Validation for 2D/3D registration. II: The comparison of intensity- and gradient-based merit functions using a new gold standard data set.
Gendrin C, Markelj P, Pawiro SA, Spoerk J, Bloch C, Weber C, Figl M, Bergmann H, Birkfellner W, Likar B, et al. Med Phys. 2011 Mar; 38(3):1491-502.