Download presentation

Presentation is loading. Please wait.

Published byJarvis O'Neil Modified over 2 years ago

1
Image Registration: Demons Algorithm JOJO 2011.2.23

2
Outline Background Demons Maxwell’s Demons Thirion’s Demons Diffeomorphic Demons Experiments Conclusions

3
Background Definition: Register the pixels or voxels of the same anatomical structure in two medical images Reasons: Different ways of obtaining images Different peoples’ different anatomical structures Current non_rigid registration methods: Demons, LDDMM (Large Deformation Diffeomorphic Metric Mapping), Hammer

4
Outline Background Demons Maxwell’s Demons Thirion’s Demons Diffeomorphic Demons Experiment Conclusion

5
Demons: Maxwell’s Demons A gas composed of a mix of two types of particles and The semi-permeable membrane ( 半透膜 ) contains a set of ‘demons’ (distinguish the two types of particles) Allow particles only to side A and particles only to side B

6
Outline Background Demons Maxwell’s Demons Thirion’s Demons Diffeomorphic Demons Experiment Conclusion

7
Demons: Thirion’s Demons Purpose: Assumption membrane: the contour of an object O in S demons (P): scatter along the membrane particles: M is the deformable grid, vertices are particles

8
Demons: Thirion’s Demons Process: Push the Model M inside O if the corresponding point of M is labelled ‘inside’, and outside O if it is labelled ‘outside’

9
Demons: Thirion’s Demons Flow chart: The selection of the demons positions Ds The space of T The interpolation method to get the value Ti(M) The formula giving the force f of a demon Simple addition or composition mapping Different demons

10
Demons: Thirion’s Demons Demons 0: Ds: sample points of the disc contour T: rigid transformation Ti(M): analytically defined f: constant magnitude forces from Ti to Ti+1: simple addition

11
Demons: Thirion’s Demons Demons 1: Ds: All pixels (P) of s where T: free form transformation Ti(M): trilinear interpolation f: to get the displacement from Ti to Ti+1: simple addition

12
Demons: Thirion’s Demons Disadvantage: The topology of the image may be changed (determined by Jacobian determinant) The transformation may be nonreversible

13
Outline Background Demons Maxwell’s Demons Thirion’s Demons Diffeomorphic Demons Application Conclusion

14
Demons: Diffeomorphic Demons Basic: The most obvious difference: composition mapping not simple addition New conceptions: Lie group, Lie algebra exponential map

15
Demons: Diffeomorphic Demons How to calculate exponential map 1)Let and choose N such that is close enough to 0, i.e. 2)Do N times recursive squaring of :

16
Demons: Diffeomorphic Demons Diffeomorphic demons algorithm: 1)Initialize the transformation T, generally Identical transformation, then 2)Calculate the new, 3)Get the new T 4)If not convergence, go back to 2), otherwise, T is the optimal transformation

17
Outline Background Demons Maxwell’s Demons Original Demons Diffeomorphic Demons Experiments Conclusions

18
Experiment First experiments (design): 100 experiments with random images to compare Thirion’s demons and diffeomorphic demons

19
Experiment First experiments (results):

20
Experiment Second experiment (design): Use synthetic T1 MR images from two different anatomies available from BrainWeb

21
Experiment Second experiments (results):

22
Experiment Third experiment: Try to apply the demons algorithm to automatic unsupervised classification of MR images in AD

23
Outline Background Demons Maxwell’s Demons Original Demons Diffeomorphic Demons Experiments Conclusions

24
Conclusion Advantages: Realize automation Good performance on non_rigid registration Relatively fast speed Disadvantage: The segmentation accuracy based on demons need to be improved

25
Thank you!

Similar presentations

OK

The Least Squares Regression Line. The problem with drawing line of best fit by eye is that the line drawn will vary from person to person. Instead, use.

The Least Squares Regression Line. The problem with drawing line of best fit by eye is that the line drawn will vary from person to person. Instead, use.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on basic etiquettes Ppt on standing orders Ppt on seasons in arabic Ppt on district industries centre Ppt on reflection of sound Download ppt on indus valley civilization seals A ppt on loch ness monster facts Ppt on writing english skills Ppt on online marketing trends Ppt on forward contracts