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Large Concentration values

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Nicollette Purcell
Posts: 28
Topic starter
(@nicopurc88)
Eminent Member
Joined: 2 years ago

Hi All,

I wanted to see if anyone else has this experience. The range of values in my raw data seems acceptable and is even similar to values a colleague has gotten in their own data collection. However, when I convert OD to concentration, the concentration values are really high. I attached a pdf with screenshots of the raw data, concentration, and processing stream for reference. The screenshot is one of the more extreme examples but in general, my concentration values seem high compared to the literature. 

Any thoughts or advice are greatly appreciated.

Nicollette

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Michael Zara
Posts: 12
(@mzara)
Active Member
Joined: 2 years ago

Hey @nicopurc88,

 

I'm curious to know if you've made any strides on this. I've been wracking my head over a similar situation as yours. To take it a step further, we've noticed large variabilities in the HRF amplitudes at the subject-level, which will influence our analysis/results at the group-level.

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Nicollette Purcell
(@nicopurc88)
Joined: 2 years ago

Eminent Member
Posts: 28

Hi @mzara,

I wish I had better news, but I'm still stuck in a rut. We have some collaborators that don't use homer and thought it was a units or conversion issue, but I don't have evidence that is the case.  I was thinking of trying to process a subject in NIRS-SPM just to see if I get different results. I'm definitely in the same boat as you though. I'll keep you posted as work through it.

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Nicollette Purcell
(@nicopurc88)
Joined: 2 years ago

Eminent Member
Posts: 28

@mzara I actually just switched back to Homer2 and reprocessed my same data and the concentration values seem to be in a more reasonable range. I think I was having some issues with unit conversion in my homer3? I'm not sure, but I've just opted to revert to Homer2 for analysis now. I attached a screenshot of the same data processed in both versions for reference.

 

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David Boas
Posts: 229
(@dboas)
Reputable Member
Joined: 2 years ago

Hey @nicopurc88, in the pdf example you provided at the top, the large concentration amplitudes all seem to come from motion artifacts.

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