Dear Nima, You can of course get better labels from a 1mm iso T1w scan. If your registration is good, then this is the way to go. Analyzing the diffusion data will give you less accurate labels, but eliminates registration errors. You can try both and keep the best looking one. Having said that: I would use SynthSeg rather than SAMSEG, which will give you a crisper 1mm isotropic segmentation. Cheers, Eugenio

-- Juan Eugenio Iglesias http://www.jeiglesias.com

From: freesurfer-bounces@nmr.mgh.harvard.edu freesurfer-bounces@nmr.mgh.harvard.edu on behalf of Taghizadeh Mortezaei, Nima ntaghizadehmortezaei@mgh.harvard.edu Date: Friday, April 11, 2025 at 12:58 PM To: Freesurfer support list freesurfer@nmr.mgh.harvard.edu Subject: [Freesurfer] Feasibility and Accuracy of Using SAMSEG with ADC Maps

Dear FreeSurfer team, I am currently using FreeSurfer v7.4.1 and I want to ask is it feasible to run SAMSEG directly on ADC maps derived from diffusion MRI for segmenting normal brain anatomy? Alternatively, would it be more accurate to perform segmentation on a T1-weighted image and then transfer the labels to the co-registered ADC image? Thank you very much for your time and support. Best regards, Nima