[Insight-developers] LabelMaps and the Perimeter Estimation

[Jim Miller]

I had run into issues with the Perimeter measurement last fall. I had communicated with Gaetan about it.  In my case, I wasn't really interested in the perimeter but rather the Roundness of an object which was being distorted by the Perimeter issue. To get around this, I wrote meself a little filter that overwrite the Roundness value stored with another measure of roundness. Here, I just made something up that sounded good to me. I had meaning to send the measure to Gaetan for consideration.  What I did was 

    labelObject->SetRoundness( labelObject->GetEquivalentRadius() / (labelObject->GetFeretDiameter() / 2.0) );

The equivalent radius is a radius of a circle with the same area as the object. The feret diameter is the diameter of circumscribing circle. So this measure has a maximum of 1.0 when the object is a perfect circle.

Jim

 


On Apr 27, 2011, at 11:52 AM, Bradley Lowekamp wrote:

> Gaetan,
> 
> Have you seen the following bug:
> http://www.itk.org/Bug/view.php?id=11934
> 
> I encountered this bug myself. It is quite serious because the roundness attribute can become quite erroneous, as I have seen it >2.0 when theoretically it should always be less then 1.0. The miscalculation is causing me to have some trust issues with using this code and relaying on the computed attributes.
> 
> In this current state I would not recommend moving the LabelMaps out of ITK review.
> 
> Your IJ paper says "More details about perimeter estimation will be published in another article". I only bring up the issue because LabelMaps are quite useful, and would like they to quickly be placed in the reliable category. 
> 
> Thanks,
> Brad
> 
> ========================================================
> Bradley Lowekamp  
> Lockheed Martin Contractor for
> Office of High Performance Computing and Communications
> National Library of Medicine 
> blowekamp at mail.nih.gov
> 
> 
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Jim Miller
Senior Scientist
GE Research 
Interventional and Therapy

GE imagination at work

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