Hi, It appears that you are trying to replicate the basics of one of our Lifespan pilot protocols on a Skyra — i.e., 1.5 mm voxels with 20 total min of dMRI scanning. But due to the longer TE and longer TR (resulting in fewer total directions), you are definitely going to have worse overall SNR than what we achieved. We highly suggest that you collect some pilot data to assess the quality of your proposed dMRI protocol with your end-measures of interest, including possibly a comparison against a protocol with larger voxels (e.g., 1.7-1.8 mm voxels) that would recover some SNR.
cheers, -MH -- Michael Harms, Ph.D. ----------------------------------------------------------- Conte Center for the Neuroscience of Mental Disorders Washington University School of Medicine Department of Psychiatry, Box 8134 660 South Euclid Ave. Tel: 314-747-6173 St. Louis, MO 63110 Email: [email protected] From: <[email protected]<mailto:[email protected]>> on behalf of "Glasser, Matthew" <[email protected]<mailto:[email protected]>> Date: Wednesday, December 7, 2016 at 11:49 AM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: [HCP-Users] FW: Skyra - BOLD and diffusion MRI protocols From: Matt Glasser <[email protected]<mailto:[email protected]>> Date: Wednesday, December 7, 2016 at 10:14 AM To: neuroimage analyst <[email protected]<mailto:[email protected]>> Subject: Re: [HCP-Users] Skyra - BOLD and diffusion MRI protocols I wouldn’t acquire multiple repetitions of the same directions, but rather more unique directions. If necessary you can acquire the DWIs with only a single phase encoding direction in an effort to get more unique diffusion directions, but it is important that you get phase reversed b0 images. As for the MB error, I don’t know how to fix it, but you should definitely be able to do better than MB=2 with a 32 channel head coil. Hopefully someone else on the list knows how to fix this. Peace, Matt. From: neuroimage analyst <[email protected]<mailto:[email protected]>> Date: Tuesday, December 6, 2016 at 8:54 PM To: Matt Glasser <[email protected]<mailto:[email protected]>> Subject: Re: [HCP-Users] Skyra - BOLD and diffusion MRI protocols Hi Matt, 32 channel head coil. I was able to run the diffusion sequence on a phantom when TR/TE was 7000/106 ms. Since the scan time with this tr is already 20 minutes, I was thinking to acquire just b0 with PA phase encoding and the other 64 directions 2b data+b0 with AP. will that be okay? my concern is snr at te will not be very good and data may not be too great and may be atleast 2 reps are desired? Thanks Regards -VM On Dec 6, 2016 6:46 PM, "Glasser, Matthew" <[email protected]<mailto:[email protected]>> wrote: What coil are you using? Peace, Matt. From: <[email protected]<mailto:[email protected]>> on behalf of neuroimage analyst <[email protected]<mailto:[email protected]>> Date: Tuesday, December 6, 2016 at 11:56 AM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: [HCP-Users] Skyra - BOLD and diffusion MRI protocols Hi, HCP Users and Developers. We have been trying to build a protocol for BOLD and DWI on our Skyra (VE11C) using the latest release of HCP pulse sequences. But we haven't been completely successful with what we wanted to achieve. A) BOLD: We were hoping to get a TR in the range of 750ms, res = 2mm3, echo spacing (ES) approx 0.65. We were able to get to echo spacing of 0.69 and all the other parameters with MB = 8. However, the sequence doesn't run and it gives us "Max amplitude overflow on gradient z axis" after MB factor exceeds 2. It appears to me that then we have to sacrifice TR and only run with MB = 2. Is there anybody with a Skyra who has able to achieve what we are hoping for and willing to share the protocol with us? OR if somebody could guide us to resolve the error of amplitude overflow. B) DWI: The idea was to have res = 1.5mm3, 2b-values at 1000 and 2500, 64 directions with the best BW and ES achievable. The sequence runs for 7 minutes out of total 13 minutes and gives gradient power amplifier error. On Michael Harms's suggestion, I adjusted flip angle to 78/160 at a TR of 5500 ms with excite/refocus pulse duration of 3840 and 7680. there was a pop up warning that RF is clipped and the maximum refocusing angle was 142 instead of 160. I placed a 64 directions diffusion vector and ran the sequence under "free" mode. Again, I will appreciate if there is anybody with a Skyra who has able to achieve what we are hoping for and willing to share the protocol with us, along with the diffusion vector sets? OR if somebody could guide us to resolve the error. Thank you. Regards --VM _______________________________________________ HCP-Users mailing list [email protected]<mailto:[email protected]> http://lists.humanconnectome.org/mailman/listinfo/hcp-users ________________________________ The materials in this message are private and may contain Protected Healthcare Information or other information of a sensitive nature. 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