Re: [HCP-Users] Changes in unprocessed diffusion data between Q1/Q2 release and 900 subjects release

[Harms, Michael]

Hi, Starting with the Q3 release, the unprocessed dMRI was “retro-reconned” from the raw k-space data using an improved image reconstruction algorithm that resulted in more “crisp” images (i.e., less spatial blurring).  So, yes, changes in SNR are completely expected. For more details, you can see http://humanconnectome.org/documentation/Q3/index.html and pages 5, 7, and 35-36 of the Q3_Release_Reference_Manual available from the preceding link. 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: <hcp-users-boun...@humanconnectome.org> on behalf of Joerg Polzehl <joerg.polz...@wias-berlin.de> Date: Thursday, April 7, 2016 at 9:22 AM To: "hcp-users@humanconnectome.org" <hcp-users@humanconnectome.org> Subject: [HCP-Users] Changes in unprocessed diffusion data between Q1/Q2 release and 900 subjects release Dear HCP Team Members,       I’m in the process of revising a manuscript on statistical modelling of DWI data. In the original version we used the single subject unprocessed data from the Q1/Q2 Release (2013).      For the revision we have rerun our analysis on the corresponding  data for the same subject (subject ID 100307)  in the 900 subjects  release (2015). Except from change in the scale of image intensities  between both datasets (by a factor of approx. 1.5)  we see significant changes in our analysis results, especially the estimated SNR in the unprocessed data, that indicate qualitative changes in data properties.       In my understanding, given what I can extract from the  reference manuals and literature, the unprocessed data  should be direct SENSE-1 reconstructions from K-space data, i.e. the follow a Rice distribution.  - have any data processing steps been applied after SENSE 1 reconstruction to get the “unprocessed” data ? If yes are there differences between  the Q1/Q2 release and the 900 subjects release ? - did the SENSE 1 reconstruction parameters change between  the Q1/Q2 release and the 900 subjects release ?  - are there any other changes that can affect statistical properties,  especially SNR in the "unprocessed” data ? Any comments would be highly appreciated. Best regards, Joerg Polzehl     --- Dr. Joerg Polzehl WIAS, Mohrenstr. 39 D-10117 Berlin, Germany email: joerg.polz...@wias-berlin.de Tel. +49 30/20372 481 Fax: +49 30/20372-303 Web: http://www.wias-berlin.de/people/polzehl/ _______________________________________________ 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. _______________________________________________ HCP-Users mailing list HCP-Users@humanconnectome.org http://lists.humanconnectome.org/mailman/listinfo/hcp-users