Relative CRLB in Osprey LCModel fitting

MRS Software Osprey
1

Hi everyone,

I hope this question isn’t too basic, but I would really appreciate your input on a detail regarding the relative CRLB% in Osprey LCModel fitting.

I understand that using relative CRLB for data screening may introduce bias, but it’s still useful for assessing spectrum quality. My specific question is about calculating the relative CRLB for GABA+ in the difference spectrum.

Should I use the absolute CRLB from the diff_CRLB.tsv file, divided by the metabolite amplitude from diff1_amplMets.tsv, and then multiply by 100% to get the relative CRLB for GABA+?

Thanks in advance for your time and help—I really appreciate it!

2

Hi @timo0302,

Good question, especially as the JSON file that accompanies the TSV outputs isn’t specific about the units of the CRLBs.

The CRLBs in the diff_CRLB.tsv file are relative CRLB values. You can also compare the PS results in the LCMoutput folder to validate that. Now, if you want absolute CRLBs, you can multiply the relative CRLBs with the tCr results (or TissueCorrected results), divided by 100.

Best,
Helge

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