:51 pm

Post Thu Apr 13, 2017 4:51 pm

Re: major background/contamination in Lu channel

Hi Mike,

If these are patient samples, could your issue be due to contamination from a treatment or contrast agent that contains lutetium? For instance Lutetium-177 dotatate (Lutathera) can be used in some cancers.

Laurence
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GregBehbehani

Master

Posts: 85

Joined: Tue Apr 12, 2016 10:17 pm

Location: The Ohio State University, Columbus, Ohio

Post Fri Apr 14, 2017 1:29 pm

Re: major background/contamination in Lu channel

Hi Mike,

I would second Mike Leipold's request for more information. I would also suggest that if you have any of that sample left, that you try diluting some of it 100- or 1000-fold in both water and nitric acid and then you can run it in solution mode and record all of the surrounding channels and their -16 channels.

I think Laurence's suggestion of Lu177 contrast agent is a great idea, but this should be primarily Lu177 and decay to Hf177, though this agent probably contains some 175 as well (if this is the case you would have an even bigger, unmeasured, signal on 177).

In any case, understanding the complete mass spectrum and whether it is present in solution (present when sample is diluted in H2O) or in the cells (present when the sample is diluted in nitric acid) will be the key to figuring out where this came from. Natural Lu is pretty rare and should have ~2% Lu176 so you should be able to readily detect that pattern. If you see a fairly even distribution of 175 and 177 that would strongly favor the idea of Lu-177 dotatate. If you just see 175 then you probably have contamination from one of your reagents (which could be in one of your pipettes). No matter how bright the signal is, you should be able to find a dilution that you can safely run. I would strongly suggest that you do try to track this down so that you don't have this coming up again (even if you have to go dig your sample tube out of the trash).

Good luck,

Greg

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