aI want to using SPM toolbox “MRTool” to calculate the T1w/T2w ratio. According to the manual, "MRTool-optnorm "  provides an enhanced registration approach for the optimized analysis of T1-w images in elderly
subjects characterized by a marked ventricular enlargement.  There are several files generated in this stage. If I want to calculate T1w/T2w ratio, which file should I input in the  "MRTool-T1T2 " window?  Especially the "anatomical T1w image" 

Thank  you!