Is this a Siemen's scanner? The actual echo spacing reported by Siemens is indeed unchanged by the use of iPAT.  But FSL wants the "effective echo spacing", which is the actual ES divided by the iPAT factor.  This assumes you are talking about iPAT/GRAPPA acceleration (which it sounds like is the case) and not "multiband" (slice) acceleration.

cheers,

-MH

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Michael Harms, Ph.D.

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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: [log in to unmask]

From: Andreas Lidström <[log in to unmask]>
Reply-To: FSL - FMRIB's Software Library <[log in to unmask]>
Date: Monday, April 28, 2014 6:08 AM
To: FSL - FMRIB's Software Library <[log in to unmask]>
Subject: [FSL] Clarification of 'Effective Echo Spacing'

Hello,

I am running RS fMRI with an esp of 0.464ms and acceleration factor of 2.

In the instructions for B0 unwrapping it says that you should divide the esp by the acceleration factor but our MR physician is perplexed by this. He says that since we are accelerating our pulse-sequence in the phase direction(y) we are simply cutting the echo train in half leaving the echo-spacing unchanged. Does this mean we should not divide our esp by 2 or is this division still correct based on something else hidden in the program?

//Andreas

 

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