Different registration methods Narendhran Vijayakumar 01252008 Different types

Different registration methods Narendhran Vijayakumar 01/25/2008

Different types registration methods • Mutual information based registration method • Cost function based registration method – Correlation and Sum of absolute difference functions • Fourier Transform based registration method – Faster than any of the methods • Independent Component Analysis – For non rigid body registration 2

Cost function based registration • Registration is achieved by minimizing the cost function Cost = a * F(I 1, I 2) – b * G(I 1, I 2) where F(I 1, I 2) - Sum of absolute difference (SAD) G(I 1, I 2) - Correlation Coefficient (CC) 3

SAD and CC definition • SAD is defined as • CC is defined as 1 [1] Peter et al, Syntegra Image Automated registration algorithms, white paper 2003 4

Comparing MI and Cost function Test images - (Translational and Rotational parameters are known) MI based registration Cost function Translational error: 0. 23± 0. 49 mm Rotational error: 0. 14± 0. 17 o Rotational error: -------- 5

Registering T 2 FLAIR and Radial Diffusion weighted MI based registration Average translation X direction – 24. 57 mm Y direction – 6. 08 mm Average rotation Counter Clockwise – 0. 23 o Clockwise – 0. 25 o Cost function Average translation X direction – 22. 46 mm Y direction – 10. 06 mm Average rotation Counter Clockwise – 0 o 6

Performance Metrics • Gold standard – Two experts individually determine which image is better registered • Overlapping Images Reg Ref Reg • Phantom – Best way to test the algorithms 7

Future Work • Brightness – How different methods behave ? • Determine the Scale parameter • FFT based method 8