# ChangeTracker is broken

**URL:** <https://discourse.slicer.org/t/changetracker-is-broken/253>\
**Category:** Support\
**Tags:** extensions-manager, changetracker\
**Created:** [May 3, 2017, 12:36pm UTC](https://discourse.slicer.org/t/changetracker-is-broken/253 "2017-05-03T12:36:46Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![finetjul](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/finetjul/32/146_2.png) [@finetjul](https://discourse.slicer.org/u/finetjul)\
**Post date:** [May 3, 2017, 12:36pm UTC](https://discourse.slicer.org/t/changetracker-is-broken/253/1 "2017-05-03T12:36:46Z")

</div>

Hi,

I tested the ChangeTracker extension in Slicer 4.6.2 and it appears to be broken.

Problem #1: Test data fails to be loaded

Problem #2: There are Python errors at step 3

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<div class="post-metadata">

**Author:** ![fedorov](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fedorov/32/14_2.png) [@fedorov](https://discourse.slicer.org/u/fedorov)\
**Post date:** [May 3, 2017, 2:58pm UTC](https://discourse.slicer.org/t/changetracker-is-broken/253/2 "2017-05-03T14:58:43Z")

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> [@finetjul](#):
>
> Problem #1: Test data fails to be loaded

This appears to be a regression (or deprecation of functionality in Slicer?). This returns `None`, although dataset URL is valid:

```auto
>>> vl=slicer.modules.volumes.logic()
>>> vl.AddArchetypeVolume('http://www.slicer.org/slicerWiki/images/e/e3/RegLib_C01_2.nrrd','Test',0)

```

> [@finetjul](#):
>
> Problem #2: There are Python errors at step 3

Surprisingly to myself (I have not used this module for years!), it completed successfully on mac with the latest nightly, no python errors, and here’s the proof!

 ![](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/1X/a09e9c1af9a8491e7212f11c39a9ffa8caa95e23.jpg)

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<div class="post-metadata">

**Author:** ![fedorov](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fedorov/32/14_2.png) [@fedorov](https://discourse.slicer.org/u/fedorov)\
**Post date:** [May 3, 2017, 3:17pm UTC](https://discourse.slicer.org/t/changetracker-is-broken/253/3 "2017-05-03T15:17:52Z")

</div>

> [@finetjul](#):
>
> Problem #1: Test data fails to be loaded

should be resolved in the tomorrow’s nightly

> <https://github.com/fedorov/ChangeTrackerPy/commit/ea508e804a5a317037ddbc1e884d44dbc53018b9>

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<div class="post-metadata">

**Author:** ![finetjul](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/finetjul/32/146_2.png) [@finetjul](https://discourse.slicer.org/u/finetjul)\
**Post date:** [May 3, 2017, 7:06pm UTC](https://discourse.slicer.org/t/changetracker-is-broken/253/4 "2017-05-03T19:06:42Z")

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Hi Andrey,

Here is the error I have when I enter step 3.

```
Traceback (most recent call last):
  File "C:\Users\Julien\AppData\Roaming\NA-MIC\Extensions-25516\ChangeTracker\lib\Slicer-4.6\qt-scripted-modules\ChangeTrackerWizard\ChangeTrackerSegmentROIStep.py", line 173, in onEntry
    Helper.InitVRDisplayNode(self.__vrDisplayNode, roiVolume.GetID(), roiNodeID)
  File "C:\Users\Julien\AppData\Roaming\NA-MIC\Extensions-25516\ChangeTracker\lib\Slicer-4.6\qt-scripted-modules\ChangeTrackerWizard\Helper.py", line 108, in InitVRDisplayNode
    propNode = vrDisplayNode.GetVolumePropertyNode()
AttributeError: 'NoneType' object has no attribute 'GetVolumePropertyNode'

```

You will find below the content of the downloaded ChangeTracker.s4ext file.

```
arch amd64
archivename 25516-win-amd64-ChangeTracker-gitd91e870-2015-06-04.zip
category Wizards
contributors Andrey Fedorov (SPL), Kilian Pohl (SPL), Peter Black (BWH), Jean-Christophe Fillion-Robin (Kitware), Ron Kikinis (SPL)
description ChangeTracker is a software tool for quantification of the subtle changes in pathology. The module provides a workflow pipeline that combines user input with the medical data. As a result we provide quantitative volumetric measurements of growth/shrinkage together with the volume rendering of the tumor and color-coded visualization of the tumor growth/shrinkage.
enabled 1
extension_id 137168
homepage http://wiki.slicer.org/slicerWiki/index.php/Documentation/Nightly/Extensions/ChangeTracker
iconurl http://www.slicer.org/slicerWiki/images/b/b9/ChangeTracker_logo.png
md5 fb0a61860be06b57f5139eff2801dd19
os win
release 
revision d91e870
scm git
scmurl https://github.com/fedorov/ChangeTrackerPy.git
screenshots http://www.slicer.org/slicerWiki/images/8/8e/Slicer4_ChangeTracker_Ad.png
slicer_revision 25516
status
```

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<div class="post-metadata">

**Author:** ![finetjul](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/finetjul/32/146_2.png) [@finetjul](https://discourse.slicer.org/u/finetjul)\
**Post date:** [May 3, 2017, 7:18pm UTC](https://discourse.slicer.org/t/changetracker-is-broken/253/5 "2017-05-03T19:18:20Z")

</div>

Please note that I don’t have any error with Slicer 4.7.0 nightly

---

<div class="post-metadata">

**Author:** ![fedorov](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/fedorov/32/14_2.png) [@fedorov](https://discourse.slicer.org/u/fedorov)\
**Post date:** [May 3, 2017, 7:23pm UTC](https://discourse.slicer.org/t/changetracker-is-broken/253/6 "2017-05-03T19:23:56Z")

</div>

Thanks @finetjul. I can reproduce it, but I can’t see immediately what is wrong. I am not sure though how valuable “stable” Slicer is, so I am a bit reluctant to spend time on fixing this, considering it works in nightly.