[Insight-users] Perplexed with Optimizer initialization
Luis Ibanez
luis.ibanez at kitware.com
Mon May 23 18:17:00 EDT 2005
Hi Yu,
If your image has number of pixels:
(200,300,400) in x,y,z respectively
and the pixel spacing is:
(0.3, 0.3, 0.7) millimeters in x,y,z respectively
then your image physical extent will be
( 200 x 0.3, 300 x 0.3, 400 x 0.7 )
= ( 60, 90, 280 )
millimeters in x,y,z respectively
The 3D diagonal of that image will be
square_root( 60^2 + 90^2 + 280^2 )
= 300.16 millimeters
so the scaling that you want to put in the
tranlational part of your transform is:
1.0 / 300.16
Note that this is just a good first value
to try. You may want to experiment by moving
it 10X or 0.lX.
Regards,
Luis
-------------------
Yu Qi wrote:
>
>
> 注：已附加转发邮件。
>
>
> ------------------------------------------------------------------------
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> ------------------------------------------------------------------------
>
> Subject:
> Re: [Insight-users] Perplexed with Optimizer initialization
> From:
> Yu Qi <felix_china at yahoo.com.cn>
> Date:
> Fri, 20 May 2005 21:41:23 +0800 (CST)
> To:
> Luis Ibanez <luis.ibanez at kitware.com>
>
>
> Hi Luis,
> I'm not sure about
> "in the range of 1/(diagonal of the image in millimeters) for translation"
> you mentioned in your email.
>
> For example, my diagonal is around 300mm
> which is the range? 0~300 or 300~300+?
>
> There was somebody told it should be in the range of 50~300, is that
> correct?
>
> Best regards,
> Yu Qi
>
> */Luis Ibanez <luis.ibanez at kitware.com>/* 写道：
>
>
>
> Hi Yu,
>
>
> You are right,
> parameters selection is a problem that is undersestimated by the
> entire medical image community.
>
> This disregards is closely related to the insufficiency of the
> publishing system and to the lack of appreciation for the practice
> of reproducibility of research work.
>
> In other words: since most published algorithms are not presented
> in a form that is intended to make easier for other to reimplement
> and run those algorithms, authors do not address the very important
> issue of parameter selection. Authors are more interested in claiming
> credit for the basic ideas behind their published algorithms.
>
> In the real world, however, parameter selection is a challenge of a
> larger scale than software development itself.
>
>
> That being said....
>
>
>
> Of, course, if you take an example, for w! hich the paramters were
> already adjusted... and you *change* the parameters... well... it
> will not always work.
>
>
> Since your question is quite generic,... we can only give you
> a generic answer. If you are interested in a more specific
> answer.... please post a more specific question.
>
>
> Generic answer:
>
>
> In the selection of parameters for registration you wan to
> do the following:
>
>
> 1) Make sure that the scaling array of parameter of the
> VersorRigid3D transform are in the range of
>
> 1.0 for rotations
> 1/(diagonal of the image in millimeters) for translation
>
>
> 2) Connect a command observer and print out the values
> of the metric and the paramters array at every iteration
>
>
>
>
> 3) Start with very small steps in the optimizer.
> E.g. in the range of 0.1
>
>
>
> Note that Algorithms *do not* and *do not have to* work for
> *every* arbitrary combination of parameters. So, you shouldnt
> expect to ! take a fine tunned example and be able to move the
> parameters at will while still getting reasonable results.
>
>
> Otherwise...
> well... there will not be any need for parameter fine tunning.
>
>
>
>
>
> Regards,
>
>
>
> Luis
>
>
>
> --------------------
> Yu Qi wrote:
> > Hi everybody,
> > I get to know ITK since only few months ago. I find it is a very
> well
> > orgnized toolkit for image registration and I made my only
> application
> > successfully!
> >
> > But there is one thing always confuses me during my programming:
> > the selection of parameters :-( . I first copy codes from user
> guide and
> > it worked. Then I want to change those parameters to see the
> influence
> > of them to the results. But it not alway turned out a success.
> >
> > Does anyone can help me with how to configure those parameters,
> > optimizer and metric? What is the most important one which I
> should take
> >! ; care first? What is the usual range of adjustment?
> >
> > Or will somebody enclose a paper about optimizers to me?
> >
> > Metric in my application: MattesMutualInformationImageToImageMetric
> > MutualInformationImageToImageMetric
> > Optimizer I used: itkVersorRigid3DTransformOptimizer
> >
> > Thank you all!
> >
> >
> >
> >
> >
> >
> >
> > *Best Regards!*
> > **
> > *Yu Qi*
> >
> >
> >
> >
> >
> ------------------------------------------------------------------------
> > *Do You Yahoo!?*
> > 150万曲MP3疯狂搜，带您闯入音乐殿堂
> > 美女明星应有尽有，搜遍美图、艳图和酷图
> > 1G就是1000兆，雅虎电邮自助扩容！
> >
> >
> >
> >
> >
> ------------------------------------------------------------------------
> >
> &! gt; _______________________________________________
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> > Insight-users at itk.org
> > http://www.itk.org/mailman/listinfo/insight-users
>
>
>
>
> ------------------------------------------------------------------------
> *Do You Yahoo!?*
> 150万曲MP3疯狂搜，带您闯入音乐殿堂 <http://music.yisou.com>
> 美女明星应有尽有，搜遍美图、艳图和酷图 <http://image.yisou.com>
> 1G就是1000兆，雅虎电邮自助扩容！
> <http://cn.rd.yahoo.com/mail_cn/tag/1g/*http://cn.mail.yahoo.com/event/mail_1g/>
>
>
>
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