Thanks Martin for your reply,

I am agree with you on point 1. What would you say in the case that we are interested in rates of decline from baseline to 12 months, but besides 6 months follow-up we also have 24 months?. Here I see more conceptual problems. In an hypothetical context of severe atrophy from 12 to 24 months, adding the 24 mo follow-up perhaps difficult registration more than improves it. What do you think?

Thanks a lot

Best

Daniel

Hi Daniel,

1. yes. But why not include 6 month in your study if you have those scans??? You will get much more reliable slope estimates with 3 time points compared to 2, so including that time point will not only help for the image processing part, but also in your statistics (you gain power).

2. I am not familiar with the mprage flag and think it mainly affects the normalization. If you are sure you need it, then also add it to the -base and -long runs, just to be safe.

best, Martin

On 01/29/2014 09:08 AM, Daniel Ferreira wrote:

Dear experts,

I have two questions regarding the longitudinal stream:

- I am including Baseline and 12 months follow-up in my study. However, I also have 6 months follow-up. I wonder if it is conceptually right to include these 6 months scans in template creation with the idea of increasing registration.

- I am applying the -mprage flag in the crossectional first step. Should I use it in the -base and -longs steps too?

Thanks very much

Daniel Ferreira