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Dear all, as a follow up on the previous messages, does anyone have experience with implementing this optimized gradient sampling scheme on a Siemens scanner? We have a 3T Skyra with software version E11C. Thanks in advance for any suggestions. Best regards Samuel Holly MRI application specialist Jessenius Diagnostic Centre Spitalska 6 Nitra Slovakia On Thu, 22 Nov 2018 10:59:11 +0000, Matteo Bastiani <[log in to unmask]> wrote: >Dear Sophie, > >I would not expect a significant difference in terms of tractography results when going from half to full sphere sampling. >However, it would definitely help when it comes to pre-processing and distortion correction. Have a look here: https://fsl.fmrib.ox.ac.uk/fsl/fslwiki/eddy#If_you_haven.27t_already_acquired_your_data for some recommendations. > >Your tractography will be influenced by other factors, such as number of acquired orientations, b-value, signal- and contrast-to-noise-ratios. If these values are too low, bedpostX might struggle to estimate complex voxel-wise fibre configurations such as 2 or 3 fibre crossings, leading to incorrect structural connectivity estimates. You could try to lower the ARD weight (-w option in bedpostX) to get more 2 and 3 fibre configurations, but you should carefully inspect the data to ensure that they look anatomically plausible (i.e., check for spatial continuity/coherence). > >You can obtain an optimised diffusion orientation sampling scheme using the FSL function gps (see here: https://fsl.fmrib.ox.ac.uk/fslcourse/lectures/practicals/fdt1/index.html#eddy). However, you should check with your local scanner operator how to export that in a format that the scanner could read. > > >Hope this helps, cheers, >Matteo > >On 22 Nov 2018, at 00:37, Sophie Huang <[log in to unmask]<mailto:[log in to unmask]>> wrote: > >Dear FSL users, > >I have a 64 Direction DTI dataset where diffusion was only sampled on the half sphere instead of the whole sphere. I noticed my tractography results showed very low connectivity between my language ROIs (pars opercularis and posterior superior temporal gyrus). I'm presuming it's due to the half sphere scheme. Do half sphere and whole sphere DTI schemes change the results substantially? > >I would like to acquire diffusion on the whole sphere in the future. Do you know what parameter/setting on a Siemens Verio 3T would need to be changed to allow for that? > >Thanks, >SH > >######################################################################## > >To unsubscribe from the FSL list, click the following link: >https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1 > > >######################################################################## > >To unsubscribe from the FSL list, click the following link: >https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1 > ######################################################################## To unsubscribe from the FSL list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1