[Insight-users] itk neighborhood operator image filter error
raghu venkatram
raghu_420 at hotmail.com
Tue, 20 Apr 2004 21:53:42 +0000
Hi Luis,
Using the gradient descent optimizer, even with 2000 iterations, my
registration does not converge. But my results do look good, as a plot of my
iterations vs my metric, my metric kind of flattens out after a certain
number of iterations.
my question is the learning rate constant throughout the process? or is it
divided my the current iteration something like r/iteration no.?
thanks,
raghu
>From: Luis Ibanez <luis.ibanez at kitware.com>
>To: raghu venkatram <raghu_420 at hotmail.com>
>CC: insight-users at itk.org
>Subject: Re: [Insight-users] itk neighborhood operator image filter
error
>Date: Tue, 20 Apr 2004 14:34:15 -0400
>
>
>Hi raghu,
>
>The optimizer scales do not need to be different among
>X, Y, and Z. Unless the anisotropy ratio as big as 1:10.
>
>The goal of the parameter scaling is to deal with large
>dynamic range differences such as degrees versus
>millimeters where the ratio is in the range of 1:100.
>
>If your metric plots shows the Metric behaving smoothly,
>you can take the risk of *increasing* (not decreasing)
>the step length of the optimizer, and probably reducing
>the number of iterations.
>
>Note however that if your registration is using all the
>allotted iterations, it means that it has not converged,
>and that you still have homework to do in parameter
>tunning.
>
>
>
> Regards,
>
>
> Luis
>
>
>
>------------------------
>raghu venkatram wrote:
>
>>Hello Luis,
>>
>>Thank you for the tip, it was ofcourse my CT volume, I was only
>>reading 2 slices. I am not sure why this is happening as I used
>>MRICro to convert both my CT and MR volumes into mayo clinic
>>analyze format and everything works fine. using ITK's dicom series
>>reader reads my MR volume and am able to wrtie it out, but it dies
>>on the third slice of my CT volume.
>>
>>Also regarding registration itself, i am using viola-wells mutual
>>information, with gradient descent and the translation transform.
>>in this set up should my my optimizer scales for x and y be equal
>>to 1 while my optimizer scale for z slightly greater than 1? my z
>>in the volume is much smaller than the inplane dimensions.
>>
>>with a step size of 18 and 500 epochs, i am getting good results,
>>and a final metric value of 0.2-0.4, a plot of the iteration vs
>>metric shows that the metric is fairly stable with this, should i
>>decrease the step size and increase the iterations further?
>>
>>
>>
>>thanks
>>
>>raghu
>>
>> >From: Luis Ibanez <luis.ibanez at kitware.com>
>> >To: raghu venkatram <raghu_420 at hotmail.com>
>> >CC: insight-users at itk.org
>> >Subject: Re: [Insight-users] itk neighborhood operator image
>>filter error
>> >Date: Mon, 19 Apr 2004 19:43:23 -0400
>> >
>> >
>> >Hi Raghu,
>> >
>> >It is likely that your process for reading the
>> >DICOM series is failing. The fact that it shows
>> >up in the Neighborhood iterator may simply indicate
>> >that you are reading an image of a single slice,
>> >for example.
>> >
>> >Please connect a ImageFileWriter directly to the
>> >output of the DicomSeries reader and save the
>> >image in another format. MetaImage will be the
>> >best choice since then you can look at the header
>> >and figure out what information from the DICOM
>> >file is getting lost on the way.
>> >
>> >Chances are that you only have a Input/Output
>> >problem and not a processing problem.
>> >
>> >
>> >I will also suggest you to try the example
>> >
>> > Insight/Examples/IO/
>> > DicomSeriesReadImageWrite.cxx
>> >
>> >for reading your Dicom images, and to make sure
>> >that you are using the series reader correctly.
>> >
>> >For example, note that you should specify the
>> >string identifying the series to be read.
>> >
>> >
>> >Please let us know what you find.
>> >
>> >
>> >
>> > Thanks,
>> >
>> >
>> > Luis
>> >
>> >
>> >-----------------------
>> >raghu venkatram wrote:
>> >>Hello Luis,
>> >> I am trying to register a MR and CT image using
ImagetoImage
>> >>mutual information measure, I have no problems whatsoever
using
>>the
>> >>analyze image format.
>> >> when i switch to dicom, and use the series reader, i can
read
>> >>both the series, but my program terminates with an error
window
>> >>asking me to notify microsoft, debug option takes me to
the
>> >>itkneighborhoodoperator filter.
>> >> is there something obvious that i am doing wrong? my
image
>>types
>> >>are unsigned short 3 dimensions.
>> >> thanks,
>> >>raghu
>> >>
>> >
>> >
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>
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