Hello everyone!

I have some questions about FS eTICV. I read on the Wiki that eTICV is not the best measure of ICV and saw the same from other articles. The alternative I decided on was measuring the TICV using CAT12 from SPM. I decided to do a scatterplot of the eTICV from FS V6 and TICV from CAT12 to see how they match each other on measurment. FS is the variable on the Y-axis and CAT12 is the variable on the X-axis. If we assume that CAT12 is more accurate than FS, then it looks as though the FS begins to become more inaccurate as the head size gets smaller.

[cid:image001.png@01D2579B.8A615E30]

So here are my questions:

1. Is my interpretation of this scatterplot correct?

2. Does FS generally have more difficulty measuring smaller heads? If so, then why?

3. Is it more advised for me to use the CAT12 TICV measure as a covariate in my future analysis? Or maybe some other program that I don't know about?