Improving the Convergence Rate in Affine Registration of PET and SPECT Brain Images Using Histogram Equalization

Figure 1

Left image: original MRI brain transaxial image. (a) Balanced diagonal elements result in global rescaling. (b) Unbalanced diagonal elements produce anisotropic rescaling along the 𝑦-axis. (c) Unbalanced diagonal elements produce anisotropic rescaling along the 𝑥-axis. (d) Specific balanced relations between off-diagonal elements in the matrix produce rotations. (e) An unbalance change in the off-diagonal elements resulting in shears along one of the two axes.