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They are identical.

TA =TR- (TR/#slices)

TA=(TR/#_slices)*(#_slices – 1)=(TR/#_slices)*(#_slices) -  (TR/#_slices)*(1)= TR- (TR/#_slices)

Make sure you either factor the solution prior to plugging in values OR make sure you perform the operations in the parenthesis first, before multiplying across.

On Thu, Jun 25, 2009 at 1:32 PM, Cory Inman <[log in to unmask]> wrote:
Good afternoon SPMers,

   I have a question concerning the calculation of TA when performing slice timing in SPM5.
I have seen several resources discussing the calculation of TA when performing slice timing.
The first one I have seen is on the help window in the bottom of the graphics GUI.  The
same formula is in the SPM 5 Manual.  This formula for calculating TA is TA = TR-
(TR/#slices).  The other formula I have run into comes from other trusted lab websites.
They say the formula for 'continuous' acquisition is TA = (TR/#_slices)*(#_slices – 1).
They come up with VERY different numbers of course, so it is essential that I know which
one is correct.  My gut tells me to go with the formula in the SPM manual. So the question
is which one is correct?  If they are both correct, but the 'continuous' acquistion formula is
for special circumstances please let me know.  Thank you for your time and guidance in
advance.  Have a wonderful day.

Cory Inman
Cognitive Neuroscience Lab
Emory University



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Best Regards, Donald McLaren
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University of Wisconsin - Madison
Neuroscience Training Program
Office: (608) 265-9672
Lab: (608) 256-1901 ext 12914
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