[Insight-users] Question about SymmetricForcesDemonsRegistrationFilter and LevelSetMotionRegisrationFilter

[Guorong Wu]

Hello all:
	In the directory /Insight/Examples/Registration there are three demons like non-rigid registration examples: DeformableRegistration2.cxx, DeformableRegistration3.cxx DeformableRegistration5.cxx respectively. DeformableRegistration2.cxx is based on Thirion's original demons algorithm, and DeformableRegistration3.cxx use symmetric forces which can avoid the non-uniformity of deformation field, while DeformRegistration5.cxx implements a deformable registration algorithm that align a fixed image and a moving image under level set motion. 
	I'v tested those three programs for sevel MR brain images finding that levelsetmotionfilter is the most efficient one. Symmetricforcefilter does great better result than Thirion's but the computation time is three times than demonsregistrationfilter. The match result of levelsetmotionfilter is about 10% better than symmetricforcefilter in every test while takes much less (about 30%) time than demonsregistraionfilter. 
	I am so interested in itkSymmetricForcesDemonsRegistrationFilter and itkLevelSetMotionRegistrationFilter that I look into the source code of these algorithms, but I am got confused in some implementations in the souce code. So I will be very appreciated if someone would give me some help. Thanks in advance.

	QUESTION1:  This is about LevelSetMotionRegistrationFilter. I'v read the paper mentioned in /Code/Algorithms/itkLevelSetMotionRegistrationFilter.h. In this paper, the process of registration is controled by two PEDs (equation 23 and equation 27). But in itkLevelSetMotionRegistrationFunction I could only find the implementation of equation 27 in function ComputeUpdate(...) at line 399. Could someone tell me where is the implementation of equation 23?
	QUESTION2:	SysmmetricForcesRegistrationFilter is the variant of triditional demons which is contributed by Corinne Mattmann. I could see the modification through the source code but cann't tell why does it take the effect. Would you like to recommmend some paper?
	QUESTION3: Most of the registraion methods is proposed in the multi-resolution framework. But the example programs does not use multi-resolution. If I try to add it to the examples what kind of work I should do or what should I take careful?

	Good Luck. 
			

　　　　　　　　Guorong Wu
　　　　　　　　grwu at sjtu.edu.cn
　　　　　　　　　　2004-07-15

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Guorong Wu	
The Department of Computer Science and Technology
Shanghai Jiao Tong University
1954 Huashan RD
Shanghai China    
200030
Tel:  +86 21 3226 1236  , 6293 2089
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