[Insight-developers] Scales estimation for registration

[Bill Lorensen]

My concern is the estimation of the translation scales. It seems the global
scale factor is used to scale the "estimated scales". I guess, indirectly,
it interacts with the learning rate. So it is also of concern.


On Mon, May 9, 2011 at 1:42 PM, Baohua Wu <baowu99 at gmail.com> wrote:

> hi brian,
>
> thank you for the information.
>
> to my knowledge, the test was passed with the synthetic data, and the
> scales worked well with several real images. i think bill's conern was
> mainly about how to set the global factor (or learning rate).
>
> we have been trying to estimate this global factor as well. some strategies
> include the norm of gradient, the parameter space, etc.
>
> baohua
>
> ----- Original Message ----- From: "brian avants" <stnava at gmail.com>
> To: "Baohua Wu" <baowu99 at gmail.com>; "Nicholas Tustison" <
> ntustison at gmail.com>
> Cc: "Stefan Klein" <s.klein at erasmusmc.nl>; "Bill Lorensen" <
> bill.lorensen at gmail.com>; "Marius Staring (registration)" <
> M.Staring at lumc.nl>; "Stefan Klein" <stefan at isi.uu.nl>; "Insight
> Developers" <insight-developers at itk.org>
> Sent: Monday, May 09, 2011 10:05 AM
>
> Subject: Re: [Insight-developers] Scales estimation for registration
>
>
> 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
>>>
>>>
>>
>>
>
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