[Insight-users] who know the implementation of MI in ITK?

[Dongfeng Han]

hello
I have read the guide book on page 452

I(a,b) =H(a)+h(B)-H(a,b)
because H(a,b)<=H(a)+h(b), so I(a,b)should be >=0;
so , we should maximize the I(a,b) for registration.
But  my output for registration two 3d volume is like below. (the
second column is the MI value)
At each iteraton is decrease and the value is non-positive.
It conflict with my analysis.
so anybody can give me some suggestion?
thanks
0   0   -0.271443   0
0   0   -0.286633   0
0   0   -0.286633   0.00620487
1   0   -0.300877   0.00620487
1   0   -0.300877   0.00304002
2   0   -0.307195   0.00304002
2   0   -0.307195   0.00132559
3   0   -0.223647   0.00132559
3   0   -0.300672   0.00132559
3   0   -0.308016   0.00132559
3   0   -0.308016   0.00116934
4   0   -0.28022   0.00116934
4   0   -0.307456   0.00116934
4   0   -0.308148   0.00116934
4   0   -0.308148   0.00112118
5   0   -0.305431   0.00112118
5   0   -0.308338   0.00112118
5   0   -0.307334   0.00112118
5   0   -0.308314   0.00112118
5   0   -0.308314   0.00107307
6   0   -0.276599   0.00107307
6   0   -0.307406   0.00107307
6   0   -0.308268   0.00107307
6   0   -0.30831   0.00107307
6   0   -0.308314   0.00107307
6   0   -0.308314   0.00107307
6   0   -0.308314   0.00107307