# How to determine if the curve is closed?

**URL:** <https://discourse.itk.org/t/how-to-determine-if-the-curve-is-closed/3237>\
**Category:** Uncategorized\
**Created:** [June 29, 2020, 3:03am UTC](https://discourse.itk.org/t/how-to-determine-if-the-curve-is-closed/3237 "2020-06-29T03:03:48Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![guo7212](https://discourse.itk.org/letter_avatar_proxy/v4/letter/g/7ab992/32.png) [@guo7212](https://discourse.itk.org/u/guo7212)\
**Post date:** [June 29, 2020, 3:03am UTC](https://discourse.itk.org/t/how-to-determine-if-the-curve-is-closed/3237/1 "2020-06-29T03:03:48Z")

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Hi all,  
I want to find the markers in CT scout. Is it possible to determine if the curve is closed?

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**Author:** ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)\
**Post date:** [June 29, 2020, 1:14pm UTC](https://discourse.itk.org/t/how-to-determine-if-the-curve-is-closed/3237/2 "2020-06-29T13:14:23Z")

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Which markers? What curve? Please provide more details.

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**Author:** ![guo7212](https://discourse.itk.org/letter_avatar_proxy/v4/letter/g/7ab992/32.png) [@guo7212](https://discourse.itk.org/u/guo7212)\
**Post date:** [July 2, 2020, 9:26am UTC](https://discourse.itk.org/t/how-to-determine-if-the-curve-is-closed/3237/3 "2020-07-02T09:26:36Z")

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Thanks.  
The application is surgical navigation. The marker is made from round aluminum sheet. The marker is like a circle in the CT scout. I want to find them from the scout. I used the Canny Edge detection method. It found many curves. Among the curves, the closed curve I thought is the marker. So I want to know is it possible to determine if the curve is closed ? Or maybe are there any better segmentation methods to find the marker ?

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**Author:** ![dzenanz](https://discourse.itk.org/user_avatar/discourse.itk.org/dzenanz/32/1093_2.png) [@dzenanz](https://discourse.itk.org/u/dzenanz)\
**Post date:** [July 2, 2020, 11:06am UTC](https://discourse.itk.org/t/how-to-determine-if-the-curve-is-closed/3237/4 "2020-07-02T11:06:15Z")

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Hough transform might be of interest to you. ITK’s implementation is called [HoughTransform2DCirclesImageFilter](https://itk.org/Doxygen/html/classitk_1_1HoughTransform2DCirclesImageFilter.html).