# Multi-echo fMRI protocols A collection of protocols for multi-echo fMRI protocols, collected by vendor, magnet strength, and sequence origin. # Siemens ## 3T ### CMRR #### [CMRR_MB-3_IP-2_ME-4_Rec-MagPhase_TR-1500](https://osf.io/y46cu/) An accelerated four-echo protocol designed for vR016 of the CMRR-MB sequence. This protocol includes in-slice and multi-slice acceleration (GRAPPA=2, MB=3) and magnitude/phase reconstruction. ##### Notes - The protocol also acquires single-band reference images and uses LeakBlock. - The protocol uses SENSE1 coil combine (as recommended by the CMRR release notes for R016 on when reconstructing phase data). - The uploaded protocol uses a multiband factor of 3 and has 48 slices. This results in a set of 16 slices for each multiband subgroup. According to [Setsompop et al. (2012)](https://doi.org/10.1016/j.neuroimage.2012.06.033), having an even number of slices in the subgroups is not recommended: > The interleaved Rsl=3 acquisition has an additional constraint if one wishes to avoid having some spatially adjacent slices acquired in rapid succession. In the simultaneous multislice acquisition with a total of Nsl, a total of Rsl subgroups each with Nsl/Rsl slices are created. The successive excitation problem occurs between the top slice of one subgroup and the bottom slice of the subgroup above it. **The problem can be avoided if the number of slices in each excitation subgroup is odd.** The use of an even number of slices per subgroup was an oversight by the protocol (not sequence) developers and we recommend changing this if you wish to use the protocol.