Unfortunately that is something that anyone using gradient echo EPI has to deal with.  Because of inhomogeneity in the magnetic field, some areas spins decay faster than other areas resulting in loss of signal.  This is not a correctable artifact unfortunately.  

Peace,

Matt.

From: Xuhong Liao <[email protected]>
Date: Sunday, November 23, 2014 at 4:24 AM
To: hcp-users <[email protected]>
Cc: Matt Glasser <[email protected]>
Subject: Re: Re: About data processing

 Hi Matt,
   
      Thank you very much for your response. 

      As your post, several slices of rsfMRI data (left-right encoded, second session) are displayed for one subject (ID: 100307) as examples. Please see attached for more details. We can observe there the BOLD signals are missing in certain brain regions, such as superior orbital frontal cortex and bilateral inferior temporal gyrus. I hope above statement is clear, if not please contact with me.

      Thanks again!

  Best regards,
  Xuhong Liao

 

---------- 已转发邮件 ----------
From: "Glasser, Matthew" <[email protected]>
To: liaoxuhong <[email protected]>, hcp-users <[email protected]>
Cc: 
Date: Fri, 21 Nov 2014 19:03:11 +0000
Subject: Re: [HCP-Users] About data processing
Can you post a picture of what you are talking about?

Peace,

Matt.

From: liaoxuhong <[email protected]>
Date: Friday, November 14, 2014 at 8:36 PM
To: hcp-users <[email protected]>
Subject: [HCP-Users] About data processing

Hi:

    I'm currently working with minimally preprocessed multiband resting-state fMRI data (preprocessing pipeline v2) for unrelated 40 subjects from HCP. Recently, we found BOLD signals are missing in certain brain regions, such as superior orbital frontal cortex and bilateral inferior temporal gyrus. Furthermore, this phenomenon is common for  rsfMRI data of all subjects we have downloaded, no matter RL or LR phase encoding. We are puzzled with the signal missing in these areas, and hence are seeking for your assistance.

Can anyone tell us how to deal with this issue?
 
Thanks.

Regards
Xuhong Liao

 


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Content preview:  Unfortunately that is something that anyone using gradient
   echo EPI has to deal with. Because of inhomogeneity in the magnetic field,
   some areas spins decay faster than other areas resulting in loss of signal.
   This is not a correctable artifact unfortunately. [...] 

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