Discrepancies in T1W/T2W ratio mean values

[Varun Chandran]

Hi everyone,

I pre-processed some T1-weighted and T2-weighted structural images to look at cortical myelin differences in a clinical population compared to the healthy controls (HCP-Development Dataset). Some individual T1W/T2W ratio (Native space) mean values for the cortical myelin seems to be much higher in GM (36.268) and WM (62.007) in the clinical population and HCP-Development dataset. Then, all the T1W/T2W ratio maps were spatially normalised to the MNI standard template, which yielded consistent mean values in the GM (1.861) and WM (2.365) across the HCP-Development Dataset. However, the many individual mean T1W/T2W ratio values remain unchanged, and some mean values has gone even little higher in the clinical population. Please can anyone provide some advice on this issue.

                                                                    thanks,

kind regards,

Varun

[Glasser, Matthew]

1. We don’t look at cortical myelin differences across participants by registering them to MNI space, we make comparisons across participants after surface-based registration, preferably using multiple modalities.
2. You cannot compare T1w/T2w across different acquisition protocols.  T1w/T2w is a relative measure that can only be compared within protocol.

 

Matt.

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