<div dir="ltr"><font color="#000000" size="3" face="Times New Roman">
<p style="margin:0in 0in 0pt"><font>Maybe you mean you do not
know the gradient value added to the theta_t in your last equation. The gradient
part includes three terms: sum, partial derivative with respect to T and the
matrix. The sum can be calculated because you know the theta_t. The derivative
can be calculated by 1) finite differencing or 2) interpolating a continuous Image
I_m and derive its analytical derivative. Both methods rely on the interpolator
you use. </font></p>
<p style="margin:0in 0in 0pt"><font> </font></p>
<p style="margin:0in 0in 0pt"><font>The first term relies on
the metric. As I know SSD which you use, CC and MI have analytical derivative.
But there are lots of metrics without analytical derivative. ITK uses finite
differencing to calculate derivative, so it can deal with any metrics although
might lose some performance for the SSD, CC and MI.</font></p>
</font></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Apr 30, 2013 at 9:51 AM, alaamegawer <span dir="ltr"><<a href="mailto:alaamegawer@yahoo.com" target="_blank">alaamegawer@yahoo.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
<br>
i mean the constant value added to initialization theta0 ,because<br>
transformation matrix became constant i mean we multiply difference *<br>
gradient * 1(from transformation matrix) then add this to theta0<br>
<br>
<br>
<br>
--<br>
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