 |
 |
Dear FSL team, We have some DWI data quality issues connected mostly with some differences in data acquisition protocols used for different subjects in our group (differences in slice numbers, TR, slice gaps, different bvecs, problem with cropped images). Could you please answer on some questions regarding DWI data and TBSS: 1) We have a part of subjects with 65 contiguous axial slices with 2 mm thickness and a part of subjects with 60 contiguous axial slices with 2 mm thickness . Lets say that whole brains of all subjects are fitted in these 65 and 60 slices DWIs. Could we use these different DWIs in singe TBSS study? And if not – how such differences will affect TBSS results? 2) Some of DWIs (65 and 60 slices) have another problem – they are cropped from above (see attachments: 4D.nii.gz.example_cropped_1.jpeg, 4D.nii.gz.example_cropped_2.jpeg). Could we use normal (non-cropped) and such cropped DWI in single TBSS study? Or such cropped DWI will affect the results? (for example I can see that FA_to_target.nii.gz of these cropped DWI is a little bit distorted). 3) Can we use DWIs with slightly different repetition times (TR of 7212 ms, 7164 ms and 6590ms) in a single TBSS study? Please note that we are looking for difference between 2 groups (patients and control) and control group has a mix of subjects with different TRs... (15 of 30 with 7212 / 7164 ms and 15 of 30 with 6590 ms). How such differences will affect TBSS results? 4) Some of patient group's DWIs have the third problem (7 of 30 in patients group). They have 65 axial slices with 2 mm thickness AND GAP between slices of 0.2-0.5 mm. So their voxels on 4D image looks a little bit extended in the superior/inferior direction (see attachment 4D.nii.gz.example_with_gap_0.5mm.jpeg). Could we use these DWIs along with no-gap DWIs in one TBSS study? And if not – how such differences will affect TBSS results? 5) All subjects from 2 groups have a slightly different bvecs. Is it ok OR would it affect TBSS results somehow Thank you very much in advance for your help. Best regards, Alexander Tomyshev Research assistant, Laboratory of neuroimaging and multimodal analysis, Mental Health Research Center of the Russian Academy of Medical Sciences, 34 Kashirskoe shosse, 115522 Moscow, Russia Mob.: +7 916 814 5708 Email.: [log in to unmask]