Re: [HCP-Users] aliasing in diffusion images

[Harms, Michael]

Hi, The only potential "gotcha" that I see in your list of parameters is that your Excite/Refocus pulse durations seem too low, and may be resulting in clipping of your pulses.  (Those pulse durations would almost certainly max out the "MBExc 1H" and "MBRef 1H" voltages on the System:Tx/Rx tab for the 32 channel coil, but I'm not sure about the 64 channel coil in conjunction with parallel transmit). Try increasing those durations to 3840 and 7680, respectively, which is what we are using in a 32 channel protocol.   If the problem persists, contact me off-list, and we can dig a little deeper. 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: mha...@wustl.edu From: "Mark A. Pinsk" <mpi...@gmail.com> Date: Monday, November 30, 2015 1:32 PM To: "Harms, Michael" <mha...@wustl.edu> Cc: "hcp-users@humanconnectome.org" <hcp-users@humanconnectome.org> Subject: Re: [HCP-Users] aliasing in diffusion images Hi Michael Any idea on where my aliasing could be coming from?  Here is a link to the data file in case it's useful to see. https://dl.dropboxusercontent.com/u/3889124/14-1-1dMRIseq1APcmrr.nii.gz thanks, Mark On Mon, Nov 23, 2015 at 9:23 PM, Mark A. Pinsk <mpi...@gmail.com> wrote: Excite pulse duration: 2560 us Refocus pulse duration: 5120 us Single band images: off MB LeakBlock Kernel: off MB RF phase scramble: off Time-shifted MB RF: off SENSE1 coil combine: ON Log physiology to file: off Invert RO/PE polarity: off Online multi-band recon: Online FFT scale factor: 1.00 On Mon, Nov 23, 2015 at 6:29 PM, Harms, Michael <mha...@wustl.edu> wrote: What are your settings on all the parameters on the Sequence:Special tab? --  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: mha...@wustl.edu From: "Mark A. Pinsk" <mpi...@gmail.com> Date: Monday, November 23, 2015 10:39 AM To: "hcp-users@humanconnectome.org" <hcp-users@humanconnectome.org> Subject: [HCP-Users] aliasing in diffusion images Hi all, I've attempted to collect diffusion data with the CMRR sequence at our Prisma, and got aliasing in the image (very apparent at higher b value).  Snapshot here:   https://dl.dropboxusercontent.com/u/3889124/b2500-MB3.tiff Any suggestions on what the issue(s) could be?   I see the same when I lower MB from 3 to 2. Here are my protocol parameters: 64-channel head/neck coil 90 interleaved transverse slices in-plane resolution = 1.5mm slice thickness = 1.5mm with no inter-slice gap field of view (FOV) = 210mm base resolution = 140 repetition time (TR) = 4200ms echo time (TE) = 87ms flip angle (FA) = 78 deg refocus FA = 160 deg phase partial fourier (PPF) = 6/8 gradient reversed fat suppression phase encode (PE) direction = anterior/posterior bandwidth = 1880Hz/Px echo spacing (ES) = 0.71ms multiband acceleration factor = 3 SENSE (R=1) image reconstruction bmax = 2500 s/mm^2 thanks! Mark _______________________________________________ HCP-Users mailing list HCP-Users@humanconnectome.org 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. 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.   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. _______________________________________________ HCP-Users mailing list HCP-Users@humanconnectome.org http://lists.humanconnectome.org/mailman/listinfo/hcp-users