[ITK Community] [Insight-users] I meet some problem when using FastMarchingImageFilter , please help me !

[Luis Ibanez]

Hi zhq,

This is explained in the ITK Software Guide
http://www.itk.org/ItkSoftwareGuide.pdf

in page 538.

The Value set in this function is a value in time.

More precisely, it is the time at which the front will start propagating
from
that node point.

The context is that the output of the FastMarching filter is a time
crossing map.

A map that tells you at what time, the front, reached every pixel.

The value that you set in node.SetValue() is the time at which you want to
start
the front propagation from that pixel.

A typical use of this value is to be able to segment an image of a "Snowman"
where the bottom of the snowman is a large sphere, the thorax is a medium
sphere and the head is a small sphere.

You generate this shape by placing FastMarching nodes at the center of each
one of those spheres and then setting the time for the bottom to be earlier
than
the time for the thorax, and leaving the time of the head for later.

In this way, the front at the bottom will have more time to propagate and
to
fill up a larger region.

A bit of experimentation with at least two nodes, and different starting
times
on each node will give you some familiarity with the effect of this
parameter.

   Hope this helps.

       Luis



On Sun, Dec 15, 2013 at 10:26 PM, zhq <15891495523 at 126.com> wrote:

> Hi ,Luis
>        I have another question about fast marching filter .
>        In the code , a sentence makes me confused .  The sentence is
> node.SetValue( 0 ) .  What dose the sentence means ? What role does the
> value play ?
>        Thanks !
> zhq
>
>
>
>
>
> At 2013-12-13 21:57:26,"Luis Ibanez" <luis.ibanez at kitware.com> wrote:
>
> Hi Zhq,
>
> When running the FastMarching example, it is critical to do the following:
>
>
> 1) Place the seed points in the locations of the anatomy,
>      that you want to segment.
>
>      Did you adjusted the location of the seed points to your image ?
>
>
> 2)  Adjust the values of Alpha and Beta in the Sigmoid filter to the range
>      of intensities of the image produced by the Gradient magnitude filter.
>
>      Have you adjusted these values ?
>
>      It is useful to save the output image of the GradientMagnitude filter
>      and inspect it directly with an image viewer.
>
>       Instructions on this are available in the software guide.
>
>
> 3)  Once you have inspected the gradient magnitude output,
>       proceed to adjust the Alpha and Beta in the sigmoid until you
>       get almost a black and white image as output.
>
>       For this, it also helps to save the image in a file and to inspect
>       it with an image viewer.
>
> 4) Finally, the "stoppingTime" parameter in the fastMarching filter
>      is also a critical parameter to define when the filter stops
> propagating
>      the front.
>
>
> Please review these check points above, and if you continue having
> difficulties, please post your input image in a public web site, so that
> we could inspect it and give it a try.
>
>
>     Thanks
>
>          Luis
>
>
>
>
> On Thu, Dec 12, 2013 at 9:34 PM, zhq <15891495523 at 126.com> wrote:
>
>> Dear all :
>>        I run the code ,FastMarchingImageFilter.cxx , which included
>> in InsightToolkit\Examples\Segmentation , a problem appears :
>>        When the code runs to the sentence , fastMarching->Update() ,
>>
>>         This process occupies 25% of the CPU, and the code stop in this
>> sentence .
>>         What the problem could be ?
>>         Thanks in advance !
>> zhq
>>
>>
>> 来自网易手机号码邮箱了解更多 <http://shouji.163.com>
>>
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>
>
> 来自网易手机号码邮箱了解更多 <http://shouji.163.com>
>
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