[IGSTK-Developers] Registration error computation

[Hui Zhang]

Hi, Andinet,

>From my understanding of registration accuracy evaluation, probably there 
would be three or four values to evaluate the accuracy of registration: FRE, 
FLE and TRE, may Predicted TRE.

FRE is the RMS registration error from the fiducial points,
FLE is the statistical error of the each fiducials,
TRE is the real error between the target point(s) and the predicted 
transformed point(s),
in there paper, they evaluate the TRE error from an equation of FLEs, and 
also the position of the target point, I called it Predicted TRE. To 
calculate the Predicted TRE, principal component analysis is performed as 
you mentioned.


To get the FRE, the input is the fiducial points (fixed and moving);
FLE, same as above;
Predicted TRE, same as above, and also the position of the target point;
TRE, target point, transform point in second space, transform matrix;


So, just as you said, ComputeTRE() can be a member function in 
igstkTransform or directly in the igstkLandmarkRegistration;
ComputeFRE(), ComputeFLE, and ComputePredictedTRE(or maybe EvaluateTRE) can 
be inside igstkLandmarkRegistration if you want to add them.

That is my option, wish it helps,

James,

Another related paper is :

Predicting error in rigid-body point-based registration
Fitzpatrick, J.M.; West, J.B.; Maurer, C.R., Jr.;
Medical Imaging, IEEE Transactions on
Volume 17,  Issue 5,  Oct. 1998 Page(s):694 - 702


----- Original Message ----- 
From: "Andinet Enquobahrie" <andinet.enqu at kitware.com>
To: "'IGSTK-developers'" <igstk-developers at public.kitware.com>
Sent: Tuesday, December 06, 2005 4:35 PM
Subject: [IGSTK-Developers] Registration error computation


> Hi Folks,
>
> I would like to get your opinion on how to integrate a registration error 
> computation scheme into igstk.   The goal is to determine the accuracy of 
> a target registration using transform parameters computed by 
> "igstkLandmarkRegistration". From West et al. paper,  target registration 
> error  (TRE) is a function of  landmark registration error and the 
> location of the target with respect to the landmarks (distance from the 
> target to the three principal axis of the landmark configuration). 
> Integration of this computation into igstk is a bit tricky since it is 
> "target" and "target location" specific.
>
> To implement this computation in igstk, I see the need for the following
>
> 1) A member variable  to store landmark configuration information in 
> "igstkTransform"  (This could probably be just a three by three matrix to 
> encode the principal axis of the landmarks configuration)
> 2) Set/Get methods in "igstkTransform" for  this new member variable.
> 3) ComputeTargetRegistrationError()  method to compute the error. This 
> method will use the location of the target and landmark configuration 
> information to compute the registration error. The computed registration 
> error could be stored in the "ErrorValue" igstkTransform member variable. 
> However, I am not sure which class this method would perfectly fit in . 
> Either in Tracker class where target transformation is reported to the 
> spatial object or  in spatialobject class itself or in a new helper 
> class...
>
> Any thoughts?
>
> Thank you
>
> -Andinet
>
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