[Insight-developers] Scales estimation for registration

[brian avants]

hi baohua

nick may have some code that is relevant.

also, you may want to let people know about your other strategies for
estimating the parameter scales.  for instance,  the methods that take
into account the norm of the gradient itself, as well as as that build
estimates of the parameter space.

brian




On Mon, May 9, 2011 at 9:24 AM, Baohua Wu <baowu99 at gmail.com> wrote:
> Stefan,
>
> Thank you for the advice. I am  glad to know your method works for scales
> and learning rate. I will try it .
>
> Baohua
>
> ----- Original Message ----- From: "Stefan Klein" <s.klein at erasmusmc.nl>
> To: "Bill Lorensen" <bill.lorensen at gmail.com>
> Cc: "Marius Staring (registration)" <M.Staring at lumc.nl>;
> <baowu99 at gmail.com>; "Stefan Klein" <stefan at isi.uu.nl>; "Insight Developers"
> <insight-developers at itk.org>
> Sent: Monday, May 09, 2011 7:43 AM
> Subject: Re: [Insight-developers] Scales estimation for registration
>
>
>> Hi Bill,
>>
>> The method in elastix works well in my experience.
>>
>> The method is explained here:
>> http://dx.doi.org/10.1007/s11263-008-0168-y
>>
>> Equation 61/62
>> But that final expression should be squared because of the definition of
>> the scales in ITK.
>>
>> The method needs to know the fixed image domain and the transform. So it
>> would fit in the same framework as Bao's class. The methods declared at
>> lines 147 to 161 should probably be protected by the way?
>>
>> Just to clarify: the AutomaticScalesEstimation in elastix only computes
>> the scales, not the global LearningRate. I guess the GlobalScalingFactor
>> serves to determine the global LearningRate?
>>
>> To automatically determine an optimal global learning rate, you would need
>> the CostFunction as well. (since multiplying the costfunction by 10 would
>> cause the optimal learning rate to be divided by 10, for example).
>>
>> Good idea to make this a separate class!
>> Kind regards,
>> Stefan
>>
>>
>>
>> On 06/05/2011 22:52, Bill Lorensen wrote:
>>>
>>> Marius, Stefan and Bao,
>>>
>>> One of the major weaknesses in ITK's registration framework is the
>>> estimation of parameters. In particular, the estimation of the scales
>>> seems to require special magic. My experience has been that the
>>> selection of a proper scaling for translation is particularly
>>> difficult. ITK traditionally (and currently) leaves the scaling
>>> decision up to the application. There are currently two possible
>>> approaches to this estimation.
>>>
>>> 1) Bao's itkParameterScaleEstimator proposed in this gerrit topic:
>>> http://review.source.kitware.com/#change,1499
>>> 2) Elastix's (http://elastix.isi.uu.nl/) AutomaticScalesEstimation
>>>    method implementation in elxTransformBase.
>>>
>>> For Marius and Stefan I have questions:
>>>
>>> a) How successful is elastix's AutomaticScalesEstimation?
>>> b) Currently this is implemented as a method in
>>>    elxTransformBase. Could it be implemented in an API similar to Bao's
>>>    itkParameterScaleEstimator?
>>>
>>>
>>> For Bao's implementation, my concern is the addition of a free
>>> parameter GlobalScalingFactor. It is not clear how to pick a proper
>>> value. To me there is as much mystery in this parameter as there is in
>>> picking a proper translation scaling
>>>
>>> Bill
>>>
>>>
>>>
>>>
>>>
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>>
>> --
>> Stefan Klein
>> +31 10 7043049
>> http://www.bigr.nl/people/StefanKlein
>>
>
>