 |
 |
Hi, Distortion correction can be done either before BBR or as part of BBR, and as long as the distortion correction before works well then the two options are likely to give similar results. If you have a lot of signal loss (and it is mainly the size of the signal loss areas that matters) then it might be beneficial to use cost function weighting in conjunction with BBR. This can be done through the FLIRT command line or through the epi_reg script (for the latter the weighting image needs to be registered to the structural space first). All the best, Mark On 4 Nov 2017, at 07:28, Tanenbaum, Aaron <[log in to unmask]<mailto:[log in to unmask]>> wrote: I distortion correction before BBR or during is fine. Aaron Tanenbaum Senior Research Technician for Professor Beau M. Ances ________________________________ From: FSL - FMRIB's Software Library <[log in to unmask]<mailto:[log in to unmask]>> on behalf of Matt Glasser <[log in to unmask]<mailto:[log in to unmask]>> Sent: Friday, November 3, 2017 5:39:51 AM To: [log in to unmask]<mailto:[log in to unmask]> Subject: Re: [FSL] Fieldmap images and BBR BBR is a rigid registration and 2D EPI images are distorted relative to 3D structural images. It is best to distortion correct data before or during BBR (I don¹t think it matters too much when it is done, just that it is done well). I would doubt that regions of signal dropout would affect BBR much, does the initial registration get things into the ballpark? Peace, Matt. On 11/3/17, 12:48 AM, "FSL - FMRIB's Software Library on behalf of Anika Guha" <[log in to unmask]<mailto:[log in to unmask]> on behalf of [log in to unmask]<mailto:[log in to unmask]>> wrote: >Hi all, > >I've noticed some signal dropout in my functional images and I think it >may be throwing off my registration. Although the functional images that >I'm working with have already been fieldmap-corrected, I am wondering if >I need to/should include my fieldmap images in order to utilize BBR >during registration. > >Does specifying the fieldmap images for b0 unwarping influence >registration with BBR? It seems like BBR accounts for areas of signal >loss pretty well (masking those areas out of the registration, lessening >their influence), so I want to make sure I'm using it correctly. Any >input would be greatly appreciated! > >Thanks, >Anika ________________________________ The materials in this message are private and may contain Protected Healthcare Information or other information of a sensitive nature. If you are not the intended recipient, be advised that any unauthorized use, disclosure, copying or the taking of any action in reliance on the contents of this information is strictly prohibited. If you have received this email in error, please immediately notify the sender via telephone or return mail.