Lianrui Zuo
Atlas
1997

Image similarity

To line up two scans, a computer needs one number for how well they match. What should that number be, when even the brightness of the same tissue differs between the scans?

Primary source F. Maes, A. Collignon, D. Vandermeulen, G. Marchal and P. Suetens, “Multimodality image registration by maximization of mutual information,” IEEE Transactions on Medical Imaging, vol. 16, no. 2, pp. 187–198, 1997. doi:10.1109/42.563664

The fixed image is a T1-weighted MRI slice. A moving image slides over it, up or down, and three scores watch: are the two values at each pixel close, do they rise and fall together, and does knowing one value predict the other? The dot on each curve marks the shift that score likes best; the right answer is always 0. Try the T2-weighted image, where the same tissue has very different brightness.

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