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January 17, 2003 05:41PM
Bob,

I am having trouble making this question
clear, so I am appending this excerpt
from the SPM slicetiming routine.
I promise this will be absolutely my
very last posting on this question !
re your last posting, I think the
explanation of the algorithm appended below
indicates that the red (corrected) curve
(kate17.gif) should be shifted rightwards
wrt the black (orig) curve, and the curve
for slice2 should be shifted leftwards.

thanks
kate
---------------------------------
From spm_slice_timing.m:

"The correction works by lagging (shifting forward) the time-series
data on each slice using sinc-interpolation. This results in each
time series having the values that would have been obtained had
the slice been acquired at the beginning of each TR.

To make this clear, consider a neural event (and ensuing hemodynamic
response) that occurs simultaneously on two adjacent slices. Values
from slice "A" are acquired starting at time zero, simultaneous to
the neural event, while values from slice "B" are acquired one
second later. Without corection, the "B" values will describe a
hemodynamic response that will appear to have began one second
EARLIER on the "B" slice than on slice "A". To correct for this,
the "B" values need to be shifted towards the Right, i.e., towards
the last value."
Subject Author Posted

3dTshift question

Kate Fissell January 03, 2003 07:04PM

Re: 3dTshift question

bob cox January 06, 2003 07:03PM

Re: 3dTshift question

bob cox January 07, 2003 03:37PM

Re: 3dTshift question

Kate Fissell January 07, 2003 04:57PM

Re: 3dTshift question

Ziad January 07, 2003 06:26PM

Re: 3dTshift question

Kate Fissell January 08, 2003 01:03PM

Re: 3dTshift question

Kate Fissell January 17, 2003 05:41PM

Re: 3dTshift question

Tom Johnstone March 02, 2003 11:44PM



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