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Sequence

The Sequence choice variable is used to select the method of correlation. The mathematics behind these functions is described in the Tina memos and published papers.

compare initiates the comparison between the image sequence and the stimulus function. The stimulus function is selected using the stimulus choice variable and the comparison performed using the technique selected with the sequence choice variable. The resultant correlation image is stored on the top of the image stack.

The 3 correlation functions are given below. $I_i$ is the image pixel at the current location taken from the $i$'th image from a sequence of $N$, $\mu_I$ is the mean value of the $I$ image sequence, $S_i$ is the $i$'th value from the stimulus function and $\mu_S$ is the mean value of the stimulus sequence.


\begin{displaymath}
\mbox{GBAM} = \frac{1}{N}\sum_i^N{(I_i - \mu_I)(S_i - \mu_S)}
\end{displaymath} (19.1)


\begin{displaymath}
\mbox{STIM} = \frac{\sum_i^N{(I_i - \mu_I)(S_i - \mu_S)}}{\sqrt{\sum_i^N{(I_i -
\mu
_I)^2}\sum_i^N{(S_i - \mu_S)^2}}}
\end{displaymath} (19.2)


\begin{displaymath}
\mbox{FRIS} = \frac{\bar{S}\cdot{}\bar{I}}{\sqrt{\frac{1}{N}...
...}}}    
\mbox{where} S_i' = \frac{S_i}{\sqrt{\sum_i^N{S_i^2}}}
\end{displaymath} (19.3)

These statisitcal measures are our interpretation of the basic statistical approaches taken in the GBAM software, STIMULATE software and by Friston's group (Tina memo 2001-002).


next up previous contents
Next: Perfusion Up: Tool Description Previous: perm params   Contents
root 2017-09-26