[3] [3] Pluim J P W, Maintz J B A, Viergever M A. Mutual-information-based registration of medical images: a survey[J]. IEEE Transactions on Medical Imaging, 2003, 22(8) : 986-1004.

[4] [4] Maes F, Collignon A, Vandermeulen D. Multimo-dality image registration by maximization of mutual information[J]. IEEE Transactions on Medical Imaging, 1997, 16(2):187-198.

[6] [6] Viola P, Wells W M. Alignment by maximization of mutual information[J]. International Journal of Computer Vision, 1997, 24:137-154.

[7] [7] Studholme C, Hill D L G, Hawkes D J. An overlap invariant entropy measure of 3D medical image alignment[J]. Pattern Recognition, 1999, 32(1):71-86.

[8] [8] Pluim J P W, Maintz J B A, Viergever M A. Image registration by maximization of combined mutual information and gradient information. IEEE Transactions on Medical Imaging, 2000, 19(8):809-814.